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Published by

The Palaeontological Association ■ London
Price LI 9-50

THE PALAEONTOLOGICAL ASSOCIATION

The Association was founded in 1957 to promote research in palaeontology and its allied sciences.

COUNCIL 1983-1984

President-. Professor A. Hallam, Department of Geological Sciences, The University, Birmingham B15 2TT

Vice-Presidents'. Dr. R. A. Fortey, Department of Palaeontology, British Museum (Natural History), Cromwell Road,

London SW7 5BD

Dr. J. C. W. Cope, Department of Geology, University College, Swansea SA2 8PP
Treasurer. Dr. M. Romano, Department of Geology, The University, Sheffield SI 3JD
Membership Treasurer. Dr. S. Kershaw, Department of Geology, West London Institute, Isleworth, Middlesex TW7 5DU
Secretary. Dr. R. Riding, Department of Geology, University College, Cardiff CFl IXL
Marketing Manager. Dr. R. J. Aldridge, Department of Geology, The University, Nottingham NG7 2RD

Editors

Dr. D. E. G. Briggs. Department of Geology, Goldsmiths' College, London SE8 3BU
Dr. P. R. Crowther, Leicestershire Museums Service, Leicester LEI 6TD
Dr. L. B. Halstead, Department of Geology, The University, Reading RG6 2AB
Dr. R. Harland, Institute of Geological Sciences, Nottingham NG12 5GG
Dr. T. J. Palmer, Department of Geology, University College of Wales, Aberystwyth SY23 2AX

Other Members

Dr. E. N. K. Clarkson, Edinburgh

Dr. D. Edwards, Cardiff

Dr. P. D. Lane, Keele

Dr. A. R. Lord, London

Dr. A. W. Owen, Dundee

Dr. D. J. SivETER, Hull

Dr. P. W. Skelton, Milton Keynes
Dr. A. Smith, London
Dr. P. D. Taylor, London
Dr. T. N. Taylor, Columbus
Dr. A. Thomas, Birmingham
Dr. H. Torrens, Keele

Overseas Representatives

Australia: Professor B. D. Webby, Department of Geology, The University, Sydney, N.S.W., 2006
Canada: Dr. B. S. Norford, Institute of Sedimentary and Petroleum Geology, 3303-33rd Street NW., Calgary, Alberta
Japan : Dr. I. Hayami, University Museum, University of Tokyo, Hongo 7-3-1, Bunkyo-Ku
New Zealand: Dr. G. R. Stevens. New Zealand Geological Survey. P.O. Box 30368. Lower Hutt
U.S.A.: Dr. R. Coffey, Department of Geology, Pennsylvania State University, Pennsylvania
Professor A. J. Rowell, Department of Geology, University of Kansas, Lawrence, Kansas 66045
Professor N. M. Savage, Department of Geology, University of Oregon, Eugene, Oregon 97403
South America: Dr. O. A. Reig, Departamento de Ecologia, Universidad Simon Bolivar, Caracas 108, Venezuela

MEMBERSHIP

Membership is open to individuals and institutions on payment of the appropriate annual subscription. Rates for 1984 are:

Institutional membership
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£38-50 (U.S. S67.50)
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There is no admission fee. Correspondence concerned with Institutional Membership should be addressed to Dr. A. R. Lord,
Department of Geology, University College, Gower Street, London WCIE 6BT, England. Student members are persons
receiving full-time instruction at educational institutions recognized by the Council. On first applying for membership, an
application form should be obtained from the Membership Treasurer. Subscriptions cover one calendar year and are due each
January; they should be sent to the Membership Treasurer. All members who join for 1984 will recCiye Palaeontology,
Volume 27, Parts 1-4. All back numbers are still in print and may be ordered from Marston Book Services,?. O. Box 87,
Oxford 0X4 ILB, England, at £19-50 (U.S. $34.50) per part (post free).

Cover: The Coralline Crag (Pliocene) bryozoan Cribrilina sp. showing a group of ten feeding zooids each with an ovicell and
paired adventitious avicularia on either side of the orifice. This specimen was figured as Lepralia punctata Hassall in G. Busk’s
Palaeontographical Society monograph of Crag Polyzoa(\'i59, pi. 4, fig. 1). It is reillustrated here by means of a new technique,
scanning electron microscopy of the uncoated specimen using back-scattered electrons, x 75.

THE DIPLOPORITA OF THE
OSLO REGION, NORWAY

hy J. FREDRIK BOCK E LIE

Abstract. The Ordovician diploporite fauna from the Oslo Region is examined morphologically and
taxonomically. The brachioles of Prolocrinitex are shown to be biserial. Pore-structures are described, including
peripore connections and the structure of the skeletal mesh work. Internal morphological structures indicate a
possible basal nerve ring and oral ring structures. Aspects of ontogeny and phytogeny dealt with include
changes in plate number, an increased complexity of pore structures, and possibly an increased complexity of
brachioles. A new family Parasphaeronitidae is described, comprising two new genera intermediate between
Sphaeronitidae and Holocystitidae on the one hand and Aristocystitidae on the other. Fifteen taxa from three
families are described, including three new genera {Tetreucystis, Para.sphaeronites, and Pachycystis) and nine
new species (Protocrinites rugatus, Haplosphaeronis bratterudensis, Eucystis langoeyensis, Tetreiicyslis kalvo-
eyensis, T. elongata, T. tetrabrachiolata, Sphaeronitidae sp. A, Parasphaeronites socialis, and Pachycystis
norvegica). The stratigraphical and geographical distribution of genera and species within the Oslo Region is
compared with the type of sediment in which they occur. Many genera have a relatively wide stratigraphical and
geographical distribution but individual species are restricted. Morphological variation is relatively great and
phylogenetic changes within the Norwegian diploporites are probably very complex.

The term cystoid is a collective name for certain echinoderms found in marine strata of Ordovician,
Silurian, and Devonian age. Cystoids possess a bladder-like body (theca) of plates with respiratory
pores. In the oral area they generally bear a number of food-gathering appendages (brachioles).
A stem may be present but many forms, particularly among the class Diploporita, were directly
attached to any available substrate by the basal plates of the theca. The echinoderm nature of cystoids
was pointed out as early as 1772 by the Swedish miner J. A. Gyllenhaal in his studies of Sphaeronites
pomum and Echinosphaerites aurantium (Regnell 1945, p. 1). Later von Buch distinguished them
as a separate group of echinoderms. Paul (1972) dropped the name Cystoidea and elevated the
two previous orders Rhombifera and Diploporita to class rank. Several questions regarding the
morphology and taxonomy of diploporites remain unanswered. The question whether or not they are
referable to the subphylum Blastozoa (Sprinkle 1973, pp. 57, 186) is answered in the present study by
the discovery of biserial brachioles in Protocrinites.

Norwegian cystoids are often so well preserved that hne details of morphology can be studied;
ontogenies, phylogenetic trends, and relationships to lithologies can be demonstrated. Detailed
geological mapping, combined with a compilation of stratigraphical and geographical distributions
within the Oslo Region (text-fig. 1 ), enables the relationship between echinoderms and lithofacies to
be studied. The only previous comparable studies in Europe were restricted to Estonian rhombiferans
Hemicoswites (in relation to reefs, Mannil 1966) and Echinosphaerites (distribution, Orviku 1927).
The large numbers of Haplosphaeronis from the Gagnum Shale and the Gagnum Limestone (lower
Ashgill) of Hadeland have enabled both ontogeny and variation within the genus to be studied. This
is important in understanding aspects of phylogeny (see Bockelie 1978rt).

STRATIGRAPHICAL OUTLINE

Norwegian diploporite cystoids are restricted to the middle and upper Ordovician (text-figs. 2-4); their
appearance is sometimes more or less synchronous with those elsewhere, such as in Britain, Sweden, and Estonia.
A comprehensive stratigraphical outline for the Oslo Region has been given by Henningsmoen (1960). The
Cambro-Silurian sequence has been divided into ten units termed Stages; the Cambrian comprising Stages 1 -2d,

IPalaeontology, Vol. 27, Part 1, 1984, pp. 1-68, pis. 1-8|

2

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 1 . Ordovician outcrops in the Oslo Region of Norway, centra) Sweden, and the Baltic

states (black).

the Ordovician 2e-5b, and the Silurian 6-10. It has long been suggested that Stage boundaries are diachronous
in the Oslo Region. This diachronism applies in particular to the Silurian, but it has also been proved for the
Ordovician (Brenchley and Newall 1975; Owen 1978, 1979; Bruton and Owen 1979). The stratigraphical
nomenclature whereby lithological units are named after their contained dominant fossil is now under revision
by the author and others, and will be replaced by a lithostratigraphic terminology based on geographic names. In
most areas the new formations will coincide with the previous stage names. The former use of a combination of
numbers and letters for the stages is not continued here but is occasionally referred to in parentheses to allow
comparison with previous work; published formation names are used. For the northern part of the Oslo Region
references are made to Skjeseth (1963). Where no published names are available, the fossil names originally
applied to the lithostratigraphic units are retained (Brogger 1887).

The Oslo Region is generally considered to be an intracratonic depression in a Precambrian basement
(Stormer 1967) with carbonate and terrigenous sediments on the Balto-Scandian foreland; a Precambrian land
mass is considered to have been the source of the terrigenous sediments. Recent dating of the Ordovician
sediments of Oslo-Askerconhrms a Precambrian age for the source rock (S. Jacobsen, pers. comm.). Carbonate
sedimentation prevailed in the more stable parts of the Balto-Scandian basin, including the middle Ordovician of
central Sweden. Sedimentation rates in the Oslo Region appear to have been variable and sporadic influxes of
mud flows to its more central portions have preserved some faunas more or less in life position.

MATERIAL, METHODS, AND PRESERVATION

Previously, museum collections of Diploporita were very limited and consisted mainly of Haplosphaeroiiis kiaeri
from the lower Ashgill. Since 1966 more than one thousand cystoids have been collected from the Oslo Region,
together with large numbers of other echinoderms. Some of these have been described by Bockelie (1973, 1 979a,
1981 ) and Bockelie and Briskeby (1980). Large slabs were collected and usually decalcified using hydrochloric
acid. The decalcified material was impregnated under one-third of atmospheric pressure. Casts were made from

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

3

silicone rubber. This method made it possible to study structures which could not have been detected by
mechanical preparation, e.g. the brachioles of Protocrinites (text-Iig. 13; PI. 1). The casts were studied using
stereophotographs and camera lucida drawings. Some drawings were made directly on to photographs and the
photographic emulsion removed. Thin sections and serial sections were made to reveal peripore connections and
plate meshwork. Some acetate peels were made, particularly from Parasphaeronites socialis n. gen., n. sp.
Standard staining methods were used to increase contrast between the primary and secondary calcite.

When preserved in shales, the cystoids are either llattened or preserved as impressions; in limestones they are
often well preserved and undistorted. In the upper Ordovician Husbergoya Shale ( = Stage 5a), the cystoids
weather more rapidly than their silty matrix (about 80-85% quartz) and are suitable for casting. Thecae are
generally incomplete but the diploporites are usually more complete than the commonly disarticulated rhombi-
ferans. Replacement and infilling of the cystoid test is common. Many specimens of different taxa show various
degrees of pyritization. Often the pore canals and the skeletal meshwork is filled with microcrystalline pyrite. In
such cases, connections of diplopore canals and other internal features may be preserved (text-fig. 20i). Pyritic
membranes found within the thecae may be traces of mesenteries. I suggest that this type of preservation results
from rapid burial in sediments of low permeability. Pyrite may have formed during subsequent decay in a slightly
reducing environment. Further pyritization occurred during later diagenesis.

Several cystoid plates, particularly from the reef environments, are filled with asphalt and thus impregnated.
This must have occurred after the decay of organic material, but before the formation of secondary calcite.
Asphalt has also been found in fossils from the non-reef environments of the middle Ordovician of Gasoya in
Baerum, Landoya in Asker, and Langesund in the southern part of the Oslo Region; the bitumen may be derived
from a local source.

Silicification of cystoids is not common, but does occur in a few localities (Tonnerud, Hadeland) in the lower
Ashgill, often in coarse-grained sediments where bryozoans, brachiopods, and corals are also silicified (Bockelie
and Bockelie 1971). Silicification of the echinoderms is of two types: (1) coarse-grained and mostly partial;
(2) fine-grained showing good surface details. Oral and basal portions were silicified before the rest of the theca.

TEXT-FIG. 2. Stratigraphical chart of the Oslo Region and correlations with Sweden and the Baltic.
Compiled data from Skjeseth (1963), Owen (1978), Bruton and Owen (1979), Brenchley and Newall
(1975), Henningsmoen (1960), Mannil (1966), and Williams c/ ai (1972). Black squares— distribution of
rhombiferans; black dots — distribution of diploporites.

4

PALAEONTOLOGY, VOLUME 27

Series

Graptolite

zones

Estonian

stages

S. Norway
Fm.

DISTRIBUTION OF ECHINODERM CLASSES INS. NORWAY

Porkuni c

Lanqoyene

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TEXT-FIG. 3. Stratigraphical distribution of Ordovician echinoderm classes in the Oslo Region.

Stratigraphical data as for text-fig. 2.

TEXT-FIG. 4. Stratigraphical distribution of diploporite genera in the Oslo Region
and number of taxa in the lower, middle, and upper Ordovician.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

5

as observed by Chauvel ( 1941 ). Silicification started from both the inside and the outside of the theca. Most of the
silicified Norwegian specimens have a rather ghost-like appearance due to incomplete silicification. There may
have been two periods of silicification, the first close to the time of burial, and a later one usually of the
coarse-grained type.

DISTRIBUTION AND COMPARISON WITH FAUNAS ELSEWHERE

The echinoderm fauna of Norway is both extensive and diverse. Ten classes are known from the
Ordovician of the Oslo Region (text-fig. 3), most of upper Ordovician age; echinoderms range from
the Arenig to the Wenlock, but Diploporita are restricted to the Caradoc and Ashgill. Genera and
species are restricted both stratigraphically (text-fig. 4) and geographically (text-figs. 5-7); most of the
fifteen taxa present are found within a formation, and some in one locality only. The earliest known
diploporite in the Oslo Region is Haplosphaeronis hratterudensis n. sp. (text-fig. 4), synchronous with
H. "oblonga in the Dalby Limestone of Jamtland and Dalarna, Sweden. Haplosphaeronis is one of
the most common diploporite genera in Sweden and Norway and ranges from the Caradoc to the
middle-upper Ashgill. Its geographic and stratigraphic distributions depend on which of the original
facies types are preserved. In the north Estonian confacies (Jaanusson 1976) Haplosphaeronis has
never been found. However, in the Dalby Limestone of the central Baltoscandian confacies it has
been recorded from several south Estonian borings (Mannil 1966, figs. 13, 14), appearing at about the
same stratigraphical level as in central Sweden (Dalarna). Haplosphaeronis occurs in the lower
Ashgill of Britain (Paul 1973, p. 3) and Belgium (Regnell 1951).

TEXT-FIG. 5. Geographical distribution of diploporites in the Oslo Region, a, in the
gracilis Zone-multidens Zone, n, in the Lower Chasmops Limestone and equiva-
lents (Sphaeronites) and in the clingani Zone.

6

PALAEONTOLOGY, VOLUME 27

In Estonia and Ingermanland three species of Protocrinites are known from the Arenig to the
Caradoc. The genus is also found in the northern part of the Oslo Region at Brummundal
(Coelosphaeridium beds of the Furuberg Formation; peltifer Zone). Sphaeronites is also restricted in
Norway. S. (Peritaphros) pauciscieritatus is present in the Lower Chasmops Limestone of Asker and
Bcerum (text-figs. 5b, 6a). I suggest that this species was restricted to a narrow ecological niche. In
Sweden, Sphaeronites ranges from the late Arenig or Llanvirn to middle or upper Ashgill, and several
species are known. In Estonia one or possibly two species occur in the Uhaku and Keila (Roomusoks
1970; Hecker 1964). Outside the Baltoscandian area, Sphaeronites is only known with certainty from
the lower or middle Ashgill of Britain (Paul 1973; Paul and Bockelie 1983).

Beyond the Oslo Region, Tetreucystis is known only from the Ashgill of Sweden and Britain.
Archaegocystis (text-figs. 2, 4) is restricted to the Ashgill of Norway and Britain, and to the Llanvirn
of Bohemia. Eucystis is locally present in the upper Ashgill of Oslo (text-fig. 6d), is relatively common
in the Ashgill of Sweden and Britain, and occurs in the Ashgill of Bohemia and Spain (Chauvel and Le
Menn 1979). It also occurs in the Devonian of Bohemia and North Africa, but has not been located in
the Silurian.

f\ ‘S’ P\

£?/ A j

1

■ Tetreucystis
» Eucystis

• Sphaeronitid indet.

* "Heliocrinites"

TEXT-FIG. 6. Geographical distribution of cystoid genera in the Oslo-Asker District,
showing the limits of certain genera. A, Sphaeronites in the Lower Chasmops
Limestone, n, Haplosphaeronis, Echinosphaerites, and Heliocrinites in the Upper
Chasmops Limestone, c, cystoids in the Lower Tretaspis Limestone, d, cystoids in
the Husbergoya Shale Member.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

7

The diversity of the Diploporita increased from the lower to the upper Caradoc and from the lower
to the upper Ashgill, coinciding with two major regressions in the Oslo Region. Consequently,
I suggest that these cystoids were present in relatively shallow water, where several ecological niches
were present (see later).

Diploporite cystoids first found their way into the Oslo Region in the late Kukruse Stage (text-
fig. 2) and reached a first maximum diversity and expansion in the late Oandu-early Rakvere Stage.
Another immigration took place in the Nabala Stage, reaching maximum expansion and diversity by
the Porkuni Stage (text-fig. 2). Similar patterns can be demonstrated with other faunal elements
(Bruton and Owen 1979). Diploporita were absent from the Oslo Region in the Arenig-lower
Caradoc, whereas six taxa were present in the middle-upper Caradoc and nine taxa in the Ashgill.
Patterns of geographical distribution of genera (text-figs. 5-7) are comparable with those of other
fossil groups, both in the early Ordovician (Skjeseth 1952) and the middle Ordovician (Stormer
1953).

FAUNAL ASSOCIATIONS AND THEIR RELATIONSHIP TO SEDIMENT TYPE

The sediments within large areas of the Oslo Region are well exposed. Formations can be traced continuously for
1 5-20 km along strike; the distribution of species has been mapped (text-figs. 5-7). Detailed studies were made in
Oslo-Asker, but only limited information exists for the rest of the Oslo Region because only parts of the area
have been mapped in detail.

The preservation of echinoderms with brachioles and arms indicates that the animals were not transported far
after death and before burial. The fauna was most probably periodically covered by rapid influxes of sediment.
Echinoderms with appendages preserved are found in the westernmost areas in middle Ordovician sediments.

TEXT-FIG. 7. Geographical distribution of diploporites. A, in the linearis Zone, n, in

the unceps Zone.

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 8. Areas where echinoderms have been found with appendages preserved
(typically in areas of irregular sedimentation, and usually high sedimentation rate).
A, Ordovician and Silurian, b, middle Ordovician only, c, upper Ordovician only.

and in the central Oslo-Asker part of the basin in upper Ordovician sediments (text-fig. 8). Diploporite genera
and species, together with their faunal associations, are listed below; lithologies are also described and an
interpretation of the environment is given.

Hciplosphaeronis bratteniderisis association. This is found in the Lower Chasmops Shale. The shale is interbedded
with limestone beds, often planar and 5- 10 cm thick. In Ringerike, where Haplosphaeronis is common, the shale
IS calcareous. The bioclastic content of the shale is slightly less than 20% in this area, decreasing to below 10%
eastwards towards Oslo. Both the frequency of limestone beds and the carbonate content of the shale decrease in
the same direction. The eastern limit of the faunal association is in Asker, about 20 km west of Oslo. Moving
south-west from Ringerike the clay content of the sediment decreases and the rock becomes more bioclastic;
these sediments are the result of a mixture between low and high sedimentation rates, and lack the
Haplosphaeronis association. North-east of Ringerike the Lower Chasmops Shale grades into a shale with
incursions of 20-50 cm thick sandstone beds which, from Hadeland northwards, also lacks Haplosphaeronis.

The fauna associated with H. hratterudensis is characterized by trepostome bryozoans (Diplotrypa sp.),
trilobites {Chasmops conicophthalma, Neoasaphus ludihtmdus, Illaenus sp., Atractopyge dentata), various
brachiopods (including Christiania holtedahli, Eoplectodonta{l) percedens, Strophomena norvegica), cephalo-
pods (Triptocerasl problematiciim), bivalves {Cyrtodontula diibia, Amhonychia aff. amygdalina, Cimamya
nndtistriolata, Grammysia sp.), gastropods {Kokenspira estona, Helicotoma sp.), ostracodes (Ullerella holte-
dahli), eocrinoids (/iuck/u heintzi), and cr'moids (Ristnacrinus sp. and others). The fauna probably lived on a soft
bottom, with moderate to low current velocities, below wave base in an offshore environment, and in the
proximal part of the basin.

Protocrinites rugatus association. This is approximately contemporaneous with the H. brat ter iidensis associa-
tion and occurs in situ at only one locality, in the Coelosphaeridium Beds, Furuberg Formation, in the
Veldre-Ringsaker area (text-figs. 2, 4). The association has also been found in a loose block at Toten (text-
fig. 5a). The cystoids occur in a silty shale interbedded with cyclic deposits of fine-grained quartz sandstones,
20-50 cm thick. The sandstones only occasionally contain fossils but the shales are usually very fossiliferous with
a bioclastic content of 2-25%.

Other echinoderms associated with Protocrinites include several undescribed crinoids, eocrinoids (Rhipido-
cystis norvegica), rhombiferan cystoids (Cystoblastu.C sp.), and more than two genera of Asterozoa. The
remaining fauna comprises brachiopods {Sowerbyella ringsakerensis, Mjoesina cf. mjoesensis, Kiaeromena cf.
juvenilis, Hedstroemia aff. robusta, Leptaena(l) indigena, Kjerulfina sp., Strophomena hirsuta, S. steinari,
Eostrophaeodonta williamsi), trilobites (including Chasmops conicophthahna, Illaenus cf. glaber, Neoasaphus
ludibundusi, Calyptaulax sp., and calymenids), algae (Mastopora concava, Coelosphaeridium cyclocrinophilum),
and hryozo'd {Diplotrypa sp.). The fauna lived on a soft bottom with terrigenous clay in an offshore environment.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

9

A periodic influx of fine-grained sand killed the fauna from time to time. Such periodicity and high sedimentation
rates prevailed in the northernmost part of the Oslo Region during the early Caradoc and may represent storm
action and/or microtectonic activity (Bockelie 1978fi).

Sphaerouites (Peritaphros) pauciscleritatus association. This is present in the Lower Chasmops Limestone
(text-figs. 2, 4) and is restricted geographically and stratigraphically (text-figs. 5n, 6a). It is found approximately
6 m above the base of the formation in 75 cm of nodular limestones. Macroscopically there is little difl'erence
between that part of the formation with Spliaeronites and that without, but microscopically there is a dilTerence
in bioclastic content (about 8 10% bioclastics in rocks containing Sphaerouites). Beyond the eastern limit of
Sphaerouites, there is a decrease in both the carbonate and bioclastic content of the rock. Beyond its western
limit the carbonate content increases slightly, and bioclastic content exceeds 15% before decreasing again
further west.

The small numbers of Sphaerouites at each locality (3-10 per m^) suggest in situ populations. Most of the
associated fauna has not been described, but it includes bryozoans (mostly stick bryozoans and small spherical
colonies), brachiopods (including Platystrophia sp., Kiaeroniena sp., Sowerhyellal sp., and various orthids),
trilobites (Cha.smops conicophthalma, Dionide sp., and calymenids), and crinoid ossicles p Encrinites snaroeensis' -
type). There is a clear dominance of filter-feeders.

The area where Sphaeronites is found was a submarine topographic high during most of the middle and upper
Ordovician (Bockelie 1978^). The sediments may have been locally consolidated in small patches and acted as a
relatively firm substrate for stem-bearing organisms, including the cystoids and crinoids. The environment was
possibly one of low sedimentation rates, or even local erosion, because small phosphate nodules and remanie
deposits occur locally.

Haplosphaeronis cf. kiaeri associations. These have a wide distribution in the Oslo Region. Future research may
prove that more than one species is present. At present the associations are known from the Encrinites Limestone
and its equivalents in the Skien-Langesund area (text-figs. 2, 5b), Ringerike, Hadeland, Oslo-Asker (text-
fig. 6b), and elsewhere; these may all be contemporaneous (text-figs. 2, 4). Haplosphaeronis always occurs in
sediments containing a mixture of calcareous shales and nodular limestones but its relationship to sediment type
has only been fully studied in Oslo-Asker (text-fig. 6b). The pattern of distribution between Asker and Oslo is
similar to that observed for Sphaeronites (text-fig. 6a). Haplosphaeronis is found both in bioclastic pockets in the
limestones and in the interbedded shales. Specimens in the limestones are often sediment-filled and show signs
of short transport. In the shales, however, they are filled with calcite and show no signs of transport. The
distributional pattern of Haplosphaeronis coincides with a presumed slight elevation on the sea bottom which,
during deposition of the top of the Upper Chasmops Limestone, was within a zone of reworking by currents.
Breccias and stromatolite-like structures have been found.

Associated with Haplosphaeronis cf. kiaeri in Asker are trilobites (Chasmops extensa, Platylichas laxatus,
Stenopareia glaber, Lonchodomas afl'. pennatus, Pseudosphaerexochus Indbosus, Calvptaiilax alT. norvegicu.s),
several undescribed bryozoans (including Diplotrypa sp., stick-bryozoans, and thin almost dendritic types),
brachiopods (including Ptychoglyptus ah', nninsteri, Hedstroemia sp., a sowerbyellid and orthids), and
ostracodes (Platybolbina sp.); a rugose coral Coelostylis toerncpdsti may occasionally be found (B. Neuman,
pers. comm. Jan. 1980). Other echinoderms, including loose plates of Cheirocrinus s.l. and crinoid ossicles have
been found in some localities.

The somewhat variable environments in which H. cf. kiaeri occurs represent a regressive stage of the
sedimentary basin. It seems that most of the faunas were living below the zone of regular wave action in most
areas. The environment was one of low sedimentation rates, occasionally non-deposition or even erosion. Some
of the limestones were exposed at times, allowing the attachment of bryozoa and crinoids. Periodically the
environment received influxes of carbonate-rich mud and bioclastic sand, probably after storm deposits or as
mass flows. Such deposits are commonly found in Asker.

Haplosphaeronis kiaeri a.ssociation. H. kiaeri has only been found in the calcareous Gagnum Shale and the
overlying Gagnum Limestone (text-figs. 2, 7a) in the Ashgill of Hadeland. The best exposures are found at
Tonnerud by Lake Randsfjord where detailed investigations (text-fig. 9b) indicate that H. kiaeri lived in both
environments represented. The animals were rapidly covered by sediment after death which helped to preserve
thecal details. The sedimentation rate was irregular, and periodically coarser elastics were brought into the
otherwise quiet bottom conditions.

In the Gagnum Shale the associated fauna consists of bryozoans (mostly Diplotrypa sp.), numerous
brachiopods (including Mjoesina nijoesensis, Leptaena minuta, Platystrophia sp., Porambonites sp.), other
echinoderms (including a dendrocystid, cheirocrinids, edrioasteroids such as Cyathotheca, and crinoids such as

10

PALAEONTOLOGY, VOLUME 27

RisUuicrimis sp.), several trilobites (including Tretaspis of the licidelaiidica type and Stygina minor), and
ostracodes (Euprimites kahalensis, Bullaeferum n. sp., Balticellal sp.). In the nodular Gagnum Limestone the
associated fauna is more varied, with more than thirty recorded taxa of brachiopods (M. Bassett, pers. comm.
Oct. 1979). It usually contains 2-5% bioclastic material, with bryozoans and rugose corals (Coelostylis n. sp.:
B. Neuman, pers. comm. Jan. 1980) also making up an important part of the fauna. The limestone represents
a more shallow water environment than the Gagnum Shale.

Archaegocystis occurs in the lower Ashgill, Sorbakken Limestone of Ringerike (text-figs. 2, 4, 7a); it derives
from Frognoya and occurs in a nodular limestone somewhat similar to the Lower Tretaspis Limestone of
Oslo-Asker. The interbedded shales in the Sorbakken Limestone are calcareous and often contain pyritized
fossils. The limestone itself is a fine calcisiltite-calcimicrite which contains frequent Chondrites burrows and
bears numerous Planolites traces. The associated fauna consists of trilobites (including Tretaspis hadelandica), a
few orthid brachiopods, stick bryozoa (rare), and crinoid ossicles (not common). The sediments were deposited
below wave base and are occasionally interbedded with coarse elastics which form thin bands at irregular
intervals.

Tetreucystis elongata association. This is restricted to the nodular Tretaspis Limestone (text-figs. 6c, 7a) of
Ashgill age on and around the island of Nesoya, west of Oslo. It surrounds a presumed topographic high on the
sea floor, containing a crinoid bank (Bockelie 19786), and may have lived in an unstable environment where
bottom currents were relatively strong. It is unknown whether or not drifting of the populations occurred, but
individuals are often found together in patches. Some specimens have been found growing on top of dead
individuals, and it may be assumed that they lived close together. The only other fossil remains occurring
commonly with T. elongata are trace fossils {Chondrites), and occasional trilobites (calymenids).

Tetreucystis kalvoeyensis association. This is contemporary with the T. elongata association and had a much
wider geographical distribution (text-fig. 6c). Several populations of T. kalvoeyensis show little, if any,
post-mortem transport. At Kalvoya in Baerum, west of Oslo, more than one hundred specimens were found
together, associated with molt stages of trilobites (Brachyaspis), trace fossils {Planolites and Chondrites), and
occasional cephalopods. The limestone has a low faunal diversity and seems to have formed in a shallow water
environment. Quartz content is high (10-1 5%) and the average grain diameter is about 1 00 /u,m (three times larger
than the average Ordovician grains from that same area). VV'hen traced further eastwards towards Oslo, cystoids
become very rare. On the island of South Skjaerholmen, in the Oslo fjord, a specimen of Heliocrinites was found
(text-fig. 6c).

Tetreucystis tetrahrachiolata association. This is found in the uppermost part of the Husbergoya Shale (text-figs.
4, 6d). The Husbergoya Shale is silty with a quartz content of 20-35% (100 ^xm average grain size) and carbonate
content of 25-50%. It can be traced for more than 15 km along strike, and there is a gradual change from Oslo
towards Asker, both in coarseness of the sediments and the fossil content. T. tetrahrachiolata is found exclusively
on the islands in Oslo (text-fig. 6d). Associated fauna consists of trilobites {Dalnianitina nmcronata, Tretaspis
sortita, Stygina latifrons), conularids, Cornulites worms, occasional brachiopods, and echinoderms (including
Eucystis kmgoeyensis, "Heliocrinites balticus', and various crinoid ossicles). The sediments are heavily
bioturbated, but show a relatively low faunal diversity; they seem to have formed well below wave base.

When traced westwards, the Husbergoya Shale on the islands in Asker contains an unidentified sphaeronitid
cystoid. Sphaeronitidae sp. A. is found in sediments of relatively high bioclastic content and its associates suggest
more shallow water than that in which Tetreucystis tetrahrachiolata and Eucystis langoeyensis occurred. The
associated fauna in Asker consists of a trilobite {Dalmanitina nmcronata), numerous brachiopods (more than ten
taxa are being described by L. R. M. Cocks), bryozoans (stick and mat forms), and occasional rugose corals;
associated echinoderms are "Heliocrinites halticus' (usually overgrown by bryozoa) and frequent crinoid ossicles
of at least two types. Cornulites and worms have also been located. The sediments are heavily bioturbated.

Two other diploporite genera from the Ashgill have a restricted distribution, Pachycystis n. gen. and
Parasphaeronites n. gen. In the Kalvsjo Formation at Kalvsjo, Hadeland (text-figs. 2, 4, 7b), Pachycystis n. gen.
occurs on the flanks of a carbonate mud mound. The terrigenous mud of the flanks is fine grained and has a
calcium carbonate content of approximately 5-10% (including fossil debris). The sediments interfinger with the
flank of the mound and are poor in corals, bryozoa, and trilobites, but rich in echinoderm fragments (including
calyces of several crinoids, thecae of Hemicosmites variahilis, and numerous crinoid ossicles); brachiopods are
not uncommon (and include Sampo sp., Glyptorthis? sp., Leptaena sp., Dolerorthis sp., a rhynchonellid,
Eospirigerina and Lingulella sp.); trilobites include "Calymene" sp. and an illaenid. The preservation of the
material and the type of sediment suggests quiet water, probably just below wave base or in a zone of weak
currents.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

Panisphaeronites n. gen. has only been located in channel fills within the upper Ashgill reef in an unnamed
formation (text-figs. 2, 4, 7b) at Ringerike. Parasphaeronites occurs in large numbers (hundreds of specimens),
closely packed, indicating that they were transported. Their thecae are filled with the same matrix as found in the
channel fill, which may indicate a relatively short period of post-mortem transport. Parasphaeronites has not
been found in the sediments surrounding the reef, and I therefore suggest that they lived either on the reef
itself, or in close proximity to it. Their thick thecal walls also support this idea. The associated fauna in the
channel fill consists of bryozoa (some of which grew on cystoids), rugose and tabulate corals, stromatoporoids,
and algae, all indicative of a shallow water environment; associated echinoderms are Hemieosmiles sciilptiis and
numerous crinoid columnals and root structures.

CHANGES IN FAUNAL ASSOCIATIONS WITH FACIES, TIME, AND SPACE

The distribution of the echinoderms is closely related to environmental conditions, including the type of
substrate, oxygen levels, nutrition, current velocities, and depth. It appears that the diploporites lived in a more
restricted range of environments than the rhombiferans, and they may have occupied narrower ecological
niches. In the Oslo Region almost all diploporites are restricted to relatively shallow water of four main
environmental types: ( 1 ) areas with a soft bottom and slow sedimentation rates; (2) areas with a soft bottom but
high sedimentation rates; (3) areas with a semiconsolidated bottom; and (4) reef or mud bank environments. The
coarseness of the sediment also seems to have been important. Some faunas are restricted to terrigenous
sediments, whereas others are found in carbonate sediments. Most stratigraphic sections contain diploporites
only in limited intervals. In regressive sections changes in the faunal composition from deeper to more shallow
water environments have been observed. Three such examples are described below.

Raudskjcer, Asker. The section comprises the upper portion of the Upper Chasmops Shale, the Llpper Chasmops
Limestone, the Lower Tretaspis Shale, and theTretaspis Limestone (text-figs. 2, 9a). The Upper Chasmops Shale

TEXT-FIG. 9. Comparison of faunas in the sections at a, Raudskjasr, Asker and B,
Tonnerud, Hadeland. The Lower Tretaspis Shale and the Gagnum Shale are correlated
lithologically, but are considered to be slightly different in time. The differences in
lithology and fauna are considered to be related to slight differences in water depth.

12

PALAEONTOLOGY, VOLUME 27

contains no diploporites, and is probably a deeper water shale. The size of the clastic grains and faunal diversity
increases gradually through the Upper Chasmops Limestone. The upper part is a bioclastic limestone with
wave-generated intraformational conglomerates. Haplosphaeronis cf. kiaeri is present through the Upper
Chasmops Limestone, but disappears towards the top of the formation where it is replaced by Helioa inites sp.
and Echinospliaerites n. sp. of the grandis group (text-fig. 9a). The same pattern is found elsewhere in Asker and
Baerum (text-fig. 6b), in Langesund and Hadeland, and in Dalarna, Sweden, towards the top of the Kullsberg
Limestone. No echinoderms with endothecal pore structures occur in this type of environment, possibly because
such pore structures were susceptible to clogging by terrigenous sediment. The replacement of Haplosphaeronis
cf. kiaeri by Heliocrinites and Echinospliaerites is probably related to depth; Haplosphaeronis cf. kiaeri lived in
deeper water. Thus there is a marked upper and lower limit to the distribution of Haplosphaeronis at Raudskjaer.

Tonnerml, Hadeland. This section comprises the Solvang Formation, the Gagnum Shale, and the Gagnum
Limestone (text-figs. 2, 9b). The upper part of the Solvang Formation is a bioclastic limestone containing
occasional Echinospliaerites of the grandis group and Haplosphaeronis. Further east, towards the Gagnum farm
Echinospliaerites is found together with both Heliocrinites and Haplosphaeronis cf. kiaeri. The overlying
Gagnum Shale is calcareous (20-60% carbonate) and echinoderms are common. Echinospliaerites occurs in the
lower part of the section, and Haplosphaeronis kiaeri is very common from 1 m above the base. H. kiaeri is
common through the Gagnum Shale and the overlying Gagnum Limestone. The sequence at Tonnerud can be
correlated with that at Raudskjaer (text-fig. 9; Bruton and Owen 1979). Haplosphaeronis is found at Tonnerud in
the deepest water sediments. Echinospliaerites, and locally Heliocrinites, are found in shallow water sediments.

Husbergoya Shale Eormation. No more than 2 m thick, this formation can be traced for about 20 km along strike
from Oslo to Asker (text-fig. 2). In Oslo terrigenous material dominates, and the fauna includes Tetreucystis
tetrahrachiolata, Eucystis langoeyensis, and "Heliocrinites balticus'. Westwards towards what is considered to
have been shallower water, Tetreucystis and Eucystis disappear, but "Heliocrinites balticus" continues and an
unidentified sphaeronitid cystoid is also present. This change is considered to be depth controlled. A 1° slope of
the sea bottom would produce a difference in depth of approximately 25 m between the two major centres of
these faunas.

Conclusion. These preliminary studies of echinoderm associations indicate that, although some faunal changes
may be referable to differences in water depths, correlations which relate all the echinoderms to depth cannot yet
be made. A generalized zonation of the diploporites in the Oslo Region is given in text-fig. 4.

COMPARISON BETWEEN EAUNAS AND COMMENTS ON ‘PROVINCIALISM’

It has become popular to talk about faunal provinces of different fossil groups, the echinoderms
included. The echinoderms were dispersed as larvae and their dispersal pattern was limited by three
major factors: ( 1 ) how long the larvae remained free-living before settling; (2) water temperature; and
(3) ocean currents. Kesling(1967, p. SI 36) suggested that the dispersal of cystoids was a slow process.
The restricted patterns of distribution of many genera and species suggest that environmental
conditions and ecological adaptations were amongst the most important controlling factors in
diploporite biogeography. However, several cystoid families had strong geographical preferences at
certain times, and this has led to a grouping of the faunas into faunal provinces. Few publications deal
with these provinces in terms of plate tectonics (Paul 1976), but it seems that the Oslo Region was in
the southern hemisphere during the Ordovician and migrated towards the equator in the upper
Ordovician and Silurian.

Estonia, central Sweden, the Oslo Region, and parts of Britain were more or less in the same
geographical province (Paul 1976). It has previously been suggested that Britain formed a faunal
province separate from that of Norway, Sweden, Estonia, and Ingermanland. Regnell (1945)
described most Swedish diploporites, but three or four extra genera may be present. The Estonian
faunas and those of Ingermanland have not been studied in detail since Jaekel ( 1 899), and additional
taxa are likely, as suggested by references made to Haplosphaeronis and Sphaeronites by Mannil
(1966) and Hecker (1964). The British Diploporita were monographed by Paul (1973); he described
several genera not previously recorded from Britain and also pointed out similarities between British
and Czechoslovakian mid-European faunas.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

13

Norwegian diploporites are strikingly different from those of other areas, particularly Sweden.
This difference is even more evident when rhombiferans are also taken into account. 1 believe that this
reflects differences in environments. The Swedish and Estonian faunas are found mostly in carbonate
platform sediments, whereas the Norwegian faunas and the Ashgill faunas of Britain occur in more
clastic deposits. In the shallow water clastic environments of the Oslo Region, notably in its northern
and south-western margins, the faunas resemble some of those found in similar environments in
Estonia and Ingermanland, e.g. Protocrinites, Bockia (eocrinoid), and Cystoblastus (rhombiferan).

The diploporite faunas of Britain, the Oslo Region, central Sweden, Estonia, and Ingermanland are
compared in text-fig. 10. The actual number of genera present in the different countries is influenced

DIPLOPORITE GENERA

Bohemia

Belgium

British isles

Norway

Sweden

Estonia

Inoermanland

Protocrinites

M.Ord.

L. -M.Ord.

Sphaeronites

U.Ord.

M.Ord.

L. -U.Ord.

M.Ord.

Haplosphaeronis

U.Ord.

U.Ord.

M. -U.Ord.

M. -U.Ord.

M.Ord.

Eucystis

U.Ord. -M. Dev.

U.Ord.

U.Ord.

U.Ord.

Tetreucystis

U.Ord.

U.Ord.

U.Ord.

Archaegocystis

M.Ord.

U.Ord.

U.Ord.

Glyptosphaerites

M.Ord.

M.Ord.

Total number of genera

5

1

7

8

5

11

TEXT-FIG. 10. Stratigraphical and geographical distribution of non-enigmatic diploporites from
Bohemia, Belgium, Britain, Norway, Sweden, and the Baltic states (Estonia and Ingermanland).
Totals of the known genera from the different areas give some information about the proportions of

enigmatic to non-enigmatic forms.

both by collecting bias and by the extent to which the faunas have been described. Seven to ten genera
may have been present in these areas during the Ordovician. It seems that individual species are very
restricted even within a single area. This may be partly a preservational feature, reflecting the state of
preservation of individual species and the type of environments preserved in different areas at
different times, but it also indicates adaptation to particular environments; the appearance or
disappearance of species, or even genera, mirror changes in environmental conditions.

There is no clear difference between the British and central and western Baltoscandian Diploporita.
On the contrary a gradual shift of the faunas from east to west can be observed. Therefore,
environment was the most important factor controlling their distribution.

APPEARANCE, EVOLUTION, AND EXTINCTION

Haplosphaeronis arose in Estonia (early Kukruse, Cn) and migrated into the Oslo Region during
a transgression in the multidens Zone. Dilferent sedimentary environments subsequently developed,
to which the diploporites adapted themselves. A regression during the uppermost Caradoc caused a
restriction of the diploporites to shallow water environments. By the Ashgill transgression several of
the typical Caradoc cystoids had disappeared. These were replaced by new faunal elements which
were adapted to shallow water environments. They reached greatest diversity by the maximum of the
subsequent Ashgill regression. The base of the Silurian was marked by a transgression of great
importance, but no diploporite cystoids seem to have survived into the Silurian in the Oslo Region.
Even during several minor transgressions and regressions during the late lower and early upper
Silurian no diploporite cystoids appeared. With very few exceptions this pattern is repeated in
contemporary deposits elsewhere in the world. Consequently, studies of these changes observed in the
Oslo Region may have a wider importance.

It is unknown why the Diploporita periodically disappeared and why there was a faunal shift
between the middle and upper Ordovician. Several factors were involved. The Ordovician sediments

14

PALAEONTOLOGY, VOLUME 27

in the Oslo Region were deposited in a relatively flat epicontinental sea (Bjorlykke 1974). Most of the
terrigenous components were either clay or wind blown quartz of silt fraction. In such environments
selection pressure was probably not very great, and faunas were relatively homogeneous over large
areas. During the Ashgill, sedimentation rates increased, there was more irregular sedimentation
( Bockelie 1 978^), and the terrigenous components probably increased by a factor of ten. Quartz grain
size increased from an average of 35 jum in the middle Ordovician to more than 100 /xm (Bjorlykke
1974) in the upper Ordovician. These changes and the development of shallow-water environments
may have increased selection pressure and resulted in specialization. Failure to evolve the structures
necessary to meet these environmental changes was probably the most important factor in
diploporite extinction.

In the upper Ordovician most cystoids have exothecal pores, beneficial in environments with high
sedimentation rates and in water with suspended sediment particles. Such areas are common in the
uppermost Ordovician in the Oslo Region. Although mudbanks and ‘reefs’ became more common in
the upper Ordovician, the climate was cooler than before; temperature gradients in the upper
Ordovician sea would have had a significant effect (Sheehan 1979). Oxygen is more soluble in cold
water than in warm water. Cystoids with exothecal pores (Diploporita and some Rhombifera) have
many pores and thus a large respiratory surface. They may have thrived in shallow, warmer water
with lower oxygen concentration. Most diploporites lacked a stem and were directly attached to
objects on the sea floor or to the substrate itself. In times of increased sedimentation, they would
easily have been buried.

During the Ordovician the Diploporita may have faced increased competition from other
echinoderms, particularly crinoids and rhombiferans. The distribution of ossicles in the Oslo Region
shows that the crinoids evolved rapidly and gradually invaded the shallow waters previously
occupied by diploporites and rhombiferans. The rhombiferans themselves seem to have been in
serious competition with the diploporites.

The cystoids were filter-feeders, so their distribution would depend on the size, composition, and
quantity of suspended food. Changes in the plankton might therefore seriously affect cystoid
distribution. The size of brachiole facets in both diploporites and rhombiferans increased during the
Ordovician (Bockelie 1979u), probably induced by change in food supply or increased competition.
Larger brachiole facets would have supported longer brachioles and thus allowed an increased food
intake.

ANATOMY, TERMINOLOGY, AND FUNCTIONAL MORPHOLOGY

Diploporita are extinct echinoderms having a more or less globular theca, a calcareous skeletal body
housing the soft tissue, and reproductive organs. The theca is composed of thecal plates, arranged
randomly or in rings {circlets). Some or all of the plates may bear exothecal respiratory
pore-structures. Diplopores, humatipores, and haplopores (text-fig. 12) are characteristic of the class.

Four major openings are present; (1) a peristome, at the centre of the food-gathering system, which
may be covered by a few large or several small cover plates; (2) a periproct which in many genera is
covered by an anal pyramid of triangular plates; (3) a small, circular gonopore\ and (4) a slit or
sieve-like hydropore, indicating the presence of a water vascular system. The hydropore and gonopore
are usually situated close together between the peristome and the periproct (cf. Celticystis, Bockelie
1979^). The location of these orifices, and the number and positions of the plates in which they are
present, are very important taxonomically.

Two to five ambulacra extend from the peristome and were responsible for food gathering. Food
was transported to the mouth along food grooves. Ambulacral appendages are very rarely preserved.
Only four diploporites with well-preserved appendages are known; Protocrinites, Calix, and
Glaphocystis have biserial appendages (Chauvel 1966, 1977); those of Asterohlastus are uniserial
(Eichwald 1 862; see discussion by Jaekel 1 899, p. 385). The theca was attached to the sea bottom by a
column of small cylindrical or annular coiumnals, or by an extension of the basal plates forming a
stem-like projection, or directly by its flat base. The attachment area can be small or of the same

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

15

diameter as the theca itself. Most diploporites were attached, but some may have been free and mobile
or even floating.

Most Norwegian Diploporita belong to the family Sphaeronitidae, with one species from the
Protocrinitidae; two new genera are erected and placed in a new family, the Parasphaeronitidae. The
oro-anal areas of most cystoids are important both for discriminating genera and at family level
(Bockelie 1972; Paul 1 973). The terminology used in this study is essentially that of Kesling (1967) and
Paul (1973). Additional morphological terms are described below.

Major thecal openings

The mouth. Located at the centre of the ambulacral system, the mouth is generally ovate. It is large in
the Sphaeronitidae and Parasphaeronitidae n. fam., but relatively small in the Protocrinitidae. It is
surrounded by a pentagonal or quadrilateral peristome which in life was covered by six palatals in the
Sphaeronitidae, and possibly also in the Parasphaeronitidae. In the Protocrinitidae, ambulacral
cover plates continued on to the peristome and covered the mouth (text-fig. 1 1 ). The peristome border
(‘oral laths’ of Prokop 1964) of the Sphaeronitidae is present between the mouth and the peristome
and on this the food grooves diverge before entering the mouth. In some Sphaeronitidae a complex
dendritic pattern of grooves occurs, whereas in others the food grooves continue down into the
mouth without branching or diverging (text-figs. 11, 29). The peristome frame is composed of six
circum-oral plates in the Protocrinitidae and Sphaeronitidae, and eight plates in the Parasphaeroni-
tidae. The terms circum-orals (CO plural COO) and periorals were adopted by Paul (1971).
Provisionally I refer to the plates which surround the mouth in the Protocrinitidae as circum-orals,
without necessarily implying a homology.

TEXT-FIG. 11. Plate configuration of oro-anal area of Norwegian diploporite genera, a, Protocrinites. b,
Sphaeronites (Peritaphros). c, Haplosphaeronis. o, Tetreucystis n. gen. e, Eucystis. F, Parasphaeronites n. gen.
G, Pachycystis n. gen. (a, Protocrinitidae. B-n, Sphaeronitidae. f, g, Parasphaeronitidae, n. fain.). M, mouth;

G, gonopore; H, hydropore; Pe, periproct.

16

PALAEONTOLOGY, VOLUME 27

Food grooves radiate from the oral corners on to the circum-oral plates. In the Sphaeronitidae they
may be located on these plates only or continue some distance down the thecal surface. The grooves
may or may not branch. Each food groove ends in a small facet, generally less than 1 mm in
diameter. The shape and size of individual facets varies at both generic and specific level and
may have taxonomic value. In Protocrinites long biserial appendages are attached to the facets,
and ambulacral cover plates are transformed into specialized brachiolar cover plates on the
brachioles (text-fig. 13). The brachioles of Protocrinites may be characteristic of most diploporites
(see below).

Paul (1973, p. 12) defined an ambulacral formula using the number of ambulacral facets per
ambulacrum, starting with ambulacrum I. This number in the Sphaeronitidae has since been related
to ontogeny (Bockelie 1978u), but the pattern of distribution over the theca may be typical at family
level. In this pattern the number of facets would be the same in radii I and V, slightly less in radii II and
III, with the smallest number of facets in radius IV (Bockelie 1978a, p. 36, fig. 5). In some species of
Tetreucystis (Sphaeronitidae) only one facet per ambulacrum may be present even in adult stages.
As reported by Paul (1973, p. 12) no cover plates have been found on the ambulacra of the
Sphaeronitidae. In the Protocrinitidae cover plates of two ‘generations’ occur: large triangular plates
along the edges of the ambulacral groove and smaller plates added between (text-fig. 13). Whether
similar plates existed in the Sphaeronitidae is unknown. It is clear that food passed along the food
grooves of Protocrinitidae and under their cover plates; by analogy, the Sphaeronitidae may have had
the same system. Most of the palatals have ambulacral orifices large enough at the peristome for food
to have entered beneath them (text-fig. 18). The oral cover plates may have been similar in the
Sphaeronitidae and the Parasphaeronitidae.

The anus. Generally circular or oval in outline, it is often as large as or larger than the mouth. When
oval, the long axis generally lies at an angle of 60-90° to the lower margin of the peristome. The anus
of Sphaeronitidae is present in inter-radius V-I, in contact with circum-oral plates COS, C06, C07,
and occasionally COl (text-fig. 1 1 ). The distance from mouth to anus varies but is generally constant
within a genus. In Sphaeronites the anus is set close to the mouth; in Haplosphaeronis the anus is closer
to the mouth than in Eucystis and Tetreucystis n. gen. but not as close as in Sphaeronites', in
Protocrinites it is separated from the mouth by at least two plate series (text-fig. 11a), while in
Archaegocystis it is also well removed. The position of the periproct of Parasphaeronitidae
may resemble that of the Sphaeronitidae (text-fig. 11), and is not unlike that of Eucystis or
Tetreucystis.

The anus was covered by a pyramid of triangular plates (anals). These plates could open outwards
in many genera (text-fig. 26c) because a ledge was present only in the lower half of the periproct
(Bockelie 1972; Paul 1973, p. 13).

The gonopore. This lies between the peristome and the periproct and is usually slightly left of a line
between them. It is a small circular pore generally about 0-5 mm in diameter. Small triangular plates
forming a pyramid have been reported in Rhombifera, but have never been found in Norwegian
material.

The hydropore. This is normally a narrow slit. In Protocrinites a circular opening occurs on top
of a small tubercle but it is not known whether this is the hydropore or the gonopore. In the
Sphaeronitidae and Parasphaeronitidae a slit is present on top of a ridge. Both the slit-shape and
the presence of a ridge would have prevented suspended particles entering; this indicates an inlet
rather than an outlet structure (see Paul 1971, pp. 27, 28). A hydropore implies the existence
of a water vascular system. Sprinkle (1973) concluded that tube-feet were not present in the
brachioles of Blastozoa. Consequently, the water vascular system may rather be related to the
pore system (see later discussion). Breimer and Macurda (1972) disagreed with Sprinkle’s
interpretation and suggested the position of a ring canal in blastoids. Internal and external
branches of the water vascular system may be present in both Rhombifera (Paul 1967, p. 234)
and Diploporita.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

17

Plates

Individual thecal plates vary in shape, pentagonal or hexagonal being the most common. They are
mostly of one generation, i.e. plates formed at an early ontogenetic stage are the only ones involved in
skeletal construction (primary plates). Some species and genera possess additional plates formed
between others later during ontogeny and termed secondary, tertiary, etc., according to their time of
formation. In the Norwegian Diploporita only primary plates occur in Haplosphaerouis, Sphaeron-
ites, Archaegocystis, and Eucystis. Secondary or multigeneration plates occur in Tetreiicystis n. gen.,
Pachycystis n. gen., Parasphaeronites n. gen., and in some indeterminable genera. Both Swedish and
British species of Sphaeronites and Eucystis may have secondary or tertiary thecal plates. Thus, the
plate pattern can be quite variable outside the oral area. Haplosphaeronis appears to be the only
diploporite genus characterized by a constant plate number.

Plate structure. Well-preserved plates of Parasphaeronites socia/is n. gen., n. sp. (Parasphaeronitidae
n. fam.) show two layers of thecal mesh, an inner coarse mesh and an outer fine mesh (text-figs. 12, 33;
PI. 8, figs. 3, 6, 7). Similar observations were made by Paul ( 1971 ). However, the coarse layer does not
show pillars and laminations as observed in Archaegocystis. The coarse layer has larger trabeculae
than the fine layer; the long axes of the trabeculae seem to be orientated at random. In P. socialis
branched haplopores occur at the boundary between these two layers (text-fig. 12; PI. 8, figs. 6, 7).
Pyrite filling the mesh of Haplosphaeronis plates and preservational features of other diploporites also
suggest the presence of two layers. Sprinkle (1973) suggested that this pattern is characteristic of all
blastozoan echinoderms.

TEXT-FIG. 1 2. Pore structures in diploporites, showing measurements and terminology, a, c, e, in plan; b, d,
F in cross-section, a, b, normal diplopores with or without a calcified periporal roof c, D, humatipore (not
present in Norwegian material). E, F, ‘haplopores’, simple and complex with unbranched and branched
canals. (Originally haplopores were single canals opening in a peripore while diplopores were peripores
with two canals. This present structure is much more complex. Notice that simple canals or simply
branched canals go through the plate centre, whereas the complex canals lie at an angle to the side of the
plate.) The plates are provided with an outer fine mesh of trabeculae (dotted) and an inner coarse mesh
structure (irregularly hatched), app, aporal portion of peripore wall; hp, haplopore; P, peripore; Pc, pore
canal; pp, poral portion of peripore wall; ppr, periporal roof; pps, periporal space; ppw, peripore wall.

Attachment. The thecae of most Norwegian diploporites were attached by a small or a broad
attachment area to any suitable substrate, e.g. cephalopod shells, brachiopods, bryozoans, trilobites,
and other cystoids. Some may have been attached to seaweed or soft-bodied animals like ascideans.
The basal plates of some sphaeronitid cystoids, especially from Sweden but also from Norway,
form a stem-like projection which was either cemented to a firm substrate or may have protruded
down into the sediment. Protocrinites was the only diploporite in Norway with a stem. The stem was
at least 1 0 mm long and rather complex, its columnals resembling those of shallow-water crinoids. No
root structures have been observed.

18

PALAEONTOLOGY, VOLUME 27

Food-gathering appendages

Appendages are only very rarely found in diploporites, but facets suggest that they were of different
types; some facets are large and indicate attachment for two or more muscular bundles (text-fig. 34a);
others are small and hardly show muscle scars or ligament pits at all (e.g. Flaplosphaeronis). The
food-gathering appendages of blastozoans are termed brachioles (see Sprinkle 1973, pp. 12-20). Two
major types of brachiole facets occur in the diploporites. Either there is only one facet present in each
of the ambulacra even at an adult stage (Holocystitidae, Parasphaeronitidae) or more than one facet
is present (most of the Sphaeronitidae, Protocrinitidae). At present only diploporites with the second
type of facets have been found with brachioles in place.

Brachioles of Protocrinites. More than a dozen specimens of the Norwegian Protocrinites rugatus
n. sp. have been found with brachioles in place (text-fig. 13; PI. 1). The brachioles are biserial,
unbranched, reach 15 mm in length, and thus exceed the total length of the theca. In cross-section
they are slightly oval or irregular. The two plates that make up the major portion of the brachiole are
of approximately equal size when seen in cross-section (text-fig. 13g, h). A set of cover plates is
present over the food groove. Four cover plates seem to be attached to every brachiole element
(text-fig. 13d, e). In this respect the brachiole resembles the eocrinoid Gogia longidactylus (see
Sprinkle 1973, text-fig. 10). In P. rugatus no traces of nerve canals were found. However, the study
was made from decalcified and cast material, and a nerve canal probably was present. In cross-section
four minor furrows parallel to the food groove were observed. These grooves could have housed the
radial extensions of the water vascular system and other vascular systems. Similar grooves have also

TEXT-FIG. 13. Brachioles of a-h, Protocrinites rugatus n. sp. from loose block, Toten, Oslo Region, and
1, J, Calix sedgwicki. A, PMO 101.133, and B, PMO 101.130, showing dorsal sutures, both biserial but
with slight differences in sutural areas, c-h, PMO 101.133, showing c, brachiole in side view with
slightly irregular brachiolar cover plates; D, details of brachiolar cover plates (c) in side view; E,
brachiolar cover plates from above showing their number and position; f, basal portion of brachiole
(br) and brachiolar cover plates, and grooves within the brachiole (g); g, h, cross-sections of brachiole
showing shape, brachiolar cover plates (c), and grooves along inside of brachiole (g). i, j, IRScNB
16001 showing i, cross-section of brachiole and j, brachioles showing complex basal portion and
biserial appendages (from Chauvel 1977, pi. 1, figs. 5, 6). Scale on left for a-h; scale on right for i, j

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

19

been observed in other primitive echinoderms. They may have increased the cross-sectional area of a
brachiole and were presumably covered with cilia. These additional furrows alongside the food
grooves increased the efficiency and capacity of the brachioles for food transport, and possibly also
for food collecting. If no podia were present in the brachioles, the alternative for trapping food
particles would have been to possess as many cilia as possible. Similar furrows occur in
Echinosphaerites and Calix.

The shape of the brachioles of P. rugatus n. sp. suggests that they could stand out almost
perpendicular to the theca; they are preserved in a retracted position, slightly bent towards the thecal
surface (text-figs. 16, 17; PI. 1, figs. 1, 6). Even though the animals were buried alive and killed by
a rapid influx of sediment, some brachioles were shed. This shows that the contact between the
brachioles and their facets cannot have been very strong. If this is typical for other cystoids, it explains
the extreme rarity of preserved brachioles, particularly in the Diploporita.

Brachioles of other diploporites. Recent work by Chauvel (1977) has proved the existence of biserial
appendages in two Aristocystitidae, Glaphocystis globulus and Calix sedgwicki. The brachiole facets
of these cystoids are grouped together around the peristome (text-fig. 1 3j), and partly interconnect to
form a rigid brachiole complex before the individual brachioles separate. The brachioles of
C. sedgwicki are more than 13 cm long, exceeding the length of the theca. Individual brachioles are
almost circular in cross-section (text-fig. 13i), and were presumably covered by small plates in life
(Chauvel 1977). At the base of and parallel to the food groove Chauvel discovered two minor
grooves. A similar complex pattern of the basal portion of the brachioles has been found in a Swedish
upper Ordovician aristocystitid (Bockelie, in prep.). On the basis of the observations above, the
brachioles of the Aristocystitidae and the Protocrinitidae differ in their basal portions but not in their
overall construction. Asteroblastus (Asteroblastidae) has uniserial brachioles (see Jaekel 1899, pi. 7,
fig. 1) but their details are unknown. Recently a diploporite with triserial arms has been found
(Parsley 1982).

Brachiole support. Two types of brachiole support seem to be present in cystoids. The Rhombifera
and some Diploporita possess flooring plates. The ambulacra can be located directly on the thecal
plates with brachiole facets (as in most diploporites), while in the majority of Rhombifera and some
Diploporita ambulacral flooring plates are found cemented on to the thecal plates. Recently an
intermediate situation has been observed in Celticystis (Bockelie 19796) where ambulacral flooring
plates occur only in the basal portion of the theca. In the remaining portion of the theca food grooves
are developed on ‘normal’ thecal plates.

Pore structures

All respiratory pore structures of the Diploporita are exothecal, i.e. the body fluid extended from the
inside to the outside of the theca and oxygen-carbon dioxide exchange took place through a
membrane covering the exothecal pores. In many cystoids the external pores may have been covered
by a calcite membrane (most of the Diploporita; see later). Two major types of external pore
structures occur in the Diploporita: humatipores and diplopores. Humatipores are characterized by
‘two internal circular pores leading to two or more tangential canals which lie beneath the flat external
surface, or in a prominent external tubercle’ (Paul 1971). They are confined to the Holocystitidae
which are not found in Norway. Diplopores are composed of a simple thecal canal, the tangential
portion of which was not normally calcified and probably formed a papula or a podium in life (Paul
1972, p. 5). The normal diplopore shows as two pores, usually paired within a shallow depression
(peripore) on the external surface of the theca. In addition to these two major types, haplopores have
been described by Bather ( 1 900) and Chauvel ( 1 94 1 ). A haplopore consists of a single perpendicular
canal, apparently ending in a single pore on the thecal surface (see Kesling 1967, p. S89, fig. 33.7).
Paul (1972, p. 9) only observed a true haplopore in a plate of Eucystis sp. Chauvel (1977) restudied
Calix, in which haplopores have long been considered characteristic, and observed both normal
diplopores and complexly branched or single ‘haplopores’ in the same individual. He stated that the
latter could end in complex sieve-like pores with a peripore. Haplopores have always been considered

20

PALAEONTOLOGY, VOLUME 27

to lack a peripore, and Chauvel concluded that they may be regarded as a variety of diplopores
rather than a pore structure on their own. It appears therefore that humatipores and diplopores are
the only types of external pore-systems in the Diploporita.

