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VOLUME 13

Palaeontology

1970

PUBLISHED BY THE
PALAEONTOLOGICAL ASSOCIATION
LONDON

Dates of publication of parts of Volume 13

Part 1, pp. 1-173, pis. 1-34
Part 2, pp. 175-333, pis. 35-62
Part 3, pp. 335-510, pis. 63-102
Part 4, pp. 511-700, pis. 103-128

22 March 1970
26 August 1970
30 October 1970
22 December 1970

THIS VOLUME EDITED BY N. F. HUGHES, GWYN THOMAS, ISLES STRACHAN, ROLAND GOLDRING,
M. R. HOUSE AND J. D. HUDSON

Dates of publication of Special Papers in Palaeontology

Special Paper No. 1
Special Paper No. 2
Special Paper No. 3
Special Paper No. 4
Special Paper No. 5
Special Paper No. 6
Special Paper No. 7

21 June 1967
31 January 1968
7 October 1968
1 May 1969
17 October 1969
26 April 1970
6 August 1970

© The Palaeontological Association , 1970

PRINTED IN GREAT BRITAIN

CONTENTS

Part Page

Armstrong, J. Zoarial microstructures of two Permian species of the bryozoan genus

Stenopora 4 581

Ash, S. R. Dinophyton, a problematical new plant genus from the Upper Triassic of the
south-western United States 4 646

Baker, P. G. The growth and shell microstructure of the thecideacean brachiopod
Moorellina granulosa (Moore) from the Middle Jurassic of England 1 76

The morphology and microstructure of Zellania davidsoni Moore (Brachiopoda),

from the Middle Jurassic of England 4 606

Bassett, M. G. Variation in the cardinalia of the brachiopod Ptychopleurella bouchardi
(Davidson) from the Wenlock Limestone of Wenlock Edge, Shropshire 2 297

Bate, R. H. A new species of Hemicypris (Ostracoda) from the ancient beach sediments
of Lake Rudolf, Kenya 2 289

Biernat, G., and Williams, A. Ultrastructure of the protegulum of some acrotretide
brachiopods 3 491

Bradshaw, M. A. The dentition and musculature of some Middle Ordovician (Llan-
deilo) bivalves from Finistere, France 4 623

Campbell, K. S. W., and Durham, G. J. A new trinucleid trilobite from the Upper
Ordovician of New South Wales 4 572

Chowdhury, T. R. Two new dicynodonts from the Triassic Yerrapalli Formation of
central India 1 132

Collins, J. I. The chelonian Rhinochelys Seeley from the Upper Cretaceous of England
and France 3 355

Cvancara, A. M. Teredinid (Bivalvia) pallets from the Palaeocene of North America 4 619

Dixon, O. A. Variation in the Visean coral Caninia benburbensis from north-west Ireland 1 52

Durham, G. J. See Campbell, K. S. W.

Edwards, D. Fertile Rhyniophytina from the Lower Devonian of Britain 3 451

Elliott, G. F. Pseudocymopolia, a Mesozoic Tethyan alga (Family Dasycladaceae) 2 323

New and little-known Permian and Cretaceous Codiaceae (Calcareous algae)

from the Middle East 2 327

— — Calcareous algae new to the British Carboniferous 3 443

Fischbuch, N. R. Amphipora and Euamphipora (Stromatoporoidea) from the Devonian
of western Canada 1 64

Good, C. W., and Taylor, T. N. On the structure of Cordaites felicis Benson from the
Lower Pennsylvanian of North America 1 29

Gould, R. E. Palaeosmunda, a new genus of siphonostelic osmundaceous trunks from
the Upper Permian of Queensland 1 10

Hancock, J. M. See Kennedy, W. J.

Hardy, P. G. Xiphosurid trails from the Upper Carboniferous of northern England 2 188

Hayami, I., and Matsukuma, A. Variation of bivariate characters from the standpoint
of allometry 4 588

House, M. R. On the origin of the clymenid ammonoids 4 664

Howie, A. A. A new capitosaurid labirynthodont from East Africa 2 210

Hubbard, J. A. E. B. Sedimentological factors affecting the growth of Visean caninioid
corals in north-west Ireland 2 191

Hughes, C. P. Statistical analysis and presentation of trinucleid (Trilobita) fringe data 1 1

and Wright, A. J. The trilobites Incaia Whittard 1955 and Anebolithus gen. nov. 4 667

CONTENTS

iv

Part Page

Jenkins, W. A. M. Chitinozoa from the Ordovician Sylvan Shale of the Arbuckle

Mountains, Oklahoma 2 261

Kato, M., and Mitchell, M. A new Orionastraea (Rugosa) from the Lower Carboni-
ferous of northern England 1 47

Kennedy, W. J., and Hancock, J. M. Ammonites of the genus Acanthoceras from the
Cenomanian of Rouen, France 3 462

Morris, N. J., and Taylor, J. D. The shell structure, mineralogy and relationships

of the Chamacea (Bivalvia) 3 379

Kirchgasser, W. T. Conodonts from near the Middle/Upper Devonian boundary in
North Cornwall 3 335

Matsukuma, A. See Hayami, I.

Matthews, S. C. A new cephalopod fauna from the Lower Carboniferous of east
Cornwall 1 112

Mitchell, M. See Kato, M.

Moody, R. T. J., and Walker, C. A. A new trionychid turtle from the British Lower
Eocene 3 503

Morris, N. J. See Kennedy, W. J.

Morton, B. The evolution of the heteromyarian condition in the Dreissenacea (Bivalvia) 4 563

Muir, M., and Van Konijnenberg-Van Cittert, J. H. A. A Rhaeto-Liassic flora from
Airel, Northern France 3 433

Murray, J. W., and Wright, C. A. Surface textures of calcareous foraminiferids 2 184

Pocock, K. J. The Emuellidae, a new family of trilobites from the Lower Cambrian of

South Australia 4 522

Reyre, Y. Stereoscan observations on the pollen genus Classipollis Pflug 1953 2 303

Sanderson, G. A., and Verville, G. J. Morphologic variability of the genus Schwa-
gerina in the Lower Permian Wreford Limestone of Kansas 2 175

Strachan, I. See Toghill, P.

Taylor, J. D. Feeding by predatory gastropods in a Tertiary (Eocene) molluscan

assemblage 2 254

See Kennedy, W. J.

Taylor, T. N. See Good, G. W.

Thomas, B. A. Epidermal studies in the interpretation of Lepidodendron species 1 145

Thulborn, R. A. The skull of Fabrosaurus australis, a Triassic ornithischian dinosaur 3 414

Toghill, P., and Strachan, I. The graptolite fauna of Grieston Quarry, near Inner-
leithen, Peebleshire 4 511

Trewin, N. H. A dimorphic goniatite from the Namurian of Cheshire 1 40

Van Konijnenberg-Van Cittert, J. H. A. See Muir, M.

Verville, G. J. See Sanderson, G. A.

Walker, C. A. See Moody, R. T. J.

Whitworth, P. H. Ontogeny of the Upper Cambrian trilobite Leptoplastus crassi-
cornis (Westergaard) from Sweden 1 100

Williams, A. See Biernat, G.

Wright, C. A. See Murray, J. W.

VOLUME 13 • PART 1

5 £,0.-54^

"P/j5

<^C- It1*"0 ^

Palaeontology

MARCH 1970

PUBLISHED BY THE
PALAEONTOLOGICAL ASSOCIATION
LONDON

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ship Treasurer, Dr. A. J. Lloyd, Department of Geology, University College,
Gower Street, London, W.C. 1, England.

COUNCIL 1969-70

President: Professor Alwyn Williams, The Queen’s University, Belfast

Vice-Presidents : Dr. W. S. McKerrow, Department of Geology, Oxford
Dr. C. Downie, The University, Sheffield

Treasurer : Dr. J. M. Hancock, Department of Geology, King’s College, London, W.C. 2

Membership Treasurer : Dr. A. J. Lloyd, Department of Geology, University College,
Gower Street, London, W.C. 1

Secretary: Dr. W. D. I. Rolfe, Hunterian Museum, The University, Glasgow, W. 2
Editors

Mr. N. F. Hughes, Sedgwick Museum, Cambridge
Dr. Gwyn Thomas, Department of Geology, Imperial College, London, S.W.7
Dr. Isles Strachan, Department of Geology, The University, Birmingham, 15
Professor M. R. House, The University, Kingston upon Hull, Yorkshire
Dr. R. Goldring, Department of Geology, The University, Reading, Berks.

Other members of Council

Dr. F. M. Broadhurst, Manchester
Dr. L. R. M. Cocks, London
Dr. C. B. Cox, London
Mr. D. Curry, Northwood
Dr. A. Hallam, Oxford
Dr. Julia Hubbard, London
Dr. J. D. Hudson, Leicester

Dr. W. J. Kennedy, Oxford

Dr. J. D. Lawson, Glasgow

Dr. E. P. F. Rose, London

Dr. C. T. Scrutton, Newcastle

Dr. V. G. Walmsley, Swansea

Professor H. B. Whittington, Cambridge

Overseas Representatives

Australia: Professor Dorothy Hill, Department of Geology, University of Queensland, Brisbane
Canada: Dr. D. J. McLaren, Institute of Sedimentary and Petroleum Geology, 3303-33rd Street
NW., Calgary, Alberta

India: Professor M. R. Sahni, 98 The Mall, Lucknow (U.P.), India

New Zealand: Dr. C. A. Fleming, Geological Survey, P.O. Box 368, Lower Hutt, New Zealand
West Indies and Central America: Mr. John B. Saunders, Geological Laboratory, Texaco Trinidad,
Inc., Pointe-^-Pierre, Trinidad, West Indies

Western U.S. A. : Professor J. Wyatt Durham, Department of Paleontology, University of California,
Berkeley 4, California.

Eastern U.S. A. : Professor J. W. Wells, Department of Geology, Cornell University, Ithaca, New York

© The Palaeontological Association, 1970

STATISTICAL ANALYSIS AND PRESENTATION
OF TRINUCLEID (TRILOBITA) FRINGE DATA

by C. P. HUGHES

Abstract. The current notation and methods of data presentation for the pits of the trinucleid fringe are
reviewed and some shortcomings noted. Using a sample of Trinucleus fimbriatus Murchison investigations show
that (i) operator errors in selecting half-fringes were negligible, (ii) major features of the pit distribution are not
dependent on the size of specimen, (iii) statistically there are no significant differences between the left and
right half-fringes, although particular individuals commonly exhibit some asymmetry. It is considered most
probable that these conditions hold true in all trinucleids and that numerical studies should be applied through-
out taxonomic studies of the group.

Since Bancroft (1929) introduced a notation for describing the trinucleid fringe and the
use of the fringe characteristics in systematic studies, the taxonomic importance of the
pit distribution on the fringe of trinucleids has increased enormously. However, the most
favoured system of pit enumeration at the present day is still that proposed by Bancroft
(1929, pp. 69-72) and subsequently emended by Whittard (1955, pp. 27-8). That this
system has remained unchanged in its essentials since its inception is surprising, as
several authors have experienced some difficulties in using it. Williams (1948), in studying
the marrolithids of South Wales, found it difficult to apply Bancroft’s scheme to the
variable numbers of swollen pits typical of these trinucleids. Cave (1957) in a population
study of Salterolithus caractaci found even Whittard’s emended form of notation un-
satisfactory to deal adequately with the variation he found within the population. More
recently Whittington (1966, pp. 86-90) found a similar degree of variation in Broeggero-
lithus nicholsoni and recognized the need for some new means of documenting the varia-
tion present and, while working within the general framework of the traditional notation,
presented data on the variation by means of simple histograms rather than attempting
to use the standard half-fringe formula. Whittington (1968) again raised the problem of
documenting the characteristics of the pit distribution when describing some North
American species of Cryptolithus where the preservation is such that data are available
for complete fringes. In that study he concluded that the full use of Whittard’s notation
was unnecessary and he concentrated on the number of pits in the complete Ex arc and
the appearance of the inner I arcs, /3 and /4, since these three aspects of the fringe pit
distribution were the most important for distinguishing the species under consideration.
He also (p. 703) raised the problem, often apparently ignored when half-fringe data have
been given in the past, that even in such well preserved material the selection of the mid-
line of the fringe is often difficult.

The main aim of the present paper is to record the methods and results of an analysis
of the distribution of pits on a trinucleid fringe made as a preliminary to the application
of statistical techniques in taxonomic studies of the trinucleids. This analysis showed
that the half-fringe may in fact be used satisfactorily to represent the characteristics of
the whole fringe and that it does not show any dependence on the size of the individual.
Although the details of the methods used here were closely linked to one particular

[Palaeontology, Vol. 13, Part 1, 1970, pp. 1-9.]

C 7173 B

2

PALAEONTOLOGY, VOLUME 13

trinucleid, namely Trinucleus fimbriatus, this type of approach is, it is believed, applicable
to all trinucleid fringes as well as to many problems concerning numerical symmetry
and size dependence of morphological features in palaeontological studies. The main
purpose of presenting these results here as a separate entity divorced from any accom-
panying systematic studies is that by so doing it is hoped to be more readily accessible
to workers in other fields, for although such techniques as employed here have on occa-
sion been used over the last 30 or 40 years, there is still a need for their much wider
application.

The present study was made as a preliminary to the redescription of the trinucleids
of the Builth region (Hughes in press) and was carried out entirely independently of
Whittington and prior to the appearance of his 1968 paper. It is of interest therefore
to note that although the types of material and approaches used were different, the con-
clusions are basically very similar. The approach adopted here has tended to be more
numerical than graphical, for although graphs and histograms of the type used by
Whittington are a very useful means of illustration, the purely statistical presentation
enables direct objective comparisons to be made between various sets of data ; such com-
parisons are not possible directly from histograms. On the other hand the statistical
presentation adopted here could be attacked as being too abstract, and it is believed that
in systematic studies the most satisfactory method may well be a conjunct use of both
methods, using the graphical aids to illustrate appropriate features. Finally, in this
paper the possibilities of extending the results of this study towards a more mathe-
matical approach to the description of the pit distribution of trinucleid fringes are
assessed.

As mentioned by Whittington (1968, p. 704) it is chiefly because of the incomplete
preservation of the fringe in the bulk of trinucleid material that the vast majority of
trinucleid species have been based on half-fringe descriptions, even in species where some
complete fringes were known. This reliance on the half-fringe has assumed a symmetrical
distribution of the pits of the fringe about the sagittal line — an assumption that has never
been put to any real test. Another possible weakness of the traditional ‘half-fringe
formula’ for describing trinucleid fringes is that it has never made any allowance for the
possibility that the pit distribution may be dependent on the size of the individual.
Although ontogenetic studies (Whittington 1941, pp. 510-1 1 ; 1959, pp. 443 ff.) show that
the fringe apparently assumes the essential adult characteristics early in the meraspid
stage of development, this does not preclude the possibility that there may be some
change in the pit distribution with increasing size.

A sample of some three hundred and fifty internal moulds of cephala of Trinucleus
fimbriatus Murchison 1839 from the black shales of basal Caradoc ( N . gracilis) age
exposed in the middle quarry, Llanfawr, Llandrindod Wells, Radnorshire was collected
for this study. This sample consisted of slightly flattened, generally well-preserved,
though incomplete remains. Despite the fragmentary nature of many specimens, samples
of about 30 were generally obtainable for any particular aspect of the pit distribution.
Although these samples were not as large as one could have hoped for, they were, it is
believed, sufficient to give adequate data of the fringe characteristics. Apart from the
obvious criterion of availability, Trinucleus fimbriatus was selected on account of its pit
distribution being relatively simple with well-developed radial and concentric elements
(see text-fig. 1).

HUGHES: ANALYSIS AND PRESENTATION OF TRINUCLEID FRINGE

3

Terminology. The terminology used throughout this study is that in standard use for trinucleids with
the exception that Bancroft’s term ‘concentric row’ is replaced by the term ‘arc’. This avoids the
possibility of confusion which has in the past occurred through some authors abbreviating one or
both Bancroft’s terms ‘concentric row’ and ‘radial row’ to ‘row’. It has been found that the standard
convention of numbering radial rows and arcs is both useful and generally satisfactory (except where
there is a complete lack of radial and concentric arrangement) in defining the various elements of the
pit distribution, although as is shown below the continued use of the ‘half-fringe formula’ should not
be encouraged. Throughout this study, symmetry is only considered with respect to the number of
pits, not their size or exact relative positioning.

text-fig. 1 . Diagram of Trinucleus fimbriatus Murchison showing the distribution of pits on the fringe
and the terminology used. The diagram shows radial row 0 and slight asymmetry developed.

STATISTICAL INVESTIGATION

Because of the nature of much trinucleid material it is highly desirable that species
should be definable without the necessity of recourse to details of the pit distribution of
the full fringe. However, this may only be done if the fringe is symmetrical, or if it is not,
any asymmetries must be small enough so as to have no significance. Further, any errors
in selecting the mid-fine of the fringe must not be significant either. Preliminary observa-
tions showed that slight asymmetry of the fringe was common and data were collected
to assess the magnitude and characteristics of the asymmetries. In the collection of
half-fringe data from material in which the complete fringe is preserved some care must
be taken to avoid biasing the data. Such bias may be caused by the systematic
misidentification of the mid-line or a personal tendency to select half-fringes showing
some atypical feature. In the collection of data therefore one half-fringe only must be
included from any one individual and some system should be used for selecting the
half-fringe to be considered; in this study left and right half-fringes were selected
alternately.

It is seen from Table 1 that of any of the three elements considered, i.e. the Ex, Ix arcs
and the number of radial rows developed, only about one-third of the specimens show
symmetrical fringes. If however all three elements are considered simultaneously, then
the percentage of bilaterally symmetrical specimens falls to 10%. Thus, although due to
the non-perfect preservation it is difficult to consider all elements of the fringe at once,
it is clear that perfectly symmetrical fringes rarely, if ever, occur.

4

PALAEONTOLOGY, VOLUME 13

As mentioned above it is important to remember that some specimens may show
apparent symmetry, or asymmetry, due to the misidentification of the mid-line of the
fringe. Thus a specimen having 2 «+l pits (full-fringe) in a particular arc would appear
symmetrical (with regard to that particular arc) if the mid-line were taken along the
central radial row, but asymmetrical if taken along either of the adjacent ridges or rows.

table 1 . Data giving the number of complete specimens of Trinucleus fimbriatus Murchison
symmetrical and asymmetrical about the sagittal line with respect to the number of pits in
the E1 and f arcs and the number of radial rows developed.

E1

No. of symmetrical specimens 10

No. of asymmetrical specimens 21

% of symmetrical specimens 32

/x Radial rows
9 6

22 16

29 37

In order to reduce such misidentifications to a minimum the mid-line was taken as
passing through the mid-point between the anterior fossulae. Specimens in which this
differed markedly from the mid-line as estimated by eye on the glabella, were rejected
as being too deformed for symmetry studies, and also for the collection of any precise
half-fringe data. Even if small errors due to mid-line misidentification are occasionally
included they will, in most cases, be sufficiently rare so as not to have any significant
effect on the final outcome, as the two half-fringe pit counts commonly differed by more
than one.

In practice the only common case that had to be decided concerning the placing of the
mid-line was whether it lay along a radial row of pits (row 0) or along the ridge to one
side of that row (which would then be row 1). If there was any systematic error being
made in the positioning of the mid-line it could cause a correlation, either positive or
negative, between symmetry and the positioning of the mid-line along the row of pits,
row 0 or along the ridge on one side. The 2x2 contingency tables given in Table 2
show that no such correlation exists for the E1 and Iy arcs considered separately or com-
bined together. Insufficient data are available on the inner / arcs, but the same result is
anticipated if such data were available.

Thus it is established that some asymmetry (in the actual numbers and not exact
positioning or size of pits) is present in the vast majority of specimens and that this
asymmetry is not to be explained by the misidentification of the mid-line of the fringe.

Before considering how much effect these asymmetries may or may not have on the
use of half-fringe data it is convenient to investigate on full-fringe data whether there
is any correlation between the pit distribution and size of the individual. Since relatively
few data were available for arcs internal to /x, the £j and /x, arcs were again taken as
representative of the arc elements of the fringe. Data showing that no correlation with
size is present are given in Table 3.

Although relatively few data are available, observations indicate that the major factor
that varies in the inner arcs is the row in which the particular arc commences (that is
also true in Cryptolithus tessellatus (Whittington 1968, pp. 709-10) and in Bettonia
chamberlaini (Hughes in press). Observations on Trinucleus fimbriatus show that this
variation only affects the pit counts in the five antero-median rows, data for each half-
fringe being given in Table 4, which indicates that this variation is not correlated with the

HUGHES: ANALYSIS AND PRESENTATION OF TRINUCLEID FRINGE

5

size of specimen. Again in the case of these data small errors may occur due to the
misidentification of the mid-line, but since the variation between the rows is small,
the effect of any such errors will be insignificant. Any attempt to number the rows from
the position of radial breakdown near the genal angles would introduce far greater
uncertainties owing to the imprecise way the radial nature of the pits is lost.

table 2. 2x2 tables illustrating the lack of correlation in Trinucleus fimbriatus Murchison
between the symmetry of the fringe for the Ex ,IX and Ex + Ix arcs and the development of
radial row 0. The value of P gives the probability that inhomogeneities as great or greater
than those observed would occur by chance in a random sample drawn from a homogeneous
population. Conventionally a value of P < 0 05 is considered as ‘significant’, that is, there
is a better than 1 9 in 20 chance that the inhomogeneities observed are truly present in the
source population. In this and all other 2x 2 tables x2 has been calculated by the unadjusted
method (see Simpson, Roe, and Lewontin 1960, pp. 189, 322-3). The values of P obtained
here by this method never indicate a significant correlation. The adjusted method always errs
on the ‘safe side’ and would never give a significant value for P when the unadjusted method
did not. Thus although the samples are small it is considered unnecessary to calculate the
more refined adjusted values (in Table 7 cell values of zero are present and so exact prob-

Ei

ability tests

were applied).
Ix

Ex+l i

Radial row 0

present

absent

present absent

present absent

Symmetrical

4

6

4 5

3 5

Asymmetrical

11

P =

10

0-50

10 12
P ~ 100

11 12*
P = 0-70

* This figure includes one specimen with a pit of radial row 0 present in the Ex arc
but absent in the Ix arc.

table 3. 2x2 tables showing the lack of correlation in Trinucleus fimbriatus Murchison
between the number of pits developed in the Ex and Ix arcs and size as measured by the
maximum cephalic width (tr.), excluding the fringe. For explanation of P see Table 2.

size in mm. 9-13 14-19 size in mm. 9-13 14-19

38-42 Ex pits 13 10 38-42 Ix pits 9 14

43-47 Ex pits 5 2 43-47 Ix pits 3 3

P = 0-67 P = 0-68

Thus it is seen from Tables 3 and 4 that for the E1 and Ix arcs and for rows 1-5 of each
half-fringe there is no correlation between the number of pits developed and the size
of the individual. Although the sample considered only includes a few, probably fairly
advanced meraspides, this finding is in general agreement with what has been inferred
in the past from ontogenetic studies.

Now that the lack of size correlation has been demonstrated, the problem as to
whether the asymmetries in the pit distribution have any significant effect on the use of
half-fringe data may be examined. If, as might be expected, the irregularities causing
the asymmetries occur randomly on left and right halves of the fringe and are also
generally small compared to any inherent variability of the species, then, provided that
the data are taken from a random sample of half-fringes, the asymmetry should not
affect the final outcome. In order to check this, left and right half-fringe counts were made
for the Ex and Ix arcs and the data summarized in Table 5.

6

PALAEONTOLOGY, VOLUME 13

table 4.2x2 tables showing the lack of correlation between the number of pits occurring in
the radial rows 1-5 of each half-fringe and size in Trinucleus fimbriatus Murchison. Size in this
table is taken as the maximum width ( tr .) of the left or right gena. For explanation of P see

Table 2.

Row 1

Left half-fringe

Right half-fringe

Size in mm.

6-7 8-10

Size in mm.

6-7 8-10

5 pits

4 9

4-5 pits

4 14

6 pits

0 2

6 pits

0 4

P ~ 1-00

P ~ 0-56

Row 2

Left half-fringe

Right half-fringe

Size in mm.

6-7 8-10

Size in mm.

6-7 8-10

5 pits

5 8

2-5 pits

5 15

6 pits

1 5

6 pits

1 5

P ~ 0-60

P ~ 100

Row 3

Left half-fringe

Right half-fringe

Size in mm.

6-7 8-10

Size in mm.

5-7 8-11

4-5 pits

5 9

4-5 pits

3 13

6 pits

2 9

6 pits

4 12

P ~ 0-40

P ~ 1-00

Row 4

Left half-fringe

Right half-fringe

Size in mm.

6-7 8-11

Size in mm.

5-7 8-11

3-5 pits

1 7

3-5 pits

3 10

6 pits

6 11

6 pits

6 16

P ~ 0-46

P ~ 100

Row 5

Left half-fringe

Right half-fringe

Size in mm.

5-7 8-11

Size in mm.

5-7 8-11

3-5 pits

0 1

5 pits

1 2

6-7 pits

6 15

6-7 pits

6 20

P = 0-70 P=l-00

table 5. Data showing the lack of significant difference between the left
and right half-fringe pit counts for the Ex and Ix arcs of Trinucleus
fimbriatus Murchison. For explanation of P see Table 2.

Ei

h

mean var.

n

mean var.

n

Left half-fringe

20-70 1 89

55

20-62 1-64

54

Right half-fringe

20-81 1-23

62

20-74 1-35

62

P > 0-9

P > 0-9

In this and subsequent half-fringe counts, row 0 when present, was taken as having
half a pit in each half-fringe. From the data of this table it is seen that for these two arcs
there are no significant differences between the two half-fringes. Table 6 gives data

HUGHES: ANALYSIS AND PRESENTATION OF TRINUCLEID FRINGE 7

comparing the number of pits in the radial rows 1-5, for both half-fringes and again it
is seen that there are no significant differences between the two.

table 6. Modes and ranges for the number of pits developed in radial rows
1-5 of both half-fringes of Trinucleus fimbriatus Murchison.

Row 1

mode

range

n

Left half-fringe

5

5-6

15

Right half-fringe

5

4-6

22

Row 2

Row 3

mode

range

n

mode

range

n

Left half-fringe

5

5-6

18

5

4-6

25

Right half-fringe

5

2-6

26

6

4-6

32

Row 4

Row 5

mode

range

n

mode

range

n

Left half-fringe

6

3-6

25

6

3-7

22

Right half-fringe

6

3-6

35

6

5-7

29

Table 7, however, shows that the number of radial rows developed is significantly
correlated to the number of pits present in the E1 arc. That is, a specimen having a high
E1 pit count does not have all the extra pits accommodated posterolaterally to enlarge
the genal flange where the pit distribution does not show radial arrangement. This
correlation indicates that since the Ex pit counts are not dependent on size, nor do the
counts for the two half-fringes show any significant differences, then the same will hold
true for the number of radial rows developed and formal tests need not be made.

Thus it has been shown in Trinucleus fimbriatus that for the Ex and Ix arcs, the numbers
of pits in rows 1-5 and the total number of radial rows developed, the half-fringe may be
taken as representative of the entire fringe, and it seems reasonable to assume that this

table 7. 2 x 2 tables showing the significant correlation between the number
of pits developed in the Ex arc in each half-fringe and the number of radial
rows present. Since cell values of zero are present exact probability tests
were used in place of y2 tests.

Left half-fringe

Number of Ex pits 18-20 21-24

12-17 rows 19 0

18-20 rows 0 12

P ~ 0

Right half-fringe
Number of Ex pits 18-20

15-17 rows 17

18-20 rows 0

P ~ 0

21-23

12

11

PALAEONTOLOGY, VOLUME 13

should also be true for the other inner arcs and the more laterally placed radial rows
(the few data that are available do in fact support this). This is supported by other studies
on trinucleids, including Bettonia and Cryptolithus (Hughes in press), and it seems likely
that these general results hold true throughout the Trinucleidae. Although much of this
other work on trinucleid fringes has suffered from a similar paucity of data for the inner
regions of the fringe, some data on the appearance of the inner arcs (/3 and /4) in Crypto-
lithus tessellatus and Cryptolithus lorettensis have been presented by Whittington (1968,
text-figs. 3-5). Formal tests on his data show that there are no significant differences
between the two half-fringes.

Thus the continued use of the half-fringe in trinucleid studies appears to be justified,
provided the variation within a population and the asymmetry exhibited by some
individuals are borne in mind. Particular caution should be exercised in assessing the
significance of the pit distribution when only a few specimens are available, and no new
taxa should be erected on slight differences in the distribution of the pits in single
specimens or small groups of individuals as has on occasion been done in the past.

In order to facilitate comparisons, it is desirable to have some convention both as
to the fringe data selected and as to the manner of their presentation. For the identifica-
tion of individual pits it is proposed to retain Whittard’s notation, but the continued
use of the half-fringe formula in specific descriptions cannot be justified, since it cannot
express the variation encountered within a species in a manner which enables direct
objective comparisons with other samples or species. The data cited will vary in detail
from one species to another but they should always be as comprehensive as possible.
It is suggested that data for the various arcs and for those radial rows in which variation
occurs should always be given. Data for other elements such as the number of radial
rows present, distribution of adventitious pits, numbers of pits along the posterior
border of the fringe, etc., should be given where appropriate, together with suitable
summarizing statistics (see below) and, where useful, illustrated by means of graphical
aids such as simple graphs and histograms. In view of the fact that most samples are
such that the bulk of the data available are for half-fringes, it is proposed that in order
to facilitate comparisons, half-fringe data are given even in cases where the full-fringe data
are also available. This ensures that in all data the error sources are, as far as is possible,
the same and differing samples are comparable. Although in this study it has been shown
that the ‘operator variation’ due to the misidentification of the mid-line of the fringe
has no significant effect, this might not always be the case for all trinucleids, since its
magnitude depends on the state of preservation and form of the pit distribution medially
as well as the skill of the operator.

The type of summarizing statistics cited will vary depending on the element of the
fringe being considered. For elements such as the various arcs where the range in the
possible number of pits present is relatively large, continuous variable statistics may be
applied, and the mean and variance given. Comparisons between samples may then be
made by the use of the tf test. This test assumes that the distribution does not depart
significantly from normality; inspection of distributions obtained shows this condition
is satisfied. In elements such as the number of pits in a radial row, where the total number
and range is small, continuous variable statistics are not applicable and the mode and
range should be quoted. Comparisons between data may then be made with non-
parametric tests (see Siegel 1956). In some cases where relatively few data are available

HUGHES: ANALYSIS AND PRESENTATION OF TRINUCLEID FRINGE 9

summary statistics may be misleading and it would be more satisfactory to present the
raw data.

While the above proposals for the description and documentation of the trinucleid
fringe are more complex than the half-fringe formulae of Whittard, it is believed that
they give a sound basis for the description of any trinucleid fringe, for they are easily
adaptable to special features that may be present (e.g. the frontal adventitious pits of
Bettonia, the data for which may be given or suitable summarizing statistics presented)
and to the type and amount of material available. Furthermore it is thought that coupled
with some qualitative description and appropriate use of graphical aids a much more
comprehensive picture of the distribution and variation of the fringe pits in a population
is obtained than could be from the traditional half-fringe formulae.

Acknowledgements. The bulk of this work was undertaken at the Queen’s University of Belfast during
the tenure of a N.E.R.C. Research Studentship, to whom thanks are given for financial support. I am
most grateful to Professor A. Williams and Dr. A. D. Wright for their encouragement and help during
my studentship. I am also indebted to Professor H. B. Whittington for allowing me access to his raw
data on Cryptolithus and for much helpful discussion. Useful discussion on the statistical techniques
has been provided by Drs. D. B. Williams and J. L. Cutbill, to whom I render my thanks.

REFERENCES

Bancroft, b. b. 1929. Some new species of Cryptolithus (s.l.), from the Upper Ordovician. Mem.
Proc. Manchr. lit. phil. Soc. 73, 67-98, pi. 1, 2.

cave, r. 1957. Salterolithus caractaci (Murchison) from Caradoc Strata near Welshpool, Mont-
gomeryshire. Geol. Mag. 94, 281-90, pi. 10.

hughes, c. p. (in press). The Ordovician Trilobite Faunas of the Builth-Llandrindod Inlier, Central
Wales, Part II. Bull. Br. Mus. nat. Hist. {Geol.).

Murchison, r. i. 1839. The Silurian System founded on geological researches in the counties of Salop,
Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester
and Stafford; with descriptions of the coal-fields and overlying formations, xxxii+768 pp., 40 pis.
London.

siegel, s. 1956. Nonpar ametric statistics for the behavioral sciences, xvii+312 pp. McGraw-Hill,
New York.

Simpson, G. G., rof, A. and lewontin, R. c. 1960. Quantitative zoology. 440 pp. New York.
whittard, w. f. 1955. The Ordovician Trilobites of the Shelve Inlier, West Shropshire. Part 1.
Palaeontogr. Soc. ( Monogr .), 1-40, pi. 1-4.

Whittington, h. b. 1941. Silicified Trenton Trilobites. J. Paleont. 15, 492-522, pi. 72-5.

1959. Silicified Middle Ordovician Trilobites: Remopleuridae, Trinucleidae, Raphiophoridae,

Endymionidae. Bull. Mus. comp. Zool. 121, 371-496, pi. 1-36.

• 1966. The Ordovician Trilobites of the Bala area, Merioneth. Part III. Palaeontogr. Soc. {Monogr.),

63-92, pi. 19-28.

• 1968. Cryptolithus (Trilobita): specific characters and occurrence in the Ordovician of eastern

North America. J. Paleont. 42, 702-14, pi. 87-9.

williams, A. 1948. The Lower Ordovician Cryptolithids of the Llandeilo District. Geol. Mag. 85,
65-88, pi. 6.

C. P. HUGHES

Department of Geology
Sedgwick Museum

Final typescript received 9 June 1969 Cambridge

PALAEOSMUNDA , A NEW GENUS OF
SIPHONOSTELIC OSMUNDACEOUS TRUNKS
FROM THE UPPER PERMIAN OF QUEENSLAND

by R. E. GOULD

Abstract. Petrified osmundaceous trunks from the Upper Permian coal measures of the Bowen Basin, Queens-
land, are assigned to a new genus, Palaeosmunda, which possesses an ectophloic, sometimes almost simple but
usually dictyoxylic, siphonostele with parenchymatous pith ; the stems bear stipulate petiole bases which contain
sclerotic rings that are rhomboidal in transverse section, upwards becoming laterally extended into flanges.
These are the first Permian Osmundaceae definitely known to exhibit a distinct pith and leaf gaps. A table of
morphological comparisons of all known Permian osmundaceous axes is presented. Discovery of Palaeosmunda
indicates that the family had a greater structural diversity and a wider geographic distribution in the Upper
Permian than was previously realized; and hence the Osmundaceae probably developed before the Permian.
Two species, P. williamsii (type species) and P. playfordii, are described in detail; the inner cortex, and sometimes
the stipules of the petiole bases of P. williamsii contain strands of sclerenchyma, while stipules and inner cortex
of the petiole bases of P. playfordii consist only of parenchyma. Evidence from association indicates that the
trunks probably bore fronds of the types referred to Sphenopteris lobifolia Morris 1845, S. polymorpha Feist-
mantel 1876, and Cladophlebis roylei Arber 1901.

Trunks and rhizomes characteristic of the Osmundaceae are apparently well suited to
preservation as fossils and the geological history of the family, based on petrified stems,
extends from Upper Permian to Recent (Andrews 1961, Miller 1967). Prior to the present
work, all known specimens of Permian osmundaceous stems came from the Soviet
Union ; where the stele is preserved, these contain a protostele or at least an ectophloic
siphonostele without well-developed leaf gaps.

Osmundaceous trunks, petrified with silica, calcite, and ferruginous material, occur
at many localities in the Upper Permian coal measures of the Bowen Basin, Queensland
(text-fig. 1). These are described as two species of a new genus, Palaeosmunda gen. nov.,
in which the stele is usually an ectophloic dictyoxylic siphonostele, but can appear
almost simply siphonostelic; the petiole bases are very similar to those of other stipulate
Permian osmundaceous stem genera. The new genus is unusual in that it is the first
Permian member of the family definitely known to exhibit a distinct pith and leaf gaps.

The specimens on which the study is based were collected by Dr. J. Armstrong, Mr.
R. Lees, Dr. B. Runnegar, Dr. F. W. Whitehouse, Mr. J. H. Williams, and the author.
Mr. W. A. Hansen and the management and staff of Utah Development Company
provided considerable assistance in the location and collection of specimens from
Utah’s Blackwater coal-mining lease. One specimen, collected in June 1956, was already
held in the collections of the Department of Geology and Mineralogy, University of
Queensland. All specimens are housed in the Department and catalogue numbers are
prefixed UQ.

In his study of the morphology of the living Osmundaceae, Hewitson (1962, p. 80)
used the term ‘bundle’ when describing the stem xylem in transverse section; he con-
sidered two (or more) xylem strands connected by even one tracheid as a single bundle.
This terminology avoids any confusion when counting the xylem strands, and is very

[Palaeontology, Vol. 13, Part 1, 1970, pp. 10-28, pis. 1-8.]

GOULD: PALAEOSMUNDA, A NEW GENUS 11

text-fig. 1 . Locality map.

12

PALAEONTOLOGY, VOLUME 13

useful in describing the stems of the family where the dictyoxylic stele is well developed.
However, where the number of gaps in the xylem ring is small, the number of ‘bundles’
does not give a complete indication of the structure of the ring. Instead, in the following
descriptions, the number of gaps appearing in a transverse section of the xylem cylinder
is given. This is equal to the number of bundles in the sense of Hewitson, provided that
there are two or more gaps; no gap, or one, results in one ‘bundle’. The term ‘radial
strand’ is used in this paper to designate any group of stelar xylem tracheids with a
prominent radial dimension when seen in transverse section, regardless of whether the
group is connected to adjacent strands or not.

Previous literature. In the second and third parts of their classic memoir on the fossil
Osmundaceae, Kidston and Gwynne- Vaughan (1908, 1909) published the first detailed
anatomical accounts of Upper Permian osmundaceous stems. They described five
species from the Upper Permian of the U.S.S.R., Zalesskya gracilis (Eichwald) Kidston
and Gwynne- Vaughan 1908, Z. diploxylon Kidston and Gwynne- Vaughan 1908,
Thamnopteris schlechtendalii (Eichwald) Brongniart 1849, Bathypteris rhomboidea
(Kutorga) Eichwald 1860, and Anomorrhoea fischeri Eichwald 1860. The steles of B.
rhomboidea and A. fischeri were not present in their specimens and that of B. rhomboidea
was described later by Zalessky (1924). Seward (1910) figured some of Kidston and
Gwynne-Vaughan’s slides and one of these, his frontispiece of T. schlechtendalii, had
not been figured previously.

In a series of papers, Zalessky (1924, 1927, 1931a, b, 1935) described and figured
further examples from the Upper Permian of the U.S.S.R. ; these comprise B. rhom-
boidea, T. kidstoni Zalessky 1924, T. gwynne-vaughani Zalessky 1924, Z. uralica Zalessky
1924, A. fischeri, T. schlechtendalii, Z. gracilis, Z. diploxylon, T. kazanensis Zalessky
1927, Z. fistulosa (Eichwald) Zalessky 1927, P etcher opt eris splendida Zalessky 1931a,
Chasmatopteris principalis Zalessky 19316, and Iegosigopteris javorskii Zalessky 1935.
Thamnopteris kazanensis was not formally described but a transverse section and some
details were figured with explanation (Zalessky 1927, pp. 26, 44, pi. 24, figs. 1-4); the
specimen is poorly preserved. Knowledge of Z. fistulosa is limited to a photograph of
its external surface (Zalessky 1927, pp. 31, 48, pi. 32, fig. 3).

Posthumus (1931) compiled synonymy lists for the genera and species of Permian and
other osmundaceous stems that had been described prior to 1928.

STRATIGRAPHY

All specimens of Palaeosmunda were collected from the Bowen Basin in freshwater
sediments which have been referred to as the Upper Bowen Coal Measures (Smith 1958,
Hill and Denmead 1960). Devine and Power (1967) have assigned these sediments in
the central western Bowen Basin, including the Blackwater district, to the Bandanna
Formation (Power 1967 usage, formerly Upper Bandanna Formation of Patterson in
Webb 1956, p. 2330). The localities for the osmundaceous fossils (text-fig. 1) are all
within the Blackwater Group (Malone 1966) as shown on the geological map of the
basin compiled by Malone, Olgers, Mollan, and Jensen (1967); in the Blackwater
district the fossil trunks occur in the upper two units of the group, the Burngrove
Formation and the Rangal Coal Measures. The Blackwater Group and Bandanna
Formation are the same lithological unit in the Blackwater-Springsure area (Power 1967,

GOULD: PALAEOSMUNDA, A NEW GENUS

13

Devine and Power 1967). The age of the Upper Bowen Coal Measures, Bandanna Forma-
tion, and Blackwater Group is generally considered to be Upper Permian (e.g. Runne-
gar 1968). Webb and McDougall (1967, pp. 483-4) reported an isotopic age of 240 m.y.
for a basal part of the Blackwater Group. Ammonoids from horizons below the coal
measures in the northern part of the basin are considered to be of Artinskian (Akta-
stinian-Baigendzhinian) age (Armstrong, Dear, and Runnegar 1967), while microfloras
from the Rewan Formation, which overlies the coal measures, are probably in part of
Scythian (Otoceratan) age (Evans 1966, p. 59).

SYSTEMATIC PALAEOBOTANY

Division pterophyta
Order filicales

Family osmundaceae
Genus palaeosmunda gen. nov.

Type species. Palaeosmunda williamsii sp. nov.

Diagnosis. Arborescent osmundaceous trunks, each with a stem surrounded by a mantle
of leaf bases and adventitious roots; branching of stem dichotomous. Stele an ecto-
phloic, generally dictyoxylic, siphonostele, sometimes almost simply siphonostelic; pith
parenchymatous; xylem ring with 0-13 gaps, consisting of 14-28 more or less contiguous
radial strands, 9-19 tracheids thick; development of leaf gaps immediate, delayed, or
incomplete; gaps very short to long; phloem, pericycle, and endodermis external only.
Cortex differentiated into inner parenchymatous zone and outer sclerotic fibrous layer,
the latter with short, wide, sclerenchyma cells lining leaf traces and inner cortex ; inner
cortex about as wide as outer cortex; leaf traces arise at 10-35° to stele, initially with
1 or 2 endarch protoxylem groups; 12-43 traces in a transverse section of cortex.
Petiole bases stipulate, containing an adaxially curved, C-shaped vascular strand, inner
cortex, and sclerotic ring; sclerotic rings somewhat rhomboidal in cross-section, up-
wards becoming laterally extended into flanges which partially or completely replace
the stipules ; rings with gradual increase of fibre diameter towards inner cortex of petiole
base, otherwise homogeneous; lateral extremities of ring usually thinner than abaxial
and adaxial portions. Roots with diarch xylem strand, arising in pairs from each depart-
ing leaf trace usually before it enters inner cortex, or rarely singly, directly from stele ;
roots often branched and forming dense mat outside mantle.

Discussion. Palaeosmunda differs from the Permian osmundaceous stem genera Bathy-
pteris Eichwald 1860, Chasmatopteris Zalessky 19316, Iegosigopteris Zalessky 1935,
Petcheropteris Zalessky 1931a, Thamnopteris Brongniart 1849, and Zalessky a Kidston
and Gwynne- Vaughan 1908, in that the stele is an ectophloic, usually dictyoxylic,
siphonostele with homogeneous metaxylem and a parenchymatous pith ; the leaf traces
in Palaeosmunda initially have one or two endarch protoxylem groups whereas the leaf
traces of these other genera are initially mesarch. Palaeosmunda lacks both the wide
cortex of Zalesskya and the spinose petiole bases of Bathypteris. There is insufficient
information available on Anomorrhoea Eichwald 1860, for any useful generic distinction

14 PALAEONTOLOGY, VOLUME 13

to be made. A table of comparisons of the species of Upper Permian osmundaceous
stems is given in folder.

Osmundacaulis Miller 1967 (an organ genus based on ‘ Osmundites ’ skidegatensis Pen-
hallow 1902), which occurs in Mesozoic and Tertiary strata, would include stems similar
to those of the new genus, but the petiole bases of Palaeosmunda are quite different.
Besides being of specific importance, the arrangement of sclerenchyma within the
petiole base in the Osmundaceae, as well as the anatomy of the stele, is of generic and
subgeneric significance (Kidston and Gwynne- Vaughan 1907, Hewitson 1962, Miller
1967). The leaf bases of Palaeosmunda can be more closely compared with those of
Anomorrhoea, Chasmatopteris, Iegosigopteris, Petcheropteris, and Thamnopteris than
with those of Osmundacaulis. The generally rhomboidal to laterally extended shape of
the sclerotic ring in transverse section is exhibited by all the Permian genera except
Zalesskya, in which the leaf bases are unknown. In contrast, the sclerotic rings of
Osmundacaulis are generally rounded ; the leaf traces in the outer cortex of the Jurassic
O. gibbiana (Kidston and Gwynne- Vaughan) Miller 1967, are, however, rhomboidal in
transverse section (Kidston and Gwynne- Vaughan 1907). The initial rhomboidal shape,
small stipules, and upward lateral extension of the sclerotic ring into flanges which
replace the stipules are well developed in Palaeosmunda ; the shape is not solely due to
the close arrangement of the bases around the stem, as they retain and even increase
the laterally flanged shape in the outer part of the mantle where they are free of any
restriction. The gradual increase in diameter of the fibres of the sclerotic ring towards
the inner cortex of the petiole base is also exhibited by T. schlechtendalii, B. rhomboidea,
and possibly by A. fischeri and I. javorskii (see Kidston and Gwynne- Vaughan 1909,
pi. 5, fig. 36; pi. 7, fig. 48; pi. 8, fig. 63; Zalessky 1935, pi. 2, fig. 7), as well as some post-
Palaeozoic species of Osmundaceae. At least I. javorskii and P. splendida, and possibly
also A. fischeri, C. principalis, and T. schlechtendalii (see Zalessky 1927, pi. 23, fig. 1),
show relatively thin lateral extremities of the sclerotic ring as in Palaeosmunda.

The development of the ectophloic dictyoxylic siphonostele in Osmundaceae by
Upper Permian is somewhat earlier than had been previously thought (e.g. Hewitson
1962, p. 84), but is not altogether surprising. Leaf gaps are partially formed in the Upper
Permian C. principalis, and T. kidstoni, also of Upper Permian age, contains some paren-
chyma cells in the inner xylem. Triassic representatives of osmundaceous stems include
Osmundacaulis herbstii (Archangelsky and de la Sota) Miller 1967, ‘ Osmundites ’ tuhaj-
kuensis Prynada (Orlov 1963, pi. 29, fig. 10), and probably ‘ Osmundites ’ winterpockensis
Bock 1960; all of these are of Upper Triassic age and O. herbstii, and probably ‘O.’
tuhajkuensis, exhibit dictyoxylic siphonosteles. The shape of the transverse section of the
sclerotic ring in the leaf bases of ‘O.’ tuhajkuensis is somewhat intermediate between
those of the Permian examples and Osmundacaulis', the two masses of sclerenchyma in
each arm of the C-shaped petiolar strand of ‘O.’ tuhajkuensis has, however, only been
found in Osmundacaulis and Osmunda. ‘ Osmundites ’ winterpockensis is based on a sand-
stone cast with no internal structure preserved (C. N. Miller, pers. comm. 1969). Other
Triassic fossil stems referred to the Osmundaceae, and used as examples to explain
the evolution of the dictyoxylic siphonostele from the protostele (e.g. Daugherty 1960,
Emberger 1962, Arnold 1964, Surange 1966), actually belong to other groups. These
include Chinlea campii Daugherty 1941, and Osmundites walkeri Daugherty 1941, which
are synonymous and belong to the Lepidophyta (Miller 1968), and the ectophloic

ANOMORRHOEA

BATHVPTERIS

CHASMATOPTERIS

IEG0SIG0PTERIS

PALAE0SMUNDA

PALAE0SMUNDA

PETCHEROPTERIS

THAMNOPTERIS

THAMNOPTERIS

THAMNOPTERIS

THAMNOPTERIS

ZALESSKYA

ZALESSKYA

ZALESSKYA

FISCHERI

RH0MB0IDEA

PRINCIPALIS

JAVORSKI 1

WILLIAMSI 1

PLAYF0RDII

SPLENDIDA

SCHLECHTENDALI 1

GWYNNE-VAUGHANI

KAZANENSIS

KIDST0NI

GRACILIS

DIPL0XYL0N

URALICA

TRANSVERSE SECTION
OF STELE

?

RECONSTRUCTION

%

0 * a

' ® @

e

7 ®

-C2)

0 / C?)

0

% 03 ^

. <a»

^ <Sj>

PA'RT

RECONSTRUCTION

©

NUMBER & POSITION OF PROTOXYLEM
GROUPS IN LEAF TRACE AS IT
LEAVES STELE

?

1 ENDARCH IN
INNER CORTEX

1 ADAXIALLY
MESARCH

1 MESARCH

1-2 ENDARCH

1 ENDARCH

1 MESARCH

1(2) MESARCH

1 MESARCH

?1 MESARCH

1 MESARCH

1 MESARCH

PROBABLY 1
MESARCH

1 MESARCH

NUMBER & POSITION OF PROTOXYLEM
GROUPS IN LEAF TRACE AS IT
ENTERS OUTER CORTEX OF STEM

1 ENDARCH

?

4 ENDARCH

2 ENDARCH

(1)2-4 ENDARCH

(1)2 ENDARCH

SEVERAL (>1-2)
ENDARCH

4-5 ENDARCH

2-3 ENDARCH

AT LEAST 2
ENDARCH

4-5 ENDARCH

2-3 ENDARCH

SEVERAL

ENDARCH

2-3 ENDARCH

NUMBER OF PROTOXYLEM GROUPS IN
LEAF TRACE AS IT ENTERS BASE
OF PETIOLE

?(> 2)

?

10-12 +

6-10 +

4-12

4-10

? MANY

10-12 +

?5-9

?

>8

?

?

?(>«)

ROOTS:— XYLEM TRACE:

ORIGIN:

DIARCH

?

DIARCH & TRIARCH

PROBABLY FROM STELE

DIARCH

FROM STELE

D! ARC H ?J*ERLCYH

FROM STELE OR DE-
PARTING LEAF TRACES

DIARCH

MAINLY FROM DEPART-
ING LEAF TRACES
ALSO FROM STELE

m a or h Rarely

UIAKCH T r | ARC H

MAINLY FROM DEPART-
ING LEAF TRACES
ALSO FROM STELE

DIARCH

FROM STELE

DIARCH

FROM STELE OR LEAF
TRACES

DIARCH

FROM LEAF TRACES

DIARCH

?

DIARCH

FROM LEAF TRACES

DIARCH

FROM STELE BELOW
DEPARTING LEAF TRACES

DIARCH

FROM STELE BELOW
DEPARTING LEAF TRACES

DIARCH

FROM STELE

NUMBER OF LEAF TRACES IN A
TRANSVERSE SECTION OF INNER
CORTEX OF STEM

?

?

?1 4-16

20-26

5-25

6-21

?

20-24

40-44

MANY

23-25

140-160

60-65+

100 +

NUMBER OF LEAF TRACES IN A
TRANSVERSE SECTION OF OUTER
CORTEX OF STEM

?20-24

?

?1 0—12

29-34

7-26

9-19

?

16-20

?20 -30

?

?5-6

?(7-8+)

?

? ( 1 2 — 1 6 +)

TRANSVERSE SECTION
OF PETIOLE BASE

♦

O

t

<#>

?

NO SCLERENCHYMA
IN STIPULES

?

?

?

PETIOLE BASES IN MANTLE:

CLOSELY ADPRESSED

LOOSELY ADPRESSED,
BUT NOT OPEN

CLOSELY ADPRESSED

CLOSELY ADPRESSED

CLOSELY ADPRESSED
NEAR STEM; CAN BE
OPEN FURTHER OUT

CLOSELY ADPRESSED
NEAR STEM, USUALLY
OPEN FURTHER OUT

CLOSELY ADPRESSED
NEAR STEM, OPEN
FURTHER OUT

CLOSELY ADPRESSED

CLOSELY ADPRESSED
NEAR STEM, OPEN
FURTHER OUT

CLOSELY ADPRESSED

? CLOSELY ADPRESSED
NEAR STEM

?

?

?

REMARKS

POSSIBLY REFERABLE
TO THAMNOPTERIS

PROBABLY REFERABLE
TO THAMNOPTERIS

PROBABLY REFERABLE
TO THAMNOPTERIS

PROBABLY REFERABLE
TO THAMNOPTERIS

CORTEX

COMPARATIVELY

CLOSELY COMPARABLE
TO Z. GRACILIS

WIDE

SOURCES OF DATA

KIDSTON & G WYNNE -
VAUGHAN 1909
ZALESSKY 1927

KIDSTON & GWYNNE-
VAUGHAN 1909
ZALESSKY 1924, 1927

ZALESSKY 1931b

ZALESSKY 1935

THIS PAPER

THIS PAPER

ZALESSKY 1931a

KIDSTON & GWYNNE-
VAUGHAN 1909
SEWARD 1910
ZALESSKY 1927

ZALESSKY 1924, 1927

ZALESSKY 1927

ZALESSKY 1924, 1927

KIDSTON & GWYNNE-
VAUGHAN 1908
2ALESSKY 1924, 1927

KIDSTON & GWYNNE -
VAUGHAN 1908
ZALESSKY 1927

ZALESSKY 1924, 1927

text-fig. 2. Morphological comparisons of Upper Permian osmundaceous stems; Zalesskya fistulosa { Eichwald) Zalessky, 1927, is omitted as no details are known. Transverse sections of stele c. x 2; inner xylem open stipple, cells not preserved in central portions containing question marks;
outer xylem close stipple; details of Thamnopteris kazanensis Zalessky, 1927, unknown. Transverse sections of leaf bases ca. x 1-55; sclerenchyma black; stippled area in inner cortex of Anomorrhoea fischeri Eichwald, i860, may be sclerenchymatous ; outlines show alternate shapes of sclerotic rings.

15

GOULD: PALAEOSMUNDA, A NEW GENUS

siphonostelic Itopsidema vancleavii Daugherty 1960, which is also probably not a
member of the Osmundaceae (Miller 1969). On the other hand, the plants with
protosteles and those with ectophloic dictyoxylic siphonosteles may have already been
separate groups by the Upper Permian.

text-fig. 3. Palaeosmunda williamsii gen. et sp. nov. Transverse sections of stele and inner cortex,
c. x 3-5 ; where discernible, protoxylem groups of xylem ring and leaf traces represented as black dots;
endodermis by a dotted line ; and generalized position of sclerenchyma strands in inner cortex by close
stipple. A, UQF53542; b, UQF50620; c, d, UQF21571 (holotype).

The oldest known petrified axes referable to the Osmundaceae all occur in Upper
Permian strata and these are compared in text-fig. 2. In view of the structural diversity
and wide geographic distribution exhibited by these axes, and the relatively stable
development of the family from Mesozoic to Recent, it is reasonable to assume that the
Osmundaceae originated well before the Upper Permian, probably even before the
Permian.

Absence of cataphylls in all specimens of Palaeosmunda from the Bowen Basin
probably indicates that the climate in which the plant grew lacked severe winters
(Steeves and Wetmore 1953; Miller 1967, p. 144). It is interesting to note that cataphylls
have not been found in any of the Permian osmundaceous axes.

Palaeosmunda williamsii sp. nov.

Plate 1, figs. 1, 2; Plate 2, figs. 1-7; Plate 3, figs. 1-8; Plate 4, figs. 1-10; text-figs. 2, 3
Holotype. UQF21571; figured in Plate 1, figs. 1, 2; Plate 2, figs. 1, 2, 6, 7.

16

PALAEONTOLOGY, VOLUME 13

Type locality. Beside the Collinsville-Mt. Coolon Road in Portion 4, Parish of Corrievahn, central
Queensland (shown on text-fig. 1 as Corrievahn); Blackwater Group (formerly Upper Bowen Coal
Measures).

Derivation of name. The species is named in honour of Mr. J. H. Williams (Mackay) who kindly
assisted in the collection of specimens from the northern part of the Bowen Basin.

Diagnosis. Palaeosmunda trunks up to 22 cm. in diameter; stems 1-3-6 cm. wide. Stele
an ectophloic dictyoxylic siphonostele, sometimes appearing simply siphonostelic,
3-5-8 mm. in diameter; pith diameter 1-4 mm.; xylem ring 0-7-2-2 mm. wide, with 0-9
gaps, composed of 15-28 radial strands, 9-17 tracheids thick; metaxylem tracheids
35-260 p (usually 50-150 p) in diameter, with regular scalariform pitting in 1-5 vertical
series on each wall. Inner cortex parenchymatous, sometimes with fibrous sclerenchyma
strands surrounding leaf traces; inner cortex 0-8-5-5 mm. wide, including 5-25 leaf
traces in a given transverse section; fibrous outer cortex 2-5-9 mm. wide, with 7-26 leaf
traces in a transverse section. Leaf traces arise with 1 or 2 endarch protoxylem groups
which usually bifurcate before they enter outer cortex; strands of sclerenchyma surround
leaf trace in outer cortex of stem, and vascular trace in inner cortex of petiole base.
Stipules parenchymatous, or with up to 30, generally small, scattered strands of scleren-
chyma fibres.

Description

General. There are 16 specimens, each consisting of a stem surrounded by a mantle
of adhering leaf bases and adventitious roots (e.g. PI. 1 , fig. 1 ; PI. 3, figs. 1, 7). The speci-
mens are up to 21 cm. long and 22 cm. in diameter, and both ends are broken across.
Some trunks are circular in cross-section, but others are oval, presumably due to com-
pression. Three specimens show dichotomy of the stem, but only one contains the actual
branching region. The stems, bounded by the sclerotic outer cortex, are 1-3-6 cm. in
diameter; the outline in transverse section is undulose due to the emerging petioles.

Stele. The pith is 1-4 mm. in diameter (PI. 2, figs. 4-7; PI. 3, figs. 4-6), and consists of
vertically elongated, rounded to polygonal, parenchyma cells, measuring 20—1 10 /x in
diameter and 40-300 p in length; the wall between two adjacent cells is 1-6 p thick. The
parenchyma cells have sometimes partially decayed and separated before preservation.

EXPLANATION OF PLATE 1

Figs. 1, 2. Palaeosmunda williamsii gen. et. sp. nov. 1, Transverse section of holotype, UQF21571,
from Corrievahn, x 2; section from midway along specimen (top of Plate 2, fig. 1); transmitted and
reflected light. 2, Details of stele, inner cortex, and part of outer cortex of fig. 1 , x 8 ; most of pith
and inner cortex not preserved; leaf traces depart from stele with 2 protoxylem groups; transmitted
light.

EXPLANATION OF PLATE 2

Figs. 1-7. Palaeosmunda williamsii gen. et. sp. nov. 1, 2, 6, 7, Holotype, UQF21571. 1, Longitudinal
section, x 1 ; lower half of specimen, details of pith not preserved. 2, Transverse section of petioles
showing stipules, x 5. 6, Transverse section from upper part of specimen, x 2. 7, Central portion
of fig. 6, x 6 ; pith partly displaced ; note endodermis of stem continuous with sclerotic cortex of
root trace at right centre. 3-5, UQF53542, from Homevale. 3, Transverse section, x 2. 4, Detail
of stele, x 8 ; leaf traces leave stele with 2 protoxylem groups. 5, Longitudinal section of pith and
xylem of stem, x 16. (1, 3, 6, 7, transmitted and reflected light; 2, 4, 5, transmitted light.)

Palaeontology, Vol. 13

PLATE 1

GOTJLD, Late Permian osmundaceous trunks

Palaeontology, Vol. 13

PLATE 2

GOULD, Late Permian osmundaceous trunks

GOULD: PALAEOSMUNDA, A NEW GENUS

17

In one specimen, a few short tracheids are present in the pith (PI. 4, figs. 1, 2), but
these occur where the stem is twisted and are associated with nearby metaxylem
strands (cf. Hewitson 1962, p. 81). No internal endodermis is present.

The xylem cylinder is generally similar to that in Osmunda and Osmundacaulis.
It is 07-2-2 mm. wide and in transverse section exhibits 0-9 gaps; i.e. in some specimens
the xylem is a continuous, but indented ring (PI. 1, fig. 2; text-fig. 3c, d), while in others
it is dissected (PI. 2, fig. 4; text-fig. 3a, b) and similar to those in most post-Palaeozoic
forms of the Osmundaceae. In transverse section the xylem cylinder has 9-24 external
lobes, while the cylinder itself consists of 15-28 radial strands, each 9-17 tracheids thick.
The protoxylem tracheids, initially mesarch in metaxylem strands below departing leaf
traces, are 6-40 fx in diameter, with a wall thickness of 3-14 [x between adjacent cells,
and exhibit one series of scalariform pits on each longitudinal wall. Metaxylem tracheids
are 35-260 ^ in diameter (commonly 50-150 fx), with a wall thickness of 6-23 /x between
two adjacent cells. The metaxylem tracheids show regular scalariform pitting in 1-5
vertical series on each wall (PI. 3, fig. 8); the transverse bars of thickening are Tl-4 /x
thick and 1-5-7 /x apart.

In most of the specimens, except for a dark line marking the position of the endo-
dermis, and strands of sclerenchyma, little cellular detail is preserved between the xylem
cylinder and the outer cortex of the stem (PI. 1, fig. 2; PI. 2, figs. 3, 4; PI. 3, fig. 2).
A parenchyma xylem sheath, 1-3 cells thick, may be present. Phloem is only preserved
in one specimen ; it probably formed a continuous layer around the xylem. Metaphloem
cells in the wedges between the xylem lobes have a diameter of 27-100 /x with a wall
thickness of 3-6 fx. Outside the phloem is a layer of flattened cells up to 7 cells thick,
which probably represents the protophloem and pericycle. The endodermis is marked
by a dark line or a stained zone, and an abrupt change from pericycle tissue to inner
cortex, but cellular detail is lacking. The endodermal diameter is 3-5-8 mm.

Cortex. The inner cortex is 0-8-5-5 mm. wide and consists of parenchyma with, in
some specimens, bundles of sclerenchyma fibres. The parenchyma is polygonal to
rounded in transverse section, and may be tangentially elongated, measuring 25-70 fx
X 10-60^; thickness of the wall between two adjacent cells is 0-7-4 /x , but may appear
up to 14 ix thick with deposits of organic and mineral matter. Where present, the bundles
of sclerenchyma fibres occur in an intermittent peripheral zone around the endodermis
below and adjacent to abaxial surfaces of the departing leaf traces (PI. 1, fig. 2; PI. 2,
fig. 7); the bundles usually surround the endodermis of the leaf trace as it leaves the
stele and they accompany it through the inner and outer cortex of the stem and into the
petiole bases. In other cases however, the sclerenchyma does not appear until further out
in the inner or outer cortex. In transverse section the bundles measure up to 540 /x
tangentially, and up to 210 /x radially. They are composed of sclerenchyma fibres which
have a diameter of 13-38 /x, a length of at least 850 /x, and a wall thickness between
adjacent cells of 6-18 fx. The primary and secondary walls are clearly shown and the
secondary wall may almost completely fill the cell. The inner cortex contains 5-24 leaf
traces in a given transverse section.

The dense outer cortex is 2-5-9 mm. wide and consists of sclerenchyma fibres
which are polygonal in cross section (PI. 4, figs. 6, 7). The majority of these fibres
have a diameter of 12-45 /x, sometimes up to 70 /X, and length of 270 /x to at least
1 1 00 /x ; the end walls are transverse, oblique, or tapering. The primary and secondary

C 7173

c

18

PALAEONTOLOGY, VOLUME 13

walls are clearly preserved and the secondary wall may consist of several layers. Total
thickness of wall between two adjacent fibres is 6-30 /j. ; intercellular spaces of up to 4 /l
are sometimes present at the angles. The longitudinal walls may be smooth or exhibit
simple, small (3-7 /jl ), round to oval, irregularly scattered pits. Large, irregularly defined
rectangular (3x7 /x-7x23 /u, 1-5-8 ^ apart) or annular pits may also be present, but
these appear to be formed by shrinkage of the original cell wall. Rare transverse septa-
tions may occur. Sometimes the lumen of a fibre is almost filled with secondary walk
A few layers of relatively larger and shorter, although otherwise similar, fibres occur
adjacent to the inner cortex of the stem and leaf traces (PI. 1, fig. 2), and also on the
outside of the stem in the depressions behind the departing petioles (PI. 4, fig. 8); these
cells usually have a diameter of 40-85 yu, and a length of 70-300 ^ . Part of the outer
cortex of one specimen appears inhomogeneous with rings of light-coloured (in thin
section) fibres surrounding the leaf traces, and darker, somewhat larger fibres in the
areas between the rings (PI. 3, fig. 1). The outer cortex contains 7-26 leaf traces in a
given transverse section. Total number of leaf traces in any one transverse section of the
whole cortex is 12-43.

Leaf traces. Traces are formed from the metaxylem strands of the stem in a manner
generally similar to that in the subgenera Osmunda and Osmundastrum of the genus
Osmunda (Hewitson 1962, Miller 1967). A protoxylem group develops approximately
in the centre of the metaxylem strand which gives rise to the leaf trace. Above this point
an island of parenchyma develops adaxially to the protoxylem group. This island
enlarges upwards and usually becomes connected by a narrow gap with the pith. Thus
the xylem strand assumes a U-shape with the narrow open end of the ‘U’ directed

EXPLANATION OF PLATE 3

Figs. 1-8. Palaeosmunda williamsii gen. et sp. nov. 1-3, UQF57604, from Byerwen. 1, Transverse
section, x 1. 2, Transverse section of stele; most of pith and inner cortex filled with silica; leaf
traces arise with 1 protoxylem group, x 6. 3, Transverse section of parts of petiole bases showing
irregular mass of sclerenchyma in sclerotic ring, and sclerenchyma strands in stipules, x 10-6.
4-6, UQF50624, from Blackwater district. 4, 5, Transverse sections of pith. 4, x42; 5, X67-5.
6, Longitudinal section of pith, x 67-5. 7, 8, UQF50620, from Blackwater district. 7, Transverse
section, x 1-5; numerous roots and petioles loosely adpressed in outer part of mantle. 8, Longi-
tudinal view of xylem tracheids of stem, x42. (1, transmitted and reflected light; 2-8, transmitted
light).

EXPLANATION OF PLATE 4

Figs. 1-10. Palaeosmunda williamsii gen. et. sp. nov. 1, 2, Longitudinal sections showing tracheids in
pith, UQF50620. 1, x42; 2, X 66. 3, Transverse section of roots, UQF53549, from Blackwater
Mine, x 10-6. 4, 5, Longitudinal sections of xylem of root. 4, UQF50624, x99; 5, UQF57604,
x 63. 6, 7, Transverse sections of sclerenchyma fibres of outer cortex. 6, UQF53552, from Black-
water Mine, x60, showing intercellular spaces; 7, UQF53549, X60. 8, Longitudinal section of
outer cortex and part of sclerotic ring of departing petiole, showing shorter fibres at outside of stem ;
longitudinal axis of section tilted to left; UQF53552, X 40. 9, Longitudinal section of sclerenchyma
strand in inner cortex of petiole, showing pitting, UQF50624, x 99. 10, Transverse section of part
of petiole base, UQF53541, from Homevale, x42; note increase in diameter of fibres of sclerotic
ring towards inner cortext of petiole.

Fig. 11. Palaeosmunda playfordii gen. et. sp. nov. Transverse surface of holotype, UQF53544, from
Blackwater Mine, x0-75; loosely adpressed petioles and numerous roots in outer part of mantle.
(1-10, transmitted light; 11, reflected light.)

Palaeontology, Vo I. 13

PLATE 3

GOULD, Late Permian osmundaceous trunks

Palaeontology, Vol. 13

PLATE 4

GOULD, Late Permian osmundaceous trunks

GOULD: PALAEOSMUNDA, A NEW GENUS

19

toward the pith, and the protoxylem group in the centre of the concave surface; the
protoxylem group may bifurcate at this stage. The curved part of the ‘U’ with the adaxial
protoxylem group (or groups) then breaks away to form the leaf trace. The leaf gap
in the stem xylem may be closed before the leaf trace breaks away, and hence the gap is
not evident in any one transverse section, the stem xylem being continuous within the
strand or through the departing leaf trace. In other cases the formation of the gap may
be delayed until after the leaf trace has entered the inner cortex; sometimes it appears
that no complete gap forms although the island of parenchyma is still well developed.
A pair of root traces usually arise with the departing leaf trace, one root trace arising
from each abaxial lateral angle of the ‘U’. However root traces may also be derived from
1 or 2 adjacent strands which partly coalesce with the original radial metaxylem strand.

The leaf traces become progressively larger and more C-shaped as they move out.
There are 1-2 adaxial protoxylem groups in the trace when it enters the inner cortex,
(1) 2-4 groups as it passes from the inner to the outer cortex, and 4-12 groups when it
enters the petiole base. The trace gains encircling layers of phloem, pericycle, endodermis,
inner cortex (sometimes including sclerenchyma strands), and outer cortex as it passes
through these zones of the stem; except for the sclerenchyma strands around the endo-
dermis, no gaps are left in the tissues concerned. Where sclerenchyma strands are present
in the stem, they surround the endodermis of the leaf trace as soon as it enters the inner
cortex (PI. 1, fig. 2); in other cases the sclerenchyma appears further out in the inner or
outer cortex, either initially located within the arms of the ‘C’ or surrounding the leaf
trace. The strands of sclerenchyma fibres are always present around the endodermis of
the leaf traces within the outer cortex of the stem.

Petioles. The petiole bases arise from the stem at angles of 10-35°; they are usually
tightly packed near to the stem, but may be closely or loosely adpressed further out in the
mantle (PI. 2, fig. 6; PI. 3, fig. 7). The bases consist of a C-shaped vascular strand sur-
rounded by the endodermis, the inner cortex including bundles of sclerenchyma fibres
just outside the endodermis, the sclerotic ring, and the stipules (PI. 2, fig. 2); apart from
the stipules, which arise with the petiole, these tissues are continuous with the corre-
sponding zones of the stem. The petiole bases enlarge upwards, ranging from a minimum
of 2-5 mm. in radial thickness by 4 mm. wide near the stem, up to 14 mm. thick by 32 mm.
wide at the periphery of the mantle of leaf bases, and the ends of the vascular strand
become more incurved.

Towards the periphery of the mantle the xylem of the petiolar strand becomes
narrower, being 3-4 tracheids thick radially near the stem and only 1-3 tracheids thick
further out; the metaxylem tracheids generally decrease in diameter from up to 100—
140 /x to 25-70 /x. In one specimen, secondary thickening similar to that of the scleren-
chyma fibres occurs in a few tracheids; these have a wall thickness of 13-28 ^ . Up to 44
protoxylem groups project on the adaxial sides of the xylem traces in the outermost
petioles. In two specimens it appears that there is an intermittent parenchyma sheath
around the xylem, consisting of polygonal cells 12-20 /j. in diameter. The xylem trace
is then completely surrounded by phloem, containing cells which are polygonal in trans-
verse section and 14—40 /x in diameter. The pericycle consists of 2 to 5 layers of polygonal
cells 17-30 ix in diameter. Large, apparently schizogenous, mucilage cavities with a
diameter of 95-140 /x sometimes occur in the adaxial pericycle region.

The endodermis is often well marked by a dark line or a colour change, but is rarely

20

PALAEONTOLOGY, VOLUME 13

preserved in detail; it is 1 or 2 cells thick, the cells measuring 14-45 /xX 12-30 /x in
transverse section, and showing distinct Casparian strips.

The parenchyma cells of the inner cortex of the petiole are polygonal in transverse
section with a diameter of 27-95 [x and a wall thickness of 0-8-5 [x. The strands of scleren-
chyma that surround the endodermis consist of fibres with a diameter of 13-55 fx,
a length of 130 /x to at least 1300 /x , and a wall thickness of 10-34 fx ; in some fibres, the
secondary wall completely fills the lumen. The end walls may be transverse, oblique, or
tapering. The longitudinal walls are usually pitted (pits 2-5-4 fx; PI. 4, fig. 9) similarly
to those of the outer cortex of the stem. Extending up the petiole, the groups at first
increase and irregularly coalesce, and then diminish in numbers and size. The con-
centration of strands varies from a complete spread almost filling the inner cortex, to
a single row just surrounding the endodermis. Sometimes 1-4 strands of fibres occur
discrete from the others in the lateral extremities of the inner cortex.

The sclerotic ring is usually rhomboidal in cross-section, upwards becoming tangen-
tially elongated; the lateral extremities extend well into the stipules and eventually
replace them (PI. 1, fig. 1 ; PI. 3, figs. 1, 7). Adjacent to the stem the size of the ring varies
from 3 x 2-5 mm. to 9 X 6 mm. with an average thickness of 0-3-0-6 mm. ; toward the
periphery of the mantle the rings are up to 3T5 X 14 mm. with a thickness of up to
0-9 mm. The lateral extremities of the rings are usually markedly thinner than the abaxial
and adaxial portions. The constituent fibres are similar to those forming the outer cortex
of the stem. The fibre diameter increases gradually toward the inner cortex of the petiole
base (PI. 4, fig. 10), although occasionally only a few layers lining the inside of the ring
are distinctly larger; the wall thickness (6-24 [x ) of all the cells is approximately the same
in any one ring. In one specimen, some sclerotic rings contain 1 or 2 masses of large, but
short, irregularly arranged, sclerenchyma cells; these are usually in the thin lateral
extremities of the ring and appear to have developed where the ring has been broken
(PI. 3, fig. 3).

The stipules consist of polygonal parenchyma cells 14-80 /x in transverse diameter with
walls 0-8-3 ix thick, although in many specimens little cellular detail is preserved (PI. 2,
fig. 2). Up to 30, generally small, strands of sclerenchyma develop in the stipular wings
of two specimens (PI. 3, fig. 3). These strands contain fibres with a diameter of 12-55 /x,
and a wall thickness between two adjacent cells of 6-28 /x. The secondary wall may com-
pletely fill the lumen. The stipular tissue extends well up the petiole base and at least to
the periphery of the closely packed mantle of leaf bases. However, the lateral extension
of the sclerotic ring replaces more of the stipules further up the petiole base, although
in some cases the stipules also increase in length; poor preservation and penetration
by adventitious roots prevents definite identification of the parenchymatous stipules
at this level.

Roots. The roots usually arise in pairs from the leaf trace before, as, or just after it
leaves the stem xylem but before it enters the inner cortex; in one specimen, however,
some root traces originate from leaf traces in the inner cortex. Roots occasionally arise
from stem xylem strands immediately above, below, or adjacent to departing leaf traces.
The xylem trace is diarch (PI. 1 , fig. 2; PI. 4, fig. 3) and it gains the tissues of the phloem,
pericycle, and endodermis as it passes through these zones of the stem. The xylem tra-
cheids are similar to those in the stem (PI. 4, figs. 4, 5). In the inner cortex the root trace
may have a narrow sclerenchyma sheath continuous with the endodermis of the stem,

21

GOULD: PALAEOSMUNDA, A NEW GENUS

but this is replaced by a sclerotic cortex as the trace enters the outer cortex of the stem
(PI. 2, fig. 7). A few layers of the cells of the inner cortex may accompany the root trace
into the outer cortex as there is a gap between the endodermis and the sclerenchyma,
but in several cases no inner cortical cells are present. Towards the outside of the mantle,
the walls of the cortical fibres nearest to the endodermis usually become progressively
thinner, thus giving the appearance of a parenchymatous inner cortex. The endodermis
often shows well-defined Casparian strips. The roots vary from less than 1 mm. to
2-5 mm. in diameter and in the majority of specimens, except for the region near the
stem, most are cut transversely by a transverse section of the trunk (PI. 3, fig. 7); this is
probably indicative of an arborescent habit (Miller, pers. comm. 1969). They are often
branched within the mantle and outside it, sometimes forming an external mat up to
3 cm. wide. The roots freely penetrate the cortex of the stem and the stipules, but not
the sclerotic rings or inner cortex of the petiole bases.

Branching. The branching of the stem does not show any abnormal characteristics.
However the single specimen containing the branching region is not well preserved.

Discussion. The species is characterized by the sclerotic strands surrounding the leaf
traces in the inner cortex of the petiole base. The stele (e.g. PI. 3, fig. 2; text-fig. 3) is
somewhat similar to that in the Jurassic Osmundacaulis dunlopi (Kidston and Gwynne-
Vaughan) Miller 1967 (see Kidston and Gwynne- Vaughan 1907; Marshall 1926;
Edwards 1933, 1934) in that leaf gaps may or may not be completely developed in the
xylem ring. Unlike some members of the Osmundaceae, the steles of P. williamsii which
show the continuous xylem ring are not just associated with branching of the stem (cf.
Hewitson 1962). Further variability of the stele is exhibited by the number of proto-
xylem groups in the developing leaf traces ; those which arise from the stele with 2
protoxylems are, like those containing only 1 protoxylem, derived from a single original
metaxylem strand of the stele and not from 2 adjacent crozier-shaped strands as is the
case in the subgenus Plenasium of the genus Osmunda (Hewitson 1962, Miller 1967).

Other occurrences. Bowen River crossing, near Gatton Vale Homestead (Blackwater
Group); Byerwen Station (Blackwater Group); south-western boundary of Homevale
Station (Blackwater Group) ; Kemmis Creek (Blackwater Group) ; and south of Utah
Development Company’s Blackwater Mine, Blackwater district (Rangal Coal Measures
of Blackwater Group; or Bandanna Formation). The localities are shown on text-fig. 1.

Palaeosmunda playfordii sp. nov.

Plate 4, fig. 1 1 ; Plate 5, figs. 1-5 ; Plate 6, figs. 1-10; Plate 7, figs. 1-9; Plate 8, figs. 1-7 ; text-figs. 2, 4

Holotype. UQF53544; figured in Plate 4, fig. 11; Plate 5, fig. 1; Plate 6, figs. 2-4, 9, 10; Plate 8,
figs. 6, 7.

Type locality. South of Utah Development Company’s Blackwater Mine, Portion 3, Parish of
Stewarton, near Blackwater, central Queensland ; Bandanna Formation, or Rangal Coal Measures of
Blackwater Group (formerly Upper Bowen Coal Measures). Locality shown as Blackwater Mine in
text-fig. 1.

Diagnosis. Palaeosmunda trunks up to 18 cm. in diameter; stems 18-37 mm. wide. Stele
an ectophloic dictyoxylic siphonostele, 3-5-1 1 mm. in diameter; pith diameter 2-6 mm. ;
xylem ring 1-2 mm. wide, with (70)3-13 gaps, consisting of 14-20, 27 radial strands.

22

PALAEONTOLOGY, VOLUME 13

9-19 tracheids thick; metaxylem tracheids 30-160 p in diameter, with regular scalari-
form pitting in 1-7 vertical series on each wall. Inner cortex parenchymatous, 1-6 mm.
wide, including 6-21 leaf traces in a given transverse section; fibrous outer cortex 1-10
mm. wide, containing 9-19 leaf traces in a transverse section. Leaf traces arise with one
adaxial protoxylem group which usually bifurcates in inner cortex of stem. Stipules and
inner cortex of petiole bases parenchymatous.

text-fig. 4. Palaeosmunda playfordii gen. et sp. nov. Transverse sections of stele and inner cortex,
c. x 3-5 ; protoxylem groups, where discernible, represented as black dots; endodermis by a dotted line.
A, UQF50622; b, UQF53566.

Description

General. This species is the most common in the material collected from the Black-
water district; more than 30 trunks, consisting of a central stem with a mantle of petiole
bases and adventitious roots (e.g. PI. 4, fig. 11; PI. 5, figs. 1, 3), were used for the
description. The specimens are up to 28 cm. long and 18 cm. in diameter with one or
both ends broken across. The stems may be dichotomously branched but, although

EXPLANATION OF PLATE 5

Figs. 1-5. Palaeosmunda playfordii gen. et sp. nov. 1, Transverse section of holotype, UQF53544,
x 1-5; pith and some of inner cortex not preserved. 2, Transverse section of UQF53553, from
Blackwater Mine, x2. 3-5, UQF53566, from Blackwater Mine. 3, Transverse section xl. 4,
Detail of stele and inner cortex, x 5. 5, Longitudinal section of pith and xylem of stem, x 24.
(1, transmitted and reflected light; 2-5, transmitted light.)

EXPLANATION OF PLATE 6

Figs. 1-10. Palaeosmunda playfordii gen. et sp. nov. 1, Transverse surface of axis above dichotomy
(actual branching region not present in specimen), UQF53560, from Blackwater Mine, x 1. 2-4, 9,
10, Holotype, UQF53544. 2, Transverse section of inner cortex, x 66. 3, Longitudinal section of
inner cortex, x 66. 4, Longitudinal section of outer cortex showing pitting, x 99. 9, Transverse
section of petiole base at point of departure from stem, x 16. 10, Detail of vascular trace in fig. 9,
X 66. 5, 6, Longitudinal sections of outer cortex. 5, UQF53566, x 44; 6, UQF53567, from Black-
water Mine, x 63. 7, 8, UQF50622, from Blackwater district. 7, Transverse section of leaf trace
at outside of inner cortex, x 16. 8, Transverse section of leaf trace in inner cortex, x 10-6. (1,
reflected light; 2-10, transmitted light.)

Palaeontology, Vol. 13

PLATE 5

GOULD, Late Permian osmundaceous trunks

Palaeontology, Vol. 13

PLATE 6

GOULD, Late Permian osmundaceous trunks

23

GOULD: PALAEOSMUNDA, A NEW GENUS

some specimens contain 2-4 axes in close proximity, the actual branching region is not
present (PI. 6, fig. 1).

Stele. The pith is 2-6 mm. wide and consists of longitudinally elongated, polygonal
parenchyma cells with a diameter of 20-83 /x, and a length of 68-300 /x (PI. 5, fig. 5);
wall thickness between two adjacent cells is 1 -5-3-5 /x, but may appear up to 10 /x
due to organic and mineral matter. There is a slight decrease in the transverse diameter
of the pith cells toward the xylem ring.

The xylem cylinder is 1-2 mm. wide and in transverse section exhibits 3-13 gaps
(text-fig. 4). It consists of 14-20 (one with 27) radial metaxylem strands, 9-19 tracheids
thick, and shows 10-16 external lobes. The protoxylem groups, which appear sub-
centrally in the metaxylem strands below the departure of leaf traces, consist of tracheids
with a diameter of 7-27 /x and a wall thickness of 4-13 /x. Metaxylem tracheids have a
diameter of 30-160 /x and a total wall thickness between two adjacent cells of 6-27 /j .
These tracheids have 1-7 vertical series of regular scalariform pits on each wall; the
bars of thickening are 1-3 /x thick and 2-5-8 /x apart. As in P. williamsii, the xylem is
dissected by gaps in some specimens (PI. 5, figs. 2, 4), while in others it is an almost con-
tinuous but externally indented ring (PI. 7, fig. 9). A parenchyma sheath 2-8 cells thick
is present in two specimens which both have fully dissected xylem rings. The sheath is
prominently developed on the outside of, and in the gaps between, the xylem strands;
it does not appear to be present between pith and xylem. The sheath consists of elon-
gated polygonal cells which have a diameter of 13-40 /x, a length of 40-120 fx, and a wall
thickness of 1 -6-5 ix.

The phloem forms a continuous layer around the xylem and xylem sheath. The meta-
phloem, which has its greatest development in the indentations between the metaxylem
strands, contain cells which are polygonal in transverse section, and presumed to be
sieve cells with a diameter of 35-96 i x, a length of at least 550 [x, and a wall thickness
between adjacent strands of 1 -6-6-8 /x ; no sieve areas, however, could definitely be dis-
tinguished. Associated with these are some smaller cells, which are rectangular to poly-
gonal in transverse view; these measure from 14-27 /x in diameter to 40 /xx 14 /x. The
metaphloem is surrounded by a continuous zone, 68-130 /x wide, of crushed cells, which
probably represents the protophloem and pericycle. Some polygonal and tangentially
elongated cells, 1 3-70 ix in diameter with a wall thickness of 3-13 /x, can be distinguished ;
these have a length of 54—270 /x.

The endodermis is marked by a different colouration and a change from the pericycle
to the larger cells of the inner cortex. It consists of slighly darker coloured, more resistant
cells which are rounded-polygonal to tangentially elongated in cross-section with a
diameter of 12-55 /x; they are rectangular in longitudinal view and up to 200 /x long.
No definite Casparian strips are visible. The total diameter of the stele to the endodermis
is 3-5-11 mm.

Cortex. The inner cortex consists of slightly tangentially and longitudinally elongated
rounded to polygonal parenchyma cells with a transverse diameter of 25-110 /x and a
length of 40-170 /x (PL 6, figs. 2, 3). The walls may be straight or sinuous, with a thick-
ness between two adjacent cells of 1-5-4 [x. The inner cortex is 1-6 mm. wide; in most
specimens this zone contains 6-13 leaf traces in a given transverse section, but one shows
20-1 traces.

The dense sclerotic outer cortical region is 1-10 mm. wide, and consists of fibres

24

PALAEONTOLOGY, VOLUME 13

which are polygonal in cross-section. The walls between two adjacent cells are
10-30 thick and clearly show the primary and secondary walls; intercellular spaces of
up to 6 /x commonly occur at the angles. The majority of cells are 13-55 p. in diameter
with a length of at least 1300-1800 p (PI. 6, figs. 5, 6); the end walls may be transverse,
oblique, or tapering. Some relatively wider (28—85 yu., but up to 160 p) and shorter
(200 /x) cells occur on the boundary with the inner cortex of the stem and the leaf
traces, and in the depressions beneath the departing petiole bases on the outside of the
stem. The longitudinal walls of the fibres may be smooth or with round to oval pits
(2-5-8 /lx. ; PI. 6, fig. 4) as in P. williamsii. Larger, more or less rectangular or annular
pits appear to be caused by shrinkage of the original wall material. The outer cortex
contains 9-19 leaf traces in a given transverse section; total number of traces in the
whole cortex in any one section is 18-38.

Leaf traces. These arise from the stem xylem similarly to the traces in the Tertiary-Recent
subgenera Osmunda and Osmundastrum; leaf gaps are usually developed. A mesarch
protoxylem group appears in the metaxylem strand of the stem and then an island of
parenchyma develops adaxially to the protoxylem. The island of parenchyma enlarges
upwards and connects with the pith to form the leaf gap while the outer endarch arch
of the xylem breaks away to form the leaf trace. The trace gains the encircling tissues
of the xylem sheath, phloem, pericycle, endodermis, inner cortex, and outer cortex as it
passes through these respective zones of the stem; each zone of the stem fills in behind
the trace and no gaps are formed.

The leaf trace arises with one endarch protoxylem group which usually bifurcates in the
inner cortex of the stem (PI. 6, figs. 7, 8); 4-10 adaxial protoxylem groups are present

EXPLANATION OF PLATE 7

Figs. 1-9. Palaeosmunda playfordii gen. et sp. nov. 1-8, UQF53547, from Blackwater Mine. 1 , Trans-
verse section of petioles in outer part of mantle, x 1 -5. 2, Part of vascular trace and inner cortex of
petiole at left centre of fig. 1, x 10-6. 3, Transverse section of part of vascular trace and inner cortex
of petiole (not shown in fig. 1), x 16. 4, Detail of vascular trace from fig. 3, x42. 5, Further
enlargement of part of vascular trace with the adaxial schizogenous mucilage cavities, x 66. 6, Longi-
tudinal section of part of vascular trace of petiole, showing zone of crushed parenchyma cells, x 99.

7, Detail of endodermis of petiolar trace, showing Casparian strips on the radial walls, x 270.

8, Transverse section of sclerotic ring of petiole base; note increase in fibre diameter toward the
inner cortex, x42. 9, Transverse section of stele, UQF50622, x6; pith and inner cortex not
preserved. (1, transmitted and reflected light; 2-9, transmitted light.)

EXPLANATION OF PLATE 8

Figs. 1-7. Palaeosmunda playfordii gen. et sp. nov. 1-5, Transverse sections of roots. 1, UQF53564,
from Blackwater Mine, X26-5; 2, Shows triarch xylem trace, UQF59129, from Blackwater Mine,
x 10-6. 3-5, Show 2 diarch xylem strands in section, UQF53547. 3, xl6; 4, x 31-5; 5, x26-5.
6, 7, Xylem tracheids of petiole containing Basidiomycete hyphae with clamp connections, holotype,
UQF53544, x480.

Figs. 8, 9. Dissociated, flanged petioles, with fronds of Sphenopteris lobifolia-Cladophlebis roylei-S.
polymorpha, and Glossopteris sp., from the Burngrove Formation at Burngrove Creek. 8, UQF53582,
xO-66 (the line is a saw cut — see figs. 10, 11); 9, UQF53575, xO-44.

Figs. 10, 11. Sections of dissociated petioles in specimen shown in fig. 8, X 2.

Figs. 12, 13. Compressions of osmundaceous trunks (probably Palaeosmunda ) from the Burngrove
Formation at Burngrove Creek. 12, UQF53581, xO-66; 13, UQF53577, xO-55. (1-7, transmitted
light; 8-13, reflected light.)

Palaeontology, Vol. 13

PLATE 7

GOULD, Late Permian osmundaceous trunks

PLATE 8

Palaeontology, Vol. 13

GOULD, Late Permian Osmundaceae

GOULD: PALAEOSMUNDA, A NEW GENUS

25

when the trace enters the base of the petiole. There are up to 44 groups in the trace in
the outer zones of the mantle.

Petioles. The petioles arise from the stem at angles of 15-30° and are usually closely
adpressed near the stem but loosely arranged in the outer part of the mantle (PI. 4,
fig. 1 1). The petiole bases consist of a C-shaped vascular trace surrounded by a parenchy-
matous inner cortex, a sclerotic ring, and lateral stipules ; except for the stipules which
arise as the petiole emerges from the stem, these tissues are derived from, and con-
tinuous with, the corresponding zones of the stem. The bases enlarge upwards, ranging
in transverse section from 3-5 mm. thick by 7 mm. wide near the stem, up to 12-5 mm.
thick and 35 mm. wide near the periphery of the mantle.

Upwards the C-shaped xylem strands become larger, but thinner, the constituent
tracheids narrower, and the ends become more incurved (cf. PI. 6, figs. 9, 10 and PI. 7,
figs. 1-5). The strands are 1-4 tracheids thick, and the metaxylem tracheids are 30-
1 10 p in diameter, rarely up to 160 p . Basidiomycete hyphae showing clamp connections
occur within some tracheids in the holotype (PL 8, figs. 6, 7). The xylem is surrrounded
by a xylem sheath up to 6 cells thick, the phloem, the pericycle, and the endodermis.
The pericycle is 2-6 cells thick, and usually contains numerous, apparently schizo-
genous, mucilage cavities with a diameter of 68-164 /x (PI. 7, fig. 5; cf. Seward and Ford
1903, p. 247, pi. 30, fig. 45); these cavities are most common on the adaxial side of the
trace, but are occasionally present on the abaxial side. Groups of compressed, irregularly
arranged parenchyma cells occur in the adaxial xylem sheath, phloem, and pericycle.
The groups are quite distinctive in longitudinal section (PI. 7, fig. 6) and compression
probably resulted from the formation of the schizogenous cavities.

The endodermis is 1-2 cells thick (PI. 7, fig. 7). The cells are polygonal in transverse
section (diameter 14-35 p) and elongated to rectangular in longitudinal view (length
80-330 p). Casparian strips 6-17 p wide are present.

The inner cortex of the petiole base consists of parenchyma cells (PI. 6, fig. 9; PI. 7,
figs. 2, 3) which are polygonal in transverse section with a diameter of 25-100 p, and
rectangular in longitudinal section with a length of 40-280 p; wall thickness between two
adjacent cells is 1-3-5 p. Sometimes the cells have been partially macerated and separated
before preservation.

The sclerotic ring contains sclerenchyma fibres similar to those in the outer cortex
of the stem. The fibres are polygonal in transverse section and generally range from
13 to 40 p in diameter; in any one ring there is usually a gradual increase in diameter
towards the inner cortex (PI. 7, fig. 8). The walls between adjacent fibres are 6-17 p
thick. The sclerotic rings are circular to rhomboidal in shape when they arise and they
broaden upwards, contributing greatly to the stipules, eventually replacing them. They
range in size from 3-7 mm. in diameter near the stem to 34-5 X 12 mm. in the periphery
of the mantle; the thickness of the ring varies from 0-2 mm. to 1 mm. and the lateral
extremities are usually thinner than the adaxial and abaxial portions.

The sclerotic ring is surrounded by a sheath of parenchymatous tissue which is
extended laterally to form the stipules ; the cells have diameters of 25-60 p.

Roots. The adventitious roots have a diameter of 0-7-2-5 mm. and usually arise in
pairs from the leaf traces before their departure from the stele. Roots may also arise
irregularly from the metaxylem strands of the stem, especially those immediately below
a departing leaf trace. The xylem trace gains the surrounding tissues of phloem,

26

PALAEONTOLOGY, VOLUME 13

pericycle, endodermis, and sclerotic outer cortex as it passes through these zones of the
stem. In most cases no cells of the inner cortex accompany the trace into the outer
cortex of the stem, the sclerenchyma being contiguous with the endodermis. In a few
examples, however, there is a narrow gap between the endodermis of the root trace and
the sclerotic outer cortex as if a layer of inner cortex was present, but no cells are
preserved. In a cross-section of the trunk, most roots, except those in the region near
the stem, are seen in transverse section (PI. 4, fig. 11) and this is probably indicative of
an arborescent habit (Miller pers. comm. 1969). The root usually has a diarch xylem
trace (PI. 8, fig. 1), but in one case it is triarch (PI. 8, fig. 2) ; some show two diarch xylem
strands in a section (PI. 8, figs. 3-5), possibly prior to branching. Sections of roots from
the inside to the outside of the mantle show the inner layers of cortical fibres pro-
gressively becoming thin-walled, thus appearing as a parenchymatous inner cortex. The
roots, which are often branched, penetrate freely throughout the mantle of leaf bases
between the sclerotic rings ; in one specimen they penetrate through the sclerotic rings
into the inner cortex of some of the outer leaf bases, possibly because these were injured
while the plant was still living. In several specimens the trunk is surrounded by a mat
of roots up to 6 cm. wide ; the silt- to very fine sand-sized sediment enclosed within this
zone is in contrast to the medium to very coarse sandstone in which the specimens occur.

Discussion. Palaeosmunda playfordii differs from P. williamsii in lacking sclerenchyma
strands in the stipules and inner cortex of the petiole bases. Speciation on the distri-
bution of sclerenchyma in the leaf bases in Osmundaceae is a well-established principle
(e.g. Miller 1967) and the distinction by presence or absence of sclerenchyma is a useful
one. The xylem ring in the specimens of P. playfordii studied, unlike that in P. williamsii,
always exhibits some leaf gaps (text-fig. 4) ; however, the variation shown is of a magni-
tude that suggests it would be possible for a xylem ring with no gaps to occur. The leaf
traces have only been found to arise with 1 protoxylem group.

ASSOCIATED FOLIAGE

The fossil flora of the Upper Bowen Coal Measures has been described and figured
by Walkom (1922), Rigby (1962, 1963), Hill and Woods (1964), and White (1964; in
Malone, Corbett, and Jensen 1964, pp. 70-7, pi. 3-13; in Olgers, Webb, Smit, and
Coxhead 1966, pp. 49-52, pi. a-d).

Many compressions of osmundaceous trunks, probably referable to Palaeosmunda,
occur in the silicified, abundantly fossiliferous siltstones of the Burngrove Formation
(Blackwater Group) outcropping in a small tributary of Burngrove Creek on ‘Tolmies
Creek’ Station, near Blackwater (Portion 10, Parish of Blackwater; locality shown as
Burngrove Creek on text-fig. 1). These specimens show the typical mantle of flanged
petiole bases, although other anatomical details are not preserved (PI. 8, figs. 12, 13).
The strata also contain impressions of plants of the types which Walkom ( 1 922) described
as Phyllotheca sp., Cladophlebis roylei Arber 1901, Sphenopteris polymorpha Feistmantel
1876, S. lobifolia Morris 1845, and Glossopteris spp. The portions of fronds referred to
S. lobifolia, C. roylei, and S. polymorpha vary from bipinnate to tripinnate and appear
to intergrade. Unfortunately, no fertile examples of these fronds have been reported.
Some layers of the Burngrove Formation contain masses of the S. lobifolia-C. roylei-
S. polymorpha fronds, flattened osmundaceous trunks, and dissociated, flanged petioles

GOULD: PALAEOSMUNDA, A NEW GENUS 27

(PI. 8, figs. 8, 9). Transverse sections of some of these dissociated petioles show the
sclerotic ring and characteristic C-shaped vascular trace which have been replaced by
calcite (PI. 8, figs. 10, 11). It is thus probable that Palaeosmunda trunks bore foliage of
this type, but this can only be inferred by association.

Acknowledgements. The author thanks Dr. G. Playford (Department of Geology and Mineralogy,
University of Queensland) for his guidance and helpful criticism of the manuscript. Dr. C. N. Miller,
Jr. (Department of Botany, University of Montana, Missoula) kindly allowed the author to examine
slides of Itopsidema vancleavii, and also read the typescript. The investigation was carried out at the
Department of Geology and Mineralogy, University of Queensland, while the author was in receipt
of a Commonwealth Post-graduate Award.

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walkom, a. b. 1922. Palaeozoic floras of Queensland. Part I. The flora of the Lower and Upper Bowen
Series. Pubis, geol. Surv. Qd. 270, 65 pp.

webb, a. w., and mcdougall, i. 1967. Isotopic dating evidence on the age of the Upper Permian and
Middle Triassic. Earth Planet. Sci. Letters 2, 483-8.
webb, e. a. 1956. Review of exploratory oil wells penetrating Permian section in central Queensland,
Australia. Bull. Am. Ass. Petrol. Geol. 40, 2329-53.
white, m. e. 1 964. Reproductive structures in Australian Upper Permian Glossopteridae. Proc. Linn.
Soc. N.S.W. 88, 392-6, pi. 22-4.

zalessky, m. d. 1924. On new species of Permian Osmundaceae. J. Linn. Soc., Bot. 46, 347-58, pi.
32—4.

1927. Permskaya flora ural’skikh predelov Angaridy. Atlas. Flore Permienne des limites ourali-

ennes de l’Angaride. Atlas. Trudy geol. Kom. 176, 152 pp., 46 pis. (in Russian and French.)

1931a. Structure anatomique du stipe du Petcheropteris splendida n. g. et sp., un nouveau

representant des Osmundacees Permiennes. Izv. Akad. Nauk. SSSR 7th ser. (1931), 705-10, pi. 1, 2.

1931 b. Structure anatomique du stipe du Chasmatopteris principalis n. g. et sp., un nouveau

representant des Osmundacees Permiennes. Ibid. 715-20, pis. 1, 2.

1935. Structure anatomique du stipe d’une nouvelle Osmondee du terrain Permian du Basin de

Kousnetzk. Ibid. (1935) 747-52, pis. 1-3.

R. E. GOULD

Department of Geology and Mineralogy
University of Queensland
St. Lucia, Queensland
Australia 4067

Typescript received 6 February 1969

ON THE STRUCTURE OF CORDAITES FELICIS
BENSON FROM THE LOWER PENNSYLVANIAN
OF NORTH AMERICA

by CHARLES W. GOOD and THOMAS N. TAYLOR

Abstract. New material of Cordaites felicis Benson is described from lower Pennsylvanian petrifactions col-
lected in eastern Kentucky. Additional information about the anatomy and epidermal pattern is provided and
an emended diagnosis is presented together with a discussion of other structurally preserved cordaitean leaves.

In 1912 Margaret Benson described a new anatomical species of cordaite leaf, Cordaites
felicis, from British petrifaction material equivalent to lower Pennsylvanian in age.
Of petrified cordaitean leaf forms, C. felicis is similar to three species which had been
distinguished as C. loculosus Felix (1886), C. robust us Felix (1 886), and C. wedekindi Felix
(1886). Subsequent to Benson’s work, Koopmans (1928) made a comparative study of
Felix’s species from material collected from the Netherlands and regards them as syno-
nyms of C. felicis. Seward (1917) considered C. felicis as probably being equivalent to
petrified specimens of C. principalis (Germar) Geinitz (Germar 1848, Geinitz 1855,
Renault 1879, Stopes 1903, Harms and Leisman 1961). Harms and Leisman (1961) have
suggested that another cordaite leaf which they studied, C. crassus Renault (Renault
1879, Seward and Sahni 1920, Darrah 1940), might also be equivalent to C. felicis
because the vascular bundles are sometimes completely separated by fibrous tissue, a
characteristic that has been generally used to delimit C. felicis. Darrah (1940) has also
mentioned a similarity between C. crassus and C. felicis, and has reported the presence
of C. felicis in a check list of an Iowa coal ball flora (Darrah 1941).

SYSTEMATIC DESCRIPTION

Order cordaitales

Genus cordaites Unger 1850

Cordaites felicis Benson 1912

Emended diagnosis. Leaves 0- 1-1-0 mm. thick with irregular surfaces and rounded mar-
gins. Vein frequency of 10-25 per cm. determined by distance from point of attachment;
veins separated by longitudinally directed fibrous partitions (primary ribs) that are con-
tinuous from abaxial to adaxial surfaces. Identical thick-walled fibres in longitudinal
bands above and below veins (primary ribs) and similar hypodermal fibrous masses
occasionally between vein and intervein partitions (secondary ribs), dichotomizing veins
in basal sections, decreasing in frequency toward tip. Mesophyll constructed of paren-
chyma plates of laterally elongate cells, vertically attached to lower and upper epidermis,
laterally to vein and intervein partitions ; vein surrounded by outer sheath 2-7 cells thick
and continuous with mesophyll plates. Mesarch xylem of 1-10 larger centripetal meta-
xylem tracheids (20-57 /x diam.) with secondary wall thickenings of closely spaced

[Palaeontology, Vol. 13, Part 1, 1970, pp. 29-39, pis. 9-11.]

30

PALAEONTOLOGY, VOLUME 13

scalariform bars and multiseriate circular bordered pits, and smaller (7-12 p diam.) less
well-developed centrifugal metaxylem tracheids that partially surround centripetal
elements, protoxylem tracheids 3-6 ^ in diam. and difficult to delimit in all veins,
presumed phloem elements typically crushed; inner sheath tracheids present on flanks
and abaxial side of bundle. Stomata sunken and longitudinally oriented in rows, 1-2
rows between vein and intervein partition on the adaxial epidermis and up to 8 rows on
the abaxial epidermis.

Type locality. The Colliery at Shore-Littleborough, Lancashire.

Stratigraphic position and age. Westphalian A.

Type material. (Lectotype) Specimen designated 365.2 (fig. 2 of Benson 1912), Palaeontological
Collection, British Museum (Natural History).

MATERIALS AND METHODS

New material of C. felicis, which forms the basis of this study, provides additional
information about the structure and phylogenetic relationships of this species. The
specimens were collected from the Lewis Creek and Shack Branch localities in eastern
Kentucky (Schopf 1961).

Anatomical features of the leaves were determined by the use of cellulose acetate
peels. Additional foliage fragments were macerated from coal balls with dilute HC1 and
provided information on the three-dimensional structure and the surface ribbing pat-
terns of the individual leaves. Surface configurations of the leaves were also observed
by chipping coal away from leaves near the surface of the coal balls. Following the tech-
nique of Florin (1931), Ledran (1960), and Harms and Leisman (1961), small pieces of
coal ball containing only cordaite leaves were completely macerated in Schulze’s
solution. Cuticles obtained by this process were examined to determine epidermal
features. Because of the nature of the material no additional clearing or staining was
necessary.

Material used in this study includes slides 3460-3745, cellulose acetate peels, and
macerated cuticles from Coal Balls 121, 144, 145, 493, 1460, and 1744, all of which are
included in the Paleobotanical Collection, Department of Biological Sciences, Univer-
sity of Illinois at Chicago Circle. Specific designations of figured specimens in this paper
are included with plate explanations.

STRATIGRAPHY

Benson’s specimens of C. felicis were obtained from the mine at Shore Littleborough,
Lancashire. The stratigraphic position of this coal, according to Hoskins and Cross
(1943) is in the Gannister beds, and is equivalent to deposits of lower Westphalian A,
while the material of C. felicis described by Koopmans (1928) is from the Finefrau and
Katharina horizons which are regarded as being equivalent to lower and upper West-
phalian A respectively. Darrah (1941) has recorded C. felicis in a check-list of species of
coal ball plants from Iowa which he indicates are equivalent to deposits of Westphalian
C. An examination of the correlation chart prepared by Moore et al. (1940), however,
shows these deposits equivalent to Westphalian D. The specimens of C. felicis used as
the basis of this paper were collected at the Lewis Creek and Shack Branch localities in

GOOD AND TAYLOR: STRUCTURE OF CORDAITES FELICIS BENSON 31

Leslie County, Kentucky (Schopf 1961). According to Schopf, the coal balls occupy the
position of the Copland Coal, immediately below the Magoffin marine zone, and are
considered the oldest coal balls known in North America, intermediate in age between
petrifactions recovered from the Lower Coal Measures of Britain and the Eastern
Interior Basin deposits of North America. Moore et al. (1940) include the Copland Coa
as equivalent to upper Westphalian B deposits. Huddle, Lyons, Smith, and Ferm (1963)
regard the stratigraphic position of the Copland Coal as equivalent to rocks of middle
Pennsylvanian age, while Prostka (1965) indicates that the Copland Coal is in strata of
either lower or middle Pennsylvanian age, but makes no precise distinction.

One approach to determining the exact stratigraphic position of the Kentucky coal
balls is to examine the floral components contained in these petrifactions. To date the
described members of the flora from the Lewis Creek and Shack Branch localities include
Mitrospermum compressum (Taylor and Stewart 1964), C alamo st achy s binneyana (Taylor
1967), Bowmanites dawsoni (Taylor 1969), and Cordaites felicis. All of these taxa, in
addition to several studies currently in progress (e.g. Conostoma anglo-germanicum,
Medullosa cf. anglica, Pachytesta cf. olivaeformis ), are known from the Lower Coal
Measures or equivalent strata. Mitrospermum compressum and Cordaites felicis have
been reported but not described from Iowa coal balls of middle Pennsylvanian age
(Darrah 1941). While the precise stratigraphic position of the beds containing the eastern
Kentucky petrifactions is known, the application of the time stratigraphic terms lower
and middle Pennsylvanian to these deposits is in dispute. On the basis of the floristics,
however, it is our opinion that the floral components which are so unlike the well-known
middle and upper Pennsylvanian age coal ball floras of North America, and so similar
to the floras of Westphalian A in Europe, should be regarded as representing time
equivalent strata of Westphalian A (= lower Pennsylvanian) in eastern Kentucky.

DESCRIPTION

External morphology. All of the specimens examined were leaf fragments; therefore no
complete transverse sections of entire leaves were available. Leaf length, width, and shape
are still incompletely known. In transverse section, the most complete leaf measures
32-0 mm. wide and is twice the maximum width reported by Benson in her description
of C. felicis. According to the magnifications accompanying Benson’s photographs of
C. felicis (1912), the leaves illustrated agree in size with the specimens reported here.
The data in the text portion of Benson’s paper, however, appear to be of the size
indicated by the photographs. It is therefore assumed that Benson’s data must be multi-
plied by a factor of ten in order to correlate with the photographs. Leaf thickness in the
Kentucky specimens ranges from 0T to 1 -0 mm. Toward the margins the leaves gradually
become thinner, but are not as thin as Benson’s reported margin thickness of 19 microns
(taken now as 190 f).

Leaf margins are bluntly rounded (PI. 10, fig. 2) and do not agree with the drawing of
a supposedly young leaf similar to C. felicis which shows pointed margins (Scott 1924).
The leaf epidermis, as exposed on the coal ball surfaces and by maceration with HC1,
typically exhibits straight, axially oriented rows of ribs of uniform breadth (PI. 10,
fig. 1). According to the terminology of earlier workers, these structures are referred
to as primary ribs, because they are the most prominent surface feature, and account for

32

PALAEONTOLOGY, VOLUME 13

raised areas on the left surface (PI. 9, fig. 2). Macerated leaves indicate that the primary
ribs are the result of longitudinally disposed fibrous hypodermal tissue associated with
the veins and partitions between veins. From the surface it is impossible to tell whether
a primary rib is associated with a vein or an intervein partition. Thinner secondary ribs
are occasionally seen between these primary ribs (PI. 10, fig. 1) and consist of smaller
masses of fibrous hypodermal tissue often situated between the veins and intervein
partitions (PI. 9, fig. 2).

The leaves show a considerable variation in degree of surface relief in transverse
section. Some have almost smooth external surfaces (PI. 10, fig. 3), while others show
an undulating surface, apparently due to crushing thinner walled cells except where the
veins and intervein partitions give additional support (PI. 9, fig. 1). Since many of the
leaves have a smooth external surface in transverse section, it seems probable that
originally there was little or no surface relief.

Internal anatomy. The most conspicuous characteristic of the internal anatomy of
Cordaites felicis is the presence of complete epidermis-to-epidermis partitions between
most of the veins (PI. 9, figs. 1, 2). In transverse section these partitions resemble ‘I’
beams (PI. 9, fig. 1); the top and bottom consisting of hypodermal masses of fibres which
are 5-15 cell layers deep and 3-10 cells wide. Individual fibres are axially elongate (PI.
9, fig. 5) and have small lumens. Fibre diameters range from 35 to 124 /a. In thicker frag-
ments the partition consists entirely of these fibre-like cells, although the lumina of those
cells in the centre of the partition are broader than the lumina of cells near an epi-
dermis (PI. 9, figs. 1 , 2). In transverse sections that measure no more than about 0-75 mm.
thick the fibres only extend about J of the distance across the leaf from both the upper
and lower epidermis (PI. 10, fig. 3). The remaining central portion of the partition is
made up of thin-walled rectangular cells with somewhat thickened corners and diameters
that range between 23 and 46 /j.. In paradermal section these cells measure 105-240 ^ in
length and 20-35 ^ in width. Individual partitions extend uninterrupted throughout
the length of the leaf fragments studied.

Approximately 10 % of the veins have neither hypodermal fibrous tissue nor thin-
walled cells between them, although they are surrounded by a common sheath. This
absence of partitions varies considerably with leaf thickness; leaf fragments thicker
than 0-6 mm. have approximately 17 % of their veins unpartitioned. Leaves between 0-3
and 0-6 mm. thick have approximately 7 % unpartitioned veins. Specimens less than
0-3 mm. thick have about 4 % unpartitioned veins. It is assumed that the thicker leaf
fragments represent the basal portion of the leaf, as has been suggested by Benson

EXPLANATION OF PLATE 9

Figs. 1-5. Cordaites felicis. 1, Transverse section of portion of leaf showing fibrous ribs, disposition
of veins, and intervein partitions (IP); arrow indicates position of inner sheath; C.B. 145 A hot,# 39,
x 60. 2, Transverse section of portion of leaf showing hypodermal fibrous masses responsible for
primary (PR) and secondary (SR) surface ribs; C.B. 145A hot, # 31, X 115. 3, Oblique section of
leaf showing mesophyll plates (MP); C.B. 145A hot, # 31, x 120. 4, Transverse section of vein and
position of outer sheath (OS); C.B. 145F (2) top, # 67, X 130. 5, Longitudinal section of leaf showing
thick-walled fibres of hypodermal masses and secondary wall thickenings of centripetal xylem elements ;

C.B. 145F (1) bot, # 9, x 155.

Palaeontology, Vol. 13

PLATE 9

GOOD and TAYLOR, Pennsylvanian Cordaites leaves

GOOD AND TAYLOR: STRUCTURE OF CORDAITES FELICIS BENSON

33

(1912), Harms and Leisman (1961), and other authors who have described various
structurally preserved cordaite leaf species. The frequency of unpartitioned veins
further supports the conclusion that divisions occur most frequently at the basal region
of the leaf (PI. 10, fig. 3). This feature of vein frequency is consistent with Benson’s
description of Cordaites felicis, and agrees with the presumed pattern of vein dichotomy
in other structurally preserved cordaite leaf species (Harms and Leisman 1961) as
well as those known only from compression specimens. Successive transverse sections
indicate that when vein dichotomy occurs it is at a very acute angle.

Incomplete partitions that do not extend from epidermis to epidermis occur between
less than 0T % of the veins. This frequency of incomplete partitions is not the case
with C. crassus and C. principalis (Harms and Leisman 1961) which are otherwise
described as being very similar to C. felicis in their internal organization.

The distribution of the veins of C. felicis is typical of most cordaite leaf species. The
number of veins and associated tissues (vascular bundle sheath) ranges from 10 to 25
per cm. and in transverse section occupies 50-75 % of the leaf thickness. Masses of
fibrous hypodermal tissue are located above and below the veins (PI. 9, figs. 1, 2) and
have the same general dimensions as those which form part of the intervein partitions
(PI. 9, figs. 1, 2). Vascular elements are surrounded by a sheath of thin-walled cells
4-7 cell layers thick that thins laterally to 2-3 cells in thickness (PI. 9, fig. 4). In transverse
section sheath cells are approximately circular in outline and have diameters that range
from 20 to 40 p while in paradermal section they are rectangular and measure 115-305 p
long and appear identical to those cells found in the centre of the intervein partitions.

The xylem in C. felicis is mesarch. One to ten broad (20-57 p) thick- walled metaxylem
elements are situated on the adaxial side of the bundle (PI. 10, fig. 5). Protoxylem ele-
ments (3-6 p diam.) occur as a small strand immediately below these cells (PI. 10, fig. 5)
but are not identifiable in all of the bundles. Centrifugal metaxylem elements, of smaller
diameters than the centripetal metaxylem cells and larger diameters than the protoxylem
tracheids, radiate out to the side of the centripetal cells from below the protoxylem
(PI. 10, fig. 5). Radial sections of veins show the centripetal elements to be very long and
characterized by secondary wall thickenings that range from closely spaced scalariform
bars to multiseriate circular bordered pits (PI. 1 1, fig. 3). Centrifugal elements are smaller
and more circular in outline than the centripetal elements and have diameters that range
from 7 to 12 p. These cells occasionally form an arc that laterally encloses the centripetal
xylem. Often, small areas of centrifugal xylem are present only on the lateral sides of
the centripetal elements (PI. 10, fig. 5).

Additional xylem elements often occur just inside the thin-walled vein sheath (PI. 9,
fig. 1 ; PI. 10, fig. 5). These cells, that range in diameter between 9 and 23 p, have been
referred to as the ‘inner sheath’ by early workers (Renault 1879, Stopes 1903). They inter-
mittently occur below and to the side of the centripetal and centrifugal metaxylem
elements (PI. 10, fig. 5) and often merge with the centrifugal xylem present laterally and
adjacent to the centripetal tracheids (PI. 10, fig. 5). Cells presumed to be phloem
can occasionally be distinguished between the inner sheath and the central portion of the
centrifugal xylem (PI. 10, fig. 5), but their general poor preservation precludes a detailed
description.

Hypodermal masses of fibrous tissue sometimes occur between the veins and intervein
partitions associated with both surfaces of the leaf (PI. 10, fig. 1). These masses are usually

C 7173

D

34

PALAEONTOLOGY, VOLUME 13

smaller groups of fibres than those associated with the veins or partitions. They are
sometimes attached to the outer sheath of veins and may be associated with a new inter-
vein partition that has arisen just distal to the point of a vein dichotomy. No constant
relationship exists between vein division and these masses of fibres. These small fibrous
masses usually occur in the thicker leaf fragments, and are responsible for the so-called
secondary ribs sometimes seen in surface and sectional views (PI. 9, fig. 2).

Palisade parenchyma is absent in Cordaites felicis, as has been reported in C . principalis
and C. crassus; however, it is present in other petrified forms. The entire internal
tissue between the veins and intervein partitions of C. felicis consists of spongy mesophyll
making up parenchyma plates that are perpendicular to the leaf surfaces, and to the
axially oriented veins and intervein partitions (PI. 9, fig. 3; PI. 10, fig. 1). Each plate is a
single cell layer in thickness and is attached to both the upper and lower epidermis (PL
10, fig. 1). The plates extend laterally between a vein and adjacent intervein partition and
in this direction can be seen to have 5 to 9 cells (PI. 10, fig. 1). In some specimens these
plates consist of flattened, laterally elongate cells suggestive of a flaccid condition of the
mesophyll tissue (PI. 10, fig. 1). Other plates, however, consist of apparently turgid cells
that are isodiametric and measure 20-30 /x in diameter (PI. 10, fig. 4). Between plates are
conspicuous lacunar areas that approximate the width of the turgid mesophyll paren-
chyma cells. Toward the veins and intervein partitions these spaces become smaller, with
the plates of parenchyma cells adjoining the intervein partition or outer sheath of a vein
(PI. 10, fig. 3). Similar appearing mesophyll cells that make up plates of photosynthetic
tissue have been described by Cross (1940) in Taxodium distichum and Esau (1965) in
Pinus. Studies of T. distichum indicate that the lacunar spaces are the result of cell
separation brought about by a slower rate of cell enlargement in the mesophyll as com-
pared with that of the surrounding tissues. The absence of extensive foliar specimens at
this time precludes a developmental interpretation of this kind for C. felicis.

In transverse section, cells of the mesophyll parenchyma appear similar to the cells of
the outer sheath, and in some instances the two cannot be distinguished (PI. 10, fig. 3).
The difference is only seen in paradermal view, where the sheath cells appear more
axially elongated than the cells of the parenchyma plates.

Epidermal structure. The epidermis consists of longitudinal rows of stomata located
above the regions where there is no hypodermal fibrous tissue, and intervening rows of
rectangular accessory cells above the fibrous tissue (PI. 11, figs. 1, 4). Accessory epi-
dermal cells are oriented parallel to the long axis of the leaf, measure 60-150 /x long and

EXPLANATION OF PLATE 10

Figs. 1-6. Cordaites felicis. 1, Slightly oblique paradermal section of leaf showing position of primary
ribs (PR) and mesophyll plates; arrow indicates secondary rib; C.B. 1460 bot, # 37, x 100. 2, Trans-
verse section of leaf at margin; C.B. 145D (1) top, # 30, x 150. 3, Transverse section of leaf showing
smooth adaxial surface and vein at level of dichotomy (arrows); note continuity of cells of outer
sheath (OS) and those of mesophyll plates; C.B. 145F (2) top, # 67, x 120. 4, Paradermal section of
leaf showing turgid nature of mesophyll plate cells; C.B. 121 J top, # 20, x 200. 5, Transverse section
of vascular bundle indicating position of centripetal (X) and centrifugal metaxylem (X'), protoxylem
elements (PX), phloem (P), and inner sheath (IS); C.B. 145A bot, # 39, x 250. 6, Transverse section
through two guard cells (G) and lateral subsidiary cells; arrow indicates cuticular extension over
stoma; C.B. 145D (1), # 31, X 1000.

Palaeontology, Vol. 13

PLATE 10

GOOD and TAYLOR, Pennsylvanian Cordaites leaves

GOOD AND TAYLOR: STRUCTURE OF CORDA1TES FELICIS BENSON 35

12-28 / u. wide, and occur in easily identifiable bands across the epidermis (PI. 11, fig. 1).
Cuticles show a faint longitudinal median line associated with some of the accessory
cells (PI. 11, fig. 2). This feature occurs only on isolated cuticles and appears to be a
property of the cuticle since no evidence of such a thickening can be seen in the same
position on sections of the epidermis. The accessory cells have end walls that are straight,
while the radial walls are irregularly thickened and exhibit primary pits (PI. 1 1, fig. 2).

The epidermal cells which occur over the regions between the fibrous tissue are variable
in shape (PI. 1 1 , fig. 5). They are usually shorter than the accessory cells over fibrous areas
and tend to be more isodiametric, often having bluntly rounded end walls. These cells
are associated with the stomatal apparatus.

Regions at the presumed basal (thick) part of the leaf which have narrow areas
between the relatively massive zones of fibrous tissue have few stomata. At all other
regions both the upper and lower epidermis contain stomata. This is not consistent with
Benson’s (1912) description of C.felicis in which stomata are reported as occurring only
on the lower epidermis.

The upper epidermis has bands that contain one or two rows of stomata (PI. 1 1, fig. 1).
Slightly narrower bands containing only accessory cells alternate with stomatiferous
bands (PI. 1 1, fig. 1). Superficially, the stomata appear scattered, but upon close examina-
tion are seen to arise from the same row or rows of cells showing no sharing of terminal
subsidiary cells.

The lower epidermis contains one or two rows of stomata positioned between the
hypodermal fibrous masses in basal areas of the leaf. The stomata are more closely
spaced than are those of the upper epidermis, often having adjacent terminal subsidiary
cells. On the thinner, presumably more distal parts of the leaf, where there are few
fibrous masses between the veins and intervein partitions, more rows of stomata appear
(PI. 1 1, fig. 4). Often 5-7, and occasionally 8 rows of stomata occur between a vein and
an adjacent intervein partition (PI. 11, fig. 4). The rows are usually staggered, all the
stomata of adjacent rows are not lined up in transverse bands as in Cordaites principalis
(Harms and Leisman 1961) and C. affinis (Reed and Sandoe 1951). Under these crowded
conditions terminal subsidiary cells are often shared with adjacent stomata in the same
cell row for several consecutive stomata. When there are fewer than 5 rows of stomata
on the lower epidermis subsidiary cell sharing is not common.

The stomatal apparatus consists of two bean-shaped guard cells (PI. 11, fig. 7), two
bean-shaped lateral subsidiary cells (PI. 11, fig. 6), and two terminal subsidiary cells
(PI. 11, fig. 7). The lateral subsidiary cells of both the upper and lower epidermis range
between 39-69 p long and 1 1-23 p wide. The terminal subsidiary cells of the upper
epidermis measure 14-70 p long and 1 1-21 p wide; those of the lower epidermis measure
20-40 p long and 11-18 p wide. The terminal subsidiary cells of both the upper and
lower epidermis measure approximately 20 p in depth. In general, the terminal sub-
sidiary cells are small when there is another stoma nearby in the same row, as is typical
of the lower epidermis where the density of stomata is considerably greater. In cases
where the same terminal subsidiary cell is shared by two stomata, the cell is almost
circular in outline.

Guard cells measure 35-46 p long and approximately 10-12 p wide. In transverse
section these cells appear noticeably depressed below the surrounding subsidiary cells
(PI. 10, fig. 6). The thick cuticle does not extend downward into the epistomal chamber

36

PALAEONTOLOGY, VOLUME 13

(PI. 10, fig. 6). No hairs or other cuticular appendages are present on the epidermis of
C. felicis.

DISCUSSION

Several anatomical species of cordaite leaves are similar to C. felicis. Of these taxa,
anatomical specimens of C. principalis from the Carboniferous and Permian of Europe,
and C. crassus, known from the Carboniferous of France and North America (Pennsyl-
vanian of Iowa), have been suggested as being closely related if not equivalent to C.
felicis. The present study indicates, however, that although these 3 species are similar
in several important features including leaf thickness, vein frequency, and stomatal
apparatus, C. felicis differs from C. principalis and C. crassus in the following important
features. The maturation pattern of the primary xylem in C. felicis and C. crassus is
mesarch, whereas in C. principalis it is exarch. Complete intervein partitions apparently
run the length of the C. felicis leaf whereas these are infrequent and generally of limited
extent in C. crassus, and are completely absent in C. principalis. In C. felicis a maximum
of 8 rows of stomata are present between the vein and intervein partition, while in C.
crassus only 8 rows are present between 2 veins. A maximum of 5 rows of stomata occur
between hypodermal fibrous masses in C. principalis, with stomata aligned between
adjacent rows; in C. felicis adjacent rows of stomata are staggered. Hypodermal fibrous
masses project far into the mesophyll between the veins only in the thicker areas of the
leaf in C. felicis, but extend from the abaxial surface through one-half of the leaf
regardless of the total thickness in C. crassus. The outer bundle sheath in C. crassus
is 6-7 cells wide on its adaxial or upper surface, narrowing on the sides and abaxial
portion. In C. felicis the sheath is 4—7 cells thick; in C. principalis it consists of 1-3
cell layers.

The petrified foliage forms C. rotundinervis Grand’Eury (1877), C. rhombinervis
Grand’Eury (1877) from the Carboniferous of France are immediately distinguished
from C. felicis by the exarch nature of the primary xylem. In addition, C. rhombinervis
and C. tenuistriatus are characterized by a mesophyll that is differentiated into a distinct
palisade and spongy region, as is C. lingulatus Grand’Eury (1877) from the Carboni-
ferous and Permian of Europe. The occurrence of forms designated as C. loculosus, C.
robustus, and C. wedekindi by Felix (1886), and C. weristeri Leclercq (1927) from petri-
faction material collected from the same stratigraphic level and in some instances
occurring in the same coal ball, as well as a tendency for one species to grade into
another, caused Koopmans (1928) to regard all as synonyms of C. felicis. Benson (1912)

EXPLANATION OF PLATE 11

Figs. 1-7. Cordaites felicis. 1, Cuticle of upper epidermis showing bands of rectangular cells above
fibrous masses with bands of stomata between; C.B. 145F (1) Maceration slide # 18, x 130. 2,
Enlargement of epidermal cells from fig. 1 showing irregular radial wall thickenings; C.B. 145F (1)
Maceration slide # 18, x400. 3, Multiseriate circular bordered pits and scalariform bars of centri-
petal xylem elements; C.B. 145F (1) bot, # 2, x600. 4, Paradermal section just beneath cuticle of
lower epidermis showing primary ribs (arrows) and stomatal rows between; C.B. 145F (1) side #17,
X130. 5, Epidermal cells associated with stomatal bands from upper epidermis; C.B. 145F (1)

Maceration slide # 18, x400. 6, Stoma and subsidiary cells of upper epidermis; C.B. 145F (1)
Maceration slide # 18, x500. 7, Two stomata and shared terminal subsidiary cells from lower
epidermis; C.B. 145F (1) side, # 17, x625.

Palaeontology, Vol. 13

PLATE 11

GOOD and TAYLOR, Pennsylvanian Cordaites leaves

GOOD AND TAYLOR: STRUCTURE OF CORDAITES FELICIS BENSON 37

notes the general similarity of the presumed upper or distal part of C. felicis to C. wede-
kindi, while sections closer to the base more closely resemble material of the C. loculosus
and C. robustus types.

Although the probability exists that several recognized cordaite foliage species
represent different parts of the same leaf our studies with the Kentucky specimens of
C. felicis do not show either a gradual or marked anatomical change taking place
through many centimetres of lamina presumably representing all parts of the leaf. For
example, intervein partitions, a feature used to delimit numerous anatomical species,
were incomplete in only 0-1 % of all of the sections of leaves examined. The consistent
absence of complete partitions in C. weristeri and C. robustus still provides a means of
distinguishing them from C. felicis. Specimens of C. loculosus are described with com-
plete intervein partitions, however, material of this type is readily recognized by the
absence of a bundle sheath. General leaf thickness, extent of bundle sheath, and slender
intervein partitions are features that Benson (1912) used to delimit C. wedekindi from
C. felicis.

In alluding to the ultimate solution of delimiting cordaite foliage through the organic
attachment of leaves to stems, Benson (1912) notes the consistent mutual occurrence
of the cordaitalean seed Mitrospermum compressum and C. felicis foliage. Whereas such
an association can have limited value in studies involving petrifaction material, such a
correlation becomes more meaningful as identical species associations are discovered
and recorded. It is, therefore, of interest that Mitrospermum compressum was reported
and described for the first time in North America (Taylor and Stewart 1964) from the
same petrifaction material that has provided the specimens of C. felicis used in this
study.

Cuticular studies of cordaite foliage by Renault (1879), Wills (1914), Florin (1931),
Reed and Sandoe (1951), and Harms and Leisman (1961) have demonstrated epidermal
patterns similar to the C. felicis type. Patterns that are unlike this type have recently been
reported in cordaitean leaves by Ledran (1958, 1960) for petrified specimens of C.
angulostriatus Grand’Eury (1877) and C. lingulatus. In C. angulostriatus the shape and
orientation of the stomata is not as consistent as it is in species such as C. felicis. More-
over, in C. angulostriatus each pair of guard cells has 4-5 subsidiary cells and the stomata
are aligned in single rows. In C. lingulatus the stomata are randomly arranged, each with
3-8 subsidiary cells. Florin (1931) has shown prominent cuticular papillae associated
with the subsidiary cells of C. lingulatus.

There appear to be at least two general types of cuticular patterns known for cordai-
tean leaves. The pattern demonstrated by C. felicis, C. principalis, C. crassus, C. affinis,
and a number of described but unnamed forms by Renault (1879), Wills (1914), and
Florin (1931), have guard cells and subsidiary cells oriented parallel to the long axis of
the leaf. Cuticular papillae are absent and the stomatal apparatus of all of these forms
are almost indistinguishable from one another.

The epidermal cell pattern characterized by C. angulostriatus and C. lingulatus shows
a consistent irregular orientation of the stomata and a wide range in the number of
subsidiary cells. Cuticular papillae are associated with subsidiary cells of this type.

When these two types of epidermis are considered along with internal structural fea-
tures and the stratigraphic position of the leaves, a potential basis for interpreting the
phylogeny of cordaitean foliage emerges. Taxa with the more regular epidermal cell

38

PALAEONTOLOGY, VOLUME 13

patterns tend to be characterized by prominent hypodermal fibrous masses separating
veins, and are generally found in lower and middle Pennsylvanian age sediments,
Cordaite leaves with less well-developed hypodermal bands between the veins and more
irregular cuticular patterns extend on into Permian age rocks. It is clear that epidermal
features of cordaitean leaves may not only be useful taxonomically, but may provide a
means of comparison between structurally preserved leaves and the large number of
presently meaningless compression species.

It is worth while here to mention the similarity between the irregular pattern of sto-
mata disposition in some cordaite foliage species and the epidermal cell arrangements of
some of the earliest coniferophyte leaves discussed by Florin (1944, 1951). In general,
Lebachia has stomata with 4-10 subsidiary cells, each typically associated with a
cuticular papilla. The orientation of the individual stoma is random within two band-
like regions on each surface of the leaf. Foliage of Ernestiodendron has stomata in single
rows. Each stoma is randomly oriented within the row and has 4-8 subsidiary cells with
papillae. The epidermal cell patterns of Lebachia and Ernestiodendron more closely
resemble the type of cordaite cuticles described by Ledran (1958, 1960) than the type
characterized by Cordaites felicis. In particular the cell patterns of C. angulostriatus and
those of Ernestiodendron foliage are almost identical. It is also interesting to note the
similarity between the arrangement and structure of stomata on the seed scales of
Araucaria cutchensis (Pant and Srivastava 1968), an Upper Jurassic compression from
India, and the arrangement and structure of stomata in C. angulostriatus. A comparison
of epidermal patterns may ultimately provide a clue to the group of Carboniferous
cordaites from which some Permian conifers have evolved.

Acknowledgements. This study was supported by National Science Foundation Grants GB-6834 and
GY-4525. We are grateful to Dr. John M. Pettitt, British Museum (Natural History), for making
Benson’s material of Cordaites felicis available for investigation.

REFERENCES

benson, M. 1912. Cordaites felicis, sp. nov., a cordaitean leaf from the lower coal measures of England.
Ann. Bot. 26, 201-7.

cross, G. l. 1940. Development of the foliage leaves of Taxodium distichum. Am. J. Bot. 27, 471-82.
darrah, w. c. 1940. The fossil flora of Iowa coal balls III: Cordaianthus. Harvard Univ. Bot. Mus.
Leaflets, 8, 1-20.

1941. Studies of American coal balls. Am. J. Sci. 239, 33-53.

esau, k. 1965. Plant anatomy, second edition. John Wiley & Sons, New York. 767 pp.
felix, j. 1886. Untersuchungen liber den inneren Bau Westfalisher Carbonpflanzen. Abhandl. zur
Geol. Spezialkarte von Preussen, 7, 1-73.

florin, r. 1931. Untersuchungen zur Stammesgeschichte der Coniferales und Cordaitales. Kungl.
Svenska Vetenskapsakad. Handl. Ill, 10.

1944. Die Koniferen des Oberkarbons und des Unteren Perms. Palaeontographica, 85, 366-456.

1951. Evolution in Cordaites and Conifers. Acta Horti Bergiani. 15, 285-388.

geinitz, H. B. 1855. Die Versteinerungen der Steinkohlenformation in Sachsen, II. Leipzig.
germer, E. F. 1848. Die Versteinerungen der Steinkohlenformation in Wet tin und Loebejun in Saalkreis,
IV. Loebejun, Halle.

grand’eury, c. 1877. La flore carbonifere du Departement de la Loire et du centre de la France. Mem.
Acad. Sci. Inst. Fr. 24.

harms, v. l. and leisman, g. a. 1961. The anatomy and morphology of certain Cordaites leaves. J.
Paleont. 35, 1041-64.

GOOD AND TAYLOR: STRUCTURE OF CORDAITES FELICIS BENSON 39

hoskins, J. h. and cross, a. t. 1943. Monograph of the Paleozoic cone genus Bowmanites (Spheno-
phyllales). Am. Midi. Nat. 30, 113-63.

huddle, j. w., Lyons, e. j., smith, h. l., and fern, j. c. 1963. Coal reserves of eastern Kentucky.
U.S. Geol. Survey Bull. 1120, 247 pp.

koopmans, r. g. 1928. Researches on the floras of the coal balls from the ‘Finefrau-Nebenband’
horizon in the province of Limburg (The Netherlands). Geol. Bur. Nederland, 1, 1-54.
leclercq, s. 1927. Les vegetaux a structure conservee du houiller Beige. Note I. Feuilles et racines de
cordaitales des coalballs de la couche Bouxharmont. Ann. Soc. Geol. Belgique, 51, 53-66.
ledran, c. 1958. Sur la nervation de quelque feuilles de Cordaites. Bull. Soc. Geol. Fr. 6 serie, 8,
39-43.

1960. Sur les cuticules de Cordaitales. Ibid. 7 serie, 2, 653-6.

moore, r., et al. 1944. Correlation of Pennsylvanian formations of North America. Bull. Geol. Soc.
Am. 55, 657-706.

pant, d. d. and srivastava, g. k. 1968. On the cuticular structure of Araucaria ( Araucarites ) cutchen-
sis (Feistmantel) comb. nov. from the Jabalpur series, India. J. Linn. Soc. (Bot.) 61, 201-6.
prostka, h. 1965. Geology of the Hyden East Quadrangle, Kentucky. U.S. Geol. Survey map GQ-423.
reed, f. d. and sandoe, m. t. 1951. Cordaites affinis : a new species of cordaitean leaf from American
coal fields. Bull. Torrey Bot. Club, 78, 449-57.

Renault, b. 1879. Structure comparee de quelques tiges de la flore carbonifere. Nouv. Archives Mus.
Hist. Nat. Paris, 2, 213-326.

schopf, j. m. 1961. Coal-ball occurrences in eastern Kentucky. Geol. Survey Research (Short papers in
the geologic and hydrologic sciences, 1-146) 95, B228-B230.
scott, d. H. 1924. Extinct Plants and Problems of Evolution. Macmillan & Co., London. 240 pp.
seward, a. c. 1917. Fossil Plants, III. Cambridge University Press, London. 656 pp.

and sahni, B. 1920. Indian Gondwana plants. Mem. Geol. Survey India, 7, 1-41.

stopes, m. c. 1903. On the leaf-structure of Cordaites. New Phytol. 2, 91-8.

taylor, t. n. 1967. On the structure of Calamostachys binneyana from the lower Pennsylvanian of
North America. Am. J. Bot. 54, 298-305.

1969. On the structure of Bowmanites dawsoni from the lower Pennsylvanian of North America.

Palaeontographica, 125 B, 65-72.

■ and stewart, w. n. 1964. The Paleozoic seed Mitrospermum in American coal balls. Ibid.

115 B, 51-8.

unger, f. 1850. Genera et species plantarum fossilium. Vienna. 627 pp.

wills, l. j. 1914. Plant cuticles from the coal measures of Britain. Geol. Mag. n.s. 1, 385-90.

CHARLES W. GOOD
THOMAS N. TAYLOR

Department of Biological Sciences
University of Illinois at Chicago Circle
Chicago, Illinois 60680
U.S.A.

Typescript received 18 January 1969

A DIMORPHIC GONIATITE FROM THE
NAMURIAN OF CHESHIRE

by N. H. TREWIN

Abstract. Eumorphoceras yatesae sp. nov. is described from a high E2a Carboniferous horizon at Croker Hill,
Cheshire. Dimorphs A and B are described under the same specific name since the initial stages of each are
identical and they are both confined to the same horizon. Possible dimorphism in the goniatite genus Eumor-
phoceras is considered.

Many authors have described dimorphism in ammonite genera, for example, Callomon
(1963), Makowski (1962), and Palframan (1966, 1967). In general the dimorphs differ
in size at maturity and the smaller form is usually taken as the male. The development of
special modifications of aperture takes place at maturity — lappets, rostra, and apertral
constrictions being frequently described. The general ornament of the shell is often
different in the two dimorphs, usually after an initial period of development where the
ornament of the two dimorphs is similar.

Dimorphism has been described in the Devonian goniatite genera Manticoceras ,
Tornoceras, and Cheiloceras (Makowski 1962) involving differences in size at maturity.
Demanet (1943) described dimorphism in Gastrioceras species found in association
where one form is characterized by a wide umbilicus and ventrally flattened whorl sec-
tion and the other by a narrower umbilicus and higher whorl section. The form with
the wide umbilicus is interpreted by him as the female, but he gives no indication of
the relative sizes of the forms at maturity. Ramsbottom and Calver (1962) also consider
it possible that dimorphism is shown by species of Gastrioceras from the G. sub-
crenatum and G. listen horizons.

Absolute differences in size at maturity cannot be demonstrated for the dimorphs of
Ewnorphoceras yatesae as the specimens are always crushed. It can be demonstrated that
in each of three marine bands two forms of Eumorphoceras are present with similar
differences in ornamentation and that in the case of the erinense-ferrimontanum pair,
and the yatesae A and B pair, the initial stages of development appear to be identical.

SYSTEMATIC DESCRIPTION

Order ammonoidea Zittel 1825
Suborder goniatitina Hyatt 1884
Superfamily goniatitacea de Haan 1825
Family goniatitidae de Haan 1825
Subfamily girtyoceratinae Wedekind 1918
Genus eumorphoceras Girty 1909

Eumorphoceras yatesae sp. nov.

Plate 12, figs. 1-5

[Palaeontology, Vol. 13, Part 1, 1970, pp. 40-6, pi. 12]

TREWIN: A DIMORPHIC GONIATITE FROM THE NAMURIAN

41

Material. All specimens are crushed in shale and preserved mainly as external moulds. Holotype
E. yatesae dimorph A. LZ 5779. Paratypes dimorph A: LZ 5782; LZ 5783. Paratypes dimorph B
E. yatesae dimorph B. LZ 5780; LZ 5784. Paratypes dimorph indeterminate E. yatesae LZ 5781
LZ 5785-90.

The specimen numbers quoted throughout the text refer to specimens deposited with the Institute
of Geological Sciences, Leeds.

mm.

Umbilical diameter

5-
4-
3-
2-
I -

° Dimorph A
x Dimorph B
® Dimorph indet.

OH 1 1 -r 1 1 1 1 1 1

2 3 4 5 6 7 8 9 IO mm.

Diameter at spiral groove

Text-fig. 1 . The relation between umbilical diameter and spiral groove diameter for Eumorphoceras

yatesae sp. nov.

Description. The crushed nature of the material does not allow an accurate measurement
of the over-all diameter to be made and so diameter measurements have been made at
the spiral groove.

Up to 8 mm. spiral groove diameter, all specimens have similar features (LZ 5781;
PI. 12, fig. 4). Ribs are present on the second whorl where there are about 12 per half
whorl. With increase in diameter ribs become more numerous until there are 17-20 per
half whorl at 7-8 mm. spiral groove diameter. The ribs arise within the umbilicus and are
radial or slightly forwardly directed for the first part of their course over the flanks. At
a point about halfway from the umbilicus to the spiral groove the ribs bend evenly
forward to meet the spiral groove.

At 8 mm. spiral groove diameter the umbilicus is 3 mm. wide and at 4 mm. diameter
it measures 2 mm. The umbilical diameter is difficult to measure in this crushed material,

42 PALAEONTOLOGY, VOLUME 13

but text-fig. 1 illustrates the general relation between umbilical and spiral groove diameter
for the species.

The spiral groove is present at 5 mm. diameter and persists to the largest diameters
seen on all specimens. Constrictions are present on some specimens which appear as
deep grooves between two sharp ribs, they are best seen at the umbilical margin or at
the spiral groove. Constrictions are not invariably present and do not appear to be
regularly spaced. On specimens larger than 8 mm. diameter dimorphs A and B can be
distinguished.

Dimorph A. In this form the ribs begin to die out at 8 mm. diameter and are repre-
sented by umbilical nodes. These are clearly seen on the holotype LZ 5779 (PI. 12, fig. 1)
and paratype LZ 5783 (PI. 12, fig. 2), where nodes are well developed and only growth-
lines are present on the flanks. The spiral groove is still strong and has a subsidiary
groove ventral to it. In the last part of the shell there are 13—14 nodes per half whorl
before the flanks become smooth at about 1 1 mm. diameter.

Dimorph B. Dimorph B is characterized by ribs which persist to at least 11 mm.
diameter but which are weak in comparison with those on the early part of the shell.
The ribs are strongest near the umbilicus (Paratype LZ 5784; PI. 12, fig. 5) but nodes
are not developed. The ribs number about 1 7 per half whorl in the latter part of the shell.
The spiral groove is still strong at 1 1 mm. diameter. These features are all seen on para-
type LZ 5780 (PI. 12, fig. 3).

The measurements of umbilical diameter made on the specimens of Dimorphs A and
B vary considerably and it appears that Dimorph A has the smaller umbilicus, but the
data are insufficient for this to be proved with certainty.

Discussion. This species falls within the original range of Eumorphoceras bisulcatum
Girty (1909), but the redescription of part of Girty’s original E. bisulcatum material
by Elias (1956) as Eumorphoceras girtyi restricts the definition of E. bisulcatum to a
Eumorphoceras with strong ribs present at 11 mm. diameter (9 mm. spiral groove
diameter). The ribs in Girty’s material are clearly sickle-shaped. According to McCaleb
et al. (1964) the ribs on E. bisulcatum die out at an early intermediate stage of 25-30
mm. diameter. Thus E. yatesae is considered distinct from E. bisulcatum in its rib shape
and in the diameter at which the ribs begin to die out. E. yatesae can be clearly dis-
tinguished from the described ‘subspecies’, ‘mutation’, and ‘varieties’ of E. bisulcatum.

EXPLANATION OF PLATE 12

Fig. 1. Eumorphoceras yatesae sp. nov. Dimorph A. Holotype LZ 5779, X 5: ribs reduce to nodes on
umbilical margin at 8 mm. spiral groove diameter. Locality 354, Croker Hill, Cheshire.

Fig. 2. Eumorphoceras yatesae sp. nov. Dimorph A. Paratype LZ 5783, X 5 : ribs reduce to nodes on
umbilical margin at 8 mm. spiral groove diameter. Locality 354, Croker Hill, Cheshire.

Fig. 3. Eumorphoceras yatesae sp. nov. Dimorph B. Paratype LZ 5780, X 5 : ribs persist weakly beyond
8 mm. spiral groove diameter. Locality 354, Croker Hill, Cheshire.

Fig. 4. Eumorphoceras yatesae sp. nov. Dimorph indeterminate. Paratype LZ 578 1 , X 5 : small speci-
men showing numerous ribs. Locality 354, Croker Hill, Cheshire.

Fig. 5. Eumorphoceras yatesae sp. nov. Dimorph B. Paratype LZ 5784, X 5 : ribs persist to about 1 1 mm.
spiral groove diameter. Locality 354, Croker Hill, Cheshire.

Fig. 6. Eumorphoceras sp. LZ 5778, X 5 : small undescribed form from E. bisulcatum grassingtonense
horizon at Croker Hill, Cheshire. (Grid Ref. 93336675, north-west side of gully 630 yd. W. 7° S.
from Dawsons.) This is possibly the ‘A’ dimorph of E. bisulcatum grassingtonense : note reduction
of ribs to nodes on the umbilical margin at an early stage.

Palaeontology, Vol. 13

PLATE 12

TREWIN, Eumorphoceras yatesae

TREWIN: A DIMORPHIC GONIATITE FROM THE NAMURIAN 43

Yates (1962) subspecies E. bisulcatum erinense and E. bisulcatum ferrimontanum differ
from E. yatesae in having ribs that persist to larger diameters, and which are nearer to
the sickle-shaped ribs of E. bisulcatum Girty.

E. bisulcatum grassingtonense Dunham and Stubblefield (1944) differs in having
markedly fewer ribs, a tendency for rib bifurcation and for thickening of ribs in the
mid-flank region.

E. bisulcatum leitrimense Yates (1962) is similar in being of small size, having ribs
that die out early, and possessing constrictions. However it appears from Yates’s figures
to have only 12-13 ribs per half whorl.

The forms described by Schmidt ( 1934) as E. bisulcatum var. varicata and E. bisulcatum
mut. /3 differ markedly from E. yatesae in having fewer ribs. Moreover varicata is
described as having short ribs which do not reach the spiral groove and mut. j3 is
characterized by pairing of the ribs.

E. stubblefieldi Moore (1946) has ribbing that dies at 8 mm. diameter, and also con-
strictions, but the spiral groove does not appear until 8 mm. diameter and the ribs are
not so numerous or as strong as in E. yatesae.

The combination of small size, up to 20 strong ribs per half whorl at 7-8 mm. diameter
and the presence of constrictions immediately distinguishes both these dimorphs from
any described Eumorphoceras. It is considered best to regard these specimens as being
dimorphs of the same species as they are both found in the same horizon, appear to be
confined to that horizon, and have identical initial stages.

Fauna associated with E. yatesae. The only other goniatite specimens present with E.
yatesae include rare fragments of an unidentifiable Cravenoceras and specimens of
Anthracoceras or Dimorphoceras which cannot be distinguished without sutural evidence.
P. corrugata (Etheridge jun.) is abundant and Posidoniella variabilis Hind appears in
the north Staffordshire basin succession for the first time at this level.

Stratigraphic position of the E. yatesae band. The horizon containing E. yatesae occurs
between the main E2a marine band which contains E. bisulcatum ferrimontanum Yates
and E. bisulcatum erinense Yates and E2bl marine band with Cravenoceratoides edalensis
(Bisat) and Cravenoceratoides bisati Hudson. The E. yatesae band is separated from the
main E2a band by a unit of protoquartzitic sandstones and shale-mudstones which is
about 40 m. thick and from the E2bl band by shales and shale-mudstones 7 m. thick.
The marker horizon with Leiopteria longirostris Hind lies about 0-5 m. below E. yatesae
and K-bentonite B4 (Trewin 1968, fig. 2) lies 3-5 m. above E. yatesae in the Pyeclough
section (Loc. 101). At Loc. 355 E. yatesae occurs from 1-T5 m. above L. longirostris.
The E. yatesi horizon is of limited stratigraphic value as it appears to be discontinuous
within the north Staffordshire basin area.

Zonal position of E. yatesae. The horizon with E. yatesae is considered to be highest
E2a faunal band present in the north Staffordshire basin area since its goniatite fauna
is dominated by Eumorphoceras, and Cravenoceratoides is absent. Thus there are three
Eumorphoceras- bearing horizons in the E2a succession of the north Staffordshire basin
area. The lowest contains E. bisulcatum grassingtonense Dunham and Stubblefield, the
middle band contains E. bisulcatum ferrimontanum Yates and E. bisulcatum erinense
Yates, and the highest band E. yatesae sp. nov.

44

PALAEONTOLOGY, VOLUME 13

CORRELATION WITH OTHER AREAS

No other described faunas can be correlated with certainty with the E. yatesae band,
but several records of iE. bisulcatum’ close below Ct. edalensis may represent this horizon.
The Eumorphoceras specimen (Zh 1023) from 368 to 369 ft. in the Alport Derbyshire
borehole (Hudson and Cotton 1943) is too poorly preserved to permit useful comparison
with E. yatesae , but the occurrence of a Cravenoceratoides fragment (Zh 1022) only a foot
above may indicate that this horizon is slightly younger than the E. yatesae band.

The author has examined the exposures in Edale, Derbyshire, but has not found any
Eumorphoceras at this level although a faunal band with Anthracoceras sp. or Dimor-
phoceras sp., Posidoniella variabilis, and Posidonia corrugata is present which probably
correlates with this horizon. The fauna is found in a bank of a small tributary stream
about 12 yards from the junction with the main stream near Loc 112 of Hudson and
Cotton (1945).

Hudson (1944) records E. bisulcatum, Posidonia and Anthracoceras 25 ft. below a band
with Ct. edalensis and C. subplicatum in Coppice Beck, Harrogate, Yorkshire. A Eumor-
phoceras fragment (RM 412) from this locality shows only the spiral groove and
comparison with E. yatesae is not possible, but this fauna must lie very close to the
position of the E. yatesae band.

A Eumorphoceras specimen (RS 1543) described by Evans et al. (1968, p. 80) from the
stream section in which the E. yatesae specimens described here were found appears to
have been obtained from higher in the succession, above the Ct. edalensis band. The
specimen is small and has 30-40 ribs per whorl, and the ribs die out at 7-8 mm. spiral
groove diameter. (The figure of 30 ribs per whorl mentioned on p. 80 of Evans et al.
(1968) is a misprint (W. H. C. Ramsbottom pers. comm.).)

Yates (1962) does not record a Eumorphoceras-btzxmg band equivalent to this band,
thus it is probably absent on Slieve Anierin, Eire.

Localities. Specimens have been obtained from the following localities, all the type material is from
Loc. 354.

Locality no.

101 Pyeclough Brook

201 Blake Brook

354 Croker Hill

Notes

250 yd. south of Bradshaw, Staffordshire. (Grid. Ref. 04656488)

Stream bank exposure upstream of bridge.

450 yd. north of Upper-Hay Corner, Staffordshire. (Grid. Ref. 05726088)
Near base of section exposed at upstream end.

450 yd. north of Dawsons, Cheshire. (Grid. Ref. 92806723)

Shale scar under tree upstream of tributary ditch.

NOTE ON APPARENT DIMORPHISM IN ARNSBERGIAN GONIATITES

The described differences between the dimorphs A and B of E. yatesae are of exactly
the same type as the differences between the subspecies E. bisulcatum erinense Yates and
E. bisulcatum ferrimontanum Yates. Both erinense and ferrimontanum appear to have
identical initial stages of development, but in ferrimontanum the ribs die out at c. 10 mm.
spiral groove diameter to leave umbilical nodes, and in erinense the ribs persist to 1 5 mm.
spiral groove diameter. These features are seen on Yates’s (1962) illustrations of these
subspecies. Comparing with E. yatesae, ferrimontanum is the ‘A’ dimorph and erinense

TREWIN: A DIMORPHIC GONIATITE FROM THE NAMURI AN

45

the ‘B’ dimorph. Both erinense and ferrimontanum occur in the same marine band and
are confined to the base of the band in north Staffordshire. Yates (1962) states that
erinense occurs slightly above ferrimontanum on Slieve Anierin within the same marine
band, but this is not the case in north Staffordshire.

The lowest Arnsbergian marine band in the north Staffordshire basin area is the
Eumorphoceras bisulcatum grassingtonense band. Well-preserved Eumorphoceras speci-
mens are scarce in this band, but apart from individuals which are identical with the
specimen figured by Yates (1962, pi. 52, fig. 3) in which the ribs die out at about 12 mm.
spiral groove diameter, there are also some small undescribed forms in which the ribs
reduce to small plications on the umbilical margin at 6 mm. spiral groove diameter, and
by 9 mm. spiral groove diameter only small nodes are present on the umbilical margin
(see PI. 12, fig. 6). Of these two forms grassingtonense is the ‘B’ dimorph and the small
undescribed form is the ‘A’ dimorph.

Thus in each of the three Eumorphoceras-bQa.rmg horizons of E2a in the north
Staffordshire basin area there exists two forms of Eumorphoceras, and in all three hori-
zons the differences between the two forms are of a very similar kind. While the present
evidence is somewhat inconclusive there appear to be increasing grounds for believing
that in the Carboniferous goniatite genera Eumorphoceras and Gastrioceras dimorphic
species existed.

Acknowledgements. The author wishes to thank Dr. W. H. C. Ramsbottom for critically reading the
manuscript and offering many useful suggestions, and also for the loan of specimens from the Institute
of Geological Sciences collection.

REFERENCES

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21-56.

demanet, f. 1943. Les horizons Marins du Westphalien de la Belgique et leurs Faunes. Mem. Mus.
Hist. nat. Belg. 101, 1-166, pi. 1-9.

dunham, k. c. and Stubblefield, c. j. 1944. The stratigraphy, structure and mineralization of the
Greenhow mining area, Yorkshire. Quart. Jl geol. Soc. Lond. 100, 209-68, pi. 21, 22.
elias, m. k. 1956. Upper Mississippian and Lower Pennsylvanian formations of south-central Okla-
homa. In Petroleum Geology of Southern Oklahoma. Symposium: Amer. Ass. Petrol. Geol. 56-134,
pi. 1-6.

evans, w. b., wilson, A. A., taylor, b. j., and price, d. 1968. Geology of the Country around Maccles-
field, Congleton, Crewe and Middlewich. 2nd ed. Mem. Geol. Surv. Great Britain, 110, x+328 pp.
pi. 1-8.

girty, g. h. 1909. The fauna of the Caney Shale of Oklahoma. Bull. U.S. geol. Surv. 377, 5-106,
pi. 1-13.

Hudson, r. g. s. 1944. The faunal succession in the Ct. nitidus zone in the mid-Pennines. Proc. Leeds
phil. lit. Soc. 4, 233—42.

and cotton, g. 1943. The Namurian of Alport Dale, Derbyshire. Proc. Yorks. Geol. Soc. 25,

142-73.

— 1945. The Carboniferous rocks of the Edale anticline, Derbyshire. Quart. Jl geol. Soc.

Lond. 101, 1-36, pi. 1.

makowski, h. 1962. Problem of sexual dimorphism in ammonites. Palaeont. pol. 12, 1-92.
mccaleb, j. a., quinn, j. h., and furnish, w. m. 1964. Girtyoceratidae in the Southern Midcontinent.
Oklahoma Geol. Surv., Circ. 67, 1-41.

moore, e. w. j. 1946. The Carboniferous goniatite genera Girty ocer as and Eumorphoceras. Proc.
Yorks, geol. Soc. 25, 387-445, pi. 22-7.

46 PALAEONTOLOGY, VOLUME 13

palframan, d. f. b. 1966. Variation and ontogeny of some Oxford Clay ammonites: Taramelliceras
richei (de Loriol) and Creniceras renggeri (Oppel), from Woodham, Buckinghamshire. Palaeontology,
9, 290-311, pi. 48-52.

1967. Variation and ontogeny of some Oxford Clay ammonites: Distichoceras bicost atum

(Stahl) and Horioceras baugieri (D’Orbigny), from England. Ibid. 10, 60-94, pi. 9-13.
ramsbottom, w. h. c. and calver, m. a. 1962. Some marine horizons containing Gastrioceras in North
West Europe. Compte Rendu 4e Congres Strat. et Geol. Carbon. Heerlen 1958. 3, 571-6, pi. 14-15.
schmidt, h. 1934. Cephalopodenfaunen des alteren Namur aus der Umgegend von Arnsberg in West-
falen. Jb. preuss. geol. Landesanst. 54, 440-61.

trewin, n. h. 1968. Potassium bentonites in the Namurian of Staffordshire and Derbyshire. Proc.
Yorks, geol. Soc. 37, 73-91.

yates, p. j. 1962. The palaeontology of the Namurian rocks of Slieve Anierin, Co. Leitrim, Eire.
Palaeontology, 5, 355-443, pi. 51-62.

N. H. TREWIN

Department of Geology and Mineralogy
Marischal College
Aberdeen, AB9 IAS

Final typescript received 13 June 1969

A NEW ORIONASTRAEA (RUGOSA) FROM THE
LOWER CARBONIFEROUS OF NORTHERN
ENGLAND

by M. KATO and M. mitchell

Abstract. Orionastraea magna sp. nov. is described from the Orionastraea Band, Upper Dibunophyllum (D2)
Zone, near Settle, Yorkshire, and the genus is briefly discussed.

Orionastraea was erected by Smith (1916, p. 3) for Carboniferous corals previously
assigned to the Devonian genus Phillipsastraea d’Orbigny. The genus has since been
broadly interpreted to include many divergent stocks. Some of the Upper Carboniferous
and Lower Permian forms are closely related to the Protowentzelella Porfiriev-SYy/a.s'-
traea Lonsdale group, whereas the true Orionastraea is believed to be phylogenetically
connected with the massive forms of Lithostrotion Fleming.

SYSTEMATIC DESCRIPTION

Class anthozoa Ehrenberg 1 834
Order rugosa Milne Edwards and Elaime 1850
Family lithostrotionidae d’Orbigny 1851
Genus orionastraea Smith 1916

1916 Orionastraea Smith, p. 3.

1917 Orionastraea ; Smith, p. 294.

1926 Orionastraea ; Hudson, p. 145.

1929 Orionastraea-, Hudson, p. 441.

1934 Orionastraea-, Hill, p. 90.

non 1936 Orionastraea-, Dobrolyubova, p. 17.

1940 Orionastraea-, Hill, p. 187.

non 1941 Orionastraea-, Soshkina, Dobrolyubova and Porfiriev, p. 151.

1950 Orionastraea-, Wang, p. 222 (pars).

1952 Orionastraea-, Lecompte, p. 473.

1956 Orionastraea ; Hill, p. F283.

1958 Orionastraea-, Dobrolyubova, p. 199.

1964 Orionastraea-, Yoh and Wu, p. 102.

1967 Orionastraea', Ivanovsky, p. 33.

Type species (selected by Smith 1917, p. 295). Sarcinula phillipsii McCoy 1849, p. 125, from the Carboni-
ferous Limestone (D2), of Corwen, Merionethshire, Wales.

Diagnosis. Astreoid, thamnasterioid or aphroid Lithostrotionidae; columella weakly
developed or absent; septa withdrawn from axis and in some from periphery also, when
dissepiments become lonsdaleoid.

Distribution. The genus is known from the upper part of the Visean of Australia, China,
Russian Platform, and Britain. Some of the Asiatic and Australian forms may be slightly

[Palaeontology, Vol. 13, Part 1, 1970, pp. 47-51, pi. 13.]

48

PALAEONTOLOGY, VOLUME 13

older than those from Europe, possibly due to difference of origin of species within the
genus. Bassler (1950, p. 247) lists ‘ Orionastraea phillipsi?' from the Permian of Chitral
region, W. Pakistan, and Dobrolyubova (1958, p. 201) also gives the genus as ranging
into the Permian. These Permian records are considered to be erroneous and should be
referred either to Lonsdaleiastraea Gerth or Wentzelellites Wu of the Waagenophyllidae
(Minato and Kato 1965). The record of the genus in Japan (Hayasaka 1932, p. 273) is
doubtful and the form may belong to Pseudopavona Yabe, Sugiyama, and Eguchi 1943.

Remarks. The following nominal species are referable to Orionastraea, although not all
are regarded as valid : Erismolithus tubiporites? ( radiatus ) Martin 1 809 ; Sarcinula tuberosa,
placenta and phillipsii McCoy 1849; Lithostrotion ensifer Milne Edwards and Haime
1851; Phillipsastraea clissiophylloides [jt'c], clissiophylloides stellata and fasciculata
Thomson 1898; Lithostrotion? columnare R. Etheridge jun. 1900; Orionastraea indivisa
Hudson 1926; O. ensifer matura, edmondsi, edmondsi laciniosa, prerete, rete, garwoodi,
garwoodi sera and garwoodi pristina Hudson 1929; O. lonsdaleoides Hill 1934; O.
kurakovensis, rareseptata and heteroseptata Dobrolyubova 1958; O. huaitoutalaensis,
minor and gigantea Lo 1962; Arachnastraea minor Wu 1964; and Lithostrotion parvi-
columnare and O. columellaris Pickett 1966.

Orionastraea is considered to be restricted to the Lower Carboniferous and to be
phylogenetically connected with the massive forms of Lithostrotion. The Upper Carboni-
ferous and Permian species from the boreal province which have been referred to
Orionastraea have rudimentary walls, ill-defined minor septa, lack columella and have
thin skeletal elements, and are related to the Protowentzelella-Stylastraea lineage. The
suggested genera for the following species are given in brackets :

Columnaria solida Stuckenberg 1895, non Ludwig 1862 (‘ Uralastraea Fomitchev); C.
zitteli Stuckenberg 1895 (‘ Uralastraea ’); C. toulai Stuckenberg 1895 ( Stylastraea );
Protolonsdaleiastraea atbassarica Gorsky 1832 ( Protolonsdaleiastraea Gorsky); Oriona-
straea asiatica Lee and Yu 1934 {Arachnastraea Yabe and Hayasaka); O. campo-
phylloides, Columnaria stuckenbergi Gerasimov (MS), O. breviseptata, O. breviseptata
major Dobrolyubova 1936; and O. hudsoni Wilson and Langenheim 1962 (all ‘ Uralas -
traea').

‘‘Uralastraea’ was proposed by Fomitchev (1953) for Orionastraea of Upper Carboni-
ferous and Lower Permian age but no type species was designated and the genus is a
nomen nudum (Hill 1957, p. 51).

EXPLANATION OF PLATE 13

Figs. 1-5. Orionastraea magna sp. nov. X 1-5. Orionastraea Band, Upper Dibunophyllum (D2) Zone,
low escarpment, | mile NE. of Brunton House, | mile S. of Feizor, which is 3 miles NW. of Settle,
Yorkshire. 1, L.S. slide PF 3387 of paratype GSM 65803. 2-5, Sections of holotype, GSM 65802;
2, L.S. slide PL 309; 3-5, T.S. slides PL 310, 312-13.

Figs. 6, 7. Orionastraea ensifer (Milne Edwards and Haime). 6, x 3 ; 7, x 2. Limestone band of Round
Point, Upper Cromhall Sandstone, Upper Dibunophyllum (D2) Zone, Clifton side of Avon Gorge,
Bristol, Gloucestershire. Sections of topotype; 6, T.S. UHR 18931a; 7, L.S. UHR 189316.

Figs. 8, 9. Orionastraea phillipsii (McCoy). X 2. Upper Dibunophyllum (D2) Zone, Hafod-y-Calch,
Corwen, Merionethshire. Sections of topotype; 8, T.S. UHR 18932; 9, L.S. UHR 18934.

Figs. 6-9 are for comparison. Note the presence of ‘annular growth’ in figs. 1, 2, 7, and 9.

Palaeontology, Vol. 13

PLATE 13

KATO and MITCHELL, Orionastraea

KATO AND MITCHELL: A NEW ORIONASTRAEA (RUGOSA)

49

Orionastraea magna sp. nov.

Plate 13, figs. 1-5

1924 Orionastraea phillipsi, exceptionally large variety; Garwood and Goodyear, pp. 219, 227,
232 (in text only).

cf. 1958 Orionastraea phillipsi (McCoy); Dobrolyubova, p. 201, pi. 34, fig. 2; pi. 35.

Name. Refers to large size of tabularia.

Holotype. GSM 65802, from the Orionastraea Band, Upper Dibunophyllum (D2) Zone, low escarpment,
£ mile NE. of Brunton House, £ mile S. of Feizor, which is 3 miles NW. of Settle, Yorkshire.

Paratypes. GSM 65800-1, 65803, horizon and locality as for holotype; GSM 66699, 66700, 66703-6,
from Orionastraea Band, Low South Bank, south side of Stockdale Beck, opposite Stockdale Farm,
2 miles E. of Settle; SME 13857, from Orionastraea Band, right bank of Cow Gill, i mile N. of New
Houses, f mile SW. of Bordley, which is 1\ miles E. of Settle. All the GSM material is in the
Garwood Collection.

Diagnosis. Corallum platy, mainly thamnasterioid, with tabularia exceptionally large,
4-5 mm. in diameter. Skeletal elements notably thin. Major septa 15. Columella absent.

Description. External characters. Corallum is compound, large, flat, expanded and platy.
The size of the corallum is not known, only broken specimens being preserved. The
largest fragments have an area of 129 x 91 mm. (GSM 66699) and a thickness of at least
44 mm. (GSM 65800-1).

Numerous fine concentric striations or wrinkles are present on the epitheca of the
corallum’s lower surface. These wrinkles indicate rapid lateral expansion of the coral.
The upper surface is comparatively smooth.

Internal characters, (a) In transverse section. The corallum is mainly thamnasterioid,
and sometimes aphroid. All internal skeletal elements are very thin.

The tabularia are round or oval and weakly differentiated from the dissepimentaria by
somewhat crowded concentric vertically inclined inner margins of dissepiments. The
diameter of tabularia is 4-5 mm., a little less in SME 13857, and their centres are 15-20
mm. apart.

Septa are very thin, but may be finely trabecular. There are 14 or 15, rarely 17,
slightly flexuous major septa. They fall short of the centre of the tabularia which are
open due to the lack of axial structure. Septa are confluent with corresponding ones of
neighbouring corallites. The columella is absent in specimens from Feizor. A few major
septa extend to the centre of tabularia in SME 13857 and also in specimens from Low
South Bank but without thickening into a columella. Minor septa are of variable length,
rarely extending to the tabularia and may sometimes not be developed.

The dissepimentaria which form the greater part of the corallum consist of confluent
septa and some large irregular dissepiments that prevent the thamnasterioid elongation
of septa. The aphroid tendency is marked in SME 13857.

(b) In longitudinal section. The tabularia are clearly differentiated from the dissepi-
mentaria. The tabulae, 25 in 10 mm., are flat or slightly dome shaped and are incomplete.
No columella is present. The dissepimentaria are composed of numerous fine, horizon-
tally elongate dissepiments and are often penetrated by the cut ends of the septa. Weak
‘periodicity’ may be discernible with slight crowding of dissepiments occurring three
times in 10 mm. (PI. 13, fig. 2).

C 7173

E

50

PALAEONTOLOGY, VOLUME 13

Remarks. The present form was listed by Garwood and Goodyear (1924, pp. 219, 227,
232) as O. phillipsi, exceptionally large variety, and the label on GSM 65801 reads
‘ Orionastraea phillipsi (McCoy), this specimen has been identified by Mr. S. Smith’.
However, McCoy’s species has a tabularium diameter of about 2-5 mm. and the large
size of the tabularia of O. magna makes it easily recognizable. It is probable that O.
phillipsii is not present at Settle (Hudson 1929, p. 452).

Hudson (1929, pp. 451-2) lists O. indivisa, prerete and rete from the Orionastraea Band
of the Settle district but the large size and thamnasterioid corallites distinguish O. magna
from these species.

In general appearance, the form resembles Orionastraea phillipsi of late D2 age
described and figured by Dobrolyubova (1958, p. 201; pi. 34, fig. 2; pi. 35) from the
Russian Platform. The Russian form, however, has slightly smaller tabularia in
comparison with O. magna, a less pronounced aphroid tendency, and also a weakly
developed columella. Dobrolyubova’s phillipsi may stand between phillipsii McCoy
and garwoodi Hudson, although it has much larger tabularia.

Distribution. O. magna is known only from the Orionastraea Band (D2 Zone) of the
Settle district. The conflicting views on the correlation of the Orionastraea Band with the
Hardraw or Simonstone Limestones of Wensleydale are discussed by Garwood and
Goodyear (1924, pp. 205-6). Hicks (1959, pp. 33-7) re-examined the evidence in the
Ingleborough area and confirmed the view of the Geological Survey (Dakyns and others
1890, pp. 25-8) that this horizon at Settle is the equivalent of the Hardraw Limestone.

Acknowledgements. The authors acknowledge the assistance of the following: the late Dr. H. Dighton
Thomas, British Museum (Natural History), Dr. F. W. Anderson, Institute of Geological Sciences
(GSM), Professor M. Minato, Hokkaido University (UHR), and Dr. C. L. Forbes, Sedgwick Museum,
Cambridge (SME). Initials in brackets are prefixes of specimens in the respective museums. Mr.
Mitchell publishes with the permission of the Director of the Institute of Geological Sciences.

REFERENCES

bassler, r. s. 1950. Faunal lists and description of Palaeozoic corals. Mem. geol. Soc. Am. 44, 1-315,
pi. 1-20.

dakyns, j. k., tiddeman, r. h., gunn, w., and strahan, a. 1890. The geology of the country around
Ingleborough, with parts of Wensleydale and Wharfedale. Mem. geol. Surv. U.K.

Dobrolyubova, t. a. 1936. The corals of the Upper Carboniferous of the western slope of the Middle
Urals and their stratigraphic importance. Trudy vses. nauchno-issled. Inst, miner. Syr'ya. 103, 1-68,
pi. 1-37 (in Russian).

1958. Lower Carboniferous colonial tetracorals of the Russian Platform. Trudy paleont. Inst.

70, 1-224, pi. 1-38 (in Russian).

fomitchev, v. d. 1953. Rugose corals and stratigraphy of Middle-Upper Carboniferous and Permian
deposits of the Donetz Basin. Trudy vses. nauchno-issled. geol. Inst, (vsegei), 1-622, pi. 1-44 (in
Russian).

garwood, e. j. and Goodyear, e. 1924. The Lower Carboniferous succession in the Settle district.
Q. Jl geol. Soc. Lond. 80, 184-273, pi. 10-21.

hayasaka, i. 1932. An astraeiform coral from Central Japan. Geol. Mag. 69, 273-5.

hicks, p. F. 1959. The Yoredale rocks of Ingleborough, Yorkshire. Proc. Yorks, geol. Soc. 32, 31-43.

hill, d. 1934. The Lower Carboniferous corals of Australia. Proc. R. Soc. Qd. 45 (12), 63-115, pi. 7-11.

1940. A monograph on the Carboniferous Rugose Corals of Scotland. Palaeontogr. Soc. [Monogr.J

(3), 115-204, pi. 6-11.

KATO AND MITCHELL: A NEW ORIONASTRAEA (RUGOSA) 51

hill, D. 1956. Rugosa: In Treatise on invertebrate paleontology (ed. R. c. moore). Part F, Coelenterata,
233-324, Univ. Kansas Press and Geol. Soc. Am.

1957. The sequence and distribution of Upper Palaeozoic coral faunas. Aust. J. Sci. 19 (3a),

42-60.

Hudson, R. G. s. 1926. On the Lower Carboniferous corals; Orionastraea indivisa, sp. n., and Thysano-
phyllum praedictum, sp. n. Ann. Mag. nat. Hist. (Ser. 9), 18, 144-51, pi. 8.

1929. On the Lower Carboniferous corals — Orionastraea and its distribution in the north of

England. Proc. Leeds phil. Lit. Soc. (Sci. Sect.), 1 (9), 440-57, pi. 1-4.

Ivanovsky, A. B. 1967. Etude de Lower Carboniferous Rugosa. 92 pp., 22 pi. Moscow. Nauka (Akad.
Nauk SSSR, Sib. Otd. Inst. Geol. Geofiz.) (in Russian).

lecompte, m. 1952. I. Madreporaires Palezoiques: In Traite de Paleontologie (ed. J. Piveteau), Part 1,
419-538. Paris.

mccoy, f. 1849. On some new genera and species of Palaeozoic corals and foraminifera. Ann. Mag.
nat. Hist. (Ser. 2), 3, 1-20, 1 19-36.

minato, m. and kato, M. 1965. Waagenophyllidae. J. Fac. Sci. Hokkaido Univ. (Ser. 4), 12 (3-4),
i-xiii, 1-241, pi. 1-20.

smith, s. 1916. Aulina rotiformis, gen. et sp. nov., Phillipsastraea hennahi (Lonsdale), and the genus
Orionastraea. Abstr. Proc. geol. Soc. Lond. No. 995, 2-5.

1917. Aulina rotiformis, gen. et sp. nov., Phillipsastraea hennahi (Lonsdale), and Orionastraea,

gen. nov. Q. Jl geol. Soc. Lond. 72, 280-307, pi. 12-14.

soshkina, e. d., Dobrolyubova, t. a., and porfiriev, g. 1941. The Permian rugose corals of the Euro-
pean part of the USSR. Paleontologiya SSSR. 5 (3) (1), 1-304, pi. 1-63.

wang, h. c. 1950. A revision of the zoantharia rugosa in the light of their minute skeletal structures.
Phil. Trans. R. Soc. (Ser. B), (611) 234, 175-246, pi. 4-9.

yabe, h., sugiyama, t., and eguchi, m. 1943. A new hexacoral-like Carboniferous coral (preliminary
note). J. geol. Soc. Japan, 50 (600), 242-5.

yoh, s. s. and wu, w. s. 1964. Fossil corals ( Tetracorals ). Science Press, Peking, 234 pp., 5 pi. (in
Chinese).

M. KATO

Department of Geology and Mineralogy
Hokkaido University
Japan

M. MITCHELL

Institute of Geological Sciences
Ring Road Halton

Typescript received 17 March 1969 Leeds, LS15 8TQ

VARIATION IN THE VISEAN CORAL CANINIA
BENBURBENSIS FROM NORTH-WEST IRELAND

by o. A. DIXON

Abstract. Caninia benburbensis Lewis occurs in abundance in upper Visean marine limestones and shales in
north-western Ireland. Study of a single assemblage reveals a range of variation which expands Lewis’s concept
of the species. The morphological affinity of certain variants to C. cylindrica (Scouler) strongly suggests that this
Tournaisian or lower Visean species is ancestral to C. benburbensis. The morphological mode clearly distin-
guishes this species from all earlier caniniid populations.

Certain Lower Carboniferous formations in north-western Ireland contain large,
caniniid corals in a profusion that has inspired repeated comment by geologists for more
than a century. The coral-rich strata are magnificently exposed at several localities
along the coast of County Sligo and have been recognized at inland exposures in several
areas of Counties Sligo, Leitrim, and Roscommon. Hubbard (1966, p. 253) summarized
the important coastal exposures and, supported by Hubbard and Sheridan (1965, pp.
193-4), strongly substantiated the idea that many of the important caniniid-rich beds
in the region are synchronous and of late Visean age.

However, large caniniid corals occur throughout the Lower Carboniferous in north-
western Ireland (generally more than 1150 m. thick) and elsewhere in the British Isles.
Attempts in the past to utilize the caniniids for stratigraphical purposes have been
inconclusive, probably due in part to misinterpretations of local stratigraphy and in
part to intraspecific variation, which impedes the precise identification of isolated
specimens. In an attempt to define the limits of variation within a single assemblage, a
collection from one of the best-known localities, Streedagh Point in Co. Sligo, was
studied.

A narrow strip of gently dipping limestones and shales is exposed along the sea coast at
Streedagh Point (text-fig. 1). The strata are cut by several, small, vertical faults with
displacements up to 6-5 m. The faults are made obvious by offset of beds containing
rich accumulations of species of the compound coral Lithostrotion — useful marker beds
for stratigraphical control within the area. The caniniid assemblage was collected syste-
matically through the sequence represented by the generalized stratigraphical column
in text-fig. 2. All but six specimens came from richly fossiliferous beds between 18 and
22-6 m. More extensive collecting was limited, as many of the corals are intractably set
in thick and resistant limestone beds.

The fossils generally are well preserved, although it is common to find the epitheca
and a thin layer of the adjacent rock silicified, while the remainder of the fossil is calcitic.
In addition, some specimens in outcrop are missing parts of the epitheca and dis-
sepimentarium. Where some of the matrix still adheres to the fossil, it is possible to
demonstrate in many instances that these parts of the skeleton were removed by abrasion
before final burial in the sediment.

The collected specimens clearly are not contemporaneous but represent several
successive palaeobiological populations. Initial attempts to attribute observed morpho-

[Palaeor.tology, Vol. 13, Part 1, 1970, pp. 52-63.]

DIXON: VARIATION IN CANINIA

53

logical variations to changes of facies or to phylogenetic change were unsuccessful, and
consequently the specimens were grouped and studied as a single population. The areal
distribution of the assemblage is sufficiently limited that each included population may

text-fig. 1 . Streedagh Point, north-western Ireland. Hachured open circles mark the principal
collecting localities. Base map courtesy of the Ordnance Survey, Phoenix Park, Dublin.

be assumed to have experienced free panmixis. The profusion of caniniids in limestones
and shales throughout this limited succession suggests, too, that the area was con-
tinually populated, and favours the treatment of the assemblage as a unit having a very
restricted time range within the entire caniniid lineage.

Foraminiferan evidence places the rocks at Streedagh Point in the lower Dx subzone

54

PALAEONTOLOGY, VOLUME 13

text-fig. 2. Diagrammatic section representing
the top 13 m. of strata exposed on Streedagh
Point. The column incorporates (and extends
about 3 m. below) the ‘coral limestone horizon’
of Hubbard (1966, fig. 11).

of late Visean age (Oldroyd 1965, p. 195),
and specimens of Dibunophyllum found with
the caniniids support this. The suggested
correlation is with the Benbulben Shale-
Glencar Limestone transition (Hubbard
1966, pp. 267-8; Oswald 1955, pp. 175-6).

SYSTEMATIC DESCRIPTION

Superfamily zaphrenticae Milne-Edwards
and Haime 1850

Family cyathopsidae Dybowski 1873
Genus caninia Michelin 1840

Caninia benburbensis Lewis
Text-figs. 3-11

1925 Caninia cf. samsonensis Salee; Lewis,
in L. B. Smyth, pp. 145-6.

1927 Caninia benburbensis Lewis, pp. 378-
80, pi. 16, figs. 5-6; pi. 17, figs. 1-4.

1930 Caninia benburbensis Lewis; Lewis,
p. 267, pi. 20, figs. 2 a-c.

1939 Caninia benburbensis Lewis; Hill,

p. 112.

Material. Adult portions of 149 coralla, the majority
lacking juvenile apical portions.

Diagnosis. Large solitary rugosans. Diameter
of tabularium 28-46 mm. Major septa
commonly number 56-78, extend well into
tabularium, mostly continuous extrathecally,
may be sinuous and split along axial planes
to various extents ; transition to a few forms
with septal crests on dissepiments. Minor
septa commonly semi-continuous extra-
thecally (continuous near theca), few pro-
ject intrathecally; transition to a few forms
lacking minor septa and a few with many
minor septa projecting intrathecally. Dissepi-
ments mainly concentric or herringboned;
transition to a few forms with predominantly
lonsdaleoid dissepiments. Large, well-defined
cardinal fossula.

Description. The specimens are large, solitary
rugosans, mainly 50-70 mm. in diameter
(maximum more than 80 mm.), and as much
as 0-9 m. long. The corallum maybe straight,

DIXON: VARIATION IN CANINIA

55

uniformly curved, sharply geniculated (one or more times), or developed in a loose
spiral. In the initial conical stage, the corallum expands at angles between 1 3 and 25°.
The adult corallum may continue to increase in diameter very gradually, may maintain
a fairly uniform diameter (except for rugae), or may be marked by constrictions of
varying magnitude.

The coral polyps rested in a deep, beaker-shaped calice, the vertical inner wall of
which is formed by the theca, or boundary between the dissepimentarium and tabularium
(cf. text-fig. 3 b). The diameter of the fully developed tabularium may range from 28
to 46 mm. However, in an adult corallum, this diameter remains fairly constant (varia-
tions of 1 or 2 mm.) despite marked constrictions of the dissepimentarium. The con-
strictions were produced when the polyp contracted inward from the inclined lip of
the calice, interrupting the formation of dissepimental tissue, but not of intrathecal
skeletal elements.

The number of major septa is commonly 56 to 78, but up to 82 may be present. The
number of septa remains nearly constant in the adult stage of a corallum. The septa
form continuous, blade-like, vertical partitions intrathecally, but vary in their con-
tinuity extrathecally. Where the septa are continuous extrathecally, the dissepiments
are of simple or herringbone type ; where the septa are discontinuous, the dissepiments
are larger and lonsdaleoid. Minor septa may be semi-continuous extrathecally, or
poorly developed (represented only by isolated septal crests on the dissepiments), or
absent. Only in a few individuals do the minor septa project intrathecally.

During ontogeny, the polyp secreted and rested on a succession of medially flattened
(or very slightly depressed) tabulae, which are sharply curved down at the margins.
A rhythmic arrangement of closely spaced incomplete tabulae and more widely spaced
complete tabulae is discernible in many specimens. The tabulae are deeply depressed in
the cardinal fossula, into which projects a short cardinal septum.

The skeletal elements within the tabularium (most commonly the septa in the cardinal
quadrants) show varied stereoplasmic thickening. In some individuals, this affects the
septa and tabulae in all quadrants, but the development is not consistent during onto-
geny. Juvenile portions tend to show more thickening than adults (compare Salee 1910,
pi. 3, fig. 1 b-f), and in adults, the skeletal structures are usually thinner in areas of
constrictions and geniculations.

Variation. It becomes evident from detailed examination of the coral morphology that
certain biocharacters were markedly affected by environmental conditions. The curves
and geniculations which the coralla show have been attributed to instability of the
bottom sediments in which the corals rested (Hubbard, in lift.). Periodic constrictions of
the epitheca in some instances are associated with geniculations and may have a related
cause. The groups of widely spaced tabulae correspond in age to constrictions of the
dissepimental zone, and Ma (1937, p. 9) related such changes in growth form to seasonal
temperature variations. Clearly, the dependence on environment of features such as
total diameter, geniculations, spacing of tabulae, and intrathecal stereoplasmic thicken-
ing, renders them of little use in classification. Other biocharacters apparently remained
unchanged during what evidently were crises in the ontogeny of individuals. The most
significant of these are the intrathecal diameter, the number of septa, and certain septal
characteristics, such as extrathecal continuity. Closely related to continuity of the septa

56 PALAEONTOLOGY, VOLUME 13

was the nature of the dissepiments, and these apparently were fairly consistent in form
throughout ontogeny.

The Streedagh assemblage comprises a wide group of variants, some recognized
before (Lewis 1927, p. 380) and others (not distinguished by Lewis) which significantly
expand his concept of the species. The main variations are summarized below. About
10 % of the studied assemblage were not classified because of poor or incomplete
preservation. All figured specimens bear catalogue numbers of the Hunterian Museum,
University of Glasgow.

Form A (Specimen C. 7471a-e). Individuals included in this group are few in number
(less than 5% of the Streedagh assemblage). They characteristically possess a pre-
dominantly lonsdaleoid dissepimentarium and consequently markedly discontinuous
septa extrathecally (text-fig. 3 a and b). However, the minor septa are commonly as
poorly developed as in more typical examples of C. benburbensis. The average intra-
thecal diameter and number of septa are both less than for the remainder of the
assemblage (text-figs. 12 and 13) but the number of specimens measured may not be
representative.

Form B (Specimens C. 7474a-f and C. 7475a-c). About 10 % of the assemblage are
closely similar to the holotype of C. benburbensis (Lewis 1927, p. 380, pi. 17, figs. 1 a-b)
and show clearly all the diagnostic features (text-fig. 7). The major septa are mostly
continuous extrathecally. Minor septa are well developed near the theca but are reduced
to septal crests on the outer dissepiments, and usually few of these septa project intra-
thecally. The dissepiments are of concentric or herringbone type, and show an irregular
spacing, generally quite closely crowded near the theca.

In a few individuals otherwise identical, many of the minor septa project 1-2 mm. into
the tabularium. Another morphological variation is shown by several consistently
smaller individuals (text-fig. 6a and b) with finer skeletal elements (although they have
the same range in numbers of septa as larger forms).

Form C (Specimen C. 7477a-e). About 10 % of the assemblage lack minor septa, but
are otherwise similar to Form B in having more or less continuous major septa and
concentric or herringboned dissepiments (text-fig. 9 a and b).

Form D (Specimens C. 7478a-l and C. 7479a-e). About 10 % of the assemblage can be
referred to this distinctive form. Specimens are generally of large size, and usually the
major septa are split along their axial planes and contorted in the dissepimentarium
(text-fig. 10). The dissepiments commonly have lost their concentric or herringbone
aspect and appear as sinuous or angulated plates between the septa. In a few otherwise
similar forms (text-fig. 11a and b), the major septa are split less commonly. The skeletal
distortions are not a result of geronticism as they are evident in more juvenile stages
of the few complete coralla studied.

Measurements of number of septa and adult intrathecal diameter fall within the range
of variation of the assemblage, but both measurements average consistently greater than
the assemblage average (text-figs. 12 and 13).

Transitional forms (Specimens C. 7472a-c, C. 7473 and C. 7476a-e). The complete
artificiality of separating the assemblage into distinct morphological types is obvious
from examination of the remaining specimens. Approximately 25 % of the total may be
described as morphologically transitional between Forms A and B, i.e. showing a
skeletal development intermediate between those with lonsdaleoid dissepiments and

DIXON: VARIATION IN CANINIA

57

text-figs. 3-6. Caninia benburbensis. Figured specimens bear catalogue numbers of the Hunterian
Museum, University of Glasgow. All are at natural size. 3 a, b. Form A. C. 7471b, C. 747 Id. Trans-
verse and longitudinal sections. Epitheca complete but partly obscured by silicification. 4, 5. Inter-
mediate forms A-B. C. 7472b, C. 7473. Transverse sections. 6a, b. Form B. C. 7474b, C. 7474d.
Transverse and longitudinal sections. Specimens represented by text-figs. 4-6 all show the effects of
penecontemporaneous abrasion.

58

PALAEONTOLOGY, VOLUME 13

text-figs. 7-10. Caninia benburbensis. 7. Form B. C. 7475b. Transverse section. Epitheca mostly
obscured by silicification. 8a, b. Intermediate form B-C. C. 7476b, C. 7476d. Transverse and longi-
tudinal sections. 9 a, b. Form C. C. 7477d, C. 7477b. Transverse and longitudinal sections. Specimens
represented by text-figs. 8 and 9 both show the effects of penecontemporaneous abrasion. 10. Form D.
C. 7478i. Transverse section. Dissepimentarium partly abraded. Silicified epitheca approximately at

dashed line.

DIXON: VARIATION IN CANINIA

59

septal crests, and those with concentric dissepiments and fairly continuous major septa.
In this group, the minor septa show varied development — virtually absent in some
(text-fig. 4) and well developed in others (text-fig. 5).

text-fig. 11a, b. Caninia benburbensis. Form D. C. 7479d. C. 7479b. Transverse and longitudinal
sections. Deep penecontemporaneous abrasion on counter-cardinal surface.

Approximately 30 % of the assemblage are individuals morphologically intermediate
between Forms B and C (text-fig. 8 a and b ). A series of individuals may be recognized
in which the minor septa gradually diminish and ultimately disappear (as in Form C).
Among these are specimens showing progressively finer skeletal elements, and generally
smaller size (as some of Form B).

Similarly, Form D cannot be separated distinctly from the remainder of the assem-
blage. Characters such as bifurcating major septa and irregular dissepiments can be seen
(although much less prominently) in various specimens which have been included in the
preceding Forms (e.g. text-fig. 7).

Remarks. The variations evident in the assemblage are most reasonably regarded as
variations within a single species. Any or all of the variants may be found on a single
bedding plane within the section, and there are no significant differences in the vertical
distribution of the various forms. The identification of complete intermediate series
among the recognized forms makes any systematic division of little practical value.

Lewis (1927, p. 380) concluded that the ancestry of C. benburbensis may be found
among earlier forms of C. cylindrica (Scouler). The latter has been reported in several
nearby areas in rocks of early Visean age (Caldwell 1959, p. 174; George and Oswald
1957, p. 173; Simpson 1955, p. 399), and this has been confirmed by personal examina-
tion of a complete Visean sequence in the Ballymote syncline south of Sligo. In this
sequence, C. cylindrica is quite common in rocks of Seminulan and pre-Seminulan age,

60

PALAEONTOLOGY, VOLUME 13

35

text-figs. 12-13. Frequency curves of Caninia benburbensis. Vertical and horizontal ruling represents
the frequency of Form A and Form D, respectively.

and C. benburbensis is found in rocks of late Seminulan age but most commonly in those
of the Dibunophyllum Zone. The essential characters which have been used to distinguish
the two species are as follows :

Caninia cylindrica

1. Tooth-like septal crests on the dissepiments (no continuous septa outside the theca).

2. Minor septa projecting about 2 mm. intrathecally.

3. Large and irregular interdissepimental spaces becoming smaller inwards and formed
by lonsdaleoid dissepiments.

DIXON: VARIATION IN CANINIA

61

Caninia benburbensis

1. Major septa predominantly continuous extrathecally and sinuous.

2. Minor septa discontinuous for one-half to two-thirds of the extrathecal distance (do
not typically project intrathecally).

3. Interseptal spaces with concentric or herringbone dissepiments.

text-fig. 14. Scatter diagram of number of septa-intrathecal diameter of Caninia benburbensis. Crosses
represent individuals of Form A; closed circles, Form D; small open circles, the remainder of the
population. The reduced major axis for the transitional group A-B coincides with that for the total
population (T). The total population mean is marked by the large double circle; others by large single

circles.

Of significance is the presence within the Streedagh assemblage of a few specimens
(Form A) with certain morphological features in common with C. cylindrica (compare
the ‘transitional forms’ of Lewis 1927, p. 380, pi. 16, fig. 6; pi. 17, fig. 4). Statistical
analysis of two readily measured parameters, number of septa and intrathecal diameter,
indicate that these forms are slightly smaller and have fewer septa than the bulk of the
assemblage (text-figs. 12, 13, and 14). Although the specimens may be too few to be
representative, they are similar in dimensions to C. cylindrica from Tournai (Salee 1910,
p. 31, pi. 2-5).

Perhaps also significant are the specimens which Salee (1910, pp. 37-9) described as

62

PALAEONTOLOGY, VOLUME 13

Caninia cylindrica var. Herculina (De Koninck). In a collection otherwise typical of the
species cylindrica, the two specimens referred to this subspecies show an extrathecal
development strikingly similar to that in typical forms of C. benburbensis, namely,
greater continuity of the major septa, and considerable reduction of the zone of large
lonsdaleoid dissepiments in favour of smaller concentric or herringbone dissepiments.

The specimens ascribed to Form A appear to possess certain distinctive morphological
characters which were retained as the caniniid lineage evolved. These characters
persisted through Visean time as the population mode gradually changed toward
larger adult individuals with more major septa, with concentric rather than lonsdaleoid
dissepiments, and with diminished minor septa.

Text-figs. 12, 13, and 14 show the distinct and perhaps significant departure of Form
D from the assemblage average. This may represent a new variation which became
established as the lineage evolved. Further study of caniniid populations higher in the
Dibunophyllum Zone may reveal whether or not this type was successful and increased
in proportion with time. As it forms an integral part of the C. benburbensis assemblage
in the lower Dx subzone, there is no justification yet for its establishment as a new species.
Lewis (1927, p. 380, pi. 17, figs. 2 a-b, 3a-c) described such forms as ‘senescent’, or a final
senile evolutionary stage of the species before it became extinct. This is questionable,
as the supposedly senescent forms appeared early in Dibunophyllidan time in extremely
successful populations, such as the ones at Streedagh Point, and the caniniid line
continued to flourish well into D2 time.

There is no general agreement on the relationship between Caninia Michelin 1840
(type species : C. cornucopiae) and Siphonophyllia Scouler in McCoy 1 844 (type species :
S. cylindrica). Both Salee (1910, p. 27) and Lewis (1927, p. 374) regarded Siphonophyllia
as a synonym of Caninia. Both genera are recognized by Hill (1956, p. F292), in which
Siphonophyllia is distinguished only on the basis of a wide lonsdaleoid dissepimentarium.
In view of the wide range of septal and dissepimental development in C. benburbensis,
and the as yet incomplete understanding of caniniid phylogeny, both benburbensis and
cylindrica have been referred herein to the genus Caninia ( sensu lato).

CONCLUSIONS

1. A wide range of morphological variation occurs in the Streedagh Point assemblage
of Caninia benburbensis, and clearly distinguishes it from all earlier assemblages.

2. Certain characters, such as total diameter, geniculations, spacing of tabulae, and
stereoplasmic thickening were distinctly dependent on ecological conditions, and varied
during ontogeny.

3. Biocharacters such as intrathecal diameter, number of septa, extrathecal continuity
of septa, and nature of the dissepiments show a regularity or constancy throughout
ontogeny which favours their use in classification.

4. Certain members of the population possess morphological features which strongly
affirm an earlier idea that C. benburbensis evolved from C. cylindrica (Lewis 1927,
p. 380). In agreement with this are their respective stratigraphical ranges in Ireland.

5. Certain members of the population show features which may presage the diver-
gence of a new species from the evolving caniniid lineage.

DIXON: VARIATION IN CANINIA

63

Acknowledgements. The author is indebted to Dr. W. G. E. Caldwell of the University of Saskatchewan
for critically reading the manuscript and to Dr. J. Hubbard of King’s College, London, for helpful
discussions and comments on the manuscript. Technical assistance provided by the University of
Glasgow in the initial specimen preparation, and the assistance of E. W. Hearn (Ottawa) in the
preparation of text-figures, are both gratefully acknowledged.

REFERENCES

caldwell, w. g. e. 1959. The Lower Carboniferous rocks of the Carrick-on-Shannon syncline. Q. Jl
geol. Soc. Lond. 115, 163-88, pi. 6.

george, t. n. and Oswald, d. h. 1957. The Carboniferous rocks of the Donegal syncline. Ibid. 113,
137-79, pi. 14-16.

hill, D. 1938-41. The Carboniferous rugose corals of Scotland. Palaeontographical Soc. Mon.
(London), 213 pp., 11 pis.

1956. Systematic descriptions. In moore, r. c. (ed.), Treatise on invertebrate paleontology. Part F,

Coelenterata, F256-F321. Univ. Kansas Press and Geol. Soc. Am.

hubbard, j. a. e. b. 1966. Population studies in the Ballyshannon Limestone, Ballina Limestone, and
Rinn Point Beds (Visean) of NW. Ireland. Palaeontology , 9, 252-69, pi. 40-1 .

hubbard, w. f. and sheridan, d. j. r. 1965. The Lower Carboniferous stratigraphy of some coastal
exposures in Co. Sligo, Ireland. Sci. Proc. R. Dublin Soc. ser. A, 2, 189-95, pi. 16-17.

lewis, H. p. 1927. Caninia cylindrica Scouler and other large Caninias from the Carboniferous Lime-
stone of Ireland. Ibid. 18, 373-82, pi. 16-17.

1930. The Avonian succession in the south of the Isle of Man. Q. Jl geol. Soc. Lond. 86, 234-90,

pi. 20-5.

ma, t. y. h. 1937. On the seasonal growth in Paleozoic tetracorals and the climate during the Devonian
Period. Paleontologia Sinica, ser. B. 2, fasc. 3, 1-106, 22 pi.

oldroyd, r. w. l. 1965. A summary of the micropalaeontology of the Lower Carboniferous of Co.
Sligo, Ireland. In hubbard, w. f. and sheridan, d. j. r. The Lower Carboniferous stratigraphy of
some coastal exposures in Co. Sligo, Ireland. Sci. Proc. R. Dublin Soc. ser. A, 2, 189-95, pi. 16, 17.

Oswald, d. h. 1955. The Carboniferous rocks between the Ox Mountains and Donegal Bay. Q. Jl
geol. Soc. Lond. Ill, 167-86, pi. 11.

salee, a. 1910. Contribution a 1’etude des polypiers du Calcaire Carbonifere de la Belgique. Le genre
Caninia. Soc. Beige Geol., Nouv. Mem. Ser. 4, Mem. 3, 62 pp., 9 pis.

simpson, i. m. 1955. The Lower Carboniferous stratigraphy of the Omagh syncline. Northern Ireland.
Q. Jl geol. Soc. Lond. 110, 391-408, pi. 18.

smyth, l. b. 1925. A contribution to the geology of Great Orme’s Head. Sci. Proc. R. Dublin Soc. 18,
141-64, pi. 3-7.

O. A. DIXON

Department of Geology
University of Ottawa
Ottawa, 2

Final typescript received 15 July 1969 Canada

AMPHIPORA AND EURYAM PHIPO RA
(STROM ATOP OROIDE A) FROM THE DEVONIAN
OF WESTERN CANADA

by N. R. FISCHBUCH

Abstract. Subsurface diamond cores of the Devonian Swan Hills Formation of central Alberta contain well-
preserved specimens of Amphipora Schulz and Euryamphipora Klovan. Three varieties of Amphipora are recog-
nized in the Swan Hills material, and are referred to the species A. angusta, A. pervesiculata, and A. ramosa\
a new species of Euryamphipora (E. mollis) and the type species E. platyformis also are present. Amphipora is
placed in the Clathrodictyidae with Euryamphipora since they have identical tissue. ‘Juvenile’ forms, which may
represent an early astogenetic stage, are found associated with mature Amphipora coenostea. The concept that
some forms of Amphipora grew without producing a peripheral rim is rejected and the absence of this feature
s considered the result of abrasion.

T he stromatoporoid genus Amphipora , so common in the Devonian carbonate rocks of
western Canada, has aroused only passing interest among Canadian palaeontologists.
Those specimens described have been referred mainly to Amphipora ramastf(Phillips),
and have been commonly considered in conjunction with other stromatoporoids as
aberrant forms. The presence and abundance of Amphipora , however, has been noted in
several recent sedimentological studies (Edie 1961 ; Fischbuch 1960, 1962, 1968; Thomas
and Rhodes 1961; Murray 1966; Jenik and Lerbekmo 1968; Leavitt 1968).

The Swan Hills reef complexes, which are found deep in the subsurface of the central
plains of Alberta, contain exceptionally well-preserved specimens of Amphipora which
abound in the lagoon and platform carbonates. Amphipora coenostea constitute up to
70 % of these rocks, are commonly oriented horizontally, and appear to have been trans-
ported over longer or shorter distances after death. The specimens used in this study
were taken from diamond cores of the Devonian Swan Hills Formation which straddles
the Givetian-Frasnian boundary (Fischbuch 1968, p. 523) and contains nine stages of
reef growth; these have been informally designated from bottom to top as Divisions
I-IX (Fischbuch 1968, p. 452). Amphipora and Euryamphipora are present in all but
Division I. Three species of Amphipora and two species of Euryamphipora are recognized
in the Swan Hills material; both genera are placed in the family Clathrodictyidae.

TAXONOMIC CONSIDERATIONS

The classification of Amphipora as a stromatoporoid has been rejected by some
palaeontologists: for example, Opik (1935, p. 3) regarded Amphipora as a calcareous
sponge. Nicholson (1886, p. 99) also believed that it should be regarded in a separate
category. Lecompte (1952) classified Amphipora with the dendroid stromatoporoids but
cautioned that ‘Dans l’etat present des observations, le genre Amphipora apparait
entierement aberrant dans le groupe des Stromatoporoides’ (1952, p. 324). Later (1956,
p. FI 42), he removed Amphipora and classified it as Incertae sedis. Its relatively slender,
cylindrical, growth form and consistently fibrous tissue is somewhat anomalous amidst

[Palaeontology, Vol. 13, Part 1, 1970, pp. 64-75, pis. 14-17.]

FISCHBUCH: AMPHIPORA AND EURYAMPHIPORA

65

other genera of the Idiostromatidae and certainly anomalous compared to the families
that exhibit melanospheric, cellular, compact, and flocculent tissue. Unfortunately it
was not assigned originally to the Clathrodictyidae, which are typified by fibrous tissue,
but rather, due to its uniformly cylindrical growth form, was conveniently placed in the

text-fig. 1. Location of Swan Hills area.

Idiostromatidae. The discovery of a tabular counterpart, Euryamphipora, by Klovan
(1966, p. 14) sheds new light on this problem. In his description, he left little doubt that
the fibrous tissue allies his genus to the family Clathrodictyidae. This, consequently,
paves the way for the entry of Amphipora into that same family, since both genera have
indistinguishable tissue. Furthermore, Birkhead(1967, pp. 31, 32), in reviewing stromato-
poroid phylogeny, suggested a relationship between Amphipora and Anostylostroma.
This evidence supports the inclusion of the genus Amphipora in the Stromatoporoidea.

F

C 7173

66

PALAEONTOLOGY, VOLUME 13

Leavitt (1968, p. 325) discussed some aspects of reproduction in Amphipora and illus-
trated marginal cysts or buds and ‘juvenile’ coenostea (Leavitt 1968, pi. 8). Other Swan
Hills limestones contain similar forms, which grade from small spherical bodies,
0-15-0-6 mm. in diameter, through incipient Amphipora- like stems, containing a simple

arrangement of one or two structural elements, to mature Amphipora stems (PI. 14, figs.
1-8). The outer rim in all specimens is formed by a single layer of transversely fibrous
tissue. The small spheres may have been formed on the outer margins of the coenostea
(Leavitt 1968, pi. 8, fig. 5). If this were so, subsequently they may have become detached,
floated freely in the water, and then attached themselves to the substrate to develop into
adult forms. This hypothesis, however, is conjectural, since nothing is known of the
reproductive habits of stromatoporoids.

The function of the axial canal remains problematic. Lecompte (1952, p. 323) rejected
the contention that it is an astrorhizal tube on the basis that there is no ramification from
it throughout the tissue. Several workers, however, have reported openings connecting
it to the galleries. The function of the marginal vesicles is also open to question. Nichol-
son (1886, p. 110) suggested that they may have been used in reproduction. Some
workers (Nicholson 1886, p. 110; Lecompte 1952, p. 323) also maintain that marginal
vesicles are not present in all forms. Convinced that some forms grew without producing
a peripheral rim, based on his observations of the Ardennes material, Lecompte (1952,
pp. 329, 330) erected two species (A. rudis, A. laxeperforata ) to include such coenostea.

FISCHBUCH: AMPHIPORA AND EURYAMPHIPORA

67

In the many specimens from the Swan Hills Formation, however, there seems to be
little doubt that absence of the outer rim is the result of abrasion. This outer envelope
of tissue is relatively thin and the slightest erosion would disrupt it or remove it com-
pletely. Most coenostea have been transported some distance and a complete sequence
of forms, ranging from those with the outer rim intact, to slightly broken, and finally
completely removed, can be observed in the Swan Hills material (PL 14, figs. 9-13).

Specimens of Amphipora described from Canada have been referred mainly to the
type species Amphipora ramosa (Phillips). There are, however, several distinct varieties
which can be grouped as follows:

1 . Those with a narrow zone of marginal vesicles, stout pillar-laminar architecture,
and relatively small axial canal.

2. Those with a narrow zone of marginal vesicles, stout pillar-laminar architecture,
and no axial canal.

3. Those with a wide zone of marginal vesicles, delicate pillar-laminar architecture,
and relatively large axial canal.

To represent the above three types, the species Amphipora ramosa (Phillips), Amphipora
angusta Lecompte, and Amphipora pervesicu/ata Lecompte respectively, were selected
from over thirty described species. They usually occur closely associated with each other
in the Swan Hills Formation, but generally one species is dominant in any Amphipora-
rich bed.

Some poorly-preserved Swan Hills specimens do not portray the dark-coloured
median line in the structural elements. These were not referred to the genus Paramphi-
pora, proposed by Yavorsky (1955) for specimens with tissue lacking a dark-coloured
median line, since the absence of this feature is probably a function of preservation. The
validity of Yavorsky’s genus has also been questioned by other workers (Klovan 1966,
p. 14; Stearn 1966a, p. 109).

KEY TO LOCATION OF SPECIMENS

The locations of wells are given in an abbreviated form, e.g. the Atlantic Kaybob 4-14 well, is 4-14-
64-19 W5, which should be read as Legal Subdivision 4, Section 14, Township 64, Range 19, West
of the fifth Meridian. Depths are measured from the Kelly Bushing (K.B.).

The type and other specimens described in this paper have been deposited at the Geological Museum
of the University of Saskatchewan under Coelenterata, Stromatoporoidea, and are numbered with the
prefix GMUS Cs. Under occurrences only well numbers are given, followed by depths in feet and
GMUS Cs numbers in parentheses.

Well number
1

2

3

4

5

6

7

8
9

10

Well name and location
Phillips et al., Kaybob 2-5-64-19 W5
Atlantic Kaybob 4-14-64-19 W5
S.O.B.C. Snipe Lake 10-21-70-18 W5
Phillips et al., Kaybob 10-4-64-19 W5
Home Regent ‘A’ Swan Hills 10-4-67-10 W5
Phillips et al., Kaybob 2-9-64-19 W5
Pan American B.A. Swan Hills 10-32-66-10 W5
Pan American B.A. Swan Hills 12-19-66-10 W5
Imperial Goose River 4-15-67-18 W5
Imperial Goose River 10-15-67-18 W5

68 PALAEONTOLOGY, VOLUME 13

11 Canadian Superior Sakwatamau 10-4-63-15 W5

12 Canadian Kewanee Swan Hills 4-16-68-10 W5

13 California Standard S.O.B.C. Snipe Lake 10-35-70-18 W5

14 Pan American ‘A-l’ Sunset House 4-16-70-19 W5

15 Pan American B.A. Swan Hills 12-29-66-10 W5

16 B.A. Goose River 10-5-67-18 W5

17 Shell Virginia Hills 12-35-64-13 W5

18 Canadian Kewanee Swan Hills 4-7-69-10 W5

19 California Standard S.O.B.C. House Mountain 4-6-70-10 W5

20 Shell Swan Hills 6-34-64-13 W5

21 Pure Sakwatamau 7-7-63-14 W5

22 Pan American B.A. ‘U-12’ Swan Hills 4-8-66-10 W5

23 Canadian Kewanee Swan Hills 10-32-68-10 W5

SYSTEMATIC DESCRIPTIONS

Family clathrodictyidae Kuhn 1939
Genus amphipora Schulz 1883

Type species. Caunopora ramosa Phillips 1841.

Diagnosis. Coenosteum cylindrical, rod-shaped, and very rarely branching. It may or
may not have an axial canal with or without irregular tabulae. Pillars and laminae
cannot be distinguished but rather are commonly amalgamated to form a coarse net-
work, which is separated from a thin outer rim by a zone of marginal vesicles. Tissue is
transversely fibrous and the structural elements (amalgamated pillars and laminae)
contain a dark-coloured median line. The outer rim does not have a median line and is
only about half as thick as the pillar-laminar elements.

EXPLANATION OF PLATE 14

All figures x 10.

Figs. 1-8. Progressive development from possible immature to mature Amphipora coenostea.

Fig. 1 . Concentration of small and irregular immature Amphipora forms composed mainly of an outer
rim with little or no internal development of structural elements; well no. 10, 9335.

Figs. 2-4. Initial stage with vague internal tissue apparent in figs. 3 and 4; well no. 10, 9335.

Fig. 5. Irregular intermediate form with definite, but separate, internal skeletal elements; well no. 10,
9335.

Figs. 6-7. Development of axial canal surrounded by an intermittent network of structural elements ;
well no. 10, 9335.

Fig. 8. Mature, completely developed Amphipora coenostea; well no. 10, 9284.

Figs. 9-13. Progressive erosion of Amphipora coenostea.

Fig. 9. Cross-section of Amphipora coenosteum with outer rim broken in two places; well no. 4, 9801.

Fig. 10. Cross-section of Amphipora coenosteum with right side of peripheral rim removed by erosion;
well no. 4, 9801.

Fig. 1 1 . Cross-section of Amphipora coenosteum with only a remnant of outer rim preserved (right
side of photo). Sediment has penetrated into the galleries and axial canal; well no. 4, 9801.

Fig. 12. Cross-section of Amphipora coenosteum with outer rim partly collapsed; well no. 6, 9884.

Fig. 13. Cross-section of Amphipora coenosteum with outer rim completely removed by erosion; well
no. 6, 9884.

Palaeontology, Vol. 13

PLATE 14

FISCHBUCH, Amphipora

FISCHBUCH: AMPHIPORA AND EURYAMPHIPORA

69

Amphipora ramosa (Phillips 1841)

Plate 15, figs. 1-5

For synonymy to 1957 see Galloway (1957, p. 442).

1957 Amphipora ramosa (Phillips), Yavorsky, p. 63, pi. xli, figs. 1-9 (Lower Devonian, Kuz-
netsk Basin, Russia).

1957 Amphipora intexta Yavorsky, p. 62, pi. xxxiv, figs. 5-9 (Middle Devonian, Kuznetsk
Basin, Russia).

71960 Amphipora ramosa (Phillips), Galloway and Ehlers, p. 98, pi. xi, figs. 1 a, 1 b (Middle

Devonian, Michigan, U.S.A.).

1961 Amphipora ramosa (Phillips), Yavorsky, p. 58, pi. xxxvi, fig. 15; pi. xxxvii, figs. 1-10
(Middle Devonian, Kuznetsk Basin, Russia).

71961 Amphipora ramosa (Phillips), Stearn, p. 946, pi. 107, figs. 9, 10 (Upper Devonian,

Alberta, Canada).

71963 Amphipora ramosa (Phillips), Stearn, p. 663, pi. 87, fig. 2 (Swan Hills Formation,
Alberta, Canada).

1963 Amphipora intexta (Yavorsky), Stearn, p. 663, pi. 87, figs. 3, 4, 5 (Swan Hills Formation,
Alberta, Canada).

1966a Amphipora ramosa (Phillips), Stearn, p. 109.

71966 Amphipora sp. Klovan, p. 30, pi. x, figs. 1-6 (Cooking Lake and Leduc Formations,
Alberta, Canada).

71966 b Amphipora ramosa (Phillips), Stearn, p. 63, pi. xxiv, fig. 2 (Hay River Formation, North-
west Territories, Canada).

1967 Amphipora ramosa (Phillips), Birkhead, p. 84, pi. 16, figs. 2a, 2b (Callaway Formation,
Missouri, U.S.A.).

Diagnosis. The coenostea are cylindrical, rarely branching, and contain an axial canal.
Coenosteal diameter ranges from 2-5 to 4-6 mm. (averaging 3-47 mm.). Structural
elements consist of fibrous tissue.

Description. This species is represented in the Swan Hills collection by 65 rock specimens,
each of which contains many coenostea. Sixteen of these specimens were used in this
description.

Cross-section. An axial canal always is present, but is not as prominent as in some
other species. It ranges in diameter from 0-4 to IT mm., with an average of 0-66 mm.
Pillars and laminae are amalgamated to form an irregular network surrounding the
axial canal. The structural elements forming this network are stout, measuring 0T-
0-25 mm. (averaging 0-2 mm.) in diameter. They are composed of light-brown tissue and
contain a dark-coloured, median fine with fibres extending from the line toward the
perimeter of the skeletal elements. Between the pillar-laminar entanglement and the
outer rim is a zone of round or oval marginal vesicles, 0T-0-3 mm. thick. The vesicles
are formed by structural elements extending, at regular intervals, across the relatively
open space immediately within the outer rim. The outer rim is composed of a single
layer of radially fibrous tissue that does not have a dark-coloured median line and is
about half as thick as the structural elements. Dissepiments, in the marginal vesicles,
galleries, and axial tube, are rare.

Axial section. The structural elements of the pillar-laminar network are commonly
unoriented, but rarely appear to splay upward and outward from the axial canal and
toward the periphery. The elements that pass through the zone of marginal vesicles meet
the outer rim at oblique angles.

70

PALAEONTOLOGY, VOLUME 13

Discussion. Amphipora ramosa, as here defined, always possesses an axial canal, and
thus differs from A. angusta Lecompte, which does not have this feature. It has thicker
structural elements, a narrower zone of marginal vesicles, and fewer dissepiments than
A. pervesiculata Lecompte. Coenostea exhibiting a splay pattern of the structural
elements in some axial sections, such as those referred to A. intexta Yavorsky, are
interpreted as variants of A. ramosa.

Occurrence. This species is found in Divisions II-VI of the Swan Hills Formation. In Divisions II— III
it is associated with A. pervesiculata, and A. angusta, and fragmented subspherical stromatoporoids, but
is one of the dominant fossils in the lagoonal facies of Divisions IV-VII. A. ramosa occurs in the cal-
cirudites, calcarenites, and calcilutites in the following wells: 1, 9725 (267), 9762 (268); 2, 9759-5 (269),
9749 (270); 3, 8798 (271); 4, 9778 (272), 9801 (273); 5, 8591 (274); 6, 9884 (275), 9854 (276); 7, 9071
(277), 8977 (278); 8, 8618 (279); 9, 9192 (280); 10, 9284 (281); 11, 9735 (282).

Amphipora angusta Lecompte 1952
Plate 1 5, figs. 6-9

1952 Amphipora angusta Lecompte, p. 324, pi. lxvii, fig. 2 (Middle Devonian, Dinant Basin,
Belgium).

Diagnosis. The coenosteum is cylindrical and does not contain an axial canal. Coenosteal
thickness ranges from 2-2 to 4-7 mm. (averaging 3-19 mm.). Structural elements consist
of fibrous tissue.

Description. Description of this species is based on fourteen rock specimens, all of which
contain many coenostea.

Cross-section. An axial canal is lacking in all specimens, and the central portion of
the coenosteum is composed of an amalgamated pillar-laminar system. Galleries are
irregular in outline but continuous open areas can be traced completely through the
skeletal system. The structural elements range from 0-1 to 0-3 mm. (averaging 0-16 mm.)
in diameter, and form a continuous network. This network is surrounded by a zone of
marginal vesicles, 0- 1-0-4 mm. (averaging 0-3 mm.) in depth. It is crossed at regular
intervals by structural elements that are commonly of equal diameter to those of the
interior network but rarely thin to the point of disappearance as they cross the vesicular
zone. In the rare instances in which the median part of these elements has disappeared,
the elements are reduced to two ‘barbs’, which project into the vesicular zone from
opposite sides. Skeletal tissue is light brown, transversely fibrous, and contains a dark-
coloured median line. The outer rim, which is about half as thick as the structural
elements, is composed of one layer of radially fibrous tissue. Dissepiments are rare.

Axial section. The interior network of intertwined structural elements is generally
completely amalgamated but rarely displays a vague upward splay pattern. The elements
pass through the zone of marginal vesicles and join the outer rim at an oblique angle.

EXPLANATION OF PLATE 15

Figs. 1-5. Amphipora ramosa (Phillips). 1, Hand specimen containing numerous coenostea, xl;
well no. 1 1, 9735 (282). 2, Cross-section, x 50; well no. 11, 9735 (282). 3, Cross-section, x 20; well
no. 11, 9735 (282). 4, Cross-section, x 10; well no. 1 1, 9735 (282). 5, Cross and axial section, x 10;
well no. 11,9735 (282).

Figs. 6-9. Amphipora angusta Lecompte. 6, Hand specimen containing numerous coenostea, X 1 ;
well no. 6, 9915 (285). 7, Cross-section, x 10; well no. 6, 9915 (285). 8, Fibrous microstructure,
x 50; well no. 6, 9915 (285). 9, Cross and axial sections, x 10; well no. 6, 9915 (285).

Palaeontology, Vol. 13

PLATE 15

FISCHBUCH, Amphipora

FISCHBUCH: AMPHIPORA AND EURYAMPHIPORA

71

Discussion. The Swan Hills specimens are similar to the Belgian holotype described by
Lecompte in that they lack an axial canal, but the average diameter of the Swan Hills
specimens is considerably greater (3T9 mm.) compared to a diameter range of 0-5-
2-0 mm. given by Lecompte. The conspicuous absence of an axial canal, however,
appears sufficient to ally the Swan Hills specimens to this species. A. angusta has slightly
thinner structural elements than, and lacks the axial canal of, A. ramosa. It is easily
distinguished from A. pervesiculata, which has thinner structural elements and a
relatively large axial canal and marginal vesicles.

Occurrence. This species is found in Divisions Il-Vtl of the Swan Hills Formation. In Divisions II and
III it is associated with A. pervesiculata, A. ramosa, and other stromatoporoids, but in the lagoonal
facies of Divisions IV-VII the above three species of Amphipora occur in great abundance to the
complete exclusion of other stromatoporoids. A. angusta occurs in the calcirudites, calcarenites, and
calcilutites in the following wells: 6, 9912 (283), 9913 (284), 9915 (285); 2, 9752 (286), 9762 (287);
12, 7957 (288); 13, 8651 (289); 14, 9093 (290); 15, 881 1 (291); 7,9099(292); 16,9189(293); 17,9341
(294); 10, 9333 (295); 18, 7842 (296).

Amphipora pervesiculata Lecompte 1952
Plate 16, figs. 1-5

1952 Amphipora pervesiculata Lecompte, p. 331, pi. lxx, figs. 3, 4, 5 (Upper Devonian, Dinant
Basin, Belgium).

71952 Amphipora laxeperforata Lecompte, p. 330, pi. lxx, figs. 1, 2 (Upper Devonian, Dinant
Basin, Belgium).

1957 Amphipora pinguis Yavorsky, p. 63, pi. xxxv, figs. 1-5 (Middle Devonian, Kuznetsk
Basin, Russia).

Description. This species is represented in the Swan Hills collection by 43 rock specimens,
19 of which are used in this description, and all contain many coenostea. The cylindrical
skeleton ranges from 2-0 to 4-9 mm. (averaging 3-3 mm.) in diameter.

Cross-section. A relatively large axial canal, 0-5-1 -5 mm. (averaging 0-82 mm.) in
diameter, is a dominant feature of all coenostea. Undifferentiated structural elements
form a continuous but relatively narrow network around the axial canal. The diameter
of these structural elements ranges from 0-1 to 0-24 mm. (averaging 0-13 mm.). They are
slightly thinner than those of other species but appear even more so due to their reduced
numbers. The conspicuous zone of marginal vesicles, 0-2-0-6 mm. wide, is crossed by
structural elements which thin perceptibly, and commonly do not extend completely
across the zone, but are broken to form opposing ‘barbs’. In some cross-sections, most,
or even all, of the marginal vesicles are joined to form a continuous open area between
the outer rim and the interior skeletal system. The outer rim, 0-03-0-06 mm. in thickness,
is composed of a single layer of transversely fibrous tissue, differing from the other ele-
ments which are also transversely fibrous but are thicker and contain a dark-coloured
median line. Dissepiments are common in most coenostea but are especially noticeable
in the large axial canal and zone of marginal vesicles.

Axial section. Structural elements are uncommon in the zone of marginal vesicles,
giving the impression of an annulus between the outer rim and the pillar-laminar
network.

72 PALAEONTOLOGY, VOLUME 13

Discussion. The Swan Hills specimens structurally are indistinguishable from the Belgian
holotype described by Lecompte but have a greater over-all diameter. Considerable
variation in size, however, seems to be characteristic of mature specimens of amphiporoid
species. A. pervesiculata differs from A. ramosa in having a larger axial canal and a much
wider zone of marginal vesicles. It is easily distinguished from A. angusta, which has no
axial canal. A. pinguis Yavorsky is indistinguishable from the Swan Hills specimens in
size of the coenosteum and axial canal. Width of the marginal vesicular zone was not
given by Yavorsky but measures about 0-25 mm. on the illustrations, and this compares
favourably with the Swan Hills specimens. A. pinguis is, therefore, a junior subjective
synonym of A. pervesiculata. A. laxeperforata Lecompte appears to be an A. pervesiculata
or A. ramosa in which the outer rim has been destroyed by abrasion.

Occurrence. This species is found in Divisions II-IX of the Swan Hills Formation. A. pervesiculata is
associated with A. ramosa, A. angusta, fragmented subspherical, and dendroid stromatoporoids in
Divisions II and III. In Divisions IV-IX it is found associated only with A. ramosa and A. angusta. It
occurs in the calcirudites, calcarenites, and calcilutites in the following wells: 5, 8472-5 (297), 8409
(298); 17, 9495 (299), 9372 (300); 15, 8931 (301), 9001 (302), 8739 (303), 8813 (304); 10, 9317 (305); 4,
9737 (306), 9729 (307); 2, 9756 (308), 9764 (309); 1, 9751 (310); 14, 9104 (311); 6, 9727-5 (312); 12,
7927 (313); 3, 8716 (314); 19, 7516 (315).

Genus euryamphipora Klovan 1966

Type species. Euryamphipora ptatyformis Klovan 1966.

Diagnosis. Coenosteum thin, tabular, undulating, and composed of a median zone of
undifferentiated structural elements representing amalgamated pillars and laminae,
which is flanked above and below by marginal vesicles. Tissue of the structural elements
is transversely fibrous and contains a dark-coloured median line.

Euryamphipora platyformis Klovan 1966

Plate 17, figs. 1-5

1966 Euryamphipora platyformis Klovan, p. 15, pi. iii, figs. 4 a, 4b; pi. iv, figs. 1-7 (Cooking
Lake and Leduc Formations, Alberta, Canada).

Diagnosis. Coenostea are flat, tabular forms, ranging from 1 to 3 mm. in thickness.
Astrorhizal canals, mamelons, and latilaminae are not present.

Description. This species is represented in the Swan Hills collection by nine specimens.

EXPLANATION OF PLATE 16

Figs. 1-5. Amphipora pervesiculata Lecompte. 1, Hand specimen containing numerous coenostea, x 1;
well no. 5, 8472-5 (297). 2, Cross-section, x 10; well no. 10, 9317 (305). 3, Cross-section showing
fibrous microstructure, x50; well no. 5, 8472-5 (297). 4, Cross-section, x20; well no. 5, 8472-5
(297). 5, Axial section showing a vague upward splay pattern of the structural elements, x 10; well
no. 5, 8472-5 (297).

Figs. 6-10. Euryamphipora mollis sp. nov. 6, Hand specimen containing tabular coenostea of Eury-
amphipora mollis sp. nov. associated with Amphipora and dendroid stromatoporoids, X 1 ; well no. 6,
9924 (325). 7, Vertical section of E. mollis showing fibrous microstructure and zone of marginal
vesicles crossed by dissepiments, x 50; well no. 6, 9924-5 (325). 8, Tangential section showing cross-
sections of structural elements, x 50; well no. 6, 9924-5 (325). 9, Vertical section, x 10; well no. 6,
9924-5 (325). 10, Tangential section, x 10; well no. 6, 9924-5 (325).

Palaeontology, Vol. 13

PLATE 16

FISCHBUCH, Amphipora and Euryamphipora

FISCHBUCH: AMPHIPORA AND EURYAMPHIPORA

73

Vertical section. The upper and lower surfaces of the coenosteum are bordered by a
thin (0-05 mm.) layer of transversely fibrous tissue, which does not contain a dark-
coloured median line. In some coenostea, the upper layer has been disrupted or removed
by erosion allowing sediment or algal ( ?) material to accumulate directly on the pillar-
laminar network (PI. 17, fig. 1). The pillar-laminar entanglement occupies the median
portion of the skeleton, and its elements range from 0T to 0-2 mm. in diameter. They are
composed of light-brown, transversely fibrous tissue and contain a dark-coloured median
line. The interior network is joined, at regular intervals, to the outer layer of tissue by
vertical elements (pillars ?), forming a continuous row of marginal vesicles 0-25-0-35 mm.
in thickness. Dissepiments are rare.

Tangential section. Where sections cut the median zone, the skeletal elements not
uncommonly are crudely oriented in subparallel rows at right angles to each other,
forming a coarse, screen-like pattern. This differs from the sheet-like laminae of other
stromatoporoids, which are pierced only by foramina and vacuoles. Tangential sections
through the relatively open marginal vesicle zone reveal the structural elements as
discrete dots, 0-1-0-15 mm. in diameter, which are joined by dissepiments.

Discussion. The Swan Hills specimens are closely similar to the holotype described by
Klovan from the Upper Devonian Redwater reef complex, although they have a slightly
thinner outer layer of tissue. This difference, however, is negligible and not of specific
significance. E. platyformis differs from E. mollis, which has more dissepiments, thinner
structural elements, and larger marginal vesicles.

Occurrence. E. platyformis is found in Divisions II-VII of the Swan Hills Formation, where it is asso-
ciated with Amphipora, fragmented brachiopods, and disarticulated ostracode carapaces. It occurs in
growth position and in the calcarenites and calcirudites in the following wells: 20, 9447 (316), 9644
(317); 21, 9408 (318); 22, 8613 (319), 8616 (320); 23, 8247 (321), 8249 (322); 8, 8777 (323); 12, 7910
(324).

Holotype. 6, 9924-5 (325).

Euryamphipora mollis sp. nov.
Plate 16, figs. 6-10

Diagnosis. Coenostea have a tabular growth habit and occur singly or in superposed
layers of several coenostea, which encrust and over-ride each other giving the whole
mass a latilaminar aspect. Some coenostea persist laterally for only short distances and
have the appearance of large ‘cysts’ formed on the underlying coenosteum. These, in
turn, are engulfed by the coenosteum above, which may have similar ‘cysts’ on its upper
surface.

Description. Euryamphipora mollis is represented in the Swan Hills collection by six
specimens.

Vertical section. Coenosteum consists of a median pillar-laminar system, 1-T5 mm.
thick, in which pillars cannot be distinguished from laminae. These structural elements
range from 0-1 to 0-15 mm. in diameter, are transversely fibrous, and contain a dark-
coloured median line. The median zone of undifferentiated structural elements is flanked
above and below by a zone of marginal vesicles, 0-4— 0-8 mm. in thickness, which is
crossed at regular intervals by vertical or oblique structural elements. These elements

74

PALAEONTOLOGY, VOLUME 13

thin perceptibly and commonly do not extend across the zone, but are broken completely
to form opposing ‘barbs’. The coenosteum is covered by a thin layer of transversely
fibrous tissue, 0-04-0-08 mm. in thickness. Where coenostea are superposed, the line of
contact can be traced by a dark-coloured median line, identical to that in the interior
elements. Dissepiments are common, especially in the marginal vesicles, where they
curve and branch outward, linking the median skeletal system to the outer, covering
layer.

Tangential section. Structural elements in the median zone are represented by discrete,
irregular masses of fibrous tissue surrounded by continuous gallery space, which is inter-
rupted only by dissepiments. Where sections cut the zone of marginal vesicles, widely
spaced skeletal elements are represented by dots, 0-1 mm. or less in diameter, not
uncommonly joined by dissepiments.

Discussion. E. mollis differs from the only other species of Euryamphipora, E. platyformis,
in having more dissepiments, a more delicate pillar-laminar system, and a larger zone of
marginal vesicles. It has a slightly ‘knotted’ structure reminiscent of Hammatostroma
nodosum, described by Klovan from the Redwater reef complex, but the laminae in the
latter species are much more closely spaced than the units described here as individual
coenostea. The genera Euryamphipora and Hammatostroma have similar fibrous
microstructure but differ markedly in laminar spacing (or coenosteal thickness). They
eventually may be found to be related to a common ancestor.

Occurrence. This species is found in Divisions II and III of the Swan Hills Formation, where it is asso-
ciated with Amphipora, Euryamphipora platyformis, subspherical stromatoporoids, and ostracode
carapaces. It occurs in growth position and in the calcarenites and calcirudites in the following wells:
6, 9924-5 (325), 9902-5 (326), 9926 (327); 5, 8640 (328); 22, 8614 (329); 2, 9770 (330).

Acknowledgements. This paper is a portion of a doctoral dissertation written at the University of
Saskatchewan under the direction of Drs. W. G. E. Caldwell and W. K. Braun. The writer gratefully
acknowledges their guidance and criticism.

REFERENCES

birkhead, p. k. 1967. Stromatoporoidea of Missouri. Bull. Am. Paleont. 52, no. 234, 23-110.
edie, R. w. 1961. Devonian reef reservoir, Swan Hills oilfield, Alberta. Can. Mining and Met. Bull. 54,
no. 590, 447-54.

fischbuch, n. r. 1960. Stromatoporoids of the Kaybob reef, Alberta. Jour. Alta. Soc. Petrol. Geol.
8, 113-31.

1962. Stromatoporoid zones of the Kaybob reef, Alberta. Ibid. 10, 62-72.

1968. Stratigraphy, Devonian Swan Hills reef complexes of central Alberta. Bull. Can. Petrol.

Geol. 16, 446-587.

galloway, j. j. 1957. Structure and classification of the Stromatoporoidea. Bull. Am. Paleont. 37,
no. 164, 345-480.

EXPLANATION OF PLATE 17

Figs. 1-5. Euryamphipora platyformis Klovan. 1, Vertical section showing tabular growth habit, X 10;
well no. 20, 9644 (317). 2, Tangential section showing orientation of skeletal elements in sub-
parallel rows, X 10; well no. 22, 8616 (320). 3, Tangential section cutting median pillar-laminar
entanglement and zone of marginal vesicles, X 10; well no. 22, 8616 (320). 4, Vertical section

showing marginal vesicle, x50; well no. 22, 8613 (319). 5, Tangential section showing fibrous
microstructure, x 50; well no. 22, 8613 (319).

Palaeontology , Vol. 13

PLATE 17

FISCHBUCH, Euryamphipora

FISCHBUCH: AMPHIPORA AND EU RYAMPHIPO RA

75

galloway, j. j. and ehlers, g. m. 1960. Some Middle Devonian stromatoporoids from Michigan and
south-western Ontario, including the types described by Alexander Winchell and A. W. Grabau.
Contr. Mus. Paleont. Univ. Mich. 15, no. 4, 39-120.

and st. jean, j. jr. 1957. Middle Devonian Stromatoporoidea of Indiana, Kentucky, and Ohio.

Bull. Am. Paleont. 37, no. 162, 29-308.

jenik, a. j. and lerbekmo, j. f. 1968. Facies and geometry of Swan Hills reef Member of Beaverhill
Lake Formation (Upper Devonian), Goose River field, Alberta, Canada. Bull. Am. Assoc. Petrol.
Geol. 52, 21-56.

klovan, j. e. 1966. Upper Devonian stromatoporoids from the Redwater reef complex, Alberta,
Canda. Bull. geol. Surv. Can. 133, 1-33.

leavitt, e. m. 1968. Petrology, palaeontology, Carson Creek North reef complex, Alberta. Bull. Can.
Petroleum Geol. 16, 298-413.

lecompte, m. 1952. Les stromatoporoides du Devonien moyen et superieur du Bassin de Dinant.
Mem. Inst. r. Sci. Nat. Belg. 117, 216-369.