Externally the pore-structures of the Diploporita are simple, but this is not the case with the canals
leading from the pores through the plates to the thecal interior. Confusion over how the entire pore
system was constructed has often been the result. The situation in most genera and species of the
Sphaeronitidae is best known where canals lead to the peripores (text-fig. 14), forming part of a
circulation system (Paul 1972, fig. 8b). In Haplosphaeronis connections of canals may or may not be
present (text-fig. 20). Parasphaeronites n. gen. shows a complex pattern of canals (text-fig. 12e, f) in
which single canals ending in a haplopore(?) go right through the plate close to the plate centre,
whereas different types of branched canals occur towards the plate edges (see also PI. 8, figs. 3, 6, 7).
These latter complex canals occasionally end in haplopores, but more usually in diplopores (text-fig.
12e, f). Many or most of the canals of Parasphaeronites n. gen. end in diplopores on the thecal surface
(PI. 7, fig. 5), but the details of their connection within the theca are not clear. In Calix, the haplopores
are located in particular portions of the theca, but their precise distribution is not known; nor is the
distribution of these complex pores known in Norwegian material. Haplopores as originally defined
may be trans-sutural and thus cross plate boundaries. This is most apparent in Aristocystitesl potens
(Chauvel 1941, p. 68).

Diplopores. These are the most common type of pore structures found in the Diploporita. They are
characterized by a pair of canals which open to the exterior in a peripore. Both pores of the peripore
are usually on the same plate, but exceptions occur (text-figs. 28, 29, 32). When present, the peripore
wall can be divided into poral and aporal portions (pp, app; text-fig. 12). In Haplosphaeronis the
aporal portions may develop spines and the poral portions may be almost reduced in some specimens
of some species. All diplopores were covered in life by a thin membrane of organic material; some
were also covered by a calcitic cupola, occasionally very thin, forming a calcified roofed diplopore
(text-fig. 12b). Such calcified diplopores can occur in distinct areas (PI. 5, figs. 2, 4). Inside the
diplopore is a periporal space (text-fig. 12b). Various Tetreucystis n. gen. and Eucystis have no pores
at thecal plate centres, which might be taken to indicate a lack of pores in extremely young specimens.
Alternatively, pores formed at very early stages may later have been resorbed. However, in young
individuals respiration could well have taken place directly through their small thin plates (Paul 1972;
Bockelie 1979u).

Cystoids have different patterns of diplopore distribution and orientation. The most typical
pattern is random, where the long axis of the peripore shows no preferred orientation (text-fig. 3 1 ), as
in some Tetreucystis and Eucystis species. Other diploporites have a preferred peripore orientation.
In Tetreucystis kalvoeyensis n. gen., n. sp. and Sphaeronites (Peritaphros) pauciscleritatus, the pore
axes radiate from an often slightly elevated plate centre (PI. 6, fig. 3; Paul and Bockelie 1983). In
Haplosphaeronis the pore axes are orientated longitudinally in an ad-aboral direction along the radii
and horizontally in the interambulacral areas of most species (text-fig. 21). This pattern is unique to
Haplosphaeronis. T. kalvoeyensis has some of its longest pore axes orientated parallel to the oral
frame (PI. 6, fig. 1). These pores may have served a sensory function in addition to the normal
respiratory function, becoming specialized and more closely connected with the oral nerve system.
Paul (1971) observed numerous pores along the inside of the oral frame of holocystitids and
concluded that they served a sensory function. Diplopores are distributed over most of the thecal
surface, and are mostly of equal size. However, in a few genera {Haplosphaeronis, Eucystis,
Tetreucystis) some diplopores at plate sutures are smaller or deformed.

Diplopores may have formed in two ways, either at the plate sutures and gradually migrating
towards the plate centre by additional growth (much like that of disjunct pore-rhombs) or
alternatively, and most likely, by resorption of the plate. Many diplopores in Haplosphaeronis near
the plate sutures are smaller than those closer to the plate centre (PI. 3, figs. 3, 5). These may be in the
position of formation, and thus resorption would have continued until maximum size of the
diplopore was reached. Many individuals of H. kiaeri have pores at plate sutures, but apparently lack

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

21

pores closer to the plate centre (PI. 5, figs. 2, 4). Instead, there are small knobs or ‘ornament’ randomly
distributed on these plates which, when ground down, prove to be deformed diplopores with an
originally calcified cupola.

The number and position of diplopores varies between individuals and some plates have more than
others. The highest number is present in the circum-oral plates of the Sphaeronitidae. This upper
portion of the theca is considered to have been in the zone of the highest water speeds passing over the
theca, and it therefore possibly had the highest respiratory potential (Bockelie \919h).

Covered diplopores. Diplopores are considered by many authors to have been covered in life by soft
tissue. However, the presence of peripores covered by a calcitic cupola has been reported from many
different genera and species of Diploporita. This has been explained as accidental preservation, or as
being related to the sealing of parts of the respiratory system to prevent toxic gases from entering.
Norwegian diploporites are often found with roofed diplopores in distinct areas, often towards the
base or the oral area. Occasionally most of the theca is covered by roofed diplopores (PI. 5, fig. 4). In
addition to the roofed diplopores there are several pores that do not have a calcitic cupola, and
probably never had one in the living state. This is particularly obvious in H. kiaeri (PI. 5, fig. 3). The
presence or absence of calcite-roofed diplopores is partly a preservational feature. Extremely
well-preserved material often has the roof preserved, as in H. kiaeri {V\. 5, figs. 2, 4) and Protocrinites
rugatus n. sp. (PI. 1 , figs. 1 , 3, 5, 8). However, both these species were usually buried rapidly. In cases
where burial was slower the roofed diplopores may have become abraded. Similar preservation on
holocystitids confirms this. Even specimens of Sphaerouites (S'.) poimmi from Oland, Sweden, are
occasionally found with extremely thin calcite roofs preserved.

The presence of calcite-roofed diplopores had several advantages. For the animal’s internal flow
system it would have helped keep a constant volume under the periporal roof. Previous suggestions
that it would also have prevented toxic gases from entering the animals attached to the sea bottom
may not be correct if the calcified diplopores were porous. (P. rugatus is provided with a stem and also
has covered diplopores.) A third explanation implies protection from predation of soft tissue or
papulae over the diplopores. There was no protection, such as spines, around most peripores (with
the exception of S. (S.) pomum and some specimens of H. kiaeri). The formation of a calcite cupola
would have reduced predation of soft tissue which might otherwise have been fatal to the animal.
Covered diplopores are more common in the upper Ordovician and Silurian diploporites than in the
lower and middle Ordovician forms.

TEXT-FIG. 14. Pore-structures of Haplosphaeronis kiaeri-, a, c, e in plan, showing thickenings and spine
development (a, b, c) on the peripore wall and b, d, f in cross-section showing angle of canals through the plates
in different parts of the theca, b, near oral area, with oxygenated body fluid moving towards oral portion, d,
midway down theca (note symmetrical arrangement of the two canals), f, near base with oxygenated body fluid
moving towards basal portion. Arrows indicate direction of flow of body fluid inside canals, a, b, c, thickened
parts of aporal portions of periporal rim; pps, periporal space; pc, canals (note they do not have the same

thickness throughout the plate).

22

PALAEONTOLOGY, VOLUME 27

Diplopores are less efficient respiratory structures than endothecal dichopores and, consequently,
more diplopores are needed to match the oxygen-carbon dioxide exchange rates achieved by cystoids
with endothecal structures. A calcitic cupola would have reduced the efficiency of respiration only
slightly, possibly as little as 10-15% (see Paul 1978).

Circulation in diplopores. In Haplosphaeronis the form of peripores differs according to their position
on the theca (text-fig. 14). In the oral area, the adoral canal of any diplopore slopes towards the oral
pole at an angle of 20-30° while the other canal is almost perpendicular to the surface. I suggest that
oxygenated body fluid passed down under the oral area in this part of the theca (text-fig. 14b). Similar
but reversed patterns have been found in the basal portion of the theca. Here oxygenated body fluid
passed down into the basal portion of the theca (text-fig. 14e). Canals between these two extreme
positions show variable angles, according to the location of the diplopore on the thecal surface.
Peripore distribution over the theca of Haplosphaeronis suggests a flow direction of body fluids
counteracting that of the external water current pattern around the theca (see Paul 1972). A similar
pattern has also been suggested for Hemicosmites (Bockelie \919a). The complex pattern of pore
systems found in Parasphaeronites n. gen. cannot be evaluated at present in terms of thecal flow
pattern. However, there appears to be a radiating pattern similar to that found in some species of
Telreucystis n. gen. and Spliaeronites.

Connections of canals inside the plates. In the aristocystitids branched haplopores have been known
since the work of Barrande (1887). In the Sphaeronitidae Paul (1972, fig. 8a, b) illustrated the two
possible models for peripore connections and argued strongly for the Y-shaped canals having fed
separate peripores. He showed how unlikely it was that the Y-shaped canal fed the same peripore,
because this would have created a mixing of oxygenated and deoxygenated currents. In some of the
Norwegian species of Haplosphaeronis the canals are filled with tiny pyrite crystals and terrigenous
mud. Careful dissolving of the thecal plates reveals canals going through the plate connected to canals
of adjacent peripores, confirming Paul’s fig. 8b (text-fig. 12).

Connections of canals of adjacent peripores occur frequently in H. kiaeri (text-fig. 20i) and have
also been observed in Eucystis globula Paul (SM A74861) and Parasphaeronites socialis n. gen., n. sp.
(text-fig. 12f; PI. 8, figs. 3, 6, 7). These connections indicate the presence of an internal circulation
system. Mapping the entire pattern of pore connections over the theca is exceedingly difficult and
time-consuming and requires exceptional preservation. Some idea of the pattern can be obtained
from Haplosphaeronis (text-fig. 20i). In this genus the diplopores are arranged parallel to the thecal
axis over most of the animal, with the peripores radiating from each of the oral corners. Connections
have only been observed between two adjacent diplopores at a time (text-fig. 20g). Pore canals merge
in such a way that one gets the impression of a dichotomously branched pattern (text-fig. 20i).

Diplopores may have been produced by coelomic evaginations, which could have led to a random
distribution of peripore connections. The radiating pattern observed in some Tetreucystis species
may be related to such a system. On the other hand, peripore connections such as those found in
Haplosphaeronis may indicate a more intricate and well linked flow system similar to the tube-feet
connections of echinoids. These differences in pore systems have considerable taxonomic implica-
tions. The second explanation accounts for the presence of a hydropore, but the first does not. Which
of the two alternatives is correct cannot be ascertained at present, but the fact that the diplopores
appear interconnected suggests the presence of a complex connective hydrovascular system. The
hydropore, which indicates the presence of a water vascular system, could thus be connected to the
pore system, rather than to a system of tube-feet located in the brachioles. Sprinkle (1973, p. 21)
suggested the absence of tube-feet in blastozoan brachioles. Paul (1967) suggested that both internal
and external branches of a water vascular system might have occurred in the rhombiferans. This is
also possible in the diploporites.

Internal morphology

Relatively little is known of the internal morphology of cystoids. Observations include mesenteria of
Echinosphaerites (Jaekel 1899; Regnell 1945) and the intestine of Caryocrinites (Rhombifera)

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

23

described by Jaekel (1918). Sinclair (1948) and Regnell (1951) also made internal observations.
Termier and Termier (1959) suggested the presence of various oral ring canals. Internal features are
known from the Oslo Region’s echinoderms, particularly Haplospluieronis.

Internal spine and basal pits. Many specimens of Haplosphaeronis have a hollow internal spine like
that described by Paul (1973, p. 21, text-fig. 12) from Sphaeronites (Peritapbros) and Haplo-
sphaeronis. This conical spine is well preserved in silicified specimens of H. kiaeri (text-fig. 22; PI. 4,
figs. 8, 9). It extends from the base for approximately one-third of the thecal height. It is a
continuation of the inside of the basal plates but the plates themselves seem to have amalgamated at
the base of the spine. However, one suture is present alongside the spine in some specimens. It may be
open for some distance and is internally strengthened by calcite. A hole is present at the adoral end of
the spine, indicating that it was hollow. An internal spine has been located in several genera of the
Sphaeronitidae {Haplosphaeronis, Sphaeronites (Peritaphros), Tetreucystis but not as yet in Eiicystis
or Sphaeronites {Sphaeronites): Paul 1973, p. 41). An internal spine may be present in the
Aristocystitidae {Calix and Pachycalix, Termier and Termier 1959), but it has not been recorded in
other diploporites.

The functional significance of the internal spine is unknown. It shows similarities to the chambered
organ of some crinoids, notably Neocrinus decorus as described by Reichensperger (1905) and
Eugeniacrinites caryophylatus (see Ubaghs 1978, p. T192, fig. 162.1), and may have served a similar
function. Regardless of its origin, the spine seems to have grown continuously during the animal’s
life, and must have served some function in both young and adult specimens.

Around the base of the spine and in contact with the inside of the basal portion of the basal plates
lie seven cavities penetrating into the thecal plates of Haplosphaeronis, one at each of the plate
sutures. In addition, a variable number of smaller cavities is found between the seven larger ones
(text-fig. 22; PI. 3, fig. 1 1). All cavities are present at approximately the same level and form conical
depressions. Several dozen specimens with this type of structure preserved have been found. In some
pyritized specimens (text-fig. 22d), a small depression surrounding the base of the spine is located
between the grooves on the inside of the thecal wall and the internal spine. This depression may have
housed an ectoneural nerve ring, and the grooves on the inside of the thecal wall may have been
locations for side canals (text-fig. 22). The grooves on the inside of the thecal wall were not
attachment areas for muscles or coeloms, since such attachment areas usually take the shape of bosses
or evaginations rather than invaginations.

An ectoneural nerve ring is known in many fossil and recent crinoids, it being the main nerve
system for innervation of arms and stem (Ubaghs 1978, p. T190), but there are great constructional
differences between the arms of crinoids and the brachioles of cystoids (Ubaghs 1978, p. T133). Even
so, an ectoneural nerve system was probably present around the base of Haplosphaeronis. Certain
internal features in the basal portions of the thecae of the diploporite Celticystis (Bockelie \ 919b) and
in the rhombiferan Hemicosmites (Bockelie 1979a) may also represent traces of an ectoneural nerve
ring. No traces of nerve canals leading from the base towards the oral area have been found.

Structures associated with the oral area. In sagittal view some specimens of Haplosphaeronis kiaeri
have cavities within the plate just under the ambulacra (text-fig. 23b; PI. 4, fig. 4). These may be parts
of a circum-oral structure, but as yet too few specimens have been studied to confirm this. Steinkerns
of decalcified specimens show an irregular underside of the theca just below the circum-oral area
(PI. 4, fig. 8) which may indicate that circum-oral structures were also present within the soft tissue
below the skeleton. Silicified specimens of H. kiaeri show five lobes (0-4 mm thick) just under the
ambulacral area (text-fig. 23a; PI. 4, figs. 3, 5). Even though details of the lobes are not adequate, there
is no doubt that at least one penta-lobate ring canal was present in the soft tissue of the circum-oral
area. Similar structures have been suggested for other diploporites (Termier and Termier 1959;
Bockelie 19796). The reconstruction of Pachycalix (Aristocystitidae) is particularly interesting in this
respect (Termier and Termier 1959; Kesling 1967, p. S245, fig. 143.2a) in which the presence of three
ring canals was suggested. Whether or not the ring canal observed in H. kiaeri is associated with the
water vascular system is not known.

24

PALAEONTOLOGY, VOLUME 27

Other internal structures. When decalcified, most specimens of Haplosphaeronis show traces of a
‘gonoduct’ and a ‘stone canal’ which are typical of other cystoids. These canals pass through the plate
on the left side of the theca. The close proximity of gonopore and hydropore makes it difficult to
decide which canal is the gonoduct and which the stone canal. However, in PMO 89996 (PI. 4, fig. 2)
the gonoduct and the stone canal are not connected, the former going straight down into the theca at
the left side of the periproct. The hydropore, which at the thecal surface is a slit on the top of an
elongated mound, becomes wider as it goes through the plate. When through the plate, the stone
canal bends to the right and is located in a groove on the inside of the theca between the peristome and
the periproct. The stone canal, which here has a circular cross-section, continues to the right and
bends towards radius V where it is located just under the ambulacrum. At this position it becomes
more flattened in cross-section and stops at the plate suture C04 : COS. It is possible that the stone
canal is connected to the penta-lobate ring canal just described. If this is the case, then it may indicate
a well-developed ring canal of the water vascular system. Sprinkle (1973, pp. 21-27) discussed
the possibility that tube-feet of the water vascular system were located in the brachioles but could
find no support for such an assumption. I agree with Sprinkle, and prefer to relate the water
vascular system to the blastozoan pore system. However, no fossil material exists to prove this
assertion.

Occasionally thin films of pyrite can be seen attached to the thecal interior which follow a pattern
not unlike that observed in Echinosphaerites by Jaekel (1899). These may represent remains of a
mesenterium, but the number of specimens involved is small.

MORPHOLOGICAL LINEAGES IN THE DIPLOPORITA

Evolutionary trends must fulfill two criteria: (1) they must involve closely related species (preferably
within one family); (2) they must be time dependent. Even if these two criteria are fulfilled, one is often
left with just the two end members, i.e. an early species and a late species. Two species of a genus might
be quite difterent, not only because they occur at different stratigraphical levels, and thus may
represent a phylogenetic lineage, but also perhaps equally important is the fact that they may occur in
two different environments. Morphological lineages can be observed in some diploporite cystoids,
but often they can only be inferred. In many cases the importance of morphological lineages in
phylogenetic evolution cannot be evaluated. Haplosphaeronis illustrates some of the problems
involved. Specimens occurring in shales are usually smaller than those in nodular limestones. The
smaller specimens may be adults in the shale populations, whereas individuals of similar size
occurring in nodular limestones may not have reached maturity. The number of brachiole facets of
this genus increased during ontogeny (Bockelie 1978a), but to demonstrate this required large
collections. One might have concluded that the number of brachiole facets changed with time,
rather than ontogeny. Some mophological lineages, or what appear to be such, are discussed
below.

Thecal plates. The number of thecal plates may increase or decrease with time in some genera. In
Sphaeronites a reduction in plate number occurs from early to late Ordovician (Paul and Bockelie
1983). In other genera this has not been studied to the same extent. There is a general tendency
towards reduction in the number of plates in many cystoids (see also Bockelie 19796). A reduction
takes place when the number of plates present in young individuals is retained to the adult stage.
Enlargement of the theca then occurs by growth of individual plates only and not by the addition of
secondary or tertiary generation plates. In this respect, Haplosphaeronis is an advanced genus because
the number of thecal plates remains constant in young and adult specimens. Celticystis (Bockelie
19796) and Protocrinites (text-fig. 16) add new thecal plates in particular ‘growth zones’. Plate
reduction with time is also marked in many primitive echinoderms. The change from a large number
of irregularly arranged calyx plates to a much smaller number usually showing good pentameral
symmetry appears to have occurred independently in several groups of both Blastozoa and Crinozoa.
In species with a large number of thecal plates, individuals seldom have the same arrangement of

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

25

calyx plates (see Protocrinites, text-figs. 16, 17). In species with a total plate number between fourteen
and thirty-five the plates are arranged in symmetrical patterns, and most individuals of the same
species have their plates arranged in the same manner.

Ambulacra. In the diploporite cystoids most genera and species have five ambulacra, but genera with
two, three, and four exist. In the Sphaeronitidae genera with four ambulacra have radius III reduced
( Tetreucystis n. gen., Diplosphaeronis). In other families genera and species with four ambulacra exist
{Trematocystis, Holocystidae; Parasphaeronites n. gen. and Pachycystis n. gen., Parasphaeronitidae).
These genera and species are parallel lineages in which radius III is reduced.

In Eucystis the number of brachiole facets and their position over the theca differs with time.
Ordovician species may have from one to four facets close to the mouth. During the upper Ordovician
and particularly in the Devonian the number of facets increased and the food grooves migrated down
over the sides of the theca (Bockelie 1978a) resulting in an increased area for food collecting. An
increase in the number of brachiole facets also oecurred in Tetreucystis n. gen. and in Haplo-
sphaerouis, but in complex ways. As mentioned previously, the highest number of brachiole facets in
Haplosphaeronis is found in Britain, whereas contemporaneous species both in Norway and Sweden
have fewer faeets. In Tetreucystis n. gen., British species have few brachiole facets, Norwegian species
have an intermediate number, and contemporary Swedish species have the highest number. What
might appear to be a phylogenetic trend may in fact have been related to contemporary ecological
conditions.

In Haplosphaeronis the brachiole facets may have different shapes (text-fig. 19). In an early species,
H. hratterudensis n. sp., the first formed facets (Bockelie 1978a) usually have a rounded outline,
whereas later ones are angular or almost square. During the late middle Ordovician and the upper
Ordovician all facets became rounded in outline (text-fig. 19c, d). A general impression is that the
facets also became larger during that same time span. Similar studies do not exist for other genera and
species, and thus it is difficult to evaluate how common such a morphological trend may be. Early
Ashgill species of Tetreucystis n. gen. generally have smaller brachiole facets than later Ashgill forms,
and species with only one facet in each ambulacrum have larger facets than those with more. How-
ever, one facet in each ambulacrum is primitive while the presence of several facets is a derived
character, as can be demonstrated in several genera and species (see also Bockelie 1978a). In Proto-
crinites young individuals have few facets, whereas older individuals have more (text-figs. 16, 17). In
Celticystis new facets are added constantly (Bockelie 19796).

Pore structures. The pore structures underwent changes throughout their history. A study of
diplopores and their changes with time has been undertaken in Sphaeronites (Vau\ and Bockelie 1983)
where there is an increase in the size of the pores and a corresponding decrease in their number. In
Haplosphaeronis the width of the peripores decreased during the Ordovician (text-fig. 25). One of the
most marked changes found in the pores of Haplosphaeronis is the elevation of the periporal floor
from a position below the thecal surface in H. hratterudensis (early Caradoc) to a position level with
or above the thecal surface in H. kiaeri (upper Ordovician). Together with this trend is an increase in
the aporal portion of the peripore to form a spine-like peripore rim (PI. 5, fig. 3).

The formation of a calcitic cupola can be observed in several genera and species throughout
the Ordovician and appears to be a parallel development. No calcitic cupola is present in H.
hratterudensis but it is very common in H. kiaeri and has also been found in British Ashgill species and
some populations of the Swedish upper Ordovician H. ohlonga. A calcitic cupola seems to accompany
an elevation of the peripore from the thecal surface. Thus in most diploporites where the peripores are
present on ‘pustules’, they have a calcitic cupola.

Haplopores have been considered the simplest type of pore structure but this may not be correct.
The internal connections of pore structures are not well known so we do not know the course of
canals through the plates in many diploporites. However, the external peripore in many of the early
Ordovician species is sunk below the thecal surface and may have a weakly developed periporal rim
and represent a simple stage (text-fig. 1 5a). During the middle Ordovician the periporal floor became
elevated in Haplosphaeronis and Sphaeronites (Peritaphros) (text-fig. 15b). By a further elevation of

26

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 15. Morphological series of changes in pore structures, a, simple, open pores, b, formation of
elevated periporal floor and slight diversion of body fluids into two separate currents, c, tri-partition of body
fluids in tangential canals, d, more complex pattern of tangential canal formation, a, b, c, cross-sections
of pore structures within the general form patterns, aj, simple peripores in Glyptosphaerites and early
Haplosphaeronis species, bj, \>2, development of an elevated periporal floor, typical of Sphaeronites
(Sphaeronites) and S. (Peritaphros) species (a broken line indicates non-calcified periporal roof; a continuous
line indicates calcified periporal roof. Cj-Cj, stages of development in Holocystitidae and Aristocystitidae in
which calcified cupola is commonly present (note elevation of the periporal floor to form knobs with large

surface areas).

the periporal floor a calcific cupola was formed over the peripore, probably to keep a constant volume
within the pore space or to protect these vital structures from predation. Most diploporite pore
structures did not evolve beyond this stage (text-fig. 1 5b). In some genera the periporal floor divided,
thus separating the currents of body fluids into the two flow directions seen in S. {Peritaphros), or into
three or more such currents (text-fig. 1 5c, d). In extreme cases the cupola became strongly elevated
(text-fig. I5C3). The trend towards the formation of humatipores in the Holocystitidae and a
pustule-like cupola may be regarded as stages in the evolution of a better protected respiratory
system.

It seems that the changes with time found in the respiratory pore structures are most important for
the class Diploporita. It is probably likely that morphological trends of the brachioles are equally
important (see above), but without suitable material, this is speculation.

SYSTEMATIC PALAEONTOLOGY

Phylum ECHiNODERMATA Bruguiere, 1789
Subphylum blastozoa Sprinkle, 1973
Class DIPLOPORITA Muller, 1854

Diagnosis. Thecal pores developed as units mostly confined to single plates, typically in the form of
diplopores, but present in some as haplopores or humatipores. Lower Ordovician (Tremadoc)-
middle Devonian.

Remarks. Brachioles of the Diploporita do not differ from those of most Rhombifera or most
Eocrinoidea. Paul (1968a, p. 594; 19686, pp. 726, 727) proposed that the name Cystoidea be dropped
and that the Rhombifera and Diploporita be given class rank. This was accepted by Sprinkle (1973,
p. 170) and is also accepted here. Sprinkle (1973) discussed whether or not the Diploporita should be

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

27

assigned to the Blastozoa. The discovery of biserial appendages in several genera of the Diploporita
strengthens the assumption that this class belongs to the Blastozoa (see also discussion by Chauvel
1977, p. 317). The diagnosis given above differs to some extent from that of Ubaghs (1978, p. T362)
who did not recognize the subphylum Blastozoa. However, this present study shows that the
Diploporita have the type of plate growth which is characteristic of other Blastozoa.

The Diploporita appear to be a fairly homogeneous group of primitive echinoderms, all having
exothecal pore systems. The Diploporita seem to form a natural group but this is not so with the
Rhombifera. As suggested by Paul (1972) and discussed by Sprinkle (1973, p. 170), the Rhombifera
consist of two distinct groups of cystoids, one with endothecal structures and one with exothecal pore
structures. It is difficult to see how one could have given rise to the other.

Superfamily glyptosphaeritida Bernard, 1895

Diagnosis. Diploporite cystoids. Ambulacra radial, extending over theca, with alternating lateral
branches (single or in groups) leading to brachiole facets; in many genera, ambulacra bordered by
alternating ‘adambulacrals’ on which facets are located. Diplopores invariably present on
ambulacra-bearing plates, in some forms also in the interambulacral areas. Most with column, a few
moulting column as adults.

Family protocrinitidae Bather, 1899

Diagnosis. Diplopores on ambulacral and interambulacral plates alike. Ambulacra extending
radially from peristome, with short branches to brachiole facets more or less alternating. Ambulacral
cover plates continue on to the oral area where they become oral cover plates. Thecal plates bearing
rather regularly alternating ambulacral plates comprising so-called ‘adambulacrals’. Brachioles
biserial.

Remarks. Genera of the family Protocrinitidae differ considerably from those of the Glyptosphaeri-
tidae. These two families are grouped together with the Dactylocystidae and the Gomphocystidae in
the superfamily Glyptosphaeritida by Kesling (1967). Glyptosphaerites, the only representative of the
Glyptosphaeritidae, has an oral cover resembling that of sphaeronitids but differs considerably
from that of all other families. Thus the Glyptosphaeritidae may be more closely related to the
Sphaeronitidae than to other families. The Protocrinitidae and the Dactylocystidae seem to form a
natural unit, quite different from the other two families of the superfamily. A subdivision of the
Glyptosphaeritida may prove necessary in the future.

Genus Protocrinites Eichwald, 1840

Type species. Protocrinites oviformis Eichwald, 1840, p. 185, from Poosaspea (Spitham), Estonia, Johvi Stage
(DI), middle Ordovician.

Diagnosis. A genus of Protocrinitidae with triangular peristome surrounded by six circum-oral plates;
five ambulacra, each containing dichotomously branched food grooves, terminating in a facet on
each thecal plate, or continuing on to biserial appendages when present; ambulacra confined to
specialized adambulacral with one facet on each adambulacral plate; adambulacral plates separated
transversely by one or occasionally two interambulacral plate series.

Remarks. This diagnosis differs from that given by Kesling (1967) in several respects, partly because
the number and distribution of circum-oral plates may be an important character of most cystoids. In
the Sphaeronitidae, this is certainly the case. Jaekel (1899) regarded Fungocystites Barrande as a
synonym of Protocrinites but later (1918) accepted the two as separate genera.

Description. The thecae are apple or egg-shaped. P. rugatus sp. nov. is small with thecal diameter 1 5 mm, whereas
P. oviformis and some P. fragnm are 50 mm. Five ambulacra, each containing dichotomously branched food
grooves, extend from the mouth. The ambulacra do not reach down to the basal plates, but stop on the third

28

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 16. Protocrinites rugatus n. sp. Adult thecae, a, b, PMO 101.132, dififerent views showing
radii IV and V and position of gonopore (G?) and periproct (Pe) in relation to ambulacrals and
interambulacrals (iam). Notice that ambulacral channels end in the growth zone (vertically ruled), c,
PMO 101.138, showing biserial brachioles (dotted), brachiole facets (F) and some diplopores radially
arranged on the ambulacral plates, s, proximal portion of the stem. Scale bar, 5 mm.

plate series up from the basals (text-fig. 16; PI. 1, fig. 8). New ambulacral facets were added to the distal portions
of the ambulacral furrows throughout life. The number of facets per ambulacrum increased from two in young
specimens to nine in larger ones. The ambulacral furrows are covered by small cover plates arranged in an
intricate pattern (text-fig. 17b; PI. 1, fig. 3). A biserial appendage up to 15 mm long extended from each of the
ambulacral facets. The appendages are as long as the theca itself (text-fig. 16; PI. 1, figs. 1, 4).

The basals of Protocrinites vary in number. According to Volborth (1846) the number in P. oviformis can vary
between three and six. In P. rugatus sp. nov. all the basals are fused into one unit. Diplopores are present all over
the theca. In Norwegian species it appears that most or all the pores were covered in life, either by an organic
membrane or, most likely, by a thin calcific membrane. This membrane was easily abraded, leaving the pores
open in specimens exposed for some time before final burial. The pores on adambulacral plates tend to be
orientated with their long axes perpendicular to the ambulacrum, as observed by Jaekel (1899, pi. 5, fig. 6u).

The periproct is situated laterally on the theca, but its position may vary (Jaekel 1899). In general, two or three
plates separate the periproct from the mouth (text-fig. 1 6a). The periproct is circular and covered by a pyramid of
five or six triangular plates. Both a gonopore and a hydropore have been reported on P.fragum (Yakovlev 1940,
fig. 1). In the Norwegian material a tubercle may be present either on the COS : C06 suture (PMO 101.138 and
101.1 36) or on the left sutural area of the upper interambulacral plate between radii V and I (PMO 101. 132 and
1 0 1 . 1 30, text-figs. 1 6a, 1 7a). This tubercle may represent either the gonopore or the hydropore. Eichwald ( 1 840)
and Jaekel (1899, pi. 5, fig. 3) also observed a tubercle on C06.

Attachment: some species had a stem, and one was certainly present in P. yakovlevi (Hecker 1964, pi. 5, fig. 5)
and P. rugatus sp. nov. (PI. 1, figs. 1, 2). In P. yakovlevi 'dw attachment disc was present. Discs may also have been
present in other species. In P.fragum no stem has been observed. Jaekel (1899, p. 430) suggested that this species
lacked a stem in adult stages. P. oviformis is known to have had a stem when young, but it was lost in adults
(Volborth 1846).

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

29

Growth: the growth pattern of Protocrinites was previously unknown. In the Norwegian material, however,
one small specimen occurs together with larger ones. The plate configurations and food-gathering appendages
give some indication of the growth pattern. In the smallest specimen (5 mm high, 5 mm in diameter) only two
brachioles are present in each of the ambulacra, whereas in larger specimens seven to nine brachioles are present
per ambulacrum depending upon the size of the theca. This indicates that new appendages were added through
life. The length of the brachioles also seems to have been related to thecal size. However, few specimens have
complete brachioles. The ratio of brachiole length to thecal size is greater in smaller specimens than in larger ones
(text-figs. 16, 17c). This may indicate that the small specimens could obtain proportionally larger quantities of
food for rapid growth.

New plates were added; the important growth zones seem to be in the third plate series from the base of the
theca (text-fig. 16). The plates in this zone do not appear to be differentiated, whereas those immediately adorally
do (text-fig. 1 6). Growth in this part of the theca did not interfere with food-gathering, nor with the stem and its
attachment to the basals. The theca also grew by normal accretionary growth of individual thecal plates
(Sprinkle 1973). The addition of new thecal elements in this growth band thus comprises: ( 1 ) addition of new
thecal plates, including adambulacrals and interambulacrals; (2) continued extension of ambulacral furrows and
ambulacral cover plates; (3) formation of new brachiole facets; and (4) possibly formation of new diplopores.
Diplopores also appear to have been formed by resorption of skeletal material wherever a new pore was needed,
and their formation may have been less important than the formation of other thecal elements in the
growth zone.

Palaeoecology. The stem-bearing Norwegian speeies lived on a muddy bottom in an unstable
sedimentary environment. P. oviformis is not uncommon in the Johvi stage in Estonia and Russia but
little is known concerning its palaeoecology. According to Jaekel ( 1 899, p. 430) P. fragum was heavy,
stemless, and probably free-living on the sea bottom. Its size and shape suggested to him slow
movement, if any. The somewhat flattened shape of the animal would have prevented it from sinking
into the soft sediment on which it lived. P. yakovlevi was attached by a stem and a disc, but nothing is
known about the environment in which it lived.

Regional distribution. Norway, Estonia, Leningrad district of Russia (Jaekel 1899; Hecker and Hecker 1957),
Thiiringen, Germany (Freyberg 1923), Burma, India (Bather 1906).

Stratigraphical range. Arenig-Caradoc.

Protocrinites rugatus n. sp.

Plate l,figs. 1-8; text-figs. I3a-h, 16, 17

Diagnosis. A species of Protocrinites with a strongly rugose plate surface and stem present.
Interambulacral rows may contain two interambulacral plates in interradius IV-V. Basals fused to
form a solid basal cup for stem attachment.

Holotype. PMO 101.138 preserved as an external mould.

Horizon and locality. Coelosphaeridium Beds of Furuberg Formation (lower Caradoc), northern part of the
Oslo Region. The type derives from a loose boulder, but equivalent sediments and associated fauna is restricted
to the Toten-Brummundalen areas in the northerninost part of the Oslo Region.

Material. In addition to the holotype, seventeen specimens (sixteen of which derive from the same boulder) are
considered to belong to this species.

Description. Theca: egg-shaped, height/width ratio varies between 1.2 and 1.7.

Plates: about a hundred in adults. The plates are regular pentagonal or hexagonal. The main addition of new
plates is considered to have taken place adoral to the basals (text-fig. 16; PI. I, fig. 8). The plate surface is usually
strongly ornamented with nodes or spines, obliterating the diplopores. Plate thickness is approximately 1 mm.
The sutures between contiguous plates are irregular and interlocking like those of Celticystis (Bockelie \919b).

Diplopores: with or without a periporal rim; periporal floor below thecal surface. Diplopores seem to have
been present on all thecal plates including the basals. The peripores are relatively small, seldom exceeding
0.40 X 0.25 mm.

Peristome: 1 x 2 mm in adults. In PMO 101.136, C05 and C06 may be partly fused, but in other specimens a
clear suture is present. The mouth is covered by numerous ambulacral cover plates which are somewhat bigger

30

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 17. Prolocrinites ntgatus n. sp. A, PMO 101.130, oral area showing six circum-oral plates (1-6)
and the relationship of ambulacral plates (am) to the inter-ambulacrals (iam); ambulacra! cover plates
continue from brachioles towards and on to the mouth as oral cover plates, b, PMO 101.133, details of
ambulacrum with cover plates of variable shape, c, PMO 101.458, juvenile specimen with complete
brachiole in radius I (dotted); each ambulacrum has two brachioles; no gonopore developed. G?,
gonopore; F, brachiole facets; vertically ruled area not exposed; scale bars 1 mm.

than cover plates in other parts of the theca (text-fig. 17 a; PI. 1, fig. 3). The ambulacral grooves are approximately
1 mm wide and covered by large triangular plates along their sides, with smaller often irregular plates
intercalated. Towards the base the ambulacral grooves become thinner (0-25 mm). The food grooves continue
on to unbranched biserial brachioles (text-fig. 17a; PI. 1, figs. 1, 5-8), the largest of which measures 15 mm. Two
cover plates seem to be attached to each brachiole element (text-fig. 13; PI. 1, fig. 7). The structure of the
brachioles thus may resemble that of the eocrinoid Gogia hugidactylus (Sprinkle 1973, text-fig. 10).

Periproct: large, round, 2-5-3-5 mm in diameter and covered by an anal pyramid of five or six triangular plates
(PI. 1, fig. 6). The periproct lies about mid-height in interradius V-I separated from the mouth by three plate
series (text-figs. 16, 17).

Gonopore/hydropore: a tubercle present on the C05 : C06 suture, or at the suture between adambulacral and
interambulacral plate just below C06, may be a hydropore.

Attachment: a flexible stem was present in life, with complex nodals and internodals. The stem is similar to that
of crinoids, and at least 8 mm long.

Palaeoecology. I believe that they all lived in fairly shallow clear water, on a muddy bottom with few
properly sessile elements, in an area commonly covered by coarser sediments at irregular intervals.

Remarks. P. rugatus differs from other Protocrinites species in the amalgamation of its basals to form
a solid socket.

EXPLANATION OF PLATE 1

Figs. 1-8. Protocrinites rugatus n. sp. Coelosphaeridium Beds, Furuberg Formation, northern Oslo Region. 1,
PMO 101.138, stereophotos of holotype, x 3. 2, PMO 101.132, lateral view showing two ambulacra and
stem, X 2. 3, PMO 101.133, stereophotos of oral area showing plate configuration and ambulacral and oral
cover plates, x5. 4, PMO 101.133, lateral view showing theca and incomplete brachioles, x 1. 5, PMO
101.130, stereophotos of biserial brachioles and ambulacrum with cover plates preserved, x 7. 6, PMO
101.130, stereophotos showing anal pyramid and brachioles, x4. 7, PMO 101.133, brachiole with
brachiolar cover plates (two cover plates to each brachiole element), x 5. 8, PMO 101.132, details of
ambulacrum with cover plates. The ambulacrum stops in the third plate series from the base. This is the
growth zone where new plates and extensions of the ambulacrum are added, x 5.

PLATE 1

BOCKELIE, Protocrinites

32

PALAEONTOLOGY, VOLUME 27

Superfamily sphaeronitida Neumayr, 1889

Diagnosis. Stemless Diploporita with variable-shaped theca; almost all plates pierced by diplopores;
peristome covered by a roof (palate) of six plates beneath which food grooves pass to the mouth; four
or five ambulacra; food grooves narrow, generally short but extending over theca in some species;
periproct covered by pyramid of triangular plates; circular gonopore and generally slit-like
hydropore between peristome and periproct, and to the left.

Remarks. Paul’s ( 1 973, p. 1 8) definition of the superfamily is accepted here, but whether or not cover
plates where present on the ambulacra is not known.

Family sphaeronitidae Neumayr, 1889

Diagnosis. ‘A family of Sphaeronitida with diplopores; peristome surrounded by six circum-oral
plates with a small additional plate (C07) between the peristome and the periproct but not in contact
with the former; four or five ambulacra with one or more ambulacral facets each’ (Paul 1973,
pp. 18, 19).

Remarks. The pore structures of Diploporita seem to be more complex than previously considered—
for instance, both haplopores and diplopores have been found in the aristocystitid Calix sedgwicki.
Some diplopores of Eucystis also branch in an unusual way.

Genus Sphaeronites Hisinger, 1828

Synonymy. See Paul (1973, p. 19).

Type species. Echinus pomum Gyllenhaal 1 772, by original designation, p. 242, pi. 8, figs. 1 -3; from the Asaphus
Limestone (Arenig), Kinnekulle, Vastergotland, Sweden (Regnell 1945, pp. 162, 163).

Diagnosis. A genus of Sphaeronitidae with globular to pyriform or fusiform theca composed of
approximately forty to two hundred plates which are irregularly arranged except in the oral area;
peristome and periproct very close together on smooth oral prominence; five ambulacra with one to
three facets each; all thecal plates uniformly covered with diplopores (except in attachment area);
attachment direct.

Remarks. The diagnosis agrees with that of Paul (1973, p. 19), except that the number of brachiole
facets in an ambulacrum may reach three.

Subgenus Sphaeronites (Peritaphros) Paul, 1973
Sphaeronites {Peritaphros) pauciscleritatus Paul and Bockelie, 1983
Plate 2, figs. 2-4; text-fig. 18a
Synonymy. See Paul and Bockelie (1983, p. 723).

Diagnosis'. ‘A species of Peritaphros with large globular theca reaching 40-50 mm in diameter in adult
specimens; thecal plates limited (fifty to sixty); diplopores polygonal (0-4 x 0-4 to 0-4 x 0-6 mm in
adult specimens), average pore density 7-40 per mm^’ (Paul and Bockelie 1983, p. 724).

T\’pes. Holotype, PMO 79687 (PI. 2, figs. 2, 3); paratypes, PMO 6183, 90042, 90043, 90289, 90293, 90297, 90347,
90349, 90350, 90351 (Paul and Bockelie 1983, p. 724).

Horizon and locality. Middle part of Lower Chasmops Limestone ( = Stage 4b/3), middle Caradoc, Oslo-Asker
District of the Oslo Region, Norway.

Remarks. Morphology and palaeoecology is described by Paul and Bockelie (1983, p. 726).

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

33

Genus Haplosphaeronis Jaekel, 1926

Synonymy. Sphaeronis Angelin, 1878 (pars); SphaeronLs auctorum; Pomocystis Haeckel, 1896; Pomosphaerci
Haeckel, 1896.

Type species. Haplosphaeronis kiaeri Jaekel, by monotopy, in Kiaer, 1926, p. 20; from the Gagnum Shale
Formation (= Sphaeronid Shale of Kiaer 1926), lower Ashgill, Hadeland, Oslo Region, Norway.

Diagnosis. A genus of Sphaeronitidae with fourteen thecal plates arranged in two circlets of seven
each; oval or dumb-bell shaped diplopores mostly arranged with their long axis in an ad-aboral
direction; five ambulacra each with from one to ten food grooves in a fan-like arrangement at corners
of peristome, confined to circum-oral plates.

Remarks. This diagnosis differs only slightly from that of Paul (1973, p. 27). Specimens containing
only one groove per ambulacrum exist, especially in young specimens of at least two species. Bockelie
(1978a) showed the number of food grooves per ambulacrum to increase with growth. The taxonomic
value of the number of such grooves is dubious. However, stratigraphically younger species do have
more grooves per ambulacrum than older species with the same thecal diameter. The type specimen
of the genus is lost or mislaid; it has not been in the type collection for at least twenty-five years.

Description. The thecae of Haplosphaeronis are variable in shape, both between and within species. Mostly they
are spherical to pyriform, but almost flat disc-shaped specimens occur. Many Norwegian specimens are shaped
like an inverted pear or are mitre-shaped. British and Swedish species have a pentalobate outline in some
populations. No stem is present. Most Norwegian specimens of both species are small, seldom exceeding 15 mm
in diameter. In Sweden, however, individuals reaching 45 mm in height and 30 mm in diameter occur locally.

Plates: there are two circlets each with seven plates. The lower circlet has more or less equal-sized plates, while
the upper circlet has five large plates bearing the ambulacra and two smaller plates (C06 and C07) inserted
between the peristome and the periproct (text-fig. I Ic). Jaekel’s (1926, p. 19) original description of the genus
appears to be correct, as discussed by Paul (1973, p. 28). Individual plates are thick (approximately I mm) and
pierced by numerous diplopores. Little is known of the plate meshwork. However, silicified specimens often
show the inner portion of the plates to be silicified more easily than the outer portion. Pyritization also occurs
by filling the mesh of the inner portion of the plate more frequently than the outer part. By analogy with
Archaegocystis, as described by Paul (1971, p. II), and with Parasphaeronites n. gen., one may assume the

TEXT-FIG. 18. A, Sphaeronites (Peritaphros) pauciscleritatus Paul and Bockelie, PMO 79687 (see PI. 2, figs.
2, 3); oro-anal area showing four oral cover plates (Ol, etc.), hydropore (H), gonopore (G), and periproct
(Pe) on the oral platform (op) which is devoid of diplopores (d). B, Haplosphaeronis kiaeri ]a.eke\. PMO 89972
from 5-5 to 6 0 m level, Gagnum Shale, Tonnerud, Hadeland; oro-anal area showing oral cover plates (Ol,
06), major thecal openings, and characteristic tubercular ornament (t). c, d, Haplosphaeronis hrattenulensis
n. sp., PMO 89201 from Lower Chasmops Limestone, Bratterud, Ringerike, holotype; c, from above and u,
in lateral view (note the radiate pattern of diplopores).

34

PALAEONTOLOGY, VOLUME 27

presence of an outer fine mesh and an inner coarse mesh. Weathered specimens of H. cf. kiaeri from 16 to 17 m
below the top of the Upper Chasmops Limestone at Raudskjasr, Asker, show the crystallographic orientation of
palatals covering the mouth (text-fig. 20h). One weathered specimen (PMO 90965) shows fine lineations,
representing cleavage, within the calcite plates. The direction seen on one plate always differs from those of the
adjoining plates. The angle of dip cannot always be ascertained, but the direction of dip changes from one plate
to the next, e.g. Ol, 03, and 05 dip away from the mouth, whereas 02, 04, and 06 dip towards the mouth.
A similar pattern has also been observed in other specimens, and may be typical for Haplosphaeronis species in
general. All thecal plates have numerous rather specialized diplopores. Small knobs or tubercular ornament may
be present between the diplopores. Occasionally these are either new pores in the process of formation, or pores
that have been reduced.

Thecal openings: the peristome is large and covered by six palatals (Paul 1971), two of which may be almost
fused (Ol and 06). The palatals are arranged in the usual manner for sphaeronitids (text-fig. 1 Ic). The periproct
is oval or pyriform with a covering pyramid of five to seven anals. The apex of the anal pyramid is frequently
directed towards the oral region (text-fig. 18d). Laths are developed on the inside of the lower edge of the
periproct, as also seen in Tetreucystis n. gen., and this suggests that three or four of the lower plates of the anal
pyramid were able to open outwards, whereas the adorally located pyramid plates were not flexible (text-
fig. 26b, c; pi. 2, fig. 6). This arrangement would have permitted faecal matter to fall down over the theca into the
zone of maximum current velocity around the theca and thus be transported away from the animal. The faecal
matter was probably in the form of small pellets. Between the peristome and the periproct, and to the left, is a
small usually circular gonopore and a slit-like hydropore (text-fig. 18b). The hydropore is always located on top
of a slightly elevated ridge, reducing the possibility that sediment particles would have entered the slit. The
gonopore may have been covered by a pyramid of small triangular plates, but this has never been observed. Such
plates are only known in fistuliporite Rhombifera.

Diplopores of Haplosphaeronis are mostly elongated and typical of the genus. They are numerous and spread
over the thecal surface, usually aligned in an ad-aboral direction. However, some of the pores near the plate
edges (probably the last ones formed) are set perpendicular to this direction. In stratigraphically older species the
perpendicular arrangement of diplopores is absent (PI. 2, figs. 7, 8). In the circum-oral plates the diplopores are
arranged in a fan-like manner (PI. 3, fig. 3) with diplopores in rows. The number of rows gives some indication as
to how many growth stages the cystoid has gone through (e.g. a specimen with five rows is probably older than a
specimen with only three rows). As many as twelve rows have been observed in some specimens of H. proiciens
Regnell. The length and width of individual peripores in the different rows may vary. The diplopores at plate
sutures are often smaller than other pores of the theca. It seems that new diplopores were added at plate sutures
throughout the growth of the theca, and reached maximum size fairly rapidly.

Ambulacral system: the peristome is always pentagonal and may have five raised ambulacral platforms at the
corners. One to ten food grooves radiate in a fan-like pattern on each ambulacral platform and terminate in small
(usually 0-5 mm in diameter) ambulacral facets at the outer edge (text-fig. 19). The brachioles were biserial, as
indicated by the small ridge between the pair of muscle-scars on each facet. The ambulacral furrow leading to the
first formed facet is always perpendicular to the adjoining oral edge, whereas later ones are not. Between adjacent
ambulacral facets and their ambulacral structures, ridges are developed to separate them. These ridges are of
different types and details of their structure may be of some taxonomic importance. Two main shapes of facet

EXPLANATION OF PLATE 2

Fig. I . Sphaeronites (Peritaphros) globulus (Angelin). Dalby Limestone, Boda Harbour, Oland, Sweden. RM Ec
4360, stereophoto of holotype showing oral-anal region, approximately x 10.

Figs. 2-4. Sphaeronites (Peritaphros) pauciscleritatus Paul and Bockelie. Lower Chasmops Limestone,
Fyrsteilen, Oslo-Asker. 2, 3, PMO 79687, cast of holotype showing 2, diplopores and 3, oral view of oral area,
X 6. 4, PMO 90042, cast of oral area in oral view, Hareholmen at Ostoya, Baerum, x b.

Figs. 5-8. Haplosphaeronis hratterudensis n. sp. Lower Chasmops Shale, Bratterud, Ringerike. 5, PMO 89201,
cast of holotype, stereophoto of oro-anal area (specimen whitened with ammonium chloride sublimate), x 4.
6, PMO 89202, stereophoto of cast showing anal region with shelf for attachment of anal plates in aboral side,
x 7. 7, PMO 89209, stereophoto of cast showing diplopores in circum-oral plates, x 6. 8, PMO 89213,
stereophoto of cast showing diplopores in basal plates, x 6.

PLATE 2

BOCKELIE, Sphaeronites (Peritaphros) and Haplosphaeronis

36

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 19. Brachiole facets of Haplosphaeronis species. The stratigraphically oldest species to the left, the
youngest to the right, a, H. bratterudensis n. sp., PMO 89201, holotype. B, H. cf. kiaeri Jaekel, PMO 102.757,
from Solvang Formation, Gagnum Farm, Hadeland. c, H. kiaeri Jaekel, PMO 101.939, from Gagnum
Limestone (27-28 m level), Tonnerud, Hadeland. d, H. midtifida Paul, SM A 74796, original of Paul (1973,
pi. 2, fig. 3). The oldest species has angular facets with deep incisions while later species have more rounded

brachiole facets with small incisions, if any.

have been observed: ones with rounded edges and ones with square or angular edges (text-fig. 20c, d). The
incisions between adjacent facets may be of two types: either deep and broad incisions, leaving fairly large spaces
between individual facets, or small and narrow incisions, only just separating the outer edges of individual facets
(text-fig. 20a, b). The deep incisions are found mostly amongst the earliest species and the smaller incisions
amongst later ones. Both types can occur together in the same individual.

Nerve system: both a basal and an oral nerve ring occur in Haplosphaeronis. Paul (1973) also suggested the
presence of an oral nerve ring, and nerve canals entering individual brachioles at their facets. Details of this are
not known.

Attachment: all Haplosphaeronis species were attached directly by their base. The attachment area is usually
concave and adjusted to the shape of objects to which thecae were attached. Specimens of Haplosphaeronis have
been found attached to other Haplosphaeronis individuals, to stick bryozoa, brachiopods, cephalopods,
trilobites, and crinoid ossicles. Many specimens show no imprints of the objects to which they were attached, and
may thus either have been attached to soft-bodied animals, such as ascideans, or to algae.

Ontogeny and phytogeny. The shapes and sizes of individuals of Haplosphaeronis (and other cystoids)
depend on the environmental conditions, such as substrate, nutrition, etc. Details of growth pattern
can only be obtained through studies of large samples. Individuals from populations at different
stratigraphical levels may vary considerably.

Ontogeny: in some populations it is possible to study parts of the ontogeny, but usually the
youngest individuals (less than 5 mm) are extremely rare. The major thecal openings (mouth, anus,
gonopore, and hydropore) increased in size isometrically during ontogeny. The number of thecal
plates remained constant, and thecal size only increased by accretionary growth along the sides of
individual plates. The attachment area increased with growth, but no relationship exists between the
size of the attachment area and the size of the animal. The most striking ontogenetic change was in the
addition of new ambulacral facets. Very young individuals all appear to have had one facet only in
each of the five ambulacra (see Bockelie 1978o). New facets were added continuously during growth
but, at a stage which might be interpreted as adult, a sudden rapid increase occurred. Whereas the
number of brachioles in Norwegian adult Haplosphaeronis is relatively large, the total number of
Swedish specimens of H. oblonga of the same diameter is lower. One explanation is that the brachioles
of Swedish species were longer; alternatively, the uptake of food was greater in Swedish than in
Norwegian populations. The addition of new diplopores during growth is not clearly understood, but
possibly new pores were formed by resorption of the skeletal mesh. Pores were added throughout
thecal growth. Pores close to the plate sutures are usually smaller than those towards the plate centre,
which may indicate that they grew until a certain size was reached. It seems that the initial growth was
more rapid than the later growth. The growth rates of thecae of Haplosphaeronis species may be
different (text-fig. 24), resulting in different shapes.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

37

TEXT-FIG. 20. Morphological features of Haphsphaeronis. a-f, types of brachiole facets and food grooves
showing A, small incisions between facets; n, deep incisions between facets; c, rounded fringes of facets; d,
angular fringes of facets; e, wide or expanded food grooves; and f, narrow food grooves, g, H. cf kiaeri
Jaekel, PMO 89933, from Upper Chasmops Shale, Solheim-Rud, Ringerike; connections of peripores within
thecal wall showing two diplopores connected and possible connection to a third diplopore (c). H, H. cf kiaeri
Jaekel, PMO 90965, from Upper Chasmops Limestone, 16-17 m below Tretaspis Shale, Raudskjasr, Asker;
orientation of cleavage planes (?) and direction of dip in weathered specimen (note that direction of dip
alternates regularly from one oral plate to the next), i, H. cf. kiaeri Jaekel, PMO 105.893, middle part of
Upper Chasmops Limestone, Nesbrukrysset, Asker; inside, showing connections of pyritized diplopore

canals (c).

TEXT-FIG. 21. Diplopores of Haphsphaeronis. A-c, H. kiaeri Jaekel from Gagnum Shale (5 5 60 m level),
Tonnerud, Hadeland. d, //. proiciens Regnell from near Fauquez, Belgium. H. kiaeri has irregular diplopores
and these are often covered with a calcified periporal roof, whereas this is not so with H. proiciens. a, PMO 89924,
basal plate, n, PMO 89970, showing boundary between circum-oral plate and basal plate, c, PMO 89920, basal
plate with most diplopores covered, d, IRScNB 16c, basal plate showing sutural area. Ps, plate suture.

38

PALAEONTOLOGY, VOLUME 27

Phylogeny: Norwegian Haplosphaeronis ranged from the Caradoc to the lower part of the Ashgill
and occurred in several different environments. Species morphology is to some extent a reflection of
the environmental conditions under which they lived. When phyletic trends are sought, it should be
kept in mind that we do not always see the same type of environment. The pattern of phyletic changes
is often very complicated when several environments of the same age are preserved, as is the case with
Haplosphaeronis.

The number of brachiole facets per ambulacrum is generally larger in Ashgill than in Caradoc
populations of individuals with the same thecal diameter. In Norway this is certainly the case. In
Sweden this cannot be conclusively stated. In Britain Haplosphaeronis occurs in the Ashgill only where
the species has numerous brachioles. The shape of brachiole facets changes from the lower Caradoc
H. hratteriidensis to the Ashgill H. kiaeri. H. bratterudensis always has square facets separated by
large spaces, often with deep incisions (text-fig. 19). In H. kiaeri the facets are rounded or
tongue-shaped and not separated by spaees (text-fig. 19c, d). During the later Caradoc several morphs
combined the two types of brachiole facets (text-fig. 19b), clearly showing the direction of evolution.
The British H. nndtifida has facets of the same type as the Ashgill species in Norway.

The most striking evolution is seen in the pore structures, which may be good stratigraphical
indicators (see above). The oldest species in Norway, H. bratterudensis, has faintly developed rims
around the diplopores or no rims at all; the peripore floor is sunk well below the theeal surface; the
peripore is ovate with a length to width ratio of 3-6. In the late middle Ordovician and the upper
Ordovician the diploporal floor migrated outwards to a position above the thecal surface. In the latest
populations of H. kiaeri from the Oslo Region the aporal portion of the periporal wall developed
spines (PI. 5, fig. 3). Such spines have also been found in the British Ashgill species, but not in the
Belgian Ashgill species which is otherwise very similar. The shift of the periporal floor from a deep
to an outer position, and the outgrowth of the periporal wall to form spines accompanied by a
narrowing of the diplopores in relation to pore length (length to width ratio is 4-5), is clearly part of a
continuous evolution (text-fig. 25). Thus the length to width ratio of the diplopores increased from 3-6
to 4-5 during the Ordovician principally by a reduction of pore width. There was also some reduction
of pore length (text-fig. 25). This change is accompanied by an increase in number of diplopores in
some (but not all) populations of H. kiaeri. Narrow diplopores have been seen in the British and
Belgian species (PI. 3, fig. 6). The changes in diplopore shape during the Ordovician may be related to

EXPLANATION OF PLATE 3

Figs. 1-5. Haplosphaeronis cf. kiaeri Jaekel. 1, 3, 5, Upper Chasmops Limestone, Raudskjasr (8 m below top),
Asker; PMO 69421, stereophotos of 1, oral area (note slightly lobate shape of theca, and complex hydropore
with slit and circular opening), x 4; 3, circum-oral plates showing diplopores with thickenings and spines on
peripore wall, x4; 5, circum-oral plates and lateral plates showing details of diplopores (note development
of spines on peripore walls, irregular diplopores at the plate suture to the right, and the thickness of the walls),
X 7. 2, 4, Solvang Formation, Gagnum Farm, Hadeland; PMO 102.759, stereophotos of silicone rubber cast
showing 2, oral region, x 4; 4, circum-oral plates with spines on peripore wall, x 6.

Figs. 6, 1 1 . Haplosphaeronis proiciens Regnell. Ashgill, near Fauquez, Belgium. 6, IRScNB 16c, stereophotos of
plates showing development of spines on peripore wall (silicone rubber cast; note the very thin walls in
comparison with fig. 5, and diplopores in horizontal position at the plate suture), x 6. II, IRScNB 199-1,
basal portion of theca showing depressions which possibly housed extensions of basal nerve ring (silicone
rubber cast), x 5.

Figs. 7, 9. Arcliaegocystis cf. granulata Paul. Sorbakken Limestone, Frognoya, Ringerike. PMO 97106 in 7,
lateral view (note radial arrangement of elongate diplopores and granulated surface) and 9, showing oral area
(outermost portion of two brachiole facets and a plate suture), x 2-5.

Figs. 8, 10. Haplosphaeronis kiaeri Jaekel. Gagnum Limestone, Tonnerud, Hadeland. 8, PMO 79921 from 14 m
level, inside of theca showing plate sutures and depressions along inside of base, possibly a location for basal
nerve ring with thickenings, x 2. 10, PMO 91008 from 27-28 m level, showing inside of oral (smallest
depression) and anal (largest depression) areas, with a furrow which previously housed the gonoduct leading
from the right side towards and between the mouth and anus before entering the body cavity, x 3.

PLATE 3

10

BOCKELIE, Haplosphaeronis and Archaegocystis

40 PALAEONTOLOGY, VOLUME 27

increased efficiency of respiration. Evolutionary changes in respiratory structures have also been seen
in other cystoids.

Upper Ordovician Haplosphaeronis species from Norway and Britain commonly have calcite-
covered diplopores either in their basal portion, on their circum-oral plates, or occasionally all over
the theca. Belgian and Swedish upper Ordovician species have not been found with covered pores;
neither have they been found in the lower and middle Caradoc populations of H. hratterudensis and
H. kiaeri. Whether covered pores are a response to local environmental conditions, some kind of
disease, or a phyletic trend towards some kind of physical protection is not clear. Covered diplopores
are relatively common amongst the Diploporita.

Pahieoecology. Haplosphaeronis seems to have occupied a wide range of ecological niches, and is
found in rocks representing environments ranging from shallow, turbulent water to depths just below
the wave base. They are distributed mostly in areas of regular sedimentation rates and dominate
certain environments in the western part of the Oslo Region. In Sweden Haplosphaeronis species are
common on the flanks of most carbonate mounds (‘reefs’) of middle and upper Ordovician age
( Kullsberg Limestone and Boda Limestone). British species were adapted to environments with more
clastic sediments and are found in silts or shales with small amounts of carbonate (Paul 1973, p. 29).
The shape of the attachment area is probably related to environmental position. The shallow water
Swedish species were often attached to a firm substrate or large crinoid ossicles; the Norwegian
species may have been attached mostly to small objects and needed to grow rapidly upwards to
compensate for rapid sedimentation, giving H. kiaeri a characteristic mitre shape. The Swedish
species in contrast, living in areas of low sedimentation rates, have a flat base.

Remarks. The holotype of the Swedish H. oblonga (RM Ec96) derives from the upper Ordovician
Boda Limestone, and not from the middle Ordovician as previously stated by various authors.
Regnell (1945, p. 171) made all the species of Haplosphaeronis erected by Angelin synonyms of
H. oblonga. H. oblonga thus comprises all Swedish Haplosphaeronis species and ranges from the lower
Caradoc (Dalby Limestone) to the middle-upper Ashgill (parts of the Boda Limestone). It is rare to
find species with such a long range. However, Angelin’s species are all strongly corroded and his
distinctions were mostly based upon differences in size. In view of the evolutionary changes found
amongst Norwegian species, it seems justified to expect similar changes to have taken place in
Swedish populations. Thecal shape shows great variation and may be more related to ecological
factors than to anything else. The number of facets was ontogenetically controlled, at least in part
(Bockelie 1978a). The shape and distribution of the diplopores currently seem to have most
taxonomic value.