1956. Stromatoporoidea. In moore, r. c. (ed.). Treatise on invertebrate paleontology. Part F,

FI 07-44, Univ. Kansas Press and Geol. Soc. Amer.
mccoy, f. 1884. A synopsis of the characters of the Carboniferous limestone of Ireland. Univ. Press,
Dublin.

Murray, j. w. 1966. An oil-producing reef-fringed carbonate bank in the Upper Devonian Swan Hills
Member, Judy Creek, Alberta. Bull. Can. Petroleum Geol. 14, 1-103.

Nicholson, H. A. 1886, 1892. A monograph of the British stromatoporoids. Palaeontographical Soc.
London. Pts. 1, 4, 39, 46, 1-234.

opik, a. 1935. Amphipora ramosa (Phillips) in the marine Devonian of Estonia. Ann. Nat. Soc. Tartu
Univ. 41, 1-8.

Phillips, J. 1841. Figures and descriptions of the Palaeozoic fossils of Cornwall, Devon, and West-
Somerset. Longman, Brown, Green, and Longmans, London.
ripper, e. a. 1937. A note on the occurrence of Amphipora ramosa (Phillips) in western Australia.
R. Soc. West. Aust. Jour. 23, 37-41.

schulz, e. 1883. Die Eifelkalkemunde von Hillesheim. Nebst einem palaeontolog Anhang. Jb. preuss.
geol. Landesanst. Berg Akad. fur 1882, 160-247.

stearn, c. w. 1961. Devonian stromatoporoids from the Canadian Rocky Mountains. J. Paleont. 35,
923-48.

1963. Some stromatoporoids from the Beaverhill Lake Formation (Devonian) of the Swan Hills

area, Alberta. Ibid. 37, 651-68.

1966a. The microstructure of stromatoporoids. Palaeontology, 9, 74-124.

19666. Upper Devonian stromatoporoids from southern Northwest Territories and northern

Alberta. Bull. geol. Surv. Can. 133, 35-68.

thomas, g. e. and Rhodes, h. s. 1961. Devonian limestone bank-atoll reservoirs of the Swan Hills area,
Alberta. Jour. Alta. Soc. Petrol. Geol. 9, 29-38.

yavorsky, v. I. 1955. Stromatoporoidea Sovetskogo Soyuza, pt. 1. Trudy Vses. Nauchno-issled. geol.
Inst., Minist. geol. Okhr. Nedr., n. ser. 8, 173 pp.

1957. Stromatoporoidea Sovetskogo Soyuza, pt. 2. Ibid. 18, 78 pp.

1961. Stromatoporoidea Sovetskogo Soyuza, pt. 3. Ibid. 44, 64 pp.

N. R. FISCHBUCH

33 Fernie Place S.E.
Calgary 27

Final typescript received 15 July 1969 Alberta, Canada

THE GROWTH AND SHELL MICROSTRUCTURE
OF THE THECIDEACEAN BRACHIOPOD
MOORELLINA GRANULOSA (MOORE) FROM THE
MIDDLE JURASSIC OF ENGLAND

by P. G. BAKER

Abstract. Analysis of the growth habit of M. granulosa from a functional point of view has proved to be of
value in the interpretation of shell microstructure. Serial sectioning of shells at 20 g. intervals has revealed that
fibre orientation may change suddenly at various levels within a shell. The paper notes the need for detailed
information regarding the orientation and location of sections through shells, as study of M. granulosa indicates
this may be of critical importance. The shell-structure differs markedly from that of Lacazella mediterranea
(Risso), as the shells of some, if not all Inferior Oolite thecidellinids were differentiated into primary and second-
ary layers. Interpretation of the microstructure has taken into account the effects of shell resorption in the
brachial valve and the development of crescentic tubercles in the pedicle valve. Some evidence has been obtained
which indicates that the pedicle opening of M. granulosa occupied a supra-apical position. Despite the general
spiriferoid appearance of the shell-structure, the detailed microstructure of various morphological features of
the two valves, together with bulk morphological similarities, are thought to suggest strophomenoid affinity.

The micro structure outlined in this paper is based on combined evidence from serial
sections and polished blocks prepared from fifty-three specimens, comprised of brachial
valves, pedicle valves, and complete shells of Moorellina granulosa (Moore), from the
Oolite Marl of Westington Hill Quarry in the Cotswolds. The stratigraphy and location
of the quarry and the exact horizon from which the material was obtained have been
described in a previous paper (Baker 1969). A further horizon has been located in a
yellow-orange clay at the base of the Oolite Marl on the west face of the quarry but the
material recovered was not sufficiently well-preserved for the study of shell micro-
structure.

In the material studied, many of the shells are recrystallized but some are well
preserved. Partially recrystallized material is useful for comparing and contrasting the
unaltered shell with diagenetic effects.

A discussion of the thecideacean environment and a detailed account of the morpho-
logy of the brachial valve (PL 18, fig. 1) is given in an earlier paper (Baker 1969).

The most prominent feature of thecideidines is the elaboration of the brachial appa-
ratus. The inevitable result of interest in this structure is that in much of the published
work the pedicle valve is neglected.

The pedicle valve of thecideaceans is subject to much less variation than the brachial
valve and the pedicle valve of M. granulosa (PI. 18, fig. 2) is morphologically very similar
to that of Bifolium faringdonense (Dav.), described by Elliott (1948). Attachment to the
substratum is by cementation and the shape of the pedicle valve is greatly influenced
by the size of the scar of the area of attachment. Ontogenetic development of the valve
concerns the appearance and development of crescentic tubercles, the change in position
of the hinge teeth and the change in the relative proportion of the hemispondylium.

[Palaeontology, Vol. 13, Part 1, 1970, pp. 76-99, pis. 18-21.]

BAKER: MOORELLINA GRANULOSA (MOORE)

77

The shell of M. granulosa is endopunctate and shows the apparently random distri-
bution noted by Elliott (1955). However, neither the models proposed by Kemezys
(1965) nor Cowen (1966), satisfactorily explain the punctation mosaic observed in
thecidellinids. An account of the punctation mosaic and the proposal of a new model
is to be published separately.

During analysis of the microstructure, particular care has been taken to attach signi-
ficance only to structures seen in at least six different specimens. Occasional peculiar
features are noted which may be important but occur so infrequently in the material
studied that firm conclusions must not be drawn from them.

Acknowledgements. The author is indebted to Dr. J. D. Hudson, Geology Department, University of
Leicester, for supervision of the preparation of this paper. Thanks are due to Dr. M. Talbot, Geology
Department, University of Dundee, for the loan of Upper Oxfordian material for comparison pur-
poses and to Mr. G. McTurk for preparing the stereoscan negatives. Finally I wish to thank Professor
P. C. Sylvester-Bradley for use of the research facilities of the University of Leicester.

Registration of material. The material figured in this paper, in the form of etched blocks and complete
specimens, together with original peels and, where available, duplicates, is to be housed in the museum
collection of the Department of Geology, University of Leicester, under the catalogue numbers quoted.

PREPARATION OF MATERIAL

A comprehensive account of the preparation of Oolite Marl material is given in
Baker (1969) and the material studied in the present paper was obtained by the same
method. For micro structure investigation however, it has been discovered that reduction
of the etching time from ten seconds in 5 % HC1, to eight seconds in 3 % HC1 yields
better results. In addition it was found that fresh resin does not make a good bond with
plain glass slides and blocks may become detached during sectioning. A more effective
bond is obtained by the use of ground glass slides.

GROWTH AND DEVELOPMENT OF THE SHELL

General. The nature of shell growth is mixoperipheral, leading to a strophic condition
(Rudwick 1959, p. 18), as, contrary to the belief of Elliott (1965), a small hypercline
dorsal interarea (by definition, Williams 1965, H59) is present (PI. 18, fig. 5). The lateral
profile is obscured by the area of attachment but in forms with a small area of attach-
ment, may be described as modified piano- to concavo-convex with a rectimarginate
commisure. Certain differences in the development of structures in the brachial
and pedicle valves have taxonomic significance and they will be discussed separately,
following an account of the general shell growth.

A comprehensive account of shell deposition in living brachiopods is given by
Williams (1956, 1966, 1968a, b ), Williams et al. (1965) and it is reasonable to suppose
the shell of Moorellina granulosa (Moore) was deposited in the same manner. Evidence
presented in this paper shows that Williams (1968a) is in error in regarding the single
layered shell of Lacazella mediterranea (Risso) as typical of the thecideidine shell struc-
ture. M. granulosa clearly shows the development of primary and secondary shell layers.

As described in an earlier paper (Baker 1969) the brachial valve of M. granulosa is
initially almost circular, later becoming broader than long. However, study of a number

78

PALAEONTOLOGY, VOLUME 13

of specimens shows that the shape of the brachial valve is really controlled by the shape
of the pedicle valve, which is itself strongly influenced by the size of the scar of the area of
attachment. Williams (1956) has shown that although cell division occurs throughout
the epithelium the enlargement of the brachiopod shell is controlled mainly by peri-
pheral zones of growth.

Various aspects of the mode of shell growth have been defined by Rudwick (1959,
p. 2). It is convenient for the purpose of demonstrating the mode of growth in M.
granulosa to use his second interpretation, i.e. that the shell surface represents a series
of sectors which were formed continuously by different arcs of the valve edge.

At a magnification of 250 x linear, the external surface of the shell of well-preserved
specimens of M. granulosa is seen to be covered with small fibres. These fibres are in-
clined radially outwards from the umbo at a low angle from the shell surface and show
an orientation normal to the growth-lines and commissure (PI. 18, fig. 3). If one assumes
that the fibres are associated with the deposition of primary shell, either mechanically
or crystallographically, their orientation directions may be used as growth vectors for
the determination of points of relatively rapid increase in various arcs of the commissure.

Rudwick has shown how growth at any point on the valve edge may be resolved into
component growth rates. By assigning a value of one growth unit to an arbitrary surface
area corresponding to Rudwick’s growth points (1959, text-fig. 1 a), provided that the
growth vectors are known, different rates of growth in different sectors of a shell can be
fairly accurately determined. To demonstrate this adequately in M. granulosa necessi-
tates the introduction of additional ‘momentary’ and ‘cumulative’ terms. The growth
vector may be regarded as the cumulative product of the arrangement of growth units
normal to the mantle edge. The total number of growth units per growth vector may be
represented as dfdx, where d represents the length of the vector and x represents the
surface area of the growth unit. Proliferation points occur where the distance between two
growth vectors has doubled and proliferation arcs are represented by lines joining series
of new proliferation points. The growth rate in any sectors may be determined by the
growth acceleration, v, which is represented by the number of proliferation arcs in any
sector. The relative growth index may therefore be expressed as v(d/dx) for any sector

EXPLANATION OF PLATE 18

Stereoscan photomicrographs of specimens of Moorellina granulosa (Moore) from the Oolite Marl,

Westington Hill Quarry near Chipping Camden. All figures are of specimens coated with evaporated
aluminium before photography.

Fig. 1. Interior view of a brachial valve (37512) showing the median septum and tuberculate sub-
peripheral rim. Bridge and brachial apparatus broken, x 40.

Fig. 2. Interior view of a pedicle valve (37513) showing the teeth, supported hemispondylium and the
sub-peripheral crescentic tubercles. Umbonal cavity filled by the broken cardinal process, x 40.

Fig. 3. External surface of a portion of the left poster o-lateral region of a brachial valve (37512) show-
ing the oriented fibres on the surface of the primary layer. Scale represents 30 fx.

Fig. 4. Lateral view of a complete specimen (37511) showing the growth habit and large free ventral
anterior surface, x 50.

Fig. 5. Posterior view of specimen (37511) showing the large, ventral and small, dorsal interareas.
Angle of incidence 40°. x 40.

Fig. 6. Profile view of an enlarged portion of specimen (37513) showing the supporting septum of the
hemispondylium, with the dental ridges continuous with the outer edges of the hemispondylial
plates. Angle of incidence 60°. x 65.

Palaeontology, Vol. 13

PLATE 18

BAKER, Moorellina granulosa

BAKER: MOORELLINA GRANULOSA (MOORE)

79

of the valve. In Rudwick’s terms, proliferation points and proliferation arcs are momen-
tary and growth acceleration and relative growth index are cumulative.

text-fig. 1. Reconstruction of the primary growth vectors of M. granulosa, plotted from oriented
fibres. Proliferation arcs dotted. Concentric lines represent visible growth-lines, a. Right half of a
brachial valve. Numbers indicate relative growth indices in different sectors, b. Right half of a pedicle
valve. Broken lines within the area of attachment represent the vector mosaic inferred by the brachial
valve. Commissure projected stereographically to allow plotting of the primary growth vectors. The
relative position of a.a. edge of the area of attachment, c. commissure and i. edge of interarea, plotted
from cellulose acetate peels, h.l. hinge-line.

Brachial valve. The growth of the brachial valve of M. granulosa, when expressed in the
manner outlined, shows a marked radial pattern with a high relative growth-rate antero-
laterally (text-fig. 1a). For the reasons outlined in Williams and Wright (1963) it is
considered that it is only necessary to plot the data for one-half of the valve.

The validity of the above interpretation obviously rests on the assumption that the
proposed association of fibre orientation with deposition of the primary layer is correct.
The author is alive to the possibility that in the material investigated, the growth vectors

80 PALAEONTOLOGY, VOLUME 13

are not recorded from the exposed ends of primary fibres but from crystallites growing on
their outer ends. However, the fibre orientation pattern shows a remarkable constancy
in the thirty external brachial surfaces examined. Even if the development of the fibres I
is diagenetic, the constancy of their orientation pattern must be in some way connected
with the micro structure of the primary layer, most probably the crystallographic orienta- '
tion of the primary fibres themselves (Cloud 1942, p. 24).

Pedicle valve. Analysis of the growth-lines of the pedicle valve of Thecidiopsis (Nekvasi-
lova 1967) has enabled determination of the mode of development. Study of M. granu-
losa shows that the pedicle valve exhibits the same development regime, which, when
advanced, produces an almost linear pattern masking the radial growth typical of
brachial valves. After the development of the area of attachment and presumably in
response to environmental influence, material is added to the anterior and antero-
lateral regions of the pedicle valve much more rapidly than in the other regions so that
the angle between the plane of the commissure and the plane of the area of attachment
changes rapidly and the anterior and antero-lateral regions of the shell develop rapidly
without appreciably increasing the length of the commissure. This means that the
deposition of the primary layer of the pedicle valve although remaining normal to the
valve margin shows a distinctly linear growth orientation anteriorly (text-fig. 1b). In
Rudwick’s terms therefore, the growth of the shell of M. granulosa is characterized by
a declining vertical component in the brachial valve and an increasing vertical com-
ponent in the pedicle valve, a cumulative growth pattern which obviously serves to lift
the anterior gape away from the substratum (PL 18, fig. 4).

Secondary layer. As shown by Williams the secondary shell consists essentially of fibres
arranged with their long axes at a low inclination to the internal surface of the primary
layer and overlapping to a greater or lesser extent according to the angle of inclination,
usually about 10°. By plotting the orientation of the long axes of exposed parts of |
secondary fibres, Williams (1968a, pp. 10-15) has demonstrated a discernible lineation
in several genera. Construction of a secondary growth mosaic for M. granulosa shows the
existence of the same spiral arc arrangement in which there is a relatively constant J
deflexion of the secondary fibres (text-fig. 2). The pattern is modified anteriorly in the
brachial valve by the development of the relatively very thickened anterior of the median
septum. There is no sign of peripheral reorientation normal to the shell edge but this
may simply be the result of the disruptive influence of the tubercle cores. Williams (1966,
p. 1148) notes the blurring of the pattern in areas of excessive calcite deposition in
terebratuloids. In the pedicle valve also, the spiral arc pattern is modified anteriorly by
the development of the crescentic tubercles. However, although Williams is able to
demonstrate the bulk migration of the mantle in the direction of growth (1968a, p. 8)
in order to account for the inclination of secondary fibres, the reason for the migration
has not been explained. Study of his text-figure makes it apparent that it is impossible
to extend the fibre series anteriorly or posteriorly without changing their inclination.
The situation is further complicated by trying to impose the model on a convex shell.
There is ample figured evidence, however, to show that his account of fibre shape must
be correct. The solution to the problem must, therefore, lie in the orientation of the fibres
themselves. The length of the fibres in any zone of the shell seems to remain fairly con-
stant, suggesting that the cells of the epithelium secreting them have a standard life and

BAKER: MOORELLINA GRANULOSA (MOORE)

81

secretory activity. Obviously the rate of cell division in the mantle groove must vary to
account for the growth characteristics of the shell. If the organization of the cells is such
that the calcite of the secondary fibres is secreted at a fairly constant rate, areas showing

text-fig. 2. Reconstruction of the secondary growth mosaic of M. granulosa, plotted from twenty-
five superimposed peels. Solid outline represents the position of the sub-peripheral rim, median
septum, and cardinal process.

a relatively slow vectoral primary growth rate, i.e. postero-lateral sectors, must suffer
from a build-up of secondary shell, unless the fibres are deflected away from the primary
growth vectors in order to prevent the shell from becoming excessively thickened. Con-
versely the fibres may be deflected towards areas where thickening of the shell is taking
place, such as the development of the median septum (text-fig. 2). This orientation deflex-
ion of the secondary fibres away from sectors of relatively decelerated deposition of
primary shell material would readily explain the forward migration of the secreting cells
and the difference in orientation between the vectors of the primary and secondary
layers (text-figs. 1a, 2).

C 7173

G

82 PALAEONTOLOGY, VOLUME 13

DEVELOPMENT OF SPECIFIC STRUCTURES
Development of the sub-peripheral rim. Very little progress regarding the determination
of the microstructure of the brachial valve was made until the mode of development of
the sub-peripheral rim was appreciated. Williams (1968a, p. 50) described local resorption
in Lacazella and resorption is found to play an important role in M. granulosa. Onto-
genetic studies (Baker 1969) show that the sub-peripheral rim appears at the pre-
forbesiform stage of development and subsequently occupies the same position relative
to the valve margin, irrespective of the size of the valve. As the sub-peripheral rim is too
prominent to be submerged by subsequent secondary shell deposition, it must migrate
outwards. Evidence that the migration is accomplished by development at the external
margin of the rim and resorption along its inner margin will be presented later. The sub-
peripheral rim is tuberculate and the generative zone of the tubercles appears to be
where the secretory activity of the outer epithelial cells changes from the deposition of
primary to the deposition of secondary fibres.

Development of the hemispondylium. Elliott (1948) noted the presence of a structure in
the floor of the pedicle valve of Bifolium faringdonense (Davidson) to which he gave the
name hemispondylium. In his opinion, the structure was not formed by the fusion of
dental plates. Elliott also noticed the presence of what might almost be called dental
ridges, buttressing the hinge teeth internally but adopted the view that they played no
part in the formation of the muscle supports (spondylium) as in other brachiopods, a
view confirmed by the present work. Some specimens of M. granulosa however, show that
the buttressing ridges which may represent rudimentary dental plates, are continuous
with the upturned outer edges of the hemispondylial plates (PI. 18, fig. 6). This arrange-
ment is an interesting feature and may be homologous with the ankylosed median
septum-dental ridge structure of the davidsoniacean Orthotetes.

Sectioned material enables resolution of the problem. Forms with a supporting septum
have the appearance of possessing a spondylium simplex (text-fig. 3a-c, g). However,
forms with a sessile hemispondylium show quite clearly that the dental ridges simply
merge with the floor of the valve (text-fig. 3d-f, h). There can be no doubt therefore,
that Elliott’s interpretation is correct and that the hemispondylial plates are not formed
by the fusion of dental plates but from secretion of secondary shell by the outer epi-
thelium adjacent to the supporting septum. The dental ridges may or may not unite
with them depending on the growth habit of the valve. In forms with well-developed
dental ridges it is possible to obtain sections which are strikingly similar to sections
through the umbonal region of pedicle valves of Derbyia (Williams et al. 1965, H404,
fig. 261 d). As Nekvasilova (1964) has recorded in Lacazella ( B ) lacazelliformis (Elliott)
and as Elliott has recorded in B. faringdonense , the hemispondylium is present in the
smallest valves studied and may be sessile or supported by a median septum. Rare
specimens may show the hemispondylial plates supported by a double septum anteriorly.
A single specimen of M. granulosa shows the hemispondylial plates supported by three
septa whilst another (PI. 19, fig. 1) shows a reticulate support. The form of the hemi-
spondylium may be correlated with the form of the area of attachment and is apparently
related to muscle efficiency (Elliott 1948, p. 20).

Development of the crescentic tubercles. Post-forbesiform and adult pedicle valves are
characterized by the development of structures along the internal edge of the valve

BAKER: MOORELLINA GRANULOSA (MOORE)

83

text-fig. 3. A-c. Three serial sections through M. granulosa to show the form of the supported hemi-
spondylium. d-f. Three serial sections, showing the form of the sessile hemispondylium. g. Three-
quarters profile reconstruction of a supported hemispondylium, showing the dental ridges continuous
with the hemispondylial plates, h. Three-quarters profile reconstruction of a sessile hemispondylium,
showing the dental ridges merging with the floor of the valve. Outline of brachial valve dotted, d.r.
dental ridge, h. root of sessile hemispondylium, h.p. hemispondylial plate, p.l. primary layer, s.l.
secondary layer, s.s. supporting septum, t. tooth, t.r. tooth ridge.

margin (PI. 18, fig. 2; PI. 19, fig 2). which Elliott in B. faringdonense has called
sub-pustulose marginal ornament. In M. granulosa these structures can be shown to be
modified tubercles and are thought to be of considerable importance. As their shape is
quite characteristic it is proposed to designate them crescentic tubercles. They appear

PALAEONTOLOGY, VOLUME 13

to be most strongly developed in the anterior and antero-lateral sectors of the valve
and show a development pattern entirely different from that of the tubercles of the sub-
peripheral rim. Crescentic tubercles do not appear until the anterior of the pedicle valve
begins to grow away from the attachment surface. They apparently grow simply by the
incremental addition of material at their distal ends and the secreting cells must occupy
an invagination of the outer epithelium so that the tubercle cores stay slightly in advance
of adjacent outer epithelial secretory cells. Their relationship with adjacent secondary
fibres would indicate that their long axes are not quite parallel with the internal shell
surface but inclined dorsally inwards at an angle of about 2°. This development pattern
of the crescentic tubercles is obviously related to the maintenance of a constant orienta-
tion relative to the tubercles of the sub-peripheral rim (text-fig. 6a, c).

DETAILED MICROSTRUCTURE

As already noted, Moorellina granulosa (Moore) offers conclusive proof that in some
Jurassic thecidellinids at least, the shell was differentiated into primary and secondary
layers. The primary layer is best seen in the pedicle valve where it is relatively much
thicker than in the brachial valve. It is possible that in some specimens the thin primary
layer may occur only sporadically as in orthoids and strophomenoids where its absence
is attributable to wear of a very thin layer. The possibility of the removal of the primary
layer is important in the interpretation of occasional pitted structures, described later,
occurring in the outer surface of some brachial valves.

The primary crystallite mat gives the typical fibrous, transverse (PI. 19, fig. 3) and
pitted, horizontal (PI. 19, fig. 4) sections described by Williams. Transverse sections
through secondary fibres show typical cross-sections (Williams 1968a, p. 9) with the
exception that the lateral areas are much reduced so that a sub-hexagonal pattern is
produced (PI. 19, fig. 5). This standard shape appears to persist throughout the secondary
layer of the pedicle valve but shows some modification in the brachial valve. Patches of
fibres in the brachial valve show dorso-ventral flattening distally so that they develop

EXPLANATION OF PLATE 19

Stereoscan photomicrographs of specimens of Moorellina granulosa (Moore). Material of all figures
coated with evaporated aluminium before photography.

Fig. 1. Interior view of a broken pedicle valve (37514) showing the hemispondylial plates supported by
a reticulate structure. Umbonal region missing, x 40.

Fig. 2. Enlarged portion of the margin of pedicle valve (37515), showing the position and characteristic
shape of the crescentic tubercles, x 170.

Fig. 3. Etched surface prepared from polished block (37516) showing the primary layer in transverse
section, lower right, and detail of the junction with the secondary layer. Section orientation : vertical,
longitudinal. Section location : pedicle valve, free anterior surface, close to the area of attachment.
Scale represents 4 /z.

Fig. 4. Stereoscanned cellulose acetate peel (37518), showing the primary layer in horizontal section,
lower right. Section orientation: perpendicular to the plane of the commissure at 75° to the long
axis. Section location : pedicle valve, left postero-lateral sector. Scale represents 8 ju.

Fig. 5. Stereoscanned cellulose acetate peel (37518) showing transverse section through secondary
fibres. Section orientation and location as fig. 4. Scale represents 5 /z.

Fig. 6. Interior of the brachial valve of a pre-forbesiform individual (37503) showing endopuncta and
the exposed inner ends of secondary fibres on the floor of the left brachial cavity. Scale represents 5 /z.

Palaeontology, Vol. 13

PLATE 19

BAKER, Moorellina granulosa

BAKER: MOORELLINA GRANULOSA (MOORE)

85

text-fig. 4. A. The distribution of the tubercle cores (dotted) in the brachial valve of M. granulosa,
plotted from twenty-five superimposed peels. The core distribution inside the sub-peripheral rim,
outlined, indicates the areas of the brachial cavities where resorption has occurred, b. Diagrammatic
representation of the probable mode of migration of the sub-peripheral rim during growth, c. Normal
and flared transverse mosaics, d. Diagram to show the shape of an individual fibre, b.c. brachial
cavity, k. keel, l.a. lateral area, p.l. primary layer, r.g. rim generation zone, r.r. rim resorption zone,
s.l. secondary layer, s.p.r. sub-peripheral rim, t.c. tubercle core.

86

PALAEONTOLOGY, VOLUME 13

flared ends (text-fig. 4c, d). The possibility that these were merely apparent transverse
sections, produced by fibre reorientation was checked against horizontal longitudinal
sections through fibres. The flared secondary fibres have a characteristic strap-like
appearance and are up to three times (10-12 /u.) the width of normal fibres. It is possible
that the modified fibres are associated with muscle scars but this could not be confirmed
in the material studied. The location of the sections however, would suggest that the
fibres occur in zones of the valve which were not areas likely to be associated with
muscle attachment.

The variability of the fibres in section and the consequent possibility of misinterpreta-
tion of sections has been noted by Williams (1966, p. 1 148). The present work has been
hindered by the same rapid changes of fibre orientation. Studies indicate that orientation
variation in the secondary layer may occur at different depths, in different sectors of a
valve, and that the micro structure of the brachial and pedicle valves of the same animal
may show significant differences. For this reason it is felt that all future plate figures
must be accompanied by accurate data concerning the orientation of sections through
the specimen and the exact location of the section on the shell. The author has attempted
to present such data in a concise form in the plate explanations, to enable other workers
to avoid or duplicate these sections in subsequent investigations.

Relatively large areas of the brachial cavities of M. granulosa are formed by the pro-
gressive resorption of the sub-peripheral rim (text-fig. 4a, b). As a result of resorption
in these areas, the fibre orientation persisting at the bases of former sub -peripheral rim
tubercles is exposed on the internal surface of the valve, producing a very disturbed
pattern (PI. 20, figs. 1, 2). Once the significance of rim resorption had been appreciated,
it was realized that undisturbed secondary mosaic would only be seen in areas which
were not affected by shell resorption. This suggested three possible sites, (a) the border

EXPLANATION OF PLATE 20

Stereoscan photomicrographs of Moorellina granulosa (Moore) except figs. 7 and 8. Material of all
figures coated with evaporated aluminium before photography.

Fig. 1. Interior view of a brachial valve (37519), showing an endopuncta and disturbed secondary
mosaic, right, in the area affected by resorption of the sub-peripheral rim. Scale represents 5 /x.
Fig. 2. Stereoscanned cellulose acetate peel (37520), showing the disturbed secondary layer of the
brachial valve and the development of flared fibres, lower centre. Section orientation : parallel with
the plane of the antero-lateral surface. Section location: right antero-lateral sector 0-12 mm. from
the external surface of the valve. Scale represents 25 /a.

Figs. 3-5. Stereoscanned cellulose acetate peel (37522).

Fig. 3. Section through the sub-peripheral rim showing the tubercle cores in cross section, offset by
one half-phase. Two partially resorbed cores are visible alcng the inner margin of the rim, top left.
Section orientation : parallel with the plane of the commissure. Section location : brachial valve, left
antero-lateral sector 0-048 mm. from the distal ends of tubercles. Scale represents 20 [a.

Figs. 4, 5. Isolated tubercle cores in areas of the brachial cavity affected by resorption of the sub-
peripheral rim (fig. 4) and tubercle cores continuous with the primary layer (fig. 5, centre and
lower right). Section orientation and location as in fig. 3, but 0T44 mm. from the distal ends of
tubercles. Scale represents 20 /a.

Fig. 6. Stereoscanned cellulose acetate peel (37523). Vertical section through the sub-peripheral rim
showing tubercle cores in oblique section. Section orientation : perpendicular to the external shell
surface at 85° from the long axis. Section location : brachial valve, right antero-lateral sector. Scale
represents 30 /x.

Figs. 7, 8. Stereoscan photomicrograph of the external surface of a brachial valve of Moorellina ornata
(Davidson) (37524), showing detail of the structures interpreted as weathered tubercle cores, x 1000.

Palaeontology, Vol. 13

PLATE 20

BAKER, Moorellina granulosa

BAKER: MOORELLINA GRANULOSA (MOORE)

87

region outside the sub-peripheral rim, ( b ) the pedicle valve, and ( c ) the brachial cavities
of pre-forbesiform (Baker 1969) individuals, where rim resorption had not yet begun.
A detailed examination of brachial and pedicle valves was then undertaken with these
considerations in mind. The border region has proved to consist entirely of primary shell
and the mosaic on the inner surface of the pedicle valve is obscured by the development
of crescentic tubercles. A pre-forbesiform brachial valve (37503) however, clearly shows
traces of the internal mosaic of the secondary layer (PI. 19, fig. 6).

The observed differences in the brachial and pedicle valves of M. granulosa have
produced significant differences in micro structure and render it necessary that the
micro structure of the two valves be described separately.

Brachial valve. A thin primary and a disturbed secondary layer associated with the
development and migration of the sub-peripheral rim are present.

A detailed investigation of the tubercles of the sub-peripheral rim was undertaken. If
the concept of resorption is correct, it should be possible to distinguish the remains of
tubercle cores in areas of the brachial cavity formerly occupied by the sub-peripheral
rim. Horizontal, transverse, oblique, and longitudinal sections were prepared in order
to establish their presence. Horizontal serial sections (PI. 20, figs. 3-5) show that the
tubercles are cored structures and that the tubercle cores are, in fact, continuous with the
material of the primary layer (PI. 20, fig. 5). The tubercle cores may be regarded there-
fore, as being composed of primary shell type material. The question of whether the
primary layer has suffered diagenesis has little significance as the material of this layer
and of the tubercle cores has the same characteristics and may logically be considered
to have the same origin. The author envisages localized patches of outer epithelium con-
tinuing to secrete primary shell. It seems probable that the mechanism of development
is similar to that which controls the initiation of punctae, as tubercles also are normally,
but not universally, offset by one half-phase (PL 20, figs. 3, 5). A plot of the tubercle cores
in superimposed serial sections through a brachial valve of M. granulosa shows that they
persist through several sections and are intimately connected with the development of
the sub-peripheral rim. They do not appear in zones of the shell which may be logically
considered to have been deposited prior to the appearance of that structure (text-fig.
4a). Horizontal sections through the sub-peripheral rim (PI. 20, fig. 3) confirm that the
tubercle cores originate near the mantle edge, in fact at the outer boundary of the sub-
peripheral rim itself, and close to the point where the secretion of secondary shell begins.
Subsequent isolation of eroded tubercle cores in the brachial cavities is brought about
by the mode of development of the sub-peripheral rim during ontogeny (PI. 20, fig. 4).
Vertical sections (PI. 20, fig. 6) show that the tubercle cores are inclined at a high angle,
almost normal to the external shell surface, with a slight outward deflection.

That the tubercle cores of the brachial valve are composed of primary shell material
would appear to be confirmed by occasional curious pitted structures occurring on the
external surface of valves. Although these occur in M. granulosa they are better preserved
in the Upper Oxfordian, Moorellina ornata (Moore) (PI. 20, figs. 7, 8). Each pit has a
central granular mound and may possibly be interpreted as some form of exopuncta.
However, in the light of observations regarding the thickness of the primary layer and
the fact that the tubercle cores are shown to be continuous with it, it would appear that
what is actually seen is the outer boundary of the secondary layer, exposed by the

88 PALAEONTOLOGY, VOLUME 13

removal of primary shell. In which case, the apparent bands are the long axes of fibres
and the central mounds of the pits are really weathered tubercle cores. This is supported
by : (a) the orientation of the fibres is correct if they constitute part of a normal spiral
arc, (6) they are the right thickness, about 4 /x, ( c ) the granular nature of the central
mound is the same as that of sectioned tubercle cores, ( d ) the diameter of the pits is the
same as the diameter of tubercle cores in section, i.e. 25-30 [x , and (e) they are too large
to be normal punctae which have a diameter of only 8-10 /x.

Pedicle valve. A well-developed primary and secondary layer are present. The primary
layer thins posteriorly and the secondary layer shows modification anteriorly as a result
of the growth habit of the valve.

Attempts to reconstruct a secondary mosaic in the manner described above, failed to
produce a decipherable pattern because the secondary layer of the pedicle valve of
M. granulosa is itself composed of two regions with regard to fibre orientation. There
is an outer, essentially normal, spiral arc orientation and an inner layer in which the
fibre orientation is intimately bound up with the development of the crescentic tubercles
(PI. 21, figs. 1, 2). In the lateral and postero-lateral sectors of the valve, the secondary
fibres show a normal spiral arc arrangement. In the zones of the anterior surface adjacent
to the area of attachment, the orientation of the fibres of both regions of the secondary
layer appear to follow the primary growth vectors and longitudinal sections produce
typical longitudinal sections through fibres (PI. 21, fig. 3). However, as growth of the
pedicle valve proceeds away from the substratum, the secondary layer is differentiated
into outer and inner regions. The orientation of the fibres in the outer region changes
in such a way that they come to lie almost parallel with the commissure. Longitudinal

EXPLANATION OF PLATE 21

Stereoscan photomicrographs of specimens of Moorellina granulosa (Moore). Material of all figures
coated with evaporated aluminium before photography.

Fig. 1. Stereoscanned cellulose acetate peel (37520). Transverse section through a pedicle valve showing
the orientation of the outer fibres of the secondary layer and the reniform tubercle cores. Section
orientation : parallel with the plane of the commissure. Section location : left antero-lateral sector,
0-4 mm. from the distal ends of the tubercles. Scale represents 50 /x .

Fig. 2. Stereoscanned cellulose acetate peel (37521). Section through the secondary layer showing fibres
deflected by the crescentic tubercles. Section orientation : parallel with the anterior surface. Section
location: pedicle valve, anterior surface, 0T68 mm. from the external surface. Scale represents 20 (x.

Figs. 3, 4. Etched surface prepared from polished block (37516). Section orientation and location as
in fig. 3 (PI. 19). Fig. 3 shows the primary layer, bottom and detail of the secondary fibres in
longitudinal section. Fig. 4 shows reorientation of the fibres of the outer region of the secondary
layer to give almost transverse section. The elongate fibres (oblique section), upper left, represent
a tubercle core sectioned near the axis. Scale represents 10 /x.

Fig. 5. Stereoscanned cellulose acetate peel (37521). Section through the secondary layer showing the
fibrous cores of the crescentic tubercles. Section orientation and location as in fig. 2, but 0-096 mm.
from the external surface. Scale represents 50 /x.

Fig. 6. Interior view of the anterior surface of a pedicle valve (37515) showing the arrangement of the
punctae in rows relative to the crescentic tubercles, x 50.

Fig. 7. Stereoscanned cellulose acetate peel (37523). Transverse section through the ventral umbonal
region showing the plugged pedicle opening and dorsally exposed pedicle sheath. Section location:
0 08 mm. from the umbo. Scale represents 50 /x.

Fig. 8. Retouched photomicrograph of fig. 7.

Palaeontology, Vol. 13

PLATE 21

BAKER, Moorellina granulosa

BAKER: MOORELLINA GRANULOSA (MOORE)

89

text-fig. 5. Reconstruction of the fibre orientation of the outer and inner regions of the secondary
layer of the free anterior of the pedicle valve of M. granulosa, from eight superimposed peels. A. Fibre
orientation of the outer region, b. Fibre orientation and tubercle cores of the inner region. Numbers
indicate the position of the tubercles in successive peels, from the internal surface of the valve.

90

PALAEONTOLOGY, VOLUME 13

sections through these zones produce almost transverse sections through the fibres of
this outer layer (PI. 21, fig. 4).

With this information available the growth mosaics of the two regions were fairly
easily reconstructed by plotting the fibres of the outer and inner regions separately. This
was achieved by plotting the primary/secondary layer junctions of serial sections, together
with the orientation direction of the fibres adjacent to the junctions. The mosaic produced
(text-fig. 5a) was interpreted as representing the growth mosaic of the outer region of the
secondary layer of the anterior surface of the pedicle valve. Similarly, a re-plot of the
remaining fibre orientation on each serial section, i.e. omitting those plotted in text-fig.

5 a, was interpreted as representing the growth mosaic of the inner region of the secondary
layer (text-fig. 5b). A suggested explanation for this anterior differentiation is offered
later, as it can be shown not to be present throughout the whole of the secondary layer.

As in the brachial valve, the structure of the crescentic tubercles was investigated with
the aid of transverse, horizontal, oblique, and longitudinal serial sections. In longitudinal
sections the tubercles are seen to be composed entirely of fibrous cones (PI. 21, figs. 2, 5)
deflecting the other fibres adjacent to them. In transverse section (PI. 21, fig. 1) the
tubercles exhibit a characteristic reniform shape. The presence of these structures may
be of profound significance and their implication is discussed later.

Compilation of the features exhibited by serial sections at various orientations allows
reconstruction of the microstructure of the shell of M. granulosa (text-fig. 6a-c).

The pseudo deltidium and pedicle sheath. Study of Lacazella (Williams et al. 1965) indicates
that neither the pedicle nor its muscle system is developed. The structure of the stropho-
menoid pseudodeltidium is still imperfectly known but it is now generally agreed that
it consists of primary and secondary material and was secreted between the teeth ridges
by the outer epithelium. Ventral umbonal regions of well-preserved specimens of M.
granulosa were carefully sectioned in an attempt to resolve the problem of the fate of
the pedicle opening in Jurassic thecidellinids. Owing to the mode of growth of the area
and the minute proportions of the structures involved, it was difficult to distinguish the
pseudodeltidium at all. Of the limited number of specimens in which it could be recog-
nized, only three showed any discernible micro structure. In these specimens, transverse [
sections close to the ventral umbo show the presence of a minute pore 50 /x in diameter
and apparently plugged by calcite having a different orientation from that of the
pseudodeltidium (PI. 21, figs. 7, 8). The pore appears at about 0-06 mm. from the
posterior of the pedicle valve and close to the area of attachment (text-fig. 7c) in what
must be regarded as a supra-apical position (text-fig. 7h). It appears to be surrounded
laterally and dorsally by a collar or ring of material in which the fibres show a concentric
orientation in the plane of section. The dorsal surface of the ring is exposed externally
and is obviously the structure interpreted as a pseudodeltidium. In subsequent sections
the pore migrates dorsally away from the area of attachment and the ring increases in
size, still maintaining its dorsally exposed surface (text-fig. 7c-f). Continuity of the
structure through several sections reveals that it is really a calcareous tube, which, if the
plugged pore represents the site of the atrophied pedicle opening, may be regarded as a
form of pedicle sheath which initially closed the delthyrium. At about 0T4 mm. from
the umbo the structure terminates (text-fig. 7g) and is replaced by the ventral umbonal
cavity, housing the posterior tip of the cardinal process. The space between the tooth

BAKER: MOORELLINA GRANULOSA (MOORE)

91

text-fig. 6. Diagrammatic reconstruction of the shell microstructure of Moorellina granulosa
(Moore), a. Block diagram showing the microstructure of the brachial valve, b. Complete specimen
showing relative position of the reconstructed segments, c. Block diagram showing the microstructure
of the pedicle valve, c.t. crescentic tubercle, i.s.l. inner secondary layer, o.s.l. outer secondary layer,
p. puncta, p.l. primary layer, s.l. secondary layer, t. tubercle, t.c. tubercle core.

text-fig. 7. a-g. Drawings prepared from cellulose acetate peels of serial transverse sections through
the ventral umbonal region of M. granulosa showing the continuity and anterior termination of the
pedicle sheath and the plugged pedicle foramen, h. Reconstruction of the ventral umbonal region from
thirteen superimposed peels. Outline of the pedicle sheath dotted and the pedicle opening, broken line.
Position of umbo projected by dotted lines, i. Diagrammatic section through the sub-peripheral rim
to show the difference in the development of endopunctae and tubercle cores, j-o. Series of six
diagrams to show the orientation of the brachial apparatus relative to a prevailing current, arrowed.
j-l, constant growth position with variable size of the attachment surface, m-o, constant orientation
at various growth positions, c. caecum, c.p. cardinal process, d.i. dorsal interarea, o.e. outer epithelium,
o.m.l. outer mantle lobe, per. periostracum, psd. pseudodeltidium, p.f. pedicle foramen, p.l. primary
layer, p.s. pedicle sheath, s.l. secondary layer, t. tooth, t.c. tubercle core, t.r. tooth ridge, v.c. ventral

umbonal cavity.

BAKER: MOORELL1NA GRANULOSA (MOORE)

93

ridges is now occupied by a plate of more normal pseudodeltidial appearance. Unfortu-
nately, at the moment there is no evidence to show whether this is a discrete plate or
whether it is the product of overgrowth by the outer epithelium at the anterior termina-
tion of the calcareous tube. Atrophy of the pedicle would explain why the tube ceased
to develop and only closes the posterior part of the delthyrium, an operation sub-
sequently taken over by the outer epithelium.

SIGNIFICANCE OF THE OBSERVED GROWTH AND MICROSTRUCTURE

Growth orientation. Obviously there must be some genetic control of the proliferation
of epithelial cells in the mantle fold and it is not possible to show absolute growth in
M. granulosa. However, the use of a system of growth units makes it possible, providing
one knows the primary growth orientation, to determine areas of rapid proliferation of
cells and, therefore, relatively rapid increase in size. The observed external fibre orienta-
tion is clearly a topological expression of shell growth. There is a very close resemblance
between the distribution of primary costae in Rhipidomel/a oblata (Hall) and the external
fibre orientation of M. granulosa but this is to be expected if addition of material is
normal to the commissure with mixoperipheral growth. This would clearly suggest that
the radial ornament of the dalmanellaceids (Williams and Wright 1963, p. 22) is topo-
logical also. Work on the orientation pattern of M. granulosa would therefore appear to
confirm their view that dalmanellaceid ornamentation patterns of ‘progressive’ species
of Watsella (Bancroft 1945, p. 190) have no supra-specific taxonomic status.

The anteriorly modified spiral arc of the pedicle valve of M. granulosa, producing a
secondary layer differentiated into two regions can only be clearly demonstrated in
valves having a large free anterior surface. If one considers the thecideacean environ-
ment (Ager 1965, 1967; Nekvasilova 1967; Baker 1969) this anterior differentiation of
the secondary layer is readily explained. Forms with a large free anterior surface (small
area of attachment) would have relatively more of the pedicle valve exposed to the
rigours of the environment. Development of crescentic tubercles would produce a struc-
ture which would secure the commissure (interlocking effect) but at the same time pro-
duce an exposed anterior surface which could be more easily breached at the relatively
weak juctions between adjacent tubercles (PI. 21, fig. 5). Differentiation of the secondary
layer anteriorly into what might be described as a cross-laminate structure would greatly
increase its strength. The above seems a logical explanation for the observed micro-
structure of the pedicle valve of M. granulosa and the relationship between fibre orienta-
tion and micro structure of other attached brachiopods is well worth investigating.
Strophomenides, for example, may have solved the problem by the modification of fibres
to produce laminae (Williams 1968a, p. 37). The fibres with flared ends noted in the
brachial valve of M. granulosa may represent an attempt in this direction.

Ecology and functional morphology. Consideration of the growth habit of the pedicle
valve in ecological terms is interesting. If the cumulative growth pattern is designed to
lift the anterior gape away from the substratum, it is difficult to see why the characteristic
is suppressed in forms with a large area of attachment. It seems probable that it is the
degree of inclination, rather than the size of the surface to which the animal attaches
itself, which is the major control. Elliott’s (1948) paper would suggest that the relatively
enormous gape (Rudwick 1968) of the thecideidines is associated with orientation of the

94 PALAEONTOLOGY, VOLUME 13

brachial apparatus relative to the ‘prevailing’ environment, probably represented by a
persistent current direction.

The above relationship seems entirely probable and supports the author’s argument.
Individuals attaching themselves to surfaces of suitable inclination already have their
commissures in the ‘ideal’ orientation position from an ecological standpoint. Such
individuals would have no need to develop elaborate anterior surfaces, although develop-
ment of even the relatively small anterior surface encountered in these specimens must
inevitably require the cumulative growth pattern postulated.

There seems to be a correlation between size of animal and degree of elaboration of the
brachial apparatus (Elliott 1948), interpreted as being related to the animal’s food-
gathering ability in a competitive sense. This may partially explain the onset of the de-
velopment changes which lead to the freeing of the anterior of the pedicle valve from
attachment to the substratum. Size of the animal is obviously critical where small size of
the attachment surface is concerned but observations indicate that size may be critical
independently. Attainment of a certain size might render necessary a change in organi-
zation, to effectively meet the increasing nutritional demands.

There are obviously other factors to be considered such as accommodation of the
brachial apparatus and the developing sub-peripheral rim, the relative efficiency of the
lophophore and the ecological niche (Rudwick 1962) occupied by any particular
individual. However, if, as there would appear to be, there is any order associated
with the growth habit of thecideidines, it is easier to reconcile this, in ecological terms,
with the attainment of a certain orientation position of the gape (text-fig. 7j-o) rather
than the size of the surface to which the animal was attached. One feels that the orienta-
tion of the gape, in terms of functional efficiency of the brachial apparatus, is the more
satisfactory explanation for the variable growth habit observed in the pedicle valves
of thecidellinids.

As M. granulosa is a member of the surf-zone fauna, the interlocking tubercles of the
two valves on such cemented forms may have acted as accessory teeth and sockets to
help secure the brachial valve in position during adverse conditions. The preponderance
of brachial valves in any collection may be a measure of the relative vulnerability that
the abnormally wide gape exposed in the existing hinge.

Microstructure. Williams, in his work on Lacazella (1968a, b) apparently abandons his
earlier interpretation (1955, 1956, 1965) that a secondary layer is present, in favour of a
shell composed only of primary material. The three earlier accounts are essentially
similar. The 1955 paper records the presence of fibre bundles almost perpendicular to
the ‘lamellar’ layer, producing the appearance of pseudopunctae but, in the absence of
a non-fibrous core, unrelated to the strophomenid spicules. These core bundles are
figured in the rather vague reconstruction of the shell of Lacazella mediterranea (Risso)
in (1965, H67), but their orientation is apparently in the wrong direction. Attention is,
however, drawn to the similarity of this type of shell structure and that of the terebratel-
laceid Megerlina lamarkiana (Dav.). The 1956 paper records the same fibrous cores in
thecidaceids but offers no information as to which were studied. It is felt that the struc-
tures described must be referred to the micro structure of the crescentic tubercles of
M. granulosa (PI. 21, figs. 2, 5, text-fig. 6c).

The absence of a secondary layer in Lacazella is interpreted as being the result of

BAKER: MOORELLINA GRANULOSA (MOORE)

95

neotenous suppression (Williams 1968a). Although changes in the secretory habit of the
epithelial cells in M. granulosa appear to follow a normal pattern, the stability of the
thickness of the primary layer does not appear to be quite as constant as Williams has
suggested and it is possible to see groups of secondary fibres apparently embedded in
primary shell. This irregularity of deposition of the secondary layer in M. granulosa
may be the first expression of its ultimate suppression.

Although M. granulosa is not costellate, it is worth noting that the external expression
of the crescentic tubercles on the inner edge of the margin of the pedicle valve, bears a
strong resemblance to the follicular eminences and embayments of the Recent Tere-
bratulina and also fossil enteletacean (Williams and Wright 1963, p. 19; Williams and
Rowell 1965, H81) brachiopods and may have served a similar purpose. Similar
structures are seen in the cemented inarticulate Crania anomala (Muller) where they are
not associated with setae but control the distribution of punctae. In M. granulosa , the
crescentic tubercles appear to exercise a similar control over the distribution of punctate
(PI. 21, fig. 6).

Elliott (1953, 1955) has arrived at the conclusion that all thecideidines are enod-
punctate with the possible exception of Davidsonella. Study of M. granulosa and M.
ornata shows that although the endopunctae are formed in a terebratuloid manner, the
cup-shaped distal enlargements and the deflexion of secondary fibres have not been seen.

Deeper issues are at stake with regard to the implication of the described tubercle
structure. They occur together with endopunctae and the initiation of punctae and
tubercle cores seems to follow the same pattern. Upon consideration of their structure,
the question arises whether the tubercles are homologous with pseudopunctae. Tubercle
cores must arise in a very different manner from endopunctae (text-fig. 7i), and therefore
if homologous with pseudopunctae, pseudopunctae and endopunctae must be totally
unrelated.

Williams (1965, H72) has stated that taleolae are comparable in texture with the
terebratuloid primary layer. Sections parallel with the plane of the commissure through
M. granulosa have shown that the tubercle cores of the brachial valve are in fact con-
tinuous with the primary layer and as far as can be ascertained, represent imperfectly
developed primary shell, secreted by persistent patches of columnar epithelium, surviving
from the tip of the outer mantle lobe.

Williams (1965) has shown that pseudopunctae are markedly asymmetrical in longi-
tudinal section, with their apices directed inwardly and anteriorly to protrude from the
internal surfaces of both valves as tubercles. The orientation of the tubercles in the
brachial valve of M. granulosa shows this approximate pattern. In the pedicle valve, it
only requires a slight exaggeration of this trend to produce, in M. granulosa, tubercle
cores running almost parallel with the plane of the valve in such a way that they emerge
as tubercles along the inner edge of the anterior margin. In which case, they may be
regarded as homologous with the pseudopunctae of davidsoniaceans such as Derbyia,
which consist of fibrous cones of the type shown to exist in the pedicle valve of M.
granulosa (text-figs. 5b, 6c, PI. 21, fig. 5).

The suspected close relationship between pseudopunctae with and without taleolae
is confirmed by the presence of both types in a single animal. A careful sectioning tech-
nique, supported by the fact that the structures are located in different valves, enables
one to show that the tubercles of the brachial valve have cores, whilst those of the pedicle

96

PALAEONTOLOGY, VOLUME 13

valve are without cores. If one considers the pure mechanics of this arrangement it
would appear to be quite logical. In the brachial valve where orientation of the tubercle
axis is near perpendicular to the surface of the valve, the development of the primary core
in the manner suggested is the simplest way of bringing about an invagination of the outer
epithelium. On the other hand, in the pedicle valve, where by virtue of the growth habit,
the orientation of the tubercles must necessarily be nearly parallel with the valve inner
surface, a primary core would become very attenuated. In this situation it would be
far easier to produce a tubercle core by a slight change in the orientation of secondary
fibres.

If one considers the tubercles in terms of this functional requirement, they may be
regarded as the modified counterpart of strophomenoid pseudopunctae. They deflect
secondary fibres in the same way and the similarity of the disposition of the fibres pre-
sumably indicates a similar pattern of development.

AFFINITIES

The affinities of the Thecideidina have been a subject of interest and speculation for a
number of years, Elliott (1948, 1953, 1958), Rudwick (1968), and Williams (1965,
1968a, b) being notable among the later works. Demonstration of a primary and
secondary shell layer in M. granulosa invalidates only Williams’s (1968a;, b ) conclusion
that Lacazella is a typical model of the thecideidine shell and in no way impairs his line
of descent. If, as Williams’s work suggests, the secondary layer of Lacazella has been
neotenously suppressed to the point of exclusion, M. granulosa occupies an attractive
position, as Jurassic forms in which this process might just be beginning, represent an
important contribution to our knowledge. One feels that the diversity of shell micro-
structure encountered in a single specimen of M. granulosa, must represent a genetic J
disturbance which could quite easily result in the ultimate suppression of the secondary
layer. The banded shell of Lacazella might in environmental terms, more easily satisfy j
the requirements for a reinforced shell and render the structurally reinforced secondary
layer of M. granulosa obsolete, thus accounting for its disappearance. The secondary
shell mosaic seems closer to terebratulide or spiriferide than any other. However, the
shape of the fibres is different and also variable within an individual, so that one may
see fibres with flared outer ends reminiscent of the laminae of plectambonitaceans.
Still other features of the micro structure may be reconciled with davidsoniaceans.

The value of functional analysis of morphology, demonstrated by Rudwick (1968)
and the significant correlation between the modification of the micro structure of M.
granulosa and environmental influence, underlines an advance in our knowledge of
taxonomic technique. Obviously, not only structures but also their significance in
environmental terms must be critically examined before assigning a species to a parti-
cular systematic position, as convergence may be encountered at the micro structure
level. It is felt therefore, that the taxonomic importance of some aspects of shell micro-
structure should not, as has happened frequently in the past on discovery of a character,
be overestimated.

The value of shell microstructure from a taxonomic point of view has been discussed
by Williams (1956, 1968 a, b ), Rudwick (1968), and Gauri and Boucot (1968). As the
present investigations have shown, there are important differences between the micro-
structure of the brachial and pedicle valves of M. granulosa. That this is not a feature

BAKER: MOORELLINA GRANULOSA (MOORE)

97

peculiar to thecidellinids has been demonstrated by Gauri and Boucot (1968) who record
that in the pentamerids Antirhynchonella, Clorinda, and Zdimir, the prismatic layer is
absent from the brachial valve. Their study of pentameraceans and the gulf which exists
between Williams’s (1968a) thecideidine model and the observed microstructure of
M. granulosa indicates that the state of our knowledge of shell microstructure in brachio-
pods is not yet sufficiently advanced to allow anything other than a tentative taxonomic
significance to be ascribed to it.

With regard to the fate of the pedicle, it appears unlikely that M. granulosa will yield
the quality of evidence to enable one to make categoric statements concerning the micro-
structure of the pedicle opening. Evidence yielded by Lacazella mediterranea (Risso)
must remain suspect in view of the neotenous modification of this species. The main
hope seems to lie in the discovery of well-preserved, larger thecideidines from other
horizons. Only limited significance should therefore be attached to the pseudodeltidium
of M. granulosa until the evidence has been strengthened. If a pedicle sheath does arise
supra-apically, then it is possible to equate this with the strophomenoid pseudodel-
tidium. Arber (1942) has recorded a very similar solid pseudodeltidium, fused with the
floor of the pedicle valve in the Orthotetinae and Rafinesquinae. However, Williams
(1956) has noted an imperforate delthyrial cover in Eospirifer. The indication that the
pseudodeltidium of M. granulosa was deposited by the ventral edge of the capsule of
a pedicle undergoing atrophy, appears to confirm the views of Arber (1942) and Williams
(1956) regarding the form of the pseudodeltidium of Lacazella.

Although it appears that the thecideacean pseudodeltidium is homologous with the
pseudodeltidium of strophomenoids, Williams and Rowell (1965, HI 88) regard the
similarity between strophomenoids and thecideaceans as an expression of convergence
and derive the thecideidines from possible suessiacean ancestors. One must agree that
the secondary mosaic is very similar to Cyrtina but encounters the same time-gap
objection raised by Williams (1956) to the affinity proposed by Kozlowski (1929) for the
lophophore platforms of some plectambonitaceids and thecidaceids.

Structurally there appears to be no significant difference between strophomenoid
pseudopunctae and the tubercles of M. granulosa. The similarity between them and
pseudopunctae of the davidsoniacean Derbyia is even closer. On this basis, it would
not be unreasonable to conclude that the tubercles of thecidellinids are homologous
with strophomenoid pseudopunctae, functionally modified.

Elimination of obscure similarities, plectambonitaceid, enteletacean, terebratellacean,
etc., leaves one with the basic problem of whether the thecideidines show strophomenide
or spiriferide affinity. An analysis of the literature shows that the systematic position
of Thecospira is of critical importance as far as the thecideidines are concerned. It seems
strange that Williams (1968a), after lengthy discussion of the low taxonomic value of a
limited number of characters, should re-assign the genus to the Spiriferida solely on the
basis of its shell structure and admitted non-spiriferoid calcareous spires. If one
considers the points of similarity between M. granulosa and Thecospira they are most
striking. Both are strophic and show the same lateral profile. Thecospira shows punctate
and obscurely pseudopunctate representatives. M. granulosa is endopunctate but probably
independently from terebratuloid endopunctation (Williams 1968c, p. 489). The simi-
larity in Thecospira and M. granulosa, of the cardinal process, the hinge articulation, the
sub-marginal structures, the coalesced punctae and lateral shift of the main adductor

C 7173

H

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PALAEONTOLOGY, VOLUME 13

muscles is thought to be more than coincidental. Differences such as the lack of
costellate ornament may not be profound, as radially arranged fibres have been re-
cognized in M. granulosa. As spiral brachidia apparently evolved twice among the
Spiriferida, there is no reason why similar brachidia should not evolve in non-spiriferide
forms, e.g. Thecospira and Cadomella (Cowen and Rudwick 1966) whose epithelia had
the ability to resorb material. If one bears in mind the neotenous origin of the
thecideidines and extends the posterior horns of the brachial lobes of M. granulosa
(Baker 1969, text-fig. 3f) back to unite with the bridge extensions, one may derive or
‘lose’ a simple spiral brachidium as a result of the demonstrated resorptive activity
taking place in the brachial cavities.

Rudwick (1968) has put forward a reasoned argument for the assignment of the
Thecideacea to the Strophomenida, close to, but distinct from the Davidsoniacea. As
outlined in the discussion of possible environmental influence, the possibility of a con-
vergent origin of the davidsoniacean characters of M. granulosa must not be overlooked
but the similarity between Moorellina granulosa (Moore), the spire-bearing Thecospira,
and known davidsoniaceans such as Derbyia and Orthotetes is thought to be much too
close to be merely convergent. The weight of evidence now accumulated would suggest
that the thecideidines show affinity closer to the davidsoniaceans than any other group.
The author must agree with Rudwick, that on the basis of our present knowledge the
Thecideacea should be assigned to the Strophomenida.

REFERENCES

ager, d. v. 1965. The adaptation of Mesozoic brachiopods to different environments. Palaeogeography ,
Palaeoclimatol., Palaeoecol. 1, f43-72.

1967. Brachiopod palaeoecology. Earth-Sci Rev. 3, 157-79.

arber, m. a. 1942. The pseudodeltidium of the strophomenoid brachiopods. Geol. Mag. 79, 179-87.
baker, p. g. 1969. The ontogeny of the thecideacean brachiopod Moorellina granulosa (Moore) from
the Middle Jurassic of England. Palaeontology, 12, 388-99.

Bancroft, b. b. 1945. The brachiopod zonal indices of the stages Costonian to Onnian in Britain.
J. Paleont. 19, 181-252.

cloud, p. e. 1942. The terebratuloid Brachiopoda of the Silurian and Devonian. Spec. Pap. geol. Soc .
Amer. 38.

cowen, r. 1966. The distribution of punctae on the brachiopod shell. Geol. Mag. 103, 269-75.

and rudwick, m. j. s. 1966. A spiral brachidium in the Jurassic chonetoid brachiopod Cadomella .

Ibid. 103, 403-6.

elliott, G. f. 1948. Palingenesis in Thecidea (Brachiopoda). Ann. Mag. nat. Hist. (12) 1, 1-30.

1953. The classification of the thecidean brachiopods. Ibid. (12) 6, 693-701.

1955. Shell-structure of thecidean brachiopods. Nature, Lond. 175, 1124.

1965. Suborder Thecideidina. In moore, r. c. (ed.). Treatise on invertebrate paleontology, part

(H) Brachiopoda, H857-62. Univ. Kansas and Geol. Soc. Amer.
gauri, k. l. and boucot, a. j. 1968. Shell structure and classification of the Pentameracea M’Coy, 1844.
Palaeontographica Abt. A. 131, 79-135.

kemezys, K. J. 1965. Significance of punctae and pustules in brachiopods. Geol. Mag. 102, 315-24.
kozlowski, r. 1929. Les brachiopodes gothlandiens de la Podolie polonaise. Palaeont. polon. 1, 1-254.
nekvasilova, o. 1964. Thecideidae (Brachiopoda) der bohmischen Kreide. Sbor. geol. ved, Praha, P3,
119-62.

1967. Thecidiopsis ( Thecidiopsis ) bohemica imperfecta n. subsp. (Brachiopoda) from the Upper

Cretaceous of Bohemia. Ibid. P9, 115-36.

BAKER: MOORELLINA GRANULOSA (MOORE)

99

rudwick, m. j. s. 1959. The growth and form of brachiopod shells. Geol. Mag. 96, 1-24.

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and Bactrynium Emmrich. Palaeontology, 11, 329-60.
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1956. The calcareous shell of the Brachiopoda and its importance to their classification. Biol.

Rev. 31, 243-87.

1965. In moore, R. c. (ed.), Treatise on invertebrate paleontology, part H, Brachiopoda. 927 pp.

Univ. Kansas and Geol. Soc. Amer.

fe 1966. Growth and structure of the shell of living articulate brachiopods. Nature, Lond. 211,

1146-8.

1968a. Evolution of the shell structure of articulate brachiopods. Spec. Pap. Palaeont. 2, 55 pp.

1968 b. A history of skeletal secretion among articulate brachiopods. Lethaia, Universitetsforlaget,

Oslo 1, 268-87.

• 1968c. Shell-structure of the billingsellacean brachiopods. Palaeontology, 11, 486-90.

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brachiopods. J. Paleont. 37, 1-32.

P. G. BAKER

Department of Biological Sciences
Derby and District College of Technology
Kedleston Road

Typescript received 6 June 1969 Derby, DE3 1GB

ONTOGENY OF THE UPPER CAMBRIAN
TRILOBITE LEPTOPLASTUS CRASSICORNIS
(WESTERGAARD) FROM SWEDEN

by P. H. WHITWORTH

Abstract. The development of the dorsal exoskeleton of the trilobite Leptoplastus crassicornis (Westergaard)
is described from the Upper Cambrian of Andrarum, Scania, Sweden. The cranidium is represented by all stages
from protaspis to holaspis, although specimens other than protaspids are disarticulated and precise degrees are
unknown ; they have therefore been allocated to seven morphological groups. The development of the meraspid
librigena, hypostome, and pygidium is also briefly described. The growth of the cranidium is closest to Peltura
scarabeoides but also shows similarities with Olenus gibbosus and Leptoplastides salteri. The nature and course
of early facial sutures is discussed. Scatter diagrams show growth to be linear and allometric.

Amongst the reference collections in the Birmingham University Geology Museum
are several slabs of black alum-shale material from the ‘Olenus Stage’ (as labelled) of
Andrarum, Scania, Sweden. These are crowded with specimens of the trilobite Lepto- I
plastus crassicornis (Westergaard) in all stages of growth, with occasional individuals
of L. norvegicus (Holtedahl), preserved as internal and external moulds. The specimens
are labelled as Eurycare angustatum (transferred to Leptoplastus by Henningsmoen 1957)
but they are considered to belong to L. crassicornis , and the association with L. norve-
gicus supports this. Such an assemblage suggests that the material comes from the
Subzones crassicornis or ovatus of the Leptoplastus (2c) Zone (Henningsmoen 1957,
chart 2). A continuous series is represented but due to fragmentation of the exoskeleton
only the protaspis stages are complete, and consequently the size groups cannot be related
to successive degrees.

The numerous specimens were measured using a micrometer eye-piece, but it must
be remembered that the measurement of protaspid length in particular (taken when the
anterior and posterior margins lie on an approximately horizontal plane) are reduced
by the strong curvature of the specimens. The ratios of length and width measurements
of cranidium and glabella, when plotted graphically (text-fig. 2), provide a remarkably
linear scatter and also demonstrate the allometric growth of these parts. Breaks in the
scatters may indicate separation of size groups by instars, but the number of these is
small when compared with the number of thoracic segments in the adult and this may
be due to the release of two or more segments into the thorax at some instars. It is
appreciated that a certain number of young stages of L. norvegicus may have been in-
cluded in the measurements, but such early stages of two closely related species are
unlikely to show any significant differences and their possible inclusion is disregarded.

Any size limits imposed to separate the protaspis, meraspis, and holaspis stages would
be entirely arbitrary and subjective, but for convenience such limits are employed. The
meraspis stage is considered to commence when the posterior transverse ridge of the
protaspis is fully developed and a distinct separation of the cranidium and pygidium
by a transverse suture is attained. The holaspid condition is based on the evidence of

[Palaeontology, Vol. 13, Part 1, 1970, pp. 100-11, pis. 22-24.]

i

WHITWORTH: ONTOGENY OF LEPTOPLASTUS CRASSICORNIS (WESTERGAARD) 101

a specimen bearing 10 thoracic segments (PI. 23, fig. 5). As the nature of the suture and
free cheeks is not known in detail for early stages the head shield is termed a cephalon
up to, and a cranidium after, the meraspid condition is reached. The axis then becomes
the glabella, the axial rings and ring furrows become the glabellar lobes and furrows.
The descriptions are based mainly in internal moulds, but the external moulds differ
insignificantly from them in all important characters.

table 1. Detailed measurements of figured cranidia. Measurements of length of cranidium and glabella
include the occipital ring, of width where this is greatest. Eye-lobe measurement is of length.

Plate

Fig.

No.

Length

Width

Length

Width

No. of

shield

shield

axis

axis

segments

Protaspis

22

1

06

0-20

0-20

019

006

5

2,3

W10

0-22

0-22

0-20

008

5

4

W77

0-26

0-26

0-21

008

6

5

W80

0-28

0-30

0-26

010

6

6

W77

0-28

0-28

0-22

009

6

7, 8

W61

0-30

0-33

0-26

Oil

7

Length

Width

Length

Width

Eye-

cranid.

cranid.

glob.

glob.

lobe

Meraspis

9

W62

0-26

0-29

0-22

0-09

(— )

10

014

0-27

0-36

0-26

0 1 1

0-20

11

W81

0-30

0-41

0-30

014

0-20

12

W47

0-30

0-42

0-30

012

0-20

13

W50

0-32

0-46

0-33

013

0-21

14

W32

0-34

0-48

0-30

0-14

0-22

15

W2

0-40

0-58

0-36

017

0-24

16

W9

0-42

0-60

0-40

019

0-26

17

W70

0-48

0-74

0-46

0-20

0-28

18

W40

0-48

0-70

0-46

0-22

0-26

19

W52

0-58

0-88

0-56

0-24

0-32

20

W53

0-68

1-20

0-63

0-32

0-40

21

W44

0-80

1-40

0-74

0-36

0-40

23

1

07

0-97

1-80

0-90

0-50

0-46

2

W55

1-28

2-60

1-16

0-68

0-68?

3

08

1-40

2-80

1-28

0-72

0-76

4

09

1-60

3-20

1-50

0-92

0-88

5

02

1-64

(— )

1-46

0-96

0-90

6

010

1-76

3-63

1-60

1-16

1-06

Holaspis

7

03

2-14

(-)

1-84

1-26

1-10

8

W56

2-48

5-28

2-12

1-40

1-24

9

W17

2-60

5-92

2-36

1-72

1-40

10

W21

2-80

60

2-56

1-76

1-40

11

Oil

3-20

(— )

2-80

2-0

1-60

12

W26

5 0

9-0

4-50

3-0

1-40

Terminology. The terminology employed in this paper is a combination of that of
Whittington 1957 and 1958 and that of the Treatise (Moore, 1959) with the additional
use of the term ring furrow to denote the transverse furrows of the protaspid cephalic
axis. As the nature of the early cephalic segmentation is not yet clear in the olenids.

102

PALAEONTOLOGY, VOLUME 13

Stormer’s (1942) terminology referring to the segmental nature of certain characters
(e.g. pre-antennal segment) is not used. Measurements of length are sagittal unless
otherwise stated and of width (tr.) where this is greatest, the latter not necessarily com-
parable. The length of the cranidium includes the occipital ring and length of the
pygidium excludes the articulating half-ring. The axial rings and furrows (excluding the
occipital furrow) of the protaspis stages are numbered from back to front in accordance
with the usual notation for adult trilobites by inference from the development of the
respective rings in the meraspid/holaspid periods.

Technique. Photography of specimens of the order of 0-25 mm. across has often proved
extremely difficult but some measure of success has been obtained here by the use of a
Leitz Wetzlar biological microscope, and the depth of field problem with highly convex
specimens has been overcome by using a 35 mm. Leitz objective incorporating an iris
diaphragm. All specimens were whitened with ammonium chloride sublimate before
photographing but the coarseness of even the finest application obscures some of the
very fine ornament and structure of the protaspids.

SYSTEMATIC DESCRIPTION

Family olenidae Burmeister 1843
Subfamily leptoplastinae Angelin 1854

Leptoplastus crassicornis (Westergaard 1944)

Plate 22, figs. 1-21 ; Plate 23, figs. 1-12; Plate 24, figs. 1-20; text-fig. 1.

Material. The specimens are individually numbered on three slabs of rock with white (W) and orange
(O) labels and are deposited in the Birmingham University Geology Museum numbered BU 395-7.

Because of the fragmentary nature of the material the descriptions have been included
under five separate headings : (a) protaspis, ( b ) meraspis/holaspis cranidium, (c) librigena,
( d ) hypostome, and ( e ) pygidium. It was found most convenient to divide the series into
seven morphological groups, for each of which the size-range, number of specimens
measured, and the plate and figure references precede each description. A fuller list of
measurements of figured cranidia is given in Table 1.

PROTASPIS

Group 1. Length (entire shield) — 0-20-0-25 mm., 6 specimens (PI. 22, figs. 1-3; text-
fig. 1 a).

The shield is circular in outline, up to 0-26 mm. wide, moderately convex becoming
more strongly bent down behind. Axis essentially of 5 rings separated by straight ring
furrows with the suggestion of an incipient 6th segment in later stages (PI. 22, fig. 3).

EXPLANATION OF PLATE 22

Leptoplastus crassicornis (Westergaard). Developmental series of protaspis and early meraspis to show
changes in relative dimensions (BU 395, 396). Individual specimen numbers as in Table 1. Fig. 1,
x80; figs. 2, 3, x70; figs. 4-9, x65; figs. 10-14, x50; figs. 15, 16, x40; figs. 17-19, x30; figs. 20,

21, x25.

Palaeontology, Vol. 13

PLATE 22

WHITWORTH, Leptoplastus crassicorne (Westergaard)

WHITWORTH: ONTOGENY OF LEPTOPLASTUS CRASSICORNIS (WESTERGAARD) 103

The axis is slightly constricted behind the 3p ring which is the widest. The frontal lobe
is longer than the others and at its antero-lateral corners are a pair of anterior pits which
continue laterally into faint furrows, bounded in front by the narrow anterior border.
A lateral border extends forwards from a small fine spine (PI. 22, figs. 2, 3) to the level

abed

e

i

f

9

h

text-fig. 1 . Reconstructions of some stages in the development of Leptoplastus crassicornis (Wester-
gaard). a. W10, x70; b. W80, X65; c. W61, X65; d. W50, x50; e. W53, X25;/. 09, Xl2;g. W21,
x9; h. W26, x 7. Approximate natural sizes are given alongside some figures to show the over-all
increase from smallest protaspis to largest holaspis. Suggested positions and shapes of librigenae
are given in figs, b-f; those in fig. b occupy a ventral position, the suture being marginal.

of the lp axial ring. There are indications on some specimens of several obliquely back-
wards directed and forwards convex furrows on the pleural regions, but they are very
faint.

Group 2. Length (entire shield) — 0-26-0-29 mm., 19 specimens (PI. 22, figs. 4-6; text-
fig. 1 b).

Here the shield, which may be up to 0-32 mm. wide, shows a 6th axial segment behind
the occipital ring representing the single segment of the protopygidium, which is
developed as a flat triangular plate of minute size (PI. 22, fig. 5; text-fig. lb). The axis

104

PALAEONTOLOGY, VOLUME 13

is still widest, but less constricted, at the 2p ring and is more strongly convex. The anterior
lobe reaches almost to the anterior margin and on either side of it the anterior pits and
border continue to increase in prominence (PI. 22, fig. 6). The lateral border is a little
wider than before and reaches forwards to opposite the lp ring furrow. The fixigenal
spines are somewhat larger and directed backwards and downwards. From opposite
the middle of the occipital ring a change in height of the pleural regions suggests the
appearance of an oblique ridge crossing their posterior part, a feature seen better in
Group 3 (PI. 22, fig. 4). The pleural regions are often seen to have a relatively coarse
reticulate ornament.

Group 3. Length (entire shield) — 0-30-0-32 mm., 5 specimens (PI. 22, figs. 7, 8; text-
fig. lc).

The shield, ranging in width from 0-30 to 0-34 mm., may be thus slightly wider than
long and is strongly convex (tr.), being better defined by deep axial furrows than before.
The frontal lobe appears to have diminished slightly in relative length and width, while
the 2p and 3p rings are of about equal width and lp and the occipital ring progressively
smaller, the abrupt narrowing behind the 3p ring being less marked (PI. 22, fig. 7). The
occipital ring is raised high above the level of the descending protopygidium. Anteriorly
a distinct eye-ridge is now seen to trend forwards and outwards from the axial furrow
near the 3p ring furrow to the antero-lateral margin where, defined from the anterior
border by a shallow furrow, it turns backwards, reaching almost to the level of the 2p
ring furrow (text-fig. lc). The anterior pits are very well defined and quite deep. The in-
flated reticulate pleural regions, still bearing traces of oblique grooves posteriorly,
descend evenly outwards all round but are abruptly less convex behind the lp ring furrow
where a shallow oblique groove and faint ridge is developed (PI. 22, fig. 7). This repre-
sents the incipient posterior border and margin of the meraspid cranidium. The lateral
border is flange-like, reaches forwards to the level of the 2p axial ring and extends
posteriorly into now quite strong spines. The small triangular protopygidium has 2
poorly defined circular segments (PI. 22, fig. 8). The length of the primary axis (5 seg-
ments) is here 0-23 mm. and the cranidial width 0-34 mm. (compare values below for
Group 4).

MERASPIS/HOLASPIS CRANIDIUM

Group 4. Length (cranidium) — 0-26-0-39 mm., 20 specimens (PI. 22, figs. 9-14; text-
fig. Id).

The width of the cranidium varies in this group from 0-35-0-60 mm., showing quite
a considerable individual variation during early growth. The cranidium shows an overall
shortening and widening due to the lateral growth of the posterior areas of the fixigenae.
The glabella becomes distinctly barrel-shaped by the relative increase in width of the 2p
and 3p glabellar lobes, the occipital ring remaining small and becoming triangular in
shape with the development in later stages of a small median tubercle or node (PI. 22,

EXPLANATION OF PLATE 23

L. crassicornis (Westergaard). Developmental series of late meraspids and of holaspids to show changes
in relative dimensions (BU 395, 397). Individual specimen numbers as in Table 1. Fig. 1, x 20; fig. 2,
x 16; fig. 3, x 14; figs. 4, 5, x 12; fig. 6, x 11; fig. 7, x 10; figs. 8-11, x9; fig. 12, x 7.

Palaeontology , Vol. 13

PLATE 23

WHITWORTH, Leptoplastus crassicorne (Westergaard)

WHITWORTH: ONTOGENY OF LEPTOPLASTUS CRASSICORN1S (WESTERGAARD) 105

fig. 1 1). The lp to 3p glabellar furrows become gradually shallower, especially medially,
while the occipital furrow deepens. The initially curved anterior border becomes distinctly
transverse but is still continuous axially with the frontal glabellar lobe. The anterior pits
and border furrow combine to form rather large triangular depressions, and the convex
anterior border extends laterally beyond the axial furrow to a distance about equal to
half the width of the glabella, turning abruptly back so that the eye-ridges become
marginal (PI. 22, fig. 13). The more clearly defined and gently curved eye-ridges extend
back to level with the posterior half of the 3p glabellar lobe and show a slight swelling
at their posterior (abaxial) end (PI. 22, figs. 10, 14). The oblique transverse ridge and
depression on the pleural regions continue to develop from the protaspis and eventually
unite with the lateral border, forming a transverse posterior margin to the cranidium
(PI. 22, fig. 14). The lateral border extends gradually further forwards from the rounded
postero-lateral corners of the cranidium, becoming narrower as it does so, to meet but
remain distinct from the eye-ridge, and is accompanied by a border furrow continuous
with that of the posterior border (PI. 22, fig. 13). It is clear that a facial suture and free
cheek is developed at early stages in this group (see discussion at end), and indeed
probably also in Group 3, but no librigenae of such dimensions have been found. As a
consequence, the lateral border may now be termed the sutural ridge and the border
spines are seen to be of fixigenal origin (i.e. metafixigenal). These latter move relatively
outwards to, at most, four-fifths of the distance out from the axial furrow (PI. 22, fig.
14). The fixigenal areas retain their reticulate pattern to the end of this group, but it
is usually lost early in Group 5. These areas commence to inflate individually and the
posterior areas to increase gradually in width, the latter also descending rather steeply
behind into the posterior border furrow (PI. 22, fig. 10).

Group 5. Length (cranidium) — 0-41-1 -00 mm., 53 specimens (PI. 22, figs. 15-21 ; PI. 23,
fig. 1 ; text-fig. \e).

Cranidial width ranges from 0-53 to 1 -80 mm. The most important changes in this group
affect the glabellar shape and segmentation and the expansion of the posterior fixigenal
areas. The glabella continues to expand at the 2p and 3p lobes at first (PI. 22, figs. 15,
18) but in later stages the lp lobe and occipital ring take up this change and begin to
widen (tr.) so that the sides of the glabella tend to become parallel (PI. 22, fig. 21). The
2p lobe becomes the longest (sag.) with the lp and occipital lobes remaining short; the
frontal lobe is also reduced. In this group one also sees the first break in continuity of the
glabellar furrows, 3p and 2p becoming very indistinct or even disappearing medially
(PI. 23, fig. 1). This is accompanied by an increase in depth of the abaxial parts of the
glabellar furrows, lp and 2p becoming almost notch-like, and by the change in direction
of these parts from transverse to inwards and backwards directed, lp is directed more
sharply backwards than 2p (PI. 22, fig. 20; PI. 23, fig. 1). The occipital furrow remains
continuous and increases in depth, turning forwards abaxially; the median occipital
node is very prominent (PI. 22, figs. 17, 19, 21).

Due to the width increase of the glabella the palpebral areas of the fixigenae become
relatively narrower in relation to it than before and become less inflated. The posterior
fixigenal areas grow rapidly abaxially and the ratios of cranidial to glabellar width
increase, indicating that the growth of these parts does not keep pace. As the fixigenae
grow so the sutural ridge is lost, the postero-lateral corners of the cranidium become

106

PALAEONTOLOGY, VOLUME 13

less well rounded, the posterior margin becomes straighter, and the fixigenal spines are
aborted (compare PI. 22, figs. 15 and 19). The eye-ridges increase in prominence and
become more transverse, and the palpebral furrow deepens. The posterior end of the
palpebral lobe is at first situated opposite the outer ends of the 2p glabellar furrows but

WIDTH

text-fig. 2. Scatter diagram showing nature of growth of cranidium and glabella of Leptoplastus '
crassicornis from 1 1 6 specimens. Those marked with a triangle are of Norwegian material, measure-
ments being taken directly from the plates of Henningsmoen 1957. Breaks in the scatters might be
interpreted as instars, but there is no conclusive evidence which can be used in support of this; no
abrupt changes in the morphological development of the cranidium alone are evident. Note relative
rates of growth in length and width (allometric) of cranidium and glabella. Measurements in milli-
metres.

in later stages it extends back to opposite the middle of the 2p glabellar lobe (PI. 23,
fig. 1). The frontal lobe becomes separated from the anterior border of earlier groups by
a distinct preglabellar furrow which abaxially defines a true narrow, convex border from
a narrow (exsag.) anterior fixigenal area (PI. 22, fig. 21). The course of the posterior
section of the facial suture turns at first slightly outwards behind the palpebral lobe,
but in later stages more strongly so, bending back to cut the posterior margin at a distance
from the axial furrow of slightly less than the length of the glabella (exc. occipital ring).

Group 6. Length (cranidium) — IT-1-9 mm., 8 specimens (PI. 23, figs. 2-5; text-fig. 1/).

In this group the cranidium attains, and further develops, the typical adult form and
the changes observed are mainly due to size increase. The maximum width of the crani-
dium in this group is about 3-5 mm. By continued increase in width of the occipital

WHITWORTH: ONTOGENY OF LEPTOPLASTUS CRASSICORNIS (WESTERGAARD) 107

ring and lp glabellar lobe the glabella soon becomes parallel sided and broadly rounded
in front (PL 23, fig. 2). The occipital ring may even become slightly wider than the rest
of the glabella and has a straighter posterior margin than previously, its abaxial margins
turning strongly forwards; the median node becomes somewhat elongate and reduced
in prominence. The median parts of lp and 2p glabellar furrows are gradually lost while
the lateral parts become deeper and develop a slight forwards convex curve (PL 23, fig. 4).
The 3p furrows also continue to get fainter. The eye-ridges are no longer curved but are
still directed outwards and slightly backwards. The anterior fixigenal areas and the
anterior border increase slowly in length (exsag. and sag. respectively) but a pre-
glabellar area is not yet developed. The posterior margin has become nearly straight,
and the convex border widens abaxially along with the border furrow which is now very
deep (PL 23, figs. 3, 4). The strongly inflated rear parts of the posterior fixigenal areas
descend steeply into this border furrow and also into the axial furrow, but the anterior
and palpebral areas are much less convex. The by now well-developed palpebral lobes
extend back almost to the level of the outer ends of the lp glabellar furrows (PL 23,
figs. 2, 4). The course of the facial suture describes a gentle curve from a median marginal
position out and back to the front end of the palpebral lobe. Thence, from the back of
the palpebral lobe, it turns immediately outwards and runs back in a gentle forwards
convex curve (text-fig. 1/), bending quite sharply back again to cut the posterior margin
at a distance from the axial furrow of a little more than the length of the glabella
(excluding occipital ring).

Judging by the size of the cranidium of a specimen which seems to have about 10
thoracic segments (PL 23, fig. 5), and that of the smallest available specimen with the
full complement of 12 segments (PL 23, fig. 7), the holaspid condition is attained when
the cranidial length reaches c. 2-0 mm. Group 7 is therefore considered to represent the
development of the holaspis (adult) stage.

Group 7. Length (cranidium) — 2-0 (approx.)-5-0 mm., 14 specimens (PL 23, figs. 6-12;
text-figs. 1 g, h).

Apart from an over-all size increase of about 2\ times the principal changes concern
the glabella. This becomes extremely convex (tr. and sag.), almost semicircular in
cross-section, and is raised high above the level of the fixigenae which have been
correspondingly reduced in convexity and height. The reduction in over-all convexity of
the cranidium continues, and in contrast to the gently arched anterior regions the posterior
fixigenae are strongly inflated behind and descend abruptly into the deep and wide
posterior border furrow. The glabella continues to widen at the occipital ring and lp
lobes so that the axial furrows become forward convergent. The preglabellar furrow
may or may not be confluent with the border furrow, so that a very narrow (sag.) pre-
glabellar area may be present (cf. PL 23, figs. 8, 10, and fig. 12). As the glabella widens
the glabellar furrows lengthen so that, from occupying only the outer one-fifth of the
glabellar width in earlier Groups, they now occupy one-third of the same, lp and 2p
furrows also exhibit a marked sinuosity (PL 23, fig. 9) and eventually become quite
strongly sigmoidal (PL 23, fig. 12), but the 3p furrows remain slightly curved and even-
tually disappear. As with the glabellar furrows in earlier groups the median part of the
occipital furrow tends to weaken (PL 23, fig. 8); the median occipital node is more
elongate and indistinct. In fig. 12 the glabellar furrows as a whole become much fainter,

108

PALAEONTOLOGY, VOLUME 13

especially abaxially, and are hardly continuous with the axial furrows. The eye-ridges
terminate adaxially opposite the 3p glabellar furrows and are finally almost transverse.

The anterolateral parts of the anterior fixigenal areas tend to grow rather rapidly
forwards and downwards, resulting in the anterior border developing a forward concave
curve with a slight median expansion. The outer ends of the posterior fixigenae are also
strongly bent downwards and invariably hidden, but the posterior sections of the facial
suture seem to approach the posterior border at a more acute angle than before.

SUMMARY OF CRANIDIAL DEVELOPMENT

The following summary also acts as a diagnosis for each of the groups described
above.

Group 1. Protaspids characterized by 5 axial segments, the absence of palpebral lobes
and eye-ridges, and by a lateral border reaching forwards to opposite the occipital
furrow.

Group 2. Protaspids with a definite protopygidium of 1 segment, defined by a groove
and incipient ridge crossing the posterior part of the pleural regions from the axis to
the fixigenal spines. Lateral border reaches forwards to opposite the lp ring furrow.

Group 3. Late protaspids with a protopygidium of 2 segments, suggestions of eye-
ridges extending back to level of 3p axial ring, and a lateral border reaching forwards
to level of 2p axial ring.

Group 4. Early meraspids in which the palpebral lobes are defined and the lateral
border becomes to sutural ridge by the migration of the suture to the dorsal surface;
the ridge reaches forwards the meet the palpebral lobes opposite 2p glabellar furrow.
Posterior cephalic border is accentuated and fixigenal spines move out relatively towards
the postero-lateral angles of the cranidium. A median occipital tubercle develops.

Group 5. Meraspids showing marked lateral growth of the posterior fixigenal areas
and corresponding outwards curve of the suture. Eye-ridges become less curved and
less oblique. Glabella widens rapidly at 3p and 2p lobes in early stages and at lp lobe
and occipital ring in later stages, becoming almost parallel sided. Glabellar furrow
gradually reduced, the median part of 3p and 2p becoming faint and disappearing.
Preglabellar furrow disappears and anterior fixigenal areas develop. Fixigenal spines
aborted.

Group 6. Late meraspids in which the glabella becomes parallel-sided and glabellar
furrows entirely lateral. Occipital ring slightly wider than glabella, occipital furrow
remains deep and continuous. Convexity (tr.) of cranidium as a whole, and of the
fixigenae, is reduced except for abaxial regions of posterior areas and their posterior
limits. Median part of lp glabellar furrow obliterated, outer parts of lp and 2p furrows

EXPLANATION OF PLATE 24

L. crassicornis ( Wester gaard). Developmental series of pygidium (figs. 1-7), hypostome (figs. 8-12) and
librigena (figs. 13-20). Figs. 1-6, x 25; fig. 7, x 15; figs. 8-12, x 25; figs. 13-16, 18, 19, x 45; figs. 17,
20, x 8. Fig. 1, W64; fig. 2, W42; fig. 3, W30; fig. 4, W65; fig. 5, W22; fig. 6, W46; fig. 7, W36; fig. 8,
018; fig. 9, Wl; fig. 10, W67; fig. 11, W13; fig. 12, W29; fig. 13, W59; fig. 14, 019; fig. 15, 022; fig.
16, 017; fig. 17, W42; fig. 18, 016; fig. 19, 027; fig. 20, 028.

Palaeontology, Vol. 13

PLATE 24

WHITWORTH, Leptoplastus crassicorne (Westergaard)

WHITWORTH: ONTOGENY OF LEPTOPLASTUS CRASSICORNIS (WESTERGAARD) 109

become curved and oblique, 3p remaining faint and transverse. Up to 11 thoracic
segments present.

Group 7. Holaspids, with very strongly convex and parallel sided to forward narrowing
glabella and fainter, strongly sigmoidal lp and 2p glabellar furrows; 3p furrows may
disappear. Preglabellar area may be present. Fixigenae not very convex except abaxial
parts of anterior and posterior areas. Eye-ridges almost transverse, palpebral lobes reach
back to level with outer ends of lp glabellar furrows. Anterior border becomes forwards
concave. Posterior sections of facial sutures cut posterior border at a more acute angle
and more abruptly than before.

LIBRIGENA

There are few complete librigenae preserved but those illustrated show some of the
changes which occur (PI. 24, figs. 13-20).

The smallest fragment (PI. 24, fig. 13), very doubtfully a free cheek, measures 0-36 mm.
long and 0T0 mm. wide. The outer margin is entire but the ?sutural margin is probably
not preserved in its original form. It may belong to an early meraspid stage as Plate 1 ,
fig. 10. The ?genal spine is short and postero-lateral. During subsequent development
(PI. 24, figs. 14-18) the librigena becomes wider than long and increases strongly in con-
vexity in the ocular region as the librigenal spine migrates forwards from a postero-lateral
(PI. 24, fig. 14) to lateral (PI. 24, fig. 17) position. The adult genal spine is very long and
robust, developing a strong outwards convex curve with a slightly reflexed tip. The
lateral border and furrow do not appear until quite a late stage.

Due to imperfect preservation of the sutural margin in most cases it is almost impossible
to assign the illustrated librigenae to respective cranidia, but from comparison of relative
sizes it appears that Plate 24, fig. 14 might belong to a late Group 4 meraspid, Plate 24,
figs. 1 5—1 8 to stages in Group 5, and Plate 24, figs. 19-20 to a late holaspid (e.g. PI. 23,
fig. 11).

HYPOSTOME

A few stages in the development of the hypostome are shown on Plate 24, figs. 8-12,
taken from quite a large number of specimens. Few changes in relative dimensions
occur, changes being mainly due to accentuation of the features present in the early
forms. The smallest hypostome (PI. 24, fig. 8) is about 1-28 mm. long and wide with a
weakly convex middle body (strongest posteriorly) and narrow, convex borders. At a
length of 0-33 mm. (PI. 24, fig. 9) the middle body has increased in posterior convexity
and is well raised above the now wider posterior border. The lateral border furrows are
pit-like anteriorly and the anterior wings very small. By the time a length of 0-60 mm.
is reached (PI. 24, figs. 10, 11) its maximum width (ant.) is 0-56 mm. and the lateral
borders are strongly constricted and ridge-like at one-third of their length from the
front. The middle body has its highest point posteriorly at a single median apex. The
posterior border is more broadly curved behind and descends almost immediately from
the border furrow. The largest hypostome (PI. 24, fig. 12) is 1T2 mm. long and wide
(ant.). It differs from the earlier stages in having a very shallow anterior border furrow,
deep and pit-like lateral border furrows at the constriction, and in the shape of the middle
body. This latter rises very high above the posterior border, is somewhat truncated

110

PALAEONTOLOGY, VOLUME 13

behind, and has a double apex at its postero-lateral corners. A narrow convex rim runs
around the margin of both lateral and posterior borders.

PYGIDIUM

The pygidia (PI. 24, figs. 1-7) are considerably less common than cranidia and no
advanced meraspid pygidia have been seen. The figures show most of the changes which j
occur during growth. It is impossible to accurately assign any but the smallest pygidia
to respective cranidial sizes.

The smallest meraspid pygidium (PI. 24, fig. 1) is 0-32 mm. wide and 0T6 mm. long
with semicircular outline. The narrow axis has 2 distinct rings and an indication of a
third, the pleural regions have 2 pairs of straight, oblique pleural furrows. At the lateral
margin is a narrow convex rim leading into the first of 3 pairs of fine marginal spines
which increase in length adaxially. The pygidium is moderately convex sagittally.

During subsequent development (PI. 24, figs. 2-7) the pygidium is seen to develop
4 axial rings and a rounded terminal piece ((PI. 24, figs. 4 and 7), 4 pairs of oblique
pleural furrows, and 4 pairs of marginal spines. The axis increases in width at the expense
of the pleurae from a quarter to a half or more (PI. 24, figs. 2 and 7) of the total width
and the median axial tubercles of the transitory pygidium are lost on the adult; the early
segments are tuberculate and pass forward into the thorax, but the later true pygidial
segments are smooth. The adult pygidial pleurae are relatively both shorter (exsag.) and
narrower (tr.) than the early segments and the marginal spines smaller. Of the latter, |
all but the 4th pair, which remain long and fine, are short and triangular in the adult.
An over-all change in shape from semicircular to triangular is seen and the sagittal
convexity of early stages is completely lost, the adult pygidial pleural lobes being flat
(in contrast to the strongly convex axis).

DISCUSSION

The development of L. crassicornis is similar in some respects to that of Olenus gibbosus t
(Strand 1927). The protaspid axis differs principally in the shape, size, and late-stage
segmentation of the frontal lobe and in that it is widest anteriorly. The transverse suture I
and ridge between the cephalon and protopygidium/transitory pygidium is developed ,
at an earlier stage and the fixigenal spines are longer. The protaspis is also somewhat
larger throughout development in O. gibbosus. In meraspid stages the sutural ridge and
fixigenal spine are retained longer, but the two species agree in the possession of a
straight anterior cranidial border.

Early protaspid development of L. crassicornis is most like that of Peltura scarabeoides
(Whittington 1958), especially in intermediate stages (Group 2 here), but the meraspid
axial development is closer perhaps to that of Leptoplastides salteri (Raw 1925).

Regarding the nature and course of the facial sutures, the interpretation of Whitting-
ton (1958, pp. 203-4) for P. scarabeoides may be equally applied in this case. The facial
suture is not clearly developed on the present material of L. crassicornis until early
meraspid stages, but the presence and nature of the sutural ridge is identical in both
species. The abrupt anterior termination of the lateral border (= sutural ridge of larger
specimens) seen in Plate 22, figs. 7, 8 and in its interpretation, text-fig. 1 c, suggests that

WHITWORTH: ONTOGENY OF LEPTOPLASTUS CRASSICORNIS (WESTERGAARD) 111

the facial suture, after running alongside the eye-ridge, crosses the border on to the
ventral surface (?doublure). As growth proceeds its course is extended backwards to cut
the border postero-laterally, and is accompanied by the loss of the metafixigenal spine.
It is clear that the metafixigenal spine, which may be (as here) essentially transient, has
previously been too freely equated with the fixigenal spines of adult olenids such as
Saltaspis and Nericiaspis. From such an assumption L. crassicorne could easily be
referred to the proparian condition during early meraspid development, but subsequent
development shows that the final condition is opisthoparian. It is unfortunate that there
are no well-preserved early meraspid librigenae (excluding the doubtful specimen in
PI. 24, fig. 13) from which one might determine the origin of the librigenal spine. It is
possible, as suggested by Palmer (1958) for Crassifimbra walcotti, that the librigenae of
protaspids may be represented at first by an entirely ventral plate, the suture thus being
marginal (see text-fig. lb). In later protaspids and early meraspids (text-fig. 1 c-e) the
librigena and facial suture become dorsal and the point where the posterior section
cuts the border migrates slowly backwards outside the sutural ridge, which thus becomes
a structure separate from the true marginal border.

Acknowledgements. Thanks go to Dr. I. Strachan for his continued assistance during the preparation of
the manuscript. The work was undertaken during the tenure of a N.E.R.C. research grant which is
gratefully received.

REFERENCES

henningsmoen, g. 1957. The trilobite family Olenidae. Skr. norske Vidensk.-Akad. Mat.-naturv. Kl. 1,
1-303, pi. 1-31.

holtedahl, o. 1910. Uber einige norwegischen Oleniden. Norsk, geol. Tidsskr. 2, 1-24, pi. 1-3.

moore, r. c. (ed.) 1959. Treatise on invertebrate paleontology. Part O, Arthropoda 1. Geol. Soc. Am.
and Univ. Kansas Press.

palmer, a. r. 1958. Morphology and ontogeny of a Lower Cambrian Ptychoparioid trilobite from
Nevada. J. Paleont. 32, 154-70, pi. 25, 26.

raw, F. 1925. The development of Leptoplastus salteri and other trilobites. Q. Jl geol. Soc. Loud. 81,
223-324, pi. 15-18.

stormer, l. 1942. Studies on trilobite morphology. II. The larval development, the segmentation and
the sutures, and their bearing on trilobite classification. Norsk, geol. Tidsskr. 21, 49-164, pi. 1, 2.

strand, T. 1927. The ontogeny of Olenus gibbosus. Norsk, geol. Tidsskr. 9, 320-9.

Whittington, h. b. 1957. The ontogeny of trilobites. Biol. Revs. 32, 421-69.

1958. Ontogeny of the trilobite Peltura scarabeoides from the Upper Cambrian, Denmark.

Palaeontology, 1, 200-5, pi. 38.

PETER H. WHITWORTH

Department of Geology
The University
Birmingham 15

Final typescript received 16 July 1969

A NEW CEPHALOPOD FAUNA FROM THE
LOWER CARBONIFEROUS OF EAST CORNWALL

by S. C. MATTHEWS

Abstract. A collection of approximately three hundred small cephalopods from a site in the Lower Carboni-
ferous of east Cornwall includes representatives of Gattendorfia sp., Gen. et sp. nov. A, Muensteroceras com- \
planatum, M. cf. rotella, Ammonellipsites princeps, A. sp. aff. asiaticus, A. sp. indet. and Gen. et sp. nov. B.

It is argued that the fauna is of an age later than those of the Hangenbergkalk (‘cul’) of Germany and possibly |.
earlier than the late Tournaisian cephalopods of Belgium (‘culla’). German conodont evidence, taken together
with some from Belgium, demonstrates that there is a range of Tournaisian age (Tn 2a-Tn 3b? in terms of the
Belgian stratigraphy, or approximately the Siphonodella crenulata Zone in terms of conodonts) of which the
cephalopod-based zonal standard makes no account. Certain North American (Mississippian) cephalopod ;
faunas which show coincidences of cheiloceratacean (including gattendorfiid) and goniatitacean (including |
muensteroceratid and ammonellipsitid) forms have not found accommodation in the European zonal scheme.

In the cases of the Chouteau limestone, Rockford limestone, and Walls Ferry limestone the evidence of cono-
donts suggests reference to that range of the Tournaisian where the European cephalopod standard fails.

Cephalopods occur only rarely in successions of early Carboniferous age. The zonal
scheme based on these fossils can be no better than the patchy record allows. So, too,
with matters of phylogeny : any discussion of the emergence of the goniatitaceans (even-
tually the dominant group of Carboniferous goniatites) is hindered by the poverty of
the evidence at present available. In these circumstances a certain degree of interest
attaches to a new fauna which appears to be of Tournaisian age and which has, as j
contemporaries, cheiloceratacean and goniatitacean forms.

This paper is concerned mainly with the question of the age of the fauna as indicated
by the most nearly mature goniatites present. A later communication will refer to the
detail of immature forms and to ontogenies, and will review the current state of in-
formation on Tournaisian goniatites.

THE NEW FAUNA FROM EAST CORNWALL

A detached sheet of Lower Carboniferous rocks forms the mass of Viverdon Down
south and east of Callington in east Cornwall. It emerged during mapping that the sheet
includes a lower succession in which shales are predominant and an upper which has
the tougher, siliceous rocks that define the topographic high. The lower succession is
exposed at SX 398665 in a cutting on the narrow road which leads south-eastward down
to the Tamar at Haltonquay. On the south-western side of the road thin cross-stratified
siltstones occur among the dark shales, and at the north-western end of the exposure,
near to the entrance to Heathfield Farm, coarse sandstones are exposed. These are taken
to be associated with the finer-grained rocks in the stratigraphy of the lower part of the
detached sheet. At a point approximately 30 metres south-east of the entrance to Heath-
field Farm, and 2\ m. above the present road level in the cutting, there is a lens of iron-
shot, relatively coarse material disposed parallel to bedding within the shale and siltstone
succession. When first discovered the remnant of the lens measured approximately

[Palaeontology, Vol. 13, Part 1, 1970, pp. 112-31, pis. 25-28.]

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 113

60 cm. by 4 cm. as exposed on the weathered face, and it proved to continue for 10 cm.
maximum in the third dimension. Only the last ‘tail’ of the lens now remains in the
exposure. Small cephalopods were visible on the site, and later preparation (under the
microscope, with needle and brush) finally freed over three hundred individual fossils.
Only molluscs are recognizable, and the minority of these are minute. There are no
conodonts.

COMMENTS ON SIZE, AND ON BURIAL AND PRESERVATION

The range of size of the goniatites is shown in text-fig. 1 . The smaller forms can be
allotted to genera by continuous association of details of form down through the size-
range. The graph of sizes of the generically indeterminable goniatites illustrates the
obvious fact that the smallest individuals present the greatest difficulties of identification.
Representatives of the ribbed ammonellipsitids and of Gen. et sp. nov. B, which is
keeled at all growth stages, can nevertheless be confidently identified down to values of
diameter in the neighbourhood of 1 mm. The size-frequency of all goniatites collected
peaks at the 1-2 mm. grade.

There are many specimens in which living chamber and gas chambers can be distin-
guished. They indicate that the smallness of the fossils cannot be due to breakage during
a transport-burial sequence of events or during preparation. Nor is this the kind of
preservation in which only nuclei survive diagenesis in a robust state. In a majority of
cases the fossils represent the stage of growth achieved at the time of death. The range
of size and the range of form (evolute near-serpenticones to tightly involute near-
cadicones, and orthocones and small, low-turreted gastropods are also present, if rare)
suggest that this close concentration of such diverse individuals cannot have experienced
any lengthy exposure to a sorting process.

The fossils are found silicified in a lens which is cut by many small siliceous veins.
The more general silicification which affects the immediately higher part of the strati-
graphy is, however, not developed here.

THE FAUNA AND ITS AGE
The following are identified :

Gattendorfia sp.

Gen. et sp. nov. A

Muensteroceras complanatum (de Koninck)

Muensteroceras cf. rotella (de Koninck)

Muensteroceras spp.

Ammonellipsites princeps (de Koninck)

Ammonellipsites sp. aff. asiaticus (Librovitch)
Ammonellipsites sp. indet.

Ammonellipsites spp.

Gen. et sp. nov. B

Indeterminable low-spired gastropods and small orthocones are also present.

C 7173 I

NUMBER OF SPECIMENS

114

PALAEONTOLOGY, VOLUME 13

Muensteroceras (49 specimens)

DIAMETER IN MM.

text-fig. 1 . Size distribution of goniatites in the new fauna from Cornwall, by genera and (top right)
for all goniatites collected.

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 115

The occurrence is stratigraphically in isolation. The nearest occurrence of any other
fossils is at a point 800 m. to the west and some 100 m. higher in the succession (as
judged from a map) where conodonts of the anchoralis- Zone are found (Matthews
1969a).

The cephalopods include Ammonellip sites princeps and Muensteroceras complanatum,
and these are the indices to the first of the units (culla) distinguished by Schmidt (1925)
in the Pericyclus- Stufe (cull, now the Ammonellipsites- Stufe — see Paproth, Teichmiiller,
and Remy 1960). But the Belgian original has been, until now, the sole western European
occurrence of these forms, and it is therefore difficult to arrive at any understanding of
stratigraphic limits for culla. Also, the new fauna from Cornwall shows these two forms
in an association altogether different from that found in Belgium (Delepine 1940a). For
these reasons it becomes necessary to examine the composition of the currently accepted
zonal scheme (which is in most essentials that advanced by Schmidt in 1925) in order to
discover the constraints that exist in the matter of judging the age of the new fauna.

The cephalopod-based standard includes, in the Lower Carboniferous, three stages,
successively the Gattendorfia- Stufe (cul), Ammonellipsites- Stufe (cull), and Goniatites-
Stufe (cuIII). Schmidt’s contribution of 1925 offered more detailed proposals than had
been available before on the succession of faunas in cull and cuIII and (this as a complete
novelty) cul subjoined to the two Lower Carboniferous stages previously recognized.
Schindewolf (1927) would have preferred to define the beginning of the Carboni-
ferous by reference to the entry of the distinctively Carboniferous goniatitaceans, with a
median saddle as their characteristic. Schmidt was guided by altogether a different con-
sideration. He brought forward the Gattendorfia- Stufe (then known as the Protocanites-
Stufe) as the earliest Carboniferous unit because field mapping, particularly the work
of Paeckelmann (1922), had indicated that the Protocanites- Stufe stratigraphy might
be regarded as an equivalent of the Etroeungt. More recently, Vohringer (1960) has
presented a detailed analysis of the stratigraphic distribution, form and phylogenetic
relationships of the cephalopods that occur in the 2 m. thick Hangenbergkalk, the type
example of cul. Vdhringer retained the definition of the lower limit of the Carboniferous
as the point of entry of Gattendorfia subinvoluta, and added clarification by showing
that Bahia is an imitoceratid. However, for want of any information from the strati-
graphy above the Hangenbergkalk (the Liegende Alaunschiefer) he was unable to propose
any upper limit to cul. Among his cephalopods there was an example of Karagan-
doceras, a genus which possesses a median saddle, but which according to Vohringer
should be regarded as precocious in this respect, and should not be identified as the first
of the major suite of goniatitaceans. Weyer (1965) has restudied the collections of
Gattendorfia- Stufe material from Dzikowiec (Ebersdorf) in Lower Silesia, and has been
able to suggest that Paralytoceras, too, anticipates later forms in its possession of a median
saddle.

Schmidt’s Ammonellipsites- Stufe units, culla, j3, y, S, were founded on occurrences of
cephalopods in respectively Belgium, Ireland, Germany (Dillmulde), and Germany
(Harz). In the case of culla, the material comes from the Calcaire de Vaux-Calcaire de
Calonne range of the stratigraphy according to Delepine (1940a). In Legrand, Mamet,
and Mortelmans (1966) the site is referred to Tn 3c. The Irish cull/3 forms (Foord 1903)
cannot be given any exact stratigraphic attribution. The Erdbacherkalk, the Ily rype
(Holzapfel 1889, Schmidt 1925) rests on pillow lavas. Its local stratigraphical relationships

116

PALAEONTOLOGY, VOLUME 13

and its content of reworked Upper Devonian conodonts have been described by
Walliser and others (1958) and by Krebs (1963). The original occurrence of the cuIIS
fauna (Schmidt 1941) was in a bed of red shale, a few centimetres thick, which outcrops
near Riefensbeek in the Harz Mountains. Plainly, there is no possibility of guaranteeing
the cul-cull relationship nor the interrelationships of the cull units by direct observa-
tion of stratigraphic superpositions. Only in the case of the cull-culll transition can
this be done, for the cuIIS horizon, with Entogonites nasutus, has now been identified in
the Rheinisches Schiefergebirge and its stratigraphic relationship to the cullla marker
horizons demonstrated (Nicolaus 1963). Schmidt’s scheme of zones of 1925 had to
depend on a presumed course of phylogenesis (based mainly on the sequence of prole-
canitids) supported at one point by Belgian evidence taken to confirm the relative age
of culla and cully. The scheme has been available for over forty years. It can be seen 1
to be weak in that it was based on evidence from a relatively small number of scattered
localities. It has survived, free from any serious challenge, because of the continuing
poverty of the evidence. But there have been occasional finds of cephalopod faunas
which could not satisfactorily be dated by reference to this standard. Notable European
examples are those from Zadelsdorf (Schindewolf 1922, 1926, 1939) and Iberg-Winter-
berg (Schindewolf 1951a). The early Mississippian goniatite faunas of the U.S.A. like-
wise have never found accommodation in Schmidt’s scheme.

An alternative means of dating rock-successions of this range of age has appeared by
the development in recent years of a zonal scheme based on conodonts. Voges’s (1959,
1960) proposals, now confirmed and further elaborated by Meischner (in press), are
based on detailed collecting from continuous sections. That information includes some
obtained from sites where cephalopods occur, such as the Hangenbergkalk and the
Erdbacherkalk. In 1 960, Voges attempted a reconciliation of the two schemes. He claimed
that culla and cull/3 were distinguishable from one another (and referred especially to
Delepine’s (19406) treatment of Irish faunas) but that cuIIjS and cully were not. His
tentative proposal was that the Siphonodella crenulata Zone should be equated with
culla, and the anchor alis Zone with cull yS/y. It should be understood that neither culla I
nor cull/3 were identifiable in the sections from which his conodonts came, and also that
the anchoralis Zone (as Voges himself showed) does not extend to the top of the Erd-
bacherkalk, the cully type. On the other hand, his proposals for cul units, based on the
evidence of the Hangenbergkalk, are irreproachable.

It is now possible to use conodonts as a means of distinguishing Belgian equivalents
of the German stratigraphic units, and the results are immediately of relevance here.
Conil, Lys, and Mauvier (1964) produced a preliminary account of the conodonts they
had discovered in the Franco-Belgian Lower Carboniferous. As Paproth (1964) has
pointed out, this made it possible to recognize Tn lb as the Hangenbergkalk correlative.

It follows that some hundreds of metres of the Belgian succession (Legrand, Mamet,
and Mortelmans 1966) intervene between the cul horizon and the culla source. This
range is unrecognized in the statement of cephalopod zones. In terms of conodonts it
is approximately the Siphonodella crenulata Zone of Voges. Further, Conil, Lys, and
Mauvier’s discovery of Scaliognathus anchoralis in Tn 3c indicates that the culla source
lies within Voges’s anchoralis Zone, and consequently that Voges was mistaken in his
tentative equation of the anchoralis Zone with cuII/J/y. A new rendering of relationships
linking cephalopod occurrences and conodont zones is offered in text-fig. 2.

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 117

The Hangenbergkalk record of cephalopods fails to close with that from the late
Tournaisian of Belgium and the cephalopod zonal scheme is seen to be discontinuous.
In the past it has been suggested that the sufficiency of the scheme was confirmed by the
work of Librovitch (1940), who dealt with an unusually rich body of material from

text-fig. 2. Rock-units in the Lower Carboniferous stratigraphy of Germany, and the conodont-zones
established there (after Yoges). Standard cephalopod occurrences may be referred to the conodont
scheme as suggested on the right of the diagram.

Kazakhstan. Librovitch proposed a succession of ‘faunal complexes’ which appeared
to repeat the sequence of stages proposed by Schmidt in 1925. The complexes do not,
however, stand as independent confirmation of the standard scheme. They were
modelled on the existing western European proposals, as Librovitch himself plainly
admitted.

The new fauna from Cornwall may be of Siphonodella crenulata-Zone age, certainly
later than the Hangenbergkalk faunas, possibly earlier than those of the late Tournaisian
of Belgium in that there is coincidence of Gattendorfia and Ammonellipsites. This
estimate of the age relative to Tn 3c is not easily made. Ammonellipsites princeps and
Muensteroceras complanatum are common to the two. The new elements in the Cornish
fauna, since they are unique to this case, have no part in a question of relative age. The
mere presence of gattendorfiids has no immediate significance, for an argument of age
based on late survival is never entirely satisfactory. But the gattendorfiids seen here
resemble the small, slightly more evolute, constricted ‘ Kazakhstania?' of the Walls Ferry
limestone of Arkansas (see below) and in this there is an indirect suggestion that the
Cornish fauna might predate Tn 3c. The fauna adds to the record of Tournaisian gonia-
tites, and it may have its place within the gap now seen to interrupt the standard
sequence of zones ; but it does not by any means close that gap nor provide any justifica-
tion for proposing a new zone.

The view that a coincidence of gattendorfiid and gon.atitacean cephalopods exists in
a post-Hangenbergkalk, pre-Calcaire de Calonne range of age is strongly encouraged

118

PALAEONTOLOGY, VOLUME 13

by the American evidence. It is necessary to refer here to the conodonts of the Siphono-
della quadruplicata-S. crenulata Zone and of the Siphonodella isosticha-S. cooperi Zone.
These may be equated with European proposals as is done in Canis (1968, table 2), but
neither should be regarded as identifying culla. Also, it should be noted that the Siphono-
della isosticha-S. cooperi Zone can be found to precede the anchoralis Zone in Europe
(Matthews 19696). The Chouteau limestone, according to Miller and Collinson (1951),
produces representatives of the following cephalopod genera: Gattendorfia, Muenstero-
ceras, Ammonellipsites, Imitoceras, Protocanites, and Prodromites. Canis (1968) refers
the Chouteau limestone to the S. quadruplicata-S. crenulata and S. isosticha-S.
cooperi Zones. The Rockford limestone of Indiana has, at the type locality, Imitoceras,
Muensteroceras, Protocanites, and Prodromites (Miller and Collinson 1951) and has
produced a Gattendorfia species in north-western Indiana (Gutschick and Treckmann
1957). Rexroad and Scott (1964) report that the Rockford limestone has the conodonts
of the S. isosticha-S. cooperi and Gnathodus semiglaber-Pseudopolygnathus multistriata
Zones. Gordon (1964) lists Gattendorfia, ‘ Kazakhs tania?', Ammonellipsites, and
Muensteroceras from the Walls Ferry limestone of Arkansas and observes that
conodonts, dominated by siphonodellids (according to W. H. Hass), are found in a bed
which lies 1 ft. below the cephalopod occurrence. Gordon (1964) reports too the
existence of a Gattendorfia specimen from the lower part of the Lodgepole limestone
of Montana and an ammonellipsitid, as yet undescribed, again from the Lodgepole.
Klapper (1966) has described conodonts of the ‘lower Siphonodella crenulata Zone’
(which, misled by German practice, he equates with culla) from the basal part of the
Lodgepole.

The record of American information is not as full as might be desired. For example,
it would be preferable to identify the exact stratigraphic provenance of cephalopod
material and to refer in every case to conodont material taken from the same horizon.
Again, greater fullness is desirable in that the outstanding ‘misfit’ (as seen from Europe),
the Marshall sandstone fauna of Michigan, cannot yet be referred to a conodont-based
age-standard. But the evidence so far available may be sufficient to show that there is
little purpose in attempting to judge the age of these early Mississippian faunas by refer-
ence to the European scheme of cephalopod zones. They appear to belong to a range of
age which goes unregarded in the cephalopod scheme and which can be distinguished
only by the evidence of conodonts.

SYSTEMATIC DESCRIPTIONS

Numbers with prefix BU refer to the Geology Museum, University of Bristol.

Measurements. The dimensions given apply in every case to the stated diameter. Abbreviations are:
D = diameter, U = umbilical segment of the diameter, WH = whorl height, Wh = distance from
the ventral crest of the whorl to the ventral crest of the preceding whorl, WW — whorl width.

Order ammonoidea Zittel 1884
Suborder goniatitina Hyatt 1884
Superfamily cheilocerataceae Freeh 1897
Family cheiloceratidae Freeh 1897
Subfamily imitoceratinae Ruzhencev 1950
Genus gattendorfia Schindewolf 1920

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 119

Type-species by original designation: Gattendorfia subinvoluta Schindewolf 1920.

1960 Gattendorfia Schindewolf; Vohringer, pp. 149-50 (see also for earlier references).
1964 Gattendorfia Schindewolf; Gordon, pp. 168-70 (see also for earlier references).

1964 Kazak hstania Librovitch; Gordon, p. 171.

1965 Gattendorfia Schindewolf; Weyer, p. 447.

Gattendorfia sp.

Plate 25, figs. 6-18; text-fig. 3 a-e

Material. BU 19635-BU 19666.
Dimensions (mm.)

Plate reference

D

U

WH

Wh

ww

Volutions

BU 19635

Plate 25, figs. 17, 18

c. 6-5

c. 2-5

c. 2-5

c. 2

c. 2

4-5?

BU 19640

Plate 25, fig. 12

5

3

1-3

—

1-5

4-75

BU 19642

Plate 25, fig. 16

4-2

1-8

1-2

—

1-5

4-5

BU 19666

Plate 25, figs. 13, 14

4-2

2

1-2

c. 1-0

c. 1-5

4-5

BU 19637

Plate 25, figs. 7, 8

3-4

1-6

1

0-9

c. 0-9

3-75

BU 19645

Plate 25, figs. 9, 10

2-7

105

0-8

c. 0-7

0-7

3

Gordon (1964, p. 172):

8-5

5-2

20

—

2-6

90

6-4

20

—

2-5

10-2

7-3

2-2

—

c. 3 0

Description. Small evolute shells with rounded whorls which are relatively high at early
stages of growth. No evidence of external ornament. Whorls each bear two conspicuous
constrictions, one succeeded by another at slightly less than half-circumference. Con-
strictions follow a shallowly sinuous course across the flanks, are so disposed to the axis
of growth that their nearest approach to the aperture is on the venter. Suture as in text-
fig. 3d, e. External lobe relatively deep.

Remarks. The sutures of these evolute forms have no match among known gatten-
dorfiids. Their character excludes a prolecanitid affinity, and so too does the presence
of constrictions. The evolute shell-form and the presence of constrictions are reminiscent
of what is seen in the persistently evolute gattendorfiid to which some refer as ‘ Kazakh -
stania\ Librovitch, in 1940, proposed the subgenus Gattendorfia ( Kazakhstania ) on the
basis of material from central Asia, and suggested it to be distinct from Gattendorfia by
its evolute form maintained throughout growth. Further, he suggested that Gattendorfia
( Kazakhstania ), with its relatively deep, lanceolate external lobe, and with constrictions,
need not be confused with the protocanitids, which are also evolute. Miller and Collinson
(1951), without discussing the matter, referred to ‘ Kazakhstania’ as a genus. It was not
until 1955 that Miller and Garner proposed that the form be raised to generic rank. They
then added an American species to the two described by Librovitch. In 1960 Vohringer
returned these evolutes to synonymy with Gattendorfia, and there is much to commend
his view. Vohringer’s full analysis of the Hangenbergkalk gattendorfiids has shown how
variable are these involution-evolution characteristics of shell form, and it seems good
to accept that the continuously evolute shell, which Librovitch saw as the definitive
characteristic of his subgenus, is not sufficiently distinctive to justify a relatively elevated
systematic position for ‘ Kazakhstania’ . Certainly, full generic status does not seem
justifiable.

120

PALAEONTOLOGY, VOLUME 13

Gordon (1964), apparently unaware of Vohringer’s opinion, identified a small, evolute
ammonoid from the Mississippian of Arkansas as ‘Kazakhstania? sp.’ He suggested that
‘ Kazakhstania? might receive also certain small, evolute, constricted ammonoids reported
from the Mississippian of Ohio by Hyde (1953). These latter strongly resemble the

text-fig. 3. Gattendorfia sp. a, b, c. Apertural aspect of BU 19645 (terminal
diameter 2-7 mm.), BU 19637 (3-4 mm.), BU 19644 (4-3 mm.) respectively.
d. Suture of BU 19645 at diameter 1-7 mm. e. Suture (reversed) of BU 19643
at diameter approximately 3-7 mm. (specimen deformed).

individuals encountered in the Cornish fauna (an observation first put to the author by
Professor M. R. House).

Weyer (1965), like Vbhringer, regarded ‘ Kazakhstania ’ as synonymous with Gatten-
dorfia. Yohringer, indeed, had gone so far as to suggest that Librovitch’s two species
were perhaps to be identified with Gattendorfia tenuis (a form which ranges through most
of the Hangenbergkalk and is still available in the topmost bed, as Vohringer’s table 1
shows). G. tenuis is, however, more involute at late stages of growth and must therefore
differ from the two forms described by Librovitch. Since Vbhringer found nothing
entirely comparable with ‘ Kazakhstania ’ in the Hangenbergkalk there remains a possi-
bility that fully evolute species may be of an age somewhat later than is represented in
that sequence. The evidence from the Hangenbergkalk (which has three gattendorfiid
species still extant in its uppermost part) need not be taken to account completely for
the vertical range of Gattendorfia. Thus, although these evolute forms lose their generic
rank, they may be thought to retain a special stratigraphic interest.

EXPLANATION OF PLATE 25

Figs. 1, 2. Gen. et sp. nov. A. Right (to display ornament) and left (to display early whorls) views of
BU 19668. X 8.

Figs. 3, 4, 5. Gen. et sp. nov. A. Apertural, lateral and oblique ventral (to display sutures) views of BU
19667. x 8.

Figs. 6-18. Gattendorfia sp. 6, BU 19641. 7, 8, BU 19637. 9, 10, BU 19646. 11, BU 19643 (deformed).
12, BU 19640 (deformed). 13, 14, BU 19666. 15, BU 19638. 16, BU 19642. 17, 18, BU 19635
(deformed). All x 8.

Palaeontology , Vol. 13

PLATE 25

MATTHEWS, Carboniferous cephalopods from Cornwall

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 121

Superfamily goniatitaceae de Haan 1825
Family goniatitidae de Haan 1825
Subfamily karagandoceratinae Librovitch 1957
Gen. et sp. nov. A

Plate 25, figs. 1-5; text-fig. 4 a, b

Material. BU 19667-BU 19669.

Dimensions (mm.)

Plate reference

D

U

WH

Wh

WW

Volutions

BU 19667

Plate 25, figs. 3-5

5

1-6

1-8

1-3

2-6

?

BU 19668

Plate 25, figs. 1, 2

4

1-4

1-6

M

2-4

3-8

text-fig. 4. Gen. et sp. nov. A. a. Apertural aspect of BU 19667 (terminal diameter
5 mm.), b. Three successive sutures of BU 19667 at diameters 3 -9-4-7 mm.

Description. Narrow, open umbilicus exposes all previous whorls. Whorls depressed,
wider than high, maximum width (also overlap) at approximately one-third whorl-
height. Ornament of approximately twenty robust umbilical ribs which fade as they
curve concave adaperturally beyond the locus of maximum whorl-width and finally
approach parallelism with the growth axis. Venter broad, rounded, unornamented.
Suture (text-fig. 4 b) has broadly splayed external lobe with median saddle.

Remarks. The form reveals its most interesting characteristic in the broad external lobe,
with its median saddle. It is therefore a goniatitacean. But like Karagandoceras and
Paralytoceras it has little else in common with the goniatitinids.

Weyer (1965), who re-examined Paralytoceras and first demonstrated its possession
of goniatitacean sutural character, decided to refer both Karagandoceras and Para-
lytoceras provisionally to the Karagandoceratinae — this in full awareness of the possi-
bility that the two genera might have arisen along quite independent courses. Weyer
preferred to attach the subfamily Karagandoceratinae to the family Goniatitidae, rather
than follow Ruzhencev (1962) in identifying a family Karagandoceratidae attached to
the Praeglyphiocerataceae. The systematic affiliation of the new genus as given here is

122

PALAEONTOLOGY, VOLUME 13

entirely in accordance with Weyer’s proceeding : a third genus is added to Karagando-
ceratinae, and this is done recognizing the possible artificiality of a Gen. et sp. nov. A —
Karagandoceras-Paralytoceras combination.

The new form has a sutural character sufficient to separate it from any goniatitinid
of conceivably comparable age, although in its relative robust ornament and in shell-form
it appears to be closer to the goniatitinids than is Karagandoceras or Paralytoceras. The
resemblance, within the Karagandoceratinae, is more with Paralytoceras, especially in
the form of the external lobe. The lateral lobes of the two sutures differ slightly, however,
and the fimbriate ornament of the more evolute, carinate Paralytoceras is altogether
different from what is seen in Gen. et sp. nov. A. Certain umbilical ornament is seen
among the ammonellipsitids, especially in the young stages of A. rotuliformis (Crick)
and in A. homoceratoides (Schindewolf). In neither case is the exact form of the ornament
comparable with what is seen here. The sutures (at much larger diameter) of these two
are also different.

Formal proposal and precise diagnosis of the new genus and species is reserved until
further, possibly relevant material has been examined. BU 19667 (which was capable
of being prepared in order to expose the median saddle) and BU 19668 probably belong
to one and the same species. BU 19668 offers no sutural information, but is consistent
with BU 19667 in shell-form and ornament. A badly preserved, relatively large third
form (BU 19669) has more sharply sculpted ribs than the other two (PI. 27, fig. 8)
and is tentatively referred to the new genus.

Subfamily muensteroceratinae Gordon 1964
Genus muensteroceras Hyatt 1884

Type species by original designation: Goniatites oweni var. parallela Hall 1860.

1961 Muensteroceras Hyatt; Kullmann, pp. 256-8 (see also for earlier references).

1961 Munsteroceras Hyatt; Pareyn, p. 96.

1963 Muensteroceras Hyatt; Campbell and Engel, p. 87.

1964 Munsteroceras Hyatt; Wagner-Gentis, p. 232.

1964 Muensteroceras Hyatt; Gordon, p. 175 (see also for earlier references).

1965 Dzhaprakoceras Popov, p. 36.

1965 Muensteroceratoides Popov, p. 36.

Muensteroceras complanatum (de Koninck 1880)

Plate 26, figs. 10, 11; text-fig. 5c

1884 Goniatites complanatus de Koninck, p. 106, pi. 46, fig. 4.

1940a Muensteroceras complanatum (de Koninck); Delepine, pp. 47-52; pi. 3, figs. 3, 4; text-
fig. 8.

EXPLANATION OF PLATE 26

Figs. 1, 2. Ammonellipsites sp. indet. Lateral and ventral views of BU 19772. x5.

Figs. 3-6, 9. Muensteroceras spp. 3, BU 19675. 4, BU 19674. 5, BU 19676. 6, BU 19672. 9, BU
19673. 6x5, others x 8.

Fig. 7. Muensteroceras cf. rotella (de Koninck). Oblique ventral (to display sutures) view of BU 19671.
X 8.

Fig. 8. Ammonellipsites princeps (de Koninck). BU 19721. X 8.

Figs. 10, 11. Muensteroceras complanatum (de Koninck). Apertural and lateral views of BU 19670. x 5.

Palaeontology , Vol. 13

PLATE 26

MATTHEWS, Carboniferous cephalopods from Cornwall

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 123

Material. BU 19670.
Dimensions (mm.)

Plate reference

D

U

WH

WW

BU 19670 Plate 26, figs. 10, 11

c. 12

c. 10

c. 6-3

c. 4-5

Delepine (1940a, 47):

65

6-7

33

18

Note. Delepine (1940a, 47) referred in his table to Plate 28, figs. 3
and 4. Obviously, a reference to Plate 27, figs. 3 and 4 was intended.

Remarks. The specimen figured shows well the involution, small umbilicus, high flanks
and sutural character (text-fig. 5c) appropriate to this species.

Muensteroceras cf. rotella (de Koninck 1 880)

Plate 26, fig. 7 ; text-fig. 5b

Material. BU 19671.

Remarks. One fragment provides evidence sufficient to justify comparison with Muen-
steroceras rotella. The umbilicus appears to be more open than that of M. complanatum ;
the suture line (text-fig. 5b), with a straight-sided external lobe stacked close to the same
element of the previous suture line, as is found in M. rotella. In this, Muensteroceras
rotella is close to the American M. oweni and M. parallelum.

It is worthwhile to note that Delepine (1940a) referred one example of M. rotella to
a relatively early position in the Tournaisian stratigraphy, and also that an ammonoid
collected from the Liegende Alaunschiefer in Germany has been suggested to be
identifiable as M. rotella (H. Schmidt’s opinion, reported in Paproth, Teichmuller and
Remy 1960, p. 8).

Muensteroceras spp.

Plate 26, figs. 3-6, 9

Material. BU 19672-BU 19718.

Remarks. Several specimens are referred to the genus Muensteroceras on the evidence
of their form. Occasionally, sutural evidence is also available. Certain small specimens
may carry a hint of faint ribbing (PI. 26, figs. 4, 9), and some constrictions (PI. 26,
figs. 3, 5).

Subfamily pericyclinae Hyatt 1900
Genus ammonellipsites Parkinson 1822

Type-species by subsequent designation of Schindewolf 19516: Ellipsolithes funatus Sowerby 1814.

1911 Pericyclus', Hind, pp. 107-8; pi. 4, figs. 3, 4, 5, 5a.

1957 Ammonellipsites Parkinson; Gordon, pp. 29-33.

1961 Pericyclus Mojsisovics 1882 emend. Hyatt 1883; Pareyn, p. 135.

1963 Pericyclus Mojsisovics; Campbell and Engel, p. 114.

1964 Ammonellipsites Parkinson; Gordon, pp. 172-3 (see also for earlier references).

1964 Pericyclus Mojsisovics; Wagner-Gentis, p. 229.

71965 Neopericyclus Popov, pp. 45-6.

Remarks. Gordon (1957) has produced a thorough review of the history of attempts to
subdivide this genus. He supplied also a key to recognition of the extant subgenera. Since

124

PALAEONTOLOGY, VOLUME 13

present information on the relative ages of the various occurrences of ammonellipsitids
is so poor, and since sutural evidence is not available in every case, there is a danger
that these subgeneric associations of ammonellipsitid species may be artificial and
phylogenetically uninstructive. No subgeneric assignments are made here.

Ammonellipsites princeps (de Koninck 1844)

Plate 26, fig. 8; Plate 28, figs. 1-7; text-fig. 5a

1844 Ammonites princeps de Koninck, pp. 579-80; pi. 51, figs. 2a, b, c, 3 a, b, c (de Koninck’s
publication is given the dates 1842-4. Delepine (1940a) refers de Koninck’s proposal
of Ammonites princeps to the year 1842).

1940a Pericyclus princeps (de Koninck); Delepine, pp. 38-40; pi. 1, figs. 12-15; text-fig. 7 (see
also for earlier references).

Material. BU 19719-BU 19761.

Dimensions (mm.)

Plate reference

D

U

WH

Wh

WW

No. of ribs

BU 19719 Plate 28, figs. 1, 2

c. 6-8

1-3

c. 3-4

c. 2-6

4-8

c. 60

BU 19720 Plate 28, fig. 7

c. 100

c. 2 0

c. 4 0

?

6-8

BU 19721 Plate 28, fig. 6

c. 5

1-2

1-8

c. 2 0

3-2

c. 50

BU 19723 Plate 28, fig. 5

3-3

10

1-4

7

2-8

c. 40

BU 19726 Plate 28, fig. 3

2-2

01

0-8

7

1-4

—

Delepine (1940a, 39):

35

10

—

—

—

42

„

34

11

—

—

—

>50

Remarks. BU 19719 shows well the sutural (text-fig. 5a) and sculptural characteristics of
the species, although ribs may be more numerous than in the larger Belgian specimens.
Other specimens (BU 19720-BU 19761), if their ornament is well preserved, may also
be referred to this species. Some further small individuals possibly fit to be compared
with A. princeps are included in Ammonellipsites spp. (below).

The relatively robust ribs curve convex-adapically across the venter, but their curva-
ture is always more slight than in the American form A. blairi. Occasional instances of
bifurcation are seen. The constrictions, up to four in number per whorl, are relatively
broadly developed, and their course parallels that of the ribs.

Ammonellipsites sp. aff. asiaticus (Librovitch 1940)

Plate 27, figs. 5, 9, 10

1940 Pericyclus asiaticus Librovitch, pp. 122-30, 268-72; pi. 16, figs. 1-6; pi. 17, figs. 1-4;
text-figs. 43-51.

1940 Pericyclus asiaticus var. simplex Librovitch, pp. 130-1, 272; pi. 17, figs. 5, 6; text-figs.
52, 53.

EXPLANATION OF PLATE 27

Figs. 1-4, 6, 7. Ammonellipsites spp. 1, 2, BU 19730 (cf. A. princeps). 3, BU 19724 (cf. A. princeps).
4, BU 19766 (cf. A. sp. aff. asiaticus). 6, BU 19729 (cf. A. princeps). 7, BU 19765 (cf. A. sp. aff.
asiaticus). All x 8.

Fig. 8. Gen. et sp. nov. A? BU 19669. x 5.

Figs. 5, 9, 10. Ammonellipsites sp. aff. asiaticus (Librovitch). 5, BU 19764. 9, 10. Lateral and ventral
(to display spiral ribbing) views of BU 19762. 5, x 8, others x 5.

Palaeontology , Vol. 13

PLATE 27

MATTHEWS, Carboniferous cephalopods from Cornwall

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 125

Material. BU 19762-BU 19771.
Dimensions (mm.)

Plate reference

D

U

WH

Wh

WW

BU 19762

Plate 27, figs. 9, 10

17

2-4

8

5-3

9

BU 19763

c. 16

c. 1-2

c. 10-5

6

c. 7-5

BU 19764

Plate 27, fig. 5

7-7

0-6

4

2-6

c. 5-8

?BU 19766

Plate 27, fig. 4

4-7

0-6

20

9

c. 3-6

?BU 19765

Plate 27, fig. 7

3-8

0-5

1-8

c. 1-4

c. 2-4

text-fig. 5. a. Ammonellipsites princeps. Suture of BU 19719 at diameter
4-5 mm. b. Muensteroceras cf. rot el la. Suture of the incomplete specimen
BU 19671, with ventral element of the succeeding suture shown.
c. Muensteroceras complanatum. Suture of BU 19670 at diameter 10 mm.,
with ventral element of the succeeding suture shown.

Description. The shell is tightly involute and the narrow umbilicus has a rounded margin.
The last whorl is relatively high, with extensive flanks and a rounded venter. On the
largest specimen (terminal diameter 17 mm.) approximately eighty ribs can be counted
on the venter. The fine ribs increase by bifurcation, and rarer intercalation, achieved
near the locus of maximum whorl-width. Of the two secondary ribs produced by
bifurcation one is immediately collinear with the primary rib and the other diverges
adapically. The ribs follow a sinuous course across the flanks with a weak, broad,
adaperturally concave curve whose turning-point is situated near half whorl-height.
There is a clear ventral sinus. In addition to these transverse sculptural elements a minor
spiral set is present, best seen in troughs between major ribs. The spiral elements are
collinear in adjacent troughs. Interference of transverse with spiral sculptural elements
results in a serrate condition seen in the better-developed transverse ribs. There are no
constrictions. The suture is unknown.

126

PALAEONTOLOGY, VOLUME 13

Remarks. The general form resembles that seen in some of the tightly umbilicate, multi-
costate species described by Delepine (1940a). None of these is exactly similar. Gordon
(1957) suggested that certain involute species described by Librovitch, A. asiaticus,
A. dichotomus, A. sokurensis, should perhaps be united in a subgenus which, if sutural
information were available, might be found fit to receive also the Belgian forms A.
divisus and A. ryckholti. The Cornish species is of this character, if not strictly identical
with any of the species mentioned. In the continuing absence of sutural information,
Gordon’s suggestion cannot be acted upon ; and the view expressed above is that there
may be little profit from such proposals of subgenera. It is perhaps worth while to note
that A. divisus and A. ryckholti come, according to Delepine (1940a), from a relatively
low part of the Belgian succession.

The closest similarity is to Librovitch’s species A. asiaticus, especially to that variety
which he distinguished by its lack of constrictions. There is a resemblance in general
form, and some similarity in the course of the ribbing, but the umbilical margin appears
to be more sharply defined in the Kazakhstan individuals. Also, they have, apparently,
coarser and less numerous ribs (17-18 per cm. here at diameter 17 mm. as against 6-10
at 30-5 mm. — unfortunately, none of the Cornish forms are large enough to permit
comparison at a common diameter).

Librovitch mentioned that A. asiaticus shows a fine spiral striation in extremely rare
cases, sufficient to give a faintly reticulate character to the ornament, and spiral striae
are seen in the present case. A spiral element occurs fairly commonly in the ornament
of early Carboniferous cephalopods. Examples in Gattendorfia were mentioned by
Librovitch (1940, p. 241) and Vdhringer (1960, p. 156). Vohringer (1960, p. 148) found
sculpture of this kind in Costimitoceras, too. Schindewolf (19516, p. 306) has listed A.
trapezoidalis, A. hauchcornei, A. kochi, A. homoceratoides and (possibly) A. plicatilis
among ammonellipsitids so ornamented (he did not mention A. asiaticus, and in A.
homoceratoides he included a case where the ‘spiral’ element is not conspicuously well
organized). The spiral sculpture-element is, then, a feature of the present individuals that
they share with A. asiaticus, but since it is one so commonly developed among early
Carboniferous cephalopods it need not be taken as compelling the conclusion that the
Cornish specimens and A. asiaticus are conspecific. In later Carboniferous ammonoids
there are, of course, numerous examples of forms which display such sculpture.

It is necessary to note here Budinger and Kullmann’s (1964) brief mention of what is
perhaps the earliest Carboniferous goniatite fauna so far recovered in the Cantabrian
Mountains. It includes ‘ Ammonellipsites {Pericyclus) aff. asiaticus (sp. iuv.)’ and imito-
ceratids. The suggestions of affinity with A. asiaticus advanced by these authors and
again here involve some measure of coincidence. The writer is not acquainted with
Budinger and Kullmann’s specimen.

The small specimens BU 19765-BU 19771 are only tentatively included. The material

EXPLANATION OF PLATE 28

Figs. 1-7. Ammonellipsites princeps (de Koninck). 1, 2, Lateral and oblique apertural (note plug of
silica filling the umbilicus) views of BU 19719. 3, BU 19726. 4, BU 19725. 5, BU 19723. 6, BU
19721. 7, BU 19722. 7,x5, all others x8.

Figs. 8-20. Gen. et sp. nov. B. 8, 9, BU 19854. 10, 11, BU 19853. 12, BU 19849 (deformed).
13, BU 19851. 14, BU 19852. 15, 16, BU 19850. 17, 18, BU 19847. 19, 20, BU 19848. All X 8.

Palaeontology , Vol. 13

PLATE 28

MATTHEWS, Carboniferous cephalopods from Cornwall

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 127

available is too limited to allow the form to be traced down confidently to the smaller
ranges of size. Certain specimens listed under Ammonellipsites spp. may deserve to be
compared with the form treated here.

Ammonellipsites sp. indet.

Plate 26, figs. 1, 2

Material. BU 19772.

Dimensions (mm.)

Plate reference D U WH WW

C 75076 Plate 26, figs. 1,2 ? c. 3-5 6-5 12-5

Description. A globose, multicostate, tightly umbilicate form. The flanks are restricted
and the venter broadly rounded. The fine ribs bifurcate, to give equal secondaries, near
the umbilical margin. Intercalation is also seen, but is less common. The course of the
ribs is almost straight until the broad ventral sinus is reached. A hint of minor, spiral
ribbing can be seen. No constrictions are found. The suture is unknown.

Remarks. The tight umbilicus and abundant fine ribs suggest comparison with the forms
mentioned for these features above, and the presence of spiral striations suggests a com-
parison with A. sp. aff. asiaticus. In this present case, however, the shell is distinctively
globose; but the single specimen is poorly preserved, the suture not revealed, and any
justification for proposing a new specific category is lacking.

Ammonellipsites spp.

Plate 27, figs. 1^1, 6, 7

Material. BU 19773-BU 19846.

Remarks. Certain of the specimens included here may tentatively be associated with
A. princeps or A. sp. aff. asiaticus by the character (relative robustness, curvature) of
their ribbing (see remarks attached to the explanation of PI. 27).

Subfamily pericyclinae Hyatt 1900?

Gen. et sp. nov. B
Plate 28, figs. 8-20; text-figs. 6 a-d

71880 Goniatites de Koninck (partim), pp. 112-13; pi. 44, fig. 9a, b.

71940a ‘ Goniatites ’ ( Pericyclus ?) Delepine, pp. 42-3; pi. 3, fig. 7.

Material. BU 19847-BU 19882.

Dimensions (mm.)

Plate reference

D

U

WH

Wh

WW

Volutions

BU 19848 Plate 28, figs. 19, 20

5

1-7

2-3

c. 1-8

2

4-2

BU 19847 Plate 28, figs. 17, 18

c. 3-8

1-4

1-3

?

c. 1-2

3-75

BU 19850 Plate 28, figs. 15, 16

3-5

1-4

1-3

c. M

1-2

3-5

BU 19853 Plate 28, figs. 10, 11

2-2

0-9

0-7

c. 0-6

M

2-75

BU 19852 Plate 28, fig. 14

2-1

0-8

0-7

0-5

0-9

2-3

BU 19854 Plate 28, figs. 8, 9

20

0-8

0-7

0-5

0-9

2-3

128

PALAEONTOLOGY, VOLUME 13

Description. Relatively evolute shell with all earlier whorls displayed. Umbilical margin
rounded. Early whorls depressed, wider than high, carry an umbilical ornament of elon-
gate, edged nodes and have a ventral carina which may be noded. At later stages the f
umbilical ornament is weaker, the ribs gradually fade as they approach the venter (which
they do not reach) and show an adaperturally concave curvature. The later whorls are
higher than wide, with maximum width at approximately one-third whorl-height. The
venter here is sharp rather than distinctly carinate. Suture, as in text-fig. 6, has a shallow,
straight-sided, external lobe with median saddle.

Remarks. This form differs from any Lower Carboniferous cheiloceratacean genus
having a keel and any umbilical or flank ornament ( Protocanites , Pseudarietites ) by
reason of its sutural character. One pseudarietidan whose suture is unknown, P. serratus,
is distinctly the latest of the Hangenbergkalk forms referred to Pseudarietites by Vohringer
(1960). Its ornament is vaguely reminiscent of what is seen at early stages of growth
here.

Several goniatitids may resemble the present form in particular characteristics of form,
but there is in no case complete correspondence. Muensteroceras acutum Librovitch and
‘ Brancoceras' enniskillense Foord both have acute, near-carinate venters, but show no
other point of resemblance. There is no agreement of sutural evidence. Ammonellipsites?
carinatus (Schindewolf) differs in its ribbing and in the degree of its involution. Its suture
is unknown. Ammonellipsites homoceratoides (Schindewolf) has umbilical ornament at
early stages. But it is at no stage carinate, and its form is more inflated than is the case
here. The A. homoceratoides suture is of another character and is in fact such as to have
led Pareyn (1961) to suggest A. homoceratoides as the source from which Beyrichoceras
sprang. It is conceivable that the A. homoceratoides example of umbilical ornamentation
arose independently of the one under discussion here.

Two Belgian forms deserve closer attention. They are Goniatites crenulatus de
Koninck and Goniatites {Pericyclus?) tuber culatus Delepine. In neither of these is the
suture known, but they bear close resemblance to the new genus in shell-form. G. (P. ?)
tuberculatus appears to be at all stages more involute and more depressed, and its um-
bilical ornament is nodose rather than costate. The last whorl bears four clear constric-
tions. None of these objections apply to the more evolute G. crenulatus, whose umbilical
tubercules show a tendency toward elongation at right angles to the umbilical border.
However the venter in the case of G. crenulatus is rounded (de Koninck 1880, pi. 49,
fig. 9b). Given information on the suture line and on the ventral form of juvenile stages,

G. crenulatus and G. (P. ?) tuberculatus might be seen to belong in this new genus.

Delepine (1940a, p. 43) wrote of G. crenulatus thus: ‘Peut-etre, quand la suture sera
connue, pourrait-on reunir ces deux especes dans un genre nouveau, intermediate entre
Pericyclus et Munsteroceras, voisin de Pericyclus au stade jeune, mais distinct de celui-ci
parce que les cotes, saillantes surtout au bord de l’ombilic, ou elles sont noduleuses,
s’attenuent tres tot, puis passent a des cotes fines, plutot des stries, comme chez
Munsteroceras ’. The possibility of proposing a new genus arises now, and it may prove
to include these two small problematical Belgian forms in specific categories distinct
from one constructed to contain the Cornish specimens. One would acknowledge
Delepine’s prescience, but should forbear at this time from speculating on any phylo-
genetic linkage of the two Belgian forms with the one described here.

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 129

The occurrence of a median saddle in this relatively evolute goniatite is especially
interesting. The near-parallel margins of the external lobe and the rounded character
of the adjacent saddles are taken as possible justifications for an assignment to the sub-
family Pericyclinae — this even though ventral ornament, the carina apart, fails.

a b c

text-fig. 6. Gen. et sp. nov. B. a, b. Apertural aspect of BU 19854 (terminal diameter
2 mm.) and BU 19847 (c. 3-8 mm.) respectively, c. Suture of BU 19854 at diameter 1 -7 mm.
d. Suture of BU 19847 at diameter 3-2 mm.

The American faunas which (it is argued above) intervene between those of the
Hangenbergkalk and of the late Tournaisian have as yet produced no representation of
goniatites with predominantly umbilical ornament.

Acknowledgements. The cephalopod fauna described here was discovered during the author’s tenure
of a Shell International Petroleum Company Research Studentship. On many occasions, Professor
Scott Simpson and Professor D. L. Dineley have freely offered their advice and encouragement. Pro-
fessor M. R. House, Dr. R. Goldring and Dr. M. K. Howarth have kindly criticized a draft of the paper.
The photographic illustrations are the work of Mr. R. Godwin of the Geology Department, University
of Bristol, which is here gratefully acknowledged.

REFERENCES

budinger, p., and kullmann, j. 1964. Zur Frage von Sedimentationsunterbrechungen im Goniatiten-
und Conodonten-fiihrenden Oberdevon und Unterkarbon des Kantabrischen Gebirges (Nord-
spanien). N. Jb. Geol. Palaont., Mh. 1964, 414-29, 2 figs.

Campbell, k. s. w. and engel, b. a. 1963. The faunas of the Tournaisian Tulcumba Sandstone and its
members in the Werrie and Belvue synclines, New South Wales. J. geol. Soc. Aust. 10, 55-122,
11 figs., pi. 1-9.

canis, w. f. 1968. Conodonts and biostratigraphy of the Lower Mississippian of Missouri. /. Paleont.
42, 525-55, 2 figs., pi. 72-4.

conil, r., lys, m., and mauvier, a. 1964. Criteres micropaleontologiques essentiels des formations-
types du Carbonifere (Dinantien) du bassin Franco-Beige. Congres Avanc. Etud. Stratigr. carb.
Paris, 1963, 325-32, pi. 1, 2.

delepine, g. 1940 a. Les goniatites du Dinantien de la Belgique. Mem. Mus. r. Hist. not. Belg. 91, 1-91,
19 figs., pi. 1-10.

19406. Contribution a l’etude des goniatites du Waulsortien d’lrlande et de Belgique. Annls. Soc.

geol. N. 64, 134—49, pi. 4.

foord, a. H. 1897-1903. Carboniferous cephalopoda of Ireland. Palaeontogr. Soc. [Monogr.] 1-234,
pi. 1-49.

C 717!

K

130 PALAEONTOLOGY, VOLUME 13

Gordon, m. 1957. Mississippian cephalopods of northern and eastern Alaska. Prof. Pap. U.S. geol.
Surv. 283, 1-61, 26 figs., pi. 1-6.

1964. Carboniferous cephalopods of Arkansas. Prof. Pap. U.S. geol. Surv. 460, 1-322, 96 figs.,

pi. 1-30.

gutschick:, r. c. and treckman, j. f. 1957. Lower Mississippian cephalopods from the Rockford i
limestone of northern Indiana. J. Paleont. 31, 1148-53, 3 figs., pi. 143, 144.
hind, w. 1910. On four new Carboniferous nautiloids and a goniatite new to Great Britain. Proc.
Yorks, geol. Soc. 17, 97-109, pi. 3-7.

holzapfel, e. 1889. Die Cephalopoden-fiihrenden Kalke des unteren Carbon von Erdbach-Breitscheid
bei Herborn. Palaont. Abh. (n.f. 1), 1, 1-74, pi. 1-8.
hyde, j. e. 1953. Mississippian formations of central and southern Ohio. Bull. Geol. Surv. Ohio, 51,
1-355, pi. 1-54.

klapper, g. 1966. Upper Devonian and Lower Mississippian conodont zones in Montana, Wyoming,
and South Dakota. Paleont. Contr. Univ. Kans. 3, 1-43, 2 figs., pi. 1-6.
koninck, l. G. de, 1 842-4. Description des animaux fossiles qui se trouvent dans le terrain carbonifere
de Belgique, iv+650 pp., atlas, 55 pi. Liege.

• 1880. Faune du calcaire carbonifere de la Belgique. II. Genres Gyroceras, Gomphoceras, Ortho-

ceras, Subclymenia et Goniatites. Annls. Mus. r. Hist. nat. Belg. (Ser. Pal.) 5, 2, 1-125, 28 figs., pi. [
32-50.

krebs, w. 1963. Oberdevonische Conodonten im Unterkarbon des rheinischen Schiefergebirges und des
Harzes. Z. dt. geol. Ges. 114, 57-84, 4 figs. pi. 9, 10.
kullmann, j. 1961. Die Goniatiten des Unterkarbons im Kantabrischen Gebirge (Nordspanien). I.
Stratigraphie. Palaontologie der U.O. Goniatitina Hyatt. N. Jb. Geol. Palaont. Abh. 113, 219-326,

12 figs., pi. 19-23.

legrand, r., mamet, b., and mortelmans, g. 1966. Sur la stratigraphie du Tournaisien de Tournai et
de Leuze. Problemes de l’etage Tournaisien dans sa localite-type. Bull. Soc. beige Geol. Paleont. !!
Hydrol. 74, 140-88, pi. 1.

librovitch, l. s. 1940. Carboniferous ammonoids of north Kazakhstan. Paleontologiya SSSR, Mos-
cow, 4 (9), 1-394, 78 figs., pi. 1-25 [in Russian, English summary].

Matthews, s. c. 1969a. A Lower Carboniferous conodont fauna from east Cornwall. Palaeontology,
12, 262-75, 1 fig., pi. 46-50.

1969 b. Two conodont faunas from the Lower Carboniferous of Chudleigh, south Devon. Ibid.

12, 276-80, pi. 51.

meischner, d. (in press). Conodont zonation of the German Carboniferous. Congres. Avanc. Etud.
Stratigr. carb. Sheffield 1967.

miller, a. k. and collinson, c. 1951. Lower Mississippian ammonoids of Missouri. J. Paleont. 25,
454-87, 14 figs., pi. 68-71.

and garner, h. f. 1955. Lower Mississippian cephalopods of Michigan. Part 3, Ammonoids and

Summary. Contr. Mus. Paleont. Univ. Mich. 12, 113-73, 16 figs., pi. 1-7.
nicolaus, h.-j. 1963. Zur Stratigraphie und Fauna der crenistria- Zone im Kulm des Rheinischen
Schiefergebirges. Beih. Geol. Jb. 53, 1-246, 32 figs., pi. 1-18.
paeckelmann, w. 1922. t)ber das Oberdevon und Unterkarbon des Sudfliigels der Herzkamper Mulde
auf Blatt Elberfeld. Jb. preuss. Landesanst. BergAkad. 42, 257-306, 2 figs., pi. 2.
paproth, e. 1964. Die Untergrenze des Karbons. Congres Avanc. Etud. Stratigr. carb., Paris, 1963, 2,
611-17, 3 figs.

teichmuller, r., and remy, w. 1960. Allemagne, Carbonifere. In pruvost, p. (ed.), Lexique |

Stratigraphique International, 5c (1), 3-307, Paris.

pareyn, c. 1961. Les massifs carboniferes du Sahara sud-Oranais, II. Paleontologie stratigraphique.

Pubis. Cent. Rech. Sahar. (ser. Geol.) 1, 15-244, 27 figs., pi. 1-28.
popov, a. v. 1965. New Visean ammonoids of the Tien-Shan. Paleont. Zh. Moscow 1965, 2, 35-49,
figs. 1-8, pi. 3, 4 [in Russian].

rexroad, c. b., and scott, a. j. 1964. Conodont zones in the Rockford Limestone and New Providence j
Shale (Mississippian) in Indiana. Bull. Indiana Dep. Conserv. Geol. Surv. 30, 1-54, 6 figs.
ruzhencev, v. e. 1962. Mollusca-Cephalopoda 1. In orlov, y. a. (ed.), Osnovy Palaeontologii 5,
437 pp., 187 figs., pi. 1-32. Moscow [in Russian].

MATTHEWS: A NEW CEPHALOPOD FAUNA FROM EAST CORNWALL 131

schindewolf, o. h. 1922. Uber eine Unterkarbonfauna aus Ostthiiringen. Senckenbergiana, 4, 8-20.

1926. Beitrage zur Kenntnis der Cephalopodenfauna des oberfrankisch-ostthuringischen Unter-

karbons. Ibid. 8, 63-96, 1 1 figs.

1927. Zur Kenntnis der Devon-Karbon-Grenze in Deutschland. Z. dt. geol. Ges. 78, 88-1 32, 5 figs.

1939. Bemerkungen zur Stratigraphie des oberfrankisch-ostthuringischen Unterkarbons. Jb.

preuss. geol. Landesanst. BergAkad. 59, 456-75, 8 figs., pi. 16, 17.

1951a. Uber ein neues Vorkommen unterkarbonischer Pericyclus-Schichtcn im Oberharz. N. Jb.

Geol. Palaont. Abh. 93, 23-116, 36 figs:, pi. 3-7.

19516. Zur Gliederung der Pericyclus-Gmppe (Cephal., Goniatit.). N. Jb. Geol. Palaont. Mh. 1951,

10, 305-10.

Schmidt, H. 1925. Die carbonischen Goniatiten Deutschlands. Jb. preuss. Geol. Landesanst. BergAkad.
45, 489-609, pi. 19-26.

1941. Eine neue Fauna mit Pericyclus von Riefensbeek im Harz. Jb. Reichstelle Bodenforsch. 60,

148-56, pi. 19-20.

voges, a. 1959. Conodonten aus dem Untercarbon I und II (Gattendorfia- und Pericyclus-Stufe) des
Sauerlandes. Palaont. Z. 33, 266-314, 5 figs., pi. 33-5.

— — 1960. Die Bedeutung der Conodonten fur die Stratigraphie des Unterkarbons I und II (Gatten-
dorfia- und Pericyclus-Stufe) im Sauerland. Fortschr. Geol. Rheinl. Westf. 3 (1), 197-228, 5 figs.

vohringer, e. 1960. Die Goniatiten der unterkarbonischen Gattendorfia-Stufe im Honnetal (Sauer-
land). Ibid. 3 (1), 107-96, 53 figs., pi. 1-7.

wagner-gentis, c. h. t. 1964. VI. Description of Goniatites. In higgins, a. c., wagner-gentis, c. h. t.,
and wagner, r. h. 1964. Basal Carboniferous strata in part of northern Leon, N.W. Spain: strati-
graphy, conodont and goniatite faunas. Bull. Soc. beige Geol. Pa/eont. Hydrol. 72, 228-48, pi. 1-4.

walliser, o. h. et al. 1958. Zum Oberdevon und Unterkarbon von Erdbach-Langenaubach (SW-Dill-
mulde, Rheinisches Schiefergebirge). Notizbl. hess. Landesamt. Bodenforsch. Wiesbaden, 87, 120-32.

weyer, d. 1965. Zur Ammonoiden-Fauna der Gattendorfia- Stufe von Dzikowiec (Ebersdorf) in Dolny
Slask (Niederschlesien), Polen. Ber. geol. Ges. D.D.R. 10, 443-64, 3 figs., pi. 6-8.

S. C. MATTHEWS

Geology Department
Queen’s Building
University Walk

Typescript received 2 June 1969 Bristol 8

NOTE ADDED IN PROOF

After this paper had gone to press the author became aware of Krebs’s (1968) valuable restudy of
the Erdbacherkalk. Krebs has been able to show that the Lower Carboniferous in the Langenaubach-
Breitscheid reef complex includes Erdbach limestone facies developments at three different levels in
the stratigraphy. His paper includes new identifications of the goniatites by Kullman and of the
trilobites by Hahn. Krebs’s information on the local stratigraphy of this important palaeontological
source is entirely welcome. It will be seen that the remarks made here on the Erdbacherkalk
(pp. 115-17) were written in ignorance of these most recent findings. It should be clear, however,
that the author’s comments on the scattered nature (geographic and stratigraphic) of the standard
goniatite occurrences remain valid.

REFERENCE

krebs, w. 1968. Die Lagerungsverhaltnisse des Erdbacher Kalkes (Unterkarbon II) bei Langenaubach-
Breitscheid (Rheinisches Schiefergebirge). Geotekt. Forsch. 28, 72-103, 4 text-figs.

TWO NEW DICYNODONTS FROM THE TRIASSIC
YERRAPALLI FORMATION OF CENTRAL INDIA

by TAPAN ROY CHOWDHURY

Abstract. Two new dicynodonts recently collected from the Triassic Yerrapalli formation of India are described.
The first, Rechnisaurus cristarhynchus, is a stahleckeriid and the first of its kind to be reported from Asia.
Rechnisaurus shows considerable similarities to Dinodontosaurus of the Middle Triassic of Brazil and Argentina.
The second dicynodont, Wadiasaurus indicus is the first kannemeyeriid to be described from India and its nearest
relative is thought to be Sangusaurus of the Middle Triassic of Zambia.

Until recently the only dicynodont reptile known from India was Lystrosaurus,
reported from the Panchet formation of the Damodar valley Gondwanas (Robinson
1958). This dicynodont is now known from a large number of skulls and associated
postcranial material and shows a close resemblance to the South African Lystrosaurus
(Tripathi and Satsangi 1963). The occurrence of a second dicynodont reptile from India
was noticed recently by Jain, Robinson, and Roy Chowdhury (1964) from the Gond-
wanas of the Par nhita- Godavari valley. This relatively large dicynodont was represented
by the anterior ends of the lower jaws, fragments of maxillae and of basicrania, and
several postcranial bones. Somewhat resembling Kannemeyeria, it was found in a red
clay horizon overlying the Permo-Triassic Kamthi formation and which was separated
from the overlying fossiliferous Upper Triassic Maleri formation by a sandstone horizon
devoid of any fossil remains. This large dicynodont was found associated with a large
thecodont reptile (a possible erythrosuchid), a moderately large theriodont reptile and
two labyrinthodont amphibians (one was possibly a capitosaur, the other perhaps a
brachyopid), thus revealing an altogether new fauna for this sub-continent. Prompted
by this discovery, Jain et al. (1964) suggested a new formation name, the Yerrapalli
formation, for the clay belt from which this new fauna was found, and tentatively sug-
gested that this is comparable in age to the Cynognathus zone of the South African
Karroo or possibly a little later. The barren sandstone belt immediately above the
Yerrapalli formation was named the Bhimaram (sometimes spelt Bheemaram) sand-
stone.

The Yerrapalli fauna was first noted from an isolated outcrop of Gondwana rocks
near Chinur, lying south of the main outcrop belt of Upper Gondwana formations
around Maleri and Achlapur and separated from the main outcrop by an oblique fault.
In 1964 when Dr. P. L. Robinson visited the main outcrop belt with Dr. E. H. Colbert
and the author, she picked up some dicynodont tusks and skull bones from a red clay
horizon lying south of Achlapur. Since dicynodonts are unknown in the overlying Upper
Triassic fauna of the Maleri formation, these fragments indicated the presence of a
distinct fauna. Chatterjee (1967) subsequently mapped the area around Achlapur and
proved beyond doubt that the same geological sequence occurs in the main outcrop area
as in the more southerly Chinur area. ‘Immediately above the Kamthi rocks a red clay
belt, with sandstones, contains representatives of the Yerrapalli fauna. Above this clay
belt lies a continuous band of sandstone equivalent to Bhimaram sandstone of the

[Palaeontology, Vol. 13, Part 1, 1970, pp. 132-44.]

CHOWDHURY : TWO NEW DICYNODONTS FROM CENTRAL INDIA 133

Chinur area. This sandstone band is succeeded by the true Maleri formation in which
excellent specimens of the Upper Triassic vertebrate fauna have been found’ (Chatterjee
1967, p. 40).

The dicynodonts described in this paper were collected from red clays of the Yerra-
palli formation by the field party of the Geological Studies Unit, Indian Statistical Insti-
tute, during field trips of 1964 and 1965. The material consists of two skulls and many
postcranial bones, but no skeleton, complete or partial, could be obtained. One skull
described here as a new genus and species, Rechnisaurus crist arhynchus, was found in
the northern area near Rechni village. The second skull, also belonging to a new genus
and species described here as Wadiasaurus indicus , was excavated from the red clays
of the southern area near Yerrapalli village. A large number of postcranial bones were
also found in the latter locality but not in actual association with the skull. As it appears
that two distinct genera of dicynodonts are present in the Yerrapalli formation, no
attempt has been made to relate the postcranial bones to either of these two genera at
present, and their description has been deferred until associated material is discovered.

SYSTEMATIC DESCRIPTIONS
Genus rechnisaurus gen. nov.

Derivation of name. The genus has been named after the village near which it was discovered.

Type species. Rechnisaurus cristarhynchus sp. nov.

Diagnosis. As for sole species at present.

Rechnisaurus cristarhynchus sp. nov.

Text-figs. 1-3

Derivation of name. This refers to the presence of a strong median ridge in the nasal region of the skull.

Material. The holotype skull only; specimen I.S.I.R.37 in the collection of the Geological Museum,
Indian Statistical Institute, Calcutta.

Type locality. One kilometre south of Rechni, Pranhita Godavari valley, Andhra Pradesh, India.
Horizon. Yerrapalli formation of the Gondwana Group, Triassic.

Diagnosis. Dicynodont of moderately large size. Skull about 38 cm. long. Large canine
teeth. Wide interorbital region. Blunt snout. Strong median ridge on anterior and dorsal
surfaces of premaxilla which continues on dorsal surface of nasal ; on either side of the
ridge lies a pair of deep depressions. Powerful antero-ventrally directed caniniform pro-
cess bearing rugose rounded flange on its postero-ventral edge. Short postorbital region.
Short and wide temporal opening. Fairly narrow intertemporal bar, dorsally concave
in cross section. No high parietal crest. Low boss immediately behind pineal foramen.
Parietal forms most of the intertemporal bar. Sharp transition between dorsal and
occipital surface.

The material and its preservation : The skull was found partly exposed in the red clays and was just
beginning to disintegrate on a ‘nala’ (gully) slope. Parts of the skull were actually found on the ‘nala’
bed, a little removed from their original place, but could be fitted on to the skull. Most of the occiput
and the zygomatic arches were probably washed away and could not be found. The preorbital half of

134

PALAEONTOLOGY, VOLUME 13

the skull is almost complete and only very slightly distorted. There is a break, however, along the suture
between the premaxilla and the nasal, and the antero-lateral part of the nasal, where it forms the
dorsal border of the nostril, is missing; the rest of the narial border is well preserved and the missing j
part could be restored quite easily. Similarly the anterior border of both the orbits is also broken and
parts of the prefrontals, lacrymals, jugals, and squamosals, forming these borders, are missing and [
have been restored in dotted outline in the illustrations. Behind the orbits, there is a transverse break
in front of the pineal foramen with some fitting surfaces to help restoration. Most of the superficial
part of the interparietal bone is missing but the rest of the intertemporal bar is well preserved. The
zygomatic arches are broken a little behind the maxillae, but the well-preserved post-orbital bar helps
in restoring the continuation of the suborbital bar up to the orbit and also indicates the position of the
more posterior extension of the zygomatic bar. The braincase and the central part of the palate are
more or less well-preserved. In the occiput, only the condyle, the foramen magnum and the median
part of the supra-occipital are preserved, with a minor break above the condyle. The squamosals are
missing save for an isolated piece near the dorsal part of the lateral wing of the right squamosal. The
quadrates and quadrat ojugals are not present. Only the symphysial part of the lower jaw was found.

Description of the skull

Dorsal view (text-fig. 1). The skull is massive and appears to have been quite broad
and triangular in outline. The top of the snout is wide and there is a strong median ridge
running from the tip of the snout, gradually widening and dying out behind the nasal-
frontal suture. On either side of the ridge lies a pair of deep depressions which become
wider posteriorly as the snout broadens ; these depressions terminate where the nasals
meet the frontals and prefrontals. The front of the snout is wide and blunt. The sides of
the snout fall sharply vertically, and thus the external nostrils do not appear in the
dorsal view of the skull. The nasals are fairly large bones with a long midline suture.
The premaxilla is rather short and wide with a strongly rugose surface. The orbits are
separated by the large frontals and are bordered dorsally by prefrontals, frontals, and
post-orbitals. The post-orbital bar has rather delicate proportions for such a massive
skull, and the post-orbital bone overlaps the parietal strongly by a process directed
posteriorly along the lateral edge of the intertemporal bar.

The preparietal bone is small, and only its anterior and posterior parts are preserved,
for in this region the specimen has a break in the skull roof which obscures the contact
between the frontal and the parietal, lateral to the preparietal. The pineal foramen is
rather small, 12 mm. long and 8 mm. wide and is quite deep. There is certainly an abrupt
elevation of the level of the skull roof just behind the pineal foramen. The pineal foramen
is bordered anteriorly by the preparietal and otherwise by the parietals.

The temporal opening must have been quite short as is evident by the short inter-
temporal bar, almost exclusively formed by the parietals. The intertemporal bar is
narrow; the paired parietals meet at a long midline suture behind the pineal foramen and
each has a raised lateral edge, thus making the dorsal face of the bar concave in section.
There is a low but prominent median boss immediately behind the pineal foramen.
At the posterior end of the parietal, on its lateral surface, the squamosal is preserved
only as a broken patch of bone forming a sutural contact. Another dissociated frag-
ment of the lateral wing of the squamosal is also present, but does not give any useful
information except to locate the postero-lateral border of the temporal opening.

Ventral view (text-fig. 2). The secondary palate, formed almost entirely by the pre-
maxilla, is rather short and its plane is set at an angle to rest of the palate, giving an
arched shape for the ventral surface of the skull.

CHOWDHURY: TWO NEW DICYNODONTS FROM CENTRAL INDIA

135

A pair of palatal ridges runs back from the tip of the premaxilla to converge into a
median ridge about halfway along the secondary palate. The vomer is not preserved, but
presumably continued the median ridge posteriorly on to the palate. Laterally the pre-
maxilla is strongly overlapped by the maxilla ; the latter bone is drawn out laterally into

text-fig. 1 . Rechnisaurus cristarhynchus, holotype. Dorsal view of skull, x J (for
abbreviations, see pp. 143-4).

a very strong caniniform process, as already mentioned. The powerful tusks have their
roots quite posteriorly placed in the maxillae, and are curved slightly inwards. Posteriorly
the maxilla is bounded laterally by the jugal and medially by the pterygoid ; there is a
large lateral fenestra in between these three bones. On the left side of the specimen, at the
root of the caniniform process, the maxilla shows on its lateral wall a sutural facet which
continues on to the lateral surface of the jugal. This facet must have received the anterior
extension of the squamosal overlapping the former two bones laterally. The posterior
part of the sub-orbital bar is missing.

The anterior rami of the pterygoids leave the maxillae, run posteriorly and meet along
a midline suture behind a short interpterygoid vacuity. The vomers are not preserved
but the palatines He on the inner sides of the anterior rami of the pterygoids and termi-
nate anteriorly against the maxillae. The ectopterygoid is missing, but there is a distinct
depressed sutural facet on the lateral side of the pterygoid which is probably for the
ectopterygoid. If the above observation is correct, the ectopterygoid must have been
a thin sheet of bone as observed in Dinodontosaurus { Cox, 1968). Behind the palate, the

136

PALAEONTOLOGY, VOLUME 13

parasphenoid and the basisphenoid-basioccipital complex show the normal dicynodont
condition. The quadrate ramus of the pterygoid, the epipterygoid and the stapes are,
however, missing.

text-fig. 2. Rechnisaurus cristarhynchus, holotype. Ventral view of skull, X \ (for
abbreviations, see pp. 143-4).

Side view (text-fig. 3). The massive caniniform process of the maxilla covers most of
the large tusk and only the anterior part of the tusk is visible in side view. The face is
steep and high; its appearance is further accentuated by the presence of a high median
dorsal ridge. The external nostrils are quite large and there is no trace of any septo-
maxilla on the narial floor, the latter being formed by the maxilla. The pre-orbital region
is quite long compared to the post-orbital region. Although only the postero-dorsal
quarter of the orbital margin is preserved, it seems likely that the orbit was subcircular
in outline. In front of the post-orbital bar, at the postero-dorsal corner of the orbit, there
is a distinct bay present, formed by a notch in the frontal bone bordering the orbit.

Discussion. Cox (1965) has divided most of the Triassic dicynodonts into two families,
the Kannemeyeriidae and the Stahleckeriidae. This classification is based on shape of
the snout, presence or absence of a parietal crest, nature of the temporal openings, and
proportion of the occiput. In Rechnisaurus, though the occiput is not known completely,
the snout is wide and blunt, a parietal crest is absent from the short inter-temporal bar

CHOWDHURY : TWO NEW DICYNODONTS FROM CENTRAL INDIA

137

and the temporal openings appear to be short and broad. All these features clearly
indicate that this new form belongs to the Family Stahleckeriidae. On the other hand the
presence of a high median ridge in the nasal region, and a prominent boss on the inter-
temporal bar immediately behind the pineal foramen, makes Rechnisaurus quite distinct
from the four other Stahleckeriid genera known. Three of these genera are known from

text-fig. 3. Rechnisaurus cristarhynchus, holotype. Lateral view of skull, X \ (for
abbreviations, see pp. 143-4).

the Middle Triassic of South America: Stahleckeria from the Santa Maria formation
of Brazil (von Huene 1935-42); Chanaria from the Chanares formation of Argentina
(Cox 1968); and Dinodontosaurus common to both these formations (Cox 1965, 1968).
The only African genus, Zambiasaurus, is known from the Middle Triassic Ntawere
formation of Zambia (Cox 1969). Rechnisaurus is the first Stahleckeriid to be reported
from Asia.

In Stahleckeria the snout is extremely blunt, consequently the nasals are very wide
bones with a very short midline suture, the preparietal bone is absent and there is no
tusk. In all these respects Zambiasaurus , according to Cox (1969) is quite closely related
to Stahleckeria and may actually be ancestral to the latter. On the other hand Dinodonto-
saurus and Chanaria are quite distinct from the above two genera. Prominent tusks are
present in the maxillae, the preparietal bone has been retained and the nasals meet
along a long suture. Rechnisaurus appears to be closer to Dinodontosaurus in all those
respects but differs in having a high median nasal ridge and a boss behind the pineal
foramen. Chanaria, though showing some similarity to these two genera, has certain
peculiarities such as a very smooth skull without any boss or regosities and a frontal
bone with a rectangular projection into the nasal.

138

PALAEONTOLOGY, VOLUME 13

Genus wadiasaurus gen. nov.

Derivation of name. In recognition of the encouragement given for the past decade by Professor D. N.
Wadia, F.R.S., F.N.I., National Professor, to the Research programme of the Geological Studies Unit,
Indian Statistical Institute.

Type species. Wadiasaurus indicus sp. nov.

Diagnosis. As for sole species at present.

Wadiasaurus indicus sp. nov.

Text-figs. 4—7

Material. Holotype skull; specimen I.S.I.R.38 in the collection at the Geological Museum, Indian
Statistical Institute, Calcutta.

Referred specimens. One isolated maxilla, I.S.I.R.39, in the same collection and two isolated quadrate
bones, I.S.I.R.40 and I.S.I.R.41.

Type locality. About 2 km. east-south-east of Yerrapalli, Pranhita-Godavari valley, Andhra Pradesh,
India.

Horizon. Yerrapalli formation of the Gondwana Group, Triassic.

Diagnosis. Skull of moderately large size. Upper tusks weakly developed or absent.
Skull triangular in outline, widest across occiput ; gradually tapers anteriorly into a blunt
snout. Maxillary flange weak, laterally compressed and projecting ventrally. Nasal ridge
short, low and narrow. Inter-orbital region moderately wide. Inter-temporal bar narrow
anteriorly but widens posteriorly up to the occipital margin. Parietal crest high. Temporal
opening long and narrow. Zygomatic arches thin and almost parallel. Occiput faces
sharply downward and backward. Lateral margins of occiput rise sharply and are sub-
parallel. Palatal surface of premaxilla bears pair of anterior ridges. Interpterygoid
vacuity wide.

The material and its preservation. The skull described here comes from the same stretch of red clays
which yielded the dicynodont bones mentioned by Jain et al. (1964). It is of a moderately large size,
40 cm. long and 32 cm. wide across the squamosals. Although nearly complete, the skull has suffered
some amount of distortion after burial and has been damaged by exposure prior to its discovery.
The maxillary flanges are compressed inward, the right flange is more compressed than the left. The
snout is bent slightly downward causing some displacement of the premaxilla and thus obscuring the
exact suture between the premaxilla and the nasals. The central part of the skull roof has been squashed,
damaging the frontals and other circumorbital bones. The pineal foramen is damaged and it is not
possible to be sure whether the preparietal is present or not. The posterior half of the right side of the
parietal crest has been displaced ventro-laterally causing some displacement of the bones bordering
the temporal opening. The post-orbital bar is fortunately very little distorted, but the posterior exten-
sion of the post-orbital bones behind the orbits has had to be restored. The palate is the least distorted
part and the displacement of the right sub-orbital bar can be corrected to give the lateral border of the
skull. The left side of the palate, however, is damaged. The right side of the occipital plate is very little
distorted though the left side is pushed inward and somewhat damaged. The quadrates and part of
the quadrato jugals have been restored from an isolated segment found near the skull which has also
been given the same specimen number in the field.

Description of the skull.

Dorsal view (text-fig. 4). The skull is triangular in outline with a somewhat narrow
snout ending rather bluntly. The maxillary flanges project sharply downward and are

CHOWDHURY : TWO NEW DICYNODONTS FROM CENTRAL INDIA

139

text-figs. 4-6. Wadiasaurus indicus, holotype. 4. Dorsal view of skull, x 5. Occipital view of skull, x £. 6. Ventral view of skull,

x £ (for abbreviations, see pp. 143-4).

140

PALAEONTOLOGY, VOLUME 13

hardly visible in dorsal view. Behind the premaxilla, the skull broadens slowly up to the
orbits, then the zygomatic arches run almost parallel, to be terminated at the level of
the occiput by the laterally expanded squamosals which form the lateral margins of
the rear of the skull.

There is a low but distinct median ridge on the premaxilla. The ridge has a groove in
the middle which widens posteriorly. The inter-orbital region is not very broad, about
28% of the skull length. The orbits look mainly outward and slightly forward. The post-
orbital bar lies halfway along the skull. The temporal openings are rather long, widest
in the middle behind the pineal region, where the parietal crest is low and probably
narrow, but the openings become slightly narrower posteriorly as the parietal crest
widens progressively.

It is very difficult to distinguish sutures on the skull roof due to the extremely damaged
nature of the bones and due to the presence of many erratic cracks. Many of these cracks
seem to follow sutures but it is almost impossible to be sure. However, the suture between
the post-orbital and the sub-orbital bar and zygomatic arch is clear.

Occipital view (text-fig. 5). The occiput is quite deep. Its dorsal half is inclined to the
skull roof at an acute angle, while its ventral half becomes almost vertical; there is a
transitional zone in between. This shape seems to be natural though it is possibly a little
exaggerated by distortion. The posterior ends of the lateral wings of the squamosals
bend inward in the dorsal half of the occiput so that the occiput as a whole has the form
of a concave plate which faces postero-ventrally. The lateral margins of the occiput rise
quite steeply and are sub-parallel, slightly diverging dorsally. As a result the occiput
is wider dorsally than it is across the quadrates.

The occipital condyle is semicircular in outline and is weakly tripartite with an excava-
tion on the upper surface and a clear notochordal pit. The foramen magnum is tri-
angular in outline.

It is not possible to follow the sutures, hence the extent of the individual bones is
difficult to delimit. However, the paroccipital process of the opisthotic projects laterally
downwards below the level of the basiphenoid tubera. In the dorsal part of its distal
end it is drawn into a posteriorly directed tympanic process.

Ventral view (text-fig. 6). The palatal face of the maxilla is marked by three anterior
palatal grooves separated by two ridges. The groove in the middle is deeper but pos-
teriorly is cut short by the convergence of the pair of ridges which meet to form a single
ridge separating the continuation of the lateral grooves. The caniniform processes of the
maxillae rise from the floor of the secondary palate and appear to be directed slightly
outward.

There is no sign of the presence of a tusk in the maxilla in the holotype skull. However,
an isolated maxilla, identical with the maxilla of the type skull except that it is somewhat
smaller, has a tusk which is quite slender and rather weakly developed. Returning to the
type skull, the inner margin of the caniniform process has two distinct faces : the anterior
face looks medially whereas the posterior face is directed postero-medially. The former
meets the premaxilla on the secondary palate and the latter meets the pterygoid-palatine
process medially and the jugal process laterally.

Behind the premaxilla, the vomer and much of the palatine are highly crushed and
the passage for the internal nostrils is completely obliterated beyond any possibility
of restoration or description. The right anterior ramus of the pterygoid is much less

CHOWDHURY : TWO NEW DICYNODONTS FROM CENTRAL INDIA 141

distorted and the suture between the pterygoid and the maxilla is quite clear. The labial
fenestra is present in its usual position. Behind their contact with the maxillae, the
pterygoids arch outward and finally make a long midline sutural contact. There is a
raised prominence here, perhaps indicating the presence of a boss, as found in Ischigua-
lastia (Cox 1965). Postero-laterally, the pterygoid extends behind the midline suture as

text-fig. 7. Wadiasaurus indicus, holotype. Lateral view of skull, X J (for
abbreviations, see pp. 143-4).

the slender quadrate ramus terminating in front of the paroccipital process near the
quadrate recess. Behind the pterygoids along the midline, there is a pair of carotid
foramina posterior to the transverse parasphenoid-pterygoid suture. The tubera are set
a little apart and their anterior faces are formed by the parasphenoid. The occiput is
broadly exposed in the ventral view of the skull.

Side view (text-fig. 7). The anterior part of the parietal crest and the area around the
pineal foramen have been restored, and the tilt of the parietal crest due to crushing has
been corrected. The facial part of the skull is moderately long and rather low in contrast
to the relatively high posterior half of the skull.

The orbits must have been oval, about 7 cm. along the antero-posterior axis, and look
outward but slightly forward. The nostrils are large, rounded, and placed anteriorly just
behind the tip of the snout. The premaxilla is beak-like and its anterior end rises sharply
on the skull roof. Posteriorly it forms the front margin of the nostril, and meets the
maxilla ventrally and the nasal postero-dorsally near the middle of the nostril. The pos-
terior margin of the nostril is bordered by maxilla below and by nasal above and the
suture between these two bones runs horizontally. When followed posteriorly this suture
meets the anterior tip of the lachrymal half way between the nostril and the orbit.

On the narial floor, there is a patch of broken bits of bone resting on maxilla. These
bits may be the remains of the septomaxilla but it is impossible to be sure of this.
Therefore, these fragments have not been included in the figure. The lachrymal is a narrow
triangular bone lying in front of the orbit. It separates the nasal and the prefrontal from
the maxilla and extends to form the antero-ventral border of the orbit.

The jugal forms most of the ventral border of the orbit. Its limits at both ends are far
from clear. An extensive overlap of the jugal by a thin anterior extension of the

142 PALAEONTOLOGY, VOLUME 13

squamosal is strongly suggested. The squamosal jugal bar is thin, compressed dorso-
ventrally, and runs straight behind the orbit at a low angle, slightly rising upwards to
the posterior end of the skull.

Discussion. There can be no doubt that in Wadiasaurus, the skull has a high parietal crest,
the occiput is deep and wide, the snout is narrow with a blunt end and the temporal
opening is long and narrow. These characters clearly indicate that this new form belongs
to the family Kannemeyeriidae as defined by Cox (1965). Wadiasaurus is still very
incompletely known, hence any comparison with other kannemeyeriid genera can only
be very general and largely tentative.

Among the genera belonging to the family Kannemeyeriidae, Sinokannemeyeria and
Parakannemeyeria, both known from the Lower Triassic Er-ma-ying formation of
Shansi, China (Sun 1963), have extremely long pre-orbital regions, 46-50% of the total
skull length, which makes them very distinct. The pre-orbital length of Wadiasaurus is
more normal for the family — about 35% of the total skull length. The most widely
distributed genus is Kannemeyeria. It is known from the lower Triassic Cynognathus
zone of South Africa (Pearson 1924, Broom 1937), the Middle Triassic Manda beds of
East Africa (Cruickshank 1965), and also from the lower Middle Triassic Puesto Viejo
formation of Mendoza, Argentina (Bonaparte 1966). Kannemeyeria is characterized by
a very narrow intertemporal bar drawn into a sharp steeply rising median crest, a
situation not found in any other kannemeyeriid genera including Wadiasaurus. The
Upper Triassic form Placerias, known from the Chinle formation of North America, is
rather a specialized end-form with the outwardly projected caniniform processes of the
maxilla drawn into a facial horn (Camp and Welles 1957, Cox 1965). A tusk is either
weakly developed or absent in Placerias but the intertemporal bar is wide and devoid
of a crest. Due to these specializations, Placerias also is quite distinct from Wadiasaurus.

The two remaining kannemeyeriid genera, Ischigualastia, from the Middle or Upper
Triassic Ischigualasto formation of Argentina (Cox, 1965), and Sangusaurus, from the
Middle Triassic Ntawere formation of Zambia (Cox, 1969) are however, tuskless.
Ischigualastia differs from Wadiasaurus in having a pointed snout, a more anteriorly
directed caniniform process and zygomatic arches which are markedly bowed outward.
Sangusaurus, known only from its premaxilla, maxilla, and the intertemporal bar, shows
some similarity with those parts of Wadiasaurus. The premaxilla, though generally
similar in the two genera, has a pointed anterior end in the former but ends bluntly in
the latter. The caniniform process of the maxilla is quite similar in the two forms but its
orientation in Sangusaurus is not exactly known. Although the relationship between the
interparietal and parietal and the exact position of the pineal foramen is not known in
Wadiasaurus, there is some resemblance between the intertemporal bars in those two
genera. In both, the inter-temporal bar widens posteriorly and their dorsal borders are
concave in section. There is an abrupt change between the dorsal and occipital faces of
the intertemporal bar in Sangusaurus, which is also, most probably, true for this region
of Wadiasaurus.

Another kannemeyeriid genus, Barysoma, from the Middle Triassic Santa Maria
formation of Brazil, is known very incompletely from a partial occiput and some post-
cranial remains. According to Cox (1969, p. 296), Barysoma ‘appears to be closely related
to Ischigualastia ’, but any comparison of Barysoma with Wadiasaurus is not possible
at this stage.

CHOWDHUR Y: TWO NEW DICYNODONTS FROM CENTRAL INDIA 143

Acknowledgements. Dr. P. L. Robinson, University College, London, took a keen interest throughout
the work and the paper was completed during my stay in London on an N.E.R.C. grant, given for the
project ‘Mesozoic vertebrates and continental sediments in Britain and India’, of which the paper forms
a part. I wish to thank sincerely Dr. C. B. Cox, King’s College, London, for much help and useful
criticism. I am also thankful to all my colleagues in the Geological Studies Unit for much help at
various stages. Mr. D. Roy and Mr. A. Lee helped in completing the illustrations. Finally my thanks
are due to Mr. and Mrs. N. V. Raja Reddy for hospitality in the field.

bonaparte, j. f. 1966. Una nueva ‘fauna’ Triasica de Argentina (Therapsida: Cynodontia Dicyno-
dontia); consideraciones filogeneticas y paleobiogeograficas. Ameghiniana, Buenos Aires, 4, 243-
96, figs. 1-29, pi. 1-2.

broom, r. 1937. A further contribution to our knowledge of the fossil reptiles of the Karroo. Proc.
zool. Soc. Lond. (B) 1937, 299-318, figs. 1-16.

camp, c. l. and welles, s. p. 1956. Triassic dicynodont reptiles. Part I. The North American genus
Placerias. Mem. Univ. Calif. 13, 255-304, figs. 1-41, pi. 30-3.
chatterjee, s. 1967. New discoveries contributing to the stratigraphy of the continental Triassic sedi-
ments of the Pranhita-Godavari Valley. Bull. geol. Soc. India, 4 (2), 37-41, fig. 1.
cox, c.b. 1965. New Triassic dicynodonts from South America, their origins and relationships. Phil.
Trans. R. Soc. London, 248 (B), 457-516, figs. 1-30.

1968. The Chanares (Argentina) Triassic reptile fauna. IV. The dicynodont fauna. Breviora,

Cambridge, Mass., 205, 1-27, figs. 1-12.

1969. Two new dicynodonts from the Triassic Ntawere formation, Zambia. Bull. Br. Mus. nat.

Hist. (Geol.). 17 (6), 255-94, figs. 1-23.

cruickshank, a. r. i. 1965. On a specimen of the anomodont reptile Kannemeyeria latifrons (Broom)
from the Manda Formation of Tanganyika, Tanzania. Proc. Linn. Soc. Lond. 176, 149-57, figs. 1-5.
huene, f. von. 1935-42. Die fossilen Reptilien des Siidamerikanischen Gondwanalandes an der Zeiten-
wende. 332 pp., figs. 1-66, pi. 1-38, Tubingen.

jain, s. l., robinson, p. l., and roy chowdhury, t. 1964. A new vertebrate fauna from the Triassic of
Deccan-India. Q. Jl geol. Soc. Lond. 120, 115-24, figs. 1-3. t
pearson, H. s. 1924. The skull of the dicynodont reptile Kannemeyeria. Proc. zool. Soc. Lond. 1924,
793-826, figs. 1-18.

robinson, p. l. 1958. Some new vertebrate fossils from the Panchet series of West Bengal. Nature,
Lond. 182, 1722-3.

sun, a. l. 1963. The Chinese kannemeyerids. Palaeont. sinica (n.s.) (C), 17, 73-109, figs. 1-51.
tripathi, c. and satsangi, p. p. 1963. Lystrosaurus fauna from the Panchet Series of the Ranigang
Coalfields. Palaeont. indica (n.s.) 37, 1-53, pi. 1-13.

REFERENCES

List of abbreviations used in the figures

BO basi-occipital

car. for. carotid foramen
ECT? ectopterygoid?
EO exoccipital

F frontal

IP interparietal

J jugal

L lachrymal

lab. fen. labial fenestra
MX maxilla

N nasal

P parietal

p. t. fen. post-temporal fenestra

PAL palatine

pin. f. pineal foramen

PMX premaxilla

PO post-orbital

PP preparietal

PRF prefrontal

PRO prootic

PSP parasphenoid-basisphenoid complex

PT pterygoid

Q quadrate

q. r. pt. quadrate ramus of the pterygoid

144

PALAEONTOLOGY, VOLUME 13

QJ

quadratojugal

tymp. tympanic process.

SO

supra-occipital

proc.

SQ

squamosal

TAPAN ROY CHOWDHURY

Geological Studies Unit
Indian Statistical Institute
Calcutta

Typescript received 10 May 1969

/

EPIDERMAL STUDIES IN THE INTERPRETATION
OF LEPIDODENDRON SPECIES

by B. A. THOMAS

Abstract. Thirteen species of Lepidodendron are described including two new species L. arberi and L. barnsley-
ense. Details of the epidermis are given and its use in species distinction and classification is considered. Cuticle
information about secondary growth is also discussed.

Lepidodendron is an arborescent lycopod stem genus characterized by the persistent
basal parts of leaves (leaf cushions) from which the apical parts have often been shed.
The compression species, like those of most other fossil lycopod genera, have been
described and classified on external gross morphology. Text-fig. 1 illustrates the cushion
features most useful in classification. However, the actual naming of a specimen,
especially a badly preserved one, is still sometimes difficult because many species appear
similar in one or more details. The lycopod cuticle has been largely ignored as a possible
descriptive character even though epidermal characters have been shown to be of great
importance in other plant groups. The value of the lycopod cuticle has already been dis-
cussed (Thomas 1966) but detailed descriptions of Lepidodendron cuticles are given here
showing how a study of them can assist in the definition and distinction of species.

Whenever possible the type specimen was examined together with several other
specimens to detect any variation within the species. However, specimens from which
cuticle could be prepared were often difficult to find. Some type specimens and many
others are preserved as impressions and some of those which are compressions have
finely cracked carbon which does not yield cuticle. Examination of the cushion surface
is sometimes useful when the cuticle cannot be prepared as the epidermal cells and
stomata are often visible.

Cuticle was prepared by macerating portions of the carbonized compression in
Schulze solution followed by clearing in dilute ammonia solution. The cuticles were
mounted unstained in glycerine jelly and examined by normal transmitted light supple-
mented in a few instances by phase contrast illumination. The cuticle preparations have
been deposited with their respective specimens.

The specimens were borrowed from or deposited in: the British Museum of Natural
History, London (BMNH); the Kidston collection of the Geological Survey and
Museum, London (K); the general collection of the Geological Survey and Museum,
London (GSM); the Geological Survey, Leeds (GSL); the Geological Survey, Edin-
burgh (GSE); the Sedgwick Museum, Cambridge (SM); the Warwickshire County
Museum, Warwick (WM); the Leicester City Museum (LM); the Royal Scottish
Museum, Edinburgh (RSM), and the Czechoslovakian National Museum, Prague
(CNM).

Acknowledgements. I would like to thank Professor T. M. Harris, F.R.S. for his help and guidance
throughout much of this study; the directors and staff of the museums for allowing me to borrow and
[Palaeontology, Vol. 13, Part 1, 1970, pp. 145-73, pis. 29-34.]

C 7173 L

146

PALAEONTOLOGY, VOLUME 13

make preparations from specimens in their collections; the National Coal Board and Open Cast Execu-
tive for permitting my access to their workings ; the site officials who helped me to collect specimens ;
the Coal Board Scientific Staff for help in certain correlation problems; the University of Reading
Research Board from whom I was in receipt of a research studentship, and the University of
Newcastle upon Tyne and the Royal Society of London for travel grants. The work was completed
during the tenure of the Lord Adams Research Lellowship at the University of Newcastle upon Tyne.

text-fig. 1 . Drawings of diagrammatic leaf cushions to illustrate their main features, a, Leaf cushions
continuous with other cushions above and below but separated from those on either side by wrinkled
areas of bark, b, Closely packed leaf cushions not continuous with other cushions above and below,
cs — cushion striations; gs — inter cushion striations; ip — infrafoliar parichnos; k' — cushion keel
above the leaf scar; k" — cushion keel below the leaf scar; k'" — cushion keel broken by transverse
notches; 1 — ligule pit aperture; 11 — lateral line running from leaf scar to cushion edge; p — foliar
parichnos ; s — leaf scar ; v — vascular print.

SYSTEMATIC DESCRIPTIONS
Lepidodendron aculeatum Sternberg
Plate 29; Plate 30, figs. 1,5; Plate 31, figs. 1-3; text-figs. 2, 3

1820 Lepidodendron obovatum Sternberg, pp. 20, 23, pi. 6, fig. 1 ; pi. 8, figs. 1a, a, b.

1820 Lepidodendron aculeatum Sternberg, pp. 20, 23, pi. 6, fig. 2; pi. 8, figs. 1b, a, b.

1820 Lepidodendron crenatum Sternberg, pp. 20, 23, pi. 8, fig. 2b.

1821 Lepidodendron aculeatum Sternberg, pi. 14, figs. 1-4.

1838 Sagenaria aculeata Presl in Sternberg, p. 177, pi. 68, fig. 3.

1838 Sagenaria rugosa Presl in Sternberg, p. 177, pi. 68, fig. 4.

1838 Sagenaria caudata Presl in Sternberg, p. 178, pi. 68, fig. 7.

1877 Lepidodendron aculeatum Sternberg; Fairchild pars, p. 77, pi. 5, figs. 1-4; pi. 6, figs. 1-5;
pi. 7, figs. 1-4; pi. 8, figs. 1, 2.

1886 Lepidodendron aculeatum Sternberg; Zeiller, p. 435, pi. 65, figs. 1-7.

EXPLANATION OF PLATE 29

Lepidodendron aculeatum Sternberg. Fig. 1, CNM CGH 365; Type specimen of Sternberg 1820, pi. 6,
fig. 2. Fig. 2, CNM CGH 658 (= Lepidodendron obovatum Sternberg 1820, pi. 6, fig. 1). Fig. 3,
CNM CGH 805 (= Sagenaria rugosum Presl in Sternberg 1838, pi. 68, fig. 4). Fig. 4, CNM CGH
792 (= Sagenaria caudata Presl in Sternberg 1838, pi. 68, fig. 7).

All at xl.

Palaeontology, Vol. 13

PLATE 29

THOMAS, Lepidodendron

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES 147

1899 Lepidodendron aculeatum Sternberg; Potonie, p. 220, text-fig. 211.

1904 Lepidodendron aculeatum Sternberg; Zalessky, p. 81, pi. 1, figs. 1-6; pi. 2, fig. 2.

1947 Lepidodendron aculeatum Sternberg; N6mejc pars, p. 49.

1959 Lepidodendron aculeatum Sternberg; Remy, p. 98, text-figs. 76, a, b.

1964 Lepidodendron aculeatum Sternberg; Crookall, p. 233, pi. 60, fig. 6; text-fig. 11a.

Material. Type specimen CNM CGH 365 from the Upper Carboniferous of Radnice, Bohemia;
CNM CGH 658 (L. obovatum Sternberg 1820, pi. 6, fig. 2.) from Radnice; CNM CGH 660 {L. cre-
natum Sternberg 1820, pi. 8, fig. 2b) from Radnice; CNM CGH 792 ( Sagenaria caudata Presl in Stern-
berg 1838, pi. 68, fig. 4) from the Upper Carboniferous, Waldenburg, Silesia; CNM 23072 from the
Mydlak horizon of Kladno; WM G. 541, from the Westphalian coal measures of Tamworth, Stafford-
shire; BMNH 1049, from the coal measures of Waldenburg, Silesia; BMNH 46685, from the West-
phalian coal measures of Ebbw Vale, Monmouthshire; BMNH 41308, from the Mushett Blackband
Ironstone, No. 6 pit, Monkland, near Airdrie, Scotland; Westphalian B.

All the specimens possess the same general cushion characters. The cushions have
inflexed, pointed upper and lower angles and rounded lateral angles. The leaf scars are
diamond-shaped, about as long as broad, and are situated about one-third the distance
down the leaf cushions. There are three foliar prints, though sometimes only one can
be seen, and two infrafoliar parichnos. The ligule pit aperture is adjacent to the upper
angle of the leaf scar and not a short distance above as it is often figured. There are
prominent keels above and below the scar and lateral lines curve from the lateral angles
of the leaf scars to the edges of the leaf cushion. The keels are normally smooth and
continuous above the leaf scar but are divided by notches below the scar. The leaf
cushion surface is smooth. BMNH 1049 and BMNH 41308 have very plain infrafoliar
parichnos but although repeated attempts have been made to prepare cuticle from them
none was obtained and I am convinced there never was any. Most specimens of this
species show the leaf cushions close together but some, e.g. BMNH 1049, have them
separated by wrinkled areas of bark. These wrinkled areas have been thought to be of
diagnostic value, for example Lesquereux (1879/80) used their presence as the main
character for his Lepidodendron modulatum. It is now commonly accepted that they are
the result of lateral expansion of the bark produced during the secondary growth of the
stem (for further discussion see Eggert 1961 and Chaloner 1967). The wrinkles have been
described as fissures or cracks in the bark by Fairchild (1877). However as cuticle was
prepared from the whole area in BMNH 1049 it is more likely that they were formed by
a secondary production of epidermis interspersed between the original epidermis of the
furrow. This formation of extra epidermis seems to have been accompanied by a stretch-
ing out and shallowing of the intercushion groove. Preparation of cuticle from the inter-
cushion areas of BMNH 1049 shows that the furrows possess roughly isodiametric
epidermal cells and stomata while the interconnected ridges have epidermal cells elon-
gate across the ridges and no stomata. The cuticle without stomata probably represents
I the secondary produced epidermal areas especially as those specimens with close
cushions have stomata within their intercushion grooves.

CNM 23072 has many isolated leaf cushions with leaves still attached. The leaves are
lat least 11 cm. long but all are incomplete and only the slightest narrowing can be seen.
Even though the leaves are attached three foliar prints are visible showing that their
jpresence is not necessarily indicative of prior leaf fall. A central median vein can be
clearly seen on all leaves and on a few an additional line is present on either side of the
jmedian, which probably represents a stomatal groove. Not all the leaves show stomatal

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PALAEONTOLOGY, VOLUME 13

text-fig. 2. Lepidodendron aculeatum Sternberg, a, CNM CGH 365; Type specimen of Sternberg
1820, pi. 6, fig. 2. B, CNM CGH 658 (= L. obovatum Sternberg 1820, pi. 6, fig. 1). c, CNM CGH
660) (= Lepidodendron crenatum Sternberg 1820, pi. 8, fig. 2b). d, CNM CGH 792 (= Sagenaria
caudata Presl in Sternberg 1838, pi. 68, fig. 7). E, CNM CGH 805 (= Sagenaria rugosa Presl in
Sternberg 1838, pi. 68, fig. 4). f, CNM 23072; showing leaves still attached to the leaf cushions. All

illustrations at x 2.

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES 149

grooves as their visibility is of course dependent on the orientation of the leaves. Such
long leaves with stomatal grooves, if found detached, would undoubtedly be determined
as Cyperites bicarinatus Lindley and Hutton, confirming the reports of the possession
of such leaves by Lepidodendron aculeatum given by Crookall ( 1966, p. 535) and Chaloner
(1967, p. 673). Unfortunately no cuticle could be prepared from these attached leaves
and no epidermal detail could be discerned by direct observation.

Cuticle description. The epidermal cells from all over the cushion surface are roughly
isodiametric and 15-20 /x across, except near the cushion edges where they are mostly
30 /x x 15 yu. and elongated towards the cushion centre. However, in BMNH 46685, where
the keel is more prominent and divided by many transverse notches, the epidermal cells
near the keel are elongated towards the keel and are typically 30 18 ju, in size. The

anticlinal walls are straight, smooth and about 2 /x thick. The perclinal walls are flat
and smooth. The stomata are about 200-250 per mm.2, randomly distributed and orien-
tated, but in BMNH 46685 they are absent on the keel lumps and very sparse in the keel
notches. Stomatal average size is about 40/lxX 18 /x and the guard cells are sunken in
pits 12-15 /x deep. There are about nine subsidiary cells to each stoma, unmodified
except for sometimes being slightly elongated away from the stomata. In the wrinkled
intercushion areas there are interconnecting strands of dark cuticle separating patches
of lighter brown cuticle. The dark cuticle has epidermal cells 30 /x x 1 5 /x elongated at right
angles to the strands, but the lighter cuticle has isodiametric cells about 20-30 ^ broad.
Stomata are about 340 per mm.2 in the lighter cuticle but are very few and restricted to
the edges of the dark cuticle. The stomata are 25-30 /xx 10 ^ in size and the guard cells
are sunken in pits 10—15 /tx deep. The ligule pit cuticle is about 0-45 mm. broad and at
least 2 mm. long. The lining cells are rectangular, 45 /x x 1 5 /x, and elongated along the pit.

Comparison. Specimens similar to Sternberg’s figures of L. obovatum and L. aculeatum
have been commonly found and described. However, the two species have not always
been interpreted in the same way and indeed many authors have changed their views
from one paper to another. Some authors have accepted only part of Sternberg’s
descriptions and figures, others have placed some of his other species in synonymy with
these two species, while a few have united the two. These varying opinions seem to have
arisen as a result of differing ideas about the value of Sternberg’s figures and the emphasis
put on different cushion characters.

A study of Sternberg’s specimens has shown that his interpretation needs to be modi-
fied. I agree basically with Nemejc (1947) in his reinterpretation but differ slightly in
the synonymy lists quoted. The illustration of the type specimen of L. obovatum (Stern-
berg 1820, pi. 6, fig. 1) fails to show accurately the upper angle of the cushions and the
keel ornamentations. The upper angle is pointed as is the lower angle and not rounded
as the illustration suggests and the keel below the leaf scar is divided by transverse
notches. When L. obovatum is interpreted in this manner, there is no difference between
it and the subsequently described L. aculeatum. Specimens of this form have been, and
indeed still are, commonly named L. aculeatum. Fischer (1904) united the two species
under L. obovatum but included in his synonymy other forms which are quite different,
e.g. the L. obovatum of Presl. This broad interpretation of L. obovatum is quite un-
acceptable and I believe the best solution is to regard L. obovatum as a confused name

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PALAEONTOLOGY, VOLUME 13

text-fig. 3. Lepidodendron aculeatum Sternberg, a, b, Leaf cushions before and after secondary ex-
pansion of the stem, x 1. c, Leaf scar with ligule pit (1) and infrafoliar parichnos (p). d. Leaf cushion
cuticle, x 400. e, Cuticle from expanded bark between the leaf cushions showing dark cuticle with
none or very few stomata and light-coloured cuticle with many stomata, x 20. a, c, e, from WM G541 ;

B, D, from BMNH 1049.

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES

151

reduced to a synonym of the more commonly used L. aculeatum. Presl, in Sternberg
(1838), described a specimen (pi. 68, fig. 6) as L. obovatum. However this is not L. obo-
vatum Sternberg, i.e. L. aculeatum Sternberg. The cushions are broader and have no
drawn out inflexed upper and lower angles. The leaf scars are broader than long while
in L. aculeatum they are about as long as broad. The cushion surface above the leaf scar
is finely striated while in L. aculeatum it is smooth. Finally the infrafoliar parichnos are
not so well defined as in L. aculeatum. Nevertheless, many workers have described
specimens as L. obovatum because they resembled Presl’s specimen named as L. obo-
vatum. Now in an attempt to discover the name that should be applied to Presl’s
specimen, I found that L. mannabachense Presl in Sternberg (1838, pi. 68, fig. 2) is
identical to the now commonly accepted form of L. obovatum. A description of this
species is given later.

Sagenaria caudata Presl, S. rugosa Presl, and Lepidodendron crenatum Sternberg
should all be referred to L. aculeatum Sternberg. The type specimen of S. caudata is an
almost flat compression and, although the original illustration is not very informative,
clearly shows the typical features of L. aculeatum. S. rugosa is best regarded as L.
aculeatum although several authors have included it in L. obovatum sensu Presl. The
type specimen differs from L. aculeatum only in having leaf scars which are slightly
broader than long; this alone seems insufficient for species distinction. In contrast,
Presl’s (1838, pi. 68, fig. 5) specimen of S. crenatum, CNM CGH 322, has leaf scars
quite unlike those of L. aculeatum and is not this species. The leaf scars are as broad as
the cushions and are situated just above their centres.

Lepidodendron serpentigerum Koenig
Plate 31, fig. 4; Plate 34, fig. 6; text-fig. 4

1825 Lepidodendron serpentigerum Koenig, pi. 16, fig. 195.

1902 Lepidodendron serpentigerum Koenig; Kidston, pp. 345, 371, pi. 51, fig. 2.

1906 Lepidodendron serpentigerum Koenig; Fischer pars, No. 75, figs. 1, 2.

1927 Lepidodendron serpentigerum Koenig; Hirmer, pp. 200, 204, text-fig. 237.

1964 Lepidodendron serpentigerum Koenig; Crookall, p. 260, pi. 61, fig. 5, text-fig. 83.

Material. Neotype, BMNH 39020 from the Westphalian Coal Measures, Newcastle upon Tyne (Crook-
all 1964, text-fig. 83); K 2498 from above the Stranger Coal, Granger Colliery, Kilmarnock, Ayrshire
(Kidston 1902, pi. 51, fig. 2; Crookall 1964, pi. 61, fig. 5), Westphalian B ; SM 3148 from the Transition
Coal Measures of the Bishopsbourne Boring, Barham Down, 4 miles south-east of Canterbury, Kent.

The three specimens are very similar in having their leaf cushions connected above
and below by inflexed cushion extensions and separated on either side by wrinkled areas
of bark. The leaf scars are two-thirds the distance up the cushions and possess three
conspicuous foliar prints. The ligule pit aperture is adjacent to the upper angle of the
leaf scar and there are two plainly visible infra-foliar parichnos. The keels are more
prominent below the leaf scars and are divided by many transverse grooves. No cuticle
could be prepared from the neotype and only small fragments from the other two.
K 2498 gave good cuticle from the wrinkled intercushion areas but poor cuticle from the
leaf cushions and SM 3148 gave reasonable cuticle from the leaf cushions but none from
the wrinkled areas.

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PALAEONTOLOGY, VOLUME 13

Cuticle description. The cuticle is similar over the whole leaf cushion surface. The
epidermal cells are about 35 p across, roughly isodiametric or slightly elongated. The
anticlinal walls are straight, smooth and about 2 p thick. The periclinal walls are flat
and granular. The stomata are about 50 p x 30 p in size and the guard cells are sunken

text-fig. 4. Lepidodendron serpentigerum Koenig. A, Leaf cushions from K2498, X 1 ; Ligule pit (1).
b. Cushion cuticle from SM 3148, x 400. c. Cuticle from intercushion areas of K2498, slide PF 3144.
The granular surface of the cuticle seen under phase contrast is represented in only a few cells of b and c.

in pits 4 p deep. The cuticle from the inter-cushion areas is thicker than that from the
cushion surface and has roughly rectangular cells, 60 p x 20 p, elongated parallel to
the intercushion striations. The anticlinal walls are straight, smooth, and 3 p thick and
the periclinal walls are flat and granular. There are no stomata in the intercushion areas.

Comparison. Lepidodendron zeilleri Zalessky (1904, p. 91, pi. 4; fig. 1, 1 a) is almost
certainly a synonym of L. serpentigerum. The only difference between the two type
specimen figures is that L. zerilleri has more rounded upper angles to the leaf scars which
is not a distinctive enough character for species separation.

Nemejc (1947, p. 62) believed that L. serpentigerum was similar to L. obovatum Presl,
non Sternberg (= L. mannabachense Presl) and L. aculeatum Sternberg and that it was
probably only a growth form of the latter. However the cushions of L. serpentigerum
are more S-shaped than both these species and possess different cushion and epidermal

EXPLANATION OF PLATE 30

Fig. 1, Lepidodendron aculeatum Sternberg, CNM CGH 660 (= Lepidodendron crenatum Sternberg
1820, pi. 8, fig. 2b).

Fig. 2, Lepidodendron veltheimii Sternberg, CNM CGH 330; figured by Presl in Sternberg 1838, pi. 68,
fig. 14.

Fig. 3, Lepidodendron mannabachense Presl, CNM CGH 355 (= Sagenaria obovatum Presl in Stern-
berg 1838, pi. 68, fig. 2).

Fig. 4, Lepidodendron mannabachense Presl (type specimen), CNM CGH 329; figured by Presl in
Sternberg 1838, pi. 68, fig. 2.

Fig. 5, Lepidodendron aculeatum Sternberg, with leaves attached to leaf cushions, CNM 23072.

All at xl.

Palaeontology, Vol. 13

PLATE 30

THOMAS, Lepidodendron

THOMAS: EPIDERMAL STUDIES OF LEPIDODEN DRON SPECIES 153

details. L. mannabachense, unlike L. serpentigerum, has striations on its leaf cushions
and has dissimilar epidermal arrangements above and below the leaf scars. L. aculeatum
Sternberg has broader leaf scars, more prominent keels, smaller epidermal cells, and
deeper stomatal pits than L. serpentigerum. The form of L. aculeatum with separated
leaf cushions also differs in the cuticle details obtained from the intercushion areas.
In L. aculeatum there are strips of epidermis with stomata alternating with strips with
no stomata whereas in L. serpentigerum the epidermis is all similar and possesses no
stomata.

Lepidodendron veltheimii Sternberg
Plate 30, fig. 2; Plate 33, figs. 4-6; text-fig. 5

1825 Lepidodendron Veltheimii Sternberg, p. 43, pi. 52, fig. 3.

1838 Lepidodendron Veltheimianum Presl in Sternberg, p. 180, pi. 68, fig. 14.

1899 Lepidodendron Veltheimianum Sternberg; Hoffman and Ryba, p. 78, pi. 15, figs. 7, 8.

1926 Lepidodendron Veltheimianum Sternberg; Kidston, p. 147, pi. 13, fig. 2.

1964 Lepidodendron veltheimi Sternberg; Crookall, p. 298, pi. 64, figs. 3-5; pi. 70, fig. 8;
pi. 71, figs. 1, 2; text-figs. 11c, 96.

Material. CNM CGH 330 from the Lower Carboniferous of Magdeburg (probably the specimen
figured by Presl 1838, although it also bears a label referring it to Sternberg 1825); K 2411 from
immediately beneath the Orchard Limestone, New Brawden Quarry, Giffnock, Renfrewshire, Upper
Limestone Group of the Carboniferous Limestone Series, Lower Namurian.

CNM CGH 330 is an impression with no carbon remaining and no visible epidermal
details, so all the information about the epidermis was obtained from K 2411. This is a
fairly thick compression on a slab of black shale. The leaf cushions are in low-angle
spirals of about 25° to the horizontal and are continuous with the cushions above and
below by inflexed apical and basal angles. The leaf scar is prominent but only one foliar
print can be seen and no infrafoliar parichnos are visible. The ligule pit aperture is
adjacent to the upper angle of the leaf scar. The keel is prominent, but interrupted in
the upper part below the leaf scar. The carbon of the compression is not cracked as in
most specimens and large pieces of well-preserved cuticle could be prepared from it.

Cuticle description. The cuticle from the grooves between the cushions is about 3-4 p
thick. The epidermal cells are isodiametric, 20 p across, or elongated up to 40 p. The
anticlinal walls are straight, smooth, and 2-3 p thick. The periclinal walls are flat and
smooth. No stomata were visible in the grooves but some are present near the edges
of the cushion. The leaf cushion cuticle is 2 p thick. The epidermal cells are isodiametric,
15-20 p, or elongated up to 40 p. The long axes of the cells tend to form curves running
from the cushion edge towards the keel and then parallel to it. The cells do not form
well-developed rows, but sometimes are in small groups appearing to have been formed
by the transverse division of one cell. The anticlinal walls are straight, smooth, and
2-4 p thick. The periclinal walls are flat and smooth. Stomata are about 60 per mm2,
on the cushion below the leaf scar but slightly less above it. They are randomly distributed
over most of the cushion, but are arranged concentrically around the lumps which make
up the keel just below the leaf scar. The guard cells are sunken in overhanging, thick-
walled stomatal pits, 15 p deep. The stomatal apertures are usually oval, but occasionally
rounded, and of average size 60 p x 40 p. The subsidiary cells are usually 8-12 in number

text-fig. 5. Lepidodendron veltheimii Sternberg. K2411. a. Leaf cushions, X 3. The lines on the
cushion indicate the direction and area covered by surface striations, but they do not represent in-
dividual striations. b, c, d. Areas of cushion surface showing direction of striations and distribution of
stomata, x 20. Slide nos. : b — PF 2699 ; c. d — PF 2700. e. Cuticle from groove between cushions,
arrows directed parallel to the groove, slide PF 2701, x 200. f, Cuticle from edge of cushion, arrow
directed away from groove, slide PF 2698, x 200. g. Cuticle from cushion surface, slide PF 2700,
x 200. h, Stoma x 500. i. Reconstructed median transverse section of a stoma, x 500. All lettering
gives the location of other figures.

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES 155

and unmodified in size and orientation but sometimes are radially elongated from the
stomatal aperture.

Comparison. Lacey (1962) has described a species of Lepidodendron from the Lower
Carboniferous of North Wales as being nearest to L. veltheimii. His plate 16, fig. 16
shows the leaf cushions to be roughly 20 X 7 mm. with very little detail except a slight
inflection of the upper and lower angles. The cuticle from the groove between the
cushions has epidermal cells 100 p X 30 p possessing thick (5-6 p) anticlinal walls. These
cells are larger and have thicker walls than those from the larger cushions of K 241 1
so it is doubtful that the two specimens belong to the same species.

Lepidodendron feistmanteli Zalessky
Plate 33, fig. 3 ; Plate 34, fig. 5 ; text-fig. 6

1875 Lepidodendron dichotomum Sternberg; Feistmantel, p. 188, pi. 32, figs. 2, 4.

1904 Lepidodendron Feistmanteli Zalessky, p. 93, pi. 4, figs. 6, 10.

1913 Lepidodendron Jaraczewski Zeiller; Bureau, p. 113, pi. 40, figs. 1, la.

1944 Lepidodendron Jaraczewski Zeiller; Bell, p. 89, pi. 51, figs. 1, 2.

Material. GSM 77179, 77180 (part and counterpart); K 3255, 4874-6, 4946, 4993 from above the
Fenton coal, Wooley and Dodworth collieries, near Barnsley, Yorkshire — communis zone, West-
phalian A; K 3605 from the Bradford coal group, Bradford colliery, Lancashire — phillipsii zone,
Westphalian C.

The largest piece of bark (GSM 77179) is 1 1 cm. broad and 33 cm. long and like all
the other specimens shows no variation in cushion size or details. The leaf cushions are
rhomboidal, strongly raised, and not continuous with the cushions above and below.
The leaf scars are in the centre of the leaf cushions and raised above the general cushion
area. The leaf scars have edges which slightly overlap the cushion and produce unequal
partition of the compression when the rock is split. The carbonized compression of the
scar is usually left in the counterpart producing what looks like a small unmarked scar
on the elevated cushions of the other part of the specimen (text-fig. 6a). No vascular
prints nor ligule pit apertures are visible on such specimens but they can be clearly seen
if the compression is removed from the sunken impressions of the counterpart. The
cushion surfaces are smooth but have very prominent keels above and below the leaf
scars and also possess strong keel-like ridges running from the edges of the leaf scars to
the edges of the cushions. No external parichnos are present.

Cuticle description. The epidermal cells on the leaf cushion surfaces are isodiametric and
1 5-20 p across, but the cells on the cushion edges are slightly elongated towards the
cushion centre. The anticlinal walls are straight, smooth, and 1-2 p thick. The periclinal
walls are flat and smooth. The stomata are 300-350 per mm.2 and are about 45-50 p long
and 1 5-20 p broad. The guard cells are sunken in pits, 3-6 p deep with very little or
no overhang of the pit aperture. The ligule pit cuticles are about 0-8 mm. long with
rectangular cells, 1 5-20 p long and 1 5 p broad, in longitudinal files.

Comparison. Fischer (1904) included L. feistmanteli in L. dichotomum Sternberg and
Hirmer (1927) believed them to be related. They are, however, clearly distinct in both
cushion and cuticle details. The leaf scars of L. dichotomum are not elevated and are
relatively further up the leaf cushion. The epidermis of L. feistmanteli is roughly the

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PALAEONTOLOGY, VOLUME 13

same over the whole cushion but in L. dichotomum it is different above and below the
leaf scar. The epidermal cells and stomata are also larger in L. feistmanteli.

text-fig. 6. Lepidodendron feistmanteli Zalessky. GSM 77179. A, Leaf cushions, x2. b, Reconstruc-
tion showing elevated leaf scar overlapping part of the leaf cushion, x 10. c. Reconstructed section
through part and counterpart of a leaf cushion compression to show the raised leaf scar and the un-
equal splitting of the carbon. Coarse shading represents the rock matrix and the fine shading the
carbonized compression, d, Leaf cushion cuticle, x400; stomata — s; slide PF 2870. e. Recon-
structed median transverse section through a stoma, x 400.

Bureau (1913) and Bell (1944) described what appear to be specimens of L. feist-
manteli as L. jaraczewski Zeiller, However L. jaraczewski has relatively longer cushions
and the leaf scars are not so raised, have no overlap over the cushion surface, and are

EXPLANATION OF PLATE 31

Figs. 1-3. Lepidodendron aculeatum Sternberg; illustrating variation in cushion ornamentation and the
separation of cushions by lateral stem expansion; x 1. 1, WM, G 541 from Tamworth, Stafford-
shire. 2, BMNH 46685, from Ebbw Vale, Monmouthshire. 3, BMNH 1049, from Waldenburg,
Silesia.

Fig. 4. Lepidodendron serpentigerum Koenig. GSM 2498 from above the Stranger Coal, Grange
Colliery, Kilmarnock, Ayrshire; x2.

Fig. 5. Lepidodendron barnsleyense sp. nov. Holotype, K 4131, from above the Barnsley Bed, Monk-
ton Main Colliery, Yorkshire; x2.

Figs. 6, 7. Lepidodendron dichotomum Sternberg. Unlocalized specimen in the Huddersfield Museum;
x 2. 6, Portion of compressed bark. 7, Impressions of cushions in the shale.

Palaeontology , Vol. 13

PLATE 31

THOMAS, Lepidodendron

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES 157

situated further up the leaf cushions. L. jaraczewski also has less prominent keels and
lateral lines running from leaf scar to cushion edge. These lateral lines are also not as
straight as in L. feistmanteli but curve downwards to meet the cushion edge below the
central broadest part of the leaf cushion.

Lepidodendron mannabachense Presl
Plate 30, figs. 3, 4; Plate 32; Plate 34, figs. 1, 2, 7, 8; text-figs. 7, 8

1838 Lepidodendron mannabachense Presl in Sternberg, p. 177, pi. 68, fig. 2.

1838 Sagenaria obovatum Presl in Sternberg, p. 178, pi. 68, fig. 6.

1886 Lepidodendron obovatum Sternberg; Zeiller, p. 442, pi. 66, figs. 1-8.

1904 Lepidodendron obovatum Sternberg; Renier, pi. 1, figs, a, b.

1947 Lepidodendron obovatum Sternberg; Nemejc (in part), p. 51.

1959 Lepidodendron obovatum Sternberg; Remy, p. 100, fig. 77.

1964 Lepidodendron obovatum Sternberg; Crookall, p. 239, pi. 60, figs. 3, 4; text-fig. 116.

1966 Lepidodendron obovatum Sternberg; Thomas, fig. 3.

Material. Type specimen, CNM CGH 329, from the Upper Carboniferous of Mannabach, Thtiringen ;
CNM CGH 335 (5. obovatum Presl in Sternberg 1838, pi. 68, fig. 6) from the Upper Carboniferous of
Chomle; K 3365, from the Westphalian of Trawden Forest, near Colne, Lancashire; K 2469, Low
main coal, Cramlington, Northumberland — Westphalian B; K 2473, Stanley Main coal, Thome’s
colliery, Wakefield, Yorkshire — Westphalian B; K 2474, Low Moor, near Bradford, Yorkshire —
Westphalian A; SM M378, from the coal measures of Wakefield, Yorkshire; SM M1476, Queen’s
seam, Broomhill colliery, near Amble, Northumberland — Westphalian B ; LM 265, 1958/1, Adam Head
No. 1 pit, Desford colliery, Leicestershire, probably Westphalian A.

Both the specimens described by Presl are preserved as impressions with no com-
pression remaining. Similar cuticles were, however, prepared from the other seven
specimens. The cushion outlines are distinct but in some specimens their upper angles
overlap the lower parts of the cushions above which is probably a compression feature
produced during fossilization. The leaf scars are within the upper halves of the leaf
cushion and have three foliar prints in their lower halves. The ligule pit apertures are
adjacent to the upper angles of the leaf scars where they can be easily overlooked if
cuticle preparations are not made. Traces of infrafoliar parichnos can be seen on some
cushions of every specimen. The keels, which are always present, are smooth above the
leaf scar but sometimes notched below it. The cushion surface below the leaf scar is
smooth but above it there are many fine striations running from the scar to the
cushion edge.

The range of leaf cushion size is a result of the different positions of the cushions on
the parent plant, as the larger shoots always bore the larger cushions. The differences
in cushion shape are small and can be regarded as variation within the species.

Cuticle description. The epidermal cells above and below the leaf scars are different. The
cells above the scars are about 20-40 p long and 10-15 p broad and elongated from the
scar to the cushion edge, while the cells from below the scars are isodiametric and
15-20 p broad or sometimes elongated towards the scar and about 30-35 px 15 p in size.
Cells from the intercushion grooves are isodiametric and 1 5 p broad, or elongated across
the groove and about 15 px 10 p. The anticlinal walls are straight, smooth and 1-2 p
thick. The periclinal walls are flat and faintly granular and occasionally have striations,
less than 1 p thick, across the cells. The stomata are about 200 per mm.2 and randomly

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PALAEONTOLOGY, VOLUME 13

text-fig. 7. Lepidodendron mannabachense Presl. A, Type specimen, CNM CGH 329. b, CNM CGH
335. c, K2469. d, SM M1476. e, K 2473. F, LM 256, 1958/1. o, SM, M378. h,K3365. i,K2474.
All at x2. j. Leaf scar with ligule pit (1), x4. The shading lines indicate the areas covered by
surface striations and their direction. They do not represent individual striations.

THOMAS: EPIDERMAL STUDIES OF LEP1DODENDRON SPECIES

159

distributed on the cushion surface, but are absent in the intercushion grooves. Stomatal
average size is about 25-30 /x x 1 2 p. and the guard cells are sunken in pits about 6 p
deep. The subsidiary cells are unmodified and about eight per stoma. The ligule pit has
rectangular cells 30 /xX 10 /x along most of its length, but roughly square cells, 10 /x
across, near its base.

text-fig. 8. Cushion cuticle of Lepidodendron mannabachense Presl. A, Leaf cushion
cuticle from above the leaf scar, from K 3365, slide PF 2815. b, ligule pit cuticle, from
K 2469, slide PF 2810. Both at x400.

Comparison. The distinction of L. mannabachense has already been dealt with above in
the discussion of L. aculeatum. Cuticle study also supports the distinction of the two
species as L. mannabachense , unlike L. aculeatum , has striations on the leaf cushions
above the scars and a corresponding difference in epidermal structure above and below
the scars.

1820 Lepidodendron dichotomum Sternberg, pars, pi. 1, 2.

1838 Lepidodendron dichotomum Presl in Sternberg, p. 214, pi. 68, fig. 2; pi. A, fig. 16.

1838 Lepidodendron Sternbergii Brongniart, p. xiv, pi. 16, figs. 2, 3.

1875 Lepidodendron dichotomum Sternberg; Feistmantel, p. 188, pi. 32, figs. 1,3.

1934 Lepidodendron dichotomum Sternberg; Nemejc, p. 1, pi. 1, figs. 2, 3; pi. 2, fig. 1.

1959 Lepidodendron dichotomum Sternberg; Remy, p. 100, text-fig. 78, a, b.

1964 Lepidodendron dichotomum Sternberg; Crookall, pars, p. 236.

Material. Type specimen, CMH CGH 315, from the Upper Carboniferous of Svinna; K. 4876, from
above the Parkgate coal, Dodworth, near Barnsley — Westphalian A; an unlocalized specimen in the
Huddersfield Museum.

Lepidodendron dichotomum Sternberg

Plate 31, figs. 6, 7; text-fig. 9

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PALAEONTOLOGY, VOLUME 13

The specimens show shoots covered with diamond-shaped leaf cushions 2-5 mm.
high and broad with angled corners. Some variation is shown in K 4876, where some
cushions are slightly different being 2 mm. long and broad but with rounded lateral
angles. Also certain shoots show different-shaped cushions in different parts; for
example one has cushions 4 mm. long and 2 mm. broad in one part while elsewhere
they are 2 mm. long and broad. The leaf scars are situated near the apices of the
cushions and are roughly diamond-shaped and one and a half times as broad as high.
Three foliar prints and two infrafoliar parichnos are present, though they are often
indistinct. The ligule pit aperture is adjacent to the upper angle of the leaf scar. A very
slightly raised keel can be seen, though it is usually more definite above than below the
leaf scar. The cushion surface above the leaf scar shows many fine striations running
from the leaf scar to the cushion edge, but the surface below the scar is smooth.

Cuticle description. The epidermal arrangement is different above and below the leaf
scars. The cells above the scars are normally about 20-30 p long and 15 p broad and
elongated from the scar to the cushion edge, although occasionally they are roughly
isodiametric. These cells are often in short longitudinal rows running from the scar
to the cushion edge. The cells below the leaf scars are normally roughly isodiametric
and 10-15 ^ broad but are sometimes slightly elongated towards the leaf scars. The
intercushion grooves have isodiametric cells 15 p across and cells 15 pX 10 p elongated
across the groove. Anticlinal walls are straight, smooth, and 2 p thick except above the
leaf scar where they are often 4 p thick. The periclinal walls are flat and faintly granular.
Stomata are very frequent below the leaf scar, 450 per mm.2, where they are randomly
distributed and orientated. However, they are normally absent above the leaf scar except
occasionally in the lower angles at the sides of the scar. Very few stomata are present in
the intercushion grooves. Stomatal average size is about 40 pX20 p and the guard cells
are sunken in pits about 6 p deep. The subsidiary cells are unmodified and are about ten
per stoma. The ligule pit is about 0-6 mm. long and 0T3 mm. broad. The cells are mostly
rectangular, 30 p x 10 p, and elongated along the pit, but are roughly square near its
base.

Comparison. Much has been written about this species. Brongniart (1828a) followed by
Presl in Sternberg (1838) restricted L. dichotomum to plates 1 and 2 of Sternberg’s (1820)
original description, excluding his plate 3. The species in this restricted sense has been
widely recorded, although Jongmans (1929) and Crookall (1964) believed many of the
specimens to be misinterpreted. Other authors have interpreted L. dichotomum in differ-
ent ways including other combinations of specimens as synonyms, but as Nemejc (1947)
has given a useful summary no further review will be included here. However, some
authors, including Nemejc (1946 and 1947) and Chaloner (1967), have included L.
dichotomum as a synonym of L. obovatum(= L. mannabachense ) believing them to be the
small and large shoots of one species. Although the smallest cushions included here as

EXPLANATION OF PLATE 32

Figs. 1-7. Lepidodendron mannabachense Presl, illustrating variation in cushion shape and size.
All at X 2. 1, SM M1476. 2, LM 256, 1958/1. 3, K 3365. 4, K 2473. 5, K 2469. 6, K 2474.
7, K 378.

The localities are given on p. 157.

Palaeontology, Vol. 13

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THOMAS, Lepidodendron

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES

161

L. mannabachense are very similar to those of L. dichotomum, I favour, at least for the
present, their continued separation. The leaf cushions of L. dichotomum, as interpreted
here, are more diamond-shaped than those of L. mannabachense and the leaf scars are

text-fig. 9. Lepidodendron dichotomum Sternberg, a, Unnumbered specimen in the Huddersfield
Museum, b, Leaf cushion cuticle from below leaf scar, c. Leaf cushion cuticle from above leaf scar.
d. Cuticle from intercushion groove; arrows are parallel to groove. Magnifications: leaf cushions

x2; cuticles x400

situated relatively higher on the cushions. The epidermal cells are larger in L. manna-
bachense, but more important is the difference in stomatal frequency between the two.
In L. dichotomum stomata are almost completely absent above the leaf scar but are
450 per mm.2 below the scar, in contrast to L. mannabachense where they are roughly
200 per mm.2 over the whole cushion surface.

All the typical shoots of L. dichotomum, as described here, are narrow. However, it is
reasonable to assume that the larger shoots of the species bore larger leaf cushions since
leaf cushion and shoot sizes are generally supposed to be interrelated (Eggert 1961).
Therefore, if L. mannabachense is not the larger form of L. dichotomum we should look

C 7173

M

162

PALAEONTOLOGY, VOLUME 13

elsewhere for such shoots. Nemejc (1934) described some specimens as L. dichotomum
which have both larger leaf cushions and broader shoots than those described here.
The leaf scars are diamond-shaped and are situated centrally on the cushions and not
near their apices as in the more typical specimens described above. No cuticles could be
prepared from Nemejc’s specimens and the rough surface of the compression prevented
direct observation of individual epidermal cells. Striations were, however, visible above
the leaf scar suggesting that the cells in this area were elongated while those below the
scar were isodiametric, but this alone is not sufficiently characteristic for species distinc-
tion as several species are known to have such epidermal arrangements. These specimens
cannot therefore be regarded as being definitely conspecific with L. dichotomum,
although such a relationship is not impossible on the available epidermal evidence.
Further work is clearly needed before the larger shoots of L. dichotomum are known with
certainty.

Lepidodendron subdichotomum Sterzel pars

Text-fig. 10, e-h

1855 Sagenaria dichotoma Sternberg; Geinitz pars, p. 34, pi. 3, figs. 2-5, 9.

1901 Lepidodendron subdichotomum Sterzel pars, p. 106.

1903 Lepidodendron dichotomum Zeiller ( ?Sternberg) ; Arber, pp. 20, 32, pi. 1, figs. 1, 2.

1904 Lepidodendron dichotomum Sternberg; Zalessky pars, pp. 9, 83, pi. 3, figs. 5, 10, 10a, 11.

1914 Lepidodendron dichotomum Sternberg; Arber, pp. 402, 445, pi. 29, fig. 36.

1922 Lepidodendron loricatum Arber pars, p. 201, pi. 13, figs. 27-32.

1925 Lepidodendron loricatum Arber; Crookall, p. 170.

1929 Lepidodendron loricatum Arber; Crookall, p. 25, pi. 3, fig. h; pi. 20, fig. h.

1929 Lepidodendron loricatum Arber; Jongmans, p. 208.

1929 Lepidodendron subdichotomum Sterzel; Jongmans, p. 313.

1947 Lepidodendron subdichotomum Sterzel; Nemejc pars, p. 57, pi. 1, fig. 7.

1964 Lepidodendron loricatum Arber pars; Crookall pars, p. 243, pi. 64, fig. 9; text-fig. 79.

Material. Syntype of L. loricatum, SM 2506, from the Sulphur Coals, Transition Coal Measures,
Bayton Colliery, Wyre Forest, Worcestershire, Westphalian C; K. 6340, No. 3 Llantwit Seam, Cross
Inn, Llantrisant, Glamorgan, Westphalian C.

The leaf cushions are close together but not continuous with those above and below.
The leaf scars are about two-thirds the distance up the leaf cushions and are often
arranged obliquely on the cushions. There is no keel above the leaf scar, only a faint keel
below the scar and no lateral lines running from the scars to the cushion edges. Three
foliar prints can be indistinctly seen about one-third the distance up the scars but there
are now visible infrafoliar parichnos. The ligule pit apertures are adjacent to the upper

EXPLANATION OF PLATE 33

Fig. 1. Lepidodendron peachii Kidston. K 2466, from the Lower Main Seam, Newsham, Newcastle upon
Tyne, x2.

Fig. 2. Lepidodendron arberi sp. nov. Holotype, K 2488, from the Lower Main Coal, Cramlington,
Northumberland, x2.

Fig. 3. Lepidodendron feistmanteli Zalessky. GSM 77179, from the Fenton Coal, Wooley, Yorkshire,

x2.

Figs. 4-6. Lepidodendron veltheimii Sternberg. K 2411, from immediately beneath the Orchard Lime-
stone, New Brawden Quarry, Giffnock, Renfrewshire. 4, Leaf cushions, x2. 5 and 6, Leaf
cushion cuticle, slide PF 2700 ; 5, Epidermal cells and stomata on and near the keel below the leaf
scar, x 25 ; 6, Obliquely compressed stomata showing pit cuticles but no guard cells, x 400.