EXPLANATION OF PLATE 4

Figs. 1-9. Haplosphaeronis kiaeri Jaekel. Tonnerud, Hadeland. 1, PMO 101.939, stereophoto of oral area
showing peristome with ambulacral platform entering mouth, x 5. 2, PMO 89996, stereophoto of steinkern
showing peristome, periproct, and traces of gonoduct (note lack of diplopores in oral and anal area; gonoduct
goes down through the plate, is embedded horizontally in the plate between peristome and periproct, and
bends towards radius IV before entering the thecal interior), x 5. 3, PMO 101.954, stereophoto of silicified
specimen in oral view (just below peristome looking down oesophagus) showing one oral lobe and parts of
two more; upper part of gonoduct at left (cf. text-fig. 23a), x 6. 4, PMO 90976, sagittal view of silicified
specimen showing cavities within circum-oral plates below ambulacral facet (cf. text-fig. 23b), x 4. 5, PMO
9 1 007, inside view showing circum-oral lobes and parts of oesophagus)?), x 4. 6, PMO 7992 1 , basal portion
of pyritized specimen showing large primary depressions at plate sutures around basal ring, and several minor
depressions, x 3. 7, PMO 79885, steinkern showing depressions (as lobes), x4. 8, PMO 101.953,
stereophoto of silicified basal portion of theca possessing hollow internal spine, surrounded by outer wall and
several local depressions (see also text-lig. 22a, d), x 6. 9, PMO 91004, coarsely silicified specimen showing
internal spine (cf. text-fig. 22b, c), x 4. 1,3-5, 8, 9, 27-28 m level and 7, 1 8-20 m below Solvang Formation in
Gagnum Limestone; 2, 5-5 6 0 m level and 6, 14 m level in Gagnum Shale.

PLATE 4

BOCKELIE, Haplosphaeronis

42

PALAEONTOLOGY, VOLUME 27

Sphaeronites shihtienensis Reed, of which no specimens were available for study, was referred with
some hesitation to Haplosphaeronis by Regnell (1945, pp. 170, 171). This species, however, differs
from both Sphaeronites and Haplosphaeronis and in my opinion does not belong to the
Sphaeronitidae, but to the Aristocystitidae.

Regional distribution and stratigraphical range. Oslo Region (middle-upper Ordovician), Sweden (middle-upper
Ordovician; Regnell 1945, p. 171), southern Estonia (middle Ordovician; Mannil 1966, pp. 41, 43, 45),
Ingermanland (middle Ordovician; Hecker 1964, pi. 4), Wales (upper Ordovician; Paul 1973, p. 3), Belgium
(upper Ordovician; Regnell 1951, p. 31), and Burma (Ordovician; Reed 1917, p. 12).

Haplosphaeronis kiaeri Jaekel, 1926

Plate 3, tigs. 8, 10; Plate 4, figs. 1-9; Plate 5, figs. 1-4; text-figs. 18b, 19c, 21 a-c, 22, 23

1926 Haplosphaeronis Ar/aen Jaekel, p. 20, pi. 1, figs. 1-7.

1926 Haplosphaeronis kiaeri Jaekel; Kiasr, p. 8.

1945 Haplosphaeronis kiaeri Jaekel; Regnell, pp. 171-174.

1945 Haplosphaeronis kiaeri Jaekel; Stormer, p. 381.

1953 Haplosphaeronis kiaeri Jaekel; Stormer, pp. 68, 87, 94.

Diagnosis. A species of Haplosphaeronis with peripores elevated above the thecal surface or level with
it, their periporal walls often developed as high ridges in the adoral portion. Diplopores often
coalescent, usually irregular or oval, occasionally dumb-bell shaped, most numerous in circum-oral
plates, but strongly reduced in size and number in the basals where they are covered by a calcified
diplopore roof. Tubercles may be present over most of the thecal surface and are most numerous in
the basal circum-oral areas.

Holotype. Unnumbered specimen in the PMO collections; pi. 1, figs. 1, 2 of Jaekel (1926). It has not been in the
PMO collections for at least twenty-five years and is probably lost. Topotype material exists in the PMO
collections.

Type horizon and locality. Gagnum Shale Formation (= Sphaeronid Shale), lower Ashgill; Tonnerudodden,
Hadeland, Oslo Region, Norway.

Material. Several hundred specimens.

Description. Theca; taller than broad, seldom exceeding 15 mm in height and 10 mm in diameter. The base is
variable in shape and size.

TEXT-FIG. 22. Internal features of Haplosphaeronis kiaeri iaeke\. A, b, PMO 101.953, from Gagnum Limestone
(27-28 m level), Tonnerud, Hadeland; silicified specimen showing internal spine (is), a basal wall structure
(ow), and basal pits (P) in A, oblique view and B, lateral view, c, reconstruction in sagittal view showing hollow
internal spine (is), wall structure (ow), and primary basal pits (PJ. D, PMO 79921, Gagnum Limestone ( 14 m
level), Tonnerud, Hadeland; oblique view of basal portion of pyritized theca showing basal wall (ow), plate
sutures (Ps), and primary (P, ) and secondary (P2) pits (note that primary pits are located at the plate sutures).

Scale bar, I mm.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

43

TEXT-FIG. 23. Internal features (oral region) of Haplosphaerpnis kiaeri Jaekel from Gagnum Limestone (27-28 m
level), Tonnerud, Hadeland; silicified specimens, a, PMO 101.954, oblique view from oral area showing lobate
circum-oral ring structure with steep sides down to the platform (p), and the slope down into the mouth tract (G,
gonopore); this silicified portion is just below the calcite skeleton of the oral area, b, PMO 90976, lateral view
showing silicified theca with a circum-oral cavity within the skeleton, and the oral plates (or), c, PMO 101 .954,
lateral view of a showing irregular upper portion of the mouth tract (mt). Scale bar, I mm.

Plates: all except C06 and C07 are pierced by numerous diplopores. An ornament frequently occurs between
the diplopores of the basal plates and is characteristic of some populations. This surface ornament is usually
reminiscent of calcified diplopores.

Diplopores: small; many coalesce or have irregular extensions ( text-fig. 21). The peripores are oval, averaging
0-49 X Oil mm (text-fig. 25). The periporal floor is usually elevated above the thecal surface. Various
populations have the aporal portions of the periporal rims developed with thickenings of the wall (PI. 5, fig. 3).
No specimens have been found within the type stratum with more than twenty facets. The small size of the
animals may indicate a stunted population. There are pronounced thickenings of the sides of the food grooves, as
seen also in the British species H. muhifida Paul. Facets usually have a rounded outline but more irregular shapes
occur; they are 0-28-0-32 mm in diameter and have a slightly raised circular central process (text-fig. 19c).

Periproct; size related to animal size; 4-2 x 3-6 mm in PMO 89972. Plates of the anal pyramid occasionally bear
small tubercles near the summit.

Gonopore: small circular pore, 1-3 mm in diameter in PMO 89972, almost in contact with the first facet in
radius I.

Hydropore: a slit of variable length. In PMO 89972 it is zigzag shaped and very irregular.

Attachment: direct, by an aboral attachment area, usually one-third to one-half the ambital diameter.

Remarks. Jaekel (1926) distinguished two subspecies by size, H. k. kiaeri and H. k. norvegica (the
latter not figured). H. k. kiaeri came from the Gagnum Shale Formation ( = Sphaeronid Shale) and
H. k. norvegica from the overlying Gagnum Limestone Formation ( = Sphaeronid Limestone). The
morphology of the pore system shows a rather complex relationship between H. hralteriidensis n. sp.
and H. kiaeri. It is difficult to decide at present whether or not a subspecific determination can l3e
made, due to the observed continuous morphological series. Jaekel’s concept of H. k. norvegica is not
clear nor did he state from which part of the limestone his material was derived. Differences in size of
Haplosphaeronis in these populations are due to various ecological features. They may reflect
differences in sedimentation rates which killed off certain populations at different growth stages.
Other populations could have been stunted by low rates of nutrition.

H. kiaeri differs from H. bratterudensis n. sp. in that the latter has wider peripores and a peripore
floor sunk below the thecal surface. H. A/am differs from the Belgian H. proiciens by the latter’s lack
of ornament and irregularities in the peripore wall. H. kiaeri differs from H. midtifida by the lack of
elevation of the oral area (in this respect H. midtifida resembles H. proiciens). H. midtifida has larger
diplopores than H. kiaeri (length 0-64 versus 0-49 mm; width 0-21 versus 01 1 mm). H. kiaeri differs
from H. ohlonga in general shape, the latter always having a broad flat base and relatively few
brachioles in relation to thecal size. However, the Swedish species also lacks ornament on the basal

44

PALAEONTOLOGY, VOLUME 27

plates as well as the irregularities of the periproctal rims seen in H. kiaeri. H. oblonga is difficult to
define; specimens from 10 to 12 m below the main bentonite band of the Dalby Limestone up to the
Boda Limestone itself have all been referred to H. oblonga, giving that species a vertical range which
includes most of the middle and all the upper Ordovician. This is most unlikely and several species
may be involved. Differences in size of specimens occurring in off- reef and reef facies have also been
observed in Dalecarlica, the reef forms being larger. H. kiaeri resembles the British H. sparsipora
more than any other species, but the latter has very wide peripores (0-26 versus O il mm). The
peripore length of H. sparsipora is 0-54 mm and falls just within the range of variation in H. kiaeri.

Numerous populations of Haplosphaeronis occur in the middle Ordovician of the Oslo Region,
mostly in the upper Caradoc of Oslo-Asker (Upper Chasmops Limestone), Skien-Langesund area
(Encrinite Limestone), Ringerike (Solvang Formation), and Hadeland (Solvang Formation). These
all differ from typical H. kiaeri in being transitional between the early Caradoc species H.
bratterudensis and the Ashgill species H. kiaeri (PI. 3, fig. 3). However, this transition is so complex
that at present I prefer to place these upper Caradoc populations in H. cf. kiaeri since they show closer
affinities to H. kiaeri than to H. bratterudensis. They usually have peripore rims, rounded brachiole
facets, and peripores more like those of H. kiaeri than H. bratterudensis (text-figs. 19b, 25). See
text-figs. 4, 9 for range and geographic distributions.

Haplosphaeronis bratterudensis n. sp.

Plate 2, figs. 5-8; text-figs. 18c, d, 19a

1953 Haplosphaeronis cf. kiaeri Jaekel; Stormer, p. 84.

Diagnosis. A species of Haplosphaeronis with submerged diplopores, equally numerous all over the
theca but missing on C06 and C07. Diplopores wide, usually lacking periporal wall, peripore below
thecal surface. No tubercles and no calcified diplopore roofs.

Holotype. PMO 89201, preserved as an external mould (text-fig. 18c, d; PI. 2, fig. 5).

Type horizon and locality. Lower Chasmops Shale containing Neoasaphus ludibundus (nniltidens Zone); shore at
Bratteriid, Ringerike, Oslo Region.

Material. In addition to the holotype some twenty specimens are referred to this species from Ringerike and
Asker.

Description. Theca: spherical, with a flat or concave base. The sides are gently curved. In most specimens the
height of the theca is about equal to its width.

Plates: the plate surface between the diplopores is relatively smooth.

Diplopores: relatively large, usually parallel-sided or slightly elliptical, averaging 0-65 x 0- 1 8 mm (text-fig. 25),
and submerged below the plate surface. The periporal wall is low or not developed. The peripore width (pwj ) is
significantly larger than in H. kiaeri (text-fig. 25; PI. 2, figs. 7, 8), whereas the length does not differ to the same
extent. In the basal area about five pores per mm^ are present, whereas the number is five or six in the circum-oral
plates.

Peristome: the mouth is oval, the adanal side being almost straight in PMO 89202 (PI. 2, fig. 6). The highest
number of brachiole facets totals twenty-three. Most of the ambulacral furrows end in angular facets with deep
incisions between them (text-fig. 19a). Commonly the first formed facets (see Bockelie 1978a, fig. 1) have
rounded fringes, and later ones have more angular fringes (text-fig. 19a; PI. 2, fig. 6). Individual facets are
approximately 0-5 mm in diameter and are not as rounded as in //. kiaeri.

Periproct: adoro-lateral, oval to pyriform, and covered by an anal pyramid of five or six plates. The periproct
lies about 1 mm below the oral margin. The anal pyramid is high, adorally inclined, and reaches almost to the
level of the top of the palate (text-fig. 18d).

Gonopore: a relatively small circular pore, 1-5 mm in diameter, almost in contact with the first facet in
radius I in the holotype.

Hydropore: a straight slit of variable length, adorally of the gonopore.

Attachment: direct, by an aboral attachment area, usually concave and about one-third to two-thirds the
ambital diameter.

Caradoc ! Ashgill

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

45

t

TEXT-FIG. 24. Thecal growth of Haplosphaeronis ohtonga (Angelin) (a, c), and H. kiaeri Jaekel (b, d). All
Swedish populations first produced a large basal surface (h < w), before attaining height. The points at which
the growth gradients change may indicate the onset of maturity (see Bockelie 1978c/). H. kiaeri has an equal
growth rate both in height and width in young stages. Maturity in this particular population was reached at a
thecal diameter of 10 mm after which the growth rate of thecal height increased (h > w). N, number of
specimens in populations studied. Data arranged in size classes, c, d, ontogenetic changes in shape of the two

species.

® 0.4

I

0.5

_i

0.6
i_

0.7

I

0.9 mm

-5

0.1

0.2

0. 3 mm

-I i_

1 4

^ 3

1 2

■ 1 1

TEXT-FIG. 25. Peripore length (A) and width (B) of Haplosphaeronis species. A trend towards a decrease both in
peripore length and width during the Ordovician is evident. 1, H. hraiterudensis n. sp. ( 101 measurements); 2, H.
cf kiaeri Jaekel, Upper Chasmops Limestone ( 1 7- 1 8 m level ), Raudskjccr, Asker (49 measurements); 3, H. kiaeri
Jaekel, Gagnum Shale (5-5-6 0 m level), Tonnerud, Hadeland ( 1 20 measurements); 4, H. kiaeri Jaekel, Gagnum
Limestone (21 -22 m level), Tonnerud, Hadeland (88 measurements); 5, II. kiaeri Jaekel, Gagnum Limestone
(27-28 m level), Tonnerud, Hadeland (80 measurements).

46

PALAEONTOLOGY, VOLUME 27

Remarks. H. bratterudensis differs from other Haplosphaeronis species (except some of the specimens
referred to H. oblonga (Angelin) by Regnell 1945) by the submerged position of the diplopores, and
by the diplopores being almost as numerous in the basal portion as in the circum-oral plates. Some
specimens from below the Kullsberg Limestone of Sweden (figured by Paul 1972, pi. 6, fig. 1) are
tentatively referred to H. oblonga. They are contemporary with the Norwegian H. bratterudensis and
show similar structures. It is uncertain if these Swedish specimens should be referred to
H. bratterudensis.

Genus Eucystis Angelin, 1878

Synonymy. Proteocystites Barrande, 1887; Carpocystites Oehlert, 1887; Proteocystites Bather, 1899; Bulhocystis
Ruzicica, 1939.

Type species. Eucystis raripunctata Angelin, 1878, p. 31, from the Boda Limestone (Ashgill) of Osmundsberget,
Dalarna, Sweden.

Diagnosis. A genus of Sphaeronitidae with pentagonal peristome; five ambulacra each with one or
several food grooves terminating in ambulacral facets on circum-oral plates or somewhere on the
thecal surface. Thecal plates arranged in three or more series and numbering twenty to fifty in total.

Remarks. As pointed out by Le Maitre (1958, p. 304) and Prokop (1964, p. 30) a close relationship
exists between Eucystis and Bulbocystis. Bulbocystis differs essentially in having a more regular
arrangement of ambulacra (Kesling 1967, p. S242). I accept Le Maitre’s view and suggest a
synonymy. Reed (1917, pi. 3, fig. 3, 3a) referred a specimen from Yunnan to EucystiscL raripunctata;
the peristome is quadrilateral and each ambulacrum bears only one facet. To which genus Reed’s
species should be referred is uncertain. Paul (1973, p. 40) pointed out that several species of the rather
variable Eucystis have stem-like projections formed by the basal plates, but no true stems are present.
The Norwegian Eucystis species has a broad flat base.

Description. Theca: the shape and size of thecae of Eucystis species varies considerably. The largest species
known is E. harrandena (Haeckel) which reaches 50 mm in height. Some species have a broad flat base, whereas
others have stem-like projections of the basal plates; this may vary even within species.

Peristome: always pentagonal; those having a quadrilateral peristome which were formerly referred to
Eucystis are now referred to a new genus, Tetreucystis n. gen.

Ambulacral system: five ambulacra are present, each with one or more facets at the end of short or long
ambulacral furrows. New ambulacral furrows are added throughout life, in a manner typical of the family
Sphaeronitidae (Bockelie 1978a); thus the total number of facets may not be a good taxonomic character.
However, the distribution of ambulacral furrows in adults may at times be reliable at species level: one short
furrow from each of the oral corners in E. pentax Paul, 1973; most facets present on the circum-oral plates in
E. angelini Regnell, 1945; and several facets below the circum-oral plates in E. raripunctata Angelin, 1878.

Periproct: the rounded, polygonal periproct is close to the mouth. It has ledges for insertion of plates; the
aboral portion could open more than the adoral portion (text-fig. 26b, c). Neither oral nor anal plates have been
found, and were probably very thin or more loosely joined to their relative openings.

Gonopore and hydropore: a circular gonopore and a slit-like hydropore are always present in positions typical
for the Sphaeronitidae, the former across the suture C07:C01, and the latter across the suture C06:C01.

Plates: the plate arrangement varies in Eucystis: most species have only three plate series but E. flava has five
or more. Only one generation of plates seems to be present. Details of the shapes of plate sutures within a species
reveal considerable variation on one theme (text-fig. 26d-g). Such variations are more common in certain
populations.

Diplopores: all plates are pierced by generalized diplopores with oval peripores but, as with other genera of
the Sphaeronitidae, their width is less variable than their length and thus seems to be an important character for
species discrimination. Covered diplopores have been found in individuals of some species.

Attachment: Eucystis was attached directly by an attachment area which differs in size from species to species.
Some of the Swedish species have a small attachment area. No traces of an internal spine have been found.

Palaeoecology. Eucystis species from Norway occur in siltstones, presumably representing shallow
water environments. They occurred, however, at greater depths than those containing rugose corals
and seem to appear in environments of unstable sedimentation below wave base. The closely related

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

47

Telreiicystis n. gen. is rare in Britain (one species) and in Sweden (one species) but is not uncommon in
Norway (three or four species). Ecological factors may have played some part in the distributional
pattern of these genera. According to Paul (1973, p. 41 ) the number of ambulacral facets may exceed
hve in each of the British species where the total number is known. In the Swedish E. angelini the
number of facets is fifteen to twenty, in E. raripimctata twelve to fifteen, and in the only Norwegian
species five to seven. This may also reflect ecological conditions. The Swedish species may derive from
more shallow water than both the Norwegian and British forms. Whereas a trend in the number
of facets, as outlined above, can be observed in Eucystis species, the reverse trend occurs in
Haplosphaeronis which lived in the same environments and which usually occur in the same beds as
Eucystis. British Haplosphaeronis generally have more facets than Norwegian species, which in turn
have more than Swedish species. As discussed elsewhere (Bockelie 1978a), ambulacral furrows and
facets are added ontogenetically, probably to increase food-gathering capacity. It is possible that this
increase also manifests itself phylogenetically; Devonian Eucystis species often have numerous and
very long food grooves (Prokop 1964).

Regional distribution and stratigraphic range. Ashgill (upper Ordovician) of Sweden, Norway, Britain, Ireland,
Bohemia, and ?Germany (E. hercynica Jaekel), Spain (Chauvel and Le Menn 1979); Devonian of Bohemia,
France, Morocco, Algeria, and Central Sahara; so far totally unknown in the Silurian.

Eucystis langoeyensis n. sp.

Plate 5, figs. 5-8; text-figs. 26a, 27c, 32b

Diagnosis. A species of Eucystis with plates in three fairly regular circlets; in the lateral and basal
plates the height exceeds the breadth (.x > y)\ plates of the lateral series hexagonal. Circum-oral plates
somewhat irregular in shape, but together forming a subcircular area. Diplopores not numerous;
more common in the lateral than in the circum-oral plates; sparse or absent in the basal series. Five to
seven ambulacral furrows and always one short furrow in radius II. Diplopores short (0-2 mm long)
with faint periporal rim.

TEXT-FIG. 26. A, Eucystis langoeyensis n. sp., PMO 90947, holotype in lateral view showing plate configurations,
some circum-oral plates (I, 2, 3), and irregular growth lines (gr) on basal plates, probably indicating that the
specimen rested on the sea bottom during life. B, c, schematic view of periproctal opening (Pe) with a lower ledge,
and an upper furrow for the insertion of periproctal cover plates; plates of the lower half were mobile whereas
those of the upper half were not; this configuration is typical of Haplosphaeronis and Eucystis. D-G, Eucystis
angelini Regnell, from Skalberget, Dalarna, Sweden; variations in the arrangement of circum-oral plates. C06
always thins towards the periproct forming a pointed end; periproct surrounded by five plates, i), 56"(, of
population; E, 1 1% of population; f, 22% of population; G, 1 1% of population.

48

PALAEONTOLOGY, VOLUME 27

Derivation of names. From Langoya, the type area.

Holotype. An almost complete specimen, PMO 90947 (PI. 5, figs. 5, 8), from Langoya, Oslo, preserved as an
external mould.

Horizon and localities. Top of Flusbergoya Shale Formation ( = uppermost part of Stage 5a), upper Ashgill,
northern Langoya, south-western Rambergoy, western Gressholmen, and Flusbergoya, Bunnefjorden, Oslo.

Material. Fourteen specimens in addition to the holotype.

Description. Theca: mostly globular with a height/width ratio close to one. Thecal diameter usually 12-15 mm.
The base is broad, usually one-third to two-thirds the ambital diameter, and slightly concave.

Plates: three circlets of plates are present. The circum-oral plates are longer than wide. The C06 : C07 suture
meets the CO 1 : C07 suture at the gonopore (seen in the holotype only). The hexagonal plates of the lateral and
basal series are elongate. The lateral plate circlet contains nine plates, the basal circlet seven, and the circum-oral
circlet always consists of seven plates. Fine ‘growth’ lines are present in the lowermost 2 mm of the basal plates of
the holotype. These lines may indicate that the specimen lived with its base in the sediment (text-fig. 26a).

Diplopores: may be present on all plates, but are often sparse or absent in the basals. In COl to C05, seven to
ten diplopores were observed in each plate, but only two in C06 and C07. In the laterals there are usually two to
three diplopores (five pores) per mm^. On one plate (5x6 mm) twenty pores were counted. In the lateral series,
diplopores are more numerous in the adoral than in the aboral part of the plates, and the long axes are more or
less perpendicular to the plate margins, thus giving a radial arrangement. In PMO 92986 diplopores in the basal
and lateral series are covered by a calcified diplopore roof. Peripore length: 0-42 + 01 3 mm; peripore breadth:
0-21+0.04 mm; length to breadth ratio: 0 09 + 0-03 (mean +1 standard deviation, based upon forty-four
measurements).

Peristome: measures 3-2 x 2-9 mm in the holotype; food grooves extend below the circum-oral plates. In radii
II, III, and V one ambulacral side-branch occurs, whereas in radii I and IV there are two such branches. Two
specimens, PMO 90877 and PMO 97139, each have five or six short ambulacral grooves and differ only slightly
from other specimens of this species (PI. 5, fig. 7).

Periproct: somewhat deformed in the holotype, but its original shape was probably subcircular, as can be seen
from PMO 90872 where its diameter is about 3-6 mm.

Gonopore: at the upper left side of the anus with a diameter of approximately 1 -5 mm.

Hydropore: on a small ridge between the mouth and the anus, about 0-6 mm from the oral margin. The
hydropore is bisected by the suture COl :C06.

Remarks. E. langoeyensis differs from the British species in usually having more than one facet in each
ambulacrum, and from the Swedish species in having fewer facets. It also differs from the other
species by the shape of the circum-oral plates. It can be distinguished from the Devonian species of
Bohemia by differences in facet distribution and surface ornament. Three species of Eucystis have
been described from Sweden, i.e. E. raripimctata, E. angelinf and E. acuminata. A large number of
specimens from the Riksmuseum, Stockholm, has been studied, resulting in some additional

EXPLANATION OF PLATE 5

Figs. 1-4. Haplosphaeronis kiaeri Jaekel. Tonnerudodden, Hadeland. 1, PMO 79913, Gagnum Shale, x4. 2,
PMO 89920, cast showing details of pores on basal plate and suture (note that many pores are covered),
Gagnum Shale, x 7. 3, PMO 90905, cast showing details of pores with development of spines on peripore
wall in circum-oral plate, 21-27 m level, Gagnum Limestone, x 6. 4, PMO 90985, cast showing basal plate
with covered pores in lower portion, open pores above and some pores partially covered, 31-32 m level,
Gagnum Limestone, x 6.

Figs. 5-8. Eucystis langoeyensis n. sp. Upper part of Husbergoya Shale (Ashgill); 5, 6, 8, island olT north-west
Langoya, Oslo; 7, Gressholmen, Oslo. 5, PMO 90947, cast of holotype showing the continuation of food
grooves into peristome border. (The number and position of ambulacral facets are characteristic of species),
X 4. 6, PMO 90871, cast showing details of diplopores (note the large pores and peripore rims, and also the
presence of some sutural pores), x 6. 7, PMO 97139, cast of young specimen with short ambulacra, x 3. 8,
PMO 90947, cast of holotype showing details of diplopores at plate suture (note the faintly developed rim and
some elongated peripores), x 6.

PLATE 5

BOCKELIE, Haplosphaeronis and Eucystis

50

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 27. Plate configuration of Eucystis species, a, b, two varieties of E. raripimctata Angelin showing
differences in COl near periproct and differences in number and extenf of ambulacral furrows (a, RM Ec
2376; B, RM Ec 2370, holotype). c, E. langoeyensis n. sp., PMO 90947, holotype showing fhe relafively small
number of facets in this species, d, E. angelini Regnell with all facets close to the mouth (compiled from RM

Ec 2056 and RM Ec 1938).

information concerning the plates of E. raripimctata and E. angelini, including a new diagram for
plate configuration of E. raripimctata (text-fig. 27a, b) to replace that of Regnell (1945, fig. 22.4). The
holotype of E. raripimctata is somewhat abnormal in that COl is in contact with the anus (text-
fig. 27b), and the ambulacral grooves of radius V are extremely long, reaching more than half-way
down the side of the periproct. In all specimens of E. raripimctata studied, COS is never in contact
with the anus, whereas this is the case with E. angelini (text-fig. 27d).

Genus Tetreucystis n. gen.

Synonymy. Eucystis (partim) auctores.

Type species. Tetreucystis kalvoeyensis n. gen., n. sp. from the Tretaspis Limestone ( = Stage 4cjS), lower Ashgill,
Kalvoya, Oslo Region, Norway.

Diagnosis. A genus of Sphaeronitidae with quadrilateral peristome. Four branching ambulacra, one
from each corner of the mouth. Theca composed of a limited number of polygonal plates in three or
more series and numbering twenty to fifty.

Remarks. There is a distinct difference in the shape of the peristome of Eucystis and Tetreucystis
n. gen. which I consider justifies the erection of the new genus for species possessing a quadrangular
mouth. Tetreucystis n. gen. has a quadrilateral peristome like Diplospliaeronis Paul, but differs from
the latter by having the periproct widely separated from the peristome, with more than three plates
between the two orifices. At present five species can be assigned to Tetreucystis n. gen.; these include
T. niimita (Forbes, 1848), T. quaclrangularis (Regnell, 1945), T. elongata n. sp., T. kalvoeyensis n. sp.,
and T. monobracliiolata n. sp.

Description. Tetreucystis agrees in most respects with Eucystis, except in the shape of the oral area and that the
ambulacral furrows seldom reach below the circum-oral circlet {T. quadrangularis being the exception). Most
Tetreucystis species have only one ambulacral furrow in each radius, but T. kalvoeyensis n. sp. has a total of
eleven or twelve facets and T. cpiadrangularis twelve to sixteen facets. The general shape of the theca, the plate
distribution, and type of pores are similar to Eucystis, apart from the rather elongated pores of T. inunita and T.
elongata n. sp.

Palaeoecology. Tetreucystis occurs in environments similar to those of Eucystis and in lithologies
such as carbonate mud mounds {T. quctdrangiilaris in Dalarna, Sweden), siltstones {T. nionobracliio-
lata n. sp. on the islands in the vicinity of Oslo, Norway), and in nodular limestones (T. munita in

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

51

the Rhiwlas Limestone at Bala, North Wales; T. kalvoeyensis n. sp. and T. elongata n. sp. in the
Baerum-Asker districts, near Oslo, Norway). T. kalvoeyensis and T. elongata seem to be mutually
exclusive, one occurring in deeper water than the other (text -fig. 6c).

Regional distribution and stratigraphic range. Ashgill of Norway, Sweden, and Britain.

Tetreucystis kalvoeyensis n. sp.

Plate 6, figs. 1-4, 7; text-figs. 29c-e, 31a

Diagnosis. A species of Tetreucystis with theca composed of plates in five or six series, each individual
plate varying in shape and size, being pentagonal or hexagonal. Circum-oral plates higher than broad
(.v > y). Diplopores usually numerous in the lateral and circum-oral plates, decreasing in number
towards the basal portion of the theca and occasionally present even in the basal plates. Ambulacra
often with three side-branches each, all confined to circum-oral plates. Total number of brachiole
facets in adult specimens ten to twelve.

Holotype. An almost complete specimen, PMO 80030, preserved as an external impression (text-fig. 29c, e; PI. 6,
figs. 1, 3).

Type horizon. Tretaspis Limestone (= Stage 4c/3), lower Ashgill.

Material. Over fifty more or less fragmentary specimens from Kalvoya (Bserum), Nesoya, Hvalstad, Raudskjaer
(Asker).

Description. Theca: variable in shape from spherical to inverted conical (text-fig. 29d, e). In the holotype, the
height is 37 mm, the width 15x13 mm.

Plates: circum-oral plates are higher than broad; lateral plates vary in shape but are usually higher than broad.
Eight or nine plates occur in the upper lateral series. In the oral region the sutures between C07 and the adjoining
lateral plates are not displayed. Thecal plates are about 0-6-0-8 mm thick. As in T. elongata n. sp., granular
ornament occurs on the plates (also seen in well-preserved specimens of Eucystis and Tetreucystis from Sweden).
The base of the theca is usually flat and may have served as an attachment area (text-fig. 29d, e).

Diplopores: occur in all thecal plates, the number decreasing towards the base, where the number of pores is
two or three per mm^, whereas in circum-oral and lateral plates it is five or six. A distinct radial arrangement of
the diplopores is developed particularly in the two upper laterals. Peripore length: 0-54 + 0 09 mm; peripore
width: 0-31 ±0 04 mm.

©

I /

TEXT-FIG. 28. Tetreucystis elongata n. gen., n. sp. from Tretaspis Limestone, west side of Nesoya, Asker, a, PMO
91311, oro-anal area of holotype, showing right side of theca with circum-oral plates (4-6), mouth (M),
hydropore (H), and periproct (Pe). B, lateral view of holotype showing some elongated diplopores. c, PMO

91312, oro-anal region, a, b, to same scale.

52

PALAEONTOLOGY, VOLUME 27

Peristome: slightly raised; the opening of the mouth is oval and the peristome border dips gently from the
peristome down to the mouth. Grooves diverge from the ambulacral furrows before entering the mouth on the
peristome border. The mouth is 4-2 x 2-5 mm. In the holotype three ambulacral side-branches occur in radii I, II,
and IV, whereas only two occur in radius V. In PMO 90982 three side-branches occur in radii II and V but they
cannot be counted in the other radii because of weathering. The side-branches never extend beyond the
circum-oral plates. The anus is oval, 3-3 x 2-5 mm. Its long axis subtends an angle of 60° with the oral margin, and
its adoral boundary lies 4-7 mm from that margin.

TEXT-FIG. 29. Tetreucystis n. gen. a, T. elongata n. sp., reconstruction of plate arrangement in the oro-anal area
(cf. text-fig. 28). B, T. elongata n. sp., PMO 9131 1, holotype from Tretaspis Limestone, west side of Nesoya,
Asker; diplopores (note their slight radial arrangement). c-E, T. kalvoeyensis n. sp. from Tretaspis Limestone,
Kalvoya, Baerum. c, PMO 80030, holotype, reconstruction of plate configuration in the oro-anal area (note the
somewhat elongated opening of the mouth, and food grooves leading on to a peristomal platform before
entering the mouth); D, PMO 9098 1 , lateral view showing shape of theca; e, PMO 80030, lateral view of holotype.

EXPLANATION OF PLATE 6

Figs. 1-4, 7. Tetreacystis kalvoeyensis n. gen., n. sp. Tretaspis Limestone (lower Ashgill), Kalvoya, Baerum. 1,
PMO 80030, cast of holotype, stereophoto of oro-anal region, x 5. 2, PMO 90982, stereophoto of oro-anal
area, x 5. 3, PMO 80030, cast of holotype showing details of diplopores in lateral circlet (note the radial
arrangement of diplopores), x 7. 4, PMO 90982, details of diplopores in circum-oral series, x 7. 7, PMO
80022, outline of specimen with left side broken, x 3.

Fig. 5. Eucystis raripunctata Angelin. Boda Limestone (Ashgill), Ostbjorka, Dalarna, Sweden. RM Ec 2370,
holotype showing peripores of upper lateral series with granulated plate surface, x 6.

Fig. 6. Tetreacystis elongata n. gen., n. sp. Tretaspis Limestone (lower Ashgill), western side of Nesoya, Asker.
PMO 91311, holotype in oral view, x 5.

PLATE 6

BOCKELIE, Tetreucystis and Eucystis

54

PALAEONTOLOGY, VOLUME 27

Gonopore: about 0-2 mm in diameter, occurs on the COl : C06 suture and about 1 mm below the hydropore.
Hydropore: 2 mm long and about 1 mm below the oral margin (text-fig. 29c).

Attachment: direct by an aboral attachment area of variable size.

Remarks. T. kalvoeyensis differs from all other Norwegian Tetreucystis species in its larger number of
brachiole facets. It differs from the contemporary Swedish T. quadrangularis in that the latter has
more and longer food grooves, reaching down on to the lateral plates.

Tetreucystis elongata n. sp.

Plate 6, fig. 6; text-figs. 28, 29a, b, 31b

Diagnosis. A species of Tetreucystis with theca composed of plates in three regular circlets, the lateral
plates having about equal height and breadth, whereas in the basal ones the height is less than the
breadth. Diplopores elongate, about 1 mm long and 0-2 mm wide, more common in the lateral plates
than in the circum-oral plates and sparse in the basal series. Brachiole facets small, 0-8 mm in
diameter, close to mouth, never exceeding four.

Derivation of name. From the elongated shape of the diplopores.

Holotype. A somewhat imperfect specimen, PMO 91311 (text-figs. 28a, b, 29b, 3 1 b; PI . 6, fig. 6), showing only the
right half of the theca (C04-C06) and in which neither the shape of most of the thecal plates nor the total plate
number can be seen.

Type horizon. Tretaspis Limestone, lower Ashgill.

Material. Several more or less fragmentary specimens from Nesoya and Nesbru, Asker.

Description. Theca: hemispherical with flat base. The plate configuration of the theca is based upon only two
specimens in addition to the holotype, PMO 91310 and 91312. Thecal height: 9-11 mm; greatest diameter:
11-12 mm. Maximum diameter of base equals the thecal diameter. Three plate circlets containing seven
circum-orals, seven to eight laterals (eight in PMO 80083), and seven basals.

Plates: plate thickness is about 0-9 mm. Granulated surfaces are common, particularly in the circum-oral
plates, as in Bohemian Eucystis (Prokop 1964). Laterals of equal length and breadth, the basals slightly shorter
than wide.

Diplopores: occur in all three plate circlets, but are less common in the basals. In the latter, five pores were
counted per mm^; in the circum-oral plates the number is only two or three. The diplopores are often arranged
with their long axes perpendicular to plate margins. Diplopores long, but quite variable in length; some cross
plate sutures (text-fig. 29b). Peripore length: 0-70 + 0T7 mm; peripore width: 0-20 + 0 04mm. Ratio of peripore
width to length: 014 + 0 06 (mean + 1 standard deviation, based upon fifty-four measurements).

Peristome: measures 2-5 x 2 0 mm. The mouth is oval. Four ambulacra extend, one from each of the oral
corners, to small brachiole facets about 1 mm from the oral corners.

EXPLANATION OF PLATE 7

Figs. 1 -4. Tetreucystis tetrahrachiolata n. gen., n. sp. Husbergoya Shale (upper Ashgill); 1 -3, Rambergoy, Oslo,
and 4, north-west Langoya, Oslo. 1-3, PMO 92983, stereophotos of cast of holotype showing 1, oro-anal
area, x 4; 2, diplopores in lower part of lateral plates, x 6; and 3, lateral view, x 2. 4, PMO 102.755,
stereophoto of cast showing oro-anal area, x 4.

Figs. 5, 9, 10. Pachycystis norvegica n. gen., n. sp. Kalvsjo Formation (upper Ashgill), Kaivsjo Quarry, Lunner,
Hadeland. 5, PMO 97103, stereophoto of cast of holotype showing diplopores on lateral series, x4. 9, PMO
97141, part of theca with diplopores, x 6. 10, PMO 97103, cast of holotype showing quadrilateral peristome
and large, circular anal area, x 5.

Figs. 6-8. Sphaeronitid indet. sp. A. Husbergoya Shale (upper Ashgill); 6, Skogerholmen, Asker, and 7, 8,
Ostoya, Bierum. 6, PMO 90264, stereophoto of cast showing ambulacrum and diplopores, x4. 7, PMO
97 1 05, cast showing circum-oral plates with branching ambulacra seen from above, x 5. 8, PMO 97 1 05, cast
showing circum-oral plate seen in lateral view, showing diplopores, x 5.

PLATE 7

BOCKELIE, Tetreucystis and Pachycystis

56

PALAEONTOLOGY, VOLUME 27

Periproct: slightly ovate with its long axis perpendicular to the oral margin. It measures 2-5 x 1 -8-2 0 mm with
the adoral boundary 1-3 mm below the oral margin (in PMO 91311).

Gonopore: 0-25 mm diameter, set just below the hydropore and close to the brachiole facet in radius 1.
Hydropore: occurring less than 0-5 mm from the oral margin. It is bisected by the COl : C06 suture (text-
fig. 28c).

Remarks. T. elongata differs from most other Tetreucystis species in the characteristic shape of its
diplopores. It resembles T. munita (see Paul 1973) but differs in that the diplopores of T. nnmita are
shorter (0-54 mm) than in T. elongata (0-70 mm), the mouth frame of T. nnmita is elevated on the
thecal surface, and the diameter of the brachiole facet in T. munita is almost twice that of T. elongata.

Tetreucystis tetrabrachiolata n. sp.

Plate 7, figs. 1-4; text-figs. 30, 31c

Diagnosis. A species of Tetreucystis with theca composed of plates in three circlets, lateral plates
higher than wide. Diplopores rounded, common in the circum-oral plates. Brachiole facets 1 -3 mm in
diameter. The number of facets rarely exceeds four.

Derivation of name. The name alludes to the almost constant number of brachiole facets, one in each of the oral
corners.

Holotype. A somewhat compressed specimen, PMO 92983, preserved as an external mould (PI. 7, figs. 1 -3). Only
two-thirds of the theca is visible; some lateral and basal plates are not preserved.

Type horizon. Husbergoya Shale Formation, upper Ashgill, Rambergoy, Bunnefjorden, Oslo.

Material. In addition to the holotype, ten specimens from several of the islands in the Oslo district.

Description. Theca: globular with flat or slightly concave base. The plate configuration cannot be seen clearly in
all specimens, partly due to cracks that confuse the issue. A composite reconstruction is made in text-fig. 30c.
The theca consists of three series of plates, including seven circum-orals, eight laterals, and seven or possibly
eight basals. Thecal height 13-20 mm; thecal diameter about two-thirds of thecal height. In most specimens the
base is about one-third the thecal diameter but in some the base is slightly prolonged. In such cases the diameter
of the base may be 5 x 7 mm (PMO 92991) or 5 x 8 mm (in the holotype).

Plates: approximately 1 mm thick. The plate surface is smooth. Both laterals and basals are higher than broad,
whereas in the circum-orals the height and breadth is the same.

xnxT-FiG. 30. Tetreucystis tetrabrachiolata n. gen., n. sp. Plate distribution of oro-anal region. A, PMO 90890,
Husbergoya Shale, south-west Rambergoy, Oslo, n, PMO 90873, Husbergoya Shale, north-west Langoya,
Oslo, c, reconstruction. M, mouth; G, gonopore; H, hydropore; Pe, periproct.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

57

TEXT-FIG. 31. Diplopores of Tetreucystis n. gen. a, T. kalvoeyensis n. sp., PMO 80030, holotype, Tretaspis
Limestone, Kalvoya, Baerum. b, T. ehngata n. sp., PMO 91311, holotype, Tretaspis Limestone, Nesoya, Asker,
c, T. telrahrachiolata n. sp., PMO 92983, holotype, Hiisbergoya Shale, Rambergoy, Oslo, d, T. c/iuuhangiilaris
(Regnell), RM Ec 2119, Boda Limestone, Dalarna, Sweden (original of Regnell 1945, pi. 14.2).

Diplopores: present all over theca, but most common in the circum-oral plates, where six to seven pores
per mm^ occur. In the lateral plates the number is four or five and in the basals only three or four. In some
specimens the basals are devoid of diplopores. There is a tendency towards a radial arrangement of diplopores.
Peripore length: 0-31 +010 mm; peripore width: 0 I8+0 02 mm. Ratio of peripore length to peripore width:
0-70 + 0 02 (mean + 1 standard deviation, based upon twenty-four measurements).

Peristome: 4-2 x 3-2 mm in the holotype, but the proportions may vary (in PMO 92984, 4-5 x 2 0 mm). In most
specimens four ambulacra extend, one from each of the oral corners, just on to the circum-oral plates. In PMO
90896 two facets have been found in radius I.

TEXT-FIG. 32. Diplopores of Eucystis species. A, E. raripimctata, RM Ec 2370, holotype, Boda Limestone,
Ostbjorka, Dalarna, Sweden, b, E. langoeyemis n. sp., PMO 90947, holotype, Husbergoya Shale, north-west
Langoya, Oslo, c, E. angelini, RM Ec 1974, Boda Limestone, Dalarna, Sweden, d, E. globula, SM A7800,
holotype, Ashgill Shales (Paul 1973, text-fig. 27c). e, E. acuminata, RM Ec 2173, holotype, Boda Limestone,
Gullerasen?, Dalarna, Sweden, f, E. hiheniica, BM(NH) E28758, Kildare Limestone (Paul 1973, text-lig. 27n). G,
E. penta.x, SM A74802, Ashgill Shales (Paul 1973, text-tig. 27f). All approximately x 10.

58

PALAEONTOLOGY, VOLUME 27

Periproct: subcircular with a diameter of 31 mm in PMO 90890.

Gonopore: below the hydropore and nearer the brachiole facet of radius I than the anus.

Hydropore; on a slightly elevated ridge, 1 -4 mm below the peristome border and bisected by the COl : C06
suture.

Remarks. T. tetrabrachiolata n. sp. is the only species of the genus occurring in the Husbergoya Shale.
The contemporary Swedish T. quadrangular is can readily be distinguished from the Norwegian
species by the presence of many more brachiole facets, and longer food grooves, reaching down into
the lateral plates. T. tetrabrachiolata is separable from T. kalvoeyensis by the latter’s larger number of
brachioles. T. tetrabrachiolata is distinguishable from T. elongata by the shape of the diplopores and
the shape of the lateral plates. It differs from T. nnmita in the shape of the pores, those of the latter
being elongate.

Genus Archaegocystis Jaekel, 1899
Synonymy. Pyrocystites Barrande, 1887 (pars).

Type species. Pyrocystites desideratus Barrande, 1887, p. 170, by original designation of Jaekel, 1899, p. 395;
Sarka Beds (Llanvirn), Osek, Bohemia.

Diagnosis. A genus of Sphaeronitidae with globular to spherical theca; plates more or less randomly
arranged; ambulacra short, confined to peri-oral plates, branching fan-wise with three to seven facets
each; diplopores oval to elongate with or without narrow unspecialized peripore rims and usually
randomly orientated.

Archaegocystis cf. granulata Paul, 1973

Plate 3, hgs. 7, 9

Material. One specimen, PMO 97106.

Horizon and locality. Ashgill; Sorbakken Limestone, Frognoya, Ringerike, Oslo Region.

Description. One sagitally divided half theca. Two ambulacra are preserved but the mouth, anus, gonopore, and
hydropore are missing. Thecal height 26 mm; thecal diameter 22 mm. Attached directly by aboral circular
attachment area, 3-5 mm in diameter.

Plates: total number unknown, but approximately five plate circlets present. Plates of slightly variable size, the
largest reaching approximately 6-7 mm. Most (possibly all) plates have diplopores arranged radially (PI. 3,
fig. 7). Plate surface covered with fine granular ornament and faint peripore rims.

Diplopores: with simple peripore rims, often strongly developed, but in several cases weak or almost missing.
Oval to elongate, rarely extremely elongate as in A. steilulifera (Salter). Length 0-25-2 0 mm (average 0-65 mm);
width OT 8-0-40 mm (average 0-32 mm); averages based on thirty-four measurements.

Peristome; not present. Outermost portions of food grooves are present, forming small knobs. Food grooves
were probably short, reaching to the centre of the circum-oral plates only.

Periproct: unknown.

Gonopore and hydropore: unknown.

Attachment: direct, by circular aboral attachment area with a diameter of 3-5 mm.

Remarks. This specimen shows most similarities with A. granulata. The lack of information about the
oral area makes the determination slightly uncertain. The mean values of diplopore lengths and
widths are not very different from those of British material (0-79 mm and 0-31 mm respectively). The
granular surface ornament of the Norwegian specimen is also very similar to that of the British form.
The characteristic surface granulation clearly distinguishes A. granulata from A. steilulifera (Paul
1973, p. 39). Some differences exist both in the shape and in the ornament between the British and
Norwegian forms. However, because no complete specimen has yet been found in Norway, a new
species is not erected.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

59

Sphaeronitidae sp. A
Plate 7, ligs. 6 8; text-tig. 33f

Material. One partial theca, PMO 90264, and two circum-oral plates, PMO 97105 and PMO 97140.

Horizon and localities. Husbergoya Shale Formation, Skogerholmen, and Ostoya, Baerum, Oslo Region.

Description. About one-third of the theca is preserved; it may have been about 40 mm high x 26 mm wide. Only
part of the upper surface remains. The theca tapers slightly towards the base, with an oval attachment area
originally about 20 x 15 mm. Base concave. Two series of roughly hexagonal thecal plates are preserved, but as
many as four or five may have been present. Thecal plates have a granular ornament. The shape of the peristome
is unknown. Food grooves of possibly two radii are preserved, representing radii II and III, or III and IV. In one
of these radii two branching ambulacra can be seen, one of which reaches below the circum-oral circlet. The two
individual circum-oral plates contain five to six side-branches off one main food groove. This main groove is
parallel to the nearest plate suture. The brachiole facets are unlike those of any other Norwegian cystoid, but
show similarities inter alia to the facets of Craterina.

Diplopores: numerous in the upper portion of the theca of PMO 90264. The diplopores are subcircular
in outline and provided with a thick peripore wall. Mean diplopore length 0-71 mm; mean width 0-50 mm;
length to width ratio F46 (based on thirty-seven measurements). No traces of mouth, anus, gonopore, or
hydropore.

Palaeoecology. Found in a shallow water siltstone sequence extending for about 10x10 km, with
abundant echinoderms, bryozoa, and brachiopods. The brachiole facets indicate the presence of
delicate brachioles, and the animals thus may have lived in clear water with moderate sedimentation
rates.

Remarks. No described cystoid is directly comparable to this species. However, it is clearly a
sphaeronitid from the type of food grooves and diplopores. To some extent it resembles Eucystis,
Archaegocystis, and Craterina, but most likely represents a new genus.

Family parasphaeronitidae n. fam.

Diagnosis. A family of Sphaeronitida with a relatively large quadrilateral peristome, surrounded by
eight peri-oral plates. The margin of the peristome is pierced by a large number of small pits;
diplopores are complex. Four ambulacra, each leading to one large brachiole facet; periproct large,
not very far down on the theca.

Remarks. Parasphaeronitidae is erected for two genera, Parasphaeronites n. gen. and P achy cyst is
n. gen. It is separable from the Sphaeronitidae by the presence of eight peri-oral plates. The family
resembles the Holocystitidae in the number and distribution of peri-orals, but differs in having
diplopores. Parasphaeronitidae differ from the Aristocystitidae in the shape of the peristome, which
in the latter family has two broad ambulacral tracts which meet at a small ovate mouth (see Paul 1 973,
p. 57).

The Parasphaeronitidae seem to represent a transition between the Sphaeronitidae and the
Holocystitidae, at least as far as the oral area is concerned. The humatipores of the holocystitids are
known only from their exterior appearance (at the outer portion of the thecal plates) and the
connections of canals through their plates are not known. In Parasphaeronites the canals are
extremely eomplicated and show patterns not unlike those of the Aristocystitidae. The Para-
sphaeronitidae thus may also show some similarities to the Aristocystitidae, as far as the internal
portions of the pore-struetures are concerned. The Parasphaeronitidae at present contains two
genera only, and both occur in the upper Ordovician (Ashgill) Kalvsjo Formation (= Stage 5a)
and an unnamed formation from Ringerike ( = Stage 5b) (Hirnantian), of the Oslo Region,
Norway.

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PALAEONTOLOGY, VOLUME 27
Genus Parasphaeronites n. gen.

Synonymy. See Parasphaeronites socialis n. sp.

Type species. Parasphaeronites socialis n. gen., n. sp.

Diagnosis. A genus of Parasphaeronitidae with large globular theca composed of numerous irregular
plates, with elevated plate centres forming irregular external surface; pores relatively close together
with broad peripore rim, giving the appearance of Sphaeronites. One large ambulacral facet at each of
the four oral corners. Periproct separated from the mouth by two plates.

Remarks. Parasphaeronites does not resemble any known cystoid. The presence of eight peri-orals
and diplopores clearly distinguishes it from all others. The diplopores show similarities to both the
Aristocystitidae and the Sphaeronitidae. Parasphaeronites is known from one species only, P. socialis
n. sp. It differs from Pachycystis n. gen. in the arrangement of thecal plates around the peristome, the
position of the periproct, the location of the gonopore, and in the more simple type of diplopores in
the latter genus.

Description. The theca is globular, usually 40-50 mm in diameter, and consists of at least forty to fifty plates. The
base is concave and irregular. The precise plate arrangement cannot be worked out easily, because the numerous
specimens are usually crushed together and the thecae generally weather more rapidly than the matrix. The
stereom of the thecal plates is often well preserved and shows an inner coarse mesh and an outer fine mesh
structure. The pore structures are very well preserved, showing a rather complex pattern of canals through the
plates. Three types of canals occur: ( I ) canals leading right through the plate from simple pores or a diplopore;
(2) Y-shaped canals leading to two different diplopores; and (3) a main canal of low angle giving off severaf
side-canals, each of which leads to a different diplopore (text-figs. 12f, 33b e; PI. 8, figs. 3, 6, 7). The periproct is
situated some way down the theca and is separated from the mouth by one plate in addition to the peri-orals. The

TEXT-EIG. 33. A, Parasphaeronites socialis n. gen., n. sp. PMO 90974, holotype showing plate configuration of
oro-anal area (drawing reversed in relation to specimen which is probably seen from inside); the quadrilateral
mouth (M) is surrounded by eight peri-oral plates (1-8); hydropore (H), possibly gonopore (G?) and periproct
(Pe) visible, b-e, P. .socialis n. gen., n. sp., schematic representation of plate growth and additions of simple and
complex canals; notice that the complex canals (branched) occur at the boundary between the fine mesh layer
(dotted) and the coarse mesh layer (irregularly hatched); simplified, f, Sphaeronitid indet. sp. A., PMO 97105,
Husbergoya Shale, V. Ostoya, Baerum, circum-oral plate showing food groove (Fg) with six side-branches and

facets (F), and diplopores on the side.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

61

shape of the periproct is difficult to establish, but it seems to be as large as the peristome. The hydropore is
a long slit-like opening crossing the sutures POl : P06. The gonopore is located somewhat lower down on the
theca and at the left side of the hydropore-periproct line. Attachment was direct, with a slightly concave base.

Palaeoecology. Parasphaeronites has been found in only one locality where it is extremely common,
filling erosion channels in a reef.

Parasphaeronites socialis n. sp.

Plate 8, figs. 1, 3, 5-7; text-fig. 33a

1897 Sphaeronites sp.; Kiaer, p. 17.

1948/? Sphaeronites sp.; Regnell, p. 35.

Diagnosis. A species of Parasphaeronites with numerous thecal plates, not arranged in definite
circlets; plates thick with elevated centres; diplopores present on most of the thecal plates, numerous,
peripore with distinct rims, peripore length 0-5-0-6 mm.

Holotype. PMO 90974, a specimen showing the oro-anal area from the inside (text-fig. 33a; PI. 8, fig. 1 ).
Material. In addition to the holotype, more than a hundred specimens.

Horizon and locality. Upper Ashgill; within channels in the reef of an unnamed formation, Ullerntangen,
Ringerike, Oslo Region.

Description. As for the genus. The holotype shows the inside of the theca (PI. 8, fig. 1); the plate diagram
(text-fig. 33a) is reversed to show the external plate configuration.

Plates; one or possibly two generations in some parts of the theca. Four plate circlets at least in the holotype.
Plates mostly elongated in oral-aboral direction. Most plates 6x4 mm. A circlet must have consisted of ten to
fifteen plates; the basal circlet probably consisted of ten plates. Plate thickness 1-2 mm.

Respiratory pores: 0-54 x 0 33 mm with broad low periporal rim, or rimless peripores. Diplopores numerous
all over the thecal surface including the basal plates, but absent near plate sutures. Some haplopores may be
present. The canals within the plates are very complex (text-figs. 12f, 33b-e; PI. 8, figs. 3, 6, 7).

Peristome: 81 x 4-4 mm, surrounding oval mouth. Small pits present on the peristome border resemble those
of holocystitids (Paul 1971).

Periproct: the shape cannot be made out but it is about 7 mm from the lower border of the peristome frame.
Gonopore: circular, 0-48 mm in diameter.

Hydropore: present 1-2 mm below the peristome frame.

Remarks. P. socialis has pore structures resembling those of Sphaeronites on its external surface. The
numerous pores all over the theca give it a high respiration potential, and in this respect it also
resembles Sphaeronites. The complex pattern of pore canals within the thecal plates makes it one of
the most difficult cystoids in Norway to study with respect to the peripore connections. However, it
can be demonstrated that individual canals led to a peripore and that a complex circulatory system
existed.

Pachycystis n. gen.

Type species. Pachycystis norvegica n. gen., n. sp., by monotypy.

Type horizon and locality. Kalvsjo Limestone, upper Ashgill; Kalvsjo, Hadeland, Oslo Region.

Diagnosis. A genus of Parasphaeronitidae with quadrangular peristome surrounded by eight
peri-oral plates. Four ambulacra, each terminating in a large facet close to the mouth. A large
periproct set closely to the peristome. Thecal plates numerous and irregular. Diplopores very
common in the oral area, diminishing in number towards the base where they are absent. Directly
attached by a slightly concave base.

Remarks. Pachycystis differs from Parasphaeronites by the periproct being close to the peristome
border in the former, and separated by two plates in the latter. The gonopore of Pachycystis borders

62

PALAEONTOLOGY, VOLUME 27

POl and the peristome, whereas in Parasphaeronites the gonopore is located closer to the peristome.
Thecal plates of Pachycystis are gently elevated, but strongly tumid in Parasphaeronites.

Description. The theca is sack-like with plates of different shape, often elongated, pentagonal, or hexagonal. No
complete specimens exist, and thus the size cannot be clearly established. Total height of the theca seems to be in
the range of 40-50 mm and diameter of 25-30 mm. POl, P03, P05, and P07 each contain one large brachiole
facet, almost circular and 2-5-3 0 mm in diameter. Two muscle scars, both elongate, occur in each of the facets.
The mouth may have been covered in life by a palate, but it has not been observed. A slit-like hydropore is
present on POl and ends at the POl : P08 suture. A possible gonopore is located at the upper left side of the
periproct, and is 0-6 mm in diameter. A large slightly ovate periproct, 7-5 x 5-5 mm, is set close to the lower
margin of the mouth frame and is bordered by POl, P07, and P08.

Diplopores are numerous in the upper half of the theca, usually 0-4 x 0-3 mm. They are densely packed in the
circum-oral portion of the theca (four or hve per mm^) but become reduced in number towards the base, where
pores are absent. The long axis of the pores do not seem to show any preferred orientation. Pachycystis was
attached directly by an attachment area which was slightly concave. Its diameter may be in the order of
20 X 20 mm from the general appearance of the theca, but has been found to be 5 x 3 mm in one specimen.

Palaeoecotogy. Pachycystis has been found only on the flanks of a mudbank at Kalvsjo, Hadeland,
where it is preserved in a calcareous shale.

Pachycystis norvegica n. sp.

Plate 7, flgs. 5, 9, 10; text-fig. 34a, b

Diagnosis. As for the genus.

Holotype. PMO 97103, an external mould of the oral area (text-fig. 34a; PI. 7, figs. 5, 10).

Horizon and locality. Upper Ashgill; Kalvsjo Formation, mud bank, Kalvsjo, Hadeland, Oslo Region.

Material. Holotype, PMO 97141 and PMO 101.835, and two moulds, PMO 97102 and PMO 97104.

Description. As for the genus. In addition some measurements have been made on the sizes of diplopores. The
peripores are slightly elongated with fairly large pores. Some of the peripores close to the plate sutures are smaller
than those elsewhere, probably indicating that new pores are formed close to sutures. Peripore length 0-35-
0-50 mm; width 0-25-0-40 mm (text-fig. 34b). Attachment was direct with a small elongate attachment area
(5x3 mm in PMO 101.835).

EXPLANATION OF PLATE 8

Figs. I, 3, 5-7. Parasphaeronites socialis n. gen., n. sp. Unnamed formation (Hirnantian), Ullerntangen,
Ringerike. ), PMO 90974, holotype, oro-anal area seen from inside (?) of theca (specimen strongly
weathered). 3, PMO 105.707, etched specimen showing details of canals in sagittal view; the hnestereom layer
(outer) is dissolved, the inner coarse mesh layer hlled with asphalt (note how the canals parallel the surface of
the coarse mesh layer), x 10. 5, PMO 55533, stereophoto of strongly convex plates with pores, x5-5. 6, PMO
105.715, SEM stereophoto showing details of complex canals with main canals and side branches towards
edge of plate (SEM 2362/61), x 20. 7, PMO 105.715, SEM stereophoto showing details of complex canals
towards plate centre (note vertical position of canals as opposed to low angle canals at plate edge) (SEM
2356/57), x20.

Eig. 2. Incertae sedis sp. A. Upper Chasmops Limestone (121 m below top), Raudskjser, Asker. PMO 103.320,
basal portion of theca with minute diplopores, x 2.

Pig. 4. Incertae sedis sp. B. Encrinite Limestone (2 m above base, within lowermost portion of reeO, Steinvika,
Langesund. PMO 105.836, basal portion of a theca showing small diplopores, x3.

PLATE 8

BOCKELIE, Parasphaeronites and Incertae sedis

64

PALAEONTOLOGY, VOLUME 27

Incertae sedis sp. A

Plate 8, fig. 2

Material. One specimen, PMO 103.320.

Horizon and locality. Upper Caradoc; Upper Chasmops Limestone, 12T m below the top, Raudskjaer, Asker,
Oslo Region.

Description. Theca: presumably roughly spherical, about 30-35 mm in diameter, showing the basal portion. Five
large lobate basal plates. Base concave, circular, 16 mm in diameter. Theca strongly weathered.

Plates: thick (1-8 mm) with few randomly arranged diplopores.

Diplopores: sparsely developed, small (0-26 x 0T6 mm) possibly with faint rims originally. All other features
unknown.

Palaeoecotogy. The specimen was attached directly in life, probably to a brachiopod. When dead, the
cystoid came loose from its attachment, fell over to the side, and was eventually covered by an
epifauna of two different types of bryozoa and crinoid roots.

Remarks. This specimen is preserved in a nodular limestone with interbedded shales. The shape of the
theca might suggest a sphaeronitid, but the minute and scattered diplopores make it difficult to
suggest its affinities. The specimen might be a representative of a new genus, and is at least a new
species. Due to lack of information about the oral area, however, I will avoid a new name.

TEXT-FIG. 34. A, B, Pachycystis norvegica n. gen., n. sp., PMO 97103, holotype, Kaivsjo Formation, Kalvsjo,
Hadeland; a, plates of oro-anal area with peri-orals ( I -8), one brachiole facet (F) in each of the four oral corners,
a possible gonopore (G?) close to the large periproct (Pe), and a narrow hydropore (H) at the POl : P08 suture;
B, diplopores. c, d, Incertae sedis sp. B., PMO 105.836, Encrinite Limestone, Steinvika, Langesund; c, plates ot
basal portion, including basals (B); d, diplopores with faintly developed or abraded peripore wall. Scale bar,

1 mm.

BOCKELIE: NORWEGIAN ORDOVICIAN CYSTOIDS

65

Incertae sedis sp. B
Plate 8, fig. 4; text-fig. 34c, d

Material. One specimen, PMO 105.836.

Horizon and locality. Upper Caradoc; within reef complex of Encrinite Limestone, 2 m above base, Steinvika,
Langesund.

De.scription. Theca: only the basal portion showing three plate series is preserved. Maximum height and width
both 1 '2 mm.

Plates: thick (2 0 mm) with few, randomly arranged diplopores. All plates primary, elongated in ad-aboral
direction; most plates hexagonal.

Diplopores: randomly distributed, 0-27 xOT2 mm, usually strongly abraded; present on all thecal plates,
including the basals. All other features unknown.

Palaeoecology. The specimen most probably lived in or very close to the reef environment and was
attached directly by its base. Its presence in the crinoid-dominated community suggests that it might
have been a low-level suspension feeder, unless it was attached to seaweed. The thick plates rather
suggest that the animal was heavy and bottom dwelling.

Remarks. This specimen is preserved in a reef limestone together with crinoids, a few Heliocrinites sp.,
and occasional specimens of Hemicosmites papaveris. The weathered state of the specimen and the
lack of the oral area makes determination even to family level impossible.

Acknowledgement.s. This work was started in Oslo and inspired by the late Professor A. Heintz, formerly head of
the Paleontologisk Museum, Oslo (PMO). I am indebted to D. Bruton and G. Henningsmoen, Paleontologisk
Museum, Oslo, T. Orvig and V. Jaanusson, Natural History Museum, Stockholm (RM), and C. R. C. Paul,
University of Liverpool, for valuable discussions and suggestions. Valuable help with the manuscript has also
been rendered by my wife, T. G. Bockelie. Lor the loan of material thanks are due to S. E. Bendix-Almgren,
Mineralogisk Museum of Copenhagen University, J. Bergstrom, Paleontological Institute of the University of
Lund, Sweden (LM), R. A. Reyment, Paleontological Institute of the University of Uppsala, Sweden (PMU), P.
Sartenaer, Institute Royale des Sciences Naturelles de Belgique (IRScNB), R. Skoglund, Swedish Geological
Survey (SGU), R. Prokop, National Museum, Prague, Czechoslovakia (NM), R. P. S. JelTeries, British Museum
(Natural History), and R. B. Rickards, Sedgwick Museum, Cambridge, England (SM). Linancial support has
been rendered from the University of Oslo, from Gustav Lindstrom’s Minnesfond, Stockholm (1972), from
Nansenfondet (1975-1976), from the Norwegian Ministry of Loreign Affairs under the cultural agreement with
Czechoslovakia (1976), and from the Schmidt Lund Award, Lield Museum of Natural History, Chicago, USA
(1979). The manuscript was prepared at the Paleontologisk Museum, Oslo, during a research fellowship from the
Norwegian Council for Science and Humanities (NAVE). Linguistically the manuscript has been corrected by
Dr. C. R, C. Paul who also made several suggestions for its improvement. To all these people and institutions I
owe my sincere thanks.

Geological maps at a scale of 1 : 5000, a list of all fossil localities, drawn sections with occurrences of cystoids
and other fossils, and the majority of the described material have been deposited in the Palaeontologisk
Museum, Oslo.

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Typescript received 10 September 1980
Revised typescript received 23 June 1982

J. FREDRIK BOCKELIE

Norsk Hydro Research Centre
Lars Hillesgate
5000 Bergen, Norway

PERMINERALIZED OVULATE CONES OF
LEBACHIA FROM LATE
PALAEOZOIC LIMESTONES OF KANSAS

by G. MAPES and G. w. rothwell

Abstract. A diverse assemblage of perinineralized conifer remains has been discovered in late Palaeozoic
limestones from the mid-continent of North America, near Hamilton, Kansas. Ovulate cones described as
Lebachia lockardii sp. nov., support the structural homologies among cordaites, primitive conifers, and modern
conifers proposed by Florin, and reveal anatomical features that are remarkably similar to those of many
extant conifers. Features not recognized from previously described cones of Lebachia are dorsiventral, bilater-
ally symmetrical fertile shoots, inverted orientation of the ovules, and the true bilateral symmetry of the
ovules. In both morphological structure and cuticular features the specimens show more variability than has
previously been documented for a single conifer species, and this calls to question the reliability of features
previously employed for generic separation of Lebachia from Ernest iodendron. The specimens also provide
the first histological evidence for ovule abscission in Palaeozoic gymnosperms, and allow for the interpretation
of several aspects of ovule ontogeny and early conifer reproductive biology.

Upper Palaeozoic conifers are a relatively common component of some northern Hemisphere
compression floras. Remains assignable to several genera, including Walchia, Lebachia, Eruestio-
dendron, Lecrosia, and Paleotaxites, have been described from Westphalian B (Scott 1974) and
more recent strata of Europe and North America. Much of our current understanding of the
earliest conifers is derived from the detailed studies and interpretations of Florin (1938-1945, 1950,
1951). However, until recently our knowledge of these forms has been limited by an almost
total absence of permineralized specimens. Notable exceptions are a single leafy twig from the
Pennsylvanian of Kansas (Elias 1948), a Permian ovulate cone tip (Moyliosirohus Miller and Brown
1973), and various wood fragments described by Florin (1938-1945) and others.

Numerous compressed Pennsylvanian and basal Permian conifer remains have been described
or reported from North America. Where preservation reveals pertinent morphology and epidermal
detail, some of these have been recognized as species of Lebachia (Florin 1938-1945; Cridland
et al. 1963; Cridland and Morris 1964; Mapes 1981). These include L. americana, L. garnettensis,
L. parvifolia, L. stricta, L. geoppertiana, L. schlotheimii, and L. stephanensis. In addition, Lecrosia
gouldii, Paleotaxites praecursor, and several species of Walchia have been reported (e.g. White
1912; White 1929; Darrah 1936; Elias 1936; Arnold 1941; Read and Mamay 1964; Darrah 1969;
Leisman 1971; Tidwell and Ash 1980; Kues and Kietzke 1981). Though some poorly preserved
cones have also been reported, the studies have dealt primarily with isolated leafy branches or
sterile foliage shoots.

As the result of extensive collecting in sediments that contain plant fragments not known from
contemporaneous coal-forming peats (viz. not from coal balls), permineralized conifer remains
have recently been discovered in mid-continental deposits of Oklahoma and Kansas (Mapes 1981;
Rothwell 19826). Permineralized specimens from these deposits range in age from middle
Pennsylvanian to late Pennsylvanian or perhaps early Permian. The most diverse flora thus far
encountered is near Hamilton, Kansas (text-fig. 1 ), and contains a wide variety of conifer remains.
Included are large numbers of plagiotropic branch systems bearing forked leaves on penultimate
and more basal branch orders and either long-needled or short-needled simple leaves on the ultimate
branches. Both compound cones bearing ovules and simple pollen cones with Potonieisporites

[Palaeontology, Vol. 27, Part I, 1984, pp. 69-94, pl.s. 9-l6.|

70

PALAEONTOLOGY, VOLUME 27

are present in the conifer assemblage (Mapes 1981). A large number of the specimens display
morphological and cuticular features that allow for their assignment to Lehachia as circumscribed
by Florin (1938-1945), and provide the first opportunity to describe internal anatomy and to
interpret development and reproductive biology in one of the most widely reported of all Palaeozoic
conifers. The material also allows us to evaluate, from anatomical evidence, the accuracy of the
structural homologies proposed by Florin for cordaites and conifers. Moreover, we can for the
first time examine the isolated parts of a single Lehachia based on both external and internal
features, and ultimately reconstruct the entire plant.

In the present study we describe and interpret several aspects of cone organization, ovule
structure, ovule development, and reproductive biology in a new species of Lehachia. Pollen cones
and vegetative organs will be addressed in subsequent studies.

MATERIALS AND METHODS

Specimens of Lehachia are from an abandoned limestone quarry located east of Hamilton, Kansas
(text-fig. 1). Conifer debris is common throughout the quarry (Leisman 1971), and ranges from
finely disaggregated cuticles and wood fragments through compressed and/or permineralized cones
and woody branching systems. The fossil flora at Hamilton is primarily gymnospermous, with
conifers dominating in number and in diversity. Numerous animal remains also occur in this
deposit, including insects (Hanson 1973), eurypterids (Anderson 1974), acanthodians (Zidek 1976),
amphibians, foraminifera, and ostracods. Brachiopods and clams from the fossiliferous matrix
have been identified as Hystriculina wahashensis, Reticulatia heucoensis, and possibly Derhyia,
Ednwndia, and Myalina spp. While these particular animal remains are sometimes poorly
preserved, their occurrence in these sediments suggests strongly that the strata are of Pennsylvanian
age (R. D. Hoare, Bowling Green State University, Ohio, pers. comm.).

The fossil-bearing unit at Hamilton quarry is a channel deposit, and consists of a basal
conglomerate which grades into fine-grained laminated limestone. Although miscellaneous fossil
remains are present in some of the clasts in the conglomerate, the permineralized plants and the
majority of the animal fossils are in the limestone. While underlying and surrounding rocks have
been recognized as the Hartford Limestone of the Topeka Limestone Formation, Shawnee Group,
Virgilian (Andersen 1974: Zidek 1976), the age of the conifer-rich horizon per se has not been
determined with certainty. In addition to the conifers, the Hamilton flora contains various
cordaitean, fern, and seed fern remains. Certain highly dissected foliage was originally reported
as the pre-ginkgophyte Dichophyllum (Andrews 1941), but has since been interpreted as Callipteris
fiahellifera (Remy et al. 1980). If this is correct, several alternatives are possible stratigraphically.
The Hamilton beds could be equivalent to one of the Permian zones 11 to 14 (Remy 1975) of
Read and Mamay (1964) or to the European Autunian (Remy and Havlena 1960, 1962; Remy
et ah 1966), or C. fiahellifera may have entered the flora earlier in the eastern and mid-continent
U.S.A. than in the European section. While Callipteris spp. have been recognized as earliest Permian
indicators, there are also reports of their occurrence world-wide in lower (older) strata (Barlow
1975; Gillespie et al. 1978). Assignment of these beds to either the upper Pennsylvanian or lower
Permian awaits additional work with the more stratigraphically diagnostic forms of the biota.

Specimens were generally revealed by splitting the limestone matrix along the bedding plain.
Morphological features were examined on the surfaces. The part and counterpart of some
permineralized specimens were glued back together and serial sectioned in transverse or longitudinal
plane. One part of other permineralized specimens was covered with liquid plastic then sectioned,
while the counterpart was macerated in 2-5% HCl for cuticular preparations. Serial sections were
prepared by the well-known cellulose acetate peel technique (Joy et al. 1956). Pertinent sections
were mounted on standard microscope slides for transmitted light study and photography. Since
the matrix was often nearly transparent while a peel was still attached, three-dimensional perspective
could often be seen. Some of these surfaces were photographed with polarized reflected light (e.g.
PI. 16, figs. 1, 2). Photography was also with unpolarized reflected light, transmitted bright-field.

MAPES AND ROTHWELL: PALAEOZOIC CONES FROM KANSAS

71

and Nomarski differential interference contrast (DIC) optics. Some macerated cuticle, tissue
fragments, and prepollen grains were mounted on microscope slides for light optical study, while
others were rinsed in distilled water, mounted on stubs with double-sided tape, and coated with
gold for scanning electron microscopy. Specimens examined in this study are M26, M83, M144,
Ml 45, Ml 47- 152, and bear acquisition numbers 3834 to 4268 in the Paleobotanical Herbarium,
Department of Botany, Ohio University, Athens, Ohio, U.S.A.

FOSS I LI FERGUS EXPOSURES AT QUARRIES
EAST OF HAMILTON, KANSAS

(NWV4, Sec. 5&8.T.24S., R.12E.,
Virgil 7V2' quadrangle, Greenwood
County)

TEXT-FIG. 1. Fossiliferous exposures at quarries
east of Hamilton, Kansas. Lebachia lockardii speci-
mens have been recovered from all of the pits. The
majority of the permineralized cones are from
excavations directly west of the Main Quarry and
the Quarry Pond.

~ Unpaved surface C

Farm road I

0

SOO Metres

72

PALAEONTOLOGY, VOLUME 27

SYSTEMATIC DESCRIPTION

Order coniferales
Family lebachiaceae
Genus lebachia Florin 1938
Lebachia lockardii sp. nov.

Plates 9-16

Diagnosis. Ovulate cones, averaging 5-0 cm long x 1-5 cm wide, borne as single terminal units on
vegetative axes with helically arranged simple or bifid leaves. Cones comprised of primary axis
with helically arranged bifid bracts and axillary fertile shoots. Fertile shoots bearing twenty-five
to thirty sterile scales and one to two fertile scales (rarely three to five) positioned adjacent to
primary axis. One terminal inverted ovule per fertile scale. Ovules bilaterally symmetrical and
winged, with rounded or cordate base and attenuated micropyle. Nucellus free from integument
distal to chalaza. Simple pollen chamber with nucellar beak; often containing Potonieisporites
grains. Stomata with five to nine unipapillate subsidiary cells. Adaxial leaf structure with stomata
in two parallel bands, each four to eight stomata wide with some shared subsidiary cells; single
bands or isolated rows of stomata occurring on some leaves. Abaxial cuticles papillate and less
stomatiferous. Unicellular hairs common at margins of leaves and bracts.

Holotype. Slides, peels, and remaining portions of specimen M26; reposited in the Palaeobotanical Herbarium,
Ohio University, as numbers; 3834-3851; 3867-3912; 3968-4092; 4267, and represented herein as Plate 9,
fig. 5; Plate 10, figs. 1-3, 5, 6; Plate 11, figs. 1, 3-6; Plate 12, fig. 4; Plate 13, figs. 1, 3, 5; Plate 14, figs. 1-8.

Paratypes. Specimens Ml 47 and M 148 reposited as above, as numbers 4093-4147; 4234-4251, and 3855-3865;
4160-4218; 4260-4262; 4268, respectively, and figured herein as (M147) Plate 9, figs. 1, 4, and (M148) Plate
11, figs. 2, 5, 7; Plate 12, figs. 5, 7, 8; Plate 13, figs. 1, 4, 6; Plate 15, figs. 1-3, 5-7; Plate 16, figs. 1-3.

Locality. Hamilton quarries; NW quarter, sec. 5 and 8, T.24S., R.12E., Virgil seven and a halffoot quadrangle.
Greenwood County, Kansas, U.S.A.

Etymology. This species is named for Walter Lockard, who recognized the potential of the unique Hamilton
fossil assemblage over twenty years ago, and has diligently obtained and generously shared his extensive field
collections for palaeontological studies.

Description. Fifteen whole and partial permineralized cones, and numerous compressed specimens were
examined. These ovulate cones are cylindrical-ellipsoidal and quite compact (PI. 9, figs. 1-4). Complete cones
are generally 4 0 to 5-5 cm long with a maximum diameter of L5 cm in their mid-regions. While large
branching systems with attached ovulate cones of L. lockardii have not been recovered, all known Lebachia
cones are terminal, and some of the L. lockardii cones retain up to 4 cm of vegetative axis below the cone
base (PI. 9, fig. 1 ). Leaves on the subtending axes are either bifid or simple, and provide a clue to the original
positions of the cones on the branch systems.

Because the ovulate cones represent compound shoots, by definition they occur on penultimate or
antepenultimate branches (= ultimate and penultimate branches of Florin 1951). The primary cone axis
represents the penultimate branch and the fertile, secondary shoot is homologous with the ultimate vegetative
branch. Each primary cone axis bears many helically arranged fertile complexes, comprised of a bifid bract

EXPLANATION OF PLATE 9

Figs. 1-5. Lebachia lockardii sp. nov., ovulate conifer cones from Hamilton, Kansas, a, primary cone axis;
b, bract; o, ovule; s, secondary shoot. 1, cone attached to vegetative shoot, M 147, x 2. 2, cone split longi-
tudinally, note attachment of secondary shoots to cone axis. Ml 50, x 2. 3, abraded cone surface with
prominent sterile scales of secondary shoots, M146, x2-5. 4, apex of cone in fig. 1, note sterile scales of
llattened secondary shoots, M 147, x 3. 5, holotype, oblique longitudinal section, showing helical arrange-
ment of bracts and the relative positions of bracts to axillary secondary shoots, M26 No. I, x 5.

PLATE 9

MAPES and ROTHWELL, Lehachia cones

74

PALAEONTOLOGY, VOLUME 27

and an axillary shoot with several sterile and fertile scales. Florin (1938, 1951) called the fertile shoots ‘flowers’
and characterized the fertile shoot axes of Lebachia ovulate cones as radially symmetrical. The often excellently
preserved and undistorted fertile shoots ( = secondary shoots) of L. lockardii are clearly bilaterally symmetrical;
their flatness is biologic, not taphonomic. The stele of the secondary shoot ( = cone scale trace of more recent
conifers) is crescent-shaped in transverse section, not radial as are the secondary shoot steles of cordaitean
strobili (Rothwell 1977; Daghlian and Taylor 1979). While unabraded external surfaces of L. lockardii cones
often retain the bihd bracts, the axillary shoots with their numerous scales are more easily recognized (PI. 9,
figs. 1-4). In the apical region of the cone, the bracts have no secondary shoots in their axils (PI. 10, fig. 4).

The primary cone axis has a eustele with the endarch xylem maturation that is characteristic of more recent
conifers. Pith and cortical cells are typically 15 to 25 /xm in diameter and always thin-walled (PI. 10, figs. 2,
3, 5). Some of these cells are elongate, have dark contents, and are up to 70 ;u,m in diameter; cells of this
type may have had secretory or storage functions. Primary xylem tracheids are narrow, average 7-5 /xm in
diameter, and have angular-spiral and scalariform wall thickenings (PI. 11, fig. 1). The secondary xylem is
compact, basically pycnoxylic, and forms a cylinder averaging 1-3 mm in diameter (PI. 10, figs. 1, 5, 6). In
transverse sections, tracheids are ovoid-polygonal (PI. 1 1, fig. 3). Throughout most of the wood the tracheids
have uniseriate pitting (PI. 11, fig. 6), but the tracheids adjacent to the primary xylem sometimes show
uniseriate oval pits and/or biseriate opposite circular bordered pits (PI. 1 1, figs. 4, 6). Rays are uniseriate to
biseriate, one to five cells high, and composed of poorly preserved parenchyma with no evidence of ray
tracheids (PI. 11, figs. 1, 3).

The bifid bracts have deeply heeled bases (PI. 9, fig. 5; PI. 10, fig. 3). Distal forking can be recognized in
transverse sections near the bract apex (PI. 14, fig. 1 at top). Similar forked leaves occur on penultimate and
antepenultimate vegetative axes, and at the cone base/vegetative branch transition zone on lateral shoots
bearing otherwise simple leaves (Florin 1951). Such bifid leaves and bracts are sometimes referred to
Gomphostrobm Marion (1890) and are vascularized by a single trace which bifurcates below the bifid apex.
The tracheids are usually poorly preserved, but scalariform wall thickenings have been observed. Ground
tissue consists of isodiametric, loosely packed parenchyma cells (PI. 10, fig. 3), many of which contain dark
contents which may be secretory. An abaxial hypodermis occurs throughout the length of the bract, but
diminishes in prominence distally. The hypodermis consists of two to four cell layers of elongate, closely
packed cortical cells directly beneath the epidermis (PI. 10, figs. 3, 5).

Lebachia leaf cuticle has been characterized by Florin (1938-1945) as thick, papillate, and amphistomatic,
with each leaf commonly bearing two broad parallel bands of haplocheilic stomata. The stomata have two
guard cells surrounded by four to eleven subsidiary cells with overarching papillae. Cuticles of L. lockardii
have these features, and contribute additional information regarding variations of the cuticular features in a
single species.

The stomatal bands of L. lockardii vary in width, length, and composition. There may be single bands or
parallel bands, and stomata occur both on abaxial and adaxial leaf surfaces. Within individual ovulate cones
of L. lockardii, there is a wide range of variation. Parallel bands, generally four to eight stomata wide, are
present only on adaxial leaf surfaces. Single bands of comparable width are sometimes seen on sterile scales.
Stomatal arrangement within a band is also variable. Generally, stomata are irregularly disposed, though
longitudinally oriented, with some shared subsidiary cells (PI. 12, fig. 1). In other areas there are more widely
separated or even single rows of longitudinally oriented stomata (PI. 12, figs. 3, 6) or isolated stomatal
apparatuses. The least stomatiferous cuticles are those of the smallest sterile scales, the cone axes, and the
abaxial surfaces of bracts. The ovulate cone cuticles of L. lockardii are certainly amphistomatic, but the
majority of the stomata are adaxial. While comparable to the species of Lebachia characterized by Florin

EXPLANATION OF PLATE 10

Figs. 1 -6. Lebachia lockardii sp. nov. a, primary cone axis; b, bract; o, ovule; s, secondary shoot; sa, secondary
shoot axis, ss, sterile scales. 1, longitudinal section of cone near apex. Note arrangement of vascular tissues,
bract, and axillary secondary shoot, M26 B side No. 5, x 14. 2, tangential section of detached ovule and
crescentic vascular trace of fertile secondary shoot, M26 No. 1, x 13. 3, bract bases in tangential section. Note
abaxial hypodermis, cortical cells with dark contents, and vascular trace at arrow, M26 A side No. 4, x 16.
4, transverse section near cone apex, M83 Top No. 25, x 14. 5, transverse section of cone, note two ovules of
one secondary shoot, M26 B Top No. 58, x 12. 6, transverse section of primary cone axis below fertile zone,
M26 ATopNo. 33, x 14.

PLATE 10

MAPES and ROTHWELL, Lehachia cones

76

PALAEONTOLOGY, VOLUME 27

(1938-1945), each stoma of L. lockardii has five to nine subsidiary cells, each with a single papilla overarching
the stomatal opening (PI. 12, fig. 6). In bands of closely spaced stomata, subsidiary cells are sometimes shared
by adjacent stomata, but papillae are usually single. More commonly, small epidermal cells intervene,
separating the subsidiary cells of adjacent stomata (PI. 12, fig. 6 at arrow). The guard cells are generally not
preserved.

Epidermal cells within and between stomatal bands vary in shape and size, and in the presence or absence
of papillae and hairs. Papillate epidermal cells are sometimes present on both abaxial and adaxial surfaces
(PI. 12, figs. 2, 7), but are most common on abaxial cuticles. In addition, they occur both in and between
the bands of stomata. Although exceptions have been noted, there is usually only one papilla per epidermal
cell. Papillae are most often on small, rather isodiametric cells, but they also occur on the tabular and the
broadly polygonal epidermal cells (PI. 12, figs. 2, 7). Uniseriate hairs are common on the margins (PI. 12,
figs. 1, 8) and can be seen on both surfaces of L. lockardii leaves. The longest hairs (up to 0-6 mm long) are
often twisted and some may be multicellular.

A feature of considerable interest characterizes certain small epidermal cells. These cells are rounded rather
than angular, and display a central circular area, av. 8-12 /xin diameter, with raised rim and often dislodged
cuticular surface (PI. 12, figs. 4, 5). These areas resemble closely the waxy plugs or cuticular flaps which cover
sunken stomata of certain species of fossil and modern Araucaria (Stockey and Taylor 1978a, b). However,
these cells are not associated with the stomata of L. lockardii. Rather, they are often surrounded by larger
epidermal cells and can be easily recognized in surface view or optical section by their coronas (PI. 12, figs. 4,
5). We interpret the corona to represent the area between the rim of the circular area and the widest lateral
extent of the walls of the small isodiametric cell, where the cell wall margin subtends that of the adjacent
surrounding epidermal cells. The surface flap or plug of cuticle probably resulted from the collapse of a small
hair or a broad low papilla. These cells resemble some of those Florin called hair bases (e.g. L. americana,
text-abb. 20a, Florin 1938-1945).

In L. lockardii numerous irregularly arranged sterile scales and one or more fertile scales are typically
present on each secondary shoot (PI. 10, figs. 1, 5). This deviation from the helical arrangement of leaves on
vegetative stems of Lebachia results from the combination of flatness of the secondary shoot axis (PI. 10,
fig. 5) and the smaller number of scales present on the side of the shoot that lies adjacent to the primary cone
axis. Where the bracts are not preserved, fertile shoots often display a fan of nine to twelve sterile scales
(PI. 9, figs. 2-4). In some transverse sections, twenty to twenty-five scales can be seen at a single level, and
serial sections indicate that more than thirty scales may be present on individual fertile shoots.

Within cones, the fertile secondary shoots are attached to the primary axis at intervals of approximately
5 mm, and average 2 0-2-5 mm long. In transverse sections below scale attachment, individual secondary shoot
axes are 0-2- TO mm in diameter, expanding up to 3 mm wide in the zone of scale attachment (PI. 10, fig. 5).
On some bedding planes isolated shoots from disaggregated cones can be recognized among the coniferous
debris. The isolated shoots are comparable to those within the ovulate cones, but never have mature ovules
attached.

The sterile scales most distally attached to each secondary shoot are usually fused at their bases (PI. 9,
fig. 4; PI. 13, figs. 4, 6), and can sometimes be macerated loose as dentate units of two to five scales. Most of
the macerated sterile scales taper to an acutely pointed apex, but a small number of scales have an abruptly
truncated tip with a central cleft and subapical protruberance (PI. 13, fig. 5). The latter scales are remarkably
similar to certain fertile scales of ovulate Cordaianthus strobili, where the ovules are either extremely immature

EXPLANATION OF PLATE 1 1

Lebachia lockardii sp. nov. Wood and leaf anatomy, bs, bundle sheath; px, primary xylem; r, ray.

Fig. 1. Radial section of wood of primary cone axis, arrow indicates secretory cells, M26 B side No. 1, x 130.

Figs. 2, 5, 7. Scanning electron micrographs of coalified sterile scales from ovulate cone maceration. 2, note
adaxial ridge at arrow, and upcurved leaf tip, M 148 Mac Leaf A, x 80. 5, epidermis, palisade, and vascular
trace with bundle sheath. Ml 48 Mac Leaf A, x 250. 7, spongy mesophyll tissue and vascular trace with
bundle sheath, M 148 Mac Leaf B, x 250.

Fig. 3. Transverse section of wood from primary cone axis. Note poorly preserved rays, M26 B Top No. 33,
X 185.

Figs. 4, 6. Bordered pits (Nomarski DIC). 4, single tracheid with uniseriate to biseriate oval pits, M26 A side
No. 1, X 820. 6, tracheids with uniserate circular pits, M26 A side No. 1, x 820.

PLATE 1 1

MAPES and ROTHWELL, Lehachia cones

78

PALAEONTOLOGY, VOLUME 27

or abortive (Florin 1951, fig. 21; Rothwell 1982a). Specimens of this type suggest that there was potentially
a larger number of fertile scales on Lehachia fertile shoots than is reflected by the number of well-formed ovules.

Papillae are common on all surfaces and prominent hairs are sometimes preserved at the scale margins.
Ground tissue of the scales is comprised of loosely packed spongy mesophyll (PI. 1 1, fig. 7) comparable to
the cortex of the bifid bracts, and a weakly developed palisade can sometimes be recognized (PI. 1 1, figs. 2, 5).

The fertile scales, or sporophylls, are comparable to the sterile scales in both anatomical and morphological
features. They are sometimes rounder in cross-section, averaging 0-3 to 0-8 mm (PI. 13, fig. 4), and are from
0-5 to 2 0 mm long (PI. 13, fig. 1). Fertile scales are always located adjacent to the primary axis, and are
either abruptly truncated, with no epidermis at the apex, or terminate in a single ovule. Some fertile shoots
bear one or two ovules, but many have none, possibly because the ovules had already dropped off, or because
none had formed.

Of particular interest are ovulate scales with histological features like those of extant plants in which organs
have been sectioned at various stages of abscission (e.g. Barnell 1939). Some specimens show good cellular
continuity between the scale tip and the chalaza of the ovule (PI. 13, fig. 2), but the width of the attachment
is noticeably reduced by a prominent groove extending around the periphery of the constricted attachment
area (PI. 13, fig. 3). In other specimens the ground tissue at the level of the groove is poorly preserved with
only the darker, apparently thicker-walled, cells at the centre of the zone connecting the ovule to the scale
(PI. 13, fig. 3). In still other instances, the cellular continuity between scale and ovule is completely disrupted
(PI. 13, fig. 4). Upon closer examination of the groove region, most of the cells of the ground tissue appear
thin-walled, relatively isodiametric, and randomly disposed (PI. 13, fig. 2). In specimens with partly or
completely disassociated ovules (PI. 13, figs. 2-4), cells in the groove region are like those in the separation
layer of abscising organs, after the cell walls have undergone enzymatic gelatinization and dissolution. Two
or three cell layers proximal to the separation layer of some fertile Lehachia scales there exists a small number
of cells that are rectangular in section view and aligned both parallel to and at right angles to the line of
abscission. Cells of this latter type conform closely to those of the protection layer often formed proximal to
the separation layer in the abscission zones of extant plants (Esau 1965). Prominent cell walls containing lignin
and/or suberin have not been observed in these Lehachia specimens.

Perhaps the most surprising feature of L. lockardii is the mode of ovule attachment. While the ovules are
terminal on the scales of the secondary shoots, they are inverted, rather than erect as interpreted by Florin
for all previously known species of Lehachia (Florin 1938-1945, 1951). The basipetal serial sequence of
transverse sections illustrated in Plate 4 clearly demonstrates the relationship of two ovules with the secondary
shoot upon which they were borne. Figure 1 is closest to the cone apex and shows the bases of both ovules.
The left ovule is sectioned just below the level of attachment to its fertile scale, while the right ovule is
sectioned above the level of attachment, and is represented only by its two basal lobes. Several sterile scale
tips can be seen at this level and the distal portion of the bract subtending the secondary shoot is at the top
of the figure. The central constriction marks the position where the bract apex forks distally. The helical
arrangement of the cone parts is indicated by the broad bract base and the secondary shoot stele diverging
from the primary cone axis at the lower left.

Progression basipetally shows the basal lobes of the right ovule join (PI. 14, fig. 2) and the ovule becomes
attached to its fertile scale. Note the cuticle in the area of the abscission zone is continuous (PI. 14, fig. 3)
except for a small mechanical break at far right. By the level represented at fig. 4, the right ovule has
separated from its fertile scale and the seed cavities of both ovules are evident. The nucellar beaks of the left
ovule and right ovule are seen in figs. 5 and 6 respectively, and the remaining sections proceed through the

EXPLANATION OF PLATE 12

Figs. 1 -8. Cuticular features, Lehachia lockardii sp. nov. 1 , bract cuticle, adaxial surface with band of stomata
and prominent marginal hair. Ml 49 Mac No. 6, x 100. 2, abaxial cuticle with many coronate and/or
papillate cells. Ml 49 Mac No. 1, x210. 3, longitudinally oriented rows of stomata, M145 Mac No. 9,
X 1 10. 4, portion of cuticle viewed from inside. Note coronate, circular rimmed cells (Nomarski DIC), M26
A side No. 1, x 740. 5, cuticle surface with apparent cuticular flaps or plugs, M148 SEM-13, x600. 6,
stomata with overarching papillae. Arrow notes epidermal cells between adjacent stomata. Ml 45 Mac No. 9,
X 260. 7, papillate epidermal cells, M148 SEM-9, x 1200. 8, hairs at bract margin, M148 Mac No. 3,
x290.

PLATE 12

A

vw

MAPES and ROTHWELL, Lebachia cones

80

PALAEONTOLOGY, VOLUME 27

narrowing, attenuated micropyles (PI. 14, figs. 6-8). The longitudinal section in Plate 13, fig. 1, and text-fig. 2,
also demonstrate the relative positions within a fertile complex. Although ovules are often found dislodged
laterally within the cones of L. lockardii, when attached they are always in an inverted orientation with
micropyle located between the primary cone axis and the base of the secondary shoot (PI. 13, fig. 1).

Approximately seventeen ovules remain within the cones of L. lockardii. Several of these are poorly
preserved, incomplete, and/or possibly abortive, but others are more complete. All of the ovules are clearly
bilaterally symmetrical (Roth well 19826) and have an attenuated micropyle. In transverse sections the
micropylar canal tapers gradually toward the apex of the ovule (PI. 14, figs. 6-8) and may be reduced to as
little as 01 mm in maximum diameter. However, none of the specimens is well preserved at the apex. The
base of the ovules is either cordate (PI. 14, fig. 1) or rounded (text-fig. 2). Individual ovules measured in
transverse sections average 2-3 mm in the major plane and 0-6 mm in the minor plane.

The integument consists of several zones of thin-walled cells (PI. 15, figs. 1-3) and is free from the nucellus
except at the chalaza. Clearly defined sarcotesta, sclerotesta, and endotesta that characterize most mature
gymnosperm ovules are not present. This may be due in part to incomplete tissue differentiation. The outer
margin of the integument is delimited by a uniseriate epidermis covered by a conspicuous dark line that
represents the cuticle (PI. 15, figs. 1, 2). The epidermal cells are uniformly thin-walled and usually have empty
lumina.

Individual epidermal cells are rectangular-polygonal and many are papillate. There are also conspicuous
uniseriate epidermal hairs preserved on many ovules (PI. 15, figs. 2, 6). Inside the epidermis there is a zone
of variable thickness where many of the thin-walled cells contain prominent dark contents. Cells of this type
are preserved only at the margins of the wings in the ovules figured on Plate 14 (PI. 14, fig. 4), but are more
uniformly preserved in other specimens (PI. 15, figs. 1-3). Immediately to the inside of this zone is another
zone of thin-walled cells which typically lack internal contents (PI. 15, figs. 1-3). The inner margin of the
integument is delimited by a conspicuous epidermis; the cells typically have dark contents (PI. 15, figs. 1, 2).
In some specimens the thin-walled cells are separated from the inner epidermis either by an empty space or
by the inconspicuous remnants of extremely thin-walled cells (PI. 15, fig. 2 at arrow). These remnants resemble
the undifferentiated sclerotesta of immature Palaeozoic ovules assignable to cordaites (Stidd and Cosentino
1976) and pteridosperms (Rothwell 1971, 1980). In two specimens there are two patches each of poorly
preserved, thick-walled cells at the level of the pollen chamber (PI. 16, figs. 1, 2 at arrows). These are preserved
in the minor plane and resemble the first differentiated areas of sclerotesta in previously described
Carboniferous cardiocarpalean ovules.

Vascular tissue has been difficult to identify within the ovules of L. lockardii, but in one speciman poorly
preserved tracheids have been located (PI. 15, fig. 7). These were observed near the base of the ovule in a
position which is comparable to that occupied by the integumentary bundles of cardiocarpalean ovules (e.g.
Mitrospermum vinculum Grove and Rothwell 1980).

As is also characteristic of Palaeozoic cordaitean ovules, the nucellus of L. lockardii is attached to the
integument at the chalaza and free distally (PI. 15, figs. 1, 2). It surrounds the megaspore membrane of
the megagametophyte, and forms a prominent pollen chamber distally (PI. 16, figs. 1, 2). In the midregion the
nucellus is several cell layers thick (PI. 15, fig. 2). Nucellar cells are usually small and thin-walled, and many
contain dark substances (PI. 15, figs. 1, 2, 4). A cuticle is present at the outer margin of the nucellus, and in
surface view reveals the size, shape, and orientation of the nucellar epidermal cells (PI. 15, figs. 4, 5).

The pollen chamber is round in transverse section (PI. 15, figs. 1 at top, 4), and tapers distally to engage
the base of the micropylar canal. The pollen chamber wall consists of one to two layers of cells that are like

EXPLANATION OF PLATE 13

Figs. 1 -6. Lehachia lockardii sp. nov. a, primary cone axis; az, abscission zone; b, bract; f, fertile scale; o, ovule;
s, secondary shoot; si, separation layer. 1, longitudinal section of attached secondary shoot and subtending
bract. Arrows indicate area where fertile scale adjoins ovule, M26 B side No. 9, x 25. 2, fertile scale and
ovule with groove at abscission zone, transverse section, M148 B Top No. 32, x 47. 3, ovule incompletely
abscised from fertile scale, note protection layer at arrow, M26 B Top No. 50, x47. ,4, transverse section
near tip of secondary shoot, showing ovule and scale from which it has abscised, M148 B Top No. 28, x47.
5, lobed tip of scale with small central protrusion, M26 Mac No. 7, x 75. 6, sterile scales with mesophyll,
central vascular trace (at arrow) and partial cuticle, M148 B Top No. 5, x 74.

PLATE 13

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82

PALAEONTOLOGY, VOLUME 27

those at more proximal levels of the nucellus (PI. 15, fig. 4). Distally, the pollen chamber wall thins to one
layer of distinct cells that form a conspicuous nucellar beak like those of many Palaeozoic trigonocarpalean
and cardiocarpalean ovules (PI. 14, figs. 5, 6; PI. 15, fig. 1; PI. 16, figs. 1, 2). Cells of the nucellar beak are
large, with conspicuous walls and empty lumina (PI. 15, fig. 1). In some sections the cells are rectangular,
and often exhibit thickened radial walls (PI. 15, fig. 1 ). There is no evidence of an organized pollen chamber
floor region.

The megagametophyte in all available specimens is represented only by a megaspore membrane and the
hollow it surrounds (PI. 15, fig. 2). The megaspore membrane is golden-brown and, when viewed with light
optics, is apparently homogeneous, not granular or pitted as are some (Pettit 1966; Zimmerman and Taylor
1970). Cellular megagametophyte tissue has not been observed.

Microgametophytes are preserved within the pollen chamber and micropyle of several ovules (PI. 14, fig.
7 at right; PI. 15, fig. 4; PI. 16, figs. 1-3). The grains are all of one type and assignable to Potonieisporites
Bhardwaj (1954). Apparently identical grains are abundant in the matrix within and immediately surrounding
the ovulate cones, and also within the pollen sacs of associated Lehachia pollen cones (Mapes 1981).
Potonieisporites is commonly reported from upper Palaeozoic strata world-wide (Wilson and Venkatachala
1964; Nygreen and Bourn 1967; Upshaw and Hedlund 1967; Gupta 1970; Neves and Belt 1971; Bharadwaj
1972; Balme 1980). It is also known in situ from compressed conifer pollen cones such as L. piniformis and
L. hypnoic/es, Ernestiodendron filiciforme, and Walchianthus crassus and W. cylindraceus (Florin 1938-1945;
Bharadwaj 1964).

Individual grains are monosaccate with a monolete suture proximally and usually two dark, crescent-shaped
areas distally (Bharadwaj 1954; PI. 16, fig. 4). The latter areas have been interpreted by previous authors as
compression folds (Bharadwaj 1956), which may delimit the germinal area on the distal surface (Potonie and
Lele 1961; Clarke 1965). Maximum saccus diameter observed was 118 jum, while the corpus diameter averages
50 fxm. The girdling saccus is formed by separation of the sexine from the nexine in the equatorial region,
and exhibits prominent internal reticulations (PI. 16, figs. 3, 4). The intrareticulum is generally finer than that
of most Florinites species. In section view the intrareticulum attaches the saccus to the corpus across the distal
pole (PI. 16, fig. 4). In our specimens the nexine is more dense optically at the point where the saccus separates
from the corpus at the margins of the distal surface (PI. 16, figs. 3, 4). This produces two dark, crescent-shaped
areas like those interpreted as folds by previous authors. It is also clear from our specimens that there is no
thin area distally, through which germination may have occurred (PI. 16, fig. 4). On the proximal surface the
corpus and saccus are more completely fused, and form a more optically dense exine (PI. 16, fig. 4). Previous
authors have interpreted the exine on the proximal surface of Potonieisporites as thicker than that of the
distal surface. Scanning electron microscopy reveals that the proximal surface of the corpus is ornamented
by irregular crowded rugae (PI. 16, figs. 5, 6). In areas where the outer surface of the exine has been removed
from the proximal surface of the grain (e.g. PI. 16, fig. 6 at rectangle), the inner exine layer ( = nexine) shows
an ornamentation of dense, irregular granula (PI. 16, fig. 5 at bottom). Therefore, in these specimens,
intrareticulations are absent from the proximal surface of the grains. In addition, the monolete suture is
clearly open in all specimens (PI. 16, figs. 4, 6). This, together with the absence of a thin area on the distal
surface, indicates that germination was proximal, and that these grains fall within the concept of prepollen
(Renault 1896; Schopf 1938; 1948; Rothwell and Mickle 1982).

EXPLANATION OF PLATE 14

Figs. 1-8. Lehachia lockardii sp. nov. Holotype, basipetal series of transverse sections illustrating ovule
attachment and orientation. All M26 B Top series, x 20. a, primary cone axis; b, bract; f, fertile scale; m,
micropyle; nb, nucellar beak; o, ovule. 1, section near levels of ovule attachment. Note broad base of ovule
at left (just below level of attachment) and bilobed segments of ovule at right (at arrows; just above level of
attachment to fertile scale). Primary cone axis and secondary shoot axis at lower left, with sterile scales and
subtending bract at top, No. 76. 2, lobes of right ovule joined. No. 75. 3, right ovule base attached at fertile
scale with cuticle continuous at arrow. Left ovule at level of seed cavity with nucellus and megaspore
membrane. No. 72. 4, right ovule flattened at level of nucellus and megaspore membrane. No. 67. 5, sterile
and fertile scales at tip of flattened secondary shoot. Left ovule with nucellar beak. No. 61. 6, left ovule
showing micropyle; right ovule with nucellar beak. No. 56. 7, micropyles of both ovules narrowing. Note
pollen grain in ovule at right. No. 53. 8, apexes of both ovules near base of fertile shoot. No. 48.

PLATE 14

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PALAEONTOLOGY, VOLUME 27

DISCUSSION

L. lockardii displays both the general morphology and the cuticular features that delimit the genus
as circumscribed by Florin, and presents the first anatomical evidence upon which to characterize
and interpret development and reproductive biology within the walchian conifers. The new species
also provides an opportunity to clarify the nature of several features that have been interpreted
as significant to the evolution of more modern conifers, and to explore the significance of variation
among specimens of the Palaeozoic Lebachiaceae. As is typical of previously described Lehachia
ovulate cones, L. lockardii consists of a primary axis that bears helically arranged bifid bracts with
axillary fertile shoots. The fertile shoots each have a short axis that bears numerous scale-like
leaves, one or two of which have terminal ovules. Fertile scales are consistently located adjacent
to the primary axis.

The different expression of features preserved by compression vs. permineralization precludes
detailed specific comparison and assignment to a previously described species. However, split
surfaces of slabs containing fertile L. lockardii reveal general morphologic features, and incomplete
branches are attached below some cones. Numerous isolated vegetative branches are also present
in the matrix and will undoubtedly yield additional information regarding branching patterns. As
described by Florin and others, the Lehachia compression species most comparable to L. lockardii
are L. parvifolia, L. americana, L. hypnoides, and L. piniformis. However, until information about
the internal features of these species has been obtained, serious questions regarding their specific
relationships to L. lockardii will remain. Features of L. lockardii that could not have readily been
determined from compression remains alone include the inverted orientation of the ovules and the
bilateral symmetry of the secondary shoots. Our permineralized, uncompressed cones clearly
demonstrate the bilateral symmetry of the secondary shoots. Each secondary shoot has a crescentic
stele and a smaller number of scales toward the primary cone axis. While these features are useful
for separation of L. lockardii from other species of the genus, some of the apparent differences
may also be due to our less complete understanding of compression specimens.

Prior to the discovery of L. lockardii, Moyliostrohus Miller and Brown (1973) was the only
Palaeozoic conifer cone known in anatomical detail. M. texanum is a silicified voltzialean cone apex
from the lower Permian of west Texas (Miller and Brown 1973). Each flattened fertile shoot bears
thirty to fifty sterile scales and one apically cleft erect ovule attached at the shoot base. Each fertile
shoot is subtended by a non-bifid bract. Cuticular features are not known, but the cone morphology
allows both for assignment to the Lebachiaceae and for generic separation from Lehachia and
Ernestiodendron. While Moyliostrohus, Ernestiodendron, and L. lockardii all have flattened fertile
shoots in the axils of helically arranged bracts, the bracts of Lehachia and Ernestiodendron bifurcate
at the tip. Mesozoic voltzialeans all display much more reduced and modified fertile shoots, and, like
Moyliostrohus, commonly have simple, non-bifid bracts (Miller 1977, 1982).

Florin was the first to perceive the basie homology among fructifications of cordaites, early
conifers, and modern conifers. Specifically, he recognized the equivalence of the fertile secondary

EXPLANATION OF PLATE 15

Figs. 1 7. Lehachia lockardii sp. nov., ovule histology, e, epidermis; mm, megaspore membrane; n, nucellus; nb,
micellar beak; pw, pollen chamber wall. 1, two ovules in transverse section. Nucellus of left ovule obliquely
sectioned through pollen chamber wall and micellar beak, M 148 B Top No. 23, x 92. 2, transverse section
through seed cavity. Arrow indicates position of undifferentiated sclerotesta. Note epidermal hairs at top and
prominent epidermal papillae at bottom, M 148 B Top No. 12, x 73. 3, two zoned ‘sarcotesta’, M 148 A Bot
No. 7, x81. 4, Potonieisporites grain in pollen chamber, M145 B Top No. 4, x71. 5, cuticle of micellar
epidermis, M148 B Top No. 13, x 105. 6, hairs on ovule integument, M148 B Top No. 19, x 170. 7,
integumentary tracheids near ovule base, M148 B Top No. 7, x 670.

PLATE 15

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86

PALAEONTOLOGY, VOLUME 27

shoots of Lehachia, Ernes tiodendron, and Cordaianthus to the ovuliferous scales found in cones
of more modern conifers (e.g. Pinus). In seeking to bring order to the heterogeneous morass of
compressed plant fossil fragments attributed to Walchia, he examined branching patterns of
vegetative shoots, cuticular features, and basic cone organization.

As characterized by Florin, L. piniformis and E. filiciforme are quite distinct. In particular he
draws attention to ovule orientation, fertile shoot morphology, and patterns of stomatal arrange-
ment. While as end members these taxa are distinct, examination of Florin’s illustrations clearly
demonstrates these features represent morphologic continua within the walchian complex. To some
extent. Florin recognized this and identified in his studies (1938-1945) several species of cones as
Walchiostrohus and Walchianthus, and several species of vegetative and fertile shoots as ‘ Walchia
{EniestiodendronlY or "Walchia (Lebachial)' . For example. Florin illustrates a continuum of
cuticular features in his photographs. Though not emphasized by Florin, many of the cuticles show
narrow bands of densely packed stomata with shared subsidiary cells in some areas, and broad
internally spacious bands with no shared subsidiary cells in other areas. In still other areas, the
bands are so wide that there appear to be single isolated rows of stomata. Examples of stomatal
pattern variation illustrated by Florin (1938-1945) for specific taxa are as follows: L. piniformis,
Taf. 1-2, abb. 16, 17; Taf. 5-6, abb. 1; Taf. 15-16, abb. 7, 26, 27; Taf. 21-22, abb. 1, 2; L. hypnoides,
Taf. 103-104, abb. 9; Taf. 107-108, abb. 16; L. parvifolia, Taf. 31-32, abb. 5; Taf. 37-38, abb. 13;
L. laxifolia, Taf. 53-54, abb. 12, 14, 15; Taf. 55-56, abb. 12, 19; L. intermedia, Taf. 77-78, abb.
6-8; L. angustifolia, Taf. 39-40, abb. 11-13; L. speciosa, Taf. 65-66, abb. 9; L. mucronata, Taf.
75-76, abb. 5, 6; E. filiciforme, Tai. 111-112, abb. 15, 16; Taf. 113-114, abb. 9; Taf. 121-122, abb.
18; Taf. 127-128, abb. 13; Walchianthus cylindraceus, Taf. 155-156, abb. 15; W. crassus, Taf.
157-158, abb. 2; and W. papillosus, Taf. 157-158, abb. 8, 10.

This variation is of particular interest as the arrangement of the stomata in either bands or rows
is the strongest point separating cuticles of Lebachia from those of Ernestiodendron. Comparison
with L. lockardii reveals a comparable range of variation among the cuticles of its ovulate cones
(PI. 12, figs. 1, 3, 6), with typical lebachiate parallel bands and also isolated rows of stomata. The
parallel bands of irregularly diposed stomata are commonly present on the adaxial surface of bracts
and large scales, while the more widely separated longitudinally oriented single rows and/or isolated
stomata usually occur on the very papillate abaxial or lower leaf surfaces.

Florin has described similar cuticles from vegetative leaves of L. parvifolia. On these, parallel
bands of stomata are present on the adaxial surfaces, and the abaxial leaf surfaces often display
‘more or less disaggregated bands of separate longitudinal rows of mostly lengthwise oriented
stomata’ (Florin 1940). L. lockardii and L. parvifolia each exhibit a considerable range of cuticular
features including those usually used to separate Lebachia from Ernestiodendron. While Florin
considered the single rows of stomata characterizing Ernestiodendron to be present on both sur-
faces of its leaves, their occurrence on the abaxial surfaces of L. parvifolia and L. lockardii calls

EXPLANATION OF PLATE 16

Figs. 1 -6. Lebachia lockardii sp. nov. and Potonieisporites. m, micropyle; nb, nucellar beak; pc, pollen chamber;
pw, pollen chamber wall. 1, oblique longitudinal section through apex of ovule showing pollen chamber,
micropyle, and patches of undifferentiated sclerotesta (at arrows). Light area in pollen chamber is crystalline
calcite surrounding grain shown in fig. 2 (polarized reflected light), M148 A Bot No. 7, x 89. 2, oblique
longitudinal section near section in fig. 1, note nucellar beak, Potonieisporite.s grain and patches of
undifferentiated sclerotesta (at arrows) (polarized reflected light), M 148 A Bot No. 9, x 89. 3, grain in pollen
chamber of fig. 2, arrow indicates monolete (Nomarski DIC), M 148 A Bot No. 9, x 440. 4, grain in section
view. Note attachment of sexine to nexine by internal reticulum on distal surface (at arrow). Also note dense
exine adjacent to open monolete on proximal surface, M26 B Top No. 55, x 680. 5, proximal ornamentation.
Tear reveals inner exine at bottom, M26 SEM-8, x 8000. 6, grain with collapsed saccus. Proximal view with
open monolete at top. Rectangle indicates area of fig. 5, M26 SEM-3, x 800.

PLATE 16

MAPES and ROTHWELL, Lehachia cones

PALAEONTOLOGY, VOLUME 27

to question the taxonomic importance of this feature. Other features that intergrade totally and
therefore cannot be considered taxonomically diagnostic are cuticular papillae and epidermal hairs.
The relative abundance of these probably more meaningfully reflects environmental stresses during
growth.

An additional cuticular feature of L. lockardii can also be seen in Florin’s illustrations and
drawings of various Lebachia species (1938-1945). Small epidermal cells with a raised central
circular area that is open or covered to some extent with cuticle, occur generally outside the stomatal
bands (PI. 12, figs. 2, 4, 5). Similar cells on many lebachian cuticles have been interpreted by Florin
as hair bases (for examples, see Florin 1938-1945: Taf. 1-2, abb. 12, 13, 19; Taf. 31-32, abb. 10,
11, 19, 20; Taf. 49-50, abb. 13, 15, 16; Text-abb. 20a). Cells of this type somewhat resemble the
podocarpalean ‘Florin rings’ described by Buchholz and Gray (1948) and Florin (1931, 1958) from
living and fossil Torreya, where the surface cuticle of the subsidiary cells is fused into an optically
distinct, diflerentially thickened, cuticular flange or ring that surrounds the stomatal opening.
Certain fossil and modern Araucaria species display epidermal features that even more strongly
resemble the distinct cuticular structures of L. lockardii and other Lebachia species. However, the
araucarian epidermal features represent sunken stomata covered with waxy plugs or cuticular flaps
(Stockey and Taylor 1978a, b), rather than single cells as in L. lockardii. Unlike those of Aruacaria
or Torreya, in no instance do the distinct circular rimmed areas on L. lockardii cuticles appear to
be associated with either abortive or regular stomata. While abortive stomata were described by
Florin for cuticles of Lebachia (1938-1945 text and illustrations such as Taf. 1-2, abb. 20; Taf.
3-4, abb. 7; Taf. 5-6, abb. 3; Taf. 17-18, abb. 13 for L. piniformis, and Taf. 39-40, abb. 18 for
L. angustifolia), especially in the middle zones between bands of regular stomata, none has been
observed on L. lockardii. On L. lockardii the circular rimmed areas apparently result from collapse
of a very large papilla or a very short broad, unicellular hair.

Ovulate cone morphology has been used as an important criterion for separating Lebachia from
Eriiestiodemirou. The morphological features of Lebachia cones are considered by Florin to be more
primitive than those of Ernestiodendron (Florin 1951 ). Though both are compound, Ernestiodemlron
cones are typically quite lax. Each fertile shoot axis is flattened with few to no sterile scales and three
to seven megasporophylls, each bearing a single terminal ovule. Ernestiodendron ovules have been
interpreted as either erect with the micropyle oriented outward, or inverted with the micropyle
oriented downward and in toward the base of the fertile shoot (Florin 1951, fig. 34). Prior to the
discovery of L. lockardii, all Lebachia ovules were interpreted as erect, with the micropyle oriented
outward and away from the primary cone axis. Interpretive drawings of two detached fertile shoots of
‘ Walchiostrobus {Ernestiodendron!)' sp. are figured by Florin ( 1 95 1 , fig. 34c, /). These are apparently
drawn from specimens illustrated in his monograph (1938-1944; Taf. 163-164, abb. 3-4, Taf.
153-154, abb. 20-22), representing partially coalified impressions from the lower Permian at
Thiiringer Forest in Germany. The fertile shoots seem to be somewhat intermediate morphologically
between those of Lebachia and Ernestiodendron as delimited by Florin, in that they each may have
numerous fertile and numerous sterile scales. One shoot apparently bears four inverted ovules; the
other bears four or five ovules that may be erect.

The ovulate cones of L. lockardii also display several morphological features which appear to
be intermediate between Lebachia and Ernestiodendron as separated by Florin. There are numerous
scales attached to the flattened fertile shoot axis, which often bears two megasporophylls ( = fertile
scales) with apparently functional terminal ovules. Some shoots also have one to three scales with
poorly preserved or possibly abortive ovules (PI. 13, figs. 2-4). In addition, attached ovules are
clearly inverted, with their micropyles oriented toward the junction of the flattened fertile shoot
and the primary cone axis, features generally considered restricted to Ernestiodendron. In general
appearance, however, L. lockardii cones are plainly lebachiate. They are relatively compact, have
numerous sterile scales per fertile shoot, and display broad stomatal bands on many leaves.

The erect ovule orientation ascribed to all previously known Lebachia species appears to be
based primarily on cones of L. piniformis and L. hypnoides. Florin considered many of the ovules
in these cones to be of Samaropsi.s-iyp&. He also recognized two ovule types on species of

MAPES AND ROTHWELL: PALAEOZOIC CONES FROM KANSAS

89

Cordaiauthus, Samaropsis for the stratigraphically older forms (Westphalian) and Cordaicarpus for
the more recent strobih (Stephanian). Compressed platyspermic ovules of both types are often
found in sediments that yield cordaites and Walchia. The biological affinities of these ovules,
however, are not always with only cordaites or conifers (Rothwell 1981). Samaropsis Goeppert
(1864-1865) designates broadly winged, compressed ovules with a cleft apex forming two horns.
Cordaicarpus or Cordaicarpon (Geinitz 1862) is employed for rounded, compressed ovules with a
narrowed border and often a cordate base. Incomplete samaropsid impressions without the broad
sarcotestal border are included in Cordaicarpus (Sev^ard 1919). Samaropsis-Mke ovules have been
observed on the cordaitean fructification Cordcuanthus piicairuae (Seward 1919), on the pterido-
sperm foliage Pecopteris pluckeneti (Schlotheim) Brongniart (Kidston 1886), and possibly on
Emplectopteris triangularis (Andrews 1961).

As emphasized above, the ovules of L. lockardii are terminal and inverted, while those of L.
piniformis, L. hypnoides, and other lebachias have all been interpreted as terminal and erect. It is
clear that Florin considered the attached Lehachia ovules to be comparable to isolated ovules such
as Samaropsis delafondi (Florin 1938-1945, Taf. 21-22, abb. 17; Taf. 161-162, abb. 20). In addition,
he describes ovules in cones of L. hypnoides as most comparable to impressions illustrated by
Goeppert (1864-1865) as '’Cardiocarpus orbicularis'. In describing these ovule impressions (Florin
1938-1945, Taf. 109-110, abb. 23-25), Florin draws attention to the fissured coaly crack in the
narrow flange beyond the seed cavity (toward the distal end of the cone), and mentions the lack
of preservation at the other end of the ovule (which he considers to be the chalazal end of the
ovule). Examination of the ovule-bearing fertile shoots macerated from cones of L. pinifornus
(Florin 1938-1945) also reveals the bilobed end of an ovule with a conspicuous groove and oval
scar below the cleft. Although Florin interpreted this groove as the micropyle, its appearance is
remarkably like the chalazal end of the isolated Samaropsis ovules that he also figured (Taf.
161-162, abb. 1-5, and especially abb. 20). Moreover, the distally directed, cordate chalaza of L.

TEXT-FIG. 2. Lehachia lockardii sp. nov. \a, reconstruction of cone segment showing general
features of axis, bract, and fertile shoot. Note orientation of ovule, which has been sectioned
longitudinally in the major plane to reveal nucellus and megaspore membrane. Vascular
tissue of axis and sectioned surface of integument represented in black. 1 b and 1 c, ovule bases
showing range of variation in structure and attachment to fertile scales. Scale bar = 1 mm.

90

PALAEONTOLOGY, VOLUME 27

of his compressed Lehachia ovules. Similarities shared by the chalaza of Florin’s Samaropsis and
L. lockardii ovules, and what Florin interpreted as the apex of L. hypnoides ovules, inelude eordate
shape, oval sear below the groove (attaehment scar of Samaropsis sp. and S. delafondi, and L.
lockardii), and gentle taper toward the other end of the ovule (cf. text-fig. 2; Florin 1938-1945,
Taf. 161-162, abb. 20; Taf. 21-22, abb. 17; and Taf. 19-20). In all these features the ovules of
Lebachia figured by Florin (1938-1945, 1951) are eonsistent with the interpretation that they may
be recurved or inverted at the tips of their fertile scales.

Ovule ontogeny and reproductive biology

The attached ovules of L. lockardii display relatively narrow ranges of variation in size, integument
structure, nucellus and pollen ehamber histology, and gametophyte disposition that suggests they
were all preserved at about the same developmental stage. Nevertheless, eomparisons with similar
features of ovules of extant eonifers and other Palaeozoic gymnosperms provide an opportunity
to interpret several features of development and reproductive biology (Rothwell 1971, 1980, 1982rz).
In general, development of the integument, nucellus (ineluding pollen ehamber), and gametophytes
are eo-ordinated with pollination, abscission, and fertilization in a sequence that is eharacteristic
of the taxon under consideration (e.g. Chamaecyparis nootkatensis, Owens and Molder 1975; Picea
engelmannii, Singh and Owens 1981; Callistophyton, Rothwell 1980). In L. lockardii the ovules
show features of the integument that are like sareotesta and endotesta of other immature
gymnosperm ovules, but no lignified selerotestal eells are present in most of our speeimens. In only
two L. lockardii ovules have possible remnants of thick-walled selerotestal cells been identified;
these are confined to two groups of cells in the minor plane of symmetry at the level of the pollen
ehamber. These areas appear as lighter patches to either side of the pollen chamber in the speeimen
figured on Plate 16 (figs. 1, 2). Their disposition is eonsistent with that of mature fibres at the
onset of selerotestal differentiation in other gymnosperm ovules (Rothwell 1971, 1980), where cells
are lignified first in the minor plane at the level of the pollen chamber and differentiation generally
proceeds basipetally (Quisumbing 1925). This interpretation is also supported by the presenee of
extremely thin-walled and delicate cells between the endotestal epidermis and the sareotesta in
some specimens (e.g. PI. 15, fig. 2 at left). Cells of this type are identical to those that have been
interpreted as immature sclerotesta in several other Palaeozoie gymnosperm ovules (Stidd and
Cosentino 1976, fig. 14: Rothwell 1971, 1980).

Several features of the nucellus in L. lockardii also suggest that the ovules are immature. During
differentiation the nueellus of gymnosperm ovules charaeteristieally beeomes progressively thinner,
until in the mature ovules it is represented by only a thin, euticular membrane (Singh 1961; Rothwell
1971). The several cell layers of nucellus preserved in the midregion and at the base of the pollen
chamber in L. lockardii are charaeteristic of early ontogenetic stages of many gymnosperm ovules,
where the integument is not fully matured. The absenee of eellular megagametophytes in the L.
lockardii ovules further suggests their immaturity. Unless the L. lockardii megametophytes did not
exhibit the free nuelear stages that typically characterize all but the most mature of other eonifer
ovules (Singh 1978), or the eellular megagametophytes of L. lockardii were not preserved, this
feature is eonsistent with the general developmental interpretation of the other tissues.

The histological features of integument, nucellus, and megagametophyte, interpreted above as
indicators of ovule immaturity, are similar to those in Pennsylvanian gymnosperms with conifer-like
reproductive biology, and also to ovules of many extant gymnosperms shortly after the stage
appropriate for pollination (e.g. Rothwell 1971; Owens et al. 1981). The occurrenee of pollen grains
in the pollen chamber of several L. lockardii ovules (PI. 15, fig. 4; PI. 16, figs. 1-3) is also consistent
with this interpretation. Shortly after pollination in many gymnosperm ovules, eontinued develop-
ment of the integument leads to closure of the mieropyle (Dupler 1920; Quisumbing 1925; Singh
1961; Rothwell 1971, 1980). Unless this developmental feature did not oeeur in L. lockardii, the
open mieropyles of all available specimens (e.g. PI. 14, figs. 7-8; PI. 16, figs. 1-2) suggest that they
were preserved soon after pollination. If true, then ovule disposition in the specimens under
investigation also provides evidence for the mode of pollination.

MAPES AND ROTHWELL: PALAEOZOIC CONES FROM KANSAS

91

As stressed in the description of L. lockardii, the ovules are inverted with the micropyle located
between the primary axis and the base of the fertile shoot (PI. 13, fig. 1). Also, the minimum
diameter of the micropyle (approx. 100 /xm) is only slightly larger than the longest measurable
dimension of the prepollen grains actually present within the pollen chamber of several ovules
(viz., 95 /xm). This combination of features makes it unlikely that the grains found their way into
the pollen chambers by wind currents alone. While the occurrence of a pollination drop mechanism
has been conclusively documented in only one Palaeozoic gymnosperm (Rothwell 1977), the
prevalence of such a mechanism is extant conifers (Singh 1978), together with the features of ovule
orientation and prepollen/micropyle size ratio, provides at least indirect evidence that a similar
mode of pollination characterized L. lockardii.

The discovery of L. lockardii and associated permineralized remains provides the first extensive
anatomical evidence for the reproductive organs of the earliest conifers, and also allows for the
description of many morphological features not discernible from compressed specimens. Features
important to our understanding of early conifer structure are the bilateral symmetry of the
secondary fertile shoots and the inverted nature of the ovules. True bilateral symmetry also sets
L. lockardii ovules apart from the cardiocarpalean ovules of Upper Carboniferous cordaites and
pteridosperms (Rothwell 1982), and reveals an additional specialization among the reproductive
structures of pre-Permian gymnosperms. The L. lockardii specimens further allow for the first
correlation of epidermal features with internal anatomy of primitive conifers. The abundance of
cuticular material forms the basis for evaluating the range of variability that may be expected of
a single lebachian species. It is now clear that in both morphology and cuticular features walchian
species may be far more variable than previously suspected.