Palaeontology, Vol. 13

PLATE 33

THOMAS, Lepidodendron

THOMAS: EPIDERMAL STUDIES OF LEPIDO DENDRON SPECIES 163

angles of the leaf scars. The leaf cushion surfaces are smooth above and below the leaf
scars.

Cuticle description. The epidermal arrangements are roughly the same above and below
the leaf scars. The epidermal cells from the central area of the cushions are isodiametric
and about 1 5-20 p across. The cells from the edges of the cushions are elongated towards
the leaf scars and are about 30 plong and 10 abroad. The anticlinal walls are straight,
smooth and about 1 p thick. The periclinal walls are flat and smooth. The stomata are
about 200 per mm.2 and of average size 38 px26 p, with superficial guard cells. The
ligule pits have rectangular cells, in longitudinal rows, which are 40pX\0p in size
along most of the pit except near the base where they are roughly 10 p square.
Comparison. Sterzel instituted L. subdichotomum for some specimens from Sachsen
which had been previously identified by Geinitz (1855) as Sagenaria dichotoma Stern-
berg (pi. 3, figs. 1-12) and Sagenaria rimosa Sternberg (pi. 3, figs. 13-15). Arber (1922)
also included the S. dichotoma of Geinitz as a synonym of his Lepidodendron loricatum
making no reference to Sterzel, although if both authors were correct in their determina-
tions, his species was merely a later synonym for L. subdichotomum. The major problem,
as usual, is deciding how much variation occurs within the species and what specimens
are conspecific. Sterzel had not included in synonymy all the figures of S. dichotoma and
S. rimosa given by Geinitz, while Arber suggested that possibly only two figures of
S. dichotoma of Geinitz were the same species as his L. loricatum. Crookall included only
a part of the S. dichotoma of Geinitz (pi. 3, figs. 2-5, 9) and only the plate 13, figs. 27-32
of Arber in his synonymy for L. loricatum, but like Arber made no reference to Sterzel.
Such an acceptance of partial conspecificity of Geinitz’s and Arber’s specimens seems
the best solution, but Sterzel’swork should not be excluded as it has priority even though
it is accepted in a reduced form. L. subdichotomum is therefore the correct name for
specimens of this form.

Those figures quoted for L. loricatum by Crookall are given in synonymy here but
three of his additional specimens are excluded. His plate 61, fig. 1 is probably L. manna-
bachense as the specimen has faint striations on the cushion surfaces above the leaf
scars ; plate 64, fig. 6 is described here as Lepidodendron barnsleyense sp. nov. ; and plate
64, figs. 7, 8 has relatively highly placed leaf scars and infrafoliar parichnos making it
unacceptable as L. loricatum, though I do not suggest another name. Three of Arber’s
specimens are also excluded from the present synonymy. Two (pi. 13, figs. 33-5) are
described here as L. arberi sp. nov. and one (pi. 13, figs. 36, 37) looks more like L.fusi-
formis Corda.

Crookall (1964, p. 242) believed that most of the specimens identified by Kidston as
L. obovatum (= L. mannabachense ) were really L. loricatum (= L. subdichotomum ) and
that the latter species was the more common in Great Britain. The confusion of these
two species by Crookall, as illustrated above by his plate 61, fig. 1, probably accounts for
this view which appears incorrect when they are interpreted with the extra evidence
afforded by epidermal studies.

Lepidodendron arberi sp. nov.

Plate 33, fig. 2; text-fig. 10, a-d

1922 Lepidodendron loricatum Arber pars, p. 201, pi. 13, figs. 33-5.

1964 Lepidodendron sp. Crookall, p. 303, pi. 72, fig. 5.

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PALAEONTOLOGY, VOLUME 13

text-fig. 10. Lepidodendron arberi sp. nov. (a-d). and Lepidodendron subdichotomum Sterzel pars,
(e-h). a, L. arberi K 2488, leaf cushions, b, Leaf scar with ligule pit aperture (1), X 6. c, Cuticle
from median area of cushion, slide PF 3085. d, Cuticle from edge of cushion, arrows parallel to groove
between cushions, slide PF 3086. e, L. subdichotomum SM 2056, leaf cushions, f, Leaf scar with
ligule pit aperture (1), x 6. g. Cuticle from median area of cushion, h, Cuticle from edge of cushion,
arrows parallel to groove between cushions. Magnifications : Leaf cushions x 2, Cuticles x 400.

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES 165

Material. Holotype, K. 2488 from the Low Main coal, Cramlington, Northumberland, similis-pulchra
Zone, Westphalian B. Paratypes, RSM, Dunlop collection, 1957.1.7428 from above the Kiltongue
Coal, Ellismuir, Bailliestown, Lanarkshire — Westphalian A; SM. 1953, 1645, from the Upper Coal
Measures of the Forest of Dean — Westphalian C.

The holotype is a small shoot preserved as a compression on dark grey shale. The
shoot possesses one dichotomy of about 40°. Individual leaf cushions are about 10 mm.
long and 5 mm. broad below the dichotomy and about 8 mm. long and 5 mm. broad
above it. The leaf scars are all about 1 mm. long and 3 mm. broad. Reasonable cuticle
was obtained from the type specimen but only fragments could be obtained from SM
1953 and RSM 1957.1.7428 and none from SM 1645.

Diagnosis. Leaf cushions close together and not continuous with those above and below.
Leaf scar broader than long and just above the cushion centre. Three foliar prints slightly
below the middle of the leaf scar. Ligule pit aperture adjacent to upper angle of leaf
scar. No visible infrafoliar parichnos. Faint keels above and below leaf scars. Lateral
lines running from leaf scars to cushion edges. Leaf cushion surface smooth above and
below leaf scar.

Epidermis similar above and below the leaf scars. Cells from centre of cushions
roughly isodiametric and 20 /x broad or elongated parallel to cushion length and 35 /x
long. Cells from cushion edges elongated toward leaf scars and about 35 /xx 15 ju. across.
Anticlinal walls straight, smooth and 2 /x thick. Periclinal walls flat, smooth. Stomata
about 200 per mm.2, randomly orientated and distributed. Average size 35 /x x 28 p.
Guard cells sunken in pits about 5 /x deep. Ligule pit about 800 /x long and 200 /. x across,
with rectangular cells in longitudinal files, 30 p long and 10 p broad except at the base
where they are 10 p square.

Derivation of name. For the late E. A. N. Arber.

Comparison. L. arberi can be distinguished from L. subdichotomum by the lower position
of its leaf scars and its possession of lateral lines and distinct keels. The cuticles of the
two are rather similar but L. subdichotomum has smaller epidermal cells in the central
areas of the cushion and has superficial, not sunken, guard cells.

Lepidodendron peachii Kidston
Plate 33, fig. 1 ; Plate 34, fig. 4; text-fig. 1 1, a, c, d

1885a Lepidodendron Peachii Kidston, p. 363, pi. 11, fig. 6.

18856 Lepidodendron Peachii Kidston, p. 421, pi. 21, fig. 6.

1929 Lepidodendron Peachii Kidston; Jongmans, p. 258.

1929 Lepidodendron peachi Kidston; Crookall, p. 25, pi. 6, fig. e.

1964 Lepidodendron peachi Kidston; Crookall, p. 245, pi. 60, fig. 1.

Material. K. 668 (type specimen), below the Armadale main, Glenfain or Guttenhole coal, Brick-
works, Falkirk, Stirlingshire — Westphalian A; K. 2466, Lower Main Coal, Newsham, Newcastle upon
Tyne — Westphalian B.

The leaf cushions are raised into hood-like structures and have rounded upper angles.
The ligule pit apertures are adjacent to the upper angles of the leaf scars and three
foliar prints are visible one-third the distance up the scars. No infrafoliar parichnos are
visible. A keel can be seen above the leaf scars but only traces can be seen below them.

166

PALAEONTOLOGY, VOLUME 13

The cushion surface is finely striated above the scars, with the striations running from
the scars to the cushion edges, but below the scars the surface is smooth. Cuticle could
only be prepared from K 2466 as the type specimen is preserved solely as an impression.

Cuticle description. The epidermal cells are different above and below the leaf scars.
The cells above the scars are about 40-60 px 10 p and elongated from the scar to the
cushion edge while the cells below the scars are roughly isodiametric and 10-15 p
across. The anticlinal walls are straight, smooth and about 1 p thick. The periclinal walls
are flat and smooth. Stomata are about 150 per mm.2 below the scar but are absent
above. Individual stomata are about 40-50 pX 35-40 p in size and have guard cells
sunken in pits 8-10 p deep. The ligule pits are about 200 p across with rectangular cells
in longitudinal files 60 p long and 10 p broad except near the base where they are 20 p
long.

Comparison. Arber (1903, p. 20) suggested that L. peachii might be identical to the speci-
men that he was figuring as L. dichotomum Zeiller ( ?Sternberg) and later (1922) included
both in his synonymy for L. loricatum (= L. subdichotomum Sterzel). However, L.
peachii can be clearly separated from this other species on both cushion and epidermal
characters. The cushions of L. peachii are strongly raised and striated above the leaf
scar but those of L. subdichotomum are flat and smooth. The upper cushion angles are
rounded in L. peachii but are pointed in L. subdichotomum and lateral lines running
from cushion scar to cushion edge are only present in L. peachii. The epidermal arrange-
ment is roughly the same over the whole leaf cushion in L. subdichotomum but in L.
peachii it is different above and below the leaf scar and in L. subdichotomum the guard
cells are superficial whereas in L. peachii they are sunken.

Lepidodendron barnsleyense sp. nov.

Plate 31, fig. 5; Plate 34, fig. 3; text-fig. 11b, e-g

1964 Lepidodendron loricatum Arber; Crookall pars, p. 243, pi. 64, fig. 6.

Material. Holotype, K. 4131 from above the Barnsley Bed, Monkton Main Colliery, Yorkshire — -
Base of the similis-pulchra Zone, Westphalian B.

EXPLANATION OF PLATE 34

Figs. 1, 2. Leaf cushion cuticle of Lepidodendron mannabachense Presl from below the leaf scar,
showing stomata and roughly isodiametric cells. Slide PF 2809 from K 2469. 1, x 200; 2, x 400.

Figs. 3, 4. Leaf cushion cuticle from above the leaf scars showing epidermal cells elongated towards
the scars, X 200; 3, Slide PF 3090 from Lepidodendron barnsleyense sp. nov., K 4131 ; 4, Slide PF
2877 from Lepidodendron peachii Kidston, K 2466.

Fig. 5. Leaf cushion cuticle from Lepidodendron feistmanteli Zalessky, X200; Slide PF 2875 from
GSM 72779.

Fig. 6. Cuticle from intercushion area of Lepidodendron serpentigerum Koenig, showing rectangular
epidermal cells and no stomata; Slide PF 3144 from K 2498.

Figs. 7-8. Ligule pit cuticle from Lepidodendron mannabachense Presl; Slide PF 2810 from K 2469;
7, Complete ligule pit showing the opening on to the cushion surface on the right and the opening
marking the attachment position of the ligule on the left, x 100; 8, Portion of ligule pit cuticle
showing the anticlinal walls standing outwards as ridges, x 600.

Palaeontology , Vol. 13

PLATE 34

THOMAS, Lepidodendron

Ur

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES

167

text-fig. 11. Lepidodendron peachii Kidston (a, c, d) and Lepidodendron barnsleyense sp. nov. (b,
e-g). a, L. peachii — K 2466. c, Cuticle from below the leaf scar, figured from the underside, slide PF
2879. d, Cuticle from above the leaf scar (arrows are parallel to cushion striations), slide PF 2877.
b, L. barnsleyense — K 4131. e, f, Cuticle from below the leaf scar, figured from above, slide PF 3089.
g. Cuticle from above the leaf scar (arrows are parallel to cushion striations), slide PF 3090.

Magnifications: leaf cushions x2; cuticles x400.

168

PALAEONTOLOGY, VOLUME 13

The type specimen, which is the only known one referable to this species, is a 3-cm.
broad slab of compressed bark on dark grey shale. Cuticle could be easily prepared from
the leaf cushions but was only obtained in very small fragments from below the leaf
scars. These fragments showed epidermal cells and stomata but were too small to permit
an accurate estimation of stomatal frequency. The ligule pit cuticles also broke up
during maceration preventing measurement of their over-all sizes.

Diagnosis. Leaf cushions rhomboidal, not continuous with other cushions above and
below with leaf scars two-thirds the distance up them. Three foliar prints one-third the
distance up the leaf scars but no visible infrafoliar parichnos. Ligule pit aperture
adjacent to upper angle of leaf scar. Indistinct kells above and below leaf scars. Lateral
lines running from leaf scars to cushion edges. Cushion surface striated above leaf scar
with striations running from scar to cushion edge; surface below leaf scar smooth.
Epidermal cells above leaf scar 30-45 /iX 10-20 /x elongated from scar to cushion edge.
Cells below leaf scar roughly isodiametric and 15 fx across. Cells from groove cuticle,
between cushions, rectangular, about 35 ^ x 30 ^ in size, elongated across the groove.
Anticlinal walls straight, smooth, about 1 fx thick. Periclinal walls faintly granular.
Stomata present below leaf scar but absent above scar and in intercushion grooves.
Stomatal average size 48 /x x 30 p. Guard cells sunken in pits, 6 /x deep. Ligule pits about
230 fx broad with cells 30-40 /x long, 15 yu, broad.

Derivation of name. From the type locality.

Comparison. L. barnsleyense can be distinguished from L. subdichotomum in having
lateral lines running from the leaf scars to the cushion edges and surface striations above
the leaf scars. Cuticle examination supports the distinction of these two species. The
epidermal arrangement is different above and below the leaf scars in L. barnsleyense but
in L. subdichotomum it is roughly the same over the whole cushion. Also the guard cells
are sunken in pits only in L. barnsleyense, those in L. subdichotomum being superficial.

The species most similar to L. barnsleyense are L. mannabachense, L. dichotomum, and
L. peachii. L. barnsleyense differs from L. mannabachense and L. dichotomum in having
neither infrafoliar parichnos nor stomata in the cushion epidermis above the leaf scars.
L. dichotomum also has its leaf scars placed higher on relatively broader leaf cushions.
L. peachii can be distinguished by its strongly raised upper cushion surface which
also possesses longer and narrower cells than the corresponding cushion surface in
L. barnsleyense. The guard cells of L. peachii are also in deeper pits than those of L.
barnsleyense. L. barnsleyense is also distinguished by having granular periclinal walls
to its epidermal cells in contrast to the other three species which have smooth walls.

Lepidodendron rhodianum Sternberg
Text-fig. 12

1820 ‘Schuppenpflanze’ Rhode, pp. 7, 8, pi. 1, figs. 1, 3.

1825 Lepidodendron rhodianum Sternberg, p. xi.

1877 Lepidodendron Rhodeanum Sternberg; Stur, p. 283, pi. 23 (40), fig. 1 ; pi. 24 (41), figs. 1-3.
1926 Lepidodendron Rhodeanum Sternberg; Kidston, p. 125, pi. 13, fig. 3.

1939 Lepidophloios laricinus Sternberg; Crookall pars, pp. 14, 18, pi. 2, fig. 2.

1964 Lepidodendron rhodeanum Sternberg; Crookall, p. 245, pi. 61, fig. 8; text-fig. 80.

THOMAS: EPIDERMAL STUDIES OF LEPIDODENDRON SPECIES 169

Material. GSE. 1296, from a borehole at Cambus, 2 miles west of Alloa, Clackmannanshire, Scotland;
5 ft. above the Castlecary Limestone, in the lower part of the Millstone Grit, Lower Namurian.

This specimen is a small piece of dark shale with three fragments of shoot referable
to L. rhodianum. The leaf cushions are close and slightly overlap the cushions above
producing an apparent pointing of their lower angles. The original figures given by

text-fig. 12. Lepidodendron rhodianum Sternberg. GSE, No. 1296. A, Leaf cushions x3; Ligule
pit (1). b. Cuticle from above leaf scar, x 200; arrows directed parallel to cushion striations. c, Re-
constructed median transverse section through a stoma, x 400.

Rhode suggest a similar feature in his specimen. The leaf scars are three-quarters the
way up the cushions and extend completely or nearly completely across their widths.
The leaf cushion surface is striated above the leaf scar but is smooth below. There are
three foliar prints, one-third the distance up the scars, two infrafoliar parichnos and a
ligule pit aperture, adjacent to the upper angle of the leaf scar.

Cuticle description. The cushion epidermal arrangement is different above and below
the leaf scars. The cells above the scars are of average size 50 p x 20 p and elongated
from the scar to the cushion edge but the cells below the scar are isodiametric and about
40 p across. The anticlinal walls are straight, smooth, and about 2 p thick. The periclinal
walls are flat and smooth. The stomata are about 40 per mm.2 and randomly distributed
over the whole cushion surface. They are randomly orientated below the leaf scar but
above the scar the guard cell apertures are orientated at right angles to the direction
of epidermal cell elongation. The guard cells are in pits about 20 p deep and are greatly
overhung by the subsidiary cells. The average size of the stomatal aperture is 43 px 16 p
and of the guard cell pair is 77 pX 54 p. The ligule pits are at least 1 -2 mm. long and
0-35 mm. broad. The pit cells are rectangular, elongated along the pit, and in vertical
rows. They are about 50 p x 20 p along most of its length but about 20 p square near the
base.

Comparison. Crookall (1939) described this specimen as Lepidophloios laricinus Stern-
berg and used it as an example of a species occurring in both the Upper and the Lower

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PALAEONTOLOGY, VOLUME 13

Carboniferous. However, L. laricinus differs in having leaf scars at the bottom of
downward-bulging leaf cushions, non-striated leaf cushions, and ligule pit apertures
separated from the leaf scars. A similar confusion occurred when Kidston (1886, p. 160)
recorded L. rhodeanum (BMNH V284) from the Upper Carboniferous although he later
(1894, p. 251) confined this species to the Lower Carboniferous. Crookall (1939, p. 18;
1964, p. 247) described this specimen of Kidston as Lepidophloios laricinus Sternberg
but it has similar leaf cushions to K3365 which is illustrated here as Lepidodendron
mannabachense Sternberg (pi. 4, fig. 3; text -fig. 7, h) and is best considered to be this
species.

L. rhodianum is similar to L. mannabachense , L. dichotomum, L. peachii, and L.
barnsleyense in having leaf cushions which are striated above the scars and smooth
below them. L. rhodianum can, however, be distinguished from these other species by
its much broader leaf scars and its epidermal characters. L. peachii and L. barnsleyense
have no stomata above the leaf scars ; L. dichotomum has very few above the scars but
very many more than L. rhodianum below the scars; L. mannabachense has more
stomata than L. rhodianum and they are smaller and in shallower pits.

DISCUSSION

The main details of the lepidodendroid cuticle have been previously given (Thomas
1966); but as specific cuticle descriptions are now available for comparison certain
features of the Lepidodendron cuticle should be discussed in greater detail.

Although the Lepidodendron cuticle is like that of some related lepidodendroid genera,
it can still sometimes be useful in generic determinations. Lacey (1962) described the
cuticle from his new species Lepidodendron perforatum but suggested that it may be
better included in Prelepidodendron Danze. Lacey’s specimens have recognizable leaf
cushions but the leaf scars are relatively larger than those of Lepidodendron and there
are no stomata on the cushion cuticles. Both scar size and cuticle detail therefore support
the exclusion of this species from Lepidodendron ; unfortunately no cuticle has been
described from a definite species of Prelepidodendron making a cuticle comparison im-
possible. Cuticle study also supports the removal of the southern hemisphere lycopod,
Lycopodiopsis pedroanum (Carruthers) Edwards (1952), from Lepidodendron where it
was originally included. The cuticle prepared from one of the paratypes, BMNH V230g,
showed much larger epidermal cells (60 p X 45 p) and much thicker anticlinal walls
(4-7 p) than any described here. The stomata also differ in distribution, being only
present on the very edges of the cushions and there only rarely.

Lepidodendron compression species are normally classified on external cushion
morphology and this is often satisfactory. Sometimes however, specimens may be
incomplete or imperfectly preserved, making identification difficult, and knowledge of
the cuticle from these specimens can be often invaluable. Epidermal cell characters can
be very useful in distinguishing species: for example in L. peachii the cells above the leaf
scar are longer and slightly narrower (40-60 pX 10-15 p) than in the similar species
L. barnsleyense (30-35 p X 1 5 p). However, care must be taken to examine the cuticle from
over the whole cushion surface as the shape and orientation of epidermal cells may vary
from area to area. The arrangement of epidermal cells divides Lepidodendron species
into two broad groups. One group has mainly isodiametric cells over the whole cushion,

THOMAS: EPIDERMAL STUDIES OF LEPIDO DEND RON SPECIES 171

e.g. L. aculeatum, L. serpentigerum, and L. subdichotomum, while the other group has
the cells above the leaf scar elongated towards the scars, e.g. L. mannabachense, L.
dichotomum, and L. rhodianum. Some species, e.g. L. veltheimii, do have areas of elon-
gated cells below the leaf scars, but no species is known which has only isodiametric cells
above and elongated cells below the scars. This cellular arrangement on the cushions
probably reflects the arrangement on the abscissed distal portions of the leaves. Those
cushions with dissimilar epidermal arrangements above and below the leaf scars prob-
ably bore leaves with dissimilar upper and lower epidermises, while those cushions
with only one epidermal arrangement probably bore leaves with similar upper and lower
epidermises. Graham (1935) described the epidermises of petrified lycopod leaves but
described no specimens with distinctly different upper and lower epidermises. He did,
however, show that some leaves possessed their stomata in two furrows on the lower
surface, while other leaves possessed no such furrows. Perhaps some association of
stomatal furrows with cushion epidermal arrangement may be proved with future work,
but as yet no definite conclusions can be drawn.

The periclinal walls of the epidermal cells should also be closely examined, preferably
with phase contrast illumination, as they are granular in some species. This granulation
seems to be uncommon as only two of the eleven species described here, L. serpen-
tigerum and L. barnsleyense, have such ornamentation.

Stomata vary from species to species in distribution, size, and depth of stomatal pit,
for example the more frequent but smaller stomata (200 per mm.2 and 30 px 18 p) of
L. mannabachense distinguish it from L. rhodianum (48 per mm.2 and 77 p X 45 p). Here,
as with epidermal cells, the whole cushion should be examined to detect any variation,
as L. peachii and L. barnsleyense only have stomata on the cushion surface below the leaf
scars and L. dichotomum , which has many stomata (450 per mm.2) below the scars, has
almost none above them.

Stomatal distribution is of further interest when comparing species with separated leaf
cushions. The areas between such cushions in L. aculeatum have regions possessing
stomata interspersed among the epidermis with no stomata, while in L. serpentigerum
the whole area between the cushions is devoid of stomata. This suggests that only part
of the intercushion area in L. aculeatum may be of secondary origin, but that all of it in
L. serpentigerum is the result of secondary lateral growth.

Stomatal pit depth is sometimes of use in species distinction. Within the species
described here is a range between the superficial guard cells in L. subdichotomum and the
23 p deep stomatal pits in L. rhodianum. Thus L. subdichotomum can be further distin-
guished from L. mannabachense and L. dichotomum, which both have 6 p deep pits, and
L. mannabachense from L. rhodianum and L. aculeatum, which respectively have pits
23 p and 1 5 p deep.

Specimens are often found which have no preserved cuticle, but the possibility of
obtaining details of the epidermis need not be disregarded as direct observation often
reveals information. The cushion areas which possessed elongated cells often appear
striated while the areas which possessed isodiametric cells conversely are not striated.
Thus it can be inferred that fine striations on a cushion surface indicate the presence or
former presence of elongated cells even though epidermal details may be unobtainable.

The cuticle is clearly an aid to the understanding and the classification of Lepidoden-
dron, but epidermal studies should be used, as in other plant groups, in conjunction with

172

PALAEONTOLOGY, VOLUME 13

gross morphological characters. An attempt has been made to detect variation within the
species but this is difficult and sometimes impossible due to a lack of suitable specimens.
What is needed is an examination of as many specimens as possible of individual species
with the ultimate aim of finding any epidermal variations possibly correlated with
relative positioning on the plant as a whole. The epidermis may therefore provide a
means of identifying the smallest shoots with the largest branches, a task which is other-
wise usually impossible. Similarly, work on suitable specimens might enable a com-
parison of leaves to be made, although large cushions possessing attached leaves are
very scarce. The present work therefore illustrates the value of such epidermal studies
but it does not answer all the questions. It shows what can be done with cuticles and the
sort of studies which should be made.

REFERENCES

arber, e. a. n. 1903. Notes on fossil plants from the Ardwick Series of Manchester. Mem. Proc.
Manchr lit. phil. Soc. 48, 1-32.

1914. On the fossil floras of the Wyre Forest, with special reference to the geology of the coal-
field and its relationships to the neighbouring Coal Measure areas. Phil. Trans. R. Soc. Ser. B, 204,
365-445.

1922. Critical studies of Coal-Measure plant impressions. J. Linn. Soc. 46, 171-217.

bell, w. a. 1944. Carboniferous rocks and fossil floras of Northern Nova Scotia. Mem. geol. Surv.
Can. 238, 276 pp.

brongniart, A. 1828a. Prodrome d'une histoire des vegetaux fossiles. Paris. 233 pp.

1828-38. Histoire des vegetaux fossiles, ou recherches botaniques et geologiques sur les vegetaux

fossiles renfermes dans les diverses couches du globe, pt. I, 488 pp., 166 pis.; pt. II, 72 pp., 30 pi.

bureau, e. m. 1913-14. Bassin de la Basse Loire. II Description des flores fossiles. Paris. Text 1914;
Atlas 1913.

CHALONER, w. G. 1967. In BOUREAU, e. Traite de Paleobotanique. II. Paris. 845 pp.

crookall, r. 1925. On the fossil flora of the Bristol and Somerset Coalfield. Geol. Mag. 62, 145-80.

1929. Coal Measure plants. London. 77 pp.

1939. The plant ‘break’ in the Carboniferous rocks of Great Britain. Bull. geol. Surv. G.B. 1,

13-24.

1964. Fossil plants of the Carboniferous rocks of Great Britain. Mem. Geol. Surv. G.B. Palaeonto-
logy, IV, pt. 3, 217-354.

1966. Ibid. pt. 4, 355-571.

Edwards, w. N. 1952. Lycopodiopsis, a southern hemisphere Lepidophyte. The Palaeobotanist, 1, 159-
64.

eggert, d. a. 1961. Ontogeny of Carboniferous Arborescent Lycopsida. Palaeontographica, B108
43-92.

Fairchild, H. L. 1877. On the structure of Lepidodendron and Sigillaria. 2. The variation of the leaf
scars of Lepidodendron aculeatum Sternberg. Ann. N.Y. Acad. Sci. 1, 77-91.

feistmantel, o. 1875. Die Versteinerungen der Bohmischen Kohlenablager ungen. Palaeontographica,
23, 175-236.

fischer, f. 1904. Zur Nomenclatur von Lepidodendron und zur Artkritik dieser Gattung. Abh. k.preuji.
geol. Landesant. 39, 80 pp.

■ 1906. In potonie, h. Abbildungen und Beschreibungen fossiler Pflanzenreste der Palaozoischen

und Mesozoischen Formationen. Lief. IV. Abh. k. preufi. geol. Landesant.

geinitz, h. b. 1855. Die Versteinerungen der Steinkohlenformation in Sachsen. Leipzig. 61 pp.

graham, r. 1935. An anatomical study of the leaves of the Carboniferous Arborescent Lycopods.
Ann. Bot. 49, 587-608.

hirmer, m. 1927. Handbuch der Palaobotanik. Munich and Berlin. 708 pp.

THOMAS: EPIDERMAL STUDIES OF LEPIDO DEN D RO N SPECIES 173

hofmann, A. and ryba, f. 1899. Leitpflanzen der paldozoischen Steinkohlenablagerungen in Mittel-
Europa. Prague. 104 pp.

jongmans, w. j. 1929. Fossilium Catalogus II, Plantae. Pars 15, Lycopodiales II, 53-525. Berlin.
kidston, r. 1885a. On some new or little known Fossil Lycopods from the Carboniferous Formation.

Ann. Mag. Nat. Hist. (5), 15, 357-65.

18856. Ibid. Proc. Roy. Phys. Soc. Edin. 8, 415-24.

1886. Catalogue of the Palaeozoic Plants in the Department of Geology and Palaeontology, British

Museum ( Natural History). London. 288 pp.

f 1 894. On the various Divisions of the Carboniferous Rocks as determined by their Fossil Flora.

Proc. Roy. Phys. Soc. Edin. 12, 183-257.

1902. Flora of the Carboniferous Period. Proc. Yorks. Geol. & Polytech. Soc. 14, 334-70.

1926. In Central Coalfield of Scotland (Area V). Mem. Geol. Surv. Scot. 145-7.

koenig, c. 1825. leones fossilium sectiles. London. 1 (1825), 4 pp., pi. 1-4; 2 (undated), pi. 9-19.
lacey, w. s. 1962. Welsh Lower Carboniferous plants. I, The flora of the Lower Brown Limestone in
the Vale of Clwyd, North Wales. Palaeontographica, Bill, 126-60.
lesquereux, l. 1879-80. Description of the coal flora of the carboniferous formation in Pennsylvania
and throughout the United States. Geol. Surv. Penn. Rept. Progress, P. Text (1879), 1, 1-354; 2,
355-694. Atlas (1880), 85 pi.

nemejc, F. 1934. Critical remarks on Sternberg’s Lepidodendron dichotomum. Bull. int. Acad, t cheque
Sci. 35 ann., 75-79.

1947. The Lepidodendraceae of the coal districts of central Bohemia (a preliminary study).

Acta Musei Nationalis Prague, 3B, 2, 45-87.

— — 1946. Further critical remarks on Sternberg’s Lepidodendron dichotomum and its relations to the
cones of Sporangiostrobus Bode. Bull. int. Acad, tcheque Sci. 41 ann. (1946), 35-43.
potonie, H. 1899. Lehrbuch der Pflanzenpalaeontologie. Berlin. 402 pp.
remy, w. and remy, R. 1959. Pflanzenfossilien. Berlin. 285 pp.

renier, A. 1904. Documents pour V etude de Paleontologie du terrain houiller. Liege. 26 pp.

Rhode, j. g. 1820. Beitrage zur Pflanzenkunde der Vorwelt. Breslau. 40 pp.

Sternberg, c. von. 1820-38. Versuch einer geognotisch-botanischen Darstellung der Flora der Vorwelt.
Leipzig and Prague, pt. 1 (1820) 24 pp. ; pt. 2 (1821) 33 pp.; pt. 3 (1823) 39 pp.; pt. 4 (1825) 42 pp.;
pt. 5 and 6 (1833) 80 pp.; pt. 7 and 8 (1838) 291 pp.
sterzel, j. T. 1901. Erlauterungen zur geologischen Spezialkarte des Konigreichs Sachsen. Section
Zwickau Werdau Blatt III.

stur, d. r. j. 1877. Beitrage zur Kenntiss der Flora der Vorwelt. I, Culm-Flora. Heft 2, Die Culm-Flora
der Ostrauer und Waldenburger Schichten. Abhandl. k. k. geol. Reichanst. Vienna, 8, 1-366.
thomas, b. a. 1966. The cuticle of the Lepidodendroid stem. New Phy tel. 65, 296-303.
zalessky, m. d. 1904. Vegetaux fossiles du terrain carbonifere du Bassin du Donetz. I, Lycopodiales.
Trudy geol. Kom. n.s. 13, 126 pp.

zeiller, r. 1886-8. Bassin houiller de Valenciennes. Description de la flore fossile. Text 1888, Atlas
1886. Etude des gites mineraux de France. Paris. 731 pp.

B. A. THOMAS

Biology Department

University of London Goldsmiths’ College
London, S.E. 4

Revised typescript received 3 June 1969

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PALAEONTOLOGY

VOLUME 13 • PART 1

CONTENTS

Statistical analysis and presentation of trinucleid (Trilobita) fringe data. By
c. p. hughes 1

Palaeosmunda, a new genus of siphonostelic osmundaceous trunks from the
Upper Permian of Queensland. By r. e. gould 10

On the structure of Cordaites felicis Benson from the Lower Pennsylvanian of
North America. By c. w. good and t. n. taylor 29

A dimorphic goniatite from the Namurian of Cheshire. By n. h. trewin 40
A new Orionastraea (Rugosa) from the Lower Carboniferous of northern
England. By m. kato and m. mitchell 47

Variation in the Visean coral Caninia benburbensis from north-west Ireland.

By o. A. dixon 52

Amphipora and Euryamphipora (Stromatoporoidea) from the Devonian of
western Canada. By n. r. fischbuch 64

The growth and shell microstructure of the thecideacean brachiopod Moorellina
granulosa (Moore) from the Middle Jurassic of England. By p. g. baker 76
Ontogeny of the Upper Cambrian trilobite Leploplastus crassicornis (Wester-
gaard) from Sweden. By p. h. whitworth 100

A new cephalopod fauna from the Lower Carboniferous of east Cornwall.

By S. C. MATTHEWS 112

Two new dicynodonts from the Triassic Yerrapalli Formation of central India.

By T. r. chowdhury 132

Epidermal studies in the interpretation of Lepidodendron species. By b. a.
THOMAS 145

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VOLUME 13 • PART 2

Palaeontology

AUGUST 1970

PUBLISHED BY THE
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LONDON
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COUNCIL 1970-1

President : Dr. W. S. McKerrow, Department of Geology, Oxford
Vice-Presidents : Professor Alwyn Williams, The Queen’s University, Belfast

Professor M. R. House, The University, Kingston upon Hull, Yorkshire
Treasurer-. Dr. J. M. Hancock, Department of Geology, King’s College, London,

W.C. 2

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Secretary : Dr. W. D. I. Rolfe, Hunterian Museum, The University, Glasgow, W. 2

Editors

Mr. N. F. Hughes, Sedgwick Museum, Cambridge
Dr. Gwyn Thomas, Department of Geology, Imperial College, London, S.W. 7
Dr. Isles Strachan, Department of Geology, The University, Birmingham 15
Dr. R. Goldring, Department of Geology, The University, Reading, Berks.

Dr. J. D. Hudson, Department of Geology, The University, Leicester

Other members of Council

Dr. F. M. Broadhurst, Manchester
Dr. L. R. M. Cocks, London
Dr. R. H. Cummings, Abergele
Dr. D. J. Gobbett, Cambridge
Dr. Julia Hubbard, London
Dr. W. J. Kennedy, Oxford
Dr. J. D. Lawson, Glasgow

Dr. W. H. C. Ramsbottom, Leeds
Dr. P. L. Robinson, London
Dr. E. P. F. Rose, London
Dr. C. T. Scrutton, London
Dr. V. G. Walmsley, Swansea
Dr. A. D. Wright, Belfast

Overseas Representatives

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land, Brisbane

Canada: Dr. D. J. McLaren, Institute of Sedimentary and Petroleum Geology, 3303-
33rd Street NW., Calgary, Alberta
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Lower Hutt

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Texaco Trinidad, Inc., Pointe-a-Pierre, Trinidad, West Indies
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sity of California, Berkeley 4, California

Eastern U.S.A.: Professor J. W. Wells, Department of Geology, Cornell University
Ithaca, New York

© The Palaeontological Association, 1970

MORPHOLOGIC VARIABILITY OF THE
GENUS SCHWAGERINA IN THE LOWER
PERMIAN WREFORD LIMESTONE
OF KANSAS

by G. A. SANDERSON and G. J. VERVILLE

Abstract. Fusulinids referable to the genus Schwagerina occur in the basal part of the Threemile Limestone
Member of the Permian Wreford Formation in Chase County, Kansas. Three hundred specimens from six
collecting localities in four townships in Chase County were used in this study. The restricted stratigraphic
range and limited geographic distribution of the fusulinid fauna within the intracratonic, cyclical succession
tend to minimize the effects of diachronism, and it is presumed that the collections are approximately contem-
poraneous.

Considerable morphologic variability is evident within the Threemile fusulinid fauna, and affinities with
several previously described species of Schwagerina can be demonstrated. Studies of measurable morphologic
parameters suggest that all the Wreford schwagerinids sampled are referable to a single population, and thus
the validity of several established taxa is open to challenge.

The Permian Wreford Limestone Formation is a cyclical, intracratonic marine unit
which is exposed in Kansas along a generally north-south trending outcrop belt (text-
fig. 1). Fusulinids referable to the genus Schwagerina have been found in the Wreford
only in Chase County. The specimens used in this study are from six outcrop localities
in four townships within Chase County (text-fig. 1).

Stratigraphically, the Wreford defines the base of the Wolfcampian Chase Group.
It is overlain by the Matfield Shale and underlain by the Speiser Shale. The Wreford
has three members, which are, in ascending order, the Threemile Limestone, the Havens-
ville Shale, and the Schroyer Limestone (text-fig. 2). In Chase County, the thickness of
the Wreford averages approximately 12 m. (Moore et al. 1951).

Fusulinids occur abundantly in the Wreford in central Chase County but only in the
Threemile Member and only in the lowermost 3-5 cm. of that unit (Hattin 1957). The
lower Threemile Member is persistently a grey, porous, cherty limestone in the area of
our collections. There are no obvious indications of lithofacies differences among the
collections, and we are assuming that a generally similar environment is represented
throughout our samples. The geological setting suggests also that the effects of dia-
chronism are minimal. These close stratigraphic, geographic, ecologic and temporal
limits which we are able to place upon the Wreford fauna make it particularly well
suited to a study of morphologic variability and population distribution.

MORPHOLOGY

The Wreford fusulinids exhibit considerable morphologic diversity. Among the
specimens illustrated on Plate 35, shape is the most apparent variable (figs. 1, 3, 8, and
11), but closer examination of the fauna shows differences also in other morphologic
characters, such as prolocular diameter, wall thickness, tunnel width, and nature of

[Palaeontology. Vol. 13, Part 2, 1970, pp. 175-83, pi. 35, 36.]

C 7393 N

176

PALAEONTOLOGY, VOLUME 13

text-fig. 2. Stratigraphic chart showing position of fusulinids.

G. A. SANDERSON AND G. J. VERVILLE: VARIABILITY OF SCHWAGERINA 177

septal folding. Any attempt to evaluate the significance of these differences leads in-
evitably to consideration of some rather basic questions, such as :

1. How many taxa (populations) are present?

2. How may they be distinguished?

3. What is their geographic distribution?

In an effort to find answers to these questions, a representative sampling was made
consisting of 50 randomly selected specimens from each of the 6 collections. Equal
numbers of oriented axial and sagittal thin sections were prepared, giving a total of
300 individuals used in this study. This extensive sampling, while statistically adequate
and systematically desirable, proved to be disturbing to the traditional method of
taxonomic differentiation by visual examination. As might be expected, the morphologic
complexity produced by the interaction of multiple variables tends to inhibit consistent
differentiation by visual inspection alone.

Only a few specimens of the total Wreford fauna are illustrated on Plate 35, but even
here the gradational nature of the morphologic parameters, such as form ratio, for
example, is quite evident, and the distinctive individuals labelled as figs. 1, 3, 8, and 11
begin to blend into a morphologic spectrum. The difficulty of separating these forms
consistently by visual means is increased progressively as the sample size is increased.
Obviously, supplemental quantitative data are required to establish definable limits to
the population or populations.

To this end, the following parameters were measured on the appropriate orientations
of the.300 sampled specimens : prolocular diameter, length, diameter, radius vector, septal
count, volution height, prothecal thickness, half length, and tunnel width. Although
they do not quantify every morphologic dimension, these parameters represent the
bulk of those commonly employed by fusulinid workers. In all, nearly 24 000 bits of
raw quantitative data were accumulated, which subsequently have been manipulated
and subjected to statistical treatment.

QUANTITATIVE ASPECTS

The quantitative aspects of the Wreford fusulinid fauna were investigated in a three-
fold manner: first, by considering the variability of specific parameters within the
sampled specimens; second, by examining ontogenetic changes within the population
or populations; and, third, by comparing all the individual specimens in the samples
with one another statistically. We considered that one or more of these approaches
should reveal the existence of a quantitative basis for taxonomic subdivision of the
fusulinid fauna.

Parameter variability

Results of the first approach are illustrated in the frequency distribution histograms
of several parameters (text-figs. 3-6). Text-fig. 3 shows the number of individuals in
each size class of prolocular diameter; on the left are plots for each of the 6 collecting
localities, using a common scale on the X-axis and stacked for purposes of comparison.
All the histograms suggest a gradation of dimension through a fairly narrow range with
a strong clustering tendency about the means, which are virtually identical in all samples.
The data in each sample have a high degree of statistical correlation. On the right side

178

PALAEONTOLOGY, VOLUME 13

of the same figure is a composite plot of all the data on the left; measurements from all
300 fusulinid specimens are included. In this larger sampling, the distribution is naturally
smoother with accentuation of the clustering tendency, but the essential characteristics
are similar to those of the separate localities. It closely approaches a continuous, sym-
metrical distribution about a mean with no indication of bimodality. There would
appear to be no reason for any taxonomic separation on the basis of this parameter.

text-fig. 3. Frequency distribution histograms of prolocular diameter, composite and
for individual localities.

A frequency distribution plot of septal count by volution produces similar histograms
(text-fig. 4). The same bell-shaped distribution may be observed in all volutions, although
the shape changes ontogenetically from more leptokurtic to more platykurtic. Repre-
sentative distributions are shown for septal counts of all specimens in the second and
sixth volutions. These counts are made from sagittal sections only, and the total specimen
count is 150. The flattening of the distribution is progressive with growth and suggests
a greater range of dimensional variability in the adult test than in the juvenile. None
the less the variation seems to be essentially continuous among all the measurements
for any given volution.

EXPLANATION OF PLATE 35

Morphologic gradation of Wreford schwagerinid fauna, x8. Figs. 1-11 are specimens 226, 31, 328,
57, 209, 306, 144, 37, 43, 153, and 287, respectively.

Palaeontology, Vol. 13

PLATE 35

SANDERSON and VERVILLE, Morphologic variability of Schwagerina

V <

G. A. SANDERSON AND G. J. VERVILLE: VARIABILITY OF SCHWAGERINA 179

It should be noted that these graphic illustrations were plotted from raw measure-
ments made on a volution-by-volution basis before adjustment for position on the
growth spiral. The adjusted data have an even smoother frequency distribution. A

text-fig. 4. Frequency distribution histograms of septal count for volutions 2 and 6.

0 .1 .2 .3 .4 .5 1.0 1.5

RADIUS VECTOR IN MM.

text-fig. 5. Frequency distribution histograms of radius vector ( p ) for volutions 2 and 5.

statistical evaluation of interpolated values at equal diameters made by Dr. J. L. Cutbill
(personal communication) of Cambridge University showed virtually all the distributions
to be statistically normal.

An analogous situation may be seen in the radius vector ( p ) distribution. Text-fig. 5
illustrates the values for volutions 2 and 5. Again the frequency histograms are essentially
symmetrical and closely clustered about the mean with a tendency toward progressive
flattening in outer volutions. In the case illustrated, the flattening is somewhat masked

180 PALAEONTOLOGY, VOLUME 13

by the scale change necessitated by size limitations of the graph. The dimensional
variability is essentially continuous, and normality of distribution can be demonstrated.
Similar plots of other parameters (e.g. text-fig. 6) give the same results; none has yet
produced any clear indication of a quantitative basis for taxonomic separation.

40 — | -i

01 23401 2 34

FORM RATIO

text-fig. 6. Frequency distribution histograms of form ratio for volutions 2 and 5.

Ontogenetic changes

Text-fig. 7 is a plot of increase in septal count with growth. Maximum, minimum,
and mean values per volution are given for the entire sampling. With the exception of
volution 1, which contains the prolocular aperture and is unique, the septal count in
all other volutions increases arithmetically, resulting in the linear relationship shown.
Again, there seems to be no compelling reason to attempt taxonomic subdivision of the
Wreford fusulinid fauna on the basis of this parameter.

The ontogenetic increase in radius vector is illustrated in text-fig. 8 with the maximum,
minimum, and mean values per volution given for all the Wreford specimens. In contrast
to the septal count, the growth curve is exponential, but there is still no suggestion
that more than one population is present in our samples.

Comparable results appear in other data plots, and the point need not be laboured.
All other measured parameters which have not been illustrated correlate closely with
those shown or exhibit similar relationships.

Statistical analyses

Various types of multivariate analysis have been used since the study of the Wreford
fauna began, and, in fact, the statistical study is continuing as more sophisticated
computer hardware and software become available. Our initial studies utilized raw
data consisting of measurements made at single volution (e.g. 360°) increments. The
volution approach does not, of course, take into account the variability in diameter of
the initial chamber and, therefore, comparisons of growth characteristics are only
approximate. Although other methods of adjustment have been investigated, the Cutbill
data standardization method (unpublished manuscript) of relating measurements to
standard reference diameters has been used in most subsequent computer applications.

G. A. SANDERSON AND G. J. VERVILLE: VARIABILITY OF SCHWAGERINA 181

NUMBER

OF

SEPTA

TEXT-FIG. 7.

p IN MM.

50

40

30

20

10

0

A A AVERAGE

■ ■ MINIMUM

12 3 4 5 6 7

VOLUTION

Plot of maximum, minimum, and mean septal counts per volution
for the total Wreford population.

text-fig. 8. Plot of maximum, minimum, and mean radius vectors per volution
for the total Wreford population.

182

PALAEONTOLOGY, VOLUME 13

Multivariate analyses run on both the raw data and the adjusted data include R-mode
factor analysis, Q-mode factor analysis, and discriminant function analysis. Results of
the tests run to date support the premise that the Wreford fusulinids probably belong
to a single continuously variable population.

FAUNAL COMPARISONS

Since we have been unable to make taxonomic subdivision of the Wreford fusulinid
fauna on the basis of either qualitative or quantitative criteria, our original questions
seem to be answered adequately by the simple recognition of a single fusulinid population
distributed essentially uniformly throughout our collections. This certainly is not a
startling conclusion in view of the geologic evidence, but a disturbing ramification
presents itself in the comparisons made on Plate 36, using 6 fusulinid pairs. One member
of each pair is a published species, in some cases the holotype, of an age roughly com-
parable to that of the Wreford ; the other is a selected member of the Wreford population
from somewhere within the morphologic spectrum. A close degree of similarity is
obvious. Perhaps these specimens are not all conspecific, but differentiation certainly
would involve extremely subtle differences — of an order well within the range of
variability of a single population such as that of the Wreford. Whether or not these
particular specimens are conspecific is rather beside the point. What is important is
that they are extremely difficult, if not impossible, to differentiate by conventional
means — that is, visually or on the basis of limited measurements. In short, there is a
reasonable doubt as to their validity, which in turn suggests the need for a reappraisal of
commonly accepted taxonomic practices, for there is abundant evidence to indicate
that similar studies could be conducted on the majority of published fusulinid faunas
with comparable results. Needless to say, our criticism is directed at the present ‘state
of the art’ and not personally at its practitioners among whom we include ourselves.

Unfortunately, there is no easy solution to the problem. Speciation among fusulinid
workers is a highly subjective process unfettered by procedural standards or guide-
lines. Such standards are urgently needed, but it would be naive, indeed, to assume
that they will be forthcoming soon. Nevertheless it should be encumbent upon authors
of new taxa to define them in such a manner that they are unequivocally distinguishable.
In our view this includes extensive sampling, adequate illustration, and detailed quan-
titative treatment of the morphologic variability spectrum of the taxon. Cutbill and
Forbes (1967) suggest possible procedures for routine taxonomic work which can be
used to advantage. Whether graphic representations are used or not, the minimum
sampling of twenty specimens suggested by Cutbill and Forbes should be practised
whenever possible. A larger sampling would be even better.

Multivariate analysis will undoubtedly play a significant role in population studies
in the future, particularly in view of increasing computer availability. Discriminant
function analysis can aid in the recognition of morphologic groupings (Harbaugh and

EXPLANATION OF PLATE 36

Faunal comparison, x 8. Figs, \a-6a are specimens 309, 49, 226, 55, 54, and 43, respectively, of the
Wreford schwagerinid population. Figs, \b-6b are Schwagerina vervillei Thompson 1954, S. colemani
Thompson 1954, S. emaciata (Beede) 1916, S. campensis Thompson 1954, S. andresensis Thompson
1954, and S. complexa Thompson 1954, respectively.

Palaeontology, Vol. 13

PLATE 36

SANDERSON and VERVILLE, Morphologic variability of Schwagerina

G. A. SANDERSON AND G. J. VERVILLE: VARIABILITY OF SCHWAGERINA 183

Merriam 1968). Factor analysis in the Q-mode and R-mode is applicable to fusulinid
studies involving populations of individuals or variable morphologic parameters (Har-
baugh and Merriam 1968, Merriam 1966). In fact, study of the spatial and temporal
variability of particular morphologic parameters may well turn out to be of greater
significance geologically than the characterization of the individual as an aggregate of
many variables. In any case, the delimiting of morphologic variability is inherent in
realistic taxonomy.

CONCLUSIONS

All available evidence indicates that the Wreford fusulinids studied apparently belong
to a single morphologic population distributed more or less uniformly through all six
collecting localities. Close similarity is demonstrable between several existing species of
Schwagerina and specimens within the Wreford population, and it is doubtful whether
all of the former represent valid species. Current taxonomic practices are in need of
review, and a shift of emphasis from the typological concept to a population-oriented
approach seems to be in order. Realistic and objective delineation of species requires
consideration of the whole spectrum of morphologic variability, and the erection of any
new taxon should entail sufficient quantitative data for adequate characterization.

Acknowledgements. We are particularly grateful to Dr. J. L. Cutbill who made the first statistical test
of our data with his data standardization routine and who has also permitted us access to unpublished
manuscript material. His counsel and encouragement are appreciated. Pan American Petroleum
Corporation provided computer and other facilities utilized in this study and granted permission for
publication. Among the Pan American colleagues who have aided materially this study, we wish to
acknowledge the efforts of Messrs. L. V. Brown, N. Di Vittorio, and K. Wignall in statistical aspects of
the project. We also wish to thank Dr. Alan B. Shaw with whom several fruitful discussions were held.

Repository. All specimens are filed by specimen number under Localities 2795-2800 inclusive at the
Research Center of the Pan American Petroleum Corporation (address below).

REFERENCES

cutbill, j. l., and forbes, c. l. 1967. Graphical aids for the description and analysis of variation in
fusuline foraminifera. Palaeontology, 10, 322-37.

harbaugh, j. w., and merriam, d. F. 1968. Computer applications in stratigraphic analysis. 282 pp.

John Wiley & Sons, Inc., New York, London, Sidney.
hattin, d. e. 1 957. Depositional environment of the Wreford megacyclothem (Lower Permian) of
Kansas. Bull. Kans. geol. Surv. 124, 150 pp., 22 pi.
imbrie, j. 1956. Biometrical methods in the study of invertebrate fossils. Bull. Am. Mus. Nat. Hist. 108,
215-52.

merriam, d. f. (Ed.). 1966. Computer applications in the earth sciences: Colloquium on classification
procedures. Kans. geol. Surv. Computer Contrib. 7, 79 pp.
moore, r. c., jewett, j. m., and o’connor, h. g. 1951. Geology, mineral resources, and ground-water
resources of Chase County, Kansas; Pt. 1, Rock formations of Chase County. Kans. geol. Surv.
11, 5-16, pi. 1.

Thompson, M. l. 1954. American Wolfcampian Fusulinids. Paleont. Contr. Univ. Kans. 5, 226 pp.,
52 pis.

G. A. SANDERSON
G. J. VERVILLE

Pan American Petroleum Corporation
Research Center
4502 East 41st Street
P.O. Box 591

Tulsa, Oklahoma-74102, U.S.A.

Typescript received 11 April 1969

SURFACE TEXTURES OF CALCAREOUS
FORAMINIFERIDS

by J. w. Murray and c. a. wright

Abstract. A comparison is made between the surface appearance of fresh calcareous foraminiferid tests, those
etched artificially, and those found in fossil representatives from the Hampshire Basin. It is concluded that most
fossil foraminiferids show some post-mortem etching of the test surface.

The texture of the wall surface and the relative size of the pores have been used as
specific characters in taxonomic studies of foraminiferids based on examination under
the light microscope. Recent descriptions of the ultrastructure of the calcareous forami-
niferid wall (Hay, Towe, and Wright 1963, Lynts and Pfister 1967, Towe and Cifelli
1967) have been illustrated by excellent electron photomicrographs of surface and
internal features. With the introduction of the scanning electron microscope to the
study of foraminiferids much more information on textures and structures will become
available.

The preparation of material for examination in the two types of electron microscope
is quite different. For the transmission electron microscope the material is replicated,
usually with carbon, and it is the replica which is examined. The scanning electron
microscope can be used to examine specimens directly, providing they have a con-
ducting layer on the surface. Foraminiferids are usually coated with a gold-palladium
mixture but other metals such as gold or aluminium have also been used with success.
The disadvantage of the metallic coating is that it obscures detail finer than its own
thickness. Hay and Sandberg (1967) state the resolution of the transmission microscope
to be 5 A and that of the scanning microscope to be 200 A. However, this disadvantage
is offset by the great depth of field of the scanning microscope.

Routine examination of Tertiary and Recent foraminiferids from the Hampshire
Basin and Western Approaches at magnifications of x20 to X6000 has provided a
large amount of information on the texture of foraminiferid walls. Magnifications of up
to x 20 000 have been used where necessary. Altogether some 1200 photomicrographs
have been taken to date.

When viewing a wall texture in detail it is important to establish whether the structures
observed are primary or secondary. Two processes can lead to post-mortem changes in
the surface texture : physical abrasion with sedimentary particles, and chemical etching
of those walls which are calcareous. These processes may operate singly or together.
The present discussion is concerned only with textures resulting from chemical
etching.

A short note by Murray (1967) described how hyaline calcareous foraminiferids which
appeared transparent when fresh could be made opaque by etching. In the examples
described below, species of Recent foraminiferids have been studied in a fresh unetched
condition and compared with forms which have been artificially etched in EDTA and
with fossil forms which show comparable textures.

[Palaeontology, Vol. 13, Part 2, 1970, pp. 184-7, pi. 37-39.]

J. W. MURRAY AND C. A. WRIGHT: CALCAREOUS FORAMINIFERIDS 185

Examples

Protelphidium anglicum Murray (1965) has a radiate, perforate, calcite test wall. In
living individuals the outer test surface is smooth and shows irregularly distributed
circular pores about 1-1 -5p in diameter (PI. 37, fig. 2). When such a specimen is etched
for 2-3 minutes in 5% EDTA, the wall becomes white and opaque (Murray 1967).
Under high magnification the pores are seen to have become polygonal and often they
are located near the centre of a polygonal ‘crystal’ (PI. 37, figs. 3-5). Occasionally the
pore is eccentric or even peripheral to the ‘crystal’. The ‘crystals’ have sutured contacts
with one another and have an uneven etched surface. This may indicate that they are
composed of bundles of fibres (R. Bradshaw, University of Bristol, pers. comm.).
These may be analogous to the plate-like units observed in the radial wall of Ammonia
beccarii (Linne) by To we and Cifelli (1967).

The same type of etched surface has been seen in Protelphidium sp. from Oligocene
rocks (Middle Headon Beds) of the Isle of Wight, England (PI. 37, fig. 5).

Nummulites rectus Curry from the Lower Barton shows the same type of etched
surface. Plate 38, figs. 1, 2 show these textures on the inside of the chamber wall in a
broken form. The same polygonal ‘crystals’ can be seen with sutured contacts and a
central pore. In the fossil forms, however, the ‘crystal’ is composed of radiating ‘blocks’,
the number present depending on the stage to which the etching has exposed the
divisions between them. Eight to ten ‘blocks’ are present surrounding the pore and
each of these has a rough texture exhibiting the same bundle-of-fibre structure. Between
the pores, ‘bundles’ of ‘crystals’ fill in the spaces, groups of ‘bundles’ being separated
by sutured contacts.

In the umbilical region of modern examples of Protelphidium anglicum there are no
pores in the wall. Etching does not reveal crystal boundaries although the previously
smooth shell becomes pitted (PI. 37, fig. 3).

Cibicides lobatulus (Walker and Jacob) also has a radiate calcite test wall. In fresh
specimens the wall is smooth (PI. 38, figs. 3, 4) but in specimens etched in 5% EDTA
the wall becomes irregularly pitted. In this species the pores are relatively large (6-1 p
in diameter) and it seems probable that the component calcite crystals of the wall
surround each pore. Etching leads to pore enlargement.

The same etched surface texture has been seen in fossil forms of this species from the
Upper Barton Beds of Hampshire. These forms also display large pores with complex
layered internal structures separated by etched wall with irregular pitted texture best
displayed in the apertural region where the pores are less abundant (PI. 38, fig. 6).

The wall structure of Ammonia beccarii (Linne) was described in detail by Towe and
Cifelli (1967). The greater part of the wall is made up of plate-like calcite units which
are very much smaller than the wall pores. When the surface is etched, the pores are
enlarged and the surface becomes uneven (PI. 39, figs. 1, 2). Etching preferentially
attacks the pores because of the large surface area of their walls.

In fossil forms of Nonion laeve (d’Orbigny), the effects of abrasion on the high points
of the chambers can be seen. This abrasion aids the chemical etching of the test by
destroying the original smooth surface. In this form (PI. 38, fig. 7) the chamber is very
severely etched to produce a rough and pitted texture compared with the smooth wall
visible along the suture and on the sutural processes. The chamber wall immediately

186 PALAEONTOLOGY, VOLUME 13

adjacent to the suture is also smooth but the wall becomes pitted on the elevated
part of the chamber.

Early stages in the etching process have been studied in fossil forms of Melonis affine
(Reuss) which has a granular perforate calcite test wall and an open umbilicus. The wall
is normally smooth and finely perforate but in some fossil forms this smooth wall is
broken up by a series of interlocking cracks with a pore at the centre of each system.
These cracks appear to be the first stages in the production of the sutured contacts
between the ‘crystals’ (PI. 39, figs. 3-5).

The common Recent miliolid Quinqueloculina seminulum (Linne) normally has an
opaque white, imperforate test in which the surface has a porcelain-like glaze. The
wall structure in general is described as ‘porcellaneous’. Under a magnification of
x 20 000, the ‘tile-roof’ pattern of calcite crystals forming the surface glaze may just be
made out (see Hay, Towe, and Wright 1963 and Towe and Cifelli 1967; also the
‘pavement-like pattern’ of Lynts and Pfister 1967). When the wall is etched in 5% EDTA,
the ‘tile-roof’ glaze can be readily seen and beneath it the very disorganized layers of
calcite rods are revealed (PI. 39, figs. 6, 7). The ‘roof-tile’ crystals average 2p in length

EXPLANATION OF PLATE 37

Figs. 1-5. Protelphidium anglicum Murray; Recent, Christchurch Harbour, England. 1, Lateral view
of specimen with attached turbellarian egg case; maximum diameter of specimen 533/x ; x 105. 2,
Details of smooth wall with pores averaging 1-1 -5/x in diameter; x 5600. 3, Chamber wall etched in
5% EDTA showing ‘crystals’ with pores and an underlying layer; the umbilical region in the upper
part of the photograph is only slightly pitted; x2100. 4, Strongly etched chamber wall (using 5%
EDTA) showing layered structure, ‘crystals’ and pores; x 1950. 5, Enlargement of fig. 4. Note
sutured boundaries between ‘crystals’ and the polygonal pores; x 5900.

Fig. 6. Protelphidium sp. ; Middle Headon Beds (Oligocene), Headon Hill, Isle of Wight. Naturally
etched wall showing many similarities with figs. 3, 4 and 5; x 1500.

EXPLANATION OF PLATE 38

Figs. 1, 2. Nummulites rectus Curry; Lower Barton Beds, Becton Bunny, Hampshire. 1, View of
inside of chamber wall to show etched ‘crystals’ composed of ‘blocks’, each ‘crystal’ being pierced
by a pore (diameter 0-5— 1/x); x 2250. 2, Enlargement of part of fig. 1 ; x 5550.

Figs. 3-5. Cibicides lobatulus (Walker and Jacob); Recent, Western Approaches. 3, View of spiral
side to show the coarsely perforate test; x 126. 4, Smooth, unetched wall with pores (diameter
6-7|U.); x 1050. 5, Wall etched with 5% EDTA; X2170.

Fig. 6. Cibicides lobatulus (Walker and Jacob) ; Upper Barton Beds (Zone H), Barton Cliff, Hampshire.
Natural etched wall; x 1650.

Fig. 7. Nonion laeve (d’Orbigny); Lower Barton Beds, Becton Bunny, Hampshire. View of smooth
unetched suture with adjacent chamber walls etched; x 2000.

EXPLANATION OF PLATE 39

Figs. 1, 2. Ammonia beccarii (Linne), Recent, Western Approaches. 1, Dorsal view of complete test
etched in 5% EDTA; note the pore enlargement; x 154. 2, Details of pores enlarged by etching;
x 1536.

Figs. 3-5. Melonis affine (Reuss); Middle Barton Beds (Zone F), Barton Cliff, Hampshire. 3, General
view; x210. 4, Incipient etching of the granular wall surface; X1130. 5, Enlargement of fig. 4;
X 2325.

Figs. 6, 7. Quinqueloculina seminulum (Linne); Recent, Western Approaches. 6, Wall etched in 5%
EDTA to reveal the surface ‘roof-tile’ layer of rectangular crystals and the underlying layer of
randomly oriented rods ; X4800. 7, Details of the randomly oriented rods ; X9350.

Palaeontology, Vol. 13

PLATE 37

MURRAY and WRIGHT, Surface textures of calcareous foraminiferids

Palaeontology , Vol. 13

PLATE 38

MURRAY and WRIGHT, Surface textures of calcareous foraminiferids

Palaeontology , Vol. 13

PLATE 39

MURRAY and WRIGHT, Surface textures of calcareous foraminiferids

J. W. MURRAY AND C. A. WRIGHT: CALCAREOUS FORAMINIFERIDS 187

and 0-3/z in width, while the dimensions of the inner rods are 1-0 and 0-2/x respectively.
Most fossil miliolids have lost their ‘roof-tile’ veneer.

It is probable that the specimens examined by Hay, Towe, and Wright (1963) had
already been etched since they described them as ‘dull and chalky’ in appearance in
comparison with the smooth tests of Peneroplis planatus. In our experience fresh
miliolids have a glaze comparable with that of the peneroplids.

Conclusions

Calcareous tests are extensively altered even by short periods of etching. In hyaline
types originally smooth perforate walls become rough; the platelets, or fibres within
the ‘crystals’ become apparent, the ‘crystal’ boundaries are hollowed out and the pores
become enlarged. When the pores have a diameter greater than that of the component
‘crystals’ of the wall, etching produces more pronounced pore enlargement than surface
textural effects. In miliolids, the porcellaneous wall be may stripped of its veneer of
‘roof-tile’ crystals leaving the underlying layer of randomly oriented calcite rods exposed.

As etching is most pronounced on the topographically high parts of tests and in-
dividual chambers, and less marked along the sutural regions, there is reason to believe
that slight abrasion of these highs may promote subsequent etching effects.

The majority of fossil examples examined by us show etching effects to a greater or
lesser extent. The recognition of such post-mortem etching is important for the proper
understanding of foraminiferid structures and for the proper interpretation of species
differences.

Acknowledgements. We would like to thank R. Bradshaw for critical comments on the manuscript.
The research was sponsored by the Natural Environmental Research Council.

REFERENCES

hay, w. h., and sandberg, p. a. 1967. The scanning electron microscope, a major break-through for
micropaleontology. Micropaleontology, 13, 407-18, pi. 1, 2.

towe, k. m., and wright, r. c. 1963. Ultramicrostructure of some selected foraminiferal tests.

Ibid. 9, 171-95, pi. 1-16.

lynts, G. w., and pfister, r. m. 1967. Surface ultrastructure of some tests of recent Foraminiferida
from the Dry Tortugas, Florida. J. Protozool. 14, 387-99.

Murray, j. w. 1967. Transparent and opaque foraminiferid tests. J. Paleont. 41, 791.

towe, k. m., and cifelli, r. 1967. Wall ultrastructure in the calcareous foraminifera: crystallographic
aspects and a model for calcification. Ibid. 41, 742-62, pi. 87-99.

J. W. MURRAY
C. A. WRIGHT

Department of Geology
Queen’s Building
University Walk
Bristol BS8 1TR

Revised typescript received 23 October 1969

NEW XIPHOSURID TRAILS FROM THE UPPER
CARBONIFEROUS OF NORTHERN ENGLAND

by P. G. HARDY

Abstract. Trails from the lower surfaces of sandstone bands in the Upper Haslingden Flags (G Stage, Namu-
rian) of the Rossendale area of Lancashire are attributed to arthropod (xiphosurid) activity. The trails are
associated with Pelecypodichnus Seilacher which here result from the activity of non-marine bivalves. The
xiphosurid trails are therefore considered of non-marine origin. The trails differ from those previously des-
cribed in that in addition to walking activity, burrowing by the xiphosurid is recorded. For convenience these
new trails are referred to Kouphichnium rossendalensis sp. nov.

Trails of xiphosurid origin have been found in loose blocks from the upper part of
the Upper Haslingden Flags (G Stage Namurian) in Rossendale, Lancashire (for details
of the stratigraphy see Wright et al. 1927). The trails occur on the sharply defined under
surfaces of flaggy sandstone bands which generally are interbedded with siltstones. The
sandstones associated with the trails exhibit a number of sedimentological structures
including large-scale planar cross-bedding, small-scale asymmetrical ripples, inter-
ference ripples, micro-cross lamination, and ball and pillow structure. The Upper
Haslingden Flags are essentially lens shaped, thinning in all directions from their
strongest development in the Whitworth area of Rossendale where they exceed 100 ft.

(30 m.) in thickness. The thickness is now known to exceed the figure quoted by Wright
(in Wright et al. 1927). Together with the sedimentological evidence of clean, well-
sorted, ripple-marked sands there seems to be evidence to suggest a sandbank type
of environment during deposition of the Flags. Trails of xiphosurid origin are well
known from various horizons including the Upper Carboniferous and have been
described by many authors. A bibliography up to 1938 is given by Caster (1938). Sub-
sequent papers include those of Caster (1940, 1941, 1944), Linck (1943), Brady (1947), j
Glaessner (1957), Hantzschel (1962), Malz (1964), King (1965), and Bandel (1967).
Limulid trails previously supposed to have been of vertebrate origin have been given
various names. Many earlier names are inappropriate and Kouphichnium (Nopcsa 1923) ;

is now generally used for these trails (see Hantzschel 1965). Previously described trails |
have featured mainly evidence of walking activity e.g. appendage marks, genal spine
drag marks, and telson marks. In this instance a new species of the genus Kouphichnium
seems justified as there is clear evidence of burrowing activity which has only been
described previously from modern Limulus trails (see Caster 1938, pi. 12, fig. 2).

DESCRIPTION

Genus kouphichnium Nopcsa 1923
Kouphichnium rossendalensis sp. nov.
Plate 40

[Palaeontology, Vol. 13, Part 2, 1970, pp. 188-90, pi. 40.]

P. G. HARDY: XIPHOSURID TRAILS

189

Holotype. Geology Department, Manchester University, SF3.

Diagnosis. Trails comprise lunate casts corresponding in outline to the shape of the
xiphosuran prosoma, often in a series, and associated with appendage and telson marks.

Description. The trails are preserved as an irregularly meandering series of lunate casts
the width of which is in general 16-17 mm. although some are smaller, 9-11 mm. The
casts are deepest at the anterior convex end, where they project 2-5-3-5 mm. below the
surface. Posteriorly each cast shallows, and most pass directly into the preceding cast
at a distance of between 0-5-2-0 cm. Where the casts are less closely spaced, and in a
few more or less isolated casts, they often resolve (see PI. 40, inset) into 2 rows of
appendage marks of circular plan which appear to be in a series en echelon. Behind
many of the lunate casts there is median telson cast which is strongest 2-3 cm. behind
the shallow end of the lunate casts. Groups of en echelon marks, each elongated in plan,
occur behind some telson casts in Plate 40. Up to 6 clear elongate casts can be seen in
one set. In no instance has the pusher impression of the maxillipeds been observed.
Very fine wrinkle-like marks occur around the convex end of some of the lunate casts.
In a few examples the convex end of the lunate cast is represented by a cloven-hoof-like
mark. Similar marks have been produced by modern Limulus (Caster 1938; pi. 12,
fig. 2) when sinking vertically into the sediment.

Interpretation. The faintness of the trails at the beginning of each series of Kouphichnium
rossendalensis sp. nov. is interpreted as due to a xiphosurid about to touch down on
the sediment surface dragging telson and appendages through the sediment for a brief
interval and retracting them again before finally landing to implant the first lunate
mark in the sediment. It is conceivable that telson and appendages were used as a
brake prior to touch down; further the use of the telson in this way would serve to
depress the prosoma towards the sediment surface. It appears that the xiphosurid
having landed on the sediment surface burrowed, then moved forward some few milli-
metres, burrowed again and so on before finally taking off into the overlying water.
Although the temporal sequence of burrowing-walking-burrowing is clear the actual
time involved is unknown. Associated with Kouphichnium rossendalensis sp. nov. is
Pelecypodichnus Seilacher formed, apparently, by non-marine bivalves. The evidence
for this statement is, (1) Pelecypodichnus of the Haslingden Flags is identical in form
and lithological association with Pelecypodichnus in the sandstones above the Lower
Mountain Mine at Upholland (Lancashire). Non-marine bivalves occur within the
burrows of Pelecypodichnus in the sandstones at Upholland, (2) Pelecypodichnus of the
Haslingden Flags is identical to Pelecypodichnus at the base of the Rough Rock at
Billinge Hill near Bollington, Cheshire. The base of the Rough Rock at Bollington
contains non-marine bivalves, (3) the Upper Haslingden Flags are followed in upward
sequence by shales known to contain a non-marine fauna (body fossils) at various
localities. The conclusion is reached that Kouphichnium rossendalensis sp. nov. is non-
marine. Two genera of xiphosurid, Belinurus and Euproops, are known from the Upper
Carboniferous. Belinurus is often found in association with non-marine bivalves (Calver
1968) and is thought to have been responsible for the trails. Specimens of Belinurus
from the Manchester Museum were measured across the prosoma, the width of which
was found to correspond closely to the total width of the trails.

190

PALAEONTOLOGY, VOLUME 13

Acknowledgements. The author wishes to thank Dr. F. M. Broadhurst for allowing him to use the
specimens and for advice. He is also grateful to Miss Susan Maher for the photographs.

REFERENCES

bandel, k. 1967. Isopod and Limulid marks and trails in Tonganoxie Sandstone (Upper Pennsyl-
vanian) of Kansas. Palaeont. Contr. Univ. Kans. Paper 19, 1-10, 4 pi.
brady, l. f. 1947. Invertebrate tracks from the Coconino Sandstone of Northern Arizona. J. Paleont.
21, 466-72, pi. 66-8.

CALVER, m. a. 1968. In MURCHISON, D. G., and WESTOLL, T. s. Coal and coal-bearing strata. Oliver and
Boyd, London, 147-77.

caster, k. e. 1938. A restudy of the tracks of Paramphibius. J. Paleont. 12, 3-60, pi. 1-13.

1940. Die sogenannten ‘Wirbeltierspuren’ und die Limulus-Fahrten der Solnhofener Plattenkalke.

Paldont. Z. 22, 12-29.

1941. Trails of Limulus and supposed vertebrates from Solnhofen Lithographic Limestone. Pan.

Am. Geol. 76, 241-58.

1944. Limuloid trails from the Upper Triassic (Chinle) of the Petrified Forest National Monument,

Arizona. Am. J. Sci. 242, 74-84. 1 pi.

glaessner, m. f. 1957. Paleozoic arthropod trails from Australia. Pdlaont. Z. 31, 103-9, pi 10-11.
hantzschel, w. 1962. In moore, r. c. (ed.) Treatise on invertebrate Paleontology. Pt. W: Miscellanea.
Geol. Soc. Amer. and Univ. Kansas Press, W177-W245.

1965. Vestigia Invertebratorum et Problematica. Fossilium Catalogus, 1. Animalia, 108, Graven-

hage.

king, a. f. 1965. Xiphosurid trails from the Upper Carboniferous of Bude, North Cornwall. Proc.
geol. Soc. 1626, 162-5.

linck, o. 1943. Die Buntsandstein Kleinfahrten von Nagold. Neues Jb. Miner. Geol. Paldont. Mh. B,
9-27.

malz, h. 1964. Kouphichnium walchi die Geschichte einer Fahrte und ihres Tieres. Natur Mus. Frank/.
94, 81-97.

nopcsa, F. 1923. Die Familien der Reptilien. Fortschr. Geol. Palaeont. 2, 1-210.
wright, w. b, sherlock, r. l. wray, d. a, lloyd, w., and tonks, l. h. 1927. The geology of the
Rossendale Anticline. Mem. Geol. Surv. U. K.

p. g. hardy
Department of Geology
The University

Final typescript received 9 August 1969 Manchester 13

EXPLANATION OF PLATE 40

Kouphichnium rossendalensis sp. nov. holotype (coll. Geology Dept., Manchester University SF3)
showing appendage marks, telson marks, and lunate casts, x 2/3. Inset, paratype showing appendage
marks arranged en echelon , x 2, specimen SF4.

Palaeontology, Vol. 13

PLATE 40

HARDY, Kouphichnium rossendalensis

SEDIMENTOLOGICAL FACTORS AFFECTING
THE DISTRIBUTION AND GROWTH OF
VISEAN C ANINIOID CORALS IN
NORTH-WEST IRELAND

by J. A. E. B. HUBBARD

Abstract. The Visean limestone-shale sequences of north-west Ireland contain a characteristic distribution
pattern of alternating coraliferous and ‘barren strata’ (called ‘inter-beds’). The varied geniculation in the assem-
blages of prone solitary caninioids in both types of strata are interpreted from comparison with observations
and experiments on modern corals, as showing a close relationship of coral growth to stability, sedimentation,
and penecontemporaneous erosion of the soft lime-mud substrate. Two types of lime-mud are found in the
axial region of the corals: fine homogeneous micrite flooring the tabulae is regarded as original infill, while
extraneous biomicrite, introduced through openings caused by penecontemporaneous erosion and boring
sponges and bryozoa is evidently of subsequent origin. Adverse environmental conditions during skeletogenesis
are believed to be responsible for the widely spaced tabulae, conspicuously thin skeleton, and suppression of the
dissepimentarium, which are irregularly developed and often associated. The effects of compactional loading
and diagenesis are outlined. Each bedding-plane strewn with adult caninioids is regarded as a winnowed death
assemblage involving many different generations and accumulating during periods of slow deposition. The
difficulties for corals living on an unlithified sea bed are discussed and some wider regional implications con-
sidered.

Bedding-planes strewn with large solitary cylindrical Rugose corals (PI. 41, fig. 1)
alternating with comparatively barren strata are common in the Visean limestone-shale
sequences of north-west Ireland. The coralliferous partings are particularly well known
from around the shores of Donegal Bay from whence they have been described since
the mid nineteenth century (see Wynne 1864, p. 38; Wynne 1885). Until now no
ecological interpretation has been attempted, but this would now seem opportune in
the light of recent work on ancient and modern carbonate sedimentology and on
modern coral habits.

METHOD

Detailed field observations form the bulk of this work because little of the material
is suitable for laboratory study. The Visean around Donegal Bay from Easky (Irish
National Grid Reference G380 385) to Muckros Head (I.N.G.R. G620 375) (see text-
fig. 1) is ideally exposed in sections showing deeply weathered, almost horizontal strata.
But crucial information has been derived from the comparatively poorly weathered
inland escarpments of Benbulben (I.N.G.R. G684 462) and Knocknarea (I.N.G.R.
G622 350). Quantitative field analyses which involved more than 3000 caninioids
include data incorporated in the 100 one-metre quadrat analysis (see Hubbard 1966,
p. 254) of the following localities: Easky (I.N.G.R. G380 385), Aughris (I.N.G.R.
G485 350), Serpent Rock (I.N.G.R. G558 460), and Streedagh Point (I.N.G.R. G627
510). Selective laboratory studies which exposed the three-dimensional relationship of
the coralla to their matrices and infilling material were implemented by means of
polished and etched specimens, thin sections, and acetate peels. In addition 160 thin

[Palaeontology, Vol. 13, Part 2, 1970, pp. 191-209, pi. 41-44.]

C 7393 O

192

PALAEONTOLOGY, VOLUME 13

sections and 320 acetate peels of the associated sediments at Streedagh Point and
Easky were studied petrographically.

Terminologically the caninioids mentioned include the solitary specimens of Caninia
spp. and Siphonophyllia spp. listed in stratigraphical accounts of the area (see Table 1).

Systematic studies show that there is much
intraspecific variation at Streedagh Point
(Dixon 1970) but all those corals quoted
are siphonophyllids, whereas outside this
locality occasional caniniids are known
notably in Co. Donegal.

EVIDENCE

1 . General distribution.

Corals occur throughout the limestone-
shale sequences of north-west Ireland but
are remarkably rich on certain bedding-
planes. There is a tendency for one member
of the fauna to predominate in each
stratum, e.g. caninioid, zaphrentoid, fasci-
culate, or cerioid lithostrotionoid corals.
But of these the caninioids are not only the
most spectacular in the variability of their
growth forms and distribution patterns,
but are also the most ubiquitous in their
sedimentary associations. They are found in
biosparites and shales as well as all inter-
mediate sediment types. Their distribution,
which may be compared with other faunal
elements, mirrors subtle lithological varia-
tions. Essentially their occurrence can be divided into two categories which have distinct
sedimentological associations, (a) caninioid-dominated bedding-planes and ( b ) inter-
beds with sparse caninioids (see Table 2); the main difference being that whereas the
former accumulates almost invariably represent condensed composite death assemblages

EXPLANATION OF PLATE 41

Fig. 1. An adult caninioid-dominated bedding-plane at Serpent Rock showing the comparatively
uniform size and variability in growth forms of the partially silicified, randomly oriented, prone
coralla of a composite winnowed death assemblage. The deep weathering of the present day inter-
tidal zone has eroded the majority of the epithecae thus exposing many internal structures in longi-
tudinal section. The corals rest on a crinoidal biomicrite, which probably equates with a high energy
organic sand substrate, but are overlain by an impure dark trace fossil-riddled micrite matrix, which
represents a lower energy rapidly deposited lime-mud. Scale of 1000 mm.

Fig. 2. A vertical polished section of a prone adult caninioid from a block of graded biomicrite at !'
Streedagh Point showing extensive penecontemporaneous erosion of the upward facing surface of the
coral. The caninioid’s lower surface rests on a more richly organodetrital biomicrite of coral-echino-
derm-brozoan debris than the overlying material which has a somewhat higher mud content. Scale
of 50 mm.

text-fig. 1. Outline map of the Sligo-Donegal
coast to show the location of the most informa-
tive sections in the Visean limestone-shale
sequences in relation to their regional setting.

Palaeontology, Vol. 13

PLATE 41

HUBBARD, Caninioid corals

J. A. E. B. HUBBARD: CANINIOID CORALS

193

the latter occasionally incorporate individuals which are thought to be preserved in
positions of growth.

(a) Caninioid-dominated bedding-planes. The bedding-planes strewn with large adult
prone caninioids (PI. 41, fig. 1) are particularly conspicuous in the shore sections of
Streedagh Point, Serpent Rock, Aughris, and Easky. This style of exposure usually
results from differential weathering of weak partings at limestone-shale interfaces.
Thus, where thin shale partings overly the corals the overlying limestone is readily

table 1 . The regional distribution and systematic status of the caninioids discussed according to the
stratigraphical lists in 1, Oswald (1955), 2, Bowes (1957, unpublished Ph.D. thesis University of
Glasgow), and 3, George and Oswald (1957).

Co. Sligo

Systematic status Benbulben Aughris

Caninia cornucopiae Michelin 1

C. benburbensis Lewis 2

C. cf. benburbensis Lewis 2

C. cf. cylindrica (Scouler) 1

Caninia sp. 2

amplexoii caniniids
Siphonophillia cylindrica (Scouler)

S. cf. cylindrica (Scouler)

S. cf. britoliensis (Vaughan)

S. cf. benburbensis (Lewis)

Siphonophyllia sp. (see Lewis 1927, p. 37)

Easky

2

2

2

Co. Donegal
West South-east
3

3

3

3

3

3

undermined and stripped off. The partially silicified coralla resting in or on the under-
lying silty biomicrites are thus left as upstanding features in the contemporary foreshore.
Where the overlying shale parting is absent or limited to an unusually thin veneer the
corals do not weather out so readily on the surface of bedding-planes, but are traceable
in bands along the cliff. The true lateral extent of these caninioid-dominated planes is
difficult to determine. Inland they give the impression of continuity over a matter of
kilometres, but coast sections expose much small-scale faulting which complicates
correlation. Certainly the evidence available suggests that the minimum continuity is
in excess of 30 m. The distribution of caninioids within these planes is more variable
and their orientation is apparently random (compare text-figs. 2 and 3). Caninioid
population densities vary from four to eleven adults per square metre. Occasionally
such concentrated accumulates pass abruptly into ‘barren’ areas within a metre, and
in these cases there is usually evidence of shoaling organic debris on the lee sides of the
caninioids.

There is a marked tendency for a uniformity of late neanic growth stages to pre-
dominate. These range up to 1064 mm. in length and 82 mm. in diameter, but average
505 mm. in length and 76 mm. in diameter. Juveniles are rare or absent. Growth forms,
however, are highly variable and random in their associations. Thus straight, gently
arcuate, and complexly geniculate forms often occur together. Though the proportion
of straight to geniculate caninioids is not constant, the latter tend to be more numerous
(text-fig. 4a). There is no correlation between the size of the corallum, the number, type,
or distribution of geniculations. Thus geniculate caninioids range from simply curved

table 2. A synoptic comparison of the caninioid-dominated strata and ‘inter-beds' to show their contrasts in population structure, population

density, epifauna, thickness, and lithological associations.

J. A. E. B. HUBBARD: CANINIOID CORALS

195

196

PALAEONTOLOGY, VOLUME 13

1- EASKY 2. AUGHRIS 3. SERPENT ROCK 4. STREEDAGH

text-fig. 2. Rose diagrams to illustrate the random orientation of the geniculate caninioids in the
caninioid-dominated bedding-planes. Each diagram represents 100 readings in which the angle of
interception of the coral is plotted.

text-fig. 3. Diagrammatic illustration of an analysis of the orientation of 100 prone, adult caninioids
on a single bedding-plane at the top of the Streedagh Point succession. Inset 4 represents the field
evidence, in which all stages of the coral growth visible are plotted. The directions in which arrows
point indicate the orientation of the calices and their geniculations are plotted to the nearest degree.
The diameters of the coralla are constant but unrepresented. The relative lengths of the intergenicular
regions are approximately in proportion. Inset 3 represents the final stage of growth only. Inset 2
shows the orientation of the coralla before the last geniculation, while inset 1 records only the first
stage of growth visible. Thus there seems to be no apparent preferred orientation either at a particular
growth stage or in toto.

cylindrical specimens to more complex S- and Z-shapes in which the geniculation(s)
occur in one plane or at random. Similarly the genicular angle may be wide and gently
arcuate or narrow and sharply V-shaped. Geniculations show no constant relation to
the situation of the cardinal quadrant, apex, or calice. The epitheca is often partially
removed from the upper surface of the corals as a result of penecontemporaneous

EXPLANATION OF PLATE 42

Close-up of a prone caninioid in a naturally eroded, longitudinal section resting in a bioturbated
coralliferous biomicrite at Serpent Rock. This illustrates the fine detail often visible in the field as
compared with laboratory preparations (PI. 44). The corallum shows repetitive suppressions of the
dissepimentarium, local asymmetrical development of the dissepimentarium, local thinning of the
septa (halfway up the coral), and a gently arcuate geniculation suggesting that this coral’s life
was periodically fraught with the dangers of silting up during adverse conditions. Scale of 100 mm.

Palaeontology, Vol. 13

PLATE 42

HUBBARD, Caninioid corals

J. A. E. B. HUBBARD: CANINIOID CORALS

197

erosion (PI. 41, fig. 2), but this damage is seldom extensive and breakages are few
numbering less than 10% of any population studied (Text-fig. 4b ).

( b ) ‘ Inter-beds’’ . In contrast to the caninioid-dominated strata these are varied in thickness,
lithology, and faunal content (Table 2). They contain few whole fossils but are composed
of a high organo-detrital content. The population is low in numbers but more varied,
containing representatives of various growth stages of a fauna which appears to be

V7A STRAIGHT b-I 'j GENICULATE

100
80
60
40
20
0

E3 ENTIRE FRAGMENTAL

text-fig. 4. Caninioid statistics: Left, histogram to show the ratio of geniculate to straight
caninioids within a single bedding-plane. Three horizons are cited at Streedagh Point. A dominance
of geniculate forms is generally discernible. Right, percentage histogram of entire and fragmental
caninioids calculated from 100 one-metre quadrats at each locality.

locally indigenous and occasionally in position of growth (Text-fig. 5). Whereas
the caninioid-dominated bedding-planes are generally marked by an abrupt change
in sedimentary style, e.g. silty biomicrite to bioturbated shale, the ‘inter-beds’ are con-
spicuous for their uniformity. At most they are graded within the individual stratum.
But there is a tendency for these ‘inter-beds’ to be terminated abruptly at their
upper surface by a caninioid-dominated bedding-plane.

2. Caninioid growth

Longitudinal axial sections exposing the tabularium, many of which are as well
etched in the field (PI. 43) as can be achieved in the laboratory (PI. 44), are plentiful in
the foreshores and yield important information on the growth of the corallum. The
arrangement of the tabulae, though variable in detail, is generally parallel to the
orientation of the external growth rings. This constancy may be used indirectly as
evidence of the probable direction of growth of the live coral.

(a) Geniculation. A gradual compensational swing of both tabulae and growth rings is
usual (Text-figs. 5 l, 2; PI. 43). Abrupt changes are rare.

(b) Attachment. Evidence is seldom found as the apical region is either buried or rarely
seen preserved. Three juveniles are known on the epitheca of one adult caninioid

198

PALAEONTOLOGY, VOLUME 13

(Text-fig. 5 3), while another juvenile attached itself to a spiriferid fragment by supporting
‘rootlets’. Only one attached adult is known from Co. Sligo; it is cemented apically to
a linoproductid fragment in the basal shales of Streedagh Point. In all four cases the
scar is evident, but small. No evidence of attachment scars is found outside the apical
region.

(c) Attitude of growth. Several young caninioids are known in upright positions which
would seem to be functionally viable (Text-figs. 5 1, 2, 3 ; PI. 44, fig. 1). These are recorded
from ‘inter-beds’ and are known from similar sediments in the escarpments of Knock-
narea and Benbulben as well as the shores of Easky, Aughris, Serpent Rock, Streedagh
Point, and Shalwy. But they are rare occurrences limited to homogeneous biomicrite
and silty biomicrite facies. Several neanic and ephebic caninioids are found in this
position where they are intergrown with fasciculate lithostrotionoids as though deriving
benefit from their shelter (PI. 44, fig. 1).

3. Preservation.

(a) Axial infill. The advanced state of diagenesis of both corallum and matrix often
obscures the original nature of the axial infill. The coralla are preserved in finely crys-
talline silica and carbonate, from which, by granular cementation of the carbonate
crystals, the intraskeletal voids are filled. Locally coarse drusy carbonate is developed,
often at the expense of the skeletal structure. Thus tabulae, septa, and dissepiments
terminate abruptly against the mosaic (PI. 43). The coarse mosaic is commonly developed
in bands of less than 50 mm. deep within the tabularium. Occasionally this extends
laterally into the dissepimentarium.

In addition to the crystalline infill, lime-mud is found locally in the axial region. This
consists of two types, (a) very fine homogeneous micrite flooring the tabulae, and ( b )
extraneous silty biomicrite which frequently completely fills the intertabular space but
shows no geopetal features. This latter infill often occurs in the genicular region of the
corallum, where the skeleton is conspicuously thin, and/or in areas where the tabulae
are disorganized.

{b) Penecontemporaneous erosion. Caninioids are seldom as extensively eroded as the
one illustrated in Plate 42, but localized erosion of parts of the corals’ outer surface is
not uncommon. Damage is usually restricted to the upward facing sector of the corallum.
Often the epitheca is breached, but penetration is known to extend as far as the tabu-
larium thus allowing the introduction of extraneous lime-mud into the axial region.
This type of damage is readily distinguished from the products of differential loading
and diagenesis (compare Tables 3 and 4).

EXPLANATION OF PLATE 43

A longitudinal section of a deeply etched, prone, geniculate caninioid. The dissepimentarium shows
pronounced constrictions on the convex side and a certain degree of asymmetry. The tabular region
is locally confused by diagenetic rupture, while the intertabular interval is somewhat masked by
the uneven distribution of carbonate mosaic and silica. Scale of 10 mm.

Palaeontology , Vol. 13

PLATE 43

HUBBARD, Caninioid corals

J. A. E. B. HUBBARD: CANINIOID CORALS

199

text-fig. 5. Caninioid corals preserved in their probable positions of growth.

(1) Field sketch of an adult geniculate caninioid at Serpent Rock illustrating the relationship of the
calice to the axial structures and bedding. There is a conspicuous parallelism of growth-lines, tabulae,
and calice, which distally are almost parallel to the bedding. The apical region is inaccessibly buried
in the matrix. The geniculate development of the corallum suggests that the young coral became
unbalanced and managed to reorient itself successfully with respect to its substrate by gradual up-
right growth, which is reflected in both growth rings and tabulae.

(2) Sketch from a peel of a young geniculate caninioid from Knocknarea illustrating the relationship
between the corallum and matrix. In the upstanding portion of the corallum the bedding terminates
abruptly against the epitheca indicating that deposition and coral growth were contemporaneous.
The calice is at a low angle, in this case almost parallel to the succeeding sedimentary laminae. The
growth history of the coral may be traced from the orientations of the tabulae and growth-lines
with respect to the bedding. During its early life the coral overbalanced and came to rest obliquely on
the sea bed, but compensation reorientation enabled the polyp to resume its upright position and
continue growing until its premature death. This probably resulted from ‘suffocation’ as there
seems to be little evidence of a break in sedimentation between the coral’s successful readjustment
and its final burial. At the calical margin the overlying bedding, which is affected by compactional
deformation, and is of post-mortem origin completely transgresses the corallum.

(3) Field sketch of a caninioid life assemblage comprising an adult supporting three juveniles at
Serpent Rock. The inferred directions of settling of the main corallum are indicated by the angular
discordance between its growth rings (lb, lib, IIIc) and those of the small coralla (la, Ila, Ilia)
which probably initially attached themselves in an erect position.

table 3. A synopsis of caninioid features which result from post-mortem causes.

Feature Area affected Frequency Cause

carbonate for skeletal

202

PALAEONTOLOGY, VOLUME 13

4. Original skeletal peculiarities.

Intertabular distance, suppression of the dissepimentarium and skeletal thinning
(see Table 4) show random development within the coralla. They are commonly
associated with one another and therefore more probably reflect the influence of
environment rather then genetic factors.

(a) Tabular distance. The intertabular distance is variable. Frequently tabulae are
grouped into more and less dense areas; these are not quantifiable, and thus are not
explicable in terms of Ma’s (1937, p. 9) seasonal growth hypothesis. In certain coralla
the tabulae are locally widely spaced and unusually thin. This type of development is
sometimes coincident with local suppression of the dissepimentarium.

(b) Suppression of the dissepimentarium. Whereas the tabularium retains a constant
diameter, the dissepimentarium frequently shows a marked reduction. In some indivi-
duals the suppression may be sufficiently intensive that the dissepimentarium is difficult
to recognize. This usually occurs in regions where the tabulae are thin and widely spaced.
Often this coincides with the sharper geniculations, but it is also found at random along
the length of straight caninioids.

(c) Skeletal thinning. This is highly variable in its occurrence and is most conspicuous
in the tabularium, where it generally coincides with the widely spaced tabulae and
restricted dissepimentarium.

These features are thus highly suggestive of temporary adverse conditions in which
the coral was unable to sustain its usual rate of skeletal secretion. Hence for survival
the coral would be forced to effect a restricted building programme in which it would
naturally concentrate on growing upwards and away from the offending sediment, by
developing widely spaced tabulae, rather than consolidating its scaffolding by dis-
sepimentarial growth.

5. Recent analogies.

Deductions based on analogies between the extinct Rugosa and modern Scleractinia
have obvious limitations because of fundamental differences in thecal formation and
the development of tabulae. Nevertheless it is still worthwhile reviewing some of the

EXPLANATION OF PLATE 44

Fig. 1 . A block of biomicrite at Serpent Rock containing a life assemblage of a slightly geniculate
caninioid growing in close proximity to a fasciculate lithostrotionoid corallum suggests that the
former derived shelter from the latter. The effect of uneven compactional loading causing ‘pinch
and flow’ structures is seen in the deformed Chrondrites rich sedimentary laminae which can be
traced from the base of the caninioid obliquely towards the right hand base of the compound coral.
Scale of 100 mm.

Fig. 2. A deeply eroded marine platform reveals several different sedimentary environments within a
distance of less than 15 cm. in what must have been a soft lime-mud substrate during Visean times.
The section is floored by a linoproductid-coral micrite, which passes up into a dark, bioturbated,
biomicrite horizon. The latter is sharply and unevenly overlain by an impersistent uniform impure
organodetrital shale, which in turn gives way to another caninioid-lithostrotionoid-linoproductoid
micrite which can be traced discontinuously from the top left to the right of centre. Scale of 100 mm.

Palaeontology, Vol. 13

PLATE 44

HUBBARD, Caninioid corals

J. A. E. B. HUBBARD: CANINIOID CORALS

203

experimental and observational findings on the habits of modern corals and considering
the extent to which these may have controlled growth in caninioids.

(a) Initial attachment. Experiments with Pocillopora larvae indicate that attachment is
readily achieved irrespective of the nature of the substrate (Edmondson 1929, p. 8).
Algae, broken glass, and the smooth sides of a glass beaker were sufficient for this
modern coral; thus the organo-detrital content of the Visean biomicrites, e.g. com-
minuted shell, crinoid ossicles, and bryozoan debris, should have been adequate for the
caninioids.

( h ) Later growth habits, (i) Upward growth is a direct response of the polyps’ need to be
above the level where it would be ‘suffocated’ by moving sediment (Manton and
Stephenson 1935, p. 308; Marshall and Orr 1931, pp. 130-1). Phototropism is a sub-
sidiary factor, being an indirect response to the polyps’ dependence on light (see
Edmondson 1929, Roos 1967). Thus in life the calice of the caninioid probably faced
upwards, and was normally parallel to, or sometimes at a low angle to the sea floor (see
text-figs. 5 l, 2, 3; PI. 44, fig. 1).

(ii) Permanent attachment throughout the coral’s life is not necessary. The modern
Bahaman solitary coral Manicena aureolata Linnaeus (Yonge 1935, p. 187; Squires
1958, p. 258) frequently frees itself and loses all trace of its former attachment on
unlithified sediments. Similarly the caninioids appear to have required anchorage only
in extreme youth.

(iii) Stability is a common problem in modern unlithified lime-muds. Present-day
coral populations in the West Indies tend to have slightly lower specific densities than
the surrounding sediments, and it is suggested that this adaptation allows Manicena
areolata Linnaeus in Bimini Lagoon (Squires 1958, Yonge 1935) to keep a constant
proportion of the corallum above the sea water-sediment interface irrespective of the
rate of sedimentation. Experimental calculations on the relative densities of caninioids
and their associated sediments suggest that this was operative in the Visean. In the
Bahamas as much as 9144 mm. of unconsolidated lime-mud is recorded (Squires 1958,
p. 236), a thickness which is more than adequate for the support of any known caninioid.
But what proportion of the caninioid remained buried during life is speculative. It
could not have survived the effects of mobile sediment in the prone condition. The
stability of the coral would have been dependent on the length of the buried portion,
the fluidity of the matrix, and current velocities in the surrounding sea water. Even in
the ideal situation, perpendicular to the sea bed, it seems unlikely that the caninioid
would be stable were more than a third of the corallum exposed above the sediment-
sea water interface, and this upstanding part might be considerably smaller.

Subsidiary factors affecting the stability of the corallum include minute textural
differences in the matrix and these together with the effects of penecontemporaneous
crystallization and early diagenesis could have had a profound effect on the permeability,
porosity and compaction of the surrounding sediment (Trask 1931, p. 275).

(iv) The effect of mobile sediment on Recent corals is crucial. In modern seas the
effects of rate, type, and direction of mobile sediment is of considerable importance in
coral growth and survival. Marshall and Orr (1931, pp. 130-1) show that the larger the
calice, the greater is the polyps’ ability to withstand temporary muddy influxes. This
is paralleled by the ubiquitous caninioids in contrast to the more selective distribution of

204

PALAEONTOLOGY, VOLUME 13

lithostrotionoid corals in the Irish Visean. Marshall and Orr also note a close correla-
tion between particle size and ‘suffocation’ i.e. the finer the particle size the more rapid
the ‘suffocation’. Similarly they note that the direction of sedimentation can be crucial
in Pocillopora, Gallaxea, Symphyllia, Fungia, and Acropora. These corals can withstand
almost unlimited amounts of sediment from above, but where sediment built up around
the lower reaches of the calice death followed within forty-eight hours. This apparently
results from the polyps’ inability to move its tentacles laterally in such circumstances.
Thus during windy weather the polyps’ chances of survival are somewhat hazardous as
the level of the sea bed keeps changing in relation to the polyp. Hence by comparison
the movement of only a small amount of Visean lime-mud could have effectively
‘suffocated’ a large number of caninioids on what is now represented by a single bedding-
plane. But more recently Goreau and Goreau (1959, p. 247) note that the polyps of
Porites and Millepora can withstand starvation during conditions of extreme muddiness.
In these conditions the polyps free themselves from the coralla and live for several weeks
without a sign of skeletal building. By analogy the thin skeletal structures in some
caninioids are attributed to similar, though slightly better conditions than those to
which Goreau and Goreau refer.

(v) Sedimentary rates. Even in modern sediments where exact records may be taken
it is difficult to distinguish sedimentary rates of consequence. Thus, where two days
yield an average of 1 mm. per day, the same locality can also record an average
of only 3 mm. in 15-35 days (see Bakus 1967, p. 45). Visean sedimentary rates
are thus speculative, but in comparative terms their variations are significant. Thus
argillaceous bands rich in trace fossils represent periods of rapid accumulation, while
well-winnowed, organo-detrital calcarenites probably represent slower accumulation,
and graded silty biomocrites probably represent an intermediate and gradational rate
of accumulation. Variations in the vertical combinations of these lithologies (see PI. 44,
fig. 2) leave little doubt that there were variations in depositional rate during the
Visean. The caninioid-dominated bedding-planes commonly rest on well-winnowed
calcarenites and are overlain by bioturbated shales which are in turn overlain by
further limestones. Some of these caninioids contain relics of extraneous biomicrite
within the intertabular areas which can be matched with the overlying sediments. This
suggests penecontemporaneous erosion of the sea bed between the deposition of the
underlying and overlying sediments. But there is no evidence of channelling, probably
because the sediments were still unlithified and highly mobile. Further indications of
breaks in the sedimentary record are provided by truncated trace fossils (see Goldring
1962) and localized epifaunal developments.

The absolute rate of sedimentation during Visean times is unknown, but indirect
estimates may be hazarded using Wells’s (1963) geochronometrical analysis of fine growth
rings, which in modern corals are added diurnally. According to Wells there were 393 days
in the Mississippian year. If this figure is accepted several counts of caninioid diurnal
growth increments would suggest that their average growth rate was 65 mm. per annum
which is identical to the Devonian Cystiphyllum americanum (Wells 1937, p. 17). Thus
an age of thirteen years can be ascribed to the longest straight caninioid at Serpent
Rock. Hence it is assumed that if vertical growth kept pace with sedimentation a rate
of accumulation of less than 65 mm. per annum is indicated. During the life of this
caninioid sediment accumulation was uninterrupted, but ultimately the supporting

J. A. E. B. HUBBARD: CANINIOID CORALS

205

sediment was winnowed away and the corallum left in a prone resting position. But
though shoaling of organic debris is not uncommon few coral case histories are as
simple as this.

A rate of accumulation of 65 mm. per annum is regarded as high by modern lime-
mud standards and compares with lagoonal environments. But in that this rate is
shown to be a temporary feature in the Visean the comparison is plausible.

(vi) Epifauna. The distribution is characteristically local. One bedding-plane may be
more affected than another at the same locality. But Easky, Serpent Rock, and Pound
Point (St. John’s Peninsula) sustain the highest caninioid-based epifauna. Aupolora is
the most common encrusting creature. It generally attaches itself to the upper surface
of prone caninioids on caninioid-dominated bedding-planes and inverted linoproductids
and davisiellids on brachiopod-dominated bedding-planes. It is also found attached to
one caninioid calice which would suggest that it is usually a post-mortem colonization
to combat the adverse effects of life on the lime-mud sea bed. One upstanding caninioid,
believed to be in position of growth, at Shalwy is encircled by an auloporid, in this
case suggesting a commensal relationship.

Penetration by boring sponges and bryozoa (see Brunton 1966) is locally common,
affecting the upper surfaces of prone caninioid thecae at Easky and Streedagh Point.
But there is no evidence of contemporaneous infestation. In section the effective depth
of penetration by boring creatures is obscured by diagenesis, but it is possible that these
passages provided another route for the introduction of extraneous micrite into the
axial region.

CONCLUSIONS

A crude, somewhat oversimplified flow diagram of the caninioids’ probable life
histories indicates the main factors affecting caninioid growth and distribution (Text-
fig. 6) and ultimate accumulation as composite death assemblages in caninioid-dominated
bedding-planes alternating with ‘inter-beds’. Mobile sediment is the key inorganic factor.

1. Caninioids grew upright for preference (Text-fig. 6, 3ia-3ic; text-fig. 5; PI. 44, fig. 1).

2. Caninioids could not live long in the prone condition as even small amounts of
mobile sediment would have soon ‘suffocated’ them (Text-fig. 6, 3iiig-3iiih).

3. Geniculation developed wherever a righting reaction was necessary as for instance:

(a) Resulting from instability induced by contemporaneous winnowing of the soft
lime-mud sea bed (Text-fig. 6, 3iiib— 3iiic— 3iiid— 3iiie) .

( b ) Resulting from instability induced by oblique attachment (Text-fig. 6, 3iia-
3iib-3iic).

(c) Resulting from instability induced by other causes not witnessed in the fossil
record, e.g. behaviour of the substrate during early diagenesis, variations in current
strengths due to salinity changes.

4. The wide caninioid calice renders them more tolerant of mobile sediment than the
associated, mainly lithostrotionoid, corals and thus accounts for the ubiquity of the
caninioids in contrast to the more environmentally restricted lithostrotionoids.

5. The corals’ susceptibility to mobile sediment renders the caninioids more complex
than other groups which reflect similar variations in Visean sedimentological conditions.
They indicate both the individual’s responses throughout life and the effects on the mass

206

PALAEONTOLOGY, VOLUME 13

1 CANINIOID SPAT BECOMES ATTACHED TO A SOLID PARTICLE ON THE VISEAN
LIME-MUD SEA BED

2 JUVENILE CORNUTE CANINIOID

*

31 VERTICAL GROWTH

RESULTING FROM

STABLE ATTACHMENT IN VERTICAL ALTITUDE

Starting from the optimum growth position negative
geotropic growth continues faster than the rate
of deposition of the matrix

Eventually continuous sedimentation
and regular growth result in a
straight cylindrical adult caniniold

3 li OBLIQUE GROWTH RESULTING FROM INSTABILITY OR OBLIQUE ATTACHMENT

(a)

Negative geotropic growth continues
deposition. The depositional rate is

Finally after uniform conditions of slow
deposition an adult caninioid seemingly
indistinguishable from 3i(c) results

(b)

faster than the rate of
slower than in case history 3i

(c")

A comparative increase in the
depositional rate causes the corallum
to grow vertically in order to
avoid suffocation by settling mud.
Thus a geniculation develops

LEGEND

Live polyp

Matrix 1 — generally biomicrite
i -i Matrix 3 — generally shale
i 1 i 1 i Substrate — generally calcarenite

The intensity of the arrow indicates the comparative
strength of the process of deposition : —

Caninioid corallum

Matrix 2 — generally shaly micrite

j ' j Matrix 4-generally biomicrite

Bottom turbulence inducing
erosion

text-fig. 6. A simplified highly idealized flow diagram which accounts for some of the possible
origins of the relationship of the various caninioid growth forms, their orientations, and their
matrices. The relative rates of coral growth, stability, sedimentation, and penecontemporaneous
erosion as reflected in individual coralla and cannot be represented accurately. A general minimal
sedimentary rate is inferred and variations in sedimentary rate are thought to be variable but not
in excess of 65 mm. per annum. Periodically, after the repetition of several of these phases, the win-
nowed accumulates of diverse growth forms of adult caninioids, now preserved in caninioid domina-
ted bedding-planes, were buried by a renewed increase in sedimentation.

J. A. E. B. HUBBARD: CANINIOID CORALS

207

3iii

VARIATION IN GENICULAR STYLE RESULTING FROM MOBILITY OF THE SUBSTRATE
COMBINED WITH THE ALTERNATION OF DEPOSITION AND PENECONTEMPORANEOUS
EROSION

Bottom turbulence involving
penecontemporaneous erosion

of the matrix

(f) The processes

involving 3iii(c)-(e)
may be repeated
innumerable times
thus accounting for
an Indefinite number
of geniculations and
variations in curvature

Penecontemporaneous erosion
and current activity over-
balance the corallum

Renewed influx of sedimentation
with the caninioid resuming
its negative geotropic tendencies

Renewed winnowing. Bottom turbulence
removes all the original matrix tumbling
and rolling the coralla

Influx of extraneous mud with
rapid deposition causes final
suffocation of any but the most
recalcitrant caninioid

Partial burial and/or subsequent
erosion may cause the upstanding
geniculate area to be breached

Subsequent deposition infills the
buried topography of the
eroded caninioid

4 RESULT

Segregations of "prone" adult caninioid — dominated
bedding - planes alternate with almost "barren" units

C 7393

P

208 PALAEONTOLOGY, VOLUME 13

of the population at the time of burial. These patterns of organic and sedimentological
variation are mirrored in the distribution of brachiopods which occur interbedded in
these sequences, of which linoproductids, pustulids, and davisellids are the most
common. They are seldom seen in position of growth but often occur as dense masses
of adults strewn inverted over shaly bedding-planes.

GENERAL DISCUSSION

Having reviewed the local factors, i.e. those pertaining to each caninioid assemblage
now found on single bedding-planes, other major or regional factors influencing survival
and distribution of all recurrent assemblages may be considered briefly. First, there are
the palaeogeographical factors which control such peculiarities as the recurrent changes
in sedimentary regime which are of a crude rhythmic nature. However, the absence of
positive evidence of an inshore facies and adjacent shoreline precludes any definite
statement as to this as a control. Further, with the exception of some limited evidence
of boring algae, no algal mats, dessication cracks, or carbonate pseudomorphs after
anhydrite, which would indicate extreme shallow water conditions are known. This
negative evidence together with the study of the caninioids previously presented,
indicates conclusively that the caninioid populations were not marginal to any shore-
line but may have occupied the dysphotic zones. Other factors which have ultimately
to be taken into account are those of a climatic nature whose effects can only be in-
directly inferred. It is probable that the Visean carbonate sediments of north-west
Ireland accumulated under climatic conditions similar to those found in the tropical
climatic belts of the present time and to be observed in such classic carbonate areas as
the Bahamas. In this area seasonal effects occur when an increase in rainfall causes a
sedimentary influx coupled with a decrease in salinity (cf. Squires 1958, pp. 234-5) and
it is conceivable that similar effects occurred in Visean times. However, absence of
marked concentrations of growth-rings in the north-west Irish Visean caninioids seems
to indicate no seasonal control of growth although the effects of exceptionally severe
tropical storms cannot be eliminated entirely.

There are wider implications to be drawn from the abundant development of Visean
caninioid assemblages in north-west Ireland. Thus favourable conditions in Ireland
seem to reflect favourable conditions globally in tropical climatic belts as comparable
caninioid developments occur in similar horizons not only in north-west Europe but
also in the U.S.S.R. and North America. So apart from the local factors which influenced
initial colonization and survival there were wider controls whose nature can only be
very indirectly inferred at the present time. It is evident that caninioid growth in one
and in all the recurrent assemblages was an extremely complex process which is not
unique to Visean times. In other systems, e.g. Middle Devonian of New York (Oliver
1951) and the Eifel (Birenheide 1962a, b, c, 1963) and the Silurian of Norway (Kiaer
1906) earlier but similar complexities governing the distribution of solitary corals seem
to have been present.

Acknowledgements. The author is indebted to Dr. F. M. Broadhurst whose comments provoked this
study and to Dr. J. M. Hancock and Professor G. Y. Craig whose stimulating comments offered further
encouragement. Too many palaeontologists and geologists to list have afforded helpful criticisms of
the manuscript but their aid is gratefully acknowledged. Specialist information on hydraulics, caninioid
systematics, and the behaviour of modern corals was kindly supplied by Mr. M. J. Kenn, Drs. O. A.

J. A. E. B. HUBBARD: CANINIOID CORALS

209

Dixon, D. R. Squires, and Professor T. F. Goreau. The departmental secretarial and technical services
are gratefully acknowledged. The research was facilitated by a grant from the University of London
Central Research Fund, and the Geological Society of London’s Daniel Pidgeon Fund.

REFERENCES

bakus, g. j. 1968. Sedimentation and benthonic invertebrates of Fanning Island, Central Pacific.
Mar. Geol. 6, 45-51.

birenheide, r. 1962a. Siedlungs- und Wuchsformen mitteldevonischer Korallen aus der Eifel. Natur
Mus. Frankf 92 (1), 21-8, 9 figs.

19626. Entwicklungs-und umweltbedigte Veranderungen bei den Korallen aus dem Eifeler Devon.

Teil I. Ibid. 92 (3), 87-94, 7 figs.

• 1962c. Entwicklungs-und unweltbedingte Veranderungen bei den Korallen aus dem Eifeler Devon.

Teil II. Ibid. 92 (4), 134-8, figs. 8-12.

1963. Standortwechsel von Korallen aus dem Eifelmeer. Ibid. 93 (10), 405-9, 3 figs.

brunton, h. 1966. Predation and shell damage in Visean brachiopod fauna. Palaeontology, 9, 355-9,
pi. 60.

dixon, o. a. 1970. Variation in the Visean coral Caninia benburbensis from Northwest Ireland. Ibid. 13.
Edmondson, c. H. 1929. Growth of Hawaiian Corals. Bull. Bishop Mus. Honolulu, 53, 1-38, 5 pis.
george, t. n., and Oswald, d. h. 1957. The Carboniferous rocks of the Donegal syncline. Quart. J.
geol. Soc. London, 113, 137-79, pi. 14-16.

goldring, r. 1962. The trace fossils of the Baggy Beds (Upper Devonian) of North Devon, England.
Palaont. Z. 36, 232-51.

goreau, t. f., and goreau, nora i. 1959. The physiology of skeleton formation in corals: II. Calcium
deposition by hermatypic corals under various conditions in the reef. Biol. Bull. 117, 239-50.
kubbard, j. a. e. b. 1966. Population studies in the Ballyshannon Limestone, Ballina Limestone and
Rinn Point Beds (Visean) of NW. Ireland. Palaeontology, 9, 252-69, pi. 40-41.
kiaer, j. 1906. Das Obersilur im Kristianagebiete. Videnskabs-Sels-kabets Skrifter, I, Math.-Naturv.
Klasse (Oslo).

ma, t. y. h. 1937. On the seasonal growth in Palaeozoic tetracorals and the climate during the Devonian
period. Palaeont. Sinica, Ser. B, 2, fasc. 3, 1-106.

manton, s. m. and stephenson, t. a. 1935. Ecological surveys of coral reefs. Great Barrier Reef Exped.

1928-29, Sci. Rept. Brit. Mus. ( N.H. ), 3 (10), 274-312, 2 figs. 16 pi.
marshal, s. m., and orr, A. p. 1931. Sedimentation on Low Isles Reef and its relation to coral growth :
Great Barrier Reef Exped. 1928-29. Ibid. 1 (5), 94-133, 7 figs.

Oliver, w. a. 1951. Middle Devonian coral beds of central New York. Amer. Jour. Sci. 249, 705-28,
2 pi. 6 figs.

Oswald, d. h. 1955. The Carboniferous rocks between the Ox Mountains and Donegal Bay. Quart. J.
geol. Soc. Lond. Ill, 167-86, pi. 11.

rods, p. j. r. 1967. Growth and occurrence of the reef coral Porites astraeoides Lamark in relation to
submarine radiance distributions. (Academic proefschrift) Utrecht.
squires, d. f. 1958. Stony corals from the vicinity of Bimini, Bahamas. Bull. Am. Mus. Nat. Hist.
115, 217-62.

trask, p. d. 1931. Compaction of sediments. Bull. Am. Assoc. Pet. Geol., 15, 271-6.
wells, j. w. 1937. Individual variation in the Rugose coral species Heliophyllum halli Edwards and
Haime. Palaeontogr. amer. 2 (6) 20 pp. 1 pi.

1963. Coral growth and geochronometry. Nature, Lond. 197, 948-50.

Wynne, A. b., 1864. On the geology of parts of Sligo, etc. Journ. Geol. Soc. Dublin, 33-41.

1885. Geological Survey of Ireland. Explanatory memoir to accompany sheets nos. 42 and 43.

younge, c. m. 1935. Studies on the biology of Tortugas corals. I. Observations on Meandra areolata
Linnaeus. Pap. Tortugas Lab. 29, 185-98, pi. 1-3.

JULIA A. E. B. HUBBARD,

Department of Geology
King’s College (London University)
Strand

London, W.C.2

Final typescript received 14 July 1969

A NEW CAPITOSAURID LAB YRINTHODONT
FROM EAST AFRICA

by A. A. HOWIE

Abstract. Cranial and post-cranial amphibian remains from two localities in the Middle Triassic Manda
Formation of the Ruhuhu area of Tanzania are described. A new species of Parotosaurus, P. pronus is pro-
posed.

In the skull, the pterygoid canal is of particular interest and may have carried the Vllth nerve. The lower
jaw has a well-developed pre-articular (hamate) process with behind it a pre-articular fossa.

The neural arches, intercentra, and ribs show considerable regional variation. Ossified pleurocentra are
described for the first time in a capitosaur.

The dermal pectoral girdle is massive. Large trabeculae on the interclavicle and clavicles have been inter-
preted as a ridge system to resist a forward pull on the dorsal process of the clavicle by a cleidomastoideus
muscle. Both fore and hind limbs are poorly ossified.

The problem of jaw opening is discussed in capitosaurs and brachyopids. It is thought that in capitosaurs a
cleidomastoideus muscle, attached to the tabular horn and to the clavicle, was used to raise the skull, while the
depressor mandibulae muscle was used to lower the mandible. In brachyopids the first part of this system was
probably an occipito-vertebral muscle.

The retro-articular process and the stereospondylous vertebral column are considered.

Labyrinthodonts have been known since Jaeger in 1824 figured remains of a
skull and vertebral column which were later recognized as belonging to the same animal,
Mastodonsaurus giganteus. Subsequently, labyrinthodonts from Carboniferous, Per-
mian, or Triassic rocks have been recovered from most parts of the world.

Since Jaeger’s account of Mastodonsaurus, capitosaurs, in the broad sense, have been
described by many authors. Contributions other than taxonomic descriptions of new
species have been made especially by Watson (1919, 1951, 1958, 1962), Huene (1922),
Nilsson (1937, 1943 a, b, 1944), and Romer (1947). Welles and Cosgriff (1965) revised
the group and placed all members of the Family Capitosauridae in three genera,
Parotosaurus, Paracyclotosaurus, and Cyclotosaurus, thus following Romer (1947) in
excluding Mastodonsaurus from the family.

Capitosaurs arose in the Lower Triassic and became extinct before the Jurassic.
Adults range in size from a skull length of 7 cm. in a specimen from Australia being
described by Cosgrilf, to approximately 70 cm. in the Upper Triassic Cyclotosaurus
hemprichi, the latter indicating a total length of at least 280 cm.

Watson emphasized various trends associated with the evolution of the capitosaurs
from Lower, through Middle to Upper Triassic times. The more obvious are: an in-
crease in size; a decrease in ossification, especially of the brain-case and limbs; an
increase in dorso- ventral flattening of the skull ; and a tendency to close the otic notch.
This last character, especially, divides the family, so that the Lower Triassic forms are
parotosaurs with open otic notches, while the Upper Triassic types are cyclotosaurs
with closed otic notches. The third capitosaur genus, Paracyclotosaurus, is Upper
Triassic, and was considered by Watson (1958) to have a closed otic notch. Although
post-cranial skeletons have rarely been described in capitosaurs, one noticeable trend
throughout the group is a gradual change from a rhachitomous vertebral column to

[Palaeontology, Vol. 13, Part 2, 1970, pp. 210-53, pi. 45.]

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 211

a neorhachitomous, and finally to a stereospondylous one at least in the anterior part of
the column.

The parotosaurs described here were collected by Dr. F. R. Parrington in the Manda
Formation of the Ruhuhu Coalfields in Tanzania. They were mentioned in 1958 and
1962 by Watson who thought they could be ancestral to a line of deep-skulled paroto-
saurs, and by Welles and Cosgriff in 1965, and are especially noteworthy for the large
amount of post-cranial material associated with two of the skulls.

Capitosaurs are thought to have been slow-moving animals, living on the bottom of
swamps or shallow streams. The huge size of the later forms, accompanied by a decrease
in ossification has led to speculation about the function of various parts of their anatomy.
Watson has discussed problems concerning the opening of their jaws, and has em-
phasized the general flattening, together with the enormous development of dermal
pectoral girdle, and several authors have commented on the strange mixture of rhachi-
tomy and stereospondyly in the vertebral column.

The Manda beds are regarded by Watson (1958, 1962), Parrington (1946), and
Crompton (1955) as being of Middle Triassic age and a detailed summary of the
stratigraphy of the area is given by Charig (1963).

Material. The capitosaur material described was collected from two of Stockley’s localities in the
Manda Formation. Stockley’s B 9, Mkongoleko, produced Dr. Parrington’s field no. 48 which consists
of two labyrinthodont skulls with mandibles, a labyrinthodont pterygoid, and a large amount of
labyrinthodont post-cranial material, the holotype of a new pseudosuchian (this specimen is being
described by Dr. A. J. Charig), and some problematical bones which are here taken to be two ischia
and six sacral ribs of an early Triassic reptile. An additional labyrinthodont skull (field no. 135) of
the same species as the above was recovered from Stockley’s B 26, Gingama.

The labyrinthodont material will be referred to below by Parrington’s field numbers. Thus the two
skulls from Mkongoleko become F.R.P. 48 I (the larger) and F.R.P. 48 II (the smaller).

The material from Mkongoleko was preserved in a sandstone, undoubtedly the ‘pink and purple
felspathic sandstone’ noted by Stockley (1932) as characteristic of the Manda Beds. The Gingama
specimen is grey in colour and its matrix is a ‘consolidated marl’.

Although much of the skull material is fragmented, the pieces are generally well preserved. Skull
F.R.P. 48 I has almost perfectly preserved ornament but the individual bones have broken apart at
their sutures, so their exact interdigitations are not always clear.

Skull F.R.P. 135 has weathered dorsally. In this specimen it was impossible to follow most suture
lines because the bone and matrix were identical in colour, and because the bone is covered with a
reticulum of suture-like cracks. However, the skull is particularly well preserved in the brain-case area.

All three skulls are a little dorso-ventrally distorted.

The post-cranial material is equally well preserved although pre-sacral neural arches tend to have
their spines separated, while several post-sacral neural arches are split in half longitudinally. Only one
intercentrum is longitudinally split.

While the skulls, lower jaws, and post-cranial material from F.R.P. 48 were not found in actual
association, they were the only labyrinthodont remains recovered from the particular site, and as they
all appear to belong to parotosaur-like labyrinthodonts of a comparable size, the post-cranial material
is taken to belong to the two skulls.

Preparation of the specimens was carried out with a dental mallet, and an airbrasive unit, and they
were reinforced with glyptal.

Parotosaurus pronus sp. nov.

The labyrinthodont material contained in F.R.P. field locality 48 is considered to
belong to a new species of parotosaur which is named P. pronus, the specific name
referring to the fact that the animal is dorso-ventrally flattened.

212 PALAEONTOLOGY, VOLUME 13

Holotype. A skull, no. 48 I : F. R. Parrington collection, University Museum of Zoology, Cambridge.

Paratypes. A second skull, 48 II. Four half mandibles. Labyrinthodont post cranial material designated
by letters. All F. R. Parrington collection, University Museum of Zoology, Cambridge.

Referred specimen. A skull, no. 135: F. R. Parrington collection, University Museum of Zoology,
Cambridge.

Type locality. F. R. Parrington field locality B 91, at Stockley's B 9, Mkongoleko, Ruhuhu Valley,
Tanzania.

Horizon. Manda Formation (K8), Teleocrater Zone (as proposed by Charig, 1963), Middle Trias.

Diagnosis. A parotosaurus with a skull broad posteriorly (B:L approximately 75)
(indices as used by Welles and Cosgriff (1965) — B = breadth of skull across quadrato-
jugals, L = skull length, S = breadth of snout one-fifth of the skull length from the tip,
H = height of the postparietals above the parasphenoid), but tapering anteriorly (S :L
approximately 32); skull deep posteriorly (H:B approximately 23); nares elongate,
lateral, long axes parallel to skull border; septomaxilla present; orbits close together
and separated by a shallow depression, well posterior, oval, long axes parallel to mid-
line; frontal and jugal enter orbital margin; pineal foramen rectangular, just posterior
to hind border of orbits; otic notches semiclosed with tabular horns distinctive,
expanded distally towards squamosal; supratemporal excluded from otic notch;
posterior skull border concave.

Anterior palatal vacuity reniform; exoccipitals barely exposed on palate; pterygoids
meeting palatines; pterygoid with facet for jaw articulation.

Processus lamellosus of exoccipital present.

Lower jaw with large pre-articular process and pre-articular fossa.

Vertebrae not longitudinally compressed; pre-sacral neural arches with antero-ventral
nodules developed; intercentra crescentic; some pleurocentra ossified.

Ribs all with uncinate processes; most with distal expansion; all with ‘knee’ bend.
Dermal pectoral girdle massive, flattened; dorsal process of clavicle well developed
and inclined inwards anterodorsally, scapulocoracoid poorly ossified.

Humerus tetrahedral, poorly ossified.

Pelvic elements separate; pubis apparently unossified.

Hind limb poorly ossified; femur with well-developed adductor ridge.

Skull

The skull of Parotosaurus pronus has the bone complement and shape characteristic
of the genus as described for P. peabodyi by Welles and Cosgriff (1965).

One character distinguishing P. pronus from other parotosaur species is the shape of
the tabular horn (text-fig. 1): it is expanded anteriorly as well as laterally towards the
squamosal so that distally the horn is nearly one-third wider than the neck which
separates it from the body of the tabular.

EXPLANATION OF PLATE 45

Parotosaurus pronus sp. nov. Type skull F.R.P. 48 I. Dorsal view. The exoccipital bones have been
displaced posteriorly.

Palaeontology, Vol. 13

PLATE 45

HOWIE, Parotosaurus

HOWIE: A NEW CAPITOSAURID LAB YRINTHODONT FROM EAST AFRICA 213

A second distinction is a roughened area of bone on the quadrate ramus of the ptery-
goid in an internal position adjacent to the quadrate (text-figs. 1, 9). This appears to
have been a continuation on to the pterygoid of the articular surface of the screw-
shaped quadrate condyle.

Excellent preservation in some parts of the occiput and the area around the brain-case
reveal several new features of capitosaur anatomy. Particularly prominent on the
occiput are a pair of tabular ridges. Below the postero-medial edge of each tabular is a

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PALAEONTOLOGY, VOLUME 13

text-fig. 2. Skull 48 I. palatal view ( x J).

rugose ridge which runs across the occiput, narrows, and is continued on to the post-
parietals. This would have served, together with a small rugosity immediately below the
distal end of the tabular, as an insertion point for some of the occipito-vertebral muscles.
However, the most conspicuous ridge on the tabular runs along the paroccipital process
(text-figs. 3, 5) and was the insertion for the cleidomastoideus muscle (see below). In
anterior view (that is, from inside the otic notch) it can be seen that this ridge is confluent
with the anterior wall of the paroccipital process. Also in this view, a further ridge can
be seen running down the paroccipital process along what appears to be the posterior
border of the subtympanic area.

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 215

text-fig. 4. Skull 48 I. Left exoccipital (xf). a, anterior view; b, medial view; c, lateral view.

At their suture on the paroccipital process both the tabular and exoccipital are
hollowed; this space was filled in life by the cartilaginous opisthotic which was not
exposed on the occiput. An antero-ventral expansion of the tabular has an unfinished
surface and a space between it and the paroccipital process is hollowed and presumably
also contained opisthotic.

The exoccipitals of the type skull are shown in three views in text-fig. 4. Text-fig. 4a
shows the jugular foramen and the foramen for nerve XII entering the exoccipital from
the cavity occupied by the medulla oblongata while text-fig. 4c shows their exits. Also
in text-fig. 4a can be seen a longitudinal hollow for the lateral edge of the basioccipital

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PALAEONTOLOGY, VOLUME 13

text-fig. 5. Skull ( x 1). a, Skull 48 II, dorsal view of parasphenoid area; b, Skull 48 I, ventral view
of otic notch; c, Skull 48 I, medial view of pterygoid body.

cartilage, and below this an area of suture with the parasphenoid. Anteriorly, beneath
the base of the paroccipital process, an oblique ridge which connects the lateral external
part of the exoccipital with the inner brain-case area is the median edge of the fenestra
ovalis.

Beside the exoccipital, the pterygoid curves anteriorly to form a cupped region be-
neath the otic notch — the subtympanic cavity — whose postero-lateral edge is the
beginning of an oblique ridge. This ridge projects less than the ‘otic flange’ described
by Watson ( 1962) and in specimen 135 is recurved so that it just fails to meet the ptery-

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 217

text-fig. 6. Skull 135 (xj). a, dorsal view of parasphenoid area; b, anterior view of left otic area;
c, antero-latero-dorsal view of right epipterygoid ; d, antero-latero-ventral view of left stapes and

surrounding area.

goid dorsally to form a canal. From the front of the subtympanic cavity a semicircular
groove leads inwards above the exoccipital suture and ends dorsal to the conical recess
in the pterygoid for the basipterygoid process of the basisphenoid. This groove is
referred to as the dorsal canal of the pterygoid and its opening above the conical recess
is the dorsal foramen (text-figs. 5, 6). Watson (1919, fig. 16) shows a similar groove but
does not describe it.

A foramen for the vena capitis dorsalis enters skull 135 just above the dorsal canal,
while in the type skull immediately below the canal and behind the parapterygoid crista,
is a sharp lip of bone which marks the lateral edge of the fenestra ovalis.

In addition to the sphenethmoid complex, specimen 135 has part of the stapes, otic
regions, and epipterygoids preserved on both sides (text-fig. 6). The right epipterygoid

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PALAEONTOLOGY, VOLUME 13

is almost complete and differs from that of P. peabodyi, rather resembling the ones
described by Wilson (1941) in Buettneria. A medial basal process of the epipterygoid
(text-fig. 6a) is pierced by a foramen which probably carried the profundus nerve (Vx)
and also the palatine branch of nerve YII. Just posterior to this basal process nerve
V must have divided so that Vx passed in front of the ascending process of the epiptery-
goid, and V2 behind it, but there is no trace of a groove for the gasserian ganglion
found in this area by Watson (1958).

Little interpretable structure can be seen in the stapes (text-fig. 6d) as its proximal
end cannot be separated from the otic ossification. The head of the stapes is thus
fused into the fenestra ovalis which is formed by the otic bones dorsally, the pterygoid
laterally, and the exoccipital medially.

The otic ossification attached to the stapes is probably the pro-otic but it has a less
well-defined shape than the pro-otic described by Welles and Cosgriff in P. peabodyi.
It lies medially to the quadrate ramus of the pterygoid and postero-dorsally to the
parapterygoid crista (which forms the rear wall of the conical recess for the basiptery-
goid process of the basisphenoid). On the left, laterally, the dorsal canal between the
pro-otic and the underlying pterygoid marks the lateral limit to the otic area. The more
antero-medial section of the pro-otic, above the parapterygoid crista is thin antero-
posteriorly, and is perforated by a foramen which probably carried part of the Vllth
nerve before it curved posteriorly to exit from the skull. Bystrow and Efremov (1940) in
their restoration of the brain and cranial nerves in Benthosuchus show nerve VII passing
into the pro-otic in a similar position as does Francis (1934, plate X) in the salamander.

Separate from and posterior to the otic region joined to the stapes is an opisthotic
ossification which still forms a core to the paroccipital process.

Lower jaws (text-fig. 7)

The bones of the lower jaw largely follow the typical parotosauran pattern as shown
by Welles and Cosgriff. One difference is that in lateral view in P. pronus the most
posterior part of the postsplenial lies ventral to the anterior wedge of the angular, the
reverse of the condition in P. peabodyi.

The pre-articular in P. pronus occupies all the median edge of the adductor fossa,
and here its hinder end is drawn dorsally into an extensive pre-articular (hamate) process
which rises 3-5 cm. above the fossa. The process is transversely thickened and is
excavated medially by the leading edge of a pre-articular fossa. A flange of the hamate
process forming the dorso-medial wall of the pre-articular fossa is continued forward
inside the jaw parallel to, but a centimetre below, the margin of the adductor fossa.
The pre-articular fossa has not been described in other labyrinthodonts although it was
present in an unidentified mandible cf. Parotosaurus in Cambridge (F.R.P. 116). In
other better-ossified labyrinthodonts which have a hamate process (e.g. Paracycloto-
saurus, Rhine ceps, Mastodonsaurus (Wepfer 1923)) the fossa has been filled by a more
anterior ossification of Meckel’s cartilage than is seen in P. pronus. It seems likely, as
suggested by Nilsson (19436) that there was also a posterior extension of Meckel’s
cartilage running beneath the angular and ending just medial to the most posterior
point of the retro-articular process. An interior flange of the angular noted by Nilsson
in Aphaneramma is present in P. pronus as a nodule of bone on the floor of the Meckelian
space at the centre of ossification of the angular.

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 219

The articular forms a screw-shaped glenoid fossa for articulation with the double
quadrate condyle of the skull, the articular area being increased by the hamate process
which articulates with the roughened patch on the pterygoid adjacent to the quadrate.

Teeth on the skull and mandible have the typical capitosaur shape and arrangement.
Alternation of teeth with replacement pits is regular on the premaxillae of all three
specimens, but becomes less regular in more posterior areas. Here there seems little
obvious order of teeth and pits, sometimes as many as twenty-three teeth appearing
without a gap. In skull F.R.P. 48 II and in one of the mandibles work with an airbrasive

unit revealed tiny replacing teeth in some of the pits. These occurred in areas where
pits regularly alternate with fully formed teeth and usually several replacing teeth are
found in a series. Often the mature teeth between pits containing replacement teeth are
old and appear to be being resorbed, showing the characteristic pattern described by
Bystrow (1938) for aged teeth. The enamel in the small replacing teeth is unconvoluted.

Preparation of a section of left mandible for Lydekkerina sp. (specimen F.R.P. 1964/
34) revealed replacement teeth in almost every pit. These were found in all stages of
development from minute to mature teeth. One tooth was emerging from a partly re-
sorbed mature tooth, while in at least five instances, two teeth were found in a single
pit. One replacement tooth was found on a coronoid bone.

Reconstruction of the skull and mandible (text-figs. 8, 9)

In the skull reconstruction the parasphenoid and septomaxilla, missing in the type
skull, were restored from skull 48 II.

With the articular in place against the quadrate it can be seen that the teeth of the
lower jaw must fit in between the two upper tooth rows. It is evident that in this position
the upper and lower jaw margins will be separated by at least the depth of the lower
teeth, so that in the jaw closed position the three rows are aligned. It can be seen in the
present reconstruction that the dentary tusks clear the palate without needing the
extra depth afforded by the anterior palatal vacuity. Text-fig. 9 shows that the tooth
rows do not meet posteriorly: this region was probably enclosed laterally by a flap of

220 PALAEONTOLOGY, VOLUME 13

skin which would prevent food escaping from the mouth. A similar situation can be
seen in Watson’s reconstruction of Paracyclotosaurus.

Post-cranial skeleton

Vertebral column. Among the capitosaurs,
Paracyclotosaurus and Mastodonsaurus
(Huene 1922) have been preserved with
their vertebral columns almost intact, but
in other forms only scattered, dissociated
elements remain.

The vertebrae in specimen F.R.P. 48
probably belonged to two animals but for
descriptive purposes they are treated as a
single, incomplete vertebral column. Neural
arches, intercentra, and pleurocentra are
present, and some regional differentiation
can be seen in them, especially in the neural
arches. The latter have been lettered and
the intercentra and pleurocentra numbered
to prevent them being inadvertently linked.

Atlas and axis are not represented in the
collection.

Neural arches. One of the more anterior
presacral neural arches, arch C (text-fig. 10),
probably supported a massive rib above
the pectoral girdle. Its spine is split longi-
tudinally and laterally bears a vertical
roughened area which marks the position
of the segmental boundary (Olsen 1936,
Panchen 1967). Beneath the neural spine
the limits of the neural canal are clearly
defined by dorsal and ventro-lateral ridges:
midway along the canal on each side is a
small foramen.

On the underside of the body of the
neural arch on either side of the neural
canal, and extending laterally as far as the
transverse processes, is an almost rectangular
facet (which Watson (1958) notes is for articulation with the pleurocentrum), while,
almost continuous with this but on the anterior surface of the arch, is a further facet.
This is deep medially beside the neural canal, but tapers laterally, and is separated from
the prezygapophysis by a marked recess. This anterior facet is apparently absent in
Paracyclotosaurus but is present in other rhachitomes and neorhachitomes and some
stereospondyls. It is said (Nilsson 1943a) to be an articular facet for the pleurocentrum
belonging to the vertebra in front. A pronounced ridge bounds both ventral and anterior

ptf.t

text-fig. 8. Parotosaurus promts sp. nov. Res-
toration of skull 48 I ( x i). a, dorsal view; b,
occipital view.

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 221

B

text-fig. 9. Parotosaurus promts sp. nov. Restoration of skull 48 I ( x £). a, palatal
view ; b, lateral view of skull and lower jaw.

facets and separates them from the neural canal medially, from the dorsal parts of the
arch body anteriorly and posteriorly, and from the transverse process laterally. Both
facets are cartilage finished, but in a slight depression between them, towards the midline
on each side, is a projecting nubbin which has a surface of finished bone. The bone
lamellae of this knob lie in the same plane as the body of the arch, almost at right angles
to the longitudinal axis of the vertebra. These antero-ventral nubbins are developed to

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PALAEONTOLOGY, VOLUME 13

text-fig. 10. Neural arches. C, M, O, S, U. (x|). a, anterior views; b, left lateral
views ; c, posterior views ; d, dorsal views ; e, ventral views. Where necessary in this
and the following figures bones have been reversed so that all views are of the left
side.

some extent in most presacral vertebrae. They vary in size and shape from a small
(4 mm.) rounded nubbin, to a raised strip of bone tapering from the midline and com-
pletely separating the ventral and anterior neural arch facets. No reference can be found
to them in other labyrinthodonts and they were not found in specimens of Eryops and
Lydekkerina examined, or in Paracyclotosaurus.

HOWIE: A NEW CAPITOSAURID LAB YRINTHODONT FROM EAST AFRICA 223

The sacral neural arch, K (text-fig. 11b) has a low spine with poorly ossified zyga-
pophyses, strongly developed body arches, and small antero-ventral bone nubbins.
There is a precocious development of the diapophyses so that they are almost circular
in lateral view and the transverse processes are correspondingly thickened.

Neural arch O (text-fig. 10), from the anterior caudal area, is remarkable for the
altered shape of its neural spine. This is taller, longer, and better ossified than in the
more anterior arches, and is narrower at the base than it is dorsally. Its post-zyga-
pophyses are poorly developed and appear merely as swellings of the posterior wall of
the neural spine immediately above the neural canal. Laterally the arch body is re-
duced so that it hardly exceeds the neural canal in width. On the left, the ventral and
anterior facets have almost merged, with only a low swelling between. There is no
transverse process, but a raised, down-facing, triangular facet lateral to the ventral
articular area probably represents the diapophysis.

In the more posterior caudal arches like arch S (text-fig. 10), the post-zygapophyses
have disappeared, but in the appropriate place the lower edges of the neural spine bend
outwards as if to form a lateral boundary to a pair of wholly cartilaginous facets.

The more helpful criteria used in arranging the presacral neural arches are as follows :
from anterior to posterior there can be seen

1. An increase in the angle between the neural spine and the body of the vertebra
carrying the transverse process,

2. A decrease in length of the transverse process,

3. 1 and 2 together produce a narrowing of the total width of the neural arch,

4. A decrease in length and width of the diapophyses: this follows from a decrease in
size of the ribs,

5. A slight over-all decrease in size,

6. On these criteria, presacral vertebrae with split arches fall anteriorly. This position
is supported by observation of the arrangement of Paracyclotosaurus in which
arches 1-12 are wholly or partially split.

Characters used in ordering the caudal neural arches are as follows :

1. A decrease in over-all size accompanied by a decrease in ossification, especially of
the post-zygapophyses,

2. A decrease in the size of the body of the arch and transverse processes, until the
latter disappear,

3. An increase in length of the spine in those arches with transverse processes, and,
thereafter, its gradual decrease.

The most posterior caudals are graded purely on size.

[ntercentra. It was found that P. proms' s intercentra could be divided into two cate-
gories, the first containing the more anterior intercentra, and the second, the more
posterior ones.

An example of the first category is intercentrum no. 7 (text-fig. 11 A). This is charac-
teristically wedge shaped in lateral view and crescentic in anterior and posterior views.
Seen from in front, the intercentrum is much less massive than anterior intercentra of
Paracyclotosaurus, its dorsal-most parts being pointed, not dorsally flattened. There

C 7393 Q

224

PALAEONTOLOGY, VOLUME 13

text-fig. 11. A, Intercentra 7, 16. a, anterior view; b, lateral view; c, posterior
view; d, dorsal view; e, ventral view, b. Sacral arch K and intercentrum, a, anterior
view; b, lateral view, c, Pleurocentra 1 and 2. d, dorsal view; e, ventral view.
(Xf).

are no indications that the element is beginning to ossify around a notochord as it was
in the anterior vertebrae of some Upper Triassic capitosaurs.

The ventro-lateral surface of the intercentrum is of finished bone and is concave
antero-posteriorly. It is traversed by three longitudinal ridges which are similar to,
though much smaller than, ridges seen beneath Eryops intercentra.

Between this ventral surface and the dorsal convex one there is often a groove which

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 225

runs on the anterior margin of the intercentrum. Posteriorly, a similar groove borders
the intercentrum below the level of the parapophyses.

The parapophysis, the oval facet for articulation with the capitulum of the rib, is
much better developed than its equivalent in Eryops, but less well developed than
anterior Mastodonsaurus parapophyses. The facet in P. pronus lies at the back of the
intercentrum in a dorso-lateral position. It is surrounded by a ridge which is especially
well developed anteriorly, so that there is often a distinct groove between the para-
pophysis and the anterior edge of the bone. All surfaces of the intercentrum except the
concave ventral and lateral ones were finished in cartilage.

An example of the second category of intercentrum is seen in no. 16 (text-fig. 11a).
It differs markedly from no. 7 in being flattened ventrally so that its lateral faces have
become distinct from the ventral face. It is shallower, and less well ossified than the
more anterior intercentra, and only a small area on its ventral surface appears to be of
finished bone. The parapophyses have moved ventrally so that their lower edges project
below the ventral line of the bone and have become triangular, with the base of the
triangle lying ventrally and the hypotenuse lying posteriorly. In this position the para-
pophysis is lying in a wider part of the intercentrum, and so the groove between it and
the anterior border of the bone has become correspondingly wider.

No. 14 may belong to the sacral vertebra (text-fig. 1 1b). It is flattened, but not to
such an extent as the apparently more posterior caudals, and its parapophyses, which
are already triangular, are larger than any others in the column.

Trends used to position the intercentra are as follows: from anterior to posterior

1. There is a decrease in over-all size of intercentra.

2. There is a change in shape from deeply crescentic and ventrally pointed anteriorly
to ventrally flattened and shallow posteriorly.

3. The parapophysis changes in position from dorsal to ventral, in shape from oval
to triangular, and its size first decreases and then increases again with the change to
triangular shape.

No haemal arches are preserved.

Pleurocentra (text-fig. 11c). Although their presence has often been postulated, and the
structure of the intercentra indicate that they were present, though probably cartila-
ginous, ossified pleurocentra have not previously been described in the Capitosauridae.
Watson (1958) has dotted them in in Paracyclotosaurus. According to Romer (1947)
they were ossified in Benthosuchus, but Bystrow and Efremov (1940) noted their absence
in that animal. Pleurocentra are present in many of the neorhachitomous Rhinesuch-
oidea, especially notable examples being Uranocentrodon (van Hoepen 1915), Lydek-
kerina, and Sclerothorax (Huene 1932). However, descriptions of pleurocentra have
usually been brief, and they are commonly illustrated in side view only. Nilsson (1943a)
does illustrate pleurocentra of the trematosaur, Lyrocephalus, in several views, and,
except that they are less elongate, their shape is similar to the pleurocentra of P.
pronus.

Although they were probably present throughout the column, only nine pleurocentra
were found. The condition of preservation and degree of ossification of these varies,
but it is possible to establish a common structure. Most surfaces are of unfinished bone.
The better-formed elements have the median end expanded, the lateral end bluntly

226 PALAEONTOLOGY, VOLUME 13

pointed, and are narrow dorso-ventrally, so that they are roughly lens-shaped. The
dorsal face is flat for articulation with the postero-ventral facet on the neural arch,
while the ventral face bulges a little especially towards the midline. These two faces
are separated laterally by a narrow convexly curved surface, but medially they meet in
a line which is a little concave, presumably to curve around the dorsal part of the
notochord. On the larger pleurocentra is a small area of finished bone which faces antero-
laterally : in the smaller pleurocentra this facet is often unfinished. In some cases this
area is concave and in one case it seems to be double, with one area lying above and

A B CD

text-fig. 12. Reconstruction of presacral vertebra ( X $). a, anterior view;
b, lateral view of two vertebrae; c, posterior view; d, ventral view. Pleurocentra
are hatched.

behind the other. In one pleurocentrum the lateral strip of bone also has a partly
finished surface. It seems that the pleurocentral element was probably only exposed
on its lateral face, at the ‘facet’ and at the lateral facing strip of bone, all other surfaces
being covered with cartilage.

Reconstruction of the vertebrae

Presacral region (text-fig. 12). Placing the neural arches in articulation shows that the
presacral vertebrae were arranged in units which averaged 3-3 cm. in length. This
leaves a gap of 0-6 cm. between successive intercentra which seems rather large in view
of Watson’s 1958 restoration in Paracyclotosaurus davidi ‘with a minimum of ligament
between them’, but no other arrangement is possible. The intercentra are situated in
front of the neural arches with their dorsal points being level, in lateral view, with the
transverse processes. It can be seen from the anterior view in text-fig. 12 that the dorsal
points of the intercentra are also level with the lateral edges of the anterior neural arch
facets. jj

It follows from this loose arrangement of the neural arch and intercentrum and the
small size of the pleurocentrum, that the latter could be placed in one of two ways. It
could form the central core of a cartilaginous block which fills the gap between the
larger elements: a rhachitomous condition; or it could adhere closely to the neural
arch so that the intercentrum fills the gap : an almost stereospondylous condition. It is
probable that the neorhachitomous vertebra is almost stereospondylous, the pleuro-
centra being placed dorsally against the ventral neural arch facet, with a minimum of
cartilage between the two. In this position the rounded median end of the pleurocentrum

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 227

projected postero-medially towards the anterior neural arch facet of the vertebra behind,
while its pointed lateral end extended a little below the level of the transverse process.

Caudal region (text-fig. 12). As no haemal arches are preserved there is little evidence
on which to base a reconstruction of this area. However, the neural canals can be
aligned, and the regions which held their cartilaginous post-zygapophyses can be placed
above the prezygapophyses of the arch behind. Haemal arches probably lay between
but below the neural arches, separated from them by a great deal of cartilage (as they
were in Uranocentrodon).

Ribs (text-fig. 13)

Few rib series of the larger Triassic labyrinthodonts have been described. Among
these, ribs are best known in Paracyclotosaurus (Watson 1958) which has an almost
complete set. Huene (1922) figured a series of ribs of the large neorhachitome Sclero-
thorax. Bystrow (1944) showed a full series of ribs for the Permian seymouriamorph,
Kotlassia, as did White (1939) for Seymouria. Finally, the ribs of Eryops are well known,
and Olsen (1936) has restored their musculature.

Although there is tremendous individual variation in the ribs it is possible to establish
a basic morphological plan. The ribs are single headed but the head is clearly divided
into ventral capitular and dorsal tubercular areas, so that it appears slipper-shaped in
proximal view. The end was cartilage capped and in life the cartilage probably divided
to give a double head. One rib, probably a posterior dorsal, with two heads supports
this supposition. From the tuberculum and capitulum, shafts of bone lead laterally to
merge on the antero-ventral border of the rib, forming its main shaft. Just distal to this
point is a ‘knee’ bend, so that the remainder of the bone curves postero-ventrally. The
‘knee’ is present in all ribs (although it is not sharp in the most posterior caudals),
unlike the situation in Paracyclotosaurus where the posterior thoracic ribs are straight.
The rib shaft terminates distally in an unfinished oval facet (the distal articulation)
which would have continued as a cartilaginous connection to the sternum. Postero-
dorsally, the shaft is drawn out to form a thin shelf of bone which in some cases runs
the length of the rib from the tuberculum to the distal articulation, while in others it is
a mere indication of a ridge. A cross-section of the rib anywhere along this shelf has
a comma shape, the main shaft forming the head of the comma, and giving off the dorsal
shelf as its tail. From the shelf develop the characteristic uncinate processes which are
found in most larger labyrinthodonts. These processes are fairly small in F.R.P. 48 a,
but in addition to them the distal end of the shelf is expanded so that there are usually
two (and in one certain case (text-fig. 13B), three) posteriorly directed processes on
each rib. Thus all ribs have two heads, a shaft with a ‘knee’ bend, and some sort of
expansion of the shaft.

Cervical ribs are apparently missing in the collection, but a cervical rib count of
two seems likely.

Rib A is like rib 4 of Paracyclotosaurus and is the largest of all ribs preserved. Re-
markable for the massiveness of its shaft and especially for the great distal expansion of
the dorsal shelf, it is placed as the first thoracic rib so that it acts as a support for the
shoulder girdle.

Of the ribs illustrated in text-fig. 13, rib D is fairly typical of anterior thoracic ribs,

PALAEONTOLOGY, VOLUME 13

228

text-fig. 13. Parotosaurus pronus sp. nov. a, sacral rib; b, rib d; c, rib X ( x J). a, antero-dorsal views;
b, posterior views ; c, postero-ventral views. On the right are proximal and on the left distal outlines

of the rib ends.

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 229

while rib X resembles the 32nd rib of Paracyclotosaurus davidi (the 4th posterior to the
sacrum). Moving posteriorly along the series from rib D to rib X there is a gradual
decrease in over-all size of the rib accompanied by a more distal position of the uncinate
process and the reduction and eventual loss of the distal expansion.

P. pronus sacral rib (text-fig. 13) resembles both the cervical and sacral ribs of Para-
cyclotosaurus davidi. The rib has well-developed capitular and tubercular areas. Its
distal end is expanded to almost the same extent as its proximal end but has twisted to
face anteriorly while the proximal end faces antero-dorsally. On its anterior face,
prominent ridges run from all four corners of the bone to meet near the middle of the
shaft.

A B C

text-fig. 14. Largest sacral rib of ? reptile ( x |). A, ventral view; b, medial view; c, dorsal view.

This rib is remarkably like the sacral rib of Benthosuchus sushkini (Bystrow and Efre-
mov 1940, fig. 41) although the extremities of the latter are less well ossified: the same
muscular ‘cristae’ are present, and the distal ends of the two ribs are almost indis-
tinguishable. The rib lacks the double processes for articulation with the ilium seen in
Paracyclotosaurus, but this region was restored by Watson. A similar rib was restored
in Buettneria’s pelvis by Sawin (1945).

In the collection from field locality F.R.P. 48 is another series of sacral ribs.

The largest of these is the best preserved (text-fig. 14). It has an extremely short, thick
shaft, and the proximal and distal ends are greatly expanded at right angles to the
shaft. Two proximal articular areas are apparent: a rounded capitulum, and running
from this, a narrow, elongate tuberculum. Both were finished by cartilage. A strong
rounded spine runs laterally from the capitulum to end medial to the anterior part of
the distal expansion, while a shorter spine connects the tuberculum with the posterior
part of the expansion. This distal expansion for articulation with the ilium is slipper-
shaped and curves a little dorsomedially, this ‘instep’ leading dorsally on to the bone
shaft. The proximal end of the rib is twisted roughly 50° relative to the distal end.

This second type of rib is like the one described by Romer (1947) as being typical of
labyrinthodonts. Certainly, variations of this rib are seen, for example, in Pelto-
batrachus (Panchen 1959), Parioxys (Shawki Moustafa 1955), Cacops (Williston 1910),
and Kotlassia (Bystrow 1944). However, this type of sacral rib is also seen in reptiles,
especially dinosaurs and in the present case it seems more likely that the shorter type of
sacral rib belonged to a reptile associated with the remains. Supporting this con-
clusion is the presence of two elongate bones which can only be interpreted here as
ischia of a large Triassic reptile, probably an early member of the Sauropodomorpha

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PALAEONTOLOGY, VOLUME 13

(Huene 1932). The sacral rib series and ischia are of a comparable size and could well
have come from the same pelvic girdle.

It seems that in labyrinthodonts the sacral rib may be one of two types. The squat
type described by Romer tends to be associated with mainly terrestrial labyrinthodonts !
with fairly well-developed locomotory powers and expanded iliac blades. In this case
the animal has a deep-sided pelvis. The second, elongate type of sacral rib is found in
labyrinthodonts which are larger, but flattened, and are probably totally aquatic. These
have unexpanded ilia and much cartilage in the pelvis, the pubis being rarely ossified.
The ischia in this case incline outwards so the pelvic girdle is dorso-ventrally flattened.

Reconstruction of the ribs

The ribs as preserved are incomplete both proximally and distally and most have
some part of the dorsal shelf missing. The latter has been restored in the figures as
described above. No attempt has been made to envisage the restored distal end of the
ribs except to note that there was probably some cartilaginous connection to a sternum,
at least in the more anterior ribs.

However, some attempt has been made to restore the proximal end of the rib, and to
fit the ribs to the vertebral column. It is apparent that the rib head as preserved will not
fit the arrangement of a diapophysis and parapophysis on the vertebra, and that to
make this fit a greater length of cartilage will have to be added to the capitulum than to
the tuberculum. The fit of the tuberculum to the diapophysis is remarkably good in P.
pronus, and Watson has noted a similarly good fit between these facets in Paracycloto-
saurus. Thus it seems likely that the cartilaginous caps on the tuberculum and diapophy-
sis were thin. If it is assumed that the cartilage between the capitulum and the parapophy-
sis belonged entirely to the capitulum then it can be seen that the capitulum of an
anterior thoracic rib would need to be extended by over a centimetre of cartilage. This
is approximately the situation reported by Watson in Paracyclotosaurus, and ribs of
Mastodonsaurus have been preserved with an ossified capitulum which extends medially
in this manner (Wepfer 1923).

Thus restored the rib head fits on to the vertebra with its dorsal shelf sloping back-
wards. In the anterior ribs successive uncinate processes probably overlapped, possibly
so that their surfaces touched.

It was noted in reconstructing the vertebrae that while the tubercular rib head was
almost the same size and shape as the diapophysis, the capitular head was much smaller
than the parapophysis and seemed to lie across its long axis. Now the proximal ends of
the ribs lie in an almost horizontal longitudinal plane, so that any movement made by
the rib would be expected to occur in a dorso-ventral direction rather than an antero-
dorsal direction. Assuming that the rib was involved in dorso-ventral movements, it
becomes possible to explain the larger size of the parapophysis. As the capitulum is
longer than the tuberculum it can be seen that if the rib is depressed or raised using the
tuberculum-diapophysis facet as a pivot, the capitulum will move a greater distance
than the tuberculum. This movement will be along an antero-dorsal to postero-ventral
line, that is, in the same line as the long axis of the parapophysis. Thus, if the rib is
depressed the capitulum would move dorsally on the parapophysis. Movements of ribs
used, for example, in respiration are more likely to be in a downwards direction but it is
probable that a little dorsal movement was also possible. The capitulum has therefore

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 231

been placed in a resting position a little above the lower limit of the diapophysis. If this
interpretation is correct, and the intercentra have been arranged in their correct order,
then the anterior ribs seem to have moved less than the posterior ones.

Pectoral girdle

Two interclavicles, two left and two right clavicles, one left and one right cleithrum,
and one primary girdle element, a right scapulo-coracoid, were found. By inspection of
their articular facets it can be shown that the interclavicles and clavicles form two
complete sets, one a little larger than the other. It is less easy to fit the cleithra to their
respective clavicles, but the approximate clavicle-cleithrum relationship can be deduced.
The scapulocoracoid is small and badly preserved, and could belong to either of the
dermal girdles. All pectoral girdle elements are reasonably well known in Triassic
labyrinthodonts.

Interclavicle (text-fig. 16). The interclavicles have the typical parotosaur shape as
shown by Welles and Cosgriff (1965).

The lateral interclavicular trabeculae on the ventral surface of the bones (Bystrow
and Efremov 1940, Welles and Cosgriff- 1965) are particularly prominent, but the
sternal trabeculae are small. In the smaller specimen, an anterior trabecula arises
opposite the sternal trabecula, and leads anteriorly to the base of the interclavicle’s
stem.

The ventral areas for articulation with the clavicles are deeply ridged especially above
the lateral trabeculae. Similar ridges on the dorsal surface of the clavicles undoubtedly
intermeshed with these, a system which apparently restricted movement between the
elements.

Clavicle (text-fig. 15). The general shape of the clavicles is similar to that seen in Para-
j cyclotosaurus davidi.

The clavicles also have well-developed trabeculae. These stretch from the median
■ border of the clavicle, from a position below the lateral interclavicular trabeculae, to
the base of the dorsal process at which point the thickened bone of the trabeculae is
continued upwards and a little medially as a dorsal spine. This spine runs postero-
dorsally to draw out the upper corner of the dorsal process into a backwards-facing
ridged articulation for the cleithrum. On the external surface of the dorsal process an
extensive antero-dorsally facing area in front of the spine is roughened according to
Watson (1958) for the cleidomastoideus muscle.

Cleithrum (text-fig. 16). The cleithra show similar features to cleithra of Benthosuchus
sushkini described by Bystrow and Efremov (1940).

In their natural orientation each cleithrum continues the postero-dorsal slope taken
by the dorsal spine of the dorsal process on the clavicle. An area for attachment to the
clavicle is shown by a system of coarse longitudinal ridges on the ventral half of the
anterior face. Above the clavicular articulation the crista cleithralis (Bystrow and
Efremov 1940) is represented by a pair of small hooked processes which expand the
; head of the cleithrum. Diametrically opposite this crista is a posteriorly directed flange,

: the lamina suprascapularis (Bystrow and Efremov 1940) which leads into a deep,

J vertically elongated recess in the head of the bone. The recess is continued ventrally as

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PALAEONTOLOGY, VOLUME 13

B

text-fig. 15. Smaller right clavicle (reversed) (x£). a, antero-lateral
view; b, postero-medial view; c, posterior view.

text-fig. 16. Parotosaurus pronus sp. nov. a, reconstruction of the smaller
pectoral girdle, lateral view; b, unreconstructed scapulocoracoid, lateral
view ( x 1).

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 233

a groove which is at first narrow but later broadens to fill the whole width of the median
surface. This area undoubtedly clasped the cartilaginous anterior border of the scapulo-
coracoid.

Scapulocoracoid (text-fig. 16). If, as seems likely, this bone resembled the scapulocoracoid
of Parotosaurus peabodyi (Welles and Cosgriff 1965) or Wetlugasaurus sp. (Riabinin
1930) then the thinner, lateral coracoid portion of the bone is missing.

The actual glenoid region is unossified but the articular facet was undoubtedly just
postero-lateral to the expanded base of the scapulocoracoid. This expanded area, the
supraglenoid buttress, is more extensive than it is in Paracyclotosaurus, and shows an
antero-ventromesial process divided from the characteristically flattened rectangular
buttress by a shallow recess.

The extent of the coracoid process is variable in related types. In Paracyclotosaurus it
is narrow. In Parotosaurus peabodyi, on the other hand, the process is wide ventrally,
but narrow dorsally. Close examination of the area of origin of the coracoid process
in the present case reveals that only a small section of bone is actually broken, the rest
of the roughened surfaces being finished in cartilage. Thus, the coracoid process was
probably like the smaller one in Wetlugasaurus sp., and even more like the immature
scapulocoracoid of Benthosuchus (Bystrow and Efremov 1940, fig. 76, d). It is not sur-
prising that P. pronus scapulocoracoid probably resembled an immature form as the
whole skeleton is poorly ossified when compared with earlier or more terrestrial laby-
rinthodonts.

As the ventral part of the coracoid plate is missing, the lateral view of the bone is
almost a longitudinal section. Thus the supracoracoid foramen is seen in section as a
deep recess arising posteriorly near the middle of the bone, and extending antero-
ventrally across it. The canal would probably have been closed laterally by bone (as it
is in Wetlugasaurus sp.) and was rounded, unlike the elongate foramen closed (pre-
sumably) by cartilage in Benthosuchus.

The narrow dorsal and anterior edges of the scapula blade apparently supported an
extensive cartilaginous cap. Dorsally this occupied the position of a suprascapula, while
laterally it formed a connection with the posterior face of the cleithrum.

The posterior margin is a true edge which curves forward from just below the dorsal
cartilage cap to the median edge of the supraglenoid buttress.

Medially, the existing surface is vertically flat, but falls away slightly anteriorly as the
subscapular fossa (Sawin 1945). Ventro-medially, behind the supraglenoid buttress is a
deep, rounded groove which was presumably finished by cartilage to form the glenoid
foramen (Riabinin 1930).

Reconstruction of the pectoral girdle (text-fig. 16). In reconstructing the pectoral girdle
of P. pronus the position of all dermal elements was easily established. It seemed best
to restore the scapulocoracoid in a high position. This allows a characteristic overlap
of the cleithrum dorsally, and sufficient room for the glenoid cavity to be placed so that
the head of the humerus can be clear of the ground.

The girdle as a whole is extensively dorso-ventrally flattened with relatively enormous
dermal elements and reduced primary girdle. The clavicles-interclavicle complex forms
an immense, ventral plate beneath the pectoral region.

The poor state of ossification of the scapulocoracoid of P. pronus indicates a weakly

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PALAEONTOLOGY, VOLUME 13

developed fore limb, a theory supported by the equally poorly ossified condition of the
fore limb bones. Thus it seems that the massive dermal shoulder girdle had little to do
with locomotion: consideration (below) of the thickened trabeculae on the clavicles
and interclavicle indicates a function for it other than limb muscle support.

Fore limb

The fore limb bones consist of a left and a right humerus, radius, and ulna. Proximal
and distal ends of all the limb bones were finished in cartilage.

Humerus (text-fig. 17). The humerus is of the reduced tetrahedral type described
by Watson in Paracyclotosaurus (the humerus illustrated by Watson is a left one and
has been incorrectly labelled right). Thus the strong muscular processes seen in Eryops
(Miner 1925) or Acheloma (Romer 1922) have been reduced, and less of the distal and
proximal ends of the bone are ossified. There are no ectepicondylar or entepicondylar
foramina.

On the proximal-dorsal surface the deltoid crest is prominent as is the antero-distal
supinator crest.

Radius (text-fig. 17). The radius has an almost straight shaft which is flattened ventrally
(posteriorly) and has its ends expanded and cupped to house their terminal cartilages.
The proximal end is rounded except ventrally, while the distal end is also flattened
postero-dorsally so that it is almost triangular in cross-section. Low ridges lie laterally,
anteriorly and medially on the shaft, and the last named forms a distal process directed
towards the ulna. There are no easily identified muscle origins or insertions.

Ulna (text-fig. 17). The lateral edge of the ulna is almost vertical, but the medial border
is concave, so that the proximal and distal ends of the bone are expanded towards the
radius. In proximal view, the cap of the ulna is rhomboidal, and the postero-lateral
corner of the rhombus is raised above the other corners as a short olecranon process.
Opposite the process, on the median edge of the rhombus is a characteristic depression.
The distal end is almost rectangular but narrows on the radial side and is sub-divided
into median and lateral facets. The shaft of the ulna is squared proximally, becomes
thin and rounded in the middle, and is expanded distally in an anterior-posterior plane.
Proximally, the lateral, medial and flexor faces of the shaft are depressed and roughened
for muscle attachment.

Pelvic girdle

The pelvic girdle is represented by a left and a right ilium and a left and a right
ischium. As these are of comparable size it seems likely that they are from the same
girdle. There is no evidence of pubes but these are rarely ossified in contemporary
related forms.

Ilium (text-fig. 18). The two ilia resemble those of Paracyclotosaurus but the blade shows
a greater posterior slope. Dorsally on the antero-medial surface of the ilium is a vertical
series of ridges, presumably for ligamentous attachment.

Ischium (text-fig. 18). The ischia are unremarkable. They are almost identical, though a

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 235

text-fig. 17. Parotosaurus pronus sp. nov. 1. Humerus, a, distal dorsal view; b, proximal ventral
view; c, distal ventral view; d, proximal ventral view. 2, Ulna; 3, Radius, a, dorsal view; b, anterior
view; c, ventral view; d, posterior view. All xf approx.

little larger, to those of Buettneria (Sawin 1945). Paracyclotosaurus has similar ischia,
but they are more antero-posteriorly elongate.

The reconstructed pelvic girdle is flattened dorso-ventrally, with the iliac blades well
separated dorsally. The sacral rib slopes backwards along the same lines as its neigh-
bouring ribs : its area of contact with the ilium is vertical and narrow, but was apparently
extended by cartilage in the living animal. This positioning of the sacral rib so that its
iliac contact lies well behind the level of the sacral vertebra seems a weak arrangement,
but other species such as the salamander Megalobatrachus are similarly built.

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PALAEONTOLOGY, VOLUME 13

An area in front of the ischia was presumably filled by cartilaginous pubes: Watson
has found impressions of flat oval elements with ossification in this region in Para-
cyclotosaurus.

A B

text-fig. 18. Reconstruction of the pelvic girdle (x£). a, lateral view; b, dorsal view.

Hind limb

The collection contains one left and two right femora, a left and a right tibia, and a
right fibula.

Femur (text-fig. 19). Except for its smaller size the femur resembles the Paracycloto-
saurus femur described by Watson.

Tibia (text-fig. 19). Proximally, the tibia is greatly expanded anteriorly (dorsally), medially
and laterally but posteriorly (ventrally) the surface is concave. This massive head tapers
to form a shaft which is circular but for a broad dorsal ridge leading distally from the
‘knee’ region to the smaller distal end. One especially prominent muscle scar covers the
proximal and anterior ‘knee’ region and is equivalent to the tuberositas tibiae of Bys-
trow and Efremov (1940): their ventral crista posterior is present proximally as a
sharp, low ridge anterior to the posterior concavity mentioned above, but fails to extend
further along the shaft.

Fibula (text-fig. 19). The fibula is remarkably like the ones described by Bystrow and
Efremov (1940) in Benthosuchus and Case (1932) in Buettneria. The most characteristic
feature of this and fibulae of related types is a reflection of the distal medio-ventral
corner of the bone forming a groove (the sulca fibularis of Bystrow and Efremov)
between it and the shaft. Muscle scars are concentrated about the extremities of the
fibula, but posteriorly there is one large scar in the middle of the shaft.

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 237

text-fig. 19. Parotosaurus pronus sp. nov. 1, Femur; 2, Fibula; 3, Tibia. ( X -|). a, dorsal view;
b, anterior view; c, ventral view; d, posterior view.

238

Other limb bones

PALAEONTOLOGY, VOLUME 13

Fourteen smaller limb bones were found. Twelve of these are of roughly the same
shape but of varying sizes and are probably phalangeal bones, metacarpals, and meta-
tarsals. These are elongated, a little dorso-ventrally (antero-posteriorly) flattened, and
have their ends expanded. The two remaining bones are paired and could be carpals
or tarsals. They are smaller and thicker than the above and have one end compressed
at right angles to the other.

DISCUSSION

Dermal pectoral girdle

Prominent on the interclavicle are the lateral trabeculae which lead from the centre of
ossification of the bone to its lateral corners. It is evident that the trabeculae are thickest
where they meet and underlie the postero-lateral edge of the clavicles. Here is the
region of maximum contact between interclavicle and clavicles with maximum inter-
locking between their articular surfaces. The clavicles in their turn are thickest in this
region. This is the lateral limit of the clavicular trabeculae which lead to the centre of
ossification of the clavicle at the base of the dorsal process and are continued dorsally
as the clavicular spine. This series of trabeculae is a system of struts well sited to counter-
act an upwards and forwards pull on the dorsal process of the clavicle. The cleidomast-
oideus muscle (if Watson’s interpetation of the scar on the external antero-dorsal
corner of the dorsal process of the clavicle is correct) is in a position to create just such
a pull. In support of this theory is the fact that only the larger, flattened, aquatic laby-
rinthodonts with similar interclavicles to P. pronus have well-developed trabeculae,
and in all these types the dorsal process of the clavicle has an enlarged cleidomast-
oideus muscle scar (especially Buettneria (Sawin 1945, fig. 9a), Benthosuchus (Bystrow
and Efremov 1940, figs. 44, 45), Paracyclotosaurus (Watson 1958, figs. 10, 11)). A
possible reason for the enlarged cleidomastoideus muscle in these flattened forms will
be discussed below.

It is evident that a strong framework in this area would also be necessary because the
animal is large and flat. A flattened girdle means that the legs are far apart. In this
position the fore limbs, working together, could, theoretically, raise the anterior part of
the body off the ground, but only if the area between them was stiff. In fact if the girdle
was stiff, it would take no more effort to lift the weight above it from two points near
the girdle’s edges, than from two points near its centre. To prevent the animal collapsing,
a system of struts would be required similar to that needed to resist the pull of a strong
cleidomastoideus muscle. But in this case the pull would act on the back of the dorsal
process of the clavicle, via the scapulocoracoid and cleithrum.

The girdle undoubtedly also functioned to protect thoracic organs from pressures
from the ground.

The flattened dermal pectoral girdle of capitosaurs is thus of use in three ways: as
a framework for a system of ridges backing up the cleidomastoideus muscle, as a strut
for the pectoral region, and as a protection for the anterior viscera.

Jaw opening

When discussing the jaw musculature of Paracyclotosaurus davidi in 1958, Watson
noted: ‘The relative position of the occipital and quadrate condyles shows that if the

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 239

lower jaw rested on the ground, as must often have been the case, it would move forward
as the mouth was opened by raising the skull.’ In 1962 he postulates, in the same animal,
a ‘great muscle, the musculus depressor mandibulae’, attached to the retro-articular
process of the lower jaw and ‘inserted onto the posterior edge of the dermal skull roof
at the highest possible point, contraction of which will raise the skull if the lower jaw
rests on the ground' (my emphasis). Panchen (1959) also uses the depressor mandibulae
to raise the skull in brachyopids and plagiosaurs. But he suggests that occipital muscles
combined with the depressor to lift the skull. However, there is an alternate system of
muscles which could be used in jaw opening to overcome some of the difficulties in-
herent in the above schemes.

Watson’s scheme employs both the occipital condyles and the quadrate condyles in a
movement governed by a single muscle. This could function only if the two sets of
condyles were in the same transverse line, otherwise, if it is assumed that the atlas does
not move posteriorly when the skull is raised against the atlas using the articular as
fulcrum then :

(a) If the occipital condyles were in the same transverse plane as, but above the
quadrate condyles, the vertebral column would be depressed as the skull was
raised,

( b ) If the occipital condyles were in the same horizontal plane as, but in front of the
quadrate condyles, the column would be elevated as the skull was raised, or

(c) If the occipital condyles were in the same horizontal plane as, but behind the
quadrate condyles, the vertebral column would again be depressed as the skull
was raised.

Watson realized this and employed point ( b ) when he showed that Eryops could not
raise its skull (1951). But he disregarded it when he noted (1951) that in capitosaurs the
! lower jaw would move forward as the skull was raised. True, capitosaurs are approach-
ing the ideal situation for Watson’s scheme, and some of them (especially Parotosaurus
orenbergensis, Konzhukova 1965), seem to have reached it.

Brachyopids, however, are far from it. In them, the occipital condyles are well
behind and above the quadrate condyles, and it can be seen (text-fig. 20) that using the
depressor mandibulae muscle to raise the skull (as shown by Panchen) must force the
occipital condyle ventrally, and with it the whole vertebral column. In brachyopids this
depression is considerable (more than one-quarter of the body depth) and implies that
either the pectoral girdle was very loosely connected to the vertebral column, or that
the pectoral area was held clear of the ground, a most unlikely position if the mandible
must be grounded.

Brachyopids, having their occipital condyles behind and above the quadrate condyles,
better illustrate a second difficulty: than an animal whose lower jaw shoots forward as
it must in a brachyopid when it raises its skull, is unlikely to be relying on that jaw for
leverage against the ground. Panchen likens the brachyopid jaw movement to that of
an active, predatory fish, implying a rapid action. But for the skull to be raised by a
depressor muscle, the lower jaw must be on the ground; if it was not, contraction of the
depressor would lower the jaw, not raise the skull. No other system supports the lower
jaw except the adductor muscles, and these are antagonistic to the depressor: if they
I were relaxed, and the jaw was not on the ground, again the depressor would lower the

C 7393

R

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PALAEONTOLOGY, VOLUME 13

text-fig. 20. A brachyopid skull ( Batrachosuchus ) in profile, a, Skull with jaws
closed, b. Skull to show the method of opening the jaws by raising the skull by con-
traction of the depressor mandibulae muscle as depicted by Panchen (1959). Note
depression of the vertebral column, c, Skull to to show method of opening the jaws
by 1, contraction of the muscles between the occiput and the vertebrae to raise the
skull, and 2, contraction of the depressor mandibulae muscle to lower the lower
jaw. Note that the vertebral column has not been depressed and that the lower jaw
is clear of the ground. Skull outline from Watson’s figure of Batrachosuchus (1956,
text, fig. 5). Lower jaw from Panchen’s (1959) reconstruction. Occipito-vertebral
muscles stippled. Depressor mandibulae muscle hatched. Batrachosuchus' s vertebrae
are restored following discussion with Dr. S. P. Welles who has a collection of inter-
centra which show that the brachyopids had rhachitomous vertebrae.

jaw. (Of course, when the animal was swimming it could feed by lowering the jaw, but
the rapid forward movement of the jaw characteristic of predatory fish could only
occur if the skull was raised.)

Finally, it is illuminating to consider the nature and attachments of the depressor
mandibulae muscle itself. Watson says that the muscle should be inserted on the highest
possible point of the skull roof. In capitosaurs this is the tabular. From the side, a

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 241

muscle inserted here looks feasible (Watson 1951, fig. 27). From behind, however, the
angle at which the muscle would have to function is poor: the depressor would have
almost as high a horizontal component as a vertical one. The situation in this case is
worsened by the nature of the quadrate condyles which are slightly screw-shaped, the
thread of the screw running from postero-lateral to antero-medial. A lower jaw rotating
about this condyle must necessarily move laterally so that the two rami separate slightly

text-fig. 21. Parotosaurus pronus skull in profile. A, skull with jaws closed. B, c, the
method of opening the jaws divided into two stages, b, contraction of the cleido-
mastoideus muscle to raise the skull (depressor muscles omitted); c, contraction of
the depressor mandibulae muscle to lower the lower jaw. Cleidomastoideus muscle
stippled. Depressor mandibulae muscle hatched.

at their median symphysis. This action would oppose the inward pull from the depressor
which would then be working at a double disadvantage. (However, it should be noted
that in brachyopids a depressor would have a better working angle as the cheek is
deeper, and the muscle could act from directly above the lower jaw.)

The proposed solution to these problems has two aspects (text-fig. 21b, c). First, the
skull is raised by specially developed occipital muscles using the occipital condyles as
the fulcrum, and, second, the lower jaw is lowered by contraction of the depressor
mandibulae muscle. In practice, the two muscles would work simultaneously (text-fig.
21c). The most obvious advantage of this system is that raising the skull against the
occipital condyles will elevate the quadrate condyles as well (that is, the opposite effect

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PALAEONTOLOGY, VOLUME 13

to the depression of the vertebral column resulting from Panchen’s scheme) and so the
lower jaw will be freed from the ground. Subsequent contraction of the depressor does
not need ground support as it is a lowering not a raising action. Under these conditions
the brachyopid jaw will shoot forward without interference from the ground.

There is evidence for a suitable occipital muscle in capitosaurs. Consideration of the
dermal girdle in Parotosaurus pronus (above) has indicated a well-developed system of
ridges which were interpreted as a support for an upwards and forwards pull by the
cleidomastoideus muscle. If the girdle is placed behind the skull it can be seen that the
area of attachment for the cleidomastoideus muscle on the dorsal process of the clavicle
is in the same plane (but behind and below) a pronounced ventro-lateral flange of the
tabular (text-figs. 3, 5). This flange runs from the tabular horn postero-ventro-medially
along the paroccipital process, ending just dorsal to the suture between the tabular and
the exoccipital. It is proposed that in capitosaurs this flange was the insertion of the
cleidomastoideus muscle which contracted to raise the skull. In this position, the
cleidomastoideus muscle would be working at an angle very similar to the depressor
muscle as visualized by Watson, but the lateral component would be reduced. However,
unlike the depressor, the cleidomastoideus muscle will not have to counteract the lateral
movement of the lower jaw. Miner (1925) restored part of the cleidomastoideus in
Eryops, attaching it to the squamosal and posterior part of the skull generally, with its
other end on the cleithrum, clavicle, and scapula, but he did not attempt a functional
explanation for it. It is interesting to note that Watson (1926) postulated, in embolo-
meres, a bony articulation between the tabular horn and the shoulder girdle via a post-
temporal element but Romer later (1947) considered that this was more likely to be a
ligamentous connection.

Use of this muscle in a skull-raising capacity may help to explain the (evolutionary)
lateral movement of the tabular horns (which eventually closed the otic notch in cycloto-
saurs), and the accompanying inward movement of the dorsal process of the clavicle
in these flattened forms, so that the origin and insertion of the cleidomastoideus came to
lie more in a longitudinal-vertical plane.

Occipito-vertebral muscles could have assisted the cleidomastoideus, but they are
unlikely to have formed the main skull-raising system in a capitosaur. A capitosaur
has a vertical occiput, so that the point of attachment of the occipital muscles is in the
same transverse plane as the occipital condyles. Consideration of text-fig. 22 shows that
a muscle attached between the occiput and the vertebral column could raise the skull
a certain amount, but it would only be really effective at the very beginning of its con-
traction, and it is doubtful whether this would be sufficient to account for the whole
range of opening. The clavicle, however, is positioned better in relation to the occiput,
and, if a muscle attached to it was used to raise the skull, the muscle would be at its
most effective position when the occiput had travelled backwards through approxi-
mately 25°, resulting in a narrow gape which will be shown below to be that most used
by a capitosaur. It thus seems highly probable that the cleidomastoideus formed the
main skull-raising muscle in a capitosaur, with the occipito-vertebral muscles perhaps
assisting at the start of the movement.

The situation is different in the brachyopids. Here the occiput slopes forward (text-
fig. 22) giving an occipito-vertebral muscle a greater effective range. It is probable,
therefore, that the brachyopid skull was at least partly raised by occipito-vertebral

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 243

text-fig. 22. Diagrams of lateral views of the skull and anterior vertebrae of
various labyrinthodonts to show the relationship of the occiput to the vertebral
column and pectoral girdle. The arcs which would be described by the point of
attachment of the occipital muscles on the skull when the latter is raised, are
indicated. No attempt is made to indicate the extent of the gape in the brachyopid
or plagiosaur but the capitosaur skull would probably not have opened further than
the arc suggests. Note that in a the dorsal process of the clavicle is in a better position
than the vertebrae for the attachment of a skull-raising muscle; in b the vertebral
column is in a better position than a (presumably) more ventral clavicle, but that in
c where the skull is held with its dorsal surface parallel to the vertebrae the position
is better still; in d the plagiosaur skull is held in a similar position, a, Parotosaurus
pronus ; B, c. Batrachosuchus as in text-fig. 20; D, Gerrothorax after Panchen (1959)
— vertebrae reconstructed from Nilsson’s (1937) figures of Gerrothorax rhaeticus.

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PALAEONTOLOGY, VOLUME 13

muscles (as suggested by Panchen) : these would certainly have a better initial moment
than a more ventral muscle from the pectoral girdle. Whether a pectoral or a vertebral
muscle was used cannot be determined until the vertebrae and pectoral girdle of
brachyopids are better known. It is evident that if a muscle from the clavicle was used
in an animal with a forward-sloping occiput, then the dorsal process of the clavicle
would have to be tall, at least as high as the vertebrae. Reconstruction of the clavicle of
Eobrachyops, an early brachyopid, from Watson’s (1956) figure and description, shows
that in that animal at least, the dorsal process was too short. Watson’s (1956) observa-
tion that in the brachyopid Platyceps wilkinsoni ‘the first three vertebrae seem to be some-
what more massively ossified than those farther back, but curiously there seem to be no
ossifications in the exoccipital condyles’ may lend support to the case for a vertebral
muscle.

The pectoral girdle is known in metoposaurs where the occiput is intermediate be-
tween capitosaurs and brachyopids, the occipital condyles projecting a little behind the
quadrate condyles, but being almost on a horizontal level with them. Here the area for
the cleidomastoideus muscles’ attachment to the clavicle is exceptionally well developed
(Sawin 1945, figs. 8e, 9a) and the muscle could apparently have been used to raise the
skull.

One point which becomes obvious when studying text-fig. 22 is that in order to in-
crease the mechanical advantage of the occipital muscles in the brachyopid and plagio-
saur skulls it would be necessary to increase the height of the neural arches. But neural
spines of these labyrinthodonts, where preserved, are low. However, the same result
would be achieved if, instead of the dorsal surface of the skull facing anteriorly, it was
horizontal, so that the vertebral column was parallel to the skull (text-fig. 22b). This
position is not unknown in aquatic animals: fish such as the herring have the skull
facing dorsally and the lower jaw facing antero-ventrally. This position of the skull
seems a more satisfactory arrangement for labyrinthodonts such as brachyopids and
plagiosaurs, with anteriorly sloping occiputs, but it would hold little advantage for a
capitosaur.

Retro-articular process

It is apparent in these labyrinthodonts that, for the depressor mandibulae muscle to
be effective, the greater the slope of the occiput, the longer must be the retro-articular
process. A better solution would be to have a shorter process which turned upward
(text-fig. 23) (as it does in capitosaurs). This would have the same effect as a long
retroarticular process except that the length of the muscle would be a little less.

Text-fig. 23 illustrates the position of the mandible in capitosaurs and plagiosaurs
at which the depressor mandibulae would be most effective. This indicates a narrow gape
in capitosaurs and a wide one in plagiosaurs (brachyopids being intermediate). If the
retro-articular process was turned dorsally (text-fig. 23c) in plagiosaurs it would be
possible for the depressor muscle to reach a point of maximum efficiency, but with a
straight process (text-fig. 23b) the point would not be reached. In the only brachyopid
jaw preserved with the retro-articular process intact, Bothriceps australis (Watson 1956),
the tip is turned up. In Batrachosuchus watsoni (Watson 1956), the retro-articular
process appears to turn up, but its tip is missing. Although the retro-articular process
is often said to be long in advanced Triassic labyrinthodonts no jaw has been described

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 245

where the process is complete and is longer than it is in Bothriceps. Panchen (1959) has
reconstructed a straight retro-articular process on the lower jaw of Gerrothorax from
Huene’s (1922) figures and description of the lower jaw of Plagiosuchus and Plagioster-
num but the posterior half of the process is missing in both these forms, and it is possible
that they did, in fact, turn dorsally.

A

B

C

text-fig. 23. Diagrammatic representations of the skulls and lower jaws of a
capitosaur and a plagiosaur to show the difference in their gapes with different
retro-articular processes, a is the angle through which the lower jaw will move
before the depressor mandibulae muscle meets the lower jaw at a right angle.
According to Parrington (1955) this is the position where the depressor muscle
achieves the greatest leverage on the lower jaw. dm are the points of origin
and insertion of the depressor muscle. Note that in a, a capitosaur, the gape is
narrow when angle a is reached. In b, a plagiosaur, the angle is never reached.
In c, a plagiosaur, the retro-articular process has been turned dorsally : now the
position of greatest leverage can theoretically be attained.

It was shown above that in capitosaurs the depressor mandibulae muscle would
appear to be most efficient when the gape was small. Additional factors actually prevent
the jaws opening far. It seems that in most capitosaurs the ventro-postero-lateral
corners of the quadratojugals are not preserved, presumably because they were cartila-
ginous. But in one or two cases (e.g. Cyclotosaurus posthumus, Fraas 1913) ossification
persists and it appears that the quadratojugals projected below the level of the quadrate
condyle. Now, the capitosaur condylar system is screw-shaped which necessitates an
outward movement of the articular along the quadrate as the jaws open. The ventro-
postero-lateral projection of the quadratojugals would prevent this movement beyond

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PALAEONTOLOGY, VOLUME 13

a certain point. Also limiting the gape is the post-condylar process of the surangular.
There are indications that this was tall, and if so, it would have prevented too great a
movement of the quadrate relative to the lower jaw.

The lateral screwing of the jaws, while not great, must increase with the gape and
this movement would have been against the action of the depressor muscles which
tend to pull the retro-articular process inwards as well as upwards. While the disad-
vantage of this action has largely been removed by using the depressor to lower the jaw
rather than raise the skull, it would undoubtedly become a limiting factor were the
jaws to try to open wide.

It seems, therefore, that the capitosaur cranial anatomy is adapted for keeping the
gape of the jaws fairly small, rather than for allowing them to open far.

The position of the eyes may have some bearing on this question. As the eyes are
placed far back and close together on the capitosaur skull, it is manifest that were the
jaw to open widely (by raising the skull), the animal would be unable to see. True, the
eyeball could probably be protruded as it is in modern frogs, but it is doubtful if this
protrusion would be enough to enable a capitosaur to see if its skull was raised far. It
seems significant that in many labyrinthodonts which are thought to have a wider
gape such as brachyopids and plagiosaurs, the eyes are larger and further forward on
the skull and would probably have been able to project sufficiently. Metoposaurs seem
intermediate : they undoubtedly had a wider gape than capitosaurs, and their eyes were
well forward.

Dorsal pterygoid canal

The floor of this canal can be seen in specimen 48 I (text-fig. 5a) and more of the
canal is shown in specimen 135 (text-fig. 6a). It runs from behind to enter the skull at an
abrupt face beside the stapes and above the conical recess and it is probable that the
canal carried the Vllth nerve with its accompanying blood vessels. If this dorsal foramen
and canal did carry nerve VII then the path of the nerve may have continued behind the
ascending oblique ridge of the pterygoid which begins near the posterior section of the
canal. This ridge rises obliquely and then turns laterally along the quadrate ramus of
the pterygoid to end at the quadrate. On the left of specimen 135 the distal lip of the
ridge almost meets the pterygoid to form a canal. On the right of the same skull, a
groove above the quadrate leads down and laterally to end near the paraquadrate fora-
men in the quadrat ojugal, and this foramen has been postulated by Bystrow and
Efremov (1940) as the point where the hyomandibular branch of nerve VII re-enters
the skull. If this system of canals did house VII it would adequately protect that nerve
from the depressor muscles. Watson (1962) describes in Rhine ceps and Wetlugasaurus
a stapedial groove which corresponds in position to the oblique ridge on the pterygoid
and suggests that this groove housed the stapes. This may have been the case in other
forms but in P. pronus the groove is much too small and extends too far laterally.
Watson notes this lateral elongation and suggests that the outer section of the groove
was to carry the ligamentous attachment of the stapes to the quadrate. But if this was
its sole purpose, the groove should have run towards the quadrate ‘boss’, shown by
Westoll (1943) to be the probable point of attachment of the quadrate ligament from the
stapes. This is not the case, as study of the same specimen of Rhineceps shows a distinct
shallow groove which originates at the lateral limit of the oblique ridge and by-passes

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 247

the quadrate boss, passing above it in just the position predicted for a nerve stretching
from the end of the oblique ridge of the paraquadrate foramen. There seems no reason
why in species where the oblique ridge obviously was large enough and in a position
to carry the stapes it should not have also carried the Vllth nerve.

The stereo spondylous vertebra

It is generally agreed that the stereospondylous centrum is an intercentrum (that is,
it corresponds to the intercentrum of amniotes), and that it lies beneath, but a little in
front of, the neural arch. Nilsson (1937, fig. 16) places the neural arch of Mastodon-
saurus in this position and Watson (1958) does the same with Paracyclotosaurus.

A B

text-fig. 24. Diagrams of stereospondylous vertebrae showing the two possible
arrangements of the neural arch on the intercentrum, a, conventional position,
b, correct position. Note 1 . The necessity to notch the intercentrum dorsally in a.

2. The relationships of the diapophysis to the parapophysis in a which would make
it impossible to fit the type of rib found in stereospondylous labyrinthodonts to the
vertebra.

However, Chowdhury (1965, fig. 7) notes the presence of both anterior and posterior
facets in stereospondylous intercentra which he assumes belong to Metoposaurus, but
he also suggests articulating the centrum with only the ventral (posterior) facet of the
neural arch. This position agrees with conclusions reached (above) about the arrange-
ment in Parotosaurus pronus. However, in this position the intercentrum is articulating
with the smaller, anterior, neural arch facet, while the larger more posterior, ventral
facet is not accounted for.

Watson, in 1958, notes that this ventral neural arch facet is for the pleurocentrum, a
statement undoubtedly true for rhachitomes and neorhachitomes, including P. pronus.
But in view of the fact that Chowdhury shows two articular facets on a stereospondylous
intercentrum (even labelling them anterior neural arch facet and posterior neural arch
facet), it seems likely that the neural arch of stereospondyls is morphologically inter-
vertebral, so that the anterior facet of the intercentrum actually articulated with the
large posterior facet of the neural arch anterior to it (text-fig. 24).

The vertebral column

Parrington (1967) has noted the disproportionate size of the head in typical labyrin-
thodonts and the fact that this must have resulted in a forward displacement of the
centre of gravity with resulting problems when the mode of walking is considered. And

248

PALAEONTOLOGY, VOLUME 13

he has suggested that a rhachitomous vertebral column served the purpose of allowing
considerable twist to the short presacral vertebral column enabling the animal to raise
the front end of the body on the appropriate side at each step of a fore limb, and so
reposition the centre of gravity of the body above the triangle of support offered by the
three legs remaining on the ground. He notes, however, that the principle may not have
applied to the larger Triassic forms which may have lived largely in water and never
have walked with the body clear of the ground. In addition, Watson (1958) has sugges-
ted that Paracyclotosaurus may have been of almost neutral buoyancy and that it
moved in water by touching the ground with its digits (much as does the ‘walking’
lungfish). It seems therefore that in capitosaurs and stereospondyls the rhachitomous
type of vertebra is no longer essential for locomotion (in Parrington’s sense).

It was once thought that all capitosaurs were truly stereospondylous, but work by
Bystrow and Efremov and others recognized in them the neorhachitomous condition
of well-developed intercentrum with reduced bony or cartilaginous pleurocentrum.
Watson (1958) has dotted pleurocentra in Paracyclotosaurus but none have been found
ossified in capitosaurs other than in P. pronus. These are obviously mere remnants of
the true rhachitomous pleurocentra, and it seems clear that the vertebrae are becoming
stereospondylous. If it is accepted that the rhachitomous condition has become un-
necessary for locomotion it becomes important to try to explain the advantage of the
stereospondylous condition.

Among labyrinthodonts two types of vertebrae are particularly associated with
aquatic life: embolomerous and stereospondylous. Parrington (1967) has suggested
that the embolomerous condition allows an eel-like form of locomotion in long-bodied
types, the greater number of central units allowing a greater flexibility in a lateral plane.
As far as they are known the stereospondyls were comparatively short-bodied and
therefore could not have swum by lateral undulations, and so some other method must
have sufficed. Probably the capitosaurs and other typical stereospondyls swam by
flexion of the tail which propelled the animal forward while the body remained largely
stiff, much as do tadpoles. Although Watson restored Paracyclotosaurus with a fairly
short tail of about twenty-five vertebrae, there is evidence that some neorhachitomes
at least may have had a longer tail. According to van Hoepen (1915) the neorhachitome
Uranocentrodon senekalensis had ‘at least thirty-six caudal vertebrae and may have had
forty-six’. Huene (1922) figured the intercentra of Mastodonsaurus giganteus, only
showing a representative number of caudal vertebrae but noting that in all probability
the tail was very long.

Often in capitosaurs the anterior vertebrae are almost stereospondylous, but the
development of the intercentra decreases towards the tail, the posterior presacral and
caudal vertebrae remaining in the rhachitomous condition. This is shown in Huene’s
figure of M. giganteus (1922, fig. 2) and is also present in Paracyclotosaurus , and, to a
much lesser extent in Parotosaurus pronus. In short, it seems that, during the Trias, in
capitosaur-like labyrinthodonts there is a gradual tendency towards stereospondyly in
the presacral vertebrae, while the tail tends to remain rhachitomous. Force produced
by a tail used as a propulsive organ must be transmitted through the vertebral column,
and a reasonably rigid strut will best serve to transmit this force. The tail, however,
would be more flexible if it remained rhachitomous. Flexibility is no doubt increased
by a large core of cartilage in the tail and Van Hoepen’s photograph of Uranocentrodon

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 249

tail vertebrae, preserved in what appears to be their natural position, shows neural
arches and haemal arches well separated, presumably by cartilage.

It seems, then, that the neorhachitomous tail could have been a flexible structure
with isolated dorsal and ventral ossifications, perhaps providing a framework for the
attachment of a tail fin; while the neorhachitomous presacral vertebral column was a
fairly rigid strut which transmitted the propulsive force produced by the tail to the body.

Taxonomic position

As is well known, the type specimen of Capitosaurus, C. arenaceus, is indeterminate
as its otic region is not preserved and, as an Upper Triassic form, it is probably a
cyclotosaur. Jaekel (1922) recognized this and coined the term Parotosaurus to refer to
capitosaurs. Romer (1947) concurs, suggesting that Capitosaurus be confined to the
type, while Parotosaurus should refer to the Early Triassic ‘ Capitosaurus ’ with open otic
notch, and Cyclotosaurus to the Upper Triassic closed otic notch type. Welles and
Cosgriff, in their much-needed (1965) revision of the family Capitosauridae, decided
to follow this scheme, but dropped Capitosaurus altogether, the type becoming Paroto-
saurus arenaceus. Further, they lump the twenty-nine genera of Triassic ‘capitosaurs’
into four, of which three, Cyclotosaurus, Parotosaurus, and Paracyclotosaurus, are
Capitosauridae.

It is manifest that the present specimens are parotosaurs, but they cannot be fitted
into any of the eight parotosaur species retained by Welles and Cosgrilf, nor to P.
orenbergensis (Konzhukova 1965). They are thus deemed to belong to a new species,
Parotosaurus pronus. The species is defined by both cranial and post-cranial material,
although Welles and Crosgriff use only cranial characters (post-cranial material is not
available for most parotosaur species). It is felt that the separation of a species on
characters of the skull roof only, as has been done in the past, is a needless generaliza-
tion when description of post-cranial bones will often clarify a species.

Parotosaurus pronus is distinguished from other parotosaurs chiefly by the shape and
position of its tabular horn. In four of the ten species of Parotosaurus the tabulars
have grown laterally towards the squamosal, like they have in P. pronus. Of these, P.
semiclausus (Swinton 1927) is obviously different: the tabular is unexpanded distally,
and only just fails to meet the squamosal; the choanae and orbits are more rounded,
the former parallel the midline, while the latter parallel the skull margins; the pineal
foramen is rounder; the jugal is excluded from the orbital margin; and the sculpture is
large and coarse. Some of these characters could apply to a young individual of P.
pronus, but in that case the otic notch could be expected to be less, not more, closed in
the younger specimen.

Although the tabular horn of P. birdi (Brown 1933) and P. peabodyi have moved
laterally, they still have no distal expansion. In addition, P. peabodyi has a much
shallower occiput. Its vertebrae differ from those of P. pronus, both intercentrum and
neural arch being extensively antero-posteriorly compressed in the former. The occiput
of P. birdi is much nearer to P. pronus. However, P. birdi has a greater exposure of
exoccipital on the palate; the orbits are far apart and slope towards the otic notch; the
cultriform process is sharply keeled ; and the occipital area extends farther posteriorly,
behind the level of the quadrates.

The last of the four is P. brookvalensis (Watson 1958). This is the only other

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PALAEONTOLOGY, VOLUME 13

partosaur where the tabular is expanded distally as it is in P. pronus, but Watson’s
reconstruction shows this as a bulbous swelling of the horn, increasing its surface area
rather than causing it to approach the squamosal. P. brookvalensis could be thought
a juvenile P. pronus but for the character of its ornament and the length of its snout,
which are both adult in proportion.

In 1958, Watson divided the Capitosauridae into shallow-skulled and deep-skulled
lines. The latter contained Paracyclotosaurus davidi and ‘Paracyclotosaurus' hemprichi,
and he suggested that Parotosaurus pronus could well be their ancestor. Welles and Cos-
griff dissolved this grouping, returning ‘ Paracyclotosaurus ’ hemprichi to Cyclotosaurus.
Indeed, there seems little to link the former species apart from their depth of skull, and
Parotosaurus birdi and P. angustifrons seem just as deep.

It is possible that P. pronus is ancestral to Paracyclotosaurus davidi. Curiously, Para-
cyclotosaurus davidi is the only form where the otic notch is closed by unornamented
bone, this area being delimited from the tabular and squamosal by well defined ridges
which follow the lines of these bones. It seems possible that the notch is open, the gap
being filled by matrix. Certainly, it is unlike the semiclosed Parotosaurus semiclausus
where tabular and squamosal closely approach one another with their opposing edges
parallel. No closed otic notch type has a similar concavity in the posterior skull margin
behind the notch, and, if the link between tabular and squamosal be removed, Para-
cyclotosaurus davidi looks remarkably like a parotosaur. In dorsal view, its skull bone
arrangement is similar to Parotosaurus pronus, but the tabular differs in being expanded
proximally as well as distally. Such a character could, however, be advanced, and would
not preclude a relationship between the two. Other advanced characters of Paracyclo-
tosaurus davidi which could have come from Parotosaurus pronus are : a greater exposure
of exoccipital on the palate, and a reduction in ossification of the brain-case region, the
latter being especially noticeable in the absence of a processus lamellosus to support
the supra-occipital. It is harder to envisage the evolution of the Paracyclotosaurus
davidi rounded nostril from the oval in Parotosaurus pronus, or the unusually broad
cultriform process from P. pronus narrow, almost keeled one. One curious feature of
Watson’s reconstruction of Paracyclotosaurus davidi is the absence of an anterior palatal
vacuity, and a (possibly related) absence of tusks in the mandible. This would set P.
davidi apart from all other capitosaurs, but inspection of casts of the areas shows that
they were missing in the original. Unless Watson has other evidence for their absence, it
seems more likely that they were present.

The post-cranial skeleton is better ossified in P. davidi than Parotosaurus pronus,
and most differences in shape can be attributed to this. Intercentra have advanced
towards the stereospondylous condition. Rib structure, however, distinguishes the two
as P. pronus ribs all carry some development of uncinate process, usually accompanied
by a distal expansion, while Paracyclotosaurus davidi ribs have no process or expansion
beyond the seventh or eighth thoracic rib.

These comparisons lead to the conclusion that Parotosaurus pronus and Paracycloto-
saurus davidi are remarkably similar, but, while Parotosaurus pronus may be more
closely related to Paracyclotosaurus davidi than to other parotosaurs, there are some
features which preclude the former being directly ancestral.

Acknowledgements. The material described in this paper is from Dr. F. R. Parrington’s collection. I
am deeply grateful to him for loan of the material and for his constant help and advice as supervisor

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 251

of the work which was originally submitted for the degree of Ph.D. Cambridge. Thanks are also due
to Dr. A. L. Panchen, Dr. S. P. Welles, and Dr. T. S. Kemp for helpful discussions and to Mr. R. D.
Norman for general assistance.

The British Museum (Natural History) kindly lent me some casts of Paracyclotosaurus davidi, and
the Australian Museum donated a cast of Parotosaurus brookvalensis.

During the third year of the study the work was supported by a Commonwealth Scholarship.

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• 19436. On the morphology of the lower jaw of Stegocephalia with special reference to Eotriassic

stegocephalians from Spitzbergen. I Descriptive Part. K. svenska Vetensk Akad. Handl. 20 (9), 1-46,
9 pi.

1944. On the morphology of the lower jaw of Stegocephalia with special reference to Eotriassic

stegocephalians from Spitzbergen. II General Part. Ibid. 21, no. 1.
olson, e. c. 1936. Dorsal axial musculature of certain primitive Permian Tetrapods. J. Morph. 59,
265-311.

panchen, a. l. 1959. A new armoured amphibian from the Upper Permian of East Africa. Phil. Trans.
B, 242, 207-81, pi.

1966. The axial skeleton of the labyrinthodont Eogyrinus attheyi. J. Zool., Lond. 150, 199-222.

1967. The homologies of the labyrinthodont centrum. Evolution, Lancaster, Pa. 21, 24-33.

252

PALAEONTOLOGY, VOLUME 13

p Arrington, f. r. 1946. On the cranial anatomy of cynodonts. Proc. zool. Soc. Lond. 116, 181-97.

1967. The vertebrae of early tetrapods. Colloques bit. Cent. Natn. Rech. Scient. 163, 269.

riabinin, a. n. 1930. A labyrinthodont stegocephalian Wetlugasaurus angustifrons nov. gen., nov. sp.
from the Lower Triassic of Vetluga-Land in Northern Russia. Ezheg. russk. paleont. Obschch. 8,
49-76, 5 pi.

romer, a. s. 1922. The locomotor apparatus of certain primitive and mammal like reptiles. Bull. Am.
Mus. nat. Hist. 46, 517-606, 20 pi.

1947. Review of the Labyrinthodonta. Bull. Mus. comp. zool. Harv. 99, 1-352.

save-soderbergh, g. 1936. On the morphology of Triassic Stegocephalians from Spitzbergen, and
the interpretation of the endocranium in the Labyrinthodontia. K. svenska VetenskAkad. Handl. 16,
1-181, 22 pi.

sawin, h. j. 1945. Amphibians from the Dockum Triassic of Howard County, Texas. Univ. Tex.
Pubis. 4401, 361-99.

schroeder, h. 1913. Ein Stegocephalen-Schadel von Helgoland. Jb.preuss. geol. Landesanst. 33, 232-
64, 7 pi.

shawki moustafa, y. 1955. The skeletal structure of Parioxys ferricolus Cope. Bull. Inst. Egypte, 36,
41-76, 9 pi.

stockley, G. m. 1932. The geology of the Ruhuhu Coalfields, Tanganyika Territory. Q. Jl geol. Soc.
Lond. 88, 610-22.

and oates, f. 1931. The Ruhuhu Coalfields, Tanganyika Territory. Mining. Mag. 45, 73-91.

watson, d. m. s. 1919. The structure, evolution and origin of the Amphibia. — The ‘orders’ Rachitomi
and Stereospondyli. Phil. Trans. B, 209, 1-73, 2 pi.

1926. Croonian Lecture. The evolution and origin of the Amphibia. Phil. Trans. B, 214, 189-257.

1951. Paleontology and modern biology. New Haven: Yale University Press.

1956. The brachyopid labyrinthodonts. Bull. Br. Mus. nat. Hist. 2, 317-92, 1 pi.

1958. A new labyrinthodont ( Paracyclotosaurus ) from the Upper Trias of New South Wales.

Bull. Br. Mus. nat. Hist. 3, 233-64, 5 pi.

1962. The evolution of the Labyrintodontia. Phil. Trans. B, 245, 219-65.

welles, s. p., and cosgriff, j. 1965. A Revision of the labyrinthodont Family Capitosauridae and a
description of Parotosaurus peabodyi n. sp. from the Wupatki Member of the Moenkopi Formation
of Northern Arizona. Univ. Calif. Pubis, geol. Sci. 54, 1-148, 1 pi.
wepfer, e. 1923. Cyclotosaurus papilio n. sp. aus der Grenzregion Muschelkalk-Lettenkohle des
nordlichen Baden, ein Beitrag zur Kenntnis des Stegocephalen-Hinterhauptes. Mit. bad. geol.
Landesanst. 9, 367-90, 2 pi.

westoll, t. s. 1943. The hyomandibular of Eusthenopteron and the tetrapod middle ear. Proc. R. Soc.
B, 131, 393-414.

white, t. e. 1939. Osteology of Seymouria baylorensis Broili. Bull. Mus. comp. Zool. Harv. 85, 325-
410, 3 pi.

williston, s. w. 1910. Cacops, Desmospondylus; new genera of Permian vertebrates. Bull. geol. Soc.
Am. 21, 249-84.

wilson, j. a. 1941. An interpretation of the skull of Buettneria, with special reference to the cartilages
and soft parts. Contr. Mus. Palaeont. Univ. Mich. 6, 71-111.

LIST OF ABBREVIATIONS USED IN THE FIGURES

Nerve

Roman numerals

foramina

A

angular

add. cr

adductor crest

a. pal. vac

anterior palatal vacuity

a. pr

anterior process

area

area of pterygoid which articulates

ART

with the pre-articular process
articular

as. pr

ascending process

avn antero-ventral bone nubbin

ba. pr basal process

bo. crest basi-occipital crest

bo. hollow hollow in exoccipital for the basi-
occipital cartilage

bone area of finished bone on the

pleurocentrum
boss quadrate boss

pt. pr conical recess for the basiptery-

goid process of the basisphenoid

HOWIE: A NEW CAPITOSAURID LABYRINTHODONT FROM EAST AFRICA 253

c

coronoid

cap

capitulum

centre

centre of ossification

ch. t. f.

chorda tympanic foramen

CL

clavicle

CLEI

cleithrum

clei. art

area for articulation with the
cleithrum

elm. m

area of attachment of the cleido-
mastoideus muscle

CO

coracoid

cr. pa

paroccipital crest

cr. pt

parapterygoid crest

D

dentary

d. f

dorsal foramen

d. ca

dorsal canal

delt. cr

deltoid crest

dia

diapophysis

dist. art

distal articulation

dist. exp

distal expansion

d. pr

dorsal process

d. pr. prart

dorsal process of the pre-articular

ECT

ectopterygoid

F

frontal

fen. ov

fenestra ovalis

hollow

hollow in tabular or exoccipital
for the opisthotic

ic. f

foramen for the internal carotid
artery

ICL

interclavicle

IL

ilium

IS

ischium

ipmx. f

interpremaxillary foramen

ipt. v

interpterygoid vacuity

J

jugal

j.f

jugular foramen

L

lachrymal

1. pr

lateral process

lam. pr

lamellar process

MX

maxilla

N

nasal

n. a.

neural arch

ne

external nostril

ni

internal nostril

obi. r

oblique ridge

ol. pr

olecranon process

OT

pro-otic ossification

P

parietal

PAL

palatine

Final typescript received 1 October 1969

pal. f

foramen for the palatine branch
of the internal carotid artery

para

parapophysis

par. pr

paroccipital process

pc

pleurocentrum

PF

post-frontal

pin. f

pineal foramen

PMX

premaxilla

PO

post-orbital

POSPL

post-splenial

PP

post-parietal

ppq. gr

groove on the pterygoid for the
palato-pterygo-quadrate carti-
lage

p. pr

posterior process

pq. f

paraquadrate foramen

pr. cult

cultriform process of the para-
sphenoid

PRF

prefrontal

prz

prezygapophysis

PSP

parasphenoid

PT

pterygoid

psp. sut

area for suture with the para-
sphenoid

pz

post-zygapophysis

Q

quadrate

QJ

quadratojugal

rart. pr

retro-articular process

SA

surangular

SC

scapula

sgl. b

supraglenoid buttress

sgl. f

supraglenoid foramen

SMX

septomaxilla

SPET

sphenethmoid complex

SPL

splenial

SQ

squamosal

ST

supratemporal

STA

stapes

ste. v

subtemporal vacuity

sup. cr

supinator crest

T

tabular

tr. in

internal trochanter

tr. 4

fourth trochanter

tub

tuberculum

V

vomer

v. c. d.

groove for vena capitis dorsalis

v. pr

ventral process

unc. pr

uncinate process

A. A. HOWIE

School of Biological Sciences
University of Sydney
Sydney, Australia, 2006

FEEDING HABITS OF PREDATORY
GASTROPODS IN A TERTIARY (EOCENE)
MOLLUSCAN ASSEMBLAGE FROM THE
PARIS BASIN

by JOHN D. TAYLOR

Abstract. The distinctive boreholes produced by two predatory gastroped superfamilies, the Muricacea and
the Naticacea, can be recognized in their molluscan prey in a fossil assemblage from the Calcaire Grossier
(Eocene, Lutetian) from Dameray in the Paris Basin. Possible predators are six species of Naticacea and two of
Muricacea. About 7000 mollusca representing 40 species were examined for boreholes of either type. The
most common prey species of the Muricacea were the epifaunal bivalve Ostrea plicata, the shallow burrowing
bivalve Venericardia serrulata and the epifaunal gastropod Omalaxis serrata. The Naticidae fed upon deeper
burrowing bivalves as well as Venericardia serrulata but very rarely upon epifaunal bivalves. Their principal
prey species was the burrowing gastropod Mesalia regularis as well as a varied selection of other burrowing
gastropods with a marked tendency towards cannibalism within the superfamily. The position of the borehole'
upon the prey species can give information on the behaviour and mode of attack of the predator.

It is widely known that members of several families of Recent gastropods obtain their
food by boring holes through the calcareous exoskeletons of prey (Carriker and Yochel-
son 1968). The families with this ability are the Naticidae, Muricidae, and the Cassidae;
of these, the two former feed regularly upon other molluscs and the latter usually feeds
upon echinoderms. Gastropod boreholes have been recognized in molluscs and brachio-
pods of many ages (Fischer 1922, 1960, 1962, 1963, 1964, 1966, Bucher 1938, Hayasaka
1933, Siler 1965, Brunton 1966, Carter 1967, Carriker and Yochelson 1968). However,
the holes, particularly in the Palaeozoic, need not have been produced by members of
the families of Recent gastropods listed above.

To the palaeontologist the recognition of these boreholes gives one of the few pieces
of positive, rather than circumstantial, evidence of feeding. Previous work on boreholes
in fossils has been limited to records of their occurrence and a discussion of possible
predators. The present study of predation on a molluscan assemblage, from the Calcaire
Grossier (Eocene, Lutetian) of the Paris Basin shows that boreholes of the Naticacea
and Muricacea can be distinguished and with certain reservations inferences about the
dietary preferences and the biology of the predators can be made.

BORING IN RECENT GASTROPODS

A detailed summary of boring mechanisms and borehole morphology has recently
been made by Carriker and Yochelson (1968). It appears that all Recent Naticacea
bore holes, and the work of Ankel (1937), Ziegelmeier (1954, 1961), and Carriker (1961)
has established that they bore by means of rotatory action of the radula assisted by a
secretion from an accessory boring organ situated at the ventral tip of the proboscis.
The hole produced by this process is neat and circular with a broad bevelled outside
rim producing a wide conical shape (see figure in Carriker and Yochelson 1968).

[Palaeontology, Vol. 13, Part 2, 1970, pp. 254-60, pi. 46.

TAYLOR: FEEDING HABITS OF PREDATORY GASTROPODS 255

Incomplete borings show a characteristic central boss. Naticids are usually infaunal
gastropods, highly active but usually only bore when they and the prey are buried in
the sand. The foot is exceptionally broad and used as a plough when moving through
the sand. The prey is grasped and virtually enveloped in the foot while being manipu-
lated into the correct position for boring to commence. Boring takes place by alternations
of rotatory rasping of the radula and the application of the accessory boring organ to
the site. When the hole is complete, the proboscis is closely applied and the contents
of the prey dragged out and pieces cut off by the jaws. Recent naticids usually feed
upon infaunal bivalves and occasionally upon gastropods when the need and oppor-
tunity arises (Paine 1963).

Independently the Muricacea have evolved a similar method of boring using the
radula with the aid of a secretion from an accessory boring organ situated in the foot.
The boring process is essentially similar to . that of the naticids but the resulting hole is
rather different. The hole is straight-sided, or tapers slightly inwards, the outer parts
may be ragged and irregular; a bevelled rim is sometimes produced but it is never as
wide or neat as that of the naticids. Members of the Muricacea are almost exclusively
epifaunal and movements appear rather clumsy when compared with those of the
highly motile naticids. In many species the foot is poorly developed and they are unable
to move rapidly in pursuit of prey and have limited, if any, powers of excavating prey
from sediment (Paine 1963). However, on rocky shores muricids are very successful
predators feeding upon byssate bivalves, limpets, and barnacles. Muricids such as
Urosalpinx and Ocenebra are common predators of oyster beds (Carriker 1955, Hancock
1960).

The ability to drill holes enables naticids and muricids to attack and eat bivalves
larger than themselves. However, when attacking gastropods the size and mobility of the
prey are important limiting factors (Paine 1963). Ansell (1960) considers that naticids
may not be able to hold and manipulate much larger bivalves successfully and con-
sequently do not recognize them as suitable food.

Carter (1967) has pointed out that there have been many attempts to show a preferred
boring site for naticids but that most of this has been inconclusive and conflicting.
Ansell (1960) reasonably considers that the site of boring by naticids depends upon the
| shape of the prey and predator and in any one species of prey there would be a preferred
site but that the position of the borings would be expected to differ for each prey /
predator combination. Muricids generally do not show preferred sites for boring when
feeding upon epifaunal prey. However, when bivalves are attached in tight byssate
groups only certain portions of the prey may be available for boring.

PREDATION IN THE CALCAIRE GROSSIER ASSEMBLAGE

Part of a large block of Calcaire Grossier limestone originating from Bed iii (Abrard
1925) at Dameray, near Epernay in the Paris Basin, has been examined. It is a loosely
! cemented shell sand composed mainly of broken and whole mollusc shells ; echinoids,
Ditrupa, polyzoa, and foraminifera are also very common.

\ Preservation of the fossils is excellent; many bivalves are preserved with the valves
together and all growth stages of many species are present, including even the plank-
tonic veliger stages of the molluscs. It appears that very little post-mortem sorting has

C 7393 S

256

PALAEONTOLOGY, VOLUME 13

taken place. The numbers of individuals of each species extracted from the rock gives
some indication of their relative abundance in the assemblage. About 7000 molluscs
were examined representing 40 species of which 29 showed evidence of predation by
boring gastropods (Table 1).

Potential predators

Molluscan genera in the Calcaire Grossier assemblage are sufficiently similar to, or
the same as Recent genera to assume that they probably had similar habits. Thus it is
possible to pick out the potential hole-boring predators in the assemblage and make
the assumption that no other gastropod genus represented in the assemblage was a
borer into other molluscs. The possibility that some holes may have been drilled by
octopus must not be discounted (Pilson and Taylor 1961), but these are much more
irregular than those of the Muricacea.

Possible hole-borers are represented by six species of Naticacea and two Muricacea.
Only two species of naticids are at all common, these being Natica epiglottina and
Euspira labellata. Wrigley (1949) considers that Lunatia, a Recent genus, is synony-
mous with Euspira ; feeding in the former has been described in detail by Zeigelmeier
(1954). Three species of Ampullina occur, A.patula , A. sigaretina, and A. parisiensis but
only the first occurs in any numbers. This genus became extinct during the Miocene
but it is so similar in morphology to Recent naticids that it is reasonable to assume that
it was a borer. The only other naticid present is Sinum clathratum of which only five
specimens were found; feeding in a Recent species of this genus has been described by
Paine (1963). Only two species of muricids were found, Pteropurpura tricarinatus
and Poirier a frondosus; whilst it cannot be assumed that all muricids are borers, these
two species are the only available potential borers of straight-sided holes in the assem-
blage. These muricids are surprisingly uncommon, only 20 specimens of P. tricarinatus
and 16 of P. frondosus were found. P. tricarinatus shows great morphological resem-
blance to the Recent ‘Oyster drill’ Ocenebra.

Predation

Each mollusc was examined for presence, type (muricid or naticid), and success or
failure of the boring. The results of this examination and the numbers examined are
shown in Table 1. Amongst bivalves the most common and most commonly attacked
species are Venericardia serrulata and Ostrea plicata. O. plicata is a cemented epifaunal
species frequently occurring in attached groups. It is attacked exclusively by muricids;
of the 103 borings seen there was a slight preference for right, upper valves (58 borings)
as opposed to the lower left valve (42 borings). There is no apparent preferred site for
the attacks. This behaviour is slightly puzzling, for it would be expected that attacks on
the attached, more inaccessible and thicker, lower valve would be fewer than on the
thin, right, upper valve, seemingly the more obvious site for attack. A similar sort of
behaviour has been observed on living species by Carriker (1955) who records that in
Urosalpinx the site of drilling is not limited to any specific region or to any position
which is easier to penetrate. Another Recent muricid predator, Nucella lapillus (Lin-
naeus), will frequently attempt to bore the thick ligamental area of Mytilus edulis
Linnaeus whilst other individuals at the same locality may be boring at the shell margins

TAYLOR: FEEDING HABITS OF PREDATORY GASTROPODS

257

TABLE 1

Prey species

Number

Naticid

Muricid

Failed

examined

bored

bored

borings

BIVALVES

Nucula mixta Deshayes

19

2

5

Nuculana galliotina Nyst.

29

0

0

Barbatia irregularis Deshayes

45

4

0

Glycimeris pulvinata (Lamarck)

215

9

2

Ostrea plicata Solander

981

0

103

Venericardia imbricata Deshayes

280

0

0

Venericardia serrulata Deshayes

2,699

101

366

Crassatella dilatata Deshayes

21

2

1

Crassatella grignonensis Deshayes

51

10

0

Crassatella trigonata (Lamarck)

177

2

2

Crassatella tumidum (Lamarck)

20

0

3

Loxocardium bouei (Deshayes)

200

2

6

1 muricid

Calpitaria distincta (Deshayes)

180

11

0

Aphrodina nitidula (Lamarck)

77

13

0

2 naticid

Castacallista laevigata (Lamarck)

62

3

0

Bicorbula gallica (Lamarck)

27

0

5

Corbula rugosa Lamarck

179

2

22

1 muricid

GASTROPODS

Bittium sp.

Calyptraea aperta Solander

65

6

0

Solarium olicatum (Lamarck)

100

0

4

Omalaxis serrata (Deshayes)

73

2

2

1 muricid

Mesalia regularis (Deshayes)

519

0

109

Rimella fissurella (Linnaeus)

886

272

0

Marginella eburnea (Lamarck)

227

12

1

Marginella ovulata (Lamarck)

200

3

0

Natica epiglottina (Lamarck)

31

5

0

Euspira labellata (Lamarck)

115

9

0

10 naticid

Ampullina patula (Lamarck)

138

17

3

11 naticid

Ampullina parisiensis (d’Orbigny)

8

2

0

Ampullina sigaretina (Deshayes)

2

0

0

Sinum clathratus (Gmelin)

6

1

0

Ancilla buccinoides (Lamarck)

5

0

0

Pteropurpura tricarinatus (Lamarck)

119

9

2

Poiriera frondosus (Lamarck)

20

0

0

Sycostoma pirus (Solander)

16

0

0

Clavilithes noae (Lamarck)

12

0

0

Ficus sp.

5

0

0

Turris sp.

145

5

0

Athleta ( Volutospina ) athleta (Linn.)
Conus parisiensis (Deshayes)

9

2

0

Ringicula ringens (Lamarck)

66

0

0

(personal observation). Venericardia serrulata is by far the most common bivalve,
usually reaching a size of 15 mm. It was a shallow burrower and shows evidence of
predation by both naticids and muricids; the latter making the most attacks. In attacks
on this species most of the muricid bores are situated at the margin of the valves.
These marginal bores at the commissure of the valves are semicircular and are frequently

258

PALAEONTOLOGY, VOLUME 13

situated in the interspace between the ribs. The bores are very similar to the illustrations
by Carriker (1961) of boring by Murex fulvescens on Mercenaria mercenaria.

In an attempt to see if there was a preferred drilling site the shell was divided up into
sectors and the frequency of attacks in each sector recorded (text-fig. 1). No preference

for right or left valves was shown, but
in both valves there was a very marked
preference for sites in the two sectors at
the ventral margin towards the midline
(PI. 46, figs. 1, 2). Naticid bores into this
species are usually completely enclosed
as opposed to the marginal borings of
muricids and situated towards the centre
of the shell. Different sizes of Veneri-
cardia show different predation rates,
most attacks taking place in the 3-6 mm.
size range and least in the 1 1-1 5 mm.
range. Small Venericardia are drilled by
small holes indicating small predators.
The regular preferred position of muricid
bores in this species, as opposed to the
indiscriminate attacks on O. plicata, is
probably accounted for by the fact that
Venericardia is a burrower and always has the same orientation in the sediment so that
the muricid must excavate and manipulate the prey in its foot prior to drilling. These
processes probably follow fixed behaviour patterns, resulting in the apparently preferred
drilling site. Epifaunal bivalves are usually byssally fixed or cemented allowing the
muricids to crawl all over their prey and attack without prior manipulation with the foot.

The larger, thicker-shelled species Venericardia imbricata which reaches 40 mm. in
length shows no evidence of predation or even attempted borings suggesting that adults
of this species are not recognized as prey. Ansell (1960) found that large, thick-shelled
individuals of Venus striatula had neither borings nor attempted borings and suggested
that Natica alderi may be incapable of manipulating large heavy specimens in the foot.

By comparison with Recent members of the family Bicorbula gallica and Corbula
rugosa can be assumed to have been very shallow burrowers, probably with their
posterior end protruding from the sediment. They are eaten almost exclusively by
muricids. In B. gallica most of the borings took place at the protruding posterior end,
but in the smaller C. rugosa most borings took place towards the midline of the shell.

text-fig. 1 . Diagram of inside of the right valve
of Venericardia serrulata showing the percentage
frequency of attacks in each sector for each valve.
215 attacked valves examined.

EXPLANATION OF PLATE 46

Fig. 1. Venericardia serrulata Deshayes showing muricid boring, x 12.

Fig. 2. Venericardia serrulata Deshayes showing muricid boring at valve margin, a common occurrence
in the species, X 18.

Fig. 3. Naticid boring in Crassatella grignonensis Deshayes, xl2.

Fig. 4. Muricid boring on flat spire of Omalaxis serrata Deshayes, x 20.

Fig. 5. Naticid boring in Ampullina patula (Lamarck) indicating cannibalism within the Naticacea,
x 11.

Fig. 6. Mesalia regularis (Deshayes) showing a naticid boring in the mid-portion of the spire, x 14.

Palaeontology , Vol. 13

PLATE 46

TAYLOR, Gastropod predation

TAYLOR: FEEDING HABITS OF PREDATORY GASTROPODS

259

Deeper burrowing bivalves (indicated by deep pallial sinuses), such as Aphrodina
nitidula, Calpitaria distincta, are attacked by naticids alone. No particular preference
for left or right valves was shown, but in A. nitidula all the bores fall within the area
bounded by the pallial lines. All naticid attacks on the burrowing Crassatella grignonen-
sis took place approximately on a line from the umbo to the midpoint of the ventral
margin (PI. 46, fig. 3). Predation on the very thin-shelled, shallow burrower Loxocardium
bouei is less than expected. A possible reason for this is that in common with several
Recent species of Cardiacea it may have had the ability to make leaping motions
by rapid flexing of the foot; an effective escape mechanism. In Nucula mixta the muricid
bores are distributed around the ventral margin, but the two naticid bores are situated
at the anterior end. Four individuals of Barbatia irregularis were attacked by naticids.
This is rather surprising as it is a byssate epifaunal bivalve and must have been attacked
very close to the sediment surface.

Predation on gastropods was more exclusively by naticids, with a wide choice of prey ;
whereas predation by muricids is limited to a few species only. By far the most common
gastropod in the fauna is a turritellid Mesalia regularis, a burrowing suspension feeder.
This species shows a very high predation rate (Table 1) and must have been a principal
item in the diet of naticids. Most of the attacks take place on individuals up to about
20 mm. in height. The hole is usually made about half-way up the spire (PI. 46, fig. 6)
with no preference for aboral or adoral sides; larger, thicker-shelled specimens of
Mesalia show no evidence of attacks.

In all naticid attacks on gastropods there is a more definite preferred site than for
attacks on bivalves. Species such as Marginella eburnea, M. ovulata, Ancilla buccin-
oides, and Euspira labellata show most of the attacks at the adoral surface very near to
the aperture. These apparently preferred sites for boring arise possibly because gastro-
pods are generally more active than bivalves and the ensuing struggles with predators
induce stereotyped behaviour patterns on the part of both attacker and attacked.
Cannibalism by naticids is common (PI. 46, fig. 5) but it is impossible to tell if this is
intra- or inter- specific, or both. An interesting feature of the cannibalism is the high
incidence of failed borings, a reflection of the high mobility of this genus. Carriker (1961)
records that laboratory-starved Polynices (naticids) exhibit a high degree of cannibalism
but in the presence of bivalves will eat these first.

The only gastropod attacked by muricids to any extent is Omalaxis serrata. Little is
known about the habits of this extinct genus, but by comparison with the related genus
Architectonica, it is assumed to have been epifaunal. Of the muricid attacks on this
species, 70 per cent took place on the flat top of the planispiral shell (PI. 46, fig. 4),
other attacks took place on the side of the whorl. The only other epifaunal gastro-
pods, Architectonica plicata, Capulus ungaricus, and Ringicula ringens, show little or no
predation by muricids.

It is noticeable that attacks on other gastropod predators such as Sycum, Athleta,
Clavilithes, and Tunis are uncommon, and where they do occur, as in Tunis, they are
confined to juveniles.

CONCLUSIONS

From an examination of the occurrence and distribution of the two different types
of gastropod boreholes in the Calcaire Grossier fossil assemblage it is possible to

260

PALAEONTOLOGY, VOLUME 13

reconstruct, at least in part, the diets of the two gastropod superfamilies. It is possible
to ascertain points of feeding overlap and possible sources of competition between the
two superfamilies. Muricacea generally feed upon sedentary epifaunal prey, and
Naticacea upon infaunal prey, both sedentary and motile; but shallow burrowing
species are liable to be eaten by members of either superfamily. The site of the attack
on the prey species can give information concerning the behaviour of the predator
and prey. Study of fossil boreholes provides one of the few positive pieces of evidence
in the reconstruction of food chains and trophic levels in fossil communities.

Acknowledgements. I am grateful to Dr. H. Brunton for reading the manuscript, and to Mr. P. Green
of the Photographic Studio of the British Museum for the photographs.

REFERENCES

abrard, R. 1925. Le Lutetien du Bassin de Paris. Essai de Monographie stratigraphique . Angers. Soc.
Fran false d'Imp. d' Angers, 1-388.

ansell, A. d. 1960. Observations on predation of Venus striatula (Da Costa) by Natica alderi (Forbes).

Proc. malac. Soc. Lond. 34, 157-64, 1 pi.
ankel, w. e. 1937. Wie bohrt Natical Biol. Zentr. 57, 75-82.

brunton, h. 1966. Predation and shell damage in a Visean Brachiopod Fauna. Palaeontology, 9,
355-9, 1 pi.

bucher, w. h. 1938. A shell boring gastropod in a Dalmanella bed of Upper Cincinnatian age. Am.
J. Sci. 36, 1-7.

carriker, m. r. 1955. Critical review of biology and control of oyster drills, Urosalpinx and Eupleura.
Spec. sci. Rep. U.S. Fish. Wildl. Serv. 148, 1-150.

1961. Comparative functional morphology of boring mechanisms in gastropods. Amer. Zool.

1, 263-6.

and yochelson, e. l. 1968. Recent gastropod boreholes and Ordovician cylindrical borings. U.S.

Geol. Survey. Prof. Pap. 593-B, 1-23, 5 pi.

carter, r. m. 1967. On the biology and palaeontology of some predators of bivalved mollusca. Palaeo-
geography Palaeoclimatol. Palaeoecol. 4, 29-65, 2 pi.
fischer, p.-h. 1922. Sur les gasteropodes perceurs. /. Conchyliol. 67, 1-56.

1960. Action des gasteropodes perceurs sur un bivalve de l’Etage Lutetien. Ibid. 100, 129-31.

1963. Corbules fossiles perforees par des gasteropodes predateurs. Ibid. 103, 29-31.

1964. Au sujet des perforations attributes a des gasteropodes pre-tertiares. Ibid. 104, 45-47.

1966. Perforations de fossiles tertiares par des gasteropodes predateurs. Ibid. 605, 66-96.

Hancock, d. a. 1960. The ecology of the molluscan enemies of the edible mollusc. Proc. malac. Soc.
Lond. 34, 123-43.

hayasaka, i. 1933. Fossil occurrence of pelecypod shells bored by certain gastropods. Mem. Fac. Sci.
Agric. Taihoku Imp. Univ. 6, 65-70.

Paine, r. t. 1963. Trophic relationships of 8 sympatric predatory gastropods. Ecology, 44, 63-73.
pilson, m. e. q., and taylor, p. b. 1961. Hole drilling by Octopus. Science, 134, 1366—8.
siler, w. l. 1965. Feeding habits of some Eocene carnivorous gastropods. Texas J. Sci. 17, 213-18.
wrigley, a. 1949. English Eocene and Oligocene Naticidae. Proc. malac. Soc. Lond. 28, 10-30.
ziegelmeier, e. 1954. Beobachtungen tiber den Nahrungserwerb bei der Naticide Lunatia nitida
Donovan. (Gastropoda, Prosobranchia) Helgol. Wiss. Meeresunters. 5, 1-33.

1961. Zur Fortpflanzungsbiologie der Naticiden (Gastropoda, Prosobranchia). Ibid. 8, 94-188.

J. D. TAYLOR

Department of Zoology
British Museum (Natural History)
Cromwell Road
London, S.W.7

Final typescript received 15 October 1969

CHITINOZOA FROM THE ORDOVICIAN
SYLVAN SHALE OF THE ARBUCKLE
MOUNTAINS, OKLAHOMA

by W. A. M. JENKINS

Abstract. Chitinozoa referable to nine genera and twelve species (five new) are recorded from the Sylvan
Shale of the Arbuckle Mountains in southern Oklahoma. They provide for the first time a means of dating, bio-
stratigraphically subdividing, and correlating the entire formation. Its chitinozoan fauna indicates that the Sylvan
Shale is of Upper Ordovician age throughout and confirms with additional fossil evidence the age of the lower
beds. No abrupt changes break the general continuity of the chitinozoan succession but on the basis of gradual
changes in the composition of its chitinozoan fauna the Sylvan Shale may be divided into three biostrati-
graphical units. The fauna occurs throughout the Arbuckle Mountains and is recognizable in the subsurface
of western Texas and in the Maquoketa Formation of eastern Iowa. It differs strikingly from the fauna in the
underlying Viola and Femvale Limestones, and from the faunas in the overlying formations of the Silurian-
Devonian Hunton Group. The occurrence of reworked Sylvan chitinozoans in upper Sylvan strata indicates that
during late Sylvan time uplift (hitherto unsuspected) took place, at least locally, in the southern mid-continent.

The fauna is described systematically. Clathrochitina Eisenack 1959 is used in its original sense; Plectochitina
Cramer 1964 is a junior synonym. Sagenachitina gen. nov. is proposed for species, hitherto referred to Clathro-
chitina, whose basal margins support finely divided networks. Acanthochitina rashidi, Ancyrochitina merga,
Clathrochitina sylvanica, Cyathochitina agrestis, and Sphaerochitina lepta are new species.

This account of chitinozoans from the Sylvan Shale is the second of two investigations
directed primarily at establishing an Upper Ordovician chitinozoan reference section
in the Arbuckle Mountains of southern Oklahoma. In a stratigraphical sense it is the
continuation of an earlier study (Jenkins 1969) devoted to chitinozoans from the
underlying Viola and Fernvale Limestones. An incidental objective was to provide,
for the first time, a means of dating and correlating the entire formation.

The Sylvan Shale is the youngest Ordovician formation in the Arbuckle Mountains,
and rests unconformably upon the slightly older Viola-Fernvale limestone succession.
It was chosen for this investigation primarily because it contains large numbers of well-
preserved chitinozoans at practically all stratigraphical levels, but several additional
factors also favoured its selection as a standard for stratigraphical reference. In particular,
it is a distinctive lithostratigraphical unit separated by regional unconformities and by its
sharply contrasting lithology from thick carbonate sequences above and below. In the
subsurface the Sylvan Shale extends across most of Oklahoma into north-western Texas
and southern Kansas and has been widely used as a marker horizon in the subsurface
mapping of an otherwise unbroken sequence of Ordovician to Devonian limestones.