From the viewpoint of phylogeny and evolution of the earliest conifers, L. lockardii allows us
to test and support, with a new type of evidence. Florin’s hypothesis of the structural homologies
among ovulate cones of cordaiteans. Palaeozoic conifers, and modern conifers. Perhaps of greatest
interest to students of fossil plant biology are the insights gained into the growth, development,
and reproduction of the earliest conifers. It is now clear that L. lockardii had ovules that were
pollinated while immature and still attached to the parental sporophyte, perhaps via a pollination
drop mechanism. Likewise, the specimens support earlier interpretations of the mode of propagule
dissemination in primitive gymnosperms (e.g. Emberger 1944; Rothwell 1982«) by providing the
first histological evidence for early ovule abscission among Palaeozoic seed plants.

While L. lockardii and the associated walchian organs allow us to begin formulating the first
whole plant biology concept for a pre-Permian conifer, the new collection and preparation
techniques employed in the study are of perhaps even greater potential significance. Through these
methods we are now able to investigate a far greater range of features for plants that have previously
been known only from compressed or mold-cast remains. In this regard we may now expect to
begin characterizing in a biological sense the plant communities that inhabited the extrabasinal
lowlands (‘Upland Floras’ of many previous workers; Pfefferkorn 1980), and thereby dramatically
enhance our understanding of late Palaeozoic tropical vegetation.

Acknowledgements. We thank H.-P. Schultze, Division of Vertebrate Paleontology, Museum of Natural
History, University of Kansas; G. A. Leisman, Emporia State University, Ks.; A. Graffham and R. Cowan,
Geological Enterprises, Okla.; and especially R. H. Mapes, Department of Geology, Ohio University, for
field assistance and access to collections. M. J. Heaton, Erindale College, University of Toronto, Ontario,
Canada; W. D. Tidwell, Department of Botany, Brigham Young University Ut.; S. H. Mamay, U.S.G.S.,
U.S.N.M., Washington, D.C.; Wm. C. Darrah, Gettysburg, Pa.; and T. L. Phillips and R. Winston,
Department of Botany, University of Illinois, Urbana, 111., communicated ideas and information regarding
comparable fTn/c/n'a-bearing sediments. We thank W. Lockard and A. Lyke for special permission to collect.
We also appreciate comments and suggestions provided by reviewers. Acknowledgement is made to the donors
of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this
research (PRF No. 13329-G2 to G.M.). This work was also supported in parts by grants from the National
Science Foundation (DEB80-10793 and DEB81-09682 to G.W.R.) and the Ohio University Research
Committee (Grant 9644 to G.M.).

92

PALAEONTOLOGY, VOLUME 27

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G. MAPES and G. w. rothwell
Department of Botany
Ohio University
Athens
Ohio 45701
U.S.A.

Typescript received 29 June 1982
Revised typescript received 8 February 1983

THE DINANTIAN TAPHROGNATHUS
TRANSATLANTICUS CONODONT RANGE ZONE OF
GREAT BRITAIN AND ATLANTIC CANADA

by PETER H. VON BITTER and RONALD L. AUSTIN

Abstract. The Taphrognathus trcmsatlaiiticiis Range Zone is proposed to replace the earlier defined, and
subsequently rejected, Taphrognathus vurians-Cavusgnatlms-Apatogmitlnis Assemblage Zone. It is based on the
occurrence and range of the conodont species Taphrognathus transatlanticus sp. nov. in strata of Visean age on
both sides of the Atlantic Ocean.

The T. transatlanticus conodont Range Zone is present in the upper part of the S2 Zone of the Avon Gorge in
Great Britain and the lower B Subzone of the Windsor and Codroy groups of Atlantic Canada. The B Subzone
has previously been correlated with the S2 (Sub)zone using megafaunal and microfloral criteria; the strati-
graphically restricted occurrence of T. transatlanticus sp. nov. supports these correlations. The B Subzone has
previously been correlated with the middle late Visean using foraminifera and algal microflora but we suggest
that it is middle Visean in age. Our suggestion is supported by previous megafaunal correlations. The upper S2
Zone and the lower B Subzone have both been correlated with the Holkerian Stage of the British Dinantian. The
fauna of the T. transatlanticus conodont Range Zone has not yet been found at the boundary stratotype section
of the Holkerian at Barker Scar, Cumbria.

The Taphrognathus varians-Cavusgnathus-Apatognathus Assemblage Zone of Great Britain was
defined by Rhodes el al. (1969, p. 43) who based it on the stratigraphic range of the conodont
Taphrognathus varians Branson and Mehl in the upper part of the S2 Subzone of the Avon Gorge
(Samples S45 to S58), despite the fact that T. varians had (and has) not been found in the Avon Gorge.
The conodonts assigned to T. varians by Rhodes et al. (1969, pi. 13, figs. 4, 5) came from Harden
Burn, Roxburghshire, but the authors did note (p. 43) that ‘specimens transitional between
Cavusgnathus and Taphrognathus . . . have been found in this assemblage zone’. Von Bitter (1976, p.
231) reported the occurrence of Taphrognathus sp. in the Lower Windsor Group of Nova Scotia and
observed them to be practically identical to the transitional specimens illustrated by Rhodes et al.
(1969, pi. 13, figs. 1-3). The same species has been recovered from the Lower Windsor Group
correlative, the Lower Codroy Group of south-western Newfoundland (von Bitter and Plint-Geberl
1979, 1982). On the basis of the rather well-defined and consistent stratigraphic distribution of the
species over an extensive area, von Bitter and Plint-Geberl (1979, 1982) defined the Taphrognathus
Zone and correlated it with the lower B Subzone of the Windsor Group, as designated by Bell ( 1 929)
on macrofaunal evidence.

Re-examination of the Avon Gorge collections of Rhodes et al (1969), as well as examination of
additional specimens from that locality recovered in 1981 by Mr. Julian Pearce working under the
direction of the second author at the University of Southampton, verifies that Taphrognathus sp. of
von Bitter ( 1 976) and Taphrognathus n. sp. A of von Bitter and Plint-Geberl ( 1 979, 1 982), rather than
T. varians Branson and Mehl, is present and moderately common in the Avon Gorge section. We
name this new species Taphrognathus transatlanticus sp. nov.

Austin and Mitchell (1975, pi. 1, figs. 5, 6, 16, 18, 19, 30) reported T. varians from the upper division
of the Lower Carboniferous Shale of County Tyrone, Northern Ireland, but this is a lower
stratigraphic level than that from which T. transatlanticus sp. nov. has been recovered. We agree with
Higgins and Varker ( 1 982, p. 154) that the occurrences of Taphrognathus sp. and Taphrognathus n. sp.
A (both = T. transatlanticus sp. nov. of this study) of von Bitter (1976), von Bitter and Plint-Geberl

[Palaeontology, Vol. 27, Part 1, 1984, pp. 95-111, pis. I7-I9.|

96

PALAEONTOLOGY, VOLUME 27

(1979, 1982), and Plint-Geberl (1981), as well as the new occurrenees in Great Britain and Atlantic
Canada reported here, are all geologically younger than the Taphrognathus Zone of Ravenstonedale,
Great Britain. The older faunas probably fall within the range of T. varians as recorded in North
America by Sandberg (1979) and in England by Metcalfe (1981).

The absence of T. varians from the Avon Gorge strengthens our conviction that the specimens
from that locality, as well as the taphrognathids from Atlantic Canada, do not represent juvenile
individuals of a species of Cavusgnathus (as initially suggested by Rhodes and Austin 1970, p. 334,
and subsequently reinterpreted by Austin 1973«, p. 527). The appearance of these unusual
taphrognathids in a single narrow stratigraphic interval of lithologically diverse rocks which
represent a wide range of environments on both sides of the Atlantic, suggests that the Taphrognathus
Assemblage Zone of von Bitter and Plint-Geberl (1982) in Atlantic Canada and the T. varians-
Caviisgnathm-Apatognathus Assemblage Zone in the Avon Gorge are the same zone and are time
equivalent. This conclusion necessitates resurrection and redefinition of the zone originally
recognized by Rhodes et al. (1969) but later supressed by Austin (1973).

THE TAPHROGNATHUS T RAN S AT LA NT IC U S CONODONT RANGE ZONE

1969 Taphrognathus varians-Cavusgnathus-Apatognathus Assemblage Zone; Rhodes et al. p. 43.

1982 Taphrognathus Assemblage Zone; von Bitter and Plint-Geberl, p. 206.
non 1982 Taphrognathus Partial Range Zone; Higgins and Varker, p. 153.

Characteristic species. T. transatlanticus sp. nov.; in the Avon Gorge, Great Britain, associated with
Cavusgnathus windsorensis Globensky and other species listed in Tables 1 and 2; in Newfoundland,

TABLE 1. Distribution of conodonts at locality 1, the Taphrognathus transatlanticus Zone of the Avon Gorge,
Great Britain. Collections are those studied by Rhodes et al. (1969) and identifications other than those of the
first two taxa are by R.L.A. Figured specimens deposited at the British Museum (Natural History). Unfigured
specimens deposited at the Department of Geology, University of Southampton.

SAMPLE

CODE AND WEIGHT OF

SAMPLE

PROCESSED (IN KILOGRAMS)

S 45

S 49

S53

S 58.

8kg

7- 5 kg

7kg

3 kg

7-5kg

-

4XXX

6X

1

3

Taphrognathus transatlanticus sp, nov.. Sp element

16

15XX

-

1

-

Cavusgnathus windsorensis Globenskv, Sp element

4.XXXX

57

-

-

-

Cavusgnathus unicornis Youngguist &• Miller, Sp element

-

1

-

-

-

Cavusgnathus charactus Rexroad, Sp element

-

18

-

-|XX

-

Cavusgnathus sp . dextral Sp element

3

-

1

-

-

Spathognathodus campbelli Rexroad, Sp element

-

-

1

-

-

Spathognathodus scitulus (Hinde), Sp element

6

20

-

-

-

Hindeodus cristulus (Rexroad). So element

1

-

-

1

-

Hindeodus sp., So element

-

1

1

-

-

Apatognathus sp.

-

1

-

-

-

Unidentified plectospathodiform element

-

1

-

-

-

Unidentified ligonodiniform element

2

10

-

-

-

Unidentified Hi element

1

9

-

-

-

Unidentified Ne element

1

3

1

-

-

Unidentified Oz element

2

3

2

-

-

Unidentified Tr element

1

3

-

-

-

Genus &• species indeterminate

X OnG fragmentary specimen. One specimen doubtful. Three of the specimens were

figured by Rhode

s etal.

(1969, pU3, figs

. 1-3) and deposited in the British Museum (Natural

History).

xxxx

Two of

these

specimens appear to be transitional with Taphrognathus

transatlanticus sp nov

VON BITTER AND AUSTIN: CARBONIFEROUS CONODONT

97

Canada, associated with the species listed in Tables 3 and 4; in Atlantic Canada, C. windsorensis is
exceedingly rare in this zone.

Limits. The limits of this range zone coincide with the stratigraphic range of T. transatkinticiis sp.
nov., as known in the Avon Gorge of Great Britain and the Lower Codroy and Windsor groups of
Atlantic Canada. In Atlantic Canada the zones above and below are respectively the Cavusgmithus
and Diplogmithodus Zones of von Bitter and Plint-Geberl (1982). These zones have yet to be
recognized in Britain, although in both Britain and Canada examples of the genus Caviisgiuitlius
appear earlier than T. transatkmticus sp. nov.

Distribution. In Great Britain this range zone is present in the upper part of the S2 Subzone of the
Avon Gorge (Tables 1 and 2) and has been identified by the authors in a mid-Dinantian fauna
reported by Davies (1980) from an isolated sample collected near Trefil, South Wales (O.S. 1 : 50,000
Sheet 161, SN 120125).

In Atlantic Canada T. transatkmticus sp. nov. and conodonts indicative of this range zone have
been identified from the provinces of Nova Scotia, Newfoundland, and Quebec at the localities listed
and described in the Appendix. In Nova Scotia the range zone is known from the lower part of the B
Subzone of the Lower Windsor Group (von Bitter 1976; Dudar 1980; R. Dhindsa, in prep.). In south-
western Newfoundland it has been recognized in the Lower Codroy Group on Fischells and
Barachois brooks, as well as in several complex stratigraphic sequences south of Codroy (Tables 3
and 4; von Bitter and Plint-Geberl 1982). In Quebec it is present in two areas of Lower Windsor
Group strata on the Magdalen Islands (Plint-Geberl 1981).

Correlation. Rhodes et al. { 1 969, pp. 43, 44) concluded that specimens of the species here identified as
T. transatkmticus sp. nov. were identical to those illustrated and designated as Taphrognathus-
Cavusgnatkus transitions by Rexroad and Collinson (1963, pi. 1, figs. 21, 23-25) from the St. Louis
Limestone. We have not seen the latter material and we are uncertain as to whether the Rexroad and
Collinson specimens are T. transatlanticus sp. nov. We agree they are similar and note that the

TABLE 2. Distribution of conodonts at locality I, the Taphrognathus transatlanticus Zone of the Avon Gorge,
Great Britain, based on conodont collections made by Mr. Julian Pearce, University of Southampton.
Identifications of all taxa other than T. transatlanticus sp. nov. and Caviisgnathiis windsorensis by R.L.A. All
specimens deposited at the Department of Geology, University of Southampton.

Lj 1 [_i 1 L-i 1 Li t Li t Li 1 Li 1 f , 1

t— iincnmciIr-icD3>

- - -1 - -- - CavusQnathus charactus Rexfoatj^ Sp element

- - - 1 1 2 3 - CavusQnathus sp.^ Sp element

- - - - 1 - - - CavusQnathus unicornis Youngquist& Miller^ Sp element

12 - CavusQnathus windsorensis Globenskyj Sp element

- 1 ------ Unidentified Tr element

11 ------ Ozarkodina compressa Rexroad^ Oz element

11 ------ Unidentified Oz element

- - 1 ----- SpathoQnathodus sp., Sp element

-11 2 - - 1 - TaphroQnathus transatlanticus sp. nov.j Sp element
-3----- - ? AnQulodus sp.

2 3 - 2 - - - - Genus and species indeterminate

Luhooohoo-:--^ Weight of sample broken down(kq)

tSJ l\> vO LH vO -<! CTn 3 r 3

98

PALAEONTOLOGY, VOLUME 27

American species, like T. transatlanticus sp. nov., is limited to a very narrow stratigraphic interval,
falling in the upper Lower St. Louis Formation and the lower Upper St. Louis Formation (ibid., table
1). Although the zone defined by the occurrence of this species was not defined by Rexroad and
Collinson (1963), it would not be unreasonable to expect it to correlate with the T. transatlanticus
Range Zone. Rather than correlating the T. varians-Caviisgnathus-Apatognathus Zone tentatively
with the Lower St. Louis Formation, as was done by Rhodes et al. (1969), we would tentatively
correlate the redefined zone with the middle of the St. Louis Formation.

Higgins and Varker (1982) concluded that the association of Cavusgnathus spp. with Taphrog-
nathus sp. reported by von Bitter (1976) from Nova Scotia probably indicated a younger age for these
occurrences than for the Taphrognathus Zone of Ravenstonedale, Great Britain. The presence of
Cavusgnathus spp. in only younger strata and the mutual exclusivity of species of Cavusgnathus and
Taphrognathus at Ravenstonedale (Higgins and Varker 1982, text-figs. 6-8), the mutual occurrence
of species of Cavusgnathus with T. transatlanticus sp. nov. in the Avon Gorge and in Atlantic Canada
(Tables 1-4), and previous correlations made by Bell (1929) and Utting (1980) and discussed in the
section that follows, cause us to agree with Higgins’ and Varker’s conclusions.

Conil et al. (1976a, table 1 1; 19766, Enclosure 2) have indicated the presence of Taphrognathus in
Zone V2a of Belgium. The species illustrated has not been examined but may be T. transatlanticus
sp. nov.

Bell (1929, p. 71 ) used megafaunal criteria to correlate the B Subzone of the Lower Windsor Group
of eastern Canada with the S2 (Sub)zone of the Avon Gorge of Great Britain. Lewis ( 1 935) could not
correlate Lower Windsor Group strata with that of the Avon Gorge since he lacked corals from the
Lower Windsor Group. He did, however, correlate the Upper Windsor Group with the upper
Dihunophylluni (Sub)zone, the megafaunal zone overlying the S2 Zone in the Avon Gorge. Finally,

TABLE 3. Distribution of conodonts at localities 2, 3, and 4 (see Appendix), the Taphrognathus transatlanticus
Zone, area B of von Bitter and Plint-Geberl (1982), south-western Newfoundland, Canada. Identifications by
von Bitter and Plint-Geberl (1982). All specimens deposited at the Royal Ontario Museum, Toronto.

“n

~n -n

“n

“n

*n

“n

“n

“n

r~\

rr

rr

r~\

□□

00

i/>

(/) {/)

(/)

ITT

(/)

(/)

(Z»

cz>

0

—)

0

0

0

QJ

QJ

B

B

3

3

QJ

--

V

^

^

— ^

0^

Co

NO

<0

A

ro

cu

A

ho

-

- -

-

1

-

-

2

-

-

-

-

-

3

6

? Bispathodus spp.

16

6

-

Spalhoanathodus sp. nov.A

7

-

Soathoanathodus campbelli

1

1 -

-

1

3

1

Cavusqnathus reqularis type, Sp element

-

1

Cavusqnathus reqularis type, Oz element

1

1

Cavusqnathus reqularis type, Ne element

5

2 5

1

-

1

13

4

1

5

2

-

1

11

2

Taphroqnathus transatlanticus so nov.,

Sp element

1

- -

-

-

-

-

-

-

-

-

1

-

3

-

Taphroqnathus transatlanticus so. nov.,

Oz element

1

1

-

-

Taphroqnathus transatlanticus sp. nov.,

PI element

1

2

-

-

1

Taphroqnathus transatlanticus sp. nov..

Tr element

1

1

Unidentified Oz element

5

-

Unidentified Hi element

3

- -

-

-

2

-

1

-

-

-

-

-

-

-

Unidentified Tr elemenf

1

- 3

1

4

3

Unidentified Hi element

-

4

2

3

1

Genus and species unidentified

-

- -

-

-

-

-

-

-

-

p

-

P

-

P

Vertebrate remains

2

2 2

2

2

2

2

2

2

2

2

2

2

2

2

Weight of Sample processed (kg)

rvj

Weight of Sample broken down (kg)

lS

— ^

0

Ln

cK

NO

U1

CO

0

Ln

0

<0

UJ

VON BITTER AND AUSTIN: CARBONIFEROUS CONODONT

99

Utting (1980) correlated that part of his miospore zone I occurring in the B Subzone of the Lower
Windsor Group with the S2 macrofaunal zone of Great Britain. Our discovery of the stratigraphically
restricted species T. transatlanticus sp. nov. in the S2 Zone of the Avon Gorge and the lower B
Subzone of Atlantic Canada strengthens the correlation made by Bell (1929) and Utting (1980).

Bell (1929) believed the B Subzone of the Lower Windsor Group to be of middle Visean age, a point
of view apparently shared by Giles (1981), but not by Mamet (1970) who placed its foraminifera and
algal microflora in Foraminiferal Zone 15. Mamet (1970, fig. 4) correlated this zone with the
European ammonoid zone Cu Ilia of middle late Visean age. Jansa et al. (1978) added support by
stating that there is no evidence in Atlantic Canada for a middle Visean marine microfauna.

TABLE 4. Distribution of conodonts at localities 5 and 6 (see Appendix), the Taphrognathus transatlanticus
Zone, area A of von Bitter and Plint-Geberl (1982), south-western Newfoundland, Canada. Identifications
by von Bitter and Plint-Geberl (1982). All specimens deposited at the Royal Ontario Museum, Toronto.

r~)

r— 1

m r~i

m

m

0

CL

0

Q.

CL

CL

CL CL

CL

0

Cl.

-

hO

1

UJ

1

1 1

1

hO

0

ho

-

-

-

-

-

-

13

Cavusanathus windsoransiSi Sd element

3

Cavusqnathus windsorensis, Oz element

1

Cavusanathus windsorensis, Ne element

4

Cavusanathus windsorensis. Hi element

-

1

Cavusanathus windsorensis, PI element

3

-

? Bispathodus spp.

11

17 11

2

6 -

5

15

Soathoqnathodus sp. nov. A

10

-

-

-

26 -

-

5

Soathoanathodus campbelli

-

1

12

2

1 -

2

-

Cavusanathus reqularis type, Sp element

-

3

-

1

- -

-

-

Cavusanathus reaularis tvpGj Oz element

-

1

-

2

- -

-

-

Cavusanathus reaularis type, Ne element

50

1

15

2

18 3

10

1

Taphroanathus transatlanticus sp. nov., Sp element

2

-

-

-

- -

7

-

Taphroqnathus transatlanticus sp. nov., Oz element

-

-

3

-

- -

9

-

Taphroqnathus transatlanticus sp. nov., Hi

element

Taphroanathus transatlanticus sp. nov., PI

element

1

-

-

-

-

3

-

Taphroanathus transatlanticus sp. nov, Tr element

2

-

2

-

6 -

-

-

Unidentified Oz element

10

15

33

4

3 1

37 9

Unidentified Hi element

6

8

2

4

-

-

-

Unidentified PI element

3

4

4

2

- -

-

-

Unidentified Tr element

2

7

1

-

2 -

-

-

Unidentified Ne element

2

5

2

-

2 -

-

38

Genus and species indeterminate

-

P

-

P

- -

-

-

^ Conodont pearls

2

2

2

2

2 2

2

2

Weight of sample processed (Kg)

Weight of sample broken down (Kg)

Ln

UJ
CE- so

sO

00

100

PALAEONTOLOGY, VOLUME 27

We suggest that the T. transatlanticus Zone (and the lower B Subzone, by extension) of Atlantic
Canada is in fact middle Visean in age. We have already stated that the T. transatlanticus Zone is
present in the B Subzone of Atlantic Canada and in the S2 Zone of the Avon Gorge. The B Subzone
coincides approximately with Cycle 2 of the Windsor Group (Giles 1981) and this cycle in turn has
been ‘equated’ (ibid., p. 1 ) with part or all of the Holkerian Stage of Great Britain. The S2 Zone of the
Avon Gorge was correlated with the Holkerian Stage by George et al. (1976, p. 11, table 1) who
indicated (p. 73) that the base of Mamet’s zone 13 is reasonably correlated with the base of the
Holkerian. Mamet (1970, fig. 2) showed the base of foraminiferal zone 13 as middle middle Visean.

We believe that the zone defined by the occurrence of T. transatlanticus sp. nov. marks a relatively
brief interval of time that may be of considerable importance in correlation. The use of the Avon
Gorge as a standard section is considered by some to be problematic in view of eonsiderable non-
sequences (Ramsbottom 1973, p. 595). The characteristic fauna of the T. transatlanticus Zone has not
been reported from the recently defined stages of the British Dinantian. The zone by implication
should be present within the Holkerian Stage (George et al. 1976) but has not been reported from
above the base of the type Holkerian section nor from below the base of the type Asbian section
(Ramsbottom 1981).

T. transatlanticus sp. nov., although a species that preferred shallow-water conditions, was
apparently not as tolerant of variable salinities as was C. windsorensis Globensky. The former
consistently defines a narrow faunal zone and occurs in a variety of marine sediments ranging from
micritic braehiopod coquinas (Miller Limestone and Maxner Limestone at localities 9, 10, and 1 1,
near Windsor, Nova Scotia) to black fissile shales (Fisher Limestone, locality 12, Miller’s Creek,
Nova Scotia).

SYSTEMATIC PALAEONTOLOGY

Order conodontophorida Eichenberg, 1930
Superfamily polygnathacea Bassler, 1925
Family cavusgnathidae Austin and Rhodes in Clark et al., 1981
Genus taphrognathus Branson and Mehl, 1941

Type species. T. varians Branson and Mehl, 1941, by original designation.

Remarks. Taphrognathus was erected to include platform conodont elements possessing a ‘median
blade’ that ‘continued into the median trench as a short carina’ (Branson and Mehl 1 94 1 ). A number
of later authors encountered specimens transitional in characteristics between species of Taphrog-
nathus and those of the genus Cavusgnathus. Rexroad and Collinson (1963) and Rhodes et al. (1969)
called these taxonomic intermediates Taphrognathus-Cavusgnathus transitions and Rexroad and
Collinson (1963) interpreted them as evolutionary intermediates between the two genera. In recent
years, the name Taphrognathus has been applied to conodonts for which a subcentral rather than a
central blade can be demonstrated (Druce 1969, 1970), or to conodonts with a blade that is not only
subcentral in position but clearly joined to the outer parapet (Baxter 1972; von Bitter 1976; von Bitter
and Plint-Geberl 1982). Cavusgnathus, as redefined by Lane (1967, 1968), does not include species
bearing platform elements that are symmetrically paired.

Neither generic category as presently defined is sufficiently broad to comfortably and unequivocally
include the new species recognized and defined by us. T. varians, the type species of the genus, is
known to be ‘Highly variable in all aspects of its morphology’ (Nicoll and Rexroad 1975, p. 27), and a
small proportion of the specimens placed by these authors in T. varians were recognized to have the
blade in a non-median position. Until the amount of variation exhibited by T. varians and other
species of Taphrognathus is better documented, we hesitate to use another generic category for
platform eonodonts whose morphology is at varianee with the type specimens of the genotype.

The element terminology which is used in the following descriptions is a slightly modified form of
that proposed by Jeppsson (1971). The modification involves capitalization of the terms: Sp; Oz; Hi;
PI; and Tr elements. This is consistent with the terminology previously used by the senior author.

VON BITTER AND AUSTIN: CARBONIFEROUS CONODONT

101

Taphrognatlius transatlanticus sp. nov.
Plates 1 7 and 18

Sp element

1969 Taphrognathus-Cavusgnathus transitions; Rhodes et al., p. 242, pi. 13, figs. 1-3.

19736 Juvenile? transition; Austin, p. 108, fig. l.lu.

19736 Ontogenetic stages of CuvM5gnu/6(«; Austin, p. 108, figs. 1.2-1. 4 only.

1976 Taphrognathus sp. von Bitter, p. 231.

1982 Taphrognathus n. sp. A; von Bitter and Plint-Geberl, p. 197, pi. 3, figs. 1-5, 7.

Oz element

1982 Taphrognathus n. sp. A; von Bitter and Plint-Geberl, p. 197, pi. 7, figs. 3, 4, 8, 14.

Hi element

1982 Taphrognathus n. sp. A; von Bitter and Plint-Geberl, p. 197, pi. 7, figs. 19, 23.

PI element

1982 Taphrognathus n. sp. A; von Bitter and Plint-Geberl, p. 197, pi. 7, figs. 10, 11, 13.

Tr element

1982 Taphrognathus n. sp. A; von Bitter and Plint-Geberl, p. 197, pi. 3, figs. 6, 8.

Material. Holotype ROM 38474; paratypes ROM 38473, 38475; other figured specimens from Canada and
those referred to in Tables 3 and 4 are also deposited in the Department of Invertebrate Palaeontology, Royal
Ontario Museum, Toronto. Specimens from Great Britain referred to in Tables I and 2 are deposited in the
British Museum (Natural History ) (figured specimens) and the Geology Department, University of Southampton
(unfigured specimens). Localities listed in Appendix.

Origin of name. With reference to the occurrence of the species, and the zone it defines, on both sides of the
Atlantic Ocean.

Type horizon and locality. Fischells Limestone of Bell (1948). Sampled as Fish-1 -1 to Fish- 1-5 by von Bitter and
Plint-Geberl (1982) (see Appendix). Locality 2, Fischells Brook, south-western Newfoundland, Canada (see
Appendix). Section starting at and proceeding downstream from the base of the first major limestone (Fischells
Limestone of Bell 1948), north-west of railroad trestle (Canadian National Topographic Series 1:50,000, Flat
Bay Map Sheet 12B/7). The type locality corresponds to most, but not all, of locality 5 of von Bitter and Plint-
Geberl (1982) and stops at the top of the third carbonate unit above the top of the Fischells Limestone. The
uppermost part of the third carbonate unit was sampled as Fish-1- 10 by von Bitter and Plint-Geberl ( 1982).

Diagnosis. A conodont species having an apparatus containing five element types, all of which, with
the probable exception of the Tr element, were symmetrically paired. All the elements are small,
including the diagnostic Sp or platform element. The Sp element is taphrognathiform and has
unornamented sub-parallel parapets. The elements often show a strong but consistent tendency
toward either recrystallization of, or overgrowth by, calcium phosphate. This phenomenon is best
developed orally, suggesting some type of instability of white matter. Whether the overgrowth or
recrystallization took place during or after the life of the species is unknown. All elements appear to
have a greater tendency to recrystallization or overgrowths than those of other species, which makes
the phenomenon useful in apparatus reconstruction.

Description. Sp element (?\. 17, figs. 1-8, 10, 1I;PI. 18, figs. 1 -10). A generally small element that occurs as both
sinistral and dextral elements (PI. 1 7, figs. 1, 2), with features that can generally only be demonstrated adequately
by scanning electron microscopy. The blade is a continuation of the outer parapet and these two parts are
separated from one another by an outer parapet notch. The inner parapet is of equal height to the outer parapet;
the inner parapet is slightly shorter and terminates at the anterior trough opening (PI. 1 7, figs. 5, 6). The parapets
are unornamented although they may be covered with apatite crystals (PI. 17, fig. 11; PI- 18, figs. 1,3-5, 7 10).
The sub-parallel parapets are separated by a moderately deep trough which is closed posteriorly by the coming
together of the parapets. The posterior end of the platform is pointed and in lateral view exhibits a vertical drop-
off (PI. 17, fig. 4).

102

PALAEONTOLOGY, VOLUME 27

The free blade bears up to seven laterally compressed denticles. The maximum number is generally five but, as
with other platform conodonts, the blade denticle number is a function of size. The cusp is the largest and most
posterior of these denticles and may be either considerably or only slightly larger than the more anterior
denticles. The posterior edge of the cusp drops off vertically into the parapet notch mentioned previously.
Aborally there is a large slightly asymmetrical basal cavity (PI. 17, fig. 3). The basal cavity starts at the posterior
tip, reaches its maximum width below the cusp, and then begins to be constricted under the blade. Throughout its
length it bears a basal groove that reaches its maximum depth in a basal pit under the cusp. The lateral edges of
the basal cavity are defined by prominent flaring aprons. These are apparently equally prominent on both the
inner and outer sides of the element.

Oz elemen! (P\. 17, fig. 12; PI. 18, fig. 14). A laterally compressed, unarched element characterized by abbreviated
anterior and posterior bars, the latter being the weaker of the two. The anterior and posterior edges of the bars
overhang the more aboral portion of the conodont in a characteristic sinuous fashion (PI. 17, fig. 12). The short
anterior and posterior bars each bear up to three denticles, anterior and posterior to the cusp respectively. The
anterior and posterior bar denticles are of differing lengths, the middle of the three often being the longest. This
variability in length is the cause of the irregular oral outline of the two bars when seen in lateral view.

Aborally the element bears a moderately large basal cavity that narrows and becomes constricted under the
anterior bar. The basal pit under the cusp is the deepest part of the basal cavity and is directed anteriorly. The
element is slightly flexed laterally and occurs as both dextral and sinistral elements. It is very similar to the Oz
element of C. windsorensis Globensky (see von Bitter 1976; von Bitter and Plint-Geberl 1982). The latter species
and T. transatlanticus sp. nov. rarely occur together in Atlantic Canada and this, as well as the criteria outlined in
Table 5, serves to differentiate their Oz elements.

TABLE 5. Morphological characteristics of the Oz elements of Taphrognathus transatlanticus sp. nov. and

Cavusgnathus windsorensis Globensky.

Taphrognathus transatlanticus sp. nov.
Oz element

Cavusgnathus windsorensis Globensky
Oz element

Relatively short anterior and
posterior bars

Irregular denticulation with middle
of three bar denticles generally
the largest

Anterior bar strong; posterior
bar weak

Relatively long anterior and posterior bars

Regular denticulation with up to five
denticles gradually and regularly increasing
in size toward the cusp

Anterior and posterior bars almost equally
strong

EXPLANATION OF PLATE 17

Figs. G15. Taphrognathus transatlanticus sp. nov. Lower Codroy Group, Newfoundland (figs. 1-3, 5, 6, 9-15),
and Windsor Group, Nova Scotia (figs. 4, 7, 8), Canada; T. transatlanticus Zone, Visean, Lower
Carboniferous. 1, holotype, ROM 38474, oral view of sinistral Sp or platform element, sample Fish-1-1,
locality 2, x 235. 2, paratype, ROM 38475, oral view of dextral Sp or platform element, sample Fish- 1-1,
locality 2, x 220. 3, paratype, ROM 38473, aboral view of Sp or platform element, sample Fish- 1-8, locality
2, X 160. 4, ROM 38471, lateral view of Sp or platform element, sample Mi-1-1, locality 9, x 135. 5,6,ROM
38474 and 38475, detailed views of sinistral and dextral Sp or platform elements, x 1200 and x 1120
respectively. 7, ROM 38472, oral view of?sinistral Sp or platform element, sample Mi-1-1, locality 9, x 150.
8, ROM 38472, detailed oral view of ?sinistral Sp or platform element, x 390. 9, ROM 38488, inside lateral
view of dextral PI element, sample Corm-1-3, locality 3, x 125. 10, ROM 38485, lateral view of Sp or

platform element, sample Corm- 1 - 1 , locality 3, x 225. 1 1 , ROM 38485, oral view of Sp or platform element,
x450. 12, ROM 38477, lateral view of Oz element, sample Corm-1-3, locality 3, x 190. 13, ROM 38490,
posterior view of Tr element, sample Corm-1-3, locality 3, x 165. 14, ROM 38489, inside lateral view of
sinistral Hi element, sample Corm-1-2, locality 3, x 47. 15, ROM 41846, inside lateral view of sinistral Hi
element, sample Cod- 1-3, locality 4, x 50.

See Appendix for locality details.

PLATE 17

VON BITTER and AUSTIN, Taphrognathus

104

PALAEONTOLOGY, VOLUME 27

Hi element (P\. 17, figs. 14, 15; PI. 18, figs. 11, 12). A relatively unarched, laterally bowed element dominated by a
large cusp and a large anterior bar denticle. The anterior bar is variable in length depending on ontogenetic stage.
Small specimens have only a very short bar whereas larger elements have a longer bar. Longer anterior bars bear
three to four denticles while short anterior bars bear one or two denticles anterior to the cusp. The anteriormost
denticle is generally the largest. The anterior bar is deflected inward very slightly and may also be directed either
orally or aborally slightly. The posterior bar is generally three to four times the length of the anterior bar and
bears a series of relatively stout posteriorly inclined denticles. The denticulation of the posterior bar is not
noticeably Tiindeodellid’ (i.e. consisting of alternating large and small denticles). Rather, the denticles increase in
size posteriorly, culminating in the large inclined posteriormost denticle. Aborally a narrow aboral groove
(PI. 17, fig. 14; PI. 18, fig. 1 1) that presumably opens into a basal cavity or basal pit under the cusp may be seen in
some specimens. This groove may be completely closed and everted (PI. 17, fig. 15), particularly in mature
specimens, preserving only the smallest of basal pit openings.

The Hi element, like the Oz element of this species, can be differentiated from the homologous elements in the
apparatus of C. windsorensis only with difficulty. The almost mutually exclusive occurrence of the two species in
Atlantic Canada and the tabulated characteristics shown in Table 6 helps to distinguish them.

PI element (PI. 17, fig. 9; PI. 18, fig. 13). A rarely preserved, laterally compressed, only very slightly arched
element. It is recognized by its association with other elements of the apparatus; by its weakly to strongly inclined
cusp approximately one-third to nearly one-half of the distance (measured from the anterior end) between the
anterior and posterior ends; by its apparently hindeodellid denticulation; and by its characteristic posteriorly
inclined, relatively large (compared with the Hi element) basal cavity. The anterior bar is not noticeably curved

TABLE 6. Morphological characteristics of the Hi elements of Taphrognathus transatlanticus sp. nov. and

Cavusgnathus windsorensis Globensky.

Taphrognathus transatlanticus sp. nov.
Hi element

Cavusgnathus windsorensis Globensky
Hi element

Slight inward anterior bar deflection
Large anterior bar denticle

Hindeodellid denticulation poorly
developed

Greater inward anterior bar deflection
Lacking large anterior bar denticle
Well-developed hindeodellid denticulation

EXPLANATION OF PLATE 18

Figs. 1-16. Taphrognathus transatlanticus sp. nov. Avon Gorge, U.K. (figs. 1-8, 10) and Lower Codroy Group,
south-western Newfoundland, Canada (figs. 9, 11-16) in part showing well and consistently developed
recrystallization and/or overgrowth of calcium phosphate; T. transatlanticus Zone, Visean, Lower Car-
boniferous. 1, BM X 755, oral view of dextral Sp or platform element, sample S53, locality 1, x 125. 2, BM
X 756, oral view of ?dextral Sp or platform element, sample S58, locality 1, x 120. 3, BM X 755, detailed oral
view of dextral Sp or platform element, x 320. 4, 5, BM X 755, detailed views of outer parapet showing
hexagonal calcium phosphate crystals, x 1270 and x 3170 respectively. 6, BM X 756, detailed oral view of
?dextral Sp or platform element, x 300. 7, BM X 757, oral view of sinistral Sp or platform element, sample
S54, locality 1, x 75. 8, BM X 758, oral view of ?dextral Sp or platform element, sample S58, locality 1, x 95.
9, ROM 38485, detailed oral view of posterior portion of platform showing well-developed recrystallization
and/or overgrowth, x 1480. 10, BM X 758, detailed oral view of ?dextral Sp or platform element showing
recrystallization and/or overgrowth (note that blade shown in fig. 8 was broken off during preparation),
X 360. 11-16, detailed views of ramiform conodont elements showing calcium phosphate recrystallization
and/or overgrowth developed on or toward the oral surface. 1 1, ROM 38489, anterior end of sinistral Hi
element, sample Corm-1-2, x 340. 12, ROM 41846, posterior end of sinistral Hi element, sample Cod-1-3,
X 130. 13, ROM 38488, anterior end of dextral PI element, sample Cod-1-3, x 235. 14, ROM 38487, cusp of
Oz element, sample Corm-1-3, x 360. 15, ROM 38490, detail of posterior projection of Tr element, sample
Corm-1-3, x 320. 16, ROM 38490, detail of lateral bar denticles, x 615.

See Appendix for locality details.

PLATE 18

VON BITTER and AUSTIN, Taphrognathus

106

PALAEONTOLOGY, VOLUME 27

laterally whereas the posterior bar is curved inward to a slight but noticeable degree. The anterior bar denticles
are directed slightly toward the cusp. Those of the posterior bar are more inclined, become progressively larger
posteriorly, and the terminating denticles may be as large as or larger than the cusp. The last feature aids in
distinguishing the PI from the Hi element. Aborally, the PI element bears a narrow basal groove which opens into
the characteristic asymmetrical posteriorly inclined basal pit under the cusp.

This element has been recovered so infrequently (Table 3) that it is difficult to differentiate it from the PI
element of C. windsorensis. The element may prove to have been vicarious. However, the fact that such samples
as Corm-1-3 and Corm-1-4 (locality 3, south-western Newfoundland) are thought (von Bitter and Plint-Geberl
1982, p. 198) to have contained the component elements of only T. transatlanticus sp. nov., and that C.
windsorensis almost never occurs with T. transatlanticus sp. nov. in Atlantic Canada, helps this differentiation.
The PI element of C. windsorensis is better known and appears to be more delicate than that of T. transatlanticus
sp. nov., lacking the latter’s large cusp and noticeably large splayed posterior denticles (ibid., pi. 7, fig. 12).

Tr element (PI. 17, fig. 13; PI. 18, figs. 15, 16). A bilaterally symmetrical butterfly shaped element possessing a
short posterior keel or process. The lateral bars of mature specimens form an angle of approximately 120° with
one another. That of juvenile smaller specimens becomes increasingly obtuse, reaching approximately 170°. The
lateral bar denticles are recurved, discrete, and number three to four in mature elements. The denticle second
from the end is the largest. The lateral bars curve inward, forming a small depression at their junction on the
outer side of the conodont. The cusp is triangular in cross-section and is recurved and keeled on the inner side.
An undenticulated keel is present at the base of the cusp on the posterior side and in its lower portion forms the
upper limit of the sub-triangular basal cavity. The basal cavity varies in size with ontogeny, being larger in
mature specimens (PI. 17, fig. 13; PI. 18, fig. 15). The basal cavity narrows laterally and becomes a narrow basal
groove that disapears one-third to one-half the distance along the lateral bars.

The element is similar to the Tr elements of C. windsorensis Globensky and Hindeodus cristulus Miller and
Youngquist. It is therefore important to note which platform elements are present in any sample containing
symmetrical butterfly shaped Tr elements. The characteristics tabulated in Table 7 may be used to differentiate
the Tr elements of the three species.

Discussion. The distinctive Sp elements of T. transatlanticus sp. nov. occur as small sinistral and
dextral elements (PI. 17, figs. 1,2, 5, 6; PI. 18, figs. 1, 3, 7). Associated with these elements in the Avon
Gorge (Tables 1 and 2) are platform elements that might initially be thought ontogenetic growth
stages of T. transatlanticus sp. nov. The first ontogenetic series based on specimens from samples S45
and S49 contains cavusgnathiform elements herein identified as C. unicornis Youngquist and Miller,
Sp element; these elements are weakly ridged on the outer parapet at all stages of their ontogeny (PI.
19, figs. 11-18). The inner parapet, however, while still faintly noded in the largest specimen
available, is not noded in smaller growth stages. The second ontogenetic series (PI. 19, figs. 19-28)

EXPLANATION OF PLATE 19

Figs. 1-10. Cavusgnatlius windsorensis Globensky, Sp elements. Locality 1, Avon Gorge, U.K.; Taphrognatlius
transatlanticus Zone, Visean, Lower Carboniferous. 1-3, oral views, partial ontogenetic growth series
showing nodosity typical of this species, sample S49; 1, BM X 759, x 75; 2, BM X 760, x 72; 3, BM X 761,
X 70. 4-6, detailed oral views; 4, BM X 759, x 150; 5, BM X 760, x 145; 6, BM X 761, x 140. 7, 8, inside
lateral views, sample S49; 7, BM X 762, x 65; 8, BM X 763, x 68. 9, 10, detailed inside lateral views; 9, BM X
762, X 135; 10, BM X 763, x 130.

Figs. 11-28. Cavusgnatlius unicornis Youngquist and Miller, Sp elements. Locality 1, Avon Gorge, U.K.; T.
transatlanticus Zone, Visean, Lower Carboniferous. 11-14, detailed oral views of ontogenetic growth series
showing initial weak ridges and nodes increasing in strength with size; 1 1, BM X 764, sample S45, x 340; 12,
BM X 765, sample S49, x 233; 13, BM X 766, sample S45, x 150; 14, BM X 767, sample S49, x 105. 15-18,
overall oral views; 15, BMX 764, x 68; 16, BM X 765, x 60; 17, BM X 766, x 60; 18, BM X 767, x 53. 19-21,
27, 28, detailed oral views of ontogenetic growth series showing initial nodosity developing into stronger
ridges with increase in size, sample S49; 19, BMX 768, x 245; 20, BM X 769, x 135; 21, BM X 770, x 135; 27,
BM X 77 1 , X 1 05; 28, BM X 772, x 1 05. 22-26, overall oral views; 22, BM X 768, x 1 00; 23, BM X 769, x 68;
24, BM X 770, x 68; 25, BM X 771, x 53; 26, BM X 772, x 53.

PLATE 19

VON BITTER and AUSTIN, Cavusgnathus

108

PALAEONTOLOGY, VOLUME 27

TABLE 7. Morphological characteristics of the Tr elements of Taphrognathus transatlanticus sp. nov.,
Cavusgnathus windsorensis Globensky, and Hindeodus cristulus Miller and Youngquist.

Taphrognathus transatlanticus
sp. nov.

Tr element

Cavusgnathus windsorensis Globensky
Tr element

Hindeodus cristulus Miller and

Youngquist

Tr element

Unden tided posterior keel present

Posterior keel may bear denticles
and may grade into a posterior bar

Posterior keel or posterior
bar absent

Cusp triangular in cross-section

Cusp sub-triangular in cross-section

Cusp elliptical to oval in
cross-section

Element bilaterally symmetrical

Discrete non-hindeodellid
denticulation on anterior bars

Element bilaterally symmetrical

Hindeodellid denticulation on
anterior and posterior bars

Element slightly asymmetrical

from sample S49 are cavusgnathiform elements, again identified as C. unicornis Youngquist and
Miller, Sp element, whose traverse ridges, although decreasing in strength and length, are still present
as nodes in even the smallest specimen recovered (PI. 19, figs. 19, 22). The nodes in this smallest
specimen are much more prominent on the outer bladed parapet. Smaller specimens almost without
nodes, and thus intermediate with the largest Sp elements of T. transatlanticus sp. nov., have not been
found. Note that the largest specimen of the first growth series (PI. 19, figs. 14, 18) should be
compared with the two largest cavusgnathiform conodonts of the second growth series (PI. 19, figs.
25-28). As in the second growth series, the smallest specimens available (e.g. PI. 19, figs. 11, 15) do not
form convincing ontogenetic intermediates with the largest platform elements of T. transatlanticus
sp. nov. However, the possibility that the illustrated specimen (PI. 19, figs. 11, 15) is a sinistral
specimen may be an indication of ontogenetic continuity between T. transatlanticus sp. nov. and C.
unicornis {ld\. 19, figs. 11-18).

Cavusgnathiform conodonts identified as C. regularis type, Sp element, associated with T.
transatlanticus sp. nov. have been reported from the Lower Codroy Group of south-western
Newfoundland by von Bitter and Plint-Geberl (1982) (Tables 3 and 4). Similar associations have
been noted in numerous samples from the Lower Windsor Group at localities in Nova Scotia and
Quebec (see Appendix). Ontogenetic transitions between the T. transatlanticus sp. nov. Sp element
and that of the C. regularis type have not been found at any of these localities, further demonstrating
the taxonomic distinctiveness of T. transatlanticus sp. nov.

The other cavusgnathiform conodont species referred to earlier as being rare in the T.
transatlanticus Zone of Atlantic Canada, but moderately common in that zone in the Avon Gorge, is
C. windsorensis Globensky (PI. 19, figs. 1-10). We believe this to be the first record of this species from
Great Britain and to be distinct from Windsorgnathus windsorensis (Globensky) of Austin and
Mitchell (1975) and Mitchell and Reynolds (1981).

Acknowledgements. We acknowledge financial support from the Advanced Studies Fund of the University of
Southampton and are grateful to that University for making transatlantic studies possible. We thank Mrs.
Monica Cornforth and Mrs. Anthea Dunkley of the Department of Geology, University of Southampton, for
the typing of drafts of the manuscript and the drafting of tables, respectively. The senior author wishes to thank
the staff and students of the Department of Geology, University of Southampton, for their friendliness and
hospitality during his stay in Southampton in spring 1981.

We thank Miss Joan Burke, Royal Ontario Museum, Toronto, for typing and editing various drafts of this
paper; George Gomolka, University of Toronto, for his able operation of the scanning electron microscope; and
Brian Boyle and Allan McColl of the Exhibit Design Services Photography Section, Royal Ontario Museum, for
their helpfulness in photographic matters.

VON BITTER AND AUSTIN: CARBONIFEROUS CONODONT

109

APPENDIX. LIST OF LOCALITIES

A. Localities from which fauna o/Taphrognathus transatlanticus Zone has been recovered and listed in Tables 1-4.
Description of lithologies and sample sites have been deposited with the British Library, Boston Spa, Yorkshire,
U.K., as Supplementary Publication No. 14021 (14 pages). They may be purchased from the British Library,
Lending Division, Boston Spa, Wetherby, Yorkshire LS23 7BQ. Prepaid coupons for such purposes are held by
many technical and university libraries throughout the world.

1 . Avon Gorge, Bristol, U.K. Riverside exposure of the uppermost part of Seminida Zone and concretionary
bed on Leigh Wood side of River Avon at ST 562737 (O.S. Sheet ST 57, 1:25,000). Traverse 9 of Rhodes et al.
(1969, p. 22, hgs. 5, 65, 66); see also Kellaway ( 1971, fig. 4).

2. Fischells Brook, south-western Newfoundland, Canada (Flat Bay Map Sheet 12B/7, 1:50,000). Section
starting at base of first major limestone, the Fischells Limestone of Bell ( 1 948), north-west of railroad trestle and
proceeding north-west toward mouth of stream. In part locality 5 of von Bitter and Plint-Geberl ( 1982).

3. Ship Cove, south-western Newfoundland, Canada (St. Fintan’s Map Sheet 12B/2, 1:50,000). Section E of
Bell (1948, p. 21). Cormorant Limestone of Bell (1948, p. 22) sampled from apparent top downward; upper
contact not exposed.

4. Barachois Brook, south-western Newfoundland, Canada (St. Fintan’s Map Sheet 12B/2, 1:50,000).
Section is approximately 91 m south of Trans-Canada Highway bridge on west side of brook. Section J of Bell
( 1 948, p. 30); locality 8 of von Bitter and Plint-Geberl ( 1 982). Barachois Limestone of Bell ( 1 948) sampled from
the apparent base upward; contact with underlying beds not exposed.

5. Codroy, south-western Newfoundland, Canada (Codroy Map Sheet 1 10/14W, 1 :50,000). Section D of Bell
(1948, p. 18); Lower Codroy Section of Baird and Cote (1964, p. 517); locality 1 1 of von Bitter and Plint-Geberl
(1982). Thickness of strata over and underlying carbonate units taken from Baird and Cote (1964, p. 517).

6. Woody Cove, south-western Newfoundland, Canada (Codroy Map Sheet 1IO/I4W, 1:50,000). Section
immediately south of outlet of Woody Head Brook. In part section D of Bell ( 1948, p. 1 7) and the upper part of
section described by Baird and Cote (1964, p. 517). In part locality 2 of von Bitter and Plint-Geberl ( 1982); refer
to their fig. 2 for position of samples.

B. Other localities in Atlantic Canada from which fauna of Taphrognathus transatlanticus Zone has been
recovered. Deposition information same as in Appendix A.

7. Johnstown, Richmond County, Cape Breton Island, Nova Scotia, Canada (Grand Narrows Map Sheet
llF/15, 1:50,000). 7a, at beach on Bras d’Or Lake. 7b, a brook section on the south-east side of the road
approximately T2 km south-west of the cemetery and church at Johnstown.

8. Port Hood Island, Inverness County, Cape Breton Island, Nova Scotia, Canada (Port Hood Map Sheet
1 1 K/4, 1 : 50,000). Units Bq and B i of von Bitter (1976) sampled. Section studied by Stacy (1953), Schenk ( 1 969),
and von Bitter ( 1976).

9. Windsor, Hants County, Nova Scotia, Canada (Windsor Map Sheet 21 A/ 16 East Half, 1 : 50,000). Section
2 of Bell (1929, p. 47). Miller Limestone of Bell (1929, p. 47) sampled.

10. Avondale (Newport Landing), Hants County, Nova Scotia, Canada (Wolfville Map Sheet 21H/East
Half, 1 : 50,000). Shore section on Avon River discussed by Bell (1929, p. 47) and studied and mapped by Waring
(1967). 10a, the Miller Limestone, exposed a short distance north-east of the wharf at Avondale. 10b, the
Belmont Limestone of Moore (in Geldsetzer et cd. 1980), of which I m + is exposed at Avondale.

1 1 . Windsor, Hants County, Nova Scotia, Canada (Windsor Map Sheet 21 A/ 16 East Half, 1 : 50,000). Section
2 of Bell (1929, p. 47). Maxner Limestone of Bell (1929, p. 47) sampled.

12. Miller’s Creek, Hants County, Nova Scotia, Canada; gypsum quarry operated by Lundy Gypsum Co.
(Windsor Map Sheet 21 A/ 16 East Half, 1:50,000). Stop 8 of Geldsetzer et al. (1980). The Belmont and Fisher
limestones were sampled from their apparent bases upward in the south wall of the quarry.

13. lie Alright, Magdalen Islands, Quebec, Canada; east shore of island, north of Cap Alright and Anse
Firman (lie du Cap-aux-Meules Map Sheet 1 lN/5, 1:50,000). Locality D of Plint-Geberl (1981).

14. lie du Cap-aux-Meules, Magdalen Islands, Quebec, Canada; west part of island, 2 km east of Point
Herisee, 2 km south-east of Cap-au-Trou (ile du Cap-aux-Meules Map Sheet 1 lN/5, 1:50,000). Locality E of
Plint-Geberl (1981).

no

PALAEONTOLOGY, VOLUME 27

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CONIL, R., GROESSENS, E. and piRLET, H. 1976fl. Biostratigraphical range chart of the type Dinantian. In bless,
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19766. Nouvellecharte stratigraphique du Dinantien type de la Belgique. Annls Soc. geol. N. 116,

363-371.

DAVIES, R. B. 1980. Conodont-distributions in some British Dinantian shelf sediments: The Gayle Limestone
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DRUCE, E. c. 1969. Devonian and Carboniferous conodonts from the Bonaparte Gulf Basin, northern Australia
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1970. Lower Carboniferous conodonts from the Northern Yarrol Basin, Queensland. Ibid. 108, 91-113,

pis. 15-18.

DUDAR, c. 1980. Conodont biostratigraphy of the Windsor Group (Lower Carboniferous), Cape Breton Island,
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EiCHENBERG, w. 1930. Conodonten aus dem Culm des Harzes. Paldont. Z. 12, 177-182.

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1-87.

GILES, p. 1981. Major transgressive-regressive cycles in middle to late Visean rocks of Nova Scotia. Mem. Dep.
Mines Nova Scot. 1981-1982, 1-27.

HIGGINS, A. c. and VARKER, w. J. 1982. Lower Carboniferous conodont faunas from Ravenstonedale, Cumbria.
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1422-1436, pis. 1, 2.

JEPPSSON, L. 1971. Element arrangement in conodont apparatuses of Hindeodella type and in similar forms.
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LANE, H. R. 1967. Uppermost Mississippian and lower Pennsylvanian conodonts from the type Morrowan
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VON BITTER AND AUSTIN: CARBONIFEROUS CONODONT

III

LANE, H. R. 1968. Symmetry in conodont element-pairs. Ibid. 42, 1258-1263.

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pis. 5-7.

MAMET, B. L. 1970. Carbonate microfacies of the Windsor Group (Carboniferous), Nova Scotia and New
Brunswick. Geol. Siirv. Pap. Can. 70/21, 1-120, pis. 1-19.

METCALFE, I. 1981. Conodont zonation and correlation of the Dinantian and early Namurian strata of the
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699-702.

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PLiNT-GEBERL, H. A. 1981. Windsor Group (Lower Carboniferous) conodont biostratigraphy, taxonomy and
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SCHENK, p. e. 1969. Carbonate-sulfate-redbed facies and cyclic sedimentation of the Windsorian Stage (Middle
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STACY, M. c. 1953. Stratigraphy and paleontology of the Windsor Group (Upper Mississippian) in parts of Cape
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and plint-geberl, h. a. 1979. Conodont biostratigraphy of the Lower Codroy Group (Lower

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1982. Conodont biostratigraphy of the Codroy Group (Lower Carboniferous), southwestern

Newfoundland, Canada. Can. J. Earth Sci. 19, 193-221, pis. 1-7.

WARING, M. H. 1967. The geology of the Windsor Group reference section, Newport Landing (Avondale), Hants
County, Nova Scotia. M.Sc. thesis (unpubl.), Acadia University, 1 12 pp.

PETER H. VON BITTER

Royal Ontario Museum
and

University of Toronto
Toronto, Canada

Typescript received 6 July 1982
Revised typescript received 25 February 1983

RONALD L. AUSTIN
Department of Geology
The University, Southampton

!*

o

y

■ .

a*

■3'

=1 f?.

PATTERNS OF STROM ATOPOROID GROWTH IN
LEVEL-BOTTOM ENVIRONMENTS

by STEPHEN KERSHAW

A BSTR ACT. Stromatoporoids in argillaceous level-bottom limestones of the Upper Visby Beds in the Silurian of
Gotland, Sweden, show a variety of features of growth form, within a spectrum of coenosteal shapes from
laminar through low to high domical. Many coenostea show interdigitations of sediment in their margins,
attributable to intermittent sedimentation, while others show abrupt changes in growth direction, which are the
results of movement, often leading to overturning. Stromatoporoids frequently survived these agents and
continued to grow, often resulting in dilTerent morphotypes from those which would have been produced in the
absence of sedimentation and movement; serious problems of shape identification and shape classification exist
as a consequence. Variations in the effects of sedimentation and movement are recognizable in the specimens
studied and the stromatoporoids therefore record a variety of events occurring at the sea bed during their lives.
The four most abundant stromatoporoid species in the Upper Visby Beds show variations in morphology.
Densastroma pexisum Yavorsky is commonest and in general has a taller shape than Clathrodictyon simplex
Nestor, Pseiidolahechia hesshmdi Mori, and Slromatopora inipexa Nestor. The reasons for such variations are
unclear but may be related to a number of factors such as sedimentation, current activity, substrate consistency,
or availability of food and oxygen.

Stromatoporoids exist as a wide range of growth forms and the difficulties involved in dividing
this range into recognizable groups of shapes are reflected in the small amount of literature
containing useful information on stromatoporoid morphotypes (e.g. Broadhurst 1966; Abbott 1973;
Kapp 1974; Cornet 1975; Kobluk 1975; Kershaw and Riding 1978, 1980). The majority of
stromatoporoids have a common plan of accretionary growth by successive layers (laminae) leading
to the familiar range of laminar, domical, and bulbous forms which can be expressed as a geometrical
array (Kershaw and Riding 1978). Dendroid stromatoporoids form a distinct group and are not
considered here.

Laminar, domical, and bulbous forms are most easily recognizable when the stromatoporoids
grew on a flat substrate and were not subjected to sedimentation or dislocation so that their shapes
are preserved as being clearly laminar, domical, or bulbous. However, stromatoporoids are relatively
shallow-water benthic organisms and as such were exposed to dynamic factors of the environment,
such as sedimentation and turbulence. Problems arise in classifying the shape of a particular
individual which preserves the effects of these factors. A domical coenosteum which was overturned
but continued to grow from undamaged surfaces developed an overall shape which is no longer
domical, but was nevertheless created by a domical style of growth. This is also true for coenostea
which have suffered frequent sedimentation, leaving them with ragged margins and an exaggerated
vertical dimension. The problem is further compounded by inherent irregularity of many growth
forms, particularly in Devonian carbonate complexes (e.g. Fischbuch 1968; Noble 1970; Cornet
1975) where a number of different types of mamelons and irregular protrusions can complicate the
shape of a coenosteum. Various combinations of these factors can lead to an individual which is not
immediately recognizable as belonging to a particular group of shapes in the Kershaw and Riding
(1978) scheme. The problems involved in analysing the biological processes which determined the
shapes are thus greatly increased.

These problems are of course a reflection of the growth and development of coenostea but a further
consideration has a powerful influence on morphological groupings of stromatoporoids: the plane of
section. Stromatoporoids, especially reef-building forms, are usually seen in vertical section in cliff

IPalaeontology, Vol. 27, Part 1, 1984, pp. 1 13-130, pi. 20. |

114

PALAEONTOLOGY, VOLUME 27

faces and drill cores and the praetice of shape classification is mostly carried out on two-dimensional
sections. Thus we are trying to classify three-dimensional shapes from two-dimensional views. Serial
sectioning would allow the three-dimensional form of a stromatoporoid to be characterized but this is
not practicable in most situations and we are, therefore, simply stuek with the problem. Plane of
section is not a severe difficulty in stromatoporoid-bearing rocks where coenostea are preserved
upright and lack the effects of changing growth direction (see Kershaw and Riding 1980), but forms
which have been overturned and contain several episodes of growth in different directions present
serious problems of classification based on a single plane of section.

In a typical assemblage of stromatoporoids there is a mixture of growth forms: (a) those which
grew as regular laminar, domical, or bulbous forms and have not been disturbed during their lives; (b)
those whieh began growth in sueh a way but subsequently were affected by dynamic environmental
factors which produced effeets attributable to movement and sedimentation; and (c) forms with
inherent growth irregularities which may or may not include the effeets of b. An example of such an
assemblage is found in the Upper Visby Beds on Gotland, Sweden. This eontains very few forms of
category c. The assemblage usefully illustrates the problems outlined above and the means by which
some of them can be filtered out so that the factors controlling the basic morphologies may be more
clearly identified. The relationships between genotype and morphotype of the stromatoporoids ean
then be more easily examined. Cornet (1975) and Kershaw (1981) have already demonstrated that an

EXPLANATION OF PLATE 20

Stromatoporoids from the Upper Visby Beds showing effects of sedimentation and movement described in the

text. All figures are vertical sections. Some material is deposited in the British Museum (Natural History) (prefix

BM(NH): the remainder (prefix SGU) with the Swedish Geological Survey.

Fig. 1 . Smooth enveloping domical coenosteum of Denastroma pexisum. Note that {a) the specimen is composed
initially of two coenostea which merged as they grew, and (b) no sedimentation events are recorded in the
specimen. Korpklint 1, x 0-6. SGU Type 1439.

Fig. 2. Upper coenosteum: smooth non-enveloping low domical form of D. pexisum showing Trypanites
borings in the upper surface. Lower coenosteum (below line): low domical ragged form of Stromatopora
impexa showing small sedimentation events interrupting growth at regular intervals. A small heliolitid colony
(centre) grew on the upper surface before the D. pexisum covered it. Ireviken 3, x 1. BM(NH) H 5442.

Fig. 3. Domical coenosteum of D. pexisum (on coral debris) showing damage at the right-hand flank, the
damaged area being encrusted by a laminar coenosteum of Clathrodictyon simplex. The latter extends
underneath the D. pexisum suggesting that at one time the right edge was uppermost. Ireviken 3, x 1 -25. SGU
Type 1440.

Fig. 4. Part of a coenosteum of D. pexisum (lower) encrusted by a bryozoan (thin white layer), in turn encrusted
by a low domical smooth, non-enveloping form of C. simplex. Haftingsklint 1, x 1-25. SGU Type 1441.

Fig. 5. Domical coenosteum of D. pexisum showing how movement has generated a bulbous outline. The right-
hand coenosteum grew first and was then turned so that its left-hand edge was uppermost (with some damage
to the fragile marginal areas on the left) and continued growth to produce a new coenosteum on the left of the
photograph. Ireviken 3, xO-8. SGU Type 1442.

Fig. 6. Complex intergrowth of laminar and domical forms of C. simplex and alveolitid tabulates with
intermittent sedimentation. The complex developed on a stable base of a halysitid colony (below line).
Ireviken 3, x 1. SGU Type 1443.

Fig. 7. Complex specimen showing development of ragged coenostea followed by overturning and regrowth.
Specimen contains mostly D. pexisum but small coenostea of C. simplex and S. impexa are involved. Ireviken
3, xO-6. SGU Type 1444.

Fig. 8. Composite specimen of D. pexisum, C. simplex, and alveolitid tabulates to produce a structure with at
least nine growth phases. It is clear that the specimen was overturned many times. Ireviken 3, x 0-6. SGU Type
1445.

PLATE 20

KERSHAW, Silurian stromatoporoids

116

PALAEONTOLOGY, VOLUME 27

understanding of stromatoporoids as organisms needs a conjunctive shape-species study: the Upper
Visby Beds contain a small suite of species and the range of shapes of each is considered here.

Importantly, stromatoporoids from the Upper Visby Beds can be easily extracted from the friable
sediment; thus unlike rock sections where complete specimens are not normally obtainable, the three-
dimensional structure of the Upper Visby specimens can be studied. Because of the availability of
entire specimens, an adequate description of the history of growth or any coenosteum from these
beds can be obtained by examination of a single (usually vertical) section through it, together with
observations of its surface features.

KERSHAW: PATTERNS OF STROM ATOPOROID GROWTH

117

THE UPPER VISBY BEDS

The Upper Visby Beds of Hede (I960) are dated as earliest Wenlock (see Jaanusson et al. 1979) and
occur as a series of outcrops of maximum thickness 15 m, along the north-west coast of Gotland
approximately following the strike of the beds (text-fig. 1). Dips are very low but there are local low
amplitude folds due largely to the deformation of these incompetent beds by the weight of the
overlying Hogklint reefs (Eriksson and Laufeld 1978). Fossil contents are very variable and this is
reflected by the occurrence of the stromatoporoids. The Upper Visby Beds are composed largely of
alternating bands of mudstones and wackestones, much of the sediment being poorly consolidated.

TEXT-FIG. 2. Detailed map of I sq. m of vertical section of the Upper Visby Beds at Halls Huk 3 showing
positions and attitudes of stromatoporoids and corals. Note the low faunal density. Heavy stipple: incomplete

argillaceous limestone bands; light stipple: shale.

18

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 3a and b. Band of coarse debris (centre, arrowed) in fine-grained strata. Stromatoporoid (SI)
overgrew a halysitid (H); the composite was overturned and SI shows continued upward growth.
Stromatoporoid S2 is preserved upright, r is a rugosan. Halls Huk 3, x 0-5.

KERSHAW: PATTERNS OF STROM ATOPOROI D GROWTH

1 19

They form part of a shallowing-up sequence which begins with the underlying Lower Visby Beds
(mostly unfossiliferous muds with little calcareous content), passes through the Upper Visby Beds,
and ends with the Hdgklint and Tofta Beds (a complex mosaic of facies comprising reefs, inter-reef
muds, and crinoidal grainstones as the main components). The Upper Visby Beds show a gradual
upward increase in calcareous content and faunal diversity, but as a whole represent a relatively deep,
generally quiet environment with a low diversity fauna. Accordingly the beds lack evidence of cross-
bedding, scouring, or channelling by currents but indications of periodic disturbance (Jaanusson et
al. 1979), particularly towards the upper parts, are present as packstone bands of skeletal debris
which include not only shell material, but also stromatoporoid and coral coenostea (text-fig. 3)
showing some damage. In addition, there are numerous examples of isolated coenostea of corals and
stromatoporoids preserved out of growth attitude within the mudstones and wackestones them-
selves; these cannot be recognized as being restricted to particular horizons because coenostea are too
sparsely distributed and because the Upper Visby Beds have a somewhat nodular appearance where
time lines are not easily delimited (see text-fig. 2). The consolidated limestone bands are frequently
heavily bioturbated, burrows being readily recognizable but having indistinct walls. Burrows are up
to 5 mm in diameter. Sharp-edged excavations in the sediment are rare.

Small reefs in the Upper Visby Beds are dominated primarily by stromatoporoids and to a lesser
extent by tabulates. There are proportionately more tabulates than in the shallower water Hogklint
reefs. The stromatoporoids used in this study have been collected only from the level-bottom
sediments of these beds and the reefs have not been studied. Collecting localities in the Upper Visby
Beds are shown in text-fig. 1 .

STROMATOPOROID MORPHOTYPES AND SPECIES

Stromatoporoids from the Upper Visby Beds are somewhat variable in growth form, ranging from
laminar to domical although most are domical. The distinction between laminar and domical is
arbitrarily based on whether the ratio of vertical height/basal diameter (V/B) is respectively less or
greater than 01. Low, high, and extended domical forms are additionally recognized; the (arbitrary)
ranges of these are shown in text-fig. 4a.

A small number of laminar and domical forms are approximately circular in plan view and are flat-
based. These show no evidence of the effects of sedimentation or movement and appear to have
grown undisturbed on a plane substrate to produce smooth enveloping forms of Kershaw and Riding
(1978), symmetrical in median vertical section. Others are identical except that the basal surface is
concave (PI. 20), the concavity being due to growth on debris of skeletal organisms or hummocks of
sediment as discussed by Kershaw (1980). The majority of specimens, however, as seen in Plate 20,
contain some interdigitation of sediment at their margins (ragged margins). Usually this only slightly
affects the overall shape to produce a series of small frills at the lower edges of what can be regarded as
smooth forms since raggedness is hardly apparent on surface inspection. In many specimens,
however, the raggedness is a major feature of the shape (PI. 20). Stromatoporoids may also show
displacement while alive (having continued to grow after displacement). These tended to develop
rounded coenostea in which the distinction between upper and lower surfaces is difficult to make.
Their constituent growth forms can therefore be seen only when sectioned. Also, even in specimens
which are apparently single coenostea, sections show that many contain several stromatoporoid and
coral coenostea of different species overgrowing each other.

Measurements on vertical rock faces (Kershaw 1979) show that stromatoporoids are low in
abundance, ranging from none to twenty-eight (average nine) individuals per square metre
representing 0-5% of the rock volume (average 1%, one-tenth of the value for the overlying
shallower-water Hdgklint reefs). Very few stromatoporoids show signs of penecontemporaneous
damage, reinforcing the impression that environmental energy was generally low, but some
overturned specimens reflect intermittent disturbance. These stromatoporoids are small, basal
diameters ranging from 20 to 250 mm with vertical heights from 2 to 70 mm although they can be

120

PALAEONTOLOGY, VOLUME 27

considerably larger (Mori 1970). Attitudes of coenostea reflect their stable convex-up shape in that
80% of the forms measured are preserved upright.

Other macrofossils are also low in abundance, particularly tabulate and heliolitid corals (often
similar in gross morphology to stromatoporoids but can be more variable in growth form) which
collectively occupy no more than a further 1% of rock volume. Low stromatoporoid abundance is
also reflected in the low diversity stromatoporoid assemblage.

Nine stromatoporoid species have been reported from these beds (Mori 1969; Nestor 1979) but few
of them occur commonly and only five were found in the sample used for this study. Densastroma
pexisiim Yavorsky is the most abundant, while Pseiidolahechia hesslamUMoYX, Stroniatopora impexa
Nestor, Clathrodictyon simplex Nestor, and Clathrodictyon Ummrssoni Nicholson are much less
common. All specimens of C. linnarssoni are incomplete and were not used in this analysis.
Identifications are based on Mori’s (1969) taxonomic work.

A range from laminar to high domical growth forms was found for all four species and suggests
genotypic variability in all the stromatoporoids. D. pexisum formed 58% of the sample and so the
environment must have been more suitable for its growth than for the other species. There is a
temptation to suggest that D. pexisum is the dominant species, but since coenostea are generally
isolated on bedding planes and the overall fossil content of these rocks is low (text-fig. 2), the idea of
dominance for D. pexisum is inappropriate. Furthermore, there is no evidence of competition
between stromatoporoids for space on topographic highs such as those created by the presence of
dead stromatoporoids or other organisms.

Specimens were collected from all the localities in the Upper Visby outcrops shown in text-fig. 1,
but only four of these were collected intensively. All specimens from these localities have been plotted
on to the parameterization scheme of Kershaw and Riding (1978)— see text-fig. 5. The reader is
referred to that paper for details of the triangular array; briefly, laminar forms plot in the bottom left-
hand corner o(^ the triangle and are increasingly domical towards the centre and top. Ragged
specimens only are plotted in text-fig. 6. Text-fig. 4b illustrates the parameters used to plot data on to
text-figs. 5 and 6. An amendment of the scheme allows an estimation of the amount of raggedness
present in a specimen by measuring vertical raggedness (RV) and horizontal raggedness (RH) and
then expressing them as ratios of V and B respectively (i.e. RH/B and RV/V). See Kershaw and
Riding (1980) for details. Table 1a contains a summary of data on raggedness for the Upper Visby
stromatoporoids. Text-fig. 4c shows the range of shapes generated by the array. Plate 20 shows
examples of specimens containing several growth episodes; these could not be plotted as entire
specimens because basal, vertical, and diagonal dimensions would be meaningless. Therefore it was
necessary to treat each growth stage as an individual coenosteum with its own B, V, and D parameters
and plot each separately in text-figs. 5 and 6. For example, Plate 20, fig. 5 contains two coenostea;
Plate 20, fig. 7 contains three. In text-fig. 7 the distribution of basal diameters of all four species is
illustrated; this is taken as a measure of coenosteal size. Although volume would be a more accurate
estimate, it is not practicable to measure because two or more coenostea of the same or different
species may form an inseparable composite and because of the variability of amount of sediment
adhering to coenostea.

Chi-square analysis of the morphologies of the Upper Visby stromatoporoids reveals that D.
pexisum is taller (higher V/B) than C. simplex and P. hesslaudi at the 5% significance level and taller
than S. impexa at the 7% level; this is regarded as sufficient for a significant difference to be accepted.
S. impexa, P. hesslaudi, and C. simplex display flatter distributions of shape, which are not
significantly different from each other. The analysis involved only the non-ragged specimens, because
ragged coenostea are exaggerated with respect to the vertical height which would give a false
impression of the inherent shape of the coenosteum. Similar analysis of basal diameters demonstrates
that C. simplex coenostea have significantly smaller diameters than those of the other species at the
01% significance level. The latter three species do not show a significant difference in basal diameters
amongst themselves.

KERSHAW: PATTERNS OF STROM ATOPOROID GROWTH

121

used in this paper. V/B is the vertical/basal ratio, b, parameters measured for use in text-hgs. 5, 6, 7 and Table I a.
V = vertical height, B = basal diameter, D (average of D 1 and D2) = diagonal length at an angle {0) of 25° from
V. RV (average of RVl and RV2) = vertical raggedness. RH (sum of RHl and RH2) = horizontal raggedness,
c, parameterization display of Kershaw and Riding (1978) showing examples of shapes generated by the scheme,
the area occupied by stromatoporoids, and the approximate divisions of form. L, LD, HD, ED, and B are
respectively: laminar, low, high, extended domical, and bulbous.

PATTERNS OF GROWTH

Stromatoporoids from the Upper Visby Beds, whether or not they have been affected by
sedimentation or movement, do show a common style of growth in layers to produce laminar or
domical coenostea; sedimentation and movement have merely disrupted that. Thus those specimens
unaffected by these processes could be regarded as being the basic shapes of stromatoporoids from
these beds. The basic shape is thus not a single form but a range of shapes from laminar through to
high domical, each with smooth enveloping laminae (Kershaw and Riding 1978). Illustrations in
Plate 20 show that sedimentation and movement had variable effects on the basic shapes of the Upper
Visby stromatoporoids and although both processes may have operated on the same specimens, their
effects can be considered separately.

Sedimentation

Several morphological features attributed to sediment choking are seen in the Upper Visby
stromatoporoids. In smooth enveloping forms sedimentation has apparently not encroached upon
coenostea during growth. However, while a lack of sediment interdigitations indicates that little or no
sedimentation occurred up to the last-formed lamina (PI. 20, fig. 1), cessation of growth at that point
could be due to rapid sedimentation completely covering the growing surface. Such forms are
uneommon; more usually in other individuals of the same species sediment is deposited on the
marginal areas and although this is typically quite low in amount it can cover a large part of the
eoenosteal surface at any stage of growth (PI. 20 figs. 2, 3, 6). Sediment forms discrete lenses and

TEXT-FIG. 5. Composite diagram showing morphology for each stromatoporoid species
from the four main collecting localities, plotted on to the triangular display of Kershaw
and Riding (1978). H, K, I, and Ha are, respectively, Hdgklint 2, Kneippbyn 3, Ireviken 3,

and Haftingsklint 1.

TEXT-FIG. 6. Composite diagram showing triangular displays of morphotypes of ragged specimens only of each
stromatoporoid species from the four main collecting sites. Note that text-fig. 5 includes these and the smooth
forms. There are no ragged forms of Clathrodictyon simplex in the sample.

124

PALAEONTOLOGY, VOLUME 27

wedges which are indicative of intermittent deposition. The opposite view, that deposition was
constant and growth episodic, is less likely because of the highly variable nature of sediment
interdigitations in the stromatoporoids. Some have no such interdigitations (PI. 20, fig. 1): others
have a few large ones (see Kershaw and Riding 1978, fig. 2), while others have several small wedges in
their margins (PI. 20, fig. 2). Furthermore, any coenosteum may show a variety of thicknesses of
sediment interdigitations and growth rates are unlikely to have varied to this degree in this fairly
stable environment. However, stromatoporoid growth rates were almost certainly not constant since
sediment deposition would presumably have caused a temporary reduction in growth rate.
Stromatoporoid growth rate is poorly researched; the only really useful indicators are latilaminae —
broad bands in coenostea thought by some to be akin to seasonal growth banding. However, great
uncertainty surrounds the significance of latilaminae (Mori 1970) and they are not clearly defined in
the Upper Visby stromatoporoids, except in P. hesslandi.

Movement

As with sedimentation events, a spectrum of movement effects is preserved in these specimens.
Coenostea which have been moved would be expected to show damage at their edges, as in Plate 20,
figs. 3 and 5. Domical coenostea, especially high domical forms, which have been overturned, have a
high chance of being righted again quickly (Brenchley and Newall 1970; Abbott 1974) and in these
cases it would not be possible to determine whether they had been overturned at all. Overturning is
most clearly seen either where specimens are preserved in a non-upright position or where the
direction of growth has changed. Note that the stromatoporoids are assumed to have grown
upwards, approximately normal to the sediment surface in the Upper Visby Beds, which is the case in
the majority of stromatoporoid assemblages. Specimens such as that shown in Plate 20, fig. 5 have
been moved only once, others two or three times (PI. 20, fig. 7), while others have a complex history of
movement, often with sediment between the growth stages (PI. 20, fig. 8). This sediment may have
been deposited between growth stages, or, because it is rich in non-carbonate mud, adhered to
stromatoporoid surfaces which touched the sea bed during movement. Stromatoporoid composites
are common. Of 149 specimens, eighty-eight are single coenostea while fifty-one contain stroma-
toporoids which grew on, or were overgrown by, a number of organisms.

While some coenostea grew on (presumably dead) rugosans, gastropods, and orthocone
nautiloids, others grew on heliolitids and tabulate corals, and the corals are also found overgrowing
stromatoporoids. Table 1b shows the relationship between each species and its substrate and
demonstrates that P. hesslandi, S. impexa, and D. pexisum are more common on mud, while C.
simplex is more frequently found encrusting other organisms. A chi-square analysis shows that C.
simplex is significantly more common on skeletal debris at the 1% level then the other three species.
The latter show no difference amongst themselves. P. hesslandi and S. impexa show a similar
distribution and together with D. pexisum had a greater tendency to grow on the muddy substrate.

Many of the stromatoporoid composites are monospecific and developed on continued growth
from undamaged surfaces of overturned specimens. Others, with or without corals, appear to have
built up as a consequence of the dead skeleton of one providing a stable surface for the next, slightly
higher than the surrounding sea bed, from which sediment could be shed. As explained by Kershaw
( 1 980), previous skeletons were almost certainly dead before overgrowth by later coenostea. Damage
of coenostea in composites which have been overturned is minimal and consists of delicate marginal
edges of coenostea having snapped off leaving sharply broken edges, frequently overgrown in later
growth phases (PI. 20, figs. 3, 5).

Internal lanunation patterns

In addition to the variations of gross morphology and basal diameter, there are, in all species
collected, differences in the arrangements of laminae within coenostea, which have a bearing on this
discussion. Both laminar and domical forms can have enveloping laminae, giving the coenostea
generally smooth outlines (text-fig. 8a, c; PI. 20, fig. 1); most laminar forms are of this type. All but a
few domical forms of all four species, while retaining a smooth outline, exhibit non-enveloping

KERSHAW: PATTERNS OF STROM ATOPOROID GROWTH

125

laminae in the upper parts. Thus the lower parts started growth as laminar forms and became domical
later on due to concentration oflaminae in the central portion (text-fig. 8b; PI. 1, figs. 2, 4, 5). Thus the
overall pattern of development oflaminae led to the same sort of smooth outline as individuals with
fully enveloping laminae.

DISCUSSION

Sedimentation and movement effects preserved in the Upper Visby stromatoporoids may have been
caused by a variety of processes and are considered in turn.

Sedimentation

Sediment settling from suspension may have produced the interdigitations seen in the stromato-
poroids indicating intermittent sediment input. The Upper Visby Beds consist of alternating bands of
mudstones and somewhat nodular limestones (text-figs. 2, 3) which may reflect regular, intermittent
sedimentation events. Alternatively, sediment in stromatoporoid margins could have been deposited
by transient currents. As mentioned earlier, there is no evidence of strong currents flowing across
these beds but the presence of occasional debris bands suggest intermittent energy pulses, such as
storm waves, stirring up the bottom currents, and redistributing sediment and benthic skeletal
material. Such an interpretation is consistent with the view that the Upper Visby Beds represent a
relatively deep water facies which would be only slightly affected by storm waves. Sediment in some
interdigitations of the stromatoporoids contain coarse shell debris; others have fine-grained material
only. Sediment may therefore have collected around stromatoporoid margins by both processes and
in each case sediment settling on the higher parts of coenostea could have been easily shed on to the
flanks. Thus laminar forms were more susceptible to choking by sedimentation than domical shapes,
while the margins of all morphotypes in the Upper Visby Beds were prone to being smothered
because of their subhorizontal aspect. That these delicate flanking areas of stromatoporoids grew in
the first place indicates a low, if not zero, sedimentation rate most of the time. This is corroborated by
three other lines of evidence: {a) the presence of (often abundant) encrusters on the undersides of
upright stromatoporoids which appear to have grown in small cavities beneath coenostea; {h) the
abundance of Trypanites domichnial borings in stromatoporoid upper surfaces (Kershaw 1980); and
(c) considerable bioturbation of the sediment.

Movement

The agents causing overturning are unclear. Very small coenostea (e.g. where B = 2 or 3 cm) were
conceivably overturned during bioturbation activity but since the bioturbation structures are rather
small, larger coenostea would have needed more force to displace them. Orthocone nautiloids are
present in the Upper Visby sediments and while alive may have predated on and dislodged
stromatoporoids and corals from growth position, although there is a lack of the type of damage to
coenosteal surfaces consistent with bite marks. The broken marginal edges of many larger coenostea
suggest sudden movement of stromatoporoids consistent with displacement by storm activity as
described above. Eddy currents produced by storm turbulence would have moved and overturned all
coenostea below a certain size although the precise factors controlling movement of objects are
complex and relate very much to local conditions as has been shown by models in flume experiments
(Brenchley and Newall 1970; Abbott 1974; Kershaw 1979). These workers have shown that a
combination of the following is involved: substrate composition and surface morphology, current
velocity, and object size and shape. The responses of model stromatoporoids to a water current in a
flume show that approximately equidimensional domical forms (where V == B) are the most stable of
all, whereas laminar shapes tend to be flipped over by currents and tall domical forms which have
a high centre of gravity are quite susceptible to overturning. Also, larger models are heavier and
have higher competent velocities. These features would be expected to apply to the Upper Visby
stromatoporoids. There is no evidence of attachment in the specimens studied and the assumption is
that they grew on the unconsolidated sediment. Reef stromatoporoids, however, can be cemented to

126

PALAEONTOLOGY, VOLUME 27

TABLE 1 . A, species totals and raggedness information for stromatoporoids from the Upper Visby Beds. R/S
(ratio of numbers of ragged/smooth specimens), RV/V (ratio of vertical raggedness/vertical height), and RH/B
(ratio of horizontal raggedness/basal diameter) are indices of raggedness. See text and Kershaw and Riding
(1980) for explanation, b, relationship between the four stromatoporoid species and their substrates. The table
was constructed by recording the substrate on which each coenosteum was found, ‘other’ includes the four
species plus tabulate, heliolitid and rugose corals, gastropods, and orthocone nautiloids.

A

Species

Total

No. ragged

Mean R/S

Mean RH/B

Mean RV/V

S. impexa

23

10

0-43

0-63

0-51

P. hesslandi

21

4

019

0-59

0-36

D. pexisum

91

16

017

0-28

0-41

C. simplex

21

0

000

—

—

B

Substrate

Stromatoporoid species

S. impexa

P. hesskmdi

D. pexisum

C. simplex

Total

Sediment

19

17

62

1

105

Other

4

4

34

17

59

Total

23

21

96

24

164

their substrate and may be in such close proximity to their neighbours that movement could be
blocked in any case.

Competent velocity is also controlled by sediment type. On sand, low current velocities scour
sediment from around objects and they can become buried as a result; at higher velocities a sandy
substrate can facilitate coenosteal movement by creating a moving carpet of sand, reducing friction
between stromatoporoid bases and the sediment. The Upper Visby Beds, however, are composed
largely of mudstones and wackestones which provided a more coherent substrate than sand.
Nevertheless, because bioturbation structures are not sharply defined, the sediment would not have
been firm when bioturbated and probably, 'therefore, when colonized by stromatoporoids. Burial of
objects by scouring of mud requires higher velocities than on sand because of the relatively lower
mobility of muddy sediments. As a result, competent velocities are less on mud and once movement
has started it is more easily perpetuated since the sediment is less yielding on impact. However,
movement also depends upon substrate morphology. At water velocities just exceeding the
competent velocity of a particular object, movement consists of a sliding motion across the sediment
and may stop if an obstacle is encountered. At higher velocities an object may overturn when
obstacles are reached and at even higher velocities overturning may occur regardless of presence of
obstacles sinee the water is forced under the base of an object during its movement across the uneven
substrate. The competent velocity of an object is increased if it is partially buried in the sediment
because it has to be exhumed before movement can occur, and this necessarily involves some erosion
of the substrate. Current surges, as would be expected during storms, can, however, produce eddies
powerful enough to dislodge large objects which are unmovable by steady flow (Kershaw 1979).

The range of shapes and sizes of stromatoporoids in the Upper Visby Beds together with the
unevenness of substrate must have given rise to a large variety of circumstances in the manner
described above with respect to movement and overturning by turbulence. Also partial burial and
variations of substrate composition played a part in determining the competent velocity for a given
individual. Although it would be satisfying to have a series of values for competent velocities of the
Upper Visby stromatoporoids, all these factors combine such that estimates for these particular

KERSHAW: PATTERNS OF STROM ATOPOROID GROWTH

127

20-

10-

S.impexa n=23

coenostea are not very accurate; however, most coenostea would have been moved by velocities
in the range 30-60 cm/s, based on experimental work with model stromatoporoids (Kershaw
1979).

Genotypic control on growth forms

Recognition of the effects of sedimentation and movement and the consequent dismantling of
composite specimens show up the true variations of coenosteal shape in the Upper Visby Beds (text-
figs. 5, 6) and these in turn betray other processes at work. Each species shows a range of
morphologies from laminar to high domical and suggest that under certain conditions laminar forms
of a particular species developed, while under other conditions a domical shape was produced. A set
of ecophenes therefore exists but the underlying controlling factors are not readily discernible. The
shapes can be explained by a number of factors and these could include sediment-shedding capability,
responses to current activity, variations in food, and oxygen supply. Variations in substrate
consistency may also have affected shapes.

Stromatoporoids in the Upper Visby Beds do not show direct evidence of any of these possibilities
but consideration of the sort of responses they might have made is worthwhile since little information
is available on stromatoporoid palaeoecology.

A sediment-shedding capability is important for benthic organisms and developing a profile
suitable for rejecting sediment landing on the growing surfaces is clearly desirable. Domical forms of
all four species would have shed sediment from the apical areas, allowing growth to continue.
Sediment interdigitations in stromatoporoid margins may well contain sediment shed from
topographically higher parts of coenostea, and the stromatoporoids could clearly survive if the lower
parts were smothered. If a domical growth style is a response to sedimentation then this suggests that
sediment was continually settling on coenostea and would also suggest that laminar forms of any
species grew in times (or areas) of little or no sedimentation. Unfortunately, the evidence of a low

128

PALAEONTOLOGY, VOLUME 27

sedimentation rate discussed earlier is compelling and laminar and domical forms do occur near each
other on approximately the same horizons (text-fig. 2). The Upper Visby sea bed was probably
uneven (Kershaw 1980) and a difiFerent interpretation is possible; a laminar form growing on a
slightly raised area may have developed into a domical form had it settled as a larva in a lower area.

Diflferences in shape could have been a response to sedimentation, but could alternatively be due to
a response to current activity for respiration and feeding. Although there is no evidence of strong
current flow across the sediment surface, bottom currents must have been sufficiently aerated to allow
the benthos to develop and this suggests the presence of at least gentle currents. Laminar organisms
on a sediment surface in relatively deep environments live in water travelling slowly due to bed
friction; the oxygen and food supply rates to them are consequently less than even a few centimetres
higher up in the water column. The apices of domical organisms are not only higher in the water
column, but because they interrupt the water flow they create eddies around them and keep the water
well mixed in their vicinity. Since most stromatoporoids are domical in the Upper Visby Beds, they
would have caused such local disruptions of water flow across the surface. It may be significant that
tabulates and heliolitid corals also show a range of shapes from laminar to high domical which may
be a response to the same stimuli.

TEXT-FIG. 8. Schematic vertical sections of stromatoporoid morphotypes from the Upper Visby Beds showing
variations in the arrangements of laminae. See text for explanation.

Variation of substrate consistency is unlikely to have governed stromatoporoid morphology in
these beds. Laminar forms would have been stable on an unconsolidated muddy substrate since
coenosteal weight was low and evenly spread. Domical forms, with a higher mass per unit area of
base, would have been better suited to firmer substrates. However, laminar forms are found not just
on the substrate surface but also encrusted on skeletons of other organisms.

The four species do nevertheless show a different response to substrates. C. simplex is signifieantly
more abundant as an encruster on the skeletons of other organisms than on the muddy substrate
(Table 1b), suggesting a preference for harder and possibly topographically higher settling points. D.
pexisum, P. hesskmdi, and S. impexcp however, show a tendency to grow directly on the muddy
substrate.

The pattern of accretion of laminae on the upper (growing) surfaces of these stromatoporoids
described earlier may be indicative of shape-controlling factors. Significantly, laminae in upper parts
of nearly all domical forms typically do not envelop earlier laminae eompletely. This feature may
represent a mechanism by which growth was concentrated in the topographically higher central area
of a coenosteum to cause local turbulence by interfering with water flow across the sediment and
thereby feed more efficiently. By limiting growth to the central portion, metabolic energy would also
have been saved if sedimentation affected the stromatoporoids since sediment clearly collected on
and ehoked the topographically lower marginal areas. Whether this could be taken to imply that the
presence of laminar and domical forms of the same species in these beds is due to variations of
interplay between water flow and sediment deposition (from suspension) is open to conjecture, but
the possibility nevertheless exists.

That D. pexisum is the most abundant of the four species studied could be explained by its generally
taller profile than in the other three (text-figs. 5, 6). An upstanding shape is optimized for collecting
food and oxygen and for shedding sediment, but also notable is that D. pexisum is generally less

KERSHAW: PATTERNS OF STROM ATOPOROI D GROWTH

129

ragged than P. hesslandi and S. inipexa (Table I ) when horizontal raggedness is considered. The
average value of RH/B of D. pexisum is lowest indicating that less of the upper surface area was
covered by sediment in ragged forms. However, similarity of the RV/V values for the three species
which have ragged forms means that, on average, the sediment wedges in D. pexisum are thicker due
possibly to the steeper sides causing sediment to collect on a smaller marginal area than in flatter
stromatoporoids. D. pexisum also has the smallest number of ragged forms of the three. No ragged
forms of C. simplex were found in the sample. This species forms small coenostea (text-fig. 7). Its
profile ranges from laminar to high domical but generally has a low profile (text-fig. 5); it may have
been unable to thrive on the muddy sea floor. Its small size and lack of raggedness suggest a slow
growth rate and a possible inability to shed sediment effectively; it may have been killed very easily by
sedimentation.

The overall impression is that D. pexisum is the most abundant due to its height above substrate
although the precise reasons as to why this should be so are as yet unclear.

CONCLUSIONS

This analysis of level-bottom stromatoporoids from the Upper Visby Beds on Gotland suggests that
in a relatively poor, low diversity assemblage, different species developed alternative growth
strategies and a variety of responses to the environmental pressures. Composite specimens reflect
current activity across the surface of these sediments which resulted in overturning.

In a wider context, overturning and sedimentation are probably the two most important physical
factors affecting the generation of stromatoporoid shapes and their effects have also been observed by
the author in Ordovician and Silurian forms from Norway, Silurian forms from England and
elsewhere on Gotland, and Devonian forms from England and Belgium in a variety of reef and non-
reef environments. Most literature on stromatoporoid morphology also shows that these factors are
common (e.g. Noble 1970; Kapp 1974; Cornet 1975). This study has documented the variety of their
effects for a small assemblage and detailed examinations of these should be carried out elsewhere too.

An interesting parallel exists between the Upper Visby stromatoporoids and those from an almost
identical environment in the Hemse Marls (Ludlow) in south-west Gotland. The most abundant
species in the latter, Pycnodicfyou densum (Mori 1970), has a similar internal structure to D. pexisum
and is also usually low to high domical, also commonly with a smooth non-enveloping growth form.
This could reflect the occupation of a similar ecological niche by two species at different times.

Acknowledgements. This work began as part of a Ph.D. study at University College, Cardiff, and continued at the
West London Institue. Robert Riding (Cardiff) supervised early stages of the study. John Miller (Edinburgh)
critically read the manuscript. Catherine Worrall ( W.L.I.) gave advice on statistical analysis. Financial aid from
N.E.R.C., the West London Institute, and the Swedish Geological survey is gratefully acknowledged. The study
is a contribution to Project Ecostratigraphy.

REFERENCES

ABBOTT, B. M. 1973. Terminology of stromatoporoid shape. J. Paleont. 47, 805-806.

1974. Flume studies on the stability of model corals as an aid to quantitative palaeoecology. Palaeogeog.,

Palaeoclimat., Palaeoecot. 15, 1-27.

BRENCHLEY, p. J. and NEWALL, G. 1970. Flume experiments on the orientation and transport of models and shell
valves. Ibid. 7, 185-220.

BROADHURST, F. M. 1966. Growth forms of stromatoporoids in the Silurian of Norway. Norsk Geol. Tidsskr. 46,
401-404.

CORNET, p. 1975. Morphogenese, caracteres ecologiques et distribution des stromatoporoides Devoniens au
Bord du Sud du Bassin de Dinant (Belgique). Ph.D. thesis (unpubl.), Universite Catholique de Louvain,
Belgium.

ERIKSSON, c.-o. and laufeld, s. 1978. Philip structures in the submarine Silurian of northwest Gotland. Sver.
Geol. Unders. Ser. C (736), 30 pp.

130 PALAEONTOLOGY, VOLUME 27

FISCHBUCH, N. R. 1968. Stratigraphy, Devonian Swan Hills reef complexes of central Alberta. Bull. Can. Petrol.
Geo/. 16,446-587.

HEDE, J. E. 1960. The Silurian of Gotland. In regnell g. and hede, j. e. (eds.). The Lower Palaeozoic of Scania;
The Silurian of Gotland; Guide to excursion nos. All and Cl 7. Int. Geol. Congr. XXL Sess. Norden.
Stockholm, 44-89.

JAANUSSON, V., LAUFELD, s. and SKOGLUND, R. (eds.) 1979. Lower Wenlock faunal and floral dynamics,
Vattenfallet section, Gotland. Sver. Geol. Unders. Ser. C (726), 294 pp.

KAPP, u. s. 1974. Mode of growth of Middle Ordovician (Chazyan) stromatoporoids, Vermont. J. Paleont. 48,
1235-1240.

KERSHAW, s. 1979. Functional and environmental significance of skeletal morphology in stromatoporoids. Ph.D.
thesis (Unpubl.), University of Wales.

1980. Cavities and cryptic faunas beneath non-reef stromatoporoids. Letluda, 13, 327-338.

1981. Stromatoporoid growth form and taxonomy in a Silurian biostrome, Gotland. J. Paleont. 55,

1284-1295.

and RIDING, R. 1978. Parameterization of stromatoporoid shape. Lethaia, 11, 233-242.

1980. Stromatoporoid morphotypes of the Middle Devonian Torbay Reef Complex at Long Quarry

Point, Devon. Proc. Ussher Soc. 5, 13-23.

KOBLUK, D. 1975. Stromatoporoid palaeoecology of the southeast margin of the Miette Carbonate Complex,
Jasper Park, Alberta. Bull. Can. Petrol. Geol. 23, 224-277.

LAUFELD, s. 1974. Reference localities for palaeontology and geology in the Silurian of Gotland. Sver. Geol.
Unders. Ser. C (705), 172 pp.

MORI, K. 1969. Stromatoporoids from the Silurian of Gotland, I. Stockholm Contr. Geol. 19, 100 pp.

1970. Stromatoporoids from the Silurian of Gotland, II. Ibid. 22, 152 pp.

NESTOR, H. 1979. Stromatoporoids. In jaanusson, v., laufeld, s. and skoglund, r. (eds.). Lower Wenlock
faunal and floral dynamics, Vattenfallet section, Gotland. Sver. Geol. Unders. Ser. C (726), 294 pp.

NOBLE, J. p. A. 1970. Biofacies analysis. Cairn Formation of Miette reef complex (Upper Devonian), Jasper
National Park, Alberta. Bull. Can. Petrol. Geol. 18, 493-543.

STEPHEN KERSHAW
West London Institute
Borough Road
Isleworth
Middx TW7 5DU
U.K.

Original typescript received 19 September 1982
Revised typescript received 30 January 1983

A LATE UPPER TRIASSIC SPHENOSUCHID
CROCODILIAN FROM WALES

by P. J. CRUSH

Abstract. The fossil material of a 760 mm long crocodilian, Terrestrisuchus gracilis gen. et sp. nov., from a late
upper Triassic fissure filling in the Carboniferous limestone of the old Pant-y-flfynon quarry near Cowbridge,
Glamorgan, is described. The quadratojugal is parallel sided and the squamosal lacks a descending process. A
hard secondary palate is formed by the maxillae and premaxillae. A fenestra pseudorotundum is present but the
pterygoids were not sutured to the braincase. The Eustachian tubes were ramified. A prearticular is present. The
teeth are recurved, flattened, and bear serrations. The ischium projects posteriorly and the pubis, bearing an
obturator foramen, borders the open acetabulum. The postero-ventrally extended coracoid joins the ossified
sternum. The carpals and tarsals are crocodilian. The fifth metatarsal is reduced but bears two phalanges. The
dorsal vertebrae are primitive. A paired row of leaf-shaped dorsal scutes were present. The earliest crocodiles are
placed in three suborders— Protosuchia, Sphenosuchia, and Triassolestia. The genus Pedeticosaiinis is included
in the Protosuchia which were ancestral to the Mesosuchia. Dibotlirosuchus, Hesperosiichus, Heaiiprotosuclius,
Pseudohesperosuchus, and Sphenosuchus form part of the Sphenosuchia. Saltoposuchus and Terrestrisuchus
belong in a new family Saltoposuchidae. Triassolestes and Hallopus are included in their own suborders. The
Hallopoda, Sphenosuchia, and Triassolestia have no known descendants.

The matrix-bearing Terrestrisuchus, and five other species of reptile, was found by Professor K. A.
Kermack and Dr. P. L. Robinson in the spring of 1952 (Kermack 1956; Robinson 1957fl). The
material was discovered on a tip in the old Pant-y-ffynon quarry, near Cowbridge, Glamorgan.
The fossils came from a fissure, of unknown location, in the Carboniferous limestone of the quarry.
The finely preserved and abundant material of Terrestrisuchus consists primarily of a number of
blocks bearing associated and, sometimes, articulated bones but, in addition, there are a large
number of individual bones that have been entirely freed from the matrix. The referral of the
individual bones to Terrestrisuchus can be easily done on the basis of the articulated material. The
fossils were prepared out mechanically using a needle mounted in a pin chuck and sharpened with a
fine-grade oilstone. The bone was strengthened with dilute poly-butyl-methacrylate lacquer.

Age of the Welsh crocodile. Robinson (1957o, b) split the vertebrate-bearing fissures of the Bristol
Channel area into two groups. The first group yielded mammals or mammal-like reptiles and she
aged these as Rhaetic or lower Liassic. The second group, including Pant-y-ffynon, lacked these
animals and were believed to be Triassic and pre-Rhaetian. In making this distinction she assumes the
older fissures to have been covered by the marine transgression of the Rhaetic. Robinson aged the
older fissures on the basis of: a theoretical consideration of the mechanism of formation and filling of
the fissures, a detailed consideration of the structure of the fissure at Emborough quarry, and the lack
of mammals. Her general interpretations cannot be proven but the fauna of Emborough is shown to
have been pre-Rhaetic as Rhaetic deposits covered this quarry. Robinson (1971) aged the Pant-y-
ffynon fissure as upper Norian because she assumed it to have passed through the conglomerate that
lies above the Carboniferous limestone, which she regarded as Norian. The relationship of the fissure
that eontained Terrestrisuchus to the eonglomerate is unknown as, in the new quarry, fissures both
pass through and start below the conglomerate. Furthermore there is no evidence that the
conglomerate is of Norian age, it eould be Rhaetian or even lower Jurassic. There is no Rhaetic
covering at Pant-y-ffynon. Faunal correlations between Robinson’s Triassic fissures suggest that they
are eontemporaneous, if the reptiles are assumed to have been evolving rapidly, except for Highcroft

(Palaeontology, Vol. 27, Part 1, 1984, pp. 131-157. |

132

PALAEONTOLOGY, VOLUME 27

whose fauna is too poorly known. Furthermore, elements of the fauna of the Triassic fissures are
closely related to Trilophosaurus (Case 1928a, b; Gregory 1945), Icarosaurm (Robinson 1962; Colbert
1965), and Saltoposuchus. Trilophosaurus comes from the Dockum beds, Icarosaurus from the
Locatong facies of the Newark group, and Saltoposuchus from the Stubensandstein. Trilophosaurus
and Icarosaurus are usually considered upper Triassic and the Stubensandstein as upper Triassic but
pre-Rhaetic. Thus these correlations, and Robinson’s age determination of Emborough, imply that
Terrestrisuchus was upper Triassic and pre-Rhaetian in age.

SYSTEMATIC PALAEONTOLOGY

Class REPTILIA
Order crocodylia
Suborder sphenosuchia
Family saltoposuchidae fam. nov.

Terrestrisuchus gen. nov.

Type species. Terrestrisuchus gracilis, sp. nov.

Diagnosis. Small terrestrial crocodilian; skull bones unornamented; skull table rounded; supra-
temporal and antorbital fenestrae elongated; frontals excluded from supratemporal fenestrae;
squamosal large and convex laterally; frontals and parietals paired; postorbital bar superficial; otic
notch formed; quadrates bear conchae, slope anteriorly, and buttress under the squamosals;
quadratojugal parallel sided; nineteen maxillary teeth; maxillae and premaxillae form a secondary
palate; anterior palatal fenestrae present; interpterygoid vacuities present; basipterygoid articula-
tions movable; pterygoids not sutured to the braincase; pterygoid flanges formed; Eustachian tubes
ramified; fenestra pseudorotunda formed; external but no internal mandibular fenestra present;
prearticular present; no pronounced retroarticular process; articular fenestrated and possessing
a dorsally directed, medial, process; teeth thecodont, recurved, flattened, bearing anterior and
posterior cristae and serrations; vertebrae platycoelous; neural spines low; about twenty-four
presacrals; two sacrals; about seventy caudals; all presacrals bear free ribs; costal articulations fuse
only on the last presacral; dorsal ribs bear only anterior flanges; double row of dorsal, ornamented,
leaf-shaped scutes; pectoral girdle lacks clavicles; ossified sternum present; slender interclavicle
present; coracoids extended postero-ventrally; supracoracoid foramen present; scapula expanded
into points anteriorly and posteriorly; limb bones hollow; humerus with a well-developed
deltopectorial crest; ulna bears a slight olecranon; carpus crocodilian; only one distal carpal; ilium
with pre- and post-acetabular processes; supra-acetabular crest well developed; acetabulum
perforated; pubis entered acetabulum; obturator foramen present; ischium projected posteriorly;
pelvic symphysis present; femur with a fourth but no lesser trochanter; tarsus crocodilian; metatarsal
five reduced but bearing two phalanges; metatarsals one to four subequal in length.

Etymology. The generic name has been chosen in order to emphasize the terrestrial nature of the early crocodiles.

Terrestrisuchus gracilis, sp. nov.

Diagnosis. As for genus. The specific name refers to the light graceful build of this animal.

Holotype. Specimen P. 47/21 and its counterpart P. 47/22. These blocks bear the remains of a single, partially
articulated, virtually complete individual. Some bones have been prepared out of these blocks and are labelled P.
47/21a, b, c and P. 47/22a, i. Department of Zoology and Comparative Anatomy, University College, London.

Paratypes. Associated and individual bones. Department of Zoology and Comparative Anatomy, University
College London.

Locality and horizon. Fissure filling in the Carboniferous limestone of the old Pant-y-ffynon quarry, about three
miles east of Cowbridge, Glamorgan, Wales; late upper Triassic.

CRUSH: TRIASSIC CROCODILIAN FROM WALES

133

description: skull

The identifications of the skull bones were based on the semi-articulated specimen P. 78/ 1 a, the closely associated
skull elements on the holotype, and the associated bones on P. 79/1 and P. 147/1. The cranial bones of
Terrestrisuchus are abundant in the material but unfortunately there are no laterospheroids, prefrontals,
premaxillae, or vomers preserved and there is no certain basisphenoid. Of the other elements, there are, on
average, between four and five examples of each. There is no evidence for the presence of a dermo-supraoccipital.
The restorations are based on an analysis of how the bones articulated with each other. The semi-articulated
specimen (P. 78/1 a) was of little use in reconstructing the skull as it is incomplete and crushed. The illustrations
(text-figs. 1-6) show what is actually known of the bones, their reconstructed form, and their postulated
articulations. The basisphenoid was not reconstructed in lateral view (text-fig. 4d, e) and no attempt was made
to reconstruct the laterosphenoids. The remains of the quadratojugal have been omitted from text-fig. In, the
remains of the quadratojugal, parietal, and frontal from text-fig. 2n, and the parietal from text-fig. 4c.

Cranium. The cranium was wedge-shaped in dorsal and lateral views and approximately square in occipital view.
The skull table was convex across its longitudinal axis, and the large, flat squamosals sloped strongly ventro-
laterally. The postorbital bar was inclined posteriorly. The large, almost centrally positioned, orbit was oval in
dorsal view and almost circular in lateral view. The antorbital fenestra, formed by the maxilla and lacrimal, was
long and narrow as was the supratemporal fenestra. The infratemporal fenestra, bordered by the broad, parallel-
sided quadratojugal, was triangular in outline. The post-temporal fenestrae were large and had a complex shape.
The palatal vacuities were approximately oval and long interpterygoid vacuities remain. The basipterygoid
articulations were movable. The choanae were elongate oval-shaped openings and a short secondary palate was
formed by the premaxillae and maxillae. In life this was possibly extended by soft tissue, across the palatines, to
shift the function choanae posteriorly. The quadrate was inclined anateriorly and the otic notch was well
developed. The skull did not possess postfrontals or interpterygoids.

Frontal. Eight specimens of the frontals are preserved allowing their complete reconstruction. These bones are
paired unlike those of the modern crocodilians which fuse before the animal leaves the egg. The frontals were flat
and smooth dorsally with straight medial edges where they sutured together. Anteriorly the dorsal surfaces bear
recessed articulations where they were overlapped by the nasals and prefrontals. Posteriorly there were
overlapping articulations with the parietals and postero-laterally flanges extended into notches within the
postorbitals. There were no articulations between postorbitals and parietals. The ventral surface of each frontal
bears a well-developed crista cranil frontale. The anterior part of the orbital surface of the frontal, lateral to this
ridge, bore a groove for articulation with the prefrontal. A process was present at the anterior end of the orbital
surface which also articulated with the prefrontal.

Jugal. Three examples of this bone are preserved and those on P. 78/la and P. 79/la allow this element to be
completely reconstructed except for the distal part of the dorsal process. This element is triradiate and consists of
anterior, posterior, and dorsal processes. The lateral surface ofthe bone is smooth. The dorsal process of the jugal
is long, slender, slightly tapering, swept back at a small angle to the vertical, and inclined slightly medially. No
articular facets for the postorbital are preserved. The postorbital bar was not recessed below the level of the skull
surface. The posterior process tapers distally. There is no evidence as to how this bone articulated with the
quadratojugal. The anterior process of the jugal is pointed and is constricted centrally. The lateral surface of this
process is convex across its length. Asonly a small amount ofthe medial surface of the jugal is visible, on P. 78/la,
its articulations with the maxilla, lacrimal, and ectopterygoid, as reconstructed, are purely suppositions.

Lacrimal. Five lacrimals are preserved and together they allow the whole bone to be described. The lacrimal
consists of an approximately triangular facial plate and a descending maxillary process. The ventral edge of the
facial plate and the anterior edge of the maxillary process bounded the antorbital fenestra. The posterior edge of
the maxillary process is slightly concave where it formed the antero-ventral edge of the orbit. The medial surface
of the lacrimal is smooth. The postero-dorsal corner of this surface is hollowed out into an approximately
triangular recess in which the prefrontal articulated. The prefrontal also fitted within a groove that runs along
the dorsal margin of this surface. The medial side of the maxillary process is built up centrally into a low ridge. The
opening into the lacrimal duct is positioned just dorsal to the termination of the maxillary process. The lateral
surface of the lacrimal was smooth. The anterior end of this surface of the facial plate bore a strong ridge, dorsally,
that fitted medial to the maxilla. Details of the ventral articulations with the jugal and maxilla are unknown.

Maxilla. Seven maxillae have been referred to Terrestrisuchus and the structure of this bone is almost completely
known. The basal portion of the maxilla consists of a long, horizontally orientated, tooth-bearing ramus the

134

PALAEONTOLOGY, VOLUME 7

ventro-lateral edge of which is nearly straight. Rising dorsally from the anterior half of the basal ramus is an
ascending lamina consisting of a facial plate and a postero-dorsally directed projection. The anterior part of the
basal portion of the bone is extended medially to form a palatal process. The lateral surface of the maxilla is
smooth except for a number of small blood and nervous foramina that run along its ventral margin. A conical
fossa is present in the facial plate anterior to the antorbital fenestra. This fossa is directed antero-ventrally and is
of moderate depth. The lateral surface of the postero-dorsal projection turns sharply medially and then ventrally
where it borders the antorbital fenestra. Articular facets for the nasals are not preserved but it is assumed that
they overlapped the dorsal edge of each maxilla. There is no evidence for the mode of articulation with the
premaxilla or for a notch between premaxilla and maxilla such as has been figured in Sphenosuchus (Walker
1970). The palatal process is rather narrow; it articulated medially with its pair and probably also with the

TEXT-FIG. 1 . Terrestrisiichus gracilis gen. et sp. nov. a-c, cranium in dorsal view: a, reconstruction; B, structure of
the preserved material; c, restoration of the articulations. For explanation of abbreviations, see page 155.

CRUSH: TRIASSIC CROCODILIAN FROM WALES

135

vomers. The posterior edge is concave and formed the anterior border of the internal naries. The maxilla lorms
the posterior portion of the anterior palatal foramen which opens out from the bottom of a pit that would have
been originally formed by maxilla and premaxilla. Specimen P. 144/1 bears oval alveoli for hiteen thecodont
teeth and three more were inserted into a common alveolar groove at the back of the maxilla. Specimen P. 1 47/ la
displays the structure of the medial surface of the anterior part of the maxilla. It shows that there was a second
ridge running dorsal to the palatal process and separated from the ventral edge of the bone by a groove. It is
suggested that this groove bore the chaonal tube and that at least the anterior part of the internal naries were
covered by a soft palate.

Maxillary teeth are well preserved on P. 147/a. They have well-developed oval roots and laterally compressed
crowns. These teeth are pointed and recurved and bear anterior and posterior cristae which are hnely serrated.

Nasal. This bone is well represented in the material and P. 108/1 bears a fine specimen that shows its original
outline. The medial edge of the bone is straight where it butt-jointed to its pair. The nasals are pointed anteriorly
and posteriorly. The frontals wedged in between them posteriorly and were overlapped by them dorsally. No
articular surfaces are preserved for the prefrontals and maxillae. A small process from the anterior end of the
bone formed a notch that housed a process of the premaxilla. The dorsal surface of the bone is smooth and whilst
it is flat posteriorly anteriorly it becomes strongly convex across its length.

Parietal. Although the six preserved parietals are all in poor condition there is sufficient material to allow this
element to be fully described. The parietal is a long narrow bone that articulated with its pair along the midline.
Details of this articulation are not preserved but it appears that the bones were simply butt-jointed together. The
anterior portion of the lateral edge of this bone formed the gently concave margin of the supratemporal fenestra.
The postero-lateral corner of the parietal is extended into a process that articulated with the squamosal and
medial to this articulation the bone is deeply notched. It is thought that the supraoccipital joined to the posterior
edge of this notch and its anterior processes buttressed against the ventral surface of the parietal but no defined
articular facets for the supraoccipital are present. The details of the squamosal articulation are not clear but it is
apparent that the postero-lateral process of the parietal fitted into a notch formed for it on the postero-medial
edge of the squamosal. The dorsal surface of the parietal is smooth. The centre of the bone is strongly convex
across its longitudinal axis which results in the skull table being arched between the supratemporal fenestrae. The
edge of the bone dipped steeply into the fenestra and its posterior margin was bent downwards on to the occipital
surface.

Postorbital. Only two postorbitals are preserved but the example on P. 79/ Ic is in excellent condition. This
element is a triradiate bone consisting of posterior, lateral, and medial processes. The posterior ramus which
overlapped the squamosal is approximately triangular in dorsal view and antero-medially formed part of the
margin of the supratemporal fenestra. The lateral process is slender and tapers towards its tip where it articulated
with the jugal. The medial process is excavated by a deep groove which housed a process of the frontal.

Prefrontal and premaxilla. No prefrontals or premaxillae have been identified in the material. They have been
reconstructed on the basis of the articulations, preserved for them, on the other cranial bones and on the
structure of this element in Sphenosucbus (Walker 1972). No restoration of the portion of the prefrontal within
the orbit has been attempted.

Quadratojugal. The quadratojugal is a very thin, fragile bone and is thus poorly preserved. Two specimens
display parts of this element and from these parts, and knowledge of the adjacent bones, the whole can be
reconstructed. The quadratojugal has been restored as an approximately parallelogram-shaped bone that
increases in width ventrally. The posterior, dorsal, and ventral edges of the bone were straight but the anterior
edge was concave. The dorsal edge buttressed under the squamosal but no details of this articulation are
preserved. Postero-ventrally the quadratojugal overlapped the lateral edge of the quadrate whilst dorsally it
articulated with the thin anterior edge of that bone.

Squamosal. Eight examples of this bone are preserved and its structure is completely known. When viewed
directly, the squamosal is approximately flat and kidney-shaped with three posteriorly placed projections. In life
its dorsal surface sloped strongly ventro-laterally. This surface is smooth and slightly convex across its length.
The lateral edge of the squamosal is convex whilst the medial is concave where it bordered the supratemporal
fenestra. The bone surface dipped very steeply into the fenestra. A number of shallow, longitudinal grooves are
present on the region of the bone which was overlapped by the postorbital. The largest of the processes of the
squamosal extended posteriorly and slightly ventrally. This process articulated with the exoccipital but it is not
known how. Medial to this exoccipital process are two more that formed a notch for the postero-lateral process
of the parietal.

A

TEXT-FIG. 2. Terresirisuchus gracilis gen. et sp. nov. a-c, cranium in left lateral view: a, reconstruction; B,
structure of the preserved material; c, restoration of the articulations.

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Eclopterygoid. Two of these bones have been identified and one, on P. 79/ la, is almost perfect. The
ectopterygoid is triradiate and consists of a jugal process and lateral and medial palatal processes. The palatal
processes both taper distally and diverge at about 80°. The lateral process overlapped the transverse process of
the pterygoid ventrally. The lateral part of the medial process also articulated with the ventral surface of the
pterygoid but its tip passed through a notch in that bone and then fitted against its dorsal surface. The jugal
process, which curves antero-dorsally, is oval in cross-section where it joins the palatal processes. Laterally this
process expands and divides to form a pair of articular surfaces for the jugal.

Palatine. The palatines are large bones that covered much of the ventral surface of the snout. Each articulated
medially with the pterygoid and vomer and laterally with the maxilla. The lateral edge of the palatine was
horizontally orientated and, as the medial edge lay dorsal to the lateral, the palate was vaulted. Four good

TEXT-FIG. 3. Terrestrisachus gracilis gen. et sp. nov. A-c, cranium in ventral view: a, reconstruction; B, restoration
of the articulations; c, structure of the preserved material.

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specimens of the palatine are preserved. This element is basically a flat plate of bone whose medial outline is
convex anteriorly and slightly concave posteriorly. The lateral outline is straight centrally but notched anteriorly
and posteriorly. The bone is thickened where it butt-jointed to the maxilla. No details of the articulations with
the pterygoid are preserved. A facet for articulation with the vomer is present on the anterior margin of the
ventral surface. The ventral surface of the palatine is smooth and approximately flat. Antero-laterally it bears a
pair of hollows and an intervening ridge and in addition it was traversed by a step-like change in height that runs
in a line directed postero-medially. These features imply that a soft palate may have extended over the palatines
and that the functional choanae may have lain behind them.

Pterygoid. The pterygoid is well known from one almost complete specimen (P. 1 12/1) and others that are well
preserved but incomplete (P. 78/la and P. 47/22). The pterygoid is composed of three processes: palatal,
transverse, and quadrate. The palatal process is a long, tapering plate of bone that extended anteriorly along the
palate adjacent to its pair across the midline. The process is straight medially but did not suture to its counterpart
and thus they were separated by a narrow interpterygoid vacuity. The lateral margin of the palatal process is also
straight except for a small, tapering, antero-laterally directed palatine process. The tip of the palatine fitted into
the notch that lies anterior to this process. The palatal process is strengthened medially by a low ridge. A deep,
conical hollow is formed at the posterior end of the palatal process where it intersects with the transverse process.
The posterior edge of the transverse process is concave whilst the lateral is slightly convex. The postero-lateral tip
of this process was extended into a point. The anterior edge bears a notch for articulation with the ectopterygoid
and longitudinal grooves mark the position of articulation of the lateral palatal process of that bone. The
transverse process is twisted along its length so that its antero-lateral corner lies dorsal to its postero-lateral
corner. The quadrate ramus of the pterygoid is approximately triangular in outline and its main surface faced
postero-medially. The original outline of this process is uncertain and it is not known how it articulated with the
pterygoid ramus of the quadrate. The posterior surface of the quadrate ramus is traversed by a ridge towards its
ventral end and just dorsal to this the bone is deeply hollowed out. This hollow formed a cotyle for articulation
with the basipterygoid process of the basisphenoid. This articulation was probably moveable. A small hook of
bone, visible in palatal view, extends from the medial end of the ridge.

Vomer. No examples of this element are present but its outline can be reconstructed with fair certainty. The
details of its structure are based on the vomer of Sphenosuchus.

Quadrate. There are seven quadrates preserved and, although none is perfect, in combination they give an
almost complete picture of the structure of this bone except for some uncertainty as to the extent of the pterygoid
process. The quadrate is a pillar-like bone that sloped strongly antero-dorsally. It consists of a triangular dorsal
part with an approximately rectangular ventral extension that expands slightly towards its distal end. The bone is
twisted centrally so that the external surface of the dorsal part faced laterally and very slightly posteriorly whilst
the ventral part faced postero-dorsally and slightly laterally. The mandibular condyle faced postero-ventrally;
this surface is expanded medially but narrows towards its lateral edge. A deep cavity or conch is present in the
posterior surface of the bone in the same position as that of a lizard. The lateral edge of the ventral portion of the
bone is broad and dorsally it merges with the lateral surface of the pterygoid ramus. The quadratojugal
articulated with this edge of the bone. The dorsal edge of the quadrate is almost straight and sloped anteriorly,
ventrally, and laterally. This edge is thin anteriorly but thickens posteriorly where it buttressed under the
squamosal. The lateral surface of the dorsal part of the bone is smooth and slightly concave. A faint ridge runs
along its dorsal margin diverging anteriorly from the dorsal edge. This ridge formed the antero-dorsal margin of
the tympanic membrane. The pterygoid ramus is very thin and its outline is not fully known. As preserved, this
projection has straight, parallel, dorsal, and ventral edges and its distal margin is slightly convex. The process
was inclined ventrally and antero-medially.

Basioccipital. The structure of this bone is well displayed by an articulated specimen on P. 78/la, and a second,
individual bone (P. 62/20) freed from most adhering matrix. The basioccipital consists of an approximately
square body connected by a narrow neck to a swelling that formed the occipital condyle, the posterior end of
which is depressed to form a small notochordal pit. The dorsal surface of the basioccipital formed the posterior
part of the floor of the cranial cavity. This surface is smooth and slightly concave across its length. Flanking this
surface are two articular facets: one for the exoccipital and a second, more anterior, facet for the basisphenoid.
The anterior edge of the basioccipital also articulated with the basisphenoid. The basioccipital is hollow and this
cavity opens into an approximately square foramen on the ventral surface of the bone. This basioccipital fossa is
presumed to be part of the ramifications of the Eustachian tube system. Basioccipital tuberii are present
posteriorly and the lateral surfaces of these projections are hollowed out into shallow cavities that faced
posteriorly and slightly laterally. These cavities were for insertion of the subvertebral muscles.

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TEXT-FIG. 4. Terrestrisuchus gracilis gen. et sp. nov. A-c, cranium in posterior view: A, reconstruction;
B, restoration of the articulations; c, structure of the preserved material; d, reconstruction of the
braincase; e, position of the fenestrae ovalis and pseudorotunda; f, reconstruction of the tympanum.

Basisphenoid. No element has been satisfactorily identihed as a basisphenoid and thus this element has been
reconstructed like that of Sphenosuchus.

Exoccipital. The exoccipitals can be completely described as six examples of this bone are preserved. The left
exoccipital, comprising specimen P. 65/67, was used as the basis of this description as it is in excellent condition
and is freed from nearly all adhering matrix. The ‘exoccipital’, as described, is composed of the fused exoccipital
and opisthotic. The paraoccipital processes were swept backwards and expand dorso-ventrally towards their
distal ends. The concave, thickened, dorsal edge of each process formed the ventral margin of the post-temporal
fenestra. The distal end of the paraoccipital process articulated with the squamosal. The supraoccipital

TEXT-FIG. 5. Terrestrisuchus gracilis gen. et sp. nov. Left mandible in A-c, lateral, and d-f, medial views,
A, D, reconstructions; n, E, structure of the preserved material; c, f, restorations of the articulations.

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141

articulated with the dorsal margins of the anterior portions of the exoccipitals and also with flanges that they sent
out above the foramen magnum. Anteriorly the exoccipital articulated with the prootic. A subcapsular process is
present antero-ventrally and the lateral surface of this articulated with basisphenoid. The fenestra ovalis was
formed at the junction with the prootic. Postero-ventral to this foramen is the foramen perilymphaticum
separated from the ovalis by a narrow interfenestral bar. The perilymphatic duct opened posterior to the
foramen perilymphaticum. This duct is confluent medially with the rest of the metotic fissure that served for the
exit of nerves IX-XI.

Laterosplienoid. No examples of the laterosphenoid have been identified but the structure of the prootics
suggests their original presence. They were certainly present in Splienosiicinis.

Prootic. Only a single specimen of the prootic is preserved and unfortunately even this bone is in poor condition.
It lies in lateral view, partially articulated with the exoccipital, on P. 47/22. The postero-dorsal edge of the prootic
attached to the supraoccipital and the dorsal edge, which is straight and was horizontally orientated, articulated
with the parietal. The prootic met the laterosphenoid anteriorly where it formed the posterior margin of the
foramen ovale for the exit of the fifth cranial nerve. A notch, dorsal to the foramen ovale, could be part of a
foramen for the middle cerebral vein. The ventral edge of the prootic articulated with the basisphenoid.

Supraoccipital. Two examples of this bone are preserved: one of these, on P. 47/22, is complete but has only its
posterior and right aspects exposed whilst the second, P. 31/1 1, has been freed from matrix but is incomplete
ventrally. The posterior part of the supraoccipital forms an occipital plate that sloped antero-dorsally at about
45°. The ventral edge of the bone articulated with the exoccipitals. The lateral margins of the occipital plate bear
parallel-sided, roughened surfaces that, by analogy with the modern crocodile, were for the attachment of
cartilages that partly filled the post-temporal fenestrae. The dorso-lateral edges of the plate are concave and
formed parts of the margins of the post-temporal fenestrae. The dorsal edge of the occipital plate articulated
with the ventral surface of the parietal by means of two oval articular facets. The posterior surface of the occipital
plate is smooth and flat except for a low, centrally positioned, dorso-ventrally directed ridge. The supraoccipital
sends projections anteriorly, from the lateral sides of the occipital plate, and these house segments of the osseus
labyrinth.