The formation crops out widely within the Arbuckle Mountains, for which reason
the samples were collected there. It is particularly well exposed and free from faulting
in a narrow outcrop 14 miles (22 km.) long, running west-north-west from Ravia to the
Washita River along the steeply dipping southern flank of the Sycamore Creek Anti-
cline (text-fig. 1). Chitinozoans from this outcrop form the basis of the present study.

In this paper, for reasons presented elsewhere (Jenkins 1969, pp. 5, 6), the base of the
Nemagraptus gracilis Zone (or its correlatives) is taken as the lower limit of the Upper
Ordovician. Thus defined, the Upper Ordovician includes the basal beds of the North

[Palaeontology, Vol. 13, Part 2, 1970, pp. 261-288, pi. 47-51.]

262

PALAEONTOLOGY, VOLUME 13

text-fig. 1. Showing the outcrop (outlined) and structural features of the pre-Pennsylvanian rocks
in the Arbuckle Mountains. The shaded portion of the index map of Oklahoma delineates the area
shown. The upper left inset map (represented by the shaded rectangle in the chart) shows the
outcrop (stippled) of the Sylvan Shale exposed in the Sycamore Creek Anticline, and the road from
Baum (on U.S. Highway 177) to the section (S) which provided the rock samples for this study.
Compiled from Ham, W. E. 1955, Geology of the Arbuckle Mountain Region, Guide Book III;
Ham, W. E. et al., 1954, Geologic Map and Sections of the Arbuckle Mountains, Oklahoma, Guide
Book III. Both published by the Oklahoma Geological Survey.

American Black River Stage and their correlatives (Twenhofel et al. 1954; Berry 1960a,
b; Kay 1960, p. 30) at the base of the Caradoc Series in Britain.

PREVIOUS RESEARCH

Previous publications concerned with chitinozoans from the Sylvan Shale are limited
to two notes (Wilson 1958, Wilson and Hedlund 1964) and an abstract (Wilson
and Hedlund 1962). The latter is from Hedlund’s (1960) substantial account of
chitinozoans, acritarchs, and scolecodonts, which was submitted as a thesis for the
Master of Science degree to the University of Oklahoma. Although unpublished,
Hedlund’s work has remained for a decade the chief source of information about

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 263

organic-walled microfossils in the Sylvan Shale, and the only attempt to describe them
systematically.

The possibility exists, however, that chitinozoans were encountered in fossil residues
of the Sylvan Shale as early as 1930. A short publication by Thomas (1930) contains
(p. 87) not only a very early (perhaps the earliest) reference to organic-walled micro-
fossils in the Lower Palaeozoic of Oklahoma, but almost certainly a passing reference
to chitinozoans. I have been unable to ascertain whether or not this paper preceded
Eisenack’s of the same year, in which chitinozoans (though not named as such) were
introduced to the scientific literature. On account of this paper’s apparent obscurity
outside North America the following relevant passage is reproduced.

. . .1 also have permission from Mr. S. W. Lowman, micropaleontologist for the Midcontinent
Petroleum Corporation, to announce a discovery he has recently made concerning the Sylvan in
Oklahoma and Kansas. He has found that after completely dissolving the shale in concentrated hydro-
chloric acid the residue will yield microfossils which are invisible upon ordinary microscopic examina-
tion. He discovered organisms similar to Sporangites found in the Woodford [Formation, which is
Devonian-Mississippian]. One species is about as large as the disc-like Sporangites huronense and
is found in the upper Sylvan from central Kansas to the Arbuckles. Another species about twice as
large as the above has been found in the upper Sylvan on the outcrop and in wells near the Arbuckles.
A few spindle-shaped forms have been found. There are reasons to believe that these are plant spores
and there are also arguments in favor of the theory that they are graptolitic in nature (Thomas 1930,
p. 87).

In all probability the ‘spindle-shaped forms’ are chitinozoans for, to my knowledge,
no organic-walled microfossils in the Sylvan Shale other than certain chitinozoans (and
possibly a few netromorph acritarchs) could be interpreted, however broadly, as
spindle-shaped. It is interesting to learn from Thomas’s paper that the speculation
about the natural affinities of the Chitinozoa, which has continued to the present day,
had already started before the group was formally established and named by Eisenack
in 1931.

GENERAL STRATIGRAPHY

Lithology and fauna. Throughout the Arbuckle Mountains the lower part of the Sylvan
Shale, up to c. 130 ft. (40 m.) thick, is a hard, splintery, very fissile, brown to dark grey
shale containing graptolites which are particularly abundant near the base. By contrast,
the upper part of the formation, up to 200 ft. (61 m.) thick, is mainly a soft, weakly
fissile to concretionary, greenish-grey shale, and is apparently devoid of macrofossils.
The topmost 30 ft. (9 m.) is a soft, massive, highly pyritic, light green clay stone, which
disaggregates completely in water and is, for this reason, only ever temporarily exposed.
The Sylvan Shale is generally slightly calcareous, and may be highly calcareous locally,
particularly in its upper 100 ft. (30 m). Dolomite beds a few inches thick occur irregu-
larly throughout the formation, and in the lower part two beds of dense brown
dolomite, each 1-3 ft. (0-30-0-91 m.) thick, extend laterally over a wide area. Outcrops
of the Sylvan Shale are strikingly delineated by sharp changes in the topography, soil,
and vegetation of the limestone country within which they are exposed.

The formation contains, in addition to one species of brachiopod (Cooper 1956, p.
244) and seven species of graptolites (Decker 1935, 1945; Ruedemann 1947, pp. 90-2,
100) in its lower part, a rich fauna of chitinozoans and acritarchs throughout. Generally,

264 PALAEONTOLOGY, VOLUME 13

however, other fossils are lacking, and the upper Sylvan in particular is seemingly
devoid of macrofossils.

The lithology and fauna of the Sylvan Shale indicate that it was laid down in tranquil
waters, and suggested to Ham (1969, p. 11) that it was deposited in deeper waters than
all other pre-Mississippian formations in the Arbuckle Mountains. It is the only pre-
Upper Devonian shale unit, moreover, to persist throughout the Arbuckle Geosyncline
and to extend beyond it over much of the southern mid-continent.

Pattern of deposition. Within the Arbuckle Mountains the Sylvan Shale’s broad pattern
of deposition is similar to that of the Viola Limestone (Jenkins 1969, p. 3). The Sylvan
sediments in the south-western Arbuckle Mountains were laid down in the rapidly
subsiding basin of the Arbuckle Geosyncline, whereas those to the north and east of a
line now approximately followed by the Reagan Fault (text-fig. 1) were deposited on a
slowly subsiding geosynclinal shelf. This led to the accumulation of less sediment in the
north-east than in the south-west and explains the general thinning of the formation
north-eastward across the Arbuckle Mountains from a maximum of 325 ft. (99 m.) in
the basin to 150-175 ft. (45-53 m.) on the shelf (Ham 1969, p. 10).

Stratigraphical relations. Over a large part of Oklahoma, including the Arbuckle
Mountains, regional unconformities separate the Sylvan Shale from a thick sequence
of older Ordovician limestones below, and a succession of Silurian and Devonian
carbonate formations above. The Sylvan lies everywhere upon the Fernvale Limestone,
and the sharp contact is well exposed in Sycamore Creek (text-fig. 1), map reference
SWJ SEJ sec. 27, T. 3 S., R. 4 E., Johnston County, Oklahoma. The dips of the
two formations appear to be the same, but close examination reveals that the top of the
Fernvale Limestone is an erosion surface that had been extensively weathered before
the shale was laid down. A 2-3 in. (5-8 cm.) thick band of oxidizing pyritic ‘rubble’,
containing phosphatized pebbles, locally marks the base of the shale, as at Sycamore
Creek, and (Ham, personal communication, May 1969) is particularly well developed
as a pyritic phosphate conglomerate, containing dolomite pebbles, in the road-cut
entrance to Rayford Quarry (text-fig. 1), map reference NWJ NEf NEJ sec. 28, T. 1
S., R. 2 E., Murray County, Oklahoma. This and related late Ordovician unconform-
ities are given some prominence, and discussed in a regional context, by Ham and
Wilson (1967, pp. 350-2) in a comprehensive account of Palaeozoic tectonic disturbances
in the central United States.

Almost everywhere within the Arbuckle Mountains the Sylvan Shale is unconformably
overlain by Silurian or Lower Devonian limestones (Amsden 1960, panel III). These
are extremely thin within the Sycamore Creek Anticline, however, and locally, as at
Sycamore Creek, they have been entirely removed by mid-Devonian erosion; the black
shales and bedded cherts of the Upper Devonian-Mississippian Woodford Formation
lie directly upon the Sylvan Shale. The Woodford Formation, which is 350-560 ft.
( 107-171 m.) thick in the Arbuckle Mountains, has been dated by conodonts as ranging
in age from Frasnian (Upper Devonian) to Kinderhookian (Lower Mississippian) ;
the Mississippian part of the formation generally is less than 1 ft. (0-30 m.) thick, and
exceptionally at least 10 ft. (3 m.) thick (Hass and Huddle 1965).

Age and correlation. The Sylvan Shale was dated Upper Ordovician by Decker (1935),
on the basis of graptolites confined to the lower part of the formation. The greater part

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 265

of the Sylvan Shale has yielded no macrofossils, however, but was placed in the Ordo-
vician on the basis of its association with the lower Sylvan. Although Decker’s age de-
termination for the lower graptolitic Sylvan has generally been accepted, the age of
the overlying ‘unfossiliferous’ beds, at least 200 ft. (61 m.) thick in the south-western
Arbuckle Mountains, has not hitherto been demonstrated.

Collection and preparation of material. Samples were collected at stratigraphical intervals of 20 ft.
(6T0 m.) throughout the Sylvan Shale succession exposed in the bed and banks of Sycamore Creek
(text-fig. 1), map reference SWJ SEJ sec. 27, T. 3 S., R. 4 E., Johnston County, Oklahoma, com-
mencing 1 ft. above the Fernvale Limestone-Sylvan Shale contact. The latter serves as an easily
recognizable reference datum, and samples are numbered according to their original stratigraphical
positions (measured in feet) above it. For example, sample Sy280 is from a stratigraphical level 280 ft.
above the contact, the prefix ‘Sy’ indicating that it is from Sycamore Creek. These samples are briefly
described in the appendix.

The collection of regularly spaced samples was made easy at Sycamore Creek by the steep inclination
of the beds and the absence of faulting. The relatively resistant shales in the lower part of the formation
are well exposed in the bed and steep banks of the creek, and samples of these were collected without
difficulty. To obtain samples of the softer shales and claystones near the top of the formation, how-
ever, it was necessary to dig through as much as 2 ft. (0-6 m.) of Recent alluvium. The total thickness
of the Sylvan Shale at Sycamore Creek, from its sharp contact with the Fernvale limestone below,
to its equally sharp contact with the Woodford Formation above, was carefully measured by Mr.
J. A. Turnbull and myself, and found to be 305 ft. (93 m.), slightly less than Decker’s (1935, p. 698)
figure of 320 ft. (97-5 m.).

In order to determine how much the character of the Sylvan chitinozoan fauna varies regionally
several samples were collected at widely scattered localities (q.v., p. 283) throughout the Arbuckle
Mountains. A few figured specimens are from outcrops along U.S. Highway 77 about 4 miles (6-4 km.)
south of Davis (text-fig. 1), map reference sec. 30, T. 1 S., R. 2 E., Murray County, Oklahoma. Their
reference numbers are prefixed ‘Da’.

The chitinozoans were prepared for microscopical examination according to the method outlined
by Jenkins (1967, pp. 439-41), and furnished with reference numbers in the manner described for the
Viola and Fernvale specimens of an earlier study (Jenkins 1969, p. 7). Most of the preparations,
including all the type material, and portions of each rock sample, are housed in the Micropalaeontology
Laboratory, Department of Geology, The University, Sheffield, England.

SYSTEMATIC PALAEONTOLOGY

Order chitinozoa Eisenack 1931
Genus acanthochitina Eisenack 1931 emend. Jenkins 1967

Type species. Acanthochitina barbata Eisenack 1931 (by original designation), Ordovician, Baltic.

Acanthochitina rashidi sp. nov.

Plate 47, fig. 20; Plate 48, figs. 1,2; text-fig. 2

Hoiotype. Plate 48, figs. 2a, b. Specimen Sy80/2/l/B; Sylvan Shale, 80 ft. (24-38 m.) stratigraphically
above base, Sycamore Creek.

Diagnosis. Small conical to pyriform test. Maximum diameter about four-fifths total
length; base convex, margin rounded. Neck weakly differentiated from chamber, short,
tapering; commonly not developed. Aperture equal to, or slightly greater than, half
maximum diameter. Numerous closely spaced slender processes; arms of adjacent

266 PALAEONTOLOGY, VOLUME 13

processes united, forming a complete reticulum that stands as high as 12 yu, above
surface of test wall.

Dimensions {in microns). 25 specimens measured.

Total

Maximum

Apertural

length

diameter

diameter

Holotype:

128

89

53

Range :

105-158

81-106

40-63

Mean:

123

93

51

Remarks. Acanthochitina rashidi is considered as a separate species because it falls
well outside Jansonius’s (1964, p. 909) definition of
Kalochitina multispinata. Wherever it has been found,
however, A. rashidi makes up continuously inter-
grading populations with K. multispinata and many
transitional forms occur. The two species are distin-
guished arbitrarily and solely on the basis of their
ornaments. Their close relationship is not reflected in
the strictly empirical system of classification followed
here, however, and they are unavoidably referred to
different genera.

Comparison. In Hercochitina downiei Jenkins 1967 pro-
cesses stand in longitudinal rows, and most frequently
are connected only to those longitudinally adjacent
to them. A. rashidi is much smaller than the type species
(total length of 25 British examples 300-485 p, mean
408 ytx), and has a much more delicate ornament; pro-
cesses on the basal margin do not differ appreciably
from those elsewhere and, in particular, are not con-
nected by a membrane.

Material. Several thousand single tests, and a dozen chains of two or three tests each.

Occurrence. Sy80-Sy200. A. rashidi is restricted to the middle of the Sylvan Shale, although forms
transitional to it, but referable to K. multispinata, occur at the younger horizons Sy220, Sy240, and
Sy260.

text-fig. 2. Acanthochitina rashidi
sp. nov. Lateral profile, x400.
For the sake of clarity only the
ornament seen in profile is shown.

EXPLANATION OF PLATE 47

Figs. 1-19. Ancyrochitina merga sp. nov., all but 19 x250. 1-8, Sy80/1/1/B, Sy60/1/1/F, B, E, Sy80 /
1/1 /A, D, C, and Sy60/1/1/H, respectively, bearing a variety of T- and Y-shaped appendices. 9-11,
Sy60/1/1/D, Sy80/1/1/E and Sy60/1/1/A, respectively, with A-shaped appendices. 12, 13, Sy80/1/1/F
(holotype) and Sy60/1/1/C, respectively, each possessing T-, Y-, and A-shaped appendices. 14-17,
Sy40/1/1/A, C, B, and D, respectively, with ornaments of simple spines and A-spines; this form
represents the species near the base of the Sylvan Shale, whereas younger Sylvan strata contain
only smooth-walled forms (figs. 1-13). 18, Sy60/1/1/G, cluster of three tests; two are in polar view,
the upper right in lateral view. 19, Sy80/1/1/G, detail showing three simple appendices, and one
with three orders of branching, in phase-contrast illumination x 400.

Fig. 20. Acanthochitina rashidi sp. nov., Syl00/2/l/B, in phase-contrast illumination, x400.

Palaeontology, Vo I. 13

PLATE 47

JENKINS, Ordovician chitinozoa from Oklahoma

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 267
Genus ancyrochitina Eisenack 1955a
Type species. Conochitina ancyrea Eisenack 1931 (by original designation), Silurian, Baltic.

Ancyrochitina merga sp. nov.

Plate 47, figs. 1-19; text-fig. 3

Holotype. Plate 47, fig. 12. Specimen Sy80/1/1/F; Sylvan
Shale, 80 ft. (24-38 m.) stratigraphically above base, Sycamore
Creek.

Diagnosis. Small fungiform test. Chamber about
half total length, wider than long; base slightly
convex, margin rounded. 8-24, generally fewer than
15, simple or branching appendices up to one-third
of the maximum diameter in length; generally 1-3,
rarely 4, orders of Y- or T-shaped branching into
2 sharply diverging, equal distal limbs. Commonly,
appendices divide (A-shaped branching) in a trans-
verse plane to form two proximal limbs which meet
the basal margin abruptly. Oral tube cylindrical or
slightly flaring, one-third to half maximum diameter in ^T’TFIC!'J‘, A ncyrocn'tma merga sp.
width; aperture fringed with hairs up to 5^ in length, appendices and the ornament of A-
Test smooth, or bearing slender, tapering, simple or spines and simple spines, x400.
A-spines with pointed tips, up to one-sixth maximum
diameter in length; thinly distributed, absent on base and basal margin.

Dimensions (in microns). 25 specimens measured.

Holotype :
Range :
Mean:

Total

length

125

100-155

128

Chamber

length

70

52-71

64

Maximum

diameter

91

70-98

81

Oral tube
diameter

35

32-46

36

Apertural
diameter
c. 35
35-55
44

Appendix

length

<30

<35

Description. The flanks of the short, wide chamber are almost straight and taper rapidly,
but with no abrupt change of curvature, into the neck. The maximum diameter generally
is 120-140% of the chamber length. Where A. merga first occurs (horizon Sy40) it
bears slender, simple spines and A-spines up to 12 p in length, distributed thinly over
the test (PI. 47, figs. 14-17). Throughout the remainder of the formation, however,
forms with smooth walls, or forms with very few short spines (< 2 p in length) on the
shoulder and neck, greatly predominate over the more ornate forms.

Comparison. A. merga is readily distinguished by the style and number of its appendices.
A. corniculans Jenkins 1969 from the Viola and Fernvale Limestones is cylindro-
conical rather than fungiform, and has only 4-6 appendices.

Material. Several thousand single tests.

Occurrence. Sy40-Sy305.

268 PALAEONTOLOGY, VOLUME 13

Genus clathrochitina Eisenack 1959

Type species. Clathrochitina clathrata Eisenack 1959 (by original designation), Wenlock, Gotland.

Diagnosis. ‘Chitinozoans shaped like Ancyrochitina ancyrea, and furnished with appen-
dices whose distal ends coalesce with a ring situated concentrically about the basal
margin’ (Eisenack 1959, p. 15).

Remarks. Clathrochitina Eisenack 1959 was conceived for cylindroconical chitinozoans
possessing distinct appendices (generally discrete processes confined to the basal margin)
that coalesce distally; Plectochitina Cramer 1964 is a junior synonym. Unfortunately,
several species lacking distinct appendices have been referred inappropriately to
Clathrochitina on the basis of finely meshed networks suspended from their basal
margins, and Plectochitina has assumed the taxonomic role originally intended for
Clathrochitina. Consequently, the genus Sagenachitina (q.v., p. 270) is here proposed for
chitinozoans with networks suspended from their basal margins; and several species
are transferred to it from Clathrochitina. The latter is considered to include, besides
the type species, Clathrochitina multiramosa (Taugourdeau and Jekhowsky 1960)
Taugourdeau 1967, C. saharica (Taugourdeau 1962) comb, nov., C. carminae (Cramer
1964) comb, nov., C. rosendae (Cramer 1964) comb, nov., and C. combazi (Cramer
1967a) comb. nov. It seems essentially a Silurian genus, being known only from the
uppermost Ordovician (this paper), the Silurian (Eisenack 1959; Taugourdeau 1962,
1967; Cramer 1964, 1967a; Taugourdeau et al. 1967, p. 85, under Plectochitina), and,
perhaps, the basal Devonian (Cramer 1964).

Cramer (1967a, pp. 84, 94; 19676, p. 47) interpreted the structure on the basal margin
of C. clathrata (type species of its genus) as a ‘perforate cingulum’ and, on the basis of
this interpretation, transferred the species to Cyathochitina Eisenack 19556. For species
previously referred to Clathrochitina, which was abandoned through the loss of its type
species, he proposed the genera Clathrochitinella and Pseudoclathrochitina. While
Cramer’s proposals may seem reasonable in the light of his structural interpretation,
the latter is entirely inconsistent with Eisenack’s (1959, p. 15, pi. 1, figs. 3, 4; text-fig. 4)
clear illustrations and lucid, unambiguous description of the genus and its type species.
Cramer’s proposals and transfer of C. clathrata are, if only for this reason, unaccept-
able, and Clathrochitinella and Pseudoclathrochitina should be abandoned along with
Plectochitina. Aside from the faulty interpretive basis upon which they rest, Cramer’s
proposals and transfer serve little more than to complicate and confuse a relatively
straightforward issue, namely the generic placement of two groups of cylindroconical
chitinozoans, one characterized by networks suspended from the basal margin ( Sagena-
chitina), the other by appendices which coalesce distally ( Clathrochitina ). The existence
of a few forms transitional between Sagenachitina and Clathrochitina is known (e.g.
Taugourdeau 1967, pi. 1, fig. 9) but scarcely complicates the issue.

Clathrochitina sylvanica sp. nov.

Plate 48, figs. 3-13; text-fig. 4

Holotype. Plate 48, figs. 11a, b. Specimen Da50/12/1/A; Sylvan Shale, 50 ft. (15-24 m.) stratigraphic-
ally above base, in outcrop on west side of U.S. Highway 77, about 4 miles (6-4 km.) south of Davis,
Oklahoma.

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 269

Diagnosis. Conical chamber slightly longer than oral tube, approximately as wide as
long; base flat or slightly convex, margin rounded. Appendices of uniform thickness
and texture, suspended at 6-15, generally 8-12, points on the basal margin; commonly
anastomosing; occasionally discrete for their full lengths and connected at their tips
by a continuous ring; equal to, or less than, maximum diameter in length. Oral tube
cylindrical, half maximum diameter in width. Test wall smooth.

text-fig. 4. Clathrochitina sylvanica sp. nov. Lateral views of two variants with
strongly developed appendices, x 400.

Dimensions (in microns ). 25 specimens measured.

Total

Chamber

Maximum

Oral tube

Appendix

length

length

diameter

diameter

length

Holotype:

120

62

78

36

< 53

Range :

110-160

60-85

75-103

36-48

12-90

Mean:

131

76

84

40

—

Description. The flanks taper fairly uniformly, and the junction of the chamber and
neck generally is clearly defined. The appendices are very strongly developed. Their
pattern of branching and anastomosing varies considerably at each horizon, but the
same, or closely similar, variants occur wherever the species has been found.

Comparison. Ancyrochitina merga is readily distinguished from C. sylvanica by its
discrete, pitchfork-shaped appendices. Damaged specimens which have lost their
appendices, however, may be exceedingly difficult to identify, but typical examples of
A. merga are, nevertheless, fungiform rather than cylindroconical, and may bear

270

PALAEONTOLOGY, VOLUME 13

simple or A-spines. Four similar species of Clathrochitina differ from C. sylvanica as
follows. C. combazi (Cramer 1967a) possesses 12-24 modestly branching appendices,
whereas C. rosendae (Cramer 1964) bears only a few. The appendices of C. clathrata
Eisenack 1959 are very short; those of C. carminae (Cramer 1964) branch elaborately
and may extend as far as 130 fj, from the basal margin. C. multiramosa (Taugourdeau
and Jekhowsky 1960) Taugourdeau 1967 is readily distinguished by about 12 short
processes attached immediately below the aperture, and connected at their tips by a
continuous ring.

Material. Approximately 400 single tests.

Occurrence. ?Syl, Syl6-Syl80. Clathrochitina sylvanica is a distinctive element in approximately the
lower half of the Sylvan Shale.

Genus sagenachitina gen. nov.

Type species. Clathrochitina oblonga Benoit and Taugourdeau 1961 (by original designation), Arenig,
Algeria.

Diagnosis. Chitinozoa with cylindroconical or campanulate tests and a network suspended
from the basal margin.

Remarks. Sagenachitina gen. nov. is not represented in the Sylvan Shale, but is proposed
for a group of closely similar species including 5 formerly referred inappropriately to
Clathrochitina Eisenack 1959. These are Sagenachitina oblonga (Benoit and Taugour-
deau 1961) comb, nov., S. aquitanica (Taugourdeau 1961) comb, nov., S. eisenacki
(Taugourdeau 1961) comb, nov., S. retifera (Taugourdeau and Jekhowsky 1960) comb,
nov., and S. striata (Benoit and Taugourdeau 1961) comb. nov. Sagenachitina differs
from Clathrochitina (q.v., p. 268) in that its basal margin supports a finely divided net-
work, rather than a relatively small number of distinct processes which coalesce distally.
Apparently it is restricted to the Ordovician (Taugourdeau et al. 1967, p. 78), whereas
Clathrochitina ( sensu Eisenack 1959) seems essentially a Silurian genus.

Acknowledgement. Sagenachitina was introduced to the literature by Jansonius (1967, p. 352) as an
informal manuscript name. It is validated here, in its original sense, with the permission and approval
of Dr. Jansonius.

Genus conochitina Eisenack 1931 restr. 19556
Type species. Conochitina claviformis Eisenack 1931 (by original designation), Silurian, Baltic.

Conochitina elegans Eisenack 1931
Plate 49, figs. 1-17

EXPLANATION OF PLATE 48

Figs. 1, 2. Acanthochitina rashidi sp. nov., x400. 1, SylOO/2/l/D, in phase-contrast illumination.

2, Sy80/2/l/B, holotype; in bright-field (2a) and phase-contrast (lb) illumination.

Figs. 3-13. Clathrochitina sylvanica sp. nov., illustrating variation in the size and complexity of the
appendices, > 250. 3, Sy60/12/1/D. 4, Syl00/12/1/A. 5, Sy80/12/1/B. 6, Sy60/ 12/1 /C, polar view.
7, Sy60/12/1/E. 8, Sy60/12/1/K. 9, Sy80/12/1/A. 10, Syl00/12/1/C. 1 1, Da50/1 2/1/A, holotype;
in bright-field (11a) and phase-contrast (116) illumination. 12, Sy60/ 12/1 /H. 13, Sy60/12/1/A.

Palaeontology, Vol. 13

PLATE 48

Wr

)

) ^ 1 !

^ • . y

mi / S)

JENKINS, Ordovician chitinozoa from Oklahoma

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 271

1931 Conochitina elegans Eisenack, p. 87, pi. 2, fig. 4 (holotype).

1934 Rhabdochitina conocephala Eisenack, p. 61, pi. 4, figs. 10-12; text-fig. 32.

1959 Conochitina elegans Eisenack; Eisenack, p. 3, pi. 2, figs. 4 (neotype), 5; text-fig. 1.

1960 Rhabdochitina conocephala Eisenack; Taugourdeau and Jekhowsky, p. 1230, pi. 9,

fig. 131.

non 1962 Conochitina elegans Eisenack; Beju and Dane!, p. 531, pi. 1, figs. 31, 32.
non 1964 Rhabdochitina conocephala Eisenack; Cramer, p. 351, pi. 22, fig. 14; pi. 23, figs. 7, 11, 12.
1965 Rhabdochitina hedlundi Taugourdeau, p. 472, pi. 3, figs. 60, 66.

1965 Conochitina elegans Eisenack; Eisenack, p. 126, pi. 10, fig. 9.

1967 Conochitina elegans Eisenack; Jenkins 1967, p. 455, pi. 71, figs. 1^1.

Dimensions ( in microns). 50 specimens measured.

Total

Maximum

Minimum

Apertural

length

diameter

diameter

diameter

Range:

204-904

62-96

50-78

61-78

Mean:

403

78

61

69

26 specimens from |

[ Range :

288-667

—

—

—

Estonia (Eisenack
1959) 1

[Mean:

467

—

—

—

26 specimens from |

' Range:

332-690

—

—

the Ostseekalk of
south Finland I

(Eisenack 1965)

[ Mean :

493

-

-

-

30 specimens from |

[Range:

200-616

58-92

—

England (Jenkins
1967)

(Mean:

388

73

Remarks. Conochitina elegans Eisenack 1931 shows the same pattern of morphological
variation in the Sylvan Shale as it does in the Caradocian Jewe and Kegel Beds, Dx-D2,
of Estonia (Eisenack 1959, p. 3, text-fig. 1), and in the Caradoc Series of England
(Jenkins 1967). Throughout the Sylvan Shale, short conical or cylindroconical forms
up to 400 /jl in length (PI. 49, figs. 8-15) predominate numerically over much longer
cylindrical forms, up to 900 /x in length, which have pronounced aboral swellings (PI. 49,
figs. 1-7). The aperture is distinctively fringed by numerous, irregular, simple or branching
processes up to 6 /x in length.

I am reasonably sure that Conochitina elegans and Rhabdochitina hedlundi Taugour-
deau 1965 are conspecific. Well-preserved typical examples of C. elegans occur at
several horizons in the Upper Ordovician Maquoketa Formation from Iowa, where
Taugourdeau obtained the type material of R. hedlundi, but no other species comparable
to C. elegans or R. hedlundi is represented.

Material. Several thousand single tests, and clusters of up to 15 tests each.

Occurrence. Syl-Sy305. The species occurs in the Caradoc Series of Estonia (Eisenack 1959, 19626)
and Shropshire, England (Jenkins 1967), and in the Ostseekalk of north Germany and south Finland
(Eisenack 1965). Taugourdeau and Jekhowsky (1960) record it, as Rhabdochitina conocephala, in
Algerian sediments referred with reservations (op. cit., pp. 1205, 1230) to the lower Silurian. Eisenack
(1964) refers to C. cf. elegans a group of forms from the Llandovery, Wenlock, and lower Ludlow of
Gotland which, while closely similar to the Ordovician type material, are not certainly conspecific
with it.

C 7393

T

272

PALAEONTOLOGY, VOLUME 13

Conochi tina cactacea Eisenack 1937

Plate 49, figs. 18-25; text-fig. 5

1937 Conochitina cactacea Eisenack, p. 222, pi. 15, figs. 14, 15 (holotype).

1959 Conochitina cactacea Eisenack; Eisenack, p. 10, pi. 1, figs. 12 (neotype), 13; text-fig.
2a, b.

non 1965 Conochitina cf. cactacea Eisenack typica Taugourdeau, p. 467, pi. 1, fig. 10.

1965 Conochitina cactacea Eisenack; Eisenack, p. 125, pi. 9, figs. 18, 19.

1967 Conochitina cactacea Eisenack; Laufeld, p. 299, fig. 9.

text-fig. 5. Conochitina cactacea Eisenack 1937. Lateral views illustrating (left) a
typical cylindroconical example with randomly distributed spines, and (right) a
pyriform test whose spines are expanded proximally and arranged in longitudinal
rows, x350.

Dimensions {in microns). 25 specimens measured.

Total

Maximum

Oral tube

Apert ural

Spine

length

diameter

diameter

diameter

length

Range:

118-240

80-123

52-77

53-73

< 15

Mean:

165

97

63

62

—

Neotype (Eisenack 1959):

123

72

42

43

—

EXPLANATION OF PLATE 49

Figs. 1-17. Conochitina elegans Eisenack 1931, x 100. 1-7, Sy60/4/l/A, D, K, Da3/4/l/B, Sy60/4/l/R,
G, and Syl00/4/l/C, respectively, long cylindrical tests with conspicuous aboral swellings. 8-10,
Sy60/4/l/S, H, and J, respectively, shorter tests with neck and chamber differentiated. 11-17,
Sy40/4/l/C, D, F, A, Sy60/4/l/T, Da3/4/l/D and Sy60/4/l/P, respectively, short to very short tests
illustrating some of the very considerable variation that is expressed in both the large and small
size-fractions of populations of C. elegans.

Figs. 18-25. Conochitina cactacea Eisenack 1937, all except 19 b x250. The figured specimens have
been chosen to illustrate the ornament; most are distorted and none shows the typical shape of this
well-known species. 18, Sy60/6/l/A. 19, Syl6/6/l/A; 19 a, showing exceptionally well-preserved
ornament in upper right quadrant of photograph; 19 b, detail of proximally-expanded spines, in
phase-contrast illumination x 1600. 20, Syl6/6/l/D. 21, Syl6/6/l/B. 22, Sy 16/6/1 /F. 23, Sy60/
6/1 /B. 24, Syl6/6/l/E. 25, Syl6/6/l/C.

Palaeontology , Vol. 13

PLATE 49

JENKINS, Ordovician chitinozoa from Oklahoma

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 273

Description. The chamber is conical with straight or swollen flanks, and makes up more
than half the total length. The base is flat, with a broadly rounded margin. The oral
tube, which occasionally is not developed, is cylindrical and approximately two-thirds
of the maximum diameter in width. The aperture is straight, or fringed with irregularly
spaced processes up to 3 /x in length. Short spines, most of which are simple, cover the
entire test. Branching spines with two distal limbs, and A-spines with two or three
discrete bases, however, are common. Spines may taper uniformly, or their proximal
portions may be widely expanded in a plane parallel with the test’s longitudinal axis.
Commonly the spines show some tendency to loosely align themselves in longitudinal
rows, and in some examples the expanded proximal portions of longitudinally adjacent
spines occasionally coalesce, forming very short ridges up to 3 /x in height. Such ridges
tend to be less strongly developed, though no less common, toward the aperture. In
general, spines are largest on the basal margin and become smaller orally.

Material. Approximately 200 single tests.

Occurrence. Syl-Sy305. C. cactacea occurs throughout the Sylvan Shale, but nowhere is it common.
The species occurs in the Ostseekalk of north Germany and Gotland (Eisenack 1965), and in the
Caradocian Dalby and Slandrom Formations of central Sweden (Laufeld 1967). A few atypical exam-
ples are known from the Wesenberg Beds, E, of Estonia (Eisenack 19626, 1965).

Genus cyathochitina Eisenack 19556

Type species. Conochitina campanulaeformis Eisenack 1931 (by original designation), Ordovician,
Baltic.

Cyathochitina agrestis sp. nov.

Plate 50, figs. 11, 18

Holotype. Plate 50, figs. 1 1 a, b. Specimen Syl/8/l/A; Sylvan Shale, 1 ft. (0-3 m.) stratigraphically above
base, Sycamore Creek.

Diagnosis. Large test. Chamber conical to swollen cylindrical, about two-thirds total
length; maximum diameter in lower half or middle of chamber, about one-third chamber
length; base flat, about three-quarters maximum diameter in width. Carina attached
some distance aborally of maximum diameter. Oral tube cylindrical or slightly flaring,
about four-fifths maximum diameter in width; aperture straight. Test wall rough.

Dimensions {in microns). 6 specimens measured.

Total

Chamber

Maximum

Oral tube

Apertural

Carina

length

length

diameter

diameter

diameter

width

Holotype:

980

660

192

148

172

<20

Range :

592-980

376-660

176-192

128-152

136-172

<25

Mean:

784

549

184

142

153

—

Comparison. In general shape this species closely resembles Acanthochitina barbata
Eisenack 1931 and Cyathochitina stentor (Eisenack 1937), but lacks the diagnostic
ornament of either (Jenkins 1967, pp. 443-5; Laufeld 1967, p. 318, respectively). It is
much larger than Cyathochitina calix (Eisenack 1931), 57 Baltic examples of which
(Eisenack 1962a) average 299 p in total length (min. 190 p, max. 450 p).

Material. 10 single tests.

Occurrence. Syl.

274

PALAEONTOLOGY, VOLUME 13

Cyathochitina ontariensis (Jansonius 1964) comb. nov. emend.

Plate 50, figs. 1-9

1964 Tanuchitina ontariensis Jansonius, p. 910, pi. 1, figs. 5, 6 (holotype).

Emended diagnosis. Elongate, cylindroconical, or campanulate test. Chamber approxi-
mately two-thirds total length; base almost flat; margin drawn out into a short sharp
carina, generally directed aborally, and situated slightly below the maximum diameter.
Neck cylindrical, half to two-thirds maximum diameter in width; collarette flaring;
aperture serrate or fimbriate, generally 8-12 p wider than neck. Wall smooth.

Dimensions (in microns). 25 specimens measured.

Total

Maximum

Neck

Apert ural

Carina

length

diameter

diameter

diameter

width

Range :

268-740

102-180

56-88

64-106

<3

Mean:

475

142

69

79

. —

Holotype (Jansonius 1964):

310

—

—

—

—

Description. The flanks may taper uniformly or be slightly swollen (PI. 50, figs. 1, 2, 4,
5), in which cases the chamber and neck are more or less clearly distinguishable.
Occasionally the test is trumpet-shaped, having concave flanks which merge with the
neck (PI. 50, figs. 3, 7). Originally the base probably was flat or almost so; in most
specimens, however, perhaps owing to compression, it is convex in the centre and con-
cave toward the margin. The carina is a continuous, uniformly wide, knife-edge rim
which, in lateral view, rarely protrudes more than 3 p beyond the general silhouette of
the test.

Remarks. This species was designated type species of Tanuchitina by Jansonius (1964),
but is here considered to fall well within the scope of Cyathochitina Eisenack 19556.

Comparison. C. agrestis sp. nov. has a much larger carina than C. ontariensis and the
shape of its test is quite different. C. stentor (Eisenack 1937) is furnished with a strongly
developed, skirt-like carina (up to 85 p in width; Laufeld 1967, p. 318) and an ornament
of strongly defined longitudinal ridges.

Material. Several thousand single tests.

Occurrence. Sy80-Sy305. The type material is from the subsurface Upper Ordovician of Ontario.

EXPLANATION OF PLATE 50

Figs. 1-9. Cyathochitina ontariensis Jansonius 1964, X 100. 1, 2, Syl00/7/l/A and B, respectively,

typical examples with slender campanulate tests and weakly developed carinae. 3, Sy80/7/l/B,
trumpet-shaped test. 4, 5, Sy80/7/l/A and Syl00/70/l/C, respectively, with well-developed carinae.
6-7, Sy80/7/l/C and SylOO/7/l/D, respectively, very short tests. 8, Sy80/7/l/E. 9, Sy80/7/l/D.
Figs. 10, 12-17, 19, 20. Desmochitina minor Eisenack 1931. 10, 14, 15, 19, 20, Syl00/9/l/A, Sy80/9/l/A,
B, C, and Syl00/9/l/B, single tests each with an operculum firmly attached at the base, x250.
12, Sy40/9/l/A, single test lacking an operculum at its base (presumably one was once present and
has since been lost), but having retained the operculum sealing its own aperture (this is set squarely
in the throat of the specimen), x250. 13, 16, 17, Sy60/9/l/B, H, and Syl00/9/l/C, respectively,
chains of tests connected aperture-to-base, x 100.

Figs. 11, 18. Cyathochitina agrestis sp. nov. 11, Syl/8/l/A, holotype; 11a, X 100; 116, carina, x250.
18, Syl/8/l/B, x 100.

Fig. 21. Desmochitina scabiosa (Wilson and Hedlund 1964), Sy60/10/1/D, cluster of four tests, x250.

JENKINS, Ordovician chitinozoa from Oklahoma

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 275

Genus desmochitina Eisenack 1931 emend. 1962a
Type species. Desmochitina nodosa Eisenack 1931 (by original designation), Ordovician, Baltic.

Remarks. For the present I share Eisenack’s (1968, pp. 155, 185) view that Hoegisphaera
Staplin 1961 is superfluous, and would place it (and its junior synonym Calpichitina
Wilson and Hedlund 1964) in synonymy with Desmochitina Eisenack 1931 emend.
1962a. Hoegisphaera was established by Staplin (1961) for ‘a new type of Paleozoic
microfossil possibly allied to the Chitinozoa’ (op. cit., p. 392), in which ‘The colour and
texture of the wall are similar to those of Chitinozoa, but the analogy cannot be carried
farther’ (op. cit., p. 419). However, it is clear that the species assigned to Hoegisphaera
are chitinozoans, and they have been widely recognized as such in the literature (Jan-
sonius 1964, p. 913; 1967, p. 350; Taugourdeau et al. 1967, p. 61; Laufeld 1967, pp.
319-20, 327-8; Jenkins 1967, p. 462; Eisenack 1968, pp. 155, 185). Three years after
Hoegisphaera had been established, Wilson and Hedlund (1964) described the genus
Calpichitina with its type species C. scabiosa. This generic name, however, was proposed
for a species (C. scabiosa) which clearly fell within Staplin’s (1961) concept of Hoegi-
sphaera, and was closely similar in size and shape to Desmochitina complanata
Eisenack 1932 (for dimensions see Eisenack 1959, p. 16). Very shortly after the establish-
ment of Calpichitina, Wilson and Dolly (1964), doubting its validity, abandoned it by
transferring the type species (C. scabiosa) to Hoegisphaera.

Desmochitina minor Eisenack 1931
Plate 50, figs. 10, 12-17, 19, 20

1969 Desmochitina minor Eisenack; Jenkins, pp. 20, 21, pi. 6, figs. 1-18 (q.v. for further
synonymy).

Dimensions {in microns). 25 specimens measured.

Total

Chamber

Maximum

Minimum {neck)

Apertural

length

length

diameter

diameter

diameter

Range :

72-120

60-108

66-86

46-60

54-64

Mean:

92

84

76

53

58

Remarks. Eight informal infraspecific taxa have been referred to Desmochitina minor
by Eisenack (1958, 1962a). The form recorded here corresponds exactly to the informal
taxon D. minor forma typica Eisenack 1958 but is considered to merit recognition
as a separate species. It occurs widely within North America and Europe, where it is
generally quite distinct. The remaining seven infraspecific taxa, and forms transitional
to them, are apparently lacking in the Sylvan Shale.

Most specimens are indistinguishable from many of the examples from Bohemia
(Eisenack 1948, text-figs. 14, 15), the Ordovician Rhenish Schiefergebirge (Eisenack
1939, text-figs. 1-3, 6), and the Swedish and British Caradoc (Laufeld 1967, fig. 25;
Jenkins 1967, pi. 71, fig. 18). They differ appreciably, however, from Eisenack’s Baltic
material (1962a, pi. 16, figs. 1-8, 10; 1965, pi. 10, figs. 16, 17) and the Viola-Fernvale
specimens recorded in an earlier study (Jenkins 1969), in that the general shape of
the chamber in lateral view tends to be spherical rather than quadrangular; the oral
tube is smaller and less sharply flaring; and chains of up to 20 tests are common.

In marked contrast to its broad pattern of morphological variation in the Viola and
Fernvale Limestones (Jenkins 1969, p. 21, pi. 6, figs. 1-18), the species is represented

276

PALAEONTOLOGY, VOLUME 13

within the Sylvan Shale by a conservative form which, throughout the formation, varies
little in size, shape, or surface texture.

Material. Many thousand single tests, and several hundred chains of up to 20 tests each. Clusters of
up to 60 tests are common at horizon Sy60.

Occurrence. Syl6-Sy260. In the lower half of the formation (Syl6-Syl40) D. minor is a numerically
important element in the chitinozoan fauna and occurs in long chains; thereafter its numbers are
drastically reduced, and the species is missing or extremely scarce near the top of the formation
(Sy280-Sy305). Its occurrence outside North America is given elsewhere (Jenkins 1969, p. 21).

Desmochitina scabiosa (Wilson and Hedlund 1964) Jenkins 1969

Plate 50, fig. 21

1958 Desmochitina sp. 2 Wilson, pi. 1, fig. 7.

1962a Desmochitina sp. Eisenack, p. 304, pi. 16, figs. 11, 12.

1964 Calpichitina scabiosa Wilson and Hedlund, p. 164, pi. 1, figs. 1 (holotype), 2-12.

1965 Desmochitina lecaniella Eisenack, p. 131, pi. 10, figs. 21, 22 (holotype).

1967 Desmochitina lecaniella Eisenack; Laufeld, p. 326, fig. 24.

1969 Desmochitina scabiosa (Wilson and Hedlund); Jenkins, p. 23.

Dimensions (in microns). 25 specimens measured.

Total

Chamber

Maximum

Apertural

length

length

diameter

diameter

Range:

50-75

43-68

52-92

48-62

Mean:

61

56

73

56

Holotype (Wilson and
Hedlund 1964):

60

79

41

Remarks. The stratigraphical ranges of D. scabiosa (Wilson and Hedlund 1964) and
D. lecaniella Eisenack 1965 both lie within the Upper Ordovician, and the two species
are so closely similar that it would seem impractical to continue distinguishing them.
Populations from the Sylvan Shale consist largely of single tests, but clusters (sensu
Kozlowski 1963) are common at several horizons.

Material. Several thousand single tests, and numerous clusters of up to 11 tests each.

Occurrence. Sy40-Sy305. Wilson and Hedlund (1964) illustrate several single tests particularly well,
and record the species approximately 50 ft. (15-24 m.) above the base of the formation, at an outcrop
on U.S. Highway 77 about 4 miles (6-4 km.) south of Davis, Oklahoma (text-fig. 1) and 20 miles
(32 km.) north-west of the Sycamore Creek section. Taugourdeau records C. scabiosa (illustrated as
C. cf. scabiosa) in the Maquoketa Formation, Richmond, of Iowa. Desmochitina lecaniella has been
recorded in the Caradocian Kegel Beds, D2, of Estonia (Eisenack 1962a, 1965); in the Ostseekalk of
north Germany, Gotland, and south Finland (Eisenack 1965); and in the Dalby Formation, Caradoc,
of central Sweden (Laufeld 1967).

Genus kalochitina Jansonius 1964

Type species. Kalochitina multispinata Jansonius 1964 (by original designation), Upper Ordovician,
Ontario.

Remarks. The chief diagnostic features of this genus are its pyriform test, reduced
neck, and ornament of numerous, generally small spines which frequently are aligned
in longitudinal rows.

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 277

text-fig. 6. Kalochitina multispinata Jansonius 1964. Lateral views illustrating
variation in the style of the ornament, x 400. a. Typical example with evenly spaced
spines, b. Typical example with spines showing tendency to align themselves in
longitudinal rows, c. Example with reduced ornament of short thorn-like spines.
d, Example furnished with ridges which appear to have formed, figuratively, as if
by fusion of closely spaced A-spines.

Kalochitina multispinata Jansonius 1964
Plate 51, figs. 1-10, 15; text-fig. 6
1958 Genus B, Wilson, pi. 1, figs. 10, 11.

1964 Kalochitina multispinata Jansonius, p. 909, pi. 2, figs. 21 (holotype), 22.

Dimensions (in microns). 30 specimens measured.

Total

Maximum

Apertural

Spine

length

diameter

diameter

length

Range:

102-156

82-103

42-60

< 12

Mean:

121

90

51

—

Holotype (Jansonius 1964) :

140

—

—

—

278

PALAEONTOLOGY, VOLUME 13

Description. The test is pyriform to conical, with a maximum diameter about four-fifths
of the total length. The neck is short, tapering, and rather weakly differentiated from
the chamber; in most individuals it has been lost or was never developed. The apertural
diameter equals or slightly exceeds half the maximum diameter.

In all populations of K. multispinata the ornament varies considerably, but, for the
most part, its range of variation is much the same throughout the formation. The
lower and upper beds (up to horizon Sy60 and above horizon Sy200) contain pure
populations of K. multispinata, but throughout approximately the middle 140 ft.
(43 m.) of the formation (horizons Sy80 to Sy200) the species makes up continuously
intergrading populations with A. rashidi. The two species are distinguished from each
other arbitrarily and solely on the basis of their ornaments (compare text-figs. 2 and 6).
Typical examples of K. multispinata are covered with closely and evenly spaced A-spines,
up to 12 p in length and possessing 2-6 proximal limbs (text-fig. 6a). In many, but by no
means all, of the more typical examples, the proximal limbs of each A-spine, and the
spines as a whole, show some tendency to loosely align themselves in approximately
30 more or less clearly defined longitudinal rows (text-fig. 6b). In addition, each popula-
tion contains individuals whose ornament is reduced to short (< 2-5 p in length) thorn-
like spines (text-fig. 6c). A rare form, seemingly of sporadic vertical distribution, is
furnished with perforate or imperforate ridges up to Sp in height (text-fig. 6 d), which
appear to have formed, figuratively, as if by fusion of very closely spaced A-spines.
Variants transitional to A. rashidi (text-fig. 2) occur from horizon Sy80 to Sy260.
Material. Several thousand single tests, and 20 chains of up to 4 tests each.

Occurrence. Syl6-Sy260. The type material is from the subsurface Upper Ordovician of Ontario
(Jansonius 1964).

Genus rhabdochitina Eisenack 1931

Type species. Rhabdochitina magna Eisenack 1931 (by original designation), Ordovician, Baltic.

Rhabdochitina sp.

Plate 51, fig. 14

Remarks. A species of very large chitinozoan is present in the Sylvan Shale, but only
2 incomplete examples are recorded here, one from horizon Sy80, the other from Syl20.

EXPLANATION OF PLATE 51

Figs. 1-10, 15. Kalochitina multispinata Jansonius 1964, all but 10 X250. 1-5, Sy40/3/l/C, Syl00/3/l/A,
E, G and Sy60/3/l/D, respectively. 6, Sy40/3/l/A, showing ornament through translucent test.
7, 8, Syl00/3/l/B and Sy40/3/l/D, respectively. 9, Da2/3/l/D, cluster of four tests showing a roughly
parallel alignment of their longitudinal axes, a particularly common phenomenon in this species.
10, Sy40/3/l/M, A-spines, in phase-contrast illumination x 1000. 15, Syl00/3/l/D, chain of two
tests.

Figs. 11-13, 16-20. Sphaerochitina lepta sp. nov., a series of tests illustrating inter alia the variable
length of the neck, x250. 11, Sy60/1 1/1/F, compressed so the longitudinal axis of the neck has
folded into the same plane as the transverse axis of the chamber (cf. text-fig. la). 12, 13, 16-18,
Sy60/ll/l/K (holotype), E, M, R, and B, respectively. These specimens are not carinate, as might
be erroneously assumed from the photographs. The sharp prominences on the chambers are not
original features but occur in tests where accommodation during compression has involved an inward
collapse of the base (cf. text-fig. lb). 19, 20, Sy 1 00/ 11/1 /C and D, with relatively long necks.

Fig. 14. Rhabdochitina sp., Sy80/5/l/A, X 100.

18

JENKINS, Ordovician chitinozoa from Oklahoma

Palaeontology, Vol. 13

PLATE 51

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 279

The tests are for the most part cylindrical, swollen at their aboral ends, and quite smooth.
The larger specimen is 180 /jl in width, and its original length exceeded 850 p.

Genus sphaerochitina Eisenack 1955a

Type species. Lagenochitina sphaerocephala Eisenack 1932 (by original designation), Silurian, Baltic.

Sphaerochitina lepta sp. nov.

Plate 51, figs. 11-13, 16-20; text-fig. 7

Holotype. Plate 51, fig. 12. Specimen Sy60/ll/l/K; Sylvan Shale, 60 ft. (18-28 m.) stratigraphically above
base, Sycamore Creek.

text-fig. 7. Sphaerochitina lepta sp. nov., X 550. a , Smooth form which is found in
the middle and upper Sylvan Shale, compressed so the longitudinal axis of the neck
has folded into the same plane as the transverse axis of the chamber, b, example of
the ornamented form which occurs in the upper Sylvan Shale, compressed laterally.

The small sharp prominences (indicated by arrows) simulate the carinae of other
species. They are not original features, however, but are common in tests where
accommodation during compression has involved an inward collapse of the base
(shaded).

Diagnosis. Small, cylindroconical or fungiform test. Chamber and neck of approximately
equal length. Maximum diameter about 150% chamber length; base flat or convex.
Neck one-third to half maximum diameter in width. Aperture straight or fimbriate.
Wall smooth, or bearing small, generally simple processes, thinly and uniformly dis-
tributed over entire test.

Dimensions ( in microns ). 25 specimens measured.

Total

Chamber

Maximum

Neck

Apertural

Process

length

length

diameter

diameter

diameter

length

Holotype:

89

55

85

32

38

—

Range :

83-120

45-60

72-88

29-33

35-43

<3-5

Mean:

97

52

79

31

39

—

Description. In size and shape, this species remains virtually the same wherever it has
been found. The test wall is relatively thin and translucent, and large secondary folds

280

PALAEONTOLOGY, VOLUME 13

are generally present. The ornament consists of cones, simple spines, and a few A-spines
with blunt or pointed tips. The species first occurs in the middle of the formation
(Syl20-Syl80) where it is represented exclusively by smooth forms. Thereafter (Sy200-
Sy305) smooth and ornamented forms occur together.

Comparison. Several species are closely similar to S. lepta, including S. schwalbi Collin-
son and Scott 1958, S. nodulosa Collinson and Scott 1958, and S. actonica Jenkins 1967.
All may be distinguished, however, by the style and distribution of their ornamental
processes.

Material. Several thousand single tests, and a dozen clusters of up to 20 tests each.

Occurrence. Syl20-Sy305.

GENERAL CONCLUSIONS

The chitinozoan fauna of the Sylvan Shale has been examined at widely scattered
localities throughout the Arbuckle Mountains, and at stratigraphical intervals of 20 ft.
(6T0 m.) throughout the 305 ft. (93 m.) thick sequence exposed in the bed and banks
of Sycamore Creek (text-fig. 1), Johnston County, Oklahoma. Preservation is generally
excellent except for the reworked material in the uppermost part of the formation
(p. 282), and rich assemblages occur throughout the area and at all stratigraphical levels.
The fauna has been referred to the following nine genera, and twelve species of which
five are new:

Acanthochitina rashidi sp. nov.

Ancyrochitina merga sp. nov.

Clathrochitina sylvanica sp. nov.

Conochit ina cactacea Eisenack 1937
Conochi tina elegans Eisenack 1931
Cyathochitina agrestis sp. nov.

Cyathochitina ontariensis ( Jansonius 1964) comb. nov.

Desmochitina minor Eisenack 1931
Desmochitina scabiosa (Wilson and Hedlund 1964)

Kalochitina multispinata Jansonius 1964
Rhabdochitina sp.

Sphaerochitina lepta sp. nov.

THE FAUNAL SUCCESSION

No abrupt changes interrupt the general continuity of the chitinozoan succession in
the Sylvan Shale sequence at Sycamore Creek, and deposition would appear to have
continued without significant interruption. Conochitina elegans and C. cactacea occur
throughout the formation, while several other species ( Ancyrochitina merga, Cyatho-
chitina ontariensis, Desmochitina minor, D. scabiosa and Kalochitina multispinata) are
present at nearly all stratigraphical levels and may be considered, for most practical
purposes, characteristic of the formation as a whole (Table 1).

On the basis of gradual changes in the composition of its chitinozoan fauna, however,
the Sylvan Shale at Sycamore Creek may be divided into three biostratigraphical units.
These are not formally proposed in this paper as zones but, since they can be recognized
seemingly unchanged 20 miles (32 km.) north-west of the Sycamore Creek outcrop in

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 281

X

o /

2

N

o /

z

CHITINOZOAN

Cyathochitina agrestis

Conochitina elegans

Conochitina cactacea

Clathrochitina sylvanica

Kaiochitina multispinata

Desmochitina minor

Ancyrochitina merga

Desmochitina scabiosa

Acanthochitina rashidi

Cyathochitina ontariensis

Sphaerochitina lepta

SYLVANSHALE

Sy305

•

•

•

•

•

•

Sy300

•

•

•

•

•

•

Sy280

•

•

•

•

•

•

Sy260

•

•

•

•

•

•

•

•

Sy240

•

•

•

•

•

•

•

•

Sy220

•

•

•

•

•

•

•

•

Sy200

•

•

•

•

•

•

•

•

•

Sy180

•

•

•

•

•

•

•

•

•

•

Sy160

•

•

•

•

•

•

•

•

•

•

Sy140

•

•

•

•

•

•

•

•

•

•

Sy120

•

•

•

•

•

•

•

•

•

•

SylOO

•

•

•

•

•

•

•

•

•

Sy80

•

•

•

•

•

•

•

•

•

Sy60

•

•

•

•

•

•

•

Sy40

•

•

•

•

•

•

•

Sy16

•

•

•

•

•

Syl

•

•

•

?

table 1. Summary of the stratigraphical distribution of chitinozoan species in one section through the
Sylvan Shale of Oklahoma. The two occurrences (Sy80, Syl20) of Rhabdochitina sp. are not shown.

282

PALAEONTOLOGY, VOLUME 13

exposures along U.S. Highway 77, it is not unlikely that after further study they will
form the basis of a more formal, and widely applicable stratigraphical subdivision.
In the lower unit, about 110 ft. (33-5 m.) thick at Sycamore Creek, the fauna diversifies
steadily from 3 to 10 species, and is strikingly characterized by large numbers of Des-
mochitina minor, which are often preserved in very long chains. Only one species,
Cyathochitina agrestis, disappears within this interval, at the top of which the fauna
attains its maximum diversity.

No new forms appear above horizon Syl20, and the fauna in approximately the
middle 160 ft. (48 m.) of the formation, from horizon Syl20 to Sy260, is remarkably
stable. It consists initially of 10 species and changes qualitatively only in that about
midway up it loses Acanthochitina rashidi and Clathrochitina sylvanica. In addition, the
numbers of Desmochitina minor above horizon Syl60 are drastically reduced and only
rarely is the species preserved in chains.

The upper biostratigraphical unit of the Sylvan Shale lies above horizon Sy260 and is
between 25 and 45 ft. (7-6—13-7 m.) thick at Sycamore Creek. It contains throughout a
reduced fauna of only 6 species, and its base is marked by the disappearance of in situ
specimens of Desmochitina minor and Kalochitina multispinata. In addition, numerous
chitinozoans are present which, judging from their condition and identity, are almost
certainly reworked from older Sylvan sediments. Their state of preservation contrasts
strikingly with that of the forms considered to be in situ. They are bleached, corroded,
perforated by the holes of ‘boring organisms’, and lack all but the stumps of their
ornamental processes.

The occurrence of reworked Sylvan chitinozoans in upper Sylvan strata indicates
that during late Sylvan time uplift took place, at least locally, in the southern mid-
continent. The area of uplifted strata is not known, however (Ham, personal com-
munication, 1969), and will need to be determined by future work demonstrating the
absence of uppermost Sylvan beds beneath the lower Llandovery Keel Formation,
which is the basal unit of the Silurian-Devonian Hunton Group. Although the pre-Keel
unconformity is well-known and widely distributed (though very poorly exposed) in
the Arbuckle Mountains, associated uplift beginning in late Sylvan time has thus far
been unsuspected.

At Sycamore Creek, the three biostratigraphical subdivisions distinguished above
correspond approximately to the three units of a tripartite lithostratigraphical sub-
division (q.v., p. 263) that is recognizable widely within Oklahoma and clearly apparent
in the Arbuckle Mountains. These are successively, a sequence of hard, very fissile,
brown to dark grey shales up to 130 ft. (40 m.) or so thick in the lower part of the
formation; a succession of soft, weakly fissile, greenish-grey shales up to 200 ft. (61 m.)
thick in the upper part ; and a thin sequence, about 30 ft. (9 m.) thick, of soft, massive,
light green claystone at the top.

LATERAL DISTRIBUTION OF THE SYLVAN CHITINOZOAN FAUNA

In order to determine how much the character of the Sylvan chitinozoan fauna varies
regionally, several samples were collected at widely scattered localities throughout the
Arbuckle Mountains. In addition to those from Sycamore Creek, which lies at the
extreme southern end of the mountains, samples were obtained from outcrops along

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 283

U.S. Highway 77 about 4 miles (64 km.) south of Davis (text-fig. 1), map reference sec. 30,
T. 1 S., R. 2 E., Murray County, in the western ‘thumb’ of the mountains; at Lawrence
(Ideal Portland Cement Company) Quarry (text-fig. 1), map reference sec. 36, T. 3 N.,
R. 5 E., Pontotoc County, in the area’s most northerly exposure of Sylvan Shale; and
at several localities in between. Assemblages of chitinozoans from these samples
indicate clearly that the Sylvan fauna extends throughout the Arbuckle Mountains and
remains essentially unchanged 20 miles (32 km.) to the north-west, and 30 miles (48 km.)
to the north, of the Sylvan outcrops on Sycamore Creek. Furthermore, the fauna is not
restricted to the immediate environs of the Arbuckle Mountains. Core samples from
borings in north-western Texas prove its very extensive lateral distribution, and demon-
strate that its composition remains essentially unchanged up to 180 miles (288 km.) west
of the Arbuckle Mountains.

Several species of Sylvan chitinozoans are present 650 miles (1050 km.) north-north-
east of the Arbuckle Mountains in outcrops of the Maquoketa Formation in eastern
Iowa. These include Conochitina elegans, Cyathochitina ontariensis, Desmochitina minor,
D. scabiosa, and Kalochitina multispinata , and provide substantial fossil evidence
that the Sylvan Shale of Oklahoma and the Maquoketa Formation of Iowa are, for the
most part, of the same general age. In so far as they correlate the two formations, they
would support Decker’s (1935, p. 698) view that in the subsurface the Sylvan Shale
grades north-eastward into the Maquoketa Formation. At the same time these fossils
provide some palaeontological evidence to substantiate Lee’s (1943, p. 40) assertion that
‘The Maquoketa shale ... in the Mississippi Valley ... is equivalent to the Sylvan shale
of Oklahoma’, and (op. cit., p. 42) his view that ‘The Maquoketa shale was originally
deposited . . . probably across the Chautauqua arch in continuation with the Sylvan
shale of Oklahoma.’

Several species not mentioned above have been identified by Taugourdeau (1965) in
poorly preserved material from two samples of the Maquoketa Formation from Iowa.
These are : Ancyrochitina ancyrea (Eisenack 1931), but Taugourdeau’s doubts (op. cit., p.
465) about this identification are clearly implied, and his specimens may well be broken
examples of A. merga sp. nov. ; Cyathochitina campanulaeformis (Eisenack 1931); C.
kuckersiana (Eisenack 1934); Desmochitina minor forma ovulum Eisenack 1962a, here
considered specifically distinct from D. minor Eisenack 1931 ; and Hoegisphaera utricula
Taugourdeau 1965. In addition, Taugourdeau (op. cit.) records Desmochitina scabiosa
(designated Calpichitina scabiosa in text, but C. cf. scabiosa in plate explanations) and
Rhabdochitina hedlundi Taugourdeau 1965 (here [p. 271] considered a junior synonym of
Conochitina elegans Eisenack 1931).

CHITINOZOAN FAUNAS FROM ABOVE AND BELOW THE SYLVAN SHALE

The chitinozoan fauna of the Sylvan Shale differs strikingly from that which precedes
it in the underlying Viola and Fernvale Limestones (Jenkins 1969), the two faunas
containing only one species, Desmochitina minor, in common. Numerous samples of
both units, collected at points throughout the Arbuckle Mountains, indicate that the
differences between the two faunas persist laterally over a wide area and are everywhere
essentially the same. As noted earlier (op. cit., p. 34): ‘The striking difference between
the Viola-Fernvale and Sylvan faunas suggests that the unconformity between the two

284

PALAEONTOLOGY, VOLUME 13

stratigraphical units probably represents a substantial period of time (although no
reliable indication of its duration can presently be given) or that the character of
chitinozoan faunas may be very much more subject to control by the environment of
deposition than has hitherto been suspected.’

Chitinozoans have been cursorily examined from the several carbonate formations
of the Silurian-Devonian Hunton Group, which overlie the Sylvan Shale in Kansas,
Oklahoma, and Texas. It would appear from this preliminary examination that the
younger faunas are entirely different from those of the Ordovician Viola, Fernvale, and
Sylvan formations, and that their affinities lie with faunas which existed contemporan-
eously in Europe (Eisenack 1955a, 19556, 1959, 1962a, 1964) and North Africa (Tau-
gourdeau and Jekhowsky 1960, Taugourdeau 1962).

AGE AND CORRELATION OF THE SYLVAN SHALE

The Sylvan Shale has been dated uppermost Ordovician on the basis of its graptolite
fauna (Decker 1935, pp. 698-700; 1936a, pp. 308-9; 19366, pp. 1256-7; Berry 1960a,
p. 31, table 2). Generally it has been correlated (Decker 1935, Twenhofel et al. 1954,
Berry 1960a) with part of the Richmond Stage, which is typically developed in the upper
valley of the Ohio River and considered approximately correlative with the Ashgill
Series of Britain. It is also correlated by graptolites with the Maquoketa Formation of
the upper Mississippi Valley (Decker 1935, p. 698; 1936a, p. 308; 19366, p. 1257; Twen-
hofel et al. 1954); the upper Maravillas Chert in the Marathon Basin of western Texas
(Twenhofel et al. 1954; Berry 1960a, p. 38, table 2); and the Polk Creek Shale in the
Ouachita Mountains of south-eastern Oklahoma and south-western Arkansas (Decker
1936a, p. 308; 19366, pp. 1256-7, table 1 ; Harlton 1953, p. 787, fig. 2; Twenhofel et al.
1954; Berry 1960a, p. 38, table 2). The fauna contains, in particular, Dicellograptus
complanatus, which gives its name to the lower graptolite zone of the British Ashgill.
Lee (1943, p. 40) asserts, but without supporting evidence, that the Maquoketa Forma-
tion and the Sylvan Shale are equivalent, and (op. cit., pp. 43, 108) uses the terms
‘Maquoketa’ and ‘Sylvan’ interchangeably.

For many years prior to the mid 1930s the age of the Sylvan Shale was in dispute,
the formation being assigned alternately to the Ordovician and Silurian Systems.
Although most authors expressed their opinions about the Sylvan’s age cautiously,
sometimes acknowledging them to be provisional, a few asserted their views with un-
warranted confidence. Indeed, in 1930 (p. 306) Levorsen, making no attempt to sub-
stantiate his claim, went so far as to state categorically that ‘Eventually the Sylvan
shale and the underlying upper Viola limestone will undoubtedly be generally regarded
as Silurian in age.’ A few years later Decker (1935) recorded graptolites of unquestion-
able Ordovician age in the lower beds of the formation, and the debate virtually ceased.

It is important to realize, however, that Decker’s discovery of graptolites did not com-
pletely solve the problem of the Sylvan Shale’s age, and that for 35 years the whole
formation has been dated and correlated on the basis of graptolites which generally
are confined to the basal beds and only exceptionally extend up through the lower 100 ft.
(30 m). The upper part of the Sylvan Shale, 200 ft. (60 m.) or more thick over much of
southern Oklahoma, apparently lacks not only graptolites but all macrofossils, and
has been placed in the Ordovician on the basis of its association with the lower Sylvan.

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 285

The present study demonstrates for the first time that the formation is Ordovician in
its entirety, and at the same time confirms with additional fossil evidence the Upper
Ordovician age of the lower beds. It is hoped, and considered likely, that when the
vertical ranges of chitinozoans in the North American type sections (or other standards
of stratigraphical reference) are better documented this study will provide a means of
correlating and more precisely dating all parts of the formation.

table 2. List of previously described species (column A) found in the Sylvan Shale
and their occurrences in reliably dated sediments outside Oklahoma.

Previously \ Occurrence

Upper Ordovician

Lower Ordovician

described species \ outside

1 Southern! Anticosti Island,

of Estonia

in the Sylvan Shale \ Oklahoma

Northern Europe

| Ontario |

Quebec

and Britain

Conochitina cactacea

X

Conochitina elegans
Cyathochitina ontariensis

X

X

Desmochitina minor

X

X

X

Desmochitina scabiosa

X (designated
D. lecaniella )

X

Kalochitina multispinata

X

Column A

B

c

D

E

The six previously described species in the Sylvan Shale occur in Upper Ordovician
sediments over a very wide area. To my knowledge only one of them, Desmochitina
minor , has been recorded in reliably dated sediments below the Upper Ordovician
(Eisenack 1958, 1962a, 6; Jenkins 1967), and none is known from sediments reliably
dated as Silurian. Four (Table 2, column B) are present in northern Europe (Eisenack
19626, 1965; Laufeld 1967; Jenkins 1967) and two (column C) occur in the subsurface
of southern Ontario (Jansonius 1964). In addition, I have encountered typical examples
of D. minor and D. scabiosa in photographs of Upper Ordovician chitinozoans from
the subsurface of Anticosti Island, Quebec; this record, based upon material kindly
provided by Dr. Jansonius, raises to four the number of species common to the Sylvan
Shale and the Upper Ordovician of eastern Canada (Table 2, columns C and D).

A new species found in the Sylvan Shale, Acanthochitina rashidi, is furnished with a
well-developed ‘raised reticulum’ (q.v., text-fig. 2; and Jenkins 1967, text-fig. 3), a rare
style of ornament which elsewhere, perhaps significantly, is known only from young
Ordovician deposits. These are, namely, the Ostseekalk of north Germany (Eisenack
1965), the Lyckholm Beds, Fx, of Estonia (Eisenack 19626), the Caradoc of Anticosti
Island, Quebec (Jansonius 1967, pi. 1, fig. u), the upper Caradocian Onnia Beds in the
Caradoc type section, Shropshire, England (Jenkins 1967), and the uppermost Caradoc
of central Sweden (Laufeld 1967, pp. 295-6, 298).

The presence in the Sylvan Shale of cylindroconical chitinozoans with strongly
developed, anastomosing appendices ( Clathrochitina sylvanica ) would appear to herald
the approach of Silurian time and emphasizes the very young Ordovician age of the
formation. Chitinozoans of this general type are elsewhere known only from sediments
of Silurian and, perhaps, earliest Devonian age (Eisenack 1959; Taugourdeau and
Jekhowsky 1960, pi. 2, fig. 32; Cramer 1964, 1967a; Taugourdeau 1967).

286

PALAEONTOLOGY, VOLUME 13
APPENDIX: DESCRIPTION OF SAMPLES

The samples used in this study are listed below in ascending stratigraphical order. They are num-
bered according to their original positions (measured in feet) above the Fernvale Limestone-Sylvan
Shale contact. Thus sample Sy280, for example, is from a horizon 280 ft. above this datum.

The total thickness of the Sylvan Shale in Sycamore Creek was measured as 305 ft. (93 m.).

Syl

Syl6

Sy40

Sy60

Sy80

Calcareous, dark brown, hard platy shale with conchoidal fracture, containing
black graptolite compressions.

Slightly calcareous, buff- to orange-weathering brown shale.

Slightly calcareous, dark grey shale containing abundant graptolites.

Slightly calcareous, dark greyish-brown shale.

Slightly calcareous, dark greenish-grey, hard splintery shale with conchoida
fracture.

Syl 00, Syl 20 Slightly calcareous, dark brown silty shale with thin yellow and grey laminae.

Syl 40 Slightly calcareous, green to greenish-brown, soft shale.

Syl 60 Slightly calcareous, green, soft shale with purple-hearted concretions.

Syl 80, Sy200 Slightly calcareous, dark greenish-grey, soft shale.

Sy220, Sy240, Sy260 Calcareous, greenish-grey, soft concretionary shale.

Sy280, Sy300, Sy305 Calcareous, light green, soft claystone, which disaggregates readily in water.

Acknowledgements. This work is the second part of a larger study of North American Ordovician
Chitinozoa carried out at the University of Oklahoma. I am indebted to the Science Research Council
of Great Britain for the award of a two-year Research Fellowship, and to Dr. L. R. Wilson for inviting
me to work in his laboratory during its tenure. I wish to record my sincere gratitude to the late Dr.
M. A. Rashid and Mr. J. A. Turnbull for assistance in the field, and to the latter for invaluable help in
measuring the Sycamore Creek section; to Dr. J. Jansonius (Imperial Oil Ltd., Calgary) for generously
permitting me to validate his manuscript genus ‘ Sagenachitina' ; to the American Association of
Stratigraphic Palynologists for a generous donation toward the cost of publication; and to Humble
Oil and Refining Company for readily agreeing to my publishing this study. I am especially grateful
to Dr. R. W. Hedlund (Atlantic Richfield Company, Dallas) who, after completing a substantial
study of organic-walled microfossils in the Sylvan Shale, offered me complete freedom to pursue
the subject and encouraged me to publish this paper.

For their critical reading of the paper in typescript I thank Miss J. B. Stough (Esso Production Re-
search Company, Houston), Dr. A. E. Marshall (Humble Oil and Refining Company, Houston) and
Drs. T. W. Amsden and W. E. Ham (Oklahoma Geological Survey).

REFERENCES

amsden, t. w. 1960. Stratigraphy and paleontology of the Hunton Group in the Arbuckle Mountain
region. Pt. VI. Hunton Stratigraphy. Bull. Okla. geol. Surv. 311 pp., 17 pi.

beju, d., and danet, n. 1962. Chitinozoare siluriene din Platforma moldoveneasca si Platforma
moezica. Petrol si Gaze, 13, 527-36, pi. 1, 2.

benoit, a., and taugourdeau, p. 1961. Sur quelques chitinozoaires de l’Ordovicien du Sahara.
Revue lnst.fr. Petrole, 16, 1403-21, pi. 1-5.

berry, w. b. n. 1960a. Graptolite faunas of the Marathon region, west Texas. Univ. Tex. Pubis. 6005,
179 pp., 20 pi.

1960 b. Correlation of Ordovician graptolite-bearing sequences. 21st Int. geol. Congr., pt. 7

97-108.

cooper, G. a. 1956. Chazyan and related brachiopods. Smithson, misc. Colins. 127 (2 parts), 1245 pp.,
269 pi.

cramer, f. h. 1964. Microplankton from three Palaeozoic formations in the province of Leon,
NW-Spain. Leid. geol. Meded. 30, 253-361, pi. 1-24.

1967a. Chitinozoans of a composite section of Upper Llandoverian to basal Lower Gedinnian

sediments in northern Leon, Spain. Bull. Soc. beige Geol. Paleont. Hydrol. 75 (1966), 69-129, pi. 1-5.

JENKINS: CHITINOZOA FROM THE ARBUCKLE MOUNTAINS, OKLAHOMA 287

cramer, f. h. 19676. An evaluation of the chitinozoan genus Clathrochitina Eisenack, 1959. Notas
Comun. Inst. geol. min. Esp. 94, 45-52.

decker, c. e. 1935. Graptolites of the Sylvan Shale of Oklahoma and Polk Creek Shale of Arkansas.
/. Paleont. 9, 697-708.

1936a. Some tentative correlations on the basis of graptolites of Oklahoma and Arkansas. Bull.

Am. Ass. Petrol. Geol. 20, 301-11.

19366. Table of tentative Lower Paleozoic correlations on basis of graptolites. Ibid. 20, 1252-7.

1945. Graptolites on well cuttings. Carter County, Oklahoma. Ibid. 29, 1043-5.

eisenack, a. 1930. Neue Mikrofossilien des baltischen Silurs. (Vorlaufige Mitteilung.) Naturwissen-
schaften, 18, 880-1.

1931. Neue Mikrofossilien des baltischen Silurs I. Palaont. Z. 13, 74-118, pi. 1-5.

1932. Neue Mikrofossilien des baltischen Silurs II. Ibid. 14, 257-77, pi. 11, 12.

1934. Neue Mikrofossilien des baltischen Silurs III und neue Mikrofossilien des bohmischen

Silurs I. Ibid. 16, 52-76, pi. 4, 5.

1937. Neue Mikrofossilien des baltischen Silurs IV. Ibid. 19, 217-43, pi. 15, 16.

1939. Chitinozoen und Hystrichosphaerideen im Ordovicium des Rheinischen Schiefergebirges.

Senckenberg. leth. 21, 135-52, pi. a-b.

1948. Mikrofossilien aus Kieselknollen des bohmischen Ordoviziums. Ibid. 28, 105-17, pi. 1.

1955a. Chitinozoen, Hystrichospharen und andere Mikrofossilien aus dem Beyrichia-Kalk. Ibid.

36, 157-88, pi. 1-5.

19556. Neue Chitinozoen aus dem Silur des Baltikums und dem Devon der Eifel. Ibid. 36, 311-19,

pi. 1.

1958. Mikrofossilien aus dem Ordovizium des Baltikums. 1. Markasitschicht, Dictyonema-

Schiefer, Glaukonitsand, Glaukonitkalk. Ibid. 39, 389-405, pi. 1, 2.

1959. Neotypen baltischer Silur-Chitinozoen und neue Arten. Neues Jb. Geol. Palaont. Abh.

108, 1-20, pi. 1-3.

1962a. Neotypen baltischer Silur-Chitinozoen und neue Arten. Ibid. 114, 291-316, pi. 14-17.

19626. Mikrofossilien aus dem Ordovizium des Baltikums. 2. Vaginatenkalk bis Lyckholmer

Stufe. Senckenberg. leth. 43, 349-66, pi. 44.

1964. Mikrofossilien aus dem Silur Gotlands. Chitinozoen. Neues Jb. Geol. Palaont. Abh. 120,

308-42, pi. 26-30.

1965. Die Mikrofauna der Ostseekalke. 1. Chitinozoen, Hystrichospharen. Ibid. 123, 115-48,

pi. 9-13.

1968. fiber Chitinozoen des baltischen Gebietes. Palaeontographica, 131 A, 137-98, pi. 24-32.

ham, w. e. 1969. Regional Geology of the Arbuckle Mountains, Oklahoma. Oklahoma Geological Survey,
Guide Book 17, Univ. Oklahoma Press, Norman.

and wilson, j. l. 1967. Paleozoic epeirogeny and orogeny in the central United States. Am. J.

Sci. 265, 332-407.

harlton, b. h. 1953. Ouachita chert facies, southeastern Oklahoma. Bull. Am. Ass. Petrol. Geol. 37,
778-96.

hass, w. h., and huddle, j. w. 1965. Late Devonian and Early Mississippian age of the Woodford
Shale in Oklahoma, as determined from conodonts. Prof. Pap. U.S. geol. Surv. 525-D, D125-32.
jansonius, j. 1964. Morphology and classification of some Chitinozoa. Bull. Canad. Petrol. Geol. 12,
901-18, pi. 1, 2.

1967. Systematics of the Chitinozoa. Rev. Palaeobot. Palynol. 1, 345-60, pi. 1.

jenkins, w. a. m. 1967. Ordovician Chitinozoa from Shropshire. Palaeontology, 10, 436-88, pi. 68-75.

1969. Chitinozoa from the Ordovician Viola and Fernvale Limestones of the Arbuckle Mountains,

Oklahoma. Spec. Pap. Palaeont. no. 5, 44 pp., 9 pi.
kay, m. 1960. Classification of the Ordovician System in North America. 21st. Int. geol. Congr., pt. 7,
28-33.

laufeld, s. 1967. Caradocian Chitinozoa from Dalarna, Sweden. Geol. For. Stockh. Forh. 89, 275-
349, figs. 1-34.

lee, w. 1943. The stratigraphy and structural development of the Forest City Basin in Kansas.
Bull. Kansas Univ. geol. Surv. 51, 142 pp.

levorsen, A. I. 1930. Geology of Seminole County. Bull. Okla. geol. Surv. 40 (3), 287-352.

C 7393

U

288

PALAEONTOLOGY, VOLUME 13

ruedemann, R. 1947. Graptolites of North America. Mem. geol. Soc. Am. 19, 652 pp., 92 pi.
staplin, f. l. 1961. Reef-controlled distribution of Devonian microplankton in Alberta. Palaeontology,
4, 392-424, pi. 48-51.

taugourdeau, p. 1961. Chitinozoaires du Silurien d’Aquitaine. Revue Micropaleont. 4, 135-54, pi.
i-6.

1962. Associations de chitinozoaires dans quelques sondages de la region d’Edjele (Sahara).

Ibid. 4, 229-36, pi. 1.

■ 1965. Chitinozoaires de l’Ordovicien des U.S.A. ; comparaison avec les faunes de l’ancien monde.

Revue lnst.fr. Petrole, 20, 463-85, pi. 1-3.

1967. Neotypes de chitinozoaires. Revue Micropaleont. 9, 258-64, pi. 1.

and jekhowsky, b. de. 1960. Repartition et description des chitinozoaires siluro-devoniens de

quelques sondages de la C.R.E.P.S., de la C.F.P.A. et de la S.N. REPAL au Sahara. Revue Inst.fr.
Petrole, 15, 1199-1260, pi. 1-13.

et al. 1967. Microfossiles organiques du Paleozoique. Les chitinozoaires (1). Analyse biblio-

graphique illustree. Published for the Commission Internationale de Microflore du Paleozoique by
the Centre National de la Recherche Scientifique, Paris.
thomas, h. s. 1930. Characteristics of the Sylvan Shale in widely separated areas. Proc. Okla. Acad.
Sci. 10, 85-87.

twenhofel, w. h. et al. 1954. Correlation of the Ordovician formations of North America. Bull,
geol. Soc. Am. 65, 247-98.

wilson, l. r. 1958. A chitinozoan faunule from the Sylvan Shale of Oklahoma. Okla. Geol. Notes,
18, 67-71, pi. 1.

and dolly, e. d. 1964. Chitinozoa in the Tulip Creek Formation, Simpson Group (Ordovician),

of Oklahoma. Ibid. 24, 224-32, pi. 1.

and hedlund, r. w. 1962. Acid-resistant microfossils of the Sylvan Shale (Ordovician) of

Oklahoma. Pollen Spores, 4, 388.

1964. Calpichitina scabiosa, a new chitinozoan from the Sylvan Shale (Ordovician) of

Oklahoma. Okla. Geol. Notes, 24, 161-4, pi. 1.

W. A. M. JENKINS

Humble Oil and Refining Company
P.O. Box 2189

Houston, Texas 77001, U.S.A.

Typescript received 5 July 1969

A NEW SPECIES OF HEMICYPRIS
(OSTRACODA) FROM ANCIENT BEACH
SEDIMENTS OF LAKE RUDOLF, KENYA

by R. H. BATE

Abstract. A new fossil species of Hemicypris ( H . posterotruncata sp. nov.) is described from ancient beach
sediments of Lake Rudolf, Kenya. The presence of marginal sockets within the duplicature of the right valve,
for the reception of the marginal denticles of the left valve, is recorded for the first time.

Towards the end of 1968 two sieved residues of beach sand (samples M4 and M7)
were received from Dr. B. Verdcourt. These samples consisted of 90% ostracod and
small gastropod shells with a very subordinate amount of smooth, water worn, quartz
grains. The beach sand was collected from two localities: M4 from a site 20 ft. below
the beach crest (east side) and approximately 100 yards out from the ridge crest to the
south of Lothagam Hill, and M7 from the west of Lothagam Hill. Both samples were
collected by Dr. M. D. Gwynne during the Royal Geographical Society South Turkana
Expedition. The map showing the location of the samples (text-fig. 1) is based on a
sketch provided by Dr. Gwynne. This paper is no. V of the South Turkana Expedition
Papers.

The ostracods, present in very large numbers, are all referable to the single new
species Hemicypris posterotruncata sp. nov. It is difficult to give a precise age dating to
the beach deposits as neither the ostracod nor the molluscs listed below are of any
assistance in this matter. All that can be said is that they are sub-Recent, possibly
Holocene or even Pleistocene in age. What is indicated, however, is that Lake Rudolf
was very much more extensive in the past than is the case at the present time.

The following molluscs have been identified by Dr. Verdcourt from the two samples
mentioned above:

Sample M3 (from which the residue M4 was obtained)

1. Bellamy a unicolor costulata (Von Mts.)

2. Cleopatra bulimoides pirothi (Jiekeli)

3. Melanoides tuberculata (Mull)

4. Caelatura chefneuxi (Neuv. and Anthony)

5. Caelatura rothschildi (Neuv. and Anthony)

6. Corbicula africana pusilla (Philippi)

7. Biomphalaria pfeifferi (Krauss)

Sample M7. Associated molluscs were nos. 1, 2, 3 and 5 together with:

Mutella nilotica (Cailliand)

Mutella alluaudi (Germain)

All the material described in this paper is in the collections of the Department of Palaeontology, British
Museum (Natural History).

The photographs were taken on the scanning electron microscope.

[Palaeontology, Vol. 13, Part 2, 1970, pp. 289 296, pi. 52.]

290

PALAEONTOLOGY, VOLUME 13

SYSTEMATIC DESCRIPTION

Subclass ostracoda Latreille 1806
Order podocopida Muller 1894
Suborder podocopina Sars 1866
Family cyprididae Baird 1845
Subfamily cypridinae Baird 1845
Genus hemicypris Sars 1903

Type species. Hemicypris pyxidata (Moniez), designated Swain (1961, p. Q221).

Remarks. Sars included three species in his new genus Hemicypris: Hemicypris pyxidata
(Moniez), H. ovata sp. nov., and H. megalops sp. nov., although he did not designate a
type species (see above). His reasons for distinguishing Hemicypris from the closely
related genus Cyprinotus Brady were that the right valve in each case was larger than

291

R. H. BATE: A NEW SPECIES OF HEMICYPRIS (OSTRACODA)

the left, the second pair of maxillae were devoid of a vibratory plate and that they all
reproduced parthenogenetically.

The validity of Hemicypris was refuted by Klie (1932, p. 471) after he had examined
material identified by Sars. Klie pointed out that the three species placed in Hemicypris

text-fig. 2. a, b, Hemicypris pyxidata (Moniez), F. 12294, Univ. Oslo; left and right views, complete
carapace, c, d, Hemicypris ovata Sars, F. 12293, Univ. Oslo; left and right views, complete carapace.
e,f Hemicypris megalops Sars, F. 12292, Univ. Oslo; right and left views, complete carapace.

by Sars did in fact possess a vibratory plate and that this was clearly visible in both
pyxidata and ovata. He further stated that, as recommended in a previous publication
of his (1930), the genus Cyprinotus should be retained for those species in which the
valves have a crenulate margin and a dorsal hump, and that Heterocypris should be
used for those species lacking a dorsal hump whether or not the valves were crenulate
at their margins. Accordingly he placed pyxidata and megalops in Heterocypris.

This arrangement of Klie’s is not, however, satisfactory as the characters of the cara-
pace play an important role in the grouping of ostracods into natural units, and the

292

PALAEONTOLOGY, VOLUME 13

possession of marginal denticles is considered here to indicate a close genetic affinity
between the species. These species should not, therefore, be placed in Heterocypris.
Coupled with a general umbonate dorsal outline the genus Cyprinotus may be clearly
divided into those forms in which the left valve is the larger ( Cyprinotus s.s.) and those
in which the right valve is the larger ( Hemicypris s.s.). In both groups it is the smaller
valve which possesses the marginal denticles. If there was but a single species having
the right valve larger than the left it would be unnecessary to retain the genus Hemi-
cypris. There are, however, twelve species having a wide geographical distribution which
may be assigned to the Hemicypris group. Should this morphological group be placed
in Cyprinotus or separately identified? If the latter case, are the characters present
sufficient for a generic or a subgeneric determination? It is considered here that the
presence of at least twelve species indicates that this group has developed sufficiently
for a generic determination to be made.

The following species are here placed in Hemicypris :

Cyprinotus pyxidatus Moniez 1892, the type species, described from a pond in Luwu in the Celebes.
Hemicypris ovata Sars 1903, from dried mud, north-eastern Sumatra.

Hemicypris megalops Sars 1903, from dried mud, north-eastern Sumatra.

Cyprinotus ( Hemicypris ) kaufmanni Vavra 1906, from an ornamental fish pond, the Bronze Horse
Temple, Nagasaki, Japan.

Cyprinotus fossulatus Vavra 1898, from Usaramo, Tanzania.

Cyprinotus decoratus Daday 1910, from the Zoological Gardens, Giza [Gizeh], Egypt.

Cyprinotus inversus Daday 1913, from Ku-Gudie, Kalahari, South Africa.

Cyprinotus fullerborni Daday 1910, from Lake Rukwa [Rikwa], Tanzania.

Cyprinotus humbertii Gauthier 1933, from Ambovombe, Malagassy Republic.

Heterocypris reticulatus Klie 1930, from Gran Chaco, Paraguay.

Hemicypris posterotruncata sp. nov., this paper, sub-Recent beach sediment, Lake Rudolf, Kenya.
Heterocypris dentatomarginata Kiss 1959, from Lake Tanganyika.

Hemicypris posterotruncata sp. nov.

Plate 52, figs. 1-7; text-fig. 3 d-i, text-fig. 4a, b

Diagnosis. Hemicypris with strongly calcified carapace, of angular outline with truncated,
broadly flattened posterior end. Dorsal margin arched, umbonate, with greatest height
passing through anterior cardinal angle ; greatest length passing well below mid-point.

Holotype. Io. 1410, carapace, figured Plate 52, fig. 1, text-fig. 3, figs. d-g. Sub-Recent beach sediment,
Lake Rudolf, Kenya.

Paratypes. Io. 1411-49, carapaces and single valves from the same locality as above.

Other material. Io. 1450a, b. Topotype material contained in the original sample (M4) ; locality as above.

Description. Carapace strongly calcified, subrectangular in outline with broadly rounded
anterior end and broad, truncated posterior end. Postero-dorsal slope long, flattened;

EXPLANATION OF PLATE 52

Hemicypris posterotruncata sp. nov. 1, left view of complete carapace, holotype, Io. 1410, x85.
2, right valve, paratype, Io. 1419, x 85. 3, internal view of left valve showing anterior and posterior
marginal denticles, paratype Io. 1415, x 85. 5, section of anterior duplicature, right valve, showing
small pits (sockets) for the reception of the marginal denticles of the left valve; paratype, Io. 1416,
x500. 6, anterior duplicature, left valve, to show marginal denticles, paratype, Io. 1415, x500.
7, central and dorsal muscle scars, internal view of right valve, paratype, Io. 1418, x85.

Palaeontology, Vol. 13

PLATE 52

BATE, Hemicypris posterotruncata

293

R. H. BATE: A NEW SPECIES OF HEMICYPRIS (OSTRACODA)

postero-ventral slope convex. Posterior cardinal angle situated very close to extreme
posterior end of carapace and prominently developed. Dorsal margin convex, umbonate
at anterior cardinal angle which is situated above, or slightly in front of mid-point of
carapace. Line of greatest height of valve passes through this cardinal angle. Extreme

text-fig. 3. a-c, Hemicypris fossulata (Vavra), K. 19043, Zool. Staatsinstitut, Hamburg; left
and right views, complete carapace and muscle scars, d-g, Hemicypris posterotruncata sp. nov.

Io. 1410, holotype; right, left, dorsal and ventral views, complete carapace, h, i, Hemicypris
posterotruncata sp. nov. Io. 1411, paratype; right and left views, complete carapace.

posterior termination of carapace is situated below mid-height and as a result line of
greatest length passes well below mid-point. Line of greatest width passes through
carapace slightly behind mid-point. Antero-dorsal slope long and obliquely convex.
Ventral margin moderately convex with shallow median incurvature.

Right valve much larger than left, overlapping it strongly in region of antero-dorsal
slope. Right valve also overlaps left along ventral margin and around posterior margin,

294

PALAEONTOLOGY, VOLUME 13

but anteriorly merely projects beyond the left. Mid-dorsally valves tend to diverge
slightly and there is no overlap or overreach of either valve.

Shell surface granular, showing no evidence of surface pitting.

Hinge is simple with dorsal edge of smaller left valve
(terminally thickened) fitting into groove situated in dorsal
margin of right valve. This dorsal groove terminally widens
to produce elongate sockets which are open at their ends
to interior of valve.

Duplicature is of moderate width anteriorly and slightly
more narrow posteriorly; selvage is particularly well
developed in left valve. Inner margin and line of con-
crescence do not quite coincide but a distinct vestibule is
not developed. Around antero-ventral and postero-ventral
parts of free margin, small marginal denticles are developed
in smaller left valve (PI. 52, figs. 3, 6). These denticles fit
into small pits (sockets) situated in duplicature of right
valve (PI. 52, figs. 4, 5). Posteriorly these sockets are over-
hung by prominent development of selvage. Marginal
denticles are a device for holding valves firmly together when closed.

Muscle scars (text-fig. 4b, PI. 52, fig. 7), typical of the Cyprididae, consist of group
of 4 laterally elongate adductor scars with 2 oval scars situated below. Prominent dorsal
muscle scars are situated above these scars, just below hinge.

Anterior radial pore canals (text-fig. 4a) are straight and simple, numbering approxi-
mately 40-45.

text-fig. 4. a. Anterior radial
pore canals, paratype, Io. 1421.
b, Muscle scars, right valve,
paratype, Io. 1418, xll5.

Length

Height

Width

Holotype, Io. 1410, carapace

0-95

0-59

0-48

Paratypes, Io. 1411, „

0-96

0-60

0-46

Io. 1412,

0-98

0-60

0-45

Io. 1413,

0-96

0-60

0-45

Io. 1415, left valve

0-95

0-55

Io. 1416, right valve

0-93

0-59

Io. 1418, „

0-88

0-54

Io. 1419, „

0-93

0-59

Remarks. Hemicypris pyxidata (Moniez) (text-fig. 2a, b) is more oval in outline and too
compressed when viewed dorsally to be confused with H. posterotruncata. Some
similarity in outline exists between the latter species and the slightly larger H. ovata
Sars which is more oval in outline and without the truncated posterior margin. Hemi-
cypris megalops Sars is close to H. posterotruncata in outline and size, but as is also the
case for H. ovata, the valvular relationships when viewed from the left are completely
different. This is evident in the camera lucida drawings (text-figs. 2c, f; 3e, i), in which
the characteristic overlap of the left valve by the right in the antero-dorsal region of
H . posterotruncata is clearly shown. This feature is not present in the other two species.

Hemicypris fossulata (Vavra) is distinguished from H. posterotruncata by the narrower,
more evenly rounded anterior and posterior ends and by the less acute posterior
cardinal angle. It has a punctate shell surface which is less pronounced than shown

R. H. BATE: A NEW SPECIES OF HEMICYPRIS (OSTRACODA)

295

by Vavra (1898, fig. 8), though this may be due to decalcification of the material during
storage.

The specimens of Hemicypris fossulata (Vavra) in the collections of the Zoologisches
Staatsinstitut, Hamburg, were collected from Kilimanjaro by Professor F. Fulleborn
(1898-1900) and determined by Daday.

The other species placed in Hemicypris ( Heterocypris dentatomarginata, Cyprinotus
fullerborni, C. humbertii and C. decoratus) all differ from H. posterotruncata in carapace
outline, whilst Heterocypris reticulatus, although of angular outline, is clearly distin-
guished by its surface ornamentation. Cyprinotus inversus Daday differs from H.
posterotruncata not only in the possession of a more smoothly convex dorsal outline
but also in the possession of straight radial pore canals in the right valve and branching
canals in the left.

Conclusions. Hemicypris Sars is retained as a valid genus. The identification of Hemi-
cypris posterotruncata sp. nov., a fossil species from ancient beach sediments of Lake
Rudolf, indicates that the genus has a longer developmental history than had pre-
viously been understood. The assignment here of one fossil species and eleven living
species to Hemicypris has extended the geographical distribution of the genus to include
South America, North, South, and East Africa, Malagassy Republic, Java, Sumatra,
the Celebes and Japan. No species have yet been recorded from outside the area
bounded by the latitudes 40° North and 40° South of the Equator. The genus Cyprinotus,
on the other hand, besides being recorded from tropical climates, is also known to
occur in the colder climates of the U.S.A., Canada, and Greenland.

Acknowledgements. I should like to record my thanks to Dr. B. Verdcourt, Royal Botanic Gardens,
Kew and to Dr. M. D. Gwynne, Balliol College, Oxford for the opportunity to examine and describe
this new ostracod species. My sincere thanks are also due to Dr. G. Hartmann, Zoologisches Staats-
institut, Hamburg for the loan of Hemicypris fossulata material and to Dr. M. Christiansen, Uni-
versity of Oslo, for the loan of Sars’s Sumatra material of H. pyxidata, H. ovata, and H. megalops.
My colleague Dr. Ken McKenzie gave much valuable advice during the preparation of this paper.

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daday, e. 1910. Untersuchungen iiber die Susswasser-Mikrofauna Deutsch-Ostafrikas. XII, Ostracoda.
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1910. Ergebnisse der mit Subvention aus der Erbschaft Treitl unternommenen zoologischen

Forschungsreise Dr. Franz Werner’s nach dem agyptischen Sudan und Nord Uganda. XV. Beitrage
zur Kenntnis der Mikrofauna des Nils. Akad. Wissenschft. Wien, pp. 1-52, pi. 1, 2.

1913. Cladoceren und Ostracoden aus Stid-und Siidwestafrika. Denkschr. med.-naturw. Ges.

Jena, 17, 89-102, pi. 5, 6.

ferguson, e. 1966. Some freshwater ostracods from the Western United States. Trans. Am. micros.
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gauthier, h. 1933. Entomostraces de Madagascar, 2. Description d’un nouveau Cyprinotus (Ostra-
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kiss, r. 1959. Quelques Ostracodes nouveaux et interessants de la region de l’extremite Nord du Lac
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1932. Die Ostracoden der deutschen limnologischen Sunda-Expedition. Arch, hydrobiol.,

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moniez, r. 1892. Entomostraces d’eau douce de Sumatra et de Celebes. II, Ostracodes. Zool. Ergeb-
nisse niederland. Ost-Indien. Leiden. 2, 129-35, pi. 10.
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swain, f. m. 1961. In moore, R. c. (ed.) Treatise on Invertebrate Paleontology, Pt. O, Arthropoda, 3,
442 pp. Univ. of Kansas and Geol. Soc. Am.

vavra, v. 1898. Die Siisswasser-Ostracoden Deutsch-Ost-Afrikas. Thierwelt Ost-Afrik. Nachbarg.,
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1906. Ostracoden von Sumatra, Java, Siam, den Sandwich-Inseln und Japan. Zool. Jb. system.

Geogr. Biol., Jena, 23, 413-38, pi. 24, 25.

R. H. BATE

Department of Palaeontology
British Museum (Natural History)
Cromwell Road
London, S.W.7

Typescript received 13 May 1969

VARIATION IN THE CARDINALIA OF THE
BRACHIOPOD PTYCHOPLEURELLA BOUCHARDI
(DAVIDSON) FROM THE WENLOCK LIMESTONE
OF WENLOCK EDGE, SHROPSHIRE

by M. G. BASSETT

Abstract. In specimens of the orthacean brachiopod Ptychopleurella bouchardi (Davidson) from the Wenlock
Limestone of Wenlock Edge, Shropshire, the cardinalia display a wide range of variation, particularly in the
development of the cardinal process. The variation can be explained partly by ontogeny but in some extreme
cases it is suggested that it reflects environmental control due to turbulent water conditions in an area of active
reef growth. These conditions led mainly to the progressive inflation of the cardinal process to produce an
optimum attachment surface for the diductor muscle bases, but in two specimens no cardinal process is developed.
In these the muscle bases appear to have covered the notothyrial platform from the earliest growth stage, thus
preventing the secretion of a cardinal process from a central strip of epithelium. The effect of this was to employ
a maximum attachment area throughout ontogeny as an alternative to the production of a bulbous cardinal
process.

The orthacean brachiopod species Ptychopleurella bouchardi (Davidson 1847) occurs
fairly commonly throughout the Wenlock Limestone (Silurian) of the type area in the
vicinity of Much Wenlock, Shropshire. Examination of the interiors of a number of
brachial valves of P. bouchardi from this area reveals that the cardinalia display a
wide range of morphological variation hitherto unrecorded in orthoid genera. This
variation is seen mainly in the development of the cardinal process and to a lesser
extent in the modification of the brachiophores and sockets. Since the valves studied
are from collections made from single bedding planes, are associated with a single type
of pedicle valve, and have a similar musculature and external morphology, the variation
is regarded as being intraspecific in nature. Undoubtedly it is due partly to the onto-
genetic development of the shell, but is here interpreted partially as a response to
environmental control.

The observations and interpretation of the variation are based largely on a collection
of 12 brachial valves from an area of about 5 sq. m. of a bedding plane in the Wenlock
Limestone of Coates Quarry, Wenlock Edge, on the north side of the road approxi-
mately 1 mile south-west of Much Wenlock (Grid Ref. SO/6045.9935; text-fig. 1).
Comparative evidence is provided by a collection of about 20 shells from a single
bedding plane in the Wenlock Limestone of the old quarry on the west side of Lincoln
Hill, Ironbridge (Grid Ref. SJ/6695.0381). Text-fig. 2 illustrates 7 representative
specimens from Coates Quarry. Specimens a-e are members of a progressive growth
series, indicated on the graph by a progressive increase in valve length coupled with an
increase in the number of growth lamellae on the exterior of the valve. The approach
to maturity of the larger specimens is further suggested by the close spacing of the
growth lamellae at the anterior margin of the valve. Specimens f and g are also mature
shells but the plot of the growth lamellae suggests that they are not a continuation of
the growth series a-e.

[Palaeontology, Vol. 13, Part 2, 1970, pp. 297-302, pi. 53.]

298

PALAEONTOLOGY, VOLUME 13

The nature of the variation

1. The cardinal process. Figs, a-e in text-fig. 2 illustrate the progressive growth of the
cardinal process in 5 of the specimens studied from Coates Quarry. At the young
growth stage represented by a the floor of the notothyrial chamber is almost flat or
slightly ridged and no definite cardinal process is developed. This probably indicates
that at this stage the diductor muscle bases were implanted discretely on to the floor

text-fig. 1. Map of the outcrop of the Wenlock Limestone along the north-east of Wenlock Edge
and its continuation to Benthall Edge, showing the position of Coates Quarry and Lincoln Hill.

of the notothyrial platform. With increased shell growth, seen in b, a low, longitudinal,
median ridge, representing an embryonic cardinal process is developed, presumably
by the secretion of secondary calcite from the strip of outer epithelium between the
muscle bases, following the pattern common to most orthoid brachiopods (Williams
and Rowell, in Moore 1965, p. HI 18). In specimen c further anterior and ventral
growth of the median ridge has led to the development of a clearly defined, slightly
lobed cardinal process. This growth was probably accompanied by a medial migration
of the diductor muscle bases from the floor of the notothyrial platform on to the lateral
surfaces of the cardinal process. The further pronounced anterior and ventral inflation
of the cardinal process seen in d and e must clearly reflect a response to the need for
the muscle bases to be attached over a wider surface area.

In specimens collected from Lincoln Hill the stages a-c can be traced in valves at
closely comparable growth stages to those described above. However, the maximum
growth in the cardinal process in shells from Lincoln Hill is only slightly beyond that of
stage c and even in larger specimens there is no extreme inflation comparable to that
in specimens d and e from Coates Quarry. The extreme growth of the cardinal process
in d and e from Coates Quarry would therefore appear to be controlled by factors
other than ontogeny.

Specimens f and g in text-fig. 2 are two aberrant shells from Coates Quarry, in which

BASSETT: BRACHIOPOD PTYCHOPLEURELLA BOUCHARDI (DAVIDSON) 299

m

<

>

text-fig. 2. Diagram to illustrate the growth and variation of the cardinalia in 7 specimens of P. bouchardi from a single bedding plane
in the Wenlock Limestone of Coates Quarry. Specimens a-e are part of a progressive growth series. Specimens f and G are two aberrant shells

in which no cardinal process is developed.

300

PALAEONTOLOGY, VOLUME 13

the cardinal process is not developed. There is no evidence in these shells that the
cardinal process has merely been broken off and although the two specimens are fairly
large the plot of the number of growth lines does not suggest that they are gerontic
members of the growth series a-e in which a condition has been reached where resorp-
tion has led to the disappearance of the cardinal process. Further evidence against this
latter suggestion is presented by a study of the pattern of growth lines within the
cardinalia. In the young shells a and B, for example, the fine growth lines on the floor
of the notothyrial chamber are straight or very gently curved and are sub-parallel to the
hinge line (see PI. 53, fig. 9). After this stage the further pronounced ventral and an-
terior growth of the cardinal process is reflected in the development of a distinctive
chevron-shaped pattern of growth lines across the notothyrial area, especially well seen
in specimen d (see PI. 53, fig. 10). In contrast, the growth lines seen in f and g (see PI.
53, fig. 11) are again sub-parallel to the hinge line, similar to the pattern seen in young
shells. This suggests that in these two aberrant specimens the cardinal process was
never developed and implies that in their early growth stages the diductor muscle bases
were attached over the whole of the central area of the notothyrial chamber so that
no medial strip of epithelium was exposed to secrete secondary calcite in the form of a
cardinal process. No shells from Lincoln Hill have been found in this aberrant condition.

2. The brachiophores and sockets. All the specimens of P. bouchardi studied from
numerous localities in the Wenlock Limestone of Wenlock Edge exhibit modifications of
the brachiophores and sockets with growth by the addition of secondary shell material.

EXPLANATION OF PLATE 53

Ptychopleurella bouchardi (Davidson). All specimens are from a single bedding plane in the Wenlock

Limestone of Coates Quarry, north side of road, 1 mile south-west of Much Wenlock, Shropshire

(Grid. Ref. SO/6045.9935). Figs. 8, 9, 10, 11 are x8; all other figs are x3.

Fig. 1. NMW.69.96.G1. Interior of brachial valve. Specimen a of text-fig. 2. Note the almost flat
notothyrial platform.

Fig. 2. NMW.69.96.G9. Interior of brachial valve. Specimen b of text-fig. 2. Note the low ridge
forming the embryonic cardinal process.

Fig. 3. NMW.69.96.G2. Interior of brachial valve. Specimen c of text-fig. 2. Note the slightly lobed
cardinal process.

Figs. 4 a-c. NMW.69.96.G3. Interior, exterior, and lateral views of brachial valve. Specimen d of text-
fig. 2. Note the deep sockets, expanded cardinal process, and secondary calcite covering the floor
of the valve.

Figs. 5a, b. NMW.69.96.G4. Interior and exterior of brachial valve. Specimen e of text-fig. 2. Note
the bulbous cardinal process, deep sockets, and expanded brachiophores.

Figs. 6a, b. NMW.69.96.G5. Interior and exterior of brachial valve. Specimen f of text-fig. 2. Note
the absence of the cardinal process.

Figs, la, b. NMW.69.96.G6. Interior and exterior of brachial valve. Specimen g of text-fig. 2. Note
the absence of the cardinal process.

Fig. 8. Enlargement of the cardinalia of fig. 1.

Fig. 9. Enlargement of the cardinalia of fig. 2. Note the embryonic cardinal process and the fine
growth lines across the notothyrial platform.

Fig. 10. Enlargement of the cardinalia of fig. 4a. Note the expanded cardinal process and the chevron-
shaped growth lines across the notothyrial platform.

Fig. 11. Enlargement of the cardinalia of fig. la. Note the absence of the cardinal process and the fine
growth lines across the notothyrial platform. Compare the growth lines with those in figs. 9 and 10.

Figs. 12 a-c. NMW.69.96.G7. Interior, exterior, and lateral views of pedicle valve.

Figs. \2>a, b. NMW.69.96.G8. Interior and exterior of pedicle valve.

Palaeontology, Vol. 13

PLATE 53

BASSETT, Cardinalia of Ptychopleurella bouchardi

BASSETT: BRACHIOPOD PTYCHOPLEURELLA BOUCHARDI (DAVIDSON) 301

This results in the building of ‘walls’ around the rims of the sockets leading to their
rounding and apparent deepening, the development of socket pads, and the thickening
of the bases of the brachiophores. In the specimens from Coates Quarry, including the
aberrant shells f and g, these modifications of the cardinalia by the addition of secondary
calcite are generally much more pronounced than in specimens from other localities.

Interpretation

The absence of a cardinal process in two shells, and the extreme modification of the
brachiophores and sockets in other specimens from Coates Quarry cannot be regarded
solely as a growth feature since these conditions are not seen consistently in shells of
comparable size from other localities. Instead it is suggested that the variation observed
in these ‘abnormal’ shells is related partially to the environment in which they lived.

The Wenlock Limestone of Wenlock Edge, and its continuation to Benthall Edge
and Lincoln Hill, forms part of a reef complex aligned in a north-east to south-west
direction. Scoffin (1965) suggested that a large bioherm which occupies the bulk of the
thickness of the Wenlock Limestone around Hilltop (Grid. Ref. SO/5700.9630), about
3| miles south-west of Much Wenlock, probably acted as a ‘barrier’ reef. No specimens
of P. bouchardi have been found by the writer to the south-west of Hilltop in the off-reef
area. Coates Quarry lies in the back-reef area about 2\ miles to the north-east of the
‘barrier’ reef and the specimens described from there were obtained from a thin shale
parting on a bedding plane lying immediately adjacent to a large symmetrical bioherm.
This and other bioherms in the vicinity probably formed part of an extensive patch
reef development in the lee of the ‘barrier’ reef (Scoffin 1965, p. 190). The bioherms
are composed of large colonial corals, stromatoporoids, algae, and crinoids, with
interdigitations of skeletal debris and lime mud, while the surrounding bedded sediments
consist of biomicrites and biosparites with thin grey shale partings. These deposits
together suggest that conditions within and around the bioherms varied from periods
of quiet water deposition to periods of moderate agitation, probably by wave action.
(The interpretation of the depositional conditions outlined here is based on the classifi-
cation of Plumley et al. 1962; the conditions within the reef area of Wenlock Edge were
probably closely analogous with those described by Plumley et al. (op. cit., pp. 93-5) in
their hypothetical example.) Relatively few other fossils are found immediately adjacent
to the bioherms, a factor which supports this interpretation.

Any brachiopods which were to survive the periodical agitation of water in this
environment would need relatively thick shells, powerful muscles with large attachment
areas, and a strong articulatory mechanism. The specimens of P. bouchardi described
from Coates Quarry possess all of these features. In some specimens the shell is further
thickened by the addition of secondary calcite over the floor of the valve. The large
dorsal adductor scars may be clearly seen in the specimens illustrated in text-fig. 2 and
Plate 53 ; it appears that the progressive inflation of the cardinal process in specimens
a-e reflects the rapid development of an optimum surface area for the attachment of the
diductor bases, while in the aberrant shells f and g the muscle bases covered the whole
of the central area of the notothyrial chamber to gain maximum attachment from
the earliest growth stage. Thus in 2 specimens a broad, firm attachment area was
employed throughout ontogeny as an alternative to the production of a bulbous
cardinal process. The deepening of the sockets would produce a strong articulatory

302

PALAEONTOLOGY, VOLUME 13

structure while the addition of secondary calcite to the whole of the cardinalia possibly
acted as a stabilizer to maintain the shell in its posterior-downward life position.
Bowen (1966, p. 1021) suggested a similar function for deposits of secondary calcite in
the notothyrial area of specimens of Atrypa reticularis (Linnaeus). The few other species
of brachiopods associated with P. bouchardi in Coates Quarry also exhibit thickening
of the shell by the addition of secondary calcite. A few specimens collected by the
writer from similar reef-bearing beds along Benthall Edge also possess many of the
features described above, including a large cardinal process, but no further specimens
have been observed in which the cardinal process is absent.

Lincoln Hill lies some 7 miles to the north-east of the Wenlock Edge ‘barrier’ reef in
the back-reef lagoonal area. Here the abundance of many species of articulated brachio-
pods and solitary corals in fine biosparite limestones, and the rarity of colonial reef
builders, suggests relatively quiet water conditions compared to areas further to the
south-west. Under these conditions it appears that the cardinalia of P. bouchardi
display only the normal features of growth. (Bioherms were probably once present in
stratigraphically higher beds at Lincoln Hill, e.g. see Murchison 1839, p. 211, but they
have long since been removed by quarrying and there is no evidence that active reef
growth took place within the beds exposed today.)

Although the above discussion is based on the study of only a small number of
specimens, it nevertheless serves to illustrate that the cardinalia of orthoid brachiopods
may vary widely within a single species in different environments. The use of such
features as stable characters for purposes of classification should therefore be treated
with caution.

Acknowledgements. This work was carried out in the Department of Geology, University College,
Swansea, as part of a larger study of British Wenlockian brachiopod faunas. I wish to thank Dr. V. G.
Walmsley for his help and guidance. Professor F. H. T. Rhodes for providing research facilities, and
Dr. T. P. Scoffin for discussing environmental conditions in the Wenlock Limestone. Financial support
from the Sir Richard Stapley Educational Trust and the Natural Environment Research Council is
gratefully acknowledged. All the specimens are housed in the Department of Geology, National
Museum of Wales, Cardiff.

REFERENCES

bowen, z. p. 1966. Intraspecific variation in the brachial cardinalia of Atrypa reticularis. J. Paleont.
40, 1017-22, pi. 118.

davidson, t. 1847. Observations on some of the Wenlock-limestone Brachiopoda, with descriptions
of several new species. London Geol. Journ. 1, 52-65, pi. 12, 13.
moore, r. c. 1965 (Ed.). Treatise on Invertebrate Paleontology, Part H, Brachiopoda. 2 vols., xxxii+
927 pp., Geol. Soc. Amer. and Univ. Kansas Press.

Murchison, R. i. 1839. The Silurian System, founded on geological researches in the counties of Salop,
Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester,
and Stafford; with descriptions of the coal-fields and overlying formations. 1-768 (2 vols.), 110 figs;
pi. 1-37. London.

plumley, w. j., risley, g. a., graves, r. w., and kaley, m. e. 1962. Energy index for limestone inter-
pretation. In Classification of Carbonate Rocks. Mem. Am. Ass. Petrol. Geol. 1, 85-107.
scoffin, x. p. 1965. The Sedimentology of the Wenlock Limestone. Unpublished Ph.D. thesis. Uni-
versity of Wales (Swansea).

M. G. BASSETT

Department of Geology
National Museum of Wales
Cardiff, cfI 3np

Typescript received 3 June 1969

STEREOSCAN OBSERVATIONS ON THE
POLLEN GENUS CLASSOPOLLIS PFLUG 1953

by Y. REYRE

Abstract. The diagnosis of the pollen formgenus Classopollis Pflug 1953 is here emended after both a review
of the literature and observation of numerous specimens recovered from Upper Triassic to Middle Cretaceous
rocks in the Sahara, Israel, and France. Following a discussion of a proper definition of the species, twelve
new species are described. Botanic affinity, taxonomic value, and stratigraphic occurence are also discussed.

Numerous species have been validly assigned to the genus Classopollis both before
and after the emendation by Pocock and Jansonius (1961). However, among isolated
grains of apparently homogeneous assemblages from African or European Mesozoic
rocks, it has proved impossible by light microscope to identify these species with
certainty. Scanning electron microscope observations indicate four possible reasons:

(a) the number of potential Classopollis species is greater than that of described species,

(b) inexactness of the majority of specific diagnosis in the description of the exinal
structure and sculpture, (c) the hierarchy of characters used to define species is variable
depending on the individual author (often it is not indicated), ( d ) it seems that certain
species have been defined on the basis of plurispecific assemblages, often unsuspected
by the authors themselves. Because of its palaeobotanic and stratigraphic importance,
a review of the genus has been undertaken using large assemblages extracted from the
following formations: Upper Triassic (above Carnian) in the Tunisian and Algerian
Sahara, Infraliassic and Lower Liassic in the Sahara and France (Saintonge, Massif
Central), Jurassic and Lower Cretaceous in the Sahara, Israel, and France.

PREVIOUS LITERATURE

The genus Classopollis was instituted by Pflug (1953), although some species were
previously assigned to other genera. Pocock and Jansonius (1961) presented an ex-
tensive review of past works and Boltenhagen (1968) completed this review by a critical
survey of the literature.

Couper (1958, pp. 156-7, pi. 28, figs. 2-7) emended the genus Classopollis Pflug 1953,

! considering that Pflug’s interpretation was inexact. After observations on pollen of
Pagiophyllum connivens Kendall, he tried to show that the genus Classopollis is a

Imorphographical taxonomic entity including all the species of the type met with in the
above-mentioned fossil. Thus he suggested a very wide generic definition in which one
must principally note an equatorial endexine thickness and a vague proximal trilete
mark; he regarded P. torosus Reissinger as the type-species. Klaus (1960, pp. 165-7,
pi. 36, figs. 57-60) emended the genus Corollina Maljavkina 1949 and included in
particular Pflug and Couper’s Classopollis species. In addition, Klaus suggested his species
Circulina meyeriana as the type-species of the genus Circulina Maljavkina 1949. In his
opinion this genus is recognizable by the following characters: a Y-form dehiscence,
a distal polar area, a sub-equatorial ring which is not bordered with a thickening,

[Palaeontology, Vol. 13, Part 2, 1970, pp. 303-322, pi. 54-59.]

C 7393 X

304

PALAEONTOLOGY, VOLUME 13

occasionally parallel folds in the ring zone, and infrastructure without midrib, line,
reticulum, or ring (striation ?).

Pocock and Jansonius (1961, pp. 443-4, pi. 1, figs 1-9) emended Pflug’s genus,
considering the attributions of Couper (1958) and Klaus (1960) as unfounded. They also
emended C. classoides Pflug which they retained as type-species of the genus, and
defined the genus with the following characters : ( a ) distally monoporate, (b) exoexine
two-layered, (c) exoexine absent or much reduced over a circular area surrounding the
distal pole and absent or reduced over a triangular area with its centre at the proximal
pole, ( d ) intexine frequently bearing a reduced trilete scar, which has no germinal
function, ( e ) exine always ornamented by striations, (/) the band, usually but not
always, marking a zone of exinal thickening. Pettitt and Chaloner (1964) studied by
electron microscope pollen grains extracted from a cone of Cheirolepis muensteri Schenk.
They assigned these grains to the morphographical species C. torosus (without naming the
author). They established that the exine of Classopollis is composite with a lamellate
endonexine and a complicated ectonexine within which they distinguished an inner
layer (ecn 2), a middle massive layer (ecn 1), and a tegillum. Burger (1966) suggested
that the columellars (equivalent to ecn 2 of Pettitt and Chaloner) join in the equatorial
belt and are reduced at the rimula. Reyre (1968 d), using scanning electron microscope
observations, established that at least in many cases trilete scars are functional, the
outer layer of the exoexine is continuous with an invariable sculpture, the appearance of
the grain is explained by variations of the intrastructure (similar to ecn 2 of Pettitt
and Chaloner). In different parts of the grain it disappears, resulting in a subequatorial
circular furrow, in a distal circular area and also in the proximal triangular area (when
that exists) ; in these places, the outer part of exoexine (tegillum and possibly columellars
of Pettitt and Chaloner) collapses and lines the lamellate endonexine which has the
shape of a separate internal spheroidal envelope.

DEFINITION OF THE SPECIES

Numerous morphographic species have been described from various stratigraphic
periods; they probably corresponded in most cases to different botanical species.
However, the assignation of a dispersed Classopollis grain to a definite species is always
difficult and often impossible.

Table 1 has been assembled from the diagnoses of five authors who have made
detailed studies on Classopollis. It shows that, strictly, only the two extreme cases of
size justify the recognition of two species on this one single character. If, however, one
takes into account for each character, only the species in which it is clearly indicated,
the number of possibilities for differentiation is one for all the characters except the
sculpture where it is four. Table 1 underlines also the concommitant variations which
affect the light visible characters. The statistical methods of symbolic dispersion dia-
grams (Pons 1964) can often record the different types or species an assemblage contains,
but do not always permit the assignment of one or a few characters particular to each
type.

For example, in the Jurassic and Lower Cretaceous rocks of the Tunisian Sahara,
five Classopollis groups have been described: Lx, L2, L3, scrabrate-verrucose group, and
gemmulate group (Medus and Reyre 1966). However, none can be assigned with any

table 1. Comparative study of published species of the genus Classopollis.

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

305

306

PALAEONTOLOGY, VOLUME 13

certainty to definite species, because each has common points with several species de-
pending on the characters under consideration. In addition, except for the gemmulate
group, none has a constant individual character which allows a possibility of erecting
a new species. L3 is something like C. classoides of Pocock and Jansonius, but the pore
diameter is smaller; it also resembles C. torosus sensu Burger but it is smaller, psilate,
and sometimes massive. In the same way, Lx resembles C. multistriatus Burger, but
it is often larger, scabrate, and finer; its pseudopore is larger and the belt can have less
striations. Only the gemmulate and scabrate-verrucose types are theoretically separated
on sculpture; the first is easily distinguished but for the second this delicate and variable
observation of sculpture cannot be made reliably with a light microscope.

Hierarchical order of use of characters. Two authors have put forward a hierarchical
order. Pocock and Jansonius indicate successively the characters (as numbered in
Table 1): 6, 2, 7, 8 and 9, 5 or 10 and 1. Their interpretation is not very clear on whether
the ornamentation mentioned refers to the sculpture or the intrastructure although it
would seem to be the latter because the authors have not mentioned the sculpture of
their species. For Burger the order of characters is as follows: 10 and 5 (which can be
different on the distal and proximal hemispheres of the grain), 2, 7, 8, and 6. Neither
authors have indicated the reasons for their choice. However, the choice of hierarchical
order is important, (a) to obtain a natural classification of Classopollis species (which
will be attempted below), and ( b ) because it will be determinative in defining the
different species. This fundamental study can only be undertaken on a homogeneous
assemblage containing only one species. In fact it is difficult to predict, and experience
shows that formations containing only one species are rare. Examples are:

1. Sample from bore-hole Lamarque 1, Aquitaine (Esso France: X = 358, 7;
Y = 314, 4), depth 1742 m., Rhetian age (Dupin 1965), contains a Classopollis assem-
blage. Two extreme types are easily distinguishable by light microscope observation of
the intrastructure. The first, type A (PI. 55, figs. 1,5) is light, almost translucent, with
a massive intrastructure. The second, type C (PI. 54, figs. 9, 1 1) is darker, with a pseudo-
reticulate intrastructure which is poorly defined in the area of the equatorial thickening.
Between these extreme types, the intrastructure can be finely or poorly pseudoreticulate
in the type B (PI. 54, fig. 10 and PI. 55, fig. 8).

2. Sample of argillaceous sandstone from bore-hole S6P6, Massif Central (B.R.G.M.:
X = 566.500; Y = 179.075; Z = 190.90), depth 47-40 m., Hettangian (B.R.G.M.
dating), contains a Classopollis assemblage of type C only (PI. 55, figs. 11, 12).

Light microscope observation. Table 2 has been made up by selecting ten grains of each
of the three types. It shows for these types whose general appearance and sculpture are
perfectly homogeneous, the following points (each character is numbered in Table 2):

1 . Size (diameter) is not fixed, but the variation is peculiar to the species

/diameter of the smallest . c , , A

varies from ^ to § .

\ diameter of the largest “ /

2. When there is a circular furrow, it exists in all the grains.

3. Length of laesurae of trilete scar varies as much as 1:4.

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

307

table 2. Character variations in the forms A, B, C (see p. 306). Measured characters: 1, size (diameter);
2, circular furrow width; 3, length of laesurae; 4, pseudopore diameter; 6, average exine thickness;
7, equatorial exine thickness; 10, type of stereoscan-visible sculpture.

Forms

i

2

3

4

6

7

10

A

30

1

8

8

-

3

echinulate

28

—

5

8

—

2-5

micro-echinulate

30

2-5

2-5

10

1-5

2-5

echinulate

30

1

3

7-5

—

2-5

27

1

6

5

2

3

9>

26

1

7-5

5

—

2-5

99

31

2-5

—

10

2

2-5

y9

27

1

—

8

1-5

2-5

micro-echinulate

25

1

2-5

4

—

2-5

echinulate

25

1-5

5

—

1-5

2-5

micro-echinulate

B

27

—

6

7-5

2-5

2-5

grumous-verrucose

27

1-5

—

6

2-5

1-5

echinulate

27

1

2-5

—

2-5

—

25

1

5

7-5

—

2-5

31

1

6

5

2-5

1-5

js

23

1

3

—

2-5

—

„

26

1-5

5

—

2

1-5

grumous-verrucose

23

1-5

5

7-5

2

2-5

echinulate

30

1-5

8

8

2

2-5

micro-echinulate

26

1-5

6

6

2

2-5

echinulate

C

24

1

5

6

1-5

echinulate

(sample 1)

28

1

—

—

1-5

2-5

„

32

1

—

—

1-5

2-5

grumous-verrucose

34

+

12

10

—

—

28

+

3

—

1-5

—

echinulate

28

1

6

5

—

2-5

26

1

—

8

1-5

2-5

18

1

4

—

1-5

—

„

24

1

■ —

8

1-5

2-5

grumous-verrucose

21

1

—

5

■ —

2-5

echinulate

28

1

7

—

1-5

—

micro-echinulate

C

30

1

6

5

1-5

2-5

grumous-verrucose

(sample 2)

28

1

—

—

1-5

—

20

1

—

—

1-5

—

32

1

8

10

1-5

2-5

})

32

1

10

8

1-5

2-5

28

1

—

—

—

—

30

1

7

8

1-5

2-5

„

24

1

■ — l

—

—

—

28

1

5

6

1-5

2-5

99

26 1

4. Pseudopore diameter varies

5 6

as much as 2:5.

1-5

2-5

6, 7. Exinal thickness remains constant at comparable points and especially when
there is an equatorial thickening.

Scanning electron microscope observations. Technical conditions for observations of
exinal sculpture by the scanning electron microscope has already been set out in detail
(Reyre 1968<7). Results of the observations are as follows:

(a) In the case of the sample 2 (optically very homogenous intrastructure) the sculp-
ture of the tegillum is identical in all the grains, grumous-verrucose (PI. 55, figs. 13, 14).

308

PALAEONTOLOGY, VOLUME 13

(b) In the sample 1 three types of sculpture are observed. The optical type A can be
micro-echinulate (PI. 55, figs. 3, 7) or echinulate; the optical type B can be micro-
echinulate or echinulate (PI. 55, fig. 10) and rarely verrucose; the optical type C can be
rarely micro-echinulate, generally echinulate (PI. 54, fig. 13) or grumous-verrucose
(cf. PI. 55, fig. 14).

(c) Interpretation: the only light microscope visible characters (1-7 in Table 2)
cannot establish how many species there are in the sample 1 or how they are distinguish-
able. Scan observations confirm that there is one species in the sample 2 and establish
that there are at least three species in the sample 1. In sample 1 one species is common
with the sample 2 (optical type C, grumous-verrucose) and two (optical types A and B,
micro-echinulate or echinulate) correspond probably to two closely related botanical
species, but one fossil pollen species is made because of the occurrence in the same
sample. It thus appears on one hand that light microscope observation alone is generally
insufficient to define the ultimate morphographical species, and on the other hand
that intrastructure of one species can have a certain variability, generally limited. It
also appears that each precise type of sculpture has the properties of one botanical
species or a group of closely related species; that suggestion comes from the results
established on actual gymnospermous pollen (Reyre 1968*/) and on higher plants such
as the closely related species of the genus Aristida L. (Bourreil and Reyre 1968) between
which slight variations of outer sculpture can be observed and are peculiar to each
species. It comes also from the observation of several homogeneous assemblages of
Classopollis the sculpture of which is identical for all the grains (as the assemblage C,
sample 2).

Inference. In the genus Classopollis, the outer sculpture of the grains is at the same time
the most consistent and the most distinguishable character of a species ; it is the ultimate
specific character necessary for diagnosing the species; the consequence is that a
diagnosis would not be valid, either from a morphological point of view or from a
botanical point of view if it does not show the exine outer sculpture observed by
electron microscope.

LIMITS OF THE GENUS

In his generic diagnosis, Couper (1958) extended the genus to all the pollen with an
equatorial thickening and a vague trilete scar. The definition of Pocock and Jansonius
(1961) was different and narrower, requiring the presence of striations, of a distal pore,
and of a proximal triangular area either with or without a trilete aperture. The form-
genus Classopollis can thus be conventionally limited to the simultaneous presence of
the above-mentioned characters. However, this convention could result in a separation
of closely related palaeobotanic entities and so we must consider that the absence of
each of these characters on one of these pollens excludes it from the genus Classopollis
when this absence results in either the absence or a notable modification of the other
characters.

Striations. Considering the pollen groups A, B, and C, in which no striations are
observed on the first two and a vague line arrangement on the third, it can be seen that
they all have a pseudopore, a subequatorial circular furrow, an equatorial thickening,
and an outer sculpture very similar to that of Classopollis with clearly defined and

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

309

continuous striations (compare PI. 55, figs. 8, 10 and PI. 57, figs. 1, 5). Further, in the
succession of types B, A, and C, it is easy to distinguish a progressive passage from a
massive intrastructure to pseudostriations. It would be unhelpful to limit the genus
Classopollis by the actual presence of striations, as Pocock and Jansonius have done.

Equatorial thickening. The pollen shown on Plate 55, figs. 5-7, has no equatorial
thickening. It is, however, in all other characters, similar to the grains of the group B,
in which it has been included. Pocock and Jansonius (1961), Groot and Groot (1962),
and Burger (1965), recorded no equatorial thickening in several of their species with
striations.

On account of these two factors I consider that the formgenus Circulina (Maljavkina)
Klaus 1960 is an exceptional case within the genus Classopollis, corresponding to the
coincidence of the limiting cases of the two characters, equatorial thickening and
ornamentation of the intrastructure.

Trilete scar. Table 2 shows clearly that a homogeneous assemblage can have a variable
trilete scar (in particular length of the laesurae). Many assemblages have only a trifid
or sinuous fold (PI. 55, fig. 4) so that it is sometimes impossible, especially with a light
microscope, to see a vestigial mark. But all the other characters are similar.

Pseudopore. All Classopollis have a more or less distinct pseudopore which is visible in
polar view or with a scanning electron microscope. In certain species, however, it is
less distinct, especially when the exine is thin. I have so far found only one form with
striations but without a pseudopore (PI. 54, figs. 8, 9) but neither does it have a trilete
scar or a circular furrow, and this justifies its inclusion in the genus Aporina Naoumova
1937 (in Boltenhagen 1968). The European Jurassic species of the formgenus Exesipol-
lenites Balme have a similar pseudopore, but no trilete scar and no circular furrow and
they cannot be assigned to the genus Classopollis. Also, some species show an outer
sculpture similar to that of recent Cupressales (PI. 59, fig. 5).

THE TYPE SPECIES

I consider the generic name Classopollis is valid because the genera Corollina Mal-
javkina 1949 and Circulina Maljavkina 1949 were defined too vaguely. Like Pocock and
Jansonius (1961) I consider that because of the impossibility of proving the exact
similarity of C. classoides Pflug with another previously published species, the name
of the type-species is classoides ; but Pflug’s diagnosis is inexact.

Of the grains selected for the diagnosis of the classoides species, it must be pointed
out that the sample studied by Pflug could, in fact, include several species. Thus, even
if Pflug’s diagnosis is exact, it is impossible to recognize the species he wished to
describe since there is no precise indication of the outer sculpture. From comparison
of the relevant figures it appears that the species C. classoides (Pflug) Pocock and Jan-
sonius 1961 does not correspond to the species represented by Pflug (1953). For reference
these authors figure (Pocock and Jansonius 1961, pi. 1) a tetrad (figs. 1, 2) from Pflug’s
residue but different from the Pflug’s classoides species by distinctive striations, circular
furrow invisible and different intrastructure. They assign to the same species a dis-
tinctly intrapunctate grain without distinct striations (fig. 4) and a massive form without

310

PALAEONTOLOGY, VOLUME 13

any striations (figs. 6, 7). It seems, therefore, that Pocock and Jansonius have also des-
cribed a plurispecific assemblage; there is also no precise indication of sculpture. In
fact the Classopollis type-species has never been fully described. Re-description of the
type species classoides from Pflug’s original residue would be difficult; after chemical
or washing operations on this residue in glycerine, how could a grain be chosen? The
new species, C. kieseri (PI. 54, figs. 9-14) which resembles Pflug’s classoides is erected in
this paper from new material ; but, in practice, for illustrating the genus Classopollis it
would be preferable to refer to another species showing all the characters proper to
this formgenus, striations in particular.

SYSTEMATIC SECTION

Diagnoses and descriptions of the species here described include in the same order
all the characters mentioned in Table 1. The high-power Scan micrographs are very
important because they show the general disposition of sculptural elements (simple,
mixed, double), the similarity or the plurality of shapes and sizes of elements, the shape
of these, their length, breadth, and abundance (number of elements on a surface unit).
All these characters are mentioned in the same order in the descriptions. The detailed
explanation of the method used for describing the exinal sculpture is indicated in a
previous paper (Reyre 1968 d), but see also the text-fig. 2. Light and electron photo-
graphs are not always of the same grain; it is difficult to take an immersion photograph
of a grain which must be recovered from the liquid before being observed by the
scanning electron microscope. However, they always represent grains of the same
optical assemblage (which is electronically observed on numerous grains). Holotypes
or paratypes of the species here described are preserved at the Geological Laboratory
of the National Museum of Natural History, Paris.

Genus aporina Naumova 1937

Remarks. This genus is separate morphographically, but the corresponding palaeo-
botanical taxa are closely related to the taxa which produced Classopolliss and may be
species of the same genus.

Aporina sp.

Plate 54, figs. 1, 2

EXPLANATION OF PLATE 54

Light microscope figures approximately x 1000; Stereoscan figures approximately x 2000 and 10000.

Figs. 1, 2. Aporina sp. 1, L.M. tetrad view showing striations. 2, S.E.M. view on which no pseudopore
is observed.

Figs. 3-5. Classopollis simplex sp. nov. 3, L.M. holotype, showing massive to micro-alveolate intra-
structure. 4, 5, S.E.M., showing the nipples of the outer sculpture.

Figs. 6-8. Classopollis quezeli sp. nov. 6, L.M. tetrad holotype, showing striations. 7, 8, S.E.M.
holotype showing the outer double sculpture rough with bowls.

Figs. 9-14. Classopollis kieseri sp. nov. 11, L.M. paratype, showing pseudovermiculate to pseudo-
reticulate intrastructure, trilete scar, subequatorial circular furrow, pseudopore and exinal thickness.
9, 10, L.M. paratypes, figures very similar to that of Pflug. 12—14, S.E.M. holotype, showing outer
sculpture of exine, hairy with spines; S.E.M. paratype, showing the trilete scar.

Palaeontology, Vol. 13

PLATE 54

REYRE, Triassic and Jurassic Classopollis

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

311

Description. No subequatorial furrow; no trilete scar; no pseudopore; intrastructure
massive; average exinal thickness 0-5 p; equatorial thickening 1 p; 4-6 striations 6 p;
band width 4-5 p. Sculpture simple, isomorphous, nearly isodiametric, slightly rough
and nearly psilate.

Size range. 17-22 p (28 specimens).

Stratigraphic position. Upper Triassic (post-Carnian) of the Sahara; bore-hole ONx (X = 31° 46' 07",
Y = 6° 25' 36", Z = 140 m.), depth 2660 m.

text-fig. 1 . Outer sculpture (designed on the distal hemisphere above) ;
from left to right : rugose, verrucose, mixed, double, echinulate or hairy
with sticks, echinulate or hairy with needles or spines. Intrastructure
(designed on the proximal hemisphere — below) : from left to right : mas-
sive, alveolate, reticulate, vermiculate, pseudoreticulate, punctate.

Genus classopollis Pflug 1953 emend.

Text-fig. 1

Emended diagnosis. More or less spherical prepollens with, both more or less marked,
a distal circular pseudopore and a proximal trilete scar; this latter is clearly visible,
but sometimes it is vestigial or a sinuous (or trifid) crease takes its place; often it is
open and it appears to have had a germinal function (unlike the pseudopore). Exine is
two-layered with distinct endoexine and exoexine. Fndoexine is shaped into an internal
spheroidal separate envelope. Exoexine composition is variable on different parts of the
grain; it is composed of an inner complicated layer which constitutes the light micro-
scope visible intrastructure and a tegillum. The tegillum is shaped into a separated
outer envelope present all over the grain and covered with an outer sculpture uniformly
distributed on the whole surface of the grain. Intrastructure is massive, alveolate,
punctate, vermiculate or pseudovermiculate, reticulate or pseudoreticulate but can be
absent, reduced, thickened, and differently organized on different parts of the grain;

312

PALAEONTOLOGY, VOLUME 13

it is absent or reduced at the distal pole (pseudopore) or only along the circular line
surrounding it, absent along a subequatorial line (circular furrow) and sometimes at
the proximal pole (triangular area), generally thickened in the equatorial zone of the
grain under the circular furrow (equatorial band) where the intrastructure elements are
organized into more or less continuous striations.

Remarks. Two reasons justify this emendation: (a) in respect of the generic diagnosis
of Pocock and Jansonius the present emended diagnosis takes into account the actual
knowledge on the structure of Classopollis grains; this is important for the under-
standing of the species and allows recognition and definition of the different species
or records by consideration of precise characters. ( b ) the limits of the formgenus
Classopollis are different from those indicated in the diagnosis of Pocock and Jansonius.

Classopollis simplex sp. nov.

Plate 54, figs. 3-5

Diagnosis. Subequatorial circular furrow present ; trilete scar present, length of laesurae
3-6 p; pseudopore diameter 2-4 p ; intrastructure massive to micro-alveolate; average
exinal thickness 1 p; no equatorial thickening; no striations. Sculpture simple-mixed,
isomorphous, heterodiametric, with nipples; nipple height 0T-0-2 p, breadth 0-2-0-3 p,
abundance 12 per p 2. Many elements overlap a little the bases of the nipples; they are
also less rounded nipples, 4 p high.

Size range. 18-24 p (40 specimens).

Holotype. Plate 54, figs. 3-5 ; size 20 p.

Stratigraphic position. Upper Triassic (post-Carnian) of the Sahara; bore-hole ONi (X = 31° 46' 07",
Y = 6° 25' 36", Z = 140 m.), depth 2660 m.

Classopollis quezeli sp. nov.

Plate 54, figs. 12-14

Diagnosis. Subequatorial circular furrow present; trilete scar vestigial; pseudopore
diameter 4 p; intrastructure massive (to micro-alveolate); average exinal thickness less
than 1 p (bowls not included); equatorial thickening 1 p; 4-5 striations ; band width 5 p.
Sculpture double, heteromorphous, heterodiametric, rough with bowls ; processes height
0T-0-2 p; breadth OT-02 p; bowls 0-9-1 p.

EXPLANATION OF PLATE 55

Light microscope figures approximately x 1000; Stereoscan figures approximately x 2000 and 10 000.

Figs. 1-10. Classopollis kieseri sp. nov. 1, L.M. paratype, showing massive intrastructure and equa-
torial thickening. 2, 3, S.E.M. view of same grain showing small spines of outer sculpture.
4, S.E.M. view of same grain showing outer layer of exoexine lacerated at the proximal pole. 5, L.M.
view of a paratype without equatorial thickening. 6, 7, S.E.M. view of same grain, sculpture micro-
echinulate. 8, L.M. holotype, showing micropseudoreticulate intrastructure and sinuous circular
furrow. 9, 10, S.E.M. holotype, showing sculpture echinulate, hairy with needles.

Figs. 11-14. Classopollis chateaunovi sp. nov. 11, L.M. paratype, showing vague pseudostriations.
12, L.M. holotype, showing pseudoreticulate infrastructure and pore. 13, 14, S.E.M. holotype,
showing grumous-verrucose sculpture.

Palaeontology, Vol. 13

PLATE 55

REYRE, Jurassic Classopollis

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

313

Size range. 18-24 p (36 specimens).

Holotype. Plate 54, figs. 12-14; size 23 p.

Stratigraphic position. Upper Triassic (post-Carnian) of the Sahara; bore-hole ONx (X = 31° 46' 07",

Y = 6° 25' 36", Z = 140 m.), depth 2660 m.

Remarks. Processes are rounded so that the surface seems nearly mammilated.

Classopollis kieseri sp. nov.

Plate 54, figs. 9-13; Plate 55, figs. 1-10

Diagnosis. Subequatorial circular furrow present, narrow (1 p) or wide (to 3 p) by
distortion and often sinuous; functional trilete scar present, length of laesurae 2-5-10 p;
pseudopore diameter 4-10 p ; intrastructure massive, pseudoreticulate or finely so;
average thickness 1-5 j n; equatorial thickening 1 -5-2-5 p; no striations, to vaguely
defined pseudostriations ; band width 8-10 p. Sculpture simple, isomorphous, isodia-
metric, micro-echinulate to echinulate (hairy with little needles); varying from grain
to grain, needle height 0- 1-0-5 p, breadth 0- 1-0-2 p, abundance 9 per p2 (large needles)
to 80 per p2 (small needles).

Size range. 21— (28)— 34 p (100 specimens).

Holotype. Plate 55, figs. 8-10; size 31 p.

Stratigraphic position. Hettangian, bore-hole Lamarque I, Aquitaine, (X = 358, 7; Y = 314, 4),
depth 1742 m.

Remarks. By scan observation of the sculpture it seems that there are three closely
related species, in which the spines or needles are constant on any one grain but may
be very small (micro-echinulate, PI. 55, fig. 7), medium (PI. 55, fig. 3) or larger (echinulate,
PL 55, fig. 10); but these characters do not each correspond to one precise intrastructure
type. For this reason and because of their simultaneous occurrence in the same sample
one Classopollis species is made.

C. kieseri resembles C. classoides Pflug 1953 in many characters visible on the illustra-
tions of this species. In Pflug 1953, plate 16, figs. 29, 30 show a pollen finely pseudoreti-
culate, with a sinuous circular furrow, a pseudopore, a trilete scar not visible but
suspected, an exine thickness of 2 p without striations.

Classopollis chateaunovi sp. nov.

Plate 55, figs. 11-14

Diagnosis. Subequatorial circular furrow present; trilete scar present, length of laesurae
5-12 p; pseudopore diameter 5-10 p; intrastructure pseudoreticulate; average exinal
thickness 1-5 p; equatorial thickening 2-5 p; only vague pseudostriations; band width
8 p. Sculpture simple, isomorphous, isodiametric, grumous-verrucose ; breadth of
grumes 0-2-0 -3 p.

Size range. 20-32 p (100 specimens).

Holotype. Plate 55, figs. 12-14; size 31 p.

Stratigraphic position. Hettangian, Massif Central, bore-hole B.R.G.M. S6P6 (X = 566.500,

Y = 179.075, Z = 190, 91), depth 47-40 m.

314

PALAEONTOLOGY, VOLUME 13
Classopollis bussoni sp. nov.

Plate 56, figs, 1^1

Diagnosis. Subequatorial circular furrow present; trilete scar present, length of laesurae
3-10 p; pseudopore diameter 4-10 p; intrastructure finely punctate; average exinal
thickness 0-5-1 p; equatorial thickening 1 p; 7-11 striations; band width 7 p. Sculpture
simple, isomorphous, isodiametric, rugose-verrucose ; height of warts 0-2 /z, breadth

0- 5-0-8 /z.

Size range. 23-32 p (100 specimens).

Holotype. Plate 3, figs. 1-3 ; size 28 p.

Stratigraphic range. Middle and Late Jurassic and Lower Cretaceous of the Sahara. Holotypes from
bore-hole SB 1 (Tunisia, X = 8 g. 21' 87" E, Y = 34 g. 91' 16" p, Z = 282 m.), depth 1210 m.,
Callovian.

Remarks. This species is included in the type Lx (Medus and Reyre 1966), see Table 1.

Classopollis rarus sp. nov.

Plate 56, figs. 5-7

Diagnosis. Subequatorial circular furrow present, with a prominent swelling; trilete
scar vestigial ; pseudopore intrastructure reduced at the distal pole, but no well-shaped
hollow is observed with electron microscope ; intrastructure punctate to pseudoreticulate ;
average exinal thickness 1 p; equatorial thickening 2/z; 7-9 striations; band width Ip.
Sculpture simple-pargeted, isomorphous, lightly heterodiametric, hairy with short
sticks processes with well-rounded tips ; height of processes 0-3-1 p, breadth 0-2-0-5 p,
abundance 15 per p2. The pargeted appearance is explained by crowding of processes
with the higher projecting above the shorter.

Size range. 23-34 p (32 specimens).

Holotype. Plate 55, figs. 5-7 ; size 32 p.

Stratigraphic position. Lower Portland of Charente, France ; bore-hole Vignolles S2 (X= 390.6, Y= 29.3,
Z= 15-50 m.), depth 14-80 m.

Classopollis aquitanus sp. nov.

Plate 57, figs. 1-5

Diagnosis. Subequatorial circular furrow present but difficult to distinguish; trilete
scar present; pseudopore diameter 5-9 p; intrastructure clearly reticulate (lumina

1- 1-5 p); average exinal thickness 1 p; equatorial thickening 1-5-2 p; 9-10 striations;
band width 10 p. Sculpture simple, isomorphous, heterodiametric, echinulate (hairy with

EXPLANATION OF PLATE 56

Light microscope figures approximately x 1000; Stereoscan figures approximately x 2000 and 10 000.

Figs. 1-4. Classopollis bussoni sp. nov. 1, L.M. holotype, view of finely punctate intrastructure and
striations. 2, 3, S.E.M. holotype, showing rugose-verrucose outer sculpture with warts. 4, S.E.M.
paratype.

Figs. 5-7. Classopollis rarus sp. nov. 5, L.M. holotype, showing punctate to pseudoreticulate intra-
structure and striations. 6, 7, S.E.M. holotype, showing rounded short sticks of the outer sculpture.

Figs. 8-10. Classopollis caratinii sp. nov. 8, L.M. holotype, showing loosely punctate intrastructure,
pseudopore, and trilete scar. 9, 10, S.E.M. views showing strongly rough sculpture.

Palaeontology, Vol. 13

PLATE 56

REYRE, Jurassic and Cretaceous Classopollis

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

315

spines); height of spines 0-3-0-9 p, breadth of base 0-1-04 p, abundance 9 per p2.
Some very short spines among the others.

Size range. 28-36 p (100 specimens).

Holotype. Plate 57, figs. 1, 4, 5; size 31 /x.

Stratigraphic position. Lower Portland of Charente, France; bore-hole Vignolles S2 (X = 390.6,

Y = 89.3, Z = 15 50 m.), depth 28-80 m.

Classopollis caratinii sp. nov.

Plate 56, figs. 8-10

Diagnosis. Subequatorial circular furrow distinct; trilete scar present, length of laesurae
2-5 /tx; pseudopore diameter 4 p\ intrastructure loosely punctate; average exinal thick-
ness 1 /u.; equatorial thickening 1-5 /x; 3-4 weak pseudostriations. Sculpture simple,
heteromorphous, heterodiametric, strongly rough; height of processes 0- 1-0-7 /lx, breadth
0-1—1 /lx; the shapes of the heteromorphous processes appear to be wrinkles, nipples, warts,
blisters, or spines, although no shape is clear.

Size range. 16-20 /x (28 specimens).

Holotype. Plate 57, figs. 8-10; size: 18 /x.

Stratigraphic position. Lower Portland of Charente, France; bore-hole Vignolles S4 (X = 390.6,

Y = 89.3), depth 21-65 m.

Classopollis martinottii sp. nov.

Plate 57, figs. 6-1 1

Diagnosis. Subequatorial circular furrow present but often difficult to distinguish;
trilete scar present, or trace; the outline of the pseudopore is not clearly marked and
the intrastructure is only reduced at the distal pole which is often folded in Stereoscan
observation; intrastructure finely punctate; average exinal thickness 1 p; equatorial
thickening 1-5 /x; 4-7 striations more or less discontinuous (lining of intra points);
band width 5 p. Sculpture simple, isomorphous, isodiametric echinulate (hairy with
spines of which the ends are not sharp but rounded); height of spines 0-4-0-5 p, breadth
of base 0-2-0-3 p, abundance 14-16 per p2.

Size range. 28-33 p (70 specimens).

Holotypes. Plate 57, figs. 9-11; size 30 p.

Stratigraphic position. Berriasian-Valanginian of Israel; bore-hole Heletz 2 (E = 115.963,
N = 110.807, K.B.+92 m.); depth 1465-71 m.

Remarks. This pollen is not easy to observe optically because of the crowded sculptural
elements.

Classopollis pujoli sp. nov.

Plate 58, figs. 1-4

Diagnosis. Subequatorial circular furrow present and large; trilete scar present, or
trace; pseudopore diameter 3-4 p; intrastructure pseudoreticulate ; average exinal
thickness 1-5 /lx; equatorial thickening 2 p; 5-6 striations; often anastomosing; band

316

PALAEONTOLOGY, VOLUME 13

width 6-7 p. Sculpture simple, isomorphous, isodiametric echinulate (hairy with needles) ;
height of needles 0-6 j x, breadth 0-15 ft, abundance 24 per ft2.

Size range. 20-6 ft (80 specimens).

Holotype. Plate 58, figs. 1-3 ; size 22 ft.

Stratigraphic position. Lower Portland of Charente, France; bore-hole Vignolles Sx (X = 390.6;

Y = 89.3); depth 6-80 m.

Remarks. C. pujoli differs from C. hammenii Burger in the three following characters:
circular furrow is more distinct, equatorial thickening more distinct, the tracery of the
intrapseudoreticulum is less distinct.

Classopollis mirabilis sp. nov.

Plate 58, figs. 5-11

Diagnosis. Subequatorial circular furrow distinctly present; trilete scar present, or trace;
pseudopore diameter 4-12 ft; intrastructure punctate to pseudoreticulate; average
exinal thickness 2 p; equatorial thickening 2-5 ft; 5-6 striations; band width 5-6 ft.
Sculpture simple, isomorphous, more or less isodiametric, echinulate (hairy with spines) ;
height of spines 1-1-5 /t, breadth of bases 0-3-0-4 ft, abundance 6 per ft2.

Size range. 24-36 /t (100 specimens).

Holotype. Plate 58, figs. 8, 10-11; size 35 ft.

Stratigraphic position. Lower Portland of Charente, France; bore-hole Vignolles Sx (X = 390.6,

Y = 89.3); depth 6-80 m.

Remarks. By light microscope observation C. mirabilis resembles C. echinatus Burger
1966; because of the absence of a clear illustration of the sculpture, it was preferable

EXPLANATION OF PLATE 57

Light microscope figures approximately x 1000; Stereoscan figures approximately x 2000 and 10 000.

Figs. 1-5. Classopollis aquitanus sp. nov. 1, L.M. holotype, showing reticulate intrastructure, stria-
tions, narrow subequatorial circular furrow. 2, S.E.M. tetrad, x 1000. 3, Detail of distal polar
area of central grain of tetrad showing vertical appearance of spines. 4, 5, S.E.M. holotype, showing
echinulate sculpture, hairy with spines.

Figs. 6-11. Classopollis martinottii sp. nov. 6, L.M. paratype, showing finely punctate intrastructure,
subequatorial circular furrow, equatorial thickening. 7, 8, S.E.M. views of same tetrad showing
end-rounded spines of the echinulate sculpture. 9, L.M. holotype. 10, 11, S.E.M. views of the
holotype. (There is a prominent scratch on the negative of fig. 7.)

EXPLANATION OF PLATE 58

Light microscope figures approximately x 1000; Stereoscan figures approximately x2000 and 10000.

Figs. 1-4. Classopollis pujoli sp. nov. 1, L.M. holotype, showing intrastructure, striations, pseudopore,
triangular proximal area, and exinal thickness. 2-4, S.E.M. holotype, showing echinulate sculpture,
hairy with needles.

Figs. 5-11. Classopollis mirabilis sp. nov. 5, L.M. paratype, showing punctate to pseudoreticulate
intrastructure. 9, L.M. paratype, showing striations, equatorial thickening, and subequatorial
circular furrow, x2000. 8, L.M. holotype, showing pseudopore. 10, 11, S.E.M. views of same

grain showing radially combed strong spines of echinate sculpture.

Palaeontology, Vol. 13

PLATE 57

REYRE, Jurassic and Cretaceous Classopollis

Palaeontology, Vol. 13

PLATE 58

REYRE, Jurassic Classopollis

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

317

to make a new species. Only scan observation of the C. echinatus holotype can indicate
whether these species are synonyms or not.

Classopollis noeli sp. nov.

Plate 59, figs. 1-3

Diagnosis. Subequatorial circular furrow present ; trilete scar present, length of laesurae
5-12 p; pseudopore diameter 3-10 p; intrastructure punctate; average exinal thickness
1 ju.; equatorial thickening 2 p; 7-12 striations, band width 7 p. Sculpture simple iso-
morphous, isodiametric, verrucose-pargeted ; height of warts 0-2-04 p, abundance 12-
15 per ju.2.

Size range. 22-40 ju. (100 specimens).

Holotype. Plate 59, figs. 1-3 ; size 30 p.

Stratigraphic position. Upper Jurassic to Aptian of the Sahara. Holotype from bore-hole Tamerna 1 ,
Algeria, (X = 4 g. 04' 03" E., Y = 37 g. 13' 72" N.), depth 1479 m. (Aptian).

Remarks. This species is one of the components of the optical type population ‘scabrate-
verrucose’ (Medus and Reyre 1966).

BOTANICAL AFFINITY AND TAXONOMIC VALUE

Barnard (1968), studying male cones containing Classopollis, established that the
genus does not belong to the Araucariales ; he underlined the similarity between Cheiro-
lepis muensteri Schenk cones described by Horhammer (1933), Masculostrobus Seward
and those of Taxus; however, he put forward no formal conclusion. Perhaps the
sculpture of the pollen exine is more significant. Three arrangements of sculptural
elements can be recognized: simple (the most common), mixed or double. From
observation of the sculpture of Recent gymnosperm pollen (Reyre 1968J) it appears
that a very important fossil plant taxon is concerned, having at least the rank of an
order. Indeed, Cupressales generally have a double sculpture, Taxodiales a mixed
sculpture, and Taxales a simple sculpture. Among Classopollis simple sculpture is by
far the most frequent. However, the elements of the sculpture are, in the main, quite
different; the species of recent Taxales show nipples or marked warts, regular and
perfectly shaped; on the contrary Classopollis show grana, warts, blisters, coarse
spines or large distinct needles. In addition, the wide variety of sculpture suggests that
there may have been a great number of species; so, if we consider Mesozoic pollen
assignable to Taxales for their structural character, we observe a very limited variety of
sculpture, as for living Taxales. All these differences seem to show that the plaeo-
botanical taxon, which produced Classopollis, if it had a morphological relationship
with Taxus (established by observation of the cones), was taxonomically distinct.

In spite of the highly evolved character of the exine, the presence of a proximal
trilete scar (sometimes vestigial) is a primitive character. Other Conifers such as
Araucariales, Taxodiales, and Taxales no longer show any trace of this ancestral charac-
ter. Therefore plants which produced Classopollis may not be assigned to any Recent
order of Coniferales; they corresponded probably to a special and very large fossil
taxon having at least the rank of an order. In any case, it is established that Classopollis
grains were produced by several botanical genera of Coniferales (Barnard 1968).

318

PALAEONTOLOGY, VOLUME 13
CLASSIFICATION

Is it possible to establish from pollen a classification likely to indicate the presumed
phylums of the palaeobotanical taxon which produced Classopollis'} Table 3 represents
the geographical and stratigraphical distribution of the species described. For each a
symbol indicates the nature of the intrastructure, the absence or presence of pseudo-
striations or distinct continuous striations, the elementary type of sculpture and nature
of the elements of this sculpture. If one considers this last character, it can be seen that
the rugose-verrucose sculpture (under this name are grouped the psilate, grumous,
rugose, and verrucose sculptures) existed in the Sahara from the Late Triassic, and
continued to be the most frequent during the Jurassic and Early Cretaceous time. On
the contrary, in Aquitaine (France), the echinate sculpture (hairy with points, spines,
and needles) is widely represented since the Rhaetian, and undergoes an extreme
development during the Early Cretaceous. It should be noted that after the species
C. kieseri found in Rhaetian and Early Liassic of Aquitaine with echinate sculpture,
there follow the Late Jurassic species C. aquitanus, C. pujoli, C. mirabilis which also
have an echinate sculpture. In the same way, in the Sahara, the double sculpture of C.
quezeli of the Late Triassic formations is also to be found in the Early and Middle
Jurassic ( gemmulate type, Medus and Reyre 1966).

In Table 3 the botanical environment indicated results of a personal interpretation
of the Stereoscan appearance of pollens (see explanation of PI. 59). It is remarkable
that in the Sahara, where disaccate pollen is almost impossible to find after the Carnian,
the succeeding species of Classopollis have a rugose-verrucose sculpture, and are
principally associated with pollen of Taxales, Araucariales, or Ephedrales. On the
other hand, in Aquitaine, numerous echinate species are associated, in the Rhaetian
as in the Early Cretaceous times, with pollens that may be compared with that of recent
Pinales of Cupressales. It would seem that different groups, linked with different
ecological conditions, have each evolved separately.

These different successions of species, during the Mesozoic era, geographically
localized with similar sculptures, suggest that sculpture is not an accidental specific
character but phyletic.

As for the intrastructure, it may be seen that in each group defined by the sculpture
(for example echinate) the massive species are principally founded in the Upper Triassic
or the Infraliassic. In the same way the absence of striations or the presence of ill-
defined striations (pseudostriations) is the most common at these times, while during the
Jurassic and Early Cretaceous one often observes very distinct striations, contrasting with

EXPLANATION OF PLATE 59

Light microscope figures approximately x 1000; Stereoscan figures approximately x 2000 and 10 000.

Figs. 1-3. Classopollis noeli sp. nov. 1, L.M. holotype, showing punctate intrastructure, striations,
and exinal thickness. 2, 3, S.E.M. holotype, showing general shape ( x 5000) and verrucose-pargeted
sculpture ( x 12 500).

Fig. 4. Mesozoic pollen with a simple sculpture assigned to a fossil species of Taxales (Reyre 1968 d),
x 5000.

Fig. 5. Pollen of a fossil (presumed Cupressales) showing outer sculpture with glomerules (Reyre 1968a').

Figs. 6, 7. Pollen assigned to a fossil Mesozoic species of Araucaria (Reyre 1968*/). 6, S.E.M. general
shape. 7, S.E.M. view showing sculpture.

Palaeontology , Vol. 13

PLATE 59

REYRE, Classopollis and other pollen

table 3. Stratigraphic and geographic localization of Classopollis species and botanical environment.

c . ia,hara „ Israel France

species Characters Environment Species Characters Environment Species Characters Environment

Aptian noeli f Gnetales,

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

319

C 7393

Y

5

320

PALAEONTOLOGY, VOLUME 13

the general intrastructure, and without a progressive organization of this intrastructure.
It would be necessary to observe all the known Classopollis species to affirm the results
concerning the distinction of the groups and the internal evolution of them. The remarks
above do permit, however, of our advancing the following inferences :

text-fig. 2. Shape and dimensions of the sculptural elements of the Classopollis species
described, approximately X 30 000. 1, simplex', 2, quezeli', 3, kieseri', 4, chateaunovi ; 5,
bussoni ; 6, rarus ; 7, aquitanus; 8, caratinii; 9, martinottii; 10, pujoli; 11, mirabilis ; 12, noeli.

1. Classopollis species should be classed according to the exine sculpture. This system
seems to be expressive of the botanical entities in the plant group which produced
Classopollis. From our present knowledge, four groups might be suggested with rugose-
verrucose, echinulate, mixed or double structure.

2. The palynological evolution inside each group might be different, but it seems
that the massive intrastructure has preceded differentiated intrastructure (alveolate,
punctate, reticulate, etc.). This is organized into more and more clear and distinct
striations. Thus a species with distinct striations may be considered highly evolved.

Although certain exceptional cases may not confirm this hypothesis, on the whole
it seems valid. It explains why species with similar intrastructures can have, in fact,
different sculptures; inversely that species with similar sculptures can have dissimilar
intrastructures.

Y. REYRE: POLLEN GENUS CLASSOPOLLIS PFLUG 1953

321

Barnard (1968, table 1) described pollen grains assignable to the formgenus Classo-
pollis extracted from fossil cones of different palaeobotanical genera; to each genus
corresponds a different intrastructure and the scanning observation of these grains
should therefore be all the more interesting. But, to discern generic and specific charac-
ters, it would be necessary to observe also pollen grains extracted from cones of other
species of the same genera.

Conclusion. Classopollis grains are the fossilized vestiges of a very important plant
group which had, during the Mesozoic, variable radiations and discontinuous evolution
according to the geographical province. No species seems to have had a world-wide
distribution, but in some countries the abundance and diversity of these pollens in
certain periods make them suitable for stratigraphic correlation.

Acknowledgements. I thank Mr. G. Kieser (Compagnie Franchise des Petroles), Mr. Chateauneuf
(Bureau de Recherches geologiques et minieres), Mr. Martinotti (‘Lapidoth’ Israel Oil Prospectors
Corporation), and Mr. Pujol (University of Bordeaux) who have been kind enough to provide me with
samples rich in Classopollis grains and who have enabled me to mention and describe them. Also I
thank Professor R. Laffitte and Miss D. Noel who allowed me to use the electron scanning microscope
(Cambridge manufacture, Stereoscan type) at the Geological Laboratory of the National Museum of
Natural History of Paris.

REFERENCES

barnard, p. d. w. 1968. A new species of Masculostrobus Seward producing Classopollis from the
Jurassic of Iran. J. Linn. Soc. ( Bot .), 61, 384, 167-76, 1 pi.
boltenhagen, e. 1968. Revision du genre Classopollis Pflug. Rev. Micropal. 11, 29-44, 2 pi.
bourreil, p., and reyre, y. 1968. Premiere etude de grains de pollen d’ Aristides (Graminees) au
microscope electronique a balayage. C.R. Acad. Sc. Paris, 267, 398-401, 2 pi.
burger, D. 1965. Some new species of Classopollis from the Jurassic of the Netherlands. Leidse.
Geol. Medel. 33, 63-9, 3 pi.

1966. Palynology of Uppermost Jurassic and Lowermost Cretaceous strata in the eastern

Netherlands. Leiden, Groen and Zoon, 276 pp., 39 pi.
couper, r. a. 1958. British mesozoic Microspores and Pollen Grains. Paleontographica, 103, B,
75-179, 31 pi.

dupin, f. 1965. Contribution a l’etude paleoplanctologique du Jurassique en Aquitaine occidentale.
Act. Soc. Linn. Bordeaux, 102, 3B, 1-19.

groot, j., and groot, catherina. 1962. Plant microfossils from Aptian and Cenomanian deposits of
Portugal. Com. Serv. Geol. Portugal, 46, 133-71, 10 pi.
klaus, w. 1960. Sporen der karnischen Stufe der ostalpinen Trias. Jahrb. geol. Bundesanst ., Wien,
sond, 5, 107-83.

medus, j., and reyre, r. 1966. Contribution a l’etude des grains de pollen appartenant au genre de
forme Classopollis (Pflug) Pocock et Jansonius. C.R. Acad. Sci. Paris. 262, 2703-6.
pettitt, j., and chaloner, w. g. 1964. The ultrastructure of the Mesozoic-Pollen Classopollis. Pollen
et Spores, 6, 2, 611-20, 1. pi.

pflug, h. d. 1953. Zur Entstehung und Entwicklung des angiospermiden Pollens in der Erdgeschichte.
Palaeontographica, 95B, 60-171, 10 pi.

pocock, s., and jansonius, j. 1961. The pollen genus Classopollis Pflug 1953. Micropaleontology, 7,
439-49, 1 pi.

pons, a. 1964. Contribution palynologique a l’etude de la flore et de la vegetation pliocenes de la
region rhodanienne. Montpellier, Fac. Sci., 713 p., 3 pi.
reyre, y. 1968a. Precisions sur la structure et la morphologie des prepollens du genre de forme
Classopollis (Pflug) Pocock et Jansonius. Consequences paleobotanique et stratigraphique. C.R.
Sci. Paris, 266, 1233-5.

322

PALAEONTOLOGY, VOLUME 13

reyre, y. 19686. Valeur taxinomique de la sculpture de l’exine des pollens de gymnospermes et de
chlamydospermes. C.R. Sci. Paris, 267, 160-1.

1968c. Valeur taxinomique de la sculpture de l’exine des pollens fossiles attribues aux gymno-
spermes ou au chlamydospermes. Ibid., 267, 488-90.

1968 d. La sculpture de l’exine des pollens des gymnospermes et des chlamydospermes et son

utilisation dans l’identification des pollens fossiles. Pollen et Spores, 10, 197-220, 7 pi.

Y. REYRE

Geological Laboratory
National Museum of Natural History

Typescript received 24 July 1969 Paris, France

PSEUDOCYMOPOLIA, A MESOZOIC TETHYAN
ALGA (FAMILY D AS YCL AD ACE AE)

by GRAHAM F. ELLIOTT

Abstract. Pseudocymopolia gen. nov. is proposed for certain dasycladaceae ranging from Portlandian to
Maestrichtian in age, and from Spain to Borneo geographically. P. orientalis sp. nov. is described, and the
relationship of the genus to Cymopolia discussed.

In 1959 I described a very distinctive dasyclad alga from the Maestrichtian of Iraqi
Kurdistan as Cymopolia anadyomenea (Elliott 1959). This alga showed the essential
branch-structure seen in Cymopolia, but the calcareous segments or units were remarkable
externally in swelling periodically into conspicuous annular projections or flanges: at
these levels the internal branch-structure was coarser than at the inter-flange levels.
These distinctive segments set C. anadyomenea apart from all other species of the
genus, which ranges from Upper Cretaceous to Recent, but it seemed reasonable to
regard the species as an early development before the very conservative morphology
of the Tertiary and Recent species was achieved.

During later reporting on the algal microflora of the Bau Limestone of Borneo,
random sections of an alga like C. anadymomenea were considered to indicate Upper
Cretaceous age for the appropriate samples. This was disputed by the field-geologists,
for the Bau Limestone is of Upper Jurassic and Lower Cretaceous age, and there was
no evidence that the disputed samples were anomalous in position. At this point
Praturlon (1964) figured a rare alga from the undoubted Lower Cretaceous of Italy as
C. alf. anadyomenea, and Dr. Radoicic of Belgrade sent me a thin-section of Yugoslav
Lower Cretaceous containing fragments of a similar alga. There is a similar record from
the Lower Cretaceous of Spain (Champetier, 1967 p. 148). In re-describing C. anady-
omenea along with other Middle East Dasycladaceae (Elliott 1968), I referred to the
Italian Borneo and Yugoslav fossils as examples of ‘an apparent homoeomorph’ of C.
anadyomenea.

Recently Dragastan described Cymopolia jurassica from the Portlandian of Rumania
(Dragastan 1968). This is yet another flanged species, based on good material and
carefully distinguished in detail by its author from C. anadyomenea Elliott and ‘C. alf.
anadyomenea Elliott’ of Praturlon, the two species available to him in the literature.

It is clear that these flanged forms range from Upper Jurassic to Upper Cretaceous
and have a wide Tethyan distribution: Spain, Italy, Yugoslavia, and Rumania in
Europe, and Iraq, Afghanistan (Kaever 1965), possibly Tibet (Morellet 1916; Elliott
1968, p. 40), and Borneo in Asia.

A re-examination of the relation of these flanged forms to normal Cymopolia spp.
is facilitated by the recently described C. eochoristosporica (Elliott 1968). This is a key
species in dasyclad evolution, for it shows an intermediate stage in the fundamental
reproductive evolution of the family. The segments are of normal cymopoliform
morphology in proportions and as seen externally, but the internal branches show the

[Palaeontology, Vol. 13, Part 2, 1970, pp. 323-6, pi. 60.]

324

PALAEONTOLOGY, VOLUME 13

transition from cladospore to choristospore organization (see Elliott 1968), making it
a kind of missing link in algal evolution. This species, from Abu Dhabi in Arabia, is
Maestrichtian in age. (It is not the earliest Cymopolia known, for the Texan C. perkinsi
(Johnson 1968), is from the Cenomanian). In Mme Segonzac’s recent review of the
Pyreneen Thanetian Cymopolia spp. (Segonzac 1968), which reached me whilst this
was being written, C. inflataramosa Segonzac shows a further intermediate stage
between C. eochoristosporica and C. elongata (Defr.) Munier-Chalmas. This detailed
study deals fully with the problem of the doubtful morphological validity of Karreria
Munier-Chalmas, touched on by me in describing the Middle East occurrences of C.
tibetica Morellet (Elliott 1968), and with the varying inflation of the primary branch
in and between different Thanetian and other species.

Since flanged species precede and overlap the primitive true Cymopolia spp. in time,
it seems doubtful that they are an aberrant early development of Cymopolia , as
was thought when only the Maestrichtian C. anadyomenea was known. They are
accordingly referred to Pseudo cymopolia gen. nov., diagnosed below, and the oppor-
tunity is taken to describe the Borneo species, which differs from all the other species,
including those not yet fully described.

Pseudocymopolia shows fully developed choristospore organization, at an earlier
geological period than the intermediate or developing choristospore structure of the
Upper Cretaceous C. eochoristosporica. Still earlier, with Eodasycladus of the Lias
(Cros and Lemoine 1966, 1967), the authors suggest that choristospore organization
was apparently achieved by sporangial swelling of one secondary branch in each
branch system i.e. a specialized form of cladospory. And Elias (1947) claimed a presumed
choristospory in Permopora which is Permian in age, though the condition is not ap-
parent from the figures given. Evidently the transition from cladospory to choristospory
took place in different genera in different ways at different times geologically.

The relationship of Pseudocymopolia to Cymopolia is thus not necessarily close,
though for taxonomic purposes both genera are placed in the Neomereae Pia 1920
( Neomeris appears in the Lower Cretaceous).

Genus Pseudocymopolia gen. nov.

Diagnosis. Thick-walled calcified dasyclad units or segments showing prominent
external consecutive annular swellings or flanges: numerous crowded verticils of
branches which are coarser at flange-levels; each branch showing one short primary
giving rise to a globular sporangium and four or more long secondaries. Upper Jurassic
to Upper Cretaceous.

Type species. Cymopolia anadyomenea Elliott (Maestrichtian of Iraq).

EXPLANATION OF PLATE 60

Fig. 1. Pseudocymopolia orientalis gen. et sp. nov. Longitudinal thin section of slightly distorted
segment, x 40. Lower Cretaceous, Bau Limestone ; Tebedu Road, Tubiti, Kuching, Sarawak, Borneo.
Syntype, reg. no. V.54126.

Fig. 2. Pseudocymopolia orientalis gen. et sp. nov. Oblique transverse thin section through terminal
thickening of slightly crushed segment, to show branch-structure, x 40. Same locality and horizon.
Syntype, reg. no. V. 54 127.

Palaeontology, Vol. 13

PLATE 60

ELLIOTT, Mesozoic Dasycladaceae (Algae)

vf

G. F. ELLIOTT: PSEUDOCYMOPOLIA

325

Other species. C. jurassica Dragastan (Upper Jurassic of Rumania), C. aff. anadyomenea (Praturlon,
Lower Cretaceous of Italy), C. cf. anadyomenea (Radoicic, Lower Cretaceous of Yugoslavia), ‘isomorfos
de Cymopolia anadyomenia Elliott’ (Champetier, Lower Cretaceous of Spain), and P. orientalis sp.
nov. (Lower Cretaceous of Borneo).

Pseudocymopolia orientalis sp. nov.

Plate 60, figs. 1, 2

Description. A Pseudocymopolia with dumb-bell-shaped segments showing prominent
rounded annular terminal thickenings connected by a much thinner shaft : the diameter
of the stem-cell cavity is approximately constant. A small example has a length of 2-86
mm., external diameter at terminal thickening 1-82 mm. (d/D ratio 34%), and external
diameter between thickenings 0-78 mm. (d/D ratio 66%). A larger but fragmentary
example shows an external diameter across the thickening of 2-76 mm. (estimated
length from this 4-33 mm.). In this large fragment the diameter of a primary branch
is 0-065 mm., of a secondary branch 0-045 mm., and of a globular sporangium 0-091
mm. The matrix appears to have been stressed and the fossils show slight signs of
distortion: some associated organic fragments, presumably more rigid than the alga
when buried, show fracturing. The material does not permit a full tabulation of detailed
structure dimensions for comparison with P. anadyomenea and P. jurassica, but the
two terminal thickenings only per segment, seems characteristic.

Comparison. P. orientalis differs from P. anadyomena in that its thickenings are rounded
and not keeled to form a flange. In this it resembles the other Lower Cretaceous and
the Jurassic species. The narrow portion of the segment between thickenings is pro-
portionally longer than is normal in other species, and these all differ in showing
several thickenings per segment. As with the Italian and Jugoslav Lower Cretaceous
species, the Borneo fossil is associated with the problematic non-dasyclad alga Litho-
codium aggregatum Elliott.

Syntypes. The specimens figured in Plate 60, figs. 1, 2, from the Bau Limestone (Lower Cretaceous) of
the Tebedu Road, near Tubiti, 32 miles SSE. of Kuching, Sarawak, Borneo. Brit. Mus. (Nat. Hist.),
Dept. Palaeont., reg. nos. V.54126, V.54127.

Other material. Specimens and fragments in thin-sections from the same formation and area.

REFERENCES

champetier, y. 1967. Estudio del Jurasico y del Cretacico de la Sierra de Fontanells (Provincia de
Valencia). Notas Comun. Inst. geol. min. Esp. 99-100, 135-76.
cros, p., and lemoine, m. 1966, 1967. Dasycladacees nouvelles ou peu connues du Lias inferieur des
Dolomites et de quelques autres regions mediterraneennes. Pt. 1 (1966) Rev. Micropaleont. 9, 1 56—
68, 2 pi.; Pt. 2 (1967) Ibid. 9, 246-57, 2 pi.

dragastan, o. 1968. Algues calcaires dans le Jurassique superieur de Roumanie. Geol. romana,
7, 59-74, 3 pi.

elias, m. 1947. Permopora keenae, a new late Permian alga from Texas. J. Paleont. 21, 46-58, pi. 18.
elliott, g. f. 1959. New calcareous algae from the Cretaceous of Iraq. Rev. Micropaleont. 1, 217-22,

1968. Permian to Palaeocene calcareous algae (Dasycladaceae) of the Middle East. Bull. Br.

Mus. nat. Hist. {Geol.) Suppl. 4,111 pp., 24 pi.

Johnson, j. h. 1968. Lower Cretaceous algae from Texas. Prof. Contr. Colo. Sch. Min. 4, 71 pp.

326

PALAEONTOLOGY, VOLUME 13

kaever, m. 1965. Mikropalaontologische Untersuchungen zur Stratigraphie Afghanistans. Erdol
Kohle Erdgas Petrochem. 18, 678-84.

morellet, l. 1916. Note sur les algues siphonees verticillees : pp. 47-9 in H. Douville, Le Cretace et
V Eocene du Tibet central. Mem. geol. Serv. India Palaeont indica, n.s. 5 (3), 1-52, 16 pi.
praturlon, A. 1964. Calcareous algae from Jurassic-Cretaceous limestone of central Apennines
(southern Latium-Abruzzi). Geol. romana, 2, 199-206, 1 pi.

1966. Algal assemblages from Lias to Paleocene in Southern Latium-Abruzzi : a review. Boll.

Soc. geol. Ital. 85, 167-94.

segonzac, g. 1968. Les Cymopolia (Dasycladacees) du Thanetien des Pyrenees. Bull. Soc. Hist. nat.
Toulouse, 104, 381-91, pi. 16-18.

G. F. ELLIOTT

Department of Palaeontology
British Museum (Natural History)
London S.W.7

Typescript received 17 July 1969

NEW AND LITTLE-KNOWN PERMIAN AND
CRETACEOUS CODIACEAE (CALCAREOUS
ALGAE) FROM THE MIDDLE EAST

by GRAHAM F. ELLIOTT

Abstract. Four Codiaceae (calcareous chlorophyte algae) are described from the Middle East. Anchicodium
sindbadi sp. nov., Tauridium kurdistanensis sp. nov., and Aphroditicodium aurantium gen. et sp. nov. are from the
Permian: Boueina hochstetteri Toula (Lower Cretaceous) is a first Middle East record. Aphroditicodium is
compared with other segmented Codiaceae from Ordovician to Recent, and their characters are tabulated.

Amongst calcareous green algae the family Codiaceae have shown a much less-
detailed and less- varied evolution than the family Dasycladaceae : this arises from the
different basic structures peculiar to the two families. In consequence, the Codiaceae,
although often abundant, have yielded few fossils of zonal value. Those encountered
by me during studies of the calcareous algae of the Middle East have been listed or
described (Elliott 1960, 1965); the present note describes four which are new or not
previously recorded from the area.

Genus anchicodium Johnson 1946

Remarks. This Upper Palaeozoic genus was described by Johnson (1946, 1961, 1963).
In thin-section it shows the characteristic codiacid pattern of poorly calcified central
threads and more heavily calcified marginal radial threads. The macro-structure, how-
ever, is unusual in being described as ‘a crustose mass from which straight or nearly
straight cylindrical stems develop’ : these stems are unusual in not being segmented so
far as is known. In consequence, evaluation of the orientation of random thin sections
is often difficult. The Middle East species now described falls in this category, but is
clearly an Anchicodium.

Anchicodium sindbadi sp. nov.

Plate 61, figs. 3, 4

Description. This species is seen in thin-section as a fragment about 7-5 mm. long and
0-68 mm. wide : it shows one lateral calcified cortical layer only. The fragment is worn
and crusted on both sides with obscure organic growths, in part formed by myxophyte
algae.

On one side of the fragment the calcite is clear and shows few threads: this is in-
terpreted as part of the pith-like medullary zone of a cylindrical stem, with largely
post-mortem calcification. On the other side the calcification, presumed original plant-
structure in origin, is crowded with codiacid-like plant threads, parallel to sub-parallel
in orientation, and directed more or less at right angles or oblique-transversely to the
longitudinal axis of the fragment. The threads are from 0-020 to 0-040 mm. in diameter,
the majority typically of 0-026-0-028 mm. diameter, the individual threads varying

[Palaeontology, Vol. 13, Part 2, 1970, pp. 327-333, pi. 61-62.]

328

PALAEONTOLOGY, VOLUME 13

somewhat throughout their length. Very few of them show undoubted branching.
These features show most clearly in the middle of the fragment : towards the ends the
plane of section cuts through the threads transversely, due to the curvature of the piece.

Holotype. The specimen figured in Plate 61, fig. 3, from Permian limestone occurring as derived
fragments in the Cretaceous Hawasina Formation (Morton 1959); Jebel Qamar, Peninsular Oman,
Arabia. Brit. Mus. (Nat. Hist.), Dept. Palaeont. reg. no. V.54131.

Other material. A second fragment, largely recrystallized, in the same thin section.

Remarks. The Cretaceous Hawasina is full of derived Permian limestone boulders,
some of great size, from which a varied Permian microflora and fauna have been
obtained. The particular thin-section from which the new Anchicodium comes also
shows fragments of the dasyclad Epimastopora, and pseudopunctate brachiopod debris.

This is the first Anchicodium recognized in this area: the record of Elliott (1960) for
Iraqi Kurdistan is now found to be a Tauridium. The specific name commemorates the
legendary Arab traveller, whose voyages from Basra would certainly have touched at
this desolate part of Arabia.

Genus Tauridium Giiveng 1966

Remarks. This genus, described by Giiveng (1966) from the Permian of Turkey, with
type species T. cuvillieri, is a typical segmented calcified codiacid. Comminuted debris
of what is probably the species described by Giiveng as T. fragilis was earlier described
by me in error as the ‘dasyclad’ Epimastopora minima (Elliott 1956), from the other
side of the Turkish-Iraqi frontier.

Translated diagnosis (free translation from Gtivenq). Alga occurring as more or less
flattened units, open at their bases. The interiors of these units are uncalcified and
hollow (matrix-filled). Only the calcified cortical zone is at present known. This is
formed of filaments sometimes oblique, sometimes perpendicular to the outer surface.
Regular and constant narrowings and swellings of the filaments give them a characteristic
‘moniliform’ appearance. The filaments divide dichotomously and their diameters
diminish towards the outer surface. Mode of reproduction unknown. Medullary
filaments rarely preserved and not well known. (Type species T. cuvillieri Giiveng.)
Upper Permian: Western Taurus, Turkey.

Tauridium kurdistanensis sp. nov.

Plate 62, figs. 3, 4

1960 Anchicodium sp. ; Elliott, p. 219.

Description. Rounded-turbinate codiacid segments as seen in thin-section outline and
presumed slightly flattened in the three-dimensional segments: length about 2 mm. or

EXPLANATION OF PLATE 61

Figs. 1, 2. Boueina hochstetteri Toula. Transverse and longitudinal thin sections of small segments,
> 40. Lower Cretaceous, Garagu Formation (Valanginian-Hauterivian); subsurface, Kirkuk no.
116 well, NE. Iraq. Reg. nos. V.54135, V.54136.

Figs. 3, 4. Anchicodium sindbadi sp. nov. Permian: from derived fragment in Cretaceous Hawasina
Formation; Jebel Qamar, Peninsular Oman, Arabia. Reg. no. V.54131. 3, Longitudinal thin section
of holotype, x 15. 4, Portion enlarged, to show thread-detail, x40.

Palaeontology, Vol. 13

PLATE 61

ELLIOTT, Permian and Cretaceous Codiaceae (Algae)

329

G. F. ELLIOTT: CODIACEAE (CALCAREOUS ALGAE)

more, width about 2 mm. The calcified cortical zone is about 0-6 mm. thick; the in-
terior, now matrix-filled, was filled with largely uncalcified plant matter during life,
and by analogy with other species of Tauridium, would at best have shown a few
weakly calcified medullary threads.

table 1. Dimensions of one swollen and constricted cortical thread throughout its full length. (S =
swellings; C = constrictions).

(Inner)

S.

C.

S.

C.

S.

C.

S.

C.

S.

C.

S.

(Outer)

Length

182

26

104

13

104

13

65

39

91

13

52

Width

78

13-20

52

13

52

20

26

20

26

13

26

microns.

The cortical zone shows very numerous typically codiacid threads showing a repeated
‘swollen-and-constricted’ pattern throughout their length. They bifurcate repeatedly
at angles of from 30° to 60°, the alternating diameters diminishing towards the exterior
along all branches. Table 1 gives the dimensions of one thread traced from the interior
margin of the cortical zone to the periphery, ignoring all side branches. The threads are
crowded, with irregular banded zones of wider spacing due to the concentricity of
periodic branching.

Holotype. Specimen shown in Plate 62, fig. 4 from the Zinnar Formation, Permian (? Artinskian);
Harur, Mosul Liwa, Northern Iraq. Brit. Mus. (Nat. Hist.), Dept. Palaeont., reg. no. V.54132.

Paratype. Specimen shown in Plate 62, fig. 3 from the Darari Formation, Upper Permian : Ora, Mosul
Liwa, Northern Iraq. Brit. Mus. (Nat. Hist.), Dept. Palaeont., reg. no. V.54133.

Other material. Debris has been seen sporadically in other thin-sections from these two
formations.

Remarks. Tauridium kurdistanensis differs from the type-species in size and shape of
segment ( T . cuvillieri is longer and ellipsoidal), in the much greater thickness of the
cortical zone (double or more), and in the more variable and often greater angle of
thread-division. From T.fragilis Giiven? it is easily distinguishable, this Turkish species
being very thin-walled (0T2-0T5 mm.).

The holotype is associated with the coral Waagenophyllum indicum (Waagen and
Wentzel) var. nov. (Hudson 1958). The paratype is accompanied by the algae Mizzia
velebitana Schubert, Gymnocodium bellerophontis (Rothpl.) Pia, Permocalculus fragilis
(Pia) Elliott and P. tenellus (Pia) Elliott.

Genus aphroditicodium gen. nov.

Diagnosis. Ovoid codiacid segments, probably slightly flattened, showing three distinct
zones in section: from within outwards, firstly, a lightly calcified medullary zone of
tangled threads more or less longitudinally arranged; secondly, a more heavily cal-
cified cortical zone of irregular branching and obscurely radial threads ; thirdly, a very
thin, densely calcified subdermal zone showing a single layer of small subdeltoid thread-
terminations widening outwards. Type-species A. aurantium sp. nov., Permian of
Northern Iraq.

Remarks. From the algae of the Permian of Iraqi Kurdistan, a new codiacid is very
rare in my experience, but the specimen now described is distinctive.

330

PALAEONTOLOGY, VOLUME 13
Aphroditicodium aurantium sp. nov.

Plate 62, figs. 1, 2

1960 Succodium sp.; Elliott, p. 219.

Description. Codiacid segment of 2-86 mm. length and 2-21 mm. width, ovoid in near-
vertical section with the presumed base incomplete, and interpreted as a terminal
segment. It shows clearly marked medullary, cortical, and subdermal zones described
below: the measured proportions of these suggest that the section is a near- vertical
(slightly oblique) cut of a terminal ovoid segment as stated, and not a more oblique
cut of a cylindrical unit. By analogy with similar segmented codiaceae, living and fossil,
the segment was likely to be somewhat flattened (thickness less than width). Older
(lower) segments from the same plant may well have differed in shape, but have not
been seen.

The inner, medullary, zone has a diameter of 0-858 mm. It shows a tangle of in-
distinct ramifying threads of 0-020-0-026 mm. diameter, more or less longitudinally
arranged. This zone was only lightly calcified in life, as in other segmented codiaceae :
and is now infilled with secondary calcification.

The cortical zone surrounds the medullary zone except at the base, where the medul-
lary threads united this segment to the preceding one. The cortical zone is from 0-572
to 0-598 mm. thickness, and shows a tangle of more distinct branching and apparently
anastomosing threads of similar diameter to the medullary threads (0-020-0-026 mm.).
These tangled threads show a very irregular and obscurely radial orientation. The original
plant calcification was probably heavier in this zone, thus accounting for the clearer
appearance of the threads.

The subdermal layer is very thin, varying from 0-052 to 0-078 mm. in thickness, and
shows dense calcification probably of original plant origin. The margin shows a single
peripheral layer of fairly close-set thread-terminations, of narrow subdeltoid outline
in section and expanding outwards. They have an external diameter of about 0-015 mm.,
and are seen to taper inwards for about 0-025 mm. They are spaced apart peripherally
by about their own diameters. Occasionally, preservation shows their connections with
the cortical threads.

Holotype. The specimen figured in Plate 62, figs. 1, 2, from the Zinnar Formation, Permian
(? Artinskian-Kungurian) ; Ora, Mosul Liwa, Northern Iraq. Brit. Mus. (Nat. Hist.), Dept. Palaeont.,
reg. no. V.54134.

Remarks. Segmented codiaceae are known from the Lower Palaeozoic to the present
day. They have in common the tripartite zoning of threads and calcification described
above for Aphroditicodium, and the classification is largely based on the differences in
the characters, at least when dealing with dissociated fossil segments. Table 2 lists the

EXPLANATION OF PLATE 62

Figs. 1, 2. Aphroditicodium aurantium gen. et sp. nov. Lr. Permian, Zinnar Formation; Ora, Mosul,
N. Iraq. Reg. no. V.54134. 1, Slightly oblique-vertical thin-section of terminal segment (holotype),
x 28. 2, Portion of sub-dermal layer enlarged, to show detail, x 84.

Fig. 3. Tauridium kurdistanensis sp. nov. Paratype: random thin-section to show thread-detail, x40.

Upper Permian, Darari Formation: Ora, Mosul, N. Iraq. Reg. no. V.54133.

Fig. 4. Tauridium kurdistanensis sp. nov. Holotype: oblique-vertical thin-section of segment, X40.
Lower Permian, Zinnar Formation: Harur, Mosul, N. Iraq. Reg. no. V.54132.

Palaeontology, Vol. 13

PLATE 62

ELLIOTT, Permian Codiaceae (Algae)

331

G. F. ELLIOTT: CODIACEAE (CALCAREOUS ALGAE)

differences between the principal genera. These are set out as distinguishable in normal
calcified thin-sections. Kozlowski and Kazmierczak (1968) have recently described
Palaeoporella mriabilis Stolley in detail from acid digests of exceptionally well-preserved
material. Detail as normally distinguishable may be seen in Obrhel’s comparison of the
same species with his new Maslovina meyenii (Obrhel 1968). Hurka (1968) who also
had access to unusually well-preserved material, decided that Palaeoporella is a dasy-

table 2. Key to internal characters of some genera of Codiaceae.

Genus

Author and Age

Longitudinal

Medullary

Threads

Radial
or Oblique
Cortical Threads

Subdermal Zone

Aphroditicodium

Gen. nov.
Permian.

Fine,

tangled.

Fine,

tangled.

Tiny close-set
deltoid terminations.

Arabicodium

Elliott 1 957
Jur.-Cret.

Fine,

skeinlike.

Fine,

branching.

Widening

terminations.

Boueina

Toula 1884
Jur.-Cret.

Coarse,

tangled.

Medium,

branching.

Close-set

terminal branchlets.

Dimorphosiphon

H0eg 1927
Ordovician.

Coarse,
few, straight.

Branching,
thinning, radial.

Fine

branchlets.

Halimeda

Lamouroux 1812
Cret.-Rec.

Thick, few,
close, straight.

Branching,
radial, swollen.

Widening

terminations.

Maslovina

Obrhel 1968
Silurian.

Medium,

adjacent.

Medium,

branching, oblique.

Expanded adjacent
branch-terminations.

Palaeoporella

Stolley 1 893
Ord.-Dev.

Fine,

straight.

Branching,
thinning, oblique.

Finest branchlets with
terminal widenings.

Succodium

Konishi 1954
Permian.

Fine,

skeinlike.

Fine,

branching.

Small, flasklike
swollen utricles.

cladacean, and not a codiacean, alga. I have not myself had access to material other than
in normal calcified limestone preservation : the English Devonian Palaeoporella (Elliott
1961) certainly seemed to be a codiacean. A very detailed modern account of Halimeda
is that of Hillis (1959).

Aphroditicodium is thus seen to be another variant on the basic segmented-codiacid
plan. It bears some resemblance to Succodium, but the subdermal layer is distinctive.
The generic name commemorates Aphrodite, fabled to have risen from the shallow
sunlit seas in which living codiaceae thrive; the specific name refers to the segment-
shape.

332

PALAEONTOLOGY, VOLUME 13

Genus boueina Toula 1884

Remarks. This genus was described from the Lower Cretaceous of Serbia (Toula 1884),
and has since been recognized from both Jurassic and Cretaceous in various countries
around the Mediterranean and in the Middle East. Although Boueina hochstetteri Toula
was extremely abundant at the Balkan type locality, and is known also from Italy and
France, and the older variety liasica occurs as far apart as Algeria and Iraq, this is the
first record of the type species in the Middle East.

Boueina hochstetteri Toula 1884

Plate 61, Figs. 1, 2

Description. Represented by clear longitudinal and transverse sections: the central
core is missing in both cases. Length of the former is 2-0 mm. incomplete; diameter of
the latter 1 -2 mm. This is much smaller than the dimensions of the type material, where
2-5-3-5 mm. diameter and up to 10 mm. in length is indicated. The branch-detail of the
calcified cortical zone corresponds exactly, however, and the specimens, earlier con-
sidered as a new Arabicodium sp., are now referred to B. hochstetteri. They come from
the subsurface Garagu Formation (Lower Cretaceous, Valanginian-Hauterivian) of
Kirkuk no. 116 well, north-east Iraq. Associated is debris of the chaetangiacid alga
Per mo calculus, corals and echinoderms.

REFERENCES

elliott, G. f. 1956. Further records of fossil calcareous algae from the Middle East. Micropaleontology,
2, 327-34, 2 pi.

1957. New calcareous algae from the Arabian Peninsula. Ibid. 3, 227-330, 1 pi.

1960. Fossil calcareous algal floras of the Middle East with a note on a Cretaceous problemati-

cum Hensonella cylindrica gen. et sp. nov. Q. Jl geol. Soc. Lond. 115, 217-32, pi. 8.

— — • 1961. A new British Devonian alga, Palaeoporella lummatonensis, and the brachiopod evidence
of the age of the Lummaton shell-bed. Proc. Geol. Ass., Lond. 72, 251-60, pi. 9, 10.

1965. The interrelationships of some Cretaceous Codiaceae (Calcareous Algae). Palaeontology,

8, 199-203, pi. 23, 24.

guvenc, t. 1966. Presence d’algues calcaires dans le Permien des Taurus occidentaux (Turquie);

description d’un nouveau genre et de quelques especes. Rev. Micropaleont. 9, 43-49, 2 pi.
hillis, l. w. 1959. A revision of the genus Halimeda (order Siphonales). Inst, marine Sci., Univ.
Texas, 6, 321-403, 12 pi.

hoeg, o. 1927. Dimorphosiphon rectangulare : Preliminary note on a new Codiacea from the Ordo-
vician of Norway. Avh. norske Vidensk Akad, 1927, no. 4, 15 pp. 3 pi.

Hudson, r. g. s. 1958. Permian corals from northern Iraq. Palaeontology, 1, 174-92, pi. 32-5.
hurka, h. 1968. liber den anatomischen Bau und die systematische Stellung des palaozoischen
Algengenus Palaeoporella Stolley. Nova Hedwigia, 15, 571-82, pi. 83.

Johnson, j. h. 1946. Lime-secreting algae from the Pennsylvanian and Permian of Kansas. Bull. geol.
Soc. Am. 57, 1087-1120, 10 pi.

1961. Limestone-building algae and algal limestones. Publ. Colo. Sch. Min., 297 pp. 139 pi.

■ 1963. Pennsylvanian and Permian algae. Colo. Sch. Min. Quart. 58, 211 pp., 81 pi.

konishi, k. 1954. Succodium, a new Codiacean genus and its algal associates in the late Permian of
southern Kyushu, Japan. J. Fac. Sci., Univ. Tokyo, (2) 9, 225-40, 2 pi.
kozeowski, r., and kazmierczak, j. 1968. On two Ordovician calcareous algae. Acta palaeont. pol.
13, 325-46, 11 pi.

morton, D. M. 1959. The geology of Oman. Proc. 5th W/d Petrol. Congr. 1, 277-94.

G. F. ELLIOTT: CODIACEAE (CALCAREOUS ALGAE) 333

obrhel, j. 1968. Maslovina meyenii n.g. et sp. neue Codiacea aus dem Silur Bohmens. Vest, iistred.
Cst. geol. 43, 367-70, 2 pi.

stolley, E. 1893. Ueber silurische Siphoneen. Neues Jb. Miner. Geol. Palaont. 1893 II, 135-46, pi. 7, 8.
toula, f. 1 884. Geologische Untersuchungen im westlichen Theile des Balkan und in den angrenzenden
Gebieten. X. Von Pirot nach Sofia, auf dem Vitos, fiber Pernik nach Trn und fiber Stol nach Pirot.
Sber. Akad. Wiss. Wien, 88, (1) 1279-1348, 9 pi.

G. F. ELLIOTT

Department of Palaeontology
British Museum (Natural History

Typescript received 17 July 1969 London S.W.7

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PALAEONTOLOGY

VOLUME 13 • PART 2

CONTENTS

Morphologic variability of the genus Schwagerina in the Lower Permian Wreford
Limestone of Kansas. By g. a. sanderson and g. j. verville 175

Surface textures of calcareous foraminiferids. By j. w. Murray and c. a. wright 1 84

Xiphosurid trails from the Upper Carboniferous of northern England. By
p. G. HARDY 188

Sedimentological factors affecting the growth of Visean caninioid corals in north-
west Ireland. By j. a. e. b. hubbard 191

A new capitosaurid labyrinthodont from East Africa. By A. A. howie 210

Feeding by predatory gastropods in a Tertiary (Eocene) molluscan assemblage.

By J. d. taylor 254

Chitinozoa from the Ordovician Sylvan Shale of the Arbuckle Mountains,
Oklahoma. By w. a. m. jenkins 261

A new species of Hemicypris (Ostracoda) from the ancient beach sediments
of Lake Rudolf, Kenya. By r. h. bate 289

Variation in the cardinalia of the brachiopod Ptychopleurella bouchardi
(Davidson) from the Wenlock Limestone of Wenlock Edge, Shropshire.

By M. G. BASSETT 297

Stereoscan observations on the pollen genus Classopollis Pflug 1953. By y. reyre 303

Pseudocymopolia, a Mesozoic Tethyan alga (Family Dasycladaceae). By
G. F. ELLIOTT 323

New and little-known Permian and Cretaceous Codiaceae (Calcareous Algae)
from the Middle East. By g. f. elliott 327

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VOLUME 13 • PART 3

Palaeontology

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The Palaeontological Association, 1970

CONODONTS FROM NEAR THE MIDDLE/UPPER
DEVONIAN BOUNDARY IN NORTH CORNWALL

by W. T. KIRCHGASSER

Abstract. Conodonts of the Polygnathus varcus (Middle Devonian, Givetian) Zone and the lower (Upper
Devonian) and upper part of the Lower Pol. asymmetricus Zone (Upper Devonian, Frasnian la) are reported
from thin turbidite limestones in the upper Trevose Slates, Marble Cliff Beds, and lower Longcarrow Cove
Tuffs and Slates, respectively, near Padstow, North Cornwall. The localities include the south side of Trevone
Bay and the overturned section along the coast at Marble Cliff. The fauna of the Schmidtognathus hermanni-Pol.
cristatus Zone, which in Germany marks the Middle/Upper Devonian boundary of the conodont chronology,
was not recovered, although some species that enter in that zone {Pol. cristatus [?] Hinde, S. wittekindti Ziegler
and S. peracutus (Bryant)) are found in the Marble Cliff Beds, associated with Palmatolepis transitans Muller,
Pol. asymmetricus ovalis Ziegler and Klapper, Pol. asymmetricus asymmetricus Bischoff and Ziegler, and abun-
dant Pol. decorosus Stauffer s.l. The first undoubted Upper Devonian conodonts occur in the Longcarrow Cove
Tuffs and Slates near the base of Marble Cliff, where faunas include Ancyrodella rotundiloba (Bryant).

Reinvestigations of ammonoid cephalopods (House 1956, 1961, 1963) from the
highly deformed grey slates around Padstow, North Cornwall, have revealed Middle
Devonian faunas in rocks long thought to be entirely Upper Devonian in age. Several
ammonoid horizons are known in the district and the sequence of faunas enabled House
to unravel the stratigraphic succession and establish a correlation with the standard
sequence in the Rheinisches Schiefergebirge. Although the broad aspects of the strati-
graphy and structure (Gauss 1966, 1967) have been worked out, many parts of the
puzzle remain unsolved because of the lack of faunal evidence in critical parts of the
succession. This contribution attempts to refine the biostratigraphy of the coastal section
near the Middle/Upper Devonian boundary by means of conodonts.

The Middle Devonian Trevose Slates are situated on the southern limb of the St.
Minver Synclinorium (House 1961) whose axis lies north of Padstow, within Upper
Devonian purple and green slates (upper Frasnian to Fammenian) (text-fig. 1). The
grey slates reappearing on the northern limb are overlain by a thick series of pillow
lavas (Pentire Point Pillow Lavas) before the entry of purple and green slates. The coastal
succession on the southern limb appears to be more complete, and here the Trevose
Slates begin in the upper Eifelian (Booby’s Bay) and extend into the upper Givetian
(Trevone Bay). The fauna of the uppermost Givetian Maenioceras terebratum Zone is
well represented in the Pentonwarra Point Goniatite Band on the south side of Trevone
Bay (House 1963). The fauna of the succeeding lower Frasnian (lowermost Upper
Devonian) Pharciceras lumlicosta (la) Zone has not been found anywhere in the district,
but the middle Frasnian Manticoceras cordatum (I (/3) y) Zone-fauna is known from
several localities, including the dark grey slates at Merope Island (Merope Island Beds),
0-6 miles (1 km.) north of Trevone Bay (House 1961, 1963). Between the Trevose Slates
and the Merope Island Beds and situated on the overturned limb of a major recumbent
syncline (Gauss 1966) are 220 ft. (67 m.) of alternating limestone and shale exposed at
Marble Cliff (Marble Cliff Beds and lower Longcarrow Cove Tuffs and Slates) which are
succeeded to the north by grey slates with tuff beds, agglomerate, and minor limestones

[Palaeontology, Vol. 13, Part 3, 1970, pp. 335-54, pi. 63-66.]

C 7619 Z

336

PALAEONTOLOGY, VOLUME 13

(House 1961, House and Selwood 1966). The Marble Cliff succession dips south beneath
the dolerite sill that forms the prominent headland north of Trevone Bay.

No ammonoids are known from either the Marble Cliff Beds or Longcarrow Cove
Tuffs and Slates, but House (1963) tentatively placed the Middle/Upper Devonian
boundary between them, assigning the Marble Cliff Beds to the Givetian largely on the

text-fig. 1. Geological sketch-map of Padstow area showing conodont localities.

evidence of Wedekindella (a characteristic Middle Devonian genus) associated with
similar limestones to the west at Poventon Bay. House and Selwood (1966, p. 53)
recorded an upper Givetian conodont age for the Marble Cliff Beds based on an unpub-
lished preliminary study by F. H. T. Rhodes of a sample collected from loose blocks at
the base of the cliff (House 1967, personal communication); this assignment was based
on a correlation with the conodont zonation of Bischoff and Ziegler (1957) from the
Rheinisches Schiefergebirge. Since the report of Bischoff and Ziegler a more refined
conodont zonation has been established within the framework of the standard ammonoid
zonation (Ziegler 1958, 1962a, 19666). This conodont chronology has proved to be
extremely useful for precise inter-continental correlation (see Glenister and Klapper
1966) and it is particularly refined around the Middle/Upper Devonian boundary.

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL 337

The samples were collected from the coastal sequence around Padstow during the
spring tides of October 1967 and January 1968.

CONODONT ZONATION ACROSS THE MIDDLE/UPPER
DEVONIAN BOUNDARY

Ziegler (19666), Krebs and Ziegler (1966), Glenister and Klapper (1966), and Orr
and Klapper (1968), among others, have thoroughly reviewed the relationship between
the conodont zonation and the position of the Middle/Upper Devonian boundary and
only a few pertinent details are noted here. In terms of the standard ammonoid zonation
in the Rheinisches Schiefergebirge, the top of the Middle Devonian is defined as the
top of the Maenioceras terebratum Zone and the base of the Upper Devonian as the
base of th q Pharciceras lunulicosta Zone (la), with the entry of Pharciceras; this boundary
has been traditionally equated with the Givetian/Frasnian stage boundary in Belgium,
but the correlation has still to be proven. An exact boundary horizon cannot be placed
in Germany because there is a gap between the ranges of Maenioceras and Pharciceras.
It is within this critical interval that Ziegler (19666) defined the Middle/Upper Devonian
boundary in terms of conodonts.

The Polygnathus v arcus Zone {y arcus- Subzone of Bischoff and Ziegler 1957) cor-
responds to the highest part of the M. terebratum Zone and is therefore regarded as
uppermost Middle Devonian (Ziegler 19626, p. 16). The Pol. varcus Zone begins with
the entry of Pol. varcus and is characterized by abundant Pol. varcus and Pol. linguifor-
mis without Spathognathodus bipennatus. Wittekindt (1966, pp. 627, 628) subdivided
the Pol. varcus Zone into a varcus- Zone without Pol. linguiformis transversus and a
succeeding transversus- Zone with Pol. linguiformis transversus. Because the well-known
species Pol. varcus and Pol. linguiformis dominate the fauna of the Pol. varcus Zone as
originally defined, and because Pol. linguiformis transversus is rare, Krebs and Ziegler
(1966, p. 747) preferred an informal subdivision of the Pol. varcus Zone into a lower and
upper part; this interpretation is followed here.

The Schmidtognathus hermanni-Polygnathus cristatus Zone (Ziegler 19666) follows
the Pol. varcus Zone and comprises the range of S. hermanni before the entry of Pol.
asymmetricus and Palmatolepis tr ansi tans. The lower boundary of the zone is not precisely
defined, as a few early growth stages of S. hermanni, as well as forms transitional
between Pol. decorosus s.l. and S. hermanni, occur in horizons that Ziegler regards as
still in the Pol. varcus Zone (Ziegler (19666, tables 1, 2, p. 659). Above the base of the
S. hermanni-Pol. cristatus Zone, S. hermanni is joined by Pol. cristatus and three new
species of Polygnathus and three of Schmidtognathus, but not at a single horizon as
implied by Ziegler (19666, text-fig. 2). The details of Ziegler’s range-charts show the
entry of these species in a staggered sequence, with some of the species (5. hermanni,
S. pietzerni ) appearing before Pol. cristatus, as in the least condensed Koppen section
at Rhenegge near Adorf. Several of these species, in addition to S. hermanni and
Pol. varcus, linger on into the succeeding Lower Pol. asymmetricus Zone, whose lower
boundary is defined by the entry of Pol. asymmetricus and Pal. transitans.

The position of the S. hermanni-Pol. cristatus Zone relative to the Middle/Upper
Devonian boundary is still a problem as the zonal fauna has not been found in rocks
bearing ammonoids. In the Rheinisches Schiefergebirge the zone appears to fill the gap

338

PALAEONTOLOGY, VOLUME 13

in the ammonoid chronology (Ziegler 19666) and is thus a problematical interval
between the Middle and Upper Devonian. It is clear from Ziegler’s analysis (pp. 672,
673) that the S. hermanni-Pol. cristatus Zone represents an important interval in cono-
dont evolution during which simple ancestral conodonts (Pol. decor osus s.l .) gave rise
to diverse and morphologically ‘advanced’ platform conodonts such as Schmidtognathus
and the Pol. cristatus group. Pol. cristatus in turn lead to Pol. asymmetricus, the stem
form of the line leading to Palmatolepis, a particularly significant genus in Upper
Devonian faunas. Thus in terms of conodont evolution Ziegler (19666, pp. 660, 661)
regarded the lower part of the S. hermanni-Pol. cristatus Zone (without Pol. cristatus)
as Middle Devonian and the more diverse upper part as Upper Devonian.

The succeeding Lower Pol. asymmetricus Zone is informally subdivided into a lower
part and upper part based on the first appearance of Ancyrodella rotundiloba (Ziegler
19626, p. 17, 196 66, p. 662). Krebs and Ziegler (1966, pp. 748, 749) assembled evidence
that proves beyond doubt that the upper part of the Lower Pol. asymmetricus Zone
(with A. rotundiloba) lies within the Pharciceras lunulicosta Zone (la) and is thus firmly
Upper Devonian; this correlation has since been confirmed in Australia (Glenister
and Klapper 1966, p. 785) and North America (Orr and Klapper 1968, p. 1069).

Krebs and Ziegler also suggested that the lower part of the Lower Pol. asymmetricus
Zone probably falls in the P. lunulicosta Zone (la) but offered no concrete evidence.
However, recent ammonoid collections from the classic section at Martenberg near
Adorf seem to support this interpretation. In April 1968, Dr. J. Kullmann, in a field
party with Professors W. Ziegler, M. R. House, and the author, discovered a new horizon
of pharciceratids low down in the Roteisenstein, which narrows the gap in the ammonoid
sequence, as typical Middle Devonian ammonoids are found only 0-30 m. below. The
new horizon lies within the 1-0 m. interval between Ziegler’s (1958) samples 0 (Pol.
varcus Zone) and 1 (upper part of Lower Pol. asymmetricus Zone). It remains to
be seen whether the faunas of the lower part of the Pol. asymmetricus Zone or the
S. hermanni-Pol. cristatus Zone can be recovered from the critical interval; Professor
Ziegler has made collections and is reviewing the details of the sequence.

The base of the Middle Pol. asymmetricus Zone is defined by the first occurrence of
Palmatolepis punctata, associated with Pol. asymmetricus, A. rotundiloba, and A. gigas,
among others ; at Martenberg this zone corresponds to the Pharciceras-Schichten (la)
as originally defined by Wedekind (1913). The Middle Pol. asymmetricus Zone has been
recognized in Australia (Glenister and Klapper 1966, p. 785) and Alberta, Canada
(Pollock 1968, p. 442), but its position in other North American sections is difficult to
determine because Palmatolepis punctata is either not found or is found associated with
higher conodont zones equivalent to the Manticoceras cordatum (I (/3) y) Zone. Muller
and Clark (1967) assigned the Squaw Bay Limestone of Michigan, with A. rotundiloba
and Pol. asymmetricus ovalis, to the Middle Pol. asymmetricus Zone but Orr and Klapper
(1968, pp. 1068, 1069) disagreed and assigned the Squaw Bay and the supposedly
equivalent tongue of the Genundewa Limestone exposed at Eighteenmile Creek, New
York, to the upper part of the Lower Pol. asymmetricus Zone. In Orr and Klapper’s
view both horizons have identical faunas, which include Pol. dengleri in addition to A.
rotundiloba. They regard Pol. dengleri as the diagnostic species because it has not been
reported higher than the upper part of the Lower Pol. asymmetricus Zone in the German
sequence (Ziegler 1958, tables 2, 10; 19626, p. 17); following this criterion Clark and

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL

339

Ethington’s (1967) fauna from Mary’s Mountain, Nevada, should also be reassigned to
the upper part of the Lower Pol. asymmetricus Zone. Krebs and Ziegler (1966, p. 737)
assigned a fauna with A. rotundiloba and A. rugosa from the Walheim section near
Aachen, Germany, to the Middle Pol. asymmetricus Zone based on the presence of well-
developed pointed anterior lobs in specimens figured as A. rotundiloba n. subsp. Krebs
and Ziegler (1966). In the present report A. rotundiloba n. subsp. is interpreted as an
early growth stage variant of A. rotundiloba (Bryant) sensu Muller and Clark (1967).
Krebs and Ziegler’s fauna could therefore also correspond to the upper part of the lower
Pol. asymmetricus Zone, which was the alternative correlation considered by these
authors.

CONODONT LOCALITIES

Trevose slates. Thin beds of blue-grey limestone are not uncommon within the grey
slates around Padstow, but few horizons can be accurately placed in the generally
northward-younging succession. Limestones at several localities, including Trevose
Head, Cataclews Point, Padstow, Rock, and further south-east, have long been regarded
as equivalent to the well-exposed sequence of closely spaced limestones at Marble Cliff
(Reid et al. 1910, Dewey 1914). At the type locality, the Marble Cliff Beds are separated
from the underlying Trevose Slates by the prominent dolerite sill that extends from
Padstow westward to the Trevose Peninsula: on the Trevose Peninsula the Marble Cliff
Beds are intruded by the sill. Throughout the area west of the Camel Estuary the critical
part of the transition between the Marble Cliff Beds and the Trevose Slates has been
obscured by the intrusion, especially where the limestones and shales are adinolized as
at Dinas Head and on the peninsula north of Trevone Bay (Fox 1895). The conodont
evidence presented here indicates that those limestones lying south of but not directly
associated with the sill are older than the Marble Cliff Beds and should be assigned to
the Trevose Slates; among these are the limestones around Rock and presumably the
limestones with Agoniatites and Wedekindella from the west and south-west side of
Polventon Bay (House and Selwood 1966, p. 53).

Loc. 1. Trevone Bay (SW 890760): Samples 30 and 31. Lower and upper beds of a
2-ft. (0-61 m.) thick series of three limestones alternating with grey slate, dipping south-
east in the low cliffs on the south side of the bay. The upper bed (Sample 31) is overlain
by 4 ft. (1 -22 m.) of slate capped by a prominent 1-foot (0-31 m.) thick bed of brown silty
slate. The sequence lies near the top of the Trevose Slates, probably a few feet above the
Pentonwarra Point Goniatite Band (Gauss 1968, personal communication).

Loc. 2. Rock (SW 935755): Sample 33. 1 -ft. (0-31 m.) thick limestone exposed in the
foreshore about 60 yd. (55 m.) east of the sea-wall.

Marble Cliff Beds and Longcarrow Cove Tuffs and Slates. The section at Marble Cliff
(Loc. 3: SW 891765) consists of approximately 220 ft. (67 m.) of alternating limestone
and shale which are overturned and dip south beneath the dolerite sill (text-fig. 2). There
are over 150 individual limestone beds ranging in thickness from less than 1 in. (2-5 cm.)
to slightly over 2 ft. (0-61 m.). The thickness of the individual limestones and of the
intervening steel-grey shales tends to be constant across the outcrop and the beds are
thinner and more widely spaced toward the base of the cliff.

The limestones are light to dark blue-grey bioclastic limestones (packed biomicrite)
and are largely composed of fine crinoidal debris. Moulds of Styliolina are common in

340

PALAEONTOLOGY, VOLUME 13

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL 341

the residues and at some horizons (notably Sample 1 7) these are associated with minute
pyritic gastropods, bivalves, ostracods, and rare ammonoid fragments. Sole-markings
and graded bedding were noted at a few horizons and these features, and the conodont
sequence as well, indicate that the succession is overturned. The only distinctive horizon
interrupting this monotonous sequence is a light greenish-grey tuff bed in about the
middle of the section. Samples 1-14 are from the Marble Cliff Beds and samples 15-20
are from the Longcarrow Cove Tuffs and Slates (text-fig. 3).

Approximately the lower 75 ft. (23 m.) of the Marble Cliff Beds, between Sample 1
and the sill, is inaccessible in the cliff face. Although the lowermost 26 ft. (8 m.) is
accessible in the west wall of Round Hole the limestones are too altered to yield signifi-
cant conodont faunas; only a single fragment was recovered from a sample near the
bottom of the Hole, 24 ft. (7-3 m.) above the intrusive contact. Two distinctive groups
of limestone, both consisting of three uniformly spaced beds, provide useful reference
horizons in the cliff section. The lower set consists of sample-horizons 2, 3, and 4 and
the higher set includes sample-horizon 8 at its base. The top of the Marble Cliff Beds
is defined as the base of sample-horizon 15, an irregularly bedded 1-ft. (0-31 m.) thick
limestone accessible in the north-east part of the outcrop.

The succeeding more argillaceous sequence near the base of the cliff (samples 1 5-20)
is here included in the Longcarrow Cove Tuffs and Slates. This series of thin, widely
spaced limestones reappears across a fault in the section at Porthmissen Bridge (oppo-
site Marble Cliff) and continues northward to Longcarrow Cove, where agglomerates
and tuffs enter the succession.

The limestones in the Padstow area appear to be turbiditic in origin and may repre-
sent bioclastic debris intermittently swept into a deep water pelagic environment
(Goldring et al. 1968, p. 7), perhaps from centres of reef accumulation in the more
tectonically active part of the basin in South Devon. Dineley (1961) proposed this
mechanism to explain similar thin-bedded limestones and shales which accumulated in
rapidly subsiding troughs immediately surrounding the South Devon reefs. The greater
part of these massive reefs or reef-like (Braithwaite 1966) limestones is lower to upper
Middle Devonian, although they continue into the lower part of the Upper Devonian
(House and Selwood 1966).

ANALYSIS OF THE CONODONT FAUNAS

The Trevose Slate horizons at Trevone Bay (Samples 30, 31) produced a fauna domin-
ated by Pol. linguiformis and Pol. varcus (text-fig. 4) which is indicative of the uppermost
Middle Devonian Pol. varcus Zone. A similar fauna recovered from Sample 33 at Rock
suggests that the scattered limestones thereabout correlate westward with the Trevose
Slates at Trevone Bay rather than with the succession at Marble Cliff. The single speci-
men of S', hermanni from Sample 31 is an early growth stage of an intermediate form
between Pol. decorosus s.l. and S. hermanni and is similar to forms figured by Ziegler
(19666) from the uppermost part of the Pol. varcus Zone in the Rheinisches Schiefer-
gebirge. The specimens of Pol. linguiformis and Pol. varcus from the Trevose Slates are
remarkably similar to the specimens figured by Rhodes and Dineley (1957) from appar-
ently upper Middle Devonian limestones at Bishopsteignton, South Devon. The remain-
ing less stratigraphically important elements of their fauna are rather different and there

342

PALAEONTOLOGY, VOLUME 13
are no other species in common with the Trevose Slate fauna. Matthews (1962) recorded
upper Eifelian conodonts from a structurally complicated sequence at Neal Point,
Cornwall, on the River Tamar and his report of Pol. xylus (= Pol. varcus ) and Pol.
varcus suggests that the Pol. varcus Zone is also represented.

The fauna of the Marble Cliff Beds (Samples 1—14) corresponds to the lower part of
the Pol. asymmetricus Zone and thus indicates a probable lower Upper Devonian age
for the limestone sequence. Important forms in the diverse but unevenly distributed
fauna include Pol. asymmetricus asymmetricus, Pol. asymmetricus ovalis, Pol. dengleri,
and Palmatolepis transitans. Although the fauna of the S. hermanni-Pol. cristatus Zone
is not represented there are several holdovers from this and the preceding Pol. varcus
Zone, including Pol. varcus, Pol. linguiformis, Pol. cristatus, Pol. sp. Ziegler (19666,
p. 669), S. wittekindti, S. hermannil , and S. peracutus.

The upper part of the Lower Pol. asymmetricus Zone, which corresponds to the lower
Upper Devonian Pharciceras lunulicosta Zone (la), begins at the base of the Longcarrow
Cove Tuffs and Slates (Samples 15-20) with the entry of Ancyrodella rotundiloba. The
fauna is less diverse than that of the Marble Cliff Beds and some stratigraphically
important forms which range above the lower part of the Lower Pol. asymmetricus Zone
were not recovered, such as Pol. asymmetricus, Pol. cristatus, and Pal. transitans. In
addition to A. rotundiloba, the fauna includes Icriodus symmetricus, Pol. decor osus, Pol.
foliatus, Pol. pennatus, and Pol. dengleri. As noted above, the overlap in the ranges of
A. rotundiloba and Pol. dengleri is diagnostic for the upper part of the Lower Pol.
asymmetricus Zone.

The conodont sequence at Trevone Bay and Marble Cliff corresponds closely with the
sequence in the lower and upper parts of Ziegler’s (19666) sections in the Rheinisches
Schiefergebirge, especially the Koppen section where the Pol. varcus and S. hermanni-
Pol. cristatus Zones and the entire Lower Pol. asymmetricus Zone are represented. Pol.
beckmanni was not recovered from the Trevose Slates and the Marble Cliff faunas do
not include Pol. caelata, Pol. ordinata, Spathognathodus sannemanni, and Schmidt-
ognathus pietzneri, among others, but considering the comparative poverty of the Cornish
faunas, these absentees do not greatly detract from the overall similarity of fauna and
faunal sequence. Because the fauna of the S. hermanni-Pol. cristatus Zone was not
recovered the Middle/Upper Devonian boundary of the conodont zonation cannot be
precisely placed. However, it must roughly correspond to the boundary between the
Trevose Slates and the Marble Cliff Beds, that is, within the series of altered rocks
associated with the dolerite sill north of Trevone Bay and on the Trevose Peninsula.

Although the bulk of the bioclastic material in the limestones is believed to be turbi-
ditic in origin, there is no evidence to suggest that any elements of the conodont fauna
were derived. However, the uneven distribution of species and the preponderance of
broken elements would seem to be the result of sorting and current reworking. The few
unusually productive horizons (for example Sample 17) are interpreted as lag deposits
in which large, robust, or structurally stable elements were relatively concentrated, such
as Icriodus, Ancyrodella and some of the lancet-shaped species of Polygnathus. In this
respect the fauna of Sample 17 resembles two assemblages Krebs and Ziegler (1966)
recovered from detrital reef limestones (lowermost Grenzschiefer) near the Middle/
Upper Devonian boundary in the vicinity of Aachen, Germany. Sorting may also account
for the absence of the more delicate broad platform elements, such as Pol. asymmetricus

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL

343

and Palmatolepis, in samples where they would normally be expected to occur. Thus in
cases where the differentiation of adjoining zones or parts of a single zone depends on
the ranges of a few diagnostic species that are not closely related and of contrasting
morphologies and hydrodynamic property, the precision of correlation of even the
furthest offshore facies may be effected by sorting. The collection of large samples from
widely spaced points along a horizon will tend to minimize the effect of sorting, but in
sections like the Marble Cliff this is not usually possible.

METRES

text-fig. 3. Stratigraphic succession at Marbie Cliff showing sample-horizons.
SYSTEMATIC DESCRIPTIONS

The fossils described are deposited in the Sedgwick Museum, Cambridge, where they
are numbered SM H9330-H9379. Other material is in the palaeontology collections of
the Department of Geology, University of Hull, England.

Ancyrodella rotundiloba (Bryant)

Plate 65, figs. 5, 6, 8, 9

1879 Polygnathus tuberculatus Hinde, p. 366, pi. 17, fig. 10 [non fig. 9 = lectotype of Pol.

tuberculatus selected by Bryant (1921, p. 25)].

1921 Pol. rotundilobus Bryant, pp. 26, 27, pi. 12, figs. 1-6; text-fig. 7.

1941 Ancyrodella rotundiloba (Bryant); Branson and Mehl, p. 202.

1957 A. rotundiloba (Bryant); Bischoff and Ziegler, p. 42, pi. 16, figs. 5-12, 14-17.

1958 A. rotundiloba (Bryant); Ziegler, pp. 44-5, pi. 11, figs. 11, 12.

1966 A. rotundiloba rotundiloba (Bryant); Krebs and Ziegler, pi. 1, figs. 10-13, 15-16.

1966 A. rotundiloba (Bryant) n. subsp.; Krebs and Ziegler, pi. 1, figs. 6-9.

1966 A. rotundiloba rotundiloba (Bryant); Glenister and Klapper, p. 799, pi. 85, figs. 9-13.

1967 A. rotundiloba (Bryant); Muller and Clark, p. 908, pi. 115, fig. 8; pi. 116, figs. 1-5;

text-figs. 5, 6.

Material. Eight specimens; SM H9330-H9334.

Remarks. Muller and Clark (1967) have determined the ontogeny and extremes of
variation in A. rotundiloba from the Squaw Bay Limestone of Michigan. The specimens
from the Longcarrow Cove Tuffs and Slates are all relatively early growth stages and
compare well with the series c to h (text-fig. 6) in Muller and Clark’s ontogenetic scheme.

344

PALAEONTOLOGY, VOLUME 13

The Cornish specimens are unusual in having only a few nodes on the upper surface, no
secondary keels and an extremely large basal cavity (or pit). In this latter feature, the
specimens are perhaps closest to the ‘typical’ examples of A. rotundiloba reported by
Krebs and Ziegler (1966) from the Walheim section near Aachen, Germany, particularly
the specimen figured by them as Plate 1, figs. 10-11 ; the two small specimens from the
same fauna, figured as A. rotundiloba n. subsp. (PI. 63, figs. 6-7, 8-9), are interpreted
as early growth stages of A. rotundiloba.

Range. Upper part of the Lower Pol. asymmetricus Zone to top of the Middle Pol. asymmetricus Zone
(Ziegler 19626, pp. 17, 19), corresponding to the Upper Devonian Pharciceras lunulicosta Zone (la)
(Krebs and Ziegler 1966, pp. 748, 749). The entry of A. rotundiloba defines the base of the upper part
of the Lower Pol. asymmetricus Zone. Sample-horizons 15—18, Longcarrow Cove Tuffs and Slates,
Marble Cliff.

Palmatolepis transitans Muller

Plate 63, figs. 1, 8

1956 Palmatolepis ( Manticolepis ) transitans Muller, pp. 18, 19, pi. 1, figs. 1, 2.

1957 Palmatolepis transitans Muller; Bischoff and Ziegler, p. 81, pi. 16, figs. 24, 25 [non figs.

23, 26, 27 = Polygnathus asymmetricus asymmetricus Bischoff and Ziegler].

1958 Palmatolepis transitans Muller, Ziegler, p. 66, pi. 1, figs. 9, 11-13; pi. 2, figs. 1-3, 8.

Material. Five specimens; SM H9335, 6.

Remarks. SM H9336 (PI. 61, fig. 8) differs from typical representatives of Pal. transitans
in having no clearly differentiated outer lobe and an unusual large flaring basal cavity.
This type of basal cavity is also seen in a specimen referred to Pal. transitans by Ziegler
(1958, p. 2, fig. 2) and is the distinguishing character of Palmatolepis ? disparalvea Orr
and Klapper from the S. hermanni-Pol. cristatus Zone in Illinois and New York.
Ziegler’s specimen is from the upper part of the Lower Pol. asymmetricus Zone at the
Martenberg section, near Adorf, in the Rheinisches Schiefergebirge.

Although the specimen at hand lacks the usually well-defined outer lobe of Pal.
transitans, it is tentatively assigned to the species because the basal cavity is posterior in

EXPLANATION OF PLATE 63

Figs. 1, 8. Palmatolepis transitans Muller. 1 a, b. Upper and lower views, SM H9335, Sample 8, Marble
Cliff Beds. 8 a, b. Upper and lower views, SM H9336, Sample 8, Marble Cliff Beds.

Fig. 2. Polygnathus dengleri Bischoff and Ziegler, a, b. Upper and lower views, SM H9351, Sample 13,
Marble Cliff Beds.

Figs. 3, 7, 10. Pol. cristatus (?) Hinde. Specimens are from the Marble Cliff Beds. 3 a, b. Upper and
lower views of early growth stage, SM H9339, Sample 8. la, b. Upper and lower views, SM H9340,
Sample 1. 10, Upper view, SM H9341, Sample 2.

Fig. 4. Pol. cf. Pol. rugosus Fluddle. a, b. Upper and lower views, SM H9365, Sample 17, Longcarrow
Cove Tuffs and Slates.

Fig. 5. Pol. decorosus Stauffer s.l. Lower view of early growth stage with large, flaring basal cavity,
illustrating transition to Schmidtognathus Ziegler, SM H9342, Sample 8, Marble Cliff Beds.

Fig. 6. Pol. linguiformis Hinde. a, b. Upper and lower views of fragment, SM H9357, Sample 15,
Longcarrow Cove Tuffs and Slates.

Fig. 9. Pol. asymmetricus asymmetricus Bischoff and Ziegler, a, b. Upper and lower views, SM H9337,
Sample 1, Marble Cliff Beds.

All magnifications x 50.

Palaeontology, Vol. 13

PLATE 63

KIRCHGASSER, Conodonts from North Cornwall

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL

345

position, the carina is only slightly curved, and it has an azygous node. It is similar in
form to Pol. asymmetricus asymmetricus Bischoff and Ziegler, but in that subspecies
the basal cavity is anterior (or in some cases central) in position and the azygous node
is weakly defined or absent.

The posterior position of the basal cavity in the earliest species of Palmatolepis appears
to be a more diagnostic character than the degree of development of the outer lobe and
asygous node for differentiating the genus from closely related species of Polygnathus.
In Pol. asymmetricus and Pol. cristatus the basal cavity is usually anterior or, more rarely,
central in position. If one follows Ziegler’s (1962a, 1966h) phylogenetic scheme along
the line from variants of Pol. decorosus Stauffer s.I. to the Pol. cristatus group to Pol.
asymmetricus ovalis, Pol. asymmetricus asymmetricus, and finally to Palmatolepis, the
basal cavity shows a tendency to migrate from an anterior to central position in Poly-
gnathus to a posterior position in Palmatolepis. There is also a parallel tendency towards
a reduction in the size of the basal cavity, so that in possessing the large flaring basal
cavity Palmatolepis ? disparalvea and the two specimens discussed above deviate from
the main evolutionary line in Palmatolepis which leads to Palmatolepis punctata Ulrich
and Bassler. Palmatolepis ? disparalvea belongs in Palmatolepis and is distinguished from
Pal. transitans s.s. by its strongly differentiated outer lobe and much coarser ornamenta-
tion.

Range. Base of Lower Pol. asymmetricus Zone to upper part of the Ancyrognathus triangularis Zone
(Ziegler 19626, pp. 17, 20). Sample-horizons 1-9, Marble Cliff Beds, Marble Cliff.

Polygnathus asymmetricus ovalis Ziegler and Klapper

1957 Polygnathus dubia dubia Hinde; Bischoff and Ziegler, p. 88, pi. 16, fig. 19; pi. 21,

figs. 1, 2.

1958 Pol. dubia dubia Hinde; Ziegler, pp. 57, 58, pi. 1, figs. 1-3, 7.

1964 Pol. asymmetrica ovalis Ziegler and Klapper; Ziegler, Klapper, and Lindstrom, pp. 422,
423.

1966 Pol. asymmetrica ovalis Ziegler and Klapper; Ziegler 1966 b, p. 671, pi. 5, fig. 6.

1966 Pol. asymmetrica ovalis Ziegler and Klapper; Glenister and Klapper, p. 828, pi. 87,

figs. 8-9.

1967 Pol. dubius Hinde; Muller and Clark, p. 916, pi. 115, figs. 5, 6.

Material. Five specimens.

Range. Base of Lower Pol. asymmetricus Zone into Upper Pol. asymmetricus Zone (Ziegler 19626,
table 2). Sample-horizons 1-8, Marble Cliff Beds, Marble Cliff.

Polygnathus asymmetricus asymmetricus Bischoff and Ziegler
Plate 63, fig. 9

1957 Polygnathus dubia asymmetrica Bischoff and Ziegler, pp. 88, 89, pi. 16, figs. 18, 20-2;

pi. 21, fig. 3.

1958 Pol. dubia asymmetrica Bischoff and Ziegler; Ziegler, pp. 57, 58, pi. 1, figs. 4-6, 8, 10.
1964 Pol. asymmetrica asymmetrica Bischoff and Ziegler; Ziegler and Klapper in Ziegler,

Klapper, and Lindstrom, p. 423.

1966 Pol. asymmetrica Ziegler, 19666, pi. 5, figs. 9, 10.

Material. Eighteen specimens; SM H9337, H9338.

346

PALAEONTOLOGY, VOLUME 13

Remarks. According to Ziegler (1962a, 19666) Pol. asymmetricus ovalis is the stem form
of the lineage that gave rise to Palmatolepis during the early part of the Late Devonian.
The important trends were (1) an increase in platform asymmetry by expansion of the
outer side to form a lobe, (2) the development of an azygous node, (3) a reduction in the
size of the basal cavity, and (4) migration of the basal cavity to a posterior position on
the platform. The last mentioned is here regarded as the most diagnostic feature for
differentiating Palmatolepis from closely related species of Polygnathus. Pal. transitans
is most closely related to Pol. asymmetricus asymmetricus. In Pol. asymmetricus asym-
metricus the outer side has not developed into a lobe, an azygous node is either missing
or weakly developed and the basal cavity is in the centre or anterior part of the platform.

Range. Base to top of Pol. asymmetricus Zone (Ziegler 1962 b, table 2). Sample-horizons 1-8 Marble
Cliff Beds, Marble Cliff.

Polygnathus cristatus (?) Hinde
Plate 63, figs. 3, 7, 10

[?] 1879 Polygnathus cristatus Hinde, p. 366, pi. 17, fig. 11.

[?] 1921 Pol. cristatus Hinde; Bryant, p. 24.

[?] 1933 Pol. cristata Hinde; Branson and Mehl 1933a, p. 147, pi. 11, fig. 10 [the holotype].

1957 Pol. cristata Hinde; Bischoff and Ziegler, pp. 86, 87, pi. 15, figs. 1-7, 10 [non figs. 8-9,

1 1-13, 16 = Pol. asymmetricus asymmetricus Bischoff and Ziegler]; pi. 17, figs. 12, 13.

1964 Pol. cristata Hinde; Orr, pp. 13, 14, pi. 3, figs. 4-8, 10; text-fig. 4.

1966 Pol. cristata Hinde; Ziegler 19666, pp. 670, 671, pi. 4, figs. 17, 18, 19-21 [?], 22, 23;

pi. 5, figs. 1, 2, 3^1 [?], 5.

1968 Pol. cristatus Hinde; Orr and Klapper, pi. 139, figs. 1-4, 8, 9.

Material. Thirty specimens; SM H9339-H9341.

Diagnosis. The platform is broad and oval-shaped (symmetrical) in outline, with a
flattened anterior and pointed posterior margins. The coarse ornamentation on the
upper surface is distinctive ; rows of discrete rounded nodes are aligned roughly parallel
to a gently curved median carina of similar but larger nodes. In late growth stages, the
more median rows tend to diverge from the carina near the anterior end, producing
furrows on both sides of the carina. The nodes are more irregularly arranged and more
closely spaced in late growth stages. The lower surface has a median keel with a well-
developed basal cavity located in the anteriormost third of the platform.

Remarks. The name Pol. cristatus Hinde rather loosely refers to broad platform cono-
donts similar to Pol. asymmetricus ovalis but which are thicker and more coarsely
ornamented. Bischoff and Ziegler (1957) and Ziegler (19666) interpreted Pol. cristatus
as a highly variable species. They included in the species forms with rather pointed
anterior platform margins and more centrally located basal cavities, as well as large
forms with relatively small densely packed nodes on the upper surface that are fused into
irregular networks or ramifying ridges. These variants were not found in the Marble
Cliff Beds. The Marble Cliff specimens are remarkably similar to the specimens figured
by Orr (1964) from the S. hermanni-Pol. cristatus Zone in the Alto Formation of
Southern Illinois.

The assignment of the specimens to Pol. cristatus Hinde is questioned because the
generally held concept of the species, which focuses on Pol. cristatus Hinde sensu

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL

347

Bischoff and Ziegler, is not in accord with Hinde’s holotype (British Museum (N.H.)
A4319), from the ‘Conodont-bed’ (= North Evans Limestone) on Eighteenmile Creek,
North Evans, New York. In this specimen, which only shows the upper side, the rows
of nodes converge posteriorly, and the outermost row parallels the platform margin;
also, some of the anterior nodes are clearly fused into ridges. Anteriorly the rows of
nodes diverge from the carina to such a degree that the anterior end of the platform
appears divided into lobes. These features, which are not seen in the hypotypes or the
specimens at hand, are more characteristic of Ancyrodella than Polygnathus.

Range. Pol. cristatus Hinde sensu Bischoff and Ziegler ranges from within the S. hermanni-Pol. cristatus
Zone (Ziegler 19666, p. 675) to the top of the Lower Pol. asymmetricus Zone (Bischoff and Ziegler
1957, table 4; Ziegler 19626, p. 19). Sample-horizons 1-8, Marble Cliff Beds, Marble Cliff.

Polygnathus decor osus Stauffer s.l.

Plate 63, fig. 5; Plate 64, figs. 1-8

1938 Polygnathus decorosus Stauffer, p. 438, pi. 53, figs. 1, 5, 6, 10, 11, 15, 16, 20, 30.

1957 Pol. foliata Bryant; Muller and Muller, pp. 1086, 1087, pi. 135, fig. 1.

1957 Pol. decorosa Stauffer; Bischoff and Ziegler, p. 87.

1957 Pol. xyla Stauffer; Bischoff and Ziegler, p. 101, pi. 5, figs. 11-17.

1964 Pol. decorosa Stauffer; Orr, pp. 14, 16, pi. 1, figs. 3, 5, 7; pi. 3, fig. 2.

1966 Pol. decorosa Stauffer s.l.; Ziegler 19666, pi. 3, figs. 1^4; pi. 4, figs. 1-4; pi. 6, figs. 7-17.

1966 Pol. xyla Stauffer; Wittekindt, p. 642, pi. 3, figs. 18, 19.

1966 Pol. decorosus Stauffer; Anderson, p. 411, pi. 50, figs. 6-8, 10, 11, 15, 19.

1967 Pol. foliata Bryant; Clark and Ethington, p. 61, pi. 7, fig. 7 [non pi. 5, fig. 7 = Pol.

foliatus Bryant],

1967 Pol. normalis Miller and Youngquist; Clark and Ethington, p. 63, pi. 4, fig. 3 [non pi. 5,
fig. 10 = Pol. foliatus [?] Bryant],

1967 Pol. foliatus Bryant; Muller and Clark, p. 916, pi. 115, fig. 4.

Material. 185 specimens; SM H9342-H9350.

Diagnosis. Polygnathus decorosus Stauffer s.l. is a morphologically simple polygnathid
with a narrow lanceolate platform and relatively long free blade. The unit is moderately
to strongly bowed and arched. The ornamentation is weakly developed and consists of
nodes or transverse ridges along the platform margins. The free blade is usually uniform
in height and carries numerous teeth of nearly equal size and height. In early growth
stages (PI. 64, figs. 1 , 2, 7, 8) the platform is symmetrical in outline (the lateral margins
are nearly parallel), shorter than the free blade, and the relatively large basal cavity is
situated at the point where the free blade joins the platform. In late growth stages (PI. 64,
figs. 3-6) the platform is more asymmetrical, about as long as the free blade, and the
basal cavity is less conspicuous and lies posterior of the join between the free blade and
the platform.

Remarks. Pol. decorosus s.l. is the most common conodont in the faunas from the
Marble Cliff. It is an extremely variable species (Ziegler 19666) and many of the Cornish
specimens show gradations toward Pol. foliatus Bryant and Pol. pennatus Hinde and
related species. Muller and Muller (1957) regarded Pol. decorosus as a synonym of
Pol. foliatus Bryant. However, in late growth stages of Pol. foliatus the platform is
broader and distinctly asymmetrical, the ornamentation on the posterior half consists of

348

PALAEONTOLOGY, VOLUME 13

numerous small nodes (Bryant 1921, p. 24; Huddle 1934, p. 99), and the teeth on the free
blade increase in height anteriorly.

Ziegler (196 6b) interprets Pol. decorosus s.l. as a stem form from which several new
species and one genus evolved during late Middle and early Late Devonian time.
These forms include : Pol. varcus (reduced platform, long free blade), Pol. foliatus and
Pol. normalis Miller and Youngquist (broad, asymmetrical platforms with noded or
ribbed ornamentation), Pol. pennatus (coarse radially ribbed ornamentation), Pol.
cristatus group (broad, symmetrical platforms with coarse nodes) and Schmidtognathus
(large, asymmetrical basal cavity). Compared to Pol. decorosus s.l., these forms also
tend to have more highly developed free blades with teeth of varying size and height
and well-defined crimps.

Range. Because of the present taxonomic tangle that surrounds Pol. decorosus and closely related
species {Pol. foliatus, Pol. normalis, Pol. pennatus, among others) and because of their relatively long
ranges, these common lanceolate polygnathids have limited biostratigraphic value. Pol. decorosus s.l.
apparently ranges from the lower Middle Devonian (Wittekindt 1966, table 1) into the upper part of
the Upper Devonian (Famennian) (Ziegler 1966 b, text-fig. 4). Sample-horizons 31, Trevose Slates,
Trevone Bay; 33, Trevose Slates, Rock; 1-13, Marble Cliff Beds; and 17, 18, Longcarrow Cove Tuffs
and Slates, Marble Cliff.

Polygnathus dengleri Bischoff and Ziegler

Plate 63, fig. 2; Plate 64, fig. 4; Plate 66, fig. 2

1957 Polygnathus dengleri Bischoff and Ziegler, pp. 87, 88, pi. 15, figs. 14, 15, 17-24; pi. 16,
figs. 1-4.

1966 Pol. dengleri Bischoff and Ziegler; Ziegler 19666, pp. 671, 673, pi. 6, figs. 1-6.

1967 Pol. dengleri Bischoff and Ziegler; Muller and Clark, p. 916, pi. 115, figs. 3, 7.

Material. Ten specimens; SM H9351-H9353.

Diagnosis. The platform is narrow, oval-shaped, and symmetrical in outline, with a
pointed posterior margin. The free blade is short and high. The ornamentation on the
flat upper surface consists of weakly developed short transverse ridges along the plat-
form margin ; the ridges do not extend into the smooth weakly developed troughs that
parallel the median carina.

EXPLANATION OF PLATE 64

Figs. 1-8. Pol. decorosus Stauffer s.l. la, b, c. Upper, lower, and lateral views of early growth stage,
SM H9343, Sample 8, Marble Cliff Beds. 2a, b, c. Upper, lower, and lateral views of early growth
stage, SM H9344, Sample 8, Marble Cliff Beds. 3, Oblique view of specimen transitional to Pol.
pennatus Hinde, SM H9345, Sample 8, Marble Cliff Beds. 4, Upper view of late growth stage, SM
H9346, Sample 17, Longcarrow Cove Tuffs and Slates. 5a, b, c. Upper, lower, and lateral views of
late growth stage, SM H9347, Sample 17, Longcarrow Cove Tuffs and Slates. 6a, b, c. Upper,
lower, and lateral view of late growth stage, SM H9348, Sample 17, Longcarrow Cove Tuffs and
Slates, la, b, c. Upper, lower, and lateral views of early growth stage, SM H9349, Sample 8, Marble
Cliff Beds. 8a, b, c. Upper, lower, and lateral views of early growth stage, SM H9350, Sample 8,
Marble Cliff Beds.

Fig. 9. Pol. linguiformis Hinde. Upper view, SM H9358, Sample 17, Longcarrow Cove Tuffs and
Slates.

All magnifications x 50.

Palaeontology , Vol. 13

PLATE 64

K.IRCHGASSER, Conodonts from North Cornwall

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL

349

text-fig. 4. Distribution of conodonts in samples from Trevone Bay, Rock, and Marble Cliff.

Remarks. The specimens are early growth stages and compare most closely with speci-
mens of Pol. dengleri figured by Ziegler (19666).

Range. Pol. dengleri enters somewhat above the base of the Lower Pol. asymmetricus Zone (Ziegler
19666, tables) and ranges to the top of the zone (Bischoff and Ziegler 1957, table 4; Ziegler 1958,
tables 2, 10; Ziegler 19626, p. 17). Sample-horizons 8-13, Marble Cliff Beds, and 15-17, Longcarrow
Cove Tuffs and Slates, Marble Cliff.

Polygnathus foliatus Bryant

Plate 65, figs. 1, 2

1921 Polygnathus foliatus Bryant, p. 24, pi. 10, figs. 13-16.

1934 Pol.foliata Bryant; Huddle, p. 99, pi. 8, figs. 14-17.

350

PALAEONTOLOGY, VOLUME 13

[non] 1957 Pol.foliata Bryant; Bischoff and Ziegler, p. 90, pi. 4, figs. 1-4 [= Polygnathus sp. ?]
[non] 1957 Pol.foliata Bryant; Muller and Muller, pp. 1086, 1087, pi. 135, fig. 1 [= Pol. decorosus
Stauffer s.l.].

1967 Pol. foliata Bryant; Clark and Ethington, p. 61, pi. 5, fig. 7 [non pi. 7, fig. 7 = Pol.
decorosus Stauffer s.l.].

Material. Fifteen specimens; SM H9354-H9356.

Remarks. See Polygnathus decorosus Stauffer s.l.

Range. Sample-horizons 1-8, Marble Cliff Beds, and 17, Longcarrow Cove Tuffs and Slates, Marble
Cliff.

Polygnathus linguiformis Hinde

Plate 63, fig. 6; Plate 64, fig. 9; Plate 66, fig. 4

1879 Polygnathus linguiformis Hinde, p. 367, pi. 17, fig. 15.

1921 Pol. linguiformis Hinde; Bryant, p. 25, pi. 11, figs. 1-9; pi. 14, fig. 2.

EXPLANATION OF PLATE 65

Figs. 1-2. Polygnathus foliatus Bryant. 1 a, b. Upper and lower views, SM H9354, Sample 17, Long-
carrow Cove Tuffs and Slates. 2a, b. Upper and lower views, SM H9355, Sample 17, Longcarrow
Cove Tuffs and Slates.

Figs. 3, 7. Schmidtognathus wittekindti Ziegler. 3 a, b, c. Upper, lower, and lateral views of early
growth stage, SM H9369, Sample 12, Marble Cliff Beds, la, b. Upper and lower views of late
growth stage, SM H9370, Sample 1, Marble Cliff Beds.

Fig. 4. Pol. dengleri Bischoff and Ziegler, a, b. Upper and lower views, SM H9352, Sample 8, Marble
Cliff Beds.

Figs. 5, 6, 8, 9. Ancyrodella rotundiloba (Bryant). Specimens are from the Longcarrow Cove Tuffs
and Slates. 5, Upper view of early growth stage, SM H9330, Sample 17. 6a, b. Upper and lower
views, SM H9331, Sample 15. 8 a, b. Upper and lower views, SM H9332, Sample 15. 9a, b. Upper
and lower views of early growth stage, SM H9334, Sample 17.

All magnifications x 50.

EXPLANATION OF PLATE 66

Fig. 1. Schmidtognathus hermanni Ziegler, a, b, c. Upper, lower, and lateral views of early growth
stage, SM H9368, Sample 31, Trevose Slates, Trevone Bay.

Fig. 2. Pol. dengleri Bischoff and Ziegler, a, b. Upper and lower views, SM H9353, Sample 8, Marble
Cliff Beds.

Fig. 3. Icriodus symmetricus Branson and Mehl. Upper view, SM H9374, Sample 31, Trevose States,
Trevone Bay.

Fig. 4. Pol. linguiformis Hinde. a, b, Upper and lower views, SM H9359, Sample 31, Trevose Slates,
Trevone Bay.

Figs. 5, 8. Bryantodus biculminatus Bischoff and Ziegler. 5, Lateral view, SM H9371, Sample 8, Marble
Cliff Beds. 8, Lateral view, SM H9372, Sample 17, Longcarrow Cove Tuffs and Slates.

Fig. 6. Hindeodella sp. Lateral view, SM H9373, Sample 8, Marble Cliff Beds.

Fig. 7. Neoprioniodus pronus (Huddle). Lateral view, SM H9376, Sample 8, Marble Cliff Beds.

Figs. 9-11. Pol. varcus Stauffer. Specimens are from the Trevose Slates, Trevone Bay. 9a, b, Upper
and lower views, SM H9362, Sample 31. 10a, b, c, Upper, lower, and lateral views, SM H9363,
Sample 30. 11a, b. Upper and lower views, SM H9364, Sample 31.

Fig. 12. Ozarkodina immersa [?] (Hinde). Lateral view, SM H9377, Sample 17, Longcarrow Cove
Tuffs and Slates.

Fig. 13. N. alatus (Hinde). Lateral view, SM H9375, Sample 12, Marble Cliff Beds.

All magnifications x 50.

Palaeontology, Vol. 13

PLATE 65

KIRCHGASSER, Conodonts from North Cornwall

Palaeontology, Vol. 13

PLATE 66

KIRCHGASSER, Conodonts from North Cornwall

.Jl-

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL 351

1957 Pol. linguiformis Hinde; Rhodes and Dineley, pp. 365, 366, pi. 37, figs. 17-19, 21;
pi. 38, fig. 3.

1957 Pol. linguiformis Hinde; Bischoff and Ziegler, pp. 92, 93, pi. 1, figs. 1-13; pi. 16, figs.

30-5; pi. 17, figs. 1-8; pi. 19, fig. 18.

1966 Pol. linguiformis Hinde; Ziegler 1966a, pi. 1, figs. 7-10.

1966 Pol. linguiformis linguiformis Hinde; Wittekindt, pp. 635, 636, pi. 2, figs. 10-12.
Material. Fifty-four specimens; SM H9357-H9361.

Remarks. Polygnathus linguiformis Hinde is common and well preserved in the Trevose
Slate faunas and comparatively rare in faunas from the Marble Cliff Beds and the Long-
carrow Cove Tuffs and Slates. Specimens from the Trevose Slates show extreme ranges
in size and in the coarseness of ornamentation. Two of the largest forms (late growth
stages) from Sample 31 have two diagonal rows of nodes in the anterior part of the
platform, which is a diagnostic feature of Pol. linguiformis transversus Wittekindt.
However, the two specimens have much more weakly developed ridges than in Pol.
linguiformis transversus and in all other features they are closest to Pol. linguiformis
Hinde.

Range. Lower Devonian (Bischoff and Ziegler 1957, p. 93) to top of Upper Pol. asymmetricus Zone,
(Ziegler 19626, p. 19). Sample-horizons 30, 31, Trevose Slates, Trevone Bay; 33, Trevose Slates,
Rock; 3-8, Marble Cliff Beds; and 15-17, Longcarrow Cove Tuffs and Slates, Marble Cliff.

Polygnathus varcus Stauffer

Plate 66, figs. 9-1 1

1940
1940
1957
1957
[non] 1957

1966
1966
[non] 1966
1966

Polygnathus varcus Stauffer, p. 430, pi. 60, figs. 49, 53, 55.

Pol. xylus Stauffer, pp. 430, 431, pi. 60, figs. 42, 50, 54, 65-7, 69, 72-4, 78, 79.

Pol. varca Stauffer; Rhodes and Dineley, p. 366, pi. 37, figs. 22, 23; pi. 38, fig. 7.

Pol. varca Stauffer; Bischoff and Ziegler, pp. 98, 99, pi. 18, figs. 32-5; pi. 19, figs. 7-9.
Pol. xyla Stauffer; Bischoff and Ziegler, p. 101, pi. 5, figs. 11-17 [= Pol. decorosus
Stauffer s.l.].

Pol. varca Stauffer; Ziegler 1966a, pi. 1, fig. 6.

Pol. varca Stauffer; Wittekindt, pp. 639, 640, pi. 3, figs. 5-10.

Pol. xyla Stauffer; Wittekindt, p. 642, pi. 3, figs. 18-19 [= Pol. decorosus Stauffer s.l.].
Pol. varca Stauffer; Glenister and Klapper, pp. 830, 831, pi. 95, figs. 12-13 [non figs. 14,
15-16 = Pol. decorosus Stauffer s.l.].

Material. Twenty-four specimens; SM H9362-H9364.

Diagnosis. Pol. varcus has a short, narrow, weakly ornamented platform and an extra-
ordinarily long free blade, up to twice as long as the platform. The ratio of platform
length to free blade length appears to remain nearly constant through all growth stages.
The sides of the platform are strongly folded upward, forming deep furrows on both
sides of the median carina. The free blade is particularly distinctive; it is uniform in
height and has a series of 10-20 teeth of variable size and shape but nearly equal height.

Remarks. All of the specimens at hand are intermediate and late growth stages, with
markedly asymmetrical platform outlines. Anterior of the platform’s midpoint, the
margins abruptly constrict, especially on the outer side. The margin on the outer side
then flares strongly outward, in a semicircular arc, and joins the free blade at a more
anterior position than does the straighter inner margin. The posterior end of the

352

PALAEONTOLOGY, VOLUME 13

platform is symmetrical and the margins converge uniformly to a point. In details of
platform outline and in development of the free blade, the specimens at hand compare
closely with specimens of Pol. Marcus figured by Rhodes and Dineley (1957) from South
Devon and by Bischoff and Ziegler (1957) and Ziegler (1966a) from the Rheinisches
Schiefergebirge.

Specimens similar to Pol. varcus but with longer, more symmetrical and more highly
ornamented platforms and shorter free blades with fewer teeth have been interpreted by
Bischoff- and Ziegler (1957) and Wittekindt (1966) as Pol. xylus Stauffer, a species which
Glenister and Klapper (1966, p. 831) regard as a synonym of Pol. varcus. Forms of this
type, for example the specimens figured herein as Plate 64, figs. 2, 7, and specimens of
Pol. varcus figured by Glenister and Klapper (1966, pi. 95, figs. 14, 15-16) belong in
Pol. decor osus Stauffer s.l. Glenister and Klapper (1966) suggested that in the ontogeny
of Pol. varcus the length of the platform increases in proportion relative to the free blade
and that the ornamentation becomes more highly developed. These changes are not seen
in the Cornish specimens, even in the latest growth stages (PI. 66, fig. 10), and it would
seem that their analysis applies more closely to Pol. decorosus Stauffer s.l. rather than
to Pol. varcus.

Range. Pol. varcus Zone (Bischoff and Ziegler 1957, p. 30) to top of Lower Pol. asymmetricus Zone
(Ziegler 19626, table 2). Sample-horizons 30-1, Trevose Slates, Trevone Bay; 33, Trevose Slates, Rock;
6-13, Marble Cliff Beds, Marble Cliff.

Schmidtognathus hermanni Ziegler
Plate 66, fig. 1

1966 Schmidtognathus hermanni Ziegler 19666, pp. 664, 665, pi. 3, figs. 5-26.

Material. Two specimens; SM H9368.

Remarks. The figured specimen from the Trevose Slates (Sample 31) is an early growth
stage and has the enlarged flaring basal cavity and narrow weakly ornamented platform
of Schmidtognathus hermanni. S. hermanni developed from variants of Pol. decorosus
Stauffer s.l. with enlarged basal cavities during the Late Middle Devonian; the link
between these species is clearly seen in early growth stages (Ziegler 19666, pi. 3, figs.
1-12).

Range. Base of S. hermanni-Pol. cristatus Zone into the lower part of the Lower Pol. asymmetricus
Zone (Ziegler 19666, p. 657). Ziegler (19666, tables 1, 2, p. 659) also reports S. hermanni from the
uppermost part of the Pol. varcus Zone. Sample horizons 31, Trevose Slates, Trevone Bay and 10,
Marble Cliff Beds, Marble Cliff.

Schmidtognathus wittekindti Ziegler
Plate 65, figs. 3, 7

1966 Schmidtognathus wittekindti Ziegler 19666, pp. 665, 666, pi. 1, figs. 11-16; pi. 2, figs. 1-10.
Material. Seven specimens; SM H9369-H9370.

Remarks. The specimens at hand are distinguished from a closely related species,
S. peracuta (Bryant), by their narrower platform and very high free blade with the
highest teeth in the middle.

W. T. KIRCHGASSER: CONODONTS FROM NORTH CORNWALL

353

Range. Upper part of the S. hermanni-Pol. cristatus Zone into the upper part of the Lower Pol. asym-
metricus Zone (Ziegler 19666, p. 666, text-fig. 2). Sample-horizons 1-12, Marble Cliff Beds, Marble
Cliff.

Acknowledgements. I particularly wish to thank Professor M. R. House for introducing me to the
geology of North Cornwall and for his generous assistance through all phases of the investigation.
I also thank Dr. G. Gauss for providing unpublished structural data on the area and for his assistance
in the field. I gratefully acknowledge the technical assistance of Mr. J. Goldspink and Mr. B. Nettleton
and the field assistance of Mr. J. Senior. Dr. R. H. Bate kindly made available the Hinde and Bryant
conodont collections at the British Museum (Natural History). The project was undertaken as part
of a year of research at University of Hull, supported by a Fulbright-Hays Grant.

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and ziegler, w. 1957. Die Conodontenchronologie des Mitteldevons und des tiefsten Ober-

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19336. Conodonts from the Grassy Creek Shale of Missouri. Ibid. 8, 171-259, pi. 13-21.

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bryant, w. l. 1921. The Genesee conodonts. Buffalo Soc. Nat. Sci. 13, 1-59, pi. 1-16.
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Basin. Mem. geol. Soc. Am. 103, 1-94, pi. 1-9.
dewey, H. 1914. The geology of North Cornwall. Proc. Geol. Ass., Lond. 35, 154-79.
dineley, d. l. 1961. The Devonian System in South Devonshire. Fid Stud. 1, 121-40.

and Rhodes, f. h. t. 1956. Conodont horizons in the west and south-west of England. Geol. Mag.

93, 242-8.

ethington, r. l. 1965. Late Devonian and Early Mississippian conodonts from Arizona and New
Mexico. J. Paleont. 39, 566-89, pi. 67-8.

fox, h. 1895. Notes on the cherts and associated rocks of Roundhole Point (Permizen Point), Cata-
clews Point, and Dinas Head, west of Padstow. Trans. R. geol. Soc. Cornwall, 11, 687-724.
gauss, g. a. 1966. Some aspects of the slaty cleavage in the Padstow area of N. Cornwall. Proc.
Ussher Soc. 1, 221-4.

1967. Structural aspects of the Padstow area, North Cornwall. Ibid. 1, 284-5.

glenister, b. f. and klapper, g. 1966. Upper Devonian conodonts from the Canning Basin, Western
Australia. J. Paleont. 40, 777-842, pi. 85-96.

goldring, R. and others. 1968. Devonian of southern Britain. Int. Symp. Devonian System, Calgary,
1, 1-14.

hinde, g. j. 1879. On conodonts from the Chazy and Cincinnati Group of the Cambro-Silurian, and
from the Hamilton and Genesee-Shale divisions of the Devonian, in Canada and the United States.
Q. Jl geol. Soc. Lond. 35, 351-69, pi. 15-17.
house, m. r. 1956. Devonian goniatites from North Cornwall. Geol. Mag. 93, 257-62.

1961. The Devonian succession of the Padstow area, North Cornwall. Abstr. Proc. Conf. Geol.

Geomorph. SW Engld, 1960, 4-5.

1963. Devonian ammonoid successions and facies in Devon and Cornwall. Q. Jl geol. Soc. Lond.

119, 1-27, pi. 1-4.

and selwood, e. b. 1966. Palaeozoic palaeontology in Devon and Cornwall, in Present views on

some aspects of the geology of Cornwall and Devon. Blackford, Truro, 45-86, pi. 1-4.

354 PALAEONTOLOGY, VOLUME 13

huddle, j. w. 1934. Conodonts from the New Albany Shale of Indiana. Bull. Am. Paleont. 21, 1-136,
pi. 1-12.

krebs, w. and ziegler, w. 1966. liber die Mitteldevon/Oberdevon-Grenze in der Riffazies bei Aachen.
Fortschr. Geol. Rheinld Westf. 9, 731-54, pi. 1-2.

Matthews, s. c. 1962. A Middle Devonian conodont fauna from the Tamar Valley. Proc. Ussher Soc.
1, 27-8.

muller, k. j. 1956. Zur Kenntnis der Conodonten-Fauna des europaischen Devons, 1. Die Gattung
Palmatolepis. Abh. senckenb. naturforsch. Ges. 494, 1-70, pi. 1-11.

and clark, d. l. 1967. Early Late Devonian conodonts from the Squaw Bay Limestone in

Michigan. /. Paleont. 41, 902-19, pi. 115-18.

and muller, e. m. 1957. Early Upper Devonian (Independence) conodonts from Iowa, part I.

Ibid. 31, 1069-1108, pi. 135-42.

orr, r. w. 1964. Conodonts from the Devonian Lingle and Alto Formations of southern Illinois.
Circ. III. St. geol. Surv. 361, 1-28, pi. 1-4.

and klapper, g. 1968. Two new conodont species from Middle-Upper Devonian boundary beds

of Indiana and New York. J. Paleont. 42, 1066-75, pi. 139-40.
pollock, c. a. 1968. Lower Upper Devonian conodonts from Alberta, Canada. Ibid. 42, 415-43,
pi. 61^1.

reid, c., barrow, g. and dewey, h. 1910. The geology of the country around Padstow and Camelford.
Mem. geol. Surv. U.K. 1-120.

Rhodes, f. h. t. and dineley, d. l. 1957. Devonian conodont faunas from southwest England.
/. Paleont. 31, 353-69, pi. 37-8.

stauffer, c. r. 1938. Conodonts of the Olentangy Shale. Ibid. 12, 411-43, pi. 48-53.

1940. Conodonts from the Devonian and associated clays of Minnesota. Ibid. 14, 417-35,

pi. 58-60.

ulrich, e. o. and bassler, r. s. 1926. A classification of tooth-like fossils, conodonts, with the descrip-
tions of American Devonian and Mississippian species. Proc. U.S. natn. Mus. 68, 1-63, pi. 1-11.
wedekind, r. 1913. Die Goniatitenkalke des unteren Oberdevon von Martenberg bei Adorf. Sber.
Ges. naturf. Freunde Berl. 1, 23-77, pi. 4-7.

wittekindt, H. 1966. Zur Conodontenchronologie des Mitteldevons. Fortschr. Geol. Rheinld Westf.
9, 621-46, pi. 1-3.

ziegler, w. 1958. Conodontenfeinstratigraphische Untersuchungen an der Grenze Mitteldevon/Ober-
devon und in der Adorfstufe. Notizbl. hess. Landesamt. Bodenforsch. 87, 7-77, pi. 1-12.

1962(7. Phylogenetische Entwicklung stratigraphisch wichtiger Conodonten-Gattungen in der

Manticoceras-Stuie (Oberdevon, Deutschland). Neues Jb. Geol. Palaont. Abh. 114, 142-68.

19626. Taxionomie und Phylogenie Oberdevonischer Conodonten und ihre stratigraphische

Bedeutung. Abh. hess. Landesamt. Bodenforsch. 38, 1-166, pi. 1-14.

1966a. Zum hochsten Mitteldevon an der Nordflanke des Ebbesattels. Fortschr. Geol. Rheinld

Westf. 9, 519-38, pi. 1-2.

19666. Eine Verfeinerung der Conodontengliederung an der Grenze Mittel-/Oberdevon. Ibid.

9, 647-76, pi. 1-6.

klapper, g. and lindstrom, m. 1964. The validity of the name Polygnathus (Conodonta, Devonian

and Lower Carboniferous). J. Paleont. 38, 421-3.

W. T. KIRCHGASSER ■,

Department of Geology
State University College
Potsdam, N.Y. 13676

Final typescript received 11 December 1969 U.S. A.

NOTE ADDED IN PROOF

Professor W. Ziegler has informed the writer that he has a paper in press with Dr. J. Kullmann
on their restudy of the Martenberg section in which they demonstrate that the boundary between
the M. terebratum and P. lunulicosta zones corresponds to the boundary between the lower and upper
parts of the S. hermanni-Pol. cristatus Zone. This correlation places the succeeding lower part of
the Lower Pol. asymmetricus Zone (and the Marble Cliff Beds) firmly in the Upper Devonian.

THE CHELONI AN RHINOCHELYS SEELEY
FROM THE UPPER CRETACEOUS OF
ENGLAND AND FRANCE

by JANICE I. COLLINS

Abstract. The Cretaceous chelonian genus Rhinochelys Seeley 1869, which is based on skull material, has been
reinvestigated. The foundations for Lydekker’s original specific descriptions are shown to be inadequate and
new diagnostic features for the genus and species are established. Only three British species are recognized: the
type species R. pulchriceps (Owen 1851), R. elegans Lydekker 1889, and R. cantabrigiensis Lydekker 1889.
R. amaberti Moret 1935 from La Fauge Valley, near Grenoble, France, is compared with the British species.
A general description of the skulls and mandibles is given. The taxonomic position of Rhinochelys is assessed
and the genus is referred to the family Protostegidae, subfamily Chelospharginae. The skulls are compared with
those of other Cretaceous turtle genera of the Protostegidae and Cheloniidae and a relationship is suggested.
It is suggested that carapace and plastral material originally described as Chelone ( Cimochelys ) benstedi (Mantell
1841) probably belongs to Rhinochelys.

The chelonian genus Rhinochelys was erected by Seeley (1869) for the type skull of
Chelone pulchriceps Owen 1851, from the Lower Cenomanian Cambridge Greensand.
Lydekker (1889) amended the description of the type species and described five new
species of Rhinochelys (R. macrorhina, R. elegans, R. cantabrigiensis, R. jessoni, and
R. brachyrhina) on skull material from British strata, ranging in age from Albian to
Upper Cenomanian. In addition to these properly described and named species, an
additional fifteen species were named but not described by Seeley (1869); they are there-
fore nomina nuda, so that the correct taxonomic positions of these specimens is not
established. The type material of all these British species is housed in the British Museum
(Natural History) and the Sedgwick Museum, University of Cambridge. The only other
species known, R. amaberti, was described by Moret (1935) from the Vraconien of
La Fauge Valley, near Grenoble, France.

The taxonomic position of Rhinochelys is at present uncertain. Seeley (1869) thought
it showed emydian affinities; Lydekker (1889) considered that it resembled the pleuro-
dires. Williston (1898) thought that it was probably related to his genus Desmatochelys
and family Desmatochelyidae, from the Cretaceous of Kansas, and Romer (1956) also
placed Rhinochelys in this family. However, Zangerl and Sloan (1960) suppressed the
Desmatochelyidae when they showed, on the evidence of post-cranial material, that
Desmatochelys has close affinities to the Cheloniidae.

As a result of the availability of new material, it is now possible to provide a more
thorough description of Rhinochelys. Examination and detailed comparison of the
British type specimens and of the other skulls of Rhinochelys has also permitted a new
assessment of the validities and synonomies of the species and of the taxonomic position
of the genus. This in turn has suggested that post-cranial material, known from the same
deposits as the skull material, may in fact also belong to the genus Rhinochelys, the
carapace of which is otherwise unknown.

[Palaeontology, Vol. 13, Part 3, 1970, pp. 355-78, pis. 67-69.]

356

PALAEONTOLOGY, VOLUME 13

TAXONOMY OF THE GENUS RHINOCHELYS

Generic diagnosis. Skull has slight posterior emargination and no ventral emargination.
Squamosal not in contact with parietal; blunt ant-orbital beak; nasal and prefrontal
bones distinct; prefrontals excluded from narial margin and from meeting medially;
epidermal sulci cross frontal and maxilla. No secondary palate; posterior margin of
internal nares formed by maxillae and palatines; vomer divides internal nares as sharp
ridge and extends only short way between palatines; palatines meet medially; grinding
(triturating) surface of maxillae and premaxillae has broad lingual ridge and deep groove
in midline; pterygoids very narrow, emarginate and meet along their length, palatal
surface slightly ridged ; basisphenoid narrowly triangular and not ridged on palate.

Type species. Chelone pulchriceps Owen 1851, p. 8, pi. vii, figs. 1-3. Lower Cenomanian Cambridge
Greensand, Barnwell, near Cambridge.

Holotype. B55775, Sedgwick Museum, Cambridge.

Remarks. As noted, twenty-two species have been ascribed to Rhinochelys by Owen,
Seeley, Lydekker, and Moret, but only seven have been described. When Lydekker
(1889) described his five new species and redescribed R. pulchriceps he used the following
diagnostic features :

1 . Size and shape of the external nares.

2. Size and shape of the nasal.

3. Inclusion of the prefrontal in the narial margin.

4. Depth of the premaxillae.

5. Swelling on the prefrontal.

6. The angle that the premaxillae make with the palate edge in profile.

7. Presence of a hook on the tip of the upper jaw.

8. The ratio of the height to the overall length of the skull.

The size and shape of the nares and nasal bones are variable features and too individual
to be of use in distinguishing species.

The inclusion of the prefrontal in the narial margin was considered to be a feature of
R. brachyrhina and R.jessoni. Close examination of the type of R. brachyrhina (text-fig.
4) reveals that the specimen is very worn and that the nares are enlarged until most of the
nasals have been lost. The suture between the nasal and maxilla practically borders
the nares, but it is clear that the prefrontal is definitely excluded from contributing to the
narial margin. The suture fines on the very well-preserved type of R.jessoni (text-fig. 3)
are not very distinct, but it can be seen with a lens that the maxilla and nasal meet and
exclude the prefrontal from the narial margin, as in all the other specimens examined.

The depth of the premaxillae was used to distinguish R. macrorhina from R. elegans.
The type of R. macrorhina (text-fig. 5 d) is a poorly preserved snout with an eroded
jaw edge. The bone is eroded for about half the depth of the premaxillae, which is
evident from the structure of the triturating surface of the palate. The relative depth
of the premaxillae is, in any case, subject to individual variation.

A peculiar lateral swelling on the prefrontal was thought to be present in R. elegans
alone. This area does not, however, appear to be more swollen on this specimen than
on any other.

J. I. COLLINS: RHINOCHELYS

357

Although the first five characters used by Lydekker are not reliable, the remaining
three (i.e. the height/length ratio, the angle that the premaxillae make with the palate
edge, and the presence or absence of a hooked tip to the upper jaw), divide the British
types into three groups, as can be seen from Table 1. Although these features can there-
fore be used as specific characters, Lydekker’s descriptions are not comprehensive
enough for practical purposes. The position becomes clear, however, when these features
are defined as follows :

1. The height Y (height measured just anterior to the orbits) relative to the length Z (length
between the frontal/parietal suture and the jaw tip).

Relative height = (Y/Z) x 100.

2. The angle between the anterior surface of the premaxillae and the edge of the palate, as seen in
profile. (This is referred to as the premaxillary angle.)

3. The presence or absence of a hooked tip to the upper jaw.

The measurements used are shown in text-figs. 1 , 2.

Nevertheless these characters alone are not considered sufficient to assign all the
specimens to valid species, and other distinctions were therefore sought. The following
features are thought to be sufficiently distinct and constant to be of value :

4. The width X (width just posterior to the orbits) relative to the length Z.

Relative posterior width = (X/ Z)x 100.

5. The angle between the two maxillae. (This is referred to as the ‘jaw angle’.)

6. The presence or absence of a ridge over the maxillary sulcus.

7. The convexity or straightness of the premaxillae in profile.

Table 1 shows all these features as they appear on the type species, Lydekker’s types,
Seeley’s named skulls, and on R. amaberti taken from Moret’s plates and figures (1935,
pi. 27, figs. 1-4). (Names in square brackets are the nomina nuda of Seeley.)

From Table 1 it can be seen that the British specimens fall into three groups and that
none is referable to R. amaberti.

In the first group, R. pulchriceps, the relative width is over 100 but this is measurable
on one specimen only; the relative height (47-51), is the lowest in the groups; the jaw
angle is broad (72-80°) ; the premaxillary angle is acute (70-74°) ; there is no ridge over
the maxillary sulcus; the premaxillae are straight in profile; and there is no hooked tip
to the upper jaw.

In the second group, R. elegans, [7?. mastocephalus ], [7?. stenicepha/us ], R. brachyrhina,
R. macrorhina, the relative width (91-96), is the narrowest in the three groups, as it does
not exceed 100; the relative height (51-61) is greater than that of the first group; the jaw
angle (50-60°) is narrower than that of the first group ; the premaxillary angle (80-90°)
is not quite a right-angle; there is no ridge over the maxillary sulcus; the premaxillae
are straight in profile; and there is no hook to the tip of the upper jaw. R. brachyrhina
and R. macrorhina are poorly preserved snouts ; however, they do not show any features
of the other groups, and are therefore doubtfully included here.

In the third group, R. cantabrigiensis, R. jessoni, [7?. cardiocephalus ], [7?. dayi], [7?.
eurycephalus ], [R. platyrhinus ], [7?. rheporhinus ], [7?. sphenicephalus ], the relative width
is the broadest of the three (87-108); the relative height (59-63) is the greatest of the
three; the jaw angle (42-56°) is slightly narrower than that of the second group; the

358

PALAEONTOLOGY, VOLUME 13

premaxillary angle equals or exceeds a right angle; it is the only group with a ridge over
the maxillary sulcus, a convex profile to the premaxillae, and a hooked tip to the upper jaw.

table 1. Skull measurements of Rhinochelys (a — absent, p — present, s — straight, c — curved)

o

o

X

>^IN

Y

— x 100

Jaw

angle

Premaxillary

angle

Ridge

over

Premaxillary Hooke

Types

(in degrees) (in degrees)

sulcus

profile

tip

R. pulchriceps

107

51

72

74

a

a

R. pulchriceps

—

47

80

70

a

s

a

R. elegans

96

57

57

85

a

s

a

R. elegans

—

56

60

80

a

s

a

[R. mastocephalus ]

95

61

54

88

a

s

a

[R. stenicephalus ]

91

55

50

86

a

s

a

R. brachyrhina

—

61

—

—

a

—

—

R. macrorhina

51

—

90

a

s

—

R. cantabrigiensis

107

62

50

90

P

c

P

R. jessoni

99

63

55

97

P

c

P

[R. cardiocephalus ]

87

61

45

94

P

c

P

[R. dayi ]

93

59

52

98

P

c

P

[R. eurycephalus ]

105

58

50

101

P

c

P

[R. platyrhinus ]

108

60

42

92

P

c

P

[R. rheporhinus ]

—

—

56

95

P

—

—

[R. sphenicephalus ]

100

60

44

93

P

c

R. amaberti

135

65

7105

93

a

s

a

In R. amaberti the relative width (135) is very broad; the relative height (65) is greater
than that of the British types; the jaw angle is obtuse (?105°) and very much broader
than that of the others; the premaxillary angle agrees with the third group but there is
no ridge over the maxillary sulcus ; the profile of the premaxillae is straight, and there is
no hooked tip to the upper jaw.

Thus we have three distinct British species, R. pulchriceps, R. elegans , and R. canta-
brigiensis. The names used are the senior taxa in the groups.

Abbreviations. The following abbreviations are used: British Museum (Natural History) — BMNH;
Sedgwick Museum, University of Cambridge, SM ; Institute of Geological Sciences, GSM. The material
used in the charts includes the following specimens in addition to those mentioned:

R. pulchriceps. BMNH 2224, R1806, 2236, R2232: Isolated lower jaws: 46373, R2238, 35184, R35185,
47211, 49920, R793. SM B55771, B55772, B55779, B55811.

R. elegans. BMNH 35193, R2225, 41796, 46371, 46371a, 35194, 35197, R27, R2228, R2229, R2230,
R2231, R2237, 35195. SM B55773, B55776, B55780, B55784, B55792, B55798, B55800.

R. cantabrigiensis. BMNH R1558, R2227, R2233, R2234, 35196. SM B55774, B55781, B55782,
B55783, B55785, B55786, B55787, B55788, B55791, B55793, B55795, B55799, B56572, B56573, B56574,
B56576, B56580.

Rhinochelys pulchriceps (Owen 1851)
Plate 67, figs. 1-8; Plate 68, figs. 1-2

1851 Chelone pulchriceps Owen, p. 8, pi. 7, figs. 1-3.

1869 R. pulchriceps (Owen); Seeley, p. xviii.

1 869 R. dacognathus Seeley, p. xviii.

1889 R. pulchriceps (Owen); Lydekker, p. 230, pi. 8, fig. 1.

J. I. COLLINS: RHINOCHELYS

359

Holotype. Skull lacking lower jaw, SM B55775.

Measurements. Holotype, over-all length 58-5 mm., width 40 mm.

Horizon and locality. Lower Cenomanian Cambridge Greensand, Barnwell, near Cambridge.

Diagnosis. Skull shallow, height Y less than half length Z; jaw angle broadly acute;
premaxillary angle acute; profile of premaxillae straight; area over maxillary sulcus
smooth; no hooked tip to upper jaw.

Rhinochelys elegans Lydekker 1889

Plate 68, figs. 3-7

1889 R. elegans Lydekker, p. 230, pi. 8, fig. 4.

1869 R. mastocephalus Seeley, p. xviii.

1869 R. stenicephalus Seeley, p. xviii.

1889 R. brachyrhina Lydekker, p. 231, pi. 8, figs. 3, 3 a.

1889 R. macrorhina Lydekker, p. 230, pi. 8, fig. 7.

Holotype. Skull lacking lower jaw, BMNH 2226.

Measurements. Holotype, over-all length 64 mm., width 39-8 mm.

Horizon and locality. Lower Cenomanian Cambridge Greensand, near Cambridge.

Diagnosis. Skull high and narrow, height Y about three-fifths length Z; width X less than
length Z; jaw angle narrow; premaxillary angle just less than right-angle; profile of
premaxillae straight; no ridge over maxillary sulcus; no hooked tip to upper jaw.

Rhinochelys cantabrigiensis Lydekker 1889

Plate 68, figs. 8-16

1889 R. cantabrigiensis Lydekker, p. 230, pi. 8, figs. 2, 2a, 2b.

1889 R. jessoni Lydekker, p. 231, pi. 8, figs. 6a, 6b.

1869 R. cardiocephalus Seeley, p. xviii.

1 869 R. dayi Seeley, p. xviii.

1869 R. eurycephalus Seeley, p. xviii.

1869 R. platyrhinus Seeley, p. xviii.

1869 R. rheporhinus Seeley, p. xviii.

1869 R. sphenicephalus Seeley, p. xviii.

Holotype. Skull lacking lower jaw, BMNH 43980.

Measurements. Holotype, over-all length 42-5 mm., width 32-5 mm.

Horizon and locality. Lower Cenomanian Cambridge Greensand, near Cambridge.

Diagnosis. Skull high, broad, domed, height Y about three-fifths length Z; jaw angle
narrow; premaxillary angle is right-angle or greater; profile of premaxillae convex;
heavy ridge over maxillary sulcus; tip of upper jaw slightly hooked.

It must now be considered whether these diagnoses are supported by any other
material.

In the collections examined, there are a further forty skulls which can be assigned to
Rhinochelys. The specific features of these are carefully tabulated on text-fig. 9.

360

PALAEONTOLOGY, VOLUME 13

J. I. COLLINS: RHINOCHELYS

361

Synopsis of text-fig. 9.

Fig. A. The jaw angle is broader in R. pulchriceps (66-80°) than in R. elegans (49-80°) and R. canta-
brigiensis (40-63°). The figure for R. cimaberti may be distorted as the measurement has been taken
from a photograph, but the jaw-angle appears to be obtuse and very much broader than the other
species at ?105°.

Fig. b. The relative height of R. pulchriceps (43-51) is less than that of the other three species, R. elegans
(51—76), R. cantabrigiensis (50-66), and R. amaberti (65).

Fig. c. The premaxillary angle in R. pulchriceps is acute (63-77°). It is generally just less than a right-
angle in R. elegans (80-100°), but in R. cantabrigiensis (89-105°) and R. amaberti (93°) it is slightly
obtuse.

Fig. d. Only two specimens of R. pulchriceps are sufficiently well preserved to allow the relative width
to be used, but these differ widely. The relative width in R. elegans (74-97) does not exceed 100; how-
ever in R. cantabrigiensis this relative width is 87-109, i.e. the width X is generally in excess of the
length Z, although there is a slight overlap. R. amaberti at 135 is very much broader.

In the few specimens with concurrent measurements, the other specific features are
present and well defined. It is inevitable that there is a degree of variation within a
biological group, but the majority in each species can be clearly differentiated using
proportional measurements and angles alone. For a list of the other material used see
p. 358.

The evidence presented here shows that these skulls can also be placed in three groups
which agree with the specific diagnoses, and that all are distinct from R. amaberti.
Analysis of these specimens also shows additional differences between the palate and
mandible of R. pulchriceps and those of R. elegans and R. cantabrigiensis. In the forma-
tion of the ridges and grooves there are differences between the palate of the type of
R. pulchriceps (PI. 67, fig. 3, text-fig. 7) and those of two other specimens, one referable
to R. elegans (SM B55792) (text-fig. 8) and the other to R. cantabrigiensis (SM B56574).

In R. pulchriceps the lingual ridge runs alongside the median groove and appears to
join the cutting edge anteriorly. The anterior tip of the premaxillae is notched. The
mandibles which fit the broad-angled jaw, and can be referred to R. pulchriceps , have
a sharp median crest which extends right across the symphysis.

TEXT-FIGS. 1-8.

Figs. 1,2 . R. elegans SM B55776. 1, Dorsal view, x 1 ; 2, Lateral view, x 1. Z, length from the frontal-
parietal suture to the jaw tip; X, width just behind the orbits; Y, depth just anterior to the orbits

Fig. 3. Type of R.jessoni showing the prefrontals are excluded from meeting medially, < 1.

Fig. 4. Type of R. brachyrhina showing the prefrontals are excluded from the narial edge.

Fig. 5. Profile of the beaks, a, R. pulchriceps', b, R. cantabrigiensis', c, R. elegans', d. Reconstructed beak
of R. macrorhina.

Fig. 6. R. amaberti (after Moret 1935, pi. xxvii, fig. 1).

Fig. 7. R. pulchriceps, palatal view, xl.

Fig. 8. R. elegans, palatal view, x 1.

Explanation of abbreviations: bo, basioccipital; bs, basisphenoid ; f frontal; fs, frontal sulcus; fp,
fenestra postotica; g, premaxillary groove; j, jugal; m, maxilla; ms, maxillary sulcus; n, nasal; p,
parietal; pa, palatine; pm, premaxilla; po, postorbital; pf, prefrontal; pt, pterygoid; qj, quadratojugal ;
q, quadrate; tf, tympanic fossa; v, vomer.

362

PALAEONTOLOGY, VOLUME 13

R.amaberti

R.cantabrigiensis

° A A

AAAAAA A A

R.elegans

4

A AA*1

AA

* A

R.pulchriceps

£

&

I 2 A A A

A | |

1

1

1 1

1 1 1

30 40

degrees

50

60

70 80

90 100 NO!

R.amaberti

2

2

R.cantabrigiensisA A

▲ M AAA

2 it

A AA AAAAAAA AA A

R.elegans

* 4* **

R.pulchriceps

A A 2

A A

-

A

A A AA A

A A

2 A A A4A
AAA A

AAA AA A A

AAA A A

A

B 1 1 1

1

1

Cl 1 1

1 1 1

40 50 60

percent

70

80 60 70 80

degrees

90 ioo no

R.amaberti

2

R.cantabrigiensis

▲ A

▲

AA AA Aa£aA

A AA

R.elegans

A AA a2a

R.pulchriceps

2

D 1 1

1

|

1 1

1 1 1

60 70

percent

90

100

120

130

140

text-fig. 9. Each triangle represents an individual measurement. All those belonging to the same
species are placed along a single horizontal line ; where more than one individual has the same measure-
ments, further triangles are added above or below this horizontal line. Measurements derived from the
type-specimens of valid species are distinguished by a circle above the triangle.

a, angle between the maxillae : the jaw angle.

b, proportion of height Y to length Z; ( Y/Z) X 100.

c, angle between the premaxillae and the palate edge: the premaxillary angle.

d, proportion of width X to length Z: ( X/Z ) x 100.

J. I. COLLINS: RHINOCHELYS

363

On the other two palates, the lingual ridge does not join the cutting edge but is separ-
ated by the confluent grooves. The premaxillae are not grooved at the tip. The narrower
mandibles, which can be referred to either of these species, have median crests which
extend only part of the way across the symphysis, leaving the tip smooth.

One other of Seeley’s types, R. dacognathus (SM B55809, B55810) can be referred to
Rhinochelys. The ‘type’ consists of two mandible tips each with a broad symphysis,
smooth ventral surface and a sharp median crest on the grinding surface which extends
across the symphysis to the tip. The angle between the rami is broad. These specimens
are here referred to R. pulchriceps.

R. graptocephalus Seeley is a poorly preserved posterior region of a skull and is
indeterminate. The other nomina nuda, R. colognathus, R. dimer ognathus, R. grypus, R.
leptognathus, and R. platycephalus , are all mandibles of various sorts, but none of
these is referable to Rhinochelys.

Using the new basis for distinguishing the species, it is evident that R. amaberti is a
separate species although known by only one specimen. The following features are
mentioned by Moret (1935) in his description: the skull is flat on top, not domed, and
has a greater relative posterior width than R. elegans; the premaxillae form a right-
angle with the palate edge and are straight in profile, not convex. To this can be added
the following observations taken from his plate (op. cit., pi. 27): the jaw angle is obtuse,
about 105°, and there appears to be no ridge over the maxillary sulcus.

CRANIAL MORPHOLOGY OF RHINOCHELYS

In the preceeding taxonomic study, the different specimens which in the past have been
placed in the genus Rhinochelys have been either rejected from, or accepted into, the
genus, and the species composition of the genus has been established. It is therefore now
possible to use those specimens which belong in the genus to make a detailed study of
the cranial morphology of Rhinochelys.

Generic description

The skulls are small to medium size (30-60 mm. long) with width about two-thirds of
the length. The posterior edge is emarginate to a depth of about a third of the length of
the parietal. The temporal fossa is well roofed over by the parietal, postorbital, and
squamosal. The squamosal does not meet the parietal. The frontal extends to form part
of the rim of the orbit and meets the nasal and prefrontal anteriorly. The prefrontal and
nasal are distinct. The prefrontals are moderate in size, do not meet medially and do
not form part of the narial margin. The nasal is moderately large; it meets the frontal
posteriorly, the prefrontal postero-laterally, the maxilla antero-laterally, and forms the
posterior margin of the external nares. The external nares are oval in shape, with
the long axis running horizontally. The antorbital beak is blunt and not produced. The
premaxillae meet in a sharp angle. The maxilla extends from the nares to meet the jugal
in the posterior part of the lower orbital rim to form a jugo-maxillary bar. The jugal
forms the postero-ventral and posterior rim of the orbit. It extends dorsally to meet the
postorbital and posteriorly to meet the quadratojugal. The quadratojugal bounds the
tympanic fossa anteriorly and antero-dorsally. The tympanic fossa is notched postero-
ventrally for the passage of the columella from the incisura columella auris.

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PALAEONTOLOGY, VOLUME 13

Palate

The palate is flat and there is no secondary palate. The maxillae and premaxillae form
a broad grinding surface which borders the internal nares. This surface is grooved inter-
nally from the cutting edge, and passes into a broad ridge on the lingual margin. There
is a deep groove at the midline which would oppose the crest on the mandible. The
posterior margin of the internal nares is formed by the palatines and maxillae. The
vomer divides the internal nares, forming a sharp ridge, and extends only a short way
between the palatines. The palatines meet medially and meet the maxillae laterally;
there is a dorsal extension which meets the ventral projections of the nasal and prefrontal
to form the anterior orbital wall. The orbito-palatal edge of the palatine is deeply
notched ; this area is not well preserved on any specimen but it does not appear that this
notch was surrounded by bone to make a posterior palatine foramen, although the notch
would serve the same function (PI. 67, figs. 3, 8). The pterygoid does not join the maxilla.
The two pterygoids meet medially and are narrow, emarginate and slightly ridged. The
basisphenoid is exposed as an antero-posteriorly elongate triangle and is flat. The
basioccipital is broad anteriorly, narrow posteriorly, and level with the palate.

Epidermal sulci

Two pairs of sulci are evident on all the skulls. One crosses the maxillae from the
orbits to the nares, running posteriorly and slightly ventrally. The other crosses the
frontal, near to the frontal-nasal suture, as a sinuous curve from the orbits, anteriorly
to the midline.

On a small skull of R. cantabrigiensis (SM B55791) the dorsal surface is further sub-
divided into a larger number of scutes by well-marked epidermal sulci. The prefrontal
scute is divided into two by a straight sulcus and in addition there are a frontal, parietal,
and two postorbital scutes clearly marked (PI. 68, fig. 16).

Mandible

The mandibles are preserved on two skulls, one referable to R. elegans (SM B55776,
text-fig. 2) and the other to R. cantabrigiensis (SM B55791, PI. 68, figs. 14, 15). The

EXPLANATION OF PLATE 67

Figs. 1-5. Rhinochelys pulchriceps. Skull of type species, SM B55775. Dorsal, palatal, anterior, and
lateral views, x 1 . Fig. 2 is an enlarged view of the tympanic fossa.

Fig. 6. R. pulchriceps. BMNH 2224, lateral view, X 1.

Figs. 7, 8. R. pulchriceps. BMNH R1806, dorsal and lateral views, x2.

EXPLANATION OF PLATE 68

Figs. 1, 2. R. pulchriceps. BMNH R1806, lateral and anterior views, x2.

Fig. 3. Type skull of R. macrorhina ( R . elegans). BMNH 35193, lateral view, X 1.

Fig. 4. Type skull of R. brachyrhina (R. elegans). BMNH R2225, anterior view, X 1.

Figs. 5-7. R. elegans. Holotype skull, BMNH 2226; dorsal, lateral, and anterior views, x 1.

Figs. 8-10. R. cantabrigiensis. Holotype skull, BMNH 43980; dorsal, lateral, and anterior views, x 1.

Figs. 11-13. Type skull of R.jessoni ( R . cantabrigiensis). BMNH R2227; dorsal, lateral, and anterior
views, x 1.

Figs. 14-16. R. cantabrigiensis. SM B55791; lateral, ventral showing the lower jaw, and dorsal
views, x 1 .

Palaeontology, Vol. 13

PLATE 67

6

COLLINS, Rhinochelys

Palaeontology, Vol. 13

PLATE 68

COLLINS, Rhinochelys

J. I. COLLINS: RHINOCHELYS

365

angle between the mandibular rami is about 5° less than the jaw angle. The symphysis
is well fused and long, about a third of the length of the rami. The ventral surface of the
symphysis is smooth and tapers in an even curve at an angle of about 40° from the grind-
ing surface. The posterior depth at the symphysis is about half the symphysial length.
The lateral medial surfaces of the rami meet ventrally to form a very sharp ridge. The
sutures between the bones are indistinct due to poor preservation.

Pieces of mandible, showing the grinding surface at the symphysis but otherwise
similar to the articulated mandibles, are fairly commonly recorded. Text-fig. 10 shows
a mandible (BMNH R401) from the Chalk of Weymouth, Dorset. The grinding surface
is concave with a sharp median crest at the symphysis, and deeply grooved with sharp
marginal ridges along the rami.

text-fig. 10. Mandible BMNH R401. a, dorsal view of symphysis; b, lateral view of anterior part;
c, transverse section of mandibular symphysis and maxillae; d, cross-section of jaw rami and maxilla.

Braincase

The posterior part of a large skull (SM B94606) (text-figs. 11, 12; PI. 69, figs. 1-4)
with part of a maxilla, premaxilla, and vomer of Rhinochelys is recorded from the Upper
Senonian, Quadrata zone of Shawford, Hampshire (loc. 1086; Brydone 1912, p. 100).

All external features preserved agree with the generic characters of Rhinochelys as
defined above, but there is not enough evidence to allocate it to a species. Most of the
brain cavity and otic capsule are well preserved and show structures which have not
as yet been described in Rhinochelys. A natural mould in chalk of the upper brain cavity
is also preserved (PI. 69, fig. 4).

Description. A heavy ridge runs across the inner surface of the roofing bones of the
temporal fossa, from the anterior part of the brain cavity to the posterior rim of the
orbit. The area is thus divided into lachrymal and temporal surfaces. A faint ridge is
discernible in the recent Chelonia. The ventral extension of the parietal meets the ptery-
goid ventrally, and the prootic and supraoccipital posteriorly. It forms the anterior
side wall of the brain cavity. The suture between the pterygoid and parietal is indistinct
and it is uncertain whether an epipterygoid is present or not.

The trigeminal nerve foramen is kidney-shaped and does not extend above the level
of the otic capsule. Posteriorly it is bordered by the prootic dorsally and by the quadrate
ventrally.

366

PALAEONTOLOGY, VOLUME 13

The prootic forms a small part of the wall of the brain case. It projects laterally with
a heavy anterior ridge to form the anterior roof of the otic capsule. The stapedial
(temporal) canal passes through it near the posterior margin.

The supraoccipital is partially preserved, but the crest is broken. It forms the roof
of the posterior part of the brain cavity. The opisthotic is an irregularly shaped bone,
extending between the prootic anteriorly, the squamosal laterally, theexoccipitalpostero-
ventrally, and the supraoccipital dorsally. It forms the posterior roof of the otic capsule
and part of the dorsal edge of the fenestra postotica.

The exoccipital forms the edge of the foramen magnum medially and of the fenestra
postotica laterally. It meets the supraoccipital dorsally, the opisthotic dorso-laterally
and the basioccipital ventrally. It does not appear to meet the pterygoid laterally, nor
does it extend over the basioccipital to form the posterior floor of the brain cavity.

The quadrate forms the lateral part of the otic capsule. The tympanic fossa is concave
with a deep notch and groove, the incisura columella auris, on the posterior margin.
Ventrally the bone meets the lateral extension of the pterygoid. The articular condyle
is eroded. A fragment of squamosal lies over the quadrate and forms the roof of the
stapedial canal.

Brain cavity. The basioccipital forms the floor of the posterior part of the brain cavity.
It is concave and broad, with a median anterior ridge which terminates abruptly in a
knob, the basi-tuberculi basalis, at the basisphenoid suture. Deep grooves flank this
knob, and the area posterior to it is rough. Hypoglossal nerve foramina open into the
postero-lateral part of this surface.

The basisphenoid is in two parts and forms the anterior floor of the brain cavity.
Posteriorly the bone is broad and concave, the surface is rough with a small median
crest which tapers out midway. The clinoid processes are two small peaks on the anterior
rim of the main part of the bone and flank the dorsum sellae. The dorsum sellae is vertical
and forms a beak which protrudes into the fossa hypophysis. The basisphenoidal
rostrum is long, narrow, and grooved ; it terminates abruptly in a vertical oval face. It
lies over the suture between the pterygoids and is flanked on either side by the sulcus
cavernosus. The abducens nerve foramen lies in the dorsum sellae just below the clinoid
process.

Otic capsule. The otic capsule is open posteriorly by a wide fenestra postotica, postero-
laterally into the tympanic fossa by the incisura columella auris, and anteriorly into the
sulcus cavernosus by the carotid canal. The main part of the capsule is divided into three
cavities, the cavum labyrinthicum (inner ear cavity) and the medial and lateral parts of
the cavum acustico-jugulare (acoustic-jugular cavity).

The inner ear cavity is antero-medial to the other two ; it opens into the brain cavity
by a large hiatus acusticus, and into the acoustic-jugular cavity by the fenestra ovalis.
In the roof lie the three cavities for the semicircular canals : the opisthotic recess posteri-
orly, the supraoccipital recess medially, and the prootic recess anteriorly. A thin
septum of bone separates the inner ear cavity from the medial part of the acoustic-
jugular cavity. This septum is pierced by a large oval fenestra perilymphatica.

The medial part of the acoustic-jugular cavity is pear-shaped and lies posterior to the
inner ear cavity. It narrows medially and opens into the brain cavity by a small round

J. I. COLLINS: RHINOCHELYS

367

anterior jugular foramen and opens into the main part of the acoustic-jugular cavity,
laterally, by an oval posterior jugular foramen. This foramen, and the fenestra ovalis
beside it, are completely surrounded by bone, and the septum which divides these is
fused to the cavity floor. In the Recent cheloniids this bony septum is free of the
cavity floor and is completed by cartilage.

The lateral part of the acoustic-jugular cavity is the largest of the three. There is
a lateral groove over the floor which passes anteriorly into the carotid canal between
the pterygoid, quadrate, and prootic. This canal joins the sulcus cavernosus medial to the
trigeminal nerve foramen, and carried the carotid artery and lateral head vein. The
stapedial artery passed dorsally from this cavity, through a canal between the prootic
and squamosal bones into the temporal fossa.

Brain cast. The chalk formed a natural cast of the upper brain cavity which is partly
preserved. The cerebral lobes are faintly discernible and are 1 1 -2 mm. wide, the olfac-
tory lobes lie 12 mm. anteriorly and are 5 mm. wide. The hind region of the brain is
flexed ventrally at an angle of 30° from the anterior part.

Measurements. Posterior width 60 mm., height 37 mm.

Discussion

The internal structure of this skull is of chelonioid type and can be compared with
skulls of other marine turtle families, the Toxochelyidae, the Cheloniidae, both described
from the Cretaceous of North America, and the Recent Dermochelyidae. (The internal
cranial morphology of the Protostegidae is not well enough known for comparison to
be possible.) There are morphological differences which need emphasizing although the
precise significance of these is uncertain.

The passage of the carotid artery and lateral head vein through the acoustic-jugular
cavity is essentially simple. In the cheloniids and toxochelyids, the blood vessels are
enclosed in the pterygoid and enter the skull close to the occipital condyle. In the Recent
cheloniids the basisphenoid, anterior part of the basioccipital, and the pterygoid are
thickened, dropping the posterior part of the palate. The ventral surface of the basi-
occipital, instead of being horizontal as in Rhinochelys, is inclined at an angle of 30°.
The pterygoid has incorporated the blood vessels within itself and these pass into the
sulcus cavernosus much as in that of Rhinochelys , but in a toxochelyid skull described
by Zangerl (19536, p. 152) the internal carotid passes directly into the basisphenoidal
rostrum and does not enter the sulcus cavernosus. The projection of the dorsum sellae
into the fossa hypophysis is found also in the Recent Eretmochelys , but in other
cheloniids and toxochelyids the dorsum sellae is sloped and concave. The basi-
sphenoid and exoccipital are both extended laterally in the cheloniids and the exocci-
pitals fuse together across the dorsal surface of the basioccipital.

It seems possible that the more complex and sturdier cheloniid skulls could have
evolved from a simple condition such as that of Rhinochelys. On investigating the skull
of a Leathery Turtle, it became clear that this too could have evolved from a skull like
Rhinochelys but not through the cheloniids or toxochelyids. Apart from specialized
features which can only be related to the group, the Dermochelys skull is more like the
skulls of the Chelonioidea than any other Cryptodire. The basic pattern of the skull is

C 7619 b b

368

PALAEONTOLOGY, VOLUME 13

very similar in the two groups but Dermochelys shows a remarkable simplicity and simi-
larity to Rhinochelys in the features that have been discussed. The palate is primary and
the posterior part is not thickened but is flat. The carotid artery and lateral head vein
pass through the acoustic-jugular cavity and are not enclosed in the pterygoid. The

text-figs. 11, 12. Rhinochelys sp. Upper Chalk skull, SM B94606. 11a, posterior view, X 1 ; 11 b, lateral
view with otic capsule removed, x 1 ; 12a, dorsal view of the floor of the brain cavity and plan of the
otic capsule; 12 b, anterior view of the dorsum sellae looking along the basisphenoidal rostrum.
Explanation of abbreviations: ajc, acoustic-jugular cavity; ajf, anterior jugular foramen; bsr, basi-
sphenoidal rostrum; btb, basituberculi basalis; c, carotid canal; ds, dorsum sellae; fh, fossa hypo-
physis; fo, fenestra ovalis;./p, fenestra postotica; ha, hiatus acusticus; o, opisthotic; pc, clinoid process;
pf posterior jugular foramen; s, squamosal; sa, stapedial arterial canal; sc, sulcus cavernosus;

so, supra-occipital.

structure of the basioccipital (except in the floor of the brain cavity), pterygoid, and
exoccipital are similar to Rhinochelys. Zangerl (1953a) suggested that the Leathery
Turtles could have descended from the Protostegidae; such a relationship might explain
this similarity, but it could alternatively be a general, primitive, condition retained by
both genera.

So far I have briefly discussed the differences within the superfamily, which are not
very extensive. It is far more interesting to demonstrate the developing pattern of

J. I. COLLINS: RHINOCHELYS

369

structural changes. The Rhinochelys skull, as the first record of the Chelonioidea (Cox
et al. 1967), is conveniently placed for such a study. Although ‘modernized’ in type, this
skull is uncomplicated by extra bone growth as is seen in the later cheloniids, and is still
close enough to the primitive stock to retain a simplicity of structure.

The chelonian skull is specialized in the formation of an acoustic-jugular cavity and
a tympanic fossa. All known chelonians possess these features in one form or another,
except the primitive Triassic Proganochelys.

text-figs. 13, 14. Proganochelys quenstedti. 13, posterior part of the palate. 14, occiput. Reconstructed
from Parsons and Williams (1961, pi. 5, 6). Magnification not stated. Explanation of abbreviations:
jf, jugular foramen ; on, otic notch ; pr, prootic.

Photographs of a well-preserved skull of Proganochelys quenstedti Baur, housed in
the Museum of Natural History at Stuttgart, were published by Parsons and Williams
(1961). While a full description of the skull has yet to be published, the photographs are
clear and show that the acoustic-jugular cavity is not floored, but is a simple concavity
in the back of the skull, very similar to that found in other primitive reptiles. Parsons
and Williams (p. 91) briefly discuss this and say:

a cultriform process is plainly visible between the separated pterygoids. Posteriorly also the situation
is primitive ; the quadrate ramus of the pterygoid does not send any flange inward to floor the cranio-
quadrate passage as on all other known turtles, and the foramina for the vena capitis lateralis, the inter-
nal carotid, and the stapedial artery, as well as the fenestra ovalis are all exposed in ventral view.

In text-figs. 13 and 14 I have interpreted this region of the skull of Proganochelys,
using the photographs shown in Parsons and Williams (1961, pi. 5, 6) but showing only
features which are well defined. The arrows indicate the areas and direction of growth
of the bones which would be required to produce the morphology of this region as found
in Rhinochelys. In Proganochelys there are two large fenestrae opening laterally. One,
close to the condyle, is the jugular foramen ; the other, antero-lateral to this, is the
fenestra ovalis. Anteriorly there are two foramina on one side but only one is apparent
on the other. One of these is for the stapedial artery and the other possibly for the lateral
head vein. The pair of foramina on the basisphenoid could possibly be the internal
carotid foramina; however these are placed in a different position from normal. In the

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PALAEONTOLOGY, VOLUME 13

modern chelonians the internal carotid artery enters the basisphenoid through the dor-
sum sellae; it is possible that the change of position of these foramina is caused by the
medial and posterior growth of the pterygoid.

The basisphenoid is slightly proud of the floor of the inner ear cavity as there is a
distinct shadow laterally. The basipterygoid processes are sutured anteriorly and laterally
to the pterygoids. The pterygoid sends only a thin bar posteriorly and laterally to the
quadrate. The articular condyle is level with the occipital condyle.

The otic notch is simply curved and open. It seems to be bordered by the quadrato-
jugal anteriorly and the squamosal dorsally and is lined by the quadrate. The quadrate
appears to be in a primitive vertical plane.

The bar of bone which separates the jugular foramen from the fenestra ovalis is prob-
ably part of the opisthotic and this bone probably also extends anteriorly to the prootic,
flooring the inner ear cavity. These conditions would then be similar to those in Rhino-
chelys where the opisthotic forms the bony septum between the medial acoustic cavity
and the inner ear cavity, and floors the latter.

As far as I can see, to reach the condition seen in Rhinochelys, the following develop-
ments have taken place:

The basioccipital has grown at point A laterally to point B. It lies ventral to the other
bones and has grown alongside the opisthotic bar forming the floor to an extended
‘jugular canal’ (medial acoustic-jugular cavity), and joins the opisthotic level with the
floor of the inner ear cavity, and the pterygoid at point B. This ‘jugular canal’ is com-
pleted by the exoccipital which has extended from point A, laterally, to form a posterior
wall. This canal opens into the brain cavity by the anterior jugular foramen and into the
main part of the acoustic-jugular cavity by the posterior jugular foramen.

The pterygoid has grown along its entire posterior margin. It has extended back-
wards to floor the lateral concavity and so forms the acoustic-jugular cavity. Posteriorly
it meets the basioccipital, underlies the floor of the inner ear cavity, completely sur-
rounds the basisphenoid (except posteriorly), and encloses the internal carotid and the
lateral head vein between itself, the prootic, and the quadrate. Medially the pterygoids
have grown under the basipterygoid processes and the cultriform process, and the
internal carotid enters the basisphenoid through the cultriform process, dorsal to the
pterygoids.

The quadrate fills the otic notch and forms the tympanic fossa. The articular condyle
is pushed anteriorly. In Rhinochelys, the original position of the otic notch is suggested
by the curved quadratojugal.

TAXONOMIC POSITION OF RHINOCHELYS

Having described the cranial morphology of Rhinochelys, it is now possible to use this
information in attempting to establish to which family the genus belongs. Seeley (1869)
said quite simply that the genus had emydian affinities, but gave no reason for this
remark. The modern concept of the Testudinidae (Romer 1956, Loveridge and Williams
1957) emphasizes the following features: the presence of a squamosal antrum, the
fenestra postotica is almost closed, the pterygoid meets the maxilla, and the nasal
bones are absent. Since none of these features is present in Rhinochelys, there seems to be
no reason for further considering this relationship.

J. I. COLLINS: RHINOCHELYS

371

Lydekker (1889) considered that the genus was probably pleurodiran and gave the
following reasons : distinct nasals are present only in the Chelydidae, the palatines unite
in the midline only in the Pelomedusidae, and there is the same relationship of bones
around the internal nares as in Pelomedusa. He said also that the narrow palatines and
pterygoids and complete roofing of the temporal fossa was more like the Cryptodires
than the Pleurodires. However, since Lydekker’s time, there has been a major revision
of the taxonomy of the Chelonia, and there are diagnostic features of the Pleurodires
in the present concept (Romer 1956) which are not present in Rhinochelys. These are:
the absence of a descending process of the prefrontal, the broad pterygoid with a rolled
up lateral expansion, and the meeting between the quadrate and the basisphenoid. On
this basis there seems to be little evidence of relationships between Rhinochelys and this
group of families.

In his description of Desmatochelys Williston (1898) compared it with Rhinochelys
and referred them both to his new family, the Desmatochelyidae. This was followed by
Romer (1956). Zangerl and Sloan (1960) suppressed the Desmatochelyidae when they
demonstrated the affinities of Desmatochelys to the Cheloniidae, on post-cranial material.
The relationship between the two genera is discussed below.

Thus Rhinochelys has not been satisfactorily assigned to any family, and this will now
be considered using modern taxonomy.

Firstly, there can be little doubt that Rhinochelys belongs to the superfamily Cheloni-
oidea, which is in the suborder Metachelydia of Zangerl (1969). The characteristics of
this superfamily as given by Romer (1956) are as follows: temporal region well roofed;
premaxillae unfused; vomer meets premaxilla, separates internal nares and separates
the palatines; parietal with descending process; epipterygoid present; pterygoids con-
stricted at mid-length, broadly in contact with one another and separate the basi-
sphenoid from the palatine; pterygoid not in contact with the maxilla. Rhinochelys
shows all these features except that the vomer does not separate the palatines.

The three families in the Chelonioidea (the Cheloniidae, the Toxochelyidae, and the
Protostegidae) are all recorded from the Cretaceous. The position of Rhinochelys is
shown most clearly by tabulating the condition in respect of a number of cranial
features in Rhinochelys and in each of these three families. The features of the Toxo-
chelyidae and the Protostegidae are taken from Zangerl (1953 a , b ), and Wieland (1900),
and of the Cheloniidae from Loveridge and Williams (1957).

As can be seen from Table 2, Rhinochelys has the salient features of the Protostegidae,
especially the structure of the mandible and palate, and is best referred to this family.
The Protostegidae contains two subfamilies, the Protosteginae (large, highly specialized
genera) and the Chelospharginae (two small and primitive genera, Chelosphargis and
Calcarichelys). Rhinochelys is obviously neither large nor specialized; in fact it is dis-
tinctive in its lack of specialization, which fits in with the subfamily Chelospharginae
as diagnosed by Zangerl (1953a, p. 128):

Small blunt straight premaxillary beak. Frontal bones large and with lateral processes towards
orbital rims. Prefrontal bones excluded from sagittal contact by nasal bones. Otic and exoccipital area
very similar to the condition in cheloniid turtles. Symphysis mandibuli long, with rami fused even in
juvenile individuals. Slight, but sharp, sagittal crest on the triturating surface of lower jaw.

The skull of Calcarichelys is not known. The skull of Chelosphargis has been described
by Zangerl (1953a, pp. 81-4, figs. 21 a-d, 22). Comparing this with Rhinochelys, the close

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PALAEONTOLOGY, VOLUME 13

relationship between the two genera is unmistakable. The shape of the temporal roofing
bones, the ant-orbital beak, the primary palate, the structure of the lower jaw and the
epidermal sulci crossing the maxilla and the dorsal bones, are closely comparable in the
two genera. Unfortunately the palate and otic region on the specimens of Chelosphargis
are not preserved in any detail. The occipital region on one specimen, however, is
described by Zangerl (op. cit., p. 82), who states that this region resembles Chelonia
rather than Dermochelys, although in his figures 22 a, b, the exoccipital does not appear
to contribute to the occipital condyle as it does in Chelonia.

table 2. Comparison of cranial features of Rhinochelys, Protostegidae, Toxochelyidae
and Cheloniidae (a — absent, p — present)

Postorbital extends back to

Rhinochelys

Protostegidae

Chelospharginae Protosteginae

Toxochelyidae

Cheloniidae

squamosal tip

a

unknown

a

P

a

Prefrontals meet dorsally

a

a

P

P

P

Vomer separates the palatines

a

unknown

a

P

P

Palatine fenestra
Pterygoids joined to maxillae

a

unknown

a

P

a

or jugals

a

unknown

a

maxillae

jugals

Secondary palate
Mandibular symphysis very
wide, about one-third length

a

a

a

a and p

P

of the rami

P

P

P

a

a

Sharp symphysial ridge

P

P

P

a

a and p

RELATIONSHIP OF RHINOCHELYS TO OTHER
CRETACEOUS TURTLES

In establishing the family position of Rhinochelys, the skull structure of the Recent
Cheloniidae is used. All the criteria of this family are based upon the structure of the
limbs, girdles, and plastron. The cheloniid method of locomotion apparently underwent
little change after its development (Zangerl 19536), but the structure of other parts of
the skeleton, including the skull, seems to have been subjected to evolutionary experiment
over the long period of time involved. From North America there are two other genera
of Cretaceous turtles, Corsochelys Zangerl (1960) and Desmatochelys Williston (1894),
which have been placed in the Cheloniidae on the evidence of the postcranial skeleton.
The skulls in these genera show features which are not present in later cheloniids.
Table 3 demonstrates the similarities and differences between these two genera, Rhino-
chelys, Chelosphargis, and the Recent cheloniids and advanced protostegids.

Corsochelys and Desmatochelys closely resemble Rhinochelys and Chelosphargis but
do not display the distinctive protostegid mandible and palate (where preserved), and
show cheloniid features. Thus there are four unspecialized genera in the Cretaceous
showing distinct features of two families (the Cheloniidae and the Protostegidae) but
also possessing many common features which are not shared by the more advanced
members of these families. It seems logical to surmise that they have inherited these
features from a common ancestry.

table 3. Comparison of cranial features of Rhinochelys, Chelosphargis, Desmatochelys, Corsochelys,
Recent Cheloniidae and advanced Protostegidae (a — absent, p — present)

J. I. COLLINS: RHINOCHELYS

373

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374

PALAEONTOLOGY, VOLUME 13

CARAPACE AND PLASTRAL MATERIAL POSSIBLY
BELONGING TO RHINOCHELYS

A number of remains of carapaces and plastra is known from the Albian to Turonian
of south-east England. Unfortunately skull material is not associated with any of these.
However, these carapaces and plastra appear (as will be shown) to be of chelospharginid
type and, now that Rhinochelys, from the same area and deposits, is known to be a
chelospharginid, it seems worth investigating the possibility that this material belongs
to Rhinochelys. The first specimen to be described was a small, probably juvenile, cara-
pace which Mantell (1841) named Emys benstedi. Owen (1841) transferred it to the
genus Chelone and also considered that it was sufficiently distinct to merit subgeneric
status, naming it Cimochelys. This has been used as a generic name by Zangerl (1960).

Description. The type-specimen of Emys benstedi is BMNH 28706. This has been broken
and part of the carapace is lost. Other material which appears to be related includes
BMNH 39112 (text-fig. 15), R1350, 47210 (text-fig. 16); GSM442; SM B20607.

The type material has unfortunately been partly lost since it was described, and there-
fore the following description is taken from Owen’s figured specimen BMNH 39112
(1851, pp. 7-8, pi. 3) which in all points resembles what remains of the type, the original
description, and the figures.

The carapace is heart-shaped with moderate fontanelles and a sharp neural keel
which is flattened anteriorly. The sides slope more or less straight from the neurals
to the peripherals. The neurals are rectangular, very narrow, long, and of even size, except
the eighth, which is triangular and half the length of the seventh. The sutures between
the costals and between the neurals correspond, instead of being offset as in the Cheloni-
idae. The costals are straight, slope at a steep angle and, about halfway along their
length, taper into broad striated ribs which continue to taper until they articulate in
deep pits in the inner surface of the peripherals. The 2nd peripheral is thin and flat and
lies across the front of the carapace. The 3rd is flat anteriorly but broadens posteriorly
to become deeply triangular in cross-section ; it is crescent- shaped and forms the broad
curved angle of the carapace. The 4th-6th peripherals are deeply triangular in cross-
section with a convex dorsal and a concave ventral surface. Each peripheral has a deep
medial pit in the inner surface for the rib articulation. The 7th— 1 1th peripherals have
shallower cross-sections. The medial border of these bones is smooth. The 8th neural,
suprapygal, pygal, 11th peripheral, 8th costal and rib, together form a solid bony
posterior to the carapace.

Epidermal shield sulci cross the 1st, 3rd, 5th, and 7th costal and neural bones (the
1st neural is not preserved but was presumably the same). These sulci form three small
peaks across the neural keel. Each peripheral is notched on the outer margin by a sulcus
which gives a serrated appearance to the carapace edge, especially posteriorly.

Plastron. The description of the plastron is taken from the type-specimen. The hyo-
and hypoplastra only are preserved and are subrectangular in outline with a moderate

EXPLANATION OF PLATE 69

Figs. 1-4. Rhinochelys sp. SM B94606. 1, Occiput, x 1. 2, Lateral view of the brain cavity with the

otic capsule removed, xl. 3, Enlarged view of the hiatus acusticus, inner ear cavity, and the
anterior jugular foramen. 4, Dorsal view of a natural cast of the upper brain cavity, x 1 .

Palaeontology , Vol. 13

PLATE 69

COLLINS, Rhinochelys

J. I. COLLINS: RHINOCHELYS

375

fontanelle in the centre. The hyoplastra are the smaller and meet medially with long
digitations, and laterally and posteriorly with short fine digitations. The digitations bor-
dering the fontanelle are fine anteriorly and become larger posteriorly, forming twelve
or so large fingers between the hypoplastra. The posterior margin of these plates has
two long fingers of bone curving backwards and inwards. In BMNH 47210, from the
Gault of Folkestone, Kent (text-fig. 16), the posterior part of the plastron is concave,
dipping steeply in from the sides to a depth of 10 mm. Comparison with the Recent
turtles suggests that this is probably a male sexual character.

text-figs. 15, 16. Cimochelys benstedi. 15, BMNH 39112; a, reconstructed carapace, xO-5; b, longi-
tudinal section ; c, anterior transverse section ; d, posterior transverse section ; e, cross-section through
the second peripheral; /, cross-section through the fourth peripheral; g, cross-section through the
ninth peripheral. 16, Plastron, BMNH 47210, reconstructed ventral view, xO-5. Explanations of
abbreviations: co, costal; n, neural; by hyoplastron; hp, hypoplastron ; pe, peripheral; py, pygal;

sp, suprapygal.

Discussion. The material was originally described by Mantell (1841) as Emys benstedi,
although the plastron resembled that of the marine turtles. Mantell considered that the
carapace was like that of the juvenile Emys because the ribs diminish in width towards
the circumference, which might indicate a gradual growth and tendency towards com-
plete infilling of the interspaces. He also pointed out that in marine turtles the broad
part of the rib is sharply demarcated from the linear part. However, the carapace in the
Testudinidae is usually solid even in juveniles and is very different from Emys benstedi.
The neurals are hexagonal and generally broader than long; the peripherals are solid
and double wedge-shaped with a thin dorsal plate under which lies the tip of the rib;

376

PALAEONTOLOGY, VOLUME 13

they are not triangular in cross-section nor open medially. The plastron is not reduced
and forms a solid bony plate which is well fused to the carapace.

Owen (1841, 1851) placed the species in Chelone on the following points: the carapace
is pointed posteriorly with moderate fontanelles, narrow neurals and peripherals which
do not join to the plastron; the central fontanelle of the plastron is more like that of the
marine turtles than that of Emys. He considered, at this time, that most marine turtles
belonged to the genus Chelone. However, he suggested a subgeneric name, Cimochelys,
as he believed that these specimens had particularly close affinities to the Emydidae.

Since Owen’s time, marine turtles of three families have been described from the
Cretaceous: the Protostegidae, Toxochelyidae, and Cheloniidae. The characteristics of
Cimochelys may therefore now be compared with those of the members of these three
families.

At family level, Cimochelys has the following features in common with the Proto-
stegidae: narrow, long, rectangular neurals; sharp neural keel; neural and costal
sutures coincide ; gradual demarcation between the costal plates and the ribs ; and sub-
rectangular (rather than saddle-shaped) hyo- and hypoplastra. In none of these features
is it like the Toxochelyidae or the Cheloniidae. Next, comparing Cimochelys with the
two subfamilies in the Protostegidae, it may be noted that it is like the Chelospharginae,
and unlike the Protosteginae, in the lack of reduction of its carapace and plastron, and
in the absence of digitations along the medial border of the peripherals (Zangerl 1953a,
p. 128). The differences in the other two genera in the Chelospharginae ( Chelosphargis
and Calcarchelys ) and Cimochelys appear to lie mainly in the degree of formation of the
peaks on the neural keel and serrations around the posterior edge of the carapace. In
Calcarichelys these appear to be accentuated, but Chelosphargis is relatively smooth.

Thus the carapace material is characteristic of the Protostegidae, subfamily Chelo-
spharginae, and closely related to Chelosphargis and Calcarichelys. Since the Rhino-
chelys skulls from similar deposits are also related to these genera, it is suggested that
Cimochelys benstedi could be the missing post-cranial material of Rhinochelys.

Synonomy.

1841 Emys benstedi Mantell, pp. 153-8, pi. 11, 12.

1841 Chelone ( Cimochelys ) benstedi (Mantell); Owen, pp. 176-7.

1851 Chelone benstedi (Mantell); Owen, pp. 1-11, pi. 6-8.

SUMMARY

A critical examination of all available British material of the Cretaceous turtle Rhino-
chelys reveals the inadequacy of Lydekker’s descriptions and generic diagnosis. Three
species only are truly distinguishable ; of these, two species (typified by the types of R.
elegans and R. cantabrigiensis) comprise the bulk of the collections, while R. pulchriceps
is the least common. R.jessoni is considered to be a junior synonym of R. cantabrigiensis,
and R. macrorhina and R. brachyrhina are considered to be junior synonyms of R.
elegans. The cranial distinctions between these species are restated and they are com-
pared with the French species R. amaberti. Charts of angles taken about the skull and
proportional measurements reveal characteristic differences between the three species.
These are definable even if superficial features have been eroded. The charts are also
of value when handling skulls of different growth stages as there appears to be little

J. I. COLLINS: RHINOCHELYS

377

ontogenetic variation. A very finely preserved brain case and otic capsule of Rhinochelys
is described from the Chalk of Hampshire.

The posterior part of the palate and occiput of a skull of Proganochelys quenstedti
Baur has been reconstructed from the photographs in Parsons and Williams (1961,
pi. 5, 6). The obvious features are discussed and a possible mode of development of the
skull into that described in Rhinochelys is suggested.

Rhinochelys is referred to the family Protostegidae, subfamily Chelospharginae,
mainly on the evidence of the mandible and palate structure. It is compared with the
skulls of other Cretaceous turtles and a close relationship in the cranial morphology
between the primitive protostegids and the primitive cheloniids is clearly shown.

Since no associated post-cranial material is recorded, all generic and specific descrip-
tions are based on skulls. Carapace and plastral remains have been described from the
Upper Cretaceous of south-east England as Chelone ( Cimochelys ) benstedi (Mantell
1841). These are referable to the same subfamily as Rhinochelys and are provisionally
referred to the same genus.

The Protostegidae, hitherto restricted to the Late Cretaceous of North America, is
extended in range to the Albian-Turonian of Europe.

Acknowledgements. I would like to thank Dr. C. B. Cox (King’s College, London) for his patient help
with the manuscript; also Dr. A. Charig and Mr. C. Walker (British Museum (Natural History)),
Dr. C. Forbes and Mr. A. G. Brighton (Sedgwick Museum, Cambridge), Mr. B. MacWilliams (Nor-
wich Castle Museum, Norwich), and Mr. C. Wood (Institute of Geological Sciences) for access to and
loan of specimens; and the Photographic Department, British Museum (Natural History) and Mr. E.
Kentish for preparing the photographs.

REFERENCES

brydone, R. m. 1912. The Stratigraphy of the Chalk of Hants. London, 116 pp., pi. 1-3.
cox, c. b. et al. 1967. Reptilia, in harland, w. b. et al. (eds.) The fossil record, London (Geological
Society), 698 pp.

kesteven, h. l. 1910. The anatomy of the head of the green turtle Chelone midas. J. Proc. R. Soc.
N.S.W. 44, 368-400, pi. 20-33.

loveridge, a. and williams, e. e. 1957. Revision of the African tortoises and turtles of the suborder
Cryptodira. Bull. Mus. comp. Zool. Harv. 115, 163-557, pi. 1-18.
lydekker, r. 1889. On remains of Eocene and Mesozoic Chelonia and a tooth of (?) Ornithopsis.
Q. Jlgeol. Soc. Lond. 45, 227-46, pi. 8.

mantell, g. 1841. On the fossil remains of turtles, discovered in the Chalk Formation of South-East
England. Phil. Trans. R. Soc. 131, 153-8, pi. 11, 12.
moret, L. 1935. Rhinochelys amaberti, nouvelle espece de tortue marine du Vraconien de la Fauge,
pres du Villard-de-Lans (Isere). Bull. Soc. geol Fr. 1, 605-19, pi. 27, 28.

Owen, R. 1841. Report on the British Reptiles. Rep. Br. Ass. Advmt Sci., 60-204.

1851. A Monograph on the Fossil Reptilia of the Cretaceous Formations. Palaeontogr. Soc.

[Monogr.] 1, i-vi, +118, pi. 1-37.

parsons, t. s. and williams, e. 1961. Two Jurassic turtle skulls: a morphological study. Bull. Mus.

comp. Zool. Harv. 125, 43-107, pi. 1-6.
romer, a. s. 1956. Osteology of the Reptiles. Chicago, xxi+772 pp.

seeley, h. G. 1869. Index to the fossil remains of Aves, Ornithosauria, and Reptilia from the Secondary
System of Strata arranged in the Woodwardian Museum of the University of Cambridge. Cambridge,
i-xxiii+143 pp.

wieland, g. r. 1900. The skull, pelvis and probable relationships of the huge turtles of the genus
Archelon from the Fort Pierre Cretaceous of South Dakota. Am. J. Sci. 9, 237-51, pi. 2.
williston, s. w. 1898. Desmatochelys lowi. Univ. geol. Surv. Kans. 4 (1), 353-69, pi. 73-78.

378

PALAEONTOLOGY, VOLUME 13

zangerl, r. 1953a. The vertebrate fauna of the Selma Formation of Alabama. Pt. 3, The turtles of the
family Protostegidae. Fieldiana, Geol. Mem., 59-133, pi. 5-8.

19536. The vertebrate fauna of the Selma Formation of Alabama. Pt. 4, The turtles of the family

Toxochelyidae. Ibid. 137-277, pi. 9-29.

1960. The vertebrate fauna of the Selma Formation of Alabama. Pt. 5, An advanced cheloniid

sea-turtle. Ibid. 281-312, pi. 30-33.

— 1969. The turtle shell, in The biology of the Reptilia (eds. c. gans, a. d’a. bellairs, and t.
parsons). London and New York, 311-39.

and sloan, r. e. 1960. A new specimen of Desmatochelys lowi Williston, a primitive cheloniid

sea-turtle from the Cretaceous of South Dakota. Fieldiana, Geol. 14, 7^10, pi. 1 , 2.

JANICE I. COLLINS

63 Oakhurst Grove
E. Dulwich
London, S.E. 22

Final typescript received 16 September 1969

THE SHELL STRUCTURE, MINERALOGY AND
RELATIONSHIPS OF THE CHAMACEA
(BIVALVIA)

by W. J. KENNEDY, N. J. MORRIS, and J. D. TAYLOR

Abstract. The superfamily Chamacea is a group which has constantly confused systematists concerning its
relationship with other bivalves. Various authors have related it to the Cardiacea, Veneracea, Crassatellacea,
Lucinacea, and the rudists (Hippuritacea).

Most classifications have placed the Chamacea with the rudists; Newell (1965) placing them into the Hip-
puritoida, a relationship which Yonge (1967) considers beyond doubt. From a review of hard and soft part
anatomy, especially shell-structure, dentition, and mineralogy, it seems likely that the Chamacea arose from a
group of byssate Cardita in the early or middle Cretaceous. Similarities to the rudists are the result of convergent
adaptions to a similar mode of life, and there is no real indication of relationship.

The Chamacea should be removed from the order Hippuritoida and placed in the order Veneroida.

The Chamidae are the sole bivalve family placed in the Superfamily Chamacea (Newell
1965). They are a small group of cemented or secondarily free bivalves which have
attracted the attention of zoologists for many years because of the problem of their
origins and systematic position. Despite this attention, the systematics of the Recent
species is in a very confused state.

Many authors have inferred that the Chamacea are closely related to the rudists (i.e.
Odhner 1919, Yonge 1967) and the most recent review of bivalve classification (Newell
1965) places them in the Order Hippuritoida, together with the Megalodontacea
and Hippuritacea. We describe the shell structure and mineralogy of recent and fossil
Chamidae below, and discuss the use of these features and the nature of the soft part
anatomy to determine the natural relationships to other bivalve superfamilies. We have
demonstrated elsewhere (Taylor, Kennedy, and Hall 1969) that shell structure and
mineralogy are constant features within bivalve superfamilies, and that they are of value
in assessing relationships within the Bivalvia.

The Chamacea are characteristic inhabitants of tropical and sub-tropical seas,
although some species, such as Chama pellucida Broderip, range into cooler temperate
waters along the coast of California (San Francisco), but are also present in warmer
waters. One species, Chama gryphina Lamarck, is present in the Mediterranean.

Chama usually inhabits rocky shores, and is a typical member of the coral reef
community. Individuals usually live cemented on rocky surfaces or upon dead coral.
Coral-dwelling Chama species are usually found on the underside of coral colonies.
Most species inhabit the sublittoral and sublittoral fringe environments, but some are
intertidal.

Arcinella arcinella (Linnaeus), a Caribbean species, is usually found free living on a
coarse gravel substrate (Nicol 1952) but occasionally cemented adults of this species
are found. The loss of cementation in Arcinella is secondary, for traces of attachment
are always to be seen on the juvenile parts of the shell. Certain fossil species such as

[Palaeontology, Vol. 13, Part 3, 1970, pp. 379-413, pi. 70-77.]

380

PALAEONTOLOGY, VOLUME 13

Chama calcarata Deshayes from the Calcaire Grossier of the Paris Basin (Eocene,
Lutetian), a shell sand facies, also show this secondary loss of cementation.

THE SHELL

1 . General morphology. The Chamacea are generally inequivalve, asymmetrical, the free
valve being the smaller. The lower valve is usually convex and the upper valve is fre-
quently more or less flattened (PI. 70, fig. 1). Many early Chamacea are rather less
inequivalve than extant forms. The secondarily free genus Arcinella (PL 70, fig. 2) has
returned to a more or less equivalve state. The shell of the Chamacea is thick; the
umbones are prosogyrous; attachment can be by either valve.

Shell ornament is variable. Some species bear irregular, concentric lamellae, which
may be long and foliaceous (PI. 70, fig. 4); others are spinose, or have irregular, low
squamae. Some species have radial ribs as well as concentric lamellae. Ornament varies
considerably with environmental conditions such as site of cementation, exposure to
wave action and encrusting biota. Arcinella is the only genus which consistently bears
long spines. Some specimens of Chama show a shallow groove running from the umbo
to the posterior ventral margin; this is often marked by a supression of strong sculp-
ture. A well-marked, heart-shaped lunule is present in Arcinella (PI. 70, fig. 2).

The interior margin of the shell is frequently crenulate, while the area between the
shell edge and the pallial line may be marked by irregular radial grooves and ridges,
which are the impressions of the radial masculature of the mantle (Jaworski 1928).

The pallial attachment area (pallial line) is wide, and the dorsal side is overlapped
irregularly by inner shell layer. The adductor muscle pads are massive and translucent ;
they and the pallial line fluoresce blue under ultra-violet light.

2. Shell geometry. Growth in the Chamacea has been considered by Yonge (1967) in
terms of radial, transverse, and tangential growth components, as discussed by Owen
(1953a). As they stand, these terms are purely qualitative and have not been mathematic-
ally defined. As such they are of limited use in the discussion of shell form.

Lison (1949) described shell coiling in mathematical terms, and more recently Raup
(1966) using the same logarithmic spiral, has provided a more comprehensive scheme
for the quantitative description of shell coiling. Thus four basic parameters may be used
to define the general form of the coiled shell. These are : the shape of the generating curve
(s), the whorl expansion rate (w), the distance of the generating curve from the axis (d),

EXPLANATION OF PLATE 70

Fig. la. Chama macerophylla Gmelin, Recent, West Indies, cemented to a pebble, x 1. 16, as above,
view of right valve, X 1 .

Fig. 2. Arcinella arcinella (Linnaeus), Recent, West Indies, dorsal view showing lunule, cementation
site and prodissoconch (arrow), x 1 . 2a, as above, lateral view of right valve showing spinose
ornament on radial ribs, x 1 .

Fig. 3. Chama pellucida Broderip, Recent, California, view of inner surface of valve, showing outer
translucent calcitic prismatic layer, x 1 .

Fig. 4. Chama frondosa Broderip, Recent, West America, showing extreme development of frondose
squamae, x 1 .

Fig. 5. Gyropleura cenomanensis d’Orbigny, Cenomanian, Le Mans, France, cemented to valve of
Scabrotrigonia, X 1-25.

Palaeontology, Vol. 13

PLATE 70

KENNEDY, MORRIS and TAYLOR, Chamacea

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

381

and the rate of whorl translation parallel to the coiling axis (t) (for full details and deriva-
tion see Raup 1966). For most bivalves d is small, and in the Chamacea it is approxi-
mately zero. The shape, s, of the generating curve is difficult to define mathematically
and is not considered here.

O o s-

98 16

xxx

7

X 14 6
X X

X 19

« -EXPANSION RATE (W)

text-fig. 1. Shell geometry of the Chamacea in relation to other bivalves. Expansion rate (w) plotted
against translation rate (t) for a series of uncemented bivalves (x), cemented Chamidae (A), and the
secondarily free Arcinella arcinella (•).

Key to numbers :

1, 2. Chama imbricata (1 = upper valve,

2 = lower valve).

3. Chama plicata Sowerby. Upper valve.

4. Arcinella arcinella (Linnaeus). Both valves.

5. Fragum unedo (Linnaeus).

6. Hippopus hippopus Linnaeus.

7. Trigonia pectinata Lamarck.

8. Codakia tiger ina (Linnaeus).

9. Mytilus galloprovincialis Lamarck.

10. Chlamys varia Linnaeus.

11. Gloripecten pallium (Linnaeus).

12. Lima squamosa Lamarck.

13. Pinctada margaritifera (Linnaeus).

14. Crassatella decipiens Reeve.

15. Cerastoderma edule (Linnaeus).

16. Tellina virgata (Linnaeus).

17. 18. Chama gryphina (Lamarck). (17
lower valve, 1 8 = upper valve).

1 9. Cardita bicolor Reeve.

Accurate measurements of w and t are difficult to make in the Chamacea because of
the irregular growth form, ornament, and the corroded nature of most shells. Measure-
ments of w and t on Chama gryphina Lamarck (text-fig. 1) show that the expansion
rate of the lower valve lies between 100-5 and 100-9, and that of the upper valve is approxi-
mately 10. The translation rate of both valves is less than 1. In a specimen of Chama
plicata Sowerby, where the umbo of the lower valve is strongly enrolled, the translation
rate lies between 3-0 and 3-5 whereas that of the upper valve is less than 0-5. Measure-
ments of Arcinella arcinella (which has reverted to the uncemented mode of life) show
an expansion rate for both valves of approximately 103-5. The translation rate is almost
zero.

382

PALAEONTOLOGY, VOLUME 13

As can be seen from text-fig. 1 the expansion rate of both valves of the cemented
Chamacea is low, usually between 10 and 102. In ‘normal’ free-living bivalves such as the
Cardiacea and Veneracea, and in Ar cine /la, the expansion rate usually lies between 102
and 104.

It is clear that the translation rate of any one individual will be variable, according to
the substrate upon which original cementation took place. Some repositioning during
growth is evident in the attached valve of many individuals, with consequent changes
in the translation rate.

3. The ligament. The ligament of the Chamacea is opisthodetic, massive, external, but

The enrolment of the umbonal area causes the
ligament to be widely split towards the anterior; each
half of the split ligament curls back into the umbones
(text-fig. 2).

Three ligament layers are present, an outer thin
periostracum, a lamellar layer, and an inner fibrous
layer. The outer lamellar layer is thick and wide, and
the inner layer is calcified and aragonitic (PI. 77, fig. 1).

The ligamental splitting is more pronounced than in
other bivalves (Stasek 1963 a, b). Yonge(1967) states
that this anterior splitting is due to the rate of growth
of the ligament posteriorly exceeding the rate of growth
of the valves; this does not seem meaningful as an
explanation. The splitting is rather a result of the
interumbonal growth produced by the low expansion rate of shell coiling, coupled with
a small translation rate. The degree of splitting depends upon the translation rate, which
may be rather higher in cemented Chamacea than in the free Arcinella. A similar degree
of ligamental splitting as is seen in the Chamacea is present in GIossus (Owen 19536).

During growth of the shell the ligament elongates in a posteriorward direction.
Previously deposited sections of the ligament are overlain by the posteriorward growth
of the massive hinge plate.

DEVELOPMENT

The dissoconch stages of Chamacea show a markedly different shell form to that of the
adult.

Dissoconchs were examined on very small cemented individuals of Chama. Odhner
(1919) figured and described some precementation dissoconchs (text-fig. 3, PI. 71,
figs. 1-5). In Arcinella arcinella the large dissoconch can frequently be seen preserved
at the tips of the umbones on adult shells (PI. 71, fig. 3).

The first of the shell growth stages is the prodissoconch, formed during the veliger
stage. Part of this may be formed by the shell gland rather than the mantle edge. In
the Chamacea examined, Chama pellucida Broderip, Chama sp., and Arcinella arcinella,
the prodissoconchs (PI. 71, figs. 1-5) are highly convex, subcircular in outline,
translucent, and ornamented only by growth-lines. The form of the prodissoconch
indicates a larva either feeding entirely upon the egg yolk during the planktonic stage

often sunk into a deep groove.

text-fig. 2. Sketch of Chama bro-
deripi Reeve (with strongly enrolled
umbos), Recent, Pacific. To show
degree of ligament splitting. (Liga-
ment in black.)

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

383

(i.e. lecitotrophic), or having direct development and some sort of brood protection
(Ockelmann 1962). Yonge (1967) indicates that larval incubation could conceivably
occur in C. pellucida and C. exogyra Conrad.

text-fig. 3. Prodissoconchs and dissoconchs of Recent Chamidae. a. Arcinella arcinella (Linnaeus),
after Odhner (1919), X60. b. Chama pellucida Broderip, Recent, California, x60. c. Chama pusilla
(Odhner), after Odhner (1919), x40. d, e. Chama gryphina Linnaeus, after Odhner (1919), x60.
f. Chama sp. East Indies, x 70.

The sharp boundary between prodissoconch and dissoconch (PI. 71, fig. 2) marks the
settlement of the animal on to a substrate. The dissoconch which is secreted by the
mantle in the Chamacea is uncemented, equivalve and possesses a sculpture and mor-
phology differing from that of the adult. This stage usually lasts until the young Chama
is from 0-5 to 1-5 mm. long, but in Arcinella arcinella the dissoconch may be prolonged
until the individual is 2-5 mm. long. The dissoconch stage is terminated by cementation.

C 7619 C C

384

PALAEONTOLOGY, VOLUME 13

Dissoconch shape is somewhat variable, although a subrectangular or ovate outline
is usual (text-fig. 3). Sculpture may consist of thin, widely spaced concentric ribs, as
in Arcinella arcinella (PL 71, fig. 3), in which the outermost parts of the ribs may be
projected into small squamae. A similar ornament is seen in Chama gryphina.

‘Pseudochama’ pusilla Odhner dissoconchs have reticulate ornament (Odhner 1919);
Chama reflexa Reeve and C. jukesi Reeve dissoconchs (Odhner 1919) have radiating !
ribs. Anthony (1905) figures an unidentified Chama dissoconch with fine radiating and
concentric ribs. Chama pellucida (PI. 71, fig. 1) has an ornament of fine radiating ribs
crossed by about six larger concentric ribs. The early stages of the dissoconch in an
unnamed Chama show a peculiar pitted ornament (PI. 71, fig. 5), although the rest of
the dissoconch bears concentric ribs only (PL 71, fig. 4).

The dentition of the dissoconch is known only from Arcinella arcinella (Odhner 1919),
Chama pellucida (Dali 1903), and an unidentified species (Anthony 1905). In all of these,
two cardinals are present in each valve.

An interesting feature of the dissoconch is the subrectangular shape, with a reduced
anterior and an elongated posterior portion (text-fig. 3). It is well known that a byssate ;
existence influences the shape of bivalves (Yonge 1962); thus in the Arcacea and some
Carditidae a rectangular shape with a long ventral margin is developed. In some Cardita j
species there is a reduction in the anterior part of the animal, which is also seen in the
Mytilacea. This purely morphological evidence strongly suggests that the dissoconch
stage of some species of Chama is byssally attached prior to cementation. The presence j
of a much larger dissoconch in Arcinella arcinella suggests that the byssate existence was
prolonged in this species. Unlike most other Chamacea Arcinella arcinella inhabits |
sandy substrates, and the long precementation byssate life may be an insurance against
the choice of an unfavourable cementation site.

DENTITION AND INVERSION

Study of the dentition of the Chamacea has given rise to much controversy in the past.
The reason for this confusion is that some Chamacea can cement themselves by either
the left or the right valve. As a result of attachment by the right valve, the hinge teeth I
normally present in the left valve appear in the same number and positions in the right
valve. As Davis (1935) has pointed out, confusion arises in the interpretation of the
teeth of this family by attempting to number teeth in these reversed individuals as though
they were in a normal right valve. There are many records of species of Chama being
attached by either the left valve or the right valve, and even those species which are

EXPLANATION OF PLATE 71

Figs. 1, 2. Chama pellucida Broderip, Recent, California. 1, Prodissoconch, dissoconch and early adult
shell. Note radial and concentric ornament on dissoconch, very different from the squamaceous
ornament of the adult. Scanning electron-micrograph, x 140. 2, Detail of the sharp contact between
the larval prodissoconch and the dissoconch. Notice close bunching of growth lines as feeding ceases
prior to metamorphosis. Scanning electron-micrograph, x 700.

Fig. 3. Prodissoconch and dissoconch of Arcinella arcinella Linnaeus, Recent, West Indies showing
concentric ornamentation. Scanning electron-micrograph, x 80.

Figs. 4, 5. Prodissoconch and dissoconch of Chama sp. from East Indies. 4, Scanning electron-
micrograph, x 80. 5, Detail showing the contact between the prodissoconch and the dissoconch,
with peculiar pitted ornamentation of the dissoconch. Scanning electron-micrograph, x 340.

Palaeontology, Vol. 13

PLATE 71

KENNEDY, MORRIS and TAYLOR, Chamacea

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA) 385

usually attached by one valve sometimes show attachment by the other (Bayer 1943,
Palmer 1928, Yonge 1967). Chama calcarata (Eocene, Paris Basin) shows attachment
by left and right valves in approximately equal proportions, and this type of variation,
plus others noted above, makes the use of the generic name Pseudochama Odhner 1919
for those species attached by the right valve of very doubtful validity.

Yonge (1967) stated that it is impossible to homologize the cardinal teeth of the
Chamacea with those of other heterodont bivalves because of the great modifications
caused by ‘tangential growth’. The teeth of many recent species of Chama are indeed
greatly modified in the adult stage, and it is perhaps easier to study dentition in some of
the less modified, fossil forms. The hinge notation used here is that elaborated by Boyd
and Newell (1968) from the Steinmann notation, in which every articulating ridge,
prominence or depression of the hinge is numbered. This notation system is more objec-
tive than that of Bernard (1895) and Munier-Chalmas (1895) which requires knowledge
of the ontogenetic development within each family.

The Boyd and Newell system is flexible and is readily convertable to the Bernard
system when homologous teeth are recognized. The two valves are illustrated beak to
beak with the right valve above the left valve (following Bernard) so that the posterior
of the valves lies to the left. The notation is devised to be directly comparable with this.
The right valve hinge is expressed by the upper of two lines of symbols and, in both
lines, the symbols are arranged from left to right to reflect a traverse along the hinge
from the posterior extremity to the anterior extremity. All the structures of the articulat-
ing surfaces are indicated. The arabic numeral T represents teeth or potentially articular
ridges. Inconspicuous or dubious teeth are indicated in brackets. Depressions in the
articulating surface which generally function as tooth sockets are indicated as an ‘O’.
Vertical lines, discontinuous in doubtful cases, are used to delimit cardinal from lateral
teeth. Various letters such as ‘r’, ‘s’, ‘n’, and ‘e’ are added to represent positions of the
resilium, septum, nymph, and elastic ligament, etc.

The basic Chama dentition is Bernard’s ‘lucinoid’ type. The hinge notation of Chama
calcarata (Eocene, Paris Basin) can be expressed as shown below, and in Plate 72,

fig- 2: Olin (0) (1) 0 1 0 1

Anterior.

Right valve
Posterior
Left valve

n (0) (1) 0 10 10

n = ligament nymph

In the left valve the anterior cardinal is large and solid, and the posterior cardinal
is long and curved. In the upper right valve, the anterior cardinal is small and ill defined,
and the posterior cardinal is long and curved. They are separated by a socket for the
reception of the large anterior cardinal of the left valve. Extra articulating ridges
are developed between the posterior laterals and the nymphs. They are indicated in
parentheses.

This species can be compared with the Recent species Chama macerophylla shown
below and in Plate 72, fig. 1 :

Right valve 0 1 n 0 1 0 1

Posterior Anterior.

Left valve

1 (0) n 1 0 1 0

386

PALAEONTOLOGY, VOLUME 13

In the left valve the massive cardinal tooth is very large and grooved. The sockets for
the reception of the cardinals of the right valve have fused to form an arcuate socket
isolating the cardinal. In the right valve a comparable fusion of the two cardinals has
taken place forming a single arcuate tooth. Loss of laterals has also occurred.

In Arcinella arcinella (an inverse form) a similar notation occurs, with the fusion of
the cardinals and sockets :

Right valve
Posterior -
Left valve

n 1

0 1 0

nO

1 0 1

Anterior.

It will be shown below that the dentition of the early Chamacea shows great resemb-
lances to that of the Carditacea.

ANATOMY

Studies on the anatomy of several species of Chamacea have been made by Anthony
(1905), Pelseneer (1911), Grieser (1913), Odhner (1919), and most recently by Yonge
(1967) who studied Chama pellucida and C. exogyra. The general anatomical features
of the soft parts are summarized below.

The mantle is similar to that of most bivalves, except that the three marginal folds
are rather small. The mantle is fused by the inner fold only, to form posteriorly the inha-
lent and exhalent siphons, and at the anterior to delimit the more extensive pedal gape.
The very short siphons represent extensions of the fused inner mantle fold. Yonge (1967)
stated that the mantle dorsal to the pedal gape is fused at the inner fold and the inner part
of the middle fold. A laterally compressed flap of mantle projects between the valves
in the hinge area, forming the mantle isthmus, the termination of which secretes the
ligament. The radial musculature of the mantle, which leaves radial markings on the
inner shell surface, has been described by Jaworski (1928).

The mantle is attached to the shell by the broad, entire line of pallial muscles, and
the adductor muscles. Other, local, points of attachment on the general outer mantle
surface are described below. The adductor muscles are large and subequal. The
anterior adductor is usually the larger, and curves ventrally to occupy most of the area
immediately within the pedal gape.

The foot is small, compressed, and usually pointed. Yonge (1967) considers that the
function of the foot is to assist in the cleansing of the mantle cavity, in particular the

EXPLANATION OF PLATE 72

Fig. 1. Chama macerophylla Gmelin, Recent, Bermuda. BMNH 1911.12.21.1322.3. a. Right valve,
hinge teeth, x2. b, left valve, x2. Abbreviations: C, cardinal teeth; L, lateral teeth; n, ligament
nymph; add, adductor muscle scar.

Fig. 2. Chama calcarata Deshayes, Eocene, Lutetian, Grignon, France, a. Right valve, showing hinge
teeth, x 2. b. Left valve, x 2.

Fig. 3. Chama sp. Maastrichtian, Cotentin, France. Silicone rubber cast, x2.

Fig. 4. Chama haueri Zittel, Cretaceous, Senonian Gosau Beds, Gosau, Austria, x 0-75. b, dorsal view.

Figs. 5, 6. Ciplyella pulchra (Ravn), Cretaceous, Danian, Faxe, Denmark xl. 5, internal cast, left
valve. BMNH LI 3601. 6, anterior view, BMNH L25558.

mm

Palaeontology , Vol. 13

C

C

PLATE 72

KENNEDY, MORRIS and TAYLOR, Chamacea

. KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA) 387

area round the anterior adductor muscle. The posterior pedal retractor muscles are
attached near the dorsal end of the adductor muscle.

The ctenidia are typically eulamellibranch and have been described in great detail
by Odhner (1919). They are highly plicate, and the gill ciliation pattern is type C (1)
of Atkins (1937). The labial palps are small, and correspond to type 2 of Stasek (1963c),
in which the ventral tips of the outermost filaments of the inner demibranches are
inserted on to, and fused to, a distal oral groove. The stomach has been discussed by
Purchon (1958, 1960) who places the stomach of two species in his types IV and V
respectively. A more recent study by Dinamani (1967) places the stomach of Chama in
his type Ilia.

Other features of the gut, heart, kidneys, nervous and reproductive systems have been
described by Grieser (1913) and Odhner (1919).

GEOLOGICAL HISTORY

The generic name Chama was used by early workers for many different groups of
Cretaceous bivalves, including rudists, Exogyra, and other oysters. Pictet and Campiche
(1864-7), Stoliczka (1870), and Kutassy (1934) have removed many of these; of the
remainder, only five appear to be valid Chama species.

Chama coquandi Vidal (1877, 92, pi. 3a, fig. 1) is a remarkable Campanian species,
in need of reinvestigation. It is inequivalve, but shows no traces of a cementation area,
there is no trace of an external ligamental groove or of muscle scars on the internal
mould, and the hinge is unknown. The morphology of the valve margin (Vidal 1877,
pi. 4, fig. 6) is comparable to that seen in other Chama species.

Chama haueri Zittel (1865, 147, pi. 7, figs. 3 a-c\ see herein PI. 72, fig. 4) and C. detrita
Zittel (1865, 147, pi. 7, figs. 4 a-b) from the Gosau Beds, Austria, of Senonian age;
C. callosa Noetling (1902, 50, pi. 12, figs. 9-10) from the Upper Cretaceous of Baluchis-
tan; and C. toeroeki Petho (1906, 269, pi. 19, figs. 15-16) from the Upper Cretaceous of
Hungary are all good Chama species.

C. haueri is based on material retaining the shell, C. detrita on internal moulds. From
our knowledge of variation in other species, these are probably synonyms, the trivial
name haueri taking priority. C. callosa may also be a synonym.

All these Cretaceous forms are similar in having an ornament of concentric lamellae
(PI. 72, figs. 3, 4).

Douville (1913, 453) also records Chamidae from the Upper Cretaceous of France,
but from horizons above that of the Gosau material. We have also seen an undescribed
form from the Calcaire a baculites (Maastrichtian) of Cotentin, France (PI. 72, fig. 3).

Chama angulosa d’Orbigny (1844, 690, pi. 464, figs. 8-9), Chama gasoli Vidal (1877,
93, pi. 4, figs. 7 a-b), and C. moritzi Strombeck (1863, 156) are all species of Gyropleura.
C. spondyloides Bayle (1856, 365, pi. 14, fig. 1) is a monopleurid rudist. C. triedra Pictet
and Campiche (1867, 5, pi. 140, figs. 4-5) and C. gracilicornis Pictet and Campiche
(1867, 6, pi. 140, figs. 6-7) are both diceratid rudists. C. boulei Basse (1933, 43, pi. 7,
fig. 6) is probably a Spondylus. C. deplanata Stoliczka (1870, 235, pi. 22, fig. 5) is probably
a Plicatula. C. bifrons Griepenkerl (1899, 362, pi. 7, fig. 2), C. costata Roemer (1841,
67, pi. 8, fig. 20), C. multicostata Wegner (1905, 192, text-fig. 19), and C. geometrica
Roemer (1840, 35, pi. 18, fig. 39) are all oysters.

388

PALAEONTOLOGY, VOLUME 13

Chama cretacea d’Orbigny (1846, 689, pi. 463, figs. 1-2) is generically indeterminate,
but does not seem to be a Chama. Chama suborbiculata d’Orbigny (1822, 100), is not
figured, whilst d’Orbigny’s description is brief. It may be a Chama, but is best regarded
as a nomen dubium until re-studied.

Little is known of Chama in Danian, Montian or Thanetian rocks. Ciplyella pulchra
(Ravn) (1902, 127, pi. 4, figs. 12-15) from the Danian Koralkalk of Denmark seems to
belong to the Monopleuridae (see p. 409). Chama ciplyensis Vincent (1928, 104, pi. 5,
fig. 17) from the Danian or Montian Poudingue de Ciply of Belgium is little known.
The description of its adductor scars suggest that it is a genuine Chama. Chama ances-
tralis Cossmann (1908, 44, pi. 1, figs. 38-40) from the Montian Calcaire Grossier of
Belgium is known from two specimens only and needs reinvestigation.

In the Eocene Chama becomes much more common, being represented by such familiar
forms as Chama squamosa, C. lamellosa, and C. gigas.

Arcinel/a (type species Chama arcinella Linnaeus) is a tropical American chamid which
appears in the early Miocene of the Florida region. It is thought to be derived from the
early to middle Miocene species Chama draconis Dali (Nicol 1952).

Most of the fossil occurrences of Chama are in association with rich shallow marine
faunas of tropical or subtropical aspect.

C. exogyra and C. pellucida occur associated with cooler water faunas, as do living
members of the same species.

SHELL STRUCTURE AND MINERALOGY

Shells of more than thirty species of recent and fossil Chamidae were examined in
connection with this work.

Mineralogical determinations were carried out by means of standard X-ray diffraction
techniques. Optical examinations of shell structure were made on shell interiors, fractured
sections, acetate peels of polished and etched sections (method in Kummel and Raup
1965), and petrographic thin sections.

Fine structure was studied on surfaces, fractured and polished and etched sections,
which were examined with a Cambridge Instrument Company ‘Stereoscan’ scanning
electron microscope.

The shell of most species examined is wholly aragonitic, with a two-layered shell.
Exceptions are Chama pellucida and Chama exogyra which have an additional outer
prismatic calcite layer. The significance of this is discussed below.

The results of our observations are summarized in Table 1. It will be seen that we
use the terms inner, middle, and outer shell layers. This is an entirely topographic, and
thus unambiguous division. We reject Oberling’s (1964) use of the terms ectostracum,
mesostracum, and endostracum for three-layered shells, mesectostracum and mesendo-
stracum for two -layered shells as this implies homology between layers in different
shells. It further suggests that two-layered shells may be derived from three-layered
forms.

As well as speaking of shell layers, we have adopted Oberling’s (1964) term myostra-
cum for the peculiar blocky prismatic aragonite laid down under sites of muscle
attachment, i.e. the pallial, pedal, and adductor myostraca.

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

389

(a) Structure of the crossed-lamellar layer. Crossed-lamellar structure forms the outer
shell layer of most species (text-fig. 4), but the middle layer of Chama pellucida and C.
exogyra (text-fig. 5).

Conventional microscopy shows the inner surface of the shell layer as a series of
elongate, branching, interdigitating lenses. These lenses are arranged with their long axes
running concentrically, i.e. essentially parallel to the shell margin over most of the shell.

text-fig. 4. (a) Transverse section, (b) longitudinal section, and (c) interior of Chama
macerophylla Gmelin to show distribution of shell layers.

More variable orientations are developed on spines, squamae, and in the umbonal
region. These lenses correspond to the outcrop of the first order lamels of Boggild (1930).

In section first-order lamels run normal to the inner surface of the shell layer (PI. 73,
fig. 1). Traced towards the shell exterior they twist and turn however, producing com-
plicated patterns. The first-order lamels branch and interdigitate in sections in much the
same way as they do on shell interiors. A strong, interlocking structure is thus produced.

First-order lamels are up to several millimetres long and of the order of 0-5 mm.
thick. Sections and peels show a striking colour banding, adjacent lamels being straw-
yellow or red-brown in colour.

Within each first-order lamel (text-fig. 6b) there are sheet-like second-order lamels
(Boggild 1930). These are in turn built of minute laths, about 1 g. in diameter and some

390

PALAEONTOLOGY, VOLUME 13

tubules in

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (B1VALVIA)

391

o

I

1

: and mineralogy <

: and fossil Chamacca

Chama selseiensis
S. V. Wood

Myoslraca
Prismatic Prismatic

Prismatic Prismatic

Crosscd-lamcllar

Crossed-lamcllar

Myostracal pillars in the
layer; scattered myo-

layer. Tubules in inner
layer

Tubules in inner layer

Myostraca

Specie Horizon and locality Mineralogy Outer layer Inner layer Pallial Adductor Observations

Arcinella arcinella Pliocene, Caloosa- Crossed-lamellar Complex crossed-lamellar Prismatic Prismatic

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA) 393

394

PALAEONTOLOGY, VOLUME 13

text-fig. 5. (a) Longitudinal section and (b) interior of Chama pellucida
Broderip to show the distribution of shell layers.

EXPLANATION OF PLATE 73
All sections are acetate peels.

Fig. 1. Outer crossed-lamellar layer of Arcinella arcinella (Linnaeus), showing first-order lamels
aligned normal to the shell interior in the inner part of the layer (lower), and the ‘bladed’ outer part
where they are aligned parallel to the shell interior. Radial section, x 32.

Fig. 2. Radial section inner complex crossed-lamellar layer of Chama calcarata Deshayes showing cone
shaped depressions in myostracal sheets, x 32.

Fig. 3. Planar section through the adductor myostracum of Chama lazarus Wood, X 100.

Fig. 4. Contact between the outer crossed-lamellar layer (left) and the adductor myostracum of
Chama radians Lamarck, radial section, x 80.

Fig. 5. Myostracal pillars in the inner, complex crossed-lamellar layer of Chama radians Lamarck.
Radial section, x 80.

Fig. 6. Radial section of the inner complex crossed-lamellar layer of Chama lazarus Wood, X 20.

Fig. 7. Myostracal sheets in the inner complex crossed-lamellar layer of Chama lamellosa Lamarck,
x 80.

Fig. 8. Contact between the outer, prismatic, calcitic layer (top) and the middle aragonite crossed-
lamellar layer of Chama pellucida Broderip, X 80.

Fig. 9. Planar section of the outer prismatic, calcitic layer of Chama pellucida Broderip, x 80.

Palaeontology, Vol. 13

PLATE 73

KENNEDY, MORRIS and TAYLOR, Chamacea

395

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

tens of microns long, joined in side-to-side contact. These sheets of laths, i.e. second-
order lamels, he normal to the sides of the first-order lamels, the long axes of the laths
being paralleTto the plane of the first-order lamels.

microstructure of the crossed-lamellar layer (b), pallial myostracum (c), complex
crossed-lamellar layer (d), and myostracal pillars (e).

Second-order lamels are inclined to the shell interior, with opposite inclinations of
dip in adjacent first-order lamels. Optical work suggests that the whole layer is built of
crystallites with only two crystallographic orientations.

These observations are summarized in text-fig. 6b. Fine structure is shown in Plate
74, fig. 1.

As well as the carbonate, there is a well-developed proteinaceous organic matrix in
the crossed-lamellar layer (PI. 74, fig. 2). This is intimately associated with the carbonate,
surrounding each lath of the crossed-lamellar structure. Unlike the regular, fenestrate
sheets of nacre organic matrix (Gregoire 1957, 1959, 1960, 1967), crossed-lamellar matrix
has a much more open, irregular structure.

396

PALAEONTOLOGY, VOLUME 13

The variation in attitude of first-order lamels seen in sections is a result of their growth
normal to the secreting surface, i.e. the marginal parts of the mantle. Where this is
variable in form, as in ribs, or in the reflected margin of Arcinella, irregularities will
develop. Indeed, in Arcinella, growth of lamels normal to the surface of the margin
produces a structure which superficially resembles the composite prismatic structure
developed in the Lucinacea (PI. 73, fig. 1).

(b) Structure of the complex crossed-lamellar layer. Complex crossed-lamellar structure
forms the inner shell layer of all Chamacea. We use ‘complex crossed-lamellar’ in the
original sense of Boggild (1930). It is thus equivalent to ‘complex’ structure of Oberling
(1964), which is not to be confused with ‘complex’ of Boggild (1930)!

This shell structure type is built of the same basic building blocks as crossed-lamellar
structure, i.e. minute laths (Text fig. 6d). Instead of building first-order lamels, the laths
build much more irregular blocks (PI. 73, fig. 6; PI. 74, fig. 3), and many different
attitudes and orientations of laths are present within the layer.

In some sections, small irregular patches of radiating laths are recognizable. Mac-
Clintock (1967) has described these as sections of spherulitic growth. His patelloid
structures are, however, different in detail from structures present in bivalves.

(c) Structure of the prismatic layer. An outer, calcite prismatic layer is present in two
recent species of Chama, C. pellucida, and C. exogyra. The occurrence in C. pellucida
has been noted by previous workers (Lowenstam 1954 a, b, 1963, 1964; Kennedy
and Taylor 1968), but the present record from C. exogyra represents only the second
occurrence of calcite in extant bivalves other than the Pteriomorpha.

However, matters are far from simple in respect of these two species.

Examination of the type specimens of C. exogyra and C. pellucida (in the collections
of the British Museum (Natural History)) shows that the specimens appear distinctive.
C. pellucida is rounded in outline, is ‘normal’ (i.e. attached by the left valve), and bears
striking translucent squamae. C. exogyra is irregular, elongate, reversed (i.e. attached
by right valve), and lacks conspicuous squamae. Other specimens of C. exogyra we
have examined show rather more conspicuous ridges, and are ‘normal’ — attached by
the left valve. These normal specimens closely resemble C. pellucida, whilst reversed
C. pellucida closely resembles C. exogyra.

These similarities, the identical and highly unusual mineralogy and structure, together
with the similar geographical range of the two species (Yonge 1967) plus the problems

EXPLANATION OF PLATE 74
All figures are scanning electron-micrographs.

Fig. 1 . Polished, etched (HC1) radial section of the middle crossed-lamellar layer of Chama pellucida,
showing three adjacent first-order lamels, X 700.

Fig. 2. As above, showing contact between the outer prismatic layer (left) and the middle crossed-
lamellar layer; notice the lace-like organic matrix network, x 700.

Fig. 3. Fractured section of the inner complex crossed-lamellar layer of Chama radians, showing laths
joined into second-order lamels having variable orientations, x 240.

Fig. 4. Inner shell surface of Chama radians, showing the outcrop of myostracal prisms, x 1,100.

Fig. 5. Polished, etched (HC1) radial section of the outer prismatic layer of Chama pellucida, x 700.

Fig. 6. Inner shell surface of Chama radians showing the opening of a tubule, x 2,250.

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KENNEDY, MORRIS and TAYLOR, Chamacea

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA) 397

of inversion in the Chamacea generally, have led us to suspect that these species may be
synonymous. This is, however, a field problem, which we cannot resolve on the basis of
material available to us.

In both species the structure of the outer prismatic layer is very similar, and different
from that occurring in all other extant bivalves. In hand specimen, the layer has a
distinctive, translucent, ‘pellucid’ appearance (PI. 70, fig. 3).

In peels and thin sections (PI. 73, figs. 8 and 9) it appears grey against the browns and
yellows of the adjacent crossed-lamellar layer. It is built up of minute, irregular, blade-
like prisms, which are orientated more or less normally to the mantle and shell interior
at the time of secretion. The prisms are rather variable in their attitude (in part as a
result of their being involved in ribs and squamae), and are arranged into blocks with
irregular polygonal outlines (PI. 73, fig. 8). These larger blocks pass into extinction quite
irregularly, and there is thus no uniformity of attitude within the blocks.

These observations are confirmed by electron-microscopy. In fractured sections, the
large prism blocks show prominent transverse striae, and are clearly built up of smaller
units (PI. 77, fig. 2). Etching brings out these smaller units (PI. 74, fig. 5), which cor-
respond to the fine prisms seen at optical level. These fine prisms are surrounded by
sheaths of organic matrix, but there are no thick conchiolin sheets such as characterize
the .other prismatic calcite layer of Pinna, Pinctada, and many other bivalves.

(d) Structure of the myostracal layers. These layers show similar features in all Chamacea
we have examined. At optical level (PI. 73, figs. 3, 4, 5, 7) myostraca are a characteristic
grey colour, contrasting with the adjacent shell layers. The myostraca are built up of
prisms, with highly irregular outlines. These prisms are orientated with their long axes
normal to the surfaces of the myostracum, with crystallographic axes lying in the same
direction (text-fig. 6c). There are no well-developed interprismatic protein walls, but
thin organic matrix envelopes surround each prism.

The pallial myostracum is a thick sheet, extending into the umbo (text-fig. 6a). The
adductor myostraca are thick, well-developed pads. In addition to these features, areas
of myostracal structure are present in the Chamacea away from well-authenticated areas
of muscle attachment. Sheets of myostracal-type prisms are present within the inner
shell layer of many species, and represent interruption of deposition of normal shell
fabric (PI. 73, fig. 7). This may be due to periodic attachment of the mantle surface, but
there is no direct evidence for this, although structure and fluorescence properties are
identical with those of normal myostracum. Pillar-like areas of myostracal structure,
called myostracal pillars (Taylor, Kennedy, and Hall 1969) occur in the inner layer of
most species of Chamacea and in the crossed-lamellar layer of a few species (Table 1).

These pillars appear in sections as elongate ovoids or strips of myostracal structure,
the long axes running normally to the shell interior (PI. 73, fig. 5). In the inner layer they
usually extend upwards from the pallial or adductor myostracum (text-fig. 6e ).

On shell interiors, myostracal pillars outcrop as minute bosses, usually O5-T0 mm.
in diameter, or as elongate ovals, often arranged in lines radiating from the umbo.

Electron-microscopy shows that the surfaces of the bosses consists of a series of irregu-
lar prisms, corresponding to those seen at optical level (PI. 74, fig. 4). The prisms are
separated by grooves, of uncertain origin.

Sections of the mantle of Chama jukesii reveal the presence of minute papillae all over

398

PALAEONTOLOGY, VOLUME 13

the mantle surface, corresponding in size and distribution to the myostracal pillars of the
shell. These papillae result from elongation of the normal mantle cells, and we take them
to be sites of additional shell and mantle attachment.

A peculiar modification of the sheets of myostracal type prisms present in the inner
shell layer is seen in Chama calcarata and Chama gigas. Here, the inner surface of the
inner shell layer is pitted. These pits correspond to depressions in the surfaces of the
myostracal sheets (PI. 73, fig. 1), and presumably reflect another mode of shell/mantle
attachment.

( e ) Layer contacts. Crossed-lamellar and complex crossed-lamellar layers are separated
by the pallial and adductor myostraca. There is usually a transition zone at the layer/
myostracum contact, rich in organic matrix. The organic matrix of the myostracum and
the crossed-lamellar or complex crossed-lamellar layers is in structural continuity. There
is often a complex interdigitation of adductor myostracum and shell layers (text-fig. 4 a).
This is probably the result of slight shifting of the animal within its shell during growth.

The contact of the crossed-lamellar layer and the outer prismatic layer of C. pellucida
and C. exogyra shows several unusual features (PI. 73, fig. 8). The surface at contact is
minutely corrugated, the corrugations apparently originating at the shell margin, as a
reflection of the position of the pallial muscles. They are subsequently buried below the
middle layer, filled by a thin zone of fine-grained aragonite, rich in organic matrix
(PI. 74, fig. 2). Elsewhere, this layer is replaced by a complex and irregular junction with
minute angular crystals protruding into the crossed-lamellar layer, as though a highly
irregular surface was grown over by crossed-lamellar structure. These relationships
closely resemble the results of partial recrystallization of aragonite to calcite.

The organic matrix of prismatic and crossed-lamellar layers is in direct structural
continuity.

(/) Tubules. Many species of Chamacea possess the remarkable shell feature which
Oberling (1964) described as tubules (PI. 74, fig. 8).

These are minute cylindrical perforations, only a few microns in diameter, which
open at the interior surface of the shell and penetrate the shell layers. Tubules are a
primary feature of the shell (Oberling 1964; Taylor, Kennedy, and Hall 1969), and
appear as minute hollow cylinders penetrating the finest elements of the shell fabric
(PI. 74, fig. 8). On the shell interior, Chama tubules lie in minute pits. The function of
tubules is at present unknown.

(g) Ligament. The ligament of the Chamacea is calcified and aragonitic, as in other
bivalves with calcified ligaments (Lowenstam 1964; Taylor, Kennedy, and Hall 1969)
(PI. 77, fig. 1).

(h) Banding. All shell layers show prominent daily growth bands (Panella and Mac-
Clintock 1968).

COMPARISON OF THE CHAMACEA WITH OTHER GROUPS

The systematic position of the Chamacea has always been in doubt. Consideration of
their affinities in the past was not helped by the allotment to this superfamily of several
other cemented bivalves such as the rudists and the pandoraceans, Cleidothaerus and

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

399

Myochama. However, as it stands today, the superfamily Chamacea can be considered
a homogeneous group.

The Chamacea have been related to the Lucinacea (Douville 1912, Nicol 1952),
Carditacea (Dali 1903), the Cardiacea (Anthony 1905), Crassatellacea (Boehm 1891),
Veneracea (Fischer 1886), and to the Hippuritacea (see references in Odhner 1919,
Newell 1965, Yonge 1967). Of all these possibilities that of relationship to the rudists is
the most commonly held. Odhner (1919) came to this conclusion after a detailed study
of Chama , and Cox (1960) in deference to the thoroughness of Odhner’s work accepted
the conclusion but thought they should constitute a separate superfamily.

The similarities of the Chamacea to the various superfamilies listed above are dis-
cussed below. A summary of some of the more easily tabulated characters of possible
relatives amongst living bivalve superfamilies is given in Table 2. The affinities with the
extinct rudists are more difficult to examine because of the lack of soft parts, but
Yonge (1967) has made certain inferences concerning rudist soft parts based on a study
of the inner shell morphology.

1. Comparison with the Carditacea

Two distinct groups can be recognized within the Carditacea.

(a) The Venericardia group, which are burrowers with generally rounded shell outlines.
The hinge plate is short and high, and the ornamentation usually consists of radial ribs.

(b) The Cardita group, consisting of byssate forms, ovoid to subrectangular in outline.
The hinge plate is usually elongate and the anterior adductor muscle is somewhat
reduced. The ornament is usually of radial ribs, but some species can produce squamae.
This group contains many tropical species associated with coral reefs and rocky
shores.

It is to this second group that the Chamacea may be compared. As can be seen from
Table 2 some soft part characters such as the degree of mantle fusion and the gill
plication are different, but others, such as labial palps and stomach types, are
similar.

The greatest similarity between the Chamacea and the Carditacea is seen in shell
characters such as the shell structure, dentition, ornament, and the similarity of the
uncemented dissoconch of Chama to the adult byssate Cardita.

Thus the outer shell layer of the Carditacea consists of crossed-lamellar structure,
with rather fine first-order lamels. The inner layer is built up of complex crossed-
lamellar structure. Myostracal pillars are present in most species; in some the pillars
are confined to the inner layer but in others they occur in both layers. Myostracal-type
prisms can also be present, as fine sheets interbanded with complex crossed-lamellar
structure in the inner layer. Tubules were present in all the species we have examined.

The dentition of the Carditidae shows striking similarities to that of the Chamacea.
Both families have a ‘lucinoid’ dentition. The notation for Cardita variegata Bruguiere,
Recent, Seychelles is:

Right valve n 0 1 0 1 0 I 1

Posterior 1 Anterior

Left valve

C 7619

n 0 1 0 1 | 0 1
d d

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

401

IS KS

I

l

z

2

402

PALAEONTOLOGY, VOLUME 13

and for Cardita tenuicosta Sowerby, Cretaceous (Albian), Gault, Folkestone (PI. 75,

% 1)

Right valve
Posterior
Left valve

1 0 1 n

0 1 0

0 1 0 n

0 10 1

Anterior.

If these are compared with that of a relatively unmodified Chama from the Eocene,
striking similarities are seen. The subsequent modification of the teeth in Chama has
been associated with the cemented habit. Both early Chama and recent Cardita have one
stout anterior cardinal and a long arcuate posterior cardinal.

Radial ribbing is the most frequent ornamentation pattern of Carditidae but some
byssate species such as Cardita crassicostata Reeve can develop large squamae (PI. 75,
fig. 4). Many Cretaceous species such as Fenestricardita fenestrata (Forbes) (PL 75,
fig. 6) have a reticulate ornament. Cardita distorta Reeve, a Red Sea species which lives
byssally attached amongst coral, has become inequivalve and very Chama- like in
appearance (PI. 75, fig. 5).

The external opisthodetic ligament of the Carditidae is frequently sunk between the
dorsal valve margins. A similar condition is seen in several heterodont superfamilies,
including the Chamacea.

The dissoconch of the Chamacea shows striking resemblances to the byssate Cardi-
tidae (text-fig. 3, PI. 71, fig. 1) both externally and internally, including the dentition.
These similarities could, however, be morphological convergence as the result of the
byssate attachment.

Certain adult Cretaceous carditid genera show a remarkable similarity in morphology
to the dissoconchs of some Recent Chama species. For instance Fenestricardita fenestrata
(Forbes) (PI. 75, fig. 6), Aptian, England, while being a typical carditid shell shape has an
ornament very similar to that shown on many Chama (PI. 71).

The less-common Trapezicardita (Casey 1961, p. 581 ; Keeping 1883, pi. 6, figs. 5 a and b\
Woods 1907, p. 148, pi. 28, figs. 12-15) from the Upper Aptian of England, has the
same ornament. More interestingly it has the shell shape of the Recent byssate Carditidae.
It is possibly these or similar carditids that are the ancestors of the Chamacea.

2. Comparisons with the Lucinacea

Douville (1912) proposed that the Chamacea were derived from the Lucinacea during
the late Cretaceous. This view was supported by Nicol (1952) on the basis of shell
morphology.

EXPLANATION OF PLATE 75

Fig. 1. Cardita tenuicosta Sowerby, Cretaceous (Albian), Gault, Folkestone, England, a, right valve
showing hinge teeth; b, left valve. Both x4.

Abbreviations: C, cardinal teeth; L, lateral teeth.

Fig. 2. Cardita beaumonti var. amelliae d’Archiac, Upper Cretaceous, Ga’ara, Ruthbah, Iraq. Right
valve, BMNH LL22245; xO-75.

Fig. 3. Mytilicardia crassicosta Lamarck, Pleistocene, Limestone creek, Gleneig River, Victoria.
BMNHL6570, Xl.

Fig. 4. Mytilicardia crassicosta Lamarck, Recent, New Holland. Left valve, X 2.

Fig. 5. Cardita distorta Reeve, Recent, Red Sea. a. Type, BMNH 1963686/2, X 1-5. b, Dorsal view.
Fig. 6. Fenestricardita fenestrata (Forbes) Cretaceous, Aptian, Sevenoaks, England. Left valve, BMNH
L23280, <3.

Palaeontology, Vol. 13

PLATE 75

KENNEDY, MORRIS and TAYLOR, Chamacea

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA) 403

This apparent resemblance between the Lucinacea and the Chamacea is well seen
only in Arcinel/a. Some Lucinacea have a groove on the posterior part of the exterior
of the shell running from the umbo to the postero-ventral margin. This is reflected on
the inside of the shell as a low ridge at the anteriorward termination of the posterior
adductor muscle scar, and is present at the shell margin as a slight nick. A similar groove
on the exterior surface is seen in some Chamacea, although it is often obscured by the
irregular surface ornament. The function of this exterior groove and internal ridge is
uncertain, but it may be associated with the insertion of the posterior adductor muscle.

In many Lucinacea and a few species of
Chama the ventral end of the anterior adduc-
tor muscle scar is detached from the pallial
line (text-fig. 7) and extended in an anterior
direction. Allen (1958) has shown that in
the Lucinacea the elongate anterior adductor
muscle is ciliated, and serves as a pre-
liminary sorting area for food particles
brought in by the anterior inhalent current.

This anterior inhalent current is peculiar to
the Lucinacea. In the Chamacea however,
both inhalent and exhalent siphons are situ-
ated at the posterior end. Yonge (1967) has
described how the foot of Chama pellucida
protrudes and moves dorsally along the outer
surface of the anterior adductor muscle, as
in other cemented genera, assisting in the
cleansing of the anterior mantle cavity.

The elongation in this instance is thus possibly related to the facility of mantle cleansing.

As can be seen from Table 2 the labial palps, gill type, and gill cilia of the Lucinacea
differ from those of the Chamacea, while they have the anterior inhalent current. Some
species have a small posterior exhalent siphon which, although formed by fusion of the
inner mantle fold, has a unique inversion retraction mechanism.

The shell of the Lucinacea consists of three layers. There is an outer composite pris-
matic layer, a middle crossed-lameller layer, and an inner complex crossed-lamellar
layer. This arrangement has been present since the Lower Lias (as in Lucina limbata
Terquem and Piette) at least. Myostracal pillars are not found, although thin sheets of
myostracal-type prisms may be present in the inner layer. Tubules are very rare; we have
found them only in the genus Codakia. Here, tubules, larger and sparser than in other
bivalve groups, are found penetrating the inner shell layer only.

The dentition is primitively ‘lucinoid’ but many Lucinacea have lost teeth, and some
are edentulous. The hinge notation for Lucina pensylvanica Linnaeus and Codakia
punctata (Linnaeus) are given below:

Lucina pensylvanica (Linnaeus)

text-fig. 7. Diagram of the anterior adductor
muscle pad and pallial line of (a) Codakia
punctata Linnaeus and (b) Chama macerophylla
Gmelin to show the comparable detachment of
the ventral end of the muscle pad in the
Lucinacea and Chamacea.

Right valve
Posterior
Left valve

0 10]

[ n

(1) 0 1 (0) (1) 0 1

0 1 0

1 0 1

n

0 1 0

1 0

1 0 1

Anterior.

404

PALAEONTOLOGY, VOLUME 13

Codakia punctata (Linnaeus)

Posterior
Left valve

; (1) ne nc nc

1 0 1

1 0

(1) (0) (1) ne nc nc

(1) 0 1 (0)

1 0 1

ne = ridge-bearing elastic ligament,
nc = ridge-bearing calcified ligament.

Anterior

This pattern shows similarities to the Chamacea but also to the Carditacea.

All living species of Lucinacea are burrowers, and fossil forms seem to have been so
since the Ordovician (McAlester 1965). Shell ornament varies from fine concentric
growth-lines to radial ribs or a reticulate pattern. The sculpture is always fairly subdued.

3. Comparisons with the Crassatellacea

The superfamily Crassatellacea is divided into three families, the Crassatellidae,
Astartidae, and Cardiniidae. The first two families are extant but the latter family became
extinct during the Jurassic.

The Astartidae and Crassatellidae show rather different characters, and Boyd and
Newell (1968) have suggested that the Crassatellacea may have had a diphyletic origin.

Both the Crassatellacea and the Astartacea have a two-layered shell. The outer layer
of both consists of crossed lamellar structure. The inner layer of the Crassatellacea is
homogeneous, whereas that of the Astartacea is made up of ‘myostracal type’ prisms
with only small traces of complex crossed-lamellar structure. The shell structure charac-
ters of the Astartidae have been present since the Lower Jurassic.

The dentition of the Crassatellacea has been related to both the ‘lucinoid’ and ‘cyrenoid’
patterns. Boyd and Newell (1968) have recently re-examined the dentition of this super-
family. They find that recent examples of Crassatellidae and Astartidae have rather
similar hinges. For the crassatellid Hybolophus speciosus (Adams) the notation is:

Right valve
Posterior
Left valve

1 0 (1) e r

10 10 1

1 0 1

10 1 e r

(0) 1 0 1 0

(1)0 1

e = elastic ligament,
r = resilifer.

Anterior

For Astarte castanea Say:

Right valve
Posterior
Left valve

1 0 (1) n

1 0 1 0(1)

1 0 1

10 1 n

0 1 0 1 (0)

(1)0 1

Anterior.

Thus both examples have rather more complex hinge teeth structures than any of the
early Chamacea.

The ligament of the Astartidae is external and opisthodetic but in the Crassatellidae
there is an internal resilium.

The sculpture of both families is concentric, frequently with raised costae but they
are often smooth or concentrically striate. Radial sculpture is never developed.

Members of both the Crassatellidae and Astartidae are shallow burrowers.

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

405

4. Comparison with the Cardiacea

The Chamacea were considered to have arisen from the Cardiacea by Anthony
(1905). His evidence was based primarily upon the ctenidia and the hinge teeth.

It can be seen from Table 2 that although the main shell layers in the Chamacea and
Cardiacea are similar, neither tubules nor myostracal pillars are developed in the latter.

Cardiacean dentition is of a ‘lucinoid’ pattern, but with well-developed laterals as
well as the usual cardinals. The development of these widely spaced laterals is a charac-
teristic of the group. The hinge of Acanthocardia aculeata (Linnaeus) can be expressed as :

Right valve
Posterior
Left valve

and Fragum unedo (Linnaeus)

Right valve
Posterior
Left valve

1 0 1 (0) n

10(1)

1 0 1

1 0 1 n

0 1 0

1 0

10 1 n

0 1 0

10(1)

1 0(1) n

1 0 1

10 10

Anterior

Anterior.

A hinge which, contrary to the opinion of Anthony (1905), is not like that of Chama.
The ctenidia of the Cardiacea, although similar to those of Chama, show similarities
to several other heterodont groups (Table 2).

All recent species of Cardiacea are shallow burrowers, although the Eocene genus
Lithocardium which gave rise to the Tridacnacea was in all probability a byssate form.

The first Cardiacea appeared in the Upper Trias and have been distinct since, early
members appearing morphologically very like Recent species.

5. Comparison with the Veneracea

The Chamacea were related to the Veneracea by Fischer (1887), who considered that
the dissoconch stage of Arcinella showed similarities of external sculpture to the adult
Venerupis.

Table 2 shows that many of the anatomical characters of the Veneracea are quite
different from those of the Chamacea. The stomachs according to the classification of
both Purchon (1958, 1960) and Dinamani (1967) are quite different. Mantle fusion is
much more extensive in the Veneracea, fusion being by way of the inner mantle folds
and the inner surface of the middle fold. Well-developed siphons are formed from these
regions of the mantle.

The dentition of the Veneracea is typically of the ‘cyrenoid’ pattern, with three car-
dinals in each valve. This is an altogether more complex dentition than that found in
the Chamacea. The notation of Callistina plana (Sowerby) from the Albian is :

Right valve
Posterior
Left valve

n 01010101

o

o

S;

n 0 1 0 10 10

10(1)

Anterior

406

PALAEONTOLOGY, VOLUME 13

and Notochione columbiensis (Sowerby), Recent, Ecuador :

Right valve
Posterior
Left valve

(n)

(0) (1) 0 10 10 10

n

(1) 0 1 0 1 0

Anterior.

The Veneracea have an outer crossed-lamellar shell layer and an inner layer usually
consisting of homogeneous structure, although in some species it is complex crossed-
lamellar. The outer layer shows certain distinctive characters. Because the shell margin
is frequently reflected, the first-order lamels of the outer part of the crossed-lamellar
layer are arranged radially. They become arranged concentrically when traced inwards,
and appear vertical in radial section. Frequently they grade into homogeneous structure
at the shell interior. The outer layer thus appears to be built of three distinct shell
structures. Both tubules and myostracal pillars are absent.

Most members of the Veneracea are burrowers, and a pallial sinus is developed
in many species. However, some species such as Gafrarium can under unfavourable
conditions, become byssate.

The ornamentation of the shell is mainly concentric, but reticulations, spines and
squamae can be developed.

6. Comparison with the rudists

It is generally thought that the origin of the rudists lies in the Megalodontacea, a
Silurian to Lower Cretaceous group of pachydonts, one of which, Pachyrisma (Lower
to Upper Jurassic), became cemented, and gave rise to Diceras (Oxfordian to Tithonian)
and subsequently the rest of the rudists (Cox 1933, Dechaseaux 1952).

Derivation of the Chamacea from the Hippuritacea (Turonian to Maastrichtian) and
Radiolitidae (Aptian to Maastrichtian) is unlikely. These forms, with their extensive
changes in symmetry, the massive conical lower valves and lid-like upper valves, the
porous calcitic shell layers, and the atrophied ligaments, are morphologically too diver-
gent to be considered the ancestors of the Chamacea. Similar arguments can be applied
to the Caprinidae (Aptian to Maastrichtian).

Greater resemblance to the Chamacea is shown by the Monopleuridae, Diceratidae,
possibly the Requinidae, some Caprotinidae, and the Megalodontacea.

(a) Megalodontacea. Members of this family were uncemented, and considering the
reduction of the anterior part of the shell, were apparently byssally attached.

The shell structure of some well-preserved examples was examined. Examples of
Megalodon pumilis Benecke and Pachymegalodon crassus Bohm from the Lower Lias
of Valle del Paradiso, Crezzana, Italy, showed a two-layered aragonitic shell, with an
outer homogeneous layer and an inner homogeneous to complex crossed-lamellar layer.
The two layers are separated by the prismatic trace of the pallial myostracum. Some
thin sheets of myostracal type prisms are present in the inner layer. Specimens of Durga
trigonalis Bohm, from the Lias near Verona, Italy, are badly recrystallized, but show
what was an originally wholly aragonitic shell with two homogeneous layers separated
by the trace of the pallial myostracum.

The hinge teeth of Megalodontidae show the pachydont condition, with massive
cardinals, the notation for Eumegalodon cucullatus (J. Sow.) and Pachyrisma grande
(Morris and Lycett) is shown below and in Plate 76, fig. 4; Plate 77, fig. 3.

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA)

407

Eumegalodon cucullatus :

Right valve
Posterior
Left valve

(1)0 1 n

0(1 010101010 1)0

0 1 (0) n

1 (0 1 0 1 0 1 0 1 0 1 0) 1

Anterior.

The traces of small teeth and sockets (bracketed above) between the two large teeth
of the left valve are remnants of an original actinodont condition.

Pachyrisma grande :

Right valve
Posterior
Left valve

1 0 n

(0) 1 0 1

(1)0 1

0 1 n

0 1 0

0 1

Anterior.

In these early derivatives of the actinodonts the ligament and its nymph are basically
dorsal to the hinge teeth. Although the dentition appears to be disrupted into cardinals
and laterals it is a modified actinodont dentition. The apparent cardinals and laterals
are not necessarily homologous with those found in the veneroid type of heterodont
dentition.

As is the case with the other rudist families discussed, this is a typical pachydont
dentition with a reduced number of large cardinal-like teeth often with their greatest
dimension vertical in relation to the plane between the valves.

Both species show a rather more complex notation than that of early Chamacea.
Furthermore, the arrangement of the more massive teeth seen in this family is very
distinctive.

(b) Diceratidae. This family can be derived directly from the Megalondontacea ; changes
in the geometry, dentition, and musculature result from the acquisition of the cemented
habit.

The dentition is simplified from the megalodontid pattern of Pachyrisma. The smaller
anterior teeth are lost. The large tooth in the left valve and the two large teeth in the
right valve become larger, longer and twisted. These changes are reflected externally
by the exogyriform shape of the shell.

The notation of Diceras arietum Lamarck is shown below and in Plate 76, fig. 1.

Right valve 1 0 n j 1 0 1

Posterior j- Anterior.

Left valve 0 1 n j 0 1 0

We have not found any specimens of Diceras well enough preserved to determine the
original shell structure.

The rudists were cemented by either the right or the left valve and evolved a virtual
inversion of dentition in later forms. Some later forms attached by the left valve have
a single tooth in that valve and two teeth in the right valve, while forms attached by the
right valve have one tooth in the right valve and two in the left valve. It is this point of
resemblance with the Chamacea which has most impressed palaeontologists and zoolo-
gists. However, early ribbed oysters could be attached by either valve, but later oysters

408 PALAEONTOLOGY, VOLUME 13

are attached only by the left valve. It would thus seem that cementation by either valve
may be a characteristic of the early history of cementation within a group. Resemblance
of Diceras to the Chamacea is thus purely coincidental.

(c) Requieniidae. This family shows certain features (such as the hinge teeth) in common
with the Diceratidae, but additional modifications such as siphonal bands and accessory
cavities appear.

Moderately unaltered specimens of Apricardia toucasi (d’Orbigny) from the Lower
Campanian of Var, France, show an outer, calcitic prismatic layer, and middle and
inner aragonitic homogeneous layers. Thin prism sheets are seen in the inner layer.

( d ) Caprotinidae (Neocomian-Turonian). Many species in this family are small and
exogyriform with an ornament of radial ribs. Together with the Monopleuridae they
show the closest morphological resemblance to Chama among the rudists.

Material sufficiently unaltered for shell structure studies was not available, but it seems
that Caprotina semistriata (d’Orbigny) from the Cenomanian of Le Mans had an outer
calcitic layer and an inner aragonitic layer or layers.

The pattern of teeth has changed from that of Diceras by a foreshortening of the
hinge plate, increase in size of the posterior tooth in the left valve, near atrophy of the
ligament, and loss of the anterior tooth in the right valve. These changes are associated
with the reduction of the free valve to a cap-shaped or opercular form. The notation can
be expressed as below :

Right valve (fixed) 010 1 0

Posterior Anterior.

Left valve (free) 101 0 1

The position of the ligament in Caprotina is indicated by an infolding of the shell wall,
marked by a shallow groove on the outer surface. The ligament is disposed vertically in
relation to the valve commissure, so that the functional distance is therefore very short.
It is doubtful whether the ligament in this case was a very effective mechanism for the
opening of the valves. No comparable ligamental structure is found in the Chamacea.

EXPLANATION OF PLATE 76

Fig. 1. Diceras arietum Lamarck. Jurassic (Oxfordian), Chatel-Censoir, Yonne, France, BMNH
L33915, xl. o, right valve, b, left valve.

Fig. 2. Caprotina semistriata (d’Orbigny). Cretaceous, Cenomanian, Le Mans, France, x 2. a, left (free)
valve. BMNH L96200. b, right (cemeted valve) BMNH L96203.

Fig. 3. Eumegalodon cucullatus (J. Sowerby). Devonian, Paffrath, Cologne, Germany. X2. a, right
valve; b, left valve. Abbreviations: C, cardinal; L, lateral; n, ligament nymph; aa, anterior adductor
muscle scar.

EXPLANATION OF PLATE 77

Fig. 1. Fractured section of the inner calcified ligament of Chama macerophylla Gmelin. Scanning
electron-micrograph, X 1000.

Fig. 2. Fractured section of the prismatic layer of Chama pellucida Broderip. Scanning electron-
micrograph, x280.

Fig. 3. Pachyrisma grande Morris and Lycett, Jurassic, Great Oolite, Minchinhampton, England.
x0-5. a. Left valve showing hinge teeth; b. Right valve. Abbreviations: C, cardinals; L, laterals;
n, ligament nymph; aa, anterior adductor muscle scar.

Palaeontology , Vol. 13

PLATE 76

(01010101010) aa

KENNEDY, MORRIS and TAYLOR, Chamacea

Palaeontology, Vol. 13

PLATE 77

KENNEDY, MORRIS and TAYLOR, Chamacea

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA) 409

(e) Monopleuridae (Kimmeridgian-Danian). The Monopleuridae can be derived from
the Diceratidae through Valletia. Certain members of this family, for example Gyro-
pleura cenomanensis (d’Orbigny) (PI. 70, fig. 5) and Ciplyella pulchra (Ravn) (PI. 72,
fig. 5), show remarkable similarity in morphology to Chama. They are small to medium-
sized, strongly exogyriform and radially ribbed. Ciplyella pulchra has commonly been
considered to be a Chama , but the form of the adductor scars and the near atrophy of the
ligament show that it is a rudist closely related to Gyropleura (N. J. M. and J. D. T.,
in. lift.).

The dentition of the Monopleuridae resembles that of the Caprotinidae, but without
the incipient splitting of the posterior tooth in the left valve seen in Caprotina (PI. 76,
fig. 2).

The teeth of Gyropleura are illustrated in a sketch by Deschaseaux (1952, 335, text-fig.
177). Gyropleura cornucopiae (d’Orbigny) from the Middle Cenomanian of north-
western Europe, and G. inequirostrata (Woodward) from the Campanian and Lower
Maastrichtian of the same area, have a similar arrangement. The dentition of Monopleura
(Deschaseaux 1952, 335, text-fig. 176) is also not significantly different.

The notation of Gyropleura cornucopiae (d’Orbigny) is shown below :

Right valve (fixed) 0 1 0

Posterior Anterior.

Left valve (free) 1 0 1

As is the case with the other rudist families discussed, this is a typical pachydont
dentition with no differentiation into heterodont cardinals and laterals. It contrasts
remarkably with the dentition of the earlier Chamacea. The teeth of Chama calcarata,
for example (PL 72, fig. 2), although twisted to lie sub-parallel to the line of the liga-
ment, still diverge slightly below the umbones and in the fixed valve may be matched
tooth for tooth with many fossil and recent Carditidae.

No well-preserved material was available for shell structure studies. Specimens of
Gyropleura cenomanensis from the Cenomanian of Le Mans, Prance, however, appear
to have an aragonitic inner layer or layers and a calcitic outer layer. The preservation
of a specimen of Gyropleura inequirostrata (Woodward) from the Upper Campanian
Chalk of Sidestrand, Norfolk, England, indicates the same arrangement.

Major differences occur in the adductor musculature between the Chamidae and the
Monopleuridae together with all other rudists. In the Megalodontacea, the posterior
adductor scar is associated with a plate or myophoric septum (PI. 76, fig. 3) which seems
to add strength to the shell in the form of a buttress. The anterior adductor scar is in
the form of a shallow, cup-shaped socket (PI. 76, fig. 3; PI. 77, fig. 3). In Diceras , the
animal becomes attached by one valve and presumably takes up a posture reclining on
one side. The umbones become widely separate, each valve becoming cornucopia shaped.
The adductor musculature attachment has had to compensate in order to remain near
normal to the direction of adduction. This compensation took the form of certain modi-
fications of the muscle attachment area. In the Caprotinidae and the Requeniidae, the
anterior adductor scar occurs on a raised platform in either valve so that the actual
length remains at a minimum. At the same time this muscle became extended parallel
to the valve margins. The posterior adductor muscle attachment sank deeper into the
space between the myophoric septum and the hinge plate in the Requeniidae. In the

410

PALAEONTOLOGY, VOLUME 13

Caprotinidae, the same septum joined with the hinge plate to form a deep accessory
cavity to house the posterior adductor muscle. In the Monopleuridae both the posterior
and the anterior muscles form elongate scars on raised platforms which tend to form
extensions to the hinge plate. They are somewhat less prominent in the fixed valve.
The Monopleuridae retain a somewhat reduced posterior myophoric septum.

In marked contrast to these developments in the rudists, the adductor muscle scars
of the Chamidae are broadly similar to those of most other heterodont groups, except
that the dorsal portion of the anterior adductor scar of both valves impinges somewhat
upon the hinge plate.

The resemblance of Gyropleura and other Monopleuridae to Chama is merely that of
convergent adaptions to the same cemented mode of life under similar habitat con-
ditions. Similar exogyriform shapes are found in totally unrelated bivalves, e.g. Ostrea-
cea, Pandoracea, Spondylidae, Unionacea, and the Chamacea.

DISCUSSION

From the comparison of the Chamacea with their possible relatives, it appears to us
that amongst these groups only the superfamilies Carditacea and Lucinacea are likely
to be closely related.

The rudists, for so long considered closely related to the Chamacea show certain
similarities, but these are only the result of convergence because of the cemented habit.

The shell structure characters of the Carditacea match exactly those of the Chamacea
(except for the development of calcite in C. pellucida and C. exogyra), whereas the
Lucinacea have an extra outer shell layer. The dentitions of the Chamacea, Lucinacea,
and Carditacea are all very similar. Certain shell morphology features such as the shape
of the anterior adductor muscle scar, and the groove on the exterior, suggest similarities
with the Lucinacea.

The Carditacea, however, contain many species which are byssally attached, and are
asymmetrical; some are inequivalve. The Lucinacea are all burrowers. The Lucinacea
and the Carditacea have had a distinct history at least as far back as the Ordovician
(McAlester 1965).

The weight of evidence suggests to us that the Chamacea were derived from a byssate
Cardita during the late Cretaceous. Chama haueri, the first authenticated Chama, is a
‘good’ Chama but rather less inequivalve than many Recent species. Transitional forms
(other than the assumption of the byssate habit) between Carditacea and Chamacea
are lacking; however, if the Cardita origin is not accepted, then possible transitional
forms are not found between the Chamacea and any other group. However, possibly
byssate Cardita are common in the Cretaceous, for example forms from the Upper
Cretaceous of Ga’ara, Ruthbah, Iraq (BMNH LL2245-8) labelled Cardita beaumonti
var. amelliae d’Archiac. They are thick-shelled, subrectangular in shape with coarse
radial and concentric ornament, on which short spines are developed (PI. 75, fig. 2).
Although perhaps too late in time to be thought of as ancestral to the Chamacea, they
show the forms among which the origin of the group should be sought. An alternative
would be probably byssate forms such as Fenestricardita (PI. 75, fig. 6).

The superfamily Chamacea should be removed from the Order Hippuritoida and
placed in the Veneroida.

KENNEDY, MORRIS, AND TAYLOR: CHAMACEA (BIVALVIA) 411

Acknowledgements. Our best thanks are to Messrs. R. J. Cleevely and C. P. Nuttall for much useful
discussion, and to Mr. A. E. Rixon for considerable assistance in preparing fossil material.

We thank the staff of the British Museum (Natural History) electron microscopy unit, under the
direction of Mr. B. Martin, for their assistance, and Dr. A. Hall for help with mineralogical deter-
minations.

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THE SKULL OF FABROSAURUS AUSTRALIS ,
A TRIASSIC ORNITHISCHIAN DINOSAUR

by RICHARD A. THULBORN

Abstract. The skull of Fabrosaurus australis is described in detail. This study is based upon previously
undescribed specimens from the late Triassic Red Beds of Lesotho.

The presence of a predentary bone at the mandibular symphysis substantiates Ginsburg’s concept (1964) of
Fabrosaurus as a member of the order Ornithischia — though there is no evidence for any close relationship
between Fabrosaurus and the Liassic Scelidosaurus. Certain cranial features (the toothed premaxilla, the inter-
parietal suture) indicate that Fabrosaurus should be referred to the family Hypsilophodontidae of the suborder
Ornithopoda. Ornithischian origins and ornithopod phylogeny are re-examined in the light of new evidence from
Fabrosaurus. Fabrosaurus seems to be a fairly direct antecedent of Hypsilophodon and appears to fulfil many of
the requirements of a genuine ‘archetypal’ ornithischian.

Prior to this decade only a few and fragmentary fossils were available to permit of
clarification of early ornithischian history. Faced with this lack of information several
investigators tended to simplify the problem by selecting the well-known Wealden orni-
thopod Hypsilophodon as an ornithischian ‘archetype’ and by attempting to derive the
varied ornithischian faunas of the later Mesozoic from similar hypothetical ancestors.
This scheme, though useful, is unsatisfactory because of the late stratigraphic occurrence
of Hypsilophodon — which appears later than stegosaurs and iguanodonts and is roughly
contemporary with the earliest ankylosaurs and psittacosaurs. The anomalous situation
of Hypsilophodon within such a scheme is quite clear — it is geologically younger than
(or at least coeval with) those dinosaurs whose ancestry it is supposed to represent. It is
in view of this unsatisfactory situation that adequate knowledge of early ornithischians,
such as Fabrosaurus, becomes of critical importance.

The genus Fabrosaurus was established by Ginsburg (1964) on the basis of a tooth-
bearing jaw fragment from the late Triassic Red Beds of Lesotho (then Basutoland).
Ginsburg concluded, from the appearance of the teeth in the holotype, that Fabrosaurus
was an ornithischian dinosaur related to the Liassic Scelidosaurus. Unfortunately the
affinities of Scelidosaurus itself are far from clear. This large armoured dinosaur is often
quoted as a fore-runner of the stegosaurs (e.g. Romer 1956); recent opinion tends, how-
ever, to confirm Scelidosaurus as an ankylosaur ancestor (Romer 1968).

The new materials described below considerably amplify knowledge of the Fabro-
saurus skull and permit reconsideration of this reptile’s affinities.

MATERIAL AND METHODS

Two specimens are described. These are listed below with brief notes on their preservation and
contents ; their original field numbers are given and will be used hereafter for reference.

Specimen B. 17. Three large blocks and numerous small pieces of matrix containing many cranial
and post-cranial bones (though few are in natural articulation). At least two individuals are present
— the smaller one being more complete.

[Palaeontology, Vol. 13, Part 3, 1970, pp. 414-32.]

R. A. THULBORN: FABROSAURUS AUSTRALIS

415

Specimen B. 23. A well-preserved and slightly crushed skull (text-fig. 1) with parts of both mandi-
bular rami. The snout is lacking and the teeth are poorly preserved.

These specimens were collected by Dr. K. A. Kermack and Mrs. F. Mussett during the 1963-4
expedition from University College, London, to Basutoland. Both specimens are preserved in the
collection of the Zoology Department at University College, London.

Specimen B. 17 was collected from the Red Beds of the Stormberg Series on the nor-
thern flank of Likhoele Mountain, near the settlement of Mafeteng in western Lesotho,
about 40 miles south-south-west of Maseru, the capital. Skull B. 23 was taken from a
hillside exposure, also in the Red Beds, between Fort Hartley and Cutting Camp in
south-west Lesotho, some 75 miles south of Maseru. The Red Beds are generally supposed
to be of Upper Triassic age.

The bones, preserved in soft, white calcareous material, are enclosed in a tough
medium-grained sandstone of bright red colour. The specimens were at first prepared
by the use of acetic and formic acids (as described by Kermack 1956). It subsequently
became clear that these acids, though effective, have certain disadvantages — they readily
attack fossil bone, they have offensive smells and they may (if specimens are not very
thoroughly washed after immersion) cause the formation of hard white efflorescences.
Thus a saturated solution of sodium citrate in water was employed as an equally effective
alternative. Since this solution does not attack bone as readily as formic or acetic acids
the specimens were safely immersed in it for periods of up to 24 hours.

DESCRIPTION

General appearance of the skull. Specimen B. 23 is only slightly damaged and adequately
demonstrates the general appearance of the Fabrosaurus skull (text-fig. 1). This incom-
plete skull has the following dimensions: maximum length, 94 mm.; maximum width
(across frontals), 48 mm. ; maximum height (with mandible), 40 mm. Fragments from
assemblage B. 17 (text-figs. 2, 3) represent skulls of roughly similar size.

The skull is of typical archosaurian aspect — diapsid, with large circular orbits and
extensive antorbital vacuities. The long and tapered snout affords the skull a triangular
profile whilst the occipital surface, inclined at about 60° relative to the long skull axis,
faces slightly in a dorsal direction. The small and elliptical upper temporal fenestra
opens dorsally; the lateral fenestra is larger, faces laterally and is almost crescentic in
outline due to the forwards extension of the quadrate.

Skull bones. To facilitate description the skull bones are considered in arbitrary groups
(after Romer 1956).

(i) Tooth-bearing bones. The tip of the snout, formed by paired premaxillae (text-figs.
1 , 6, 8), is laterally compressed and has a V-shaped outline in dorsal view. Each pre-
maxilla is extended dorsally into two processes separated by the large and oval external
naris. The broad pre-narial process is directed dorsally and slightly to the rear; its
contact with the nasal cannot be observed — though it is likely (since the nasals are very
extensive) that this process was not very tall. The long and acutely pointed post-narial
process extends postero-dorsally at about 50° relative to the tooth row and is tightly
sandwiched between the nasal and the maxilla on the side of the snout.

Ee

C 7619

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PALAEONTOLOGY, VOLUME 13

The bar-like dentigerous part of the maxilla (text-figs. 1-4 and 8) is about 7 mm.
deep (skull B. 23) and has a flat lateral surface. The maxilla extends posteriorly to under-
lie the anterior ramus of the jugal — the two bones being separated by a long, straight,
and oblique suture. A broad and flat process extends postero-dorsally from the front of

. ICM .

text-fig. 1. Fabrosaurus australis. Skull B. 23 as preserved. xO-75. Matrix indicated by regular stip-
pling. a, right dorso-lateral view; b, dorsal view; c, left lateral view; d, occipital view.

A, angular; D, dentary; F, frontal; J, jugal; L, lacrimal; M, maxilla; MD, mandible; N, nasal;
NV, fragments of cervical vertebrae; P, parietal; PF, prefrontal; PM, premaxilla; PO, postorbital;
PP, paroccipital process; Q, quadrate; S, supra-orbital; SA, surangular; SP, splenial; SQ, squamosal;

SU, supra-occipital.

the maxilla so as to define the antero-ventral angle of the shallow, triangular antorbital
vacuity. The thin bony wall medial to the vacuity is a simple sheet-like extension of the
maxilla; this wall is gently convex in a vertical direction and is broken postero-ventrally
by a small rounded notch.

(ii) Skull roofing bones. Paired nasal bones (text-figs. 1 , 8) form the roof of the snout
and meet in a long and straight median suture. The nasal is at least as long as the frontal
and attains its maximum width (12 mm. in skull B. 23) close to the anterior tip of the

R. A. THULBORN: FABROSAURUS AUSTRALIS

417

adjacent prefrontal. Anterior to the prefrontal the nasal curves down from the nearly
flat skull roof to form part of the facial region. Posteriorly the nasal overlaps the frontal
— the line of junction running postero-laterally from the mid-line.

Paired frontal bones (text-figs. 1, 8) form the skull roof between the orbits. Each
frontal is roughly quadrilateral in outline, about 31 mm. long (skull B. 23) and is slightly
arched in a longitudinal direction. At its postero-lateral corner the dorsal surface of the

B

text-fig. 2. Fabrosaurus australis. Partial skull from assemblage B. 17. x 1.

Matrix indicated by regular stippling. A, left lateral view ; b, ventral view.

AOV, antorbital vacuity; H, ossified first ceratobranchials ; PE, pre-articular.

Other letters as for text-fig. 1.

frontal bears a deeply impressed crescentic pit which defines the anterior limit of the
upper temporal opening. Anterior to this pit the dorsal tip of the postorbital is set into
a deep V-shaped notch in the lateral edge of the frontal. The posterior tip of the pre-
frontal occupies a shallow groove in the antero-lateral corner of the frontal. The thin,
sharp, and arched lateral edge of the frontal forms the overhanging upper rim of the
orbit.

Paired parietals (text-figs. 1 , 8) form the broadly convex zone of skull roof between
the upper temporal openings. Each parietal is firmly joined to the frontal of the same
side by a sinuous transverse suture and is extended postero-laterally as a vertical sheet
of bone between the occipital surface and the upper temporal opening. The lateral tip

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PALAEONTOLOGY, VOLUME 13

of this expanded portion is applied to the posterior face of the squamosal. The very
distinct inter-parietal suture is quite straight and is confluent with that between the
frontals.

(iii) Circumorbital bones. The jugal (text-figs. 1, 2, 8) is gracefully arched to the exterior
and has slender processes directed anteriorly, posteriorly, and dorsally. The anterior
branch, roughly circular in cross-section, extends to the postero-ventral angle of the
antorbital vacuity; its rounded dorsal edge forms the lower rim of the orbit whilst its
recessed ventral margin accommodates the postero-dorsal edge of the maxilla. The

I CM

text-fig. 3. Fabrosaurus australis. Isolated right maxilla from assemblage B. 17. x 4.

Matrix indicated by regular stippling. Lateral view.

broader posterior jugal ramus is damaged in all examples and its extent cannot be
determined The tapered dorsal branch of the jugal is inclined slightly to the rear and
is distinctly twisted (the lateral surface being turned to the front).

The tri-radiate postorbital (text-figs. 1, 8) curves over from the side of the skull on to
its dorsal surface, the dorsal and ventral branches of the bone defining the postero-
dorsal corner of the orbit. In this region the rim of the orbit is thickened and bears, on
the medial surface, a small cavity. The flat and slender ventral branch of the post-orbital
occupies a long and shallow groove on the dorsal ramus of the jugal. The shorter and
broader antero-dorsal branch is set into the postero-lateral corner of the frontal above
whilst the third, posterior, branch meets an anterior extension of the squamosal to form
the stout horizontal bar between superior and lateral temporal openings.

The lacrimal (text-figs. 1, 2, 8) is a small bar of bone, some 10 mm. long, which runs
anteror-dorsally on the side of the skull from the anterior tip of the jugal. Its antero-
ventral edge thus defines the posterior limit of the antorbital vacuity. The lacrimal is

R. A. THULBORN: FABROSAURUS AUSTRALIS

419

inclined at about 45° relative to the line of the tooth row and is broader in front (6 mm.)
than behind (4 mm.).

The prefrontal (text-figs. 1, 8) is a long, narrow, flattened, and strap-like bone forming
the margin of the skull roof from a point midway over the orbit to the area where lacri-
mal, nasal, and maxilla all meet above the antorbital vacuity. Left and right prefrontals
are completely separated by the frontals and nasals. The narrow posterior tip of the
bone is set into a notch in the antero-lateral edge of the frontal whilst the broadly
rounded anterior end overlies the nasal. The thin and sharp lateral edge of the prefrontal
forms the antero-dorsal rim of the orbit ; anteriorly this edge is thickened and planed off
to form an attachment surface for the supra-orbital.

(iv) Bones of the cheek region. The squamosal (text-figs. 1, 8) forms the lateral and
posterior margins of the upper temporal opening and is extended postero-laterally to
overlap the upper end of the quadrate. A tapered triangular portion runs forwards to
meet the posterior ramus of the postorbital — the two bones being separated above the
lateral temporal opening by a long, straight, and oblique suture. Posteriorly the squamo-
sal turns sharply in a medial direction to form the postero-lateral corner of the skull
roof. This corner is acutely pointed and is ornamented with deeply incised transverse
striae. The posterior face of the squamosal is overlain by a plate-like portion of the
parietal forming the dorso-lateral part of the occiput. A very slender ventral process
from the squamosal is applied to the anterior edge of the quadrate. Though the only
example of this process (on the left side of skull B. 23) is damaged it is clear that it
extended down the front of the quadrate for at least half the height of this latter.

No quadrato- jugal has been recovered. Its probable form is indicated in the skull
reconstruction (text-fig. 8).

A single quadrate is preserved (text-fig. 1). This example, on the left side of skull B. 23,
is damaged antero-ventrally and has suffered slight displacement to the front. The quad-
rate is a latero-medially compressed plate of bone which is noticeably twisted — the
lateral surface being turned to the rear at the ventral end. The thickened and buttress-
like posterior margin is arched to the front; at its ventral end this buttress is transversely
expanded to form a thick and roller-like condyle lying some 7 or 8 mm. below the level
of the maxillary teeth. The sheet-like and slightly concave anterior part of the bone
projects into the lateral temporal opening — accounting for the narrow outline of the
opening. The dorsal tip of the quadrate fits tightly into a depression in the ventral
surface of the squamosal.

(v) Bones of the palate. In the incomplete skull from assemblage B. 17 (text-figs. 2, 4)
the right half of the palate is exposed in dorsal aspect. The bones displayed (pterygoid,
ectopterygoid, palatine, and vomer) appear to have suffered little distortion or dis-
placement. The palate seems to have been quite long, narrow, and moderately vaulted.
A narrow inter-pterygoid vacuity is inferred whilst post-palatine fenestrae must (if
present at all) have been very small.

The palatal (anterior) ramus of the tri-radiate pterygoid is a long, low vertical blade
which runs forwards close to the mid-fine. This paper-thin and sharp-edged process is
17 mm. long and nearly 3 mm. high. It is separated from the mid-line by the vomer — an
arrangement which suggests that left and right palatal rami were not in contact and
implies the existence of a narrow inter-pterygoid vacuity. Posteriorly the palatal ramus
merges, by means of a sharp flexure, with the medial edge of the widely expanded quadrate

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PALAEONTOLOGY, VOLUME 13

ramus of the pterygoid. This latter ramus, a triangular sheet of bone about a millimetre
thick, presumably extended postero-laterally to meet the medial face of the quadrate in
normal reptilian fashion. Anteriorly the quadrate ramus is constricted and runs into the
third, transverse, ramus from the pterygoid. This transverse ramus is represented in

specimen B. 17 only by a fragment of bone
overlying the dorsal surface of the palatine. The
dorsal surface of this constricted zone between
quadrate and transverse rami bears a short and
shallow longitudinal groove which doubtless
accommodated a posterior extension of the
ectopterygoid. The ectopterygoid is represented,
in fact, by a small scale-like fragment of bone
overlying the anterior end of this groove. An
extremely similar arrangement is seen in a
variety of reptiles — e.g. phytosaurs (Camp 1930),
pelycosaurs (Romer and Price 1940), pseudo-
suchians (Walker 1961).

The ectopterygoid lies anterior to the pterygoid
and seems to be considerably smaller than this
latter (though its full extent is not clear owing to
breakage). Its posterior extension on to the ptery-
goid is described above. An equally thin anterior
extension overlies the middle of the depressed
dorsal surface of the palatine. In addition the
ectopterygoid is produced laterally as a short
(5 mm.), stout, and curved bar which serves to
brace the medial surface of the maxilla.

The palatine is situated anterior to the ptery-
goid and antero-medial to the ectopterygoid.
There is no trace of any (post-palatine) vacuity
between palatine and ectopterygoid. A slender
antero-lateral process from the palatine is applied
to the medial surface of the maxilla; medial to
this the deeply embayed anterior edge of the
palatine represents the rear margin of the in-
ternal naris. Medial and posterior to the internal
naris the palatine forms an extensive sheet of
bone, some 9 mm. wide, which is flexed into a
deep trough running postero-laterally. The floor
of this trough contains the thin anterior part of the ectopterygoid whilst its medial edge
meets the tip of the anterior pterygoid ramus.

The vomer is represented (specimen B. 17) by a sheet-like fragment of bone, 12 mm.
long and 5 mm. high, which lies vertically in the mid-line between the palatines.

(vi) Bones of the occiput (text-figs. 1, 8). The account is based upon skull B. 23. In
this skull the ventral parts of the occiput are obscured by fragments of cervical vertebrae
and cannot (for the present at least) be described. The occipital surface is inclined, at

text-fig. 4. Fabrosaurus australis. Right
half of palate in partial skull from assem-
blage B. 17 (see also text-fig. 2). Dorsal
view, x2. Matrix indicated by regular
stippling.

APT, anterior (palatal) ramus of pterygoid ;
E, ectopterygoid (fragments) ; IN, rear
margin of internal naris; M, maxilla; PA,
palatine; QPT, quadrate ramus of ptery-
goid; V, vomer.

R. A. THULBORN: FABROSAURUS AUSTRALIS

421

about 60° relative to the long axis of the skull, so that it faces dorsally as well as
posteriorly. It is quite broad (44 mm. across the squamosals) and not exceptionally
high (38 mm. including quadrate).

The dorsal part of the occiput is formed, in its central region, by the median supra-
occipital. This transversely arched bone is of quadrilateral outline, some 15 mm. high,
and attains a maximum width (ventrally) of 14 mm. Since its ventral margin is damaged
it is difficult to estimate how far this bone contributed to the border of the foramen
magnum. The lateral edge of the supra-occipital meets the posterior face of the parietal
— forming the dorso-lateral part of the occiput. Towards the margin of the occiput the
parietal overlaps the posterior face of the squamosal — which curves away on to the side
of the skull. The intervening suture runs ventro-laterally, roughly parallel with that
between supra-occipital and parietal. The ventro-lateral corner of the supra-occipital
meets the dorsal edge of the exoccipital, which extends laterally away from the foramen
magnum as the long (14 mm.) and stout paroccipital process. The expanded lateral
tip of this process is doubtless composed of the opisthotic bone, though there is no suture
serving to separate this from the confluent exoccipital. The paroccipital process is arched
very slightly to the anterior; it is directed laterally, and almost imperceptibly in a ventral
direction, to terminate in a vertically expanded sheet which is applied to the posterior
face of the squamosal.

(vii) Bones of the mandible (text-figs. 1, 2, 5, 8). A composite description is derived
from all available examples. Each long and slender mandibular ramus is slightly arched
to the exterior in its middle and anterior regions. The jaw has a length of about 92 mm.
(estimated for skull B. 23) and is latero-medially compressed — so that cross-sections are
of elliptical outline. The retroarticular portion is extended as a salient finger-like process
whilst the coronoid apophysis is little more than an indistinct rounded eminence on the
dorsal surface. A widely open external mandibular fenestra lies at mid-height and just
in front of the coronoid process. This opening is of lenticular outline, measuring 8 mm.
(maximum length) by 3 mm. (maximum height). A similar, though larger, fenestra in the
medial jaw surface is located slightly anterior to the external one.

The jaw rami are joined anteriorly by means of the median predentary. This scoop-
shaped bone has the outline, in ventral view, of a blunt arrow-head — being composed of
a large median portion bearing two smaller lateral processes or ‘wings’. The median
portion, some 10 mm. long and 4 mm. wide, extends posteriorly between the left and
right dentary bones (though it is not clear if these were completely separated).

Behind the predentary the dentary bone forms the anterior two-thirds of the lateral
jaw surface. This lateral surface is convex in a vertical direction and is confluent ventrally
with the broadly rounded inferior margin of the jaw. Posteriorly the dentary ends in a
wide V-shaped notch defining the anterior limit of the external mandibular fenestra.
Above the fenestra the dentary overlies the surangular; below the opening it overlaps
the angular and is drawn out posteriorly as a thin and flattened process applied to the
thick ventral margin of the jaw. The dentary also forms the anterior third of the medial
jaw surface. This surface is generally similar to the lateral surface just described and
shows no indications of any foramina adjacent to the tooth row. Posteriorly this medial
dentary surface is overlain by the paper-thin anterior part of the splenial.

The splenial forms the ventro-medial surface of the jaw behind the dentary and is
extended posteriorly as a thin tongue-like process on the ventral surface of the

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PALAEONTOLOGY, VOLUME 13

retro-articular process. In the middle of the jaw ramus the splenial is widely expanded to
form the greater part of the medial surface — except dorsally, where a narrow zone of
the underlying dentary is exposed adjacent to the tooth row. This central region of the
medial jaw surface is generally flat; posteriorly it is depressed, leading down into the
large inner mandibular fenestra.

The angular forms the postero-ventral part of the jaw, below the surangular and behind
the dentary. The lateral surface of the bone is generally flat, curving round ventrally to
merge with the thick inferior margin of the jaw. Angular and surangular are separated

text-fig. 5. Fabrosaurus australis. Mandibular symphysis from assemblage B. 17. Ventral
view, x 5. Matrix indicated by regular stippling, broken edges by diagonal shading.

DL, left dentary; DR, right dentary; PD, predentary; T1 to T6, left premaxillary teeth
numbered from front.

by a distinct suture from the posterior angle of the external jaw fenestra. This suture
runs obliquely in a postero-dorsal direction so that the angular and surangular appear
to form roughly equal portions of the lateral jaw surface. Posteriorly this same suture is
down-curved — so that a slender process from the angular underlies the retro-articular
process (formed predominantly of the surangular).

The surangular, overlying the angular, forms the retro-articular process and the pos-
tero-dorsal limit of the external jaw fenestra. Since the retro-articular process is deflected
medially the lateral surface of the surangular is convex from front to back. This lateral
surface is demarcated from the dorsal margin of the retro-articular process by a thick
and dorsally arched ridge. The long (10 mm.) and tapered retro-articular process has
a bluntly rounded tip and is drawn out medially into a horizontal flange nearly 5 mm.
wide. The ventral surface of this flange is gently excavated whilst its most medial tip is
extended ventrally as a short and blunt projection.

5mm

R. A. THULBORN: FABROSAURUS AUSTRALIS

423

In front of the retro-articular process, on the dorsal jaw surface, lies the glenoid
fossa — a broad and shallow transverse groove. This region of the jaw is doubtless formed
by an articular element, though the sutures which might define its limits cannot be
discerned. Medial to the angular lies the pre-articular bone; little may be said of this
apart from the fact that it seems to be of rather limited anterior extent.

(viii) Accessory skull elements. The partial skull from assemblage B. 17 (text-fig. 2) has
a pair of slender rod-like bones preserved between the mandibles. That of the right side
lacks only the posterior tip and has a length of 28 mm. ; it is marked with fine longitu-
dinal striae and has a diameter of T5 mm. Its anterior end is slightly inflated (to a
diameter of 2-5 mm.) whilst the bone is sharply flexed in the middle — the ends diverging
at about 150°. These curved bony rods are the ossified first ceratobranchials — which are,
as Romer (1956) points out, the parts of the hyoid complex most frequently encountered
in fossil reptiles.

The right orbit of skull B. 23 (text-fig. 1) contains a single undamaged sclerotic plate.
This is paper-thin, roughly triangular (narrowest anteriorly) and is bent so that its
lateral surface is concave from dorsal to ventral edges. It has a length of 4 mm. and
a maximum width of 2-5 mm. The left orbit of the same skull contains fourteen similar
plates (or parts of plates) which are disposed in overlapping arrangement to form a circle
(mean diameter 12 mm.) ventral to the supra-orbital bone.

Each orbit of skull B. 23 also contains a long (20 mm.) and rod-like supra-orbital
bone which is arched to the exterior. Anteriorly the bone is truncated by a facet for
attachment to that part of the orbital rim formed by the thickened lateral edge of the
prefrontal. The right supra-orbital has been displaced medially ; that within the left orbit
shows more clearly the natural relationships of the bone.

Dentition

The teeth are described from specimen B. 17 alone. Skull B. 23 contains teeth which
are unmistakably those of Fabrosaurus, but these are so poorly preserved that they yield
little useful information. In the following descriptions the terms used in dentistry will be
employed. The tooth surface facing outwards, towards the lips, is termed buccal ; the
surface directed inwards, towards the tongue, is lingual. That surface facing the jaw
symphysis is mesial whilst the surface facing the jaw articulation is distal. The tip of the
root is defined as the apex of the tooth whilst the other, masticatory, end of the tooth is
termed occlusal.

Premaxillary teeth (text-figs. 5, 6, 8). The left premaxilla from assemblage B. 17 bears
six teeth (text-fig. 6), apparently the full complement. The most posterior tooth in this
example displays a long and narrow root of circular cross-section and illustrates the
thecodont mode of tooth implantation. Each crown appears in buccal profile as a tall
(3-5 mm.) and slightly rounded triangle where the acute occlusal tip is slightly recurved.
The last two premaxillary crowns are shorter than those in front and foreshadow the
squat triangular crowns in the maxilla. At the alveolar margin the crown is distinctly
inflated to the exterior and attains a maximum mesio-distal width of nearly 2 mm. The
rest of the transversely convex buccal surface is perfectly smooth (save for an extremely
faint vertical ridge near the occlusal end).

The smooth and convex lingual surface is marked, near the distal edge, with a distinct
vertical furrow. The distal edge of the crown is considerably thinner and sharper than

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PALAEONTOLOGY, VOLUME 13

the mesial edge. The fifth premaxillary crown (from the front) has its distal edge
ornamented with minute denticles; in the last (6th) crown both mesial and distal edges
are finely denticulate. These posterior teeth thus form a transition to the obviously
denticulate maxillary teeth.

Maxillary teeth (text-figs. 2, 3, 7, 8). The best-preserved example of the maxilla (text-
fig. 3) bears eleven teeth — so that their original number might be estimated at thirteen

text-fig. 6. Fabrosaurus australis. The premaxilla and its teeth, a, Left premaxilla from assemblage
B. 17. Lateral view x2-5. EN, inflected ventral margin of external naris; PN, pre-narial ramus.

b. Last (6th) crown in left premaxilla. Buccal view, x 10. DI, distal edge; G, furrow; ME, mesial edge.

c, d, Buccal and distal views of an anterior crown from the right premaxilla. Both x 10. B, buccal

surface; E, sharp distal edge; LI, lingual surface. Other letters as above.

or fourteen. In buccal (or lingual) profile each crown has the outline of a low and
symmetrical triangle where the occlusal tip is formed by the intersection of slanting
mesial and distal edges. The largest crowns, in the middle of the tooth row, are about
3 mm. tall and have similar mesio-distal widths; the smallest crowns, 1—1 -5 mm. tall,
are situated at the rear of the maxilla and are perfect replicas of the larger ones.

Each crown is compressed in a bucco-lingual direction and has its inclined mesial and
distal edges ornamented with very characteristic denticles. These short and blunt
denticles are all parallel and none exhibits any curvature or ‘hooking’ at its tip. The

R. A. THULBORN: FABROSAURUS AUSTRALIS

425

median denticle is similar to those flanking it and is not appreciably enlarged; there are
about seven denticles to each side (mesial and distal) of the median one. The denticles
are all of similar size — though locally a very small ‘accessory’ denticle may be inter-
calated between two otherwise normal ones.

The smooth and transversely convex buccal crown surface is strongly inflated close
to the junction with the root; ill-defined transverse ridges link this swollen area with the
most mesial and distal of the marginal denticles. The lingual surface is noticeably
flatter than the buccal surface and bears a very faint median ridge. In mesial or distal

i 5 mm |

text-fig. 7. Fabrosaurus australis. Cheek tooth from assemblage B. 17.
a, buccal view; b, mesial or distal view; c, lingual view. All x 5.

view (text-fig. 7) it may be seen that the whole crown is slightly deflected in a lingual
direction and that there is a weak constriction where the crown joins the narrower root.

Dentary teeth. These are identical to the maxillary teeth. They are of equivalent
number and exhibit precisely comparable marginal denticles.

Arrangement of the teeth. Premaxillary, maxillary, and dentary teeth all have their
crowns completely enamelled and are all disposed in simple marginal rows. Where the
dentigerous bones are broken transversely small replacement teeth may be observed
close to the lingual sides of the functional teeth.

Teeth extend right to the front of the premaxilla whilst the predentary is toothless.
It may also be observed that the teeth in any jaw bone alternate both in size and in
situation. The smaller crowns are regularly intercalated between larger ones (which are
also located slightly nearer the lateral margin of the jaw).

The Fabrosaurus dentition is heterodont — the teeth in the premaxilla differing radi-
cally in appearance from the cheek teeth (i.e. those in maxilla and dentary). This change
in form between the premaxillary and maxillary teeth is not abrupt but is marked by the
appearance, at the rear of the premaxilla, of transitional crowns which are of intermediate
shape and bear weakly developed marginal denticles.

DISCUSSION

The systematic position of Fabrosaurus

The materials described above may safely be referred to the genus Fabrosaurus since
the teeth of this reptile are highly distinctive and are unlikely to be mistaken for those

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PALAEONTOLOGY, VOLUME 13

of coeval ornithischians (or, for that matter, for those of Triassic saurischians). Gins-
burg (1964) inferred ornithischian affinities for Fabrosaurus on the evidence of the cheek
teeth alone. The identification (above) of a diagnostic predentary bone at the mandibular
symphysis fully substantiates the concept of Fabrosaurus as an ornithischian dinosaur.

The next matter is to assign Fabrosaurus to a particular suborder (and, subsequently,
to a family) within the Ornithischia. On the basis of dental similarities Ginsburg sug-
gested that Fabrosaurus might be allied to the Liassic Scelidosaurus. There are, indeed,
basic resemblances between the teeth in these two animals; in both cases the completely
enamelled crown is compressed in a bucco-lingual direction and possesses an angular
and denticulate occlusal margin formed by the intersection of inclined mesial and distal
edges. Teeth conforming to this general description are, however, encountered through-
out the order Ornithischia and cannot be taken as diagnostic of particular suborders
or families. Such teeth are seen, for example, in ornithopods ( Hypsilophodon ), in stego-
saurs ( Stegosaurus ), in ceratopsians ( Triceratops ), and in ankylosaurs ( Edmontonia ).
These dental characters, though suggestive of ornithischian affinities for Fabrosaurus ,
do not provide sound evidence of any immediate relationship with Scelidosaurus.
Further, there are numerous minor distinctions between the teeth in these two animals.
The blade-like Scelidosaurus tooth is much taller than that in Fabrosaurus and tends to
a distinct asymmetry; the marginal denticles of the Scelidosaurus tooth are much more
variable in size, are distinctly ‘hooked’ at their tips, and are arranged in a divergent
(rather than parallel) pattern. These differences are, however, of no real use in any
attempt to assign the two animals to specific subordinal groups — a direct consequence
of the basic conservatism of tooth structure within the Ornithischia.

Amongst ornithischian dinosaurs the skull of Fabrosaurus resembles most closely
that of the Lower Cretaceous Hypsilophodon (as figured by Galton 1967). The pro-
nounced similarities with Hypsilophodon indicate that Fabrosaurus should be placed
alongside this former genus in the family Hypsilophodontidae of the suborder Ornitho-
poda. Fabrosaurus falls naturally into this category (reserved for ornithopods of primi-
tive aspect) when one considers that certain of its cranial features (e.g. the toothed pre-
maxilla, the inter-parietal suture) are decidedly atypical of ornithischian dinosaurs and
may best be matched in the thecodont reptiles — putative ancestors of the Ornithischia.

Though the skulls of Fabrosaurus and Hypsilophodon are essentially similar in con-
struction there are several minor distinctions. The post-narial process of the Hypsilopho-
don premaxilla separates the nasal from the maxilla on the side of the snout; in
Fabrosaurus, in contrast, the maxilla is in contact with the nasal for a short distance in
front of the orbit. Similar contact between maxilla and nasal is seen, incidentally,
in thecodonts such as Euparkeria and Sphenosuchus.

The Fabrosaurus maxilla is distinguished from that of Hypsilophodon by its shallow-
ness and by its lack of any longitudinal recess above the tooth row. The large and widely
open antorbital vacuity is triangular in Fabrosaurus, sub-circular in Hypsilophodon.
The Fabrosaurus lacrimal is straighter and is not arched over the antorbital vacuity.

The upper temporal openings of the Fabrosaurus skull are separated by a broad and
flat zone of skull roof ; in Hypsilophodon, and in most other ornithopods, there is only
a very narrow zone between these skull openings. The Fabrosaurus parietals are divided
by a distinct median suture. This very unusual feature, which cannot be matched in
Hypsilophodon (where the parietals are fused in normal ornithischian fashion), is seen

text-fig. 8. Fabrosaurus australis. Reconstruction of skull. All figures xO-5. a, right lateral view of
whole skull, b, occipital view, c, medial view of left mandible, d, ventral view of left mandible, e, dorsal

view, f, palatal view.

Lettering as for text-fig. 1, except for: CA, coronoid apophysis; E, ectopterygoid; G, glenoid fossa;
PA, palatine; PD, predentary; PE, pre-articular; PT, pterygoid; QJ, quadrato-jugal; RP, retro-
articular process ; V, vomer.

Following parts are not known and are shown in generalized fashion — quadrato-jugal, bones around
foramen magnum, prearticular, ventral surface of brain-case.

also in Euparkeria and, more unexpectedly, in Protoceratops (Brown and Schlaikjer
1940).

The Fabrosaurus mandible is generally similar to that of Hypsilophodon though the
retro-articular portion is rather more prominent and the coronoid eminence is dis-
tinctly less well developed.

The 6 teeth in the Fabrosaurus premaxilla extend to the front of the snout;
Hypsilophodon has 5 premaxillary teeth (Galton 1967) and these are preceded by a wide

428

PALAEONTOLOGY, VOLUME 13

edentulous space. The cheek teeth of Hypsilophodon (numbering 10 or 11 in maxilla or
dentary) are distinguished from those of Fabrosaurus (numbering 1 3 or 14) by their greater
height, their prominent surface ridging and the very marked variation in size of their
marginal denticles.

Ornithischian origins

The presence of ornithischians in late Triassic sediments certainly suggests that the
origins of the group are to be sought at some considerably earlier date. This concept of

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text-fig. 9. Suggested phytogeny for the Ornithopoda. The ‘Fabrosaurs’ (. Fabrosaurus , Tatisaurus,
Pisanosaurus) are referred to the family Hypsilophodontidae together with Heterodontosaurus, Echino-
don, Hypsilophodon, Parksosaurus, and Thescelosaurus.

a very early start to ornithischian history, whilst unsupported by fossil evidence, is
reinforced simply by the geographic and structural diversity of the known Triassic
ornithischians — Fabrosaurus , Geranosaurus (Broom 1911), and Heterodontosaurus
(Crompton and Charig 1962) from southern Africa; Tatisaurus (Simmons 1965) from
China; Pisanosaurus (Casamiquela 1967) from South America.

The skulls of Geranosaurus , Pisanosaurus, and Tatisaurus are known only from frag-
ments; the better-known Heterodontosaurus skull has a remarkably specialized dentition
including ‘canine’ teeth. Thus it is natural to turn to the relatively well-known and
unspecialized Fabrosaurus skull in the search for persistent primitive features which

R. A. THULBORN: FABROSAURUS AUSTRALIS

429

might be indicative of ornithischian ancestry. There are, in fact, only a few characters
in Fabrosaurus which are noticeably atypical of later ornithischians and which might
justifiably be termed primitive. Several cranial features, including the widely open
antorbital vacuity, the large external mandibular fenestra and the weakly developed
coronoid process, may be closely paralleled in a wide range of thecodont reptiles (e.g.
Ornithosuchus, Euparkeria, Stagonolepis). It is immediately evident that such features
are of no practical use in any attempt to locate the possible ancestors of the Ornithischia
— simply because of their very frequent occurrence in diverse members of the
Thecodontia. Similarly the inter-parietal suture of the Fabrosaurus skull is matched in
numerous thecodonts (Euparkeria, Ornithosuchus, Machaeroprosopus, etc.) and gives
no precise clue as to ornithischian origins.

Ewer (1965) supports the general contention advanced by Broom (1913) that the theco-
dont family Euparkeriidae probably includes the ancestors of all the major lineages of
later archosaurs — including the Ornithischia. Whilst saurischian dinosaurs may be
derived from hypothetical Euparkeria-hke ancestors with no very excessive stretching
of the imagination it is considerably more difficult to derive ornithischians from the
same source — mainly because of irreconcilable differences in ankle and pelvis structure
(see Ewer 1965). Whilst it is reasonable to assume that the ancestry of the Ornithischia
extends back ultimately into the Euparkeriidae this still does not clarify the problem of
ornithischian history between Lower and Upper Trias. The members of the Eupar-
keriidae exhibit no obvious trend towards the ornithischian state of organization whilst
the earliest known ornithischians, such as Fabrosaurus, present very few primitive
characters. Due largely to inadequacies of information concerning Middle Triassic
archosaur faunas there is a very considerable hiatus between the Euparkeriidae and the
earliest ornithischian dinosaurs. There are, in consequence, no apparent ‘intermediates’
between the Lower Triassic Euparkeria and the Upper Triassic Fabrosaurus.

The outlines of ornithopod phytogeny

It is probable that all of the varied ornithischian types of the later Mesozoic have
arisen from ancestors which are to be grouped, ultimately at least, within the Hypsilo-
phodontidae. This scheme is quite reasonable since any later ornithischians (most
particularly the iguanodonts and the hadrosaurs) may be derived from hypothetical
Hypsilophodon- like ancestors without any great difficulty. This much, at least, of orni-
thischian history is fairly clear and has been adequately expressed by earlier authors
(e.g. Romer 1945).

Pronounced cranial similarities between Fabrosaurus and Hypsilophodon have already
been noted. Fabrosaurus, rather than Hypsilophodon, would seem to fulfil the require-
ments of a genuine ornithischian ‘archetype’ — simply by virtue of its much earlier
stratigraphic location. The basic resemblances between these two dinosaurs also indicate
that they are linked in an evolutionary sense — i.e. Hypsilophodon appears to be a fairly
direct descendant of Fabrosaurus. Echinodon, a diminutive reptile from the British
Purbeck, constitutes a very satisfactory intermediate between Fabrosaurus and Hypsilo-
phodon, both in relative stratigraphic position and in morphology. Echinodon was origin-
ally described as a lizard (Owen 1861); it shows, however, thecodont implantation of the
teeth (not acrodont or pleurodont as in true lizards), cheek teeth of ornithischian aspect,

430

PALAEONTOLOGY, VOLUME 13

and the ‘special foramina’ described by Edmund (1957) as characteristic of ornithischian
dinosaurs. The premaxillary teeth of Echinodon point to hypsilophodont affinities.

These three dinosaurs ( Fabrosaurus , Echinodon, Hypsilophodon ) represent a hypsilo-
phodont lineage persisting from the late Trias to the Lower Cretaceous. Parksosaurus,
from the North American end-Cretaceous, appears to be the latest known representa-
tive of this lineage. These hypsilophodonts retain primitive features (e.g. the premaxillary
teeth) which are not encountered in other ornithischians and which demonstrate the need
for coherence of these forms in any evolutionary scheme. This same lineage is shown,
in consequence, at the core of the ‘evolutionary tree’ of the ornithopods (text-fig. 9).

Heterodontosaurus, with its peculiarly specialized dentition, represents the earliest
evolutionary divergence from the basic hypsilophodont stock. Since both Fabrosaurus
and Heterodontosaurus are referred to the family Hypsilophodontidae it is probable that
these two shared a common ancestry at some date earlier in the Trias, implying, in turn,
that ornithischian origins were monophyletic. This latter inference is strengthened by
the essential homogeneity of structure throughout the Ornithischia.

Tatisaurus and Pisanosaurus appear to have unspecialized dentitions and may be
regarded as fairly close relatives of Fabrosaurus. The great geographic range of this
‘fabrosaur’ group points to some pre-Upper Triassic episode of migrations and dis-
persal. Since most known Triassic ornithischians come from southern Africa the centre
of this hypsilophodont dispersal might reasonably be expected to occur in this region.
This impression of a centre of origin might, however, merely reflect former intensity of
interest, and of collecting, in the African Trias. At any rate the ‘fabrosaurs’ appear to
have been much more adaptable and successful than Heterodontosaurus and the (per-
haps) allied Geranosaurus, characteristics that one would naturally anticipate in the
‘root-stock’ of the ornithischian dinosaurs. Heterodontosaurus seems, in contrast, to
have been a very specialized and localized (African only) off-shoot of the basic hypsilo-
phodont lineage. Whilst the ‘fabrosaurs’ successfully faced the environmental changes
concomitant with the close of the Triassic period, Heterodontosaurus did not, pre-
sumably because it was adapted for a very specific mode of life. There are no apparent
post-Triassic derivatives of Heterodontosaurus.

The first armoured and quadrupedal ornithischians, exemplified by Scelidosaurus,
appear at the beginning of the Jurassic. The disappearance at the end of the Trias of
armoured, quadrupedal, and herbivorous pseudosuchians such as the aetosaurs (Walker
1961) might, in fact, be explained in terms of competition from similarly adapted orni-
thischians. The derivatives of Scelidosaurus, if there be any, cannot be determined at
present.

At some date early in the Jurassic the Fabrosaurus-Hypsilophodon line of hypsilo-
phodonts gave rise to the larger and more specialized iguanodonts. Known iguanodont
remains extend from the Middle Jurassic (Crypto draco') into the late Cretaceous (Cras-
pedodon) and it is probable that there are several distinct evolutionary lines within
this family itself — though these may not be discussed here. The arrangement shown
(text-fig. 9) is in direct contrast to the scheme proposed by Colbert (1951) — where it is
suggested that Hypsilophodon might have arisen from a ‘camptosaurid stem’.

Ostrom (1961) has suggested that the hadrosaurs might have been derived from
Camptosaurus- like iguanodonts by way of intermediates like the poorly known
Claosaurus. This scheme is utilized here (see text-fig. 9).

R. A. THULBORN: FABROSAURUS AUSTRALIS

431

Towards the close of the Jurassic period the basic hypsilophodont stock, exemplified
at this point in time by Echinodon, gave rise to several small ornithopod types which
are of decidedly primitive aspect (e.g. Laosaurus, Nanosaurus). At roughly the same
time a number of diminutive forms ( Psittacosaurus , Protiguanodon ) emerged from a
(presumably) similar source to become highly suggestive of ceratopsian ancestry.

The basic hypsilophodont stock persisted to the very end of the Cretaceous period
with the appearance of Parksosaurus. The last divergence from this lineage, just before
the extinction of dinosaurs in general at the end-Cretaceous, is represented by Thescelo-
saurus. Thescelosaurus possesses a femur which is longer than the tibia (the reverse
being true in the otherwise comparable Parksosaurus) ; this feature suggests that Thes-
celosaurus might have filled an ecological niche similar to that previously exploited by
the iguanodonts (which had a similar tibio-femoral ratio). If this is so it constitutes
evidence that some form of iterative evolution (involving repeated divergences from
a main stem towards a single goal) was an operative factor in ornithopod history.

It may be concluded that Fabrosaurus and its allies represent the earliest known
portion of a hypsilophodont lineage which extended through the greater part of the
Mesozoic era and which gave rise, even if indirectly, to well known and very specialized
ornithischian groups — iguanodonts, hadrosaurs, ceratopsians, and the like. The ‘fabro-
saurs’ appear, in fact, to fulfil the requirements of genuine ornithischian ‘archetypes’.
Heterodontosaurus seems, in contrast, to represent an early and rather specialized
hypsilophodont divergence which failed to survive the close of the Triassic period.

Acknowledgements. My particular thanks go to Dr. K. A. Kermack, of the Department of Zoology,
University College London, for allowing me to work upon the unique specimens described above.
I am also indebted to Dr. A. J. Charig, of the British Museum, Natural History, for permitting me
to examine specimens in his care ( Heterodontosaurus , Echinodon, and Scelidosaurus). Miss S. J.
Plummer has kindly read and criticized the manuscript. This work was made possible through pro-
vision of a research grant from the Natural Environment Research Council.

REFERENCES

broom, r. 1911. On the dinosaurs of the Stormberg, South Africa. Ann. S. Afr. Mus. 7, 291-308.

1913. On the South African pseudosuchian Euparkeria and allied genera. Proc. Zool. Soc. Lond.

1913, 619-33.

BROWN, B. and schlaikjer, e. m. 1940. The structure and relationships of Protoceratops. Ann. N.Y.
Acad. Sci. 40, 133-266.

camp, c. l. 1930. A study of the phytosaurs. Mem. Univ. Calif. 10, 1-161.

casamiquela, R. M. 1967. Un nuevo dinosaurio ornitisquio triasico ( Pisanosaurus mertii ; Ornithopoda)
de la formacion Ischigualasto, Argentina. Ameghiniana, Rev. Asoc. Pal. Argent. 4, 47-64.
colbert, e. h. 1951. Environment and adaptations of certain dinosaurs. Biol. Rev. 26, 265-84.
crompton, a. w. and charig, a. j. 1962. A new Ornithischian from the Upper Triassic of South
Africa. Nature, Lond. 196, 1074-7.

EDMUND, A. G. 1957. On the special foramina in the jaws of many Ornithischian dinosaurs. Royal
Ontario Mus. Div. Zool. Pal. Contr. 48, 1-14.

EWER, r. F. 1965. The anatomy of the Thecodont reptile Euparkeria capensis Broom. Phil. Trans R
Soc. Lond., B248, 379^135.

GALTON, P. M. 1967. On the anatomy of the ornithischian dinosaur Hypsilophodon foxii. Ph.D. thesis,
King’s College, University of London.

ginsburg, l. 1964. Decouverte d’un Scelidosaurien (Dinosaure ornithischien) dans le Trias superieur
du Basutoland. C. r. hebd. Seanc. Acad. Sci., Paris, 258, 2366-8.

Ff

C 7619

432

PALAEONTOLOGY, VOLUME 13

kermack, k. a. 1956. Tooth replacement in mammal-like reptiles of the suborders Gorgonopsia and
Therocephalia. Phil. Tram. R. Soc. B240, 95-133.

ostrom, J. H. 1961. Cranial morphology of the hadrosaurian dinosaurs of North America. Bull. Am.
Mus. nat. Hist. 122, 35-196.

owen, r. 1861. On the Reptilia of the Wealden and Purbeck Formations. Part V. Palaeontogr. Soc.
[Monogr.].

romer, A. s. 1945. Vertebrate paleontology, 2nd ed. Chicago, 687 pp.

1956. Osteology of the reptiles. Chicago, 772 pp.

1968. Notes and comments on vertebrate paleontology. Chicago, 304 pp.

and price, L. w. 1940. Review of the Pelycosauria. Spec. Pap. Geol. soc. Amer. 28.

simmons, d. j. 1965. The non-Therapsid reptiles of the Lufeng Basin, Yunnan, China. Fieldiana,
Geol. 15, 1-93.

walker, A. D. 1961. Triassic reptiles from the Elgin area: Stagonolepis, Dasygnathus and their allies.
Phil. Trans. R. Soc. B244, 103-204.

A RHAETO-LIASSIC FLORA FROM AIREL,
NORTHERN FRANCE

by m. muir and J. h. a. van KONiJNENBURG-van cittert

Abstract. An assemblage of fossil plants from the Upper Triassic/Liassic of Airel (Manche), Northern France,
is recorded, and two new species, Hirmerella airelensis sp. nov. and Classopollis harrisii sp. nov., are described
and figured. In situ and dispersed pollen is compared and a lycopod megaspore and microspore described. The
assemblage is compared with others from France and Wales.

The plant material described in this paper was recovered from some sandy, light-grey
clay collected from Airel in the Carentan basin, near Caen, France. Various suggestions
have been made about the age of the deposit (Larsonneur 1962, 1963) ranging from
Norian to Hettangian. The assemblage is limited, but is generally comparable with the
assemblages described by Levet-Carette (1964) and Briche, Danze-Corsin, and Laveine
(1963) from deposits in the neighbourhood of the Boulonnais. Their material came from
fissure-fillings in the Carboniferous, while our material appears to be lacustrine, the
plants being associated with ostracods and charophytes (Larsonneur 1963).

The macrofossils are in a remarkably good state of preservation; they are almost
uncompressed, and the spiral leaf arrangement is evident. Leafy shoots, fragments of
leaves, female cone-scales, male cone axes, fragments of microsporophylls, and separate
pollen masses were recovered and are here described. Dispersed megaspores, micro-
spores, and pollen from the clay were also examined.

Methods of study. Selected macrofossils were treated by maceration in Schulze’s solution
followed by dilute ammonia. The male cone fragments were recovered by bulk macera-
tion of the clay, which was disintegrated in water, and then treated with Schulze’s
solution. Specimens were then mounted in glycerine, and examined and photographed
with a Leitz Ortholux microscope. Some of the macrofossil cuticles, pollen masses, and
megaspores (both macerated and unmacerated) were mounted on Durofix, coated with
gold/palladium and examined on a Cambridge Instrument Company ‘Stereoscan’
scanning electron microscope.

The microfossils were recovered by a standard method, i.e. disintegration of the clay
in H202, followed by HC1, HF, and HC1 treatment. The residue was then macerated in
concentrated nitric acid and washed in distilled water. The microspores were then
mounted in glycerine jelly and examined and photographed in a Zeiss photomicroscope.

SYSTEMATIC DESCRIPTIONS
Genus hirmerella Hoerhammer emend. Jung
Type species. H. ( Cheirolepis ) muensteri (Hoerhammer) Jung.

Hirmerella airelensis sp. nov.

Plate 78, figs. 1-5; Plate 79, fig. 2; Plate 80, fig. 1 ; text-fig. 1a
[Palaeontology, Vol. 13, Part 3, 1970, pp. 433-42, pi. 78-80.]

434

PALAEONTOLOGY, VOLUME 13

text-fig. 1. Hirmerella airelensis sp. nov. a , Holotype; x2-5. b. Isolated male cone axis; X 30.
c. Partly broken female cone scale, x 5.

Holotype. Specimen 2845 : division of Palaeobotany and Pollen-morphology, Museum and Herbarium
of the State University of Utrecht.

Diagnosis. Leaves spirally arranged; rather variable; free part 2-5 mm. long, 2-4 mm.
wide, leaf-base cushion 2-3 mm. long, 2-4 mm. wide. Cuticle from 1 to 8 p. thick, usually
about 4-6 /x; margin scarious, especially near the apex. Upper cuticle: stomata
mostly arranged in short longitudinal rows, but some irregularly scattered; rows
separated laterally by 3-10 epidermal cells in thin cuticles, 2-6 in thick ones; stomata
within rows separated longitudinally by 2-10 epidermal cells in thin cuticles, 1-6 in

MUIR AND van KONIJNENBURG-van CITTERT: RHAETO-LIASSIC FLORA 435

thick ones; guard cells sunken, not usually visible; 4-6 subsidiary cells forming a thick,
raised ring around the guard cells, often striated and, especially in the thick cuticles,
papillate; encircling cells present but not clear; normal epidermal cells in rows, papil-
late, varying from rectangular with thin walls, to almost square with thick walls; thick
walls often pitted. Lower cuticle similar to the upper, but with more stomata, and with
few papillae on the epidermal cells.

Description. The material consists of a large number of well-preserved small shoots,
usually not more than 2 cm. long. Most of the material is uncompressed and shows the
spiral arrangement of the leaves very well.

The leaves vary considerably in size and proportions, from rather long narrow ones,
with a large free part, and a rather thin cuticle, to broader ones with a short free part
and a rather thick cuticle. All kinds of intermediates between these two extremes have
been found. We believe that the long narrow leaves are immature, whilst the broader
ones are older, although they may represent sun and shade leaves. It is known that the
young and old leaves of recent conifers commonly differ considerably in cuticle thickness
and size of the epidermal cells (Napp-Zinn 1966). We very often find Classopollis
harrisii sp. nov. pollen grains sticking to the thicker cuticles, which reinforces our
opinion that they are older leaves.

Discussion and comparison. These shoots can certainly be placed within the genus
Hirmerella, but they differ in some respects from the type species Hirmerella muensteri.

In H. muensteri, the cells of the upper cuticle do not have papillae, while in our
species, these are prominent. There are more, and longer, rows of stomata, and the
stomata are more closely crowded together within rows in H. muensteri than H. airelen-
sis (Plate 78, fig. 6); the stomata appear to be indistinguishable in the two species.

The presence of male and female cone-scales and of pollen grains which resemble
those of H. muensteri confirm the placing of the new species within the genus Hir-
merella.

This material resembles very closely that described by Lewarne and Pallot (1957)
and Harris (1957) from the Rhaeto-Liassic of Cnap Twt, South Wales, although these
authors did not mention papillae on the upper cuticle, but thickenings. Re-examination
of the material shows the ‘central thickenings’ to be papillae, and the stomata are
rather widely spaced in short rows. Although the Welsh material agrees more in
morphology with our species, it was referred to Cheirolepis (now Hirmerella) muensteri.
Lemoigne (1967) has described some leafy shoots from Saint Fromond (Manche) in the
same region of the Carentan Basin as Airel. Although they were referred to the ‘Cupres-
sales’, in their over-all morphology and cuticular detail, they appear to be identical
with our material. The stomata are very similar, and papillae are present as well. There
seems to be no basis for their assignation to the ‘Cupressales’, and we believe that they
should be placed in Hirmerella airelensis sp. nov.

Our material is closely comparable with that described by Chaloner (1962) from the
Henfield borehole. He found that the isolated leaves are similar in all respects with
those from Cnap Twt described by Lewarne and Pallot (1957) and Harris (1957). He
mentions the papillae on the epidermal cells, but refers his material to Cheirolepis
muensteri. We believe that these leaves, although fragmentary could be referred to
Hirmerella airelensis.

436

PALAEONTOLOGY, VOLUME 13

Wood (1961) describes Cheirolepis muensteri from Lyme Regis, Dorset, England.
While his material is similar to ours, it differs in having very thick cuticles (15-20 p)
and not showing papillae on the walls of the epidermal cells.

Isolated female cone-scales. About ten isolated female cone-scales were found (text-
fig. lc). Among them are a few isolated bract scales which yield good cuticles. The
cuticles are like those of Hirmerella muensteri as described by Hirmer and Hoerhammer
(1934) except that they show papillae on the upper (outer) sides of the cells, which are the
same as those occurring on the vegetative shoots.

Some ovuliferous scales were found too, showing a clear five-fold division (see text-
fig. lc). In one case, a six-fold division was observed, the middle appendage being split.
No complete seeds were discovered, but one megaspore membrane (7 mm. long) was
found in a bulk maceration.

The female cone-scales agree closely with those of Hirmerella muensteri except for
the papillae on the cuticle of the bract scale, and demonstrate that this new fossil conifer
must be placed within the genus Hirmerella. Harris (1957) stated that he had found
female cone-scales like those of Hirmerella muensteri , but he does not give any descrip-
tion or drawing. There are no preparations of female cone-scales in his material kept at

EXPLANATION OF PLATE 78

All transmitted light photographs of macerated cuticles.

Figs. 1-5. Hirmerella airelensis sp. nov. 1, Upper cuticle, showing papillae in the cells; X250. 2,
Thin lower cuticle, showing stomata; x 250. 3, Stoma, showing striations on the subsidiary cells;
X750. 4, Detail of epidermal cells showing pitting of walls ; X750. 5, Cell outlines and stomatal
arrangement at edge of upper and lower cuticle; x250.

Fig. 6. Hirmerella muensteri (Schenk) Jung. Cell outlines and arrangement of stomata, for comparison
with fig. 5; note absence of papillae; x250.

EXPLANATION OF PLATE 79

Figs. 1, 3. Stereoscan photographs of pollen mass of Classopollis harrisii sp. nov. 1, General mor-
phology of the whole mass; x 300. 3, Morphology of single grain (centre), with series of pustules
on surface representing collapse of outer surface of wall over the coarse bacula ; x 1 500.

Fig. 2. Stereoscan photograph of edge of cuticle of Hirmerella airelensis sp. nov., showing the papillae,
and three stomata arranged in a row; x250.

Fig. 4. Pollen mass of Classopollis harrisii sp. nov. showing an immature grain with a thin wall and
tetrad mark; x 1000.

Figs. 5-8. Classopollis harrisii sp. nov.; x 1000. 5. Very immature grain showing prominent triradiate
mark, and weakly developed wall structure. 6, Smooth inner body, isolated by pressing the cover
slip. 7, Co-type of dispersed pollen species, showing all general features. 8, Holotype of dispersed
pollen species, showing coarse baculae clearly.

EXPLANATION OF PLATE 80

Fig. 1. Hirmerella airelensis sp. nov., slightly compressed shoot showing leaf arrangement; Stereoscan
photograph, x25.

Fig. 2-5. Bacutriletes tylotus (Harris) Potonie. 2, Stereoscan photograph showing the general mor-
phology and triradiate mark; x200. 3, Transmitted light photograph of B.M. specimen V 32623
of Lewarne and Pallot, for comparison with fig. 2; x200. 4, Detail of fig. 2; x400. 5, Detail of
fig. 3; x400.

Figs. 6, 7. Heliosporites reissingeri (Harris) Chaloner 1969. 6, Detail of spine and surface; X 1000.
7, whole grain; x600.

Palaeontology , Vol. 13

PLATE 78

MUIR and van KONIJNENBURG van CITTERT, Mesozoic conifer cuticles

Palaeontology , Vol. 13

PLATE 79

MUIR and van KONIJNENBURG van CITTERT, Mesozoic conifer pollen

Palaeontology, Vol. 13

PLATE 80

MUIR and van KONIJNENBURG van CITTERT, Mesozoic conifer and spores

MUIR AND van KONIJNENBURG-van CITTERT: RHAETO-LIASSIC FLORA 437

the British Museum (Natural History), where all the other Rhaeto-Liassic material
is deposited, and so comparison with Harris’s material is not possible.

The female cone- scales described by Lemoigne (1967) are papillate, but have eight
appendages, and so appear to differ somewhat from the Airel specimens, but the illus-
trated specimens appear to be broken, and may, in fact, only have five or six appendages.

Isolated male cones. Fragments of male cones are common in the Airel material, but no
complete cones have been found, here or elsewhere. There is one isolated male cone
axis (3 mm. long), showing the spiral arrangement of the microsporophylls clearly,
but there are no microsporophylls adhering (text-fig. 1b). Isolated microsporophylls
are common, but none of them has the pollen sacs attached. Microsporophyll heads are
almost peltate, the stalk being slightly tilted and attached nearer to the base. They are
about 2 mm. long and 2-5 mm. wide. Just below the stalk, there are two regions (one on
either side) which are very sunken and polished, indicating the places of attachment of
the pollen sacs. The Cnap Twt material of Harris (1957) also had two attachment areas.
In Hirmerella muensteri (Hoerhammer 1933, Hirmer and Hoerhammer 1934, Jung
1968), however, there are up to twelve pollen sacs on one microsporophyll. Barnard
(1968) found a situation similar to this in his material from the Liassic of Iran.

Isolated pollen sacs are also found, usually about T5 mm. long, 0-5 mm. wide, and
almost circular in section. The wall of the pollen sac is very thin ( c . 0-5 p) and composed
of rectangular cells. They yield pollen grains in different stages of maturity which are
described under C/assopollis harrisii sp. nov.

These isolated male cone fragments can be assigned with reasonable certainty to
Hirmerella airelensis sp. nov. since the leaves are the only macrofossils in this material.
The evidence of association is thus strong. Harris (1957) also described male cone
fragments from Cnap Twt which he attributed to Cheirolepis muensteri, by far the most
common macrofossil in that assemblage, although he found some dispersed cuticles of
other species as well.

We believe that those fragments can be attributed to Hirmerella airelensis instead of
H. muensteri because of their association with the leaves. Both male cone fragments
differ from H. muensteri in having probably only two pollen sacs in each microsporophyll,
while H. muensteri has a ring of twelve on each microsporophyll.

Genus classopollis Pflug 1953
Type species. C. classoides Pflug 1953.

Classopollis harrisii sp. nov.

Plate 79, figs. I, 3-7

Holotype. Specimen 2845a: division of Palaeobotany and Pollen Morphology, Museum and Her-
barium of the State University of Utrecht.

Dimensions. Maximum diameter 37-0 p; minimum diameter 22-2 p; average size 25-6 p. Holotype:
maximum diameter 37-0 /x; minimum thickness of wall 1 /x; maximum thickness of wall 6/x.

Diagnosis. Pollen grains spherical; characterized by an equatorial thickening which is
divided off from the distal polar area by a thin ring furrow; no striations visible; no

438

PALAEONTOLOGY, VOLUME 13

distal pore seen; proximally triradiate, tetrad mark usually not distinct; exine two-
layered; outer layer tegillate; inner layer thin, indistinct. Exine varies in thickness from
1 to 6 p.

Description. These well-preserved grains can clearly be placed within the genus
Classopollis, but are distinguished from previously described species by the absence of
equatorial striations, and by the apparent absence of a distal pore (Plate 79, figs. 7, 8).
The pollen grains have never been observed in tetrads, and this too is a distinctive
feature. It can be separated from Circulina meyeriana Klaus 1960 by the prominent exine
structure in C. harrisii.

Discussion. Almost the entire assemblage of dispersed spores from this locality consists
of Classopollis harrisii sp. nov. (over 99% of the entire assemblage). This is typical of
Rhaeto-Liassic assemblages, and less common earlier, suggesting that the assemblage
is more likely to be Rhaetian than Norian.

The dispersed pollen grains can be closely compared with most of the pollen in situ
in the pollen sacs and pollen masses associated with Hirmerella airelensis sp. nov., but
the in situ pollen shows considerable variation. This probably reflects different stages in
the development of the pollen grains. None of the pollen found, whether in situ, or
dispersed, occurs in tetrads. This suggests that the grains went through the stage of tetrad
formation before sporopollenin was deposited, and only separated grains are pre-
served. This would also tend to explain why the tetrad mark is not well developed on
many grains.

We have found in situ some very small grains (11*1 p to 18-5 p maximum diameter)
which all possess very thick-walled, smooth inner bodies. The inner bodies are completely
spherical and rarely show any sign of either a tetrad mark or distal pore; sometimes, they
possess an equatorial thickening which has no internal structure, although it is occasion-
ally delimited by a ring furrow. The wall structure of the outer body is poorly developed,
and the wall material is rather thin (Plate 79, fig. 5).

In the same pollen mass are more mature grains which still possess an inner body,
but this is rather thin-walled and has no equatorial thickening (Plate 79, fig. 6). The
outer layer of the exine has become thicker and its tegillate structure has become much
more obvious. The equatorial region of the outer wall is frequently detached from the
inner body, and the furrow ring clearly developed. Occasional striated grains are found
at this stage of development.

In sporangia with mature grains, the inner body is almost undetachable, either because
it is very thin, or because it has become closely attached to the outer layer. No striations
are visible, but the ring furrow is very distinct. The dispersed pollen recovered from the
clay is exactly like this. Inner bodies are only occasionally visible.

Comparison. These spores agree well with those described by Harris (1957) from the
Rhaeto-Liassic of Cnap Twt and Ewenny, South Wales. He described the inner body
of the grains and commented that its variability of preservation may be due to preserva-
tion of the intine ‘partly impregnated with oil’. The electron microscope studies of
Pettitt and Chaloner (1964) on Classopollis from Cnap Twt, show the presence of an
internal layer corresponding to the inner body, as well as the coarse inwardly pointing
baculae of the outer wall. These baculae can be seen on the Stereoscan photographs of

MUIR AND van KONIJNENBURG-van CITTERT: RHAETO-LIASSIC FLORA 439

pollen in pollen masses (Plate 79, figs. 1, 3) standing up as positive projections with the
external layers of the exine collapsed over them. Our pollen grains agree in size with
those of Harris, and the only difference appears to be that Harris described thin areas
on the inner bodies which he believed to represent the polar regions. However, we believe
that our grains are similar to those described by Harris, if not identical; Harris did not
name a species.

Classopollis harrisii sp. nov. differs from C. belloyensis Pocock and Jansonius 1961
in the lack of separation of the two layers of exine in the mature grains.

Rioult and Levet-Carette (1966) described three species of Classopollis under the
generic name of Classopollenites from Cotentin, and assigned a Lower Lias age to the
assemblage. In spite of the near geographical position, none of these species appear to
be identical with C. harrisii : Classopollenites tripartitus is triangular in outline, and is
ascribed by Rioult and Levet-Carette to the Pteridosperms, although not with any great
certainty.

Classopollenites ( Classopollis ) classoides Pflug is equatorially striated and although
the wall structure of Classopollenites minor is similar to that of C. harrisii, it is described
as having a prominent tetrad mark, and distal pore.

Pollen associated with Brachyphyllum scottii Kendall 1948 resembles C. harrisii
sp. nov. closely, being normally non-striate, but has much finer wall structure, and
occasionally occurs in tetrads. The Masculostrobus pollen described by Barnard (1968)
associated with Brachyphyllum expansum from Iran differs from ours in the large number
of striations on the equatorial thickening.

Genus bacutriletes (van der Hammen 1954) Potonie 1956
Type species. B. ( Triletes ) tylotus (Harris 1935) Potonie (1956).

Bacutriletes tylotus (Harris 1935) Potonie 1956

Plate 80, figs. 2-5

1935 Triletes tylotus Harris, p. 162.

1956 Bacutriletes tylotus (Harris) Potonie, p. 35.

1957 Triletes tylotus Harris; Lewarne and Pallot, p. 77, fig. 3 a, d.

1962 Bacutriletes tylotus (Harris) Potonie; Marcinkiewicz, p. 471.

Dimensions. Maximum diameter 475 p; minimum diameter 350 p (10 specimens); height of spines
20-5 p; width of spines 6-12 p; spines separated by distances of 5-10 p.

Description. Our megaspores are very similar to those described by Lewarne and Pallot
(1957). The triradiate mark is indistinct, but slightly elevated (illustrated fig. 3a of
Lewarne and Pallot, but not described). The spines show a slight characteristic cross
striation, also described from the Welsh material.

Discussion and comparison. The only megaspore comparable with this species is Triletes
sparassis Murray 1939, from which it differs in the size and shape of the ornamentation.
Bacutriletes tylotus has much more distinct spines.

440

PALAEONTOLOGY, VOLUME 13

Genus heliosporites Schulz 1965
Type species. H. altmarkensis Schulz 1965.

Heliosporites reissingeri (Harris 1957) Chaloner 1969
Plate 80, figs. 6, 7

1950 Cf. Selaginella kraussiana Reissinger, p. 104, pi. 12, fig. 28.

1957 Lycospora reissingeri Harris, p. 305, fig. 6, A, d.

1969 Heliosporites reissingeri (Harris 1957) Chaloner 1969.

Dimensions (10 specimens). Maximum over-all diameter, 49 /x; minimum over-all diameter, 35 fi;
average width of cingulum, 10 /u.; average length of spines, 10 /x.

Diagnosis. Harris (1957) gave a full diagnosis for this species, but the striations on the
contact faces were not seen.

Description. The spores are clearly identical with those described by Harris (1957) as
Lycospora reissingeri. A new combination of Heliosporites reissingeri (Harris 1957) has
been proposed by Chaloner (1969).

CONCLUSIONS

The resemblance of this material to that described by Lewarne and Pallot (1957) and
Harris (1957) and to the pollen studied by Pettitt and Chaloner (1964) from the fissure
depths of Cnap Twt, Glamorgan, is remarkable. The cuticles of our material, with their
distinctive stomatal arrangement and papillae are similar to those described from Wales.
The male cones and pollen masses are also identical, and although our assemblage is
rather restricted, the dispersed spores and pollen are also the same. We believe that the
association of organs is so strong that the conclusion that the leafy shoots, female cone-
scales, male cone fragments, and dispersed pollen grains come from one and the same
plant is inescapable.

Unlike Lemoigne (1967) we do not believe that his (and our) material is Cupressalean.
His assignment was based mainly on the wood fragments he found; Mr. van der Burgh
studied some of our wood fragments and looked at Lemoigne’s illustrations, and he
believes that wood of this type may occur not only in the Cupressaceae, but probably
also in other fossil conifer families such as the Voltziaceae and Cheirolepidaceae. The
wood fragments described by Harris (1957) also look very like Lemoigne’s and ours
although our material was not fusainised. It does appear, therefore, on the evidence of
association, that the wood fragments also belong to the same plant as the leaves, female
cone-scales, male cone fragments, and pollen.