Mandible. As reconstructed (text-figs. 5 and 6) the mandible is long and slim with a very long dentary and well-
developed splenial. The angular is also large but, in contrast, the other bones are rather small. The articular is a
fragile bone with medial and dorsal foramina. A dorsal process extends, from the articular, medial to the
quadrate cotyle. The symphyseal area is small and the splenials do not reach the ends of the dentaries.

Angular. Five angulars are preserved and together they give a complete picture of the structure of this bone. The
angular is long and slender and whilst it formed much of the lateral wall of the posterior end of the mandible it
was only slightly exposed medially. The bone is rod-like anteriorly but posteriorly it is flattened; it tapers to a
point anteriorly and posteriorly. The anterior portion of the bone is rounded off ventro-laterally and is hollowed

TEXT-FIG. 6. Terrestrisuchus gracili.s gen. et sp. nov. Transverse sections of the left mandible, for

positions of the sections see text-fig. 5f.

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out medially forming the Meckelian canal. The anterior portion of the angular lay against the dentary and htted
into a groove in the splenial. More posteriorly the bone articulated dorsally with the surangular and medially
with the prearticular. More posteriorly still it fitted against the articular.

Articular. Only two of these elements are preserved and both are on P. 78/ la in articulation with the other skull
bones. The left of these is well preserved but has only its ventral surface exposed. The lateral, medial, and
posterior aspects, and part of the dorsal surface, of the right are visible but the bone has been crushed latero-
medially. The articular is a thin walled, hollow bone and foramina open into it on its dorsal and medial surfaces.
The medial foramen is large and oval but only a portion of the dorsal opening is visible. The articular surface for
the quadrate lay posterior to the medial foramen. The bone supporting the deep cotyle for the quadrate is thin
and, unexpectedly, interrupted by the dorsal foramen. Posterior to the articulation for the quadrate the medial
part of the articular is expanded dorsally into a tapering process. This element articulated laterally with the
angular and anteriorly with the prearticular. Unlike this bone in the modern crocodile, the articular had, at the
most, only a very small contact with the surangular.

Coronoid. A single, right coronoid is contained, in lateral view, on P. 63/8. This bone is in very poor condition
and was only identified because of its association with a splenial. The specimen is crushed and, as preserved, its
surface is slightly convex. The complete posterior edge is concave where this element would have bordered the
mandibular fossa. Anteriorly the bone is convex where it fitted into the coronoid notch of the splenial. No
articular facets for the splenial are preserved.

Den tar y. This element is better represented than the other bones of the lower jaw as there are six examples
preserved. The dentary is a long slender bone whose distal end curves slightly dorsally. Anteriorly the ramus of
the dentary is parallel sided but posteriorly it increases in height. The lateral edge of the bone is smooth and,
anteriorly, bears a low ridge that runs parallel to its dorsal margin. The medial surface is traversed by the
Meckelian canal. This canal terminates in a small hollow anteriorly where it was joined to its pair on the
opposing dentary. The area of the symphysis is smooth. The dentary articulated medially with the splenial and
postero-ventrally with the angular. More posteriorly still it articulated with the surangular.

Dentary teeth. The alveoli of the dentary are positioned along its lateral side. When preserved the teeth are fairly
even in their development although there is evidence of a slight increase in height centrally. The dentary has been
restored with twenty-four teeth although this may be slightly more than were originally present. The posterior
end of the dentary has been restored without any teeth. There is no direct evidence for this unusual condition and
it is postulated because of the length of the mandible and the sizes of the other bones. The anterior dentary teeth
bore anterior and posterior cristae; they were slim, pointed, and recurved. The roots were oval in cross-section.
The more posterior teeth were laterally compressed although otherwise they were pointed, bore anterior and
posterior cristae, and were recurved like the anterior teeth. They differ from the latter in bearing serrations on
their posterior edges. These are only visible ventrally but it is probable that they extended all along the posterior
cristae.

Prearticular. A single, right prearticular is preserved on P. 78/ la, and it is exposed in medial and lateral views.
This bone expands posteriorly and whilst its ventral edge is almost straight its dorsal edge is slightly concave. The
postero-medial surface is strongly convex but anteriorly the bone is flattened. Posteriorly it articulated with the
articular and anteriorly it fitted lateral to the splenial. Postero-ventrally it fitted against the medial edge of
the angular but more anteriorly it shifted its articulation on to the dorso-medial edge of that bone.

Splenial. Five splenials are preserved and the right on P. 63/8 is almost complete. The dorsal edge of this element
is very slightly concave anteriorly and very slightly convex posteriorly. The posterior margin of the bone is incised
by a large notch that articulated with the coronoid and a smaller, ventrally placed notch against which the
angular fitted. The ventral edge of P. 63/8 is poorly preserved and has been reconstructed as slightly convex. The
medial surface of the bone, as preserved, is flat. The ventro-lateral margin of the bone forms a groove which
formed an articular surface for the angular.

Surangular. A single surangular is present on P. 78/ la and, unfortunately, this bone has been fractured centrally
and its anterior end has been lost. The posterior part of the bone is approximately triangular and it has an antero-
dorsal extension that runs above the external mandibular foramen. Anteriorly the dorsal edge of the bone
projects medially so that it has an inverted V-shape in cross-section. This anterior process of the surangular fitted
within the dentary. The lateral surface of the bone is convex across its longitudinal axis. Postero-ventrally a ridge
is visible running parallel to the posterior part of the external mandibular foramen. Posteriorly this crest turns to
run postero-dorsally and the angular buttressed under it. Below this ridge the ventro-lateral surface articulated
with the medial surface of the angular.

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description: postcranial skeleton

Pectoral girdle. The material contains nine specimens of the scapula, eleven of the coracoid, three of the ossified
sternum, but only one of the interclavicle. These allow a reconstruction of the pectoral girdle (text-fig. 7a, b)
where only the shape of the interclavicle is in doubt. The scapula is waisted with a flattened dorsal portion drawn
out into a point anteriorly and posteriorly. The convex dorsal edge of the blade is poorly finished and it is likely
that it bore a cartilaginous suprascapula. The bone has an oval cross-section at its narrowest point and thickens
ventrally. The ventral part of this element bears a distinct acromial ridge and its posterior edge is thickened to

TEXT-FIG. 7. Terrestrisiichus gracilis gen. et sp. nov. a-b, reconstruction of the pectoral girdle in left
lateral and ventral views; c-f, left humerus, P. 47/22, in anterior, posterior, medial, and lateral views;
G, left radius and ulna, P. 47/22, in lateral view.

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support the glenoid articular surface. This articulation is oval and slightly concave; it faced posteriorly,
ventrally, and slightly medially. The medial surface of the ventral part of the bone lacks the process found in
Sphenosuchus. The coracoid consists of a thickened central region supporting the glenoid articulation, and a
much thinner anterior plate perforated by the supracoracoid foramen. The anterior plate is approximately
triangular in outline. Posteriorly the bone is drawn out into a long tapering extension. The ventral surface of this
process bears a deep trough bounded dorsally by a horizontally directed ridge. This ridge is homologous with the
biceps tubercle in Sphenosuchus (Walker 1972). The edges of the sternum fitted into these troughs as shown by
the articulated girdle of Pseudohesperosuchus (Bonaparte \91\b). The portion of the glenoid articular surface
supplied by the coracoid is oval in outline and flat. This facet faced posteriorly, dorsally, and laterally. The
coracoid is very similar to the problematical bone of Hesperosuchus (Colbert 1952). The preserved specimen of
the interclavicle is very damaged and its original shape and length are uncertain. As preserved, this bone is
elongated, flattened, and has parallel edges. The sternum is a thin, fragile bone. This ossification is smooth on
both surfaces, its lateral edges are convex, and it is pointed anteriorly and posteriorly. The interclavicle fitted
against its antero-ventral surface.

Humerus. There are sixteen humerii preserved and text-fig. 7 c-f shows the most complete of these which is only
slightly damaged distally. The humerus is a long, slender bone that was held vertically (text-fig. 14). The head
extends about a third of the way along the length of the bone and is set off at a small angle to the direction of the
shaft. This means that the centre of the thickened, proximal, articular surface is slightly medial to the line of the
shaft. The deltopectorial crest is well developed; its surface is convex laterally and concave medially. In lateral
view the crest has a triangular outline and rises to a point just over half-way along its length. The central region of
the shaft is thin walled and has a circular cross-section. The capitellum, or radial condyle, and medial convexity
are well developed. They are separated by a groove or trochlea that articulated with the olecranon of the ulna.
In life the distal articular surfaces faced downwards which implies that the forearm was held in an extended
position.

Antebrachium. The ulna is a slender bone with a long shaft but only slight proximal and distal expansions (text-
fig. 7g). The proximal part of the bone is formed into an olecranon. The head of the bone is approximately
triangular in proximal view with a concave anterior edge that fitted against the flattened proximal end of the
radius. The ulna has a double flexure giving it a very slight S-shape in lateral view. The shaft is circular in cross-
section and thin walled. The distal end of this element is slightly expanded posteriorly giving it a tear-drop
outline in distal view and its medial surface is flattened anteriorly where it fitted against the distal end of the
radius. The distal articular surface is slightly concave. The radius is also a slender bone with poorly developed
proximal and distal expansions. The proximal end is flattened antero-posteriorly, whilst the distal expansion is
oval in distal view. The shaft of the radius is straight and parallel sided; it is hollow with a slightly oval cross-
section.

Carpus andmanus. The carpus is fully crocodilian and is composed of just four ossifications: the radiale, ulnare,
pisiform, and the fused remains of distal carpals three and four (text-fig. 8a, e-h). In addition, although the
proximal carpals are relatively longer, their articular surfaces can be homologized with those of the modern
crocodile. Specimen P. 72/1 includes an almost perfect set of these bones comletely freed from matrix. Thus on
the reconstruction only the details of the articulations and the terminal phalanges on digits one, four, and five are
conjectural. The radiale is a slender bone with a slight distal expansion and a more pronounced proximal one
where it contacted the radius and ulna. The articular surface for the radius is oval in shape whilst that for the ulna
is triangular. The lateral surface of the distal portion of this bone bears a trough for muscular insertion. The
ulnare is more expanded distally than proximally. The proximal articulation for the ulna is approximately
triangular whilst the distal for the fused distal carpals is tear-drop shaped. The pisiform is an irregular pear-
shaped bone. It is small relative to those of Protosuchus and the modern crocodiles suggesting that the wrist was
less flexible in Terrestrisuchus. The bone representing the distal carpals is flattened and triangular in proximal
view. The manus has been reconstructed as digitigrade. The preserved ungual phalanges are curved, pointed, and
bear grooves on their lateral and medial surfaces. It would thus appear that digits two and three at least
terminated in a claw.

Pelvis. Eleven specimens of the ilium are preserved, sixteen of the pubis, and six of the ischium. The fine quality of
these bones allows the pelvic girdle to be completely reconstructed (text-fig. 8b-d). The iliac blade, which is
rather low, extends anteriorly into a long, laterally compressed process whilst the posterior projection is deeper
anteriorly but tapers distally. Part of the rib of the first sacral vertebra attached to the ventral edge of the anterior
projection whilst the rest attached to the base of the ilium (text-fig. 13a). The rib of the second sacral vertebra
attached to the base of the ilium and also fitted around a strong ridge that runs along the ventral edge of the

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anterior view; b-d, reconstruction of pelvis, based on P. 72/1, in anterior, left lateral, and dorsal views
(in B the second sacral vertebra and ischia are not included); e-f, left radiale, P. 72/1, in anterior and
lateral views; g-h, left ulnare, P. 72/1, in posterior and lateral views.

medial surface of the posterior projection. The ventral edge of the ilium is notched where it bordered the
acetabular foramen. The bone forming the medial wall of the acetabulum is thin and the supra-acetabular ridge
is strongly developed. The ilium is thickened where it supports the articulations for the pubis and ischium. The
pubes are well developed and their anterior ramii were joined medially although it seems likely that there was a
break in the symphysis below the acetabulum. Each pubis bears a well-developed, oval, obturator foramen. The
ischia bore flattened posterior projections that joined along the midline. The dorsal part of the ischium is
thickened where it buttressed against the ilium. The anterior edge is thin and straight for articulation with the
pubis. The antero-dorsal margin of the ischium is rounded off where it bordered the acetabular foramen.

Femur, tibia, and fibula. Although fourteen specimens of the femur are preserved, none is quite perfect. Text-hg.
9a shows the best example which is on block P.24/39a. The femur is a slender bone with a slightly developed head
which is flattened and twisted on the shaft such that it was directed antero-medially. In this position it would
have buttressed under the supra-acetabular ridge of the ilium if the femur were, as reconstructed, held vertically.
There is no greater or lesser trochanter but the proximal part of the shaft bears a weakly developed fourth
trochanter. The proximal end of the femur bears another trochanter which takes the form of a low ridge running
along the posterior margin of the head. The shaft has a slight sigmoid flexure that is much less apparent than in
the modern animal. The medial and lateral condyles are well developed for articulation with the tibia. The fibula
articulated with a facet on the lateral edge of the lateral condyle. The tibia is a slender bone (text-hg. 9b, c) that
was slightly longer than the femur. There is no complete fibula present and the illustrated specimen, P. 130/1

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PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 9. Terrestrisuchus gracilis gen. et sp. nov. A, restoration of right femur, based on P. 24/39a, in
postero-medial view; b-c, left tibia, P. 1 1/1, in posterior and anterior views; d, left fibula, P. 130/1, in

lateral view.

(text-fig. 9d), is incomplete distally. This element is a slender bone that is flattened proximally and bears a
slight crest, for muscle insertion, on the lateral surface of its anterior edge. The distal expansion of the bone
is slight.

Tarsus andpes. There are just four bones in the tarsus: the astragalus, calcaneum, and distal tarsals three and four
(text-fig. 10e-j). The proximal tarsals articulated together by a ball and socket joint, with the astragalus
functionally part of the crus whilst the pes, distal tarsals, and calcaneum moved as a unit on the astragalus and
fibula. The calcaneum bears a well-developed tuber. The reconstruction of the tarsus is based on specimen P. 47/
21a which comprises a virtually perfect set of tarsals completely freed from matrix. The medial surface of the
calcaneum bears a circular socket, which accepted the peg of the astragalus, and a projecting lip of bone that lay
posterior to the peg. Distal tarsal three, as preserved, is approximately cylindrical in shape. Distal tarsal four is
larger than the other distal tarsal and consists of two expansions set at right angles to each other. The anterior of
these lay horizontally whilst the posterior lay vertically and both were triangular in outline. The first four
metatarsals are long and were approximately equal in length whilst the fifth is reduced. The fifth is primitive for a
crocodile in that it is still about half the length of metatarsal four and bears two phalanges although these have
been reduced to two small nubbins of bone. The proximal expansion of metatarsal five is bulbous and it bears a
flange that fitted behind the proximal expansion of metatarsal four. The phalangeal formula is 2, 3, 4, 4, 2.

Armour and gastralia. A single row of scutes was present on each side of the dorsal midline but there is no
evidence of any ventral or dorsal paramedial scutes. The armour is not shown in the reconstruction. The thoracic

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TEXT-FIG. 10. Terrestrisuchus gracilis gen. et sp. nov. A, reconstruction of cervical vertebrae, based on P.
79/1; B, reconstruction of cervical ribs; c, left scute, P. 123/1, in dorsal view; d, axis, P. 47/22a, in right
lateral view; e, reconstruction of left tarsus and pes in anterior view; f, right calcaneuin, P. 73/1, in
anterior view; g, right astragalus, P. 1 10/1, in anterior view; h-j, right distal tarsal four, P. 47/2 la, in

anterior, dorsal, and lateral views.

scutes are basically leaf-shaped (text-fig. 10c) with an anterior peg that fitted into a triangular groove on the
ventral surface of the adjacent plate. Each scute bears a prominent ridge along its midline and is sculptured medial
to this ridge. A muscle scar is present postero-laterally. The gastralia, which are single ossifications, are broad,
flattened, and V-shaped. The lateral projections of these elements curved slightly dorsally.

Atlas-axis complex. The atlas intercentrum, pro-atlas, and axis rib are not present in the material and the other
atlantal elements are poorly preserved. The axis is in good condition on F. 47/22a (text-fig. IOd). The remains of
the atlas neural arch show that it consisted of a dorsal flange that lay nearly horizontally and protected the dorsal

148

PALAEONTOLOGY, VOLUME 27

part of the spinal cord, and a cresentric ventral part that articulated with the atlas intercentrum, the basioccipital
condyle, the odontoid, and the axis centrum. The atlas rib was a cylindrical rod of bone. Only a damaged nodule
of bone is preserved representing the odontoid which was sutured, not fused, to the axis centrum. The figured
specimen of the axis lacks an anterior zygapophysis. Specimen P. 78/ 1 a shows this to have been an oval facet that
faced dorso-laterally. There is only a single articular surface for the axis rib.

Cervical vertebrae and ribs. The cervical vertebrae have been reconstructed (text-fig. 10a) on the basis of an
articulated, although damaged, cervical series on P. 78/1 and individual examples ofV2-6, V8, and V9 which are
well preserved on P. 79/1. The only doubtful parts of this restoration are the exact shapes of the neural spines
which show some variation. A slight hypapophysis is present on V3 but such a flange is not found on the axis or
on any of the more posterior vertebrae. The parapophyses on V3 and V4 are approximately oval in outline whilst
more posteriorly they become triangular. On Vertebrae V3-5 the articular surface of the parapophysis merges
with that of the diapophysis but posteriorly they are distinct. On the anterior vertebrae the parapophysis is
supported by a strong ridge but this has faded out by V7. The structure of the transverse process, bearing the
diapophysis, changes markedly along the sequence V3-9. On V3 the transverse process is just a slight
protuberance with a ridge running back from it but the diapophysis moves progressively postero-dorsally along
the series V3-9 and the transverse process increases in length. On V6 and V7 the transverse process is dorso-
ventrally flattened and bears two ridges running along its anterior and posterior margins. On V8 a third ridge is
developed postero-ventrally and on V9 a fourth antero-ventral ridge is present. The neural spines are flattened
without trace of any dorsal thickening. A deep pit is present at the base of the posterior edge of the neural spine
whilst a shallower one is present below its anterior edge. The anterior and posterior zygapophyses are well
developed. The suture between the neural arch and centrum runs through the transverse processes on V3-5 and
just below it on V7.

5mm

avr pr ancr pr pa;dia

an cr

pv r av r

pv r

TEXT-FIG. 1 1. Terrestrisuchus gracilis gen. et sp. nov. Reconstruction of dorsal vertebrae, VI 0-1 6 and

VI9-24.

CRUSH: TRIASSIC CROCODILIAN FROM WALES

149

The cervical ribs are generally poorly preserved but P. 79/ la bears a well-preserved rib of V4 and P. 78/ lb
shows the structure of those of V8 and V9. It is thus possible to reconstruct the cervical ribs with confidence (text-
fig. 10). The ribs of V3 to V7 are all similar and each extends anteriorly into a pointed, tapering process and
posteriorly into a shaft that projected parallel to the vertebral column. The tuberculum and capitulum diverge at
about 45° to one another. The rib of V8 possesses a pointed anterior process but the shaft is now longer and
extends ventro-laterally. The anterior projection of V9 has been converted into a thin, rounded flange and the
shaft now extends to curve around the body. There is no evidence for the presence of a cartilaginous uncinate
process on any of the ribs.

Dorsal vertebrae and ribs. Specimen P. 78/ lb bears VI 0-18 in association but these vertebrae are not well
preserved. Block P. 72/1 contains the last seven presacrals, in better condition, in articulation with the two
sacrals. There are some fine examples of individual vertebrae (P. 30/1, P. 80/1) and the dorsal column can be
reconstructed (text-fig. 1 1 ) although not with quite the same confidence as the cervicals. The number of presacral
vertebrae has been taken as twenty-four as this is the number present in Protosiichus and Orthosiichus. The
material of Terrestrisuchus only allows a minimum number of twenty-three to be established. There is no
distinction between thoracic and lumbar subregions as even the final presacral vertebra bears a free rib. The
structure of the centrum is basically unchanging along the dorsal series except that it becomes relatively longer
posteriorly. The articular surfaces of the centra are platycoelous but the anterior is more deeply hollowed out
than the posterior. The parapophysis moves dorsally within this vertebral series and by V12 has migrated to just
antero-ventral to the transverse process. At the posterior end of this series it moves closer to the diapophysis and
finally merges with it on V24. Posterior to VI 3 this articulation is supported by a crest anteriorly. Unlike the
situation in the modern crocodile the parapophyses are never borne on the transverse processes. The ridges
supporting the transverse process are the same on VIO and VI 1 as those on V9, however by V13 the anterior
ridge has disappeared and the antero-ventral ridge joins to the parapophysis. The three remaining ridges are
present all the way back to V23. The structure of the neural spines is well preserved on V 14 and VI 6, on P. 78/ lb,
and there is no trace of any dorsal thickening. The zygapophyses of VIO and VI 1 are like those of the cervical
vertebrae but by V 1 5 they have come to lie more horizontally. Pits were present at the bases of the neural spines
of all the dorsal vertebrae.

A fairly large number of dorsal ribs are preserved but few are in good condition. Text-fig. 12 shows what is
believed to be an accurate restoration of these bones. The only significant reconstruction has been in the lengths
of their shafts. All the ribs are dichocepalous except for that of V24 which is holocephalous. Rib ten on P. 78/ la is
well preserved. The tuberculum is broad and flattened whilst the capitulum is circular in cross-section. The
anteriorly projecting flange lies at about 45° to the plane of the articular processes. Rib sixteen, on the same
specimen, is in fine condition. The tuberculum has now become just a small projection but the capitulum is well
developed. The anterior flange is now triangular in outline and lies in the same plane as the heads of the bone.
The ribs reduce posteriorly until that of V23 is just a flattened piece of bone with no shaft and barely
distinguisable articular facets. The rib of V24 is exceptional in that it extended horizontally; it is flattened and has
an approximately rectangular outline.

TEXT-FIG. 12. Terrestrisuchus gracilis gen. etsp. nov. Reconstruction of dorsal

ribs, VI 0-24.

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PALAEONTOLOGY, VOLUME 27

Sacral vertebrae. The first sacral vertebra is represented by four specimens one of which, P. 1/1, has been
completely freed from matrix and is in excellent condition. The second sacral vertebra is less well represented in
the material, but there is a fine specimen showing the centrum and rib in ventral view (P. 24/39e). The
reconstruction of the sacrum on text-figs. 8b, d and 13a is thus considered to be accurate. The ribs of the first
sacral vertebra are short and stout and they attach to transverse processes that arise from the complete dorso-
ventral extent of the pedicels. Their distal articular surfaces for the ilia consist of a large ventral portion that
faced ventrally, laterally, and slightly posteriorly, and a long tapering anterior extension. The transverse
processes of the second sacral vertebra also originate from the whole height of the pedicels. The distal articular
surfaces of these ribs are expanded anteriorly but taper posteriorly. Each articular surface bears a deep groove
for articulation with the ilium.

Cauda! vertebrae. The tail of Terrestrisuchus was very long and the number of caudal vertebrae has been
estimated at about seventy. The tail can be split into two regions, 1 and 2, on the basis of the presence or absence
of lateral processes (text-fig. 1 3b-j). These processes consist of ribs sutured to transverse processes. The proximal
vertebrae of region 1 have short, stout centra and the main part of the neural spine is short and square. There is a
small antero-dorsally directed accessory spine developed at the base of the anterior edge of the main neural spine.

a n s

n s

an z

5mm

n s

2 mm

TEXT-i'iG. 13. Terrestrisuchus gracilis gen. et sp. nov. A, reconstruction of sacrum in left lateral view;
B-K, reconstruction of caudal vertebrae, in left lateral view, proximal region 1, medial region 1, distal
region 1, proximal region 2, and medial region 2; g-j, distal region 2, P. 47/21, in right lateral view.

CRUSH: TRIASSIC CROCODILIAN FROM WALES

151

The lateral processes of these vertebrae exceed the length of the centrum and are swept back posteriorly and
slightly dorsally. The centra of the vertebrae of the medial part of region 1 are more laterally compressed than
those of the proximal region. The lateral processes project more directly laterally and are shorter than those on
more anterior vertebrae. The distal vertebrae of region 1 show some change in the shape of the neural spine
which now slopes posteriorly but the accessory spine is still present. The centrum is now more laterally
compressed than those of the medial vertebrae and is relatively shorter. The lateral processes are further
shortened. The more posterior of these vertebrae bear a small boss placed centrally on the lateral surface of the
centrum. The proximal vertebrae of region 2 have centra that are relatively longer than those of the anterior
vertebrae. There is still an accessory spine but the main neural spine is now very low and extended into a point
posteriorly. The only difference in the medial vertebrae of this region is that the neural spine is rounded off
posteriorly. More distally the bones become relatively longer and first lose all trace of neural spines and then
zygapophyses.

Haemal arches. The extent of the haemal arches is uncertain although it is known that they were present
anteriorly but did not continue to the end of the tail. They are basically rods of bone with a dorsal expansion that
is pierced by a foramen. This expansion becomes relatively smaller towards the distal end of the tail. There is no
evidence for the regional differentiation found in the chevrons of the modern crocodile.

Reconstruction and size. As restored Terrestrisuchus has a short trunk, long upright limbs, and a very long tail
(text-fig. 14). The pelvis was held high above the pectoral girdle and both the manus and pes were digitigrade.
The total length has been estimated to lie between 490 and 770 mm. It is not possible to be certain but it seems
most likely that this material represents a small species rather than a collection of juveniles.

TEXT-FIG. 14. Terrestrisuchus gracilis gen. et sp. nov. Reconstruction based upon P. 47/21, 22.

DISCUSSION

Crocodilian affinities. Terrestrisuchus is considered to be a crocodile because of the presence of an
elongated radiale and ulnare, whose structure can be homologized with those bones of the modern
erocodile. Other apomorphic characters for the order Crocodylia, present in this genus, are the
absence of a descending process from squamosal to quadratojugal and the presence of a parallel-
sided quadratojugal. (The quadratojugal of Pseudohesperosuchus is assumed to be specialized.)
Terrestrisuchus has other character states considered by Langston (1973) and Nash (1975) to be
diagnostic of the Crocodylia: external nares terminal in position; some development of a secondary
palate; choanae posterior to the external nares; quadrate inclined and bordered by a long slender
quadratojugal; pterygoids wide with deep wings; advanced crurotarsal joint; femur without a marked
fourth trochanter and no development of a greater trochanter; external surfaces of the dorsal scutes
sculptured.

152

PALAEONTOLOGY, VOLUME 27

A proposed classification of the crocodiles:

Order Crocodylia Gmelin 1788
Suborder Triassolestia nov.

Family Triassolestidae Bonaparte 1970

Genus Triassolestes Reig 1 963

Suborder Sphenosuchia nom transl., ex. infraorder Sphenosuchia, Bonaparte 1971 incertae sedis:
Dihothrosuchus Simmons 1965
Family Saltoposuchidae nov.

Genera Saltoposiichus Huene 1921, Terrestrisuchus gen. et sp. nov.

Family Hemiprotosuchidae nov.

Genus Hemiprotosucims Bonaparte 1969
Family Sphenosuchidae Huene 1922

Genera Pseudohesperosuchus Bonaparte 1969, Sphenosuchus WdiUghion 1915, Hesperosuchus
Colbert 1952

Suborder Protosuchia Mook 1934
Family Protosuchidae Brown 1933

Genera Erythrochampsa Haughton 1924, Notochampsa Broom 1904, Pedeticosaurus Van
Hoepen 1915, Protosuchus Brown 1933, Orthosuchus Nash 1968, Stegomosuchus Huene
1922, Eupneumatosuchiis Crompton and Smith 1980
Family Platyognathidae Simmons 1965

Genus Platyognathus Young 1944
Suborder Hallopoda Marsh 1881
Family Hallopodidae Marsh 1881

Genus Hallopus Marsh 1877
Suborder Mesosuchia Huxley 1875
Suborder Eusuchia Huxley 1875

The order Crocodylia is conventionally split into three suborders: Eusuchia, Mesosuchia, and
Protosuchia. These are retained but an additional suborder is proposed, Triassolestia, for
Triassolestes. This, the suborder Hallopoda, for Hallopus, and the suborder Sphenosuchia are all
included in the Crocodylia. The suborder Triassolestia contains only Triassolestes in its own family,
Triassolestidae. Triassolestes (Reig 1963; Bonaparte 1971o) is very tentatively included in the
Crocodylia because of the presence of elongated carpals but otherwise it differs from the other
crocodiles in having a coracoid without a dorso-ventral or postero-ventral projection and a non-
crocodilian tarsus. In addition to these primitive characters it has some specialized features in that it
has a reduced metatarsal one and the pes is functionally tridactyle. The suborder Sphenosuchia has
been divided into three families: Saltoposuchidae, Hemiprotosuchidae, and Sphenosuchidae. These
are linked by the presence of: a caracoid with a postero-ventral projection, a quadrate conch, and
an ossified sternum (this character state is paralleled in Hallopus). The Hemiprotosuchidae and
Sphenosuchidae, although distinct, are more closely related to each other than either is to the
Saltoposuchidae. They are linked by the following character states: interpterygoid vacuities closed;
frontals entering the supratemporal fenestrae; fused parietals; and scutes square or rectangular. All
of these character states were developed in parallel in the Protosuchia. Terrestrisuchus and
Saltoposuchus are classified together on the basis of the presence of a kidney-shaped squamosal.
Additionally, a comparison of the skull, mandibular, and postcranial remains reveals many
similarities in detail and argues strongly for their close relationship. The animals do differ in certain
skull features sufficiently to separate them generically. For instance, the maxilla of Saltoposuchus
lacks the fossa found in this bone of Terrestrisuchus. The Hemiprotosuchidae is a monotypic family
specialized in that the supraorbital is incorporated into the skull roof (Bonaparte 1969, 1971). The
members of the Sphenosuchidae are linked by the possession of: a reduced squamosal overlapped
postero-laterally by the opisthotic, a longitudinal crest on the parietals, and a depression on the
frontals (the latter two character states have been independently developed in the Protosuchia). The

CRUSH: TRIASSIC CROCODILIAN FROM WALES

153

suborder Protosuchia is split into two families; the Protosuchidae with seven members and the
Platyognathidae that contains only Platyognatlms. The Protosuchia are a group that have many
apomorphic characters: two supraorbital elements; absence of an obturator foramen in the pubis;
entry of the frontals into the supratemporal fenestrae; midline fusion of the parietals (the last two
character states are variable in this suborder and are also found in the Sphenosuchia); dorso-ventrally
expanded eoracoid and ischium; rod-shaped pubis partly or fully exeluded from the acetabulum; the
absenee of an obturator foramen in the pubis; dorsal ribs flanged anteriorly and posteriorly;
metatarsal five without phalanges; ventral scutes present (this character is variable); immovable
basipterygoid artieulations; quadrate and pterygoid fused to the braincase; straight groove on
squamosal for ear flap; rectangular squamosals; square or rectangular scutes; and loss of
interpterygoid vacuities (the last two character states were developed in parallel in the Spheno-
suchia). The members of the Protosuchidae are united by having conieal teeth that are unserrated.
The posterior teeth of Eupneumatosuchus are flattened, however. The teeth of the South American
sphenosuchid genera also lack serrations. The new material, recently described by Crompton
and Smith (1980), of Protosuchiis and Eopneumatosuchus has helped to confirm the close relation-
ships of the Protosuchidae. Eopneumatosuchus itself clearly belongs in the suborder Protosuchia.
Platyognathus (Young 1944; Simmons 1965) has a number of specializations which indicate that

Eusuchia

Mesosuchia

Pseudosuchia

TEXT-FIG. 15. Phylogeny of the Crocodylia.

154

PALAEONTOLOGY, VOLUME 27

it belongs in a family of its own: fused mandibular ramii (Sphenosuchus has developed this character
state in parallel); procoelous vertebrae; teeth with a polygonal transverse section; terminal and
confluent external naries; and anterior mandibular teeth projecting forward (this character state may
also be present in Notochampsa). Although the classification presented here postulates much parallel
evolution in the early crocodiles it is believed to have reduced it to a minimum. It is recognized that
with better information on the less well-known genera the classification would probably alter.

Interrelationships of the suborders. There appears to have been a radiation of the Crocodylia
represented by the Protosuchia, Triassolestia, and Sphenosuchia at the end of the Triassic (text-fig.
15). The upper Jurassic Hallopoda may have had a common ancestry with the Protosuchia as
although Hallopus is specialized (Walker 1970, 1972) in having a functionally tridactyle pes, and a
posteriorly rotated pubis has three characters otherwise only found in the Protosuchia— a dorso-
ventrally expanded ischium and a rod-shaped pubis that is fully excluded from the acetabulum.
These suborders, the Sphenosuchia and the Triassolestia, are proposed to have had a common
pseudosuchian origin. The Sphenosuchia cannot be ancestral to the Protosuchia, as has often been
thought, because of the presence of the quadrate conch and the structure of the coracoid. It is not
considered possible to derive the coracoid of Protosuchus from those of the sphenosuchids.
Furthermore, the secondary palate of the latter, as evidenced by those of Terrestrisuchus and
Sphenosuchus, are not homologous with that of Orthosuchus but are convergent with the type found
in birds (Walker 1972). Sphenosuchus itself is further removed from a protosuchian ancestry by its
functionally tridactyle pes. The supraorbital of Hemiprotosuchus bars it from a protosuchian
ancestry. The specialized structure of Triassolestes means that the Triassolestia cannot be the
ancestral group of the protosuchids. The terrestrial, cursorial, quadrupedal crocodiles represented by
the Hallopoda, Sphenosuchia, and Triassolestia have no known descendants and seem to have been
a relatively short-lived phenomenon. These forms are diverse when they first appear at the
Triassic- Jurassic boundary and by the end of the Jurassic are only represented by one highly
specialized genus, Hallopus. Other terrestrial crocodiles evolved within the Mesosuchia but they
never attained the same degree of cursorial adaptation. The early forms may have been outcompeted
by the coelurosaurs as the latter became more highly adapted for a bipedal, cursorial mode of life. The
Protosuchia diverged ecologically from the Sphenosuchia and adopted a way of life similar to that of
the modern crocodiles.

Origin of the Crocodylia. The thecodonts have long been considered ancestral to the later
archosaurian groups including the crocodiles and thus membership of this order was investigated in
the light of knowledge of the structure of Terrestrisuchus, in an attempt to trace the early crocodilian
suborders back to a common ancestor. The thecodonts were reviewed by Romer (1972) who divided
them into four suborders. The first suborder Proterosuchia contains three families Proterosuchidae,
Erythrosuchidae, and Prestosuchidae which are primitive groups showing no crocodilian affinities.
The fourth family Proterochampsidae has specializations excluding it from a crocodilian ancestry as
do the next two suborders Aetosauria and Phytosauria. The final suborder Pseudosuchia contains
a wide variety of forms some of which have been classified here as crocodiles. Some of the
pseudosuchids are specialized, and some are primitive, but no species gives any indication of the
origin of the crocodiles.

Dihothrosuchus. This animal is poorly preserved and consists only of cranial fragments, a number of
articulated vertebrae, and parts of a forelimb. Simmons (1965) considered it to be similar to
Hesperosuchus which suggested a crocodilian affinity. It is tentatively included in the Sphenosuchia
because of the presence of a postero-ventral projection on the coracoid.

Saltoposuchus. This genus was first described by Huene (1921) who divided it into two species
Saltoposuchus connectens and S. longipes. Study of the material reveals that the remains are of four
individuals of only one species. Within those numbered 12596 and 12597 the individual called S.
longipes is simply a larger specimen of S. connectens. Furthermore, the material attributed to
Procompsognathus, on find number 12597, is also of Saltoposuchus. In these remains there was an

CRUSH: TRIASSIC CROCODILIAN FROM WALES

155

angular, identified by von Huene as a clavicle of S. connectens, from find 12597 which did not form
part of the other two individuals. There are therefore the remains of three animals, all of the species S.
connectens, on the two numbered finds from Heugelschen. The individual identified as S. loiigipes
from Burreschen is also S. connectens. Knowledge of the material of Terrestrisuchus has made
possible some reinterpretations of the material of Saltoposuchus. In find 12596 Huene’s pterygoid is a
left squamosal in dorsal view, his palatine a left quadrate in antero-lateral view, and his metatarsal an
ulna. In find 12597 Huene’s humerus fragment is a left frontal; his clavicle is a left angular in medial
view; the pterygoids are squamosals in ventral view; the prefrontal is a left jugal in lateral view; the
quadratojugal is a left quadrate and the right quadrate is a left quadrate. Walker (1968, 1970) was
correct in assigning this genus to the Crocodylia. He correctly reidentified the ‘lacrymaf as a jugal,
but was mistaken in suggesting that the ischium was a coracoid. He suggested that the pubes belong
to Procompsognathus but this is not the case.

Acknowledgements. It is a pleasure to express my thanks, for his encouragement, to Professor K. A. Kermack, of
University College London, who provided the material for this paper. Also to Mrs. F. Mussett for much useful
advice, to Dr. A. Walker for allowing me to study Sphenosiichus, and to Dr. R. Wild for his hospitality whilst I
was working on Saltoposuchus at the Staatliches Museum fiir Naturkunde, Stuttgart.

Explanation of abbreviations used in text-figs.

a n s

accessory neural spine

e n

external naries

op

opening into cranial

ac r

acromial ridge

f o

fenestra ovalis

cavity

a c

alveolar canal

fp

fenestra pseudorotunda

or

orbit

an

angular

f

hbula

p v

palatal vacuity

an cr

anterior crest

for

foramen

pal

palatine

an e

anterior extension

fm

foramen magnum

pa

parapophysis

an r

anterior ridge

f pe

foramen perilym-

par

parietal

av r

antero-ventral ridge

phaticum

pd

perilymphatic duct

a f

antorbital fenestra

ft

fourth trochanter

pi

pisiform

a p f

anterior palatal foramen

fr

frontal

pr

posterior ridge

an p

anterior process

g

glenoid

pz

posterior zygapophysis

an z

anterior zygapophysis

gr

groove

pv r

postero-ventral ridge

ar

articular

il

ilium

po

postorbital

as

astragalus

itf

infratemporal fenestra

p o b

postorbital bar

bo

basioccipital

i

interclavicle

ptf

post-temporal fenestra

bs

basisphenoid

ifb

interfenestral bar

pa

prearticular

cal

calcaneum

i n

internal naries

Pf

prefrontal

cap

capitellum

i V

interpterygoid vacuity

p m

premaxilla

cp

capitulum

is

ischium

po

prootic

c

coracoid

j

jugal

P

pterygoid

CO

coronoid

1

lacrimal

p rq

pterygoid ramus of

cqp

cranio-quadrate passage

1 c

lateral convexity

the quadrate

d c

deltopectoral crest

Ip

lateral process

pu

pubis

d

dentary

1 r

longitudinal ridge

q

quadrate

dia

diapophysis

m fo

mandibular fossa

qpp

quadrate process of the

d 1-5

digits one to five

m

maxilla

pterygoid

das

distal articular surface

m f

maxillary fossa

qj

quadratojugal

dc 3, 4

distal carpals three and

me c

Meckelian cartilage

ra

radiale

four

m c V

middle cerebral vein

r

radius

dt3,4

distal tarsals three and

m c

medial convexity

ri

ridge

four

m i

muscle insertion

S 1,2

sacral vertebrae one and

e

ectopterygoid

m s

muscle scar

two

ex

exoccipital

n

nasal

sa 1, 2

sacral ribs one and two

e m f

external mandibular

n s

neural spine

sc

scapula

foramen

0

olecranon

scu

sculpturing

156

PALAEONTOLOGY, VOLUME 27

sh

shaft

sp

splenial

troh

trochlea

s

sternum

sq

squamosal

tu

tuberculum

s c p

subcapsular process

t c

temporal canal

t m

tympanic membrane

s t f

subtemporal fenestra

t

tibia

t r

tympanic ridge

sf

supracoracoid foramen

to

tooth

u

ulna

s o

supraoccipital

tp

transverse process

111

ulnare

s fe

supratemporal fenestra

ts 1-6

transverse sections one to

V

vomer

sur

surangular

six

su

suture

tro

trochanter

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HUENE, F. von. 1921 . Neue Pseudosuchier und Coelurosaurier aus dem Wurttembergischen Keuper. Acta Zool.
2, 329-403.

1922. The Triassic reptilian order Thecodontia. Amer. J. Sci. 4 (5), 22-26.

KERMACK, K. A. 1956. An ancestral crocodile from South Wales. Proc. Linn. Soc. 166, 1-2.

LANGSTON, w. 1973. The crocodilian skull in historical perspective. In gans, g. and parsons, c. (eds.). The
biology of the reptilia, 4. Academic Press, New York, 263-284.

NASH, D. 1975. The morphology and relationships of a crocodilian Orthosuchus stormbergi, from the upper
Triassic of Lesotho. Ann. S. Af. Mus. 67 (7), 227-329.

REiG, o. A. 1963. La presencia de dinosaurios saurisquios den los ‘Estratos de Ischigualasto’ (Mesotriasico
superior) de las provincias de San Juan y la Riojo (Republica Argentina). Ameghiniana, 3(1), 3-20.

ROBINSON, p. L. 1957a. The Mesozoic hssures of the Bristol Channel area and their vertebrate fauna. Jl Linn. Soc.
(Zool.) 43, 260-282.

19576. An unusual sauropsid dentition. Ibid. 43, 283-293.

1962. Gliding lizards from the upper Keuper of Great Britain. Proc. Geol. Soc. Land. 1601, 137-146.

1971. The problem of faunal replacement on Permo-Triassic continents. Palaeontology, 14, 131-153.

ROMER, A. s. 1972. The Chanares (Argentinia) Triassic reptile fauna. 16. Thecodont classification. Breviora Mus.
Comp. Zool. 395, 1-24. 395-245.

SIMMONS, D. J. 1965. The non-therapsid reptiles of the Lufeng basin, Yunnan, China. Fieldiana Geol. 15, 1-96.

STEEL, R. 1973. Encyclopedia of Paleoherpetology. Part 16, ed. O. Kuhn, Gustav Fisher Verlag.

WALKER, A. D. 1968. Protosucluis, Proterochampsa and the origin of phytosaurs and crocodiles. Geol. Mag. 105,
1-14.

CRUSH: TRIASSIC CROCODILIAN FROM WALES

157

WALKER, A. D. 1970. A revision of the Jurassic reptile Hallopus victor Marsh with remarks on the classihcation of
the crocodiles. Phil. Tram. 257B. 323-372.

1972. New light on the origin of birds and crocodiles. Nature, Lond., 237, 257-263.

YOUNG, c. c. 1944. On a supposed new pseudosuchian from upper Triassic saurischian-bearing red beds of
Lufeng- Yunnan, China. Am. Miis. Novitate.s, 1264, 1 4.

Typescript received 11 December 1982
Revised typescript received 24 March 1983

P. J. CRUSH

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Sonning Common
Reading, Berkshire

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THE AFFINITIES OF THE
CRETACEOUS AMMONITE NEOSAYNOCERAS
BREISTROFFER, 1947

by w. j. KENNEDY and c. w. wright

Abstract. The cryptic micromorph ammonite Neosayrioceras BreistrofFer, 1947 is redescribed and shown to be
a Cenomanian offshoot of Salaziceras Breistroffer, 1936 of the Flickiidae. Salaziceras and Neosaynoceras are
separated from the remaining Flickiidae as Salaziceratinae subfam. nov.

The Albian-Cenomanian marls of Algeria and Tunisia, Madagascar and Tanzania, and Texas and
northern Mexico are well known for their rich faunas of diminutive pyritic ammonites (Pervinquiere
1907, 1910; Collignon 1928-1929, 1931, 1964; Bose 1928; Adkins 1928; Young 1979). Some of these
are no more than nuclei of larger species, but others are genuinely diminutive, frequently
paedomorphic taxa, unknown for reasons of preservational potential or environmental preferences
in other facies (Kennedy and Hancock 1971; Kennedy and Wright 1981). The affinities of genera and
subgenera Euhystrichoceras Spath, 1933, Prionocycloides Spath, 1925, and Sakondryella Collignon,
1964, among these dwarfs, with the Mortoniceratinae were demonstrated by Kennedy and Wright
(1981), and the origins of the Flickiidae in Lyelliceratidae by Wright and Kennedy (1979). We deal
here with the diminutive and highly distinctive genus Neosaynoceras Breistroffer, 1947 (p. 76), type
species Saynoceras gazellae Pervinquiere, 1907 (p. 1 1 5, pi. 5, figs. 1-6), which is known only from the
lower Cenomanian of Algeria, Tunisia, and Madagascar. The largest known specimens are less than
1 5 mm in diameter and show modification of ornament suggestive of maturity (crowded sutures, and
excentric coiling). When introducing S. gazellae in 1907, Pervinquiere placed it between Holcodiscus
Uhlig, 1882 and Parkinson, 1811 and regarded it as a perisphinctid; Roman ( 1938, p. 391 )

concurred with this assignation, but Breistroffer (1947, p. 76) regarded it as a degenerate
acanthoceratid. In the Treatise Wright (1957, p. 414), following Breistroffer, assigned it to the
Acanthoceratinae without comment. It is argued below that Neosaynoceras is a Cenomanian
offshoot of Salaziceras Breistroffer, 1947 of the Flickiidae.

SYSTEMATIC PALAEONTOLOGY

Repositories of specimens. The following abbreviations are used to indicate the repositories of specimens cited:
GPIT— Geologisches und Palaontologisches Institut, Tubingen; OUM— University Museum, Oxford; SP—
Collections of the Sorbonne, now in the Universite Pierre et Marie Curie, Paris. The Collignon Collection is now
housed in the Universite de Dijon.

Family flickiidae Adkins, 1928
Genus Neosaynoceras Breistroffer, 1947

Type species. Saynoceras gazellae Pervinquiere, 1907 p. 115, pi. 5, figs. 1-6, by the original designation of
Breistroffer (1947, p. 76).

Diagnosis. Small; largest known specimens less than 15 mm diameter. Phragmocone a globose
cadicone, smooth or with faint radial folds and shallow furrows at first which develop into primary
ribs with bullate inner and outer ventrolateral tubercles linked across the venter by riblets or striae.

{Palaeontology, Vol. 27, Part I, 1984, pp. 159-167, pi. 21.]

160

PALAEONTOLOGY, VOLUME 27

The outer ventrolateral tubercles are opposite or alternate on the venter, more commonly the latter.
Body chambers are strongly ribbed and tuberculate and markedly scaphitoid with the inner edge
occluding part of the umbilicus; tubercles become spinate and the shell resembles a Horse Chestnut
(Aesculus) seed case. The suture line is simple with rounded terminations to the constituent elements
of lobes and saddles; E/L is narrow and asymmetrically bifid, L broad with few incisions, L/U2 small
and little subdivided.

Discussion. Few genera resemble Neosaynoceras, and this is a major factor in the difficulty
experienced in deciding its affinities. The most obvious comparison is with the Scaphitaceae,
especially given the obviously scaphitoid coiling of the body chamber of some specimens (PI. 21, figs.
1, 4, 20) and the looping of ribs between outer ventrolateral tubercles (PI. 21, figs. 3, 12), a style of
ornament shown by several Scaphites (e.g. Wiedmann 1965, pi. 57, figs. 1-7) of essentially the same
date. The test of scaphitid affinities lies in the suture line. Scaphitids have quadrilobate early sutures,
after a quinquilobate primary suture (see Doguzhaeva and Mikhailova 1982) and also ‘pseudolobes’
in the saddle L/U, resulting from the widening of this saddle and the deepening of its central lobule
(Wiedmann 1965; Kullman and Wiedmann 1970). Unfortunately the preservation of the Madagascar
material of Neosaynoceras gazellae available to us has not allowed the exposure of the early sutures.
The mature suture lines, however, show no trace of development of ‘pseudolobes’, which are manifest
in contemporary Scaphitaceae. Consequently we dismiss the idea of affinities with this group, despite
the scaphitoid body chambers.

Affinity with the Acanthoceratidae is suggested because these are the only contemporary group in
which strong ventrolateral tuberculation commonly develops, as in lower Cenomanian genera
Mantelliceras Hyatt, 1903, Sharpeiceras Hyatt, 1903, and Graysonites Young, 1958 of the
Mantelliceratinae, or Acompsoceras Hyatt, 1903 of the Acanthoceratinae. Study of the early
development of these taxa shows that their early ontogeny (well shown in similarly sized specimens
figured by Pervinquiere 1907, 1910 and Collignon 1928-1929, 1931) involves early acquisition of
umbilical, inner, and outer ventrolateral tubercles, plus in some lateral or even siphonal tubercles
(e.g. Acompsoceras), and ribs at a stage where Neosaynoceras is almost smooth. These early
Cenomanian acanthoceratids also lack constrictions or furrows and looping of ribs between ventral
tubercles.

The closest analogues to Neosaynoeeras lie in the late Albian Salaziceras Breistroffer, 1936 (p. 64,
type species Ammonites salazacensis Hebert and Munier-Chalmas, 1875, p. 1 14, pi. 5, fig. 6). Scholz
(1979) illustrates the ontogeny of the genus in detail and, although the taxonomic treatment may be
questioned, specimens named Salaziceras salazacense peyrolasense Scholz, 1979 (p. 93, pi. 21, figs. 16,
18-20; text-figs. 25, 26b, 27c-g, k, n-q) have nuclei with furrows and folds like those of
Neosaynoceras nuclei (e.g. Scholz 1979, pi. 21, figs. 18-20), while specimens described as Salaziceras
breistrofferi pseudonodosa Scholz, 1979 (p. 96, pi. 21, figs. 23, 24, 26; text-fig. 27r) develop a single
ventral tubercle linked across the venter by a looped rib (text-fig. 1o-q). Scholz also introduced
a subgenus Salaziceras {Noskytes) Scholz, 1979, type species S. (TV.) bakonyense Scholz, 1979 (p. 97,
pi. 22, figs. 1-5; text-figs. 27s, 28) for species with a transient juvenile stage with siphonal tubercles
and an adult body chamber with strong ventral tubercles linked across the venter by looped ribs (text-
fig. 1g-h, k-n, r-s), the adult aperture developing a remarkable constriction and ventral rostrum
(text-fig. 1h, l, m). Examination of casts of the types of S. {N.) bakonyense throws doubt on the
existence of a true siphonal tubercle. In one paratype it is displaced from the siphonal line, while in the
other it is visible on a few ribs only and is likely to be a malformation.

It also appears possible that Noskytes, which has a highly specialized aperture, is the microconch of
Salaziceras. In any case, the common morphological features of these tuberculate upper Albian
Salaziceras and lower Cenomanian Neosaynoceras suggest close affinity, and that Neosaynoceras is
a descendant of Salaziceras in which the single ventrolateral tubercle of S. breistrofferi pseudonodosa
and of "Noskytes' body chambers has been replaced by inner and outer ventrolateral tubercles. The
suture lines of both genera are simplified, but this is no strong indicator of affinity, rather reflecting
their small size.

TEXT-FIG. 1. A-D, Metascaphites thomasi (Pervinquiere, 1907), holotype, the original of Pervinquiere 1907, pi. 4,
figs. 30, 31, from Djebel Mrhila, Tunisia. Sorbonne Collections, now in the Universite Pierre et Marie Curie,
Paris. E~F, M. thomasi (Pervinquiere, 1907), GPIT 1486/243, the original of Scholz 1979, pi. 22, fig. 6. g-h, k-n,
R-s, Salaziceras {'Noshytes') bakonyense Scholz, 1979. G-H, GPIT 1426/240, a paratype, the original of Scholz
1979, pi. 22, fig. 3; k-m,’GPIT 1486/238, a paratype, the original of Scholz 1979, pi. 22, fig. I; n, GPIT 1486/241,
inner whorls of the holotype, the original of Scholz 1979, pi. 22, fig. 4; r-s, GPIT 1486/242, a paratype, the
original of Scholz 1979, pi. 22, fig. 5. i-J, T-u, S. (Salaziceras) hreistrajferi hreistrofferi Scho\z, 1979. i-j, GPIT
1486/237, a paratype, the original of Scholz 1979, pi. 21, fig. 28; t-u, GPIT 1486/236, the original of Scholz 1979,
pi. 21, fig. 27. o-Q, S. (S.) hreistrofferi pseudonodosa Scholz, 1979, GPIT 1486/235, a paratype, the original of
Scholz 1979, pi. 21, fig. 26. The originals of e-u are from the upper Albian of the Bakony Mountains, Hungary.

All figures are x 2.

162

PALAEONTOLOGY, VOLUME 27

10mm

TEXT-FIG. 2. Suture lines and whorl sections, a-b, Metascaphites subthomasi
Wiedinann, 1962, GPIT Ce 1162/76, holotype, the original of Wiedmann 1962,
pi. 13, tig. 8, text-figs. 57, 58, from the upper Albian of Izurdiaga, Navarra, Spain,
c, Scaphites {Scaphites) peroni var. inornata Pervinquiere, 1910, the original of
Pervinquiere 1910, pi. 2, fig. 15, from Berrouaghia, Algeria. Sorbonne Collections,
now in the Universite Pierre et Marie Curie, Paris, d, e, M. thomasi (Pervinquiere,
1907), holotype, the original of Pervinquiere 1907, pi. 4, figs. 30, 31, from Djebel
Mrhila, Tunisia. Repository as for c. f-t, Neosaynoceras gazellae (Pervinquiere,
1907). F, the lectotype, the original of Pervinquiere 1907, pi. 5, fig. 2, from Pont du
Fahs, Tunisia; G, t, the original of Pervinquiere 1907, pi. 5, fig. 4; h, the original of
fig. 6, both from Guern er Rhezal, Tunisia. Repository as for c. i, OUM KX1604;
j, OUM KXI614; k, OUM KXI61I; l, p, q, OUM KX1609; m, OUM KX1606;
N, R, OUM KX1610; o, OUM KX1607; s, OUM KX1613. All specimens from the
lower Cenomanian of Beraketa-sur-Sakondry (Manera), Madagascar.

KENNEDY AND WRIGHT: CRETACEOUS NEOSAYNOCERAS

163

A further diminutive taxon with ventral tubercles is Metascaphites Wiedmann, 1962 (p. 212),
proposed as a subgenus of Scaphites, with Scaphitesl thomasi Pervinquiere, 1907 (p. 121, pi. 4, figs.
30, 3 1 ; text-fig. 39) as type species. The holotype by monotypy, and a specimen from the upper Albian
of Hungary, are shown in text-fig. 1a-f. When introducing this genus, Wiedmann also included
a second species Metascaphites suhthomasiW\tdmann, 1962 (p. 218, pi. 13, fig. 8; text-figs. 57, 58) for
a fragment of only three camerae from the mid-upper Albian of Irzudiaga, Navarra, Spain. M.
subthomasi has a basically quadrilobate suture with well-developed ‘pseudolobe’ (text-fig. 2a) and is
a scaphitid. In contrast, M. thomasi shows only a part of the external suture (text-fig. 2d, e), which
complements that of the other known specimen (text-fig. 3d) from Hungary. These closely recall the
sutures of Salaziceras (Salaziceras) and S. {Noskytes), and indeed Scholz included M. subthomasi in
Noskytes. This is nomenclatorially irregular, and those who believe Noskytes noskensis and M.
thomasi to be congeneric must use the latter generic name, which has priority. The Spanish M.
subthomasi is a Scaphites allied to Scaphites peroni Pervinquiere, 1910 (p. 26, pi. 2, figs. 10-16),
especially the variety inornata which has a similar whorl section and suture. Irrespective of the
relationship between Noskytes and Metascaphites, the latter is easily separated from Neosaynoceras
by its possession of only one row of ventrolateral tubercles.

Occurrence. Lower Cenomanian of Algeria, Tunisia, and Madagascar.

TEXT-FIG. 3. Sutures, a, Salaziceras (Salaziceras) salazacen.se (Hebert
and Munier-Chalmers, 1875) at a whorl height of 8-7 mm. b, c, S.
kNoskyte.s') hakonyen.se Scholz, 1979. B at a whorl height of 5-5 mm;
c at 2 mm. d, Metascaphites thomasi (Pervinquiere, 1907) at a whorl
height of 8 mm. a-d are copies of Scholz (1979, text-figs. 27b, sb, sa, r).

164

PALAEONTOLOGY, VOLUME 27

Neosaynoceras gazellae (Pervinquiere, 1907)

Plate 21, figs. 1-22; text-fig. 2f-t

1907 Saynoceras gazellae Pervinquiere, p. 115, pi. 5, figs. 1-6.

1925 Saynoceras gazellae Pervinquiere; Diener, p. 96.

193 1 Saynoceras gazellae Pervinquiere; Collignon, p. 77 (37).

1938 Saynoceras gazellae Pervinquiere; Roman, p. 391.

1947 Neosaynoceras gazellae (Pervinquiere); Breistroffer, p. 92 (76).

1947 Neosaynoceras gazellae (Pervinquiere) var. globosa Breistroffer, p. 92 (76).

1957 Neosaynoceras gazellae (Pervinquiere); Wright, p. L414, fig. 534: la, h.

1964 Neosaynoceras gazellae (Pervinquiere); Collignon, p. 26, pi. 323, figs. 1430-1432.

Types. Pervinquiere (1907, p. 115) based this species on eight specimens, of which three were figured. We have
traced four of these in the Collections of the Sorbonne, Paris (now housed in the Universite Pierre et Marie Curie,
Paris), including the lectotype designated by Breistroffer (1947, p. 76) (the original of Pervinquiere 1907, pi. 5,
figs. 2a, h, 3) and the holotype of var. globosa Breistrolfer (1947, p. 76) (the original of Pervinquiere 1907, pi. 5,
figs. 4a-c, 5a, b) from the lower Cenomanian of Pont du Fahs and Guern er Rhezal, Tunisia.

Other specimens studied. More than a hundred specimens from the lower Cenomanian of Beraketa-sur-
Sakondry, Madagascar, including the originals of Collignon (1964, pi. 323, figs. 1430-1432).

Description. The smallest specimens we have seen are 4-5 mm in diameter. At this size, the shell is a globose
cadicone, with a deep conical umbilicus and very depressed whorls, the whorl breadth to height ratio ranging
from 1 -56 to 1 -73. The umbilical wall slopes outwards, with a rounded shoulder and very broad, rounded venter.
Moulds are either smooth or bear low radial folds from a diameter of 3-4 mm onwards; these are stronger on the
flank, but weaken and may disappear on the venter. Some specimens also bear occasional shallow transverse
furrows or constrictions. As size increases, the lateral folds strengthen progressively, and develop into distinct
ribs (PI. 21, figs. 15, 17) of which there may be up to sixteen per whorl in the largest specimens, although there is
wide variation (PI. 2 1 ). As the ribs strengthen, inner and outer ventrolateral tubercles develop, elongated parallel
to the ribs and generally blunt. There is again wide variation in the relative development of both tubercles and
ribs. In general, the outer ventrolateral tubercles are slightly offset and linked across the venter by low riblets or
striae (PI. 21, figs. 3, 12), which either loop or occasionally zigzag between them.

Few specimens have any part of the adult body chamber preserved but, of those that do, most show sutural
crowding at a phragmocone diameter of 7-9 mm, with a single Madagascar example septate at 14 mm diameter.
At this diameter, ribs are well developed for the preceding whorl and tubercles for the preceding quarter of
a whorl (generally from 6 to 7 mm onwards) (PI. 21, figs. 14, 18). The whorl section remains depressed at the end
of the phragmocone with a whorl breadth to height ratio of 1-47 to 1-89, but it becomes markedly polygonal in
costal section as a result of the development of ribs and tubercles (PI. 21, figs. 2, 16).

Body chambers have been seen to extend for up to two-thirds of a whorl, but none is complete. Coiling
becomes markedly scaphitoid (PI. 21, figs. 1, 4, 20) with the umbilicus partly occluded; the body chambers have

EXPLANATION OF PLATE 21

Figs. 1-22. Neosaynoceras gazellae (Pervinquiere, 1907). 1-3, lectotype, the original of Pervinquiere 1907, pi. 5,
figs. 2, 3; 4, 5, paralectotype, the original of Pervinquiere 1907, pi. 5, fig. 1; 6-8, paralectotype, the original of
Pervinquiere 1907, pi. 5, figs. 4, 5; 9-1 1, paralectotype, the original of Pervinquiere 1907, pi. 5, fig. 6. 1-3, from
Pont du Fahs, Tunisia; 4-11, from Guern er Rhezal, Tunisia. All specimens are from the Sorbonne
Collections, now in the Universite Pierre et Marie Curie, Paris. 12, 13, OUM KX1608; 14-16, the original of
Collignon 1964, pi. 323, fig. 1430; 17-19, the original of Collignon 1964, pi. 323, fig. 1431; 20-22, the original
of Collignon 1964, pi. 323, fig. 1432. 12-22, from Beraketa-sur-Sakondry (Manera), Madagascar.

Figs. 23, 24. Scaphites (Scaphites) peroni var. inornata Pervinquiere, 1910, the original of Pervinquiere 1910,
pi. 2, fig. 15, from Berrouaghia, Algeria. Repository as for figs. 1-11.

All figures x 3. Arrows indicate where septation ceases.

PLATE 21

KENNEDY and WRIGHT, Neosaynoceras and Scaphites

166

PALAEONTOLOGY, VOLUME 27

flattened sides; the section remains depressed (whorl breadth to height ratio up to 1-8) and polygonal. Tubercles
strengthen into finger-like spines (PI. 21, fig. 2), ventral and ventrolateral ribbing declines, and the mould
resembles a miniature Horse Chestnut seed case.

Typical suture lines are shown in text-fig. 2f-p. Although there is variation in detail, E is broad with a large
median element, and E/L broad and asymmetrically bifid with a large incision adjacent to L. L is broad and
shallow with more or less uniform simple lobules, and L/U smaller, simple, and bifid. The preservation precludes
development of I, but septal faces (PI. 21, fig. 16) show it to have been narrow.