Heliosporites reissingeri and Bacutriletes tylotus have been found associated both at
Airel and Cnap Twt, and this leads us to suggest that they represent the megaspores and
microspores of one lycopodiaceous plant.

In our material we have evidence of a large amount of the Hirmerella conifer, which
must have comprised almost a pure stand, and a lesser amount of the lycopod. The more
varied assemblage found by Harris (1957) in the fissure fillings, which are comparable
with those of the Boulonnais from which a plant assemblage was described by Briche

MUIR AND van KONIJNENBURG-van CITTERT: RH AETO-LIASSIC FLORA 441

et oil. (1963) and Levet-Carette (1964), probably includes plant fragments washed in
from some distance away, while our material, being lacustrine, is probably more or less
local in origin.

Acknowledgements. We are grateful to Mr. Robin Stevenson, Kingston College of Advanced Tech-
nology, Great Britain, and the 1966 year of geology students from the University of Utrecht, the
Netherlands, for collecting this material for us; also to Mr. Rypkema who made the drawings.

REFERENCES

barnard, p. d. w. 1968. A new species of Masculostrobus Seward producing Classopollis pollen from
the Jurassic of Iran. J. Linn. Soc. Lond. ( Bot .) 61, (384), 167-76.
boltenhagen, E. 1968. Revision du Classopollis Pflug. Rev. Micropaleont., 11, 29-44.
briche, p., danze-corsin, p. and laveine, j.-p. 1963. Flore infraliassique du Boulonnais (macro- et
microflore). Mem. Soc. geol. Nord, 13.

chaloner, w. G. 1962. Rhaeto-Liassic plants from the Henfield Borehole. Bull. geol. Surv. G.B., 19,
16-28.

1969. Triassic spores and pollen, tschudy, r. h. and scott, r. a. (eds.) Aspects of Palynology.

John Wiley, New York.

Harris, t. m. 1935. The fossil flora of Scoresby Sound, East Greenland. Part IV. Medd. Gronland,
112, (1). 1-176.

1957. A Rhaeto-Liassic flora in South Wales. Proc. Roy. Soc. Lond.. B147, 289-308.

hirmer, M. and hoerhammer, L. 1934. Zur weiteren Kenntnis von Cheirolepis Schimper und Hirmeriella
Hoerhammer mit Bemerkungen iiber deren systematische Stellung. Palaeontographica , B79, 67-84.
hoerhammer, L. 1933. Uber die Coniferen-Gattungen Cheirolepis Schimper und Hirmeriella nov. gen.

aus dem Rhaet-Lias von Franken. Bibl. Bot. Stuttgart, 107, 1-34.
jung, w. w. 1968. Hirmerella muensteri (Schenk) Jung nov. comb., eine bedeutsame Konifere des
Mesozoikums. Palaeontographica, B122, 56-93.

kendall, M. w. 1949. On a new conifer from the Scottish Lias. Ann. Mag. nat. Hist., Ser. 12, 2, 299-
307.

klaus, w. 1960. Sporen der karnischen Stufe der Ostalpinen Trias. Jb. Geol. Bundesanst. Wien,
Sonderbd., 5, 107-84.

larsonneur, c. 1962. Facies, Faune, et Flore du Keuper superieur-Rhetien dans la region d’Airel
(Manche), Bordure sud du Bassin de Carentan. Mem. Soc. Sci. Nat. et Math. Cherbourg, 50, 72-116.
— — 1963. Contribution a l’etude du Trias superieur du Bassin de Carentan (Manche). Bull. Soc.
Linn. Normandie, Ser. 10, 4, 23-32.

lemoigne, y. 1967. Paleoflore a Cupressales dans le Trias-Rhetien du Cotentin. C.R. Acad. Sci. Paris,
Ser. D, 5, 715-18.

levet-carette, J. 1964. Etude de la microflore infraliassique d’un sondage effectue dans le sous-sol de
Boulogne-sur-mer (Pas-de-Calais). Ann. Soc. geol. Nord, 83, 101-28.
lewarne, g. and pallot, j. m. 1957. Mesozoic plants from fissures in the Carboniferous Limestone of
South Wales. Ann. Mag. nat. Hist., Ser. 12, 10, 72-9.
marcinkiewicz, t. 1962. Rhaetian and Lias Megaspores from borehole Mechowo near Kamien
Pomorski. Inst. Geol. Prace, 30, 3, 469-94.

Murray, n. 1939. The Microflora of the Upper and Lower Estuarine Series of the East Midlands. Geol.
Mag. 76, 478-89.

napp-zinn, k. 1966. Anatomie des Blattes, I. Gymnospermen. Encyclopedia of Plant Anatomy, 8 (1),
1-369.

pettitt, j. m. and chaloner, w. g. 1964. The ultrastructure of the Mesozoic pollen Classopollis.
Pollen et Spores, 4, 611-20.

pocock, s. a. J. and jansonius, j. 1961. The pollen genus Classopollis Pflug 1953. Micropaleontology,
7, 439-49.

potonie, r. 1956. Synopsis der Gattungen der Sporae dispersae. I. Teil, Sporites. Beih. Geol. Jahrb.
23, 1-163.

reissinger, a. 1950. Die ‘Pollenanalyse’ ausgedehnt auf alle Sedimentgesteine der geologischen Vor-
gangenheit. Zweiter Teil. Palaeontographica, B90, 99-126.

442 PALAEONTOLOGY, VOLUME 13

rioult, m. and levet-carette, j. 1966. Microflore infraliassique du Cotentin. Ann. Soc. geol. Nord,
85, 283-99.

schulz, e. 1962. Sporenpalaontologische Untersuchungen zur Rhat-Lias-Grenz in Thuringen und
der Altmark. Geologie, 11, (3), 308-510.

1967. Sporenpalaontologische Untersuchungen Rhatoliassischer Schichten in Zentralteil des

Germanischen Beckens. Palaont. Abh., B2, (3), 427-633.
wood, c. J. 1961. Cheirolepis muensteri from the Lower Lias of Dorset. Ann. Mag. nat. Hist., Ser. 13,
4, 505-10.

MARJORIE MUIR

Geology Department:
Imperial College
Prince Consort Road
London, S.W. 7

JOHANNA H. A. Van KONIJNENBURG-Van CITTERT

Division of Palaeobotany
Museum and Herbarium
University of Utrecht
Utrecht, The Netherlands

Revised typescript received 20 October 1969

CALCAREOUS ALGAE NEW TO THE BRITISH
CARBONIFEROUS

by GRAHAM F. ELLIOTT

Abstract. The first British records of two Lower Carboniferous algal taxa known from the U.S.S.R. and else-
where are given: Ungdarella deceanglorum sp. nov., representing the Ungdarellaceae, an extinct red algal family;
and Exvotarisella maponi gen. et. sp. nov., representing the tribe Bereselleae of the family Dasycladaceae (green
algae). U. deceanglorum is from the Visean of Wales, probably lower D2 Zone: E. maponi comes from the
D2 Zone of Northumberland. Exvotarisella is considered to be structurally the most advanced genus of the
Bereselleae.

During an examination of that part of the Garwood collection of fossil algae in the
British Museum (Natural History) two interesting occurrences were noted of algae
described from Russia and well known from elsewhere, but not until now from Britain.
The genera represented are Ungdarella, referable to the Rhodophyceae or red algae
but not to any living family of this class, and a new genus of the dasycladacean tribe
Bereselleae (Chlorophyceae or green algae). Both occur in this country in the Lower
Carboniferous, Visean, D2 Zone, and are now described below.

RHODOPHYCEAE

Family ungdarellaceae Maslov 1956
Genus ungdarella Maslov 1950

Remarks. This genus was described by Maslov (1950) from the Russian Upper
Carboniferous and subsequently recognized in Iraq, Turkey, Austria, Spain, the north-
west African Sahara, and the U.S.A. with a total range of Lower Carboniferous
(Visean) to Upper Permian (Toomey and Johnson 1968). It is a calcified branching
twig-like form, compared by Maslov and others in internal structure with two living
non-calcified red algae, Ahnfeldtia and Cystoclonium, though not identical with either
nor referable to the families Phylloporaceae and Rhodophyllidaceae to which they
belong.

Ungdarella deceanglorum sp. nov.

Plate 81, figs. 1-5

Diagnosis. Small slender species of Ungdarella, with almost completely uncalcified
medullary zone, and with less conspicuous cortical cell-detail than in other species.

Description. Calcified cylindrical branching thallus, twig-shaped, branches near-circular
in cross-section and slightly irregular, length about 3 mm. or more (2-86 mm. seen),
diameter often 0-26 mm. (0T4— 0-39 mm. seen). Branching at irregular intervals, the angle
of divergence ranging from 45 to 1 1 0°. Internally the thallus shows a thick calcified cortical
zone surrounding an uncalcified central medullary zone: this latter is almost always a
third or a little less of the outer diameter. Thus in specimens of the common diameter of

;[PalaeontoIogy, Vol. 13, Part 3, 1970, pp. 443-50, pi. 81-83.]

444

PALAEONTOLOGY, VOLUME 13

0-26 mm. the medullary zone is 0-078 mm. diameter, surrounded by a cortical zone
0-091 mm. thick. This medullary zone is filled with clear calcite, or with strings and
groups of dolomite crystals. In other species of Ungdarella this zone is occupied by
calcified medullary cells, arranged in single or several axial strings, though not as heavily
calcified as the cells of the outer, cortical zone. In two sections only of the British species
it was possible from the arrangement of the dolomite crystals, colour of the calcite,
etc., to measure single presumed medullary cells: they were 0-045-0-050 mm. long by
0-020 mm. wide, and 0-039 mm. long by 0-026 mm. wide. Both were central in posi-
tion, and it is uncertain whether the remainder of the uncalcified medullary space was
occupied by parallel strings of similar cells, or whether it formed the place of origin
of the divergent cortical cells before they became calcified. This uncalcified medullary
zone distinguishes U. deceanglorum from other species of the genus, whose authors were
able to measure and describe medullary cells when sufficient material was available
(cf. U. uralica, PI. 83, fig. 6).

The cortical cells are well calcified and form the whole thickness of the outer zone.
They show as close-packed parallel single strings or files of cells, inclined at an acute
angle of 10-15° to the long axis of the branch, so that they traverse a considerable length
before reaching the exterior. A slight irregularity is occasioned by sporadic division, the
new cell-strings continuing close-packed with the others. The individual cells are about
0-016 mm. long and 0-013-0-014 mm. wide, squarish in cross-section but in sections
taken adjacent to and below the sites of thallus-branching the proportions alter:
examples are 0-013 mm. long by 0-020 mm. wide, and 0-010 mm. long by 0-013 mm.
wide. The main lateral cell-walls are much more conspicuous than the transverse septa
in vertical section. In oblique transverse sections the steep inclination of the cell-strings
occasions a curious appearance, one side of the section showing a concentric structure
and the other an irregularly radial one.

U. deceanglorum has the characteristic thin-section appearance of other species of the
genus: a bleached wood or watered silk effect. The cell-details of Ungdarella are not
conspicuous as in the Solenoporaceae or Corallinaceae, and in U. deceanglorum this
negative character is especially marked.

Holotype. The specimen figured in Plate 81, fig. 1 from the Lower Carboniferous, White Limestone
Division, probably Lower D2: Bron-heulog Quarry, Trefor Rocks, 1 J miles east of Llangollen, Den-
bighshire, Wales. (Wedd 1927, pp. 109, 129, 148.) Brit. Mus. (Nat. Hist.), Department of Palaeontology,
reg. no. V55400.

EXPLANATION OF PLATE 81

Figs. 1-5. Ungdarella deceanglorum sp. nov. Lower Carboniferous. White Limestone Division, probably
lower D2; Bron-heulog Quarry, Trefor Rocks, Llangollen, Denbighshire, Wales. All from reg.
no. V55400. 1, Holotype, longitudinal section showing branching of thallus, fine oblique divergent
files of cortical cells, and medullary zone replaced by light transparent calcite or dark dolomite
crystals. Other, random cuts in section; x 30. 2, Longitudinal section of another branching speci-
men; x 30. 3, Longitudinal and transverse sections, the former showing files of cortical cells, and
medullary zone replaced by transparent calcite with central string of dolomite crystals suggesting
original single string of large medullary cells; x 40. 4, Two transverse sections, slightly oblique; the
larger showing clearly the radial appearance of cortical cell-structure on one side of the section and
concentric appearance on the other, typical of such sections; x 40. 5, Another longitudinal section
showing layered appearance of cortical cells, and medullary zone replaced in different areas by light
transparent calcite or areas of dark dolomite crystals; x 40.

Palaeontology, Vol. 13

PLATE 81

ELLIOTT, Carboniferous Rhodophyceae (Algae)

ELLIOTT: CALCAREOUS ALGAE NEW TO THE BRITISH CARBONIFEROUS 445
Paratypes. The specimens figured in Plate 81, figs. 3, 4; from the same thin-section as the holotype.
Other material. Numerous other random sections.

Remarks. Toomey and Johnson (1968) gave detailed comparison-tables for structures
and measurements of all described Ungdarella spp. up to date. U. deceanglorum is a
smaller, more slender species, with smaller cortical cells, than both the type U. uralica
Maslov, and the other Visean species U. maslovi Chanton. The non-calcified medullary
zone of the British species is characteristic. The species throws no light on the disputed
basal attachment in this genus (Toomey and Johnson 1968, p. 560), and no reproductive
structures have been recognized.

Of the two living non-calcified red algae with which Ungdarella has been compared,
Ahnfeldtia shows irregularly concentric rings of secondary thickenings, considered to
be in part associated with successive dichotomies (Fritsch 1945, p. 495). In U. decean-
glorum the apparent concentricity arises from the angle of cut across the normal cortical
cells. Cystoclonium shows near-vertical medullary cells, but those of the cortex are much
more irregular and directed outwards at a much greater angle from the branch-axis than
in U. deceanglorum. Although these comparisons are valid, and Ungdarella probably was
a red alga, the relationship is not necessarily close.

Associated in the type thin-section are small foraminifera, brachiopod, and echinoderm
debris, and the dasycladacean alga Koninckopora inflata (de Kon.) Wood.

The specific name commemorates the old British tribe of Deceangli, whose territory
in Roman times lay in what is now Flintshire and part of Denbighshire.

CHLOROPHYCEAE-BERESELLEAE

The Bereselleae are a tribe of tiny dasycladacean algae of Carboniferous age, the genera
mostly described from the U.S.S.R., and reviewed by Kulik (1964), and later recognized
from rocks of the same age in Turkey and in the north-west African Sahara.

The British examples now recorded were first noted in a Garwood Collection thin-
section labelled ‘Oxford Limestone, Bean Bed, base D2; Northumberland’. This is a
well-known band at the base of the Lower Carboniferous Middle Limestone Group in
the Northumberland Province: the limestone contains small partly pyritic organic
nodules with Girvanella, first recognized and studied by Garwood. Search in the collec-
tion produced a limestone specimen labelled similarly to the thin-section, but further
annotated by Garwood. From this it appears that the limestone came from one of two
old exposures of the Oxford Limestone at Wisplaw. This locality is four miles north-
north-east of Alnwick, Northumberland ; the old exposures are mentioned in Carruthers
(1930, p. 46). The Oxford from which the limestone takes its name is a tiny locality
four miles south of Berwick-on-Tweed. Further thin-sections cut from the limestone
were closely similar to the original section, and showed more Bereselleae.

Subsequent discoveries, summarized and discussed in a recent study of the Lower
Limestone Group of the Otterburn, North Tyne area of Northumberland by Frost
(1969), have shown that the Oxford Limestone does not mark the base of the D2 Zone,
which occurs considerably below this (Frost 1969, pp. 299-301, fig. 6). The Oxford lime-
stone is therefore not basal D2 as Garwood considered, but well within this zone.
The nodules with Girvanella are determined by Frost as Osagia (Twenhofel 1919), a

446

PALAEONTOLOGY, VOLUME 13

form-genus applied to some Palaeozoic nodular associations of small algal filaments
and encrusting nubeculariform foraminifera (cf. Johnson 1946, 1947).

CHLOROPHYCEAE

Family dasycladaceae Kiitzing 1843 orth. mut. Hauck 1884
Tribus bereselleae Maslov and Kulik 1956
Genus exvotarisella gen. nov.

Diagnosis. Large atypical member of the Bereselleae showing primary, secondary, and
tertiary branches as in the subgenus Trinodella but with thick primary and secondary
branches (unlike Trinodella where all branches are uniformly thin), and with tertiary
branches much longer than primary and secondary branches (in Trinodella the primary
branches are longer than the secondary and tertiary branches). Lower Carboniferous,
D2: Northumberland, England. Type-species: E. maponi sp. nov.

Exvotarisella maponi sp. nov.

Plate 82, figs. 1-5, Plate 83, figs. 1-5

Description. Calcareous hollow dasyclad cylinder, straight or gently curved, of up to
5 mm. or more length (5-096 mm. seen broken), with diameters of 0-26-0-45 mm.
external and 0-104-0-195 mm. internal (d/D 40-47%). Verticils of horizontally directed
lateral branch-systems, each estimated to contain 14-20 primary branches. The verticils
are set 0-039-0-065 mm. apart along the stem-cell cavity; between them the stem-cell
cavity constricts slightly, to give a regular internal annulation. In general the detailed
dimensions are more or less proportional to external size, but relatively long, slim speci-
mens occur noticeably. Primary branches of about 0-026 mm. diameter at the stem-cell,
extending outwards for 0-026 mm. before bifurcating. Secondary branches diverging
at about 45°, with diameter of 0-013 mm. and length of 0-026 mm.; tertiary branchlets
about 0-005 or 0-006 mm. diameter, but 0-052-0-078 mm. long. Each primary probably
divides into four secondaries, and each secondary probably into four tertiaries : possibly
with some variation in this character.

Holotype. The specimen figured in Plate 82, fig. 2; from the Lower Carboniferous, Northumberland
Middle Limestone Group, Oxford Limestone, D2 Zone: Wisplaw, Alnwick, Northumberland. Brit.
Mus. (Nat. Hist.), Dept. Palaeont., reg. no. V55393.

EXPLANATION OF PLATE 82

Figs. 1-5. Exvotarisella maponi gen. et. sp. nov. Oxford Limestone, Bean Bed; Lower Carboniferous,
Do Zone. Wisplaw, Alnwick, Northumberland. 1 , Longitudinal section of slightly curved and sinu-
ous large example, ordinary preservation, x30; reg. no. V55398. 2, Holotype, slightly oblique
transverse section, pyritic preservation, showing pyrite-filled branch-structure with primary,
secondary, and tertiary branching, x60; V55393. 3, Paratype; oblique-transverse section, pyritic
preservation, showing internal annulation and pyrite-filled primary, secondary, and tertiary branches,
x60; V55399. 4, Longitudinal section of slightly sinuous individual, ordinary preservation, x40;
V55391. 5, Slightly oblique transverse section, pyritic preservation, individual with long, slim,
atypical branches (cf. Dvinella or Trinodella), x 60; V55396.

Palaeontology , Vol. 13

PLATE 82

ELLIOTT, Carboniferous Chlorophyceae (Algae)

ELLIOTT: CALCAREOUS ALGAE NEW TO THE BRITISH CARBONIFEROUS 447

Paratype. The specimen figured in Plate 82, fig. 3; same locality and horizon as holotype. Brit. Mus.
(Nat. Hist.) Dept. Palaeont., reg. no. V55399.

Other material. Very numerous sections in seventeen thin-sections prepared from the same sample.

Remarks. Although the general appearance of members of the Bereselleae is charac-
teristic, distinction between the component genera is often difficult. This is due to the
extreme fineness and close grouping of the lateral branches, so that the exact nature of
the preservation is very important.

Of the five genera or subgenera of the Bereselleae described hitherto, Beresella,
Samarella, and Goksuella show various groupings of single lateral branches (primaries) :
in DvineUa these primaries divide once into several secondaries, and in Trinodella these

text-fig. 1. Diagrammatic two-dimensional representation of branching in DvineUa, Trinodella, and
Exvotarisella (left to right). There are at least four branches at each point of division in the actual
three-dimensional specimens, and the relative branch-lengths vary between different species of DvineUa
and similarly between species of Trinodella.

in turn divide into tertiaries (Maslov and Kulik 1956, Giivenc 1966). Goksuella is set
apart by a branching thallus ; in all the others the thallus is a single, straight or curved,
rod-hke structure.

In the Northumberland fossils preservation is usually poor for elucidation of detail;
in thin-section the areas of branch-structure, representing consecutive verticils, appear
as grey truncate cones, amorphous or with the branch-structures indistinct. Calcite
crystals may be continuous from the stem-cell filling into the replacement calcite of the
walls, so that the boundary is only traceable by a faint colour-change. Some of the
branches have the appearance of division, but this could be due to bunched primaries.

There exists a minority of specimens showing partial pyritic preservation, usually
found in the vicinity of the organic partly pyritic nodules with Girvanella and encrusting
organisms. Here again, preservation has been capricious, and in most cases the pyrites
fills the stem-cell, or encrusts the outer surface of the tubular dasyclad, but does not
penetrate into the branch-systems. It is only with the very small minority of specimens
showing pyritic branch-infilling that the diagnostic reference may be made. These show
primaries branching into secondaries with great clearness, but care has to be taken to
distinguish between true tertiary branching and the regions of apparent overlap between
bunched secondaries (cf. Dvinella, Khvorova 1949). Thus the tertiary branching charac-
teristic of Trinodella and Exvotarisella can be definitely seen only on very few specimens,
which appear to be favourably orientated sections of those showing secondary branching

C 7619 G g

448 PALAEONTOLOGY, VOLUME 13

as in Dvinella. The earlier portions (lower thallus) of individuals of Trinodella and
Exvotarisella may by analogy with other dasyclads be expected to show simpler,
Dvinella structure only, as mentioned below (p. 449).

The position is, then, that definite Bereselleae are not uncommon in the Oxford Lime-
stone of Wisplaw. The minority of individuals which are preserved to show fine detail
are all recognizable as the new genus or may be supposed to be so. None of the others
show equal clarity of detail to be definitely referable to other genera. It would seem
reasonable, therefore, to suppose that all are referable to the one genus and species,
though there are one or two doubtful individuals. The types chosen show fine detail
and in this respect are not typical of the majority of the specimens : the branch-dimensions
given above under ‘Description’ are based on the former. It is true that in Saharan
Carboniferous rocks examined by me more than one genus of Bereselleae occurs in the
same section, but in these Bereselleae are so abundant as to make up an appreciable
portion of the rock-volume. In the Northumberland rock they form a minor element
only.

Exvotarisella maponi is easily distinguishable from another tiny English Carboniferous
dasyclad, Nanopora anglica (Wood 1964), which shows simple straight primaries set
almost equidistantly, and not bunched.

Exvotarisella differs from the three species of Trinodella tabulated by Kulik (1964),
by its large size, thickened primary and secondary branches, and in the differing relative
proportional lengths of primary, secondary, and tertiary branches and branchlets, though
this last character differs between the species of Trinodella. The branch-thickening is
important: in most Bereselleae the branches are of uniform thickness, usually about
0-002 or 0 005 mm. diameter, whether single, or dividing once as in Dvinella or twice
as in Trinodella. Only in Dvinella gracilis Kulik are the secondaries of lesser diameter
than the primaries. Trinodella is less common than Dvinella and is placed by the Russians
as a subgenus of the latter. In an interesting correlation between the structure of the
Bereselleae and their ecology (based on the nature of the sediments in which the fossils
occur) Kulik (1964) supposed that the coarser sediments in which Dvinella and Trinodella
are preserved indicate shallow, disturbed-water environments. In these the tendency to
formation of a more massive calcareous dasycladacean envelope with fewer verticils
led to a compensatory mechanism for assimilation by division of the lateral branches.
From this point of view, their branching is simply a variant of the densely clumped, thin,
single branches of the more simple genera, which flourished in deeper quieter waters.

EXPLANATION OF PLATE 83

Figs. 1-5. Exvotarisella maponi gen. et. sp. nov.; Oxford Limestone, Bean Bed, Lower Carboniferous,
D2 Zone, Wisplaw, Alnwick, Northumberland. 1 , Thin-section of rock showing several examples of
Exvotarisella, normal preservation, x 30 ; reg. no. V55395. 2, Transverse section of example showing
incomplete pyritic penetration of branch-system, x60; V55395. 3, Transverse section, slightly
distorted individual, with good pyritic penetration of part of the branch-system, x60; V55396.
4, Longitudinal section, showing pyrite-filled stem-cell with very little pyritic penetration of the
branches, x40; V55394. 5, Longitudinal section, curved individual, normal preservation apart
from pyritic filling of part of the stem-cell adjacent to pyritized organic nodule (portion seen top
right), X 30; V55397.

Fig. 6. Ungdarella uralica Maslov ; Longitudinal section of fragment to show coarse cell-structure and
well-calcified medullary cells (for comparison with U. deceangloruni), x40; Zinnar Formation,
Permian (Artinskian-Kungarian), Ora, Mosul Liwa, northern Iraq.

Palaeontology, Vol. 13

PLATE 83

ELLIOTT, Carboniferous Chlorophyceae (Algae)

ELLIOTT: CALCAREOUS ALGAE NEW TO THE BRITISH CARBONIFEROUS 449

In Exvotarisella, however, the thickening of short primaries and secondaries followed
by sprays of longer tertiaries, and the larger size of the thallus, shows a trend known in
many other genera and part of the main stream of dasyclad evolution, leading to transfer
of the sporangial bodies from stem-cell to side-branches (Pia 1920, Rezak 1959, Elliott
1968). From this point of view Exvotarisella is the most advanced genus of the Beresel-
leae, and if it did not share in the general extinction of its tribe, it is the one most likely
to have evolved into something else.

Trinocladus of the Cretaceous and Palaeocene (Pia 1936, Elliott 1968) is a genus in
which swollen primaries and secondaries are followed by tertiary branchlets. It is known
that this full branch-development occurred in the later-formed portions only of the plant,
the older earlier portions showing simpler branch-structure only. It seems very likely
that this occurred in Exvotarisella also.

The English genus and species are dedicated to Mapon, the Celtic Apollo, once
worshipped in the region of Hadrian’s Wall, Northumberland, and elsewhere.

REFERENCES

carruthers, R. G. et al. 1930. The geology of the Alnwick district. Mem. Geol. Surv. Engl. Wales,
expl. sheet 6.

chanton, n. 1966. Nouvelle contribution a l’etude des algues calcaires du Carbonifere saharien. Bull.
Soc. geol. Fr. (7) 7, 402-9, pi. 8.

elliott, g. f. 1968. Permian to Palaeocene calcareous algae (Dasycladaceae) of the Middle East. Bull.
Br. Mus. nat. Hist. {Geol.), Suppl. 4.

emberger, j. 1958. Note preliminaire sur les algues du Carbonifere du Sahara occidental. C.r. somm.
Seanc. Soc. geol. Fr., 1958, 2, 16-17.

fritsch, F. E. 1945. The structure and reproduction of the algae, vol. 2. Cambridge.

frost, d. v. 1969. The Lower Limestone Group (Visean) of the Otterburn District, Northumberland.

Proc. Yorks, geol. Soc. 37 (3), 13, 277-309, pi. 9, 10.
guvenc, t. 1966. Representants des Bereselleae (Algues calcaires) dans le Carbonifere de Turquie et
description d’un nouveau genre: Goksuella n.g. Bull. Soc. geol. Fr. (7)7, 843-50, 1 pi.

Johnson, j. h. 1946. Lime-secreting algae from the Pennsylvanian and Permian of Kansas. Bull. geol.
Soc. Am. 57, 1087-120, 10 pis.

1947. Nubecularia from the Pennsylvanian and Permian of Kansas. J. Paleont. 21, 41-5, pi. 17.

khvorova, i. v. 1949. A new genus of Dasycladaceae from the Middle Carboniferous of the Moscow
Tectonic Valley. Dokl. Akad. Nauk SSSR, 65, 749-52. (In Russian.)
kulik, ye. l. 1964. Beresellids from the Carboniferous of the Russian Platform. Paleont. Zhurn., 1964,
2, 99-114, pi. 8. (In Russian.)

maslov, v. p. 1950. La valeur des Algues rouges pour la stratigraphie de l’U.R.S.S. Dokl. Akad. Nauk
SSSR, 70 (1). (In Russian.)

1956. Nouvelle famille d’ Algues rouges fossiles et deux nouveaux genres de Cyanophycees

fossiles du Carbonifere. Ibid. 107 (1), 151-4. (In Russian.)

and kulik, ye. l. 1956. Nouvelle tribu d’ Algues (Bereselleae) du Carbonifere de PU.R.S.S.

Ibid. 106, 126-9. (In Russian.)

pia, j. 1920. Die Siphoneae Verticillatae vom Karbon bis zur Kreide. Abh. zool. bot. Ges. Wien, 11 (2),
263 pp., 8 pi.

1936. Calcareous green algae from the Upper Cretaceous of Tripoli (North Africa). J. Paleont.

10 (1), 3-13, pi. 1-5.

rezak, r. 1959. New Silurian Dasycladaceae from the southwestern United States. Colo. Sch. Min.
Quart. 54 (1), 115-29, pi. 1-4.

toomey, d. f. and Johnson, j. h. 1968. Ungdarella americana, a new red alga from the Pennsylvanian of
southeastern New Mexico. J. Paleont. 42, 556-60, pi. 75, 76.
twenhofel, w. h. 1919. Pre-Cambrian and Carboniferous algal deposits. Am. J. Sci. (4), 48, 339-52.

450 PALAEONTOLOGY, VOLUME 13

wedd, c. b. et al. 1927. The geology of the country around Wrexham; Part 1. Mem. Geol. Surv. Engl.
Wales, expl. sheet 121.

wood, A. 1964. A new dasycladacean alga, Nanopora, from the Lower Carboniferous of England and
Kazakhstan. Palaeontology, 7, 181-5, pi. 31, 32.

GRAHAM F. ELLIOTT

Department of Palaeontology,
British Museum (Natural History)
London S.W. 7

Typescript received 29 October 1969

FERTILE RHYNIOPHYTINA FROM THE
LOWER DEVONIAN OF BRITAIN

by DIANNE EDWARDS

Abstract. A new genus Steganotheca is erected to include plants from the Downtonian of South Wales with
naked dichotomously branching axes and terminal sporangia, which are longer than wide, sharply truncated
apically, and with tapering bases. Comparison is made with other members of the Rhyniophytina (Banks 1968).
Sterile Silurian axes probably belonging to the same genus are briefly mentioned. The first occurrence of
Cooksonia in the Lower Old Red Sandstone of Scotland, consisting of naked dichotomously branching axes
terminating in oval to circular sporangia, is described from the Cairnconnan Group of the Lower Devonian in
Angus; it is placed in a new species.

The fossils described in the first part of this paper were collected from the Capel Horeb
Quarry, Breconshire. Although the majority, including all the fertile ones, were found
at the eastern end of the quarry in the lowest of the Long Quarry Beds in the grey
Downtonian of the Lower Old Red Sandstone (Potter and Price 1965), some were
collected from the older Ludlovian rocks (Lower Whitcliffian). The plants are preserved
as heavily carbonized compressions in which little structure can be detected. They were
treated in the way described by Edwards (1968), but bulk maceration of the rock was
relatively unsuccessful. All the fossils and preparations have been deposited at the
National Museum of Wales, Cardiff.

Although Cooksonia is commonly found in the Downtonian and Breconian rocks of
South Wales and the Welsh Borderland, it has hitherto not been recorded from Scotland.
The fertile specimens described in the second part of this paper were all collected at Aber-
lemno quarry near Turin Hill, Angus. Two of the specimens are in my possession while
the third, which is designated the holotype is housed in the Royal Scottish Museum. Also
found in this Quarry are Zosterophyllum myretonianum, Prototaxites, and Parka. The
plants, associated with occasional fish and eurypterid fragments, are preserved as pinkish-
red impressions in a fine-grained, grey sandstone. Very occasionally casts of axes are
present or a film of granular carbon covers the specimen. In neither case does structure re-
main, and the account presented here is merely a description of the fossils immersed in 70 %
alcohol and examined using a hand lens or binocular microscope. Some of the plants
have been developed by removing the covering rock layer with tungsten steel needles.

Most of the rock was collected from the tips on the floor of the quarry, but some
fossils were also visible on the quarry face where a hard jointed sandstone is interbedded
with the shale and softer fissile sandstone layers in which the plants are found. The rocks
form part of the Cairnconnan Group of the Dittonian of the Lower Old Red Sandstone
of Angus, probably equivalent to the Gedinnian of Europe (Waterston 1965).

SYSTEMATIC DESCRIPTION
Family rhyniaceae Kidston and Lang 1919

Genus steganotheca gen. nov.

Type species. Steganotheca striata sp. nov.

[Palaeontology, Vol. 13, Part 3, 1970, pp. 451-61, pi. 84-87.]

452

PALAEONTOLOGY, VOLUME 13

Diagnosis. Naked dichotomously branching axes with erect terminal sporangia. Sporan-
gia longer than wide with tapering bases and truncated apices; apices formed by
terminal lens-shaped structure of coaly material; sporangia with almost parallel sides.

Steganotheca striata sp. nov.

Plate 84, figs. 1-6, Plate 85, figs. 1-8

Diagnosis. Axes with at least four dichotomies, 0-4— 0-8 mm. wide, with central line.
Surface longitudinally striated. Sporangia 1 -8-2-7 mm. long and 1-0-1 -5 mm. wide;
tapering at base; apex truncated; apex formed by terminal lens-shaped structure of
coaly material, up to 0-25 mm. thick; surface of sporangium obliquely striated; parallel
sides.

Locality. Capel Horeb Quarry, abandoned quarry on the A40 between Trecastle and Llandovery
Nat. Grid. Ref. SN 844323.

Horizon. Long Quarry Beds, Grey Downtonian, Lower Old Red Sandstone of South Wales.

Holotype. Specimen 69-64 G32a and counterpart; Department of Geology, National Museum of
Wales, Cardiff; Plate 84, figs. 1, 2, 5, 6, Plate 85, fig. 1.

Description of specimens. Most information was obtained from three fertile specimens
found in a fine-grained grey sandstone, interbedded with micaceous layers.

(a) Specimen 69.64.30a and b (PI. 84, figs. 3, 4). This fossil consists of a slightly flexuous
branching system of over-all length 5-0 cm. The width of the axes remains almost
constant through three successive dichotomies ranging between 0-7 mm. at the base and
0-5 mm. distally, where each axis widens into the base of a sporangium. The axis surface
is striated, representing perhaps the outlines of epidermal or cortical cells. A faint
central fine is sometimes seen when the rock is held at a suitable angle to the incident
light. The reconstruction given in text-fig. 1 is derived from part and counterpart. The
sporangia are cup-shaped, 2-5 mm. high and 1-5 mm. wide on average. The coaly
residue in the truncated sporangium apex is much thicker than that in the rest of the
sporangium wall, forming a terminal lens-shaped structure (PI. 85, fig. 4). The coaly
residue from the axes, sporangia, and distal thickened region was macerated in Schulze’s
solution for several days, but no structure was discernible.

(b) Specimen 69.64.G31a and b (PI. 85, figs. 2, 3). This specimen consists of an axis
0-4-0-5 mm. wide and 18 mm. long which dichotomises once. One of the branches ends

EXPLANATION OF PLATE 84

Figs. 1-6. Steganotheca striata sp. nov. 1, 2, Dichotomously branching fertile axes, 69.64.G32a and
b; x 1-2. 3, 4, 69.64.G30a and b; Xl-2. 5, 6, Sporangia from 69.64.G32a; x7-7.

EXPLANATION OF PLATE 85

Figs. 1-8. Steganotheca striata sp. nov. 1, Sporangia from 69.64.G32a; X7-7. 2, 3, Sporangium and
counterpart, 69.64.G31a and b; x8; note the conspicuous striations in fig. 2 and the thickened
apical region in fig. 3. 4, Cup-shaped sporangium with apical thickening, 69.64.G30a; x8. 5,6,
Sterile Downtonian axes from Capel Horeb, 69.64.G33, xl-2; 69.64.G34, X7-5. 7, Cells from
Downtonian axis recovered after maceration, 69.64.G35; x 430. 8, Film pull of Downtonian axis
showing cell walls, 69.64.G36; x 126.

Palaeontology, Vol. 13

PLATE 84

EDWARDS, Early Devonian Rhyniophytina

Palaeontology, Vol. 13

PLATE 85

EDWARDS, Early Devonian Rhyiiiophytina

D. EDWARDS: FERTILE RH YNIOPHYTINA

453

text-fig. 1. Reconstructions of Steganotheca striata sp. nov. a. Drawn from 69.64.G32a and b; x 1-8
b. Drawn from 69.64.G30a and b; x 1-8.

in a sporangium 1-8 mm. high and 1-0 mm. wide. The axis surface is longitudinally
striated. The sporangial features described above are again clearly seen here (PI. 85,
fig. 3). In addition, the sporangium surface is striated, with the fines running diagonally
across the sporangium. This is most clearly seen in the counterpart (PI. 85, fig. 2). The
heavily carbonized distal region is not present on the latter.

(c) Specimen 69.64.G32a and b (PI. 84, figs. 1, 2). A reconstruction of the plant is given
in text-fig. 1. It consists of a ‘bushy’ three-dimensional branching system in which at
least^ten of the axes end in sporangia. Branching is dichotomous with a wide angle

454

PALAEONTOLOGY, VOLUME 13

(c. 60°) at each branching point. The axes vary between 0-5 and 08 mm. in diameter.

The sporangia are, on average, 2-4 mm. high (ranging between 2-0 and 2-7 mm.) and
T2 mm. wide (1-0-1 -5 mm.). The majority have truncated tips (PI. 84, figs. 5, 6) with
heavily carbonized areas similar to those already described. A few, however, are rounded
at the apices (PI. 85, fig. 1). These are also unusual in that they terminate very short
lengths of axis above the ultimate dichotomy. It is therefore suggested that these oval
sporangia are immature ones, though it should be noted that they are no smaller than
the others.

Summary of description. Steganotheca striata is a small bushy plant, at least 5-0 cm. high,
consisting of naked, dichotomously branching axes with terminal sporangia. Its basal
parts are unknown. Branching is strictly dichotomous, with the angle at the branching
point ranging between 45° and 75°. The length of axis above a branching point is
approximately the same in both arms, and the branches terminating in sporangia are
of equal length. The distance between the sporangium and last branching point is usually
long compared with the distances between successive dichotomies. The sporangia them-
selves are almost twice as long as wide. Their apices are truncated and terminate with
a heavily carbonized lens-shaped region. The base of each sporangium is not clearly
defined. No spores have been isolated and very little is known of the structure of the
sporangium wall.

Associated with the fertile specimens are numerous short lengths of axis, the majority
being Y-shaped, but some unbranched and some with two successive dichotomies. These
axes are approximately the same width as the fertile ones (average 0-55 mm. in the former,

0-6 mm. in the latter) and the angles at branching points are similar. It is therefore
probable that these fragments belong to the same genus as the fertile ones (PI. 85,
figs. 5, 6).

Nearly all the axes have faint surface striations which probably represent the outlines
of elongate cells of the epidermis or cortex. A thin central strand is seen on some of the
sterile axes, but this is more obvious on film pulls of axes, because the coaly residue of
the central area forms a continuous band, while that of the remainder of the axis is
cracked and often incomplete. Pieces of rock-bearing axes have been macerated and the
carbon recovered cleared with Schulze’s solution. Fragments of carbon have also been
picked off the rock and film pulls and cleared in the same way. No tracheids have been |
seen. Very occasionally film pulls bear the remains of cell walls, those running parallel
to the long axis of the branch being most often preserved. They are 9-20 p apart, the
distance tending to vary proportionally with the width of the axis. Very narrow axes j
are 10-12 cells wide. Occasionally transverse end walls are seen. These are perpendicular
or oblique to the longitudinally running walls (PI. 85, fig. 8).

Little or no cuticle is recovered on maceration. Some fragments of a ‘stringy’ nature
are sometimes found. These are most probably the longitudinal walls described above. :
There is no definite cellular structure visible, but occasionally two walls meet suggesting
tapering cells (PI. 85, fig. 7).

Other material. Plant fragments in the Silurian (Ludlovian) part of the quarry are
surprisingly abundant. They are found in a very fine-grained, grey sandstone, but unlike
the Downtonian plants are not associated with micaceous layers. The remains fall into

D. EDWARDS: FERTILE RH YNIOPH YTINA

455

three categories: (a) Some bedding planes are almost completely covered with small
pieces of axis and patches of coaly residue (PI. 86, fig. 2). ( b ) Slightly longer axes are
concentrated sporadically, sometimes in the depressions of ripple marks, and are again
associated with patches of coaly residue (PL 86, fig. 1). (c) Isolated fragments sometimes
over 2-0 cm. long with one or two dichotomies are found scattered throughout the
deposit (PI. 86, fig. 3).

These Silurian axes look very similar to the Downtonian ones. They range from 0-7 to
0T mm. in width (on average 0-4 mm.). Surface striations and central strands are often
seen. Film pulls and maceration products showed similar cellular organization (PL 86,
figs. 4-7). No tracheids have been found. In the absence of fertile specimens it cannot be
determined with certainty that these axes belong to Steganotheca.

Discussion. Banks (1968), in his new classification of the psilophytes, divided the group
into three subdivisions. The one relevant to this discussion is the Rhyniophytina in which
plants with terminal sporangia ( sensu Kidston and Lang 1917) are placed. Banks has
included two families in a single order, the Rhyniales. In the Rhyniaceae, the terminal
sporangia are ‘usually fusiform and may dehisce longitudinally’ (Banks 1968, p. 76)
while in the Cooksoniaceae they are globose. Because there is considerable variation in
sporangial shape within both the families recognized by Banks, in this paper I prefer to
compare all the genera with solitary terminal sporangia included in the Rhyniophytina,
with the plants from Capel Horeb.

In the Rhynie Chert flora (Kidston and Lang 1917, 1919), Rhynia major and R.
gwynne-vaughanii both have terminal sporangia which are longer than they are wide
on dichotomously branching naked axes. The sporangia of R. major are considerably
larger than those in Steganotheca but those in R. gwynne-vaughanii are of comparable
size. Horneophyton lignieri sporangia are columellate, while the sporangia are branched.
Since the Rhynie plants are petrifactions and unknown in the compressed state, com-
parison is difficult. It seems probable however that, if preserved as compressions, the
two Rhynia species, at least, would have well-defined sporangia with good distinction
between sporangium and axis, and rounded apices.

The genus Sporogonites (Halle 1916), although investigated by a number of workers,
is still somewhat of an enigma. On present evidence, it is unlikely that it is a vascular
plant. The elongate, obovoid sporangia, terminating long, unbranched axes are larger
than those in the Welsh plant. The sporangium apex is rounded and the tapering base
merges into the thick upper part of the stalk. The sporangium is longitudinally grooved
and columellate. It may be difficult to understand why Sporogonites, with its clearly
defined sporangial characters, should not be eliminated immediately from this dis-
cussion. Cookson (1949) pointed out that, in heavily compressed fossils, the columella
and ridges are unlikely to be preserved, and concluded that the critical character is
whether or not the axis is branched. The Capel Horeb specimens have branched axes
and none of the distinctive characters seen in Sporogonites.

Hicklingia edwardii (Kidston and Lang 1923) from the Middle Old Red Sandstone
of Scotland with its almost spherical sporangia differs from the older plant in sporangial
shape and arrangement. In Taeniocrada decheniana (Krausel and Weyland 1930) the
terminal sporangia are larger, and borne in clusters on flat ribbon-shaped axes. The
dimensions of the Lower Devonian genus Eogaspesiea (Daber 1960) are similar to those

456

PALAEONTOLOGY, VOLUME 13

text-fig. 2. Diagrams to show variation in sporangium shape and size in certain Rhyniophytina; x4.
a, b, Rhynia major (Kidston and Lang 1919); inner line shows extent of spore cavity and is not a
thickened border, c, R.gwynne-vaughani (Kidston and Lang 1917, 1919). d-g, Sporogonites exuberans
(Halle 1916). h-j, Cooksonia crassiparietilis (Yurina 1964). k, l, Cooksonia sp. (Croft and Lang 1942).
m, n, Cooksonia sp. (Obrhel 1962). o, p, Steganotheca striata sp. nov. q, C. rusanovii (Ananiev 1959,
1960). r-t, C. pertonii (Lang 1937). u, v, C. hemisphaerica (Lang 1937). w-y, C. caledonica sp. nov.

in Steganotheca , but the sporangia are oval. Hedeia corymbosa (Cookson 1935), another
Lower Devonian genus, resembles Steganotheca because the dichotomously branching
axes terminate in elongate sporangia with their tips all at the same level forming a
corymb-like arrangement. In Hedeia, however, the whole system is compacted to form
a definite fructification. In addition, it differs in sporangial shape and size.

When Lang erected the genus Cooksonia in 1937, he distinguished it from early genera
on the basis of sporangial shape. From his diagnosis, any plant assigned to the genus
should have a combination of the following characters: (1) terminal, short, wid

D. EDWARDS: FERTILE RH YNIOPHYTINA

457

sporangia, (2) dichotomously branched, naked axes, (3) central vascular cylinder com-
posed of annular tracheids. Of these, in my opinion, the most significant and definitive
are the short and wide sporangia. There has been a tendency to place any poorly pre-
served Lower Devonian fossils, where the sporangia are terminal and few anatomical
details are known, in the genus Cooksonia. The variation in sporangial shape and size
is illustrated in text-fig. 2. On the basis of sporangial shape, the Capel Horeb fossils
are clearly not assignable to the genus Cooksonia. Heard (1939), however, described a
single fertile specimen from the Downtonian of the Capel Horeb locality, in which
dichotomously branching axes terminated in ‘capsule-like’ sporangia (5 mm. long by
2 mm. wide). There is little doubt in my mind that this fossil, named Cooksonia down-
tonensis by Heard, should be transferred to the new genus, Steganotheca. The lack of
distinction between sporangium and stalk might account for the discrepancy in spor-
angial length. The impression of the plant gained from Heard’s illustrations supports
my conclusion. In addition, in the line-drawing of the fertile specimen, published by
Hoeg (1967) at the tip of the left-hand sporangium is a lens-shaped region, limited by
a dotted line, which corresponds to the apical feature described above. Heard, however,
did not mention this apical feature, nor the oblique striations on the sporangium wall.
The morphological nature of this apical thickening is questionable. It is possible that it
was similar to the operculum of a bryophyte, but it is unlikely that it could ever be stated
with certainty that it was concerned with dehiscence. It is equally possible that the
thickness of coaly residue is a preservation feature produced by compression of the flat
top of the sporangium. Oxidation of various parts of the sporangia have yielded nothing.

In conclusion the fossils described above present a new combination of characters,
not seen in any of the above genera. The new genus Steganotheca is therefore erected
to include fragments of plants which possess the following characteristics : ( a ) Dichoto-
mously branched, naked axes; ( b ) Erect terminal sporangia, longer than wide with
parallel sides, truncated apices and bases tapering into the axes beneath; (c) Fine stria-
tions running obliquely across the sporangium wall; ( d ) Thick, heavily carbonised,
lens-shaped region at sporangium apex.

Heard’s specimen has not been made the type of this new taxon, because his material
is missing and, secondly, because the new fossils show the distinctive sporangial
characters not mentioned in Heard’s specific diagnosis.

Genus cooksonia Lang 1937

Type species. Cooksonia pertonii.

Original diagnosis. Dichotomously branched, slender, leafless stems with terminal
sporangia that are short and wide. Epidermis composed of elongated, thick-walled cells.
Central vascular cylinder consisting of annular tracheids.

Cooksonia caledonica sp. nov.

Plate 87, figs. 1-10

Diagnosis. Incomplete plant at least 6-7 cm. high. Naked dichotomously branching
axes 0-4-1-8 mm. wide (average 0-65 mm.). Terminal spherical to oval sporangia, some

458

PALAEONTOLOGY, VOLUME 13

also reniform. Border (0- 1-0-2 mm. wide) sometimes present. Globose sporangia
1 -2-2-0 mm. high (average 1-7 mm.) by 1 -3-2-2 mm. wide (average 1-8 mm.). Oval ones
1*1—1 -8 mm. high (average 1-6 mm.) by 1 *8—3*0 mm. wide (average 2-4 mm.). Axis
widens slightly below sporangium.

Locality. Aberlemno Quarry, Aberlemno, approximately 1| miles north-north- west of Turin Hill,
Angus; Nat. Grid Ref. 527551.

Horizon. Cairnconnan Group, Dittonian Stage Lower Old Red Sandstone of Scotland.

Holotype. Specimen R.S.M. 1967. 30. 2P and C; Royal Scottish Museum, Edinburgh.

Description of specimens. Very occasionally scattered among the long, relatively un-
branched axes of Zosterophyllum myretonianum were found narrower dichotomously
branching axes, which in the absence of fertile parts, would be assigned to the form
genus, Hostimella. One piece of rock and its counterpart (R.S.M. 1967.30. 2P and C),
found by Dr. C. D. Waterston, was completely covered with these axes lying parallel
to each other (PI. 87, figs. 1, 3). The longest exposed axis was 4-0 cm. long. The slightly
flexuous axes branch dichotomously, with an angle of 55-60° at the branching point.
Longitudinal striations are sometimes visible on the surfaces of the axes, but what could
definitely be called a central strand has not been seen.

A slightly asymmetrical positioning of the branches above a dichotomy indicates
a tendency to pseudomonopodial branching, but there is no inequality of axis diameter.

Scattered in the matrix and sometimes attached to short lengths of axis are circular
to oval bodies, presumably sporangia (PI. 87, figs. 5, 6-10). The globose ones measure,
on average, 1-8 mm. wide and 1-7 mm. high, while the oval sporangia are 2-4 mm. wide
and 1-6 mm. high on average. The height of all the sporangia is slightly less than the
width. Occasionally a narrow border less than 0-1 mm. wide extends around the convex
margin of the sporangium (PI. 87, fig. 8). In profile, this is either apparent as a ridge
separated from the rest of the sporangium by a sharp depression, or as a groove (PI. 87,
fig. 8). This border could be removed easily.

One specimen (PI. 87, fig. 10) appears to represent two sporangia almost superimposed,
but only one subtending axis is visible. It is possible that this is in fact a dehisced

EXPLANATION OF PLATE 86

Figs. 1-7. Sterile axes from Silurian at Capel Horeb. 69.64.G37; X2-3. 2, 69.64.G38; x 5. 3,
69.64.G39; X7-7. 4, Axis recovered on film pull, central strand indicated by arrow; 69.64.G40,
x 126. 5, Film pull of axis with longitudinal cell walls and transverse banding (indicated by arrows),
the latter are formed because the carbon tears when the film pull is removed and are not tracheidal
thickenings; 69.64.G41, X430. 6, 7, Film pulls from axes showing cell walls, 69.64.G42 and G43;
x 126.

EXPLANATION OF PLATE 87

Figs. 1-10. Cooksonia caledonica sp. nov. 1, R.S.M. 1967.30.2P before uncovering; Xl-1. 2, Speci-
men illustrated in fig. 1 showing dichotomously branching axes with terminal sporangia; xl-1.
3, R.S.M. 1967.30.2C; Sterile axes with isolated sporangia indicated by arrows; x0-9. 4, Sporan-
gium from specimen DE 33/22; note pad of tissue in base of sporangium; x 7-7. 5, Isolated almost
circular sporangium (R.S.M. 1967.2C); x 8. 6, Sporangia as in fig. 2; x8. 7-10, Isolated sporangia
(R.S.M. 1967.30.2P and C); x 8 : 7, Oval sporangium with axis entering its base. 8, Oval sporangium
with border, here represented by a depression. 9, Globose sporangium. 10, Two superimposed
sporangia or single dehisced sporangium.

Palaeontology, Vol. 13

PLATE 86

EDWARDS, Silurian (Ludlovian) plants

Palaeontology , Vol. 13

PLATE 87

EDWARDS, Early Devonian Rhyniophytina

D. EDWARDS: FERTILE RH YNIOPH YTINA

459

sporangium, split into two valves, although the original assumption should not be
ignored. The variation in sporangial shape is illustrated in text-fig. 3. In some cases, the
tip of the axis extends a short way into the base of the sporangium.

text-fig. 3. Diagrams showing variation in size and shape of sporangia of Cooksonia caledonica

sp. nov. ; x 9.

text-fig. 4. a. Drawing of Cooksonia caledonica sp. nov.
from R.S.M. 1967.30. 2P; x 1. b. Reconstruction on the
plant; x 1.

One branching system, on uncovering, was found to exhibit four orders of branching
with a distinct decrease in axis diameter from base to apex. The most complete part
terminated in three relatively large sporangia (PI. 87, figs. 1, 2, 6). Text-fig. 4 a shows what
has actually been seen, but text-fig. 4b is a probable reconstruction of the plant assuming
that the branching pattern seen in text-fig. 4 a is repeated. This assumption is supported

460 PALAEONTOLOGY, VOLUME 13

by the fact that a row of sporangia, of which the attached ones form one end, is visible
on the specimen.

Specimen DE 33/22 in my own collection is again fertile. Here an axis, 0-6 mm. wide
at its base, dichotomises once and one branch terminates in an oval to reniform spor-
angium 1-7 mm. wide and 1-2 mm. high. The axis increases in width just below the
sporangium and forms a pad of tissue (TO mm. wide) in its base (PI. 87, fig. 4). This is
particularly noticeable on the counterpart where the sporangium itself is fainter. In
another specimen (DE 33/19) a dichotomously branching system bears a single, here
almost spherical sporangium, T5 mm. high and T6 mm. wide. The axis widens into the
sporangium base. No border is present.

Discussion. This Scottish plant is clearly a member of the genus Cooksonia and com-
parison with the four species already placed in the genus shows that it differs sufficiently
to be a new species (text-fig. 2).

In C. pertonii (Lang 1937) the sporangia are more irregularly shaped than in the
Scottish plant and a border has not been seen. The latter differs from C. hemisphaerica
(Lang 1937) and the plants designated Cooksonia sp. by Croft and Lang in 1942, both
in sporangial shape and size. Not enough is known about Ananiev’s Cooksonia rusanovii
(Ananiev 1959, 1960) described from rather fragmentary remains. Although sporangial
shape is similar to that in the new plant, the arrangement of sporangia in the Russian
specimens is different and even suggests that the plants belong to another genus.

In sporangial characters the Scottish plant most closely resembles C. crassiparietilis
described by Yurina (1964) from the Lower Devonian of Karaganda, U.S.S.R. One
of her specimens consists of a naked dichotomously branching axis about 2 cm. long,
varying in width between 1-5 mm. and 4-0 mm., the latter below a branching point.
The terminal sporangia are reniform to circular in shape, and are 3-5-5-67 mm. wide
and 2-75-4-50 mm. high. Each sporangium has a thickened border and the surface is
ornamented by fine ribs diverging from the point of attachment. The wall itself is three-
layered. Spiny spores have been isolated. These sporangia, although much larger, are
similar in shape to those in the Scottish plant. An odd feature of the Russian specimens
is that more than one, presumably vascular, strand is visible in the axis immediately
below a sporangium. There is no indication of this in the Aberlemno specimens.

In conclusion, it is considered that the new Scottish Cooksonia differs sufficiently from
the existing species to warrant the erection of a new species.

Acknowledgements. I thank Dr. K. R. Sporne for his advice throughout this work and Dr. C. D.
Waterston for his generosity in allowing me to work on the Aberlemno flora. Most of this research
was carried out during the tenure of an N.E.R.C. fellowship and the Ethel Sargent Research Fellow-
ship at Girton College, Cambridge.

REFERENCES

ananiev, a. r. 1959. Die wichtigsten Fundstellen von Devonflora im Ssajan-Altaj Berggebiete. Tomsk.
[In Russian; German summary.]

1960. Age of the Izik and Shunet Suites according to the flora on the northern slope of Batenevo

Ridge. Trudy tomsk. gos. Univ. 146, 5-28, 4 pis. [In Russian; N.L.L. Translation Service.]
banks, h. p. 1968. The early history of land plants. In Evolution and environment; a symposium
presented on the one hundredth anniversary of the foundation of the Peabody Museum of Natural
History at Yale University, drake (ed.). New Haven and London (73-107, figs. 1-9).

D. EDWARDS: FERTILE RH YNIOPH YTINA

461

cookson, i. c. 1935. On plant remains from the Silurian of Victoria, Australia, that extend and connect
floras hitherto described. Phil. Trans. R. Soc. Lond. B225, 127-48, 2 pis.

1949. Yeringian (Lower Devonian) plant remains from Lilydale, Victoria, with notes on a collec-
tion from a new locality in the Siluro-Devonian period. Mem. natn. Mus. Viet. 16, 117-31, 3 pis.
croft, w. n. and lang, w. h. 1942. The Lower Devonian flora of the Senni Beds of Monmouthshire
and Breconshire. Phil. Trans. R. Soc. Lond. B221, 131-63, 3 pis.
daber, r. 1960. Eogaspesiea gracilis n.g. n. sp. Geologie, 4, 418-25, 2 pis.

edwards, d. 1968. A new plant from the Lower Old Red Sandstone of South Wales. Palaeontology,
11, 683-90, 3 pis.

halle, T. G. 1916. Lower Devonian plants from Roragen in Norway. K. svenska Vetensk Akad. Handl.
57, 1-46, 4 pis.

heard, A. 1939. Further notes on Lower Devonian plants from South Wales. Q. Jl. geol. Soc. Lond.
95, 223-9, 2 pi.

hoeg, o. A. 1967. Psilophyta. In Traite de Paleobotanique, vol. 2, boureau, e. (ed.). Paris. [In French.]
kidston, r. and lang, w. h. 1917. On Old Red Sandstone plants showing structure from the Rhynie
Chert Bed, Aberdeenshire. Part I. Rhynia Gwynne-Vaughani, Kidston and Lang. Trans. R. Soc.
Edinb. 51, 761-84, 10 pis.

1919. Part II. Additional notes on Rhynia Gwynne-Vaughani Kidston and Lang; with descriptions

of Rhynia major n. sp. and Hornea lignieri n.g., n.sp. Ibid. 52, 603-27, 10 pis.

1923. Notes on fossil plants from the Old Red Sandstone of Scotland. I. Hicklingia Edwardi.

Ibid. 53, 405-7, 1 pi.

krausel, r. and weyland, h. 1930. Die Flora des deutschen Unterdevons. Abh.preuss. geol. Landes-
anst. n.f. 131, 1-92, 14 pis.

lang, w. h. 1937. On the plant remains from the Downtonian of England and Wales. Phil. Trans.
R. Soc. Lond. B227, 245-91, 7 pis.

obrhel, J. 1962. Die Flora der Pfidoli-Schichten (Budnany-Stufe) des mittelbohmischen Silurs. Geo-
logie, 11, 83-97, 2 pis.

potter, j. f. and price, J. h. 1965. Comparative sections through rocks of Ludlovian-Downtonian
age in the Llandovery and Llandeilo districts. Proc. geol. Ass., Lond. 76, 379^102.
waterston, c. d. 1965. Old Red Sandstone. In The geology of Scotland, craig, g. (ed.). Edinburgh.
yurina, a. l. 1964. New Devonian species of the genusCooksonia. Paleont. Zh. (Special Reprint No. 1),
107-13, pi. 15. [In Russian.]

Typescript received 16 December 1969

DIANNE EDWARDS
Botany Department
University College of South
Wales and Monmouthshire
Cathays Park
Cardiff

AMMONITES OF THE GENUS ACANTHOCERAS
FROM THE CENOMANIAN OF ROUEN, FRANCE

by w. j. Kennedy and j. m. Hancock

Abstract. Although Acanthoceras only forms a minority of the ammonites from the Craie de Rouen, the locality
is important as being the type locality of Acanthoceras rhotomagense, the type species of the genus and the most
oft-quoted species. This study shows that almost all the Acanthoceras from Rouen can be regarded as one vari-
able species which can be conveniently divided into five varieties, only one of which, A. rhotomagense var. clava-
tum, is new. A. rhotomagense is a widespread species and marks an horizon low in the Middle Cenomanian.
Acanthoceras basseae sp. nov., also from Rouen, is a rarity.

Well-preserved fossils from the chalk at Rouen were described as early as 1822 by
Cuvier and Brongniart. Casual references in the literature and labels in museums show
that it has been much collected from ever since, but there are few descriptions of the
section. The best is still that of Bucaille in Lennier (1880) quoted by Jukes-Browne and
Hill (1903, p. 253), but there are also brief descriptions by Dollfus and Fortin (1911)
and Follet (1943). Jefferies (1963, fig. 10) showed the position of the fossil-rich horizon
in relation to the Plenus Zone. The section given here (fig. 1) is based on our own field
notes.

The Cenomanian Chalk of Normandy contains several glauconitic horizons, well
shown in the coast sections at St. Jouin and Cap de La Heve. These glauconitic develop-
ments are probably reflections of local differential uplift, on top of which sedimentation
was relatively slow. Some of these glauconitic developments are accompanied by phos-
phatisation. It is one such bed at Cote St. Catherine in Rouen which has yielded the
many fossils commonly known as the fauna of the Rouen Chalk; strictly, the Craie de
Rouen includes all the chalk at Rouen below that with Inoceramus labiatus and Hebert
(1884) even included the beds containing ‘Ammonites' inflatus and Turrilites bergeri that
we should now consider Upper Albian.

As far as we know from our own field work, there is only one horizon at Rouen itself
which contains well-preserved, light-brown, phosphatic internal moulds. All museum
specimens used in this study are in a similar preservation, or have traces of phosphatic
test, and we have ignored the few specimens labelled ‘Rouen’ in other preservations.
When we refer to ‘the Rouen fauna’ we mean that from the fossil-rich bed.

SYSTEMATIC DESCRIPTIONS
Family acanthoceratidae Hyatt 1900
Genus acanthoceras Neumayr 1875
(= Metacanthoplites Hyatt 1900)

Type species. Ammonites rhotomagensis Brongniart ex Defrance MS in Cuvier and Brongniart 1822;
designated by De Grossouvre 1894.

[Palaeontology, Vol. 13, Part 3, 1970, pp. 462-90, pi. 88-97.]

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 463

text-fig. 1. Vertical section showing the stratigraphical position of the fossil-bed of the Craie de
Rouen at Cote St. Catherine, Rouen. Sketch-map shows the position of an exposed section.

Generic characters. Decorated ammonites, rather evolute: whorl height normally 6-5-
12-5 times as great as the depth of the impressed area, not changing markedly with age
but commonly becoming slightly more evolute.

Intercostal whorl section is roughly square sometimes slightly depressed, not changing
appreciably during ontogeny. The whorl section through the ribs is markedly angular,
commonly on some variant of a square with diagonals cutting the corners; sides may be
parallel or diverging slightly towards the umbilicus.

h h

C 7619

464

PALAEONTOLOGY, VOLUME 13

The ribs are strong, generally straight, showing a weak forward projection. Most
ribs begin on the umbilical slope, are nearly always strong on the lower part of the sides
where they commonly, but by no means invariably, develop a bullate tubercle. Near the
top of the side there is a tubercle developed that is the most persistent series in the genus,
sometimes developing into great spires; only in one aberrant species, ‘A’. cornigerum
Crick, are they lost.

Above this upper lateral tubercle is the angular shoulder, on which the ribs show a
further forward projection, and nearly terminate at a series of ventro-lateral tubercles,
although there is usually a weak connecting rib across the venter between pairs of ventro-
lateral tubercles. This connecting rib is sometimes lost in the middle or later stages of
ontogeny. The upper lateral and ventro-lateral tubercles may be bullate or clavate or
neither. The venter is flat. On the early whorls there is a siphonal tubercle which may
persist as strongly as the ventro-lateral tubercles to considerable diameters, but more
commonly weakens and disappears before a diameter of 100 mm. is reached.

The above two paragraphs apply to full-length (primary) ribs. In young individuals
there are one, or more rarely two, shorter (secondary) ribs intercalated between any
two primary ribs. Such ribs begin gently, above the level of the basal lateral tubercles on
the primary ribs, and thereafter behave as primary ribs. The persistence of secondary
ribs varies greatly from species to species, and in some forms (which might be better
classified as Calycoceras ) lasts throughout the septate stage.

In some species the ribbing weakens slowly during ontogeny, but the very slight
amount of change in any features during the ontogeny of the septate portion was even
noted by Brongniart (1822).

Acanthoceras is a large genus growing up to a third of a metre or more in diameter.
Such large specimens have generally been obtained from the Chalk, and it is not always
possible to say from these how much space is occupied by the adult body chamber.

De Grossouvre (1894) in amending and restricting Neumayr’s genus, laid stress on the
suture line : ‘Je reserverai done le nom generique &' Acanthoceras aux formes a lobes et
selles large, de forme approximativement rectangulaire, dont le premier lobe lateral
presente une fourche terminal nettement accusee, et je prendrai comme type de ce genre
Acanthoceras rhotomagense.’’ We would add that the lateral lobe is narrow compared
with the first lateral saddle in the middle of which an accessory lobe, nearly half as long
as the first lateral lobe, is commonly developed; neither de Grossouvre (1894, fig. 12)
nor d’Orbigny (1841, pi. 106, fig. 3) shows this adequately.

All the above description is based on internal moulds, and it should be noted that the
shell of Acanthoceras is thick (possibly as much as 2 mm. in some large specimens) so
that the appearance of an individual with the shell is somewhat different from the mould.
On the shell the second-order ribs, for example, begin lower on the sides, and even the
first-order ribs are stronger on the umbilical slope than is apparent from the mould.
Moreover, the shell possesses decoration not present on the mould: strong striations
parallel to the ribbing are common (see Sharpe 1855, pi. 16, fig. 2a). In addition there
is sometimes a faint longitudinal striation.

Relations with other genera. Even as restricted by De Grossouvre (1894) Acanthoceras
at first included many forms which are today separated generically. Indeed, every genus
in the family, with the exception of Mammites Laube and Bruder, 1886, has been erected

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 465

since 1894. Happily, only a few of these newer genera are liable to be confused with
Acanthoceras s.s.

Mantelliceras Hyatt, 1903; type species Ammonites mantelli J. Sowerby; Lower
Cenomanian. This genus is the ancestor of Acanthoceras, but probably by way of Calyco-
ceras. Early writers tended to distinguish Mantelliceras by the absence of siphonal
tubercles, but this distinction can only be used on juveniles. More distinctive of Mantel-
liceras is the persistence of short ribs, the disappearance of lower ventro-lateral tubercles
at diameters of 80 mm. or earlier (in rare individuals it may last longer), and the dis-
appearance of all tuberculation on the adult, maturity usually being reached at much
smaller sizes than in Acanthoceras ; moreover, some species of Mantelliceras, including
the type, possess mid-lateral tubercles.

Calycoceras Hyatt, 1900; type species Ammonites navicularis Mantell; Middle to
Upper Cenomanian. Calycoceras appears to be derived from Mantelliceras early in the
Middle Cenomanian by the development of a siphonal tubercle, and by increasing the
relative strength of the umbilical ribbing or bullae. Calycoceras retains the short ribs
and ventral ribbing of Mantelliceras but develops (in some species) the angular whorl
section of Acanthoceras, and like Acanthoceras often loses the siphonal tubercles long
before the ventro-lateral ones. Hence some Calycoceras can only be distinguished with
certainty from Mantelliceras by strong umbilical bullae, e.g. Calycoceras cottreaui
(Collignon), C. nitidum (Crick). However, there are some species of Mantelliceras which
also have umbilical bullae in the middle stages, e.g. Mantelliceras lymense (Spath) (Per-
vinquiere 1907, pi. 16, fig. 16) that Spath (1926) thought was an Upper Cenomanian
Eucalycoceras. These distinctions still leave forms whose generic attribution is difficult.
Thus Acanthoceras whitei Matsumoto from southern India, figured by Kossmat (1897,
pi. 1, fig. 1), which retains short ribs to a diameter of nearly 100 mm., and whose
ribbing does not weaken on the venter, might be better assigned to Calycoceras. In
Acanthoceras gr. jukes-brownei (Spath) short ribs are retained to a diameter of more
than 300 mm.

Euomphaloceras Spath, 1923; type species Ammonites euomphalus Sharpe, 1855;
Middle and Upper Cenomanian. Euomphaloceras develops from Acanthoceras in the
Middle Cenomanian by the intercalation of extra ribs or extra tubercles on the venter,
e.g. ‘‘Acanthoceras'' inermis Pervinquiere (= A. evolutum Spath). We figure examples of
these transitional forms from Rouen (PI. 92, fig. 4; PI. 93, fig. 1).

Protacanthoceras Spath, 1923; type species Ammonites Bunburianus Sharpe; Middle
and Upper Cenomanian. The stratigraphically persistent distinctive feature of this tiny
genus, is the triple row of equal-sized clavae, rather closely spaced on the venter. On the
adult body chamber of some species these tubercles fuse into smooth chevron-ribs across
the venter. The early species (where the genus is diverging from Acanthoceras ) grade into
flat-sided spinose Acanthoceras. As has been remarked by Thomel (Porthault et al. 1966)
Protacanthoceras has also been misused for species such as Eucalycoceras harpax
(Stoliczka) which have strong ribbing on the sides, and grow to a much greater size.

Plesiacanthoceras Haas, 1964 (= Paracanthoceras Haas, 1963, non Furon, 1935);
type species Metoicoceras Wyomingensis Reagan 1924. We agree with Matsumoto and
Obata (1966) in regarding this as a synonym of Acanthoceras. Haas gave two distinc-
tions : (i) the ventral tubercles ‘are, even at an early stage, very inconspicuous and strongly
clavate and then assume the aspect of an intermittent keel which soon fades away’. This

466

PALAEONTOLOGY, VOLUME 13

could be part of a description of the holotype of Acanthoceras rhotomagense. (ii) ‘Also
the ribs persist into maturity in A. rhotomagense, in contrast to the present form.’ The
abundant European and African material shows that the persistence or disappearance
of ribs may be no more than a sub-specific difference. Moreover, in Acanthoceras
wyomingense (Reagan) itself low, broad ribbing persists at least to a diameter of 220 mm.

Acanthoceras rhotomagense (Brongniart)

The Acanthoceras rhotomagense population from Rouen can be divided into 5 mor-
phological varieties as described below. The general features of the population are:
Acanthoceras with between 15 and 30 ribs per whorl; short ribs are only present in early
growth-stages; the siphonal tubercle is lost early in development. Compressed individuals
have weak ribs and tubercles, but as the degree of inflation increases, the tuberculation
and ribbing become progressively stronger.

Acanthoceras rhotomagense (Brongniart 1822) forma typica
Plate 88, figs. 1-5; Plate 89, fig. 1 ; text-figs. 2, 6b, 7

1 822 Ammonites Rhotomagensis Brongniart, p. 606, pi. 6, fig. 2.

71867 Ammonites Rothomagensis Lamk; Gueranger pars; pi. 2, figs. 2 and 6 only.

1912 Acanthoceras rhotomagensis Defrance in Brongniart; Douville, fiche 238.

1956 Acanthoceras chasca Benavides-Caceres, pp. 466-7, pi. 53, figs. 1-4.

Lectotype. Selected by Douville (1912); the specimen figured by Brongniart in Cuvier and Brongniart
1 822, pi. 6, fig. 2, now in the Sorbonne, Paris.

Diagnosis. Acanthoceras with flat sides, barely depressed to barely compressed whorl
sections, and 21-3 ribs per whorl. The short ribs are lost at an early growth-stage
(normally by about 40 mm. diameter). There are moderately strong umbilical bullae,

EXPLANATION OF PLATE 88

All figures are of natural size. Specimens are coated with ammonium chloride. All ammonites are from

the fossil-bed of the Craie de Rouen.

Figs. 1-5. Acanthoceras rhotomagense Brongniart. \a,\b. Side and ventral view of R8. la, lb. Ventral
and side view of SI 4. 3 a, 3 b, 3c, Ventral, front and side views of a plaster-cast of the lectotype in the
Sorbonne; cast kindly provided by Mme E. Basse de Menorval. 4a, 4b, Side and front views of
a juvenile, A635f. 5, Original figures of the lectotype by Brongniart in Cuvier and Brongniart,
1822, pi. 6, fig. 2.

Figs. 6a, b. Acanthoceras rhotomagense intermediate between var. subflexuosum Spath and var. clava-
tum var. nov. Front and side views of SI 1.

EXPLANATION OF PLATE 89

All figures are of natural size except fig. 3 c. Specimens are coated with ammonium chloride.

Figs. 1 a-c. Acanthoceras rhotomagense (Brongniart); from quarry on Chard side of boundary fence,
£ mile north of Tytherleigh, near Chardstock, Devon; presumably from the Middle Cenomanian
basement bed of the Chalk; ventral, front and side views of C 73088.

Figs, la, b. Acanthoceras rhotomagense var. sussexiense (Mantell); from fossil-bed of the Craie de
Rouen; individual showing change from normal to pathological condition; front and side views of
C 74797.

Figs. 3 a-e. Spinose Calycoceras with an Acanthoceras nucleus; from fossil-bed of the Craie de Rouen.
a, b, Side and ventral views, c, Side view x 2. d, e, Side and ventral views, all of S9.

Palaeontology, Vol. 13

PLATE 88

KENNEDY and HANCOCK, Acanthoceras from Rouen

Palaeontology, Vol. 13

PLATE 89

KENNEDY and HANCOCK, Acanthoceras from Rouen

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 467

round to clavate lower ventro-lateral tubercles, clavate upper ventro-lateral and siphonal
tubercles. The siphonal tubercles are lost early in ontogeny.

Description of lectotype. The lectotype is a small, wholly septate, phosphatic internal
mould. The umbilicus of one side of the specimen is filled by phosphatised sediment.

The specimen is moderately evolute, about two-fifths of the previous whorl being
covered. The whorl section is barely depressed; in intercostal section the sides are flat,
the shoulders round, and the venter flat. The costal section is polygonal, approximately
a square with the corners truncated, the flat sides slightly convergent ; the shoulders are
flat and the venter is slightly depressed. The umbilicus is small, quite deep, with a round,
undercut wall and a round shoulder.

There are 21-2 ribs at a diameter of 38-5 mm., alternating more or less regularly long
and short. Each long rib arises at the umbilical seam, strengthens across the umbilical
wall and develops an elongate umbilical bulla on the lowest part of the side. On the sides
the ribs are moderately strong, becoming increasingly prominent as the diameter
increases. They are straight, and slightly narrower than the interspaces. All bear a well-
marked lower ventro-lateral tubercle which is slightly bullate. This is connected by a
strong, round, forwardly directed rib to a slightly clavate and stronger upper ventro-
lateral tubercle. The ribs are slightly depressed between these two tubercles.

The upper ventro-lateral tubercles are connected across the venter by a broad, low,
round rib, lower than the upper ventro-lateral tubercles, and bearing a clavate siphonal
tubercle. This siphonal tubercle is weaker than the upper ventro-lateral tubercles even
at the earliest stage visible (approx. 15 mm.).

The shorter ribs arise gently some way up the sides and become equal to the long ribs
at the shoulder and across the venter. Some are tenuously connected to the umbilical
tubercles of the long ribs. The last three ribs are all long.

The suture is simple and of normal Acanthoceras type.

Discussion. This form is an intermediate between A. rhotomagense var. subflexuosum
and A. rhotomagense var. sussexiense. If it had not been the type form of the genus
we should not have felt it necessary to give a name to it; its characters are not sufficiently
distinctive for it to be easy to assign a specimen to it. It is not even a common form like
A. rhotomagense var. sussexiense : indeed, we have been unable to find anywhere another
specimen identical with the lectotype. This is the more disturbing when one recalls that
the lectotype is relatively small (less than 40 mm. in diameter) so that the ontogeny may
be somewhat different from what we believe. However, we have seen sufficient closely
comparable material to be certain that: (i) This is a variety which loses its shorter
ribbing at a comparatively early stage: the last three ribs on the type all start at the
umbilical edge, but in other specimens short ribs can occur later than this — to diameters
of 50-60 mm. (ii) This is not the variety which gives rise to the Mid-Cenomanian
Euomphaloceras: these all seem to be offshoots of A. rhotomagense var. sussexiense
whatever detailed pattern the extra decoration on the venter takes.

There is an adult specimen in the Rouen museum (uncatalogued but labelled 7 on one
side) with a diameter of 375 mm., although the aperture is missing and there is only a
quarter whorl of body chamber (which has begun to become more evolute). On the
body chamber, which begins at 305 mm., the angular whorl shape seen on phragmocones
is maintained; the two ventro-lateral tubercles are joined by a rib of about the same

468

PALAEONTOLOGY, VOLUME 13

height, whilst pairs of upper ventro-lateral tubercles are set only 27 mm. apart across
the ventral depression. On the septate portion the ventro-lateral tubercles are not clavate,
and the umbilical bullae are no more than abrupt terminations of the bottom end of the
ribs. The ribbing is directed slightly forward.

We figure an adult specimen from England (WJK 2466) which is very close to A.
rhotomagense although slightly transitional to A. rhotomagense var. clavatum in that
the ventro-lateral tubercles on the late septate portion are clavate (text-figs. 6b, 7). The
body chamber occupies two-thirds of the last whorl, and the aperture is simple, with

text-fig. 2. Suture line of the lectotype of Acanthoceras rhotomagense (Brongniart).

After Douville 1912; magnification not stated.

a gently sinuous margin. The tubercles weaken on the body chamber, as strong, sharp
ribs develop which pass right across the venter. This body chamber decoration is similar
in many species of Acanthoceras, making it difficult to identify isolated body chambers.

Both Mantell’s and Brongniart’s works were published in 1822. We have accepted the
general view that Brongniart’s Ammonites rhotomagensis has priority over Mantell’s
Ammonites sussexiensis (see Sharpe 1853-6, p. 34). This view is not invalidated by the ;j
fact that Brongniart had already seen Mantell’s plates whilst he was writing his own
work; and Mrs. Mantell’s execrable figures of this species could never have given
Brongniart the idea he was describing a closely allied form.

A. rhotomagense is distinguished from A. r. var. sussexiense by the more compressed
whorl section, weaker umbilical and lower ventro-lateral tubercles, giving an impression
of longer ribs; the siphonal tubercle is also lost earlier.

It is distinguished from A. r. var. subflexuosum by the stronger tuberculation, more
widely spaced ribs, and commonly by the narrower, flat venter.

Acanthoceras adkinsi Stephenson (1953, pp. 200-1, pi. 47, figs. 3, 4) is very close to i
A. rhotomagense differing with certainty only in the maintenance of short ribs to a

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 469

diameter of at least 74 mm. The slightly greater whorl compression of A. adkinsi cannot
itself be regarded as even a subspecific difference.

Acanthoceras stephensoni Adkins (1928, p. 246, pi. 31, figs. 1, 2) which Matsumoto
and Obata (1966) say ‘is closely allied to the broadly ribbed variety of A. rhotomagense' ,
is distinguished by flat, unribbed flanks.

Acanthoceras rhotomagense var. subflexuosum Spath 1923
Plate 90, figs. 1-4; text-fig. 8

1826 Ammonites rhotomagensis Defrance; J. de C. Sowerby v. 6, p. 25, pi. 515, fig. 1.

1867 Ammonites Rothomagensis Lamk; Gueranger pars, pi. 2, figs. 1 and 5 only.

1923 Acanthoceras subflexuosum sp. nov.; Spath, p. 144.

71940 Acanthoceras cf. subflexuosum Spath; Fabre, p. 233.

1951 Acanthoceras subflexuosum Spath; Wright and Wright, p. 28.

Holotype. BM 43983a, from the Lower Chalk of Sussex (figured by J. de C. Sowerby 1826, v. 6, pi. 515,
upper figure), original designation by Spath 1923, p. 144 n. 3.

Diagnosis. This is a form of Acanthoceras rhotomagense with a similar degree of com-
pression to A. rhotomagense but with a broader, faintly round, venter. The tuberculation,
other than some umbilical bullae, is weaker. The ribbing is slightly denser (typically
25-9 ribs per whorl), and is distinctly, albeit weakly, flexuous.

Description of holotype. The holotype is a small, slightly distorted and abraded, limonite-
coated, composite internal mould in grey chalk. Most of the inner whorls and all the
ornament of one side have been destroyed. The suture is not visible.

The holotype is moderately evolute, about a quarter of the previous whorl being
covered. The whorl section is compressed; in intercostal section the sides are flat and
almost parallel, the ventro-lateral shoulders broadly round and the venter flat. The costal
section is compressed-polygonal, with the greatest breadth at the umbilical bullae. The
umbilicus is small, moderately deep, with a steep umbilical wall and round umbilical
shoulder. There are 28 ribs at a diameter of 58 mm., alternating more or less regularly
long and short. The long ribs appear to arise at the umbilical seam, strengthen across
the umbilical wall, and develop into elongate umbilical bullae just outside the umbilical
shoulder. On the sides the ribs are strong, broad, and round, as wide or slightly narrower
than the interspaces. The ribs are gently flexed, each passing slightly forwards across
the lower part of the sides, and then backwards to a very weak bullate lower ventro-
lateral tubercle, then forwards again to a weak clavate upper ventro-lateral tubercle.
The venter is rather narrow, with a row of weak clavate siphonal tubercles, connected
to the similar upper ventro-lateral tubercles by low, broad, round ribs, separated by
narrow interspaces. The shorter intercalated ribs extend across the upper two-thirds of
the flank and the venter.

Discussion. This name was introduced by Spath without any description. The holotype
is both a juvenile and an extreme variant of this variety, having unusually strong ribs
and being unusually compressed, although this latter character may be very slightly
exaggerated by crushing.

The ribbing in this variety is weak, but that in Acanthoceras flexuosum Crick is
even weaker. Moreover, the ribbing on Crick’s species has a rather strong forward

470

PALAEONTOLOGY, VOLUME 13

table 1. Measurements of Acanthoceras : all specimens are from the fossil bed in the Craie de Rouen
except the holotype of A. rhotomagense var. subflexuosum, the lectotypes of A. r. var. sussexiense and
A. r. var. confusum, the paralectotype of A. r. var. confusum, C73088, and WJK 2466.

Collection key: S = Sorbonne; A = Ecole des Mines, Paris; C (or number without prefix) = British
Museum (Natural History); GSM = Institute of Geological Sciences, London; CC = J. M. Hancock
collection; R or WJK = W. J. Kennedy collection.

Measurements of diameter, whorl height, and whorl width have been made between ribs ; equivalent
measurements across ribs are obviously greater. When ribbing and tubercles are taken into account,
whorl sections often appear more compressed than intercostal measurements of whorl height and
whorl width would indicate, a. = approximately.

Number of

Whorl

Whorl

Width of

ribs on

Number of

Number of

Specimen

Diameter

height

width

umbilicus

last whorl

primaries

secondaries

Acanthoceras rhotomagense forma typica

Holotype

(Sorbonne)

37-8

17

19-6

8-3

21

11

10

S13

60-5

27

27-8

16-6

19

13

6

S14

87

37-3

39 a.

15-8

22

15

7

S31

85-5

(34-5)

(37-8)

28

18 a.

14 a.

4 a.

S18

39

17-4

20

11

22

10

12

A636

32

16

18 a.

8-5

23

11 a.

12 a.

A646

74-5

32

33 a.

21

22

18 a.

4 a.

R6

Rouen Mus.

24

26

adult

375 a.

132

23

23

0

C73088

109

42-5

36

25

21

4

Acanthoceras rhotomagense intermediate between var. clavatum and rhotomagense

s.s.

S24

52-6

20-7

21-8

15-6

21

13

8

S25

85-6

35-9

36-7

25-3

23

17 a.

6 a.

A645

48-0

20-3

21-5

13-8 a.

22-3 a.

11 a.

11 a.

A649

800

32-5

35-9

25-5

17

13

4

A659

62-9

25-7

27 a.

19-8

18

14

4

WJK 2466

270

90

95

100

20

20

0

Acanthoceras rhotomagense var. clavatum

Holotype

A660

90-8

36-7

38-3

27-7

22 a.

17 a.

5 a.

S15

35-2

34-5

S21

60-8

26-6

23-9

15-9

20-1

9-10 a.

S22

29-6

29-1

19-2

20 a.

S23

74-3

29-8

29-6

21-7

20 a.

Acanthoceras rhotomagense var. subflexuosum

Holotype

43983a

590

26-2

23-0

15-4

28-9

14 a.

14 a.

S3

114-5

45-2

49-5 a.

34-4

27

S4

107

44-0

48-4

33-4

26

22

4

S10B

14

6-2

7

17-18 a.

A642

59-4

26-6

28-5

16 a.

29-30

19

10-11

A651

54-7

24-9

26

14-8

27

12-14

13-15

A663

109-6

45-7

46-5

32-9

30

20-2

8-10

C74792

18-4

9-7

9

3-5

19

Acanthoceras rhotomagense aff. var. sussexiense-subflexuosum

A682 80 32-5 41 a. 23-7 27 17 10

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 471

Number of

Whorl

Whorl

Width o/

nfo on

Number of

Number of

Specimen

Diameter

height

width

umbilicus

last whorl

primaries

secondaries

Acanthoceras rhotomagense var. subflexuosum transitional to A. r. var.

clavatum

Sll

59-6

25-1

24-3 a.

15-0

24

Acanthoceras rhotomagense var. sussexiense

Lectotype

BM 5691

145

54-7

62

52-2

23-4

23-4

0

Cl 030

200

74-8

69-5

72

20

20

0

SI

98-7

36-3

47-5

31-2

24 a.

S10A

26-5

11-2

13-8

7

17 a.

S20

60-6

26

29-6

18-7

25

15

10

S26

49

20-6

26-5

15-9

19

16

3

S27

97-6

36

49-8

25

S28

18-8

8-7

10-7

4-6

18

8

10

S29

26-3

10-4

14-3

7-5 a.

18

S3 3

45-2

191

23-7

12-6

20 a.

11 a.

9 a.

A635

19-6

8-2

10-5

4-8

17

8

9

A654

92

36-3

43* a.

36

23

22

1

A655

115

45

58

39-5

25

13-15

10-12

R3

18-6

21-8

Rll

42

50

CC710

47

19

22-8

14-6

19

14

5

CC711

23-6

26-6

Acanthoceras rhotomagense aff. var. sussexiense

C74799

27

12-7

15

7-7

15

12

3

A644

47

20

23 a.

14-8

15

10 a.

5 a.

A674

36-8

14-9

11-2

16

9

7

Acanthoceras rhotomagense var. confusum

Lectotype

Gueranger,

pl. 3, fig. 1
Paralectotype

20

19 or 20

Gueranger,
pl. 2, fig. 4

(70)

(26-5)

(23)

20

20?

assuming figures x 1

S8

90-5

34

43-5

26-8

18

14 a.

S10D

14-2

5-3

7-9

3-2

15

8

S17

36

14-3

20-6

10

18 a.

13 a.

A635d

20-3

8

12-8 a.

4-9

17

9 a.

A637

28-1

12

16-2

7-6

16

12

A 647

61-4

24

33* a.

19-3

18

11

A653

124

51-5

68 a.

48

18

18

C74791

66

28

30

22

21

15

Transitions between Acanthoceras rhotomagense var. clavatum and Acanthoceras adkinsi

S19

60

28-2

26-6

13-7

25

13

A 650

54-2

24-3

140

29

12

CC712

51-4

24-5

22 a.

13 a.

29 a.

Acanthoceras basseae
Holotype

S5 700 24-8 27-5 16-3 21 14-15

SI 6 21-5 24 1

A684 49-4 21-4 a. 23-5 a.

Oor 1

0?

4 a.
7

5 a.
7 a.
4

7

0

6

12

17

6-7

15-3

472

PALAEONTOLOGY, VOLUME 13

sweep, and smaller but sharper lower ventro-lateral tubercles (although the sharpness
may well be because the shell is preserved). A. flexuosum at the least is a closely allied
species.

Acanthoceras adkinsi Stephenson (1953, pi. 47, figs. 3, 4) apparently belongs to the
Acanthoceras rhotomagense group; it differs from A. rhotomagense var. subflexuosum
in having fewer ribs (23 instead of 25-9); BMNH C74794 from Rouen appears to be
an intermediate.

Acanthoceras rhotomagense var. sussexiense (Mantell 1822)

Plate 89, fig. 2; Plate 91, figs. 1-2; Plate 92, figs. 1-2; text-figs. 3, 4, 5, 6a
1822 Ammonites Sussexiensis Mantell, pp. 114-15, pi. 20, fig. 2.

1854 Ammonites Rhotomagensis Defiance; Sharpe, pp. 33-4, pi. 16, figs. 1 a-c, 3a, b (figs. 2a, b
transitional to A. r. rhotomagense).

EXPLANATION OF PLATE 90

All figures are of natural size except fig. 3b ; all specimens are coated with ammonium chloride.

Figs. la-c. Acanthoceras rhotomagense var. subflexuosum Spath; from Lower Chalk of Lewes, Sussex.
Side, front, and ventral views of the holotype 43983a.

Figs. 2a, b. Acanthoceras rhotomagense aff. var. subflexuosum Spath; unusually inflated juvenile from
the fossil-bed of the Craie de Rouen. Front and side views of A635e.

Figs. 3a-c. Acanthoceras rhotomagense var. subflexuosum Spath; juvenile from the fossil-bed of the
Craie de Rouen, a, c. Front and side views, b. Side view x 2, of S10B.

Figs. 4 a, b. Acanthoceras rhotomagense var. subflexuosum Spath; from the fossil-bed of the Craie de
Rouen. Side and front views of A663.

EXPLANATION OF PLATE 91

All figures are of natural size. Specimens are coated with ammonium chloride.

Figs, la, b. Acanthoceras rhotomagense var. sussexiense (Mantell); from the Lower Chalk of Hamsey,
Sussex. Side and front views of the lectotype, BM 5691.

Figs. 2a, b. Acanthoceras rhotomagense var. sussexiense (Mantell); from the fossil-bed of the Craie
de Rouen. Side and front views of A635a.

Fig. 3. Acanthoceras aff. rhotomagense (Brongniart) transitional to a spinose Calycoceras; from the
fossil-bed of the Craie de Rouen. Side view of SI 8 (front view in PI. 97, fig. 3).

EXPLANATION OF PLATE 92

All figures are of natural size. Specimens are coated with ammonium chloride. All from the fossil-bed

of the Craie de Rouen.

Figs, la, b. Acanthoceras rhotomagense var. sussexiense (Mantell); Side and front views of A654; note
slight asymmetry in the position of the siphonal tubercle in this individual.

Figs. 2a, b. Acanthoceras rhotomagense var. sussexiense (Mantell); Side and front views of a juvenile,
S28.

Figs. 3a, b. Acanthoceras aff. rhotomagense var. sussexiense (Mantell). Ventral and side views of A674;
note the narrow venter, relatively compressed whorl, and low rib density.

Figs. 4 a, b, c. Euomphaloceras sp. close to Acanthoceras rhotomagense var. sussexiense (Mantell);
Front, side, and ventral views of S6 ; note the rounded whorl-section and the intercalation of extra
ventral tubercles.

Figs. 5a, b. An intermediate between Calycoceras and Acanthoceras. Side and front views of C74795.

Figs. 6a, b. Acanthoceras aff. rhotomagense var. sussexiense (Mantell). Side and front views of C74799,
paralectotype of Acanthoceras hippocastanum (J. de C. Sowerby); note low rib density combined
with relatively narrow venter.

Palaeontology, Vol. 13

PLATE 90

KENNEDY and HANCOCK, Acanthoceras from Rouen

Palaeontology , Vol. 13

PLATE 91

KENNEDY and HANCOCK, Acanthoceras from Rouen

Palaeontology, Vol. 13

PLATE 92

KENNEDY and HANCOCK, Acanthoceras from Rouen

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 473

non 1854 Ammonites Sussexiensis Mantell; Sharpe, p. 34, pi. 15, fig. 1 (= Euomphaloceras inerme
(Pervinquiere)).

1863 Ammonites rhotomagensis Brongniart; Pictet pars; pi. 2, figs. 1 a-e only.

1878 Acanthoceras rhotomagensis Brongniart; Bayle, pi. 63, figs. 1-3; ?4 — 5.

non 1923 Acanthoceras sussexiense\ Spath, p. 144 n.

1926 a Acanthoceras vectense Spath, p. 82.

1931 Acanthoceras hippocastanum Sow; Collignon, pi. 4, fig. 1.

1951 Acanthoceras vectense Spath; Wright and Wright, p. 28.

1951 Acanthoceras sussexiense (Mantell); Wright and Wright, p. 28.

1963 Acanthoceras mirialampiense Wright, p. 606, pi. 84, fig. 3; pi. 85, fig. 1.

Lectotype (here selected). BM 5691 from the Lower Chalk of Hamsey, Sussex, bearing Mantell’s original
green label, ‘xx, 2’. This is possibly the original of Mantell 1822, pi. xx, fig. 2. Two smaller specimens
(BM C. 73637, 5690) in the Mantell collection labelled Ammonites sussexiensis belong elsewhere.

Diagnosis. Form of Acanthoceras rhotomagense characterized by a more depressed
quadrate whorl section than A. rhotomagense itself, with strong, dense, rounded, slightly
rursiradiate instead of prorsiradiate ribs, all of which are long in the middle and later
growth stages. There are strong umbilical bullae and lower and upper ventro-lateral
tubercles, the latter two rows fusing in the adult, and a small siphonal tubercle weakening
in the middle and later stages.

Description of lectotype. This is a large, very well-preserved if slightly distorted, com-
posite internal mould in grey chalk, with a rusty limonitic coat. Just under half the
later whorl is body chamber, where the specimen develops pathological ribbing.

The coiling is evolute, about a fifth or a sixth of the previous whorl being covered.
The whorl section is depressed, with the greatest breadth at the umbilical bullae ; rounded
quadrangular in intercostal section, with flat sides, broadly round shoulders, and a flat
venter; costal section trapezoidal-polygonal. The umbilicus is broad and moderately
deep, the umbilical wall round and undercut, and the shoulder round. There are 23 ribs
per whorl at 77 mm. diameter, 25 at 134 mm, and 24 at 150 mm. The specimen is
pathological beyond 130 mm.

All the visible ribs are long; each arises at the umbilical seam, strengthens across the
umbilical wall and develops a strong umbilical bulla just outside the umbilical shoulder.
The bulla is developed to a varying degree on different ribs, strengthening with increasing
diameter. The ribs also become stronger with increasing diameter; they are more or
less straight across the whorl sides, broad and round, equal to or slightly wider than the
interspaces, subdued at mid-flank, rectiradiate in the earlier growth stages, rursiradiate
in the later stages. Each rib bears a strong, slightly spinose lower ventro-lateral tubercle.
From this tubercle the ribs project slightly forwards across the shoulder to a clavate
upper ventro-lateral tubercle. Upwards of a diameter of 120-30 mm. the two ventro-
lateral tubercles increasingly coalesce. The ribs are broad, round, and continuous across
the venter, and up to a diameter of 90 mm. there is a weak clavate siphonal tubercle.
At greater diameters this tubercle is lost. There is a weak siphonal depression at diameters
of 120 mm. upwards.

The last septum is at a diameter of 120 mm., where there is the median siphonal
depression on the ribs and the ventro-lateral tubercles have almost coalesced. The type
has been damaged in life at the beginning of the secretion of its final body chamber, and
as a result has developed irregular ventral ribbing, an irregularity which becomes more

474

PALAEONTOLOGY, VOLUME 13

pronounced on later parts of the body chamber. There are thus only four ribs on the last
quarter whorl. These ribs are high, distant, and very much narrower than the interspaces,
with a strong umbilical bulla and a lower ventro-lateral tubercle now flat and horn-like.
There is an upper ventro-lateral tubercle present on the penultimate rib.

Discussion. The lectotype can be matched with the better-preserved material from Rouen,
where it is the commonest form. This material shows that the changes during ontogeny
are relatively slight (as is usual in Acanthoceras), the strong ornament being present from
the earliest stages (see PI. 92, fig. 2). Thus the siphonal tubercle only weakens very slowly,
and during most growth stages is as strong as, or only a little weaker than the upper
ventro-lateral tubercles, which are themselves weaker than the lower ventro-lateral
tubercles.

There is some degree of variation in the density of the ribbing: 22-6 ribs per whorl.
There is considerable variation in the persistence of short-ribbing which disappears
within the range 37-60 mm. diameter.

With less inflation (sometimes accompanied by weaker decoration) there are transi-
tions to A. rhotomagense (e.g. Ecole des Mines A 658). Transitions to A. rhotomagense
var. confusum are more common : in these there is increasing spinosity, fewer ribs, and
sometimes increasing rib strength.

Being common, A. rhotomagense var. sussexiense has often been figured, usually
under other names, particularly A. rhotomagense (e.g. Wright (in Arkell et al. 1957,
L415, fig. 7) has used the figure of Bayle (1878) to illustrate the type species). A. vec tense
Spath (1926a) is a synonym: the apparent differences arise from the pathology of the
lectotype of A. r. var. sussexiense ; the holotype of A. vectense (GSM 7756) shows well
the backward sweep of the ribs in the later stages (text-figs. 3, 4).

Those Acanthoceras from Rouen which show any development of Euomphaloceras-
like multituberculation or rib insertions on the venter, are all close to A. r. var. sus-
sexiense in general style of ornament (PI. 92, fig. 4; PI. 93).

Acanthoceras crassiornatum Crick (1907, p. 185) differs in having coarser, more
widely spaced ribbing, a more compressed whorl section, and more strongly clavate
upper ventro-lateral tubercles.

Acanthoceras robustum Crick (1907, p. 189) has weaker, broader, more widely spaced
ribs, with all tubercles, except the siphonal series, weaker.

Acanthoceras quadratum Crick (1907, p. 192, pi. 13, fig. 2) has only 21 ribs at
a diameter of 108 mm. compared with 25 in the lectotype of A. rhotomagense var.
sussexiense.

Acanthoceras aff. rhotomagense var. sussexiense (Mantell)

Plate 92, figs. 3, 6

We have seen a number of specimens which have the decoration of A. rhotomagense
var. sussexiense but which are markedly more compressed. In this respect they are
transitions to Acanthoceras simulans Spath (Schliiter 1871, pi. 7, fig. 3), although that
species has multiple siphonal tuberculation.

Acanthoceras hippocastanum (J. de C. Sowerby) (lectotype, herein designated, is the
original specimen figured by Sowerby (1829, pi. 514, fig. 2, GSM 37667)) was based upon

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 475

text-fig. 3. Acanthoceras rhotomagense var. sussexiense (Mantell). From Bonchurch, near Ventnor,
Isle of Wight; horizon unrecorded. Side view of GSM 7756, the holotype of Acanthoceras vectense

Spath. x 1 .

476

PALAEONTOLOGY, VOLUME 13

text-fig. 4. Acanthoceras rhotomagense var. sussexiense (Mantell). Front and ventral view of specimen in fig. 3,
the holotype of Acanthoceras vectense Spath. x 1 .

text- fig. 5. Acanthoceras rhotomagense var. sussexiense (Mantell). From the fossil-bed of the Craie de Rouen. Side

view of C1030; x 1.

478

PALAEONTOLOGY, VOLUME 13

two specimens; the paralectotype (C74799) figured in Plate 92, fig. 6, is from Rouen,
and is better referred to as A. aff. rhotomagense var. sussexiense.

Acanthoceras rhotomagense var. confusum (Gueranger 1867)

Plate 94, figs, Plate 95, fig. 1

1856 Ammonites hippocastanum Sowerby; Sharpe, pp. 37-8, pi. 17, figs. 4a, b, c; figs. 3a, b
represent a form halfway to A. r. sussexiense.

1863 Ammonites rhotomagensis Brongniart; Pictet pars, pi. 2, figs. 2 a-c and 3 only.

1867 Ammonites confusus Gueranger, pp. 5, 6, pi. 2, fig. 4; pi. 3, fig. i; pi. 8, fig. i.
non 1907 Acanthoceras confusum Gueranger; Pervinquiere, p. 268, pi. 13, figs. 4a, b.

71907 Acanthoceras quadratum Crick, p. 192; pi. 13, fig. 2.

Lectotype. The lectotype, herein designated, is the specimen figured by Gueranger (1867) in plate 3,
fig. 1 and plate 8, fig. 1 , from Gueranger’s ‘Zone a Perna lanceolata ’ in the lower part of the Middle
Cenomanian of the Sarthe. We have been unable to find this specimen in the Musee de Tesse at
Le Mans, and it is probably lost. Gueranger did not provide a scale for his plates but the magnifi-
cation of plate 3 is almost certainly in the range 0-3-0-4. The paralectotype specimen figured in plate 2,
fig. 4, is also probably lost. We reproduce Gueranger’s figures in Plate 94.

Diagnosis and description. This is a form of Acanthoceras rhotomagense which is more
depressed, and more strongly tuberculate than A. rhotomagense var. sussexiense, and
which has only 19-21 ribs per whorl. The lectotype is an adult with the last 2-3 ribs of
the body chamber distinctly approximated and all tuberculation lost.

Discussion. This variety represents a continuation of the trend towards coarser ribbing
and stronger ornament seen in A. rhotomagense var. sussexiense, from which it is dis-
tinguished by the fewer (and sometimes heavier) ribs and a general clumsy appearance.

EXPLANATION OF PLATE 93

All figures are of natural size; both specimens are coated with ammonium chloride.

Figs. 1 a, b, 2a, b. Euomphaloceras transitional from Acanthoceras rhotomagense var. sussexiense
(Mantell), showing intercalation of extra ribs on the relatively rounded venter.

Figs. 1 a, b. From the fossil-bed of the Craie de Rouen; front and side views of S2.

Figs, la, b. From Nogent-le-Rotrou (Eure et Loir); horizon unknown but matrix suggests Craie de
Theligny (Middle Cenomanian). Ventral and side views of A657 ; note that the intercalatory ribs on
the venter carry tubercles of equal strength to those on the primary ribs.

EXPLANATION OF PLATE 94

All figures except 1 and 2 are of natural size. Specimens except those in figs. 1 and 2 are coated with

ammonium chloride.

Figs. 1 and 2. Acanthoceras rhotomagense var. confusum (Gueranger); from the upper part of the
Sands with Perna lanceolata (lower part of Middle Cenomanian) in the Sarthe.

Fig. 1. Lectotype; copy of Gueranger 1867, pi. 3; upper figure; reduction unknown.

Fig. 2. Paralectotype; copy of Gueranger 1867, pi. 2, fig. 4; magnification unknown but possibly
natural size.

Figs. 3 a-e. Acanthoceras rhotomagense var. confusum (Gueranger) ; from the fossil-bed of the Craie de
Rouen. Various views of different growth stages of the same juvenile, S10D.

Figs. 4a, b. Acanthoceras rhotomagense var. confusum (Gueranger); from the fossil-bed of the Craie de
Rouen. Side and front views of A647.

Figs. 5a, b. Acanthoceras transitional between rhotomagense var. clavatum var. nov. and adkinsi
Stephenson; from the fossil-bed of the Craie de Rouen. Side and ventral views of A650.

Palaeontology, Vol. 13

PLATE 93

KENNEDY and HANCOCK, Acanthoeeras from Rouen

Palaeontology, Vol. 13

PLATE 94

KENNEDY and HANCOCK, Acanthoceras from Rouen

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 479

There are many transitions between the two varieties. As with most coarsely ornamented
ammonites there is much variation in the detail of the decoration.

As can be seen from the synonymy, and from an examination of museum collec-
tions, this variety has been frequently mis-identified as Acanthoceras hippocastanum (J.
Sowerby) which is a much younger species of the Naviculare Zone (Upper Cenomanian).
It differs from A. rhotomagense var. confusum in (i) being adult at small diameters
(perhaps one-fifth of the size of an adult A. r. var. confusum ); (ii) being more inflated;
(iii) retaining alternately short and long ribs throughout; (iv) retaining strong siphonal
tubercles throughout; (v) ribbing between lower and upper ventro-lateral tubercles
remaining weak. Of all figures purporting to represent A. hippocastanum, only Sower-
by’s original can in truth be referred to that species.

Acanthoceras jukes-brownei (Spath) and A. whitei Matsumoto both differ in retaining
alternately short and long ribs throughout the septate portion.

Acanthoceras latum Crick (1907, 195, pi. 12, fig. 2, 2a) is a closely allied species with
a rapidly expanding whorl section, fewer ribs (about 15 per whorl) which are generally
weaker, a much broader venter, and particularly large spinose lower ventro-lateral
tubercles. A. quadratum Crick has weaker ribbing than the average individual but is
probably synonymous.

Acanthoceras confusum tunetana Pervinquiere (1907, 268-9, pi. 13, figs. 4 a, b ) is a
form with few ribs (17 per whorl) and finger-like horns in the position of the lower
ventro-lateral tubercles, but no other tubercles : it is best considered as a separate species.

Acanthoceras sherborni Spath (= Ammonites cenomanensis Sharpe non d’Archiac) is
close to A. r. var. confusum ; the type is lost. The chief differences of A. sherborni are:
(i) slightly fewer ribs (17 at a diameter of 155 mm. — Sharpe’s figure is reduced); (ii)
greater compression; (iii) the apparent loss of the lower ventro-lateral tubercle giving
rise to squarer shoulders. Some of these features could be exaggerated by the imperfect
preservation in the Lower Chalk of Dover.

Acanthoceras rhotomagense var. clavatum var. nov.

Plate 96, figs. 2-3; Plate 97, fig. 5

Holotype. A660 in the Ecole des Mines, Paris, from the Craie de Rouen, Ste Catherine, Seine-Maritime,
France, here figured as Plate 96, fig. 2.

Diagnosis. A compressed form of Acanthoceras rhotomagense with 21-3 weak ribs per
whorl which loses umbilical bullae early in ontogeny; has weak, rounded lower
ventro-lateral tubercles, and very large, markedly clavate upper ventro-lateral tubercles
on each side of a depressed venter.

Description. The holotype is a well-preserved, wholly septate, phosphatic internal mould,
retaining traces of phosphatised shell. It is evolute, about two-fifths of the previous
whorl being covered. The whorl section is compressed, with the greatest breadth just
below mid-flank. The sides are broadly rounded in intercostal section, with a narrow,
high, round venter.

There are an estimated 21 ribs on the outer whorl, nearly all of which extend down to
the umbilical edge. They are weak close to the umbilical wall, and strengthen across the

C 7019 i i

480

PALAEONTOLOGY, VOLUME 13

sides, so that they reach a maximum development at mid-flank, although there is much
variation in the strength of the early formed part of the rib. The ribs are slightly flexuous,
and narrower than the interspaces. Each bears a low, round lower ventro-lateral tubercle
which weakens with increasing diameter. This tubercle is connected by a low, forwardly
directed rib to a very large clavate upper ventro-lateral tubercle, which becomes more
pronounced as the diameter increases. These upper ventro-lateral tubercles form closely
spaced pairs across the venter, and rise high above the intervening flat siphonal area.
There are traces of a weak, spirally elongate, siphonal swelling.

The early whorls are poorly visible but show that variation in rib strength was much
more marked up to a diameter of about 35 mm., whilst a distinct siphonal tubercle (as
strong as the upper ventro-lateral tubercles) was present.

The suture line is well preserved, and is of normal Acanthoceras type (see PI. 96,
fig. 2d).

Discussion. The strong upper ventro-lateral clavae, weak ribs, and compressed section
are the distinctive features. We have seen two specimens transitional to A. rhotomagense.
There are also specimens transitional to A. rhotomagense var. suhflexuosum in some of
which much of the ribbing is exceptionally weak.

A. rhotomagense var. clavatum resembles A. wintoni Adkins and the ‘plesiotype’ of

EXPLANATION OF PLATE 95

Both figures are of natural size, and the specimen is coated with ammonium chloride.

Figs, la, b. Acanthoceras rhotomagense var. confusum (Gueranger); from the fossil-bed of the Craie de
Rouen. Front and side views of A653; the last suture is at a diameter of approximately 110 mm.

EXPLANATION OF PLATE 96

All figures are of natural size. Specimens are coated with ammonium chloride. All are from the fossil-

bed of the Craie de Rouen.

Figs. la-c. Acanthoceras intermediate between A. rhotomagense (Brongniart) and A. rhotomagense
var. clavatum var. nov. Side, ventral and front views of A659.

Figs. 2 a-c. Acanthoceras rhotomagense var. clavatum var. nov. Side, ventral and front views of the
holotype A660.

Fig. 3. Acanthoceras rhotomagense var. clavatum var. nov. Side view of a paratype S21.

EXPLANATION OF PLATE 97

All figures are of natural size. All specimens are coated with ammonium chloride except fig. 2a. All

ammonites are from the fossil-bed of the Craie de Rouen.

Figs, la, b. Acanthoceras basseae sp. nov. Side and front views of the holotype S5.

Figs. 2 a-c. Acanthoceras aff. basseae sp. nov. Ventral, front and side views of a specimen in the Museum
d’Histoire Naturelle de Rouen. The close spacing of the clavate tubercles on the venter, and the rapid
disappearance of these tubercles shown in the ventral view, mean that this ammonite could equally
well be referred to Protacanthoceras.

Fig. 3. Acanthoceras aff. rhotomagense (Brongniart) transitional to a spinose Calycoceras. Front view
of SI 8 (side view in PI. 91, fig. 3).

Figs. 4a, b. Protacanthoceras sp. Side and front views of C 74796.

Figs. 5a, b. Acanthoceras basseae sp. nov. Ventral and side views of a paratype A684.

Fig. 6. Acanthoceras rhotomagense var. clavatum var. nov. Front view of S21 (side view on previous
plate).

Figs, la, b. Protacanthoceras sp. Side and front views of A52.

Figs. 8a, b. Acanthoceras basseae sp. nov. Ventral and side views of a paratype S16.

Palaeontology, Vol. 13

PLATE 95

KENNEDY and HANCOCK, Acanthoceras from Rouen

Palaeontology, Vol. 13

PLATE 96

KENNEDY and HANCOCK, Acanthoceras from Rouen

Palaeontology , Vol. 13

PLATE 97

KENNEDY and HANCOCK, Acanthoceras from Rouen

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 481

Stephenson is even closer (1953, pi. 45, figs. 7, 8; pi. 46, fig. 1). However, in A. rhoto-
magense var. clavatum there are more ribs, the siphonal tubercle weakens and disappears
much earlier, the ribbing on the venter is weaker (it is also weak in Stephenson’s
plesiotype), short ribs are absent beyond diameters of 60 mm. (and often do not reach
that), and most individuals have flatter sides. Acanthoceras very close to A. wintoni occur
in the Chalk basement bed at Snowdon Hill, Chard, Somerset.

There is an allied form (authors’ collections, e.g. cc560) from Snowdon Hill, Chard,
in which the lower ventro-lateral tubercles are completely lost, which is homeomorphous
with Mantelliceras couloni except for the lack of short ribs.

Acanthoceras basseae sp. nov.

Plate 97, figs. 1, 4

Holotype. The unregistered specimen (bearing our label ‘5’) in the collection of the Sorbonne figured as
Plate 97, fig. 1, from the Craie de Rouen, Ste Catherine, Seine-Maritime, France.

Diagnosis. Slightly compressed, evolute, square-whorled, slowly expanding Acantho-
ceras with 18-22 ribs per whorl.

Description. The holotype is a well-preserved phosphatic internal mould, the last third
of the outer whorl being body chamber. It is evolute, about a sixth of the previous whorl
being covered. The whorl section is slightly compressed, with the greatest breadth at the
umbilical bullae. The intercostal section is trapezoidal (the sides diverging towards
the umbilicus) with rounded corners. The costal section is similar, but the corners of
the trapezium are truncated.

There are 21-2 ribs on the outer whorl, most of which extend down to the umbilical
seam. They are weak across the umbilical wall; 12-13 develop a pronounced, trans-
versely elongate umbilical bulla of varying strength at or just outside the umbilical
shoulder, five lack the bulla, and four arise just below mid-flank. The ribs pass across
the sides with gentle flexure, weakening at mid-flank, and connect to a round lower
ventro-lateral tubercle which weakens with age. This is connected by a strong rib to a
weakly clavate upper ventro-lateral tubercle, which also weakens with age. A very faint
low rib extends across the venter, bearing a low clavate siphonal tubercle which again
weakens with age.

The early whorls are well exposed, and show strong umbilical bullae on long ribs
which alternate with shorter ribs or ribs which extend to the umbilicus as mere striae.
Occasional ribs branch in twos from an umbilical bulla.

The suture line is of normal Acanthoceras type.

Discussion. There are no transitions from A. basseae to any of the forms of A. rhoto-
magense described above, the slowly expanding whorl size giving all specimens a charac-
teristic and immediately recognizable almost serpenticone appearance.

Three other specimens can be accommodated here: an unregistered fragment in the
Sorbonne (our number 16); A684 in the Ecole des Mines (PI. 97, fig. 4), both topotypes;
and an English specimen from Eastbourne (ex. J. Parmenter collection no. 7670) from
the same horizon as the Rouen fossil bed.

The three complete specimens all have body chambers, whilst the other fragment is
small, suggesting that this was a small species.

text fig. 6 (see opposite )

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 483

text-fig. 7. Side view of the same ammonite figured in text-fig. 6b. x 0-57.

text-fig. 6. a, Acanthoceras rhotomagense var. sussexiense (Mantell). Front view of specimen in text-fig. 5.
b, Acanthoceras rhotomagense (Brongniart) transitional to A. r. var. clavatum var. nov. From Band 10 in the
Lower Chalk at Folkestone = Turrilites acutus assemblage-horizon of the Rhotomagense Zone which is
slightly higher than the fossil-bed of the Craie de Rouen. Front view of WJK 2466. x 0-66.

PALAEONTOLOGY, VOLUME 13

text-fig. 8. Acanthoceras rhotomagense var. subflexuosum Spath. From Band 9 of the Lower Chalk
at Folkestone, Kent = the Turrilites costatus assemblage-horizon of the Rhotomagense Zone. Side
view of WJK 5138. xO-86.

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 485

There is also a specimen in the Natural History Museum at Rouen (PI. 97, fig. 2)
which is transitional between this species and Protacanthoceras in that it shows an early
and very rapid loss of all ventral tuberculation whilst retaining ventral ribbing which is
becoming chevron-shaped.

There is some superficial resemblance between A. basseae and A. sherborni (the type
of which, as already noted, is lost). Sharpe’s figure shows that the ribbing is more
regular in A. sherborni, and the species is not adult until a much greater size.

GENERAL COMPOSITION OF THE AMMONITE FAUNA

Out of some 90 ammonites that we ourselves have collected at Rouen or were given
as a general collection by Dr. R. P. S. Jefferies, more than two-thirds are Sciponoceras
gr. baculoide (Mantell), Turrilites costatus Lamarck and transitions to T. acutus Passy,
and Schloenbachia coupei (Brongniart) and varieties. The following, in order of abund-
ance by genus, comprise less than a third: Scaphites (chiefly S. obliquus J. Sowerby),
Acanthoceras rhotomagense, Calycoceras gentoni (Brongniart), Hamites ( Stomohamites )
simplex d’Orbigny, Anisoceras sp., Puzosia sp., Austiniceras sp.

As shown in this paper, museum collections also contain Acanthoceras transitional
to Euomphaloceras and Protacanthoceras.

We have seen in the Rouen museum: Forbesiceras including F. largilliertianum
(d’Orbigny), Acompsoceras, and several rarities we could not identify at sight (possibly
Gaudryceratinae). Follet 1943 (quoted in Sornay (1959)) records a number of other
forms of which the following are stratigraphically significant: Calycoceras naviculare
(Mantell), Mantelliceras cf. tuberculatus (Mantell), Hyphoplites falcatus (Mantell).
These may be misidentifications, or are not from the Rouen fossil bed (some museum
specimens labelled ‘Rouen’ are undoubtedly from another bed), or represent remanie
material such as occurs in other chalk basement beds.

AGE OF THE FAUNA

As early as 1858 Saemann recognized a ‘niveau a Ammonites rotomagensis' in the
middle part of the Cenomanian of Le Mans. This effectively Middle Cenomanian dating
of the Rouen fauna is in complete agreement with the list by one of us (Hancock 1959)
of the ammonites from the Sables at Gres du Mans a Scaphites equalis et Turrilites
costatus.

Detailed collecting from southern England by one of us (Kennedy 1969) has pro-
vided some subdivisions of the Middle Cenomanian. The Rouen fossil bed corresponds
to an horizon in the lower part of the Middle Cenomanian characterized by Acanthoceras
rhotomagense, Turrilites costatus common and T. acutus uncommon, Sciponoceras
abundant (and in south-east England abundant Orbirhynchia gr. mantelliana ) called
the T. costatus faunal horizon (Table 2).

Superposition in the Lower Chalk of south-east England, shows that within a metre
above the horizon of the T. costatus assemblage occurs a T. acutus assemblage which is
to be found in a better preservation in the Chalk basement bed at Snowdon Hill, Chard,
in Somerset. In this younger fauna Turrilites acutus is common and T. costatus rare,
Calycoceras is more common and includes spinose species of the group of C. newboldi
spinosum (Kossmat), and Sciponoceras is normally rare.

486

PALAEONTOLOGY, VOLUME 13

It is of interest to compare the Acanthoceras of the two faunas. Many of the individuals
in the T. acutus assemblage cannot at present be distinguished from some forms in the
earlier T. costatus assemblage, e.g. A. rhotomagense, A. r. var. sussexiense and A. r. var.
confusum , but the assemblage as a whole is different: in particular the T. acutus assemb-
lage includes species we have not seen from Rouen, including: A. flexuosum Crick, A.
deciduum Hyatt? (although the type is said to be from Rouen), A. aff. wintoni Adkins,
A. aff. sherborni Spath.

table 2. Cephalopod zonation of the Cenomanian stage in southern England and northern France.
The horizons at which ammonites have been found are limited to those beds in which preservation has
occurred ; there may be other faunal horizons to be discovered in both the Mantelli and Rhotomagense

Zones.

Zone Faunal Horizons beds mentioned in paper

Acfinocamax plenus

Metoicoceras gourdoni
Metoicoceras geslinianum

( clear subdivisions not
yet recognised in north-
west Europe; for south-
east France, see Thomel
in Porthault et al 1966)

Acanthoceras jukes- brownei

Chalk basement bed, Snowdon Hill .

fossil bed, Craie de Rouen.

'Zone a Perna lanceolate'.

Mantelliceras dixoni
Mantelliceras mantelli Mantelliceras saxbii

Hypoturril ites carcitanensis

Acanthoceras rhotomagense Turrilites acutus

Turrilites costatus

Calycoceras naviculare

The horizon of the Rouen fauna in the Normandy coast sections is still slightly
uncertain. Jukes-Browne and Hill (1903, p. 253) equated it with their bed 14 at St. Jouin
(= bed 7 of Lennier = Zone a Scaphites of Cayeux 1951 = bed 8 of Rioult 1961).
Moreover, M. Cayeux has kindly shown one of us four specimens of Acanthoceras from
this bed, three of which are forms of Acanthoceras rhotomagense and the fourth is
Acanthoceras transitional to Protacanthoceras. But the same bed is said to contain both
Mantelliceras and Hyphoplites of the Lower Cenomanian. We suspect that the Rouen
fauna comes from the upper part of this 4-m. bed. The records of Rioult (1961) suggest
that the Rouen fauna is also occurring in his bed 10.

In Texas the whole fauna from the Lewesville member of the Tarrant Unit, described
by Stephenson (1953), is very close, but is probably slightly younger. This conclusion is

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 487

supported by the occurrence of Turrilites aff. acutus (= T. dearingi Stephenson) in the
same fauna.

The fauna from the north end of False Bay in Zululand, described by Crick (1907),
is slightly enigmatic. Apart from species not known elsewhere, much of the fauna cor-
relates with the Turrilites acutus assemblage, but A. quadratum Crick is probably synony-
mous with A. r. confusum and A. latum Crick is close. It is at least possible that several
horizons are represented.

CONCLUSIONS

An examination of Acanthoceras populations from the Middle Cenomanian Craie
Chloritee of Rouen shows that most individuals belong to a single species, Acanthoceras
rhotomagense. This species is highly variable: some individuals are compressed, with
weak ribs and tubercles, others are inflated, expanding rapidly, and bearing coarse ribs
and tubercles. Five names are useful to describe the population, as shown in text-fig. 9.

In accommodating almost the whole range of Acanthoceras from Rouen into five
varieties, we have been influenced not only by numerous transitional specimens between
varieties, but by the existence of individuals which combine characters of apparently
disparate varieties. Thus, whilst A. r. var. sussexiense apparently grades naturally
into A. r. var. confusum, a specimen such as BMNH C74791 combines the general
decoration of A. r. var. confusum with a rib count and a whorl compression of A.
rhotomagense. Such anomalous forms are sufficiently common to highlight the danger
of creating new species of Acanthoceras on the basis of single specimens. This variation
is comparable to that seen in many Cretaceous ammonites we have examined. Thus
there is no doubt that many Calycoceras, Mantelliceras, and Schloenbachia assemblages,
at present divided into many ‘species’, represent but a single population.

It is also clear that Acanthoceras populations from successively higher horizons can
be recognized elsewhere. Thus the faunas from Snowdon Hill, Chard (Somerset), are
from a slightly higher horizon, and show a slightly different population structure. It is
possible to collect individual specimens from this locality which fall within the range of
the Rouen material, although the populations differ. These sort of observations make
detailed synonymies difficult, because individual specimens from unknown horizons
elsewhere in the world may hardly bear separation from the forms named here, although
the populations whence they are derived may have a structure quite different from the
Rouen assemblage. This seems to be one of the greatest difficulties of ammonite
systematics. Acanthoceras as described by Crick (1907), Stephenson (1953), and Wright
(1963) are particularly difficult to place in this respect.

We should regard the following Acanthoceras as being of the rhotomagense group :
A. adkinsi Stephenson, A. bellense Adkins, A. crassiornatum Crick, A. expansum
Crick, A. flexuosum Crick, A. hazzardi Stephenson?, A. laticostatum Crick, A. latum
Crick, A. munitum Crick, A. quadratum Crick, A. robustum Crick, A. sherborni Spath,
A. stephensoni Adkins, A. tapara Wright, A. tarrantense (Adkins), A. wintoni Adkins.
These are characterized by : (i) early loss of short ribs so that all the ribs are the same
length on middle and late growth stages; (ii) loss of the siphonal tubercle during
growth; (iii) flat sides. They characterize the early part of the Middle Cenomanian.

This group of ammonites has an almost world-wide distribution in the Middle
Cenomanian. It certainly occurs in north-west Europe, South Africa, Madagascar,

488 PALAEONTOLOGY, VOLUME 13

(A. adkinsi)

i

1 .8%
|

A. rhotomagense 3.1%

II

A. r. clavatum

, 9.3%

4.3%

/ I

i

i

' j 0.6%

i

1 .2%

8.6%

„A. r, subflexuosum

i

8%

3.7%

r. sussexiense A.aff.r. sussexiense

29% 3.1%

! '' 2.5%

5.5%

(Euomphaloceras)

A. r. confusum

16%

A, basseae 2.5%

text-fig. 9. Diagrammatic relation between varieties of Acanthoceras found in the Craie de Rouen
with percentages of the different forms based on the identification of 162 specimens, mainly in museum
collections. Percentages set half-way between two names represent intermediate forms.

Australia, Peru, and Texas. It is apparently absent in the western interior of the
United States where its place is possibly occupied by A. amphibolum Morrow and its
relatives; Matsumoto and Obata (1966) suggest that A. hazzardi of Texas is probably
nonspecific with A. amphibolum.

Acanthoceras such as A. jukes-brownei and A. whitei retain alternately long and short
ribs to large diameters, and in our experience characterize the upper part of the Middle
Cenomanian.

Acanthoceras hippocastanum is an Upper Cenomanian form as discussed on p. 479.
When Acanthoceras from Britain are fully described there seems little doubt that a far
more rational taxonomy will prevail, whilst international correlation of the divisions of
the Middle Cenomanian will be possible.

Acknowledgements. This work would not have been possible without the help of the staff at the follow-
ing museums: the Sorbonne, Paris (Dr. M. Beauvais; Mme E. Basse de Menorval helped us greatly
in finding specimens, and had casts of the lectotype of Acanthoceras rhotomagense made for us) ; the

KENNEDY AND HANCOCK: AMMONITES OF THE GENUS ACANTHOCERAS 489

Ecole des Mines, Paris (Mme D. Letia); Museum d’Histoire Naturelle de Rouen (M. J. Foucher and
M. Leclerc); British Museum (Natural History) (Dr. M. K. Howarth and Mr. D. Phillips); the Institute
of Geological Sciences (Dr. R. Casey). M. L. Cayeux kindly allowed us to use his private collection.

We are indebted to Mr. C. W. Wright for encouragement, advice, and the use of his outstanding
collection of Cretaceous ammonites. We are grateful to Miss H. Cooper for help with the photography.

Dr. Kennedy started his work on the English species whilst in receipt of a studentship from the
Natural Environment Research Council.

Abbreviations. See explanation of table 1.

REFERENCES

adkins, w. s. 1928. Handbook of Texas Cretaceous fossils. Univ. Texas Bull. 2838, 385 pp., 37 pis.
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benavides-caceres, v. E. 1956. Cretaceous system in northern Peru. Bull. Amer. Mus. nat. Hist. 108,
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collignon, m. 1931. Paleontologie de Madagascar 16 — La faune du Cenomanien a fossiles pyriteux
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cuvier, g. and brongniart, a. 1822. Description geologique des couches des environs de Paris . . .

In cuvier, G., Recherches sur les Ossemens Fossiles, 2, 239-648, 18 pis.
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20 pp.

douville, r. 1912. Ammonites rhotomagensis. Palaeont. Universalis, 238.

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follet, a. 1943. Note paleontologique sur le Cenomanien de la Cote-Sainte-Catherine. Bull. Soc. Amis
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grossouvre, a. de. 1894. Recherches sur la Craie Superieure 2: Les ammonites de la Craie Superieure.
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gueranger, e. 1867. Album paleontologique du departement de la Sarthe, Le Mans, 20 pp., 25 pis.
haas, o. 1963. Paracanthoceras wyomingense (Reagan) from the Western Interior of the United States
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1964. Plesiacanthoceras, new name for Paracanthoceras Haas, 1963 non Furon, 1935. J. Paleont.

38, 610.

Hancock, j. m. 1959. Les ammonites du Cenomanien de la Sarthe. Comptes Rend. Cong. Soc. Sav. —
Dijon 1959 — Colloque sur le Cretace Superieur Frangais, 249-52.
hebert, E. 1884. Notions generates de Geolog ie, 110 pp., fig. 54. Paris.

hyatt, A. 1900. Cephalopoda. In zittel’s Textbook of Palaeontology (1st English edition, eastman
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1903. Pseudoceratites of the Cretaceous, stanton, t. w. (ed.). Mon. U.S. geol. Surv. 44, 351 pp.,

47 pis.

Jefferies, r. p. s. 1963. The stratigraphy of the Actinocamax plenus Subzone (Turonian) in the Anglo-
Paris Basin. Proc. Geol. Ass., Lond. 74, 1-33.

jukes-browne, a. j. and hill, w. 1903. The Cretaceous Rocks of Britain 2: The Lower and Middle
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Kennedy, w. J. 1969. The stratigraphy and correlation of the Lower Chalk of south-east England. Proc.
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kossmat, f. 1897. Untersuchungen fiber die Sfidindische Kreideformation (pt. 2). Beitr. Palaont. Geol.
Ost.-Ung. Or. 11, 1-46, pi. 1-8.

laube, c. c. and bruder, g. 1887. Ammoniten der bohmischen Kreide. Palaeontographica, 33, 217-39,
pi. 23-29.

490 PALAEONTOLOGY, VOLUME 13

lennier, g. 1880. Exposition Geologique et Paleontologique du Havre en 1877. Bull. Soc. geol.
Normand. 6, 869 pp., 6 pi.

mantell, g. 1822. The fossils of the South Downs. London.

matsumoto, t. and obata, i. 1966. An Acanthoceratid Ammonite from Sakhalin. Bull. Nation. Sci.
Mus., Tokyo, 9, 43-52, pi. 1-4.

orbignv, a. d\ 1840-2. Paleontologie Frangaise. Terrains Cretaces 1: Cephalopodes. 662 pp., 148 pis.
pervinquiere, l. 1907. Etudes de Paleontologie Tunisienne 1: Cephalopodes des terrains Secondaires.
Carte Geologique de la Tunisie.

pictet, f.-j. 1863. Melanges Paleontologiques 1. Mem. Soc. Phys. Hist. nat. Geneve, 17, 1-39, 8 pis.
porthault, b., thomel, g., and villoutreys, o. de. 1966. Etude biostratigraphique du Cenomanien
du bassin superieur de 1’Esteron (Alpes-Maritimes). Bull. Soc. geol. Fr. (7) 8, 423-9, pi. 8-11.
rioult, m. 1961. Problemes de geologie Havraise. Bull. Soc. geol. Normand. 51, 1-17.
saemann, l. 1858. Note sur la distribution des Mollusques fossiles dans le terrain cretace du departe-
ment de la Sarthe. Bull. Soc. geol. Fr. (2) 15, 500-24.
schluter, c. 1871. Cephalopoden der oberen deutschen Kreide (pt. 1). Palaeontographica, 21, 1-24,
pi. 1-8.

sharpe, d. 1853-7. Description of the fossil remains of Mollusca found in the Chalk of England 1 :
Cephalopoda. Palaeontogr. Soc. [ Monogr .].

sornay, j. 1959. Le Cenomanien. In Basse de menorval, e. et sornay, j., Generalites sur les faunes
d’ammonites du Cretace superieur Frangais. Comptes Rend. Cong. Soc. Sav. — Dijon 1959 — Colloque
sur le Cretace Superieur Frangais, 7-26.

sowerby, J. de c. 1823-46. The Mineral Conchology of Great Britain. 4 (pars) — 7, pi. 384-648. London.
spath, l. f. 1923. On the Ammonite Horizons of the Gault and Contiguous Deposits. Summ. Progr.
geol. Surv. G.B. 1922, 139-49.

1926a. On New Ammonites from the English Chalk. Geol. Mag. 63, 77-83.

1926 b. On the Zones of the Cenomanian and the Uppermost Albian. Proc. Geol. Ass., Lond.

37, 420-32.

Stephenson, l. w. 1953. Larger Invertebrate Fossils of the Woodbine Formation (Cenomanian) of
Texas. Prof. Pap. U.S. geol. Surv. 242, 226 pp., pi. 8-59.
wright, c. w. 1963. Cretaceous ammonites from Bathurst Island, Northern Australia. Palaeontology,
6, 597-614.

and wright, e. v. 1951. A survey of the fossil Cephalopoda of the Chalk of Great Britain.

Palaeontogr. Soc. [Monogr. ].

W. J. KENNEDY

Department of Geology and Mineralogy
Parks Road
Oxford oxl 3pr

J. M. HANCOCK

Department of Geology
King’s College
Strand

London W.C. 2

Final typescript received 9 February 1970

ULTRASTRUCTURE OF THE PROTEGULUM
OF SOME ACROTRETIDE BRACHIOPODS

by GERTRUDA BIERNAT and ALWYN WILLIAMS

Abstract. Electron microscopic studies of the exteriors of a number of acrotretacean genera show that their
protegula were ornamented by shallow pits, usually with a coarser set, about 2 fim in diameter, partially or com-
pletely segregated from one another by groups of smaller ones about 300 nm across. The pattern is identical
with the mould of a bubble raft, and consideration of the structure of the periostracum of living terebratellaceans
suggests that the pits ornamenting the acrotretacean protegulum are the moulds of a highly vesicular perio-
stracum up to 3 /im thick with a thin (10 nm) inner sealing membrane. Such a periostracum would have afforded
larvae extra buoyancy immediately prior to their settlement on the substrate. The absence of pit ornamentation
from the adult shell is believed to indicate the development of an inner sealing membrane which was sufficiently
thick to mask the vesicular nature of the adult periostracum. Nothing comparable with this ornamentation is
known in other Acrotretida, although the protegulum of Eoconulus, which may be an aberrant craniacean,
included a mineral mesh of regular, alternating, circular holes about 8 fim in diameter which have been attributed
to differential secretion beneath a non-vesicular periostracum comparable with that covering living Crania.

The brachiopod shell usually bears traces of important ontogenetic changes in composi-
tion, structure, and secretory rates because resorption by the mantle is restricted to
internal surfaces of the valves. In Recent species, the topography of external surfaces
reflects growth variation at an ultrastructural level, and although the exteriors of
calcareous-shelled fossils are usually masked by adherent micritic calcite of diagenetic
origin, those of extinct chitino-phosphatic inarticulate brachiopods can normally be
freed of such accretionary deposits by differential etching in acetic acid. The diagenetic
processes which allow for this fortunate circumstance are not well understood. Pre-
sumably, the chitin and protein of the periostracum and of those layers alternating with
apatite within the shell, break down into organic complexes which persist as continuous
sheets to preclude any gross recrystallisation of the calcium phosphate, either in con-
tinuity with, or independently of, the rock matrix. Consequently even ultramicroscopic
details of the topography of the external mineral or organic surfaces of most fossil
inarticulates, may, in favourable conditions, be preserved for examination. This fact
became evident in a survey of some Acrotretida under the scanning electron microscope.
Except for Recent specimens of Crania and Discinisca, all acrotretide shells examined
have been etched out of a variety of sediments; yet many show, to differing degrees of
perfection, a previously unsuspected ornamentation of pits on the external surface of
the protegulum. As will be shown, the pits may be interpreted as moulds of the under-
surface of a distinctive type of periostracum which has its counterpart in living Tere-
bratulida and which may even have contributed to the buoyancy of acrotretide larvae
during the planktonic phase of their existence.

In the text, references are made to the protegular structure of a number of undescribed
species. Formal systematic accounts of these will be published in due course by G.
Biernat, who is currently investigating the Ordovician Inarticulata of Poland.

Materials and methods. The section of the periostracum illustrated in this paper was prepared by fixing
a young Waltonia inconspicua (Sow.) in 3% gluteraldehyde made up in 3% sodium chloride buffered
(Palaeontology, Vol. 13, Part 3, 1970, pp. 491-502, pi. 98-101.]

492

PALAEONTOLOGY, VOLUME 13

to pH 7-2 with phosphate buffer. Material was subsequently decalcified in 5-5% EDTA, washed with
sucrose, and treated for 1 hour with 1% osmic acid; all these solutions were buffered to pH 7-2 with
phosphate buffer. Following dehydration, the specimen was embedded in Epon-Araldite resin and the
sections stained with alcoholic uranyl acetate and aqueous lead citrate. Surfaces of dried periostracum
were replicated for the transmission electron microscope by casting them in cellulose acetate strips
which, before being dissolved away, were shadowed with gold-palladium at 1 to 1 and coated in carbon.
Shell surfaces and sections studied under the ‘Stereoscan’ scanning electron microscope, were coated
with gold-palladium.

THE PROTEGULUM

The protegulum is usually described as the first-formed shell of the brachiopod,
secreted simultaneously over the entire surfaces of both mantles in the larval or early
post-larval stages of development. The precise sequence of events leading to its appear-
ance, however, is poorly known. Percival (1944, pp. 9-10) reported that, subsequent to
the attachment of the larva of Waltonia inconspicua (Sow.) and during the last stages
of enclosure of the anterior lobe by the reversing mantle, there is ‘clear evidence of the
formation of a hard shell’. At this stage in development the shell is about 120 pm. long and
consists of an outer periostracum and an inner layer of calcite crystallites. The protegu-
lum of Notosaria nigricans (Sow.) has the same two-layered structure and is also secreted
at about the same time after the settling of the larva on the substrate (Percival 1960,
p. 448). In contrast, the protegulum of living inarticulates is, as far as is known, secreted
before larval attachment. According to Yatsu (1902, p. 31) the mantle lobes of the
larva of Lingula unguis (Linneus) are differentiated from a rudimentary ring-like flap
when the larva is free-swimming. They then secrete a thin chitinous shell in one piece
which is folded across the posterior margin to form a pair of semicircular valves about
1 40 |um in radius. Similarly, the protegulum is known to have been secreted in the youngest
free-swimming larva of Pelagodiscus or any other discinid yet recovered (Chuang 1968,
p. 265) and to have been present in the earliest identifiable individuals of Crania and
Discinisca which were already attached to the substrate (Williams and Rowell in
Williams et al. 1965, p. H50). Despite this difference in the timing of the deposition of the
protegulum relative to the free-swimming stage in brachiopod ontogeny, correlation of
the skeletal successions shows that the secretory regimes of the outer epithelium of the
rudimentary mantle lobes follows the same sequence in widely different species. Studies
of newly formed cells at the mantle edge of articulate brachiopods (Williams 1968) as
well as unpublished observations of the mantle generative zones in Lingula and Glottidia,
suggest that the first-formed cover of the outer epithelium is likely to have been always
a mucopolysaccharide. Such a cover is probably maintained by continuous exudation
over the entire surface of the larva until the outer and pedicle epithelia become differ-
entiated and secrete the first persistent layer of the exoskeleton. Over the outer epithe-
lium of the mantle lobes, this layer, the periostracum, is invariably composed of protein
and/or chitin. The first-formed periostracum is exuded very rapidly and may immediately
become the seeding sheet for deposits of calcite or apatite crystallites. Consequently it
is always possible for the outer surface of such a mineral layer to form a mould of the
topography of the inner periostracal surface, especially when that surface is only a
sealing membrane about 10 nm thick.

The structure of the fossil protegulum is invariably incomplete and its precise boun-
daries may not be determinable even on the umbones of well-preserved shells. In general,.

BIERNAT AND WILLIAMS: PROTEGULUM OF ACROTRETIDE BRACHIOPODS 493

all external covers of organic origin are lost from the surfaces of fossil shells through
the processes of weathering and diagenesis, and only the inner mineral layer remains.
Indeed in those specimens where the protegulum was exclusively organic in composition,
a mould could be the only surviving trace of the structure and this condition may be
characteristic of some of the species discussed below. There is no infallible guide for
determining the limits of the protegulum on adult shells. Protegula are known to range
from less than 100 to more than 1000 /xm in length, and from semi-elliptical to subcircular
in outline. The outline is usually accentuated as a distinct step in the general profile of
the umbones so that protegula appear to sit on the apices of the valves as extra-skeletal
pieces. More importantly, no growth-lines should occur on the surface of a protegulum
because it is secreted simultaneously over the entire mantle lobe. This criterion and the
expectation that the protegular outline is normally accentuated have been used for the
identification of acrotretide protegula.

THE ACROTRETACEAN PROTEGULUM

The fabric of the protegulum of an undescribed species of Torynelasma may be taken
as typifying that of acrotretacean protegula in general. The ventral protegulum, which is
about 100 jum wide (PI. 98, fig. 1), is not ornamented by raised concentric ridges charac-
teristic of the adult shell, but by a series of shallow circular to elliptical pits (PI. 98, fig. 2).
The pits vary in diameter by more than a factor of ten, although they actually fall into
two grades. The coarser pits range from 2 to 4-5 /xm in diameter and are separated from
one another by ridges, about 350 nm wide, which swell out into flattened areas, up to
4 /xm wide, intervening between groups of coarser pits. These flattened areas, as well as
some of the ridges, bear the finer grade of pits which are about 350 nm in diameter.
All pits are more or less flat-bottomed and about one-tenth as deep as the maximum
diameter. The entire fabric of pits and ridges is preserved in apatite crystallites (each
about 175 nm in diameter) which are stacked normal to the surface. The junction
between the protegulum and later shell is abrupt; within a micron of being fully
developed the pits pass into very shallow dimples which in turn give way to the first
concentric ridges ornamenting the surface of adult shells (compare PI. 98, fig. 5). The
pits are impressed on the external surface of a mineral layer or lamina, about 2 /xm
thick, which is underlain by up to six laminae of comparable thickness (PI. 98, fig. 3).
These laminae are composed of apatite crystallites stacked more or less normal to
their external and internal surfaces. They are separated from one another by gaps
about 170 nm wide which were probably occupied by organic sheets. The entire fabric
is reminiscent of laminar deposition in the craniaceans (Williams and Wright, in press),
although the mineral constituent is calcium phosphate not calcium carbonate, and the
accretion of laminae may involve continuous vertical growth of densely distributed
apatite seeds instead of the spiral growth of calcite rhombohedra.

Sampling among other members of the Acrotretacea suggests that the protegular pit
pattern of Torynelasma is characteristic of the superfamily. Sixteen species belonging
to twelve genera, ranging in age from Middle Cambrian to late Ordovician, have pro-
vided the information given in Table 1 . In addition, the protegular surface of Ceratreta
hebes Bell from the Upper Cambrian Dry Creek Shale of Montana showed identifiable
traces of pits although they were too poorly preserved to be accurately measured or

494

PALAEONTOLOGY, VOLUME 13

figured. In all species the protegulum, which varied in maximum diameter from 90 to
135 /xm, was ornamented by pits fundamentally the same in structure and arrangement
as those of Torynelasma. There is a variation in the size and distribution of pits, which
may ultimately prove to be of systematic value. Thus the pits ornamenting the surface
of the protegula of Conotreta (PI. 99, fig. 1), Linnarssonella (PI. 99, fig. 2), Myotreta
(PI. 98, figs. 5, 6), and Rhysotreta (PI. 98, fig. 4) are comparable in size range with those

table 1. The ranges of larger pits ( a ) and the diameter of smaller pits ( b ) forming the ornamentation
on the protegula of the listed species. The horizons and locations of the specimens providing these
data are given in descriptions of plates except for the unfigured Scaphelasma septatum Cooper and
Torynelasma toryniferum Cooper, both of which were represented by topotypic material from the mid-
Ordovician Pratt Ferry Formation, Pratt Ferry, Alabama.

Angulotreta postapicalis Palmer

(a)

larger pits (pm)
about 1-5

(b)

smaller pits (nrri)

Apsotreta expansa Palmer

1 -0-2-3

—

Conotreta depressa Cooper

1-25-2-5

450

Curticia minuta Bell

0-8-3-2

320

Ephippelasma sp.

0-8-1-69

600

Linnarssonella girtyi Walcott

1 -9-3-8

—

Myotreta cf. crassa Goryansky

20-4-6

500

Prototreta sp.

0-96-1-6

320

Rhysotreta corrugata Cooper

1-55-3-1

300

Scaphelasma septatum Cooper

0-9-3 0

300

Scaphelasma sp.

1 -1-2-3

700

Spondylotreta concentrica Cooper

0-8-1 -7

150

Spondylotreta sp.

0-7-2-0

—

Torynelasma sp.

2-2-4-5

360

Torynelasma toryniferum Cooper

1 -2-2-3

380

of Torynelasma, whereas the coarser grades found in Ephippelasma (PI. 99, fig. 3), Pro-
tot re ta (PI. 99, fig. 4), Scaphelasma (PI. 99, fig. 5), and Spondylotreta (PI. 100, fig. 3) are
significantly smaller. There are also differences in the frequency distribution of the
coarser pits, which are more closely packed together in Conotreta , Myotreta, and Pro-
totreta, so that intervening flattened areas bearing clusters of fine pits, as in Torynelasma,
are comparatively rare. In Prototreta, the fine pits appear to have been obliterated in

EXPLANATION OF PLATE 98

Scanning electron micrographs.

Figs. 1-3. Various aspects of protegulum of pedicle valve of Torynelasma sp., Arenig marly limestone,
Bartoszyce, Peribaltic Depression, Poland. 1, lateral view of exterior of protegulum (x625).
2, arrangement of pits on exterior of mid-region of protegulum ( X 5800). 3, laminar layering of
mineral parts of protegulum as seen on fracture surface more or less normal to shell with exterior to
top of micrograph (x2700).

Fig. 4. Details of pit arrangement in mid-region of exterior of protegulum of topotypic pedicle valve
of Rhysotreta corrugata Cooper (1956), mid-Ordovician Pratt Ferry Formation, Pratt Ferry, Alabama
( x 6500).

Figs. 5, 6. Exterior of dorsal protegulum of Myotreta cf. crassa Goryansky (1969), Arenig marly
limestone, Bartoszyce, Peribaltic Depression, Poland. 5, junction between protegulum and adult
(bottom left-hand corner) shell (x 1300). 6, detail of pits on left lateral part of surface ( x 2600).

Palaeontology, Voi 13

PLATE 98

B1ERNAT and WILLIAMS, Ultrastructure of acrotretide protegula

BIERNAT AND WILLIAMS: PROTEGULUM OF ACROTRETIDE BRACHIOPODS 495

most parts of the protegulum by recrystallization, and the rare occurrence of such pits
in other Cambrian stocks has been attributed to diagenesis rather than a natural sup-
pression of their development. There is certainly evidence of a gross recrystallization
affecting even the coarser grades of pits in Linnarssonella where outlines indicative of
hexagonal prisms have been superimposed here and there on a relict pattern of normally
distributed subcircular pits.

A profound change in the distribution of pit ornamentation in early Spondylotreta
seems, also, to be attributable to post-mortem alteration of the shell. In S. parva Wright
(1963, p. 238) and S. concentrica Cooper (PI. 100, fig. 3) from the Ashgillian and Porter-
field limestones of Ireland and Alabama respectively, the pit pattern, although variably
preserved in both species, is seen to be normally developed and restricted to the pro-
tegulum; but in an undescribed species of Spondylotreta from Tremadocian cherts of
Poland, pits were found over the entire shell surface. In the specimen examined, the
protegulum was ornamented by an array of pits with diameters ranging from 600 nm to
2 fim and a density count of 23 per 100/xm2inthe mid-region (PI. 100, fig. 4). Pits of similar
size and depth, but with half the frequency distribution of those in the protegulum,
also occur in the adult shell where they are limited to those exposed parts of the outer
surfaces of overlapping lamellae which must have been covered by periostracum
(PI. 100, fig. 5). Despite this evidence, we believe pits on the adult shell, at least, to be
solution features, because the specimens bearing them had been dissolved out of the
cherts by hydrofluoric acid, and valves of Helmersenia and Siphonotreta recovered
during the same operation bore similarly distributed pits (PI. 100, fig. 6). It is still
possible that the pits were formerly the sites of surface depressions which originated
during shell deposition and were only enlarged during etching. This we believe to be
unlikely, and we attribute the denser distribution of pits in the protegulum of the
Tremadocian Spondylotreta to the existence of a normal array of pits, on which was
superimposed a pattern of solution hollows, like those on the adult part of the shell.

No acrothelidid species has been examined but the protegulum of Curticia, the
monotypic representative of the third acrotretacean family, is known to be pitted in the
same way as that of acrotretids (PI. 100, figs. 1, 2). It would, therefore, be surprising if
the protegulum of any acrotretacean proved not to be so ornamented.

INTERPRETATION

In seeking an explanation for these distinctive arrays of pits, attention must be paid
to a number of clues like the depth of the pits, their possible relationship to a restored
periostracum comparable with those of living brachiopods, and to any similarities
between such patterns and naturally occurring structures. In relation to their diameter
and the thickness of the shell, the pits are undeniably shallow. In Myotreta, Spondylo-
treta, Riiysotreta, and Torynelasma, the depth of a pit appears not to be more than
one-fifth of the diameter, and less than 1 fim absolutely compared with thickness of about
15 jxm for the shell underlying the protegulum in adult valves. Hence the pits are not
endopunctae in the sense that they were occupied by epithelial extensions persisting
throughout life. Nor is it likely that they were exopunctae if the implication is that the
pits were temporary sites of caecal extensions of the outer epithelium, possibly acting
as food storage centres, which later became sealed off by shell deposition after

k k

C 7619

496

PALAEONTOLOGY, VOLUME 13

withdrawal of the caeca. Terminal branches of mantle papillae penetrating the shell of
living Terebratulida and Craniacea correspond to specialized microvilli and vary only
narrowly in diameter immediately beneath the periostracum. In fact, the particular
pattern of size variation must surely also preclude any possibihty that the pits afforded
accommodation for patches of specialized epithelium thereby facilitating some function
of the mantle, like sensitivity to changes in light or hydrostatic pressures.

In our estimation, the distribution of pits is in itself a key to their origin. The patterns
are exactly matched in bubble rafts formed on the surfaces of liquids by groups of rela-
tively large bubbles which are partially or completely separated from one another by
clusters of smaller ones. The only difference is that the surface of a raft is compositely
convex, whereas that of the protegulum is compositely concave as though it were the
mould of a bubble raft. The difference becomes important when one considers the
nature of the periostracum that must once have covered the protegular surface. In all
brachiopods, the inner sealing membrane of the periostracum acts as the seeding surface
of the first apatite or calcite crystallites secreted by the epithelium; and it follows that,
if the crystallites form a bubble raft mould, the inner membrane of the periostracum
must have been one of the bounding surfaces of such a raft. Further inferences about the
periostracum can now be made. Assuming that the vesicles making up the periostracal

EXPLANATION OF PLATE 99

Scanning electron micrographs.

Fig. 1 . Details of pit arrangement in mid-region of exterior of protegulum of topotypic pedicle valve
of Conotreta depressa Cooper (1956), mid-Ordovician Pratt Ferry Formation, Pratt Ferry, Alabama
( x 3900).

Fig. 2. Recrystallization superimposing a crystal fabric, as in centre of micrograph, on a pit pattern
in mid-region of dorsal protegulum of Linnarssonella girtyi Walcott (see Bell and Ellinwood (1962)),
Upper Cambrian Morgan Creek Member, Blanco Co., Texas (x2600).

Fig. 3. Distribution of pits on exterior of ventral protegulum of Ephippelasma sp., Llanvirn shales,
Bartoszyce, Peribaltic Depression, Poland (X2600).

Fig. 4. Details of pitted ornamentation in mid-region of ventral protegulum of Prototreta sp., Middle
Cambrian Meagher Limestone, Horseshoe Hill, Montana ( x 6250).

Fig. 5. Details of pitted ornamentation in mid-region of dorsal protegulum of Scaphelasma sp., Llan-
virn marls, Ketrzyn, Peribaltic Depression, Poland ( x 6000).

Fig. 6. Traces of pitted ornamentation on external surface of damaged protegulum of topotypic pedicle
valve of Apsotreta expansa Palmer (1954), Upper Cambrian Riley Formation, Llano Co., Texas
( x 2600).

EXPLANATION OF PLATE 100

Scanning electron micrographs.

Figs. 1 , 2. General view and detail of pitted ornamentation on mid-region of exterior of protegulum of
topotypic brachial valve of Curticia minuta Bell (1941) Upper Cambrian Pilgrim Formation, Little
Belt Mountain, Montana ( x 2500, x 6250 respectively).

Fig. 3. Distribution of pits in mid-region of exterior of protegulum of topotypic pedicle valve of
Spondylotreta concentrica Cooper (1956), mid-Ordovician Pratt Ferry Formation, Pratt Ferry,
Alabama ( x 6500).

Figs. 4, 5. Exterior of brachial valve of Spondylotreta sp., Tremadoc cherts, Wysoczki, Holy Cross
Mountains, Poland. 4, distribution of pits in relation to recrystallized fabric in mid-region of
protegulum ( x 6000). 5, presence of pits only on those parts of overlapping lamellae that make up
external surface of adult shell (x 1700).

Fig. 6. Distribution of external pits near margin of ventral protegulum of Siphonotreta cf. acrotreto-
morpha Goryansky (1969), Tremadoc cherts, Wysoczki, Holy Cross Mountains, Poland (x 1300).

Palaeontology, Vol. 13

PLATE 99

BIERNAT and WILLIAMS, Ultrastructure of acrotretide protegula

Palaeontology, Vol. 13

PLATE 100

BIERNAT and WILLIAMS, Ultrastructure of acrotretide protegula

BIERNAT AND WILLIAMS: PROTEGULUM OF ACROTRETIDE BRACHIOPODS 497

bubble raft had not been flattened, and that the bounding membranes were not much
thicker than 20 nm, the larger vesicles can be estimated to have been up to 5 pm in
diameter and would have constituted the thickest part of the periostracum (text-fig. 1).

Information now available about the periostracum of living Terebratulida shows that
none of these inferences is unreasonable, although the estimated maximum thickness
is greater than any yet known for Recent species. The terebratellacean periostracum

text-fig. 1 . Diagrammatic restoration of the organic parts of the acrotretacean protegulum to show
the inferred relationship between the periostracum and the underlying layer of calcium phosphate

crystallites.

has already been described (Williams 1968, p. 276) as consisting of an array of level-
topped protein rods which arise from a series of labyrinthine protein partitions (PI. 101,
fig. 6). These partitions, which are extensions of the outermost part of a triple unit
membrane forming the base of the periostracum, enclose smaller mucin spheroids and
larger, more irregularly shaped vesicles. The inclusions are shown in section in Plate
101, fig. 6 and in external surface views of dried periostracum in Plate 101, figs. 4, 5,
where they form patterns strikingly like those on the acrotretacean protegulum. Even
the dimensions are comparable with those estimated for Ephippelasma, Prototreta, and
Scaphelasma, ranging from 240 nm to 2 /im for vesicles and from 200 to 380 nm for
mucin inclusions in the periostraca of four living species [Macandrevia cranium (Muller),
Magasella sanguinea (Leach), Terebratalia transversa (Sowerby), and Waltonia incon-
spicua (Sowerby)]. Indeed the consistently smaller size of inclusions in the Terebratulida
undoubtedly accounts for much of the discrepancy in the thickness of the periostracum,
which is not usually greater than about 1 -5 pm in the species cited. Moreover the flat-
bottomed nature of many of the protegular pits in acrotretaceans suggests that the larger
inclusions, at least, were partially collapsed during deposition of the crystallite mould
so that thicknesses of about 3 /mi may have been more characteristic of the superfamily.

498

PALAEONTOLOGY, VOLUME 13

Despite the inferred likeness between the acrotretacean and terebratellacean perio-
straca, the primary shell of living terebratellaceans does not, as far as is known, bear
any superficial ornamentation that faithfully reflects the internal vesicular structure of
the covering periostracum (PI. 101, fig. 3). The reason for this apparent lack of moulding
lies in the thickness of the basal layer of adult terebratellacean periostracum, which
may be up to 100 nm thick and obviously polymerizes as a fairly rigid, even foundation
for the rest of the periostracum. Indeed when the basal layer is less than 40 nm thick
it shows signs of being moulded to periostracal inclusions (PI. 101, fig. 6). Consequently
it seems reasonable to conclude that the inner sealing membrane of the periostracum
covering the acrotretacean protegulum was probably not much more than about 10 nm
thick.

The attribution of topographic differences in the external surfaces of shells to varia-
tion in the thickness of the periostracal sealing membrane may explain the absence of
pit ornamentation from the surface of adult shells. The periostracum covering the adult
shell of acrotretaceans may have been similar in microstructure to that over the pro-
tegulum; but exudation of a significantly thicker sealing membrane by the post-larval
mantle lobes may have masked the vesicular fabric of the middle periostracal layer, and
so precluded the secretion of mineral moulds of such a microstructure.

In summary, then, the periostracum of acrotretaceans is inferred to have consisted
mainly of a relatively thick layer (up to 3 /xm) crowded with protein-bounded vesicles
and mucin droplets such as are found in the periostracum of living Terebratulida (text-
fig. 1). No information is available about the outer membrane although it may have been
fibrillar like those known in living species. The inner sealing membrane, however, is
likely to have been very thin (say 10 nm) in the protegula and relatively thick (up to
100 nm) in the adult shells of all acrotretaceans.

THE PROTEGULA OF OTHER ACROTRETIDA

To date it has been possible to examine only a few genera belonging to the Discinacea
and Siphonotretacea, although a recently completed study by Williams and Wright
(in press) of the Craniacea affords a comprehensive survey of that group.

The periostracum of living Crania anomala (Muller) consists of a mucopolysaccharide
layer up to 5-5 /x m thick, bounded by an outer membrane bearing fibrillar rods, and a

EXPLANATION OF PLATE 101

Figs. 1-4, scanning electron micrographs. Figs. 5, 6, transmission electron micrographs.

Fig. 1 . Regular distribution of pits on mid-region of exterior of protegulum of brachial valve of Eoco-
nulus sp., Llanvirn Kundsky member, Abja, W. Estonia (x 1400).

Fig. 2. Exterior of pedicle valve showing mineral meshwork in young part of valve of Dictyonites
perforata Cooper (1956), mid-Ordovician Pratt Ferry Formation, Pratt Ferry, Alabama (x625).

Figs. 3, 4. Exterior of brachial valve of Waltonia inconspicua (Sow.), Lyttleton Harbour, New Zealand.
3, torn piece of periostracum turned to one side to show underlying surface of primary shell in young
part of valve (X5250). 4, vesicular nature of periostracum affects topography of outer sealing
membrane in more mature shell (x 12 000).

Fig. 5. Single stage negative replica of periostracum of Terebratalia transversa (Sow.), Seattle Harbour,
Washington, showing vesicular nature of middle layer (x 14 200).

Fig. 6. Section of young periostracum of Waltonia inconspicua (Sow.), Lyttleton Harbour, New
Zealand, showing moulding of inner sealing membrane (below) to two larger vesicles and a
smaller mucin droplet between them (x45 000).

Palaeontology, Vol. 13

PLATE 101

BIERNAT and WILLIAMS, Ultrastructure of acrotretide protegula

BIERNAT AND WILLIAMS: PROTEGULUM OF ACROTRETIDE BRACHIOPODS 499

thin inner membrane of protein. The mucopolysaccharide layer is devoid of vesicular
structures so that the inner surface is evenly disposed; and it is appropriate that no pit
ornamentation is found on any external surface of living Crania, nor is it known on any
fossil craniacean.

In contrast, the protegulum of Eoconulus is ornamented by an array of shallow, flat-
bottomed circular pits varying in diameter from 5-5 to 11-5 pm and up to 750 nm deep
(PI. 101, fig. 1). The pattern is different from that characteristic of the Acrotretacea in
that, as far as it has been possible to observe, the pits are regularly spaced in alternate
rows and segregated from one another by flattened ridges (about T3 pm wide) which
do not bear traces of finer pits, although the specimen examined was sufficiently well
preserved to reveal a fabric of apatite crystallites each about 400 nm across. Among
living Terebratulida, no periostracal fabric is known which involves the arrangement of
vesicles in regular arrays. On the contrary, the pattern is inconsistent with the processes
leading to the exudation of vesicles by outer epithelium. In the circumstances, it seems
more reasonable to interpret this pattern as representing a truly differential secretion of
calcium phosphate by the epithelium. The function of such a mineral mesh is unknown.
Presumably while apatite crystallites were being secreted to form the mineral framework,
exudation of periostracum continued in those areas that ultimately appear as pits and
formed discrete circular pads internally to the periostracum as shown in text-fig. 2.
In all respects except size, the mineral framework of the protegulum of Eoconulus is
envisaged as having been very like that of the adult shell of Dictyonites (PI. 101, fig. 2).
Examination of D. perforata Cooper has shown that the protegular surface is not pitted
and that the bars forming the open mineral network of the adult shell are similarly free
of ornamentation apart from the inevitable interstitial gaps between the apatite crystal-
lites constituting the bars. Even the circular pores defined by the apatite network must
also have been occupied by a thickened pad of the inner sealing membrane of the
periostracum in the way inferred for the protegulum of Eoconulus.

Study of two siphonotretacean stocks suggests that this superfamily may have been
characterized by an external ornamentation of pits. Specimens of both genera, however,
were dissolved from Tremadocian cherts by hydrofluoric acid and, like those of Spon-
dylotreta recovered by the same process, have to be interpreted with caution. Valves
of Siphonotreta were much better preserved than those of Helmersenia and are figured
here (PI. 100, fig. 6) although a similar pattern of pits also occurs on the exteriors of the
latter. As in Spondylotreta, the entire surface of the shell of Siphonotreta, including the
sides of the spines, are ornamented by densely distributed pits ranging in diameter from
1 to 3 /xm. There are even indications of clusters of finer pits which are less than 1 pm in
diameter. Yet we still think it reasonable to assume that the pits, like those in the adult
shell of Spondylotreta, are solution phenomena.

The remaining superfamilial group to be considered, the Discinacea, is represented
by a number of living species, one of which ( Discinisca strigata Broderip from Costa
Rica) was available for study. Unpublished researches on this species show that the
periostracum has a complex lamellar structure on an ultramicro scopic scale, but no
vesicles accumulate in this cover and neither the protegulum nor the adult shell has
pitted surfaces. Extinct discinaceans examined include Orbiculoidea nitida Phillips from
the Carboniferous Shales of Capel Rig, Gore, Scotland, and Schizotreta sp. from Tre-
madocian cherts of the Holy Cross Mountains, Poland. In these species too there were

500

PALAEONTOLOGY, VOLUME 13

no traces of a microscopic external ornament other than the usual granular appearance
of the crystallite fabric, and it seems safe to assume that a pattern of microscopic pits
never developed on the discinacean shell.

mucopolysaccharide layer

text-fig. 2. Diagrammatic restoration of the organic parts of the protegulum of Eoconulus to show
the inferred relationship between the periostracum and the underlying mesh of calcium phosphate

crystallites.

CONCLUSIONS

Ignoring the pitted aspect of the entire external shell surface of Spondylotreta, Sipho-
notreta, and Helmersenia, which was almost certainly effected by hydrofluoric acid,
a scrutiny of the exteriors of thirteen acrotretacean genera indicates that their protegula
were always ornamented in a distinctive way. The species examined range in age from
Middle Cambrian to Upper Ordovician and, since the pattern is best interpreted
as the mineral mould of a highly vesicular periostracum with a thin inner sealing
membrane, the first-formed shells of all acrotretaceans are assumed to have been so
covered. The dense distribution of pits and the size of those moulds presumed to have
accommodated the larger subspherical vesicles, suggest that the protegular periostracum
was effectively a bubble raft between 1 and 3 /x m thick. Such a periostracum could have
imparted buoyancy to planktonic larvae during the later stages of their development,
thereby promoting the dispersion of the species.

As already mentioned, the absence of pitted ornamentation from the external surface
of the adult shell does not necessarily preclude the continued secretion of a vesicular
periostracum. Exudation of a thickened inner sealing membrane would not only have
masked the bubble raft effect of the middle periostracal layer, but also shown the same
transition from one condition to the other through a zone of ill-defined traces of pits
as are seen in Plate 98, fig. 5. Such a thickening would have coincided, not so much with

BIERNAT AND WILLIAMS: PROTEGULUM OF ACROTRETIDE BRACHIOPODS 501

a change from a planktonic to a benthic or epiplanktonic mode of life, as with the first
appearance of a pair of circumferential outer mantle lobes contributing cells by a
‘conveyor belt system’ to the expanding ventral and dorsal mantles. The inferred
sequence of secretion of the periostracum along the inner face of the outer mantle lobe
has been illustrated in text-fig. 3. Thus, the difference between the surface ornamentation
of the protegulum and adult shell in acrotretaceans is envisaged as reflecting a prolonga-
tion of one of the phases of a secretory regime, although the sequence of phases remained
constant.

mantle groove periostracum protegular shell

thickened inner
sealing membrane

outer epithelium

text-fig. 3. Diagrammatic reconstruction of a very young acrotretacean (lophophore and other organs
omitted) to show the inferred relationship between the change in the thickening of the inner sealing
membrane of the periostracum and the micro-ornamentation of the mineral shell.

Stratigraphic and morphological evidence favours the acrotretaceans as ancestral to
the three other superfamilial groups comprising the Acrotretida (Williams and Rowell in
Williams et al. 1965, p. H172). Ultrastructural comparisons of the shell, however, do
not afford any further information on affinity. In respect of the relationship between the
thickness of the inner sealing membrane of the periostracum and the topography of the
underlying mineral layer, it is noteworthy that the sealing membranes of both Discinisca
and Crania are only about 10 nm thick, but in neither species is the periostracum
vesicular, and the underlying mineral shell surface lacks a pitted ornamentation. This
condition seems also to have been characteristic of the protegular mineral shell of all
extinct discinacean and craniacean species so that it seems reasonable to assume that
the protegula of those stocks, too, was covered by a similar periostracum. Yet nothing
is known about the derivation of the featureless mid-periostracal layers of Discinisca
and Crania which consist solely of fibrils scattered in a polysaccharide matrix. Judging

502

PALAEONTOLOGY, VOLUME 13

from the structure of the periostracum of living articulates (Williams 1968, p. 274), a
vesicular periostracum is the more prevalent condition; and, since it seems to have
covered the protegula of acrotretaceans, the simple periostracum of the later-appearing
discinaceans and craniaceans may represent a paedomorphic substitution in the larval
stage of their development. Further study of better-preserved siphonotretaceans will
have to be undertaken to determine whether they belonged to the discinacean or acro-
tretacean stage of development, or whether they were characterized by the neotenous
persistence of a larval vesicular periostracum throughout life, so that the entire shell
surface was pitted in the manner of the acrotretacean protegulum.

Acknowledgements. We are greatly indebted to Professor W. C. Bell (University of Texas), Dr. Howard
Brunton (British Museum (Nat. Hist.)), Dr. G. A. Cooper (U.S. National Museum), and A. J. Rowell
(University of Kansas) for promptly responding to urgent requests and sending us vital American and
British material for examination, thereby greatly enlarging the scope of this paper. Much of the elec-
tron microscopy was carried out on a ‘Stereoscan’ scanning electron microscope supplied through a
N.E.R.C. grant, and to that Research Council we extend our thanks as we do also to Dr. Jean Graham
for assistance in the preparation of the text-figures and to Dr. Katharine McClure for cutting the
sections of the periostracum of Waltonia.

REFERENCES

bell, w. c. 1941. Cambrian brachiopoda from Montana. J. Paleont. 15, 193-255.

— — and ellinwood, h. l. 1962. Upper Franconian and Lower Trempealeanan Cambrian trilobites
and brachiopods, Wilberns Formation, Central Texas. /. Paleont. 36, 385-423.

chuang, s. h. 1968. The larvae of a discinid (Inarticulata, Brachiopoda). Biol. Bull. 135, 263-72.

cooper, G. A. 1956. Chazyan and related brachiopods. Smithson. Misc. Coll. 127, 1-1245.

Goryansky, w. u. 1969. Inarticulate brachiopods from the Cambrian and Ordovician beds of the north-
west of the Russian Platform. 173 pp. NEDRA, Leningrad.

palmer, A. R. 1954. The faunas of the Riley Formation in Central Texas. J. Paleont. 28, 709-86.

percival, E. 1944. A contribution to the life-history of the brachiopod Terebratella inconspicua
Sowerby. Trans. R. Soc. N.Z., 74, 1-23.

■ 1960. A contribution to the life-history of the brachiopod Tegulorhynchia nigricans. Q. J. Micro-

scop. Sci. 101, 439-57.

williams, a. 1968. A history of skeletal secretion among articulate brachiopods. Lethaia, 1, 268-87.

et al. 1965. Treatise on invertebrate paleontology (ed. more, r. c.): Part H, Brachiopoda. 927 pp.

Lawrence (Univ. of Kansas).

and wright, a. d. 1970. Shell structure of the Craniacea and other calcareous inarticulate brachio-
poda. Spec. Pap. Palaeont. No. 7.

wright, a. d. 1963. The fauna of the Portrane Limestone. 1. The inarticulate brachiopods. Bull. Brit.
Mus. {Nat. Hist.) Geol. 8, 221-54.

yatsu, n. 1902. On the development of Lingula anatina. J. Coll. Sci. Tokyo, 17, 1-112.

GERTRUDA BIERNAT

Polska Akademia Nauk
Zaklad Paleozoologii
Warszawa

Al. Zwirki i Wigury 93

ALWYN WILLIAMS

Department of Geology
The Queen’s University of Belfast
Belfast bt7 Inn

Typescript received 18 November 1969 Northern Ireland

A NEW TRIONYCHID TURTLE FROM THE
BRITISH LOWER EOCENE

by r. t. j. moody and c. a. walker

Abstract. A new trionychid turtle, Eurycephalochelys fowleri gen. et sp. nov., is described from a skull found
in the Bracklesham Beds (Cuisian, Lower Eocene) of Sussex. Comparisons are made between this first known
trionychid skull from the British Eocene, and other fossil and Recent members of the Trionychidae.

In 1966 Mr. R. Fowler discovered the first known skull of a British Eocene trionychid
in the Cakeham Beds of the Bracklesham Beds at East Wittering, Sussex.

Shell remains of trionychid turtles in the Lower to Upper Eocene deposits of England
are fairly common and have been described as several new species of the genus Trionyx
Geoffroy 1809. However, only a few indeterminate fragments of skulls have been found.
Skull and shell have never been found together, so that the new specimen cannot be
related to the previously described fossil forms. For this reason, and because of the
considerable differences between this skull and Recent trionychid skulls, we have elected
to place it in a new genus.

It may be that future finds of skulls associated with post-cranial material will enable
at least some of the species of Trionyx based on British Eocene turtle shells to be trans-
ferred to the new genus; it may even be that E. fowleri will prove to be conspecific with
one of those. Similarly it is possible that Eurycephalochelys may be congeneric with
some genus of Eocene trionychid from elsewhere, known at present only from the remains
of its shell.

Suborder cryptodira
Superfamily trionychoidea Fitzinger 1 826
Family trionychidae Bell 1828

The following trionychid characters are seen in the new genus: Temporal region
emarginate, with no contact between parietal and squamosal. Premaxillae fused. Post-
orbital small; naso-palatine foramen large; palatine fenestra present but small. Ptery-
goids make contact with maxillae and are separated from each other by basisphenoid.
Quadrate encloses stapes.

Genus eurycephalochelys gen. nov.

Type species. Eurycephalochelys fowleri gen. et sp. nov.

Diagnosis. Quadrate condyle situated relatively far back, so that it lies well behind
stapedial foramen, well behind level of foramen magnum, and more or less at level of
back of basioccipital, with occipital condyle projecting only a short distance behind it.
Forwardly directed flange of quadrate almost horizontal.

[Palaeontology, Vol. 13, Part 3, 1970, pp. 503-10, pi. 102.]

504

PALAEONTOLOGY, VOLUME 13

Internal maxillary foramen in medial wall of vertically rising part of maxilla. Jugal
bar originates well below lowest point of orbital margin. Foramen magnum, and brain
cavity immediately anterior thereto, wider than high.

Snout region short and broad, with distance from tip of premaxilla to front of orbit
much greater than antero-posterior diameter of orbit. Maxilla very deep, depth probably
much greater than vertical diameter of orbit. Postorbital bar narrow, slopes backwards
and upwards. Area of quadrate exposed on dorsal surface not larger than area of prootic
but of approximately equal size. Tympanic cavity shallow. Steep sides of choanal vault
rounded.

Eurycephalochelys fowleri sp. nov.

Plate 102, figs. 1-5

Diagnosis. The only species of its genus.

Material. Holotype only, BMNH R8445, an almost complete skull without lower jaw. Cast in the collec-
tion of Mr. R. Fowler (Moschatel, Church Road, East Wittering, Sussex).

Occurrence. An oyster bed within the Cakeham Beds, Bracklesham Beds, Cuisian (Lower Eocene);
foreshore at East Wittering, Sussex.

Measurements (in millimetres).

Actual length (premaxilla — occipital condyle) 157

Estimated total length, including supra-occipital spine 215

Maximum actual width (quadrate — quadrate) 1 32

Width across external nares 23

Tip of premaxilla — front of orbit 42

Minimum depth of maxilla beneath orbit 30

Maximum length of orbit 26

Estimated depth of orbit 26

Estimated length of anterior palatine foramen 8

Estimated length of intermaxillary suture 13

Estimated length of choanae 17

Width across choanae 20

Maximum width across maxillae in palatal view 87

Maximum dimension of articulating surface on quadrate 29

Condition of preservation. The specimen is an almost entire skull lacking the lower jaw.
It has been slightly crushed dorso-ventrally at the posterior end and the whole bone
surface is partially eroded, making sutures difficult to see.

The single, median premaxilla and the maxillae are almost complete. The frontals
and prefrontals are lost. Both jugals are damaged ; on each side the process reaching up
towards the postorbitals is eroded and most of the jugal bar is missing. The parietals
are complete posteriorly and laterally. The prootics, opisthotics, and quadrates are
present on both sides with little distortion. Only the basal part of the supraoccipital is
preserved, the sagittal crest having been lost. The squamosals are lacking but their suture
scars on the quadrates are clearly visible. The palate is incomplete but the approximate

EXPLANATION OF PLATE 102

Eurycephalochelys fowleri gen. et sp. nov. BMNH R8445. Views of skull; 1, palatal; 2, occipital;
3, dorsal; 4, left lateral; all x J. 5, quadrate showing the position of the stapedial foramen, x 1.

Palaeontology, Vol. 13

PLATE 102

MOODY and WALKER, Trionychid turtle

MOODY AND WALKER: A NEW TRIONYCHID TURTLE

505

margins of the anterior palatine foramen can be seen. The pterygoids are imperfect and
only part of the basisphenoid remains. The ventral surfaces of the parietals are badly
preserved whilst the articular areas of the quadrates are worn. Erosion of the occipital
region has obscured the sutures.

Description. There is a large internal maxillary foramen (text-fig. 1) in the medial wall
•of the maxilla, bordered dorsally by the maxillary-jugal suture and antero-medially by
a ridge which forms the inner edge of the orbital floor. This ridge sweeps upwards
anteriorly to form an acute angle with the orbital rim.

text-fig. 1. Eurycephalochelys fowleri gen. et sp. nov. BMNH R8445. Dorsal
view of skull, x i. Abbreviations : bo, basioccipital ; bs, basisphenoid; imf, internal
maxillary foramen ; j, jugal; m, maxilla; op, opisthotic; p, parietal; pm, premaxilla;
pr, prootic ; pt, pterygoid ; q, quadrate ; soc, supraoccipital.

A dorsal view of the skull (text-figs. 1, 5a) shows that the lateral surface of the anterior
region faces upwards as well as outwards, displaying a series of maxillary foramina a
short distance above the cutting edge and running parallel to it. Posteriorly, the lateral
surface of the parietal is rounded and slopes gently to the prootic. The area of that part
•of the quadrate which is normally exposed on the dorsal surface is not larger than
the area occupied by the prootic, but is of approximately equal size. There appears to be
no sutural contact between the prootic and opisthotic on the dorsal surface of the skull;
however, the bone surface in this region is very eroded and the exact location of the
sutures must remain in doubt.

A lateral view of the specimen (text-figs. 2, 5b) shows that the facial angle is steep and
the flexure of the skull quite pronounced. The distance from the tip of the premaxilla

506

PALAEONTOLOGY, VOLUME 13

to the anterior edge of the orbit is greater than the antero-posterior orbital diameter.
The maxilla is very deep, its depth probably exceeding the vertical diameter of the orbit.
The jugal bar originates well below the lowest point of the orbital margin, being directed
outwards and downwards as well as backwards. The postorbital bars, although worn,
seem to have been narrow and slope backwards and upwards much as in Cyclanorbis
Gray 1852.

pm

text-fig. 2. Eurycephalochelys fowleri gen. et sp. nov. BMNH R8445. Left lateral
view of skull, x Abbreviations as in text-fig. 1 .

<i

35°

I

text-fig. 3. Diagram showing position of stapedial foramen
(a-d) in various trionychids relative to quadrate condyle.
A, Chitrcr, B, Trionyx, Lissemys, Cyclanorbis and ? Pelochelys ;
c, Cycloderma; d, Eurycephalochelys.

The most important feature of the skull, shown clearly in this view, is the position of
the articular region of the quadrate in relation to the stapedial foramen. The articulation
lies well behind and below the stapedial foramen, so that a line connecting the two
would form an angle of 35° with the perpendicular (in other trionychids it lies almost
immediately beneath it) (text-fig. 3) ; it lies well behind the level of the foramen magnum
(instead of anterior to it); and it lies more or less at the antero-posterior level of the
back of the basioccipital, with the occipital condyle projecting only a short distance
behind it (instead of at the level of the front of the basioccipital, with the occipital
condyle projecting far behind it). The forwardly directed flange of the quadrate, which
rises to meet the quadratojugal, is almost horizontal (instead of oblique).

MOODY AND WALKER: A NEW TRIONYCHID TURTLE

507

The palate (text-figs. 4, 5c) is the least complete region of the skull. The premaxilla
is relatively large ventrally, forming the central portion of the blunt snout. The maxillae
are broad with gently sloping surfaces running from the cutting edge to the triturating
area, each reaching its maximum width at the level of the jugal bar. Although the vomer
and most of the palatines are missing, the approximate form of the central area of the
palate can be indicated (text-fig. 5). The intermaxillary suture would have been of

r pm

text-fig. 4. Eurycephalochelys fowleri gen. et sp. nov. BMNH R8445.
Palatal view of skull, x §. Abbreviations as in text-fig. 1.

medium length, but somewhat shorter than the length of the choanae, which are more
anterior in position than in Trionyx. The lateral slope into the choanal vault is rounded
and quite steep. The suture between the basioccipital and the basisphenoid lies anterior
to the articular surfaces of the quadrates, whereas in related trionychids it lies as far
back as the condyles or even slightly posterior to them.

The occiput cannot be described in great detail because of the damage caused by
weathering. There is evidence of an ascending process on the pterygoid running up
towards the opisthotic, but it is not possible to say whether those two elements actually
met; the prootic fenestra would nevertheless have been at least partly divided. The shape
of the foramen magnum and the brain cavity immediately anterior to it is wider than
high; other genera of this group show the reverse condition. The only clearly traceable
suture in this view is that between the quadrate and the pterygoid, which is normal in
position.

508

PALAEONTOLOGY VOLUME 13

text-fig. 5. Eurycephalochelys fowleri gen. et sp. nov. BMNH R8445. Reconstruction of skull;
a, dorsal; b, lateral; c, palatal.

Remarks. The main characters of the genus Eurycephalochelys which separate it from
other trionychids are listed in the first paragraph of the diagnosis. In some details it
resembles Trionyx , in others Cyclanorbis or Cycloderma Peters 1854. The palate is super-
ficially like that of Trionyx , but in Eurycephalochelys the choanae are further forward,
their anterior margins lying far in front of the widest part of the maxilla ; indeed, in this
feature Eurycephalochelys comes midway between Trionyx and Cyclanorbis. The choanae
are longer than the intermaxillary sutures in Eurycephalochelys, Cyclanorbis, and

MOODY AND WALKER: A NEW TRIONYCHID TURTLE

509

Cycloderma, but shorter in Trionyx; their form would have been round or oval in Eury-
cephalochelys, elongate in Cycloderma. (The form and length of the choanae are based
on our reconstruction.)

There was almost certainly a sutural contact between the pterygoid and opisthotic in
Eurycephalochelys. It may be noted that this contact is also present in Cycloderma and
Cyclanorbis {Eurycephalochelys appears to be closer to the latter in its detailed form)
but absent in Trionyx and Chitra Gray 1844. Loveridge and Williams (1954) figured
a Recent specimen of Trionyx triunguis (Forskal 1775) with such a feature (AMNH
36599).

Only one other species of trionychid has been described from the Bracklesham Beds :
Trionyx bowerbanki Lydekker 1889. The holotype (BMNH 38960) consists of an imper-
fect nuchal plate with a form of sculpturing rather different from that typical of
Trionyx. This species may prove to be conspecific with E. fowleri when associated
material comes to light.

The only trionychid which is known from the European Eocene and which includes
both skull and shell material is a specimen from the Upper Montian of Trieu de Leval
(Hainault, Belgium), housed in the Institut Royal des Sciences Naturelles de Belgique
(no. 1.720). Dollo (1909) listed this specimen as T. levalensis, but he never actually
described it and the name must be considered a nomen nudum. We have examined the
skull fragments and are convinced that it is quite different from the skull described here.

Conclusions. Eurycephalochelys shows similarities to several genera, but the lack of
comparative material makes it impossible to relate it to anything else at present.

Acknowledgements. We wish to thank Mr. R. Fowler for making this specimen available for descrip-
tion; Dr. A. J. Charig (British Museum (Natural History)) for criticising the manuscript; Dr. G. E.
Quinet (Institut Royal des Sciences Naturelles de Belgique) for the photographs of the Dollo speci-
men, Trionyx levalensis, which we later examined ; the American Museum of Natural History for the
loan of the type skull of Trionyx tritor Hay 1908; and Messrs. T. Parmenter and F. Greenaway for
taking the photographs.

Abbreviations. BMNH — British Museum (Natural History); AMNH — American Museum of Natural
History.

REFERENCES

bell, t. 1828. Characters of the Order, Families, and Genera of Testudinata. Zool. J. 3, 513-16.
dollo, l. 1909. The fossil vertebrates of Belgium. Ann. N.Y. Acad. Sci. 19 (1), 99-119.
fitzinger, l. J. F. J. de. 1 826. Neue Classification der Reptilien nach ihren natiirlichen Verwandtschaften.
Wien.

forskAl, p. 1775. Descriptiones Animalium.

geoffroy st.-hilaire, e. f. 1809. Sur les tortues molles, nouv., genre sous le nom de Trionyx et sur
la formation des carapaces. Ann. Mus. Hist. nat. Paris, 14, 1-20, pi. 1-5.
gray, J. e. 1 844. Catalogue of the tortoises, crocodiles and amphisbaenians in the collection of the British
Museum. London.

1852. Descriptions of a new genus and some new species of tortoises. Proc. zool. Soc. Lond. 133-5.

1873. Notes on mud-tortoises ( Trionyx Geoffroy) and the skulls of different kinds. Ibid.

38-72.

hay, o. p. 1908. The fossil turtles of North America. Publ. Carneg. Inst. 75, 529-32, figs. 687-9.
loveridge, a. and williams, e. e. 1957. Revision of the African tortoises and turtles of the Suborder
Cryptodira. Bull. Mus. Comp. zool. Harv. 115 (6), 164-577, pi. 15-18

510 PALAEONTOLOGY, VOLUME 13

lydekker, R. 1889. Catalogue of the fossil Reptilia and Amphibia in the British Museum ( Natural
History). London, 3, 3-23.

owen, r. and bell, t. 1849. Fossil Reptilia of the London Clay and of the Bracklesham and other
Tertiary beds. Chelonia. Palaeontogr. Soc. [ Monogr .], 45-61, fig. 19.
peters, w. k. h. 1854. Obersicht der auf seiner Reise nach Mossambique beobachteten Schildkroten.
Mber. dt. Akad. Wiss. Berl. 215-16.

R. T. J. MOODY

Department of Geology and Geography
Kingston Polytechnic
Penrhyn Road
Kingston upon Thames
Surrey

C. A. WALKER

Department of Palaeontology
British Museum (Natural History)
Cromwell Road
London
S.W. 7

Typescript received 7 November 1969

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PALAEONTOLOGY

VOLUME 13 • PART 3

CONTENTS

Conodonts from near the Middle/Upper Devonian boundary in North
Cornwall. By w. t. kirchgasser 335

The Chelonian Rhinochelys Seeley from the Upper Cretaceous of England and
France. By janice i. collins 355

The shell structure, mineralogy, and relationships of the Chamacea (Bivalvia).

By W. J. KENNEDY, N. J. MORRIS, and J. D. TAYLOR 379

The skull of Fabrosaurus australis, a Triassic ornithischian dinosaur. By R. A.

THULBORN 414

A Rhaeto-Liassic flora from Airel, northern France. By m. muir and j. h. a.

VAN KONIJNENBURG-VAN CITTERT 433

Calcareous algae new to the British Carboniferous. By g. f. elliott 443

Fertile Rhyniophytina from the Lower Devonian of Britain. By dianne
EDWARDS 451

Ammonites of the genus Acanthoceras from the Cenomanian of Rouen,
France. By w. j. Kennedy and j. m. Hancock 462

Ultrastructure of the protegulum of some acrotretide brachiopods. By
GERTRUDA BIERNAT and A. WILLIAMS 491

A new trionychid turtle from the British Lower Eocene. By r. t. j. moody
and c. A. WALKER

503

?:v * * *-* **ri**0^m^*r -> V ' - - - <? 4-f

VOLUME 13 • PART 4

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Palaeontology

DECEMBER 1970

PUBLISHED BY THE
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LONDON

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© The Palaeontological Association , 1970

THE GRAPTOLITE FAUNA OF GRIESTON
QUARRY, NEAR INNERLEITHEN,
PEEBLESSHIRE

by p. toghill and i. strachan

Abstract. The graptolite fauna of the Upper Llandovery beds at Grieston Quarry, Peeblesshire, is described.
It includes Glyptograptus ? nebula sp. nov. (the youngest British diplograptid yet found) and Monograptus
drepanoformis sp. nov. The relationship of the type Monoclimacis griestoniensis association to the griestoniensis
Zone recorded elsewhere is discussed.

Grieston Quarry (NT 3130 3618), 1 mile WSW. of Innerleithen, Peeblesshire, lies
in an area of steeply dipping Upper Llandovery greywackes (Gala Group of Lapworth
1870) and has long been known for yielding relatively abundant graptolites indicative
of a higher level in the Llandovery than any of the surrounding area. The quarry pro-
vided the type specimens of Monoclimacis [ Graptolites ] griestoniensis (Nicol 1850), and
although this species is now an Upper Llandovery zone fossil (Wood 1906), there has
been no review of the Grieston Quarry fauna since Nicol’s original (1850) account.

Nicol first recorded graptolites from Grieston (1848, p. 204) but gave little information
and no specific names. His main account (1850, pp. 53-5) was in fact quite detailed,
including joint directions, but it did not include a map and in some cases it is difficult to
relate exact horizons in the present quarry with his descriptions. He recorded three
graptolite horizons but thought the highest of these might be a repetition due to faulting.
The rest of his account consisted of a general discussion of the Silurian rocks of south-
east Scotland and the structure of the whole Southern Uplands, ending with notes on
the graptolites. His fauna included Graptolites sedgwickii, G. distans, G. tenuis, G. con-
volutus, G. ludensis, and the new species G. griestoniensis. The last three were described
in some detail along with another form from nearby Thornilee Quarry. In conformity
with the knowledge of the period, he correlated the Grieston Slates with the Llandeilo
flags of Wales.

Lapworth (1870, p. 206) placed the ‘Slates of Thornilee and the Grieston’ at the top of
his Gala Group, and recorded from Grieston Quarry, in addition to Nicol’s fauna,
Diplograptus sp., Graptolites colonus, and Retiolites geinitzianus. In his later detailed
work, ‘On Scottish Monograptidae’, Lapworth (1876) recorded some of his monograp-
tids from Grieston Quarry, including Monograptus priodon, M. barrandei, M. exiguus,
M. crispus, and M. convolutus var. proteus. Remarkably, he did not accept M. gries-
toniensis as a valid species, but considered it (1876, p. 350) to be a peculiar view of
M. hisingeri (Carruthers) (= nudus Lapworth). However, Elies and Wood (1911,
pp. 413-14) accepted the species without question, and presumably with Lapworth’s
approval. Peach and Horne (1899, p. 206) gave few details of the quarry and gave
as a fauna: Monograptus priodon, M. convolutus, M. vomerinus, M. sedgwickii, and
Retiolites geinitzianus. Elies and Wood figured specimens of M. priodon, M. acus,
M. nudus, M. griestoniensis, and R. geinitzianus from Grieston.

[Palaeontology, Vol. 13, Part 4, 1970, pp. 511-21, pis. 103-105.]

C 7719 L 1

512

PALAEONTOLOGY, VOLUME 13

The fauna described below is based mainly on Nicol’s original collection from
Grieston Quarry, which he donated to various institutions, together with collections
made later by Nicholson, B. M. Wright, and Lapworth, as well as the authors.

LITHOLOGIES AND FAUNA OF GRIESTON QUARRY

The quarry exposes 43 m. (140 ft.) of flaggy greywackes which dip consistently
north-west at between 60° and 65°. The detailed succession comprises alternations of
greyish-green flaggy shales and fine- to medium-grained greyish-green and bluish-grey
greywackes, with occasional nodular horizons. The greywackes, which are normally up
to 0-9 m. (3 ft.) thick, but occasionally thicker, contain abundant small-scale sole markings,
showing the strata to be the right way up. Some of the finer -grained greywackes, and
all of the shales, split into uniform flags or ‘slates’, and these have been quarried in the
past for roofing material.

The quarry is affected by a set of joints striking at 10°, and two joint planes in particu-
lar are conspicuous features on the quarry face. Both of these are mineralized and
slickensided, and although Nicol thought one at least was a fault, there appears to have
been little or no displacement along them. The more easterly of these cuts the lower
part of the section and dips E. 10° S. at 80°. The second dips at 37° in the same direction
and its face forms the present western limit of the quarry.

Nicol (1850, p. 54) recorded three fossiliferous horizons, two lower beds 3T m. (10 ft.)
apart, and a third 21-24 m. (70-80 ft.) higher. As a fault intervened (in fact the more
easterly of two major joints) he thought the third bed may have been a repetition of the
first or second. The lowest bed ‘. . . a bed of slate . . . lately opened’ contained the
best-preserved graptolites, but the middle bed contained Graptolites sedgwickii in abun-
dance. We have located the majority of Nicol’s original collection, which comprises
large slabs of bluish-grey greywacke containing well-preserved specimens, and likely
to have come from the ‘lowest bed of slate’ which was being freshly worked at the
time.

We have recently found this horizon 3-7 m. (12 ft.) above the base of the section, near
the eastern corner of the quarry, and have collected large slabs of greywacke with well-
preserved graptolites, and clearly the same material as in Nicol’s collection. Another
less-fossiliferous horizon occurs only 0-9 m. (3 ft.) above the base of the section, but
we have been unable to find any other fossiliferous horizons in situ.

However, there are fragments in the quarry talus of fossiliferous micaceous grey-
wacke, quite unlike the lithology of the main fossil horizon, but which matches closely
collections made from Grieston by Nicholson, Wright, and Lapworth, not long after
Nicol’s original investigations. This lithology has not yet been found in situ on the quarry
face. It may be from Nicol’s middle or highest horizon, but we are referring to all
this material as horizon 2, and the horizon of Nicol’s original collection as horizon 1 .

The fine-grained greywacke slabs of Nicol’s collection, and samples collected by us
from horizon 1 , 3-7 m. (12 ft.) above the base of the section contain the following common
species : Monoclimacis griestoniensis (Nicol), Monograptus priodon (Bronn), and Mono-
graptus spiralis (Geinitz) sensu Elies and Wood, together with rarer examples of M.
discus Tornquist, Retiolites geinitzianus angustidens Elies and Wood, Pseudoplegmato-
graptus obesus (Lapworth), and one example of Diversograptusl sp.

TOGHILL AND STRACHAN: GRAPTOLITE FAUNA OF GRIESTON QUARRY 513

The micaceous greywackes of horizon 2 yield the following common species : Mono-
graptus drepanoformis sp. nov., M. priodon, M. spiralis, Pristiograptus nudus (Lapworth),
and Glyptograptusl nebula sp. nov., together with rarer examples of Monoclimacis
griestoniensis, Retiolites geinitzianus angustidens, and Pseudoplegmatograptus obesus.

These two horizons show some notable differences in their fauna. In particular
Monoclimacis griestoniensis is only common at horizon 1. Monograptus discus is re-
stricted to horizon 1, whereas M. drepanoformis, Pristiograptus nudus, and Glypto-
graptus ? nebula are common at, but restricted to, horizon 2.

THE AGE OF THE GRIESTON QUARRY BEDS

The fauna listed above represents an horizon in the griestoniensis Zone (Upper
Llandovery) as defined at Trannon (Wood 1906, pp. 657-60), and as well as the zone
species the following are common to both localities : Pristiograptus nudus, Monograptus
discus, M. spiralis, and M. priodon. It is worth noting that the Trannon area itself has
not been reviewed since 1906. The highest fossiliferous band of the griestoniensis Zone
at Trannon yields Monoclimacis vomerinus crenulata, the zone species of the overlying
crenulata Zone. This species is absent at Grieston, and so is Monograptus marri, a
species common to all but the highest horizon of the griestoniensis Zone at Trannon.
It seems likely that the exact horizon of the Grieston Quarry beds may be immediately
below the highest fossiliferous beds of the griestoniensis Zone at Trannon (Wood 1906,
p. 658).

The terms ‘Grieston Slates’ and ‘Grieston Shales’ have been applied to the beds of
Grieston Quarry, the former term by Nicol (1850) and Lapworth (1870), and the latter
by the Geological Survey (Peach and Horne 1899). Both Nicol and Lapworth con-
sidered that the term Grieston Slates could be applied to strata outcropping along the
strike north-east and south-west of Grieston Quarry. Until a detailed investigation into
the whole of the Gala Group is carried out in this area it seems unlikely that any term
applied to the beds exposed in the quarry can be safely applied outside its confines.
Thus we feel it is best to refer to the beds in the quarry as a horizon within the Gala
Group (probably near the top). Lapworth himself expressed some doubt as to whether
his divisions within the Gala Group had anything more than local geographical
significance (1870, pp. 206-7).

Although the exact relationships of the beds of Grieston Quarry to those of the
surrounding area are not yet certain there is no doubt that they contain the youngest
(yet proven) graptolite fauna of the area. All the other graptolite localities of the Gala
Group to the east and south-east, around Galashiels (Lapworth 1870, pp. 204-9, 279-84;
Peach and Horne 1899, pp. 201-6) yield graptolites indicative of the underlying crispus
and turriculatus Zones.

The specimen of M. vomerinus crenulata figured by Elies and Wood (1910, pi. 41,
fig. 4 d) from Williamshope, in fact comes from Meigle Quarry, but is a poorly preserved
specimen of M. galaensis (Lapworth).

Lapworth (1870, p. 280) did not consider that the greywackes to the north of the
Grieston slates belonged to the Gala Group as they were not found in the Gala district,
and he stated : ‘. . . the Gala Group may provisionally be considered as terminated by the
Thornilee Slates which appear to form the centre of a synclinal’. Thus although he

514

PALAEONTOLOGY, VOLUME 13

grouped ‘The Slates of Thornilee and the Grieston’ together (1870, p. 206) at the top of
the Gala Group he must have considered the Thornilee Slates to overlie those of ‘the
Grieston’.

Between Grieston Quarry and the Ordovician-Silurian boundary 6 miles to the
north-west occurs a barren greywacke sequence which presumably must represent the
whole of the Llandovery below the griestoniensis Zone, so that a major synclinal axis
somewhere near to Grieston Quarry seems quite likely, and all the beds north of this
axis must young consistently to the south-east.

The whole of this area has a dominant Caledonoid strike (NE.-SW.) and another
of the structural problems posed by the area is that at Douglas Burn (Peach and Horne
1899, pp. 141-2), only 6 miles south-west of Grieston Quarry, and on exactly the same
strike, occur black graptolitic shales with Ordovician graptolites indicative of the basal
Caradoc zone of Nemagraptus gracilis. Thus any synclinal axis through Grieston Quarry
must rapidly plunge to the north-east.

SYSTEMATIC DESCRIPTIONS

Specimens from various institutions are prefixed as follows: Q, Palaeontology Department, British
Museum (Natural History) ; SM A, Sedgwick Museum, Cambridge ; GSM, Geological Survey Museum ;
GSM Geol. Soc. Coll., Geological Society of London Collection, now in the Geological Survey
Museum.

Monoclimacis griestoniensis (Nicol)

Plate 103, figs. 1-5; text-figs. 1 a-h
1850 Graptolites griestoniensis Nicol, p. 63, fig. 2.

1911 Monograptus griestoniensis (Nicol) ; Elies and Wood, pp. 413-14, text-figs. 279a-/, pi. 41,
figs. 5 a-d.

1940 Monoclimacis griestoniensis griestoniensis (Nicol); Pribyl, p. 10, pi. 3, figs. 1-3.

1945 Monoclimacis griestoniensis (Nicol); Waterlot, p. 77, pi. 32, fig. 333.

1952 Monoclimacis griestoniensis griestoniensis (Nicol); Munch, pi. 39, figs, la, b.

Lectotype. GSM 11,800 (PI. 103, fig. 3; text-fig. la), ?Nicol’s type slab, horizon 1, Grieston Quarry,
Innerleithen. Figured Elies and Wood 1911, pi. 41, fig. 5a.

Discussion of lectotype. It is not clear from Nicol’s original two figures whether they are different
magnifications of the same specimen, or two different specimens. He may thus have illustrated a holo-
type or two syntypes, but in any case no specimen in his original collection can be matched exactly
with his original figures. Elies and Wood (1911) stated that GSM 11,800 was Nicol’s type slab but
there seems to be no evidence for this, and in fact Nicol presented his original material, in the form of

EXPLANATION OF PLATE 103

Figs. 1-5. Monoclimacis griestoniensis (Nicol), horizon 1, Grieston Quarry, Nicol Collection. 1, 2,
GSM Geol. Soc. Coll. 6957, ? Nicol’s original specimen, figured 1850, p. 63, figs. 2a, b; 1 x3;
2, (enlargement of part of same) x 10. 3, Lectotype, GSM 11,800, figured Elies and Wood 1911,
pi. 41, fig. 5 a, x3. 4, GSM Geol. Soc. Coll. 6957, x3. 5, SM A21678, figured Elies and Wood
1911, pi. 41, fig. 5c, proximal end showing sicula, x 10.

Fig. 6. Diversograptusl sp., horizon 1, Grieston Quarry, Nicol Collection, GSM Geol. Soc. Coll.
6957, x 6. Also seen on fig. 4.

Figs. 7, 8. Pristiograptus nudus (Lapworth), horizon 2, Grieston Quarry, Wright Collection.
7, Q3078c, X9. 8, Q3081c, X 10.

Palaeontology, Vol. 13

PLATE 103

TOGHILL and STRACHAN, Grieston Quarry

TOGHILL AND STRACHAN: GRAPTOLITE FAUNA OF GRIESTON QUARRY 515

1

h

,

h

g

p

.fi

text-fig. 1. Monoclimacis griestoniensis (Nicol), horizon 1, Grieston Quarry, Innerleithen, Peebles-
shire. All original Nicol Collection./ x 5, remainder x 12. a, lectotype GSM 1 1,800, proximal portion,
figured Elies and Wood 1911, pi. 41, fig. 5a; b, c, d, SM A21678, figured Elies and Wood 1911, pi. 41,
fig. 5c; e, SM A21681, figured Elies and Wood 1911, p. 413, text-fig. 219b;f, GSM Geol. Soc. Coll.
6957, possibly Nicol’s original specimen (1850, p. 63, fig. 2); g, SM A21680, figured Elies and Wood
1911, pi. 41, fig. 5d; h, SM A21679.

greywacke slabs, to various institutions, including the Geological Society of London. The specimens
presented to the latter are now in the Geological Survey Collections, and one of these, GSM Geol.
Soc. Coll. 6957, according to their catalogues, contains the type specimen. Indeed one specimen on this
slab (PI. 103, figs. 1, 2; text-fig. If) compares favourably with Nicol’s original drawing, but it is im-
possible to be certain. In any case Pribyl (1948) selected GSM 11,800, Elies and Wood, 1911, pi. 41,
fig. 5 a as lectotype. This is unfortunate as this specimen is a distal fragment, and better and more
complete specimens are available from Nicol’s type collection.

516

PALAEONTOLOGY, VOLUME 13

Material. Numerous specimens on greywacke slabs from Grieston Quarry (horizon 1) presented by
Professor James Nicol to the Geological Society of London, Sedgwick Museum, Geological Survey
of Great Britain, and British Museum (Natural History). Rare specimens from horizon 2, Grieston
Quarry, B. M. Wright and H. A. Nicholson Collections, British Museum (Natural History).

Diagnosis. Long, slender, straight or slightly arcuate monograptid, up to 0-8 mm. wide,
thecae 10-8 in 10 mm. of typical Monoclimacis type; proximal thecae showing little
curvature and having everted apertures; distal thecae of typical climacograptid shape.

Description. The rhabdosome is long and slender, either straight or showing slight but
continuous ventral curvature. The longest fragment is 90 mm. long, but the greatest
width is only 0-8 mm. In the most complete specimen (PI. 103, fig. 5; text-figs. 1 b-d)
the width increases from 0-2 mm. at the first theca to a maximum of 0-7 mm. at th 50,
after 75 mm. The sicula is 1-4 mm. long and reaches just past the aperture of the first
theca. The thecae number 10-8 in 10 mm., and gradually increase in length from 0-7
to 1 -8 mm. after 75 mm. They overlap only | at the proximal end but this value increases
distally to f . The proximal thecae are almost straight with only a very slight geniculum,
and the apertures are slightly everted. The geniculum becomes distally more pro-
nounced, until the angle between the supra- and infra-genicular walls is 90°, and then
the typical Monoclimacis appearance is reached. When well preserved the geniculum is
produced into a flange which gives the aperture a hooded appearance (text-fig. Id).

Occasionally the rhabdosome is preserved in dorsal or ventral view, and then it has
the appearance of a series of vertebrae (Elies and Wood 1911, p. 413, text-fig. 279/).
This is due to the expansion of the thecae at the aperture, associated with the over-
lying genicular flange of the next theca.

Remarks. This well-defined species is presumably the ancestor of the main Wenlock
vomerinid stock, since it is earlier than M. crenulata at Trannon, and other Llandovery
forms such as M. galaensis can only doubtfully be regarded as monoclimacids (Rickards
1968). This new description agrees with that of Elies and Wood, except that the length of
sicula given here, 1-4 mm., is more than twice the 0-6 mm. given by them. One of us
(P. T.) has examined specimens of M. griestoniensis collected by Wood from Trannon
and figured by Elies and Wood (1911, p. 413, figs, a, d-f). These agree in dimensions
with those from Grieston Quarry.

Occurrence and associates. At Grieston Quarry Monoclimacis griestoniensis is common on
Nicol’s original greywacke slabs which presumably come from horizon 1 . It is associated
commonly with Monograptus priodon, M. spiralis, and M. discus. It only occurs rarely
at horizon 2 associated with Pristiograptus nudus, M. drepanoformis sp. nov. and Glypto-
graptusl nebula sp. nov.

EXPLANATION OF PLATE 104

Figs. 1-4. Monograptus drepanoformis sp. nov., horizon 2, Grieston Quarry. Fig. 2 Nicholson Collec-
tion, remainder Wright Collection. 1, Holotype, Q30726, xl6. 2, Q3089a, x 10. 3, Q30736,
X 14. 4, Q3081a, X 12.

Figs. 5-9. Monograptus spiralis (Geinitz) sensu Elies and Wood. Fig. 5, horizon 1 ; remainder, horizon
2, Grieston Quarry. 5, GSM 11,801, Nicol Collection, x 10. 6, Q3080«, x8, Nicholson Collec-
tion. 7, Q30816, x 10, Wright Collection. 8, Q30806, x8, Nicholson Collection. 9, Q3074<7,
X 6, Wright Collection.

Palaeontology Vol. 13

PLATE 104

TOGH1LL and STRACHAN, Grieston Quarry

TOGHILL AND STRACHAN: GRAPTOLITE FAUNA OF GRIESTON QUARRY 517

The type locality is the only well-documented occurrence in Scotland, but the species
occurs commonly in the Cross Fell Inlier (Burgess, Rickards, and Strachan 1970). It is
common in Wales where it was designated the index fossil for the Upper Llandovery
(Tarannon) griestoniensis Zone by Wood (1906) in the Trannon area. It has recently
been recorded from the Welsh Borderland associated with late Upper Llandovery
(Telychian) shelly fossils (Cocks and Rickards 1969). It occurs elsewhere in Europe
(Pribyl 1940, Munch 1952); North Africa (Waterlot 1945); and Australia (Thomas and
Keble 1933), but has not been recorded from North America.

text-fig. 2. Monograptus drepanoformis sp. nov., horizon 2, Grieston Quarry, Innerleithen, Peebles-
shire. All x 7 approx. B. M. Wright Collection except b, which is Nicholson Collection, a, holotype,
Q30726; b, Q3089 b\ c, Q3081a; d, Q3073 b; e, Q3079;/, Q30816.

Monograptus drepanoformis sp. nov.

Plate 104, figs. 1—4; text-figs. 2a- f

Holotype. BMNH Q30726 (PI. 104, fig. 1, text-fig. 2d), Grieston Quarry, horizon 2, Innerleithen,
Peeblesshire; B. M. Wright Collection.

Material. Numerous specimens from horizon 2, Grieston Quarry.

Derivation of name. Greek, sickle-shaped.

Diagnosis. Short rhabdosome, up to 1 mm. wide, with tight ventral curvature, but
slightly recurved dorsally at the proximal end. Thecae with little overlap, 12-10 in 10 mm.
with conspicuous open hooks, and a tendency to expand throughout their length giving
a triangulate appearance.

Description. The rhabdosome is short, up to 10 mm. and shows conspicuous ventral
curvature, although the extreme proximal end is recurved with slight dorsal curvature.
The sicula is 1 -2 mm. long and reaches as far as the apex of the first thecal hook. The
width increases from 0-3 mm. at the widest part of the first theca to a maximum of
0-8-1 -0 mm. reached after only 10 thecae. Ten to twelve thecae occur in 10 mm. and
these are 1-0 mm. long, including the hooks, and the overlap is always slight. The first
two or three thecae have a straight proximal portion which is of constant width passing
into a conspicuous open hook at the aperture. The third, or fourth, and later thecae
expand throughout their length and thus have a triangulate appearance, but again the
apertural region is a conspicuous open hook with the aperture pointing directly back-
wards.

518

PALAEONTOLOGY, VOLUME 13

Remarks. The over-all shape resembles M. crispus Lapworth, but the rhabdosome is
shorter, and the proximal end not so slender or so recurved. The triangulate distal thecae
are similar to M. flagellaris Tornquist, but the apertural region is hooked, and not
coiled as it is in the latter. Earlier records of M. crispus from Grieston Quarry can
probably be referred to this new species.

Occurrence and associates. M. drepanoformis occurs commonly at horizon 2 in Grieston
Quarry but not on any of Nicol’s greywacke slabs from horizon 1 . It is associated with
M. priodon, M. spiralis, Pristiograptus nudus, and Glyptograptusl nebula sp. nov.

Monograptus spiralis (Geinitz) sensu Elies and Wood
Plate 104, figs. 5-9; Plate 105, fig. 14

1913 Monograptus spiralis (Geinitz); Elies and Wood, pp. 475-6, text-figs. 331a-c, pi. 48,
figs. la-d.

Discussion. Elies and Wood (1913) included in Monograptus spiralis forms with both
regular and irregular curvature, and they remarked on the large size of specimens
from the griestoniensis Zone. In his review of the genus Spirograptus, Pribyl (1944)
restricted Monograptus spiralis to forms with a very regular spiral curvature, and thus
comparable to Geinitz’s original figures (1842, pi. 10, figs. 26, 27).

The specimens here referred to M. spiralis (Geinitz) sensu Elies and Wood have
proximal ends with open spiral curvature (PI. 104, figs. 5, 7) but distally the curvature
can be regular or irregular, and the thecae often appear on the inside of the curved
stipe (PI. 105, fig. 14). Distal fragments (PI. 104, figs. 8, 9) are often straight, and similar
to those figured by Elies and Wood (1913, p. 476, figs. 3316, c ).

Some of these forms are similar in over-all appearance to Monograptus tullbergi
Boucek, M. tullbergi spiraloides (Pribyl) and M. falx (Suess), which are recorded from
the griestoniensis and crenulata Zones of Bohemia. However, the proximal end of
M. tullbergi (Boucek 1931, p. 301, fig. 9/) appears to have slender, almost straight
thecae, whereas distally the thecae are more hooked than triangulate. The irregularly
curved M. tullbergi spiraloides appears to have a more robust proximal end (Pribyl 1944,
pi. 5, fig. 10) than M. spiralis sensu Elies and Wood, as does M. falx (Suess) (Pribyl
1944, pi. 5, figs. 1-6).

EXPLANATION OF PLATE 105

Figs. 1-7. Monograptus priodon { Bronn). 1 and 2 from horizon 1, remainder from horizon 2, Grieston
Quarry. 1 , 2, SM A22477, Nicol Collection ; 1 X 1 ; 2, enlargement of part of same, x 8. 3, Q3073c,
x 9, Wright Collection. 4, Q3083, x 14, Wright Collection. 5, Q3074e, x 13, Wright Collection.
6, Q3074/, xl3, Wright Collection. 7, Q3077a, x9, Nicholson Collection.

Fig. 8. Retiolites geinitzianus angustidens Elies and Wood, horizon 2, Grieston Quarry, Nicholson
Collection, Q30896, x 2-5.

Figs. 9-13. Glyptograptusl nebula sp. nov., horizon 2, Grieston Quarry. 9, 12, Nicholson Collection,
remainder Wright Collection. 9, Q3071o, xl3. 10, Q30746, xl3. 11, Q3072a, xll.
12, Holotype, Q30716, x 13. 13, Q3075a, x 13.

Fig. 14. Monograptus spiralis (Geinitz) sensu Elies and Wood, horizon 1, Grieston Quarry, Toghill
Collection, Q3111, xl-5.

Palaeontology, Vol. 13

PLATE 105

\

TOGHILL and STRACHAN, Grieston Quarry

TOGHILL AND STRACHAN: GRAPTOLITE FAUNA OF GRIESTON QUARRY 519

1870 Diplograptus sp. Lapworth, p. 206.

Holotype. BMNH Q30716 (PI. 105, fig. 12, text-fig. 3b), Grieston Quarry, Innerleithen, Peeblesshire,
B. M. Wright Collection.

Material. Numerous specimens from horizon 2, Grieston Quarry.

Diagnosis. Short, ‘dwarfed’ diplograptid with thin ‘ghost-like’ periderm. Sicula and
virgula always conspicuous. Width either uniform at 05-0-6 mm. or decreasing some-
what distally. Thecal form often obscure but probably glyptograptid.

text-fig. 3. Glyptograptusl nebula sp. nov., horizon 2, Grieston Quarry, Innerleithen, Peeblesshire.
All x7 approx, a, b, i, H. A. Nicholson Collection, remainder B. M. Wright Collection, a, Q3071a;
b, holotype, Q30716; c, Q3073a; d, Q3074a; e, Q30746; /, Q3075a; g, Q30766; h, Q30756;
i, Q3077 ; j, Q307 6o; k, damaged specimen Q3072a; /, Q3078o.

Description. The rhabdosome is short and narrow, and no specimens longer than 4 mm.
have been found. The periderm is very thin so that the sicula and virgula always show
through and the latter is always distally prolonged, sometimes to twice the length of
the rhabdosome. The sicula is always conspicuous and is relatively long (1-3—1 -6 mm.)
and robust compared with the whole rhabdosome. It is completely embedded in the
rhabdosome and in most cases reaches up to the apertures of the second thecal pair,
although the exact position of its apex is sometimes difficult to see.

No more than 5 thecal pairs are ever present, and the width is either uniform at
0-5-0-6 mm. or decreases distally to around 0-4 mm. The thecae themselves are alter-
nate, 0-8 mm. long, and show little overlap. Their shape is rather obscure but appears
to vary between a glyptograptid and a climacograptid type, but on the whole are more
like the former. The free ventral wall is occasionally produced into a denticle (text-fig.

Remarks. This is the youngest British diplograptid and is presumably the ‘small Diplo-
graptus ’ recorded by Lapworth (1870, p. 206) from Grieston Quarry.

Occurrence and associates. This new species is common at horizon 2 in Grieston Quarry,
associated with Pristiograptus nudus, Monograptus spiralis, M. drepanoformis, M. prio-
don, and (rarely) Monoclimacis griestoniensis. It does not occur on the greywacke slabs

Glyptograptus ? nebula sp. nov.
Plate 105, figs. 9-13; text-figs. 3 a-l

3k).

520

PALAEONTOLOGY, VOLUME 13

of horizon 1. Wilson (1954, unpublished Ph.D. thesis) recorded a probably identical
Climacograptus sp. from the turriculatus to griestoniensis Zones of the Cautley area
(NW. Yorkshire).

Notes on some of the remaining fauna

Specimens of Monograptus priodon (Bronn) from Grieston Quarry are often well
preserved and can be of considerable length. They have been figured by Elies and
Wood (1913, pi. 42, figs. 2a, b ), and one specimen figured here (PI. 105, figs. 1, 2) is
that referred to by M’Coy (1851, p. 6) as Graptolites sedgwickii. References to G. sedg-
wickii in Nicol’s original account can, on a modern basis, be referred to M. priodon.

One fragment of Diversograptus ? has been found on one of Nicol’s original slabs
(PI. 103, fig. 6). Although not diversiform this single fragment is similar to branching
diversograptids which one of us (P. T.) has collected from the Cyrtograptus grayi band
of Penwhapple Burn, Girvan.

Acknowledgements. We would like to thank Dr. R. B. Rickards (Sedgwick Museum) and Dr. A. Rush-
ton (Institute of Geological Sciences) for the loan of specimens in their care. We are also grateful to
various members of the Ludlow Research Group for advice given on an excursion to Grieston Quarry
in September 1969.

REFERENCES

boucek, b. 1931. Preliminary communication on some new species of graptolites from the Silurian
of Bohemia. Vest. st. geol. Ust. csl. Repub. Prague, 7, 293-306.
burgess, i. c., rickards, r. b. and strachan, i. 1970. The Silurian Strata of the Cross Fell area. Bull,
geol. Surv. Gt. Br. No. 32, 167-84.

cocks, L. r. m. and rickards, r. b. 1969. Five boreholes in Shropshire and the relationships of shelly
and graptolitic facies in the Lower Silurian. Q. Jl geol. Soc. Lond. 124, 213-38, pi. 9-11.
elles, g. l. and wood, e. m. r. 1901-18. A monograph of British Graptolites. Palaeontogr. Soc.
[Monogr.].

geinitz, H. b. 1842. t)ber die Graptolithen. Neues Jb. Miner. Geogn. Geol. Petrefakt, vol. for 1842,
697-701, pi. 10.

lapworth, c. 1870. On the Lower Silurian Rocks of Galashiels. Geol. Mag., 1 Dec., 7, 204-9, 279-84.

1876. On Scottish Monograptidae. Ibid. 2 Dec., 3, 308-21, 350-60, 499-507, 544-52, pi. 10-13, 20.

m’coy, f. 1851. Description of the British Palaeozoic fossils in the Geological Museum of the Univer-
sity of Cambridge. In sedgwick, a. and m’coy, f. 1851-5. British Palaeozoic rocks and fossils.
Cambridge, Fasc. 1, 1-184.

munch, a. 1952. Die graptolithen aus dem Anstehenden Gotlandium Deutschlands und der Tschecho-
slowakei. Geologica, Berl. 7, 1-157, pi. 1-62.

nicol, J. 1848. On the geology of the Silurian rocks in the valley of the Tweed. Q. Jl geol. Soc. Lond.
4, 195-209.

1850. Observations on the Silurian Strata of the south east of Scotland. Ibid. 6, 53-65.

peach, b. n. and horne, j. 1899. The Silurian rocks of Britain. 1, Scotland. Mem. geol. Surv. U.K.
Glasgow.

pribyl, a. 1940. Revise ceskych graptolitu rodu Monoclimacis Freeh. Rozpr. ceske. Akad. Ved. Umeni,
Sect. 2, 50, No. 23, 1-19, pi. 1-3.

1944. The Middle-European monograptids of the genus Spirograptus Gurich. Ibid., Sect. 2, 54,

No. 19, 1-46, pi. 1-11.

1948. Bibliographic index of Bohemian Silurian graptolites, Prague.

rickards, r. b. 1968. The thecal structure of Monoclimacis ? galaensis. Lethaia, 1, 303-9.
thomas, d. e. and keble, r. a. 1933. The Ordovician and Silurian Rocks of the Bulla-Sunbury area
and discussion of the sequence in the Melbourne area. Proc. R. Soc. Viet. 45, 33-84.
tornquist, s. l. 1892. Undersokninger ofver Siljansomradets Graptoliter. II, Monograptidae. Acta
Univ. Lund, 28, no. 10, 1^17, pi. 1-3.

TOGHILL AND STRACHAN: GRAPTOLITE FAUNA OF GRIESTON QUARRY 521

waterlot, g. 1945. Les graptolites du Maroc. Part 1 . Protectorat de la Republique Frangaise au Maroc,
Service Geologique. Notes et Memoires, no. 63, 1-112, pi. 1-50.

Wilson, d. w. r. 1954. The stratigraphy and palaeontology of the Valentian Rocks of Cautley (Yorks
W.R.). Unpublished Ph.D. thesis, University of Birmingham.
wood, e. m. r. 1906. The Tarannon Series of Tarannon. Q. Jl geol. Soc. Loud. 62, 644-701.

PETER TOGHILL

Department of Palaeontology
British Museum (Natural History)
Cromwell Road
London S.W. 7

ISLES STRACHAN

Department of Geology
University of Birmingham
Edgbaston

Revised typescript received 20 February 1970 Birmingham 15

THE EMUELLIDAE, A NEW FAMILY OF
TRILOBITES FROM THE LOWER CAMBRIAN OF
SOUTH AUSTRALIA

by k. j. pocock

Abstract. Study of the adult morphology and the ontogeny of a new group of trilobites from the Lower
Cambrian of South Australia has led to the erection of 2 new genera, Emuella and Balcoracania, each with 2
species, which are considered to belong to a new family, here named the Emuellidae. The members of this
family are characterized by a unique combination of cephalic and thoracic features; the cephalon possesses
a complete set of functional sutures of the ptychopariid type, long crescentic eye lobes widely separated from the
glabella, and a geniculate posterior border; the thorax is divided into a short prothorax, in which the 6th seg-
ment is macropleural and fused to the 5th, and an extremely long opisthothorax containing numerous segments.
The family is here included in the suborder Redlichiina.

Study of the ontogeny of two of the species has allowed the cephalic development to be subdivided into stages,
which are related, where possible, to meraspid degrees. The fused 5th and 6th segments are released as a unit
into the thorax, and the macropleural spine of the 6th has not been observed in the transitory pygidium.

The formation of the opisthothorax results from an abrupt reduction of the space available for the pleurae of
segments succeeding the macropleural segment. The macropleural segment serves the role of protection, aids
stability, and in the larval stages possibly buoyancy; the fusion of this segment to the preceding assists in control
of the former.

The Emuellidae are considered to preserve the structure of possible ancestors of the Olenellina on one hand,
and the Redlichiina on the other.

The trilobites described in this paper were first found by Dr. B. Daily of the Geology
Department, University of Adelaide, on the western side of Cape D’Estaing, Kangaroo
Island, South Australia (Daily 1956). Subsequently the author discovered a second
locality on the eastern side of the Cape (Pocock 1964, p. 459). In 1961, Messrs. Dalgarno
and Johnson, of the Geological Survey, South Australian Department of Mines, made
a remarkable discovery of a similar trilobite, near Blinman, in the Flinders Ranges,
South Australia. Further work by the author has located related trilobites in Kangaroo
Island, and extended the known range of occurrence in the Flinders Ranges.

GEOGRAPHIC AND STRATIGRAPHIC DISTRIBUTION

The known occurrences of members of the group are restricted to Lower Cambrian
rocks of the Adelaide Geosyncline. They are, however, widely separated geographically,
one locality being in the eastern portion of the Flinders Ranges, and the others on the
northern coast of Kangaroo Island, c. 350 miles away.

The Kangaroo Island localities are at Cape D’Estaing, approximately 12 miles W. of
Kingscote (text-fig. 1). The fossiliferous beds occur in sections on either side of the Cape,
outcropping on wave-cut platforms and in cliffs behind. On the eastern side, in the
Emu Bay section of Pocock (1964), Balcoracania dailyi gen. et sp. nov. occurs in a zone,
approximately 30 ft. thick, near the top of the White Point Conglomerate, in association
with a species of Estaingia, Hyolithes, and an unidentified brachiopod; Emuella dalgarnoi
gen. et sp. nov. occurs 250 ft. stratigraphically above, in a 2-ft. thick bed within the

[Palaeontology, Vol. 13, Part 4, 1970, pp. 522»52, pis. 100110.]

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 523

Emu Bay Shale and immediately above beds containing Estaingia bilobata Pocock and
a species of Redlichia (Pocock 1964). On the W. side of the Cape, in a section which can
be correlated in part with the Emu Bay section, Emuella polymera gen. et sp. nov. occurs
in a thin bed near the base of the sequence, and B. dailyi occurs in the overlying 60 ft.
All the fossiliferous beds at this locality occur in the upper part of the White Point
Conglomerate (text-fig. 2).

text-fig. 1. Locality Maps. Inset 1, Balcoracana Creek area, Flinders Ranges, South Australia.
Inset 2, Kangaroo Island, South Australia; 1, Emu Bay section; 2, Cape D’Estaing section.

The Flinders Ranges locality (text-fig. 1) is at Balcoracana Creek, 14 miles ESE. of
Blinman. Here Balcoracania flindersi gen. et sp. nov. occurs in a 30-ft. thick section
of the Billy Creek Formation, approximately 500 ft. above the base.

The White Point Conglomerate and the Emu Bay Shale are considered to be upper
Lower Cambrian. The evidence upon which this determination is based was reviewed
by Daily (1956) and Pocock (1964).

The Billy Creek Formation is underlain by the Oraparinna Shale of middle Lower
Cambrian age (Walter 1967), and overlain by the Wirrealpa Limestone, which Daily
(1956) considered lower Middle Cambrian. The Billy Creek Formation at this locality
is 3300 ft. thick, and the trilobites occur approximately 2800 ft. below the Wirrealpa
Limestone and are thus probably upper Lower Cambrian.

524

PALAEONTOLOGY, VOLUME 13

At the present time it is not possible to correlate the Flinders Ranges and Kangaroo
Island sections, so the stratigraphic position of B.flindersi with respect to the other species
is not known.

conglomerate
arkosic sdsl.
siltstone
silly shale
mol tied limestone

100 ft.

-50 ft.

L0

2

text-fig. 2. Stratigraphic columns ; parts of the stratigraphic successions of Lower Cambrian age of
Kangaroo Island, South Australia. 1, Emu Bay section; 2, Cape D’Estaing section.

MODE OF OCCURRENCE

At the Kangaroo Island localities, the trilobites occur on the bedding planes largely
as disarticulated moults, interspersed with a few complete individuals. Both larval and
adult specimens occur in the collections of E. polymera and B. dailyi, but only adults of
E. dalgarnoi have been found. The trilobites occur in fine-grained siltstones or silty
shales of slightly varying character.

In the Flinders Ranges, B.flindersi occurs in a sequence of greenish-brown tuffaceous
shales. Specimens are rare for the greater part of the fossiliferous sequence, and are
represented exclusively by moults ; however one bed, about 4 in. thick, near the top is
richly fossiliferous, one bedding plane being almost covered with complete individuals,
both larval and adult. Such an occurrence, in a sequence of sparsely fossiliferous rocks
in which only moults are found, combined with the tuffaceous nature of the shale, sug-
gests that the assemblage results from mass mortality, perhaps associated with volcanic
activity.

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 525

Mass mortality has been invoked many times to explain the nature of some fossil
assemblages, and volcanic activity has often been suggested as the cause. Brongersma-
Sanders (1957) reviewed this subject, and pointed out the necessity for care in invoking
such a phenomenon. In this case, evidence independent of that provided by the presence
of tuffaceous material, and the preponderance of complete exoskeletons, is available.
The size frequency distribution of the specimens from the bedding plane (text-fig. 3)

A| mm

text-fig. 3. Size frequency distribution of Balcoracania flindersi. Individuals
collected from the Balcoracana Creek locality. A1 is the cranidial length.

shows a large number of very small specimens compared to the large. Craig and Oertel
(1966) constructed theoretical models for various populations, in terms of size and age
frequency distributions, and pointed out that most fossil assemblages differ from
theoretical models in the absence of large numbers of young (small) individuals. In
addition, mass mortality results in a frozen size frequency distribution of a living
population, in which small individuals will be very abundant. The size frequency dis-
tribution of B. flindersi thus approximates that of a living population in the high pro-
portion of small individuals, and the assemblage probably resulted from mass mortality.

METHODS AND TECHNIQUES

Reconstruction of distorted specimens. Although some degree of distortion and/or flattening is present
in all collections, its range is limited and the number of specimens large enough for an accurate re-
construction to be made. Illustrations of reconstructed trilobites, both adult and larval, were made
directly from photographs of selected specimens with the aid of a magnifying light table.

Quantitative analysis. A limited statistical analysis of variation has been made using mainly the
methods of regression analysis recommended by Shaw (1956). However the parameters for the ‘best
fit’ lines were calculated by the method given by Simpson, Roe, and Lewontin (1960, p. 234).

526 PALAEONTOLOGY, VOLUME 13

The measurements on which the analysis is based are given in the Appendix, and the dimensions
used are shown in text-fig. 4.

Terminology. The terminology recommended in the Treatise on invertebrate paleontology. Part O,
Trilobita (Harrington et al. 1959), is used with some modification, necessitated by the morphology of
the trilobites described (text-fig. 4).

The term ‘anterior fossulae’ has been applied to small depressions in the axial furrows at or near the
anterior edges of the glabella (Harrington et al. 1959, 0120). In the trilobites described below, depres-
sions occur in the axial furrows at their junctions with both the anterior border furrow and the anterior
edge of the eye ridge; the term ‘anterior furrow fossulae’ is applied to the former, and ‘eye ridge fos-
sulae’ to the latter. In larval forms the informal term ‘cheek’ is used, owing to the difficulty in dis-
tinguishing palpebral and posterior areas in very small specimens; ‘cheek furrow’ is used to describe

text-fig. 4. Dimensions measured, terminology, and ventral morphology. 1, Dorsal view of cranidium.
2, Ventral view of cranidium with hypostome in situ. 3, Ventral view of hypostome. 4, Dorsal view of
macropleural unit. All diagrams based on specimens of Balcoracania dailyi.

a furrow extending onto the cheek from the junction of the axial and glabellar furrows. In the hypo-
stome the terms ‘anterior lateral border’ and ‘border furrow’ are applied to the marginal portions
between the anterior wing and the lateral notch. The terminology of Shaw and Ormiston (1964) is
applied to the librigena. In the thorax, the 6th segment is macropleural and fused to the 5th ; the term
‘macropleural unit’ is applied to this combination and ‘interfurrow platform’ to the area between the
5th and 6th pleural furrows.

In the systematic description and discussion, all angles are in the horizontal plane, are average
values, and are given with reference to the sagittal direction unless otherwise specifically stated.

The widely used terms protaspid, meraspid, and holaspid stages are used. In view of the limited
number of protaspides, no division of this stage is applied. Difficulties arise, however, in the application
of the meraspid stage. The trilobites described have a short prothorax and an extremely long opistho-
thorax. Thus in the view of workers who consider the prothorax is homologous to the ‘normal’ thorax
of other trilobites (e.g. Hupe 1953a, c; Harrington et al. 1959), the trilobites described below would
have only 5 meraspid degrees, being considered holaspid on the appearance of the 6th (and last)
prothoracic segment, with 50 or so articulating opisthothoracic segments still to be released. In
addition, at degree 6 the cephalon is still far removed from the adult condition. On the other hand the
cephalon does attain the adult condition, except for size, whilst a considerable number of opistho-
thoracic segments are yet to be released from the transitory pygidium.

The above considerations illustrate that the usual divisions of the stages of larval development are
not always easily applicable. If other cases become known in which cranidial development is com-
pleted before thoracic development, a formal division of the meraspid period on this basis may become
justified. At present, however, in view of the small number of such cases, such a division does not
appear justified.

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES

527

SYSTEMATIC PALAEONTOLOGY

All specimens are deposited in the Palaeontological Collection of the University of Adelaide, South
Australia (AUGD, F series).

Suborder redlichiina Harrington 1959 (in Harrington et al. 1959)

Family emuellidae fam. nov.

Diagnosis. Small to medium opisthoparian trilobites. Glabella with 3 transglabellar
furrows in adult; axial furrows converge from occipital ring to anterior glabellar furrow;

text-fig. 5. Reconstruction of adult morphology of members of the Emuellidae. A, complete dorsal
exoskeleton of B. daily i; B, cranidium of B.flindersi ; c, cranidium of E. dalgarnoi ; d, cranidium of
E. polymera. Magnification x 10.

frontal lobe expanded, rounded laterally; preglabellar field narrow or absent. Eye ridge
wide, long, directed slightly postero-laterally, palpebral lobe crescentic. Posterior area
with fulcrum. Posterior border with section abaxial to fulcrum directed antero-laterally.
Anterior section of facial suture diverges anteriorly to border furrow, curves sharply
inwards and crosses anterior border diagonally, before becoming marginal- ventral;
connective suture concave abaxially ; rostral plate short (tr.), notched laterally; posterior
c 7719 m m

528

PALAEONTOLOGY, VOLUME 13

section of facial suture divergent; hypostomal suture functional. Hypostome with de-
pressed anterior wings; median body with large subtriangular anterior lobe, subdivided
anteriorly by median depression ; small posterior lobe. Librigena with long genal spine. !

Thorax with prothorax of 6 segments, and extremely long opisthothorax of between
42 and 55 segments. Sixth prothoracic segment macropleural and fused to 5th. Macro-
pleural spine long, extends to level of pygidium. Pygidium a minute segmented disc,
with border entire.

Discussion. The Emuellidae bear similarities to certain of the Olenellidae and Red-
lichiidae. The Emuellidae share with the Olenellidae the division of the thorax, and
macropleurality; they differ in the number of segments and the fusion of prothoracic
segments, and with regard to cephalic features in the possession of a complete set of
functional sutures. The cephalic features are similar to those of some of the families of
the Redlichiina, but the latter lack the characteristic thorax of the Emuellidae.

Genus emuella gen. nov.

Type species. Emuella polymera sp. nov.

Plates 106, 107; text-fig. 5 c, d.

Derivation of name. From Emu Bay, Kangaroo Island, South Australia.

Diagnosis. Preglabellar field absent. Anterior border furrow shallows abruptly anterior jj
to frontal glabellar lobe. Palpebral lobe relatively short, curved. Posterior border with I
section abaxial to fulcrum directed antero-laterally at 45° and slightly depressed. '
Librigena with advanced genal spine. Thorax with axis more than half thoracic width;
pleurae very 1 * 3 4 5 6 short. Pleural furrow terminates before pleural spine. Thorax with
at least 48, and known maximum of 58 segments. Strong closely spaced granules on
dorsal surfaces.

Emuella polymera sp. nov.

Plate 106; Plate 107, figs. 1, 2; text-fig. 5d.

Derivation of name. ‘Polymera’ — for numerous thoracic segments.

Holotype. AUGD F16643 (PI. 106, fig. 1). It was considered essential that a specimen with an articu-

EXPLANATION OF PLATE 106

Figs. 1-7. Emuella polymera gen. et sp. nov. White Point Conglomerate, Cape D’Estaing, Kangaroo
Island, South Australia. 1, Holotype, FI 6653, x 10; internal mould of cephalon and thorax; crani-
dium sagittally compressed, librigenae rotated, macropleural spines incomplete. 2, F16643, x 14;
incomplete internal mould of cephalon and thorax; posterior portion of opisthothorax missing.

3, FI 6645a, x 6; incomplete internalmould of cranidium; right posterior area asymmetrically distorted.

4, FI 66456, x 6; counterpart of fig. 3, showing ornament of cranidium, structure of palpebral lobes.

5, FI 6648, x9-5; internal mould of cranidium showing anterior furrow and eye ridge fossulae.

6, FI 6658, x20; external mould of hypostome and attached rostral plate; rostral plate incomplete
but anterior section of right connective suture can be seen. 7, F16647, X9; internal mould of
librigena showing the long posterior section of the facial suture, the changes in convexity of the
genal field, and the widening of the doublure adjacent to the connective suture; the mould of the
lateral border is incomplete and collapsed onto that of the doublure.

Palaeontology , Vol. 13

PLATE 106

POCOCK, Lower Cambrian Emuellidae

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 529

ated cephalon and thorax be chosen. Although isolated cranidia show some diagnostic features much
better, they were not selected for the above reason.

Dimensions ofholotype. Length of cranidium 2-8 mm.; palpebral width of cranidium 3-7 mm.; length
of prothorax 1-6 mm.; over-all sagittal length of specimen 9 0 mm.

Material. Approximately 50 internal and external moulds, mainly disarticulated.

Occurrence. White Point Conglomerate, upper section of formation; on W. side of Cape D’Estaing,
Kangaroo Island, South Australia.

Diagnosis. Axial furrows converge evenly from posterior edge to anterior glabellar furrow; furrows
deep, distinct around slightly expanded frontal glabellar lobe. Glabellar furrows shallow, indistinct.
Anterior cranidial border furrow almost transverse. Palpebral lobe short, highest at mid point,
posterior end opposite middle glabellar furrow or lobe. Posterior border constant width, abaxial sec-
tion directed antero-laterally at 40°. Posterior border furrow even depth. Anterior section of facial
suture diverges anteriorly at 10°. Axial rings of prothorax rise sharply to posterior, with first 4 bearing
sagittal, elongate nodes on posterior margin. Thorax with at least 48 segments.

Description. Cephalon subtrapezoidal in outline, gently convex (tr. and sag.). Cranidium gently convex
(tr.). Glabella with 3 transglabellar furrows; axial furrows converge evenly from posterior margin to
anterior glabellar furrow, diverge and curve around slightly expanded frontal lobe. Preglabellar furrow
confluent with anterior border furrow, straight or slightly curved anteriorly. No preglabellar field.
Glabella strongly convex (tr.), with slight median ridge extending to anterior glabellar furrow; gently
convex (sag.), highest at anterior glabellar lobe, slopes down steeply to anterior border furrow, more
gently to posterior. Occipital furrow transverse, or curves slightly to posterior, narrowest and deepest
abaxially. Transglabellar furrows shallow and indistinct, posterior and middle furrows almost trans-
verse, anterior furrow curves slightly forwards (PI. 106, figs. 3, 4). Occipital ring approximately half
mid palpebral cranidial width, widest sagitally; posterior edge curves outwards, half sagittal width
projecting beyond margins of fixigenae. Length (sag.) of glabellar lobes decreases from posterior to
anterior, but frontal lobe longest. Axial furrow slightly to deeply impressed below fixigena from
posterior margin to eye ridge, rises and becomes indistinct over eye ridge, deeply impressed from eye
ridge to anterior border furrow. Anterior furrow fossulae present at junctions of axial furrows and
anterior border furrow (PI. 106, figs. 3-5). Anterior border medium width, gently convex. Anterior
border furrow almost transverse across cranidium (PI. 106, fig. 3), moderately deep and narrow
abaxially, shallows and broadens abruptly, anterior to frontal lobe (PI. 106, figs. 3-5).

Eye ridge wide, long, gently convex, (tr. and exsag.), directed to posterior at 20° to transverse direc-
tion; anteriorly almost grades into gently downsloping frontal area, marked only by indistinct furrow,
posteriorly slopes steeply down to distinct furrow continuous with palpebral furrow and aligned
abaxially with anterior glabellar furrow (PI. 106, fig. 4); degree of separation of eye ridge from frontal
lobe by axial furrow varies considerably. Palpebral lobe short, less than glabellar length, anterior end
opposite anterior glabellar furrow, posterior end opposite middle glabellar lobe (PI. 106, figs. 3, 4);
moderately convex (exsag.), convex upwards with mid point highest ; slopes up steeply from palpebral
furrow becoming convex (tr.); separated indistinctly from eye ridge by change in convexity (PI. 106,
figs. 4, 5), in some large specimens by indistinct furrow. Palpebral furrow deep, wide, slopes down
to posterior. Palpebral area slightly convex (tr.), horizontal to down-sloping posteriorly. Posterior
area long (exsag.), almost as wide (tr.) as occipital ring, with distinct fulcrum at opposite posterior
end of palpebral furrow. Posterior border narrow, convex, even width; horizontal and transverse from
axial furrow to fulcrum; abaxial to fulcrum, slightly downsloping and directed antero-laterally at
approximately 40° to postero-lateral corner of cranidium (PI. 106, figs. 3, 4). Posterior border furrow
originates at base of axial furrow, widens abaxially (confluent with posterior end of palpebral furrow) ;
deep adjacent to border, shallows away from it; over-all shape triangular (PI. 106, figs. 3-5).

Anterior section of facial suture diverges anteriorly at 10°, curves sharply inwards at border furrow,
crosses anterior border diagonally to intersect anterior edge opposite junction of axial and border
furrows (PI. 106, figs. 3, 5), then marginal ventral; connective sutures cross doublure, concave abaxially
(PI. 106, fig. 7). Palpebral section of facial suture short, convex abaxially, diverges to posterior at 15°;
posterior section relatively long, slightly convex abaxially, diverges to posterior at 50°, and slopes
down to cut posterior border opposite posterior glabellar furrow (PI. 106, figs. 3-5).

530

PALAEONTOLOGY, VOLUME 13

Librigena (PI. 106, fig. 7) with long genal spine. Lateral border moderately convex (tr.), approx.
i mid-palpebral width of librigena. Lateral border furrow distinct, rises steeply to border and slopes
up gently to genal field abaxially; curves sharply inwards near base of genal spine, continuous with
posterior border furrow, becomes wider and deeper adaxially. Posterior border narrow, convex, con-
tinuous with posterior border of fixigena, slopes down abaxially to join lateral border. Genal field
slopes up gradually from border furrows, becomes convex upwards at mid width (tr.), then forms
narrow horizontal or slightly depressed surround, below vertically upturned adaxial edge forming eye
socle. Genal spine long, advanced (PI. 106, fig. 2), moderately wide at base, tapers slowly and curves
inwards towards posterior; subcentral ridge extends posteriorly.

Cephalic doublure same width as borders. Rostral plate crescentic, length (tr.) equal to maximum
width of frontal glabellar lobe, notched abaxially (PI. 106, fig. 6). Doublure of librigena convex ven-
trally, widens and flattens immediately posterior to connective suture (PI. 106, fig. 7); lateral doublure
continuous with posterior doublure around base of genal spine. Ventral side of genal spine flat to
slightly rounded. Occipital ring with narrow, almost vertical doublure.

Hypostome (PI. 106, fig. 6; text-fig. 4) with median body subdivided into large subtriangular anterior
lobe, and smaller subrectangular posterior lobe. Median body surrounded by furrows and narrow
upturned borders; lateral notch towards anterior. Median furrows straight, converge to posterior,
not reaching sagittal line. Posterior section of anterior lobe of median body strongly convex (tr.),
continuous sagittally with posterior lobe, slopes down anteriorly and divides into 2 down-sloping ridges
directed antero-laterally and separated by median concave depression ; abaxially ridges slope steeply
down to prominent anterior wings. Anterior border slopes up from border furrow, trapezoidal in
shape; anterior edge curves slightly forwards along line of hypostomal suture; abaxial section slopes
downwards and postero-laterally at 50° to anterior wing. Anterior border furrow slightly convex
forwards in central portion, slopes down postero-laterally to anterior wings. Anterior lateral border
furrow straight, directed postero-laterally, slopes up from anterior wing to lateral notch; very narrow
anterior lateral border. Median furrow originates at posterior end of anterior lateral furrow. Posterior
lobe of median body strongly convex (tr.), parallel-sided to slightly tapering posteriorly; postero-
lateral corners rounded with prominent bosses; lobe slopes down steeply to lateral border furrows,
more gently to posterior border furrow. Lateral border furrow originates abaxial to median furrow,
deepens to posterior with fossulae near posterior end; lateral border slopes up steeply from furrow,
convex outwards forming shoulder. Posterior border relatively wide (sag.), horizontal (sag. and tr.),
posterior lateral comers rounded. Posterior border furrow distinct abaxially, absent sagittally where
ridge slopes down from posterior lobe across furrow; small fossulae in furrow abaxial to ridge.

Rostral plate attached along hypostomal suture to median section of anterior border of hypostome;
anterior wings free (PI. 106, fig. 6). Hypostome extends posteriorly to level of posterior glabellar furrow
when in situ.

Cranidial ornament of closely spaced granules with pointed tips covers all dorsal surfaces except
furrows (PI. 106, fig. 4). Librigena with long, slightly wrinkled, subparallel terrace lines on posterior
and most of lateral doublure; become less regular, and anastomose adjacent to connective suture;
pattern of terrace lines on rostral plate unknown. Ventral surface of genal spine with longitudinally

EXPLANATION OF PLATE 107

Figs. 1, 2. Emuella polymera gen. et sp. nov. White Point Conglomerate, Cape D’Estaing, Kangaroo
Island, South Australia. 1, FI 6649, x5; internal mould of complete prothorax and incomplete
opisthothorax, showing articulating half rings and pleural spines of most segments. 2, F16651,
x 8; internal mould of left side of macropleural unit and some opisthothoracic segments, showing
long pleural spine and almost completely unmodified posterior pleural band of 5th segment.

Figs. 3-6. Emuella dalgarnoi gen. et sp. nov. Emu Bay Shale, Emu Bay, Kangaroo Island, South
Australia. 3, F16660, x4-5; almost complete internal mould; right connective suture visible,
imprint of hypostome on frontal glabellar lobe. 4, Holotype, FI 6659, x 8 ; almost complete internal
mould; cephalon slightly compressed sagittally, right librigena rotated clockwise, posterior segments
of opisthothorax tilted to anterior. 5, F16661, x5-5; external mould of cranidium, showing
ornament and muscle scars on occipital and glabellar furrows. 6, F16661, x 18; detail of latex
mould of specimen in fig. 5 ; showing posterior border and border furrow, and sutural ridge.

Palaeontology, Vol. 13

PLATE 107

POCOCK, Lower Cambrian Emuellidae

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 531

elongate granules in subparallel rows. Occipital ring bears sagittal, longitudinally elongate tubercle
on posterior margin (PI. 106, figs. 3, 4).

Thorax (PI. 106, figs. 1, 2; PL 107, figs. 1, 2) with prothorax of 6 segments, with macropleural 6th
fused to 5th, and opisthothorax of at least 42 segments (PI. 106, fig. 1). Axis more than half total
thoracic width, almost parallel sided to 4th segment then tapers evenly to posterior; moderately to
gently convex (tr.), steep abaxially, rather flat sagittally ; axial furrows distinct. Pleurae geniculate, very
short (tr.), with pleural spines.

Prothoracic segments 1-4 similar; axial ring narrow (sag.), gently to moderately convex (tr.), rises
from transverse furrow to posterior edge, with small sagittal node on posterior edge ; transverse furrow
with deep apodemal slit abaxially, widens and shallows abaxially (PI. 107, figs. 1, 2); articulating half
ring crescentic, f width axial ring (sag.), central portion flat, horizontal, abaxially slopes down to axial
furrows (PI. 107, figs. 1, 2). Pleura strongly geniculate, fulcrum less than half length (tr.) from axial
furrow. Pleural furrow shallow, wide adaxially, tapers diagonally across pleura, terminates before
pleural spine; slopes up steeply to anterior pleural band, more gently to posterior band. Anterior
pleural band widens to fulcrum, abaxially slopes down and out to form facet; extreme antero-lateral
corner becomes horizontal (PI. 107, fig. 2). Posterior pleural band narrow, convex, even width. An-
terior and posterior pleural bands abaxially produced into short pleural spine notched at base; spine
of 1st segment very short, slightly oblique to posterior situated at mid width (tr.) of pleura (PI. 107,
fig. 1); succeeding segments with spines progressively longer, directed more strongly backwards and
situated more posteriorly (PI. 106, fig. 2; PI. 107, fig. 1). Pleurae progressively lengthen towards
posterior (PI. 106, fig. 2; PI. 107, fig. 2). Doublure extends to base of pleural spine.

Macropleural unit consists of 5th and 6th segments, 5th segment similar to preceding segments;
axial ring rises steeply to posterior, normal width sagittally; pleura wider, longer than 4th; pleural
furrow more oblique, deeper, slopes up almost vertically to anterior, more gently to posterior; anterior
pleural band widens more rapidly, facet larger, and fulcrum more strongly developed (PI. 107, fig. 2);
posterior band even width; pleural spine longer than preceding, near posterior edge of pleura (PI. 107,
figs. 1, 2). Line of fusion of pleurae of 5th and 6th sharp, with posterior pleural band of 5th un-
modified (PI. 107, fig. 2) to indistinct (PI. 106, fig. 1). 6th segment macropleural; axial ring normal,
posterior edge almost transverse; transverse furrow deep with strong apodemal slits abaxially, shallows
sagittally; apodemal slit extends onto pleural field for short distance (PI. 107, fig. 1); interpleural
furrow extends from slit to base of 5th pleural spine; articulating half ring crescentic, | width axial
ring; pleural furrow originates adaxial and slightly posterior to extremity of apodemal slit (PI. 106,
fig. 2), widens slightly and deepens to fulcrum, then tapers abruptly and terminates forming notch (PI.
107, fig. 2); furrow slopes up vertically to anterior, more gently to posterior; ventrally furrow appears
as pronounced ridge at angle to apodeme, directed strongly to posterior; anterior pleural band widens
rapidly abaxial to fulcrum, slopes down and out, extreme antero-lateral comer forms horizontal flap
fused to 5th just adaxial to base of pleural spine (PI. 1 07, fig. 1 , 2) ; interfurrow platform asymmetrically
convex (exsag.), slopes up gently from 5th pleural furrow, horizontal centrally, then drops almost
vertically to 6th pleural furrow; posterior pleural band raised, convex, even width, with distinct notch
at base of macropleural spine, just abaxial to fulcrum (PI. 107, fig. 2); macropleural spine wide, ex-
tremely long, tapers gradually and curves inwards to posterior (PI. 106, fig. 2; PI. 107, fig. 1), convex
to V-shaped anteriorly, flattens to posterior, median ridge extends from posterior edge of interfurrow
platform down spine; spine formed by anterior and posterior pleural bands of 6th segment extends
to level of pygidium. Doublure of macropleural unit extends from antero-lateral corner of 5th, across
base of 5th spine to notch on posterior border of 6th.

Axial ring of 1st opisthothoracic segment similar in size and morphology to normal prothoracic
axial ring (PI. 107, fig. 1); pleura blade shaped, curved to posterior following posterior edge of 6th
segment, fulcrum less than \ length (tr.) from axial furrow; pleural furrow wide, deep, diagonal, tapers
to point just abaxial to notch of 6th; furrow slopes up steeply to anterior, moderately steeply to
posterior; anterior pleural band overlapped by posterior band of 6th when articulated (PI. 107, fig. 1)
posterior pleural band convex, raised; pleural spine relatively long, advanced slightly to parallel curve
of posterior edge of 6th, curves to posterior; formed by anterior and posterior pleural bands. Succeed-
ing segments with pleurae progressively shorter and more transverse (PI. 106, fig. 2); pleural spines
long, directed progressively more to posterior and becoming less advanced; fulcrum migrates adaxially
and pleurae become more strongly geniculate to posterior (PI. 106, fig. 2; PI. 107, fig. 1). At least 42

532

PALAEONTOLOGY, VOLUME 13

segments in opisthothorax; most posterior segments extremely narrow (sag.), lack distinct pleural
furrows (PI. 107, fig. 1). Doublure of pleurae extends to base of pleural spines.

Thoracic ornament of granules similar to those of cephalon, distributed evenly and closely spaced
on dorsal surfaces.

Pygidium unknown.

Emuella dalgarnoi sp. nov.

Plate 107, figs. 3-6; text-fig. 5c.

Derivation of name. After Mr. R. C. Dalgarno, joint discoverer of the Flinders Ranges locality.

Holotype. AUGD F16659 (PI. 107, fig. 4). Specimen shows almost complete thorax and pygidium
articulated to a cephalon, which although slightly distorted, displays most of the diagnostic characters.

Dimensions of holotype. Length of cranidium 3-6 mm.; mid-palpebral width of cranidium 4-8 mm.;
length (sag.) of prothorax 2-3 mm.; over-all sagittal length 11-3 mm.

Material. Approximately 20 internal and external moulds; 3 almost complete specimens, 1 well-
preserved cranidium, remainder very fragmentary.

Occurrence. Upper part of Emu Bay Shale, Emu Bay, Kangaroo Island, South Australia.

Diagnosis. Axial furrows converge strongly from posterior margin to occipital furrow, slightly converg-
ing to almost parallel to anterior glabellar furrow, then shallow around moderately expanded frontal
glabellar lobe. Transglabellar furrows wide, shallow, distinct. Anterior cranidial border furrow curves
to anterior. Palpebral lobe relatively short, posterior end opposite posterior glabellar furrow. Posterior
border widens from axial furrow to fulcrum, directed antero-laterally at 45°; low, narrow ridge extends
from posterior lateral comer of cranidium along line of posterior section of facial suture. Posterior
border furrow with notch abaxial to fulcrum. Anterior section of facial suture diverges anteriorly at
20°. Axial rings of prothorax without nodes. Thorax with 58 segments.

Discussion. E. dalgarnoi is distinguished from E. polymer a by the possession of a longer palpebral lobe
and consequent differences in the posterior section of the facial suture. The structure of the posterior
border and border furrow also differs greatly, with E. dalgarnoi having a distinct notch at the fulcrum
and a low ridge along the line of the posterior section of the facial suture. The anterior section of the
facial suture is noticeably more divergent in E. dalgarnoi than in E. polymera.

Description. Axial furrows converge strongly from posterior margin to occipital furrow, converge
slightly (PI. 107, fig. 4) to almost parallel (PI. 107, fig. 5) to anterior glabellar furrow, then diverge and
curve around moderately expanded frontal glabellar lobe. Frontal glabellar lobe occasionally with
slight anterior median depression resulting in bilobed appearance (PI. 107, fig. 5). Occipital furrow
curves slightly to posterior, moderately deep and wide abaxially, narrows and shallows abruptly
sagittally; muscle spots atadaxial ends of broad portion of furrow (PI. 107, fig. 5). Transglabellar furrows
similar to occipital, posterior furrow curves slightly to posterior, middle transverse, anterior furrow
curves slightly to anterior (PI. 107, fig. 5). Occipital ring approximately half mid-palpebral cranidial
width, constant width, projects very little beyond posterior margin of fixigena. Axial furrow very
slightly impressed, deepest at junction with glabellar furrows, anteriorly reaches anterior border
furrow, with small anterior furrow fossula at junction (PI. 107, fig. 5). Anterior border furrow curves
to anterior, shallowest opposite frontal glabellar lobe. Eye ridge wide, directed to posterior at 30°
to transverse line. Palpebral lobe relatively short, less than £ glabellar length, anterior end opposite
anterior glabellar lobe, posterior end opposite posterior glabellar furrow; slopes up steeply from
palpebral furrow, flat on adaxial side, becomes convex dorsally; slightly convex (exsag.) with highest
point towards posterior end (PI. 107, fig. 3, 5); continuous with eye ridge. Palpebral furrow very wide,
slopes down to posterior, but with small fossula alongside mid point of ridge. Posterior area relatively j
long (exsag.), f width (tr.) occipital ring, with fulcrum opposite posterior end of palpebral lobe (PI. 107,
figs. 3, 5). Posterior border transverse from axial furrow to fulcrum, widens and rises rapidly, anteriorly
drops steeply to border furrow, outer edge concave to posterior (PI. 107, fig. 6); abaxial to fulcrum,
border directed antero-laterally at 45°, width constant; upper surface horizontal, anteriorly drops

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 533

vertically to border furrow. Narrow ridge, below level of posterior border, extends from posterior
lateral corner, along line of posterior section of facial suture (PL 107, figs. 5, 6). Posterior border furrow
widens to fulcrum, then with distinct notch (PI. 107, figs. 5, 6); abaxially slopes down slightly, con-
tinuous with furrow running along base of sutural ridge (PI. 107, fig. 6).

Anterior section of facial suture diverges anteriorly at approximately 20°; rostral plate same width
(tr.) as frontal glabellar lobe, notched laterally (PI. 107, fig. 3). Posterior section of suture relatively
long, diverges to posterior at 45°; section from palpebral ridge to posterior border straight, then
sharply convex abaxially across border (PI. 107, figs. 5, 6).

Cranidial ornament of pointed granules; closely spaced on glabellar lobes, borders, eye lobes;
sparsely distributed on palpebral area of fixigena, anterior lateral sections of cranidium; absent in all
furrows (PI. 107, figs. 5, 6). Paired muscle spots present on abaxial portions of occipital and glabellar
furrows (PI. 107, figs. 5). Genal field of librigena with scattered granules.

Hypostome unknown.

, Thorax with axis approximately half total thoracic width. Maximum number of 52 opisthothoracic
segments observed (PI. 107, fig. 4). Pygidium (PI. 107, fig. 4) minute furrowed disc, without distinct
division into axial and pleural fields; 4 or 5 furrows, transverse sagittally, curving to posterior abaxially;
entire lateral and posterior borders.

Genus balcoracania gen. nov.

Type species. Balcoracania dailyi sp. nov.

Plate 109; text-figs. 5a, b

Derivation of name. After Balcoracana Creek, Flinders Ranges, South Australia.

Diagnosis. Preglabellar field narrow, down-sloping, or absent. Palpebral lobe long,
crescentic. Posterior border with section abaxial to fulcrum directed antero-laterally
at 60°, and strongly depressed. Librigena with genal spine only slightly advanced. Thorax
with axis less than half thoracic width. Pleural furrows terminate at base of pleural
spines. Thorax with 53-61 segments. Fine closely spaced granules on dorsal surfaces.

Discussion. The cephala of Balcoracania differ from those of Emuella in having a longer
palpebral lobe and consequently shorter posterior section of the facial suture; the
abaxial section of the posterior border is much more strongly depressed and not directed
forward as strongly. With regard to the thorax, in Balcoracania the axis is narrower than
in Emuella , and the pleural furrows extend to the base of the spines.

Balcoracania dailyi sp. nov.

Plates 108, 109; text-fig. 5a

Derivation of name. After Dr. B. Daily, who first discovered members of this group.

Holotype. AUGD F16663 (Plate 108, fig. 1). Specimen is only one known with the cephalon articulated
to a reasonably complete thorax.

Dimensions of holotype. Length of cranidium 4-7 mm. ; mid-palpebral width of cranidium 4-4 mm. ;
length of prothorax 3-4 mm.; over-all sagittal length of specimen 13-4 mm.

Material. Approximately 150 internal and external mounds, mostly isolated cranidia, librigenae,
thoracic segments, and several hypostomes.

Occurrence. Upper section of White Point Conglomerate, W. side of Cape D’Estaing, Kangaroo Island,
South Australia.

Diagnosis. Axial furrows converge moderately from posterior margin to middle glabellar furrow,
almost parallel to anterior glabellar furrow, then curve indistinctly around slightly expanded frontal

534

PALAEONTOLOGY, VOLUME 13

glabellar lobe. Preglabellar furrow indistinct, almost transverse; narrow (sag.) downsloping pre-
glabellar field. Prominent anterior border fossulae. Glabellar furrows distinct only laterally.

Description. Cephalon subsemicircular in outline, moderately convex (tr. and sag.). Cranidium 1
moderately convex (tr.). Axial furrows converge moderately from posterior margin to middle glabellar
furrow, almost parallel to anterior glabellar furrow, then curve around very slightly expanded frontal
glabellar lobe. Glabella strongly convex (tr.), weak median ridge extends from posterior to anterior
glabellar furrows; gently convex (sag.), highest at anterior glabellar lobe, slopes down steeply to
preglabellar field, more gently to posterior. Occipital furrow deepest abaxially, curves slightly to posterior
(PI. 108, fig. 2). Transglabellar furrows distinct abaxially, but very shallow and indistinct sagittally
(PI. 108, fig. 5); posterior furrow directed slightly to posterior abaxially, transverse sagittally (PI. 108,
fig. 1); middle furrow transverse; anterior furrow directed slightly to anterior abaxially. Occipital
ring less than half mid-palpebral, cranidial width, maximum width sagittally, posterior edge convex to
posterior; posterior half of ring projects beyond margin of fixigenae (PI. 108, figs. 2, 3). Frontal
glabellar lobe with central portion flat to slightly convex, occasionally with anterior median depression,
giving bilobed appearance. Axial furrow slightly impressed below fixigena from posterior margin to
eye ridge, rises and becomes indistinct over eye ridge, not impressed on sides of frontal lobe, anteriorly
joins anterior border furrow (PI. 108, figs. 2, 3, 5). Deep anterior furrow fossulae at junction of axial and
anterior border furrows (PI. 108, fig. 5). Preglabellar furrow very indistinct, almost transverse; narrow
(sag.) down-sloping preglabellar field (PI. 108, figs. 2, 5). Anterior border medium width, margin con-
vex to anterior; abaxially convex, raised, but flattens and widens opposite frontal glabellar lobe
(PI. 108, fig. 2). Anterior border furrow moderately deep and narrow abaxially, rises abruptly, broadens
and shallows opposite frontal glabellar lobe (PI. 108, figs. 2, 5).

Eye ridge wide, long, directed to posterior at 25° to transverse line. Palpebral lobe wide (tr.), long,
approximately f glabellar length, anterior end opposite anterior glabellar lobe, posterior end opposite
occipital furrow or posterior half of posterior glabellar lobe; lobe slopes up flatly from palpebral
furrow, abaxial edge convex upwards and outwards; rises to posterior with posterior end high above
posterior area (PI. 108, figs. 3, 5); lobe indistinctly separated from eye ridge by change in convexity or
occasionally by indistinct longitudinal furrow. Palpebral furrow wide, deepens and slopes down steeply
to posterior. Palpebral area slightly inflated, slopes down to posterior border furrow. Posterior area short
(exsag.), wider (tr.) than occipital ring, depressed, with fulcrum opposite posterior end of palpebral
lobe (PI. 108, figs. 2, 4); horizontal from axial furrow to fulcrum, slopes down steeply abaxial to ful-
crum. Posterior border directed slightly to posterior from axial furrow to fulcrum, antero-laterally at
50-55° abaxial to fulcrum. Posterior border furrow widens abaxially, deep adjacent to border, shallows
away from it; almost straight-sided, confluent abaxially with palpebral furrow (PI. 108, figs. 3, 4).

Anterior section of facial suture diverges anteriorly at 25°, curves sharply inwards at border furrow,
crosses anterior border diagonally; from point where facial suture cuts anterior cranidial edge, con-
nective sutures cross doublure, sharply concave abaxially (PI. 108, fig. 7). Rostral suture marginal
ventral. Palpebral section of facial suture convex abaxially, diverges at 15° to posterior. Posterior

EXPLANATION OF PLATE 108

Figs. 1-8. Balcoracania dailyi gen. et sp. nov. White Point Conglomerate, Cape D’Estaing, Kangaroo
Island, South Australia. 1, Holotype, FI 6663, x8; external mould of almost complete specimen;
macropleural spines incomplete, posterior segments of opisthothorax and pygidium missing, i
2, FI 6665a, x6; internal mould of cranidium showing preglabellar field, fossulae, posterior area;
both palpebral lobes incomplete. 3, F16665 b, x6; counterpart of specimen in fig. 2; showing
palpebral lobes. 4, FI 6664, x 18; internal mould of portion of cranidium showing posterior area;
mould of the abaxial section of posterior border removed to show that of doublure. 5, F16666,

X 8 ; internal mould of cranidium showing anterior border furrow and eye ridge fossulae. 6, FI 6667,
X9-5; detail of specimen in fig. 8, showing ornament of lateral librigenal doublure. 7, FI 6669,

X 3-5; internal mould of anterior section of librigenal border and doublure, showing the courses of
the connective suture and the anterior section of the facial suture, and the ornament. 8, FI 6667,

X 7 ; internal mould of librigena, with moulds of lateral border and most of posterior border missing,
showing lateral and posterior doublures respectively, and convexity of genal field.

Palaeontology, Vol. 13

PLATE 108

POCOCK, Lower Cambrian Emuellidae

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 535

section relatively short, diverges to posterior at 55°, slopes down steeply to posterior border furrow,
then curves sharply inwards across border (PI. 108, figs. 3, 8). Posterior lateral corner of cranidium
opposite occipital furrow (PI. 108, figs. 2).

Librigena (PI. 108, figs. 6-8) with long genal spine, slightly advanced. Lateral border furrow curves
sharply inwards near base of genal spine, continuous with posterior border furrow; widens, deepens
and slopes down adaxially (PI. 108, fig. 8). Posterior border narrow, convex, high above furrow
adaxially, slopes down abaxially to join lateral border. Genal field slopes up gradually and rather
flatly from border furrow, sharply upturned at adaxial edge to form eye socle; moderately convex
(exsag.), posterior lateral section slopes down steeply (PI. 108, fig. 8).

Cephalic doublure same width as border anteriorly and laterally; posterior fixigenal doublure tapers
rapidly to point just abaxial to fulcrum (PI. 108, fig. 4). Rostral plate equal in length (tr.) to maximum
width of frontal glabellar lobe. Doublure of librigena moderately to strongly convex, widens and
flattens adjacent to connective suture (PI. 108, fig. 6). Lateral and posterior librigenal doublures con-
tinuous (PI. 108, fig. 8). Ventral side of genal spine slightly rounded to flat.

Hypostome (PI. 109, figs. 4, 5) similar in basic morphology to that of E. polymera, but differs or
illustrates more clearly the following features: anterior wings very prominent, depressed; wing pro-
cesses visible in well preserved specimens (PI. 109, fig. 4); position of wing results in anterior lateral
border and furrow being directed postero-laterally (PI. 109, fig. 5) or transversely (PI. 109, fig. 4).
Anterior border wide, steeply upsloping, crossed by narrow line in some specimens (PI. 109, fig. 4);
line symmetrically concave about sagittal line, abaxially intersects anterior edges at extremities of
hypostomal suture. Median furrow with macula at posterior end (PI. 109, fig. 5). Posterior lobe of
median body strongly convex (tr.), parallel sided (PI. 109, fig. 4) or tapers slightly to posterior; posterior
lateral corner rounded, with prominent boss (PI. 109, fig. 5). Lateral border up-sloping with small
shoulder at mid length (PI. 109, fig. 5); border furrow with very deep fossula below shoulder.

Cranidial ornament of fine granules covering all dorsal surfaces; occipital ring with elongate sagittal
node on posterior edge (PI. 108, fig. 3); terrace lines on extreme outer edges of anterior and lateral
borders (PI. 108, fig. 3). Librigena with fine granules on genal field, adaxial portion of lateral border,
and dorsal surface of genal spine (PI. 108, fig. 7); abaxial portion of lateral border with wrinkled
terrace lines, separated by subparallel rows of elongate granules becoming more numerous towards
genal spine (PI. 108, fig. 7); lateral and posterior doublures with long regular terrace lines, become
anastomosing adjacent to connective suture (PI. 108, figs. 6, 8); ventral surface of genal spine with
elongate granules in parallel rows. Rostral plate with terrace lines.

Thoracic axis narrow, less than half thoracic width, pleurae correspondingly long (tr.) (PI. 108, fig. 1).
Axial furrows converge slightly from 1st to 6th segment, rapidly converge to about mid length (sag.)
opisthothorax, then almost parallel to level of pygidium (PI. 108, fig. 1). Axial rings of prothoracic
segments rise only slightly to posterior, without nodes (PI. 108, fig. 1). Pleurae of segments 1-4 equal
length (tr.). Pleural furrow diagonal, tapers abaxial to fulcrum, terminates at base of pleural spine
(PI. 108, fig. 1). Pleural spine formed by anterior pleural band only. Anterior pleural band slopes down
antero-laterally abaxial to fulcrum to form facet; no modification to antero-lateral corner (PI. 109,
figs. 1, 2). Macropleural unit with line of fusion of pleurae generally indistinct, marked by slight furrow
to base of 5th pleural spine (PI. 109, fig. 3) or almost completely effaced (PI. 109, fig. 1); anterior pleural
band of 6th slopes down to join 5th pleural spine without modification (PI. 109, fig. 1). Thorax with
53 segments.

Pygidium minute, furrowed, borders entire.

Discussion. B. dailyi is easily distinguished from the species of Emuella by the possession of a narrow,
down-sloping, preglabellar field, and a long palpebral lobe, the structure of which also differs.

Balcoracania flindersi sp. nov.

Plate 109, figs. 7, 8; text-fig. 5b
Derivation of name. From the Flinders Ranges, South Australia.

Holotype. AUGD F16683 (PI. 109, fig. 7). Specimen with articulated cephalon and thorax.

Dimensions of holotype. Length of cranidium 3-7 mm.; mid-palpebral width of cranidium 4-5 mm.;
length of prothorax 2-7 mm.; over-all sagittal length 10-1 mm.

536

PALAEONTOLOGY, VOLUME 13

Material. Approximately 280 replaced tests, internal and external moulds; exoskeletons mainly arti-
culated, but some disarticulated elements.

Occurrence. Lower part of the Billy Creek Formation, Balcoracana Creek, Flinders Ranges, South
Australia.

Diagnosis. Axial furrows converge evenly from posterior margin to anterior glabellar furrow, then
curve out and around markedly expanded frontal glabellar lobe. No preglabellar field or anterior
border fossulae. Transglabellar furrows distinct, deep.

Description. Axial furrows converge evenly from posterior margin to anterior glabellar furrow, then
curve out and around markedly expanded frontal glabellar lobe. Occipital furrow, transglabellar
furrows deep, distinct ; posterior furrow convex to posterior, middle transverse, anterior furrow convex
to anterior (PI. 109, figs. 7, 8). Occipital ring less than half mid-palpebral cranidial width. Frontal
glabellar lobe markedly expanded, rounded laterally and anteriorly; reaches anterior border furrow;
no preglabellar field; anterior border and border furrow unmodified; no anterior furrow fossulae
(PI. 109, figs. 7, 8). Palpebral lobe long (exsag.), wide (tr.), crescentic; anterior and opposite anterior
glabellar lobe, posterior and opposite occipital furrow. Palpebral area usually highly inflated, slopes
down steeply to posterior.

Thorax (PI. 109, figs. 6, 8) with long opisthothorax; maximum number of 61 thoracic segments
observed.

Discussion. B. flindersi is primarily distinguished from B. dailyi by the morphology of the anterior
part of the cranidium, by the degree of expansion of the frontal glabellar lobe, absence of preglabellar
field, and anterior furrow fossulae. It is clearly distinguished from the species of Emuella by the length
of the palpebral lobe and the structure of the posterior area of the fixigena, especially the strong de-
pression of the section abaxial to the fulcrum.

A comparison of the morphology of the adults of the four species is presented in
Table 1, and of the adult cephala in text -fig. 5.

Intraspecific variation. In all collections some sort of deformation has taken place, and
this factor must be considered in an evaluation of the intrinsic variation of the species.
The range of morphological variation is approximately the same for the various charac-
ters or groups of characters in each of the species. The following groups exhibit a cor-
related variation :

EXPLANATION OF PLATE 109

Figs. 1-6. Balcoracania dailyi gen. et sp. nov. White Point Conglomerate, Cape D’Estaing, Kangaroo
Island, South Australia. 1, FI 6679, xlO; internal mould of left side of macropleural unit and
1st opisthothoracic segment, showing an articulating facet and pleural spine of 5th segment, and
extension of apodemal slit onto interfurrow platform along line of fusion of pleurae. 2, FI 6678,
x 9-5; external mould of portion of thorax showing ornament. 3, F16680, x 10; internal mould of
left side of macropleural unit; extent of doublure shown by gap surrounding mould from base of
5th spine to notch on posterior border of 6th segment. 4, F16673, x 8 ; internal mould of hypostome
and detached rostral plate; hypostome with maculae and prominent postero-lateral bosses; rostral
plate with notched abaxial ends. 5, F16671, x 10; internal mould of hypostome showing anterior
line, depressed anterior wings, and deep fossulae in lateral borders. 6, FI 6676, x5; portion of
external mould of macropleural unit and 1st opisthothoracic segment, showing articulating half
rings, prominent junction of apodeme and pleural furrow, and overlap of posterior pleural band of
6th over anterior pleural band of opisthothoracic segment.

Figs. 7, 8. Balcoracania flindersi gen. et sp. nov. 7, Holotype, F16683, x 10; internal mould of cephalon
and incomplete thorax; cranidium with imprint of hypostome and rostral plate. 8, F16655, x5;
several almost complete specimens on bedding plane.

Palaeontology, Vol. 13

PLATE 109

POCOCK, Lower Cambrian Emuellidae

537

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES

(a) Convexity of the palpebral area and the degree of impression of the surrounding
axial and palpebral furrows : the palpebral area varies from almost flat (tr.) to highly
convex; in the former case the furrows are only slightly impressed or are represented
merely by a change in slope; in the latter the surrounding furrows are deeply impressed.
However it must be remembered that in B. flindersi high convexity of the palpebral
area appears to represent the norm.

table 1. Comparison of aspects of the morphology of members of the Emuellidea. The limits of
variation for these characters are given in the text.

(b) Junction of the eye ridge and frontal glabellar lobe : this appears to be the most
variable of all characters and the most difficult to distinguish between genuine and
spurious variation. The eye ridge may be almost completely separated from the frontal
lobe by the axial furrow, or join it without significant interruption; this appears largely
independent of the degree of impression of the axial furrow elsewhere. However, the
eye ridge is never completely separated from the glabella.

( c ) Frontal glabellar lobe, preglabellar and anterior border furrow: the outline and
convexity of the frontal glabellar lobe varies considerably in B. dailyi, and to a lesser
extent in the other species. The outline varies from slightly rounded laterally, with an
almost straight anterior edge, to almost circular, being correlated respectively to high
and low convexity (sag. and tr.). An important variant is a slightly bilobed outline,
resulting from a shallow anterior median depression. In all except B. flindersi, forms
with high convexity of the frontal lobe have the section of the anterior border furrow
opposite the lobe raised with respect to its abaxial sections, and thus have more distinct

538 PALAEONTOLOGY, VOLUME 13

text-fig. 6. Scatter diagrams and ‘best fit’ lines for adults of the Emuel-
lidae. A1; the total cranidial length plotted against (1) D5, the occipital
post-palpebral length; (2) C, the palpebral length. All dimensions given
in micrometer divisions where 1 -00 mm. = 32 micrometer divisions. The
symbol • denotes specimens of B. dailyi, x specimens of B. flindersi,

O specimens of E. polymera, and A those of E. dalgarnoi.

border fossulae than those forms with low convexity. In B. dailyi high convexity of the
lobe is also associated with a slightly longer (sag.) preglabellar field.

(d) The length and level of the palpebral lobe, and morphology of the posterior limb:
although the differences in these morphological characteristics form the primary basis
for discrimination of the genera and species, each species has a considerable and occa-
sionally overlapping range.

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES

539

Quantitative analysis. Limited analysis was undertaken, primarily to provide a quantita-
tive description of the species and additionally to supplement the purely qualitative
discrimination of the genera and species.

Qualitative work suggests that the length of the palpebral lobe, and in particular the
position of its posterior end, are important for the taxonomic discrimination of the
genera and species, although a considerable range of intraspecific variation is ob-
served. Accordingly these characters were selected for analysis, the occipital post-
palpebral length (D5) and the palpebral length (C) being plotted against the cranidial
length (Aj) and ‘best fit’ lines fitted (text-fig. 6) ; the values for the dimensions are given
in the Appendix, and the equations of the ‘best fit’ lines in Table 2.

table 2. The equations of the ‘best fit’ lines, calculated by the method (Bartlett’s method) given by
Simpson, Roe, and Lewontin (1960, p. 234). Ax is the total cranidial length, C is the palpebral length,
and D5 is the occipital post-palpebral length.

Ai-Ds Ai-C

E. polymera

D5 =

-0-4+0-34A!

C =

0-4+019A!

E. dalgarnoi

d5 =

-1-8+0-35A!

c =

1-3+0-23A!

B. flindersi

d5 =

0-3+0-26A!

c =

lT+0-22Ax

B. dailyi

d5 =

-0-7+0-26A!

c =

0-7+0-27A!

The plot of occipital post-palpebral length against cranidial length indicates that the
two genera can be clearly distinguished quantitatively on the basis of the position of
the posterior end of the palpebral lobe. However the parameters obtained for E. dalgarnoi
are somewhat anomalous, in that the gradient of the ‘best fit’ line is not significantly
different from that of E. polymera. The small number of specimens in the sample of
E. dalgarnoi may be a factor affecting the values of the parameters. The plot of palpebral
length against cranidial length, however, shows that the two species can be distinguished
quantitatively on the basis of their palpebral lengths. The anomalous values for Balcora-
cania flindersi suggest that the anterior end of the palpebral lobe is lower than in the
other species, and this can be verified both qualitatively and quantitatively.

ONTOGENY

Larval stages are known for the species B. flindersi, B. dailyi, and E. polymera. B.
flindersi is represented by over 150 specimens, and the major features of the ontogeny
were elucidated by a study of this material; B. dailyi is adequately represented by 30
specimens, but only a few specimens of E. polymera are known. The order of description
of the ontogenies thus differs from that of the adults.

The methods and procedures adopted vary slightly depending upon the size and nature
of the sample, but are basically similar to those described below.

All specimens were prepared, measured, photographed, and described individually.
A reconstruction of an early meraspid cranidium was made, and compared with a
holaspid cranidium on a modified D’Arcy Thomson diagram (text-fig. 7), using the
techniques described by Palmer (1957, p. 106). The line of least ‘distortion’ is the line
of bilateral symmetry, and specifically the length of the glabella increases at a rate most
nearly equal to that of absolute size. However the length of the glabella is very difficult to
measure accurately on extremely small specimens, and the cranidial length (Aj) is used

540

PALAEONTOLOGY, VOLUME 13

instead as the standard dimension. The use of this dimension involves some error, as
the anterior border appears and develops during ontogeny; however, it is considered
that the practical advantage of accurate measurement offsets the theoretical disadvan-
tages. The morphology of each specimen is then tabulated against cranidial length (in
ascending order). Examination of the table and the D’Arcy Thompson grid shows that
several characters underwent progressive change with increase in cranidial length; of
these, three were selected, the anterior border and border furrow, the palpebral lobe,

text-fig. 7. Proportional change in dorsal cephalic features of B. flindersi during development.
Left, Cranidium of Stage II; Right, Holaspid cranidium.

and the anterior section of the facial suture. On the basis qf the changes, subclasses
were distinguished for each of the three characters, and the size ranges of each subclass
noted. Considerable overlap in the range of the subclasses existed, as the characters
change at different rates; however, it was found that the sets of data could be combined
to give a number of stages of cranidial development, with an acceptable maximum over-
lap of the cranidial lengths (Tables 3, 6).

The development of the meraspid thorax is incompletely known, and although re-
lated, where possible, to stages of cranidial development, is described separately (Tables
4,7).

The hypostomes present range in length upwards from 0-50 mm., and it is evident
that at least the specimens in the lower part of the range have been separated from
larval cranidia. Two problems arise: to match the hypostomes with the equivalent
cranidia and thus to stages of cranidial development, and to determine an upper size
limit, below which the hypostomes may be considered as ‘larval’.

Examination of adult specimens of cephala with hypostomes ‘in situ ’ or close to that
position, shows that the posterior edge of the hypostome reaches approximately the
level of the posterior glabellar furrow. The sagittal length of the hypostome is thus
slightly less than f of the cranidial length (Aj), and accordingly an upper limit for the
length of larval hypostomes can be fixed. It is unwise, however, to apply this factor
to smaller specimens, as it is well known (Whittington 1957, 1959) that the hypostome
is proportionately larger in the larval stages than in the adult in some cases. It is there-
fore necessary to find some dimension of the hypostome which can justifiably be
assumed to bear a constant relationship to some dimension of the cranidium, over the

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 541

complete ontogeny. In the adult, the hypostome is attached to the posterior edge of the
rostral plate, along the line of the hypostomal suture. Thus the length of the posterior
edge of the rostal plate is equal to that of the anterior edge of the hypostome, excluding
the anterior wings, which are free (text-fig. 4). As it can be assumed that the functional
relationship between the rostral plate and hypostome does not change, the relationship
between the two dimensions is fixed throughout ontogeny.

The length of the anterior edge of the rostral plate can be measured directly from
the cranidium in most cases, as there is a slight change in curvature at the point where the
facial suture intersects the anterior edge of the border, and it is from this point that the
connective suture originates. The lengths of the anterior and posterior edges of the rostral
plate can be taken as identical, within the limits of mensurational error. The length of
the articulating section of the anterior edge of the hypostome (H4) can be measured
directly in most cases.

On the above basis, the hypostomes may be matched with a range of cranidia, and
thus to a stage of cranidial development (Tables 5, 8).

The resulting descriptions and tabulations are subjective to some extent, owing to
(a) the gradational nature of the morphological changes; ( b ) the size overlap between
morphological subclasses ; (c) overlap in size between meraspid degrees ; and (d) method
of allotting hypostomes to cranidial stages. However it is considered that, in general,
an accurate representation of the ontogeny results.

Ontogeny of Balcoracania flindersi

{a) Development of the cephalon (Table 3)

Stage I: Cranidial lengths 0-38-0-49 mm. (includes the protopygidium in this stage): protaspides
(text-fig. 8 1). Only 3 specimens were found, smaller than the size range for meraspides of degree 0, and
only 1 of these was well enough preserved to verify the presence of the protopygidium. However the
position of the specimens prevented adequate photography. The specimen is subelliptical in outline, and
almost hemispherical, being slightly flat sagittally. It is divided into a large cephalon (or cranidium)
and a narrow (sag.) protopygidium by a transverse line. The axis is narrow, flat to slightly depressed,
and is defined for the posterior f of its length by distinct parallel furrows, and for the remainder by
indistinct furrows diverging at 45°. The axis is divided into 5 rings by indistinct transverse furrows,
the most anterior furrow being at the point of divergence of the axial furrows. Cheek furrows are
present, but indistinct.

The protopygidium is narrow (sag.), approximately J the total length (sag.). The axis tapers pos-
teriorly, but is indistinct.

Stage II: Cranidial lengths 0-50-0-64 mm.; meraspid degrees 0-1 (text-fig. 8 n; PI. 110, figs. 2-4).
Numerous specimens falling within this size range have distinct occipital rings and posterior margins,
showing them to be meraspid cranidia. Two specimens with attached transitory pygidia, and 1 meraspid
degree 1 , are included within this range.

The cranidium is subcircular in outline, sagittally subhorizontal, margins steeply down-sloping.
The glabella is moderately convex (tr.), J the maximum cranidial width; the glabellar and occipital
furrows are all distinct and transverse, with an additional indistinct furrow, aligned with the anterior
edge of the eye ridge, partially subdividing the frontal lobe (pre-anterior furrow). The axial furrows
are parallel from the posterior margin to the anterior furrow or slightly pinched in at the latter, then
diverge at about 45° to the anterior edge. The frontal glabellar lobe is thus expanded to the anterior
(although partially subdivided). The eye ridge is distinct, directed slightly to the posterior, and steeply
down-sloping abaxially. The palpebral lobe is very short, depressed below the level of the cheek and
downsloping abaxially; no distinct palpebral furrow; the posterior end of the lobe is opposite the
anterior glabellar lobe or middle glabellar furrow. The cheek has a narrow (exsag.) subhorizontal

542

PALAEONTOLOGY, VOLUME 13

portion then slopes steeply downwards abaxially and posteriorly. The cheek furrows are short and
parallel the eye ridge (PI. 1 10, fig. 2). The posterior border is geniculate, with a short transverse sec-
tion, and a longer section directed antero-laterally at 25-30°, almost to the base of the palpebral lobe.
The anterior sections of the facial sutures converge strongly, intersecting the anterior edge at the same
places as the axial furrows, the posterior sections are extremely short and diverge at about 30°.

table 3. Larval development of B. flindersi based upon stages of development of the cranidium.

CHARACTER

STAGE /

STAGE //

STAGE III

STAGE IV

STAGE V

STAGE Via

STAGE Vlb

STAGE Vic

FRONTAL

GLABELLAR LOBE

SUB -

TRIANGULAR

SIDES ROUNDED
SLIGHTLY

SIDES ROUNDED

ROUNDED

UNCHANGED

UNCHANGED

UNCHANGED

UNCHANGED

ANTERIOR BORDER

ABSENT

ABSENT

ABSENT OR
MINUTE, D0WN-
SL0PING STEEPLY

NARROW,

DOWNSLOPING

CONVEX ABAXIAL-
LY, HORIZONTAL
SAGITTALLY

UNCHANGED

UNCHANGED OR
NARROW, CONVEX,
RAISED.

CONVEX, RAISED,
NARROW TO
MEDIUM

ANTERIOR BORDER
FURROW

ABSENT

ABSENT

ABSENT

ABSENT

DISTINCT ONLY
ABAXIALLY

UNCHANGED

UNCHANGED,
OR EVEN
DEPTH

EVEN DEPTH

PALPEBRAL LOBE

INDISTINCT,

DEPRESSED

DOWNSLOPING
ABAXIALLY,
BELOW CHEEK
LEVEL; 0 -17
GLAB. LENGTH

HORIZONTAL,
BELOW CHEEK
LEVEL; 0-2
GLABELLAR
LENGTH.

CONVEX, BELOW
CHEEK LEVEL;

O' 23 GLABELLAR
LENGTH

CONVEX,

SLIGHTLY BELOW
CHEEK LEVEL
0-27 GLABELLAR
LENGTH

CONVEX,
SAME LEVEL
AS CHEEK;
0-30 GLABEL
LAR LENGTH

UNCHANGED,
0 • 33

GLABELLAR

LENGTH

UNCHANGED

PALPE8RAL FURROW

ABSENT

ABSENT

INDISTINCT

DISTINCT

UNCHANGED

IMPRESSED

UNCHANGED

UNCHANGED

POSTERIOR END
OF PALPEBRAL
LOBE

OPPOSITE ANT.

GLABELLAR

FURROW

OPPOSITE ANT.
LOBE - POST.
FURROW

OPPOSITE
MIDDLE FURROW -
MIDDLE LOBE

OPPOSITE
MIDDLE LOBE-
POST. FURROW

OPPOSITE
POST. FURROW

UNCHANGED

OPPOSITE
POST. FURROW
- POST. LOBE

OPPOSITE POST.
LOBE- OCCIPITAL
FURROW

POSTERIOR BORDER
(ABAXIAL TO FULCRUM)

ABSENT

DIVERGES AT
25 - 30°

DIVERG|S AT
30 - 35°

DIVERGES AT
35- 40°

DIVERGES AT
40- 45°

UNCHANGED

DIVERGES AT
45-50°

DIVERGES AT
50-55°

POSTERIOR BORDER
FURROW

ABSENT

INDISTINCT

DISTINCT,

STRONGLY

GENICULATE

MODERATELY

GENICULATE

WEAKLY
GENICULATE
WIDENS ABAXIALLY

UNCHANGED

STRAIGHT,

WIDENS

ABAXIALLY

UNCHANGED

GENAL SPINE

-

-

EXTREMELY

SMALL

EXTENDS TO
LEVEL OF 1 ST,
OR 2ND SEGMENT

-

-

-

EXTENDS TO
LEVEL OF 5TH.
SEGMENT

ANTERIOR SECTION
OF FACIAL
SUTURE

’

CONVERGES

CONVERGES

CONVERGES

SLIGHTLY

SAGITTAL TO
ANTERIOR BORDER
FURROW

UNCHANGED
OF DIVERGES

DIVERGES

SLIGHTLY

DIVERGES

MODERATELY

LENGTH OF
CRANIDIUM (Ai)

0-38 - 0 49mm.
(12- 15 -5 mic.
divs.)

0 50— 0- 64mm.
(16 — 20-5 mic.
divs.)

0 65-0-79mm.
(21- 25- 5mic.
divs.)

0-80- 0 94mm.
(26- 30 -5 mic.

0 95 - 1 24 mm.
(31 - 39 5mic

l-25-l-36mm.

(40-43-5mic

1 37— I- 49mm.
(44- 47-5mic
divs.)

1 • 50 — 3- 16mm.
(48- 100 mic.

MERASPID DEGREE

(PR0TASPIS)

0-1

(1) -2 -3

(3) - 4-6

7- II - ?

?

•?

16? — 18 - 53 -(60)

Stage III : Cranidial lengths 0-65-0-79 mm.; meraspid degrees (1), 2 and 3 (text-fig. 8 m; PI. 110,
figs. 5, 6). The axial furrows are deeply impressed, from the posterior edge to the anterior glabellar
furrow, faint over the eye ridges, then indistinct on the sides of the frontal lobe. The frontal lobe is
rounded laterally, and either reaches the anterior edge, or an extremely narrow, down-sloping anterior
border. In the latter case the border and the lobe are separated by a distinct change in slope. The
frontal lobe is subdivided by a pre-anterior furrow. The palpebral lobe is short, subhorizontal (tr.
and sag.), depressed below cheek level, and with an indistinct palpebral furrow; the posterior end of
the lobe is opposite the middle glabellar furrow or just below it. The cheek furrows parallel the eye
ridges. The posterior border is horizontal, and separated from the cheek by a distinct border furrow;
the border is again strongly geniculate, with the abaxial section directed antero-laterally at 30-35°. The
anterior sections of the facial sutures converge strongly, and the posterior sections are very short and
diverge at 45°.

The librigena has a small genal spine, which is directed almost sagittally to level of the occipital
furrow.

Stage IV: Cranidial lengths 0-80-0-93 mm. ; meraspid degrees (3), 4, 6 (text-fig. 8 iv; PI. 1 10, figs. 7-9).
Axial furrows converge slightly to anterior glabellar furrow, then curve out and around an expanded
frontal lobe which is separated from the anterior edge by a narrow down-sloping anterior border.
The palpebral lobe is convex (tr. and exsag.), below the level of the cheek, and separated from it by

543

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES

a distinct palpebral furrow. The posterior end of the lobe is opposite the middle glabellar lobe or
posterior furrow. The cheek is wider and flatter than in previous stages; cheek furrows parallel the
eye ridge. The posterior border is convex, geniculate, with the abaxial section directed antero-laterally
at 35-40°. The librigenal spine reaches the level of the 1st or 2nd thoracic segment.

text-fig. 8. Development of B. flinders i. Roman numerals indicate the stage of
cranidial development as described in the text. I, protaspis; II, meraspis, degree 0;
III, meraspis, degree 2 ; IV, meraspis degree 6 ; V, meraspis, degree 10 ; VIZ>, meraspis,
degree 15. Magnification constant at approximately x50.

Stage V: Cranidial lengths 0-94-1-24 mm.; meraspid degrees 7-11 (text-fig. 8 v; PI. 110, figs. 10, 11).
The frontal glabellar lobe is rounded, and slopes down to a distinct anterior border furrow. The an-
terior border is convex abaxially, but narrows and flattens opposite the frontal lobe. The axial and
palpebral furrows are deeply impressed and the cheek sometimes shows traces of furrows. One ex-
ceptionally well-preserved specimen shows the anterior cheek furrow extending from the middle
glabellar furrow to the posterior end of the palpebral lobe, and retains traces of the pre-anterior
glabellar furrow. The palpebral lobe is convex (tr. and exsag.), slightly below the level of the cheek,
and with its posterior end opposite the posterior glabellar furrow or posterior lobe. The posterior
border furrow is deep, weakly geniculate, widens abaxially and becomes confluent with the palpebral
furrow. The abaxial section of the posterior border is at 40-45°. The anterior section of the facial
suture is directed sagittally to the border furrow, then crosses the border diagonally to cut the anterior

Nn

C 7719

544 PALAEONTOLOGY, VOLUME 13

edge opposite the sides of the frontal lobe; the posterior sections are short, diverging, and slightly
convex abaxially.

The librigena has a distinct lateral and posterior border and furrow. The genal spine extends to the
level of the 4th thoracic segment.

Stage Via : Cranidial lengths 1-25-1 -36 mm.; includes at least meraspid degree 12 (PI. 110, fig. 12).
The length of the frontal glabellar lobe is \ of the total glabellar length. The palpebral lobe is relatively
long, on approximately the same level as the cheek, and with its posterior end opposite the posterior
glabellar furrow and lobe. The abaxial section of the posterior border is at 40-45°. The anterior section
of the facial suture is directed sagittally or diverges slightly to the anterior border furrow.

Stage VIb: Cranidial lengths 1-37-1-50 mm. (text-fig. 8 vi b\ PI. 110, fig. 13). The anterior border is
unchanged or becomes convex, with the same width abaxially and sagittally. The posterior end of the
palpebral lobe is opposite the posterior glabellar furrow or lobe. The abaxial section of the posterior
border is at 45-50°. The anterior section of the facial suture diverges slightly to the anterior border
furrow.

Stage IVc : Cranidial lengths 1-50-3-16 mm.; includes meraspides of degrees 18-55 (PI. 116, figs. 14,
15). The cephala of this group have basically attained the holaspid morphology. With increase in size
the anterior border continues to widen and the length of the frontal glabellar lobe decreases in pro-
portion to the total glabellar length. The posterior end of the palpebral lobe is opposite the posterior
lobe or occipital furrow, the abaxial section of the border is at 50-55°, and the anterior sections of the
facial sutures are divergent.

(b) Development of the thorax (Table 4)

Degree 0 (2 specimens). The transitory pygidium is triangular in shape, with its maximum width
(tr.) at the anterior edge which articulates with the posterior edge of the cranidium between the
fulcral points. The axial furrows are shallow and taper to a point on the posterior edge. The pleural
field slopes down strongly abaxially, and there is a continuous lateral and posterior margin. The axis
is subdivided into 3 or 4 rings in one specimen, and 3 in the other ; in both specimens the anterior part
of the pleural field is indistinctly furrowed.

Degrees 1-4. The prothoracic segments released from the transitory pygidium possess normal axial
and articulating half rings, and geniculate pleurae. At degree 1 , the pleural furrows are poorly developed

EXPLANATION OF PLATE 110

Figs. 1-15. Balcoracania flindersi gen. et sp. nov. 1, F16700, xl7; larval hypostome, matched with
cranidial. Stage IV. 2, F16687, xl5; cranidium. Stage II, showing cheek furrows. 3, F16688,
x 15; meraspis, degree 0, Stage II. 4,F16689, x 1 5 ; cranidium, Stage II, showing distinct palpebral
lobes. 5,F16690,x 15; cranidium. Stage III, showing distinct cheek furrows. 6,F16691, x 15;meraspis,
degree 3, Stage III. 7, F16692, x 15; cranidium, Stage IV, showing narrow down-sloping anterior
border. 8, F16693, xl5; crushed and asymmetrically distorted meraspis, degree 6, Stage IV.
9, FI 6694, xl5; meraspis, degree 6, Stage IV. 10, FI 6695, xl5; cranidium, stage V, showing
distinct cheek furrows. 11, FI 6696, x 15; incomplete meraspis, degree 11, Stage V. 12, FI 6697,
xl5; cranidium, Stage Via, showing pre-anterior lateral glabellar furrows. 13, F16698, xl5;
cranidium. Stage VI b. 14, F16699, x 15; meraspis, degree 18, Stage Vic; cephalon partly exfoliated,
librigenae slightly displaced, portion of opisthothorax and transitory pygidium missing. 15,
FI 6682, x 15; holaspid cranidium, partly exfoliated.

Figs. 16-18. Emuella polymera gen. et sp. nov. 16, F16701, xl5; cranidium. 17, F16702, xl5;
cranidium showing minute anterior border, anterior position of palpebral lobes. 18, x 3; portion
of bedding plane showing F16701-2 in relation to a holaspid cephalon.

Figs. 19-22. Balcoracania dailyi gen. et sp. nov. 19, F16703, X 15; cranidium, Stage I. 20, F16704;
cranidium, Stage II, showing posterior position of palpebral lobe. 21, FI 6705, x 15; incomplete
cranidium, Stage III, showing distinct development of anterior border and border furrow. 22,
F16706, X 15; meraspis, degree 10, Stage IV, showing transitory pygidium with entire margins.

Palaeontology , Vol. 13

PLATE 110

POCOCK, Lower Cambrian Emuellidae

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES

545

and pleural spines have not been observed; at degrees 2-4, the furrows become more distinct and
spines develop. The axial furrows converge evenly to the posterior and are aligned with those of the
pygidium; the pleurae are progressively shorter (tr.) to the posterior, and their abaxial ends are
aligned with the lateral borders of the pygidium.

The morphology of the transitory pygidium is basically as for degree 0, with very little increase in
absolute size. The number of rings on the axis varies from 3 to 4, and the pleural field shows the
pleural and interpleural furrows of the two most anterior segments; posteriorly the furrows are in-
distinct.

table 4. Development of the meraspid thorax and transitory pygidium in B.flindersi. Ax, total cranidial
length of the articulated cephalon is given in micrometer divisions where 1-00 mm. = 32 divisions.

Meraspid degree

Cranidial length

(A)

Cephalic stage

Segments in
transitory pygidium

0

17

II

3

0

17

II

3-4

1

20

II

4

1

21

III

5

2

23

III

2-3

3

24

III

3-4

3

25

III

2-3

3

26

IV

3

3

26

IV

3

4

26

IV

3

4

27

IV

1

6

28

IV

3

6

29

IV

1-2

6

29

IV

6

6

30

IV

1-2

6

30

IV

4

10

34

V

2

11

38

V

3

18

67

Vic

3

18

72

Vic

3-4

19

72

Vic

3

27

80

Vic

3

53

100

Vic

3-4

Degree 6 (4 specimens). The prothorax has already attained the characteristic adult morphology;
the 5th segment is fused to the macropleural 6th, with the line of fusion visible on the interfurrow
platform. The macropleural spine extends to the posterior edge of the transitory pygidium, curving
inwards slightly at the posterior end. The axis tapers strongly but evenly to the posterior. The pleurae
shorten progressively from the 1st to the 5th segment. The anterior edge of the transitory pygidium
articulates with the posterior edge of the 6th between the notches on the posterior border.

Degrees 10-55. The prothorax is as described for degree 6; the opisthothoracic segments are normal.
The pleural furrows are generally more distinct towards the anterior, and in the higher degrees do not
occur on most of the posterior opisthothoracic segments and the transitory pygidium. The transitory
pygidium may have up to 6 distinct axial rings, but generally only the 2 most anterior segments are
distinct on the pleural field. The absolute size of the pygidium increases little.

(c) Development of the hypostome (Table 5)

The hypostome attains the adult morphology when its length (sag.) is approximately 1-45 mm.; from
this point onwards the only change is an increase in size. Independent confirmation is given by the fact
that the length of the cranidium matched with a hypostome of this size falls within the size range of

546

PALAEONTOLOGY, VOLUME 13

Stage Vic, the stage in which the cranidium attains the holaspid condition. Changes during ontogeny
primarily affect two groups of characters: ( a ) the size and position of the anterior wings; the position
is expressed by the ratio of lengths (sag.) from the anterior edge respectively to the level of the anterior
wings and to the level of the lateral notch; ( b ) the shape of the posterior lobe of the median body.

The smallest hypostome is matched with cranidia in the upper portion of the size range of Stage III
and the lower portion of Stage IV. The posterior lobe of the median body is triangular with the bound-
ing lateral furrows converging to the posterior from the lateral notch. The anterior wings are very small,
only slightly depressed, and the ratio of lengths is 1:2, i.e. the wings are towards the anterior end.
With increase in size the posterior lobe becomes subrectangular, with a transverse posterior border
furrow developing; the anterior wings become more pronounced and depressed, and move progres-
sively to the posterior, the ratio changing to 2:3 (PI. 110, fig. 1).

table 5. Development of the hypostome in B. flindersi. Hi is the sagittal length of the hypostome,
H4 is the transverse length of the hypostomal suture, R4 is the transverse length of the rostral suture
and A4 is the total cranidial length; all measurements are expressed in micrometer divisions where
1 -00 mm. = 32 divisions. H4, measured on the hypostome, is approximately equal to Rx, which is
measured on the cephalon; thus for any given value of H4, a range of values for A4 can be obtained.

The hypostome can then be matched to the equivalent stage (or stages).

Hi

H (= Rx)

A1 of equivalent
cephalon

Cephalic stage

18

15

24-28

III, IV

19

16

28-32

IV, V

26

18

30-34

IV, V

27

18

30-34

IV, V

29

20

34-36

V

32

21

34-38

V

32

22

40-43

Via

35

24

42-43

Via

38

27

45-46

VI h

38

28

45-46

VI b

42

30

47-57

Vic

46

32

55-67

Vic

Ontogeny of Balcoracania dailyi

(a) Development of the cephalon (Table 6; text-fig. 9)

Stage I: Cranidial lengths 0-50-0-70 mm.; all specimens appear to be meraspid cranidia (text-fig.
9 i; PI. 110, fig. 19).

The cranidium is subcircular in outline with steeply down-sloping margins. The glabella is moderately
convex (tr.) and narrow; the glabellar furrows are distinct and transverse. The axial furrows are deep
posteriorly, subparallel but pinched in sharply at the anterior glabellar furrow; anteriorly the furrows
are faint, diverging around an expanded frontal glabellar lobe. The frontal lobe reaches the anterior
edge, and is partially subdivided by short pre-anterior glabellar furrows. The eye ridge is distinct,
directly slightly to the posterior, and slopes steeply downwards abaxially. The palpebral lobe is short,
depressed below the cheek level, horizontal (sag. and tr.), and is only indistinctly defined by a palpebral
furrow; the posterior end of the lobe is opposite the middle glabellar furrow or lobe. The cheek is
narrow, steeply down-sloping abaxially and posteriorly, and is subdivided by cheek furrows parallel
to the eye ridge. The posterior border is narrow, horizontal or slightly downsloping, and separated from
the cheek only by a change in slope. The border is geniculate with short transverse section and a longer
section directed antero-laterally at 25-30°. The anterior sections of the facial suture converge strongly
to intersect the anterior edge at its junctions with the axial furrows. The posterior sections are ex-
tremely short, and curved.

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 547

table 6. Larval development of B. dailyi based upon stages of development of the cranidium.

text-fig. 9. Development of B. dailyi. Numerals indicate stages of cranidial development as described
in the text. I, II, and III, meraspid cranidia; IV, meraspis, degree 6. Magnification constant at ap-
proximately x50.

Stage II: Cranidial lengths 0-72-0-93 mm. (text-fig. 9 n; PI. 110, fig. 20). The axial furrows converge
evenly from the posterior edge to the anterior glabellar furrow, then diverge around an expanded and
rounded frontal glabellar lobe. The frontal lobe is separated from the anterior edge by a narrow down-
sloping anterior border. The palpebral lobe is convex (tr. and exsag.), below the cheek level, but dis-
tinctly defined by a palpebral furrow; the lobe is relatively long (J glabellar length) with the posterior
edge opposite the posterior glabellar furrow or just anterior to it. The cheek is wider (tr.) than in
Stage I, less steeply down-sloping; the cheek furrows are indistinct. The posterior border is narrow,
convex, and the border furrow is distinct. The abaxial portion of the border is directed antero-laterally

548

PALAEONTOLOGY, VOLUME 13

at 35-40°. The anterior sections of the facial suture are directed sagittally for a short distance before
curving inwards; the posterior sections are short, diverging and slightly convex abaxially.

Stage III : Cranidial lengths 0-94-1 T4 mm. (text-fig. 9 m; PI. 110, fig. 21). The frontal glabellar lobe
is rounded laterally, and slopes down to an anterior border furrow. The anterior border is narrow,
slightly raised and convex abaxially, horizontal to slightly down-sloping opposite the frontal lobe.
The anterior border furrow is distinct abaxially, shallow and indistinct opposite the frontal lobe. The
palpebral lobe is convex (tr. and exsag.), on the same level as the cheek, and defined by a distinct
palpebral furrow; the posterior end is opposite the posterior glabellar furrow. The abaxial section of
the posterior border is directed antero-laterally at 40-45° ; the posterior border furrow is slightly curved.
The anterior sections of the facial suture diverge slightly to the border furrow.

Stage IV: Cranidial lengths 1-16-1-48 mm. ; specimens falling within this size range include both cranidia
and cephala with attached thoraces and pygidia, of degrees 6-13 (text-fig. 9 iv; PI. 110, fig. 22).

The frontal glabellar lobe is rounded. The anterior border is narrow and convex, both abaxially and
sagittally; the border furrow is deep abaxially, but shallows abruptly opposite the frontal lobe, with
small anterior furrow fossulae. A minute, down-sloping preglabellar field is present, but not distinctly
separated from the frontal lobe. The palpebral lobe is above the cheek level, about J of glabellar
length, with its posterior end opposite the posterior glabellar furrow or lobe. The abaxial section of the
posterior border is directed antero-laterally at 50°. The posterior border furrow is almost straight,
widening abaxially and sloping downwards abaxially. The anterior section of the facial suture diverges
at 10° to the border furrow.

The librigena is narrow (tr.) with the genal spine very short, extending through the size range from
the level of the posterior border to that of the 1st or 2nd thoracic segment.

table 7. Development of the meraspid thorax and transitory pygidium in B. dailyi. Als total cranidial
length of the articulated cephalon is given in micrometer divisions where 1-00 mm. = 32 divisions.

pid degree

Cranidial length
Wi)

Cephalic stage

Segments in
transitory pygidium

6

38

IV

3

6

40

IV

4-5

6

40

IV

4

6

44

IV

3

10

45

IV

4-5

10

48

V

3

12

48

V

5

13

46

V

4-5

13

48

V

5

14

50

V

4-5

17

54

V

3

21

53

V

3-4

22

61

V

9

24

75

V

4-5

28

75

V

7-8

35

115

V

4

39

107

V

6

(b) Development of the thorax (Table 7)

No meraspis of a degree less than 6 is known from this species. The development from this degree is
basically the same as in B.flindersi, but a greater variation in the number of segments in the transitory
pygidium is observed, both within a degree and between degrees. Three specimens of degree 6 show 3 or 4
axial rings, and 1 or 2 complete sets of pleurae on the pygidium, but another specimen shows 6 dis-
tinct, and at least 1 indistinct axial rings, and 3 distinct sets of pleurae; the 2 most anterior segments
appear fully formed, but their abaxial ends are continuous with the lateral border of the pygidium.

549

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES

1 specimen of degree 21 possesses a pygidium with 9 distinct axial rings; the anterior 3 segments are
completely formed, and appear to be only semi-ankylosed to each other and the rest of the pygidium.
In this specimen the pygidium is 40% longer than in others with a normal complement of segments.

( c ) Development of the hypostome (Table 8)

The changes taking place during the development are similar to those in B. flindersi. The smallest
hypostome is matched with a cranidium of Stage I, and the smallest with the holaspid morphology
with a cranidium larger than those of Stage IV.

table 8. Development of the hypostome in B. daily i. Explanation as for the table 5.

H !

H, (= R1)

A i of equivalent
cephalon

Cephalic stage

20-5

12

19-21

I

22

16

23-25

II

25

18

25-28

II

25

20

28-35

II, III

28

20

28-35

II, III

33

22

35-38

III, IV

39

28

44-47

IV

42

29

48-50

IV

45

29

48-50

IV

53

39

69-

IV

Ontogeny of Emuella polymera (Plate 110, figs. 16-18)

Only 10 specimens of this species are known which are considered larval, and of these, only 2 retain
the meraspid thorax. Accordingly the development is not divided into stages, as with the species of
Balcoracania.

The smallest specimen found had a sagittal length of 0-40 mm., and appears to be a protaspis; how-
ever it is badly preserved and details are obscure. At a cranidial length of about 0-67 mm., a narrow
down-sloping border appears in front of the frontal glabellar lobe, the palpebral lobe is below cheek
level and extends posteriorly to the level of the middle glabellar lobe, and the anterior section of the
facial suture has a very short sagittally directed section; one specimen of this size (PI. 110, fig. 16)
shows a pre-anterior glabellar furrow, and cheek furrows. This cranidial size corresponds to meraspid
degree 1. At about 0-88 mm., the anterior border has become horizontal abaxially, the palpebral
lobe extends to the level of the middle glabellar furrow, and the frontal lobe is outlined by deep axial
furrows. A well preserved specimen shows that the cheeks are still furrowed. With further increase
in size from 1-00 to 1-40 mm., the anterior border becomes horizontal to slightly convex, the border
furrow develops fossulae, the palpebral lobe extends just beyond the middle glabellar furrow, and the
anterior sections of the facial suture become slightly divergent. A meraspid degree 7 is included in
this range. At approximately 1-7 mm., the cranidium exhibits the holaspid morphology.

No hypostomes which could be considered larval are known.

Discussion

The studies of the ontogenetic development of the three species reinforces the basis
of the taxonomic discriminations made on the adult morphology; in particular, the
species of Balcoracania, which are morphologically very close in the adult, can be clearly
discriminated by their ontogenetic development.

The cephala of the three species undergo similar types of changes during their onto-
geny, but the individual changes occur at different rates in each species. Thus the
cranidia exhibit different combinations of characters at a given age (measured against
cranidial length). In addition other features which are characteristic of the adult of the

550

PALAEONTOLOGY, VOLUME 13

species appear or are attained at some stage during the ontogeny. In E. polymera the ;
characteristic relative length and position of the palpebral lobe is attained at an ex-
tremely early stage. In contrast, the preglabellar field which characterizes B. dailyi
develops rather late compared with other features.

The size at which the cephalon attains the holaspid morphology differs in the genera.

In E. polymera it is reached at a cranidial length of 1 -7 mm. , in the species of Balcoracania
at 1-5 mm.

The development of the thorax is extremely similar in all species. It follows the
general pattern outlined by Whittington (1957, 1959), with two important modifica-
tions; the release of the macropleural unit, and the change from prothoracic to opistho-
thoracic segments. With regard to the macropleural unit, it is significant that in
B.flindersi where numbers are sufficient for all stages of early meraspid development to
be represented, no meraspis of degree 5 has been discovered. It is evident that the 5th
and 6th segments develop together in the transitory pygidium, and are released into
the thorax as a unit. At degree 6, the 6th segment is already macropleural, and the spine
reaches the level of the posterior edge of the transitory pygidium. However no trace
of the macropleural spine has been found in transitory pygidia of degrees 0-4, indicating
that the spine develops very rapidly, ostensibly during the period of the moult at which
the macropleural unit is released into the thorax.

After the release of the macropleural unit into the thorax, there occurs a change
in the size of the segments released, and the opisthothorax develops.

In all species the length of the transitory pygidium and the number of segments, as
indicated by the number of furrows on the axis, vary both within an individual degree
and between degrees (Tables 4, 7). Also the length of the cranidium varies considerably
for a given degree, and considerable overlap may occur between successive degrees;

3 specimens are known of degree 3 with a range of cranidial lengths which overlaps
that for specimens of degrees 4 and 6. It thus appears that segments may be added to
the transitory pygidium during individual degrees, implying the occurrence of more
than one moult within a degree. In addition, in meraspides of degree 6 or more, speci-
mens occur with considerably more segments in the transitory pygidium than the
average. In these cases the most anterior 2 or 3 segments appear to be fully formed, and
only semi-ankylosed to the pygidium. It thus seems probable that in the development
of the opisthothorax, more than one segment may occasionally be released during some
moults.

Comparison of the rates of cephalic and thoracic development raise some points of
interest. At degree 6 the cranidium has a length of 0-88 mm. in B.flindersi, but 1-25 mm.
in B. dailyi ; the cranidial development is thus further advanced in B. dailyi at this stage
of thoracic development. In both species, however, the cranidium attains the holaspid
condition at a cranidial length of 1 -50 mm. ; in B.flindersi this stage is reached at degree
16, and in B. dailyi at degree 13. The larval development of the thorax is thus far from
complete and significantly lags behind that of the cranidium.

FUNCTIONAL MORPHOLOGY

The characters of the thorax of the Emuellidae are analysed on a basis of function,
both in the adult trilobite and during development, and an attempt is made to seek
causes framed in terms of adaptation.

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 551

Division of the thorax. The division of the thorax into a prothorax, characterized by a
constant number of segments with normal pleurae, and an opisthothorax with a variable
number of segments with pleurae clearly reduced in size, was previously only known in
the Olenellidae (Hupe 1953a, b, c, 1955; Harrington et al. 1959).

In the Olenellidae the number of prothoracic segments varies from 1 1 in Neltneria ,
to 17 in Fallotaspis and Nevadia. The number of opisthothoracic segments differs more
widely, from 2 to 30, but in general is low.

The division of the thorax has been considered to be a primitive character and to
be lost in more advanced trilobites (Hupe 1953a, b\ Harrington in Harrington et al.
1959). The number of segments in the opisthothorax has also been equated to the degree
of ‘primitiveness’, those with many segments being considered the least evolved. In
addition, the prothorax has been considered homologous to the thorax of normal
trilobites, because of the fixity of the number of segments, and the opisthothorax as
homologous with the pygidium. In most of the Olenellidae in which the prothorax is
relatively long and multisegmented, and the opisthothorax short and with only a few
segments, the homology may seem justified. However in Paedeumias robsonensis (Bur-
ling), in which the opisthothorax is as long as the prothorax and contains more than
twice the number of segments, it appears difficult to justify its homology with the normal
pygidium. It is even more difficult in the case of the Emuellidae where the opisthothorax
is twice the length of the prothorax, and has between 48 and 55 segments; in addition
the prothorax contains only 6 segments. It is considered that such a homology is in-
accurate, or at least misleading.

In attempting to explain the phenomenon on the basis of functional morphology,
three questions must be faced; why does the change occur, at what point does it take
place, and what causes the eventual termination of segmentation ? An attempt is made
to answer these questions with reference to the Emuellidae, and to test the validity of
the resulting hypothesis by comparison with the Olenellidae.

In the prothorax of the Emuellidae, the posterior edges of the first 4 normal segments
are directed transversely, but those of the 6th segment are directed postero-laterally,
from the axial furrow to the notch at the base of the macropleural spine. If the 7th
segment is to articulate in the normal fashion with the posterior edge of the 6th, its
pleurae must necessarily be reduced in length, as the axial ring can only have normal
taper. It is considered that in this case, it is the abrupt space reduction, consequent
upon the change in direction of the posterior border of the macropleural segment, which
initiates the change in the nature of the segments released from the transitory pygidium.

In the adult, the segments of the opisthothorax form a perfectly graded series between
the posterior border of the 6th segment and the anterior pygidial border (text-fig. 5a).
In the ontogeny of the Emuellidae, meraspid degree 6 shows the transitory pygidium
articulating with the posterior border of the 6th, in the same relative position and
manner as does the 7th segment in the adult, and displaying a perfect gradation with
the prothorax (text-fig. 8). In succeeding meraspid degrees, the absolute size of the
transitory pygidium increases only very slightly, whilst that of the 6th segment increases
more rapidly, and the opisthothorax remains perfectly graded with respect to both.
Thus the release of segments from the transitory pygidium ceases when the ratio of the
lengths (tr.) of the posterior border of the 6th and the anterior pygidial border becomes
constant. It is notable in this connection that in the ontogeny of the Emuellidae, the

552 PALAEONTOLOGY, VOLUME 13

cephalon attains the holaspid condition whilst segments are still being released into the
opisthothorax.

In the Olenellidae, only Neltneria has the last prothoracic segment macropleural,
and it is notable that the number of prothoracic segments is less than in other members [
of the family. In Neltneria the posterior edges of the pleurae of the 11th segment have
only very short transversely directed sections before the spine curves to the posterior;
thus the space available for pleurae of succeeding segments is reduced. In addition
the mechanics of articulation necessitate a progressive inclination of the pleurae to the
posterior, with the last opisthothoracic segment having its pleurae wrapped around the
sides of the pygidium. In the Olenellinae and Fallotaspis, it is the 3rd prothoracic seg-
ment which is macropleural. The posterior edge of the macropleural segment is trans-
verse for most of its length, thus it does not cause an abrupt decrease in the space
available for succeeding segments. However it does reduce the space, and causes the
pleurae of succeeding segments to be progressively inclined to the posterior, and it
appears to be this factor which finally causes a change in the nature of the segments
released. As this is a more gradual process than in the Emuellidae, a greater number
of prothoracic segments are released. In the Olenellidae which possess an opisthothorax,
but not macropleural spines, e.g. Elliptocephala, Nevadia, the segments have pleurae
progressively inclined to the posterior, and possessing long pleural spines. In those
without division of the thorax, e.g. Holmia, the pleurae are again inclined progressively
to the posterior, but do not possess long pleural spines; consequently space reduction
does not reach a critical point.

It is thus considered that the division of the thorax can be explained as a response to
a space reduction, either abrupt or gradual, which necessitates a change in the nature
of the segments, in order to maintain the ability to articulate freely. It may be significant
however, that the phenomenon has only been observed in Lower Cambrian trilobites.
Possibly only primitive trilobites had this ability, or that more advanced ones solved
similar problems in a less dramatic fashion.

Macropleurality . This feature occurs in many Cambrian and post-Cambrian families.

In the Cambrian it is widespread, with most genera of some families exhibiting this
feature; these include the Olenellidae, Neoredlichiidae, Bathynotidae, Paradoxididae,
Zancanthoididae, and Dolichometopidae. In post-Cambrian families, such as the
Shumardiidae, Asaphidae, Remopleurididae and Cyclopygidae, expression of the feature
is usually confined to a single genus.

In the Emuellidae the last segment of the prothorax is macropleural. The spine, which
is formed by both anterior and posterior pleural bands, tapers gradually to the posterior,
curving inwards slightly, and extending to the level of the posterior edge of the pygidium
or just beyond it. The doublure of the segment extends from the base of the pleural
spine of the 5th, to which the 6th is fused, to the notch on the posterior border of the
6th. The spine is thus hollow, almost flat on top, slightly V-shaped to rounded below.

In the ontogeny of the Emuellidae, the spine appears abruptly at meraspid degree 6,
without having previously appeared in the transitory pygidia of earlier degrees. The
general form is the same as in the adult, with the spine extending to the level of the
posterior edge of the transitory pygidium. In succeeding degrees, the length of the spine
increases to maintain the same relative position.

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 553

In view of the high correlation between the lengths of the macropleural spine, and
the opisthothorax and pygidium at all ontogenetic stages, it is considered that the spine
serves both to stabilize and protect the opisthothorax. In a rest position on the sea
floor, the flattish base of the spine would be opposed to the bottom, rather than the
delicate pleural spines.

Hupe (1950, 1953c) suggested that the macropleural segment is the genital segment
containing the gonopores on the basis that as the trilobites themselves are primitive,
they are near the original condition where gonads and gonopores are metameric, and
would be localized on segments of particularly primitive character. Hupe considered
that the macropleural segments are the most primitive because of their narrow axis,
and then compared the position of the macropleural segments in trilobites with the
position of the gonopore in the Insecta, Myriapoda, Crustacea, and Chelicerata (Hupe
1950, fig. la), concluding that the opisthogoneate and progoneate tendencies of the
‘Atennulata’ existed in trilobites in the Lower Cambrian.

There is little evidence that the macropleural segments are the most primitive; in
fact in any one trilobite it is the macropleural segment which, by definition, is the most
specialized. There is no evidence of a structure on the dorsal surface of the macropleural
segment which could be interpreted as a gonopore; thus if the gonopore is located on the
ventral side, some modification of the ventral morphology might be expected. However,
in the Emuellidae, the doublure of the segment is strictly comparable in structure and
position to that of normal prothoracic segments. If it is assumed that the gonopores
were carried in the soft ventral integument, there seems to be no reason why the macro-
pleural segment alone should carry them. The suggestion, based on comparison with
a hypothetical annelid ancestor, that the gonopores will occur on most, if not all thoracic
segments (Raymond 1920, and others), appears the more reasonable.

The contention by Hupe (1953Z>) that macropleural segments in Lower Cambrian
trilobites have two preferred positions, one anterior and one posterior, appears to have
greater validity. The Olenellidae are characterized by having the 3rd prothoracic seg-
ment macropleural, the Emuellidae and Neltneria the last. Other related families display
a similar division, but at least 2 genera ( Olenelloid.es and Bathyuriscidella ) possess 2
macropleural segments, more or less symmetrically placed in the thorax. The significance
of the apparent division is not known.

In all genera whose adults possess macropleural segments, and whose ontogeny is
known, the macropleural segment either appears in the transitory pygidium and is
released at the appropriate meraspid degree (Olenellidae, Shumardia ), or develops
suddenly at the time of release from the transitory pygidium. In no known case does the
macropleural segment develop after release into the thorax. This implies that the seg-
ments have some adaptive significance in the larval stages or that sexual maturity is very
precocious. Hupe (1953c, p. 116), whilst allowing a possible secondary adaptive function
connected with pelagic life, considered that the presence of such segments would be
almost universal if this were the case; he accordingly considered sexual maturity to be
precocious, and that a presumed change from allometric to isometric growth during
the early meraspid period marked this change (1953Z>, p. 121). However, this alleged
change is based on little data, is unsupported by statistical testing, and in any event
is not necessarily indicative of sexual maturity. Therefore it is considered that the first
alternative, that of adaptation to a pelagic existence is the more likely possibility.

554

PALAEONTOLOGY, VOLUME 13

Indeed Hupe’s reasons, i.e. lack of universality, for rejecting this as the primary cause* ,
apply equally well to the interpretation of the macropleural segments as genital.

In Paradoxides (Westergard 1936, Whittington 1957, 1959) the 1st and 2nd segments
are both strongly macropleural when they first appear, but regress during meraspid
development, the 1st more rapidly than the 2nd, so that at degree 15 (Whittington 1957*
fig. 5b) only the 2nd is macropleural. In the adult, the 2nd segment is only weakly
macropleural. The same sort of phenomenon occurs in both the Olenellidae and Red-
lichiidae, and may be comparable to the regression, during the same period, of the
fixigenal and intergenal spines of the Olenellidae and Paradoxididae. Whittington (1957,
p. 450) has attributed to the latter a role of support and buoyancy in a supposed pelagic
life. It is reasonable to suggest that the macropleural spines had a similar adaptive
function. In the Emuellidae it seems probable that the spines also served a protective
function, a role which continued into the adult stages. However, the retention of the
macropleural spines in adults of most genera raises several problems. The spines may
retain a function of stabilization or protection in some cases, but in others they occur
in genera belonging to families in which the other members appear well adapted to
their habitat and mode of fife, e.g. Octinellus in the Illaenidae. The question thus arises
as to whether the adaptive function is secondary or not. In this context Hupe’s suggestion
as to the primary function cannot be dismissed.

Raw (1953) suggested that the presence of macropleural spines is related to mero-
cyclism inherited from a polychaete ancestor, occurring most frequently in primitive
forms and becoming lost when the segments achieve a graded condition. Macropleurality
undoubtedly occurs most commonly amongst Lower Cambrian forms, but even here
it is difficult to match macropleurae with cycles of segmentation. Raw (1953, p. 94)
cited Olenelloides armatus (Peach) as an example where one macropleural segment
alternates with two normal segments. This genus is generally regarded as aberrant, but
even here it is necessary to consider the cephalic spines as representing macropleurae.
Palmer (1957, p. Ill) attempted to apply merocyclism to Olenellus and Paedeumias, but
found it necessary to combine it with the hypothesis of secondary segmentation (Stormer
1941) in order to fit merocycles. The presence of contiguous macropleural segments in
the larval stages of Paradoxides and other genera casts grave doubts on Raw’s concept.

In post-Cambrian trilobites the sporadic occurrence of macropleural segments in more
than one position affords another difficulty; in Acidaspis, Hupe (1950) listed seven
species with five different positions of the macropleural segment.

Manton’s studies on the functional morphology of modern arthropods are interesting
in the above context, since she concludes that body form is largely determined by loco-
motory habits (Manton 1952, 1960, 1964).

Fusion of thoracic segments. The Emuellidae have the 5th and 6th segments of the
prothorax fused together. Only one other genus, Bathynotellus, shows a similar fusion
of segments within the thorax, and in addition one of the segments involved is macro-
pleural. However, it is believed that there is a different functional basis for the fusion
in the two cases.

In the Emuellidae the fusion of the otherwise normal 5th segment to the 6th appears
to be simply a device to increase the muscular control over the long macropleural spine,
and so aid in support and stability. The apodemal slit of the 6th is very strongly de-

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 555

veloped, and the fusion of the 5th allows its abaxial extension onto the inter-furrow
platform. It also allows the elongated apodemal slit to abut against the adaxial end of
the 6th pleural furrow, so that ventrally it forms a large transverse apodeme buttressed
by an accessory ridge. On the pleural field, the development of a horizontal flap between
the anterior lateral corner of the 6th and the pleural spine of the 5th ( E . polymera )
appears to be a strengthening device.

In Bathynotellus, the thorax has 13 segments, but the posterior ones are fused into a
unit which has 3 axial rings and a macropleural spine; the pygidium is large, and its
articulation with the macropleural unit is similar to that between the macropleural unit
and transitory pygidium of meraspid degree 6 of the Emuellidae. In order to understand
the situation in Bathynotellus, it is necessary to consider the allied genus Bathynotus.

Bathynotus has a thorax of 13 segments, with the 11th macropleural, the posterior
2 with considerably reduced pleurae, and a large pygidium. The macropleural spine is
directed posteriorly, and in combination with the pygidium reduces the space available
for the development of the pleurae of the two segments between them. It has been sug-
gested above that a similar space reduction has resulted in the development of an
opisthothorax in the Emuellidae and Oleneliidae. However, the large pygidium in the
Bathynotidae suggests that they were more advanced than the other two groups, and
had stabilized the number of thoracic segments. The reduced segments thus cannot
perhaps be homologized with a true opisthothorax, which is always associated with
a small pygidium. It is evident that the problem was solved in a different way, by fusion
of the two posterior segments to the macropleural 11th. Thus the 11th, 12th, and 13th
segments in Bathynotus are homologous with the macropleural unit of Bathynotellus.

TAXONOMIC POSITION

The genera Emuella and Balcoracania possess a unique combination of cephalic
and thoracic morphology that sets them apart from other groups of trilobites, and it is
proposed that they should be placed in a separate taxon of familial rank, the Emuellidae.

The relation of the Emuellidae to other taxa can only be judged on morphological
similarity. Some of the diagnostic characters of the family are found only in Cambrian
trilobites, others occur in both Cambrian and post-Cambrian trilobites. However, when
assessing the taxonomic position of the family, similarities in Cambrian and particularly
Lower Cambrian trilobites are accorded most weight.

The combination of diagnostic characters of cephalon, thorax, and pygidium in the
Emuellidae imposes certain conditions on the type of comparison which can validly
be made. In particular, it is considered that the presence of a large pygidium largely
invalidates comparisons based on the cephalon alone, and this is used as a premise for
detailed comparisons of the cephala which follow.

The taxonomic position is assessed with regard both to features of adult morphology,
and of ontogenetic development.

Comparisons of adult morphology

( a ) Thorax and pygidium. The division of the thorax is known, apart from the Emuel-
lidae, in some members of the Oleneliidae. The occurrence and nature of the division
in this family has already been discussed, but in general the genera are usually

556 PALAEONTOLOGY, VOLUME 13

characterized by a long prothorax (11-17 segments), and a short opisthothorax, the
exception in the latter case being Paedeumias robsonensis (Burling), which has at least
29 opisthothoracic segments.

The occurrence of macropleurality has also been discussed. The presence of such
segments in genera of so many obviously unrelated families casts grave doubts on the
taxonomic value of this character, unless used in association with other thoracic features.
In this context, the combination of macropleurality and thoracic division in some mem-
bers of the Olenellidae is particularly important.

The Bathynotidae also show a combination of thoracic features similar to the Emuel-
lidae, particularly Bathynotellus, in which fusion of segments is combined with macro-
pleurality. However, it has been suggested above that the similarities are largely the
result of convergence, and additionally the presence of a large pygidium in Bathy-
notellus precludes a close relationship.

{b) Cephalon. In the cephalon of the Emuellidae, the combination of sutural pattern,
structure of the eye lobes, and of the posterior limb, constitute the essential diagnostic
features ; the glabellar shape is of lesser importance.

The sutural pattern consists of functional rostral, connective, hypostomal, and facial
sutures. The cephalon is of the ‘ptychopariid’ type in the terminology of Rasetti (1952),
and is considered to be the primitive type from which all others are secondarily derived
(Harrington in Harrington et al. 1959, pp. 68, 158). Many taxa have members of this
type, and those with Cambrian representatives include the Redlichiacea, Ellipso-
cephalacea, Paradoxididae, and Ptychopariidae.

The eye lobes consist of wide, essentially continuous eye ridges and palpebral lobes,
extending in crescents from the frontal glabellar lobe, with the palpebral sections
widely separated from the glabella. Genera of many families possess similar eye lobes,
with the Cambrian groups Dolerolenidae, Ellipsocephalidae, Protolenidae, Bathy-
notidae and Ptychopariidae bearing the greatest resemblance.

The geniculate posterior limb of the Emuellidae appears to have no parallel in any
other Cambrian family.

The glabella tapers forward to the anterior glabellar furrow, but has a variably ex-
panded frontal glabellar lobe. The ontogeny of the members of the Emuellidae, together
with the presence of variants with a bilobed frontal glabellar lobe, suggests that this
shape may be due to the persistence of a larval characteristic into the adult. Thus the
presence of an expanded frontal lobe in other genera does not necessarily mean a close
relationship; conversely a regularly tapering glabella need not indicate a distant re-
lationship.

The over-all morphology of the cephalon is most similar to some members of the
Dolerolenidae, Protolenidae, and Ptychopariidae. Of these, the genera Dolerolenus,
Bergeroniellus, and Estaingia of the so-called protolenoids, Protolenus of the un-
doubted Protolenidae, and members of the Antagminae, are probably the closest. In
addition some of the Olenellidae are discussed, because of special similarities in the
thorax to the Emuellidae.

Dolerolenus differs from the Emuellidae in the possession of an evenly tapering
glabella, the faintness of the eye ridges, and the length of the posterior limb which is
also transversely directed; the genal spine is also much shorter and not advanced.

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 557

Berger oniellus and Estaingia resemble the group in the structure and position of the
eye lobes, with the subgenera B. {Berger oniaspis) and B. ( Olekmaspis ) being the closest.
The glabella of Estaingia approaches the shape of that of Balcoracania dailyi in par-
ticular. The shape of the glabella of Bergeroniellus varies slightly, but is generally slightly
tapering to the anterior. Both genera differ from the Emuellidae in the presence of
wide preglabellar fields and transverse posterior limbs. Protolenus is similar to Estaingia
except for a narrower preglabellar field and evenly tapering glabella, and so shares
most of the above dissimilarities.

Of the Antagminae, Eoptychoparia, Poulsenia, and Proliostracus have a tapering
glabella, and eye lobes similar to the Emuellidae. Poulsenia , in particular, has only a
short preglabellar field, and the frontal lobe bears a similar relationship to the anterior
border furrow, as does B. dailyi. The anterior sections of the facial sutures cut diagonally
across the border, and vary from slightly divergent {Eoptychoparia), to rather strongly
converging {Poulsenia). In all genera the posterior limb is in marked contrast to that of
the Emuellidae.

In the Olenellidae the major differences are associated with the sutural pattern, the
eye lobes and the posterior border.

(c) Conclusions. The strong similarities in the thorax of the Olenellidae and the
Emuellidae suggest a close relationship, but the indications are that the latter are
probably the more primitive group. The structure of the cephalon also suggests that the
Olenellidae are the more advanced, as the ‘olenellid’ sutural pattern is now thought
to have been secondarily derived from the ‘ptychopariid’ type, which is displayed
by the Emuellidae (Hupe 1953a, Harrington in Harrington et al. 1959). Together these
features suggest that an ‘emuellid’ stock may have given rise to the olenellid branch.
This, however, does not settle the question of their placement within the existing taxono-
mic framework, for the very presence of the characters which suggest this relationship
precludes the placement of the Emuellidae within the suborder Olenellina.

The other groups which show similarities to the Emuellidae belong to suborder
Redlichiina (Dolerolenidae, Protolenidae), suborder Bathynotina (Bathynotidae), and
suborder Ptychopariina (Antagminae). Of these, the Bathynotidae and the Antagminae
exhibit the least similarities to the Emuellidae. Accordingly it is suggested that the family
be placed in the suborder Redlichiina.

Within the suborder the position is not clear. The Dolerolenidae and the Protolenidae
bear approximately the same degree of over-all similarity to the Emuellidae, but are
placed in different superfamilies (Poulsen in Harrington et al. 1959), the Dolerolenidae
in the Redlichiacea, and the Protolenidae in the Ellipsocephalacea. In addition the
Dolerolenidae are thought to be transitional between the two superfamilies (Sdzuy
1959), and the protolenoids {Bergeroniellus, Estaingia ) transitional between the Ellipso-
cephalacea and the Paradoxidacea (Opik 1961, Pocock 1964).

Comparisons of developmental history

Whittington (1957, p. 462) stated that ‘the nature of the developmental history and
the morphology of the protaspis . . . offer additional criteria for judging relationships
between families and larger groups’. The ontogenies of the Emuellidae are compared
with those known from groups which, on the basis of holaspid morphology, appear

558 PALAEONTOLOGY, VOLUME 13

to be related: the Olenellidae, Redlichiidae, Dolerolenidae, Protolenidae, and Ptycho-
pariidae.

Protaspides have not yet been recognized in the Olenellidae, but the meraspid de-
velopment is broadly known from the investigations of Whittington (1957, 1959) and
Palmer (1957). The ontogeny of Redlichia chinensis (Walcott) has been studied by
Kobayashi and Kato (1951); at least one protaspis and several meraspides are described.
The ontogeny of the Dolerolenidae is not well known but Kobayashi and Kato (1951,
text-fig. 1) illustrated several protaspides of Dolerolenus, redrawn from Bornemann
(1891). In the Protolenidae, Suvorova (1956) described larval stages of Lermontovia and
Berger oniellus\ all specimens appear to be meraspid cranidia. Protaspides of Strenuella,
a related protolenid, have been described by Kautsky (1945). Amongst the Ptycho-
pariidae, the ontogeny of Sao is well known (Whittington 1957).

A comparison of the ontogenies of the families listed above with those of the Emuel-
lidae, appears to affirm the degree of relationship deduced from the holaspid morphology,
but fails to solve the problems which arise. Of the families considered, the protaspides
and early meraspides (considered to be of greatest diagnostic value) of the Ptychopariidae
are furthest from those of the Emuellidae. The remaining families are all members of
the Order Redlichiida, and thus some similarity is to be expected.

In these families there is a similar reduction of the size of the frontal glabellar lobe,
but to varying and generally greater degrees than in the Emuellidae, and a similar de-
velopment of the anterior border and preglabellar field. The presence of a preglabellar
field in the meraspides of all groups is not considered a major difference, as in the
Emuellidae its initial development can be seen in B. dailyi. The most important remain-
ing characters of the protaspides and early meraspides are the cheek furrows, bilobation
of the frontal glabellar lobe, and the fixigenal spines. The Emuellidae have distinct
cheek furrows, occasional bilobation, but lack fixigenal spines; the Redlichiidae have
distinct furrows, definite bilobation, but also appear to ack spines; the Dolerolenidae,
although very incompletely known, appear to possess only the cheek furrow; the
Olenellidae have furrows and spines, but apparently lack the bilobation; the Proto-
lenidae lack cheek furrows, but are bilobed, and some, but not all, species have fixigenal
spines. It is thus apparent that all families bear some relationship to each other, but
the degree of relationship is difficult to determine.

It is accordingly considered that the placement of the Emuellidae in the suborder
Redlichiina is reasonably based, but its superfamilial position is best left open for the
present.

EVOLUTION

Intrafamilial relationships. On the basis of adult morphology, E. dalgarnoi is intermediate
between E. polymer a and the species of Balcoracania ; the morphology of the palpebral
lobe, the posterior limb and the facial sutures, all lie between the limits for these struc-
tures in the other species. However, with so few species and incomplete stratigraphic
information, further speculation is unwise.

Evolutionary position of the Emuellidae. In the possession of a ptychopariid sutural
pattern, thick long eye lobes, expanded frontal glabellar lobe, long thorax combining

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES 559

macropleurality and division, and a diminutive pygidium, the Emuellidae appear to be
very primitive, and must be placed near the origin of redlichiid evolution.

It has been suggested that the Olenellina have evolved from a redlichiid-like trilobite
with a ptychopariid sutural pattern (Hupe 1953a, Harrington in Harrington et al. 1959).
The Emuellidae possess such a cephalon, and combine with it thoracic features which are
shared only with some of the Olenellina, i.e. long, multisegmented thorax, division into
pro- and opisthothorax, and macropleurality. Although the known members of the
Emuellidae occur far too high in the Cambrian to be direct ancestors, they exhibit all
the features which might be expected of such an ancestor. Thus, the Olenellina may have
evolved from an ‘emuellid’-type ancestor by migration and eventual loss of the facial
sutures, and by reduction of the opisthothorax. Other members of the Redlichiida
may have evolved from a similar ancestral stock by loss of the opisthothorax, retention
of the basic sutural pattern, reduction of the frontal glabellar lobe, and development of
the preglabellar field. The loss of the opisthothorax is foreshadowed in some of the
Olenellina, and the development of the preglabellar field in B. dailyi. It is interesting to
note that the changes taking place in the early meraspid stages of members of the
Redlichiina are strikingly similar to the complete ontogeny of the Emuellidae.
Acknowledgements. I am indebted to Professor M. F. Glaessner (University of Adelaide) for supervising
the work and critically reading the manuscript; Professor H. B. Whittington (Sedgwick Museum,
Cambridge) and Professor A. R. Palmer (State University of New York, Stonybrook) for advice
throughout this study and reading sections of the manuscript; and Dr. M. Wade and Dr. B. McGowran
(University of Adelaide) for general discussions of the subject.

Dr. B. Daily (University of Adelaide) kindly lent material from his own collections; and Mr. T. A.
Barnes (Director, South Australian Department of Mines) authorized the release to the University of
material in his department.

This research work formed part of a thesis submitted for a Ph.D. degree, University of Adelaide.
The Department of Geology, University of Malaya, assisted in the preparation of the manuscript.

APPENDIX

Measurements of selected dimensions of adult specimens of the Emuellidae. All measurements are
given as micrometer divisions where 1-00 mm. = 12 divisions.

1. Emuella polymera

A1

C

A

Aj.

C

A

16

2

6

45

10

13

22

5

7

46

10

15

26

6

8

46

10

16

26

5

8

47

10

15

30

6

10

47

8

14

31

7

11

51

10

20

32

7

11

52

11

16

34

7

13

55

12

20

35

6

12

58

10

20

37

8

10

60

13

20

37

8

12

60

11

20

38

7

15

73

15

23

39

7

13

75

14

25

40

8

14

82

14

26

40

8

13

86

18

28

43

8

14

88

16

30

43

9

14

O O

0 7719

PALAEONTOLOGY, VOLUME 13

2. Emuella dalgarnoi

Ax

C

As

A !

C

A

34

8

10

51

13

16

35

7

9

66

16

21

35

8

10

70

18

20

44

12

15

76

18

24

45

11

14

106

22

38

48

12

16

Balcoracania flindersi
Ax

C

A

Ax

C

Dh

23

5

5

58

16

14

25

6

6

60

14

19

31

8

10

60

15

15

32

8

8

60

14

14

33

8

9

60

14

19

33

8

12

60

14

13

40

10

9

70

18

19

44

10

13

72

14

14

48

12

14

72

20

18

48

14

13

74

16

22

50

11

12

76

18

26

50

12

16

76

16

20

54

14

13

78

18

17

56

16

14

80

16

26

56

14

9

84

20

24

56

12

14

Balcoracania dailyi
Ax

C

A

Ax

C

A

23

7

7

47

14

13

25

9

6

48

14

11

26

8

6

50

15

14

27

8

5

55

14

15

28

9

8

58

15

15

29

9

7

58

15

14

30

10

7

60

15

14

30

9

8

60

18

16

30

10

6

64

17

17

31

8

8

67

20

16

33

9

9

68

19

21

34

10

8

70

20

20

35

10

8

70

20

20

42

12

12

72

20

18

44

13

12

76

20

18

44

14

10

78

24

16

45

13

11

78

22

17

78

25

20

POCOCK: THE EMUELLIDAE, A NEW FAMILY OF TRILOBITES

561

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daily, b. 1956. The Cambrian in South Australia; in El sistema Cambrico, su palaeogeografi yel
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191-3.

1953a. Contribution a l’etude du Cambrien inferieur et du Precambrian III de 1’ Anti- Atlas

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1953c. Classe des Trilobites, in piveteau, j., Traite de Paleontologie, Masson (Paris), 3, 44-

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1955. Classification des trilobites. Annals Paleont. (Paris), 39, 91-325 (111-345).

kautsky, f. 1945. Die Unterkambrische Fauna ven Aistfakk in Lappland. Geol. For. Stockh. Fork.
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kobayashi, t. and kato, f. 1951. On the ontogeny of Redlichia chinensis, with description of Alutella
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manton, s. A. 1952. The evolution of arthropodan locomotory mechanisms. Part 2, General introduc-
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1960. Concerning head development in arthropods. Biol. Rev. 35, 265-82.

1964. Mandibular mechanisms and the evolution of arthropods. Phil. Trans. R. Soc., ser. B,

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opik, a. a. 1961. The geology and palaeontology of the headwaters of the Burke River, Queensland.
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pi. 19.

pocock, k. J. 1964. Estaingia, a new trilobite genus from the Lower Cambrian of South Australia.
Palaeontology, 7, 458-71, pi. 75, 76.

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raw, f. 1953. The external morphology of trilobites. J. Paleont. 27, 82-129.

Raymond, p. e. 1920. The appendages, anatomy and relationships of trilobites. Mem. Conn. Acad.
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407.

shaw, a. b. 1956. Quantitative trilobite studies. I, The statistical description of trilobites. J. Paleont.
30, 1209-24.

1957. Quantitative trilobite studies. II, Measurement of the dorsal shield of non agnostidean

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shaw, f. c. and ormiston, a. 1964. The eye socle of trilobites. Ibid. 38, 1001-2.
simpson, G. G., roe. A., and lewontin, R. c. 1960. Quantitative zoology. New York.
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Suvorova, n. p. 1956. Cambrian trilobites from the eastern Siberian Platform, Part 1. Protolenidae.

Trudy paleont. Inst. Akad. Nauk S.S.S.R, 63, 1-158, 12 pi. [in Russian].

Walter, m. r. 1967. Archaeocyatha and the biostratigraphy of the Lower Cambrian Hawker Group,
South Australia. J. geol. Soc. Aust. 14, 139-52, pi. 7, 8.

562 PALAEONTOLOGY, VOLUME 13

westergard, a. h. 1936. Paradoxides oelandicus beds of Oland. Sver. geol. Unders. Afh., (6) 394,
1-66, pi. 1-12.

Whittington, h. b. 1957. The ontogeny of trilobites. Biol. Rev. 32, 421-69.

1959. In moore, r. c., ed., Treatise on invertebrate paleontology. Part O, Arthropoda I. Geol.

Soc. Am. and Univ. Kansas Press.

K. J. POCOCK

Department of Geology
University of Malaya
Kuala Lumpur

Typescript received 23 January 1970 Malaya

THE EVOLUTION OF THE HETEROMYARIAN
CONDITION IN THE D REIS SEN ACE A
(BIVALVIA)

by BRIAN MORTON

Abstract. Inspection of the valves of living members of the Corbiculacea and Dreissenacea and fossil Dreis-
senacea in the collections of the British Museum (Natural History) has revealed that the evolution of the
heteromyarian form in present-day Dreissenacea in all probability arose from an established isomyarian cor-
biculid stock.

Descriptions of the taxa examined are given, and the stages in the evolution of the Dreissenacea dis-
cussed.

Dreissena polymorpha Pallas was first encountered in the River Volga and the Black
Sea in 1754 by Pallas, who being struck by the superficial similarity of the animal to
members of the Mytilacea named it Mytilus polymorphus. In 1835 Van Beneden estab-
lished that it differed fundamentally from true mytilids and suggested the generic name
Dreissena. Gray (1840) was responsible for separating Dreissena even further from the
mytilids by suggesting that it should be placed in a separate superfamily, the Dreis-
senacea.

Toureng (1894a, b ) showed, on the basis of the structure of the central nervous
system and blood vascular system that Dreissena was not related to Mytilus, whilst
Atkins (1937) and Purchon (1960) respectively showed that on the basis of the structure
of the ctenidia and stomach the Mytilacea and Dreissenacea are unrelated. Yonge and
Campbell (1968) showed that Dreissena is very different from the mytilid Septifer
which has, like Dreissena, its anterior adductor muscles inserted on a shell shelf situated
near the umbo. It is now generally considered that the similarities which exist between
Dreissena and the Mytilacea are the result of convergent evolution of the heteromyarian
condition in the two groups.

The possession by Dreissena of so many anatomical features that are typically
‘eulamellibranch’ (Morton 1969a) suggests that the close relatives of Dreissena should
not be sought amongst the ‘filibranch’ bivalve phylogenies but amongst other eulamel-
libranchs. Taylor et al. (1970) have shown that on the basis of the microstructure of the
shell, Dreissena is most like members of the Corbiculacea. This observation supports
the grouping by Newell (1965) of the Dreissenacea with, amongst others, the Cor-
biculacea in the suborder Articina.

Fossil Dreissenacea in the collections of the British Museum (Natural History) and
present day Dreissenacea and Corbiculacea were studied to discover if there is any
evidence for the hypothesis of a common ancestry between the isomyarian Corbiculacea
and the anisomyarian Dreissenacea. The methods of classification of the Bivalvia
(Newell 1965) and of the Dreissenacea adopted by Keen (1969) are used in this paper.

To facilitate discussion of the evolutionary history of the Dreissenacea, short
descriptions and simple figures of the left valves of some of the taxa examined follows.

[Palaeontology, Vol. 13, Part 4, 1970, pp. 563-72.]

564

PALAEONTOLOGY, VOLUME 13

DESCRIPTION OF SHELLS

Superfamily dreissenacea Gray in Turton 1840
Family dreissenidae Gray in Turton 1840 (ICZN No. 76)

Genus dreissena Beneden 1835 (ICZN No. 872)

Subgenus Dreissena s.s.

Dreissena ( Dreissena ) polymorpha (Pallas)

Text-fig. 1

Material. A large collection of recent specimens from reservoir No. 2, Walthamstow, London.

Description. Shell solid, slightly inequivalve;
inequilateral, beaks in anterior half; sub-
triangular, elongated and swollen; flattened
ventrally, with byssal notch anteriorly. Speci-
mens up to 5-0 cm. in length. No internal
nacreous layer, ligament internal, extending
along dorsal fine less than -J- distance of pos-
terior margin. Hinge plate without teeth.
Anterior adductor and anterior byssal re-
tractor muscles located on hinge plate,
adjoined to each other. Anterior adductor
text-fig. 1 . Dreissena polymorpha. Interior view of left smaller than posterior; pallial line not in-
valve. (For key to lettering see p. 571.) dented by sinus. Margin smooth; growth

rings well defined ; colour yellowish or brown,
marked with zigzag alternating bands of brown and yellow.

Mode of life. Byssally attached, epifaunal, in shallow fresh and estuarine waters.

Range. Eocene — Recent. Old World.

Subgenus Dreissenomya Fuchs 1870
Dreissena ( Dreissenomya ) aperta (Deshayes) 1836
Text-fig. 2

Material. One specimen from the Upper Tertiary, Pontian (Bosphorian) of the Stoichitza valley,

Cocorova-Mehedintzi, Rumania. BMNH
LL 18451.

Description. Shell solid, equivalve; in-
equilateral, beaks in anterior half; tend-
ing to be rectangular or broadly oval
with posterior margins rounded, enlarged
and gaping. Well-defined byssal notch
anteriorly; specimen 2-5 cm. in length.
No internal nacreous layer to shell. Liga-
ment internal, extending along dorsal
text-fig. 2. Dreissena (. Dreissenomya ) aperta. Interior view line i distance of posterior margin. Hinge
of left valve. (For key to lettering see p. 571.) plate with two rudimentary cardinal teeth.

Anterior adductor and anterior byssal
and/or anterior pedal retractor muscle scars located on hinge plate on each side of and closely adjoined
to cardinal teeth. Anterior and posterior adductor muscle scars of approximately equal size; pallial
line with well-defined sinus. Margin smooth.

MORTON: EVOLUTION OF THE HETEROMYARIAN CONDITION

565

Inferred mode of life. Bysally attached, infaunal, siphonate, apparently associated with such non-
marine forms as Theodoxus and the aberrent non-marine Cardiacea. In fresh and estuarine waters.

Range. Miocene-Pliocene. Old World.

Genus congeria Partsch 1885
Congeria subglobosa Partsch
Text-fig. 3

Material. One specimen from the Miocene of Nussdorf,
near Vienna. BMNH L22134.

Description. Shell solid, equivalve; inequilateral, beaks in
front of mid-line directed forwards; angular, nearly square
in outline. Specimen 8-5 cm. long; no internal nacreous
layer to shell. Ligament internal, extending along dorsal
line almost | length of posterior margin. Growth-lines
distinct, well-defined byssal notch. Hinge plate with single
poorly developed cardinal tooth, covered in life by anterior
adductor muscle. Anterior byssal and/or anterior pedal
retractor muscle scar also located on hinge plate, posterior
to anterior adductor muscle scar. Anterior adductor muscle text-fig. 3. Congeria subglobosa. In-
scar smaller than posterior. Pallial line not indented by terior view of left valve. (For key to
sinus. Margin smooth. lettering see p. 571.)

Inferred mode of life. Bysally attached, infaunal, in fresh and estuarine waters.

Range. Oligocene-Pliocene. Old World.

Congeria zsigmondyi Halad

Text-fig. 4

Material. Eleven specimens from the Miocene of San-
genfeld, Temes, Hungary. BMNH L71758-68.

Description. Shell solid, equivalve; inequilateral, beaks
in anterior half ; angular, rhomboidal in outline. Speci-
men 2-5 cm. in length; no internal nacreous layer to
shell. Ligament internal extending along dorsal line \
distance of posterior margin. Byssal notch anteriorly.

Hinge plate without teeth. Anterior adductor and an-
terior byssal and/or pedal retractor muscles located
on hinge plate, latter posterior to anterior adductor
and having its insertion on ‘hinge lobe’ projecting
down from hinge plate. Anterior adductor muscle scar
smaller than posterior. Pallial line not indented by sinus.

Margin smooth.

Inferred mode of life. Byssally attached, infaunal, in fresh and estuarine waters.

Range. Oligocene-Pliocene. Old World.

Congeria subcarinata botenica Andrusov

Text-fig. 5

Material. A single specimen from the Miocene of the Pricales valley, Susitza-Mehedintzi, Rumania.
BMNH, unregistered.

text-fig. 4. Congeria zsigmondyi. Interior
view of left valve. (For key to lettering see
p. 571.)

566

PALAEONTOLOGY, VOLUME 13

text-fig. 5. Congeria subcarinata
botenica. Interior view of left valve.
(For key to lettering see p. 571.)

Description. Shell solid, equivalve; inequilateral, beaks in an-
terior half; approximately triangular in outline, flattened ven-
trally and with anterior byssal notch. Specimen 5-5 cm. in
length. No internal nacreous layer to shell. Ligament internal,
extending along dorsal line almost \ distance of posterior
margin. Hinge plate without teeth. Anterior adductor and
anterior byssal and/or pedal retractor muscles located on
hinge plate, latter posterior to anterior adductor. Anterior
adductor muscle scar smaller than posterior. Pallial line not
indented by sinus. Margin smooth.

Inferred mode of life. Byssally attached, epifaunal, in fresh and
estuarine waters.

Range. Oligocene-Pliocene. Old World.

Congeria triangularis Partsch

Text-fig. 6

text-fig. 6. Congeria triangularis. In-
terior view of left valve. (For key to
lettering see p. 571.)

Material. Four specimens from the Miocene, Pontian of
Radmanest, Krasso, Hungary. BMNH L71 686-9.

Description. Shell solid, equivalve; inequilateral, beaks in an-
terior half; sharply triangular in outline, flattened ventrally
and with anterior byssal notch. Specimen 4-0 cm. in length.
No internal nacreous layer to shell. Ligament internal, ex-
tending along dorsal line almost \ distance of posterior
margin. Hinge plate without teeth. Anterior adductor and
anterior byssal and/or pedal retractor muscles located on
hinge plate, latter posterior to anterior adductor and having
its insertion on ‘hinge lobe’ projecting down from hinge
plate. Anterior adductor muscle scar much smaller than
posterior. Pallial line not indented by sinus. Growth-lines
distinct. Margin smooth.

Inferred mode of life. Byssally attached, epifaunal, in fresh and estuarine waters.
Range. Oligocene-Pliocene. Old World.

Genus mytilopsis Conrad 1858
Mytilopsis sallei (Recluz)
Text-fig. 7

text-fig. 7. Mytilopsis sallei. Interior view
of left valve. (For key to lettering see p. 571.)

Material. A large collection of recent specimens from
Visakhapatnam harbour, India, where they seem to
have recently been introduced from Central America.

Description. Shell brittle, equivalve; inequilateral,
beaks in anterior half; subtriangular, elongated, not
swollen; slightly flattened ventrally, convex dorsally.
Well defined byssal notch anteriorly. Specimen 1-4
cm. in length. No internal nacreous layer to shell.
Ligament internal, extending along dorsal line less
than \ distance of posterior margin. Hinge plate with-
out teeth. Anterior adductor and anterior byssal
retractor muscles inserted on hinge plate, latter
posterior to anterior adductor and having its insertion

MORTON: EVOLUTION OF THE HETEROMYARIAN CONDITION 567

on ‘hinge lobe’ projecting down from hinge plate. Anterior adductor muscle scar smaller than pos-
terior. Pallial line not indented by sinus. Margin smooth.

Mode of life. Byssally attached, epifaunal, in shallow estuarine and sea waters.

Range. Upper Oligocene-Recent. Central America and India.

Other species in the genus Mytilopsis include:

Mytilopsis leucophaeta Conrad Eastern North America.

Mytilopsis cochleata Kickx Northern Europe.

Mytilopsis africanus Beneden West Africa.

All the above mentioned species bear a very close resemblance to M. sallei and for this reason are not
described or illustrated.

DISCUSSION

One of the most characteristic features of the shell of Dreissena (text-fig. 1) is the
possession of a shell shelf upon which is inserted the anterior adductor muscle and the
anterior byssal retractor muscle. Amongst other bivalves the same type of structure
occurs in the Mytilid genus Septifer, although in this genus only the anterior adductor
muscle has its insertion upon the shelf (Yonge and Campbell 1968). It has been suggested
by Yonge and Campbell (1968) that the possession of this structure in these two stocks
is the result of convergent evolution by adaptation to similar modes of life. It would
seem that the forward extension of the umbones and the extremes of ventral (morpho-
logically anterior) flattening in these two species has necessitated the evolutionary
development of an anchorage, other than the valve itself, for the anterior adductor
muscles. Yonge and Campbell pointed out that the possession of this shelf in these two
genera not only permits the retention of the anterior adductors but enhances their
function. They also suggested that the formation of the shell shelf in these two genera
was achieved by a pushing forward of the mantle tissues in the region just within the
area of insertion of the anterior adductors. This process (although perhaps only occur-
ring in isolated instances in the Mytilacea, e.g. Septifer) is a feature of all fossil and
living Dreissenacea. It is suggested that the shell shelf in the Dreissenacea has a deep
evolutionary significance and is homologous to the hinge plate of other bivalves.

Taylor et al. (1970) showed that the detailed structure of the shell of Dreissena
polymorpha most closely resembles that of certain corbiculids. Inspection of fossil
Dreissenacea similarly suggests the possibility of a common ancestry for these two
groups of bivalves.

Each valve of Corbicula possesses two adductor muscle scars of approximately equal
size and two smaller pedal retractors. The shell is equilateral, with a small internal
ligament, and three cardinal teeth lying on the hinge plate immediately below the
umbo (text-fig. 8a). In another corbiculid, Villorita cyprinoides, the first signs of anterior
flattening are seen, accompanied by extension of the ligament and posterior region of
the shell. This has resulted in this species in the reduction of the anterior portion of
the hinge plate and the movement of the anterior adductor and pedal retractor muscles
towards the umbo. The extension of the dorsal (posterior) region of the shell has re-
sulted in the greater development of the posterior adductor and pedal muscles, relative
to the anterior muscles (text-fig. 8b).

Yonge (1962) showed that bivalves in many phylogenies have retained into adult
life an essentially larval characteristic, the byssus, and that the neotenous retention of

568

PALAEONTOLOGY, VOLUME 13

this structure has, in many cases, influenced the form of the shell. The effect of the
retention of the byssus in forms essentially similar to present-day Villorita would have
been to produce forms in which the processes of ventral flattening were extreme, neces-
sitating not only a change in mode of life but also of function of some organ systems.
The fossil record shows some Driessenacea in which these changes can be observed;
and although these forms have become extinct, it is suggested that they may represent
stages through which the ancestors of present-day Dreissenacea passed.

text-fig. 8. Diagram showing the possible course of evolution of the heteromyarian form in the
Dreissenacea, from an isomyarian ancestor, a, Corbicula ; b, Villorita ; c, Hypothetical ; d, Dreissenomya ;
E, Corigeria zsigmondy i; F Mytilopsis; G, Dreissena polymorpha.

Dreissenomya aperta (text-figs. 2, 8d) possesses a rectangular-shaped shell, in which
the anterior (ventral) margin has only a small degree of flattening, whereas the posterior
(dorsal) margin is extended, with elongation of the ligament and enlargement of the
posterior adductor and posterior byssal and/or pedal retractor muscles. In addition
there is a well-defined pallial sinus, indicating that the animal had long siphons, and
was therefore adapted to an infaunal mode of life. Anteriorly the presence of a byssal
notch shows that the animal was attached to the substratum. The coexistence of a
pallial sinus and byssal notch can perhaps be explained by the animal living attached
to a solid substratum, but either partly or wholly buried by a surface covering of mud
or silt. Yonge and Campbell (1968) noted that Dreissena polymorpha, although attached
to stones by its byssus, is frequently found covered in mud and silt, alive and well.
Situated on the hinge plate of Dreissenomya are the scars of the anterior muscular
system, the anterior adductor muscle lying over and below (anterior to) the most
anterior of the two cardinal teeth. Above (posterior to) the cardinal teeth is the muscle

MORTON: EVOLUTION OF THE HETEROMYARIAN CONDITION 569

scar that represents the site of insertion of the anterior byssal and/or pedal retractor
muscles.

The neotenous retention of the byssus in the ancestors of the Dreissenacea and the
Corbiculacea must also have had an accompanying effect upon the relative importance
of the pedal retractor muscles. Whereas in the burrowing Corbiculacea pedal retractors
were necessary for the movements of the foot associated with burrowing, in the essen-
tially epifaunal Dreissenacea their importance is diminished as the foot has ceased to
be an organ of locomotion [except for the first year of fife (Morton 1969c)] and is now
merely used as a tool for the planting of byssal threads. In order for the byssus to fulfil
its function as an anchor to the animal, enlargement of the byssal retractor muscles
has occurred. It seems possible that the retention of the byssus in the ancestors of the
Dreissenacea also resulted in a change in importance of different areas of mesoderm,
so that the emphasis was displaced from development of pedal retractors to develop-
ment of byssal retractors. Yonge (1962) showed that a small byssal gland is present in
certain members of the Sphaeriacea. Assuming that this gland possesses at least a pre-
sumptive muscle mesoderm, then it is no big step to accept the view that the retention
of the byssus caused preferential development of byssal muscles instead of pedal muscles
in the ancestors of the Dreissenacea.

Congeria subglobosa shows another facet of the development of the heteromyarian
form in the Dreissenacea. The shell is almost square in outline, and extremely solid.
It seems unlikely that this bivalve could lead an epifaunal mode of life, since, although
possessing a byssus, movement of water would put a great strain upon the byssal
apparatus. The animal was probably attached to stones, but was covered by mud or
silt. The anterior adductor muscle scar (text-fig. 3) surrounds a vestigial cardinal tooth,
whilst the muscle scar of the anterior byssal and/or pedal retractor muscle is situated
slightly further posteriorly than in Dreissenomya. Ventral flattening of an animal similar
to C. subglobosa would result in the hypothetical creation of a form very similar to
the living Dreissenacea. Perhaps representing a stage in the development of this form
is C. zsigmondyi, in which the ventral margin of the shell is very much flatter (text-fig. 4),
although the animal was in all probability a burrower. The anterior adductor muscle
scar occupies the now familiar position underneath the umbo, whilst the anterior
byssal and/or pedal retractor muscle scar is situated on a ‘hinge lobe’ projecting down
from the hinge plate. Apart from the lack of ventral flattening this animal is very similar
to Mytilopsis (text-fig. 7). Ventral flattening has been accomplished in Congeria tri-
angularis (text-fig. 6) resulting in a form very similar to Mytilopsis.

Congeria subcarinata botenica (text-fig. 5), however, although flattened ventrally, is
slightly different from C. zsigmondyi and C. triangularis in that the muscle scar of the
anterior byssal retractor is not situated on a ‘hinge lobe’ but on the hinge plate itself
near the anterior adductor muscle scar, a situation very similar to that in Dreissena
polymorpha (text-fig. 1). It would seem that in the Dreissenacea, the positioning of the
insertion of the anterior byssal retractor muscle has proceeded in two separate ways.
Text-fig. 8 indicates a possible way in which the heteromyarian form could have evolved
in the Dreissenacea. From a corbiculid type, e.g. Corbicula (text-fig. 8a), the elongation
of the posterior border of the shell (caused not by the retention of the byssus, but
probably so as to give greater efficiency in feeding whilst burrowing) has resulted in
a form characterized by Villorita (text-fig. 8b) in which the evolutionary modification

570

PALAEONTOLOGY, VOLUME 13

of the anterior adductor muscular system has begun. This condition is extended in
a hypothetical stage (text-fig. 8c) in which the progressive elongation of the posterior
border of the shell and reduction in the anterior border has brought the anterior muscles
on to the hinge plate and nearer the umbo. The effect of the neotenous retention of the
byssus upon such an animal would have enhanced the evolutionary changes already
started in the Corbiculacea, and perhaps produce a whole range of animals all basically
pre-adapted to the future development of an epifaunal mode of life. Most became
extinct, and only a few species have survived to the present day.

Dreissenomya (text-fig. 8d) and Congeria zsigmondyi (text-fig 8e) are extinct forms
that show the way in which the heteromyarian condition could have evolved in the
Dreissenacea. The insertion of the anterior byssal retractor on the hinge plate itself in
such fossils as C. subglobosa and C. subcarinata botenica and present-day Dreissena
polymorpha (text-fig. 8g) probably marks an evolutionary divergence from such forms
as C. zsigmondyi, C. triangularis and present-day species of Mytilopsis (text-fig. 8f), in
which the insertion of this muscle has progressed even further posteriorly along the
hinge plate, with the formation of a ‘hinge lobe’ specially for its insertion. This adaption
undoubtedly improves the efficiency of action of the byssal retractor. It is significant
in separating Dreissena from Mytilopsis.

The evolution of the heteromyarian condition in the Dreissenacea is presumed to
have taken place under conditions that differed from those in which Dreissena now
lives. Yonge and Campbell (1968) suggested that it probably occurred in the intertidal
or shallow sublittoral regions in the sea and that subsequently acquired powers of osmo-
regulation allowed the animals to migrate up rivers into fresh waters. Morton (1969a)
supported this view. It is envisaged that the marine ancestor of both the Corbiculacea
and the Dreissenacea underwent adaptive radiation, producing a wide range of forms
capable of surviving in a variety of habitats. The ancestors of the present day Veneracea
and Glossacea remained in the sea, while the ancestors of the Corbiculacea and Dreis-
senacea invaded estuaries, and there underwent further radiation. During their period
in the sea the ancestors of the Corbiculacea and Dreissenacea left some forms on the
sea-shore, e.g. Mytilopsis, and in estuaries, e.g. Dreissena (Morton 1969 b), Corbicula
japonica (Fuji 1957), and Villorita cyprinoides (Dinamani 1957). Dreissena has, in some
localities, also invaded fresh waters, where it is ideally adapted to the exploitation of
rocky surfaces. D. polymorpha is probably as cosmopolitan in the fresh waters of the
Old World as Mytilus is in the seas. The fossil infaunal Dreissenacea probably
represent distant relatives of Dreissena and Mytilopsis which reflect the evolutionary
trend in these two forms. The evolution of the Corbiculacea and Dreissenacea in many
ways parallels the evolution within the Unionacea, both groups having given rise to
burrowing forms, e.g. Sphaerium and Anodonta, and epifaunal forms, e.g. Dreissena
and Etheria.

The heteromyarian condition in present day Dreissenacea is a direct consequence
of the evolutionary trend described which, it is suggested, proceeded from an established
eulamellibranch stock. Available evidence suggests that the ancestors of the modern
corbiculids gave rise to forms which ultimately produced the species of Mytilopsis, and
Dreissena polymorpha. The neotenous retention in these genera of primitive characters,
e.g. the byssus and a free swimming veliger larva, has made them extremely successful j
in the exploitation of rocky surfaces of fresh and estuarine waters. The evolution of the

MORTON: EVOLUTION OF THE HETEROMYARIAN CONDITION

571

heteromyarian form in the Dreissenacea mirrors in many ways the evolution of the
same form in the filibranch Mytilacea.

Summary. It is considered that the evolution of the heteromyarian form in the Dreis-
senacea, culminating in the evolution of such recent forms as Dreissena polymorpha
and species of Mytilopsis has taken place comparatively recently and from established
eulamellibranch stock.

The neotenous retention of the byssus in forms ancestral to the modern Corbiculacea
has contributed the greatest influence to this process. The effect of this process upon the
ancestral isomyarian parent stock has been :

1 . The extension of the posterior border of the shell, and ligament.

2. Reduction of the anterior (ventral) border.

3. Passage of the anterior adductor muscle and anterior byssal and/or pedal retractor
muscles on to the hinge plate, with a corresponding reduction in the development
of the cardinal teeth.

4. The relatively greater development of the posterior adductor and posterior byssal
and/or pedal retractor muscles.

5. An increase in importance of the byssal retractors compared with the pedal retractors.
Stages in this evolutionary transition from an isomyarian to a heteromyarian form

can be seen in fossil Dreissenacea.

Acknowledgements. I am indebted to Drs. J. D. Taylor and N. J. Morris (British Museum (Natural
History)), for advice in the preparation of this paper; Professor R. Turner (Harvard University) for
supplying specimens of Mytilopsis, and Professor R. D. Purchon (Chelsea College of Science and
Technology) for discussion on the evolution of the Dreissenacea. The work was supported by a research
studentship at the Chelsea College of Science and Technology.

Key to lettering

aa Anterior adductor muscle scar

ab/pr Anterior byssal and/or pedal retractor muscle scar

abr Anterior byssal retractor muscle scar

b Byssal notch

h Hinge plate

l Ligament

pa Posterior adductor muscle scar

pb/pr Posterior byssal and/or pedal retractor muscle scar

pbr Posterior byssal retractor muscle scar

pl Pallial line

ps Pallial sinus

T Cardinal tooth

u Umbo

REFERENCES

atkins, d. 1937. On the ciliary mechanisms and interrelationships of Lamellibranchs. Part III: Types
of lamellibranch gill and their food currents. Q. Jl microsc. Sci. 79, 375-421.
dinamani, p. 1957. On the stomach and associated structures in the backwater clam, Villorita cyprinoides
(Gray) var. cochinensis (Hanley). Bull. cent. Res. Inst. Univ. Kerala, 5, 123-48.

Fuji, a. 1957. Growth and breeding season of the brackish-water bivalve, Corbicula japonica, in Zyusan-
Gata Inlet. Bull. Fac. Fish., Hokkaido Univ. 8, 178-84.
gray, J. e. 1840. In turton, w. Manual of land and freshwater shells of the British islands, 2nd ed., 277.

572

PALAEONTOLOGY, VOLUME 13

keen, M. 1969. In moore, r. c., ed., Treatise on invertebrate paleontology. Part. N, Bivalvia. Geol. Soc.
Am. and Univ. Kansas Press.

morton, b. s. 1969a. Studies on the biology of Dreissena polymorpha Pall. 1, General anatomy and
morphology. Proc. malac. Soc. Lond. 38, 301-21.

19696. Ibid. 3, Population dynamics. Ibid. 38, 471-82.

1969c. Ibid. 4, Habits, habitats, distribution and control. Water Treatment and Examination,.

18, 233-40.

newell, n. d. 1965. Classification of the Bivalvia. Am. Mus. Novit. No. 2206, 1-25.
purchon, r. d. 1960. The stomach in the Eulamellibranchia; stomach types IV and V. Proc. zooL
Soc. Lond. 135, 431-89.

taylor, J. d., Kennedy, w. j. and hall, a. 1970. The shell structure and mineralogy of the Bivalvia.

Part 2, Chamacea-Poromyacea, Conclusions. Bull. Brit. Mus. (Nat. Hist.). Zool. (in press).
toureng, m. 1894a. Sur le systeme nerveux du Dreissensia polymorpha. C. r. hebd. Seanc., Acad. Sci.,
Paris. 118, 544.

18946. Sur l’appareil circulatoire du Dreissensia polymorpha. Ibid. 118, 929-30.

yonge, c. m. 1962. On the primitive significance of the byssus in the Bivalvia and its effects in evolution.
J. mar. biol. Ass. U.K. 42, 113-25.

and Campbell, j. i. 1968. On the heteromyarian condition in the Bivalvia with special reference to

Dreissena polymorpha and certain Mytilacea. Trans. R. Soc. Edinb. 68, 21-43.

BRIAN MORTON

Department of Zoology
The University
Hong Kong

Revised typescript received 14 April 1970

A NEW TRINUCLEID TRILOBITE FROM THE
UPPER ORDOVICIAN OF NEW SOUTH WALES

by k. s. w. Campbell and gwenda j. Durham

Abstract. The new genus and species of trinucleid trilobite Parkesolithus gradyi described herein is the first
member of the family to be described from Australia though there have been occasional records of occurrences.
It is found in Upper Ordovician siltstones near Parkes, New South Wales.

In 1967 Dr. A. E. Grady discovered numerous specimens of a trinucleid trilobite in
poorly outcropping black siltstones on the property of Mr. S. K. Mill, ‘New Durran’,
approximately 15 miles W. of Parkes, New South Wales (grid reference 598899 Forbes
1:250 000 Topographical Sheet). Parkes is situated approximately 170 miles WNW.
of Sydney. Ordovician rocks have been suspected to occur in the area for more than
half a century (Andrews 1910). Recently an extensive Late Ordovician fauna of brachio-
pods, trilobites, ostracods, and conodonts has been discovered in the vicinity of the
trilobite locality (Packham 1967). These have been recovered from an unnamed lime-
stone that lies an unknown distance stratigraphically below the trinucleid-bearing silt-
stone. Packham has suggested that the limestone fauna is of late Wilderness age in
terms of the American sequence, or Gisbornian in terms of the Australian graptolite
sequence.

Associated with the trinucleids are a few poorly preserved brachiopods and numerous
specimens of the graptolites Orthograptus truncatus socialis (Lapworth), O. truncatus
intermedius Elies and Wood and Climacograptus cf. scharenbergi Lapworth. These
indicate an Eastonian (Caradocian) age which is consistent with Packham’ s determina-
tion of the age of the under-lying limestone.

No trinucleids have been described previously from Australia. There are, however,
various records of the group, for example ‘a cryptolithid close to Eirelithus’ from
probable Middle Ordovician siltstones in Tasmania (Banks 1962), ‘fragmentary trinu-
cleids’ in the limestone mentioned above from Parkes (Packham 1967), and Trinucleus
from the Upper Ordovician Cliefden Caves Limestone and Malongulli Formation of
central New South Wales (Packham et al. 1969, pp. 80-1).

The text-figure and the plate are the work of Mrs. J. A. Davis and Mr. L. Seeuwen
respectively.

SYSTEMATIC DESCRIPTION

Family trinucleidae Hawle and Corda 1847
Subfamily cryptolithinae Angelin 1854
Genus parkesolithus gen. nov.

Type species. Parkesolithus gradyi sp. nov. from an unnamed formation in the Upper Ordovician, west
of Parkes, N.S.W.

Diagnosis. Cephalon similar in shape to that of Cryptolithus ; small eye tubercles present
just medial to the highest point of the cheek and opposite the anterior edge of furrow'2p;

[Palaeontology, Vol. 13, Part 4, 1970, pp. 573-80, pi. 111.]

574

PALAEONTOLOGY, VOLUME 13

glabella with furrow lp formed of a double pit, and 2p and 3p almost imperceptible
externally but forming distinct, strongly arcuate muscle areas internally; occipital ring
sharply crested but not produced into a spine; glabella and cheeks unornamented;
upper lamella with pit rows Ex, E2, I1? and I4 (and usually I2) continuous around the
entire structure, and I3 present laterally; regularity of pit rows lost on postero-lateral
parts of fringe; a strong continuous list present between Ex and E2; lower lamella with
very weak girder. Thorax with 6 segments. Pygidium subtriangular in outline; 8+ I
weak axial rings; 7+ pleural ribs weak but distinct; posterior border prominent and
steep.

Remarks. We accept the subfamilial divisions of the Trinucleidae proposed by Whitting-
ton (1941) with the addition of the Hangchungolithinae of Lu. The shape of the glabella,
the deep but small glabellar furrows lp that are in close juxtaposition to the occipital
furrow, the very weak furrows 2p, the virtual absence of the furrows 3p, the flat to gently
concave dorsal fringe, and the absence of radial sulci on the fringe, all indicate that
Parkesolithus is more closely related to the Cryptolithinae than any of the other sub-
families. Eye tubercles are not normal in members of this subfamily as it is at present
constituted (Whittington in Moore 1959). We are not inclined to place much weight on
this feature, however, since eye tubercles do occur in such genera as Eirelithus Lamont.

If, as most workers believe, the number of E rows of pits on the fringe is of funda-
mental taxonomic importance, Parkesolithus is closely related to Broeggerolithus
Bancroft. However, there are considerable differences. The preglabellar fringe of Broeg-
gerolithus has E4_2 and I4_2 complete; I3 is introduced laterally and usually forms the
innermost row, though I4 is occasionally present inside it. In Parkesolithus, on the other
hand, Ex_2, I12, and I4 are continuous in front of the glabella and I3 is introduced be-
tween I2 and I4 antero-laterally (see discussion under the specific description for the
identification of I3_4). The two genera also differ in the following: the pronounced list
between Ex and E2 on the upper lamella of Parkesolithus does not occur in Broeggero-
lithus; 2 p in Parkesolithus is deeper than in Broeggerolithus ; the girder is much stronger
in Broeggerolithus ; the postero-lateral margin of the cephalon is turned back to form
a large triangular genal angle in Parkesolithus, but is almost transverse in Broeggero-
lithus; the genal spines are directed obliquely outwards in Broeggerolithus but almost
directly backwards in Parkesolithus. In our opinion these differences outweigh the
similarity of the two E rows.

In the shape of the cephalon, glabella, genal spines, glabellar furrows, muscle scars,
and pygidium Parkesolithus is closely comparable to Cryptolithus, but there are many
differences in the fringe and girder structure. Typical species of Cryptolithus have a
single E row, fewer complete I rows, new I rows introduced against the cheek rather
than between existing rows, and a pronounced girder on the lower lamella. There
are, however, species doubtfully assigned to Cryptolithus that have some features in
common with Parkesolithus, the best known being C. ? bedinanensis Dean (1967) from
the Caradocian Bedinan Formation of Turkey. On the upper lamella of the fringe this
species has a distinct list inside the outermost row of pits, and many specimens have four
continuous rows of pits in front of glabella whereas most species of Cryptolithus s.s.
have three. Parkesolithus has five. Furthermore, the insertion of new rows takes place
antero-laterally between existing rows rather than against the cheek (Dean, pi. 4, figs.

CAMPBELL AND DURHAM: A NEW TRINUCLEID TRILOBITE 575

4, 5, 6, 8). However, examination of the material convinces us that Dean was correct
in interpreting the position of the girder as inside the outermost row of pits as is normal
for Crypt olithus. His plate 3, fig. 7 tends to emphasize unduly the pseudogirders inside
the girder proper. We are not inclined, therefore, to place C. ? bedinanensis in Parke-
solithus despite the above-mentioned similarities.

Parkesolithus gradyi sp. nov.

Plate III, figs. 1-15

Material. Holotype 21293; paratypes 21288-9, 21295a-b, 21301, 21304, 21306, 21308-10, 21315a-b,
21318a-b, 21321a-b, 21327a-c, 21328, 21331—4, 21337a-b. Geology Department, Australian National
University Collection.

Description

Cephalon. Outline semicircular, approximately twice as wide as long (sag.) ; no accurate
estimate of height available because of distortion; lateral margins at genal angle parallel
and extend into genal spines which are faintly convex outwards and extend almost
straight backwards; genal spines posterior to fringe approximately equal to median
length of cephalon, unornamented and almost square in cross-section with a faint
furrow along the ventral surface and an even fainter one along the dorsal surface;
precise termination of spine not observed but spine tapers very gradually over its
anterior three quarters and then more rapidly.

Ratio of length to width of glabella is approximately 3 : 2 (variation cannot be deter-
mined owing to crushing); outline expands slightly to lp and then more rapidly, giving
a mildly pyriform outline; greatest width and height located about two-thirds of the
length of the glabella from the occipital furrow; anterior margin gently rounded and
only slightly deflecting the continuous rows of pits on the fringe.

Occipital ring narrow and convex in posterior profile, sharply crested on the pos-
terior half in sagittal profile ; no occipital spine ; axial furrow broad and shallow, deepening
laterally into small occipital pits which are located inside the axial furrow; occiput con-
siderably lower than the anterior portion of the glabella and about one-tenth of the
length of the glabella. Glabellar furrow lp of two pits lying in the same shallow depres-
sion on the lateral slope of the glabella; the more posterior pit moderately deep and
circular medially but with a shallow antero-lateral extension, and situated immediately
in front of the tiny occipital pit; the more anterior one is two or three times larger,
shallower and oval in outline with the long axis directed antero-medially well up on the
flanks of the glabella, the deeper posterior portion almost in contact with the posterior
depression. 2p situated on the lateral slope of the glabella directly anterior to the oval
depression of lp, scarcely visible externally, but internally forming a shallow horseshoe-
shaped ridge open posteriorly, the posterior extremities being slightly more prominent
than the remainder. 3p a very faint comma-shaped depression on the slope of the
glabella slightly more than midway along its length, the deeper part of the depression
being higher on the slope of the glabella and the long axis pointing medially. All three
pairs of depressions lie inside the axial furrow.

Axial furrows parallel, broad, shallow, and straight except for a slight curvature at
the widest point of the glabella; anterior pits small and separated from the fringe by
a low ridge. No ornament on the glabella and no median tubercle.

C 7719 P P

576

PALAEONTOLOGY, VOLUME 13

text-fig. 1. Reconstruction of Parkesolithus gradyi gen. et sp. nov.

Cheeks slightly convex with the highest point near the postero-lateral corner; cheeks
distinctly lower than the glabella and slope away gently medially to the axial furrow
and more steeply to the fringe; posterior border furrow moderately deep; a shallow
extension of the posterior border furrow present a short distance along the posterior
border beyond the fulcrum; most specimens with a tiny pit (separate from the fringe
pits but probably one of them) in the triangular space between the posterior border,
the posterior border furrow and the inner edge of the fringe (see PI. Ill, figs. 14-15).

EXPLANATION OF PLATE 111
Parkesolithus gradyi gen. et sp. nov.

Fig. 1. Latex cast of the first two thoracic segments; x2; 21304 ANU.

Fig. 2. Latex cast of ventral surface showing the pleural tips and the broken apodemes; x 1-4; 21318a
ANU.

Figs. 3 and 4. Latex cast of ventral surface showing complete apodemes; x 2 and x 4; 21301 ANU.
Fig. 5. Latex cast of dorsal surface; x2; 21308 ANU.

Fig. 6. Latex cast of exterior of pygidium; x 3-5; 21332 ANU.

Figs. 7 and 8. Latex casts of dorsal surfaces of two cephala; 7 is a juvenile holaspid; x 5 and x 1-4;
21310 and 21334 ANU.

Fig. 9. Latex cast of dorsal surface cephalon; x2; 21327a ANU.

Fig. 10. Mould of internal surface of thorax, pygidium and lower lamella; x 1-5; 21315a ANU.

Fig. 11. Latex cast of dorsal surface of thorax and pygidium, and ventral surface of lower lamella;
x 1-5; 21315b ANU.

Fig. 12. Latex cast of dorsal surface of pygidium; x 1-9; 21289b ANU.

Fig. 13. Latex cast of ventral surface of cephalon showing lower lamella; x 1-6; 21309 ANU.

Figs. 14 and 15. Internal moulds of two cephala; x 1-5, x2; 21295a and 21293 ANU.

Palaeontology, Vol. 13

PLATE 111

CAMPBELL and DURHAM, Parkesolithus gradyi gen. et sp. nov.

CAMPBELL AND DURHAM: A NEW TRINUCLEID TRILOBITE 577

Pair of small circular eye tubercles opposite the anterior edge of furrow 2p, on the
inner slope of the cheeks c. one-quarter of the distance from the axial furrow to
the fringe; no ornamentation on cheeks but extremely faint eye ridges extend from the
eye tubercles anteromedially to the axial furrow opposite the 3p muscle scar on some
specimens.

Posterior border short, highest along the sharp posterior edge and sloping gently
forwards into the symmetrical posterior border furrow; border longer (exsag.) behind
the first few pits on the fringe and then gradually fades away laterally; posterior border
of fringe almost straight and inclined at an angle of 45° to posterior border of cheeks ;
articulatory furrow along posterior border very shallow, if present at all. Doublure on
the occipital ring very short and with a slightly thickened edge.

Upper lamella of fringe. Anteriorly and antero-laterally fringe slopes gently down for
half its width then turns up slightly, resulting in a gently concave fringe with the inner
and outer margins being on the same level. Laterally and postero-laterally fringe less
concave, especially its inner part which actually becomes convex and very steep near
the posterior border, and is on a much higher level than the still slightly concave outer
part ; a prominent concentric ridge developed inside E4 around the entire circumference
except in the most posterior part of the genal angle where it fades out abruptly; fringe
narrowest in front of the glabella ; on all specimens E4, E2, I4, and I4 complete in front
of glabella; on most specimens I2 also complete; I3 never complete and most anterior
pits of this row inserted near the line of the axial furrow, i.e. about R4_7 ; I4 bent dis-
tinctly forwards in front of the glabella on all specimens, but I2 only slightly distorted
if at all. Anteriorly and antero-laterally pits radially arranged ; three or four innermost
rows usually arranged radially as far back as a line joining the eyes; in this region radial
arrangement of pits sometimes gives a false impression of weak sulci; anterior radial
rows straight, antero-lateral ones slightly arcuate. Laterally and postero-laterally, pits
mostly irregularly arranged with many additional ones inserted. Normally ten pits
present along the posterior border of the fringe. All pits approximately the same size
but outermost row and innermost row smaller on some specimens.

Pit count ( half-fringe )

Row

No. of pits

Mean

No. of

E2 (outermost row)

38-44

42

specimens

9

E4 (first row inside ridge)

30-6

32

7

L— I2

30-6

31

7

Other rows too irregular to count.

Lower lamella of fringe. Girder at very weak angulation, only slightly stronger than the
weak pseudogirders on either side; girder continued down along genal spine as the inner
ventral carina on some specimens (PI. Ill, fig. 13) but not on others (PI. Ill, fig. 11);
outer ventral carina of the spine is a continuation of the outer fringe margin; no sign
of any prominent ridge or furrow between E4 and E2 corresponding to the ridge on the
upper lamella.

Thorax. Six segments in the thorax; axis tapers slightly towards the pygidium; axial
furrow shallow, deeper at the back than the front of each segment giving a regular

578

PALAEONTOLOGY, VOLUME 13

notched appearance; axial ring short (sag. and exsag.), axially one-third of the total
length of the segment; ring rises steeply from the articulating furrow to a crest, j
immediately behind which is a shallow furrow that extends the full width of the ring.

Deep transverse slit-like apodemal pits set well in from the axial furrow with a slight
depression on their outer and a much deeper one on their inner margin; apodemes set
about mid-length on the segment; articulating furrow symmetrical with a uniform slope
anterior and posterior and a well-rounded base; articulating half-ring on all segments
short, on the anterior segment its anterior margin being almost transverse but on sub-
sequent segments gently convex forwards ; articulatory processes relatively short.

Pleurae of third and fourth segments c. 1-75 times as wide as the axis; anterior and
posterior pairs slightly shorter than the middle pair; anterior pleurae shorter so as to
fit against the posterior border of the cheeks and fringe of the cephalon. Anterior edges
of the first pleural segment on opposite sides of fulcrum set at an angle of 45°; posterior
edge also bends slightly posteriorly at fulcrum; pleural tip moderately sharp. On more
posterior segments angulation of pleural tip progressively less pronounced ; last segment
with a blunt almost square pleural tip, a virtually straight posterior edge and an anterior
edge with only a slight angulation close to the pleural tip. Fulcrum moves progressively
outwards on more posterior segments and on the last one is almost at the extremity;
pleural furrow on anterior segment of uniform length (exsag.) throughout, deepest at the
axial furrow, shallowing laterally and then deepening again towards the pleural tip;
furrow transverse between the axial furrow and the fulcrum, then curving posteriorly
to terminate almost on the posterior edge of the pleural tip; furrows progressively
broader and shallower on more posterior segments (and have progressively more round-
ed lateral terminations) until on the last segment the furrow occupies most of the segment
surface. Posterior band on anterior segment lanceolate and flat-topped; on second
segment of uniform length (exsag.) and sharp crested; on third segment unusually high
and sharp crested and diminishing in size distally to fulcrum; and on segments four,
five, and six, triangular in outline, rounded on top, and progressively shorter (exsag.). ;

Tips of pleurae downturned to form an almost vertical lateral doublure; no inflected
ventral doublure present. Apodemes on all segments strong; all transverse and with
a distinct swelling and ventral projection at their median end; some also with a much
smaller lateral swelling.

Pygidium. Two to three times as wide as long depending on size (the larger are relatively
wider) with subtriangular axis extending to the posterior margin; eight definite rings
visible on the dorsal surface, and possibly one or two more on exceptionally well- |
preserved specimens, the more posterior ones being very faint; rings deflected forwards
medially, the amount of deflection decreasing posteriorly; anterior ring furrows deepest
laterally but longest sagittally, the most anterior one almost bisecting the anterior ring;
on more posterior segments ring furrows visible only on the medial part of the axis;
articulating half ring short but with a pronounced arcuate anterior outline. Axial
furrow broad, shallow, and only slightly deepened opposite the ends of the more
anterior ring furrows.

Anterior margin of the pleural regions of the pygidium straight and sharp ; inner half
of pleural region smooth and gently concave except on the most anterior segment where
it is almost flat; outer half gently concave and rising to a sharp ridge on the posterior

CAMPBELL AND DURHAM: A NEW TRINUCLEID TRILOBITE 579

border; outside this ridge doublure widest and gently convex on either side of the axis,
but more steeply sloping and progressively narrower postero-laterally and laterally,
becoming vertical at the anterior end of the pygidium; line of border ridge arcuate but
actual posterior margin of pygidium sub-triangular; axis meets border ridge posteriorly
producing a gently rounded crest on the ridge; very fine terrace lines on the posterior
doublure fading medially behind the axis.

Seven ‘pleural ribs’ readily distinguished; ribs clearly marked only in the outer half of
the pleural field, straight to slightly curved in outline and symmetrically sloping front
and back; ribs meet border ridge at their distal extremities but do not interrupt crest of
ridge; extremely delicate interpleural furrows occasionally seen and cut obliquely across
these ‘pleural ribs’ which are thus seen to be composed of the posterior band of a given
segment adaxially and the anterior band of the next succeeding segment distally (see
text-fig. 1).

Pair of deep apodemal pits in the first ring furrow set well in from the axial furrow;
on each side of second ring furrow a pair of ovate, subequal, slightly raised muscle
scars reach two-thirds of the distance to the median line from the axial furrow; on
subsequent ring furrows outer scar of pair tends to maintain its size whereas the inner
one gradually diminishes, but on most posterior furrows outer scar also diminishes
rapidly; paired arrangement probably maintained right to posterior extremity; eleven
pairs of scars (in addition to the apodemes) present on largest and most complete
specimen.

Remarks. The material is all crushed to some extent so that it is difficult to determine
the exact proportions of the various structures, or in many specimens such details as
the pit arrangement on parts of the fringe. With regard to the latter character, however,
enough specimens are known for us to be confident of the interpretation given above.
We may have been unconventional in the way that we have interpreted the interruption
of I3 and the continuity of I4 in front of the glabella. Some authors may prefer to inter-
pret I3 as continuous and I4 as interrupted. In our opinion this would be unjustified
since it is possible to consider the I4 pits as forming a continuous, but gently flexed
row in front of the glabella in all specimens, whereas continuity cannot be considered
for I3 without an angular change in direction of the row. But even more important is
the fact that on some specimens, particularly 21321a-b, the pits of the I3 row diminish
in size towards the line of the axial furrow and the row wedges out between I2 and I4,
the pits of which retain their normal size. It is also worth noting that on one specimen,
21328C, I2 fails immediately in front of the glabella, but on nine others it appears to
be complete.

The girder is variably developed but is always weak and virtually indistinguishable
from the ridges on either side. It has been recognized by its continuity with the carina
on the venter of the genal spine and/or by the slight change in slope of the lamella on
its inner side. In most specimens there is no doubt about its recognition. Take, for
example, the specimen figured on Plate 111, fig. 11. The carina on the genal spine does
not continue strongly into any one of the ridges, though it could continue into the
outermost ridge only by a distinct flexure. On the other hand, on the antero-lateral
and anterior parts of the specimen the second ridge in from the margin marks a
change in slope of the inner and outer parts of the lamella. The normal situation is

580

PALAEONTOLOGY, VOLUME 13

shown on PI. Ill, fig. 13. In our opinion it is not possible to interpret any ridge other
than the one inside the second row of pits as the girder on any of our specimens.

The radial arrangement of the pits which occurs on the anterior and antero-lateral
parts of the fringe often does not extend across the Ex-Ea ridge to row E2, and on several
specimens the pits of this latter row are definitely offset. The regularity of all rows tends
to break down postero-laterally. Sometimes it is not possible to recognise even E1?
and occasionally there is an odd pit on the ridge between Ex and E2.

There may possibly be some doubt about our interpretation of the glabellar furrows
and muscle scars. We have chosen to use the terminology lp to 3p for these structures
despite the fact that the anterior ones can scarcely be described as furrows. The occipital
apodeme is very small and shallow and could easily be overlooked. The double structure
in front of it that we have labelled lp, is clearly the homologue of lp together with the
posterior muscle scar of Whittington’s (1968) interpretation of Crypt olithus. Since in
all other trinucleids on which the glabellar furrows are clearly defined they are three in
number, and since the two pits in question lie more or less in the one depression, it
seems unlikely that they represent separate glabellar furrows.

Finally, we have chosen to refer to the downturned edge of the pygidium and the
corresponding parts of the pleural tips as the doublure rather than the border as is
the usual practice. These parts carry terrace lines as is normal on the doublure; there
is no completely inflected exoskeleton such as might be expected if the parts in question
are really the border; and the sharp crest around the extremities of the pygidium
corresponds with the border of other trilobites. It seems clear to us therefore that the
doublure has been modified in shape to serve some special function in the trinucleoids.

REFERENCES

Andrews, e. c. 1910. The Forbes-Parkes Goldfield. Mineral Resour. N.S.W. 13, 1-109.
banks, m. r. 1962. Ordovician System, in spry, a. h. and banks, m. r., eds., Geology of Tasmania.
J. geol. Soc. Aust. 9, 147-76.

dean, w. t. 1967. The correlation and trilobite fauna of the Bedinan Formation (Ordovician) in south-
eastern Turkey. Bull. Br. Mus. nat. Hist. Geol. 15, (2), 83-123, pi. 1-10.
packham, g. H. 1967. The occurrence of shelly Ordovician strata near Forbes, New South Wales.
Aust. J. Sci. 30 (3), 106-7.

et al. 1969. In packham, g. h., ed., The geology of New South Wales. J. geol. Soc. Aust. 16, 1-654.

Whittington, h. b. 1941. The Trinucleidae — with special reference to North American genera and
species. J. Paleont. 15, 21-41, pi. 5-6.

1959. In moore, R. c., ed., Treatise on invertebrate paleontology. Part O, Arthropoda I. Geol. Soc.

Am. and Univ. Kansas Press.

1968. Crypt olithus (Trilobita): specific characters and occurrence in Ordovician of eastern

North America. J. Paleont. 42, 702-14, pi. 87-9.

K. S. W. CAMPBELL
GWENDA J. DURHAM

Geology Department
Australian National University
Canberra, A.C.T.

Typescript received 29 December 1969 Australia

ZOARIAL MICROSTRUCTURES OF TWO PERMIAN
SPECIES OF THE BRYOZOAN GENUS STENOPORA

by JOHN ARMSTRONG

Abstract. The zooecial walls of Stenopora ovata Lonsdale and S. crinita Lonsdale consist of laminae which are
built of variably shaped and variably disposed tabular units. It is suggested that the acanthopores of S. crinita
and S. ovata are rods of calcite that together with the surrounding wall laminae were deposited by the steno-
porid zooids. The mechanisms of growth of the laminae and their components are discussed.

Traditionally the laminae that comprise the skeletons of members of the bryozoan
orders Cyclostomata, Trepostomata, Cryptostomata, and Cystoporata (i.e. Board-
man’s and Cheetham’s (1969) tubular Bryozoa) have been interpreted as growth sur-
faces. Laminae were believed to have been added to the skeleton one layer at a time
with the depositing epithelium paralleling the laminae. However, Boardman and Cheet-
ham (1969) have now recognized exceptions to this growth model in Pliocene to Recent
heteroporid Cyclostomata. Whereas the wall laminae of many tubular Bryozoa are
convex distally (e.g. Stenopora herein), the laminae making up the walls of these
heteroporid skeletons, together with the appearances of the skeletal components on
zooecial surfaces, suggest that calcium carbonate was added simultaneously to the
exposed edges of numerous laminae. Such laminae enlarge in an edgewise direction
and are oblique to growth surfaces. For zoaria having distally convex wall laminae,
Boardman and Towe (1966) had suggested that the laminae were in fact deposited layer
by layer, each layer being essentially completed before the succeeding one was initiated.
In this scheme, the depositing epithelium parallels the laminae that it is secreting.
Nevertheless, as a result of their findings from Recent heteroporid specimens, Board-
man and Cheetham (1969) speculated that ‘quite possibly many Bryozoa having
laminae that closely parallel depositing epidermis will prove to have shingled and edge-
wise crystal development’.

Results presented herein were obtained from a study of two species of the trepostomatous genus
Stenopora in which the wall laminae are convex distally. The work was undertaken to detail the
characteristics of laminar parts of the skeletons of these species and to determine the nature of acan-
thopores which occur in the zooecial walls. One specimen (FI 5872) of Stenopora ovata Lonsdale and
one specimen (F60038) of Stenopora crinita Lonsdale were used; both specimens now being retained
in the type collections of the Department of Geology, University of Queensland. The illustrations in
Plates 112 and 113 are optical photomicrographs of thin sections and the photographs in Plates 114
to 1 17 are electron-micrographs of polished sections (PI. 114-16) and broken skeletal surfaces (PI. 1 17).
The polished sections were cut perpendicular to (transverse section) and parallel to (vertical section)
the direction of growth of the zooecia. The surfaces of the sections were polished with a sequence of
abrasives finishing with a l-/xm. diamond abrasive. Before replication, the surfaces of the sections
were etched for a few seconds with a mixture of 1 % nitric acid in ethyl alcohol. The normal two-stage
carbon replicating technique was employed; the intermediate medium being nitrocellulose. The broken
surfaces used were obtained by splitting the zooecial walls and directly replicating, without any
polishing or etching, the fractured surface. Shadowing of the replicas at angles of approximately 30°
was with 1 to 1 mixtures of gold and palladium.

[Palaeontology, Vol. 13, Part 4, 1970, pp. 581-7, pis. 112-117.]

582

PALAEONTOLOGY, VOLUME 13
ZOARIAL STRUCTURE

The zoaria of Stenopora ovata and S. crinita consist of zooecial tubes separated by j
laminar walls containing acanthopores.

The zoarium of the studied specimen of Stenopora crinita is massively branching with [
a broad immature zone surrounded by a mature zone about one half as wide. The
branches are up to 8 cm. in diameter. Zooecial tubes are polygonal and their walls are
usually thin (PI. 113, fig. 7). No diaphragms are present in any of the zooecia and an-
nular thickenings of the walls occur only in the mature zone where they are small and
widely separated. Acanthopores are present only at wall junctions.

The zoarium of the studied specimen of Stenopora ovata is encrusting a brachiopod
shell and is about 1 cm. thick. Zooecial tubes are polygonal to smoothly rounded and
lack diaphragms. Annular thickenings of the walls are well developed throughout the
zoarium (PI. 113, figs. 3, 4). Acanthopores are present only at wall junctions (PI. 112, i
figs. 1-3).

LAMINAR MICROSTRUCTURE

The zooarial walls of Stenopora are composed of laminae of the order of 1-5 pm.
thick (PI. 115, fig. 6; PI. 117, figs. 1-4). In vertical sections perpendicular to the walls
the laminae are convex distally (PI. 113, figs. 3, 4, 6; PI. 114, fig. 2; PI. 115 figs. 1, 2:

PI. 1 16, figs. 1-3). Laminae successively overlie each other both in the walls and annular
thickenings and they terminate at the surfaces of the walls (PI. 113, figs. 3, 4, 6; PI. 114,
figs. 1, 2; PI. 115, fig. 2). In transverse section the laminae are also arched and they are
convex away from the closest inter-zooecial angle (PI. 1 14, fig. 1 ; PI. 115, fig. 3). Because
the laminae are convex distally, transverse sections of the zooecia often show the walls
with apparently non-laminated central regions bordered on each side by a zone having
an obvious laminar structure (PL 1 14, fig. 1). This apparent layering of the wall is simply
the result of sectioning a series of parallel sharply convex laminae. Towards the surfaces
of the walls the laminae are perpendicular to transverse sections, whereas medially the
tangential relationship between the wall laminae and the section yields the massive
appearance of this part of the wall. Adjacent to acanthopores the laminae are deflected
distally (PI. 113, figs. 1, 2, 5) and they comprise a series of ‘cone-in-cone’ structures.
Transverse sections usually reveal the laminae concentrically arranged around acan-
thopores (PI. 112, figs. 1, 2; PL 114, fig. 5; PL 115, figs. 4, 5) although in the walls of
the specimen of Stenopora crinita this concentric arrangement is not developed except

EXPLANATION OF PLATE 112

Figs. 1-3. Stenopora ovata Lonsdale. FI 5872, transverse sections of the zoarium illustrating zooecia
and acanthopores. I,x60. 2, x250. 3, x25.

EXPLANATION OF PLATE 113

Figs. 1-5. Stenopora ovata Lonsdale. FI 5872. 1, vertical section parallel to wall illustrating an

acanthopore and the adjacent inclined wall laminae, x 95. 2, enlargement approximately by 3 of
part of the acanthopore in fig. 1. 3, 4, moniliform appearance of zooecial walls in vertical section,
both x 85. 5, vertical section parallel to wall illustrating acanthopores and wall laminae, x 60.

Figs. 6 and 7. Stenopora crinita Lonsdale. F60038. 6, vertical section of thickened portion of a zooecial
wall illustrating disposition of the wall laminae, x 60. 7, transverse section of zoarium illustrating
the thin walled polygonal zooecia with inorganic lining, x 20.

Palaeontology, Vol. 13

PLATE 112

ARMSTRONG, Bryozoan microstructure

Palaeontology , Vol. 13

PLATE 113

ARMSTRONG, Bryozoan microstructure

ARMSTRONG: MICROSTRUCTURES OF BRYOZOAN GENUS STENOPORA 583

in thicker parts of the walls (PI. 1 14, figs. 3-5). Growth-lines and annular thickenings
in the walls of the zooecia of Stenopora ovata and S. crinita are concave distally reaching
their most distal points at the inter-zooecial wall junctions (PI. 113, fig. 5).

Longitudinal sections of the walls immediately distal to the annular thickenings of
Stenopora crinita show the wall with a massive central portion that is surrounded by
one or more laminae, the number of laminae increasing distally (PI. 116, figs. 1-3).
This massive material was present above all of the examined annular thickenings of
S. crinita and although its origin is conjectural, the consistent appearance of the material
seems to suggest that it was a primary deposit laid down by the stenoporid zooids.
Similar massively granular regions occur above some of the annular thickenings of
Stenopora ovata (PI. 115, figs. 1, 2). Above other annular thickenings of S. ovata there
appear to be superimposed laminae like those in normal parts of the walls.

The components making up the laminae of Stenopora crinita were observed in replicas
of broken surfaces of the walls. The laminae are built of tabular units which are two to
five times wider than they are thick, and twice to many times longer than they are wide
(PI. 117, figs. 1-4). Boundaries between the tabular units of a lamina are marked by
grooves in the surface of the lamina. The laminae consist of both irregularly and
regularly shaped units. Surfaces of the laminae sometimes bear ridges, and these seem
to be associated only with the more regular laminar units (PI. 17, figs. 1, 2). The surfaces
of the regular units are also often marked with fine chevron-shaped ridges and grooves
(PI. 117, figs. 1, 2). Armstrong (1969) described a somewhat similar situation in the
shells of the strophomenid brachiopods Streptorhynchus pelicanensis and Terrakeasolida.
The shells of these species consist of thin sheets, each of which is composed of tabular
blade-like units. The blades of a particular sheet are parallel to each other, but almost
invariably they are not parallel either to the blades in contiguous sheets above and below
or to the blades in adjacent coplanar sheets. Surfaces of the sheets are covered with
crossing sets of parallel ridges and grooves (Armstrong 1969, pi. 57, fig. 3; pi. 58, figs.
1 , 2), the grooves representing the boundaries between the blades of that sheet and the
ridges being the parts of that sheet which have infilled the inter-blade grooves in the
base of the sheet above.

ACANTHOPORES

Commonly occurring in the skeletons of bryozoans are structures referred to as
acanthopores. Bassler (1953) defined an acanthopore as a ‘cylindrical tube adjoining
zooecial walls and parallel to them in growth; formed of cone in cone layers with
narrow central tubule which may be crossed with minute diaphragms; position often
marked superficially by projecting spines’, and he stated that they ‘undoubtedly re-
present zooids with some definite function’ (Bassler 1953, p. G 91). Previously, in dis-
cussing the morphology of trepostomatous zoaria, Cumings and Galloway (1915) had
referred to acanthopores as ‘hollow thick walled tubules’. They speculated that the
small spines formed by the projection of acanthopores beyond the surface of the
zoarium had a protective function (Cumings and Galloway 1915, pi. 15, figs. 51, 52).
Subsequent to Bassler (1953) many references to, and definitions of, acanthopores have
implied their tubiform nature Boardman 1960, pp. 28, 29; Ross 1961, pp. 21, 32,
text-fig. 7; Ross 1966, p. 1 12; Boardman and Utgaard 1966, p. 1087; Cuffey 1967, p. 53).
Recently, however, Tavener-Smith (1969) has suggested that acanthopores in the

584

PALAEONTOLOGY, VOLUME 13

trepostomatous Leioclema asperum are solid rods of calcite and that they did not house
accessory zooids. Tavener-Smith implies that the calcite of the acanthopores of this
species is of zooidal rather than inorganic origin.

The structures termed acanthopores in the studied specimens of Stenopora are so
identified because they consist of apparently ‘tubular’ structures running parallel to
the zooecia in the walls (PI. 1 12, figs. 1-3 ; PI. 113, figs. 1, 2). The wall laminae dip away
from the acanthopores in a proximal direction (PI. 113, figs. 1, 2, 5). In the studied
specimen of S. ovata the acanthopores vary from 10 to 60 pm. in diameter with 90%
of them being between 10 and 40 pm. and 70% having a diameter between 15 and
25 pm. Boundaries between the acanthopores and the surrounding wall laminae are
abrupt and well defined (PI. 113, fig. 2; PI. 1 14, figs. 3-5; Pis. 115, figs. 4, 5). Longitudinal
sections of acanthopores show the rods of calcite to be continuous and to lack indica-
tions of growth surfaces (PI. 114, fig. 6). Laminae do not seem to be continuous into
acanthopores. In longitudinal sections adjacent to acanthopores (PI. 114, fig. 2) there
is a zone in which the boundaries between the laminae are widely spaced. In these areas,
the laminae, being tangential to the adjacent acanthopore, are almost parallel to the
section and consequently they simulate an elongate massive structure that is occasionally
crossed by growth lines. Tavener-Smith’s (1969) figure 6 is similar to Plate 114, fig. 2
herein and may also have been adjacent to rather than in an acanthopore. All acan-
thopores in the studied specimens of Stenopora ovata and S. crinita consist of an ap-
parently homogeneous calcite rod and none are occupied by the sedimentary and
carbonate mineral infillings that occur in the zooecia of these specimens. Carbonate
minerals in the zooecia of the studied specimens of Stenopora ovata and S. crinita
include calcite, ferroan calcite, and ferroan dolomite, whereas the zooecial walls and
acanthopores consist only of calcite. These facts suggest that the calcite of the acan-
thopores has not been secondarily introduced and there seems little doubt that the
acanthopores of Stenopora ovata and S. crinita , like those of Leioclema asperum de-
scribed by Tavener-Smith (1969) were never minute tubes. Indeed, the nature of the
acanthopores in Stenopora ovata and S. crinita can only be reconciled with the viewpoint
that the calcite of both the acanthopores and the wall laminae was deposited by the
stenoporid zooids. Conceivably, as Tavener-Smith (1969) suggested, many of the ‘calcite
filled tubules’ constituting the acanthopores of other bryozoans might also be of zooidal
rather than inorganic origin.

The rods of calcite and the laminae of the zooecial walls probably owe their different

EXPLANATION OF PLATE 114

Figs. 1-6. Stenopora crinita Lonsdale. F60038. 1, transverse section of wall. Closest wall junction
was in direction of lower right corner of figure, x 500. 2, vertical section of wall adjacent to an
acanthopore, x 750. 3, 4, 5, wall junctions containing acanthopores, all x 250. 6, vertical section
of zooecial wall illustrating an acanthopore. Massive calcite in left part of wall is the acanthopore,
x 750.

EXPLANATION OF PLATE 115

Figs. 1-6. Stenopora ovata Lonsdale. FI 5872. 1, 2, vertical sections of the distal portions of annular
thickenings, x 1000 and x 500 respectively. 3, transverse section of wall close to its junction with
other walls; this junction is located in direction of base of figure, x 250. 4, 5, transverse sections
of wall junctions with acanthopores, x 350 and x 250 respectively. 6, laminae that make up walls
of zooecia, x 3000.

Palaeontology, Vol. 13

PLATE 114

ARMSTRONG, Bryozoan microstructure

Palaeontology, Vol. 13

PLATE 115

ARMSTRONG, Bryozoan microstructure

ARMSTRONG: MICROSTRUCTURES OF BRYOZOAN GENUS STENOPORA 585

natures to the different biological conditions attendant to their deposition. Doubtless,
considerations about the mode of formation of acanthopores cannot be divorced from
speculations about their function. Both Bassler (1953) and Cuffey (1967) support the
view that acanthopores, as tubes, must have housed specialized zooids. The fact that
the acanthopores of Stenopora ovata and S. crinita consist of rods of calcite does not
necessarily rule out this possibility, for such ‘heterozooids’ could conceivably have
produced a continuous deposit of calcite. However in view of the size of the acanthopores
of the studied specimens of Stenopora (they are between 10 and 60 fim. in diameter)
there would seem little likelihood that these acanthopores could have housed discrete
individuals. The calcite of these acanthopores is probably the secretory product of
areas of specialized zooidal epithelium.

In this context it is interesting to note the amazing similarity between the acanthopores
of Stenopora and the taleolae of the pseudopunctae that occur in many brachiopod shells.

Pseudopunctae consist of rods of calcite (taleolae) inclined obliquely forwards into
the shell. Around them the sheets of the shell are deflected towards the interior of the
shell to form cone-in-cone-like structures. Transverse sections of pseudopunctae show
the taleolae concentrically surrounded by the deflected sheets of the shell. Taleolae
were enlarged by the addition of calcite to their exposed ends on the internal surface
of the shell. The textural similarity between the calcite of taleolae and the calcite forming
the areas of attachment of the adductor and diductor muscles in brachiopod shells lead
to suggestions that taleolae were the loci of attachment of small tendons or tonofibrils
(Williams 1953, 1956, 1968; Williams and Rowell 1965; Armstrong, in press).

In the studied specimens of Stenopora the acanthopores are unique because of the
probable manner of their deposition. Whereas the wall laminae are thought to have
been deposited both successively and by edgewise growth (see later), it seems that
calcium carbonate could have been continuously added to the distally exposed ends of
acanthopores throughout the life of a stenoporid colony. In view of the similarity
between acanthopores and taleolae, and considering the suggested function of taleolae,
the possibility that epithelial differences account for the distinctive aspects of acan-
thopores and laminae, together with the inference that the deposition of the calcium
carbonate of acanthopores once initiated could have continued on uninterrupted,
enable speculation that acanthopores may have served some attachment type of func-
tion. Tavener-Smith (1969) has discussed the relationships inferred to have existed
between the zooarium and the epithelial tissues of the trepostomatous Leioclema
asperum. Loci of attachment for the frontal epithelium (see Tavener-Smith 1969, fig. 1)
of stenoporid soft parts would probably have been most conveniently located along
the distal edges of the walls. Acanthopores could have served such an attachment
purpose in addition to having the protective function envisaged by Cumings and Gallo-
way (1915), Tavener-Smith (1969) and other authors.

GROWTH

Boardman and Cheetham (1969, text-fig. 2) have discussed three possible modes by
which the wall laminae of the tubular bryozoa may be deposited. They suggest that
wall laminae which are convex proximally are deposited in edgewise directions with
calcium carbonate being added simultaneously to the distal edges of numerous laminae.
Evidence for this growth mechanism is obtained from recent heteroporid specimens.

586

PALAEONTOLOGY, VOLUME 13

Carbon replicas taken from the surfaces of the zooecial walls of these specimens show !
the edges of numerous laminae to which calcium carbonate seems to be being added
(Boardman and Cheetham 1969, pi. 28, figs. 2, 3). The resulting laminae are obliquely
inclined to the depositing epithelium. After studying a recent species of the Cyclostomata i
with distally convex wall laminae Boardman and Towe (1966) suggested that from |
one to a few laminae were concurrently being added to the wall surface by the develop- '
ment and coalescence of seeds of calcite on the surface of an earlier formed lamina.
The laminae produced are parallel to the depositing epidermis and are coincident with
growth-lines. Boardman and Cheetham (1969) speculated that such a growth mechanism
is also suggested by the appearance of the surfaces of the laminae on the walls of
Denispora corrugata (Boardman and Cheetham 1969, pi. 28, fig. 1). In this illustration
small crystals seem to have formed on the surface of an already existing lamina. The
components of this lamina are visible and they are irregularly shaped and of variable
size (Boardman and Cheetham 1969, pi. 28, fig. 1). The third possible mode of laminar
growth is depicted in Boardman’s and Cheetham’s (1969) text-fig. 2c. Boardman and
Cheetham speculate that the laminae in some tubular bryozoa with distally convex
wall laminae may also have been enlarged in an edgewise direction. In this scheme the
wall laminae begin axially and aborally, and extend distally by edgewise growth.

The walls and acanthopores of Stenopora were presumably deposited by epithelial
cells comprising tissue referred to by Tavener-Smith (1969, fig. 1) as inner epithelium.
Although Stenopora lacks diaphragms, the relationship which existed between its soft
parts and its skeleton was probably similar to that depicted by Tavener-Smith for
Leioclema asperum. Irregular laminar units like those in parts of Plate 117, fig. 3 are
similar to the irregular units making up the lamina in Boardman’s and Cheetham’s
(1969) plate 28, fig. 1, and those authors consider that the lamina in the latter figure
was formed by the coalescence of numerous small crystals established on the preceeding
lamina. Conceivably the parts of the laminae of Stenopora crinita with irregularly
shaped components were deposited in this manner. However, the more regularly shaped
units like those which possess the chevron markings (PI. 1 17, figs. 1, 2) strongly resemble
the units making up the edgewise growing laminae in Boardman’s and Cheetham’s
plate 28, figs. 2, 3. The occurrence of ridges on the surfaces of the laminae consisting
of these more regular units in Stenopora crinita may be significant. Possibly because of
the concurrent growth of several laminae, the calcium carbonate being added to a
particular lamina was able to infill the inter-component grooves in the base of the
next overlying laminae. Growth of one lamina at a time, where each lamina was essen- J
tially completed before the first crystals of the succeeding lamina were established,
would not have permitted this to occur. Thus the available evidence seems to suggest
that the walls of Stenopora crinita grew both by the successive addition of some laminae

EXPLANATION OF PLATE 116

Figs. 1-3. Stenopora crinita Lonsdale. F60038, vertical sections of the distal portions of annular
thickenings of the walls, x 250, x 250, and x 500 respectively.

EXPLANATION OF PLATE 117

Figs. 1-4. Stenopora crinita Lonsdale. F60038. Views of the surfaces of several of the laminae that
make up the walls of the zooecia. Note the ridges and the chevron-shaped markings in figs.

1 and 2 (see p. 583), figs. 1-3, x 500. fig. 4, x 1500.

Palaeontology, Vol. 13

PLATE 116

ARMSTRONG, Bryozoan microstructure

Palaeontology, Vol. 13

PLATE 117

ARMSTRONG, Bryozoan microstructure

ARMSTRONG: MICROSTRUCTURES OF BRYOZOAN GENUS STENOPORA 587

and by the edgewise enlargement of other laminae. It is unknown, however, whether the
different growth mechanisms envisaged for the laminae of Stenopora crinita were re-
stricted to different parts of the walls, and it is difficult to develop a model with both
types of growth occurring in the same skeleton.

Considerably more work will be required before the growth of stenoporid skeletons
is completely understood, and undoubtedly, much data about the distribution and
directions of growth of the edgewise and successively growing laminae in the zooecia
will be obtained when growing surfaces of zooecial walls are able to be studied.

Acknowledgements. I am grateful to Professor Dorothy Hill, F.R.S. and Dr. J. S. Jell, Department of
Geology, University of Queensland, and Dr. R. Wass, Department of Geology, University of Sydney,
for reading the manuscript and offering several helpful suggestions. Mr. Bob Grimmer of the Electron
Microscope Unit at the University of Queensland carried out all of the preparative work.

REFERENCES

Armstrong, j. 1969. The crossed-bladed fabrics of the shells of Terrakea solida (Etheridge and Dun)
and Streptorhynchus pelicanensis Fletcher. Palaeontology, 12, 310-20.

in press. Microstructure of the shell of the brachiopod, Wyndhamia clarkei.

bassler, R. s. 1953. Bryozoa. In moore, r. c., ed., Treatise on invertebrate paleontology. Part G. Geol.
Soc. Am. and Univ. Kansas Press. 253 pp.

boardman, r. s. 1960. Trepostomatous Bryozoa of the Hamilton Group of New York State. Prof.
Pap. U.S. geol. Surv. 340, 87 pp.

and cheetham, a. H. 1969. Skeletal growth, intracolony variation, and evolution in Bryozoa:

A review. J. Paleont. 43, 205-33.

and towe, k. m. 1966. Crystal growth and lamellar development in some recent cyclostome

Bryozoa. Spec. Pap. geol. Soc. Am. 101, p. 20.

and utgaard, j. 1966. A revision of the Ordovician bryozoan genera Monticulipora, Peronopora,

Heterotrypa, and Dekayia. J. Paleont. 40, 1082-1108.
cuffey, r. j. 1967. Bryozoan Tabulipora carbonaria in Wreford megacyclothem (Lower Permian) of
Kansas. Paleont. Contr. Univ. Kans. 43, Bryozoa, Article 1, 96 pp.
cumings, e. r. and galloway, j. j. 1915. Studies of the morphology and histology of the Trepostomata
or monticuliporoids. Bull. geol. Soc. Am. 26, 349-74.
ross, j. p. 1961. Ordovician, Silurian, and Devonian Bryozoa of Australia. Bull. Bur. Min. Resour.
Aust. 50, 172 pp.

1966. The fauna of the Portrane Limestone, IV: Polyzoa. Bull. Br. Mus. nat. Hist. Geol. 12,

109-35.

tavener-smith, r. 1969. Wall structure and acanthopores in the bryozoan Leioclema asperum. Lethaia,
2, 89-97.

williams, a. 1953. North American and European stropheodontids : their morphology and systematics.
Mem. geol. Soc. Am. 56, 67 pp.

1956. The calcareous shell of the Brachiopoda and its importance to their classification. Biol.

Rev. 31, 243-87.

1968. Evolution of the shell structure of articulate brachiopods. Spec. Pap. Palaeont., No. 2,

55 pp.

and rowell, a. j. 1965. Brachiopod anatomy. In moore, r. c., ed., Treatise on invertebrate

paleontology. Part H, Brachiopoda. Geol. Soc. Am. and Univ. Kansas Press, pp. 6-155.

J. ARMSTRONG

Union Oil Dev. Corp.
P.O. Box H 68
Australia Square
Sydney
N.S.W. 2000

Typescript received 29 January 1970

VARIATION OF BIVARIATE CHARACTERS
FROM THE STANDPOINT OF ALLOMETRY

by itaru hayami and AKIHIKO matsukuma

Abstract. In fossil biometry simple ratios between two linear measurements have been frequently applied as
a third variable for representation of the variation of a bivariate character. Theoretically, however, it is obvious
that its frequency distribution is sometimes strongly influenced by the heterogeneity of sample, especially the
age distribution of a fossil population, and is apt to be artificially skewed and platykurtic. In order to analyse I,
the real state of frequency distribution of bivariate characters and to apply further advanced statistical tech-
niques for taxonomic identification and discrimination, it may be necessary to use some other index which is '
little, or preferably not at all influenced by growth. In this respect the diagonal distance from each point to the
reduced major axis on a double logarithmic scatter diagram may be a more desirable index, if a single power
function represents the relative growth of the organism. The advantage of this method is also recognized
empirically by a comparative study on an actual fossil sample of Glycymeris rotunda from the Pliocene of central
Japan. Some comments are given as to the definition of isometry and allometry.

Modern palaeontology focuses on the population rather than the individual. A bio-
metrical study of individual variation seems to be important, primarily because it may
offer fundamental and objective information for the consideration of classification and
evolution. There are various kinds of individual variation which are controlled by
different factors. As classified by Mayr, Linsley, and Usinger (1953) and again by Mayr
(1969), some are genetic and the others are non-genetic. Here we intend to discuss
mainly non-sex-associated continuous variation and methods for the representation of
bivariate characters in a population. It is no doubt important to consider from a
biological viewpoint whether the variation is genetic or non-genetic. Unfortunately,
however, the distinction is usually not easy in fossils. We presume that such bivariate
characters as are discussed here might be controlled both by genes and environ-
ments.

Various kinds of characters may be used for the representation of continuous varia-
tion. In neontology individual variation can be well recognized on the basis of a uni-
variate character, if the population proves to be composed of individuals of almost the
same age. This method is logically appropriate and certainly applicable also in palaeonto-
logy, if the character does not change as the organism grows. For instance, the number
of simple radial ribs of bivalves can be regarded as a good character. Such characters
are, however, usually restricted to count, whereas linear measurements themselves are
hardly applicable as the growth-invariant index.

Many previous authors have shown histograms of bivariate characters in order to
express the individual variation, taking the simple ratio between pairs of linear measure-
ments as the index. Ratios are, in fact, often more useful than linear measurements in
taxonomy. It is, however, obvious that this conventional method bears some theoretical
difficulties, because such a ratio may change to some extent through the growth of
organism. In this respect the dynamic concept of relative growth should be introduced
in the study of individual variation. We have been devoting ourselves to seek good
indices for the representation of bivariate characters from the standpoint of allometry.

[Palaeontology, Vol. 13, Part 4, 1970, pp. 588-605.]

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 589

As such indices may deserve general application in palaeontology, we intend to discuss
the problem in some detail and to evaluate them on the basis of some actual data.

PROBLEMS

When one intends to discuss the continuous variation of a sample and to apply any
advanced statistical techniques for the estimation of the nature of a population, it may
be necessary as an initial condition to recognize or presume normal frequency distri-
bution of characters. Therefore, one should select the most adequate and meaningful
index for each character especially carefully and strictly in order to represent the varia-
tion with the combination of two variables.

text-fig. 1 . Hypothetical scatter diagram
showing the concept of isometric variation,
where the simple ratio y/x is applied as an index.
di— a or tan 0— tan 6 means the deviation for
an arbitrary individual.

text- fig. 2. Hypothetical scatter diagram
showing the concept of ‘initial index varia-
tion’. The line y = ax+b is the reduced major
axis for a sample, b—b means the deviation
for an arbitrary individual.

The ratio between two linear measurements, which is the simplest index, has been
used frequently in fossil biometry. Many authors distinguished one species from another
on the basis of the difference of mean simple ratios. Some biometricians applied Student’s
t-test for the discrimination of populations. In this case, as shown in text-fig. 1, the

relation of a linear equation: _ v ,n

y — ui A f 1 1

is presumed for the growth of each individual. If the average value of at is defined as a,
the growth of a typical individual is represented by the following equation :

y — ax

(2)

590

PALAEONTOLOGY, VOLUME 13

In this case at— a or tan --tan 9 is regarded as the deviation of bivariate character
from the mean. We may provisionally call this expression isometric variation.

Some authors (e.g. Omori and Utashiro 1954) suggested another statistical method to
show the variation of a sample, where the following linear equation was regressed by I
means of the least-squares criterion from all the given individuals:

y = ax+b. (3)

They presumed that the slope a is nearly constant in one species and that the initial
index (y-intercept) b is a variable mainly related to the intraspecific or geographic
variation. In that method, although the presumption of the constancy of a is quite
dubious, the growth of each individual would be expressed by the following formula:

y = ax+bi (4)

where bt or bt—b is regarded as the index for the variation (text-fig. 2).

Such an estimation of variation on the basis of either the slope or the initial index
of a linear equation is, however, generally inadequate, because the relative growth of
an organism is not necessarily linear. The simple ratio between two linear measurements
is actually variable as the organism grows. The histograms of isometric variation would
be apt to be flat-topped (platykurtic) and skewed in comparison with the ideal normal
distribution, if the sample were composed of individuals of different ages (text-fig. 3).

There are several methods for obtaining a regressed line of best-fit. As discussed
by Teissier (1948), Kermack and Haldane (1950), Imbrie (1956), Miller and Kahn
(1962), and others, the method of reduced major axis seems to be more reasonable and
advantageous in biometrical studies than the conventional regression analysis y on x
or x on y. In a statistical study of Cenozoic Argopecten, Waller (1969) found empirically
that the reduced major axis fits a greater variety of point distributions than Bartlett’s
line.

The slope of the reduced major axis is given as :

(5)

where sx and sy are the standard deviations of x and y respectively. If the two variables
of the equation (3) are substituted by the mean values of x and y, the initial index of
this axis is readily determined. Incidentally, the slopes of ordinary regressed lines of
y on x and x on y are given by r.sy/sx and sjr.sx respectively, where r is the correlation
coefficient between two variables. Because r is positive and smaller than 1, the gradient
of the reduced major axis is equal to the geometric mean of the slopes of two ordinary
regressed lines. Therefore, the reduced major axis is also intuitively more reasonable
than ordinary regressed lines, if the two variables are equal in dimensions.

The initial index of the linear equation, however, may be biologically meaningless,
even if it is obtained by the method of reduced major axis. Moreover, it is a great
difficulty for the methods of ‘initial index variation’ that the state of the frequency
distribution is strongly influenced by the heterogeneity of the sample, especially by
the age distribution within a population. This may be a serious objection in comparing
fossil populations, because the age distribution must be controlled not only by the
biological condition but also by sorting in the process of sedimentation.

On the other hand, it is much more reasonable to consider that a pair of variables,

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 591

which are closely related to growth, increase approximately in accordance with a
non-linear function. This relation has long been called allometry (or heterogony)
(Huxley 1932, Huxley and Teissier 1936, Gould 1966). In this respect isometry is better

PLATYKURTIC

text-fig. 3. Hypothetical frequency distributions
of heterogeneous samples, showing artificially
platykurtic, skewed and bimodal tendencies.

regarded as a special case of allometry. Since the pioneer work of Nomura (1926), a
power equation: y = ^ (6)

has been generally applied in the study of allometry, where the exponent a is called
the specific growth ratio (or relative growth coefficient) and /3 the initial growth index.
The adequacy of this function has been recognized empirically in many organisms.

As pointed out by some authors (e.g. Shimizu 1959, Rohrs 1961, Gould 1966), the
method of study of ontogenetic allometry may be classified broadly into two categories:
one is the direct examination of individual relative growth, and the other is the estima-
tion of average relative growth deduced from many individuals of various growth
stages. The former is no doubt more advantageous than the latter in many respects
(Gould 1966, Obata 1967), but cannot be pursued in the study of fossils, unless the

C 7719 Q q

592

PALAEONTOLOGY, VOLUME 13

morphology of every growth stage is preserved in an individual. Furthermore, we must
treat the sample representing a population instead of the individual in a quantitative
study of variation. In other words we should focus on the population allometry, paying
attention also to the individual growth.

>v

ir u>

text-fig. 4. Hypothetical scatter diagram text-fig. 5. Data of text-fig. 4 plotted as log x
showing the concept of allometric variation of logy on a double logarithmic paper
a bivariate character. The power function (Z = log x, Y = log y).

y = /3x“ represents the average allometry for
a sample.

The allometric equation (6) is just equivalent to the following linear equation:

logy = a. log x -j- log /3. (7)

The equation of average ontogenetic allometry for a sample can be obtained by the
regression of log y on log x (or vice versa) or more desirably by the method of reduced
major axis with transformation of the original linear measurements into logarithms.
Imbrie (1956) showed empirically that better results would be obtained by the method
of reduced major axis and by the transformation of original bivariate data into log-
arithms. As exemplified in text-figs. 4 and 5, it is reasonable to consider that the
deviation for each individual is well represented by some standardized distance from the
fine of average allometry (= reduced major axis). Although there are several different
methods to measure the deviation, we like to discuss the frequency distribution of the
distance collectively in terms of allometric variation.

REPRESENTATION OF ALLOMETRIC VARIATION

In order to recognize allometric growth it is convenient to plot the original bivariate
data on a double logarithmic paper (see text-fig. 5). If a linear relation was expected

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 593

between log x and log y in the scatter diagram by intuition or high value of correlation
coefficient, a power equation for the average ontogenetic allometry could be justified.

Sometimes, however, the average relative growth of an organism might better be
regarded as a more complicated function. Some authors have expressed such a relation
by the composition of connected lines of different slopes, where ‘di or poly-phasic
allometry’ might be suggested. In such a case the sample may better be split, though
artificially, into several classes of different ontogenetic stages in accordance with the
expected ‘critical point(s)’, before the
equation of average ontogenetic allometry
is determined. Simpson, Roe, and Lewon-
tin (1960, p. 413) and many others intro-
duced such a procedure. In the study of
average allometry, however, this state
may hardly be discriminated from the
gradual change of specific growth ratio.

Therefore, precise examination on the
individual relative growth may be also
necessary for the recognition of ‘poly-
phasic allometry’. This problem was
discussed on a theoretical and biological
basis by Gould (1966). He is of the
opinion that the so-called ‘poly-phasic
allometry’ and ‘critical point(s)’ are
usually nothing but pure artifacts of an
improper procedure [personal communi-
cation from Dr. S. J. Gould (17 September
1969)].

Many authors have assumed that a is
constant in one population or even in one
species and that /3 is related principally
to the individual or geographic variation. Actually, however, the value of a must vary
to some extent among individuals of the same population. This is, in fact, a very trouble-
some problem, because the variability of a could not be clarified without a detailed
analysis of individual growth. Therefore, it is not quite adequate to discuss the variation
by means of the initial growth indices for individuals on the assumption of strictly
parallel lines to the fine of average allometry.

More adequate and easily measurable index is the actual distance from each point
to the line of average allometry (the reduced major axis) on a double logarithmic scatter
diagram (text-fig. 6). At least five kinds of measurements are available for the distance,
namely, 7-distance, Z-distance, diagonal distance, perpendicular distance, and triangle-
root distance. They can be computed in the following manner:

1. 7-distance ( dT ). The distance measured parallel to the 7-axis. If logy and log
x are substituted by 7 and X respectively, the equation of average allometry (7) is
transformed into the following simple formula:

Y=ocX+ log/?. (8)

text-fig. 6. Various distances from the reduced
major axis. A (Z*, 74) are the coordinates for an
arbitrary individual. dY (= AB): 7-distance; dx
(= AC): Z-distance; d (= AD): diagonal distance;
dP (= AP) : perpendicular distance.

594 PALAEONTOLOGY, VOLUME 13

When the coordinates for the point B are designated as (Xi} 7'-), the 7-distance for an
arbitrary individual is obviously given as :

dy = Yi- Y'i = Yi-aXi- log j8. (9)

This index was applied already by Richards and Kavanaugh (1945) and quoted by
Simpson, Roe, and Lewontin (1960) in relation to the analysis of ‘di-phasic’ allometry.

2. 7-distance (d^), the distance measured parallel to the 7-axis. If the coordinates for
the point C are defined as (7;, Yt), the 7-distance is represented as:

IWog/3

-7.

Therefore,

2

-c7,-log/3)V(«2+l)

2a

AP

AB

AC

BC

^ AP

AB.AC

AB.AC

BC

Therefore,

dv —

dy .dx

V( dy+d'x )

V{(AB)2+(AC)2}
Yt-a Xj-logfS

V(a2+i) ’

(10)

3. Diagonal distance (d). Imbrie (1956) suggested that one of the most reasonable
indices for the deviation is the diagonal distance (AD) from each point to the line of
average allometry which is determined by the method of reduced major axis. This
index could be calculated in the following manner:

GO

4. Perpendicular distance ( dP ). This is of course the shortest distance (AP), which is
measured perpendicularly from each point to the line of average allometry. It is
actually similar to the deviation in the method of ‘major axis’, where the fine of best-
fit is obtained by minimizing the sum of the squares of the perpendicular distance.
Kermack and Haldane (1950) and Imbrie (1956) pointed out its inappropriateness for
the determination of the line of average allometry, because its slope may change with
the unit of measurement. In discussing the deviation from the already determined line
of average allometry, however, this distance seems to be one of the meaningful indices.
Because APBA is a similar figure to AABC (see text-fig. 6), the value of perpendicular
distance can be determined in the following manner:

(i2) :

5. Triangle-root distance (dR). A reduced major axis is obtained by minimizing the
sum of the areas of triangles AABC. Therefore, the square root of the area of each
triangle may be also a useful index for the deviation, although it can be hardly measured
directly on a scatter diagram

d = y|AB.ACj _ J^dy.dx j = Yi-aXi-Xogp

(13)

The actual values of these distances are always positive for the points above the fine
of average allometry and always negative for those below the line. This may be a
convenient nature for further statistical treatment.

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 595

As readily recognized from the formulae (9)— (13), the values of these distances are
completely proportional to one another.

dY • dx : d dp : dp —

l.V(a2+l). 1 . 1

a 2a ^/(a2+l) *j(2oi)

(14)

Therefore, the following relation is also recognized as to the absolute values of distances

for an arbitrary individual:

\d\ > \dR\ > \dP\.

(15)

The value of sample standard deviation also depends upon the above proportional
expression (14). Consequently one would obtain essentially the same pattern of fre-
quency distribution, whatever distances might be applied as the index. Every distance
may be applicable for the representation of variation, but, we think, the diagonal
distance is the best, when the two variables are the same in dimensions. However,
provided that one variable is dependent on the other (whorl height of coiling shell
versus volution number for example), it may be desirable to apply the T-distance from
the ordinary regressed line (Y on X).

Generally speaking, the degree of variability should be expressed on the basis of the
value of sample standard deviation (s) in comparison with the sample mean (M), as
Pearson’s coefficient of variation ( V ) is defined as :

v _ 100s
_ ~Af'

(16)

In discussing the variability of the distance from the reduced major axis, Teissier (1948)
gave the following expression for the variance of diagonal distance, using the vector

sum of dY and dx:

si = &(!— 0(&-h4)}

(17)

where sx and sY are the sample standard deviations of X and Y, and r is the the corre-
lation coefficient between the two variables. As discussed by Imbrie (1956), the value
of the variability of <7_should be represented by the value of sd in comparison with the
joint mean of X and Y.

1 00s, j

VC Y2+Y2)

=

(1 — /~)(Vy + Yr)!
2(X2+ Y2) r

(18)

(Imbrie (1956) actually gave the coefficient of variability for twice the diagonal distance
of the present usage.) In applying this parameter to this coefficient we could discuss the
variability of a bivariate character. It is generally supposed that the variability of
diagonal distance is smaller than that of the simple ratio, if the relative growth of an
organism is better represented by a power function than a linear equation.

AN EMPIRICAL EVALUATION OF ALLOMETRIC VARIATION ON THE
BASIS OF ACTUAL DATA

As discussed above, it is theoretically certain that the variation of distance from the
line of average allometry (reduced major axis in double logarithmic field) is a more
desirable representation for a bivariate character than that of a simple ratio. We might
be able to recognize the advantage of the former method also empirically, if these two
methods were applied independently to the same sample. In the present article we intend
to take a fossil sample of Glycymeris (Bivalvia) as an illustrative example.

596

PALAEONTOLOGY, VOLUME 13
The following is the basic information about the sample here analysed.

Specific name. Glycymeris rotunda (Dunker).

Locality. Loc. 4, Ugari, Fukuroi City, Shizuoka Prefecture, central Japan (collected by A. Matsukuma).
This is probably the same as Loc. 525 described by Makiyama (1941).

Horizon. Hosoya tuffaceous siltstone member of the Kalcegawa group.

Age. Kechienjian stage (Pliocene).

Statistical sample. Only right valves were used. The sample is composed of 203 individuals which were
collected randomly from a fossil bed. They consist of individuals of quite various size, although smaller
ones are relatively abundant (see text-fig. 8).

For the sake of convenience the following characterization is applied for the linear measurements
and related auxiliary variables (see also text-fig. 7).

x: The length of the dental plate measured from the umbo to the posterior extremity.
y: The length of the dental plate measured from the umbo to the anterior extremity.
z: The simple ratio between the two linear measurements (y/x).

X: The common logarithms of x [X = log x].

Y: The common logarithms of y [Y = log y].

The values of x and y were measured strictly along the direction parallel to the basal line of ligament
area. The mensuration was carried out by means of a specially designed comparator which was recently
introduced by Shuto (1969, p. 49).

1 . Analysis of isometric variation

From the bivariate data of the 203 individuals the following fundamental values were
calculated in relation to the isometric variation:

_ 1

203 <4 Xj

1-16651,

V3 = = 10-105.

As shown in text-fig. 9 and also in Table 1, the null hypothesis for goodness-of-fit of
the actual data to a normal distribution is accepted.

Kurtosis is the property of being more pointed or flatter than a normal curve. As
noted by Simpson, Roe, and Lewontin (1960, pp. 146-7), the best measure of kurtosis
(Ks) is given as follows: x)4

Ks

Ns 4

-3,

(19)

where N is the number of individuals and s the sample standard deviation. In this case
we obtained the following value as the kurtosis coefficient for the distribution of z:

Ks =

£(*,-z)4 3

2034

-0-5257.

Because the value is negative, the distribution is flatter than the normal curve and may
be said to be platykurtic. We presume that this tendency is partly due to the gradual

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 597

text-fig. 7. Linear measurements (in millimetres) adopted in the present study.
x : The length of dental plate from the umbo to the posterior extremity; y: The
length of dental plate umbo to the anterior extremity.

y

text-fig. 8. Scatter diagram for a sample of Glycymeris rotunda (Dunker) from a fossil
bed of the Kakegawa group at Loc. 4, Ugari, Fukuroi City, Shizuoka Pref., Japan. The
reduced major axis does not fit to the original bivariate data especially in small individuals.

598

PALAEONTOLOGY, VOLUME 13

change of z through the growth of each individual. In fact, the average value of z is
much larger in smaller individuals than in larger ones.

Skewness is a parameter showing the property of asymmetric frequency distribution.
It is commonly given as: y/ _ -x3

(20)

TABLE 1

Calculation of x2 for goodness-of-fit of the observations of z to a normal distribution

Simple ratio

Normal

Observed

frequency

Expected

frequency

{Oi-Ed*

C y/x )

probability

m

{Ed

Ei

z— 3sz~z— 2sz

(0-8128^0-9307)

0-0215

5

4-36

0-0939

z—2sz^z—sz

(0-9307~l-0486)

0-1359

32

27-59

0-7049

Z — Sz~Z

(1-0486 — 1-1665)

0-3413

64

69-28

0-4024

Z'~Z + 5z

(l-1665~l-2844)

0-3413

71

69-28

0-0427

z+sz — z+2s2

(l-2844~l-4023)

0-1359

30

27-59

0-2105

z+2^a~z+352

(1-4023^1-5202)

0-0215

1

4-36

2-5894

Total

0-9974

203

202-46

4-0438

X2 = ^ = 4-04 [with 3 degrees of freedom].

Xo-05(V = 3) = 7-81.

0-25 < P < 0-30.

For reference: If the data of z are regrouped to interval 0-5^, the result of x2 test is as follows:
X2 = 11-95 [with 7 degrees of freedom]

Xo-05(„=7) = 14-07.

010 <P < 0-15.

This coefficient is positive in a right-skewed distribution and negative in a left-skewed
distribution. In the present sample the following value was obtained for the skewness
of the distribution of z. _-x3

sk=^kr = -°-22S0-

The left-skewed distribution is possibly related to the sample heterogeneity especially
the relative abundance of small individuals.

Incidentally, we obtained the following values as to the correlation coefficient between
the two linear measurements and the reduced major axis.

rxy — 0-9896 [0-9862—0-9921 for the 95 per cent confidence interval],
y = 0-924x-f 0-959.

2. Analysis of allometric variation

The reduced major axis (best-fitted line of average allometry) for the present sample
was determined in the following manner:

0-64791, Y = 0-71253,

sx — 0-25213, ^ = 0-21411.

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 599

The following value was obtained for the correlation coefficient between X and Y :
rXT = 0-9948 [0-9931—0-9961 for the 95% confidence interval].

Therefore, the correlation between the two variables is very significant. The slope of
reduced major axis is given by the formula (5),

a

SY

SX

0-21411

0-25213

= 0-84920.

From the formula (8), log jS = Y—aX.

text-fig. 9 Frequency distribution of z (= y/x). text-fig. 10. Frequency distribution of d (dia-
The broken lines show the expected values in gonal distance from the reduced major axis),
theoretical normal distribution. The broken lines show the expected values in

theoretical normal distribution.

By the substitution of X and Y,

log /3 = 0-71253-0-84920x0-64791 = 0-16232.

Therefore, the reduced major axis for the present sample is represented by the following
equation: 7 = 0-84920X+0- 16232 or y = 1 -4532X0'84920.

The standard error of the slope (a) is given as:

Consequently, the interval of a with 95% confidence is:

a± l-96aa = 0-84920±0-01192.

Therefore, the relative growth is certainly allometric. The diagonal distance (d), which

600 PALAEONTOLOGY, VOLUME 13

is measured from each point to this reduced major axis in a double logarithmic field,
is given as :

d = fi)V02+l) = 0-77245(3^— 0-84920^— 0-16232).

2a

The computation of d for 203 individuals results in:

Z = 0-00002 [negligible]
sd = 0-01697.

Table 2

Calculation of x 2 for goodness-of-fit of the observations of d to a normal distribution

Diagonal distance

Normal

Observed

frequency

Expected

frequency

(Oi-Eif

(d)

probability

m

C Ed

Ei

d—3sd d—2sd

(- 0-0509 0-0339)

0-0215

4

4-36

0-0297

d-2sd~ d— sd

(-0-0339 0-0170)

0-1359

28

27-59

0-0061

d—sd~ d

(-0-0170 ~0)

0-3413

66

69-28

0-1553

d ~ d+sd

(0 ~ 0-0170)

0-3413

77

69-28

0-8603

d-\-sd • ' d + 2sd

(0-0170 ~ 0-0339)

0-1359

26

27-59

0-0916

d-\-2sd <7+35-(j

(0-0339 ~ 0-0509)

0-0215

2

4-36

1-2774

Total

0-9974

203

202-46

2-4204

2(0 £V)2

— % ^ 1 — 2-42 [with 3 degrees of freedom].

Xo*05(V = 3) = 7-81.

0-40 < P < 0-50.

For reference: If the data of d are regrouped to interval Q-5sd, the result of x2 tests is as follows:
X2 = 10-00 [with 7 degrees of freedom].

Xo-o5(x=7> = 14-07.

0-15 <P <0-20.

If the formula (18) were applied for the estimation of variability, the coefficient of
variation might be shown:

v 1 100^ = 1-697 = .

d V(^2+^2) V(0-64792+0-71252)

As shown in text-fig. 10 and also Table 2, the frequency distribution of d is also re-
garded as normal. The distribution seems to be also platykurtic in view of the negative
value of kurtosis coefficient :

Ks =

3

2034

-0-3570.

The skewness for the distribution of d is given as :

= m-ir

203 4

-0-0292.

It means a slightly left-skewed distribution.

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 601

3. Comparisons and discussions

Now, we intend to compare the result obtained by the method of diagonal distance
with that by the method of simple ratio. The obtained value of sample correlation
coefficient between X and Y is significantly higher than that between x and y. We
presume that the appropriateness of the index for a bivariate character is indicated to a
certain extent by the smallness of the coefficient of variation. Although direct com-
parison may not be meaningful, the value of Vd is obviously much smaller than Vz.

The result of x2 test for the frequency distribution of d supports the null hypothesis
of a normal distribution. The value of x2 (with the same degrees of freedom) is more or
less smaller and the probability for a normal distribution higher than those for the
distribution of z (Tables 1 and 2). In this respect the pattern of histogram of d is more
safely assumed to fit a theoretical normal curve than is that of z.

As to the coefficients of kurtosis and skewness, a similar assumption is possible. The
values of Ks and Sk indicate that the frequency distribution of d is less platykurtic and
less left-skewed than that of z.

As indicated in text-fig. 8, neither the isometric line, y = IT 665 lx, nor the reduced
major axis, y = 0-924x-f0-959, fits the original bivariate data. On the other hand,
as shown in text-fig. 11, the reduced major axis in double logarithmic field seems to
represent well the relative growth of this sample. Therefore, so far as the present
sample is concerned, monophasic allometry is well recognized. Judging from the
comparative data aforementioned, it is concluded empirically that the diagonal distance
from the reduced major axis is a more desirable index for the expression of a bivariate
character than is the simple ratio between two variables.

STATISTICAL DEFINITION OF ‘ISOMETRY’ AND ‘ALLOMETRY’

In order to identify or to discriminate samples purely statistically, Imbrie (1956) and
Miller and Kahn (1962) introduced a method of significance test for the difference of
two reduced major axes. It is, in fact, a very useful method, if the relative growth of
each sample shows monophasic allometry.

The standard errors of the slopes or reduced major axes are given as:

(21)

(22)

where oq and a2 are the slopes of two reduced major axes, r1 and r2 are the correlation
coefficients between two variables and Nx and N2 are the numbers of individuals in
respective samples. Provided that the numbers of individuals are not too small, one can
recognize by means of the following value whether the difference of slopes is significant
or not „ —a

z = M,Tk)' (23)

If |Z| < T96, the difference of slopes is not significant with 95% confidence, and if
|Z| > T96, the two samples can be discriminated by the difference of specific growth
ratio.

602

PALAEONTOLOGY, VOLUME 13

Y

text-fig. 1 1 . Double logarithmic scatter diagram for a sample of Glycymeris rotunda
(Dunker) [the same sample as shown in text-fig. 8.] Because the reduced major axis
fit well to the data, the relative growth can be regarded as monophasic.

Applying the method of this significance test, we can define statistically the terms of
‘isometry’ and ‘allometry’. In the case of ideal isometry, though such a state is actually
non-existent, the slope is, of course, strictly equal to 1 without error. Consequently, if
the value of Z is calculated by the following equation :

Z = (24)

one can judge with 95% confidence whether the relative growth is isometric or allo-
metric, as follows:

if — 1 -96 < Z < 1 -96, the null hypothesis for ‘isometry’ would be accepted,
if Z < — 1 -96, negative allometry would be suggested, and
if Z > 1-96, positive allometry would be suggested.

Because the simple ratio between two variables is an index on the assumption of
isometry, the allometric variation is certainly a more reasonable representation than the

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 603

isometric one, if the null hypothesis were rejected by the above-mentioned significance
test.

text-fig. 12. Statistical discrimination of ‘isometry’ and
‘allometry’. N: number of individuals. Confidence 95%.

CONCLUDING REMARKS

It would be logically inadequate to discuss the variation of a bivariate character
without considering the relative growth of the organism, if the sample is composed
of individuals of various growth stages. If the simple ratio between two linear measure-
ments were used as the index, we might have much trouble in analysing the real state
of variation, especially in applying advanced statistical techniques for the recognition
of a normal distribution of character and random sampling as well as taxonomic
identification or discrimination. As pointed out by Simpson, Roe, and Lewontin
(1960), a platykurtic and skewed distribution may be due to the heterogeneity of sample.
In the analysis of bivariate characters it is necessary to apply an index which is less
influenced by the age distribution.

604 PALAEONTOLOGY, VOLUME 13

On the other hand, if the organism proved to grow approximately in accordance
with a simple power function, the individual variation within a sample could be analysed
more reasonably by means of the distance from each point to the line of average alio- I
metry on a double logarithmic scatter diagram. Although at least five kinds of distance I
(dY, dx, d, dP, and dR in this paper) are available for the index, this representation may
be collectively called allometric variation. It is believed that this representation is more
advantageous than the conventional method of simple ratio in the following respects:

1. The coefficient of variation may be reasonably small in comparison with that of
simple ratio.

2. The standard deviation, skewness, and kurtosis as well as the shape of the histo-
gram may be scarcely, if not at all influenced by the age distribution in a population
and other sample heterogeneity.

3. Normal frequency distribution of bivariate characters would be recognized more
reasonably on a firm basis.

4. The tendency for artificially skewed and platykurtic distribution could be avoided.

5. A comparison between different samples could be well based on the significance
test for the difference of slopes and positions of reduced major axes. This procedure
was fully explained by Imbrie (1956, pp. 235-8). The contingency of age distribution in
samples might be negligible also in this case.

6. As pointed out by Gould (1966), the study of average allometry may not be an
adequate approach to individual ontogeny, when strong natural selection takes place.
The present analysis of allometric variation, however, is considered to be sometimes
informative also for the consideration of the influence of natural selection and environ-
mental factors.

The advantage of this method is also recognized empirically by a comparative study
in which a sample of fossil Glycymeris from the Pliocene of Japan is treated as an
illustrative example.

As noted by Kotaka (1953), the method of rejection ellipse may be a useful method
for taxonomic identification and discrimination of fossil populations. In discussing the
relation of characters on the basis of simple ratios, however, this approach may bear
some difficulty, unless the ontogenetic transformation and the age distribution of samples j
are sufficiently considered.

On the contrary it may be an objection that the present method is somewhat time- j
consuming to justify its general application. More complicated techniques would be
required in the organisms showing ‘polyphasic’ allometry. The recent rapid development j
of computers, however, would make the application easy, and, we believe, biometricians s
should not mind taking this trouble.

Acknowledgements. We express our sincere thanks to Dr. Stephen Jay Gould of Harvard University
and Dr. Norman D. Newell of the American Museum of Natural History for their invaluable sugges-
tion about the method of the reduced major axis and for their kind supervision of the manuscript.
Acknowledgements are also due to Professor Tatsuro Matsumoto, Professor Ryuzo Toriyama,
Dr. Tsugio Shuto, Mr. George Kato, and Mr. Tomowo Ozawa of the Department of Geology,
Kyushu University; Professor Akio Kudo, Miss Kami Honda, and Mr. Kiyoshi Kawazu of the
Department of Mathematics of the same university; and Dr. Ikuwo Obata of the National Science
Museum (Tokyo) for their kind assistance and fruitful discussions.

HAYAMI AND MATSUKUMA: VARIATION OF BIVARIATE CHARACTERS 605

REFERENCES

gould, s. J. 1966. Allometry and size in ontogeny and phytogeny. Biol. Rev. 41, 587-640.
huxley, J. s. 1932. Problems of relative growth. 276 pp. London.

and teissier, g. 1936. Terminology of relative growth. Nature, 137, 780-1.

imbrie, j. 1956. Biometrical methods in the study of invertebrate fossils. Bull. Am. Mus. Nat. Hist.
108, 215-52.

kermack, k. A. and haldane, J. b. s. 1950. Organic correlation and allometry. Biometrika, 37, 30-41.
kotaka, T. 1953. Variation of Japanese Anadara granosa. Trans. Proc. Pal. Soc. Japan [n.s.], 10, 31-6.
makiyama, j. 1941. The Kechienjian fauna series no. 1: Evolution of gastropod genus Siphonalia
etc. Mem. Fac. Sci., Kyoto Imp. IJniv. [B], 16, 75-93.
mayr, E. 1969. Principles of systematic zoology. 428 pp. New York.

linsley, E. G., and usinger, R. L. 1953. Methods and principles of systematic zoology. 336 pp.

New York.

miller, r. l. and kahn, j. s. 1962. Statistical analysis in the geological sciences. 483 pp. New York.
Nomura, e. 1926. An application of a — kbx in expressing the growth relation in the freshwater bivalve
Sphaerium heterodon Pils. Sci. Rep. Tohoku Imp. Univ. [4], 2, 57-62.
obata, i. 1967. Notes on relative growth in palaeontology. Fossils (14), 20-39 [in Japanese].
omori, m. and utashiro, t. 1954. Some problems on the variation of Pecten albicans. Seibutsu-kagaku,
special volume (for evolution), 16-22 [in Japanese].

Richards, o. w. and kavanaugh, a. j. 1945. The analysis of growing form. pp. 180-230. In Essays on
growth and form, le gros clark, w. e. and medawar, p. b., eds., Oxford.
rohrs, m. 1961. Allometrieforschung und biologische Formanalyse. Zeit. Morph. Anthrop. 51, 289-321.
shimizu, s. 1959. Relative growth. 287 pp. Tokyo [in Japanese].

shuto, t. 1969. Neogene gastropods from Panay Island, the Philippines. Mem. Fac. Sci., Kyushu Univ.
[D], 19, (1), 1-250, pi. 1-24.

simpson, G. G., roe, a., and lewontin, r. c. 1960. Quantitative zoology, revised ed. 440 pp. New York.
teissier, g. 1948. La relation d’allometrie: sa signification statistique et biologique. Biometrics, 4,
14-48.

waller, t. r. 1969. The evolution of the Argopecten gibbus stock (Mollusca: Bivalvia), with emphasis
on the Tertiary and Quaternary species of eastern North America. Paleont. Soc. Mem. 2, [/. Paleont.,
43, Suppl. to No. 5], 1-125, pi. 1-8.

ITARU HAYAMI
AKIHIKO MATSUKUMA

Department of Geology
Faculty of Science
Kyushu University
Fukuoka 812, Japan

Typescript received 12 February 1970

THE MORPHOLOGY AND MICROSTRUCTURE
OF ZELLANIA DAVIDSONI MOORE
(BRACHIOPODA), FROM THE MIDDLE JURASSIC
OF ENGLAND

by P. G. BAKER

Abstract. Investigation of Oolite Marl samples from the mid Cotswolds has yielded occasional minute brachio-
pods which are undoubtedly specimens of the little-known species Zellania davidsoni Moore 1855. The material
studied has enabled determination of the correct orientation, growth, development, and microstructure of the
shell and provides the first record of the internal morphology of the pedicle valve. Adolescent and adult shells
may be recognized, which enables the mode of development of certain internal structures to be determined.
Sectioned material shows that the shell of Z. davidsoni is differentiated into primary and secondary layers of
a type which, although unusual, may be reconciled with the shell of primitive terebratulides. Although Z.
davidsoni occurs together with thecidellinids the form of the shell is thought to be indicative of a sheltered en-
vironment. Microstructural features exhibited by shells support the view that Zellania is of terebratellacean
affinity. The paper records the probable location of Moore’s type specimens, missing since before 1927.

Zellania is a rare, little-known micromorphic brachiopod genus of uncertain affinities,
which occurs in the Jurassic of England. Material of the species Z. davidsoni (Moore
1855) has been obtained during a study of the brachiopod fauna of the Oolite Marl
(Upper Aalenian, murchisonae zone) of the Cotswolds, South England.

Information on Z. davidsoni is singularly lacking. The account in the Treatise on
Brachiopoda has perpetuated a misinterpretation of the type material by Moore in his
original description.

Of the specimens of Z. davidsoni figured in the Treatise (fig. 741, 1 a-c, H857) and
presumably, in the absence of the types, taken from Moore (1855), la is in fact a pedicle
valve and lb figures the exterior of a brachial valve.

The type specimens of Z. davidsoni were found to be missing from the Moore collec-
tion, held in Bath City Reference Library, when it was catalogued by Dr. Wallis in 1927.
The only zellanid material in the collection was a tube containing three specimens iden-
tified as types of Zellania oolitica Moore, ref. no. M3036. Study of these specimens
reveals that they bear little resemblance to any of the published figures (Moore 1860,
Davidson 1874) of Z. oolitica but are certainly specimens of Z. davidsoni bearing a
very close resemblance to Moore’s figured types. The author is of the opinion therefore,
that it is the type material of Z. oolitica which is missing and inadvertently represented
by the specimens of Z. davidsoni (M3036) which should be reinstated as the types of
Z. davidsoni.

The rarity of Z. davidsoni in the Oolite Marl is indicated by the fact that the collection
of specimens over a period of more than four years has yielded only two complete
pedicle valves, four complete brachial valves and twenty-eight complete specimens,
together with numerous brachial and a few pedicle valve fragments. It is possible that
the rarity of the species may be, in part, an artefact of the fragility of the shell. The rarity
of the pedicle valve is undoubtedly due to its form and lack of the strengthening effect

[Palaeontology, Vol. 13, Part 4, 1970, pp. 606-18, pis. 118-120.]

607

BAKER: ZELLANIA DAVIDSONI MOORE (BRACHIOPODA)

of structures such as the ridge and septum which occur in the brachial valve. The weak-
ness of the pedicle valve may be gauged by the fact that it is often crushed into the
brachial valve during compaction of the sediment. The observations contained in this
paper are therefore based on a very small collection. However, the uniformity of charac-
ter exhibited by the material studied indicates that the observations are nevertheless
valid.

Acknowledgements. The author is indebted to Dr. J. D. Hudson, Department of Geology, the Univer-
sity of Leicester, for supervision of the preparation of this paper. Thanks are due to Mr. G. McTurk
for preparing the stereoscan negatives and to Mr. P. Pagan, City of Bath Reference Library for access
to zellanid material from the Moore collection. I wish to thank Professor P. C. Sylvester- Bradley for
use of the research facilities of the Department of Geology, the University of Leicester.

Registration of material. The material figured in this paper, together with original and duplicate peels
is to be housed in the museum collection of the Department of Geology, the University of Leicester,
under the catalogue numbers quoted.

PREPARATION OF MATERIAL

The material studied was obtained during the collection of thecidellinids from the
Oolite Marl. A detailed account of the preparation of Oolite Marl residues and the
investigation techniques employed, is given in Baker (1969) with minor amendments
in Baker (1970).

Early attempts to section Z. davidsoni by the methods employed for M. granulosa
were unsuccessful because peculiarities of the microstructure of the shell allowed blocks
of shell to be lifted away during the production of cellulose acetate peels. This, combined
with the relatively very thin zellanid shell and poorly consolidated matrix led to rapid
disaggregation of the shell layers. Vacuum embedding was tried with considerable suc-
cess but some difficulty with peel bubbling was still encountered owing to the porous
matrix. This can be eliminated by running hot paraffin wax on to the specimen prior
to each successive stage of sectioning. The wax soaks into the matrix and solidifies.
The wax overlying the shell material is, of course, removed as the block is ground pre-
paratory to re-etching but sufficient wax remains in the matrix to act as an effective
sealant.

MORPHOLOGY

Information concerning the morphology of Zellania davidsoni is limited. The accounts
in Moore (1855) and in the Treatise on Brachiopoda (1965) concern only the brachial
valve and need some amplification. Detailed examination of the internal ridges (Moore
1855) (inner ridges, Treatise) of the brachial valve in serial transverse section (PI. 120,
fig. 7) shows that they are structurally ridges (by definition, Williams 1965 HI 52),
though appearing more in the manner of outwardly inclined flanges (PI. 118, fig. 7;
text-figs. 1b, 2k-p). They occupy a position similar to that of the sub-peripheral rim
of thecidellinids (Baker 1969) but arise in a different manner (Baker 1970) and apparently
performed a function similar to the lophophore platform of the plectambonitacean
Leptellina. There is no evidence that the structure seen in the brachial valve of Z.
davidsoni is any way related to the lophophore platform of Leptellina. It is by defini-
tion not a flange. It performed a function different from that of the thecidellinid

Rr

C 7719

608

PALAEONTOLOGY, VOLUME 13

sub-peripheral rim. In order to avoid confusion therefore, it is proposed to refer to the
structure as a sub-marginal ridge.

Figures of the interior of the brachial valve in Moore, C. (1855) and Elliott (in Moore, i
R. C. 1965) indicate a depression at the end of the median septum (clearly visible in
specimen M3036). Studies show that the septum is a hollow structure for much of its
length (PI. 119, figs. 1-3, text-figs. 1b, 2p-r) and that the floor of the cavity is endo-
punctate in the normal manner (PI. 119, fig. 1). It is proposed to refer to this cavity
as an intra-septal cavity. Counterparts of the sub-marginal ridge and median septum
are found in the pedicle valve and it is proposed to term them lateral ancillary ridges and
ancillary septum respectively.

Growth and external morphology. Z. davidsoni (PI. 118, figs. 1-4) is a very small form. The
growth is mixoperipheral, leading to a strophic condition, with a rectimarginate com-
missure. The width : length ratio of the shell is in the order of T2 : 1 and specimens rarely
exceed T3 mm. in length. Specimens in which the protegulum (PI. 118, fig. 4) and
growth-lines are visible, show that the width: length ratio does not change appreciably
throughout the life of the animal. Small forms, here correlated with adolescents (PI. 118,
fig. 6), are almost biconvex. During growth the pedicle valve retains its convexity but
the brachial valve shows a declining vertical growth component (Rudwick 1959) so
that adults have a characteristic plano-convex lateral profile (PI. 118, fig. 2). The adult
shell outline is typically shield-shaped (PI. 118, fig. 1) but subject to some variation,
adolescents particularly having a more rounded outline (PI. 118, fig. 5). The interareas
are anacline and relatively well developed, the dorsal interarea being only slightly
smaller than that of the pedicle valve. The pedicle opening (PI. 118, fig. 4), as stated in the
Treatise on Brachiopoda , is amphithyridid and it is relatively very large. Stereoscan
photomicrographs reveal that the feeble striate ornamentation of shells is in fact a series
of radially arranged fissures (PI. 119, figs. 7, 8) penetrating the primary shell but not
extending down into the secondary shell layer. At X 250 magnification incipient striae
are found to be present on smooth shells also.

Z. davidsoni is unusual in that the umbo of the brachial valve projects posteriorly
to a greater degree than the umbo of the pedicle valve and gives the appearance of being

EXPLANATION OF PLATE 118

Stereoscan photomicrographs of Zellania davidsoni Moore, from the Oolite Marl, Westington Hill

Quarry near Chipping Campden. All specimens coated with evaporated aluminium before photo-
graphy.

Figs. 1-4. Brachial, lateral, anterior and posterior views of an adult specimen (37530), showing the
shield-shaped outline, fig. 1; the posterior extension of the brachial umbo and plano-convex
lateral profile, fig. 2 (tilt angle 88°); the rectimarginate commissure, fig. 3; the interareas, protegula
and large amphithyridid pedicle opening, fig. 4. x 60.

Fig. 5. Pedicle view of an adolescent shell (37531) showing the rounded profile. Shell surface coated
with crystallites, x 66.

Fig. 6. Near lateral view of an adolescent shell (37532) showing the relatively more biconvex lateral
profile. x60.

Fig. 7. Interior view of an adult brachial valve (37533) showing the cardinal process, sockets, and the
sub-marginal ridge and hollow median septum with denticulate anteriors. x 55.

Fig. 8. Interior view of an adolescent brachial valve (37534) showing the short sub-marginal ridge
and short median septum with no intra-septal cavity, x 60.

Palaeontology , Vol. 13

PLATE 118

BAKER, Zellania davidsoni

BAKER: ZELLANIA DAVIDSONI MOORE (BRACHIOPODA) 609

a pedicle valve, probably accounting for the error in the Treatise (Elliott, in Moore
1965, H857). The significance of this arrangement in terms of life-attitude will be dis-
cussed later.

Interior. Brachial valve. The adult brachial valve (PI. 118, fig. 7) is regularly endo-
punctate, with a large notothyrium. Its internal morphology is dominated by the
sub-marginal ridge and a hollow median septum. These structures were present in the
valves of all sizes studied, although degree of development was found to vary. In smaller
specimens the ridge terminates in the lateral zones of the shell. The cardinal process
is very small and transversely concave in a manner similar to that of thecidellinids
(Baker 1969, text-fig. 2b) but not contributing to the formation of socket ridges (PI. 1 19,
fig. 1 ; text-fig. 2a-d). The muscle pattern is not known but two depressions at the base
of the cardinal process may represent diductor muscle scars. The socket ridges are very
prominent (PI. 1 19, fig. 2) and in fact bound the notothyrium, the outer socket ridge
being represented by the edge of the dorsal interarea. In none of the stereoscanned
material has the granulation described by Moore (1855) been seen. Certain shells how-
ever, show the development of crystallites on the internal surface and it is possible that
it is to these that Moore was referring. If, in fact, the specimens M3036 are the types of
Z. davidsoni this speculation becomes virtual certainty. The interior of the brachial
valve represented has this crystallite covered surface and has been coated with glue,
obviously for the purpose of repairing the damaged median septum. The optical effect
of the glue-coated crystallites is to produce an apparently granular interior. The presence
of this septum is important as Davidson 1874, p. 113, states that in Z. oolitica there is
no indication of the presence of a septum in either valve.

Interior. Pedicle valve. The pedicle valve (PI. 119, figs. 4, 5) is concave, endopunctate,
with a large open delthyrium bounded by what may presumably be regarded as tooth
ridges although the teeth themselves are very weakly developed. They appear as two
posteriorly arching flaps, almost indistinguishable from the secondary shell material
of the ventral interarea and invariably broken in separated valves. The apex of the
delthyrium is occupied by a concave plate, lying between the tooth ridges on the floor
of the valve in the position of a pedicle collar. Serial sections show the development of
a small ridge, the lateral ancillary ridge (text-fig. 2i-n) also sub-marginal in position and
situated in the postero-lateral and lateral zones of the shell (PL 119, fig. 6). The orienta-
tion of these ridges is such that they abut against the edge of the sub-marginal ridge
when the valves are closed. There are no visible muscle scars but transverse sections of
shells show a callus on the floor of the valve which may have been the site of muscle
scars. From the anterior of this thickened region, a thin blade-like septum extends
almost to the anterior of the valve (text-fig. Id) and is almost in contact with the
median septum when the valves are closed.

Development of structures. On the basis of faunal analyses conducted for other studies,
Z. davidsoni may be regarded as comprising approximately 0-04% of the brachiopod
fauna of the Oolite Marl in Westington Hill Quarry (Baker 1969); and even if the
number of specimens is drastically reduced by fragmentation it is indeed a rare species.
Any attempt at detailed ontogenetic studies would therefore be fruitless. Owing to the
delicate nature of the shell, valves are usually fragmented but sufficient material has

610

PALAEONTOLOGY, VOLUME 13

text-fig. 1. Three-quarter profile reconstructions from photomicrographs and serial sections to
illustrate the internal morphology of the determinable growth stages of Z. davidsoni. a, b adolescent
and adult brachial valves, c, d adolescent and adult pedicle valves, a.l.r. ancillary lateral ridge, a.s.
ancillary septum, b.c. brachial cavity, c.p. cardinal process, d. denticle, del. delthyrium, d.i. dorsal
interarea, e.ch. exhalent channel, i.ch. inhalent channel, i.s.c. intra-septal cavity, i.s.r. inner socket
ridge, m.p. muscle platform, m.s. median septum, not. notothyrium, o.s.r. outer socket ridge, s. socket,
s.m.r. sub-marginal ridge, t. tooth, t.r. tooth ridge.

been recovered to enable determination of the mode of development of various struc-
tures and the recognition of certain growth stages (text-fig. 1a-d).

It is possible to distinguish specimens which, by their invariably smaller size, although
morphologically similar to the larger shells, may be regarded as adolescent forms. The
largest shells do not exceed a length of T4 mm. and the argument that they represent
adults is essentially that outlined in earlier studies (Baker 1969). The primitive aspect of
the cardinalia and the small size, together with the form of the pedicle opening and
probable form of the lophophore, suggests that, like the thecidellinids, Zellania is the
product of neotenous modification.

611

BAKER: ZELLANIA DAVID SONI MOORE (BRACHIOPODA)

Development of the sub-marginal ridge and median septum. Existing accounts state that
the inner ridges (sub-marginal ridge) are reflexed anteriorly into a posteriorly directed
septum. In fact, adolescent brachial valves show that the sub-marginal ridge and median
septum arise separately (PI. 118, fig. 8), and are extended anteriorly as growth proceeds.

0 • 5mm.

ksep

0-828 0-851 0-92 0 989

text-fig. 2. Drawings prepared from microprojected cellulose acetate peels of serial transverse sections
through Z. davidsoni showing the morphological features in section. Number indicates distance o
section in mm. from the brachial umbo, a-d reproduced at x 2 scale to show microstructure. Ap-
parently thick pedicle valve, f-h due to obliquity of valve posteriorly relative to the plane of section
(see Westbroek 1969). Recrystallization shaded, a.l.r. ancillary lateral ridge, a.s. ancillary septum,
c.p. cardinal process, e.ch. exhalent channel, i.s.c. intra-septal cavity, i.s.r. inner socket ridge, m.p.
muscle platform, m.s. median septum, p.c. pedicle collar, p.l. primary layer, s. dental socket, s.l.
secondary layer, s.m.r. sub-marginal ridge, t. tooth.

At this adolescent stage of development the sub-marginal ridge extends little more than
half the length of the valve and the median septum is a low structure, extending from
near the anterior margin, posteriorly, about half-way to the cardinal process. It is only
hollow at the extreme anterior end.

In adult brachial valves the sub-marginal ridge extends almost to the anterior margin
and may extend in the direction of the median septum as a row of denticles (PL 118,
fig. 7). The posterior termination of the median septum however, maintains a constant
position relative to the socket ridges and cardinal process (PI. 118, figs. 7, 8). Increase in
the size of the structure must therefore, be achieved by addition of material at the
anterior end and, as the walls diverge, so the intra-septal cavity increases in size.

Serial sections (PI. 120, fig. 7; text-fig. 2k-p) show that the ridge, on the evidence of
the orientation of fibres, develops from the floor of the valve. Therefore, both the ridge
and median septum, in terebratuloid terms, represent ascending elements, a point of

612

PALAEONTOLOGY, VOLUME 13

significance in consideration of affinities. The ridge increases in size by the simple in-
cremental addition of secondary material. Exactly how this occurs is not clear, but the
development of denticles may be an initial feature of the anterior extension of the sub-
marginal ridge and also the median septum (PI. 1 19, fig. 3). Posteriorly the sub-marginal
ridge forms the inner socket ridges, and the dental sockets are obviously much deepened
as the ridge develops.

The sub-marginal ridge is not vertical but directed outwards (PI. 119, fig. 2; text-fig.
2 k-p). As material is added at the summit therefore, the size of the brachial cavities
must be increased. A similar trend is exhibited by the median septum. As it increases
in height, the walls become more divergent (PI. 119, figs. 1-3; text-figs. 1b, 2p-r) so
that the intra-septal cavity increases in size. The result of this development pattern is
the development of a border morphologically similar to that of certain thecidellinids
(Baker 1969) but differing structurally and with no migration as encountered in the
sub-peripheral rim of Moorellina granulosa (Moore) (Baker 1970).

Development of the pedicle valve. The two complete pedicle valves discovered, judging
from their small size, apparently belonged to adolescent individuals. The teeth are
missing but the only discernable difference between these and the valves of serially
sectioned larger forms appears to be a relative decrease in the prominence of the lateral
ancillary ridges as the sub-marginal ridge of the brachial valve becomes more well
developed. The development of the callus on the valve floor and the development of the
thin ancillary septum are apparently late ontogenetic features as they are not seen in
adolescent valves of the size studied.

MICROSTRUCTURE

The material studied shows that in Z. davidsoni the endopunctate shell, although very
thin, was clearly differentiated into primary and secondary layers (PI. 1 19, fig. 8 ; PI. 120,

EXPLANATION OF PLATE 119

Stereoscan photomicrographs of specimens of Zellania davidsoni Moore. Material of all figures coated
with evaporated aluminium before photography.

Fig. 1. Interior view of a brachial valve fragment (37535) showing the endopunctation and cardinal
process. The left dental socket is damaged and the hollow anterior region of the median septum
has been broken away to reveal the endopunctate floor of the intra-septal cavity, x 60.

Fig. 2. Profile view of specimen (37535) to show the relative prominence of the inner socket ridges
bounding the notothyrium, the inclined sub-marginal ridge, left, and the divergent anterior of the
median septum. Angle of tilt 70°. x65.

Fig. 3. Enlarged view of specimen (37533) to show detail of the denticulate anterior of the hollow
median septum and sub-marginal ridge, x 110.

Fig. 4. Interior view of an adolescent pedicle valve (37536). Detail obscured by a heavy coating of
crystallites but the left lateral ancillary ridge is just visible, upper left. Teeth missing, x 58.

Fig. 5. Posterior view of specimen (37536) showing the delthyrium bounded by tooth ridges. Angle of
tilt 57°. x 70.

Fig. 6. Profile view of the interior of a fragment of an adolescent pedicle valve (37537) showing the
lateral ancillary ridge, centre-left. Angle of tilt 70°. x 150.

Fig. 7. Enlarged portion of the exterior of the brachial valve of specimen (37538) showing the radial
Assuring of the primary shell layer, x 400.

Fig. 8. Stereoscan photomicrograph of a cellulose acetate peel of a transverse section through the
shell of specimen (37543) showing the fissures in the prismatic primary layer, upper, and the fibrous
secondary layer. Section location: Pedicle valve, right antero-lateral sector, x 1080.

Palaeontology , Vol. 13

PLATE 119

BAKER, Zellania davidsoni

BAKER: ZELL AN I A DAVIDSONI MOORE (BRACHIOPODA) 613

fig. 2). Although the punctae deflect the secondary fibres in a normal (Williams 1968a)
terebratulide manner (PI. 120, figs. 5, 6), the microstructure of the layers themselves
differs from the normal terebratulide pattern.

text-fig. 3. Block reconstruction of the shell of Z. davidsoni from photomicrographs
of cellulose acetate peels, to show the form of the primary layer and the orientation
and variability of the fibres of the secondary layer. 1. lamina, p. puncta, p.l. primary
layer, r.f. radial fissure, s.l. secondary layer.

Primary layer. The zellaniid primary layer is thin and apparently of an unusual type.
Reference has already been made to the radially arranged fissures in the primary shell
(PI. 1 19, figs. 7, 8 ; PI. 120, fig. 1). In transverse sections (PI. 1 19, fig. 8) the shell material
is seen to be of crystalline type and without the normal pitted appearance described
by Williams (1968a). The persistence of the radial arrangement of the fissures and their
failure to penetrate the secondary layer must indicate a more than coincidental relation-
ship with the primary shell material. The radial pattern is relieved at intervals by cross-
joints so that the primary layer in effect, consists of a series of sub-rectangular blocks
of prismatic calcite (text-fig. 3). The primary layer is usually poorly preserved because
the physical characteristics described contribute to its easy removal mechanically, as
evidenced by the difficulties encountered during the preparation of cellulose acetate
peels.

Secondary layer. Stereoscan photomicrographs of etched secondary shell surfaces and
investigation by horizontal, transverse, and longitudinal serial sections, shows that the
secondary shell mosaic also is of rather unusual type. Even the most careful orientation
of sectioned material has failed to produce anything approaching a typical (Williams
1968a) terebratulide or spiriferide transverse mosaic except at the base of the teeth

614

PALAEONTOLOGY, VOLUME 13

(horizontal sections). Horizontal (PI. 120, fig. 4) and transverse (PI. 120, fig. 5) sections
show that the secondary shell material appears typically as a series of sheets or very 1
broad (20-30 fim. wide) laminae which are, in longitudinal section, disposed with
normal (Williams 1956, 1966, 1968a) secondary orientation relative to the primary layer
(PI. 120, fig. 8). Horizontal sections show that the orientation of laminae changes rapidly,
so that, in places, a zigzag rather than a spiral arc (Williams 1968a) secondary growth
mosaic is produced.

General observations. At present the origin and purpose of the radial Assuring is un-
known, but it may represent the diagenetic expression of some peculiarity in the mode
of deposition of the primary shell material. The uncertainty of whether the fissures are
of primary or diagenetic origin is obviously a point of considerable importance because,
if primary, the features indicate in Zellania the existence of a new type of primary shell
material. Owing to the rarity of material resolution of the problem will be difficult.

A certain amount of indirect evidence is available : (a) shells coated with crystallites, and
in which some recrystallization has obviously occurred, show obliteration of the Assuring
effect, ( b ) the fissures are most clearly seen in the best-preserved material, (c) they are
a pronounced feature of all horizontal sections through the primary layer and (d) it is
difficult to envisage a diagenetic process which would, universally, affect the primary
layer to such an extent, with no apparent effect on the secondary layer. Williams (19686)
suggests that the finely crystalline covering of Billingsella represents the recrystallized j
primary layer. Similar recrystallization may have occurred in Zellania, but it is odd that
the fine of demarcation between recrystallized and unaltered material should be so

EXPLANATION OF PLATE 120

Stereoscan photomicrographs of Zellania davidsoni Moore. Material of all figures coated with evaporated

aluminium before photography and all, with the exception of fig. 3, taken from cellulose acetate peels.

Fig. 1. Horizontal section through the primary shell layer of specimen (37540) showing the radially
arranged fissures and block-like nature of the primary shell. Section location: Brachial valve,
anterior sector, x 1200.

Fig. 2. Horizontal section through the shell of specimen (37541) showing the primary/secondary layer
junction, broken line. Shell partially recrystallized. Section location: Brachial valve, left antero-
lateral sector, x 1200.

Fig. 3. External surface of specimen (37542) from which the primary layer has been removed, showing
detail of the fibre mosaic at the external surface of the secondary shell layer. Normal proximal,
centre right, and laminar distal, centre, regions of fibres are visible. Figure location : Brachial valve,
left antero-lateral sector, x 900.

Fig. 4. Oblique section through the secondary shell layer showing endopunctae and the secondary
fibres arranged as overlapping laminae. Section location. Brachial valve, right lateral sector. Section
orientation: Parallel with the plane of the commissure, x 550.

Fig. 5-7. Transverse sections through specimen (37543).

Fig. 5 shows the primary layer, upper and the fibres of the secondary layer deflected by punctae.
Section location : Brachial valve, right antero-lateral sector, x 540.

Fig. 6. Enlarged section to show detail of an endopuncta and deflected secondary fibres. Section loca-
tion as Fig. 5. x 2000.

Fig. 7. Transverse section through the sub-marginal ridge showing the orientation of the secondary
fibres. Section location. Brachial valve, right lateral sector, x 400.

Fig. 8. Longitudinal section through specimen (37544) showing the orientation of the secondary fibres
relative to the primary shell layer, lower. Section location: Pedicle valve, 0-086 mm. to the left
of the mid-fine, x 1000.

Palaeontology , Vol. 13

PLATE 120

BAKER, Zellania davidsoni

BAKER: ZELLANIA DAVIDSONI MOORE (BRACHIOPODA)

615

abrupt, and also that the structure is present in all sections involving primary shell.
Williams (1968a, p. 31) states that the primary layer of all specimens of Spiriferina
walcotti (Sow.) examined is recrystallized but that the secondary shell is normally
well preserved. He notes a strong lineation in the primary layer (Williams 1968a,
pi. 11, fig. 5) normal to the shell surface and is of the opinion that this lineation may
represent an original fabric. The evidence available, therefore, indicates that the micro-
structure of the zellanid primary layer is of secretory rather than diagenetic origin.
Some transverse sections of secondary shell (PI. 120, fig. 6) are very similar to the re-
crystallized secondary mosaic of Nisusia ferganensis (Williams 1968 b, p. 487). However,
if recrystallization in Zellania extended below the primary layer, so that some of the
secondary fibres have been recrystallized whilst retaining their morphological charac-
teristics, the observed features of the primary layer may also be regarded as original.

The zellaniid laminae are curiously like the flared fibres of Moorellina granulosa
(Moore) described in Baker (1970, p. 84). In M. granulosa, only the distal ends of the
fibres are affected but in Z. davidsoni this expansion has a tachygenetic expression
and affects all but the extreme proximal end of the fibre. The unmodified proximal ends
of some secondary fibres (PI. 120, fig. 3) are similar to the secondary fibres (Williams
1968a, pi. 7, fig. 4) of Terebratulina caput-serpentis (Linne). However, the microstructure
of the shell as a whole most closely resembles that of the stringocephalacean Mutationella
podolica (Siemiradzki), illustrated in Williams (1968a, pi. 11, figs. 1-3).

PALAEOECOLOGY

Z. davidsoni occurs together with thecidellinids and other, larger, brachiopods; the
probable environment of the thecidellinids is discussed in Baker (1969). It may be
argued that Zellania, by association, occupied the same environment. The close mor-
phological similarity between certain internal characters of Zellania and thecidellinids
has been noted, but it has been clearly shown that the structures arise in different ways
and probably performed different functions. Morphological similarity produced by con-
vergent evolution is to be expected if the animals did occupy a similar environment.
However, there are certain features of the organization of Z. davidsoni which render the
above argument hazardous.

Analysis of the micro structure of the thecidellinid Moorellina granulosa in functional
terms (Baker 1970) reveals the development of a reinforced shell which is entirely in
agreement with the turbulent environment suggested by Ager, Baker, and Nekvasilova
(in Baker 1969). The pedicle opening of Z. davidsoni is disproportionately large relative
to the size of the animal. Moorellina is a cemented form and it is possible that Zellania
required a large pedicle for anchorage. However, the shells of the two genera are in
direct contrast. In M. granulosa the shell is thick and reinforced. In Z. davidsoni the
shell is thin and very brittle; so brittle in fact that shells are often crushed by a degree
of compaction of sediment which does not deform Moorellina at all. Such a shell could
not survive in anything other than a sheltered environment. Dr. J. D. Hudson (personal
communication) has suggested that Zellania may have occupied a sheltered micro-
environment, e.g. protected cavities under large shells ( Ostrea , etc.). This would afford
protection whilst the animal was alive but when the pedicle decayed the shell would be
liberated into the turbulent general environment. The cardinal process and teeth of

616

PALAEONTOLOGY, VOLUME 13

M. granulosa are strongly developed. The cardinal process of Zellania is small and the
teeth are very fragile so that unless transportation of the shell occurred before the
musculature of the animal decayed, the valves would almost certainly become dis-
articulated. It seems likely that the musculature would decay before the pedicle, thus
allowing separation of the valves. Of the material collected however, complete speci-
mens are the most common although the broken teeth of the pedicle valves and per-
forations in some brachial valves (PI. 118, figs. 7, 8) do indicate a degree of abrasion
consistent with some transportation.

There exists therefore, the apparent anomaly of a strong pedicle and a weak shell.
Analysis of the shell characters of Z. davidsoni in environmental terms is indicative of a sub-
littoral mud-grade environment (Ager 1965) into which the thecidellinids, the organo-
detrital remains and the peri-reefal brachiopods (Baker 1969) were drifted. It is possible to
reconcile a large (rather than strong) pedicle with this view, as it would afford anchorage in
a soft substratum, although the anatomy of the pedicle itself is unlikely ever to be described.

The association of micromorphic brachiopods with shell debris is noted by Swedmark
(1967) who records the occurrence of Gwynia capsula (Jeffreys) in a sub-tidal mineral
sand containing a high proportion of fine broken shell. In this environment the animal
apparently seeks the shelter of serpulid tube fragments.

Circumstantial evidence is provided by speculation concerning the life-attitude and
the functional significance of the internal structures of Zellania. Analysis of the growth
habit of M. granulosa indicates a growth pattern designed to lift the brachial apparatus
away from the attachment surface (Baker 1970). This growth habit requires that the
brachial valve be uppermost in position. The posteriorly projecting brachial umbo of
Z. davidsoni may indicate similar orientation. The convex pedicle valve, possibly par-
tially buried in the sediment, would enable the dorsally oriented, relatively plate-like
brachial valve to be lifted clear of the sub-stratum (text-fig. 4a). This hypothesis is
supported by a consideration of the functional significance of the sub-marginal ridge
and ancillary structures. From a consideration of the thecidellinid brachial apparatus
it is probable that the inner surface of the sub-marginal ridge and the sides of the
median septum (text-figs. 4b, c) supported a simple schizolophe (Rudwick 1968). Study of
brachiopod feeding mechanisms (Rudwick 1965, H206) indicates that in schizolophous
forms the valves gape fairly widely and the filaments form a bell-like inhalent chamber.
If Zellania occupied a mud-grade environment it is possible that under certain con-
ditions, e.g. high turbidity, the valves did not gape as widely as normal. The denticulate
anterior of the brachial valve (text-fig. 1b) may, therefore, represent the point of entry
of the inhalent current when the valves were almost closed (text-figs. 4a, c). In this case
it is thought that the exhalent apertures were situated postero-laterally in the zones
occupied by the lateral ancillary ridges. The current flow would now be influenced by
the degree of gape of the valves, as the exhalent apertures would be closed as the sub-
marginal ridge and lateral ancillary ridges came together (text-fig. 4a). The virtual
compartmentation of the shell (text-fig. 2) must have some significance and may be an
expression of the lack of turbulence in the water, thus assisting in the separation of the
inhalent and exhalent currents produced by the filaments of the lophophore.

These arguments, of course, apply equally well to occupation of a sheltered micro-
environment but it is considered that the sum of the morphological and microstructural
features of Z. davidsoni favours the postulated mud-grade environment.

BAKER: ZELLANIA DAVIDSONI MOORE (BRACHIOPODA) 617

AFFINITIES

The close morphological similarity between the internal characters of Zellania and
thecidellinids has been noted, but it has been clearly shown that the structures arise in
different ways, and therefore contradict Moore’s (1855) view that thecideaceans and
Zellania are related. In the Treatise, Zellania is tentatively linked with the terebratel-
laceans. The material studied shows all degrees of preservation but there is little doubt
that the secondary mosaic is of modified terebratulide or spiriferide type. The similarity

text-fig. 4. A. Diagrammatic reconstruction of the possible life-attitude of Z. davidsoni with the
valves gaping slightly. A small portion of the pedicle valve is omitted to show the postulated exhalent
aperture. B. Transverse section through X-X', fig. C. to show the postulated position of the schizolophe
relative to the sub-marginal ridge and median septum. C. Diagrammatic representation of the interior
of a brachial valve of Z. davidsoni showing the probable form and position of the lophophore and
inhalent and exhalent apertures, a.l.r. ancillary lateral ridge, b.c. brachial cavity, b.v. brachial valve,
e.a. exhalent aperture, e.c. exhalent current, i.c. inhalent current, 1. lophophore, m.s. median septum,
ped. pedicle, s. socket, s.m.r. sub-marginal ridge.

between some secondary fibres of Z. davidsoni and secondary fibres of Terebratulina
caput-serpentis (Linne), and the similarity between the primary shell of Zellania and
Spiriferina walcotti (Sow.), has been noted. The sub-marginal ridge is very like the loop of
stringocephalids such as Rensselandia johanni (Hall) in a sessile position. However, the
shell micro structure of Z. davidsoni appears to most closely resemble that of the Lower
Devonian stringocephalacean Mutationella podolica (Siemiradzki). Studies strongly in-
dicate that the secondary shell mosaics of even distantly related brachipods may show
a similar initial development pattern, although subsequently diverging. The evidence
presented in the present paper, although not solving the problem of immediate affinity,
indicates that the microstructure of Zellania may partially recapitulate the phylogeny
of the genus. It is generally accepted that recapitulation in organisms can occur, although

618

PALAEONTOLOGY, VOLUME 13

its value as an evolutionary criterion is open to criticism. If it is possible for the secretory
regime of the secondary fibres to recapitulate phylogeny, accompanied by tachygenesis,
the process may be arrested and the evidence thus preserved in neotenous forms such as j
ZeUania. The dorsal cardinalia are of billingsellacean type, i.e. primitive, and work in I
progress, on very young terebratulides, shows that the initial development of the cardinal |
process of Moorellina, Zellania , and terebratulides follows the same pattern and sup-
ports the hypothesis of recapitulation.

Stehli (in Moore 1965, H739) derives both the Terebratulidina and Terebratellidina
from mutationellin ancestors. The shell of Zellania shows mutationellin affinities.
Owing to the enormous time-gap it would be ambitious to suggest that Zellania is
descended from a stringocephalacean ancestor. However, consideration of features such
as the recapitulatory nature of secondary fibre secretion, the development of the sub-
marginal ridge from ascending elements and the typical endopunctation certainly suggest
that Z. davidsoni may be closely related to terebratellacean stock.

REFERENCES

ager, d. v. 1965. The adaptation of Mesozoic brachiopods to different environments. Palaeogeo-
graphy, Palaeoclimatol, Palaeoecol, 1, 143-72.

baker, p. g. 1969. The ontogeny of the thecideacean brachiopod Moorellina granulosa (Moore) from
the Middle Jurassic of England. Palaeontology, 12, 388-99.

1970. The growth and shell microstructure of the thecideacean brachiopod Moorellina granulosa

(Moore) from the Middle Jurassic of England. Ibid., 13, 76-99.
davidson, t. 1874. Supplement to the British Jurassic and Triassic Brachiopoda, 4, 113, Suppl.
PI. 11. Palaeont. Soc. ( Monogr .), London.

elliott, G. F. 1965. Zellania. In moore, r. c., ed., Treatise on invertebrate paleontology, Part H, Brachio- \
poda, H857. Geol. Soc. Am. and Univ. Kansas Press.
moore, c. 1855. On new Brachiopoda from the Inferior Oolite of Dundry. Proc. Somerset Arch. Nat .
Hist. Soc. 5 (for 1854), 107-28, pi. 1.

rudwick, m. J. s. 1959. The growth and form of brachiopod shells. Geol. Mag. 96, 1-24.

1965. Ecology and Palaeocology. In moore, r. c. ed., Treatise on invertebrate paleontology , j

Part H, Brachiopoda, HI 99-21 3. Geol. Soc. Am. and Univ. Kansas Press.

1968. The feeding mechanisms and affinities of the Triassic brachiopods Thecospira Zugmayer |

and Bactrynium Emmrich. Palaeontology, 11, 329-60.
stehli, F. G. 1965. Palaeozoic Terebratulida. In moore, r. c., ed., Treatise on invertebrate paleontology ,
Part H, Brachiopoda, H730-40. Geol. Soc. Am and Univ. Kansas Press.
swedmark, b. 1967. Gwynia capsula (Jeffreys) an articulate brachiopod with brood protection. Nature ,
213, 1151-52.

westbroek, p. 1969. The interpretation of growth and form in serial sections through brachiopods,
exemplified by the trigonorhynchiid septalium. Palaeontology, 12, 321-32.
williams, a. 1956. The calcareous shell of the Brachiopoda and its importance to their classification.
Biol. Rev. 31, 243-87.

1966. Growth and structure of the shell of living articulate brachiopods. Nature, Lond. 211,

1146-8.

1968a. Evolution of the shell structure of articulate brachiopods. Spec. Pap. Palaeont. 2, 55 pp.

19686. Shell-structure of the billingsellacean brachiopods. Palaeontology, 11, 486-90.

et al., 1965. Glossary of morphological terms. In moore, r. c., ed., Treatise on invertebrate

paleontology. Part H, Brachiopoda, HI 39-55. Geol. Soc. Am. and Univ. Kansas Press.

p. G. BAKER

Department of Biological Sciences
Derby and District College of Technology
Kedleston Road
Derby, de3 Igb

Typescript received 6 February 1970

TEREDINID (BIVALVIA) PALLETS FROM THE
PALAEOCENE OF NORTH AMERICA

by ALAN M. CVANCARA

Abstract. Well-preserved teredinid pallets from the Cannonball Formation (Danian) of North America
are the oldest known for that continent and constitute the second occurrence for the Palaeocene. The Cannon-
ball pallets establish the existence of the extant genus, Nototeredo, in the earliest Palaeocene. All Cannonball
teredinids are included within N. globosa (Meek and Hayden).

Fossil teredinid bivalve mollusks are represented usually by globular shells or cal-
careous tubes lining borings in wood. Unfortunately these structures are of very little
taxonomic use (Turner 1966, pp. 61, 64-5). The pallets, hard structures at the base of
the siphons for closing the tube, are used primarily for generic and specific determina-
tion. Because fossil pallets are discovered rarely, the purpose of this paper is to describe
and illustrate well-preserved specimens from the Cannonball Formation (Palaeocene)
of central North America (North Dakota).

The Cannonball pallets are the oldest known in North America; elsewhere only in
Iraq have they been taken from rocks as old as the Palaeocene (Elliott 1963). Turner
(1966, p. 14-17) has reviewed the fossil record of the Teredinidae and noted the re-
latively few occurrences of pallets from the Tertiary.

The Cannonball Formation is a clastic sequence, of up to 1300 m. (Fox and Olsson
1969, p. 1397) of largely poorly consolidated, light greyish-green sandstone and medium
to very dark grey mudstone. I have synthesized the detailed stratigraphy elsewhere
(Cvancara 1965). Recently, the age of the Cannonball, based on planktonic foramini-
ferids, has been assigned as earliest Palaeocene or early Danian (Fox and Olsson 1969,
p. 1400). Macrofossils of the Cannonball consist mostly of gastropod and bivalve mol-
lusks, (Stanton 1920, Cvancara 1966), with few crustaceans (Holland and Cvancara 1958)
and small coelenterates (Vaughan 1920). Vertebrate fossils, with the exception of shark
teeth, are generally rare.

The specimens figured in this paper are deposited at the University of Michigan
Museum of Paleontology (UMMP).

SYSTEMATIC DESCRIPTION

Class bivalvia Linnaeus 1758
Family teredinidae Rafinesque 1815
Genus nototeredo Bartsch 1923

Type species. Teredo edax Hedley 1895.

Diagnosis. Pallets oval to broadly oval, with short stalk. Blade thin, outer face convex,
inner face concave. Blade segmented, with segments closely packed and appearing
arranged concentrically near tip, where small depression may be present. Shells like

[Palaeontology, Vol. 13, Part 4, 1970, pp. 619-22, pi. 121.

620

PALAEONTOLOGY, VOLUME 13

those of Teredo, Lyrodus, and Bankia. Tubes concamerate at posterior end. (After
Turner 1966, p. 78; only those characters apparent in fossil species are included.)

Nototeredo globosa (Meek and Hayden) 1858

(for synonymy see Cvancara 1966, p. 350)

Diagnosis. Pallets (PI. 121, figs. 4, 6-9, 11, 13) elongate, flattened-spoonlike. Stalk
hollow, exposed part very short, only about £ of total length of pallet. On inner face of
blade, stalk evidenced as only low, rounded ridge, almost imperceptible on distal half
of blade.

Hypotypes. UMMP 47370 and 57578-86.

Material. See Cvancara (1966, p. 357) for all material; twenty-two, mostly incomplete, pallets are
included.

Remarks. Teredinids in the Cannonball Formation are evidenced largely by shells
(PI. 121, figs. 1-3, 5, and 10) and tubes, which may be concamerate (PI. 121, fig. 12).
The tubes fine borings which occur in well-preserved petrified wood or in very fine-
grained sandstone and sandy claystone in which little, if any, of the wood structure
remains.

Thin-sections were cut of teredinid-bored wood from six Cannonball localities (in-
cluding localities 1 and 4, listed below under Occurrence ). All wood specimens from the
six localities were from the lower middle or lower part of the formation. Because of pre-
servation inadequate for details essential for accurate identification, the taxonomy of
the bored wood is uncertain. However, both ‘hardwoods’ and softwoods’ are represented,
and five species are apparently demonstrated from the six localities. Either Sequoia or
Metasequoia is possibly present, and perhaps Magnolia, taken at localities 1 and 4.

Pallets were found at two localities, associated with the Magnolia ? wood at locality 4
and with unidentified wood at locality 2. At both localities they have been noted in
direct association with shells (PI. 121, figs. 11 and 13, and Cvancara 1966, pi. 9, fig. 28).
Pallets were found usually attached to the sides of tubes and they, with the shells, were
encrusted uncommonly with calcite (PI. 121, fig. 11).

EXPLANATION OF PLATE 121

Nototeredo globosa (Meek and Hayden). Cannonball Formation, Palaeocene. All figures are x 4 un-
less otherwise indicated.

Figs. 1-3. Right exterior, posterior and dorsal views of conjoined valves. Hypotype. UMMP 47370;
locality 1.

Figs. 4, 7. Outer and inner faces of two different pallets. Hypotypes, UMMP 57578 and UMMP 57581,
respectively; locality 2.

Fig. 5. Interior of left valve. Hypotype, UMMP 57579; locality 2.

Figs. 6, 9. Oblique and proximal views of two pallets in tube. Hypotype, UMMP 57580; locality 2.

Fig. 8. Outer face of pallet attached to tube. Hypotype, UMMP 57582; locality 2.

Fig. 10. Exterior of right valve in tube. Hypotype, UMMP 57583; locality 1.

Fig. 11. Two valves and two pallets, all calcite-encrusted, attached to tube. Hypotype, UMMP 57584;
locality 4; x2.

Fig. 12. Concamerate tubes, that on extreme left with a calcite-encrusted valve. Hypotype, UMMP
57585; locality 3; x 2.

Fig. 13. Tubes with shell and pallets; one tube (left) has conjoined valves and a single pallet and
another (right) contains two pallets. Hypotype, UMMP 57586; locality 2.

Palaeontology Vol. 13

PLATE 121

CVANCARA, Paleocene Nototeredo

CVANCARA: TEREDINID (BIVALVIA) PALLETS 621

I have placed all Cannonball teredinid material within Nototeredo globosa (Meek
and Hayden) although pallets, for assignment to Nototeredo, have been taken only at
two localities. The specific name ‘ globosa’ was based originally upon tubes and shells,
but it is retained because it was the first name applied to teredinid specimens now known
to occur in the Cannonball Formation. I have chosen to assume that all Cannonball
teredinid shells, tubes, and pallets were secreted by the same species unless further
pallet finds should indicate otherwise.

Occurrence. Pallets have been collected from the middle and lower middle parts of the
Cannonball Formation, whereas other teredinid specimens have been taken essentially
throughout the unit. Although I have noted teredinid material from 28 Cannonball
localities, the specimens illustrated here are from the following four localities :

1. South-facing hillside, NWJ sec. 26, T. 139 N., R. 81 W., north-west edge of Mandan Foundry,
off north end of 12th Avenue Northeast, Mandan, Morton County, North Dakota; University of
Michigan accession, 1961/Tpa-23. Lower part of Cannonball Formation.

2. South-facing (left) cutbank of Heart River, SEf sec. 10, T. 138 N., R. 83 W., about 7-4 air km.
west-south-west of Mandan, Morton County, North Dakota; University of Michigan accession
1962/Tpa-10. Middle part of Cannonball Formation.

3. South-facing, upper part of Mitchell Butte, SWf sec. 7, T. 134 N., R. 83 W., about 2 air km. east-
south-east of Flasher, Morton County, North Dakota ; University of Michigan accession, 1961 /Tpa-
10. Lower middle part of Cannonball Formation.

4. West-facing (right) cutbank of Heart River, near centre of sec. 21, T. 136 N., R. 86 W., about
6-5 air km. south of Almont, Grant County, North Dakota; University of Michigan accession,
1962/Tpa-28. Lower middle part of Cannonball Formation.

SIGNIFICANCE OF CANNONBALL PALLETS

As noted in the introduction, the Cannonball pallets are the oldest known in North
America and the second occurrence recorded from the Palaeocene. Those reported
from the Palaeocene of Iraq (Elliott 1963) were described from thin-sections of petrified
wood; the Cannonball specimens have been taken from empty tubes and can be studied
directly.

The Cannonball specimens also establish the existence of the genus Nototeredo at
least as early as earliest Palaeocene. This genus is presently world-wide and occurs in
fully marine, tropical to cold temperate seas. The Cannonball species is closest to the
living N. norvagica Spengler which probably occurs largely along the Atlantic European
Coast and in the Mediterranean (Turner 1966, pp. 16, 78, and 258).

Acknowledgements. I wish to thank Dr. R. D. Turner, Harvard College, for aid in the generic assign-
ment of the Cannonball teredinids. Dr. C. A. Arnold, University of Michigan, identified the teredinid-
bored wood. Dr. F. D. Holland, Jr., University of North Dakota, critically reviewed the manuscript.

REFERENCES

cvancara, a. m. 1965. Bivalves and biostratigraphy of the Cannonball Formation (Paleocene) in
North Dakota. Unpubl. Ph.D. Dissertation, Univ. Michigan, Ann Arbor, 470 pp., 10 pi.

1966. Revision of the fauna of the Cannonball Formation (Paleocene) of North and South

Dakota. Part 1. Bivalvia. Contr. Univ. Mich. Mus. Paleont. 20, 277-374, pi. 1-9.
elliott, G. F. 1963. A Paleocene teredinid (Mollusca) from Iraq. Palaeontology, 6, 315-17, pi. 51-2.
fox, s. k., jr. and olsson, r. k. 1969. Danian planktonic Foraminifera from the Cannonball Formation
in North Dakota. /. Paleont. 43, 1397-1404, pi. 168-9.

622 PALAEONTOLOGY, VOLUME 13

Holland, f. d., jr., and cvancara, A. m. 1958. Crabs from the Cannonball formation (Paleocene)
of North Dakota. J. Paleont. 32, 495-505, pi. 74.

stanton, t. w. 1920. The fauna of the Cannonball marine member of the Lance formation. Prof,
pap. U.S. geol. Surv. 128-a, 1-60, pi. 1-9.

turner, R. D. 1966. A survey and illustrated catalogue of the Teredinidae ( Mollusca : Bivalvia). Cam-
bridge, Mass. 265 pp.

vaughan, t. w. 1920. Corals from the Cannonball marine member of the Lance formation. Prof,
pap. U.S. geol. Surv. 128-A, 61-6, pi. 10.

ALAN M. CVANCARA

Department of Geology
University of North Dakota
Grand Forks
North Dakota 58201
U.S.A.

Typescript received 7 February 1970

THE DENTITION AND MUSCULATURE OF SOME
MIDDLE ORDOVICIAN (LLANDEILO) BIVALVES
FROM FINISTERE, FRANCE

by MARGARET A. BRADSHAW

Abstract. The dentition and musculature of palaeotaxodontid and palaeoheterodontid bivalves from the
Middle Ordovician of Finistere is described. These characters suggest that a number of species currently grouped
in the genus Ctenodonta show closer affinity to Cardiolaria, Praeleda, and Tancrediopsis. The two species of
Praeleda examined are considered to have had a reversed (nuculoid) orientation. The palaeoheterodontids
Redonia deshayesi and Actinodonta naranjoana exhibit reduction of hinge teeth during ontogeny, due to fusion
and resorption. An early Palaeozoic bivalve phylogeny is suggested, based on the development of the dentition
within this fauna.

The Middle Ordovician bivalves of the Crozon Peninsula (Finistere) have been referred
to in many publications. Earlier work was summarized by Kerforne (1901), who attri-
buted the forms present to species described from beds of similar age in Portugal and
Spain (Ribeiro, Sharpe, and Jones 1853, de Verneuil and Barrande 1855). Subsequent
work has been summarized and expanded by Babin (1966) in a major work on the
Palaeozoic Mollusca of Brittany.

The present work is more detailed and restricted to bivalves. Particular attention
has been given to the dentition and its development during ontogeny, and to accessory
muscle scar patterns.

This study is based on material from coastal sections near La Mort Anglaise (831487
and 838495) and south-east of Crozon (912441). These grid references refer to square
UU of the U.T.M. international grid. The most perfectly preserved bivalves are found
as disarticulated valves in numerous thin fossil bands in shales, and are present as inter-
nal and external moulds. Isolated steinkerns sometimes occur outside these fossil bands.
The most prolific beds were found in the Schistes de Morgat (Llandeilo). A more de-
tailed description of the nature of these fossil bands and their constituents can be found
in Bishop, Bradshaw, Renouf, and Taylor (1969).

The bivalves frequently show tectonic distortion, and identification on general shape
alone is therefore unsound. The dentition, combined with the positioning of the acces-
sory muscle scars, was found to be more reliable.

The Llandeilian bivalves of the Crozon Peninsula were listed by Babin (1966) as:
Order Palaeotaxodonta : Ctenodonta bussacensis (Sharpe) 1853, Ctenodonta ciae (Sharpe)
1853, Ctenodonta costae (Sharpe) 1853, Ctenodonta ribeiroi (Sharpe) 1853, Ctenodonta
britannica Babin 1966, Palaeoneilo hopensacki (de Verneuil and Barrande) 1855, Palaeo-
neilo beirensis (Sharpe) 1853, Palaeoneilo ctenodontoides Babin 1966; Order Panto-
dontida: Actinodonta naranjoana (de Verneuil and Barrande) 1855, Redonia deshayesi
Rouault 1851, emend. Gouzien 1934.

The placing of many of the palaeotaxodontids in the genus Ctenodonta is not
supported by a comparison with the type species, Ctenodonta nasuta (Hall). The

[Palaeontology, Vol. l3 Part 4, 1970, pp. 623-45.]

C 7719 S S

624

PALAEONTOLOGY, VOLUME 13

palaeotaxodontids of the Crozon Peninsula exhibit several small, but significant,
differences amongst themselves, and a revised fist of the more abundant palaeo-
taxodontids is suggested :

Sub-class PALAEOTAXODONTA
Order nuculoida

Cardiolaria beirensis (Sharpe) 1853.

Tancrediopsis ezquerrae (Sharpe) 1853.

Praeleda ciae (Sharpe) 1853.

Praeleda costae (Sharpe) 1853.

Each genus of the fauna is reviewed separately in the following pages. As Ctenodonta
ribeiroi and Ctenodonta britannica are inadequately represented in the material collected,
they are not discussed. The description of each species refers to the actual shell, but
the accompanying figures are of internal moulds, as the dentition in many cases was
too delicate to withstand the making of latex casts.

In all accompanying illustrations the muscle scars are indicated as follows: Anterior adductor
muscle — AA; Posterior adductor muscle — PA; accessory muscles — a. Other symbols used are ex-
plained in the figure captions. With incomplete specimens the suggested outline has been dotted in.

All figured specimens have been deposited in the museum of the Department of Geology, Univer-
sity of Canterbury, New Zealand.

Orientation. The orientation of the palaeotaxodontids was deduced from the nature
of the teeth along the hinge line and the positions of the accessory muscle scars. Two
orientations are present, a normal orientation as shown by Cardiolaria beirensis and
Tancrediopsis ezquerrae, and a reversed (nuculoid) orientation shown by Praeleda costae
and Praeleda ciae. A fuller explanation is given at the beginning of the section on the
reversed forms.

PALAEOTAXODONTIDS OF NORMAL ORIENTATION
Cardiolaria beirensis (Sharpe) 1853
Text-figs. 1-4

1853 Nucula beirensis Sharpe, p. 150, pi. 9, figs. 11-12.

1853 Nucula bussacensis Sharpe, p. 151, pi. 9, figs. 13-14.

1855 Nucula hopensacki de Verneuil and Barrande, p. 989, pi. 28, fig. 8.

1876 Ctenodonta beirensis de Tromelin and Lebesconte, p. 654.

1876 Ctenodonta bussacensis de Tromelin and Lebesconte, p. 683.

1886 Ctenodonta beirensis Barrois, p. 680.

1886 Ctenodonta bussacensis Barrois, p. 685.

1901 Ctenodonta beirensis Kerfome, p. 194.

1901 Ctenodonta bussacensis Kerforne, p. 195.

1901 Ctenodonta hopensacki Kerforne, p. 196.

1912 Palaeoneilo hopensacki Douville, p. 439, fig. 6.

1934 Ctenodonta bussacensis Gouzien, p. 179.

1966 Ctenodonta bussacensis Babin, p. 45, text-figs. 5 and 6; pi. 1, figs. 4 and 5.

1966 Palaeoneilo hopensacki Babin, p. 73, text-figs. 23 and 24; pi. 11, figs. 10 and 11.

1966 Palaeoneilo beirensis Babin, p. 74, text-figs. 25; pi. 11, fig. 9.

The general morphology and dentition of Cardiolaria beirensis is clearly illustrated
in text-figs. 1-4. The most significant point concerning the dentition is the marked

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

625

difference in adult forms between the anterior and posterior series of teeth. The anterior
teeth are few (4-6 in adult), massive, and vary amongst themselves in shape, size and
position. The posterior teeth are more numerous (15-20 in adult), uniform in size and
placement, and usually chevron in shape. In the adult the posterior series of teeth tends
to override the anterior, and there is resorp-
tion in this region. The dentition undergoes
appreciable change during ontogeny. Re-
crystallization has destroyed the dentition
of individuals smaller than 5 mm. in length
and 3-5 mm. in height, but at this size the
two series of teeth are almost indistinguish-
able, appearing continuous (text-fig. 1). With
increase in size the two series of teeth become
more distinct and discontinuous (text-fig. 2).

With further growth the overriding of the
first anterior tooth by the proximal end of
the posterior series becomes emphasized, and
the two series become separated by a narrow
flat region (text-figs. 3 and 4).

Fusion of anterior teeth in the left valve
accompanies the growing discordance be-
tween the two series of teeth. In medium-
sized individuals (approx. T3 cm. length,

1 cm. width) a bifid tooth opening ventrally
is situated in the left valve. Certain specimens indicate that this bifid tooth is composed
of a chevron tooth fused to a smaller, ridge-like tooth that lies ventral and posterior to
it (illustrated by the opposite valve in text-fig. 3). In the right valve a corresponding
spike-like tooth lies between two normally developed teeth, close to the ventral margin
of the dental plate. In only one medium-sized valve has a bifid tooth been seen in the
right valve. This specimen (text-fig. 2) was obtained from beds older than the bulk of
the material studied. A larger valve of identical shape from the same horizon shows no
trace of the bifid tooth.

In the largest forms available (text-fig. 4) the bifid tooth is retained, and the flat
region between the two series of teeth appears prominent. This featureless area is in-
teresting as Cardiolaria is the only palaeotaxodontid member of the Crozon Peninsula
bivalve fauna to exhibit a well-marked area where resorption of teeth occurs. Bernard
(1896) records the progressive resorption of teeth adjacent to the internal ligament of
Tertiary and modern nuculids. The featureless area of Cardiolaria beirensis does not
resemble the clearly defined resilifer of modern palaeotaxodontids, but it may indicate
a very early stage in the migration of the external ligament onto the hinge plate.

The adductor muscle scars of Cardiolaria beirensis are rounded and equal in size,
although the anterior scar is much more deeply impressed. The posterior pedal accessory
muscle scar is too feeble to be visible, but those to the anterior, adjacent to the adductor
scar, are very prominent. These accessory scars he in the thickness of the myophoric
plate where it abuts the hinge plate (text-figs. 1, 2). Most specimens appear to possess
only one anterior pedal accessory muscle scar, but very well-preserved specimens

text-fig. 1 . Cardiolaria beirensis. Internal
mould of a juvenile right valve showing simple,
continuous dentition. Pointed umbo missing.
The unequally impressed musculature and the
strong anterior myophoric plate are already
distinct at this stage. Note the general simi-
larity of tooth shape and size. The anterior
teeth appear slightly thicker and more oblique
to the dental plate. Specimen B. 10. Llandeilo.

G.R. 838495.

626

PALAEONTOLOGY, VOLUME 13

text-fig. 3. Cardiolaria beirensis. Internal mould of right valve (hinge only)
showing anterior and posterior teeth and the area of resorption between them.
The mould of an anterior bifid socket is indicated (bs). Specimen B.4. Llandeilo.
G.R. 838495.

5mm

text-fig. 2. Cardiolaria beirensis. Young adult. Internal mould of right valve, umbonal
region missing, showing the developing differences between the anterior and posterior
series of teeth. The extreme posterior teeth are obscured. The mould of a bifid anterior
tooth (bt — appearing as socket) and the position the two anterior pedal muscle scars are
indicated. Specimen K.3. Llanvirn. G.R. 803469.

ant.

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

627

indicate it to be composed to two juxtaposed elliptical scars lying with their common
long axes sub-parallel to the anterior part of the hinge plate. In these specimens a
smaller scar is also present between the juxtaposed scars and the anterio-dorsal edge
of the anterior adductor muscle scar. The close grouping of these scars is further in-
dication of the normal orientation of Cardiolaria. The two elongate, juxtaposed scars

bt

5mm

text-fig. 4. Cardiolaria beirensis. Internal mould of the hinge region
only of a large left valve, showing the hinge plate clearly composed
of two distinct dental sections. The few anterior teeth are massive,
and the mould of a bifid tooth (bt) is indicated. The regular posterior
teeth are numerous and vary from an asymmetrical chevron shape with
a longer ventral limb, to ridge-like below the umbo. Both series of
teeth show resorption where the posterior series overrides the anterior
series. Specimen A.8. Llandeilo. G.R. 831487.

resemble the anterior protractor and retractor found in Acila divaricata figured by Dris-
coll (1964, fig. 3). The accompanying smaller scar in Cardiolaria, which is slightly
ventral to these scars, is probably the smaller anterior protractor also visible in Acila
divaricata.

Discussion. Cardiolaria beirensis is here interpreted as including Ctenodonta beirensis,
C. bussacensis, and C. hopensacki of previous authors. Originally the three species were
based on differences in general shape, but these characters alone have proved of little
value in distorted faunas.

Babin (1966) has attempted to distinguish the species on the nature of the sub-
umbonal teeth together with detailed variation in shape. However, he admits that
without the sub-umbonal teeth the forms are difficult to distinguish in distorted faunas.
Since the character of these teeth is related to stages in ontogeny, the maintenance of
separate species can no longer be supported. Babin divides the three species into two
genera, Ctenodonta and Palaeoneilo, which he places in two separate subfamilies,
Ctenodontinae and Palaeoneilinae. He considers the former to be characterized by
continuous teeth below the umbo and the latter by two series discontinuously arranged
below the umbo.

However, McAlester (1968) describes the lectotype of Palaeoneilo, Palaeoneilo con-
stricta (Conrad), as having ‘fine taxodont dentition’ a characteristic that is borne out
by his illustrations (pi. 15, especially fig. 15). The teeth are continuous along the hinge,
and the illustrated specimens appear in no way similar to Ctenodonta hopensacki or
C. beirensis. Furthermore, the range of Palaeoneilo is generally accepted as being
Devonian-Triassic.

The specific name beirensis is retained on the grounds of priority (Sharpe 1853, p. 150),

628

PALAEONTOLOGY, VOLUME 13

but the species possesses no characters attributable to the type species of Ctenodonta,
Ctenodonta nasuta (Hall). It does, however, show striking resemblances to the type
species of Cardiolaria ( Cardiolaria barrandei) figured by McAlester (1968, pi. 10),
having the same distinct anterior myophoric plate and the two unequal series of teeth.
For this reason Ctenodonta beirensis is here transferred to the genus Cardiolaria.

text-fig. 5. Tancrediopsis ezquerrae. Internal mould of a right valve, tilted
to show the dental plate. The chevron-shaped posterior teeth decrease
steadily in size towards the umbo below which they are ridge-like and
low. The series is straight except just anterior of the umbo. The anterior
teeth are fewer in number and show abrupt decrease in size at both ends of
the series. The highest posterior tooth is equal in size to the highest anterior
tooth. The junction of the two series is visible anterior of the umbo. Speci-
men A.12. Llandeilo. G.R. 831487.

Tancrediopsis ezquerrae (Sharpe) 1853
Text-figs. 5, 6

1853 Nucula ezquerrae Sharpe, p. 149; pi. 9, fig. 7.

1876 Ctenodonta ezquerrae de Tromelin and Lebesconte, p. 624.

1886 Ctenodonta ezquerrae Barrois, p. 680.

1901 Ctenodonta ezquerrae Kerfome, p. 196.

1966 Ctenodonta costae Babin, p. 52, text-figs. 13, 14, 15; pi. 1, figs. 6 and 7.

Unlike the other palaeotaxodontids of the fauna which possess teeth of different size
and shape on each side of the umbo, the dentition of Tancrediopsis ezquerrae is very
uniform in shape and size. The teeth are arranged in two series with more teeth present
in the posterior series (text-fig. 5). The arrangement of the teeth on the two parts of the
dental plate is closer to that in Cardiolaria than in Praeleda. The dentition appears
continuous along the hinge plate but well-preserved specimens with the sub-umbonal
region unobscured show that the two series are slightly offset (text-fig. 5). There is no
indication of resorption in this region.

Young specimens of Tancrediopsis ezquerrae possess teeth that are pustule-like in
shape rather than chevron. With increase in size of the individual the chevron shape
develops with the formation of a strong groove down the side of the tooth facing away
from the umbo.

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

629

The sub-equal adductor muscle scars are situated at the distal ends of the hinge
plate beyond the last teeth. A distinct pedal accessory muscle scar is present close to
each adductor muscle scar (text-fig. 6). In both cases the accessory scar lies adjacent
to the edge of the hinge plate, and the posterior pedal scar is more obviously dorsal
to its related adductor muscle scar than is the anterior pedal scar.

a

text-fig. 6. Tancrediopsis ezquerrae. Left side view of articulated in-
ternal moulds showing the characteristic oval shaped adductor muscle
scars whose long axes converge ventrally, and the positions of the
accessory muscle scars. Specimen 0-5. Llandeilo. G.R. 806468.

In addition three umbonal scars have been consistently observed. Two of these lie
along the dorsal side of the umbonal cavity close to the hinge plate (text-fig. 6). The
position of these scars is interesting as McAlester (1963) mentions faint impressions just
below the posterior hinge plate in Tancrediopsis contracta which he suggests may re-
present pedal or visceral muscle scars. A further umbonal muscle scar lies ventrally
placed in the umbonal cavity and is level with the adductor muscle scars.

Discussion. The general morphology of Ctenodonta ezquerrae of previous authors has
little in common with the type species Ctenodonta nasuta, and it would seem more
desirable to place the species in another genus.

McAlester (1963, p. 4) writes: ‘The name Tancrediopsis will, however, probably
prove useful in the future as a generic sub-division of the heterogeneous assemblage of
Ordovician forms now included in “ Ctenodonta!'.'’ It is suggested that Ctenodonta
ezquerrae has closer affinities with Tancrediopsis than any other genus described to date.

The oval, dorsally impressed adductor muscle scars of Ctenodonta ezquerrae are
very similar to those preserved in the type species Tancrediopsis contracta (Salter) which

630

PALAEONTOLOGY, VOLUME 13

have long axes also converging ventrally. The strongly inflated valves, the regular but
faint growth-lines, and the strong chevron teeth almost continuous along the hinge,
are additional similarities. As in Tancrediopsis contracta, two distinct pedal muscle
scars are present in Ctenodonta ezquerrae adjacent to the umbonal edge of the adductor
muscle scars.

Although Ctenodonta ezquerrae does not possess the almost equilateral valves of the
type species of Tancrediopsis, nor the two sub-equal series of teeth, the author feels
that it has closer affinities to Tancrediopsis than to any other described genus of palaeo-
taxodontid, and transfers it accordingly.

PALAEOTAXODONTIDS OF REVERSE ORIENTATION

Orientation. A general discussion on the problem of palaeotaxodontid orientation
would be inappropriate in a paper of this type. A separate contribution is in prepara-
tion.

However, with regard to the forms described here, the dentitions of Praeleda and
Cardiolaria indicate that their orientations are opposite. In Cardiolaria the larger chev-
ron teeth are always found along the shorter side of the valve on a plate whose inner
edge is straight or arched dorsally (text-fig. 4). Praeleda is the reverse. The largest teeth
are found on the longer side of the valve, but still on a plate whose inner edge is arched
ventrally. The lower ridge-like teeth are present on a narrower plate, arched dorsally
(text-fig. 7). It has been shown above that Cardiolaria has a normal orientation as
indicated by the grouping of certain accessory muscle scars.

Where the shape of the teeth can be established in detail, the relative movement of
the two valves can be determined and the position of the external ligament and regions
of maximum opening inferred (the latter probably determined by the retraction of a
large foot as in modern Nucula). The inferred positions in Praeleda and Cardiolaria are
opposite.

Consequently, in the descriptions of Praeleda, the shorter end will be referred to as
posterior, and the extended end as anterior.

Despite tectonic distortion, Praeleda costae and Praeleda ciae can be readily dis-
tinguished from each other by the shape and disposition of the teeth and the relative
positions of the accessory muscle scars.

Praeleda costae (Sharpe) 1853
Text-figs. 7-10

1853 Nucula costae Sharpe, p. 149, pi. 9, fig. 4.

1855 Nucula costae de Verneuil and Barrande, p. 989.

1876 Ctenodonta costae ? de Tromelin and Lebesconte, p. 641.

1886 Ctenodonta costae Barrois, p. 680.

1891 Ctenodonta costae Barrois, p. 189, pi. 1, fig. 6.

1901 Ctenodonta costae Kerforne, p. 196.

1934 Ctenodonta costae Gouzien, p. 179.

1966 Palaeoneilo ctenodontoides Babin, p. 76, text-figs. 26-8; pi. 1, figs. 9-10; pi. 11, figs.

6, 12, 13.

In Praeleda costae (text-fig. 7) the two series of teeth are arranged at an angle to each
other on the hinge plate, the junction lying just anterior to the umbo. Seventeen to

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

631

twenty-two teeth are usually present along the adult hinge, either divided equally be-
tween the two series or with more in the posterior series. Those in the anterior series are
large and prominent, possessing an inconsistent chevron shape. The most anterior teeth
commonly show the more usual curved chevron form with angles directed towards the
umbo, but in many specimens the teeth closer to the umbo show a reversal of this shape
with angles directed away from the umbo. The posterior teeth are low and ridge-like,

text-fig. 7. Praeleda costae. Internal mould of right valve, anterior to right, showing muscle scars
and the two different types of teeth on each side of the umbo. Specimen 0-1. Llandeilo. G.R.

806468.

frequently curved with the concave side towards the umbo. In some cases the teeth
appear to have a grossly asymmetrical form with the ventral limb developed at the
expense of the dorsal limb. Where this form is visible the angle of the chevron is directed
towards the umbo.

In juvenile forms of Praeleda costae (text-fig. 8) the adductor muscle scars are rounded
and equal, but in the adult (text-fig. 7) the anterior adductor scar is larger and oval in
shape with its long axis roughly parallel with the anterio-dorsal margin of the shell.
In addition five pedal accessory muscle scars are usually visible. Three of these are
umbonal in situation commonly arranged in the form of a triangle with its apex ventral
and the base slanting downwards anteriorly. The scar closest to the umbo is frequently
the strongest. A pedal accessory scar is present at the distal end of the anterior hinge
plate, adjacent and dorsal to the anterior adductor muscle scar. Another prominent

632

PALAEONTOLOGY, VOLUME 13

5mm

text-fig. 8. Praeleda costae. Internal mould of small left
valve, anterior to left, showing early dentition and
muscle scars. Specimen F.30. Llandeilo. G.R. 912441.

text-fig. 9. Praeleda costae. Internal mould of distorted right valve, anterior to right.
Note accessory muscle scars. Specimen C.l.b. Llandeilo. G.R. 912441.

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

633

accessory scar lies half-way along, and ventral to, the posterior part of the hinge plate.
This scar is quite isolated from the posterior adductor scar, and its position is charac-
teristic of the species.

text-fig. 10. Praeleda costae. Internal mould of a distorted left
valve, anterior to left, showing a more concordant junction be-
tween the two series of teeth than is usual for this species. Part
of the external mould of a pronounced lunule is also visible.

Specimen F.31.b. Llandeilo. G.R. 912441.

Praeleda ciae (Sharpe) 1853

Text-figs. 11, 12

1853 Nucula ciae Sharpe, p. 149, pi. 9, fig. 5.

1876 Ctenodonta ciae de Tromelin and Lebesconte, p. 641.

1886 Redonia ciae Barrois, p. 659.

1901 Ctenodonta ciae Kerforne, p. 195.

1923 Ctenodonta ciae Kerforne, p. 180.

1966 Ctenodonta ciae Babin, p. 49, text-figs. 10-12; pi. 1, fig. 9.

The teeth of Praeleda ciae are fewer than in Praeleda costae, and are arranged without
disruption along the hinge plate (text-fig. 11). Approximately 16 teeth are present in
the adult, either divided equally between the two series or with slightly more in the
anterior series. The teeth of the anterior series have a clear, regular chevron form, curved
in profile with angles directed towards the umbo. They merge steadily into the small
ridge-like sub-umbonal teeth, which in turn pass posteriorly into the low, ridge-like
posterior teeth.

In the adult the adductor muscle scars are unequal, the anterior scar being larger
and oval in shape with its long axis roughly parallel with the anterio-dorsal margin of

634

PALAEONTOLOGY, VOLUME 13

the shell. Five pedal accessory muscle scars are generally visible. Two of these are found
dorsal and adjacent to both adductor muscle scars. A further three scars are present
in the umbonal region, usually situated in a straight line slanting downwards towards
the anterior. The lowest scar is frequently the strongest.

5mm

text-fig. 11. Praeleda ciae. Internal mould of right valve, anterior to right and tip of umbo
missing. The anterior teeth are prominent and curved, the posterior teeth lower and ridge-
like. The two series are continuous below the umbo where the teeth are low and ridge-like.

Specimen B.19. Llandeilo. G.R. 838495.

Comparisons. Praeleda costae is particularly interesting as it is the more variable of the
two species and sometimes exhibits a dental plate similar to that of Praeleda ciae , e.g.
text-fig. 10. The two patterns of dentition are fundamentally similar, and only seem
different because of variations in the relative growth-rates of the two portions of the
hinge plate, which have a direct bearing on their angular relationship.

The pattern of accessory muscle scars in the two species is basically similar, but their
different development in each has allowed them to be used for specific definition. An
internal mould of average preservation will only show the strongest of the accessory
scar impressions, and a distinctive pattern is obvious in each species. But certain well-
preserved specimens of each species show numerous accessory scars in a basically similar
pattern. The right valve of Praeleda costae, in text-fig. 9, shows the usual triangular
arrangement of umbonal accessory scars. However, there is an additional scar in the
middle of the base line so that this line resembles the usual pattern of umbonal scars
found in Praeleda ciae. In text-fig. 7, a right valve of Praeleda costae, an additional small
accessory scar is visible dorsal to the posterior adductor scar and closely adjacent to the
distal posterior teeth. This appears to be the pedal scar commonly preserved in Praeleda
ciae next to the posterior adductor scar. In text-fig. 12, a right valve of Praeleda ciae.

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

635

a prominent umbonal accessory scar is present half-way along the umbonal cavity and
adjacent to the posterior hinge plate. It is suggested that this scar is comparable to the
posterior accessory scar found in Praeleda costae close to the posterior teeth and half-
way along the series.

Discussion. Ctenodonta ciae, C. costae, and C. ezquerrae were all recorded from the
Llandeilian of the Crozon Peninsula by Kerforne (1901). However, Babin (1966)

text-fig. 12. Praeleda ciae. Internal mould of right valve, anterior to right. The specimen is
slightly crushed, but otherwise well preserved, showing numerous umbonal accessory muscle
scars. The curved anterior teeth are also distinct. Specimen C.6. Llandeilo. G.R. 912441.

regarded Ctenodonta ezquerrae as a synonym of Ctenodonta costae in his sub-family
Ctenodontinae. At the same time he erected a new species Palaeoneilo ctenodontoides
in his second sub-family the Palaeoneilinae.

Babin’s figures of Ctenodonta costae are in no way similar to photographs of the
holotype from Bussaco housed in the British Museum on which the Crozon identifica-
tion were based. On the contrary, his figures closely resemble photographs of the holo-
type of the distinctive Ctenodonta ezquerrae. In addition, his figures of the newly erected
species Palaeoneilo ctenodontoides are identical to the holotype of Ctenondonta costae,
and for these reasons it would appear that the species Palaeoneilo ctenodontoides Babin
is invalid.

636

PALAEONTOLOGY, VOLUME 13

In common with the other palaeotaxodontids of the Crozon Peninsula fauna, Cteno-
donta ciae and Ctenodonta costae show little similarity to the type species Ctenodonta
nasuta, and would be best included in another genus.

The two forms show closest resemblances to Praeleda Pfab in general shape, dentition
and accessory muscle scars. The type species Praeleda compar (Barrande) figured by
McAlester (1968, pi. 7) appears very similar to Ctenodonta ciae. The dentition is in
two series, and although more teeth are present to the posterior, the larger teeth are
found to the anterior. A distinct pedal accessory scar is visible dorsal to the anterior
adducted muscle scar, and in Paratype B (pi. 7, figs. 7 and 9) three umbonal accessory
scars are also visible in a fine slanting towards the anterior. The three umbonal scars
are also obvious in an illustration by Pfab (1934, pi. Ill, fig. 2).

McAlester (1969) has fisted Praeleda as a synonym of Deceptrix, but there are reasons
for retaining this genus. Praeleda compar, P. costae, and P. ciae seem to form a group of
species more closely related to each other than they are to Deceptrix. There is also
similarity between Praeleda and the contemporaneous genus Praenucula. Whereas
Deceptrix shows a sub-circular, equilateral form, all three species of Praeleda, and
Praenucula, exhibit an anteriorly elongate shape. Although the inflation of the umbo
varies within Praeleda costae, P. ciae, the anteriorly elongate shape is constant. Variation
in the dentition is more common. Although the dentition of some individuals of Prae-
leda (e.g. Praeleda costae, text-fig. 7) is remarkably similar to Deceptrix, others are quite
different and approach Praenucula. It is highly likely that these two Ordovician genera
were ancestral to later Palaeozoic forms such as Deceptrix, and the anteriorly elongate
bivalves with an internal ligament such as Nuculanella.

PALAEOHETERODONTIDS
Actinodonta naranjoana (de Verneuil and Barrande) 1855
Text-figs. 13-15

1855 Area naranjoana de Verneuil and Barrande, p. 989, pi. 26, fig. 12.

1901 Areal naranjoana Kerforne, p. 194.

1901 Dolabra lusitanica Kerforne, p. 194.

1923 Areal naranjoana Kerforne, p. 180.

1966 Actinodonta naranjoana Babin, p. 233, text-fig. 60; pi. x, figs. 5, 7, 11.

Five to seven teeth are generally present in each valve of Actinodonta naranjoana.
These vary in both length and orientation but give a crude impression of radiating
ventrally from below the umbo, the shortest teeth being in the centre of the series
(text-fig. 15). It seems unwise to use the terms ‘cardinal’ and ‘lateral’, to describe the
teeth, as these have associations with the true heterodonts, and in the strictest sense
imply that the lateral teeth extend posteriorly or anteriorly beyond the external liga-
ment. This does not appear to be the case in Actinodonta naranjoana. Furthermore,
lateral and cardinal teeth are regarded as being distinctly separate from each other,
usually having different orientations. The author considers it undesirable to number
these teeth in any way until the affinities of Actinodonta are better known.

The posterior teeth are elongate, extending from the umbo to the posterior adductor
scar. They are for the most part parallel with the dorsal margin, and are crenulated

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

637

text-fig. 13. Actinodonta naranjoana. Internal mould of well-preserved left
valve, hinge incomplete, showing general morphology and pattern of adduc-
tor and accessory muscle scars. Specimen C. 14. Llandeilo. G.R. 912441.

text-fig. 14. Actinodonta naranjoana. Internal mould of sub-umbonal and anterior
hinge regions of left valve showing dentition. Part of the proximal end of the elon-
gate socket is visible to the right. Each of the four anterior sockets (appearing as
teeth) have different forms owing to varying stages in the bending of a simple ridge.
Just posterior of the umbo tip are two distinct sockets that become fused in other
forms. Two anterior accessory muscle scars (anterior retractor and protractor) are
clearly visible anterior to the umbo. Specimen C.24. Llandeilo G.R. 912441.

along the anterior two-thirds of their length. Two such elongate teeth are present
in the left valve and one in the right valve.

The most anterior tooth on the hinge is strong, and parallel with the dorsal margin.
The following two or three teeth towards the umbo show a gradual change in orientation
to one almost at right-angles to the dorsal margin (text-figs. 14, 15). The pattern of these
teeth suggest a vague similarity to the lateral and cardinal teeth of the true heterodonts,
although the analogy is incomplete. The short perpendicular teeth of Actinodonta are
formed from the flexed tip of a longer plate that is almost parallel to the dorsal margin
(see particularly text-fig. 14). There would thus appear to be 2 or 3 anterior cardinals
and one anterior lateral in Actinodonta. However, it should be remembered that all
these teeth of different orientation have in fact formed from different dental lamellae.

638

PALAEONTOLOGY, VOLUME 13

In the right valve of Actinodonta, in addition to the teeth described above, there is
a short tooth below the umbo parallel to the proximal end of the long posterior tooth.
This tooth provides evidence for fusion along the dental plate. In some forms two such
teeth are visible below the umbo (text-fig. 14). However, in others these appear to have
become reduced to a single tooth of two distinct fused components (text-fig. 15). In
other forms only a single smooth-tipped tooth is visible. In a single specimen fusion
has also been observed among the anterior teeth of the right valve. The ventral tips of
two adjacent teeth have become fused to form a chevron-shaped tooth opening dorsally,
the reverse of a similar process observed in Cardiolaria.

a PA

valve showing a dental plate possibly further developed than that shown in fig. 14.

The anterior sockets (appearing as teeth) have become differentiated into three that
are almost at right-angles to the dorsal margin, and one that is parallel to it. Between
these and the long posterior socket is a single socket that clearly shows two fused
sections. The anterior adductor and anterior accessory muscle scars are distinct.

Specimen C.14.b. Llandeilo. G.R. 912441.

The pattern of muscle scars commonly visible in Actinodonta naranjoana is shown in
text-fig. 13. The two closely positioned anterior accessory pedal scars visible in text-figs.
13, 14, and 15, are strongly reminiscent of the two juxtaposed anterior pedal scars
present in both Cardiolaria beirensis and Redonia deshayesi. The umbonal accessory
scars of Actinodonta naranjoana show a similarity in pattern to those observed in Tan-
crediopsis ezquerrae (text-fig. 6), and to some extent, those found in Redonia deshayesi
(text-fig. 20).

Redonia deshayesi Rouault 1851, emend. Gouzien 1934
Text-figs. 16-21

1851 Redonia deshayesi Rouault, p. 364, figs. 1, 2.

1851 Redonia duvaliana Rouault, p. 365, fig. 1, 2.

1853 Redonia deshayesiana Sharpe, pi. 9, fig. 1.

1853 Redonia duvaliana Sharpe, pi. 9, fig. 2.

1955 Redonia deshayesiana de Vemeuil and Barrande, pi. 16, fig. 10.

1855 Redonia duvaliana de Verneuil and Barrande, pi. 16, fig. 11.

1876 Redonia deshayesiana de Tromelin and Lebesconte, p. 641.

1876 Redonia duvaliana de Tromelin and Lebesconte, p. 641.

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

639

1901 Redonia deshayesiana Kerforne, p. 198.

1901 Redonia duvaliana Kerforne, p. 198.

1934 Redonia deshay esi Gouzien, p. 179.

1934 Redonia duvali Gouzien, p. 180.

1966 Redonia deshayesi Babin, p. 246, text-fig. 67; pi. x, figs. 13-16.

text-fig. 16. Redonia deshayesi. Internal mould of distorted adult right valve, show-
ing the inequilaterally placed prosogyral umbo, and the strong anterior myophoric
plate. The pallial line is simple and the anterior musculature more deeply impressed
than the posterior. The mould of a chevron socket is visible anterior to the umbo,
and a long socket posterior to it. Specimen A.4. Llandeilo. G.R. 831487.

The general morphology of Redonia deshayesi is shown in text-figs. 16-21. Previous
descriptions of this genus have contained little detail on the nature and development of
the dental plate.

3 Two teeth and two sockets are present in each valve of Redonia deshayesi, and all
show a similar oblique orientation to the dental plate. In the left valve of an adult
Redonia deshayesi (text-fig. 17) a strong asymmetrical chevron tooth is present below
the umbo. Posterior to this and following the same oblique orientation is an elongate
tooth persisting as far back as the posterior adductor muscle scar. The two limbs of the
chevron tooth form an acute angle opening posteriorly, and the tooth is highest at its
angulation. The dorsal limb of the chevron is extremely short, and the bulk of the tooth
is formed by the longer ventral limb which lies nearly parallel to that part of the hinge
immediately below the umbo.

C 7719

Tt

640

PALAEONTOLOGY, VOLUME 13

In the right valve of an adult Redonia deshay esi (text-fig. 16) a strong, short, ridge-like
tooth exists below the umbo posterior to a deep, chevron-shaped socket. The second
tooth of this valve is situated close to the posterior adductor muscle scar, and though
elongate, is shorter than the posterior tooth of the left valve. The posterior teeth of
both valves terminate dorsally against what is considered to be the site of an external,
opisthodetic ligament.

Whereas members of Palaeotaxodonta show an increase in the number of teeth with
age, Redonia indicates reduction of teeth during ontogeny.

text-fig. 17. Redonia deshay esi. Internal mould of adult left valve showing dentition,
and adductor and accessory muscle scars. Umbonal region missing. Specimen B.17.

Llandeilo. G.R. 838495.

As mentioned previously, recrystallization has obliterated the detail from hinges of
very young individuals. In forms approx. 5-5 mm. in length, 4 mm. in height (text-figs.
18, 19) an extra pustule-like tooth is present in each valve anterior to the teeth retained
in the adult. At this size the adult teeth are already elongate, though the chevron tooth
of the left valve appears only as a ridge with a very small dorsal limb curving round the
anterior tip of the adjacent socket.

Fusion between the chevron tooth and the anterior pustule-like tooth occurs during
growth of the individual. The angle of the chevron moves anteriorly as a result of this
fusion and appears constricted before the process is completed (text-fig. 21). In con-
sequence the anterior pustule-like tooth of each valve becomes obliterated, and in the
adult left valve all evidence of fusion has disappeared.

Partial fusion between the posterior teeth is also obvious in Redonia deshayesi,
similar to that already observed in Actinodonta naranjoana. This can be best seen by
studying the internal moulds of sockets. In text-fig. 17 the moulds of two sockets
(appearing as teeth) are visible, the most posterior socket mould appearing to overlap
and touch that to the anterior. In text-fig. 20 the most anterior long socket mould
(mould of pit-like socket also present) appears slightly bifid, and a distinct ridge extends
along its dorsal flank posteriorly to merge into the second socket mould. Thus, fusion
between the tips of two oblique posterior teeth appears to have taken place in the right
adult valve of Redonia and is most obvious in younger individuals.

The musculature of Redonia is clearly visible in text-figs. 16-21. Two anterior pedal
accessory muscle scars are visible adjacent to the adductor scar where the myophoric
plate abuts the hinge plate, but these frequently have the appearance of a single narrow

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES

641

text-fig. 18. Redonia deshayesi. Internal mould of young right valve showing
an extra socket (appearing as a tooth) to the anterior. Umbo of specimen
missing. Specimen F.23.a. Llandeilo. G.R. 912441.

text-fig. 19. Redonia deshayesi. Artificial cast of specimen F.23.a shown in
fig. 15. Note the strong myophoric plate and the impressed anterior adductor
muscle scar with adjacent accessory scars. The distinct chevron-shaped tooth
to the anterior is not present in the adult. Llandeilo. G.R. 912441.

scar with its long axis oblique to, and converging anteriorly on, the hinge plate (text-fig.
17). Well-preserved specimens of Redonia show these scars to be slightly oval and
juxtaposed, showing a strong resemblance to those in Cardiolaria beirensis. A comparison
with Acila divaricata figured by Driscoll (1964, fig. 3) would suggest that one of these
scars is an anterior protractor muscle scar, and the other the anterior retractor muscle

642

PALAEONTOLOGY, VOLUME 13

text-fig. 20. Redonia deshayesi. Internal mould of young left valve showing
additional socket (appearing as a pustule-like tooth) to the anterior. Adductor
and accessory muscle scars are clearly visible. Specimen J.5. Llandeilo. G.R.
912441.

text-fig. 21. Redonia deshayesi. Internal mould of right valve showing form of
dentition following the fusion of anterior teeth in the left valve with the mould
of the chevron socket appearing constricted. Specimen F.18. Llandeilo. G.R.

912441.

scar. The smaller anterior protractor scar visible in Cardiolaria beirensis has not been
observed in Redonia deshayesi. In addition, a posterior pedal accessory scar is often
visible adjacent to the dorsal edge of the posterior adductor muscle scar (text-figs. 16,
17, 20). Two further accessory scars have been observed in the umbonal region (text-
figs. 16, 18, 20), resembling those visible in Actinodonta naranjoana (text-fig. 13). It is
highly likely that Redonia developed from a form with a dental plate similar to that of
Actinodonta. The fusion of teeth in both forms follows a similar pattern but has been
more extreme in Redonia.

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643

DISCUSSION OF THE EVOLUTIONARY RELATIONSHIPS
OF THE CROZON PENINSULA BIVALVE FAUNA

From the variety shown by Ordovician bivalves it seems likely that at least two,
and perhaps three, ancestral stocks, with basically different dental patterns, had evolved
from the early Mollusca during the Cambrian.

Following Vogel (1962) and Babin (1966) it is suggested that one ancestral stock was
almost equilateral, with a dental plate bearing a simple ridge on each side of the umbo
parallel to the dorsal margins. Forms such as Lamellodonta (Cambrian) and Babinka
(Ordovician) probably developed from this stock. The origins of Lyrodesma may also
lie here.

text-fig. 22. The Crozon Peninsula bivalves in a suggested Lower Palaeozoic phylogeny.

The second ancestral stock may have had a multiple-ridged dental plate, each ridge
either perpendicular to the dorsal margin or slightly oblique to it (text-fig. 22). It may
have shown some resemblance to juvenile forms of Cardiolaria beirensis (text-fig. 1).

The developing dentition of the Crozon Peninsula bivalves indicate two main lines
of development from such a multiple-ridged ancestral stock (text-fig. 22). One trend is
marked by a simple increment in teeth as the animal grows, the other by a tendency
towards reduction in teeth by fusion and resorption. The diverse forms seen in the
Ordovician fauna represent cladogenesis within these two lines. At its simplest these
two lines can be viewed in terms of Douville’s ‘active’ and ‘burrowing’ branches of
bivalve evolution.

Active forms would tend to develop chevron teeth from the primitive dentition to
counter the stresses produced by foraging. The most active types probably used a large
foot for ploughing through sediment and labial proboscides for food collection, in
a manner similar to modern Nucula. The primitive opisthodetic ligament and the need
for a large anterior opening during retraction of the foot would encourage the develop-
ment of a differentiated dental plate with larger anterior teeth as seen in Praeleda.
The anterior part of the shell would tend to become enlarged to provide protection
and accommodation. Later Palaeozoic bivalves with a reversed orientation and an
internal ligament probably developed from these forms.

644 PALAEONTOLOGY, VOLUME 13

Another branch of this line, represented by Cardiolaria, may have evolved towards
a secondary burrowing condition. The inherited ‘active’ type of dentition would become
modified. With a change in the direction of growth within the valve and less frequent
protrusion and retraction of the foot, there would be no tendency to increase the number
of large anterior teeth. The myophoric plate and deeply impressed anterior musculature
of Cardiolaria probably reflect its mode of fife. Since the adductor muscles are used to
close the shell, the anterior adductor, strengthened by the adjacent plate, suggests a more
violent and sudden action by this muscle than its posterior counterpart. If Cardiolaria
still possessed the anterior inhalent current associated with certain palaeotaxodontids,
the action would produce an abrupt cleansing current out of the posterior region of the
shell.

Tancrediopsis may represent a third branch, distinct from Praeleda and Cardiolaria.
Tancrediopsis has a dentition similar to that of later siphonate nuculanids, and may have
been a burrowing bivalve.

The second major line, in which tooth resorption and fusion takes place, appears to
be represented by burrowing forms (text-fig. 22). The dentition of Actinodonta in par-
ticular suggests modification of the ancestral dental plate by elongation of its posterior
components and flexing of some anterior teeth. When clear (text-figs. 14, 15), the curved
anterior teeth have one long and one short limb. It is not difficult to envisage that
resorption at the junction of the two limbs, to leave them isolate, would result in a
dentition associated with the heterodontids.

Actinodonta and Redonia appear to be closely related, the latter showing a greater
reduction of teeth. In addition, the general morphology of Redonia closely resembles
that of Cardiolaria, particularly in the possession of a deeply impressed anterior mus-
culature and an anterior myophoric plate. They could be regarded as homeomorphs.
Actinodonta shows some parallels with Tancrediopsis in its musculature, and it is possible
that both forms had posterior inhalant currents.

The cyrtodontids are generally accepted as being closely related to the later pterio-
morph bivalves. From the trends reviewed in the Crozon Peninsula fauna it seems likely
that they evolved during the Cambrian from the hypothetical multiple-ridged ancestor,
in a slightly different direction from Actinodonta and Redonia, rather than from the
duplicate ridged form.

Acknowledgements. The author gratefully acknowledges the help of the British Museum of Natural
History for supplying photographs of type material. Acknowledgement is also due to Dr. R. Carter
for his helpful and critical reading of the manuscript, and to Mr. D. Jones for the preparation of
photographs from the original figures. The author would like to thank Professor M. Gage for the use
of facilities in the Department of Geology, University of Canterbury. The author is also grateful to
Dr. J. D. Bradshaw for initiating interest in the Ordovician bivalves, and for his helpful and tolerant
criticism of the manuscript and many useful discussions.

REFERENCES

babin, c. 1966. Mollusques Bivalves et Cephalopodes du Paleozoique Armoricain, All pp. Brest.
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geol. Fr. 3e, 14, 652-78.

— — 1886. Constitution de la rade de Brest. Ibid., 14, 678-707.

1891. Memoire sur la faune du Gres Armoricain. Ann. Soc. geol. Nord. 19, 134-237.

BRADSHAW: MIDDLE ORDOVICIAN BIVALVES 645

Bernard, f. 1896. Deuxieme note sur le developpment et la morphologie de la coquille chez les lamel-
libranches. (Taxodontes). Bull. Soc. geol. Fr. 3e, 24, 54-82.
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driscoll, e. g. 1964. Accessory muscle scars, an aid to protobranch orientation. J. Paleont. 38, 61-6.
gouzien, v. 1934. Contribution a l’etude geologique de la presqu’ile de Crozon suivant la voie ferree de
Telgruc a Camaret. Bull. Soc. geol. Miner. Bret. (1930), 176-91.
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1923. Etude stratigraphique de la vallee de lTlle entre Saint-Medard. Bull. Soc. geol. Miner.

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mcalester, a. l. 1963. Revision of the type species of the Ordovician nuculoid pelecypod genus Tan-
crediopsis. Postilla, Yale Peabody Mus. 74, 1-19.

1964. Preliminary suggestions for a classification of nuculoid bivalves. J. Paleont. 38, 397-400.

1968. Type species of paleozoic nuculoid bivalve genera. Mem. geol. Soc. Amer. 105. 143 pp.

1969. In moore, r. c., ed., Treatise on invertebrate paleontology. Part N, Mollusca 6, Bivalvia,

1 and 2 951 pp. Geol. Soc. Am. and Univ. Kansas Press.

Newell, n. d. 1965. Classification of the Bivalvia. Am. Mus. Novit. 2206, 25 pp.
pfab, l. 1934. Revision der Taxodonta des bohmischen silurs. Palaeontographica, a. 80, 195-253.
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neighbourhood of Bussaco, Portugal. Q. Jl geol. Soc. Lond. 9, 135-61.
rouault, m. 1850-51. Memoires sur le terrain paleozoique des environs de Rennes. Bull. Soc. geol.
Fr., 2e, 8, 358-99.

de tromelin, g. and lebesconte, p. 1876. Essai d’un catalogue raissone des fossiles siluriens des de-
partments de Maine-et-Loire, de la Loire-Inferieure et du Morbihan avec observations sur les terrains
paleozoiques de l’Ouest. Congres. Ass. Fr. Av. Sci., Nantes (1875), 601-61.

1876. Presentation de fossiles paleozoiques du department d’Hle-et-Vilaine et note additionelle

sur la faune silurienne de l’Ouest de la France. Ibid. 683-7.
de verneuil and barrande c. 1855. Descriptions des fossiles trouves dans les terrains silurien et
devonien d’Almaden, d’une partie de la Sierra Morena et des Montagnes de Toledo. Bull. Soc. geol.
Fr. 2e, 12, 182-203.

vogel, k. 1962. Muscheln mit Schlosszahnen aus dem spanischen Kambrium und ihre Bedeutung
fur die Evolution de Lamellibranchiaten. Abhandl. Math. Nat. Kl. Acad. Wiss. und Lit. Mainz ,
192-244.

MARGARET A. BRADSHAW

c/o Department of Geology
University of Canterbury
Christchurch
New Zealand

Final typescript received 1 April 1970

DINOPHYTON, A PROBLEMATICAL NEW PLANT
GENUS FROM THE UPPER TRIASSIC OF THE
SOUTH-WESTERN UNITED STATES

by SIDNEY R. ASH

Abstract. Dinophyton gen. nov. is based on ultimate and penultimate shoots bearing spirally arranged, out-
ward directed, linear leaves and on some associated, bilaterally symmetrical organs superficially resembling
pinwheels. The pinwheels have four arms and bear an empty cup-like structure at the centre. Cuticles of the
pinwheels are very similar to those of the shoots and it is concluded that the two organs belonged to the same
plant. The function of the pinwheel is uncertain ; it may have been seedbearing or possibly had a role in vegeta-
tive propagation. Dinophyton does not resemble any known plant when all of its characters are considered and
for this reason is tentatively assigned to the gymnosperms. The type species, D. spinosus sp. nov., has been
collected from ten localities in rocks of Late Triassic age in Texas, New Mexico, and Arizona.

Two of the more common plant fossils found in the Upper Triassic Chinle Formation
and Dockum Group of the south-western United States are described in this report.
One resembles the shoot of a modern conifer with medium-sized needle-leaves (see
text-fig. 2a). The other looks superficially like a pinwheel with four arms or a leaf whorl
of Annularia (see PI. 124, figs. 1-6). Close examination shows, however, that the struc-
ture is bilaterally, not radially, symmetrical and actually more closely resembles an
upside-down Latin cross (see text-fig. 2b). Cuticular study demonstrates that the two
fossils probably are parts of the same plant, although the function of the bilaterally
symmetrical structure is questionable. Possibly it bore an ovule but since that can
not be proven at this time the structure will be referred to as a pinwheel. Neither the
shoot nor the pinwheel can be identified with any known plant, fossil or living, so they
are both referred to Dinophyton spinosus gen. et sp nov.

Although the early Mesozoic gymnosperms of the world are poorly known it is
apparent that a number of unusual forms developed during this important time in
plant history. Their classification and relationships are uncertain and it is difficult
to assign many of them to presently recognized groups. Dinophyton is assigned
tentatively to the gymnosperms because further classification of the fossil would be
premature and must await the results of future research.

Cuticles used in this study were prepared by the standard maceration technique as
follows : Compressions and coaly material were placed in concentrated nitric acid and
potassium chlorate for a few hours. Then the cuticles were washed with water and
cleared with dilute ammonia. Any rock material that still adhered to them after macera-
tion was removed by placing the specimens in concentrated hydrofluoric acid for a day
or so. Several of the fairly complete fossils were embedded in plastic but the majority of
the material was mounted unstained in glycerine jelly. All slides and specimens have
been deposited in the U.S. National Museum (USNM), Washington, D.C.

Previous investigations. Plant fossils of Late Triassic age have been known from the
south-western United States for many years. They occur mainly in the Chinle Formation

[Palaeontology, Vol. 13, Part 4, 1970, pp. 646-63, pis. 122-124.]

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS

647

in New Mexico and Arizona although a few have been collected from a generally
equivalent unit, the Dockum Group in west Texas. A number of palaeobotanists have
worked on this flora but over-all progress has been slow and erratic and it is apparent
that there is still much to learn about these plants.

text-fig. 1 . Index map of the south-western United States.

The principal report on the Triassic plants of the Southwest was published by
Daugherty (1941). A detailed review of the flora and a history of its investigation were
published recently (Ash 1970a, b, c ). These reports show that the Chinle Formation
contains 51 well-characterized species. The Dockum contains 6 species, 5 of which
also are known from the Chinle Formation. Only two species in the Chinle and Dockum
floras occur in any other formation and it appears that the floras in the Chinle and
Dockum are more closely related to each other than to any other flora.

LOCALITIES

Specimens of the shoot of D. spinosus and the pinwheel have been collected from
ten different localities in the Upper Triassic rocks of west-central Texas, west-central
New Mexico, and east-central and north-central Arizona (text-fig. 1). The distance
between the easternmost locality (in Texas) and the westernmost (in north-central
Arizona) is about 700 miles. In Texas the fossils occur in the Dockum Group ; in New
Mexico and Arizona they occur in the Chinle Formation. Both units are considered more
or less equivalent (Reeside et al. 1957, p. 1464) and a chart showing the currently

648

PALAEONTOLOGY, VOLUME 13

accepted nomenclature and correlation of the subdivisions of the two units is given in
Table 1. The approximate stratigraphic level of the ten localities mentioned in this
report are also indicated on the correlation chart.

Texas. The remains of both the shoot of D. spinosus and the pin wheel have been collected
from a locality in west-central Texas about 15 miles south-east of Crosbyton in the
drainage of Home Creek. They occur in a discontinuous bed of brownish mudstone in
the lower part of the Tecovas Formation of the Dockum Group and about 20 ft. above
the Permian rocks in that area. Hand specimens of the mudstone frequently show poorly
preserved plant remains including fragments of the new species, the bennettite Otoza-
mites powelli and some small, round unidentified seeds. Bulk maceration of the mud-
stone, however, yields many fragments of the distinctive cuticle of D. spinosus. Most of
the fragments are large enough to show that both the shoot and the pinwheel are present
at the locality. Scale leaves of several unidentified conifers and the cuticles of a number
of large and unknown leaves were also noted in the bulk macerations from the locality.

New Mexico. All of the localities in New Mexico which have yielded specimens of
D. spinosus are in the west-central part of the state and in the Monitor Butte Member
of the Chinle Formation. A few well-preserved examples of the shoot and the pinwheel
have been collected from a locality approximately 4 miles south-west of Thoreau in
sec. 13, T. 13 N., R. 14 W. They occur in a bed of soft, greenish, sandy mudstone in the
lower part of the Monitor Butte Member and are associated with several other plant
fossils including a fern resembling Cladophlebis reticulata, Otozamites powelli, and some
unidentified leaves and seeds.

Many shoots and pinwheels have been collected from four localities about 1 mile
south of the Fort Wingate Trading Post. Two are in beds of soft greenish mudstone
and sandstone in the lower part of the Monitor Butte Member where it is exposed in
road cuts along the highway from Fort Wingate to McGaffey. They have been assigned
USGS fossil plant locality numbers 10058 and 10059 and part of the flora they contain
has been described recently (Ash 1967, 1970a). It includes the ferns Todites fragilis
Cynepteris lasiophora, Phlebopteris smithii, Wingatea plumosa, Clathropteris walkeri, and
Cladophlebis daughertyi, the bennettite O. powelli and several unidentified leaves, seeds,
and fragmentary cones. Two localities in the upper part of the Member have also
yielded specimens of D. spinosus. One is in a bed of grey mudstone exposed in the
badlands a few thousand feet east of the Fort Wingate-McGaffey highway and the two
localities mentioned above. It is referred to as USGS fossil plant locality 10061 and
a portion of the flora it contains has also been described (Ash 1967, 1968, 1970a).
That flora includes T. fragilis, C. lasiophora, C. daughertyi, O. powelli, Williamsonia
nizhonia, and a number of unidentified leaves, seeds, and cone scales. Also the wings
of an unidentified insect, apparently related to the modern locusts, has been reported
from the same locality (Breed 1970).

One of the most productive localities for Dinophyton in the Fort Wingate area is on
the dissected plateau between the Fort Wingate-McGaffey highway and the badlands
containing the previously mentioned locality (no. 10061). The new locality is about
150 ft. west of that locality and is assigned USGS fossil plant locality number 10088.
Here the fossils occur in a bed of dark brown shale which is about 5 ft. thick. These
rocks are very fossiliferous and the remains of five new conifers, and several unidentified

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS 649

table 1 . Correlation chart of the Upper Triassic rocks in the southwestern United States. The asterisks
(*) mark the approximate stratigraphic position of fossil plant localities containing Dinophyton.
Chart adapted from Reeside and others (1957, pi. 1).

Series

Stages

ARIZONA

North- centra I
part

East-central

part

NEW MEXICO

West-central

part

TEXAS

West-central

part

Rhaetian

Glen

Canyon
Group
-?

Glen

Canyon

Group

Norian

Upper

Triassic

Karnian

Owl

Rock

Member

Petrified

Forest

Member

Owl

Rock

Member

Petrified Forest Mbr.

Upper
* part

/Sonsela
(Sandstone
\ Bed

Lower
* part

Monitor

Butte

Member

Glen
Canyon
Group
_?

Owl

Rock

Member

Upper

part

Sonsela

Sandstone

Bed

Lower

part

Monitor
* Butte

Chinle

Formation

leaves have been collected from them. Other fossils which have been observed there
include phytosaur teeth, coprolites of several sizes, and the remains of the branchiopod
Cyzicus ( Estheria ) sp. The unit is of limited lateral extent and is exposed at only a few
other places on the plateau. It is generally a foot or less in thickness at these localities
and contains few plant fossils although abundant coprolites and the shells of Cyzicus
are usually present.

Arizona. At least two of the several fossil leaf localities in Petrified Forest National
Park in east-central Arizona contain the remains of D. spinosus. One of them is in a thin

650 PALAEONTOLOGY, VOLUME 13

layer of paper coal in the lower part of the Petrified Forest Member of the Chinle about
1 50 ft. below the Sonsela Sandstone Bed and about 20 ft. above the Newspaper Rock
Sandstone of Stagner (1941). The locality is in the badlands south of the principal road
through the Park in the NE J, sec. 22, T. 18 N., R. 24 E. (USGS fossil plant locality
10090). Specimens of the pinwheel are particularly abundant at this locality whereas
the shoot is uncommon. Remains of many unidentified leaves including those of several
conifers are also present in the paper coal. The second locality is in a bed of coaly
material and associated sediments in the upper part of the Petrified Forest Member of
the Chinle about 90 ft. above the Sonsela Sandstone Bed. It is in a small hill approxi-
mately \ mile west of the principal road through the Park in the NEJ, sec. 29, T. 17 N.,
R. 24 E. (USGS fossil plant locality number 10089). The coaly material contains
abundant plant fossils but most are unidentified. One of the conifers in the flora, how-
ever, was recently described as Pagiophyllum simpsonii (Ash 1970<7).

Two localities in the Shinarump Member of the Chinle Formation about 10 miles
south-west of the Gap Trading Post at the abandoned A and B uranium mine in north-
central Arizona contain large quanities of the foliage of D. spinosus but only a relatively
few examples of the pinwheel. Several specimens of the penultimate shoots with attached
ultimate shoots were collected at both localities but most of the material consists of
fragments of just the ultimate shoots. The only other fossils noted at the localities are
the shoots of an unidentified scale-leaf conifer and the leaf of Otozamites powelli. At
these localities fossils are represented typically by limonite encrusted impressions in
hard black shale or coarse-grained, tan sandstone. Cuticles are not preserved and
identification is based only on the gross morphology of the fossils.

SYSTEMATIC DESCRIPTIONS
Genus dinophyton gen. nov.

Type species. Dinophyton spinosus sp. nov.

Diagnosis. Shoots with many spirally arranged, spreading, needle-like, persistent foliage
leaves and a few small leaves. Foliage leaves linear, round in section, containing two
parallel veins, apices obtuse to more or less acuminate, base broad, petiole absent.
Small leaves clasping, less than 2 mm. long, apices acuminate, attached by entire base.
Narrow stumps attached to stem of certain ultimate shoots among typical adult leaves.
Possible ultimate female reproductive organ consisting of a pinwheel or cross-shaped
structure composed of four appendages and containing a cup which may have held an

EXPLANATION OF PLATE 122

Figs. 1-10. Dinophyton spinosus gen. et sp. nov. 1, Apical region of penultimate shoot with portions
of five ultimate shoots, USNM 43671, x 1. 2-7, Fragments of ultimate shoots. 2, USNM 43672,
xl. 3, USNM 43673, Xl. 4, USNM 43674, X 1. 5, USNM 43675, X 1. 6, USNM 43676, X 1.
7, USNM 43677, x 2. 8-10, Fragmentary penultimate shoots with one or more attached ultimate
shoots. 8, USNM 43678, x 1. 9, USNM 43679, x 2. 10, USNM 43680, x 2. Variation in lengths
of leaves is from about 1 cm. in figs. 3 and 5 to about 2 cm. in fig. 2. Specimen in fig. 5 is from
USGS fossil plant locality 10060; others from USGS fossil plant locality 10061, and all from
Monitor Butte Member, Chinle Formation, Fort Wingate area, New Mexico.

Palaeontology, Vol. 13

PLATE 122

ASH, Problematic Triassic plant

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS 651

ovule. Stomata occurring on both sides of leaf and pinwheel, mostly monocyclic, stomatal
pit rectangular, longitudinally orientated. No other parts of the plant are known.

Derivation of name. The name is derived from dine which means ‘The People’ in the language of the
Navajo Indians who have inhabited north-western New Mexico and adjacent areas for several hundred
years. Dine is what the Navajo call themselves.

Dinophyton spinosus sp. nov.

Plates 122-124; text-figs. 2-6

1967 Gymnospermous shoots. Ash, pp. 128-30, fig. 3.

19706 Foliage of undescribed conifer, Ash, p. 37, fig. 2f.

Holotype. USNM 43639. Paratypes: USNM 43637, 43638, 43649.

Distribution. The shoot of D. spinosus and the pinwheel occur in the Tecovas Member
of the Dockum Group near Crosbyton, Texas; in the Monitor Butte Member of the
Chinle Formation near Thoreau and Fort Wingate, New Mexico; in the Petrified
Forest Member of the Chinle in Petrified Forest National Park, Arizona; and in the
Shinarump Member of the Chinle Formation near Gap, Arizona.

Diagnosis. Axis of penultimate shoots 1-2 mm. wide, straight, bearing leaves similar
to foliage leaves of ultimate shoots. Ultimate shoots arising alternately at intervals of
15-20 mm. and at an angle of about 35-45° from penultimate shoots, axis about 0-8 mm.
wide, bearing many spirally arranged (phyllotaxis probably 2/5), closely set, spreading,
outward directed, long, linear foliage leaves and a few, rather small, clasping leaves.
Foliage leaves (text-fig. 3) arising from an inconspicuous oval, decurrent leaf cushion
about the same width or slightly smaller than leaf, cushion gradually merging with
stem. Free part of leaf straight, round in section, projecting at an angle of about 30-50°
to stem, about 10-25 mm. long, about 0-35-0-75 mm. broad, sides parallel except in
vicinity of base and apex, occasionally narrowing slightly near base to meet leaf cushion,
in upper part narrowing abruptly to an obtuse to more or less accuminate apex. Leaf
typically containing two veins about 70-90 pm. wide, arising dichotomously from one
vein in base of leaf, unbranched, generally parallel except in leaf base where they diverge
and in apical region where they unite, resulting vein appears to continue to within
a very short distance of apex. Small leaves inconspicuous, concealed by adult leaves,
rare, occurring at base of some adult leaves, usually one to three leaves present at one
position, small leaves elongate, obtusely pointed, clasping, size ranges from 170-340 pm.
wide near base, 500-1700 pm. in length. Narrow stumps about 300 pm. wide, 3-3-5 mm.
long arising from stem at several places between foliage leaves on certain shoots.

Cuticle of leaf (text-fig. 4) tough, about 5 pm. thick; cuticle of stem slightly thinner
and more delicate, rib-like projections or flanges of cuticle at position of anticlinal
walls of epidermal cells, flanges about 3 pm. high. Stomata present on leaf and on stem
in approximately equal numbers (about 100 per mm.2), rather widely spaced in poorly
defined rows a single stoma wide on leaf and stem. Stomatal rows not sunken, typically
separated by 2-5 rows of ordinary epidermal cells, individual stomata in rows separated
by 2-6 ordinary epidermal cells. Stomata mostly monocyclic with 2-4 lateral and two
terminal subsidiary cells, rarely amphicyclic, subsidiary cells having thickened inner
walls, otherwise unmodified except by position, rarely shared, stomatal pit rectangular,

652 PALAEONTOLOGY, VOLUME 13

text-fig. 2a. Reconstruction of part of an ultimate shoot of
Dinophyton, approximately x 5. The position, size, and number of
trichomes is generalized.

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS 653

about 10-14 /x m. x3-6 /xm., longitudinally orientated, shallow, guard cells slightly
sunken, thinly cutinized. Ordinary epidermal cells similar on leaf and stem, longitudinally
oriented, polygonal (range noted 7-21 /x m. wide, 24-56 /xm. long) in and adjacent to
margins. Anticlinal cell walls strongly marked, about 1-2 /xm. thick, straight to curving
with only slight irregularities. Outer periclinal cell walls containing small irregularly
distributed pits (usually less than 0-5 /xm. in diameter) and often bearing a single,
cutinized, simple, usually unicellular hair or low papillae about 7-24 /xm. wide at base,

text-fig. 2b. Reconstruction of the adaxial side of the pinwhee,
of Dinophyton showing the nomenclature used for the several
parts of the organ, approximately x 5. The position, size and
number of trichomes is generalized, c, cup; st, stalk; la, lateral
appendage; da, distal appendage; pa, proximal appendage.

14-450 /xm. long, sides of hair taper gradually from base to acutely pointed apex, base
of hair a simple ring on an ordinary epidermal cell. Hypodermal cells having straight
to curving walls about 0-5 /xm. thick, cells generally rectangular along margins, often
about 15/xm. x45 /xm., elsewhere polygonal, isodiametric to elongate, usual size about
22 /xm. x 30 /xm.

Pinwheel organ ( ?ovuliferous) dorsiventrally flattened, bilaterally symmetrical, con-
sisting of four appendages forming a structure shaped like a pinwheel (text-fig. 5) or
more accurately a Latin cross, a small hollow, elipsoidal structure or cup (which might
have contained an ovule) positioned at intersection of appendages and a narrow stalk
attached to and near proximal end of cup. Cup 2-3 mm. wide, 3-5 mm. tall, long axis
orientated along long axis of cross, proximal end open, free part of wall ( ?integument)
divided into three evenly spaced lobes and an elongated stalk-like structure. Lobes
acutely pointed, 1 -5-2-0 mm. wide and tall, stalk narrows slightly then drawn out into

text-fig. 3. Shoot of Dinophyton spinosus gen. et sp. nov. a, Upper portions of six isolated and slightly
macerated leaves showing characteristic venation and typical obtuse to acuminate apices. Four short
specimens on left, slide USNM 43644; two large specimens on right, slide USNM 43645; all x5.
b, Fragments of four leaves showing characteristic venation. Specimen on right from basal region
of leaf and shows bifurcating vein ; other specimens from areas above the basal region. Two specimens
on left, slide USNM 43645 ; two specimens on right, slide USNM 43644; all x 5. c, Paratype showing
apex of shoot surrounded by small leaves with a few fragmentary full-size foliage leaves near base of
drawing, slide USNM 43649; X 5. d. Portion of shoot with remains of three narrow stumps among
typical foliage leaves ; one stump between two leaves on right side of drawing, slide USNM 43647 ;
x5. e, Holotype, slide USNM 43639; x5. f. Exterior of shoot cuticle from which all but the base
of one leaf has been naturally broken off. Irregular holes indicate position of leaves and darkly stippled
areas are folds in cuticle; numbers indicate leaf sequence; slide USNM 43648, x 10, g, h, Typical
foliage leaf with three small leaves at base; slide USNM 43646. g, x5. h, x25. Specimens in a-e,
g, h from Monitor Butte Member of Chinle Formation, Fort Wingate area. New Mexico. Four short
specimens in a, and two specimens on right in b from USGS fossil plant locality 10088; two long
specimens in A, two specimens on left in b and specimens in c-e, g, h from USGS fossil plant locality
10061. Specimen in f from USGS fossil plant locality 10089, lower part of Petrified Forest Member,
Chinle Formation, Petrified Forest National Park, Arizona. For simplification trichomes are not
shown in these drawings.

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS

655

text-fig. 4. Cuticles of shoot and pinwheel structure of Dinophyton spinosus gen. et sp. nov. a.
Cuticle of leaf, margin to right; compare with cuticle of pinwheel (text-fig. 6e), epidermal cells
generally smaller; slide USNM 43657, x 100. b, Cuticle from typical leaf showing distribution and
orientation of stomatal apertures (short lines) and trichomes (large dots); slide USNM 43658,
x25. c. Cuticle from axis of shoot showing stomata and trichomes; cells smaller than on leaf; slide
USNM 43655, x 100. d, Stoma on cuticle of pinwheel appendage; slide USNM 43651, x400. e.
Stomata and trichomes on leaf cuticle; slide USNM 43658, x400. f. Stomata and trichomes on
cuticle of pinwheel appendage; slide USNM 43656, x400. Specimen in a from USGS fossil plant
locality 10088, Monitor Butte Member, Chinle Formation, Fort Wingate area, New Mexico. Speci-
mens in b and e from lower part of Tecovas Member, Dockum Group, near Crosbyton, Texas. Speci-
mens in c, d, and f from USGS fossil plant locality 10089, lower part of Petrified Forest Member,
Chinle Formation, Petrified Forest National Park, Arizona.

C 7719

uu

656

PALAEONTOLOGY, VOLUME 13

TEXT-FIG. 5.

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS

657

a long, narrow, linear structure about 05-0-7 mm. wide, 2-3 mm. long, broken end not
eroded. Appendages linear to oblanceolate, sides generally parallel to subparallel, round
in section, apexes usually acute, appendages sometimes slight constricted in basal
regions, margins usually entire, occasionally showing low teeth. Lateral appendages of
same size (range noted about 1-2 mm. wide, 5-12 mm. long), attached to side of cup,
containing two parallel veins. Distal appendage typically slightly longer than lateral
appendages (range noted 1-2-5 mm. wide, 9-15 mm. long), attached to distal end of
cup, containing two parallel veins about 120 /a m . wide; apex sometimes bifurcate for
a short distance. Proximal appendage usually shorter and narrower than other ap-
pendages, about 1 mm. wide and 4-8 mm. long, attached to back of cup between centre
and stalk, containing one vein.

Cuticle of pinwheel (text-fig. 6), except for that lining cup, generally similar to cuticle
of leaf. Stomata present on appendages, stalk and exterior of cup in approximate equal
numbers (about 50 per mm.2), typically longitudinally orientated, but larger proportion
obliquely orientated than on shoot, otherwise identical. Ordinary epidermal cells some-
what larger and more irregular than cells on leaves and stems, epidermal hairs more
abundant, especially on cup and stalk, than on shoot. Hypodermal cells present, similar
to those on shoot. Upper part of cup and lower part of lobes lined with cuticle, lining
extending at least 350 /mi. below base of lobes and to within about 100 /mi. of the apex
of the lobes where it joins typical external cuticle. Internal cuticle delicate, thin, 1 /mi.
or less in thickness, composed entirely of ordinary epidermal cells, cells mostly poly-
gonal, equidimensional to distinctly elongated, of various sizes, largest noted 30 x 75 /mi.
often smaller, elongated cells usually arranged longitudinally in rows, near margins
2-3 rows of rectangular cells (range noted, 7-20 p m. wide, 15-70 /mi. long) typically
present, anticlinal cell walls about 2-3 /mi. thick, straight to curving, smooth, few
irregularities, periclinal cell walls smooth, flat. Hypodermal cells present, similar to
those on foliage. Female cone as a whole, ovule, male cone, and pollen unknown.

Attribution. Although the shoot of Dinophyton and the pinwheel have not been found
connected the two structures are attributed to the same plant because of the evidence

text-fig. 5. Pinwheel organ of Dinophyton spinosus gen. et sp. nov. a. Obliquely flattened fragment of
side and back of a cup showing from left to right, the proximal appendage (slightly distorted), the
stalk, and a lateral lobe; slide USNM 43640, x 10. b, d, paratype. b, Adaxial side of pinwheel. d,
Abaxial side; specimen unmacerated and broad lines in appendages probably represent veins; slide
USNM 43637, x 5. c, Paratype specimen compressed laterally, with front of cup to right, showing
both lateral lobes and front lobe of cup; left lateral appendage bent downward nearly completely
hiding the stalk; slide USNM 43638, x5. e, Fragment of back of cup showing stalk at front and
proximal appendage behind it; slide USNM 43641, x 10. f. Apex of one lateral lobe of a cup showing
typical distribution of trichomes; slide USNM 43642, x25. G, h. Cup viewed from adaxial and
abaxial sides; only bases of four appendages and stalk shown; slide USNM 43643, x 10. i. Broken
end of stalk showing typical distribution of trichomes; slide USNM 43654, x 25. J, Upper portions of
eight isolated, slightly macerated distal appendages showing apical variation and veins; upper left
specimen slide USNM 43659, next to right slide USNM 43661, remainder slide USNM 43660, all x 5.
Specimens in A, c, g-i, and second specimen from left in top row of j from USGS fossil plant locality
10089, lower part of Petrified Forest Member, Chinle Formation, Petrified Forest National Park,
Arizona. Specimens in B, d-f, and all other specimens in j from USGS fossil plant locality 10088,
Monitor Butte Member, Chinle Formation, Fort Wingate area, New Mexico. For simplification
trichomes not shown in a-e, g, h, j.

658

PALAEONTOLOGY, VOLUME 13

F G

text-fig. 6. Cuticle of pinwheel of Dinophyton spinosus gen. et sp. nov. A, Cross-section of cuticle of
distal appendage showing cutinized anticlinal flanges; slide USNM 43650, x200. b, Fold in lower
cuticle of appendage viewed from below showing outlines of polygonal epidermal cells with cutinized
anticlinal flanges; slide USNM 43651, x 200. c, One square mm of cuticle of distal appendage showing
distribution and orientation of stomatal apertures (short lines) and trichomes (large dots); slide
USNM 43651, x25. d, Stoma, slide USNM 43651, x400. e, Cuticle from proximal appendage;
heavily stippled area near right side represents a fold (cf. leaf cuticle in text-fig. 4); slide USNM 43651,
xlOO. f, Interior cuticle from a cup lobe; margin marked by narrow elongated cells; note total
absence of stomata and trichomes; slide USNM 43652, x 100. g, Exterior cuticle from a cup lobe,
margin marked by narrow elongated cells; note stomata and abundant trichomes; slide USNM 43653,
x 100. Specimens in a-e from USGS fossil plant locality 10090, lower part of Petrified Forest Member,
Chinle Formation, Petrified Forest National Park, Arizona. Those in f and g from USGS fossil plant
locality 10088 Monitor Butte Member, Chinle Formation, Fort Wingate area, New Mexico.

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS 659

of association and the evidence of similar cuticle. Careful collecting has shown that
when the remains of one structure are found at a locality examples of the other are
always present also. Both the shoot and the pinwheel are now known to occur together
in rocks of Late Triassic age at ten localities extending from west-central Texas to
north-central Arizona, a distance of about 700 miles. No locality is known where only
one of the structures occurs.

The distinctive cuticle of the leaf of Dinophyton is easily distinguished from all other
Chinle cuticles, the stomata and the papillae being highly characteristic. On the other
hand, the resemblance between the cuticles of the shoot of Dinophyton and the pinwheel
is very close as they agree in: (1) the form and size of stomata; (2) the form and size of
the papillae and hairs on the ordinary epidermal cells; (3) the general shape and arrange-
ment of the epidermal cells; (4) the form of the anticlinal walls of the epidermal cells;
and (5) the form and size of the tiny pits on the outer periclinal walls of the epidermal
cells. Accordingly it is concluded that both the shoots and ‘pinwheels’ described in this
report are parts of the same plant.

Some slight differences have been noted in the cuticles but they are considered un-
important. For example, the epidermal cells are somewhat smaller on the shoot than on
the lateral appendages of the pinwheel and the anticlinal walls of the epidermal cells
are somewhat thinner on the shoot (about 1-2 /xm.) than on the lateral appendages of
the pinwheel (about 2-3 ^m.). In addition the stomata and papillae are about twice as
abundant per square millimetre on the shoot as on the lateral appendages of the pin-
wheel, but papillae are just as abundant on the stalk of the pinwheel as on the leaf of
Dinophyton. None of these differences are thought to be significant. Thomas (1925,
p. 338), in his study of the Caytoniales, showed that the epidermal cells on the petiole of
Sagenopteris phillipsi were larger than the epidermal cells on the stalk of the fruit
Caytonia nathorsti. Nevertheless, he attributed them to the same plant because of
several similarities. Harris (1964, pp. 12-13, 23) confirmed Thomas’s observations and
also attributed the two forms to the same plant. Their findings are just the reverse of
mine on Dinophyton but it suggests the cell size is not of great importance when there
are a great number of similarities as in the present situation. As noted elsewhere in this
paper the number of stomata on the two organs may be only an indication of the
primary role each played in the life of the plant and are not of importance when attribu-
tion is concerned.

Discussion. The function of the stumps (text-fig. 3d) on the ultimate shoot axes of some
specimens is uncertain. Possibly they are the bases of the pinwheels but there is no
definite information to support this except that the stump and the stalk of the pinwheel
are about the same diameter. The ends of the stumps and the stalks are not eroded or
worn, suggesting that abscission has taken place. The small leaves at the bases of some
of the adult leaves are also of uncertain function. They do not appear to have originated
with the stumps, as in the best example of a stump there is no evidence of such leaves.
Small leaves are present at the bases of some adult leaves on the same specimen and
there is no indication that they surround a stump or any other organ. At present, no
special function is attributed to these leaves; perhaps they were merely diminutive
leaves; in this connection the shoot apex shown in text-fig. 3c is surrounded by many
of the same sort of small leaves.

660 PALAEONTOLOGY, VOLUME 13

Isolated but complete leaves of Dinophyton are rarely found at any locality. They are
uncommon even in the dark, highly fossiliferous shale at locality 10088 and in the
coaly material at localities 10089 and 10090. Usually the isolated leaves which are found
at these localities are fragmentary, consisting of only the apex and the upper portion
of the lamina. A number of short lengths of the ultimate shoot have also been isolated
from bulk macerations of material from the same localities. In most of these specimens
the leaves were still attached to the axis of the shoots even though they had undergone
a certain amount of rough treatment during both deposition and more recently in the
laboratory when they were recovered from the rock and macerated. Examinations of
these specimens shows that the leaves are still fairly firmly attached to the axis. Actually
the upper portions of the leaves are usually missing suggesting that the leaves have
more of a tendency to break apart at some point above their base rather than to separate
from the axis at the base. A few shoot axes which do not bear leaves were found only
in bulk macerations from locality 10090; they are exceptional occurrences. The leaves
in these cases typically have not separated cleanly from the axes as irregular holes in the
cuticles show where the leaves were attached (text-fig. 3f).

At practically all localities the foliage of Dinophyton is represented only by fragments
of the ultimate shoot about 5-10 cm. long, rarely longer. A few penultimate shoots
with attached ultimate shoots have been found in New Mexico at locality 10061 (see
PI. 123, figs. 8-10) and at the two localities near Gap, Arizona. Most of the foliage
referable to Dinophyton at these localities, however, consists of short lengths of the
ultimate shoots. The comparative rarity of complete, isolated leaves and the common
occurrence of specimens of the ultimate shoots with attached leaves suggests that the leaves
were normally retained and that the ultimate shoots themselves were deciduous as in
some modern members of the Taxaceae, Podocarpaceae, Araucariaceae, and Taxodiaceae.

It is possible that the strands in the leaves of Dinophyton which are thought to be
veins are actually resin ducts such as occur in the leaves of the modern Abies lasiocarpa.
Resin ducts in modern conifers, however, usually do not rejoin as the strands do in the
leaves of Dinophyton. A careful but unsuccessful search was made for evidence of
vascular elements in the strands. High magnification showed that they consist mainly
of dark, generally structureless material and occasional discontinuous lines which could
be anticlinal walls of cells. Usually the strands were visible only in leaves which had been
either treated with a commercial bleaching solution for a few hours or had been macerated
for about half an hour or less. Continued bleaching or maceration caused them to dis-
appear entirely. In a number of leaves only a single wide strand is present; this could
be due to two strands drifting together prior to fossilization giving the appearance of
a single strand.

Several lines of evidence seem to indicate that the leaves of Dinophyton were round

EXPLANATION OF PLATE 123

Figs. 1-9. Dinophyton spinosus gen. et sp. nov.; macerated compressions of pinwheel, all x5.
1, USNM 43670. 2,USNM43662. 3,USNM43663. 4,USNM43664. 5,USNM43665. 6, USNM
43666. 7, USNM 43667. 8, USNM 43668. 9, USNM 43669. All specimens collected from USGS
fossil plant locality 10090 in bed of paper coal, lower part of Petrified Forest Member, Chinle
Formation, Teepee Buttes area, Petrified Forest National Park, Arizona.

Palaeontology , Vol. 13

PLATE 123

ASH, Problematic Triassic plant

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS 661

in cross-section and were not flattened appreciably, if at all, during life. The leaf cushion
is round to oval on the few shoot axes known that have lost their leaves and also on the
many leafy shoots which have been macerated. Apices of the leaves often do not appear
to be compressed and look very much like tips of cones. During maceration the leaves
swell and become round as if returning to their original shape. Swelling also occurs
sometimes when the fossil is embedded in plastic. The leaves do not have specialized
margins which typically are found on the edges of most flattened conifer leaves. Finally,
the frequency of stomata on the leaves seems to be about the same on all parts of the
leaf. The difference in frequency of stomata on the foliage (about 100 per mm.2) and
the pinwheel (about 50 per mm.2) is puzzling.

Comparisons. The leaves of Dinophyton can be easily distinguished in shape and size
from the leaves of all plants in the Chinle Formation (Ash 19706). Only one conifer,
Pagiophyllum sp. D, could conceivably be confused with Dinophyton as they both have
leaves of about the same size, but the leaves are distinctly falcate and not linear as in
Dinophyton. The two species can easily be differentiated on the microscopic level even
if only a small fragment of cuticle is available. In Dinophyton the stomata are mainly
monocyclic and possess small (10-14x3-6 jam.) rectangular stoma tal pits, in contrast
to the Pagiophyllum stomata which are amphicyclic and have comparatively large
(20-5 x 12-15 pm.) oval stomatal pits. In the Pagiophyllum the anticlinal walls of the
epidermal cells are thicker and more irregular than comparable cell walls on the leaves
of Dinophyton. Also the outer periclinal walls of the epidermal cells on the leaves
contain large angular pits whereas in Dinophyton they contain tiny round pits and often
bear single, simple papillae. The stomatal pits are overhung by cuticle projections from
the subsidiary cells whereas in Dinophyton the subsidiary cells do not have any such
projections or papillae.

Of plant fossils known to me, Dinophyton compares most closely with Rissika media
Townrow 1967, from the Middle Triassic rocks of South Africa. The gross morphology
of the foliage of the two species is remarkably similar (Townrow 1967, pi. 1, fig. e, and
PI. 123, figs. 2-7 of this paper). Both species have leaves of about the same size and
with approximately the same proportions. The leaf attachment (spiral with decurrent
bases) and the leaf apex (obtuse with an acuminate tip) are very close in certain specimens
of the two species. In addition on the microscopic level the anticlinal cell walls of both
species are straight and narrow and the cells are usually rectangular to polygonal in
shape. In both species the stomata are usually monocyclic with two-four lateral and
two terminal subsidiary cells, and the stomatal pits are rectangular.

The two species have dissimilarities which are probably more significant and include
round, closely set leaves (1 mm. or less apart) which are not modified by twisting into
two lateral rows in Dinophyton as against the flat, remotely-set leaves (2-5 mm. apart)
which are modified by twisting into two lateral rows in R. media. The ultimate shoots
of the present species do not seem to bear any small leaves at their base as do the foliar
spurs of R. media. Dinophyton does have small leaves at the base of some adult leaves
but they are not present in R. media. In R. media the stomatal pits are overhung by two
to four projections of cutin which extend from the subsidiary cells and walls of the
ordinary epidermal cells are smooth; in Dinophyton the outer periclinal walls of the
ordinary epidermal cells often bear a single, simple cutinized papillae. The apical seed

662

PALAEONTOLOGY, VOLUME 13

cones and the three-lobed ultimate seed-bearing structures of R. media cannot be matched
in Dinophyton and it is concluded that the two fossils are not very closely related.

Pinus monophylla is the only conifer I know with leaves which are round in section.
The way they are borne on the stem, however, is fundamentally that of the other species
of Pinus and different from Dinophyton where they arise directly on the stem. Apart from
having stomata with rectangular pits on all surfaces the cuticle of P. monophylla is
unlike that of Dinophyton.

The shoots of the new species resemble those of many other fossil and Recent conifers
and taxads but in no case in all characters. Many genera have narrow leaves but most
are dorsiventrally flattened and the leaves, though arranged spirally, curve basally to
bring them into the horizontal plane. The narrow leaves contain one vein in contrast
to the leaves of Dinophyton which apparently have two veins. Two separate veins
would be unusual in a conifer leafless than 1 mm. in width but the ‘veins’ of Dinophyton
may be merely two woody strands of a single ‘mid vein’ as it is ordinarily called in a
living conifer.

It is the microscopic features which are so anomalous. In conifers with dorsiventrally
flattened needle leaves the stomata are limited to a band on each side of the mid-rib
and confined to the lower side; occasionally they are on both sides but the upper
commonly has fewer. In only P. monophylla are there stomata on all sides of the leaf
in about equal numbers. The equal frequency of stomata on the leaves and stem is
anomalous as conifer stems bearing needles have but few stomata on the stem, for the
leaves are the specialized photosynthetic organs. The form of the stoma (in a pit sur-
rounded by 4-6 unspecialized subsidiary cells) and their arrangement in short longitu-
dinal files is easy to match in living and fossil conifers of various families but is not
exclusive to conifers. It is for example seen in Czekanowskia ( ?Ginkgoales) and in
Stenopteris ( ?Pteridosperms.) In many genera (Taxaceae, Sciadopitys, etc.) strong out-
growths occur on the subsidiary cells which might almost be called ‘trichomes’ but are
not so named. In some conifers and taxads small outgrowths from the marginal cells
of the leaf are frequent, and they form microscopic teeth; but in none does one see flat
subsidiary cells and strong, hollow, conical outgrowths on the ordinary epidermal cells
(properly called trichomes). This feature is foreign to conifer and taxad families and
gives the cuticle a strange aspect. Very similar trichomes are seen in certain Stenopteris
species and in a good many Ginkgoales but there, if trichomes occur, the subsidiary
cells are usually more or less papillate.

The strange little pinwheel structure is perhaps very incompletely known; I have
assumed that it originally bore an ovule, but another possibility is that it is a vegetative
reproductive unit, a kind of bulbil (cf. Lycopodium selago ) in which case it is perhaps of

EXPLANATION OF PLATE 124

Figs. 1-10. Dinophyton spinosus gen, et sp. nov. 1-6, Compressions of pinwheel. 1, USNM 43681,
xl. 2, USNM 43682, xl. 3, USNM 43683, X 2. 4, USNM 43684, X 2. 5, USNM 43681,
x2. 6, USNM 43685, x2. 7-10, Cuticle of distal appendage of pinwheel, slide USNM 43686,
x 250. Specimens in figs. 1-6 from Monitor Butte Member, Chinle Formation, Fort Wingate area,
New Mexico; figures 1, 2, 4, 5 from USGS fossil plant locality 10061, 3 from USGS fossil plant
locality. 10060, 6 from USGS fossil plant locality 10058. Cuticle in figs. 7-10 from USGS fossil
plant locality 10090 in bed of paper coal, lower part of Petrified Forest Member, Chinle Formation,
Teepee Buttes area of Petrified Forest National Park, Arizona.

Palaeontology , Vol. 13

PLATE 124

ASH, Problematic Triassic plant

ASH: DINOPHYTON, A PROBLEMATICAL NEW PLANT GENUS

663

less taxonomic significance. No bulbil occurs in the conifers or taxads, but Dinophyton
has not yet been proved to be either. It is reasonable to regard the four little outgrowths
or appendages as small leaves and these could well have surrounded an ovule. One
possibility is that the structures were attached singly on ordinary vegetative shoots but
it is only suggested by a few examples of outgrowths or stumps which might be pedicels.
Certainly if these organs bore a median ovule it is unlike the ovuliferous part of any
known conifer or taxad.

Summary. Dinophyton has more features in common with the conifers and taxads than
with any other group, but in detail the shoots are distinct by having: (1) a cuticle uni-
form over the whole surface of the leaves and stem; (2) many trichomes all over the
leaf and the stem; and (3) stomata all over the leaf and the stem. The curiously shaped
detached organs here called ‘pinwheels’ do not at present help at all in placing Dino-
phyton, but it seems reasonable to regard Dinophyton as a gymnosperm of unknown
affinities.

Acknowledgements. The advice of Professor T. M. Harris and Dr. P. D. W. Barnard, the University of
Reading, and Dr. H. N. Andrews, the University of Connecticut is acknowledged with thanks. I am grate-
ful to Mr. Charles Bonner, Hays, Kansas for helping with the preparation of the reconstruction of an
ultimate shoot of the fossil in text-fig. 2a and to Dr. Donald Becker, Fremont, Nebraska who pre-
pared the thin sections used in text-fig. 6a. The assistance given me by the Museum of Northern Arizona,
Flagstaff in the collecting of material for this report is appreciated.

REFERENCES

ash, s. r. 1967. The Chinle (Upper Triassic) megaflora, Zuni Mountains, New Mexico. New Mexico
Geol. Soc. 18th Ann. Field Conf. Guidebook, 125-31.

1968. A new species of Williamsonia from the Upper Triassic Chinle Formation of New Mexico.

J. Linn. Soc. Lond. (Bot.), 61, 113-20, pi. 1.

1970a. Ferns from the Chinle Formation (Upper Triassic) in the Fort Wingate area. New Mexico.

U.S. Geol. Survey Prof. Paper 613-D, 1-52, 5 pi.

19706. Review of the plant megafossils. In Symposium on the Chinle Formation. Mus. N. Arizona.

1970c. History of paleobotanical investigations. Ibid.

1970(7. Pagiophyllum simpsonii, a new conifer from the Chinle Formation (Upper Triassic) of

Arizona. J. Paleont. 44.

breed, william. 1970. The Invertebrates. In Symposium on the Chinle Formation. Mus. N. Arizona.
daugherty, l. h. 1941. The Upper Triassic flora of Arizona. Carnegie Inst. Wash. Publ. 526, 1-108,
pi. 1-34.

green, f. e. 1954. The Triassic deposits of northwestern Texas. Ph.D. Dissertation, Texas Tech. College,
Lubbock, pp. 1-196, pi. 1-15.

Harris, t. m. 1964. The Yorkshire Jurassic flora, II, Caytoniales, Cycadales and Pteridosperms. Brit.
Mus. (Nat. Hist.), 212 pp., 7 pi.

reeside, j. b. et al. 1957. Correlation of the Triassic formations of North America, exclusive of
Canada. Geol. Soc. Am. Bull. 68, 1451-1513.

stagner, H. r. 1941. Geology of the fossil leaf beds of the Petrified Forest National Monument.

In daugherty, L. H. 1941. Carnegie Inst. Wash. Publ. 526, 9-17.
thomas, h. h. 1925. The Caytoniales, a new group of angiospermous plants from the Jurassic rocks
of Yorkshire. Phil. Trans. R. Soc. 213 B, 299-363, pi. 11-15.
townrow, j. a. 1967. On Rissikia and Mataia, podocarpaceous conifers from the lower Mesozoic
of southern lands. Pap. Proc. R. Soc. Tasm. 101, 103-36, pi. 1-2.

SIDNEY R. ASH

Weber State College
Ogden, Utah, U.S.A.

Typescript received 20 January 1970

ON THE ORIGIN OF THE CLYMENID AMMONOIDS

by M. R. HOUSE

Abstract. The stratigraphical and morphological evidence relating to the abrupt appearance of the endo-
siphonate clymenids in the early Famennian (Upper Devonian) is reviewed. An origin from goniatites of the
Tornoceras stock is suggested. A series of morphologically intermediate forms is described from the earliest
Upper Famennian of the Holy Cross Mountains of southern Poland. This series leads to Tornia, a new genus
here described, which is homoeomorphic with Platyclymenia but with a ventral siphuncle. Attention is drawn
to the fact that some clymenids show a ventral siphuncle in their early ontogeny.

The origin of the Upper Devonian endosiphonate clymenids, or Clymeniina, has been
the subject of considerable past speculation. There have been some, even recently,
who would derive the group direct from the Nautiloidea. But these have usually avoided
the implications of their enthusiasm. The traditional view, essentially since Branco’s
classic ontogenetic work of 1890, has been to consider them as derived from the gonia-
tites, but some have preferred a monophyletic, others a polyphyletic origin. The purpose
of this paper is to review the stratigraphical and morphological evidence bearing on the
subject and to describe, from the earliest Upper Famennian of southern Poland, certain
goniatites which seem to be transitional between the Tornoceratidae and the earliest
clymenids. These may provide a solution to the problem.

From their sudden first appearance in the early Upper Famennian the clymenids
diversified rapidly as is indicated by an accompanying diagram (text-fig. 1) based mainly
on the work of Wedekind and Schindewolf. Evolutionary diversification is both in
shell form and suture pattern. Extremes in shell form are reached by the bizarre tri-
angular Soliclymenia and trilobed Wocklumeria. Sutural variation grades from the
utter simplicity of Platyclymenia to the multilobed Sphenoclymenia, superficially homoeo-
morphic with Beloceras but of distinct ontogeny, and Wocklumeria and Epiwocklumeria
with ventral sutures closely homoeomorphic with Imitoceras. Their diversity was
short lived. The close of the Famennian saw the extinction of the group. Clymenid
evolution and sutural derivation has been described at length by Schindewolf in a series
of papers : he favours a monophyletic origin of the group and has produced substantial
evidence to support this (Schindewolf 1937, 1949a, b, 1955).

Munster (1831, p. 182) was the first to recognize the endosiphonate clymenids which
he described under the name Planulites {non Parkinson 1822), a name later corrected to
Clymenia (Munster in Goldfuss 1832, p. 489). It is unfortunate that the apt name En-
dosiphonites (Ansted 1838, p. 416) proposed as an alternative during the description of
Cornish material is invalid. The complex nomenclatorial history of Clymenia and its
relatives has been reviewed by Schindewolf (1949, p. 63; 1955, p. 418 et seq.) and Turner
(1962).

OPINIONS ON CLYMENID AFFINITY

Following von Buch’s use of siphuncle position to separate nautiloids from the am-
monoids, Munster placed Planulites and Clymenia with the former. This view was

[Palaeontology, Vol. 13, Part 4, 1970, pp. 664-76, pis. 125—126.

HOUSE: ON THE ORIGIN OF THE CLYMENID AMMONOIDS

665

FAMENN IAN

L.CARB.

CHEILOCERAS

PLATYCLYMENI A

CLYMENIA

WOCKLUMERIA

SAND.I DELPH.

19 1H15 101

1 ANN.

19 A

HOE' V SPEC.

SUBARM. 1 SPHAER.

23 iilio 1

GONIOCLMENIIDAE

^COSTACLYMENIA SPHENOC^MENI A

GON IOC LYME N 1 A

KALLOCLymenIA

SELLACLYMENIA

WOCKLUMERIIDAE

PACHYCLMENIA

BILOCLYMENIA

WOCKLUMERIA

EPIWOCKLUMERliO

/ : /

! j/HEXACLYMENIIDAE

HEXACLYMENI

SOLICLYMENIA]

PARAWOCKLUMERIIDAE

'TRIACLYMENIA) :

KAMPTOCLYMENIA

™ I

[PARAWOCKLUMERIA

™"'U j

PROGONIOCLYMENIA

GlATZIELLIIDAE

j / j :

jPOSTGLATZIELLA

1 / : CLYMENIIDAE

PLATYCLYMENI

vucmia

text-hg. 1 . Diagram showing the ranges of genera and families of the Clymeniina. The family group-
ings are those of Schindewolf (in Moore 1957). Pecked lines indicate ranges which are uncertain. The
numbers for the Delphinus to Hoevelensis Zones correspond to bed numbers of Wedekind (1908)
at Enkeberg: those for the Subamata to Sphaeroides Zones are those of Schindewolf (1937) at the
Honnetal railway cutting.

curiously strengthened when Edwards (1849, p. 50) erected the Family Clymenidae
with Clymenia and the Tertiary Aturia only, being misled by the sutural similarities of
the latter with the Kosmoclymenia group. Although the relations with Aturia were soon
disentangled, clymenid affinities were usually given in early textbooks, following
Munster, as with the Nautiloidea, for example by Roemer (in Bronn 1859-6, p. 495),

666 PALAEONTOLOGY, VOLUME 13

Sedgwick and McCoy (1851-5, p. 312, 401), Woodward (1851-6, p. 87), Blake (1882,
p. 36) and others. But a current of disagreement was growing, led by Quenstedt (1849,
p. 68) and followed by Hyatt (1883-4), Nicholson and Lydekker (1889, p. 853), Hoernes
(1886, p. 400) who gave clear placing of the group with the Ammonoidea even before
Branco (1890, p. 34) published his work on the early stages of ammonoids which finally
convinced other workers on cephalopods. From 1890 almost all writers have accepted
the ammonoid relation as being the most probable. The list includes Foord and Crick
(1897), Freeh (1890, 1897-1902), Wedekind (1908), Schindewolf (1922, 1955), Miller
(1938), Petter (I960), and Bogoslovski (in Ruzhencev, ed., 1962), that is all the most
significant contributors on the Devonian Ammonoidea. Recent exceptions are Flower
(1961, p. 574) and Donovan (1964, p. 271).

Of those who favoured an origin of the clymenids from typical ammonoids opinion
has differed as to their precise source. Freeh (1890, p. 399) derived them both (from
Anarcestes and Agoniatites, presumably a generalization, and Schindewolf (1949, p. 206)
favouring the anarcestid descent, derived them from Archoceras or a related form
(1955, p. 422). These views typify the monophyletic standpoint.

Polyphyletic origin of the clymenids found Sobolew (1914a, b) as its chief exponent.
Sobolew sought to derive all the diverse-sutured clymenids from their Devonian
goniatite homoeomorphs. The dorsal migration of the siphuncle was held to take place
along over ten unrelated lines of descent (see also Schindewolf [1949] since Sobolew’s
major work is very rare in western libraries: I am indebted to Professor Makowski
for a copy). No stratigraphic evidence has been found to support most of these links,
and Schindewolf, in several papers, has as a result of ontogenetic work and careful
collecting produced a picture of an evolutionary radiation of clymenids from a simple
sutured stock of Hexaclymenia type. Sobolew’s suggestions therefore raise more
problems than they solve.

STRATIGRAPHICAL EVIDENCE

Until recently it was supposed that clymenids were represented in the middle Frasnian
by the anomalous Acanthoclymenia (Freeh 1897, p. 177k; Schindewolf 1955), but it has
since been demonstrated that Acanthoclymenia is a manticoceratid and quite unrelated
to the clymenids (House 1961). The elimination of the anomalous Frasnian records
clarifies the picture and it is now clear that clymenids enter the stratigraphical record
a little above the base of the Upper Famennian and above the Cheiloceras Stufe of the
German terminology. This has now been demonstrated in unambiguous sections in
North Africa (Petter 1960), Spain (Kullmann 1960, 1963), England (House 1963), and
Australia (Jenkins 1968), but especially in Germany (Wedekind 1908, Schindewolf 1922,
Lange 1929). Similar relations hold in the U.S.A. (House 1962), Canada (House and
Pedder 1963) and China (Chang 1958) although in these latter areas less detailed faunal
successions have been described.

A brief review will now be given of the main German sequences which have been
described showing the entry of the clymenids. This is intended as a nomenclatorial
revision and the taxonomic assignments have been corrected as far as possible. The
available type material has been re-examined but for Wedekind’s material the bed
numbers are rarely recorded with the specimens (most labels having been burnt) and

HOUSE: ON THE ORIGIN OF THE CLYMENID AMMONOIDS 667

the determinations are based also on his figures and descriptions. Since Wedekind’s
photographic illustrations are hardly ever given their correct size, and ventral views
rarely given, some new illustrations of primary types are given here (PI. 126).

The first detailed succession described was that on the western part of Enkeberg
given by Wedekind (1908, pp. 569-71). The ammonoid sequence is as follows: youngest
beds above, oldest below :

Bed 10 (9 cm.): Platyclymenia ( Platyclymenia ) sandbergeri (Wedekind) (not listed from
this bed on p. 621 or on the table), Rectoclymenia roemeri (Wedekind), Cyrtodymenia
involuta (Wedekind), P. ( Pleurodymenia ) cydoptera (Wedekind), Genudymenia (?)
dunkeri (Munster), Prolobites delphinus (G. and F. Sandberger), Sporadoceras angus-
tisellatum Wedekind, S. munsteri (von Buch), S. inflexum Wedekind, S. discoidale
Wedekind, Praeglyphioceras pseudosphaericum Freeh, and Pseudodymenia planidor-
sata (Munster).

Bed 11 (10 cm.): P. (PI.) brevicosta (Munster), P. (P.) steinmarmi (Wedekind), Cyrto-
dymenia angustiseptata (Munster), P. (P.) enkebergensis (Wedekind), R. subflexuosa
(Munster), S. discoidale Wedekind, S. miinsten (von Buch), S. inflexum Wedekind,
S. biferum (Phillips), Prolobites delphinus (G. and F. Sandberger), and Ps. planidorsata
(Munster).

Bed 12 (9 cm.): P. (IP.) pompecki (Wedekind), C. involuta (Wedekind), C. lotzi (Wede-
kind), P. (PI.) cydoptera (Wedekind) (figured here PI. 126, figs. 8, 9; this specimen
may have come from Bed 10, the precise source is not indicated), G. f rechi (Wede-
kind), G. gumbeli (Wedekind), G. angelina (Wedekind) (not recorded from this bed
on p. 618), R. roemeri (Wedekind), G. angustiseptata (Munster), R. subflexuosa
(Munster), S. angustisellatum Wedekind, S. munsteri pseudosphaericum Freeh, and
Prol. delphinus (G. and F. Sandberger). Hexaclymenia hexagona (Wedekind) (figured
here in PI. 126, figs. 18, 19) was recorded on p. 619 as coming from this bed but was
not listed on p. 570.

Bed 13 (11 cm.): C. lotzi (Wedekind), G. phillipsi (Wedekind) (figured here PI. 126,
figs. 10, 11), G. frechi (Wedekind), S. angustisellatum Wedekind, S. munsteri (von
Buch), and Prol. delphinus (G. and F. Sandberger).

Bed 14 (12 cm.): P. (P.) steinmanni (Wedekind) (figured here PI. 126, figs. 6, 7; also
recorded from Bed 14 on p. 570 which could have been the source of the figured
specimen), C. involuta (Wedekind) (recorded from this bed on p. 570 but not on
p. 610), and S. biferum (Phillips). G. angelina (Wedekind) (refigured here on PI. 126,
figs. 14, 15) is recorded from this bed on p. 618 and on the table but not on p. 570.
P. (P.) sandbergeri (Wedekind) (figured here PI. 126, figs. 12, 13) is also recorded
from this bed on p. 621 and on the table, but not on p. 570.

Bed 15 (9 cm.) and Bed 16 (15 cm.): no ammonoids recorded.

Bed 17 (9 cm.): Pseudodymenia sandbergeri (Giimbel), Ps. sandbergeri dillensis Drever-
mann, Ps. dorsatum (Wedekind), Dimeroceras padbergensis Wedekind.

In this succession Platyclymenia s.s. and Cyrtodymenia are the first clymenids to
appear above beds with abundant Pseudodymenia , Dimeroceras, and Sporadoceras
(Beds 22-17) with Cheiloceras abundant lower still (Beds 25-31). Although not rele-
vant to the present discussion the discrepancies in Wedekind’s various records and the
textual inconsistencies should be noted. Also the magnifications which he gives for his

668

PALAEONTOLOGY, VOLUME 13

illustrations are mostly incorrect. The large number of species he erected is also suspicious,
and doubtless most of these will be redundant when a modern statistical analysis of the
fauna is undertaken.

When the Enkeberg section was revised by Lange (1929) the collecting was not done
with the same scrupulous attention to the detailed succession that characterized Wede-
kind’s work, and the stratigraphic revision was at the crude level of zones (as on text-
fig. 1) only. One cannot therefore feel other than cautious in accepting some of the
changed ranges which he recognized. Thus Lange (1929, p. 16, 97) records Platy-
clymenia ( Variodymenia ) kayseri as common in Zone Ilia, the Sandbergeri Zone, from
Wedekind’s Beds 19-16, and the entry of other clymenids above in Beds 15-10 is not
recorded in detail, and in failing to do so Lange leaves himself open to the suggestion
that he did not correctly interpret Wedekind’s bed numbers. This matter, however, is
a trivial one which will only be resolved by the next reviser of the Enkeberg section.
In recording clymenids in Zone Ilia he was following Schindewolf as will be seen below.

Another detailed succession showing the entry of clymenids is the sequence at Hof
described by Schindewolf (1922, p. 256; Wurm 1961, p. 118). Here the entry of clymenids
is recorded as follows (again taxonomic revisions have been made).

Bed 11 (0-25 m.): S. discoidale Wedekind, S. munsteri (von Buch), R. subflexuosa
(Munster), C. involuta (Wedekind), C. wedekindi Schindewolf, P. (P.) sandbergeri
(Wedekind), P. (P.) prorsostriata Schindewolf, P. ( Trigonoclymenia ) crassicosta
(Wedekind), and others.

Bed 10 (T8 m.): S. munsteri (von Buch), S. discoidale (Wedekind), R. rotunda Schinde-
wolf, C. sulcata Schindewolf, Genu, frechi (Wedekind), Genu, borni Schindewolf.

Bed 9 (c. 1-2 m.): R. sandbergeri (Gumbel), Ps. sandbergeri dillensis (Drevermann),
S. munsteri (von Buch), S. contiguum (Munster), Praeg. pseudosphaericum Freeh
R. ( ?) kayseri Drevermann, C. pulcherrima (Wedekind), Genu, frechi (Wedekind).
Bed 8 (2-5 m.): Ps. planidorsata (Munster), Cheiloceras sp., S. biferum (Phillips).

Schindewolf referred Bed 8 to II/3, the upper part of the Cheiloceras Stufe (Pompeckji
Zone), Bed 9 to Ilia (Sandbergeri Zone), and Beds 10 and 11, and the overlying Bed 12
to III/3. Since Prolobites delphinus was not recorded it is to be inferred only that the
latter group represent the Delphinus Zone.

This review serves to emphasize that the stratigraphical evidence shows that the earliest
known clymenids all have sutures showing a lateral lobe and dorsal lobe only ( Platy -
clymenia s.s. Rectoclymenia , Cyrtoclymenia ) with some ( Genuclymenia ) with a slightly
more complex pattern. Later follow the other subgenera of Platyclymenia and later still,
in the Clymenia Stufe, Kosmoclymenia and Cymaclymenia. C. ornata, an early form of
the latter, is illustrated here (PI. 126, figs. 16, 17): the figured specimen is Munster’s,
Schindewolf recorded this species in the lower part of Zone V/3.

ORIGIN FROM THE TORNOCERATIDAE

It is the purpose here to suggest that a group of derivatives of the common Devonian
Tornoceras stock which occur in the early Upper Famennian are morphologically
transitional between typical tornoceratids and the earliest clymenids. The critical fauna

HOUSE: ON THE ORIGIN OF THE CLYMENID AMMONOIDS

669

is from the Lower Famennian of Kielce in the Holy Cross Mountains. Some of this is
illustrated here (PI. 125, 126).

The Kielce Tornoceratids

In 1913 Dybczynski published a brief account of a prolific locality for pyritized
goniatites in the Holy Cross Mountains on the outskirts of the town of Kielce, from
which he had collected over 5000 specimens. Sobolew (1913, 1914 a, b) gave a lengthy
account of this fauna with many illustrations, but described them using a complex
generic nomenclature based on a root with morphologically descriptive prefixes and
suffixes. Sobolew’s genera, but not his species, have been declared invalid by Opinion
132 of the ICZN (Schindewolf and others 1936). The pyritic fauna is of great diversity
and is almost wholly of early Famennian age. The evidence for this will briefly be dis-
cussed.

The main source of the material described by Sobolew was from shales overlying the
Frasnian and perhaps earliest Famennian limestones at the Kiedelna quarry. Housing
developments have now covered most of the site, but in 1962 the author was able to
collect from weathered shales (but not in place) a poor fauna including Raymondiceras
and Sporadoceras (with spiral ornament) confirming that a position succeeding the
Cheiloceras Stufe recorded in the quarry below is proven. Fortunately Dr. H. Makowski
has kindly made available a collection from Kielce thought to come wholly from the
shales overlying the quarry and the Sieklucki’s Brickpit there, and which forms the
remnants of a pre-war collection of the Geology Department of the University of
Warsaw.

Interest here centres on the remarkable suite of tornoceratids and their precise age.
Rare early clymenids occur in the fauna and some were figured by Sobolew. The most
readily determined tornoceratids are those similar in shell and suture form to T. cre-
briseptum from the Three Forks Shale of Montana (House 1965, p. 115). The Montana
fauna contains Platyclymenia, Raymondiceras, and Rectoclymenia and has been referred
to the Delphinus Zone. The main source at Kielce would appear to be earlier than this.
(The Delphinus Zone is where the clymenids first appear, text-fig. 1). Sobolew’s fauna
included Sporadoceras and Imitoceras, both of which, in Germany, enter in the upper
half of the Cheiloceras Stufe (Pempeckji Zone). Although there is no reason to suppose
that the Kielce pyritic fauna is from a single horizon, the evidence suggests that the
fauna studied here covers the range of the Pompeckji and Sandbergeri Zones. That is,
the bulk of the fauna correlates with horizons immediately preceding the known entry
point of the clymenids. Higher horizons, with clymenids are also known and were
mentioned by Sobolew.

SYSTEMATIC PALAEONTOLOGY

The whole of the Kielce material is in need of description but the material at present
available is so meagre in comparison with that formerly known and destroyed during
the Second World War, that this would be unwarranted at present. Dybczynski (1913)
described a number of species and the specific names given by Sobolew are still valid
despite the ruling of the ICZN on his genera. The Kielce tornoceratids which are the
concern here comprise some belonging to the Tornoceras crebriseptum Raymond group.

670 PALAEONTOLOGY, VOLUME 13

which perhaps, should be recognized as a new subgenus. Others of the transitional series
fall in Protornoceras and the end point in which the lateral lobe has ceased to exist
except as a vestigal remnant comprise a small group for which the new generic name
Tornia is here proposed.

Suborder goniatitina Hyatt 1884
Superfamily cheilocerataceae Freeh 1897
Family tornoceratidae Athaber 1911
Genus tornoceras Hyatt 1884

Type species. By original designation Goniatites uniangulare Conrad.

Tornoceras (T.) crebriseptum Raymond Group

Discussion. The tornoceratids which form the starting point of the morphological series
leading to Tornia belong to a group represented by forms referable to T. (T.) crebriseptum
(for a description of the type material see House 1965). The Montana type material
already shows evidence, in the internal mould, that the umbilicus is open, although
testate specimens may not have been. Were the latter point settled in the affirmative
then they should be referred to Protornoceras or a new genus group. The suture, with its
subdued form and flat ventro-lateral saddle is also distinctive (PI. 125, fig. 1). Quite
closely similar types occur in the Kielce fauna but these differ in showing small con-
strictions over the venter (PI. 125, figs. 2-5) which, suturally are even closer to the
Montana material. In view of the priority of Raymond’s work over that of Dybczynski
and Sobolew these may be referred to as T. (T.) aff. crebriseptum pending revision of the
whole fauna.

Genus protornoceras Dybczynski 1913

Type species. By original designation Tornoceras (. Protornoceras ) polonicum Dybczynski, 1913, p. 512.

Discussion. The current use applies this generic name to all open umbilicate tornoceratids
without the ventro-lateral grooves and other characters which distinguish Aulatornoceras.
Middle Devonian examples, such as P. foxi House (1963 p. 19, pi. 2a, d-g, text-fig.
8 a-g) seem clearly to be unrelated directly to those of the Lower Famennian and should,
at some stage, receive another generic name. The Polish material forms the type for the
genus and some representatives are figured here (PI. 125, figs. 6-22). Many specific
names belong here which we owe to Dybczynski, Sobolew, and Wedekind. The group
is a variable one and many of these names will be lost in synonomy when they come
to be revised.

The importance in the present context is that as well as showing a progressive opening
of the umbilicus the group also shows sutural characters linking it with the crebriseptum

explanation of plate 125

Figs. 1-5. Tornoceras ( Tornoceras ) spp. 1, T. (T.) crebriseptum Raymond, holotype from the Three
Forks Shale of Montana in the Carnegie Museum, Pittsburgh No. 464; x2. 2-5, T. (T.) aff.
crebriseptum (Raymond) from Kielce; 2, x2-5; 3-5, x2.

Figs. 6-22. Protornoceras spp. 6-8, P. cf. planidorsatum (Wedekind) from Kielce; X2. 9-19,
P. simplificatum (Sobolew) from Kielce; 9, 10, x 2-5, 11-13, X2, 14-19, x3. 20-22, P. cf. zuberi
Dybczynski from Kielce; x2-5.

Palaeontology, Vol. 13

PLATE 125

HOUSE, Origin of Devonian clymenid ammonoids

HOUSE: ON THE ORIGIN OF THE CLYMENID AMMONOIDS

671

group of Tornoceras s.s. Further, in the Polish material all morphological gradations
can be seen from sutures typical of Tornoceras s.s. to those in which the elements become
progressively subdued (text-figs. 2b, c; PI. 125, figs. 6-20; PI. 126, figs. 1, 2).

text-fig. 2. Early Famennian tornoceratids from the Sieklucki Brickpit Kielce, Poland; all x20.
A, Tornia mirabile (Dybczynski), suture at 1 3 mm. diameter, b, Protomoceras cf. zuberi Dybczynski,
suture at 11-9 mm. diameter (also figured on PL 125, figs. 21, 22). c, Protomoceras simplification
(Sobolew), suture at 15 mm. diameter (also figured on PI. 125, figs. 17-18). d, Tornoceras (71) aff.
crebriseptum Raymond, suture at 11-8 mm. diameter (also figured on PI. 125, fig. 2).

Genus tornia gen. nov.

Type species. Here designated Tornia mirabile Dybczynski 1913, p. 514, pi. 1, fig. 4, pi. 2, fig. 4.

Diagnosis. Open umbilicate tornoceratids with ventral siphuncle, biconvex growth-lines
and mature suture forming a broad shallow lateral lobe, a narrow ventral lobe and a deep
linguiform dorsal lobe.

Remarks. Morphologically this form is identical with some platyclymenids apart from
the ventral position of the siphuncle. Relic traces of the typical tornoceratid adventitious
lobe can be seen in the broad lateral lobe, but this cannot be crossed by a radial line
drawn from the umbilicus and in this respect differs from the presumed Protomoceras
antecedents (e.g. PI. 125, figs. 21, 22 PI. 126, figs. 1,2;), and there is no arched latero-
umbilical saddle as is also characteristic of tornoceratids. The genus closely approaches
homoeomorphy with the Middle Devonian genus Agoniatites.

xx

C 7719

672 PALAEONTOLOGY, VOLUME 13

Tornia mirabile (Dybczynski)

Plate 126, figs. 3-5, text-fig. 2a

Neotype. The holotype having been lost one specimen belonging here will be described and is designated
the neotype : this is an internal haematite mould showing some 90° of body chamber. A tendency to
orad sutural approximation and evidence of shell thickenings in the body chamber suggest maturity.
This specimen is in Professor H. Makowski’s collection at the Polski Akademia Nauk, Warsaw.

The shell form (see PI. 126, figs. 4, 5) is open umbilcate but the earliest whorls are not seen. Ex-
perience with this preservation having shown that the inner whorls are rarely shown by sectioning,
this has not been risked on the neotype, but moderately evolute early whorls are indicated. The
whorl form shows a well-rounded venter, somewhat flat sides and a steep and rounded umbilical
shoulder.

Dimensions {in mm.)

D

WW

WH

UW

Holotype (data from Dybczynski)

17

6

c. 8

4

Specimen from Sieclucki’s brickpit

16-7 (max.)

—

—

—

(Neotype)

14-4

4-1

5-9

4-3

Growth-lines, as discernible on an internal mould are biconvex, forming a slight
salient on the umbilical shoulder, a broad slightly prorsiradiate sinus on the flanks and
a short, stubby ventro-lateral salient or short lappet passing to a U-shaped ventral
sinus. On the body chamber diffuse shell thickenings appear to have followed the same
course.

The sutures vary a little among themselves. A small V-shaped ventral lobe passes
to a very broad and weak lateral saddle of slightly varying very shallow depth. Traces
of the position of the lateral lobe of the supposed ancestral Protornoceras can be discerned
as a very slight ventral facing slope on the lower flanks. The dorsal suture has not been
seen, but in the nearest Protornoceras in which a clear lateral lobe can be seen (PI. 126,
fig. 2), it shows that a typical tornoceratid deep lobe was present.

Remarks. This sole neotype specimen from the Sieklucki Brickpit is the end member of
the sequence described under Protornoceras. The suture is homoeomorphic in its elements

EXPLANATION OF PLATE 126

Figs. 1, 2. Protornoceras aff. zuberi Dybczynski from Kielce; x 3.

Figs. 3-5. Tornia mirabile (Dybczynski) from Kielce; x2.

Figs. 6-9. Platyclymenia (P.) Spp. 6, 7, P. (P.) steinmanni (Wedekind), holotype (figured Wedekind
1908, pi. 43, figs. 12, 12a) from Bed 14 at Enkeberg. xl. Univ. Gottingen Coll. 8, 9, P. {IP.)
cycloptera (Wedekind), holotype (figured Wedekind 1908, pi. 43, fig. 11) from Bed 11 or 12 at
Enkeberg; x2, Univ. Gottingen Coll.

Figs. 10, 11. Genuclymenia phillipsi (Wedekind), holotype (figured Wedekind 1908, pi. 39, fig. 26,
pi. 43, fig. 6) from Bed 13 at Enkeberg; x2, Univ. Gottingen Coll.

Figs. 12, 13. Platyclymenia {P.) sandbergeri (Wedekind), lectotype here designated (figured Wede-
kind 1908, pi. 44, figs. 9, 9a; 1914, pi. 2, fig. 7 as P. wysogorskii Freeh) from Beds 14 to 12 at En-
keberg; x2, Univ. Gottingen Coll.

Figs. 14, 15. Genuclymenia angelina (Wedekind), holotype (figured Wedekind 1908, pi. 44, fig. 6) from
either Bed 13 or 14 at Enkeberg; x 1, Univ. Gottingen Coll.

Figs. 16, 17. CymaclymenialZ ) ornata (Munster); Munster’s holotype in the Bayerische Staatssammlung
fiir Palaeontologie und Historische Geologie, Munich ; x 2.

Figs. 18, 19. Hexaclymenia hexagona (Wedekind), holotype (figured Wedekind 1908, pi. 43, figs. 7, 7a)
from Bed 12 at Enkeberg; x 1-78, Univ. Gottingen Coll.

Palaeontology , Vol. 13

PLATE 126

HOUSE, Origin of Devonian clymenid ammonoids

HOUSE: ON THE ORIGIN OF THE CLYMENID AMMONOIDS 673

with Agoniatites, but the lateral lobe is much shallower. No Frasnian agoniatitids being
known, and the Protornoceras link being demonstrable, a phylogenetic derivation
from Agoniatites is not possible. Only the specimen figured by Sobolew as Gomi-re-
protomeroceras ( Tornoceras ) alobatum Sobolew (1913, pi. 9, figs. 5, 6, ?non text-fig. 105)
seems also to belong in Tornia; but this form is significantly more evolute than the
holotype and substantially more so than the neotype specimen here described. However,
the involvement of new species within Sobolew’s generic formulae is so complex a matter
that it is unfortunate that they were not also invalidated by the ICZN. The destruction
of his collection in the Second World War renders the use of his names even more
difficult and those of Dybczynski are preferred in this case although his collection is
also untraced.

The comparison with the varied early clymenids (PI. 126, figs. 6-19) in shell form and
in the course of the growth-lines, and where present, ribbing is sufficiently close to
raise no great problems in their derivation from Tornia. No other Devonian goniatite
shows so close a sutural resemblance to these early clymenids as does Tornia. A ventral
suture has been demonstrated in the early stages of some clymenids (see references given
later) and this suggests that the permanent adoption of the endosiphonate condition
falls wholly within the Clymeniina.

SUMMARY AND CONCLUSIONS

The demonstration that the Frasnian Acanthoclymenia is not a clymenid concentrates
attention on the Lower Famennian sequences where clymenids appear. The Polish
fauna of Protornoceras and Tornia at this level gives a morphological series leading to
the earliest known clymenid genera. The reasons for favouring an origin of the cly-
menids from goniatites rather than nautiloids is summarized below :

1. The form of the protoconch. As Branco (1890, p. 35, pi. 7, figs, a-e), Schindewolf
(1923, p. 24 et seq.) and others have observed the egg-shaped, often laterally elongate
protoconch of the clymenids finds its closest analogy with those of the goniatites. What
early stages of Devonian nautiloids homoeomorphic with coiled ammonoids are known,
for example centroceratids (Flower 1952), are different. Similarly the form of the pro-
suture (Branco 1880, pi. 8, fig. lb; Schindewolf 1923, text-fig. 2) is very similar to that
of goniatites particularly the Tornoceras group (see House 1965).

2. The lack of an umbilical perforation. This is the rule in the clymenids and of the
goniatites from which it is here argued they are derived. It does not appear to be a
character of the groups of nautiloids from which Donovan (1964, p. 271) would derive
the clymenids. There is no doubt, however, that information on the early stages of some
relevant Devonian nautiloid genera is lacking.

3. Transitional position of the siphuncle. As Branco (1880, pi. vn, fig. 3b) and Schinde-
wolf (1955, p. 420) have described, some early clymenids show a ventral siphuncle in
the early stages. Later the siphuncle migrates to a dorsal position. Sandberger (1853,
pi. 6, fig. 1) has illustrated sagittal sections of Clymenia compressa showing that in early
whorls, but not the earliest, the siphuncle is often well away from the dorsum.

To these factors the present paper adds a description of forms which show evidence of :

4. Transitional shell form. The sequence of tornoceratids described here from the

674 PALAEONTOLOGY, VOLUME 13

Lower Famennian of Southern Poland shows a progressive opening of the umbilicus and
lateral forward projection of the adult aperture which approaches that of the earliest
known clymenids.

5. Transitional Suture Forms. The same sequence shows a simplification of the
Tornoceras suture to one showing a deep dorsal lobe, and a shallow lateral lobe : both
features of the earliest known clymenid genera. The trend culminates in the new genus,
Tornia.

6. Stratigraphic intermediates. The horizon of the new intermediate forms appears to
lie just below the level at which clymenids appear.

It seems to the author that it is the summation of this evidence which makes an
origin of the clymenids from goniatites, and a specific origin from the Tornoceras stock,
probable.

Some comments may be made on another contendor as ancestor, Archoceras (Schinde-
wolf 1955) which is a late Frasnian and earliest Famennian genus. For several reasons
it does not seem very suitable. There is a clear gap in the record of Archoceras before
the appearance of clymenids. The sutural pattern of the genus, although simple (House
1962, p. 367, text-fig. 7), is not such as to enable ready derivation of the clymenid suture.
The large lateral saddle is directly the reverse of the shallow lateral lobe of the earliest
clymenids. Also the deep ventral lobe, combined with a deep dorsal lobe, makes the
septum highly arched orad, and hence any migration of the siphuncle across this is
difficult to envisage. The suitability of Tornia and its relatives is particularly shown here
since the septal mid-line actually slopes dorsad along the line of the siphuncle migration.
When Acanthoclymenia was thought to be a Frasnian clymenid, Archoceras did seem
to offer attractions, but these have now been lost.

What the functional advantages of a dorsal siphuncle were it is difficult to assess, but
the rapid evolution after the inception of the character suggests that the survival value
was considerable. The wholesale extinction of the clymenids at the close of the Devonian
need not be related to any change in this factor necessarily since goniatite groups are
also affected by the extinctions. But during the late Famennian the diversification of the
clymenids seems matched by an over-all decline of goniatite stocks. Migration of the
siphuncle occurs in other ammonoid groups also ( contra Donovan 1964, p. 271), for
example in the Permian Pseudoholorites and Neoaganides (Miller and Furnish 1957,
p. 1044), but at no other time in ammonoid history does the fully dorsal siphuncle
position appear to have been adopted again.

Acknowledgements. Thanks are due especially to Professor H. Makowski for allowing me to study
collections in Warsaw and to loan and figure material from his personal collection at the Polski
Akad. Nauk : to Dr. G. Biernat and Dr. H. Osmolska for their kindness in guiding me in the Kielce
area and the Holy Cross Mountains generally. Also to Professor H. Schmidt and Professor O. H.
Walliser for allowing me to photograph Wedekind’s type collection at Gottingen and Marburg re-
spectively.

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676

PALAEONTOLOGY, VOLUME 13

schindewolf, o. h. 1922. Beitrage zur Kenntnis des Palaozoicums in Oberfranken, Osthiiringen und
dem Sachsischen Vogtlande. 1. Stratigraphie und Ammoneen fauna des Oberdevons von Hof a. S.
Neues Jb. Miner. Geol. Palaont. 49, 250-357, 393-509, pi. 14-18.

1923. Entwurf einer natiirlichen Systematik der Clymenoidea. Centralbl. Min., Geol. Palaont.

(1923), 23-30, 59-64.

et al. 1936. Status of the ‘Gattungsbezeichnungen’ of Sobolew 1914. Smithson, misc. Colins.

73 (8), 39, 40.

1937. Zur Stratigraphie und Palaeontologie der Wocklumer Schichten (Oberdevon). Abh. preuss.

geol. Landesanst., N.F. 178, 1-132, pi. 1-4.

1949a. Zur Nomenklatur der Clymenien (Cephalop., Ammon.). Neues Jb. Miner. Geol. Palaont.

Mh. 7, 64-76.

19496. Zur Phylogenie der Clymenien (Cephalop., Ammon.). Ibid. 7, 197-209.

1955. Zur Taxionomie und Nomenklatur der Clymenien. Ein Epilog. Ibid. 10, 417-29.

Sedgwick, A. and mccoy, F. 1851-5. A synopsis of the classification of the British Palaeozoic rocks with
a systematic description of the British Palaeozoic fossils in the Geological Museum of the University
of Cambridge, xcviii+iv+viii+661 pp., 25 pi.

sobolew, d. 1914a. Skizzen zur Phylogenie der Goniatiten. Izv. varshav. politekh. Inst. 192 pp., pi. 1-9
(a Russian translation is dated 1913).

* 19146. Uber Clymenien und Goniatiten. Palaont. Zeit. 2, 1, 248-378, pi. 8-9.

turner, J. s. 1962. The type species of Aganides, Clymenia and Cyrthoceratites. Geol. Mag. 99, 183, 4.
wedekind, r. 1908. Die Cephalopoden fauna des hoheren Oberdevon am Enkeberge. Neues Jb. Miner.
Geol. Palaont. 26, 565-634, pi. 39-15.

1914. Monographic der Clymenien des Rheinischen Schiefergebirges. Abh. K. Ges. Wiss. Gottingen,

N.F. 10, 1-73, pi. 1-7.

woodward, s. P. 1851-56. A manual of the Mollusca\ or a rudimentary treatise of recent and fossil shells.

xvi+486 pp., 24 pi. London.
wurm, A. 1961. Geologie von Bayern. 556 pp. Berlin.

m. r. house

Department of Geology
The University
Kingston upon Hull

Typescript received 15 April 1970 Yorkshire

THE TRILOBITES INCAIA WHITTARD 1955 AND
ANEBOLITHUS GEN. NOV.

by c. P. hughes and a. j. wright

Abstract. The restudy of British and Peruvian type material together with new material from New Zealand has
led to the revision of Incaia and to the belief that it represents a distinct trinucleid stock, known at present only
from Peru and New Zealand, for which the subfamily Incaiinae is erected. The British species ‘ Incaia ’ simplicior
Whittard is excluded from the genus and is proposed as the type of Anebolithus gen. nov.

As part of a more general study of the Trinucleidae at present being undertaken by
Hughes, the Peruvian type material of Incaia and British material previously attributed
to the genus have been re-examined. Study of a new species of Incaia from New Zealand
recently recognized by Wright yields data needed to characterize the genus more fully.
Whittard (1966, pp. 273-4, text-fig. 9) believed that British material from the Shelve
region was congeneric with Incaia nordenskioeldi (Bulman 1931) but the present study
shows this not to be so. ‘ Incaia ’ simplicior Whittard from the Arenig ( Didymograptus
hirundo Zone) of the Shelve Inlier in the Welsh Borderland is proposed as the type
species of Anebolithus gen. nov.

Incaia is no longer thought to be closely allied to the Trinucleinae and it is believed
that it represents a distinct, possibly primitive, trinucleid stock known at present only
from South America and New Zealand.

SYSTEMATIC DESCRIPTIONS

Terminology. The terminology applied throughout is essentially that proposed in the Treatise, Part O
(Harrington, Moore, and Stubblefield 1959). However, the term ‘arc’ (referring to the pits on the
trinucleid fringe, e.g. Ex arc) is here preferred to Bancroft’s (1929) term ‘concentric row’ (see also
Hughes 1970).

Family trinucleidae Hawle and Corda 1847
Subfamily incaiinae subfam. nov.

Remarks. The small number of arcs, with pits arranged in radial sulci, combined with
the development of large lateral eye tubercles, characterize this monotypic subfamily.

Genus incaia Whittard 1955

Diagnosis. Incaiinae with semicircular cephalon; simple, narrow fringe with no pits
external to the girder; pits of internal series consist of two or three arcs with pits sunk
in radial sulci. Glabella typically trinucleid, pyriform and with three pairs of lateral
glabellar furrows ; no median node. Genal regions with prominent eye tubercles situated
close to axial furrows and approximately opposite mid-point of glabella. Genal spines
relatively short extending posteriorly a distance equal to the cephalic length. Thorax
typically trinucleid. Pygidium relatively long, being only about two and a quarter times
as wide as long; pleural fields faintly furrowed; axis well segmented.

[Palaeontology, Vol. 13, Part 4, 1970, pp. 677-90, pis. 127-128.]

678 PALAEONTOLOGY, VOLUME 13

Type species. Trinucleus nordenskioeldi Bulman, 1931.

Distribution. The type species is from the Upper Llanvirn of SE. Peru. The only other known occur-
rence of the genus is from the Caradoc ( Nemagraptus gracilis Zone) of New Zealand.

Discussion. In 1955 Whittard, working only from Bulman’s figures, believed that ‘7V
nordenskioeldi was unique in that it possessed a glabella probably without lateral
furrows, large eye-tubercles close to the axial furrows and a simple fringe consisting
essentially of only two arcs which Whittard interpreted as ‘presumably representing
Ex and Ix\ Following the discovery of trinucleids in Shropshire possessing very simple
fringes with the girder external to all the pits, Whittard examined the type specimens of
Incaia nordenskioeldi. He then modified his earlier views regarding the position of the
girder, stating (1966, p. 273) that ‘there is no indication of a girder separating external
from internal series of pits, although the preservation is such that if a girder existed it
should be observable; furthermore, in all cases, I^2 occur in close association in sulci,
and it would be unreasonable to separate them into Ej and Ix ; finally, surrounding the
fringe there is a peripheral tumid border or rolled margin which clearly resembles the
peripheral girder of Myttonia.’’ Whittard thus clearly believed that in /. nordenskioeldi
the girder was external to all the pits.

The present study has reaffirmed Bulman’s statement (1931, p. 86) that all the material
of I. nordenskioeldi consists of internal and external moulds of cranidia with upper
lamella, and that no specimens are known with the lower lamella preserved. It is thus
a little difficult to understand Whittard’s categorical remarks concerning the existence
and position of the girder. He apparently believed that the absence of any structure
between the two arcs on the upper lamella which might correspond to a girder on the
lower lamella, indicated that there was no such girder. Whilst arcuate structures are
commonly developed on the upper lamella between the various arcs, these need not
correspond to the position of the girder on the lower lamella in any way [for example
in Cryptolithus (see Whittington 1968, pi. 89, figs. 1, 2)]. Furthermore, the absence of any
such arcuate structures on the upper lamella need not mean that a girder is absent (for
example in Trinucleus and Stapeleyella). The other evidence cited by Whittard as sup-
porting his claim of a peripheral girder is also inconclusive. Although the pits of the two
main arcs are fairly close together there is ample space for a girder to be developed between
them. The so-called ‘tumid border or rolled margin’ referred to by Whittard is simply
a slightly convex marginal rim (PI. 127, fig. 7). Although not unlike that developed in
Myttonia, this rim is of little significance as similar rims are present in many trinucleids
[for example Cryptolithus and Salterolithus (see Whittard 1958, pi. 10, fig. 1, pi. 12,
fig. 3)]. Thus it is believed neither position nor existence of the girder is determinable
from the type material. In the New Zealand species described below the lower lamella is
known and the girder is, in fact, positioned external to both the arcs of pits. Since the
cephalon of this new species is so similar to that of I. nordenskioeldi it is here considered
that they are congeneric, and that the girder in /. nordenskioeldi is probably peripheral.

The affinities of Incaia are rather uncertain. Whittard, who did not attach any great
importance to the presence of lateral eye tubercles, believed Incaia to be intermediate
between Myttonia and Lordshillia, possessing the peripheral girder of Myttonia and
the ordered radial arrangement of the fringe pits of Lordshillia. The present authors,
however, believe the development of lateral eye tubercles (a feature absent in the

HUGHES AND WRIGHT: TRILOBITES

679

majority of trinucleids), together with the fringe characteristics, is of considerable
generic importance, and it is held that Incaia is in no way closely related to the early
Ordovician trinucleids of the Welsh Borderland. Of trinucleids known from other parts
of South America and Australasia, none shows any apparent close affinity to Incaia.
Of these forms, however, the majority are very different from those known from the
rest of the world, e.g. Famatinolithus, Guandacolithus (Harrington and Leanza 1957),
‘ Cryptolithus’ empozadensis (Rusconi 1953), ‘ Onnia ’ verrucosa (Rusconi 1956). From
Australia the only form known in any detail is a new species (Moors MS. 1966)1 from
New South Wales. This species, while exhibiting some similarities in fringe charac-
teristics to Lloydolithus and Protolloydolithus, possesses lateral eye tubercles similar
to those of Incaia.

Thus although our present knowledge is rather scant, it seems possible that many
trinucleids from the present southern hemisphere with lateral eye tubercles may have
evolved in isolation. This would necessitate an isolated stock of trinucleids within the
‘southern province’ of Whittington (1966). Some support for such a concept is given
by some other trilobite groups, notably the thysanopygid asaphids of South America
which also appear to have evolved in isolation. The probable occurrence in the New
Zealand Tremadocian of Pseudohysterolenus (Wright 1968), otherwise known only
from Argentina (Harrington and Leanza 1957), further suggests an early Palaeozoic
‘austral’ faunal province.

The significance of the lateral eye tubercles with reference to the evolution and origin
of the trinucleids is at present uncertain. Orometopus, which has eye tubercles, has often
been quoted as a probable trinucleid ancestor, but this is by no means established.

Incaia nordenskioeldi (Bulman)

Plate 127, figs. 3, 9, Plate 128, figs. 1, 2

1931 Trinucleus nordenskioldi Bulman, p. 85, pi. 11, figs. 2, 3.

1955 Incaia nordenskioldi (Bulman); Whittard, pp. 31-2.

1966 Incaia nordenskioldi (Bulman); Whittard, pp. 273-4, text-fig. 9.

Diagnosis. Incaia having 1^ fully developed with about 16 pits in each arc (half-fringe);
occasional pits of I3 developed, especially posterolaterally; only two or three sulci
present between the mid-line and the axial furrow. Eye tubercles slightly posterior of
glabellar mid-length. Thorax and pygidium unknown.

Type locality and horizon. Upper Llanvirn between Limpucuni and Itchubamba, SE. Peru (see text-fig. 1 ) .

Bulman (1931, pp. 8-10) discussed the probable location of these two places and concluded that
Limpucuni probably lay to the west of San Juan del Oro and that Itchubamba was between Lim-
pucuni and Quiaca. Efforts by the present authors have also failed to discover the exact position of
these places. Map B drawn from information supplied by the Royal Geographical Society shows a
somewhat different relative positioning of some of the places in the area, but it should be noted that
the accuracy of mapping in this area is only to within about 20 minutes both of longitude and latitude.
Maps published at about the time of the Nordenskioeld expedition show one track leading northwards
from Sandia through Ichubamba (note spelling) and another from Quiaca to San Juan del Oro. This
latter one passes through Huichw//uni which may be near Limpucuni (Bulman stated 1931, p. 10,
‘Huich/yuni is said to be near Limpucuni’). It is uncertain whether Ichubamba is equivalent to Itchu-
bamba, but in any case it seems unlikely that the expedition passed through Ichubamba. It is quite

1 A further new trinucleid is now known from New South Wales (see Campbell and Durham, this issue,
pp. 573-80.

680

PALAEONTOLOGY, VOLUME 13

feasible however that they may have made a detour off to the west of the Quiaca-San Juan del Oro
track and made collections on the ridge that runs up between the two tracks mentioned above. Such
collections could then quite well be labelled as ‘between Limpucuni and I(t)chubamba.’ The exact
locality for the type material of I. nordenskioeldi must thus remain uncertain.

Material. Ar. 42445a/b (419, 420); Ar. 42446 (418); Ar. 42447 (366); Ar. 42448 (367). Specimens Ar.
42447 and Ar. 42448 are part and counterpart. Numbers given in brackets are original numbers cited
by Bulman (1931, p. 86).

Dimensions

A

I

K

Ar. 42445 (419)

4-8

c. 110

2-3

Ar. 42446 (418)

4-2

c. 10 3

2-7

Ar. 42447 (366)

5-5

10-6

3-2

All measurements in millimetres. A — maximum sagittal cephalic length; I — maximum transverse
cephalic width ; and K — maximum transverse glabellar width.

Discussion. A full redescription is not deemed necessary until new material becomes
available, but the following points are of note in addition to the comments already
made in the discussion of the genus concerning the position of the girder. All the
known specimens are deformed to some extent and are preserved in a rather soft pinkish-
brown shale. It is thought that this rather indifferent mode of preservation accounts
for the doubtful occurrence of lateral glabellar furrows and it is probable that three
pairs of shallow, typically trinucleid lateral glabellar furrows were developed as are
known in I. bishopi (see below). The rather large, so-called eye tubercles close to the
axial furrows however are consistently developed and it is believed that they represent
some form of lateral eye (PI. 128, fig. 2). This is also supported by the New Zealand
material. As pit counts can be made with any certainty on only three specimens, the
figure of ‘about 16 pits’ in each arc (half-fringe) given in the diagnosis should not be
taken as a truly diagnostic figure. Further specimens almost certainly would indicate
some range in the number of pits developed. Bulman (1931) compared I. nordenskioeldi
with Trinucleus coscinorrhinus; differences noted by Bulman between the species would
now seem to be of generic or even higher significance.

Incaia bishopi sp. nov.

Plate 127, figs. 1, 2, 4-6, 8; Plate 128, figs. 3, 4, 6-14; text-fig. 3

Diagnosis. Incaia with fully developed in radial sulci with approximately 23 pits
(half-fringe) ; about 8 sulci between axial furrows; I3 pits not known with certainty, no

EXPLANATION OF PLATE 127

Figs. 1, 2, 4-6, 8. Incaia bishopi sp. nov. All specimens from scree material, Paturau River, New
Zealand, locality S3/526, grid ref. 907010 1, Internal mould, VA5a x3. 2, Dorsal surface
of cranidium showing caecae, latex cast, DC350b x 3. 4, Dorsal surface of fringe, latex cast of
holotype, VA6b x5. 5, Internal mould, VA4a x3. 6, Ventral surface of fringe, latex cast of
holotype, VA6a x 4. 8, Internal mould showing three lateral glabellar furrows, VA7 x 4.

Figs. 3, 9. Incaia nordenskioeldi (Bulman). All specimens from Upper Llanvirn between Limpucuni
and Itchubamba, SE. Peru. 3, Internal mould, Ar. 42446 x 6. 9, Internal mould of holotype, Ar.
42445a x6.

Figs. 7, 10. Anebolithus simplicior (Whittard). Specimen from Mytton Flags, (Arenig), small quarry
160 yd. N. 35° E. of Snailbeach Reservoir, Shropshire, England, grid ref. SJ 377023. 7, Lateral
view, 10, Dorsal view of internal mould, holotype GSM102178 x6.

Palaeontology, Vol. 13

PLATE 127

HUGHES and WRIGHT, Incaia and Anebolithus

text-fig. 1. a. Map showing the area of SE. Peru from which Incaia nordenskioeldi (Bulman) was
collected, together with its general position in western South America (inset) ; redrawn from Bulman
1931, text-figs. 1, 2. b. Map drawn from information supplied by the Royal Geographical Society.

682

PALAEONTOLOGY, VOLUME 13

E arcs developed ; 3 pairs of lateral glabellar furrows ; median node absent ; lateral eye ■
tubercles located at mid-length of cephalon, close to axial furrows ; genal caecae some-
times developed. Pygidium with up to 5 weakly developed pleural ribs; up to 16 axial j
rings.

Localities and material.

S3/526 (Collections GS9504, VI 593) Type locality. Scree material, Paturau River. Grid ref. 907010
(909012). Specimens VA4-18, 20-4, 26-72, 74-7, 84, 88-115, 118-20, DC350-2, 354-7.

S3/527 (Coll. GS10209) River boulder, Paturau River, Grid ref. 912024 (912024) (Not 899025 as 1
Cooper [1968, p. 79] stated) Spec. DC358.

S3/552 (Coll. V2710) Scree material, Higgins Branch (tributary of Paturau River). Grid ref. 907971 I
(909969). Specs. VA78-80, 87.

S3/553 (Coll. V2715) River boulder, Paturau River. Grid ref. 908012 (910015) Specs. VA19, 81-3, |

85-6, 121.

S3/554 (Coll. V2716) Scree material, Paturau River. Grid ref. 905006 (907008). Spec. VA73.

All 1. bishopi material is deformed tectonically, and fine morphological features (such as posterior j
pygidial axial rings and lateral glabellar furrows) are often obliterated. S3 is the Collingwood sheet of ij
the N.Z. 1:63360 map series. Grid references are taken from the second edition (1967); grid references
in brackets are taken from the 1945 edition. Numbers 526, etc., refer to collection or locality numbers jj
on that sheet.

Horizon. Bishop (1965) described the type locality (S3/526) where Nemagraptus gracilis is now known
to occur (R. A. Cooper pers. comm.), indicating an early Caradoc age. Bishop (1969) proposed the
name Golden Bay Group for strata in which all Incaia bishopi localities occur (see also Bishop, in
press).

Type material. Specimen VA6 (counterparts a and b) is here selected as holotype. Paratypes which
are not topotypes are: VA19, VA73, VA78-83, VA85-7, VA121, DC358.

Description. Cephalon semicircular, tending to be relatively wider and more rectangular
in smaller specimens (VA65) (see text-fig. 4 and Table 1). Glabella typically trinucleid,
being pyriform with hemispherical pseudofrontal lobe, maximum width varying from
about one-quarter the cephalic width in small specimens to about one-third in larger
individuals (see text-fig. 5). Three pairs of lateral glabellar furrows are developed;
posterior pair (VA4, 5, 23, 24) transverse, shallow, constricting the glabella just an-
terior of the broad, shallow occipital furrow to form a prominent occiput; median

EXPLANATION OF PLATE 128

Figs. 1, 2. Incaia nordenskioeldi (Bulman). Both specimens from Upper Llanvirn between Limpucuni
and Itchubamba, SE. Peru. 1, Internal mould, Ar. 42447 x6. 2, Latex cast of holotype, Ar.
42445b X 6.

Fig. 5 llncaia bishopi sp. nov. From scree material, Paturau River, New Zealand, locality S3/526 grid,
ref. 907010. Fringe fragment, VA25 x 8. Orientation uncertain.

Figs. 3, 4, 6-14. Incaia bishopi sp. nov. All from scree material, Paturau River, New Zealand, locality
S3/526 grid. ref. 907010 with the exceptions of VA19 and VA121 (figs. 4, 8) which are from a river
boulder, Paturau River, New Zealand, locality S3/553 grid. ref. 908012. 3, Ventral surface of
fringe fragment showing genal spine, latex cast VA14a x 4. 4, Dorsal surfaces of two pygidia,
upper specimen VA19b, lower VA121, latex cast, x4. 6, Internal mould of pygidium, VA8a x 3.
7, Internal mould of pygidium, VA2 la x4. 8, Internal mould of pygidium, VA19a x4. 9, Internal
mould of glabella showing reticulate ornamentation, VA81 x5. 10, Internal mould of pygidium,
VA9a x 3. 1 1, Dorsal surface of pygidium, latex cast. DC351b x 3. 12, Internal mould of pygidium,
VA10 x4. 13, Internal mould of pygidium, VA 11 x3. 14, Internal mould of pygidium, VA20a x 4.

Palaeontology, Vol. 13

PLATE 128

HUGHES and WRIGHT, Incaia from Peru and New Zealand

684

PALAEONTOLOGY, VOLUME 13

glabellar furrows just posterior to mid-length of glabella, developed as small shallow
rounded depressions; anterior furrows (VA7, PI. 127, fig. 8) simply small rounded pits.
Axial furrows deep anteriorly, with well-developed apodemal pits, shallowing and
widening posteriorly. Genal regions moderately convex with simple curving caecae
preserved on some specimens (e.g. DC350, PI. 127, fig. 2; VA26). Eye tubercles pro-
minent in all specimens as slightly elongated (exsag.) (VA4, PI. 127, fig. 5; VA22)
ridges located immediately outside the axial furrows at about mid-length of the cephalon.

text-fig. 3. Reconstruction of Incaia bishopi sp. nov. in dorsal
view; surface ornamentation omitted. Magnification c. x2-5.

Posterior margin straight, border furrow broad and very shallow laterally, merging
axially with axial furrows. No occipital spine present.

Fringe slightly convex, with a smooth, weakly concave rim. Width up to 2 mm.
(exsag.) anteriorly being at a maximum in front of apodemal pits; laterally fringe be-
comes more steeply declined and narrower. Pits confined to radial sulci which are about
as wide and rounded as the intervening ridges. Sulci radially arranged except medially
where they are locally divergent (VA5, PI. 127, fig. 1 ; VA65). Approximately 23 pits of
arcs I]_2 are developed on each half-fringe, the two arcs being separated in sulci of the
upper lamella by a low rounded ridge which is only very weakly manifested on the
intervening ridges and becomes weaker laterally. One poorly preserved specimen
(VA65) anteriorly exhibits what may be I3 pits, but relatively well-preserved specimens
(e.g. VA5, 8, 64, DC350) clearly lack such pits. Minor irregularities (perhaps due to
tectonic deformation) are present in some specimens (VA30, 73) in the development of

HUGHES AND WRIGHT: TRILOBITES

685

short sulci with only one pit, or a twin pit, developed. Ventral side of lower lamella with
angular girder inclined at about 15° to the horizontal (VA6, 15), possessing sparse
terrace-lines. Girder continued along the genal spines as an angular ventral edge.
Dorsal edge of genal spines, which extend posteriorly for a distance approximately
equal to the length of the remainder of the cephalon, is also angular, giving an approxi-
mately rhomboidal cross-section. Ventral edge of lower lamella does not lie in a plane ;

table I. Table of the width-length ratios for three cephala and two pygidia of Incaia bishopi sp. nov.,
both before and after correction by the use of Wellman’s method (Wellman 1962). All measurements

in millimetres.

Specimen No.

Original (deformed)
Dimension (mm.)

Uncorrected W=L

Corrected W=L

VA 5 (cephalon)

19- 0

1 1-0

1-73 s 1

213 : 1

DC 350 (cephalon)

250

10-5

2-38 : 1

1341

DC 352 (cephalon)

6-8

40

1-70 :|

2-95 = 1

VA 1 12 (pygidium)

101

5-2

1-94 : 1

2-42=1

DC 351 (pygidium)

20-4

6-3

3-24 : 1

1-77 = 1

preglabellar edge and genal flange are relatively dorsally elevated but posterior portion
of genal spine approximately coplanar with the rest of the girder (VA6) (see Stormer
1930, p. 106). Suture line apparently intra-marginal except postero-laterally where it
becomes dorsal (VA6, 29, 30) cutting across the genal spine without isolating any pits.

External surface of glabella ornamented with a fine reticulate pattern of delicate
ridges (VA63; VA81, PI. 128, fig. 9). Pleural lobes of some pygidia bear fine, close-set
pits (see PI. 128).

Hypostoma unknown.

Thorax typically trinucleid with six segments (VA4, PI. 127, fig. 5; VA5, PI. 127, fig. 1 ;
VA16). Axis about one-quarter of total width. Anterior half-ring elevated; axial furrows
deep. Pleurae flat, deflected ventrally and posteriorly distally. Pleural furrow expanded
laterally, commences near the antero-median angle of pleurae.

Pygidium varies in shape from obtusely sub-triangular (e.g. VA8, PI. 128, fig. 6) to
semi-elliptical (e.g. VA9, PI. 128, fig. 10). Much of this shape variation however is
thought to be due to deformation, and it seems likely that undeformed pygidia were
generally slightly more than twice as long as wide, with the smaller individuals being
relatively slightly longer (see text-fig. 6). The two pygidia to which Wellman’s ingenious
method (Wellman 1962) was applied, however, appear to indicate an opposite trend (see
Table 1) (see also discussion of biometric data, p. 686). Anterior margin not quite

686

PALAEONTOLOGY, VOLUME 13

straight, each side being slightly deflected posteriorly. An elongate triangular anterior
border is delimited on each pleural lobe by an angular furrow extending from in front
of the anterior axial ring and becoming deeper laterally (VA9, PI. 128, fig. 10; VA19,
PI. 128, fig. 4). Curvature of postero-lateral margins varies with outline, having a more
curved margin in sub-triangular specimens. Axis slightly more convex (tr.) than the
moderately convex pleural lobes which bear a fine reticulate ornament. Axis varies
from one-quarter to one-fifth of width of pygidium, tapers posteriorly to merge into the
deflected margin as a broad low swelling. Twelve or thirteen axial rings generally

table 2. Bivariate statistics for the type sample of Incaia bishopi sp. nov. A — maximum sagittal cephalic
length; B — maximum sagittal glabellar length; I — maximum transverse cephalic width; W — maximum
transverse pygidial width; Z — maximum sagittal pygidial length. Measurements are in millimetres.

x:y

X

var. x

y

var. y

r

re

a.

var. a

a

var. a

n

I:B

16-17

22-966

4-67

2-966

0-93

0-93

1-23

0-0490

0-36

0-0044

6

I: A

15-37

19-697

819

7-496

0-91

0-91

1-15

0-0361

0-62

0-0109

8

W:Z

12-12

21-768

5-40

3-554

0-78

0-79

0-91

0-0526

0-40

0-0108

8

present, up to a maximum of sixteen (VA8, PI. 128, fig. 6; YA11, PI. 128, fig. 13);
inter-ring apodemal pits developed between anterior eight rings. Axial furrows
prominent anteriorly, becoming broader, shallower, and more rounded posteriorly.
Pleural lobes have up to three to five weakly developed, flat-topped ribs convexly
curved anteriorly. Declined border is deepest medially, becoming steeper and lower
antero-laterally, terrace-lines present.

Biometrical data. Sufficient data are available for some selected bivariate analyses to
be made. Text-figs. 4-6 give plots of the selected parameters, the various bivariate
statistics being given in Table 2.

The use of standard bivariate techniques on such distorted material is justifiable
provided there was no (primary) current or other orientation of the fossils. However,
with tectonically distorted fossils it is impossible to be certain that the (undistorted)
material had a random two-dimensional distribution. Therefore this must be assumed.
The validity of the statistical approach depends partly on this assumption; it is further
assumed that the attitude of the regression line is not affected by the deformation. The
small number of specimens may contribute to an erroneous result in the statistical
technique (Table 2) as well as the graphic technique (Table 1). Only two bedding
surfaces were suitable for study by Wellman’s (1962) method in bearing more than
one specimen. The lack of agreement between results from the two methods does not
indicate where errors occur.

Discussion. This species is of interest as it provides confirmation of the presence of the
lateral eye tubercle in Incaia and the position of the girder, as well as showing details of
the glabella, thorax and pygidium. I. bishopi differs from /. nordenskioeldi in that it
has considerably more sulci medially in front of the glabella (i.e. between the extensions
of the axial furrows). Furthermore in I. nordenskioeldi the lateral eye tubercle appears
to be slightly more posteriorly placed.

HUGHES AND WRIGHT: TRILOBITES

687

maximum transverse cephalic width in mm.

text-fig. 4. Plot of maximum transverse cephalic width against maximum sagittal cephalic
length. • — I. bishopi sp. nov. ; A — I. nordenskioeldi (Bulman). Encircled points indicate that
at least one of the measurements is approximate. All data for I. bishopi is from topotypic
material (S3/526, see p. 682).

£

E

o

E

maximum transverse cephalic width in mm.

text-fig. 5. Plot of maximum transverse cephalic width against maximum transverse glabellar
width. • — I. bishopi sp. nov. ; A — I. nordenskioeldi (Bulman). Encircled points indicate that
at least one of the measurements is approximate. All data for 7. bishopi is from topotypic
material (S3/526, see p. 682).

Yy

C 7719

688

PALAEONTOLOGY, VOLUME 13

E.

3

E

o

E

®

10 15 20

maximum transverse pygidial width in mm.

text-fig. 6. Plot of maximum transverse pygidial width against maximum sagittal pygi-
dial length for I. bishopi sp. nov. ; all data from topotypic material (S3/526, see p. 682).
Encircled points indicate that at least one of the measurements is approximate.

llncaia bishopi sp. nov.

PI. 128, fig. 5

Locality and material. Specimens VA25, 116, 117 and DC353 from locality S3/526 (see p. 682).
Horizon. As for I. bishopi (see p. 682).

Discussion. These four specimens, all fragmental fringe casts, differ from I. bishopi in
having at least three arcs of pits developed. The best of these specimens (VA25, PI. 128,
fig. 5) is of the same order of size as a cephalon of 7. bishopi such as YA17 or 65 which
almost certainly possess only 2 arcs. However it is known that trinucleid species may
exhibit variations in the fringe which may or may not be linked to different growth
stages. Thus these specimens of isolated casts of fringe fragments cannot conclusively
be said to belong to or differ from 7. bishopi. No girder is discernable on any of these
specimens.

Subfamily trinucleinae Hawle and Corda 1847
Genus anebolithus gen. nov.

PI. 127, figs. 7, 10

Diagnosis. Cephalon semicircular with simple, narrow fringe with no pits external to
the girder; pits of internal series consist of three arcs with pits sunk in radial sulci.
Glabella typically trinucleid, pyriform with three pairs of lateral glabellar furrows;
median node present. No eye tubercles developed on genal regions. Thorax typically
trinucleid. Pygidium about four and a half times as wide as long, pleural fields faintly
furrowed anteriorly, axis segmented.

Type species. Incaia simplicior Whittard 1966.

HUGHES AND WRIGHT: TRILOBITES

689

Type locality and horizon. Small path-side quarry in northerly trending valley 160 yd. N. 35° E. of
the north-eastern corner of Snailbeach Reservoir, Shropshire, England (grid ref. SJ 377023) ; Mytton
Flags, Arenig ( Didymograptus extensus Zone) about 2000 ft. above Stiperstones Quartzite.

Distribution. The genus at present is restricted to the type species. However, a further occurrence of
the genus is shortly to be described from the lower Llanvirn of the Builth-Llandrindod Inlier (Hughes
1971).

Discussion. Although the details of the fringe are similar to Incaia, the lack of large
lateral eye tubercles and the presence of a median glabellar node together with other
minor morphological features (for full description of morphology see Whittard 1966,
pp. 274-6) suggest that Anebolithus is closely related to the other Trinucleinae of the
Welsh Borderland, e.g. Bergamia, Stapeleyella, and not to Incaia. The combination of
peripheral girder and radially disposed pits warrants the erection of Anebolithus , which
appears to be in an evolutionary series between Myttonia, with marginal girder but
irregular pits, and Lordshillia with radially arranged pits but with one arc external to
the girder.

Acknowledgements and abbreviations. One of us (C. P. H.) is grateful to Dr. V. Jaanusson of the Swedish
State Natural History Museum, Stockholm for kindly loaning the type specimens of Incaia. His
thanks are also due to Professor H. B. Whittington and Dr. A. W. A. Rushton for much helpful dis-
cussion, and to the Institute of Geological Sciences, London for the loan of Whittard’ s original material.

Sincere thanks are extended by Wright to the following : D. G. Bishop of the New Zealand Geological
Survey who discovered the initial I. bishopi locality (S3/526), encouraged work on the fauna and guided
Wright to the locality; Dr. R. A. Cooper, N.Z.G.S., who assisted with collecting, provided the deter-
mination of Nemagraptus gracilis from locality S3/526 and, with W. M. Briggs, Jr., assisted with
photographic equipment; Dr. C. A. Fleming who made the N.Z.G.S. collections available for study;
Victoria University students who assisted in collecting; E. F. Hardy who drafted text-fig. 2. Field
work by Wright was supported by grants, from Victoria University of Wellington and the New
Zealand Universities Grants Committee, which are gratefully acknowledged.

Both authors would like to extend their thanks to Mr. John Lewis for his skill in preparing the text-
figures other than text-fig. 2.

All relevant specimens are referred to by individual numbers; suffixes a or b indicate counterparts;
prefixes denote collection in institutions where material is housed, as follows :

Ar. — Swedish State Natural History Museum, Stockholm.

DC — New Zealand Geological Survey, Lower Hutt.

VA — Geology Department, Victoria University of Wellington, Wellington.

GSM — Institute of Geological Sciences, London.

A copy of all the original measurements made on specimens is lodged with each of the first three of
the above institutions together with a further copy in the Geological Society, London.

REFERENCES

Bancroft, b. b. 1929. Some new species of Cryptolithus, (s.l.), from the Upper Ordovician. Mem. Proc.
Manchr. lit. phil. Soc. 73, 67-96.

bishop, d. g. 1965. Two new Palaeozoic fossil localities in northwest Nelson. N.Z. Jl Geol. Geophys.
8, 1232-3.

1969. S2 Kahurangi (1st edition) ‘Geological map of New Zealand’ 1:63360. Department of

Scientific and Industrial Research, Wellington, New Zealand.

■ (in press) S3 Collingwood (1st edition), ibid.

bulman, o. m. b. 1931. South American graptolites with special reference to the Nordenskiold collec-
tion. Ark. Zool. 22A (3) 1-111.

cooper, r. a. 1968. Lower and Middle Paleozoic fossil localities of north-west Nelson. Trans. R. Soc.
N.Z. Geol. 6, 75-89.

690 PALAEONTOLOGY, VOLUME 13

Harrington, h. j. and leanza, a. f. 1957. Ordovician trilobites of Argentina. Dept. Geol. Univ. Kansas,
Spec. Pub. 1. 276 pp. 140 figs.

Harrington, h. J., moore, r. c. and Stubblefield, c. J. 1959. Morphological terms applied to Trilobita.
In moore, r. c. (ed.), Treatise of invertebrate paleontology. Part O. Geol. Soc. Am. and Univ. Kansas
Press, pp. 117-26.

hawle, i. and corda, A. J. c. 1847. Prodrom einer Monographic der bohmischen Trilobiten. 176 pp.,
7 pi. Prague.

hughes, c. p. 1970. Statistical analysis and presentation of trinucleid (Trilobita) fringe data. Palaeonto-
logy, 13, 1-9.

1971. The Ordovician trilobite faunas of the Builth-Llandrinod Inlier, Central Wales, Part II.

Bull. Br. Mus. nat. Hist. (Geol.) (in press).

moors, h. t. 1966. Some of the stratigraphy and palaeontology of the Cliefden Caves District, near
Mandurama. Unpublished M.Sc. thesis, Department of Geology and Geophysics, University of
Sydney, Australia.

rusconi, c. 1953. Trilobitas ordovicicos y cambricos de Mendoza. Bol paleont. B. Aires. (25), 1-8,
figs. 1-10.

1956. Fosiles ordovicicos de la quebrada de los Bueyes, (Mendoza). Revta Mus. Hist. nat.

Mendoza, 9, (1, 2), 2-15, pi. 1.

stormer, l. 1930. Scandinavian Trinucleidae, with special reference to Norwegian species and varieties.
Skr. norske Vidensk-Akad. Mat.-naturv. Kl. 1930, 4, 1-111, pi. 1-14, figs. 1-47.

wellman, h. w. 1962. A graphical method for analysing fossil distortion caused by tectonic deforma-
tion. Geol. Mag. 99, 348-52, pi. 16.

whittard, w. f. 1955. The Ordovician trilobites of the Shelve Inlier, West Shropshire, Part I. Palaeon-
togr. Soc. ( Monogr .) 1-40, pi. 1-4.

1958. The Ordovician trilobites of the Shelve Inlier, West Shropshire, Part III. Ibid. 71-116,

pi. 10-15.

1966. The Ordovician trilobites of the Shelve Inlier, Shropshire, Part VIII. Ibid. 265-306,

pi. 46-59.

Whittington, h. b. 1966. Phylogeny and distribution of Ordovician trilobites. J. Paleont. 40, 696-737.

1968. Cryptolithus (Trilobita): Specific characters and occurrence in Ordovician of eastern North

America. J. Paleont. 43, 702-14.

wright, a. j. 1968. Ordovician conodonts from New Zealand. Nature, 218, 1232-6.

c. p. hughes
Department of Geology
Sedgwick Museum
Cambridge, CB2 3EQ

A. J. WRIGHT

Geology Department
Victoria University of Wellington

P. O. Box 196
Wellington, New Zealand
Present address:
Department of Geology
Oregon State University
Corvallis, Oregon 97331
U.S.A.

Typescript received 26 February 1970

THE PALAEONTOLOGICAL ASSOCIATION

Annual Report of the Council for 1969-70

Membership. On 31 December 1969 there were 1257 members (717 Ordinary, 111 Student, and 429
Institutional). The net decrease of 73 members since last year is largely explained by the transfer of
Institutional Members to Blackwell’s agency, resulting in greater financial benefit to the Association.
The number of subscriptions through the agency was 282, a net increase of 24 on last year’s figure.

Finance. During 1969 the Association published Palaeontology in four parts at a cost of £9286.
Volume 2 has been reprinted at a cost of about £1200, of which £449 has been paid. Special Papers 4
and 5 have been published and Special Paper 6 is in the press; the total cost of these will be about
£2400 of which £1235 has been paid. Administration costs have been slightly higher than usual, but
relative to costs of printing have remained small. Good sales of Special Paper 2 enabled the Associa-
tion to repay £552 of the £1000 loan from the Royal Society.

Although the Association only published four parts of Palaeontology in 1969 against five parts in
1968, total expenditure rose to £11740, slightly higher than even last year’s record level. Each part of
Palaeontology is costing about £300 more than it was two years ago. Income from subscriptions
has fallen slightly, and subscriptions in 1969 only covered 70% of the cost of publishing Palaeontology.
However, regular sales plus subscriptions paid in arrear covered the other 30%.

Total income in the year was higher than ever because of good sales of Palaeontology and Special
Papers, and exceeded expenditure by £2127. This has been added to the Publications Reserve which
stands at £11650. This would be sufficient to publish one volume of Palaeontology even after provision
has been made for the payment of Special Papers in the press. The maturity of £200 5% Defence Bonds
and the increased Publications Reserve have enabled the Association to increase and diversify their
investments.

Sales of Special Papers have been encouraging. There are now 154 regular subscribers, and the
earlier numbers have continued to sell well. However, we are still dependent on donations in order to
cover the initial costs of printing Special Papers and the Association is indebted to: the Shell Oil
Co. for a fourth grant of £250 for Special Papers-, the Hebrew University of Jerusalem for a donation
of £540 towards the cost of No. 4; the Esso Oil Co. for a donation of £328 towards the cost of No. 5;
and the Victoria University of Wellington, New Zealand for a donation of £100 towards the cost of
No. 6.

Publications. The four parts of Volume 12 of Palaeontology were published during 1969; they con-
tained 41 papers and consisted of 718 pages and 130 plates. Special Papers in Palaeontology 4, 5, and 6
(for 1969) were published; they contain a total of 209 pages and 34 plates.

Meetings. Five meetings took place during 1969-70. The Association is grateful to the Council of
The Geological Society of London, the Director of the British Museum (Natural History), Professor
D. T. Donovan (University College, London), and Professor F. W. Shotton (University of Birmingham)
for generously granting facilities for meetings, to Dr. L. R. M. Cocks for leading the field meeting, and
to the local secretaries for their efficient services.

a. The Twelfth Annual General Meeting was held in the rooms of the Geological Society of London,
Burlington House, London W. 1, on Wednesday, 5 March 1969, at 5.00 p.m. The Annual Report
of the Council for 1968-9 was adopted and a ballot was held for the election of the Council for
1969-70. Dr. Pamela L. Robinson of University College, London, delivered the Twelfth Annual
Address on ‘Problems in the study of Triassic vertebrates’.

b. A Field Demonstration Meeting was held on ‘Some Llandovery brachiopod localities in Shrop-
shire’, on 3 May 1969; the meeting was organized by Dr. L. R. M. Cocks.

c. A Demonstration Meeting on ‘Micropalaeontology’ was held in conjunction with the 11th Euro-
pean Micropalaeontological Colloquium at the British Museum (Natural History) on Saturday,
20 September 1969 at 2.00 p.m. Dr. C. G. Adams was local secretary.

692

PALAEONTOLOGY, VOLUME 13

d. A Special Discussion Meeting on a ‘Proposal for an archive of palaeontological data’ was held
at University College, London, on Wednesday 5 November 1969 at 2.00 p.m. The local secretary
was Professor D. T. Donovan.

e. A Symposium on ‘The occurrence and preservation of fossils’ was held in the Geology Department,
University of Birmingham, from Tuesday to Thursday, 16-18 December 1969. About 85 persons
attended to hear fourteen papers and to see fourteen demonstrations. Dr. I. Strachan was local
secretary.

Council. The following were elected members of Council of the Association for 1968-9 at the Annual
General Meeting on 5 March 1969: President : Professor Alwyn Williams, F.R.S. ; Vice-Presidents:
Dr. W. S. McKerrow, Dr. C. Downie; Treasurer: Dr. J. M. Hancock; Membership Treasurer: Dr. A. J.
Lloyd; Secretary: Dr. W. D. I. Rolfe; Editors: Mr. N. F. Hughes, Dr. Gwyn Thomas, Dr. I. Strachan,
Professor M. R. House, Dr. R. Goldring; Other members: Dr. F. M. Broadhurst, Dr. L. R. M. Cocks,
Dr. C. B. Cox, Mr. D. Curry, Dr. A. Hallam, Dr. Julia A. E. B. Hubbard, Dr. J. D. Hudson, Dr. W. J.
Kennedy, Dr. J. D. Lawson, Dr. E. P. F. Rose, Dr. C. T. Scrutton, Dr. V. G. Walmsley, Professor
H. B. Whittington.

Circulars. Four Circulars (Nos. 57-60), containing full details of the affairs of the Association, were
distributed to Ordinary and Student Members during the year, and to Institutional Members on
request.

BALANCE SHEET AND ACCOUNTS
FOR THE YEAR ENDING 31 DECEMBER 1969

Liabilities £ s. d.

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Provision for cost of publication of Palaeontology, Vol. 12,

as per Income and Expenditure Account . . . 9286 4 5

Less Expenditure incurred to 31 December 1969 . . 5764 4 5

Sundry creditors

Assets

£

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d.

Office Equipment at cost ......

41

18

2

Less depreciation to date ......

25

18

2

Investments at cost

Equities Investment Fund for Charities — 1403 units

1798

2

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1500

0

0

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3000

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2000

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1073

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751

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202

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Deposit Account .......

119

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Current Account — Sheffield

2628

13

2

„ „ London .....

-

-

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£ s. d

12 420 17 8

448 0 0

213 19 0

3522 0 0

19 19 0

£16 624 15 8

£ s. d.

16 0 0

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Report of the Auditors to the Members of The Palaeontological Association. We have examined the
above Balance Sheet and annexed Income and Expenditure Account which in our opinion give re-
spectively a true and fair view of the state of the Association’s affairs as at 31 December 1969 and of its
income and expenditure for the year ended on that date.

Thorton Baker & Co.

Chartered Accountants, Auditors

694 PALAEONTOLOGY, VOLUME 13

Income and Expenditure Account
FOR THE YEAR ENDED 31 DECEMBER 1969

£

s.

d.

£

s.

d

Expenditure

To Provision for the cost of publication of Palaeontology, Vol. 12

Part 1

2299

13

1

Part 2

2386

11

4

Part 3

2300

0

0

Part 4

2300

0

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9286

4

5

Add Extra costs

Vol. 11, Part 5

293

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9579

17

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Less Overprovision — Volume 11, part 4

29

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9 550

7

5

Reprinting back issues ......

1 463

0

8

Administrative expenses

Postage and stationery

270

5

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Audit Fee ........

19

19

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Duplicating and dispatch of circulars ....

259

11

6

Meeting expenses .......

26

1

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Sundries

77

2

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Membership Treasurer — Honorarium

52

10

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705

9

5

Depreciation of equipment ......

6

0

0

Excess of Income over Expenditure for the year, transferred to

Publications Reserve Account .....

2897

16

0

£14 622 13 6

12 420 17 8

£12 420 17 8

To Balance as per Balance Sheet

THE PALAEONTOLOGICAL ASSOCIATION

695

Income

By Subscriptions for 1969 ....

Subscriptions for 1968 ....

Sales of Publications

Gross Income

Offprints Profit

Premium on Redemption of 5% Defence Bonds
Investment Income (gross)

5% Defence Bonds

Bank Deposit Account ....
Equities Investment Fund for Charities
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H% National Development Bonds .

7-3/8% Kirkby U.D.C

Foreign and Colonial Investment Trust Ltd.
8% City of Chester Loan
9% Treasury Stock 1994
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Texaco ......

Burmah Oil Co. Ltd

Special Papers

Sales

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By Balance at 31 December 1968

Add Excess of Income over Expenditure
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£ s. d.

6467

9

7

373

10

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4218

10

5

431

2

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50

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0

6

13

9

111

18

5

236

4

1

110

0

0

110

12

6

8

8

8

15

6

10

14

8

9

6

5

0

250

0

0

175

0

0

100

0

0

2147

7

0

667

13

5

165

14

5

2980

14

10

1235

2

0

2897

16

0

-

-

-

£ s. s.

6841 0 4

4649 12 9

60 0 0

669 18 0

46 2 10

525 0 0

1745 12 10

85 6 9

£14 622 13 6

9523 1 8

2897 16 0

£12 420 17 8

INDEX

Pages 1-173 are contained in Part 1 ; pages 175-333 in Part 2; pages 335-510 in Part 3; pages 511-691 in Part 4
Figures in Bold Type indicate plate numbers.

A

Acanthoceras, 462; basseae, 481, 97; rhotomagense,
466, 88, 89; rh. clavatum, 479, 96, 97; rh. confusum,
478, 94, 95; rh. subflexuosum, 469, 90; rh. sus-
sexiensis, All, 89, 91, 92.

Acanthochitina rashidi, 265, 47, 48.

Actinodonta naranjoana, 636.

Algae, calcareous: Mesozoic Tethyan dasyclad, 323;
new British Carboniferous, 443 ; Permian and
Cretaceous Codiaceae from Middle East, 327.

Ammonellipsites, 123; princeps, 124, 26-8; sp. aff.
asiaticus, 124, 27; sp. indet., 127, 26.

Ammonia beccarii, 185, 39.

Ammonoidea: Acanthoceras from Cenomanian of
Rouen, 462; Carboniferous fauna from Cornwall,
112; dimorphic goniatite from Namurian of
Cheshire, 40; origin of clymenids, 664.

Amphibia: see Vertebrata.

Amphipora, 68; 14; angusta, 70, 15; pervesiculatus, 71,
16; ramosa, 69, 15.

Ampullina patula, 46.

Anchicodium sindbadi, 327, 61.

Ancyrochitina merga, 267, 47.

Ancyrodella rotundiloba, 343, 65.

Anebolithus, 688 ; simplicior, 127.

Aphroditicodium, 329; aurantium, 330, 62.

Aporina sp., 310, 54.

Apsotreta expansa, 99.

Arcinella arcinella, 70, 71, 73.

Armstrong, John. Zoarial microstructures of two
Permian species of the bryozoan genus Stenopora,
581.

Arthropoda: Hemicypris from Kenya, 289; xipho-
surid trails, 188. See also Trilobita.

Ash, Sidney R. Dinophyton, a problematical new plant
genus from the Upper Triassic of the south-western
United States, 646.

Australia : new Lower Cambrian trilobite family from
S. Australia, 522; Permian osmundaceous trunks
from Queensland, 10; trinucleid trilobite from New
South Wales, 573.

B

Bacutriletes tylotus, 439, 80.

Baker, P. G. The growth and shell microstructure of
the thecideacean brachiopod Moorellina granulosa
(Moore) from the Middle Jurassic of England, 76.

— The morphology and microstructure of Zellania
davidsoni Moore (Brachiopoda) from the Middle
Jurassic of England, 606.

Balcoracania, 533; daily i, 533, 108-10; flindersi, 535,

109.

Bassett, M. G. Variation in the cardinalia of the
brachiopod Ptychopleurella bouchardi (Davidson)
from the Wenlock Limestone of Wenlock Edge,
Shropshire, 297.

Bate, R. H. A new species of Hemicypris (Ostracoda)
from ancient beach sediments of Lake Rudolf,
Kenya, 289.

Biernat, Gertrude, and Williams, Alwyn. Ultra-
structure of the protegulum of some acrotretide
bachiopods, 491.

Biometry: variation of bivariate characters from
standpoint of allometry, 588.

Bivalvia: dentition and musculature of Ordovician
bivalves, 623 ; evolution of heteromyarian condition
in Dreissenacea, 563; shell structure, mineralogy
and relationships of Chamacea, 379; teredinid
pallets from Palaeocene, 619.

Boueina hochstetteri, 332, 61.

Brachiopoda: growth of thecideacean Moorellina,
76; morphology of Zellania from English Jurassic,
606; ultrastructure of acrotretide protegulum,
491; variations in cardinalia of Ptychopleurella,
297.

Bradshaw, Margaret A. The dentition and muscula-
ture of some Middle Ordovician (Llandeilo) bi-
valves from Finistere, France, 623.

Britain: Carboniferous calcareous algae, 443; epi-
dermal studies of Lepidodendron, 145; fertile Lower
Devonian Rhyniophytina, 451. See also England,
Ireland, Scotland.

Bryantodus biculminatus, 66.

Bryozoa: zoarial microstructure in Stenopora, 581.

C

Calycoceras sp., 89.

Cambrian: new trilobite family from S. Australia,
522; ontogeny of Leptoplastus from Sweden, 100.

Campbell, K. S. W., and Durham, Gwenda J. A new
trinucleid trilobite from the Upper Ordovician of
New South Wales, 573.

Canada: Devonian stromatoporoids from, 64.

Caninia benburbensis, 54.

Caprotina semistriata, 76.

Carboniferous: calcareous algae from Britain, 443;
cephalopod fauna from Cornwall, 112; dimorphic
goniatite from Cheshire, 40; epidermal studies in
Lepidodendron, 145; Orionastraea from N. England,
47 ; sedimentological factors affecting coral growth
and distribution, 191; structure of Cordaites felicis,
29; variation in Caninia, 52; xiphosurid trails from
N. England, 188.

Cardiolaria beirensis, 624.

INDEX

697

Carditcr, beaumonti var. amelliae, 75; distorta, 75;
tenuicosta, 75.

Chama, 387; calcarata, 72, 73; frondosa, 70; haueri,
72- lamellosa, 73; lazarus, 73; macerophylla, 70,
11, 77; pellucida, 70, 71, 73, 74, 77; radians,
73, 74.

Chitinozoa: from Ordovician of Oklahoma, 261.

Chowdhury, T. Roy. Two new dicynodonts from the
Triassic Yerrapalli Formation of Central India,
132.

Cibicides lobatulus, 185, 38.

Cimochelys benstedi, 375.

Ciplyella pulchra, 72.

Classopollis, 3 1 1 , 437 ; aquitanus, 3 1 4, 57 ; teo/ii, 314,
56; caratinii, 315, 56; chateaunovi, 313, 55; harrisii,
437, 79; kieseri, 313, 54, 55; martinottii, 315, 57;
mirabilis, 316, 58; «oc//, 317, 59; pujoli, 315, 58;
quezeli, 312, 54; rarus, 314; 56; simplex, 312, 54.

Clathrochitina sylvanica, 268, 48.

Coelenterata : see Corals, Stromatoporoidea.

Collins, Janice I. The chelonian Rhinochelys Seeley
from the Upper Cretaceous of England and France,
355.

Congeria, 565 ; subglobosa, 565 ; subcarinata botemca,
565; triangularis, 566; zsigmondyi, 565.

Conochitina, 270; cactacea, 272, 49; elegans, 270,

49.

Conodonts: from Devonian of North Cornwall, 335.

Conotreta depressa, 99.

Cooksonia caledonica, 457, 87.

Corals: new Carboniferous Orionastraea, 47; sedi-
mentological factors affecting growth and distribu-
tion of Visean caninioids, 191 ; variation in Caninia
benburbensis, 52.

Cordaites felicis, 29, 9-11.

Cornwall: Carboniferous cephalopod fauna, 112;
Devonian conodonts, 335.

Crassatella grignonensis, 46.

Cretaceous: Acanthoceras from France, 462; cal-
careous algae from Middle East, 327; chelonian
from England and France, 355; stereoscan observa-
tions on Classopollis, 303; Tethyan dasyclad alga,
323.

Curticia minuta, 100.

Cvancara, Alan M. Teredinid (Bivalvia) pallets from
the Palaeocene of North America, 619.

Cyathochitina, 273; agrestis, 273, 50; ontariensis, 274,

50.

Cymaclymenia (?) ornata, 126.

D

Dentition, of Ordovician bivalves, 623.

Desmochitina, 275; minor, 275, 50; scabiosa, 276, 50.

Devonian: conodonts from Cornwall, 335; fertile
Rhyniophytina from Britain, 451; origin of cly-
menid ammonoids, 664; stromatoporoids from
Canada, 64.

Diceras arietum, 76.

Dictyonites perforata, 101.

Dimorphism, in Namurian goniatite, 40.

Dinophyton, 650; spinosus, 651, 122-4.

Di versograptus ? sp., 520, 103.

Dixon, O. A. Variation in the Visean coral Caninia
benburbensis from north-west Ireland, 52.

Dreissena, 564; (£>.) polymorpha, 564; ( Dreissenomya )
aperta, 564.

Durham, Gwenda J. See Campbell, K. S. W.

E

East Africa: new Triassic labyrinthodont from Tan-
zania, 210. ‘

Edwards, Dianne. Fertile Rhyniophytina from the
Lower Devonian of Britain, 451.

Elliott, G. F. Pseudocymopolia, a Mesozoic Tethyan
alga (Family Dasycladaceae), 323.

— New and little-known Permian and Cretaceous
Codiaceae (calcareous algae) from the Middle East,
327.

— Calcareous algae new to the British Carboniferous,
443.

Emuella, 528 ; dalgarnoi, 532, 107 ; polymera, 528, 106,
107, 110.

England: cardinalia of Wenlock brachiopod Ptych-
pleurella, 297; cephalopod fauna from Cornish
Carboniferous, 112, chelonian from Upper Creta-
ceous, 355; conodonts from Cornish Devonian,
335; dimorphic Namurian goniatite, 40; growth
of thecideacean brachiopod, 76; morphology of
Jurassic brachiopod Zellania, 606; Orionastraea
from Lower Carboniferous, 47 ; surface features of
calcareous foraminiferids, 184; turtle from Eocene,
503; xiphosurid trails from Upper Carboniferous,
188.

Eoconulus sp., 101.

Ephippelasma sp., 99.

Eumegalodon cucullatus, 76.

Eumorphoceras\ yatesae, 40, 12; sp., 12.

Euomphaloceras sp., 92.

Euryamphipora, 72; mollis, 73, 16; platyformis, 72,

17.

Eurycephalochelys, 503 ; fowleri, 504, 102.

Evolution, of heteromyarian condition in Dreisse-
nacea, 563.

Exvotarisella maponi, 446, 82, 83.

F

Fabrosaurus australis, 414.

Fenestricardita fenestrata, 75.

Fischbuch, N. R., Amphipora and Euryamphipora
(Stromatoporoidea) from the Devonian of Western
Canada, 64.

Foraminifera : morphologic variability of Schwa-
gerina, 175; surface features of calcareous foramini-
ferids, 184.

France : Acanthoceras from the Cenomanian of Rouen,
462 ; Cretaceous chelonian Rhinochelys, 355 ; denti-
tion and musculature of Ordovician bivalves, 623 ;
feeding habits of Eocene predatory gastropods, 254;
Rhaeto-Liassic flora, 433; stereoscan observations
on Classopollis, 303.

698

INDEX

G

Gastropoda: feeding habits of predatory gastropods,
254.

Gattendorfia sp., 119, 25.

Genuclymenia ; angelina, 126; phillipsi, 126.

Germany: clymenid ammonoids, 664.

Glycimeris rotunda, 597.

Glyptograptus? nebula, 519, 105.

Good, C. W., and Taylor, T. N. On- the structure of
Cordaites felicis Benson from the Lower Pennsyl-
vanian of North America, 29.

Gould, R. E. Palaeosmunda, a new genus of siphono-
stelic osmundaceous trunks from the Upper Per-
mian of Queensland, 10.

Graptolites: fauna of Grieston Quarry, Peeblesshire,
511.

Gymnosperms: Dinophyton, problematical new Tri-
assic genus, 646; Rhaeto-Liassic flora from northern
France, 433; structure of Cordaites felicis, 29.

Gyropleura cenomanensis, 70.

H

Hancock, J. M. See Kennedy, W. J.

Hardy, P. G. New xiphosurid trails from the Upper
Carboniferous of Northern England, 188.

Hayami, I., and Matsukuma, A. Variation of bi-
variate characters from the standpoint of allo-
metry, 588.

Heliosporites reissingeri, 440, 80.

Hemicypris, 290 ;fossulata, 293; megalops, 291 ; ovata,
291 ; posterotruncata, 292, 52 ; pyxidata, 291.

Hexaclymenia hexagona, 126.

Hindeodella sp., 66.

Hirmerella, 433: airelensis, 433, 78-80; muensteri, 78.

House, M. R. On the origin of the clymenid ammo-
noids, 664.

Howie, A. A. A new capitosaurid labyrinthodont
from East Africa, 210.

Hubbard, J. A. E. B. Sedimentological factors
affecting the distribution and growth of Visean
caninioid corals in north-west Ireland, 191.

Hughes, C. P. Statistical analysis and presentation of
trinucleid (Trilobita) fringe data, 1 .

— and Wright, A. J. The trilobites Incaia Whittard
1955 and Anebolithus gen. nov., 677.

I

Icriodus symmetricus, 66.

Incaia, 611', bishopi, 680, 127, 128; nordenskioeldi,
679, 127, 128.

India, new Triassic dicynodonts from, 132.

Ireland: sedimentological factors affecting coral
growth and distribution, 191; variation in the
Visean coral Caninia, 52.

J

Jenkins, W. A. M. Chitinozoa from the Ordovician
Sylvan Shale of the Arbuckle Mountains, Okla-
homa, 261.

Jurassic: growth of the thecideacean brachiopod
Moorellina, 76; morphology of brachiopod Zellania,
606; Rhaeto-Liassic flora from France, 433; stereo-
scan observations on Classopollis, 303; Tethyan
dasyclad alga, 323.

K

Kalochitina, 276; multispinata, 277, 51.

Kato, M., and Mitchell, M. A new Orionastraea
(Rugosa) from the Lower Carboniferous of
Northern England, 47.

Kennedy, W. J., and Hancock, J. M. Ammonites of
the genus Acanthoceras from the Cenomanian of
Rouen, France, 462.

Kennedy, W. J., Morris, N. J., and Taylor, J. D. The
shell structure, mineralogy and relationships of the
Chamacea (Bivalvia), 379.

Kenya: new Hemicypris from Lake Rudolf beach,
289.

Kirchgasser, W. T. Conodonts from near the Middle/
Upper Devonian boundary in North Cornwall,
335.

Kouphichnium rossendalensis, 188, 40.

L

Lepidodendron, 145; aculeatum, 146, 29-31; arberi,
163, 33; barnsleyense, 166, 31, 34; dichotomum, 159,
31 ', feistmanteli, 155, 33, 34; mannabachense, 157,
30, 32, 34; peachii, 165, 33, 34; rhodianum, 168;
serpentigerum, 151, 31, 34; subdichotomum, 162;
veltheimii, 153, 30, 33.

Leptoplastus crassicornis, 100, 22-4.

Linnarssonella girtyi, 99.

M

Matsukuma, A. See Hayami, I.

Matthews, S. C. A new cephalopod fauna from the
Lower Carboniferous of east Cornwall, 112.

Melonis affine, 186, 39.

Mesalia regularis, 46.

Microfossils: See Chitinozoa, Conodonts, Pollen.

Microstructure: of Jurassic thecideacean brachiopod
shell, 76; surface features of calcareous foramini-
ferids, 184; stereoscan observations on Classopollis,
303; of Chamacea, 379; of protegulum of acrotre-
tide brachiopods, 491 ; of bryozoan Stenopora, 581 ;
of brachiopod Zellania, 606.

Middle East, Permian and Cretaceous calcareous
algae from, 327.

Mitchell, M. See Kato, M.

Mollusca: feeding habits of predatory gastropods in
a Tertiary molluscan assemblage, 254. See also
Ammonoidea, Bivalvia.

Monoclimacis griestoniensis, 514, 103.

Monograptus; drepaniformis, 517, 104: priodon, 520,
105; spiralis, 518, 104, 105.

Moody, R. T. J. and Walker, C. A. A new trionychid
turtle from the British Lower Eocene, 503.

Moorellina granulosa, 16, 18-21.

Morris, N. J. See Kennedy, W. J.

INDEX

699

Morton, B. The evolution of the heteromyarian con-
dition in the Dreissenacea, 563.

Muensteroceras, 122; complanatum, 122, 26; cf.
rotella , 123, 26; spp., 123, 26.

Muir, M. and van Konijnenburg-van Cittert, J. H. A.
A Rhaeto-Liassic flora from Airel, northern France,
433.

Murray, J. W. and Wright, C. A. Surface features of
calcareous foraminiferids, 184.

Myotreta cf. crassa, 98.

Mytililcardia crassicosta, 75.

Mytilopsis sallei, 566.

N

Neoprioniodus; alatus, 66; promts , 66.

New South Wales: trinucleid trilobite from Ordo-
vician, 573.

New Zealand : new Ordovician trilobite from, 677.

Nonion laeve, 185, 38.

Nototeredo globosa, 620, 121.

Nummulites rectus, 185, 38.

O

Omalaxis serrata, 46.

Ontogeny, of Upper Cambrian trilobite, 100.

Ordovician: chitinozoa from Oklahoma, 261; denti-
tion and musculature of bivalves from France, 623 ;
new trinucleid from New South Wales, 573 ; stati-
stical analysis of trinucleid fringe data, 1 ; trilobites
Incaia and Anebolithus, 677 ; ultrastructure of acro-
tretide protegulum, 491.

Orionastraea, 47 ; ensifer, 13 ; magna, 49, 13 ; phillipsii,

13.

Ostracoda : new Hemicypris from Kenya, 289.

Ozarkodina immersa [ ?], 66.

P

Pachyrisma grande, 77.

Palaeoecology : of Visean corals, 191.

Palaeosmunda, 13; playfordii, 21, 4-8; williamsii, 15,

1-4.

Palmatolepis transitans, 344, 63.

Parkesolithus, 573 ; gradyi, 575, 111.

Parotosaurus proms, 211, 45.

Permian: calcareous algae from Middle East, 327;
morphologic variability of Schwagerina, 175;
osmundaceous trunks from Queensland, 10; zoarial
microstructures of bryozoan Stenopora, 581.

Peru : Ordovician trilobite from, 677.

Platyclymenia; (P.) sandbergeri, 126; steinmanni, 126;
(IP.) cycloptera, 126.

Pocock, K. J. The Emuellidae, a new family of trilo-
bites from the Lower Cambrian of South Australia,
522.

Poland: clymenid ammonoids, 664; acrotretide
brachiopods, 491.

Pollen: Rhaeto-Liassic flora from northern France,
433; stereoscan observations on Classopollis, 303.

Polygnathus, 345; asymmetricus asymmetricus, 345,
63; a. ovalis, 345; cristatus (?), 346, 63; decorosus

s.l., 347, 63, 64; dengleri, 348, 63, 64, 66; foliatus,
349, 65; linguiformis, 350, 63, 64, 66; cf. rugosus,
63; varcus, 351, 66.

Praeleda, 630; ciae, 633; costae, 630.

Pristiograptus nudus, 103.

Proganochelys quenstedti, 369.

Protacanthoceras sp., 97.

Protelphidium, 185; anglicum, 185, 37; sp., 185, 37.

Protornoceras, 670; cf. planidorsatum, 125; simpli-
ficatus, 125; cf. zuberi, 125, 126.

Pro to tret a sp., 99.

Pseudocymopolia, 324; orientalis, 325, 60.

Pteridophyta : epidermal studies of Lepidodendron,
145; fertile Rhyniophytina from Britain, 451; Per-
mian osmundaceous trunks from Queensland, 10.

Ptychopleurella bouchardi, 297, 53.

Q

Quaternary: new Hemicypris from Kenya, 289.

Queensland: new Permian osmundaceous trunks, 10.

Quinqueloculina seminulum, 186, 39.

R

Rechnisaurus cristarhynchus, 133.

Redonia deshayesi, 638.

Reptiles: see Vertebrata.

Retiolites geinitzianus angustidens, 105.

Reyre, V. Stereoscan observations on the pollen genus
Classopollis Pflug 1953, 303.

Rhabdochitina sp., 278, 51.

Rhinochelys, 356; amaberti, 360; brachyrhina, 360, 68;
cantabrigiensis, 359, 68; elegans, 359, 68; jessoni,
360, 68; macrorhina, 360, 68; pulchriceps, 358, 67,
68; sp., 69.

Rhysotreta corrugata, 98.

S

Sagenachitina, 270.

Sanderson, G. A. and Verville, G. J. Morphologic
variability of the genus Schwagerina in the Lower
Permian Wreford Limestone of Kansas, 175.

Scaphelasma sp., 99.

Schmidtognathus, 352; hermanni, 352, 66; wittekindti,
352, 65.

Schwagerina, 175; andresensis, 36; campensis, 36;
colemani, 36; complexa, 36; emaciata, 36; vervillei,

36.

Scotland: graptolite fauna of Grieston Quarry
(Silurian), 511.

Silurian: graptolite fauna of Grieston Quarry,
Peeblesshire, 511; variation in cardinalia of
brachiopod Ptychopleurella, 297.

Siphonotreta cf. acrotretomorpha, 100.

South Africa: skull of Triassic dinosaur from, 414.

Sphaerochitina lepta, 279, 51.

Spondylotreta concentrica, 100.

Statistical analysis: trinucleid fringe data, 1.

Steganotheca, 45 1 ; striata, 452, 84, 85.

Stenopora, 581; crinita, 113, 114, 116, 117; ovata,
112, 113, 115.

700

INDEX

Strachan, I. See Toghill, P.

Stromatoporoidea: from Devonian of Canada, 64.

Sweden: ontogeny of Cambrian trilobite, 100.

T

Tancrediopsis ezquerrae, 628.

Tauridium kurdistanensis, 328, 62.

Taylor, J. D. Feeding habits of predatory gastropods
in a Tertiary (Eocene) molluscan assemblage from
the Paris Basin, 254. See also Kennedy, W. J.

Taylor, T. N. See Good, C. W.

Terebratalia transversa, 101.

Tertiary: evolution of heteromyarian condition in
Dreissenacea, 563: feeding habits of predatory
gastropods from Paris Basin, 254; new British
Eocene turtle, 503; surface features of calcareous
foraminiferids, 184; teredinid pallets from Palaeo-
cene of N. America, 619.

Tethys: Mesozoic Tethyan dasycladacean alga, 323.

Thomas, B. A. Epidermal studies in the interpretation
of Lepidodendron species, 145.

Thulborn, R. A. The skull of Fabrosaurus australis, a
Triassic ornithischian dinosaur, 414.

Toghill, P. and Strachan, I. The graptolite fauna of
Grieston Quarry, near Innerleithen, Peeblesshire,
511.

Tornia, 67 1 ; mirabile, 672, 126.

Tornoceras, 670; (T.) crebriseptum, 670, 125.

Torynelasma sp., 98.

Trace fossils: xiphosurid trails from Upper Carboni-
ferous, 188.

Trewin, N. H. A dimorphic goniatite from the
Namurian of Cheshire, 40.

Trias: capitosaurid labyrinthodont from East Africa,
210; dicynodonts from India, 132; dinosaur from
S. Africa, 414 ; problematical new plant from U.S. A.,
646; Rhaeto-Liassic flora from France, 433; stereo-
scan observations on Classopollis, 303.

Trilobita: Incaia and Anebolithus, 677; new Lower
Cambrian family, 522; ontogeny of Leptoplastus,

100; statistical analysis of fringe data, 1; trinucleid
from New South Wales, 573.

Trinucleus fimbriatus, 3.

U

Ungdarella, 443; deceanglorum, 443, 81; uralica, 83.

U.S. A.: chitinozoa from Ordovician of Oklahoma,
261; Dinophyton, a problematical new Triassic
plant, 646; morphologic variability of Schwagerina
from Permian of Kansas, 175; structure of Cordaites
felicis, 29; teredinid pallets from Palaeocene, 619.

V

van Konijnenburg-van Cittert, J. H. A. See Muir, M.

Variation: in Visean coral Caninia, 52; in Wenlock
brachiopod, 297 ; of bivariate characters from stand-
point of allometry, 588; of Permian Schwagerina
from Kansas, 175.

Venericardia serratula, 46.

Vertebrata: capitosaurid labyrinthodont from East
Africa, 210; chelonian Rhinochelys from Upper
Cretaceous, 355; dicynodonts from Trias of India,
132; skull of Fabrosaurus australis, 414; trionychid
turtle from British Eocene, 503.

Verville, G. J. See Sanderson, G. A.

W

Wadiasaurus indicus, 138.

Walker, C. A. See Moody, R. T. J.

Waltonia inconspicua, 101.

Whitworth, P. H. Ontogeny of the Upper Cambrian
trilobite Leptoplastus crassicornis (Westergaard)
from Sweden, 100.

Williams, A. See Biernat, G.

Wright, A. J. See Hughes, C. P.

Wright, C. A. See Murray, J. W.

Z

Zellania davidsoni, 606, 118-20.

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PALAEONTOLOGY

VOLUME 13 • PART 4

CONTENTS

The graptolite fauna of Grieston Quarry, near Innerleithen, Peebleshire.

By p. toghill and i. strachan 511

The Emuellidae, a new family of trilobites from the Lower Cambrian of
South Australia. By k. j. pocock 522

The evolution of the heteromyarian condition in the Dreissenacea (Bivalvia).

By b. morton 563

A new trinucleid trilobite from the Upper Ordovician of New South Wales.

By K. S. W. CAMPBELL and GWENDA J. DURHAM 573

Zoarial microstructures of two Permian species of the bryozoan genus Stenopora.

By J. ARMSTRONG 581

Variation of bivariate characters from the standpoint of allometry. By itaru
HAYAMI and AKIHIKO MATSUKUMA 588

The morphology and microstructure of Zellania davidsoni Moore (Brachio-
poda) from the Middle Jurassic of England. By p. g. baker 606

Teredinid (Bivalvia) pallets from the Palaeocene of North America. By a. m.

CVANCARA 619

The dentition and musculature of some Middle Ordovician (Llandeilo) bivalves
from Finistere, France. By Margaret a. bradshaw 623

Dinophyton a problematical new plant genus from the Upper Triassic of the
south-western United States. By s. r. ash 646

On the origin of the clymenid ammonoids. By M. r. house 664

The trilobites Incaia Whittard 1955 and Anebolithus gen. nov. By c. p.
hughes and a. j. wright 677

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BY VIVIAN RIDLER, PRINTER TO THE UNIVERSITY

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