Discussion. The generic discussion outlines features which differentiate N. gazellae from the most
closely comparable species of Salaziceras, Nosky tes, and Metascaphites. Separation of inflated forms
as var. glohosa Breistrofler, 1947 is unnecessary. Saynoceras boulei Collignon, 1931 (p. 76 (36), pi. 7
(3), fig. 22) is probably not a species of Neosaynoceras. It differs from N. gazellae in having relatively
well-developed umbilical tubercles which give rise to single or paired ribs with conical inner
ventrolateral tubercles, three times as numerous as the umbilical and feeble outer ventrolateral
tubercles that disappear on the body chamber, with occasional siphonal tubercles on a siphonal
ridge. These all suggest that it is an acanthoceratine, perhaps allied to some species of
Protacanthoceras, e.g. P. arkelli Wright and Kennedy, 1980 (figs. 24-26) or P. proteus Wright and
Kennedy, 1980 (figs. 50, 52).

Occurrence. Lower Cenomanian pelagic marl facies of Algeria, Tunisia, and Madagascar.

DISCUSSION

Wright and Kennedy (1979) included Salaziceras in Flickiidae, since there was good evidence of
a phyletic line from Salaziceras to Ficheuria and thence to the rest of the family, and since Salaziceras
was already a dwarf form with simplifying suture line. Scholz’s (1979) demonstration of the
morphological range within Salaziceras and the present linking of Neosaynoceras to Salaziceras
shows that within Flickiidae there were two trends: one to forms with smooth shells and simple
sutures, the other to strongly ornamented forms with tuberculate venters and more normal sutures. It
is reasonable to distinguish these as subfamilies and we therefore group Salaziceras (including
Nosky tes and Metascaphites) and Neosaynoceras in Salaziceratinae subfam. nov., distinguished by
strong ornament and normally frilled sutures, leaving Ficheuria, Flickia, and Adkinsia in Flickiinae
sensu stricto.

Acknowledgements. We thank Dr. D. Pajaud of the Universite Pierre et Marie Curie, Paris, for allowing us access
to the Pervinquiere Collection, and the late General M. Collignon of Moirans, Isere, for the loan of his collection
of Madagascar Neosaynoceras. The technical assistance of the staff of the Geological Collections, University
Museum, Oxford, is gratefully acknowledged, as is the financial assistance of the Natural Environment Research
Council and Wolfson College, Oxford.

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PERViNQUiERE, L. 1 907. Etudes de paleontologie tunisienne. 1 , Cephalopodes des terrains secondaires du systeme
cretacique. MOn. Carte geol. Tunisie, 428 pp., 27 pis.

1910. Sur quelques ammonites du Cretace algerien. Man. Soc. geol. Fr. 42, 86 pp., 7 pis.

ROMAN, F. 1938. Les Ammonites Jurassiques et Cretaces. Masson, Paris, 554 pp., 53 pis.

SCHOLZ, G. 1979. Die Ammoniten des Vracon (Oberalb, dispar-Zone) des Bakony-Gebirges (Westungarn) und
eine Revision der wichtigsten Vracon-Arten der West-Mediterranen Faunenprovinz. Pakieontographica,
165A, 1-135, pis. 1-30.

SPATH, L. F. 1925. On Upper Albian Ammonoidea from Portuguese East Africa. With an appendix on Upper
Cretaceous Ammonites from Maputoland. Ann. Transv. Mas. 11, 179-200, pis. 28-37.

1933. A Monograph of the Ammonoidea of the Gault. Part 10. Palaeontogr. Soc. [Monogr.], 411-442,

pis. 43-48.

UHLiG, V. 1882. Ueber einige mit Mundsaum versehene Ammoniten. Jb. K.-K. geol. Reiclisanst., Wien, 32,
393-395.

WIEDMANN, J. 1962. Ammoniten aus der vascogotischen Kreide (Nordspanien). 1, Phylloceratina, Lytoceratina.
Palaeontographica, 118A, 1 19-237, pis. 8-14.

1965. Origin, limits and systematic position of Scaphites. Palaeontology, 8, 397-453, pis. 53-60.

WRIGHT, c. w. 1957. In moore, r. c. (ed.). Treatise on invertebrate paleontology. Part L, Mollusca 4, Cephalopoda
Ammonoidea. Geological Society of America and University of Kansas Press, New York and Lawrence,
xxii + 490 pp.

and KENNEDY, w. J. 1979. Origin and evolution of the Cretaceous micromorph ammonite family Flickiidae.

Palaeontology, 22, 685-704, pis. 87-89.

1980. Origin, evolution and systematics of the dwarf acanthoceratid Protacanthoceras Spath, 1923

(Cretaceous Ammonoidea). Bull. Br. Mas. nat. Hist. Geol. 34, 65-107.

YOUNG, K. 1958. Graysonites, a Cretaceous ammonite in Texas. J. Paleont. 32, 171-182, pis. 27-29.

1 979. Lower Cenomanian and late Albian (Cretaceous) ammonites, especially Lyelliceratidae, of Texas and

Mexico. Bull. Texas Meml Mus. 26, 99 pp., 9 pis.

W. J. KENNEDY
C. W. WRIGHT
Geological Collections
University Museum, Oxford 0X1 3PW

Typescript received 19 January 1983

Revised typescript received 4 May 1983 Wolfson College, Oxford 0X1 3PR

n

I

is

A NEW SUBFAMILY OF THE
PTERASPIDIDAE (AGNATHA, HETEROSTRACI)
FROM THE UPPER SILURIAN AND
LOWER DEVONIAN OF ARCTIC CANADA

by D. K. ELLIOTT

Abstract. New Pteraspididae from the upper Silurian and lower Devonian of arctic Canada dilfer from
established members of the family in possessing a single orbito-cornual plate and a pineal plate enclosed by the
dorsal disc. A new subfamily of the Pteraspididae, the Anchipteraspidinae, is raised to accommodate hve species
of the new genera Anchipteraspis, Ulutitaspis, and Rhachiaspis. Consideration of the growth and structure of
the shields of the Anchipteraspidinae indicates their close relationship to both the Cyathaspidinae and early
members of the Pteraspidinae. It is proposed that the Pteraspididae were developed from the Cyathaspidinae
by processes both of fusion and subdivision of the shield and that the Psammosteida developed from the
Pteraspidinae by similar processes.

Large numbers of heterostracans have been collected from Silurian and Devonian strata in the
Yukon, British Columbia, and Northwest Territories and in recent years much of this material has
been described (Denison 1963, 1964; Dineley 1964, 1968, 1976; Broad 1973; Broad and Dineley 1973;
Dineley and Loeffler 1976; Loeffler and Jones 1976, 1977; Elliott 1983; Elliott and Dineley 1983).
These descriptions have provided valuable information on the evolution of the Heterostraci, and
indicate that the Canadian arctic was probably a centre of early development and radiation for this
group. Evidence from these faunal descriptions indicates that anaspids, thelodonts, cyathaspidids,
and amphiaspids probably developed earlier there than elsewhere (Thorsteinsson 1967; Broad 1973),
and more recent work (Elliott and Dineley 1983) has recorded the earliest known occurrence of
Protopteraspis suggesting that pteraspidinids also evolved initially in this area. Eurther evidence for
this view is provided in this work in which three new genera and five new species of heterostracans are
described. These new genera are grouped as a new subfamily of the Pteraspididae and provide a link
between that family and the Cyathaspididae, indicating an evolutionary connection.

The fauna is Upper Silurian and Lower Devonian in age and comes from the Peel Sound and
Somerset Island Formations of Prince of Wales and Somerset Islands, Northwest Territories.
Collections were made by the author in 1976 and by Bristol and Ottawa University parties in 1966,
1967, and 1974.

MATERIALS AND METHODS

The specimens described were preserved in slightly calcareous sandstones or calcareous siltstones.
Both matrices allowed preparation by the transfer method of Toombs and Rixon (1950) in which the
specimens were embedded in clear plastic and the matrix then removed with a dilute solution of acetic
acid. This process enables the lateral line sensory canal system to be traced when the shields are
viewed by transmitted light.

The measurements and ratios employed (Table 1 ) follow very closely those used by Denison (1964)
when describing cyathaspidids, except that the post-branchial length was not employed due to the
difficulty of deciding the precise position of the branchial opening in pteraspidids. The specimens are
the property of the National Museum of Canada, Ottawa, and bear their catalogue numbers
(prefixed NMC).

[Palaeontology, Vol. 27, Part 1, pp. 169-197, pis. 22-24.)

170

PALAEONTOLOGY, VOLUME 27

TABLE 1 . Statistical comparison of dorsal shields of members of the Anchipteraspidinae.
(Parameters selected for measurement are those used by Denison 1964.)

Dimensions (mm)

Ratios

Med. length

Max. width

Orb. width

Orb. length

Pineal length

Max. width
Med. length

Orb. width
Med. length

Orb. length
Med. length

Pineal length
Med. length

Anchipteraspis crenulata

Range 260-28-5

200-23 0

9-5-I0-5

30-3-5

4-5-5-0

0-78-0-81

0-35-0-39

0-11-0-14

015-019

Average 26-8

21-2

10-0

3-2

4-8

0-79

0-37

0-12

0-17

N= 4

4

4

4

4

4

4

4

4

Ulutitaspis notidana

Range 32-5-35 0

22-0-23 0

I20-13-5

40-5-5

6-5-7-5

0-63-0-71

0-34-0-40

0-12-0-15

019-0-21

Average 33-5

22-3

12-6

4-8

7-0

0-67

0-37

014

0-20

N= 4

6

6

6

5

4

4

4

4

Ulutitaspis truncata

Range 20 0-2T5

18-5-190

9-5-10-5

30-40

4-5-6-5

0-93-0-97

0-45-0-53

0-1 5-0-20

0-23-0-32

Average 20- 1

18-8

9-7

3-3

51

0-95

0-48

0-17

0-26

N= 4

4

4

4

4

4

4

4

4

Ulutitaspis aquilonia

Range 25-5-290

21 ■5-240

11-5-130

30-4-5

40-6-5

0-80-0-84

0-42-0-45

011-0-15

0- 19-0-22

Average 28-6

23-3

12-3

4-4

6-0

0-82

0-43

0-14

0-20

N= 4

4

4

4

4

4

4

4

4

Rhachiaspis pteriga

Range 32-5-340

25-0-270

110-12.5

4-0-4-5

60-6-5

0-74-0-82

0-32-0-39

0-12-0-14

019-0-20

Average 32-6

25-6

116

41

6-2

0-78

0-35

0-13

019

N= 4

4

4

4

4

4

4

4

4

STRATIGRAPHY

The heterostracans described here were collected from the lower member of the Peel Sound
Formation on Prince of Wales Island and the Somerset Island Formation on Somerset Island
(text-fig. 1).

Rocks of the Peel Sound Formation occur over much of Prince of Wales Island and in gentle
synclines in the Cape Anne-Pressure Point and Creswell Bay areas of Somerset Island. Originally
named by Thorsteinsson and Tozer {in Fortier et at. 1963) the formation consists of red sandstones
and siltstones, grading upwards into oligomict conglomerates and pebbly sandstones, deposited over
a large delta system as subaerial alluvial fans prograding from the rising Boothia Uplift. On Prince
of Wales Island, Miall (1970) separated the formation into lower and upper members. The lower,
consisting of interbedded limestone, siltstone, sandstone, and oligomict conglomerate, is exposed
only as a narrow band along the flank of the Boothia Uplift and has yielded large numbers of
ostracoderms (Broad 1973; Broad and Dineley 1973; Loeffler and Dineley 1976; Elliott and Dineley
1983). The upper member is characterized by the disappearance of virtually all but conglomerate in
the succession (Miall 1970). The Transition Bay localities on Prince of Wales Island all occur in the
lower member of the Peel Sound Formation. This member is transitional between the marine Read
Bay Formation and the upper member of the Peel Sound Formation.

On Somerset Island the localities occur in the Somerset Island Formation (Miall et at. 1978) which
has been erected to include the transition beds between the Peel Sound sandstones and conglomerates
and the underlying Read Bay limestones. It comprises a lower member eonsisting of grey and mottled
planar-bedded limestones, and an upper member consisting of interbedded grey laminated dolostone
and limestone, red quartzose siltstone, red dolosiltstone, and minor nodular limestone. The original

ELLIOTT: PTERASPIDS FROM ARCTIC CANADA

171

Read Bay-Peel Sound contact, defined (Thorsteinsson and Tozer 1963) at the occurrence of the
oldest red siltstone unit, has been retained as the boundary between the two members of the Somerset
Island Formation. The formation was deposited in predominantly intertidal and supratidal
environments as the lowest part of a regressive sequence culminating in the conglomerate of the Peel
Sound Formation. This unit is considered to be an age equivalent to the lower member of the Peel
Sound Formation on Prince of Wales Island (Miall et al. 1978), both units representing the
lowermost beds of a prograding clastic wedge, though separated by the Boothia Uplift and showing
differences in lithology.

LOCALITIES

Prince of Wales Island

Locality 1. 96° 32' W. 72° 11' N. Gorge 26-4 km north of Transition Bay. 15 m above base of Peel Sound
Formation. Grey, medium-grained sandstone grading up into poorly sorted conglomerate. Fauna: Torpedaspis
elongata\ Corvaspis; ITraquairaspis sp.; cyathaspidids indet.; Ulutitaspis notidana gen. et sp. nov.

‘Unnamed gorge’ of Broad ( 1973); Broad and Dineley (1973). 22-5 km north ofTransition Bay. 96° 28' W. 72°
10' N.

Locality 2. North side of gorge, 10-5 m above top of Read Bay Formation. Medium-grained grey sandstone with
quartz clasts at base. Heterostracans concentrated at base where shields are stacked and current aligned.

TEXT-FIG. I. Collecting localities and geology of Prince of Wales and Somerset Islands and Boothia Peninsula.

172

PALAEONTOLOGY, VOLUME 27

(Locality 7 of Broad (1973); Broad and Dineley (1973); G.S.C. locality C-10045.) Fauna: Boothiaspis alata; B.
angus1a\ B. ovata; Torpedaspis elongala; Poraspis cf. P. polaris; Corvaspis sp.; 1 Traquairaspis sp.; Ulutitaspis
tnmcata gen. et sp. nov.

Locality 3. North side of gorge, 95-6 m above top of Read Bay Formation. 1 m thick medium to fine-grained
sandstone, red at base and showing desiccation cracks. Fish occur throughout. (Locality 7 of Broad (1973);
Broad and Dineley (1973); G.S.C. locality C- 10046.) Fauna: Torpedaspis elongata-, Boothiaspis sp.; Corvaspis sp.;
ITraquairaspis sp.; cyathaspidids indet.; acanthodian spines; Ulutitaspis notidana gen. et sp. nov.

Locality 4. North side of gorge. 60-3 m above top of Read Bay Formation (Broad, pers. comm. 1977). Probably
equivalent to locality 3. 7 m of grey-green, fine-grained sandstone with dolomitic matrix. All ostracoderm
material is black. Fauna: Lingula sp.; Poraspid cf. P. polaris; Corvaspis cf. C. kingi; ? Traquairaspis sp.;
Ulutitaspis sp., gen. nov.

Locality 5. South side of gorge. 80-7 m above top of Read Bay Formation. 1-3 m of red medium-grained, finely
laminated sandstone. Matrix dolomitic and calcareous. Fauna: Corvaspis cf. C. kingi; ITraquairaspis sp.;
Ulutitaspis notidana gen. et sp. nov. {Listraspis sp. in Broad (1973); Broad and Dineley (1973)).

Somerset Island

Locality 6. 93° 45' W. 72° 52' N. Kanguk Gorge, 8 km north of Creswell Bay. Upper member of Somerset Island
Formation. Fauna: Corvaspis sp.; ITraquairaspis sp.; Rhachiaspis pteriga gen. et sp. nov.

Locality 7. 95° 17' W. 73° 58' N. Cliffs on the north-east side of Pressure Point. Locality approximately 45 m
below the top of the lower member of the Somerset Island Formation. (Locality 5 (part) of Broad (1973); Broad
and Dineley (1973); G.S.C. locality C-10049.) Fauna: Torpedaspis elongata; Boothiaspis ovata; Pionaspis
acuticosta; ? Traquairaspis sp.; Acanthodii indet.; Ulutitaspis notidana gen. et sp. nov.; Rhachiaspis pteriga gen. et
sp. nov.

Locality 8. 95° 14' W. 73° 59' N. Stream valley 1 -6 km east of Pressure Point. 15-2-3 1-4 m above the base of the
upper member of the Somerset Island Formation (Gibling pers. comm. 1977). Grey, white, and buff, coarse to
fine-grained, crossbedded sandstone. (Locality A of Dineley ( 1 968); locality 5 (part) of Broad ( 1 973), Broad and
Dineley (1973); Corvaspis locality of Dineley and Loeffler (1976); G.S.C. locality C-10050.) Fauna: Torpedaspis
elongata; Boothiaspis alata; Corvaspis arctica; Hemicyclaspis murchisoni; ? Traquairaspis sp.; Acanthodii indet.;
Ulutitaspis aquilonia gen. et sp. nov.

Locality 9. 95° 14' W. 73° 57' N. Small bluff on the north-east side of the stream draining the north side of the coll
4 km south-east of Pressure Point. Reported (Broad and Dineley 1973) as being 260' above the base of the Peel
Sound Formation. Remapping by Miall (Miall and Kerr 1977) places this locality in member 1 or 2 of the
redefined Peel Sound Formation. Slightly calcareous, white, crossbedded sandstone. (Locality 5 (part) of Broad
(1973), Broad and Dineley (1973); G.S.C. locality C- 10052.) Fauna: Torpedaspis elongata; Corvaspis sp.;
Pionaspis sp.; ? Traquairaspis sp.; olbiaspid indet.; Cyathaspidids indet.; Rhachiaspis pteriga gen. et sp. nov.

Locality 10. 94° 09' W. 74° 08' N. Near sea level in small graben 8 km west of Cunningham Inlet. 21-3 m above the
base of the upper member of the Somerset Island Formation. Blue, slightly calcareous sandstone. (Locality F of
Fortier et al. (1963); locality 5 (part) of Broad (1973), Broad and Dineley (1973); G.S.C. locality C-10053.)
Fauna: Torpedaspis elongata; Corvaspis sp.; Pionaspis sp.; ? Traquairaspis sp.; Acanthodii indet.; Anchipteraspis
crenulata gen. et sp. nov.

SYSTEMATIC PALAEONTOLOGY

Order heterostraci Lankester 1 868
Family pteraspididae Claypole 1885

Diagnosis. (Amended after Denison 1970.) Heterostraci with dorsal shield composed of rostral and
pineal plates, a dorsal disc with a dorsal spine attached to its posterior margin, and paired branchial,
orbito-cornual, or orbital and cornual plates, the latter occasionally reduced or absent. Ventral shield
formed by a large ventral disc, variably developed paired lateral, oral, and sometimes postoral plates,
and in Doryaspis a pseudorostrum. Branchial openings more or less posteriorly placed at or near
the lateral margin of the dorsal shield, typically at the posterior ends of the branchial plates and
commonly bounded posteriorly by cornual plates. Sensory canals of dorsal disc arranged in two

ELLIOTT: PTERASPIDS FROM ARCTIC CANADA

173

longitudinal pairs connected on eaeh side by three commissures, normally radially arranged.
Ornamentation fine and commonly crenate. Scales small, numerous, and rhomboid.

Remarks. The family Pteraspididae was divided into two subfamilies by Denison (1970), the
Doryaspidinae containing the aberrant pteraspidid Doryaspis, and the Pteraspidinae containing all
other forms. A further subfamily, the Anchipteraspidinae, is established in this work to include forms
that possess a single orbito-cornual plate and a pineal plate enclosed by the dorsal disc.

Subfamily anchipteraspidinae subfam. nov.

Diagnosis. Dorsal shield composed of rostral and pineal plates, a dorsal disc with posterior dorsal
spine and paired branchial, dorsal, and orbito-cornual plates. Pineal plate totally enclosed by the
dorsal disc. Branchial openings more or less posteriorly placed and bounded dorsally by the orbito-
cornual plate. Narrow pre-oral surface ornamented by dentine ridges. Dorsal sensory eanal system
composed of paired lateral and medial longitudinal canals joined by three pairs of lateral
commissures. Inter-orbital canal forming posteriorly directed loop on the dorsal dise, median
longitudinal eanals not contacting inter-orbital canal. Ventral shield formed by a large ventral disc.

Genera assigned. Anchipteraspis gen. nov., Ulutitaspis gen. nov., Rhachiaspis gen. nov.

Remarks. In the complement of plates the Anchipteraspidinae shows most similarity to the
Pteraspidinae though in some features the relationship to the Cyathaspididae can still be clearly seen.
The main points of difference are that the pineal plate in the Anchipteraspidinae is still totally
enclosed by the dorsal disc whereas that of the Pteraspidinae is situated on the margin between the
dorsal disc and the rostral plate; also the orbital and pineal plates of the Pteraspidinae are represented
by one plate, the orbito-cornual, in the Anchipteraspidinae.

An enclosed orbit is characteristic of the Pteraspididae though this feature is also found in
a number of cyathaspidids, notably in the Ctenaspidinae and in Listraspis. Denison ( 1 964) has shown
that in the cyathaspidid Listraspis this enclosure is due to the fusion of a sub-orbital plate to
the dorsal shield. There is no clear evidence as to the method of enclosure of the orbit in the
Anchipteraspidinae though there is disruption to the ornamentation below the orbit in several
specimens which may indicate fusion of a sub-orbital plate.

Fusion of the branchial plate to the dorsal shield is likewise a pteraspidid feature. In the
Cyathaspididae the simple, notched plate is normally separate though in Listraspis a plate of typically
cyathaspidid type is fused to the dorsal shield and in the Ctenaspidinae the branchial plate appears to
have become incorporated in the dorsal shield as a lateral lamina and ventrolateral plate.

The pattern of the dorsal lateral line canals in the Anchipteraspidinae is very close to that found in
the primitive pteraspidinid Protopteraspis, showing two pairs of longitudinal canals joined by three
sets of commissures, a posterior loop of the inter-orbital canal, and no contact between the medial
dorsal eanals and the inter-orbital canal. No cyathaspidid shows as regular and complete a pattern.

The separate dorsal spine is not a cyathaspidid feature. Though spines are present in such forms as
Cyathaspis and Listraspis there is no evidence that they are more than an outgrowth of the dorsal
shield (Kiaer 1932; Denison 1964).

Classification within the Cyathaspididae and the Pteraspididae is based on characters derived
almost entirely from the dorsal shield, and the most important of these is the mode of formation of the
shield. In the Pteraspididae the plates comprising the dorsal shield were initiated at a juvenile stage,
remained separate during the life of the animal while increasing in size by peripheral accretion, and
fused only at maturity (White 1935, 1958, 1973; Heintz 1938; Denison 1973). In the Cyathaspididae
the shield formed at maturity (Denison 1964) though in some forms the epitega functioned as
separate units in the growth of the superficial layer (Dineley and Loeffler 1976). Evidence from
a speeimen of Ulutitaspis aquilonia gen. et sp. nov. (NMC 13844, PI. 2, fig. 3; text-fig. 7b) shows that
the animal continued growing after development of the dorsal disc had been initiated. This effectively
separates the Anehipteraspidinae from the Cyathaspididae and shows that their affinities lie with the
Pteraspididae.

174

PALAEONTOLOGY, VOLUME 27

Genus Anchipteraspis gen. nov.

Type species. A. crenulata gen. et sp. nov.

Name. Greek ‘anchi’ meaning almost and Pteraspis, the type species of the subfamily Pteraspidinae.

Diagnosis. Dorsal shield small and broad, and with a very blunt rostrum. Ornamentation of
extremely fine ridges ( 1 7/mm) with well-developed alternating lateral projections at the base. Narrow
orbito-cornual plates with smooth lateral margins indented at the level of the branchial openings.
Inter-orbital canal forming posteriorly directed loop on dorsal disc.

Anchipteraspis crenulata gen. et sp. nov.

Plate 22, figs. 1-3; text-fig. 2

Name. Latin ‘crenulata’ meaning minutely crenate, referring to the ornament of very fine crenate ridges.

Type material. Holotype NMC 13854, dorsal shield; Plate 22, figs. 1, 3; from locality 10, Peel Sound Formation,
Somerset Island.

Other material. NMC 13853, 13855, 13856, 13857, dorsal shields.

Diagnosis. As for genus, the type being the only species. For dimensions see Table 1.

Locality. 10.

Description. The rostrum is broad and very short with a rounded anterior margin. The dorsal surface is convex
and a conspicuous groove separates it from the convexity of the dorsal disc (NMC 1 3854; PI. 22, fig. 1 ). Laterally
the plate margins form deep pre-orbital lobes (PI. 22, fig. 3) bounding the ventral pre-oral surface. The posterior
margin of the ventral pre-oral surface is slightly concave, no median lobe is developed. The surface is very
narrow, only 0-75 mm wide, and is little more than a maxillary brim similar to that found in Listraspis (Denison
1964) and ornamented with fine transverse dentine ridges.

The dorsal disc is domed anteriorly with parallel lateral margins and an almost transverse posterior margin,
slightly concave to either side of the median process. In NMC 13855 a median ridge is present anterior to the
dorsal spine. The pineal plate is large and oval and ornamented with ridges parallel to the plate margins.

The dorsal spine is only seen in NMC 13855 where it is incomplete and distorted. Anteriorly the median ridge
of the dorsal disc appears to merge with the spine through an area of short irregular ridges, a feature common in
the subfamily. Laterally the plate junction is demarcated by a distinct groove. Only the base of the spine is
preserved but the ridge pattern suggests that it would have been backswept.

The large orbits are laterally placed, and the orbito-cornual plates form laminae with smooth lateral margins
that maintain a constant width of about 2 mm to a point just past the branchial openings where they are
constricted (NMC 1 3854; PI. 22, figs. 1 , 3). Posteriorly the laminae flare out to form posterqlateral points similar
in shape to the cornual plates of Pteraspidinae. The ornamentation is generally longitudinal and continuous on
both dorsal and ventral surfaces indicating that this is one plate, but in the holotype the ornamentation is

EXPLANATION OF PLATE 22

Fig. 1. Anchipteraspis crenulata gen. et sp. nov. NMC 13854. Dorsal view, x 3.

Fig. 2. Anchipteraspis crenulata gen. et sp. nov. NMC 1 3853. Lateral view, showing branchial plate and branchial
opening, x 3.

Fig. 3. Anchipteraspis crenulata gen. et sp. nov. NMC 13854. Internal view of dorsal shield showing posterior
part of orbito-cornual plate and impressions of internal organs, x 3.

Fig. 4. Ulutitaspis truncata gen. et sp. nov. NMC 13835. Dorsal view, x4.

Fig. 5. Ulutitaspis truncata gen. et sp. nov. NMC 13836. Ventral pre-oral surface, x 10.

Fig. 6. Ulutitaspis truncata gen. et sp. nov. NMC 1 3838. Dorsal view showing internal mould with impressions of
internal organs, x 4.

PLATE 22

ELLIOTT, Anchipteraspis and Ulutitaspis

176

PALAEONTOLOGY, VOLUME 27

disrupted at the level of the branchial constriction suggesting the incipient development of separate cornual and
orbital plates. Below the orbit the ornamentation is also disrupted and broken into short ridges (NMC 13854;
PI. 22, figs. 2; text-fig. 2a). This almost certainly indicates the final stage of enclosure of the orbit either by the
fusion of a sub-orbital plate as occurs in Listraspis (Denison 1964), or by the growth of the orbital plates
ventrolaterally around the orbits.

The branchial plate is attached dorsally to the medial edge of the ventral surface of the orbito-cornual plate,
and is directed slightly medioventrally. The anterior end of the plate is blunt and the posterior margin,
terminating at the base of the cornual extension of the orbito-cornual plate, is gently convex (PI. 22, fig. 2; text-
fig. 2a). The branchial opening is large and elongated and occurs about a third of the way from the posterior
margin of the shield. The upper margin of the opening is damaged in NMC 1 3853 which shows it in lateral view,
but in NMC 13854 it is clearly roofed by the ventral surface of the orbito-cornual plate.

A small plate is fused to the anterior margin of the branchial plate in NMC 13853 (PI. 22, fig. 2; text-fig. 2a).
A similar plate occurs in the same position in Listraspis (Denison 1964) and is certainly a lateral plate that has
become fused to the dorsal shield.

The dorsal sensory canal system is visible only in NMC 13855 (text-fig. 2b). The pattern is very similar to that
found in Protopteraspis, the most primitive genus of the subfamily Pteraspidinae. Two pairs of longitudinal
canals, medial and lateral, are joined by three pairs of transverse commissures. The medial canals terminate
anteriorly before reaching the loop formed on the dorsal disc by the inter-orbital canal. The lateral canals join the
inter-orbital canals behind the orbits before continuing ventrally.

No ventral shields are known for this genus.

Remarks. This genus is separated from Rhachiaspis gen. nov. by its smaller size and narrower orbito-
cornual plates. It differs from Ulutitaspis gen. nov. chiefly in the smooth lateral margins present on
the orbito-cornual plates.

The canal system shows considerable similarity to that found in Protopteraspis in having the same
complement and arrangement of canals. However, it retains a certain rectangularity of arrangement
that is closer to the pattern normally developed in the Cyathaspididae than to the radiating pattern
found in the Pteraspidinae.

Anchipteraspis is very similar in some aspects to the cyathaspidinid Listraspis canadensis (Denison
1964). The overall proportions are very similar as is the shape and relationships of the branchial
plates. The orbito-cornual plate of Anchipteraspis is also very similar superficially to the laterally
extended lateral epitegum of Listraspis. However, there is no separate pineal plate in Listraspis
though a large pineal prominence is developed. There is also no indication of a posterior dorsal spine
in Listraspis; a distinct postero-median process is developed but the ridges of the central epitegum
curve into it showing that it is part of this epitegum and not a separate spine.

Genus Ulutitaspis gen. nov.

Type species. U. notidana gen. et sp. nov.

Name. Eskimo ‘ulutit’ meaning a saw, and Greek ‘aspis’ meaning shield referring to the serrated lateral margins
of the dorsal shield.

Diagnosis. Dorsal shield small and gently arched, with generally high width ratio. Rostrum blunt,
with well-developed median rostral process and broad ventral pre-oral surface ornamented with
dentine ridges. Lateral margin of the orbito-cornual plate serrate for two-thirds of its length, the
serrations increasing in size posteriorly. Cornual extension following deep notch at the level of the
branchial opening. Well-developed, slender, posterior dorsal spine. Ornamentation of fine crenate
ridges, becoming coarse and smoothly rounded at the lateral margins of the rostral and orbito-
cornual plates.

Ulutitaspis notidana gen. et sp. nov.

Plate 23, figs. 1, 2; Plate 24, fig. 1; text-figs. 3, 4

Name. Greek ‘notidanos’ meaning with pointed dorsal fin, referring to the pointed dorsal spine.

TEXT-FIG. 2. Anchipteraspis crenulata gen. et sp. nov. A, lateral view of dorsal shield, NMC 13853. b, dorsal
sensory canal system, NMC 13855. Explanation of abbreviations for this and subsequent text-figs.: bro,
branchial opening; brp, branchial plate; cep, central epitegum; cop, cornual plate; dd, dorsal disc; dsp, dorsal
spine; gl, growth line; iol, interorbital canal; Idl, lateral dorsal canal; lep, lateral epitegum; lop, lateral oral plate;
mdl, medial dorsal canal; mdr, median dorsal ridge; or, orbit; orp, orbital plate; or-cop, orbito-cornual plate; pa,
pineal macula; pi, pineal plate; rep, rostral epitegum; ro, rostral plate; sol, supraorbital canal; sop, suborbital
plate; tc, transverse commissure; vps, ventral pre-oral surface.

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Type material. Holotype NMC 1 3823, dorsal shield; Plate 23, figs. 1 , 2; from locality 3, lower member of the Peel
Sound Formation, Prince of Wales Island.

Other material. NMC 13824-13832, 13834, dorsal shields; NMC 13833, ventral shield.

Diagnosis. Shield relatively slender (width ratio 0-63-0-71) with blunt almost transverse margin to
rostrum. Dorsal spine slender and backswept. Small pineal plate. Straight lateral margin to cornual
extension. Inter-orbital canal forming particularly deep narrow posteriorly directed loop on the
dorsal disc. For dimensions see Table 1.

Localities. 1, 3, 5, 7.

TEXT-FIG. 3. Ulutitaspis notidana gen. et sp. nov. NMC 13823. a, dorsal view, b, detail of orbital area, c, dorsal
spine in lateral view. For explanation of abbreviations see text-fig. 2.

EXPLANATION OF PLATE 23

Fig. 1 . Ulutitaspis notidana gen. et sp. nov. NMC 1 3823. Internal mould of dorsal shield showing impressions of
internal organs, x 3.

Fig. 2. Ulutitaspis notidana gen. et sp. nov. NMC 13823. Dorsal view, x 3.

Fig. 3. Ulutitaspis uquilonia gen. et sp. nov. NMC 13844. Dorsal view showing growth lines, x4.

Fig. 4. Ulutitaspis aquilonia gen. et sp. nov. NMC 13840. Dorsal view, x 4.

PLATE 23

ELLIOTT, Ulutitaspis

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Description. U. notidana has a gently arched dorsal shield and is narrower than the other members of the genus,
having a width ratio of only 0-67 on average. The ornamentation is of crenate ridges but these are coarser than in
Anchipteraspis cremdata, averaging 1 1/mm on the dorsal disc, and decreasing to 7/mm on the lateral margin of
the orbito-cornual plate where they become broad and rounded and lose the lateral projections at the base.

The rostral plate is short and broad and bears transverse dentine ridges. Posteriorly the ridges are parallel to
the plate margin, anteriorly they break up into short ridges and denticles which extend on to a ventral laminae
formed by the downturning of the anterior and lateral edges of the rostrum. This laminae forms a deep pre-
orbital lobe and a shallow median lobe. Ventrally the pre-oral surface is ornamented with transverse dentine
ridges, it is up to 2 mm deep and bears a slight posterior median projection (PI. 24, fig. 1).

The broad elliptical ridge pattern of the dorsal disc is interrupted anteriorly by the small pineal plate. Centrally
the ridges run almost longitudinally, meeting at a slight angle over a low median crest, variably developed before
the dorsal spine.

The dorsal spine is long and gently sloping, its posterior point reaching a height of 4 mm above the dorsal
shield in the holotype. The spine is ornamented with longitudinal dentine ridges, coarse and broadly rounded on
the dorsal edge, fine and serrate on the lateral margin where they meet those of the dorsal disc at a sharp angle.
Anteriorly there is an area of short irregular ridges spreading from the dorsal disc and obscuring the margin with
the dorsal spine.

The orbito-cornual plates have oblique ridges meeting those of the dorsal disc at a slight angle. As in the other
members of the subfamily there is an area of disrupted ornamentation below the orbit, indicating that the
process of orbital enclosure has not yet reached the final stage seen in the Pteraspidinae. Above the orbits the
plates are expanded to form medial projections indicating development towards the pineal plate. The lateral
laminae of the plates have a serrated margin, the serrations increasing in size posteriorly and in the holotype
reaching a final depth of T5 mm and length of 2-5 mm (PI. 23, fig. 1; text-fig. 3a). At the level of the branchial
opening the laminae narrow abruptly and in some specimens a break in ornamentation is present at this point.
The cornual part of the plate has a straight lateral margin and a rounded point projecting past the posterior
margin of the shield.

The branchial plate is known only from two partial specimens. In NMC 13826 the internal aspect of the
opening can be seen, showing it to have an abrupt, vertical anterior margin and a chamber that is triangular in
cross-section. The branchial plate is fused to the ventral surface of the orbito-cornual plate which also roofs the
branchial opening.

The dorsal sensory canal system is well preserved in the holotype and in NMC 1 3830 (text-fig. 4). It follows the
pattern normal for the subfamily, though the loop formed on the dorsal disc by the inter-orbital canal is very
narrow and extends further back than in any other species. In the holotype the lateral longitudinal canals are well
within the lateral margins of the dorsal disc. In NMC 1 3830 the lateral canals are close to the plate margins but
the similar areal extent of the canal systems in the two specimens suggests that further growth has taken place in
the holotype after enclosure of the canals.

The one ventral shield is an internal cast and shows nothing of the dentine ridge pattern or the canal system.
The shield is gently arched and has a blunt anterior border with a slight median concavity and a strongly convex
posterior border.

Remarks. U. notidana is separated from U. truncata and U. aquilonia by its larger size and more
slender form. Rhachiaspis pteriga is similar in size but possesses broader orbito-cornual plates with
smooth lateral margins, and a vertical dorsal spine. A. crenulata is smaller, lacks a serrated margin to
the orbito-cornual plate, and has a more curved lateral margin to the cornual extension.

Ulutitaspis truncata gen. et sp. nov.

Plate 22, figs. 4-6; text-fig. 5

Name. Latin ‘truncare’ meaning to shorten, referring to the shortness of the dorsal shield.

Type material. Holotype NMC 13835, dorsal shield; Plate 22, fig. 4; from locality 2, lower member of the Peel
Sound Formation, Prince of Wales Island.

Other material. NMC 13836-13839, dorsal shields.

Diagnosis. Dorsal shield small, strongly arched, and with a very high width ratio (0-93-0-97). Dentine
ridges on rostrum curve round two centres on the anterior margin. Well-developed ventral pre-oral
surface. For dimensions see Table 1.

ELLIOTT: PTERASPIDS PROM ARCTIC CANADA

181

TEXT-FIG. 4. Ulutitaspis notidana gen. et sp. nov. Dorsal sensory canal system, a, NMC 13823. b, NMC 13830.

For explanation of abbreviations see text-fig. 2.

Locality. 2.

Description. This is an extremely broad form with a width ratio greater than any other member of the
Pteraspididae and rivalled only by Ctenaspis and Listraspis among the Cyathaspididae.

The broad rostrum has a rounded anterior margin and the dentine ridges curve around two anterolateral
centres so that medially the ornamentation is longitudinal (PI. 22, fig. 4; text-fig. 5a). The ridges coarsen in this
area to 7/mm from 1 5/mm on the posterior margin of the plate, and also break up into short ridges and denticles
running on to the ventral lamina. The ventral pre-oral surface is deeper and broader in this species than in the
other members of the genus. In the holotype it is 2 mm deep and ornamented with transverse dentine ridges
averaging 9/mm (PI. 22, fig. 5; text-fig. 5e).

The dorsal spine is present in the holotype where it is slender and slopes back at a shallow angle, reaching 3 mm
above the dorsal shield though the tip is broken. Laterally the ridges of the spine meet those of the dorsal disc at
a sharp angle and a shallow sulcus is formed at the plate junction. Anteriorly the plate boundary is indistinct
owing to the presence of an area of short irregular ridges. On the posterior point of the median process in the
holotype two small scale-like areas are delineated by the ornamentation (text-tig. 5o). These probably indicate
the presence of small scales absorbed into the posterior margin of the shield.

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xnxT-FiG. 5. Ulufilaspis tnmcata gen. et sp. nov. a, dorsal view; b, c, d, details of orbit, orbito-cornual plate and
dorsal spine; NMC 13835. e, ventral pre-oral surface; f, detail of orbit; NMC 13836. G, dorsal sensory canal
system, NMC 13835. For explanation of abbreviations see text-fig. 2.

ELLIOTT: PTERASPIDS FROM ARCTIC CANADA

183

The orbito-cornual plates are similar to those found in the other members of the genus, differing only in their
greater width. The posterior point is blunt and the outline of the cornual part of the plate is similar to that of
U. notidana. In this species the ornamentation below the orbit is not broken into short lengths as is the case in the
type species and in Anchipteraspis cremdata. This may indicate that in this species the process of orbital enclosure
has been completed.

The branchial plate is generally similar to that of A. cremdata though there is no fused lateral plate on the
anterior termination. The branchial opening is set well back under the cornual part of the orbito-cornual plate
and is posteriorly directed.

The dorsal sensory canal system is similar to that found in the other members of the genus (text-fig. 5g). The
only difference lies in the proportions, due to the shortness of the shield in U. truncata.

There are no specimens of the ventral shield.

Remarks. The presence of orbito-cornual plates with serrated lateral margins confine this species to
the genus Ulutitaspis. It is distinguished from the other members of the genus by its small size, very
high width ratio, and details of rostral ornamentation.

The change in ornamentation on the posterior point of the posterior median process in the
holotype probably indicates the attachment of small scales, a feature that is not infrequently found on
the posterior margin of dorsal shields in the Pteraspididae. It has been suggested by Denison (1960,

1 964) that the dorsal spine in the Pteraspidinae originated by this process. A large median dorsal scale
becoming incorporated into the dorsal disc and subsequently developing to form a spine whilst
maintaining its status as a separate plate. The Anchipteraspidinae provide no information to support
this view, rather they indicate that the dorsal spine originated as an outgrowth of the dorsal shield
that subsequently developed as a growth centre and became a separate plate.

Ulutitaspis aquilonia gen. et sp. nov.

Plate 23, figs. 3, 4; text-figs. 6, 7

Name. Latin ‘aquilonaris’ meaning north and referring to the area in which it was discovered.

Type material. Holotype NMC 13840; Plate 23, fig. 4; from locality 2, upper member of the Somerset Island
Formation, Somerset Island.

Other material. NMC 1 3841 -1 3844, dorsal shields.

Diagnosis. Dorsal shield oval in outline and gently arched, between 25-5 and 29 0 mm long and with
a width ratio of 0-80 to 0-84. Rostrum short and rounded, posterior extension of the orbito-cornual
plate long and curved. For dimensions see Table 1 .

Locality. 8.

Description. The specimens of this species are generally poorly preserved. In the holotype (PI. 23, fig. 4; text-fig.
6a) the posterior median process is missing and the length has been estimated with information from NMC
13844.

The rostrum is broad and rounded, with transverse ornamentation. There is a broad ventral pre-oral surface,
ornamented with transverse dentine ridges and up to 2-5 mm deep in the centre where the posterior margin bears
a low median lobe.

The pineal plate is larger than in the other members of the genus and in the holotype is ornamented with short
longitudinal ridges. The longitudinal ornamentation in the midline of the dorsal disc breaks up into an area of
short ridges in front of the dorsal spine, but in NMC 1 3844 (PI. 23, fig. 3; text-fig. 7a) the dorsal disc is marked by
growth lines, indicated by irregularities in ridge pattern. Two almost complete growth lines can be traced and the
first of these shows an anterior notch for the pineal body. The later growth line curves round the margin of the
pineal plate, however, and between the pineal plate and the notch in the first growth line is an area of short
irregular ridges. This appears to show that the organism increased in size between the development of the two
growth lines as the pineal organ clearly moved forward in that time. The dorsal spine is known from two
specimens (NMC 13840 and 13844, text-fig. 7c) both incomplete. The shape, however, appears to be very similar
to that in the other members of the genus.

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The orbito-cornual plates are incomplete in the holotype but they are sufficiently well preserved to show the
lateral serrations. The posterior termination to the plate is preserved in NMC 13841 (text-fig. 6c) which shows it
to be a sharply pointed projection with a convex outer margin and straight inner margin. This contrasts with the
shorter blunt terminations to the plate in U. notidana and U. tnmcata.

The branchial plate is known only in internal view (NMC 13841) and is relatively short with a large branchial
opening.

The dorsal sensory canal system is essentially the same as that found in the other members of the genus (text-
fig. 7a).

There are no specimens of the ventral shield.

Remarks. This species is separated from the others in the genus by the width ratio of the dorsal shield,
which lies between that of the other two species, and by the slender, pointed posterior terminations to
the orbito-cornual plates which differ from the short blunt terminations found in the other forms.

The evidence provided by the growth lines on the dorsal disc of NMC 13844 is of the greatest
importance. These lines record the mode of growth of the shield and not only show that the dorsal
disc was initiated at a median growth centre and developed by peripheral accretion but also that the
animal continued growing during the early stages of this process. This is indicated by the fact that
though the first growth line shows a notch for the pineal plate the final position of the plate is further
forward showing an increase in size of the organism between the formation of the two growth lines.

TKXT-FiG. 6. Ulutitaspis aquilonia gen. et sp. nov. A, dorsal view; B, detail of lateral serrations; NMC 13840.
c, posterior termination of left orbito-cornual plate, NMC 13841. For explanation of abbreviations see

text-fig. 2.

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185

This mode of growth of the shield is unlike that in the Cyathaspidinae, in which growth of the animal
had ceased when the shield started forming, and more like that found in the Pteraspidinae, where the
plates were initiated at an early stage in the growth of the animal and remained separate, though
increasing in size by peripheral accretion, until the adult stage was reached.

Ulutitaspis sp. indet.

Plate 24, fig. 2

Material. NMC 13846, dorsal shield.

Locality. 4.

Description. The dorsal shield is estimated to have been about 26 mm long and 1 7 mm wide. It is crushed and the
posterior and left side are missing. The ornamentation is in all respects similar to that found in Ulutitaspis and the
plate margins can be clearly seen. The anterior part of the orbito-cornual plate is present on the right side and
the margin is serrated. The posterior part of the plate is missing, however, as is the dorsal spine. The bone is black
and opaque and hence it is not possible to see any details of the dorsal sensory canal system.

TEXT-FIG. 7. Ulutitaspis aquilonia gen. et sp. nov. A, dorsal sensory canal system; li, detail of growth lines on dorsal
shield; c, dorsal spine; NMC 13844. For explanation of abbreviations see text-fig. 2.

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PALAEONTOLOGY, VOLUME 27

Remarks. This specimen shows enough of the features of the genus to be attributed to Ulutitaspis. It occurs at a
locality within the stratigraphc range of U. notidana and most resembles that species, its width ratio of 0-65 and
orbital width ratio of 0-38 falling within the size range for that form. It is very much smaller than any of the
specimens of U. notidana, however, with a length of 26 mm and width of 1 7 mm compared with an average of
33-5 mm and 22-3 mm for U. notidana. As the specimen is incomplete no definite relationship can be determined
and it is therefore referred merely to Ulutitaspis sp.

Genus Rhachiaspis gen. nov.

Type species. R. pteriga gen. et sp. nov.

Name. Greek ‘rhachis’ meaning backbone or ridge and ‘aspis’ meaning shield, referring to the prominent median
dorsal ridge.

Diagnosis. Dorsal shield large and strongly vaulted, dorsal disc elongated and bearing a sharp median
dorsal crest. Posterior margin deeply excavated between the median process and a pair of lateral
processes. Spinal element waisted, the anterior part occupied by a spine with a vertical anterior
margin, the posterior part with a median groove. Narrow ventral pre-oral surface with ornament of
transverse dentine ridges. Orbito-cornual plates broad, upswept anteriorly and with broad curved
cornual extensions.

Rhachiaspis pteriga gen. et sp. nov.

Plate 24, figs. 3-6; text-fig. 8

Name. Greek ‘pteron’ meaning wing and ‘megas’ meaning large, referring to the very broad orbito-cornual
plates.

Type material. Holotype NMC 13851, dorsal shield; plate 24, figs. 4-6; from locality 7, lower member of
Somerset Island Formation, Somerset Island.

Other material. NMC 13847, 13848, 13850, dorsal shields; NMC 13849, 13852, ventral shields.

Diagnosis. As for genus, the type being the only species. For dimensions see Table 1.

Localities. 6, 7, 9.

Description. The dorsal shield is large and broad with a short rostral plate. The ventral pre-oral surface forms
a narrow band only 1 mm deep, ornamented with transverse dentine ridges and with a slight median lobe on the
posterior margin.

The dorsal disc is elongated, rounded anteriorly, and almost parallel sided. It bears a conspicuous median
crest extending from the centre of growth to the dorsal spine. In NMC 13847 this crest is extremely narrow and
vertical and appears to merge with the dorsal spine, though in the holotype they are clearly separate. The
posterior margin of the disc is very deeply excavated between the well-developed posterior median process and
a pair of smaller posterolateral processes. The pineal plate is small and cannot be clearly seen in any specimen. In
the holotype it interrupts the anterior ridge pattern of the dorsal disc and appears to be ornamented with short
longitudinal ridges.

EXPLANATION OF PLATE 24

Fig. 1. Ulutitaspis notidana gen. et sp. nov. NMC 13828. Dorsal shield in internal view, x 2-5.

Fig. 2. Ulutitaspis sp. gen. nov. NMC 13846. Dorsal view, x 3.

Fig. 3. Rhachiaspis pteriga gen. et sp. nov. NMC 13849. Ventral shield, x 3.

Fig. 4. Rhachiaspis pteriga gen. et sp. nov. NMC 13851. Dorsal shield in lateral view, x 3.

Fig. 5. Rhachiaspis pteriga gen. et sp. nov. NMC 13851. Dorsal view, x 3.

Fig. 6. Rhachiaspis pteriga gen. et sp. nov. NMC 13851. Dorsal view of internal mould showing impressions of

internal organs, x 3.

PLATE 24

ELLIOTT, Ulutitaspis and Rhachiaspis

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PALAEONTOLOGY, VOLUME 27

The spine is characteristic in this genus. The base is divided into anterior and posterior parts by a median
constriction, the anterior part bearing the dorsal spine which has an almost vertical leading edge and slopes
posteriorly (PI. 24, fig. 4). The spine is broken in the holotype and neither its total height nor the shape of its
termination are known. Posteriorly the plate expands to the margin of the shield and in the holotype has a
median sulcus ornamented with longitudinal ridges, separating a pair of lateral prominences ornamented with
transverse ridges. This feature can only be seen in the holotype, where the surface detail is poor, but may indicate
the presence of fused dorsal ridge scales.

The orbits are prominent and laterally directed and there is no disruption of ornamentation below them. The
lateral laminae of the orbito-cornual plates are very broad, and are very much upswept just behind the orbits.
This feature can be seen in all the specimens and is not a distortion produced during preservation, it results in
a concave dorsal surface to the plate anteriorly which fades away towards the middle of the plate.

The branchial plate is known only from internal casts and is similar to those found in other members of the
subfamily.

The dorsal sensory canal system is not well preserved and it has been reconstructed (text-fig. 8a) based on
NMC 13847 and 13851. It appears to show a pattern similar to that found in other members of the
Anchipteraspidinae, though it is not possible to see if a complete loop is formed by the inter-orbital canal, nor if
the median dorsal canals terminate before meeting the inter-orbital canal.

Of the two ventral shields known NMC 13849 is the best preserved (PI. 24, fig. 3), and shows the ventral
dentine ridge pattern and sensory canal system. Its shape is very similar to that found in the Pteraspidinae, with
anteriorly a median depression, probably the site of attachment for sub-oral and oral plates, and posteriorly
a slight median process. The generally elliptical ornament is interrupted anteromedially, the longitudinal median
ridges meeting the transverse anterior ridges in an area of swirls and whorls.

The canal system is incomplete but appears to follow the pteraspidid pattern with an anterior median loop and
paired lateral canals giving rise to a number of lateral transverse commissures.

TEXT-FIG. 8. Rhachiaspis pteriga gen. et sp. nov. a, dorsal sensory canal system (based on NMC 13847 and 13851 ).
B, reconstruction of dorsal shield. For explanation of abbreviations see text-fig. 2.

ELLIOTT; PTERASPIDS FROM ARCTIC CANADA

189

Remarks. This distinctive form is separated from the other members of the Anchipteraspidinae by its
large size, broad upswept orbito-cornual plates, and vertical dorsal spine.

The keel-like median dorsal ridge, merging with the vertical dorsal spine, and the broad orbito-
cornual plates are probably developments to aid the stability of the animal in swimming, as are the
greatly extended cornual plates and tall dorsal spines developed in some pteraspidids. The upswept
anterior to the orbito-cornual plates would also have helped to give uplift to the anterior part of
the body by increasing the area of the anterior bearing surface. These developments suggest that
R. pteriga was an active and capable swimmer.

The waisted shape of the spine base is unknown elsewhere in the Pteraspididae. The posterior part
of the plate is unfortunately not clear in the only specimen that shows it; it may represent included
dorsal ridge scales as are present in the type specimen of Ulutitaspis tnmcata.

AGE OF THE FAUNA

The Somerset Island localities occur almost exclusively within the Somerset Island Formation.
Localities at West Creswell Bay and Cape Anne have been dated as early Pridolian (Miall et al. 1978)
based on conodont faunas including Ozarkodina confluens and Pelekysgnathus sp. The base of the
formation becomes younger eastwards across northern Somerset Island (Jones and Dixon 1977) and
in the north-east part of the island the underlying Read Bay Formation is Pridolian. A fauna
including O. confluens has been reported from the Leopold Formation in this area (Loeffler and Jones
1976, 1977) in association with ostracodes and ostracoderms, and dated (Uyeno in Loeffler and Jones
1977) as late Ludlow or early Pridolian. Thorsteinsson (1980) considers that the basal beds of the
Somerset Island Formation on Boothia Peninsula are latest Ludlovian in age, on the basis of the
presence of Pedavis sp. aff. P. thorsteinssoni (Uyeno 1980). The cyathaspidid Torpedaspis elongata
occurs with this conodont on Boothia Peninsula and also occurs in the lower part of the Somerset
Island Formation in north-western Somerset Island indicating a similar age there.

A number of the vertebrates provide independent evidence of age. Boothiaspis alata occurs in both
members of the Somerset Island Formation at Pressure Point and also in the lower member of the
Peel Sound Formation at Transition Bay. It also occurs in the Devon Island Formation on Ellesmere
Island where it is associated with a monograptid dated as Pridolian by Thorsteinsson on Cornwallis
Island (Broad 1973). Ariaspis ornata is known from the lower member of the Somerset Island
Formation at Pressure Point but it has also been reported from Beaver River (Denison 1963) and the
Delorme Formation (Dineley and Loeffler 1976). Though originally assigned an early or middle
Ludlovian age on the basis of associated invertebrates, the age could range from Wenlockian to
Pridolian (Dineley and Loeffler 1976) as Monograptus duhius which occurs above the Beaver River
fauna is now known to extend from the Llandoverian to the Pridolian (Broad and Lenz 1972).

Hemicyclaspis murchisoni, which occurs in the upper member of the Somerset Island Formation at
Pressure Point, is regarded as an index fossil for the lowest Downtonian of Britain (White 1950), now
considered to be equivalent to the early Pridolian (Loeffler and Dineley 1976). It therefore appears
that the whole of the Somerset Island Formation is latest Ludlovian or Pridolian in age.

On Prince of Wales Island only the Transition Bay localities can be dated and correlated with those
on Somerset Island. Invertebrate dating of the sequence through the lower member of the Peel Sound
Formation has yielded upper Silurian ages (Bolton and Copeland in Broad and Dineley 1973; Bolton,
pers. comm. 1 976) for the whole of the sequence. Thorsteinsson ( 1 980) concludes that the age range of
the lower member of the Peel Sound Formation on Prince of Wales Island is late Ludlovian to early
Pridolian, based mainly on the presence of Hemiarges higener towards the top of the lower member.
This trilobite is found at widely separated localities within the arctic archipelago, but wherever it can
be related to diagnostic fossils it appears to be confined to beds of Pridolian age (Thorsteinsson 1 980).
Miall et al. (1978) consider the lower member of the Peel Sound Formation on Prince of Wales Island
to be equivalent in age to the Somerset Island Formation though the rock types difier.

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GROWTH AND DEVELOPMENT OF THE DERMAL SHIELD

The lack of a universally agreed interpretation of the mode of growth of the heterostracan shield
has resulted in the development of many divergent views on the evolution of the order. The
Anchipteraspidinae show several features that are of value in illustrating the growth of the
heterostracan shield and the evolutionary relationships between the heterostracan families. They
show superficial similarity to both the Cyathaspididae and the Pteraspididae; however, both these
groups have been shown to possess dissimilar modes of growth.

Growth of the Cyathaspididae. The cyathaspidid dorsal shield is divided into rostral, lateral, and
central areas termed ‘epitega’ (Stensid 1958), delineated by dermal ridge patterns and originally
thought to be merely superficial divisions (Kiaer 1932; White 1935). The view that in some genera at
least the epitega were distinct plates (Kiaer and Heintz 1935; Moy-Thomas 1939; Obruchev 1945;
Stensid 1958) was supported by Denison (1964), who showed that the superficial layers developed
first, possibly in separate epitegal units, and that the subsequent formation of the deeper layers may
have occurred as one unit. It has now been demonstrated (Dineley and Loeffler 1976) that in some
cyathaspidids the superficial layer not only grew independently in the epitegal areas but that growth
took place incrementally. In Pionaspis amplissima (text-fig. 9a) successive growth lines indicate that
formation of the shield did not start until the individual reached full size, and then continued by
peripheral accretion from centres within each epitegum until the edges met and fused.

Growth in the Pteraspididae. Though it was originally thought (Zych 1931; White 1935) that
development of the pteraspidid shield was not initiated until the individual had reached almost full
size, as in the cyathaspidids, study of growth stages (Heintz 1938; White 1958) has demonstrated that
after an early unarmoured stage the plates developed separately though remaining in contact
peripherally (text-fig. 9c). Growth of the shield appears to have been initiated at a total length of
about 23 mm (Denison 1973; White 1973), and ultimate fusion of the plates was delayed for a
progressively longer period of time as the family evolved (White 1958). Evidence from thin sections
shows that, as in the cyathaspidids, growth of the superficial layer preceded that of the cancellous and
basal layers (Denison 1973; White 1973).

Growth in the Anchipteraspidinae. In the Anchipteraspidinae growth lines are visible on a number of
specimens but only on one are they complete enough to throw any light on the process of growth in
the subfamily. A specimen of Ulutitaspis aquilonia (NMC 13844, PI. 23, fig. 3; text-fig. 9b) shows
a series of growth lines on the dorsal shield, the first of which has a clear anterior notch for the pineal
body (text-fig. 7b). The pineal body is further forward, however, and a further growth line curves
round it indicating that the animal continued growing after the initiation of shield formation. The
second growth line appears to mark the stage at which growth of the animal ceased; however, it is still
inside the lateral dorsal canals and indicates that they had not been invested by the shield at this point.

From this evidence it appears that the Anchipteraspidinae had developed the ability to continue
growth once the shield had started to form but that the ability was still limited, comparable to the
stage reached in the primitive pteraspidinid Protopteraspis in which the shield fused shortly after
investing the lateral dorsal canals of the sensory canal system.

EVOLUTIONARY RELATIONSHIPS OF THE PTERASPIDIDAE

Various authors have derived the Pteraspididae from a number of different heterostracan families.
Tarlo (1962, 1967), Obruchev (1967), and Halstead (1973) agreed in deriving the Pteraspididae from
the Traquairaspididae, a view followed by Broad (1971) and more recently by Dineley and Loeffler
(1976). Stensio (1958) believed that the ancestors of the Pteraspididae were forms like the
psammosteids in which belts of smaller scales separate the larger plates. Obruchev (1945) believed
that the Pteraspididae evolved from the Cyathaspididae and Denison (1964, 1973) followed this
view.

ELLIOTT: PTERASPIDS PROM ARCTIC CANADA

191

TEXT-FIG. 9. Growth stages in heterostracan dorsal shields, a, Pionaspis amplissima (from Dineley and Loeffler
1976). B, Ulutitaspis aquilonia, NMC 13844. c, Belgicaspis crouchi (from White 1973). For explanation of

abbreviations see text-fig. 2.

The discovery of the subfamily Anchipteraspidinae provides new and stronger evidence in favour
of the development of the Pteraspididae from the Cyathaspididae. Evidence from the arrangement of
plates in the dorsal shield shows that evolutionary development was not totally by a process of fusion
or of subdivision of dermal elements but by a combination of the two processes, thus supporting the
views of Denison (1964) and Westoll (1967).

Denison (1964, pp. 465-466) set out the arguments in favour of the derivation of the Pteraspididae
from the Cyathaspididae and this plan was also followed by Broad (1971) and Dineley and Loeffler
(1976) in their argument for a derivation from the Traquairaspididae. I have used the same headings
in the following assessment of the contribution of the Anchipteraspidinae towards a solution of the
problem.

1. The known geological record of the two groups was cited as favouring the derivation of the
Pteraspididae from the Cyathaspididae by Denison (1964); however, Dineley and Loeffler (1976)
showed that this was equally true for a derivation from the Traquairaspididae which range from the
Wenlockian to the early Dittonian. Recent work on Protopteraspis from the Canadian arctic (Elliott
and Dineley 1983) suggests that they are Pridolian in age in this area which may therefore be an
evolutionary centre for the genus. In many localities they are preceded in the same stratigraphic
sections by members of the Anchipteraspidinae. The cyathaspidid Lisiraspis canadensis which shows
most similarity to the Anchipteraspidinae and is probably the most closely related form is known
only from British Columbia. It was dated as late Downtonian by Denison (1964); however, this date
has been questioned by Dineley and Loeffler (1976) who do not feel so precise an estimate can be
gained given the present level of knowledge on the cyathaspidids and traquairaspidids on which it
is based.

2. Denison viewed the epitega, branchial plates, and ventral shield of the Cyathaspidinae as
comparable to the plates of the pteraspidid shield; however, Dineley and Loeffler (1976) considered

192

PALAEONTOLOGY, VOLUME 27

that these were more closely comparable to plates in the traquairaspidid head shield. The
Anchipteraspidinae appear to occupy an intermediate position in which the plates can be directly
compared with those found in both the Cyathaspididae and the Pteraspididae.

In cyathaspidids the branchial plate is usually flat, elongated, and notched on the dorsal margin to
form the branchial opening. It is also generally separate, though in Listraspis it is fused to the dorsal
shield and in the Ctenaspidinae it has also been incorporated into the dorsal shield. The branchial
plate of pteraspidids is fused to the dorsal shield, and even in the earliest representatives is enfolded to
form a branchial duct. Though in the Anchipteraspidinae the plate is normally flat and fused to the
dorsal shield, in U. truncata a branchial duct is formed by the partial enfolding of the branchial plate.
This plate would require little change to form a branchial plate of pteraspidid type.

The orbito-cornual plates of the Anchipteraspidinae can also be directly compared with the
separate orbital and cornual plates of the Pteraspididae and the orbital and lateral epitega of the
Cyathaspididae. In the Anchipteraspidinae the plate is clearly demarcated into an orbital and
a cornual part by an abrupt narrowing, and in the holotype of Anchipteraspis crenulata the
ornamentation of the plate is disrupted at this point, possibly indicating the incipient development of
separate plates. Denison (1964) has suggested that the cornual plates of pteraspidids were derived
from a pair of scales attached to the posterolateral corners of the dorsal shield, a view apparently
supported by the scale-like posterior cornual plates present in juvenile specimens of Lampraspis
tuherculata (Denison 1973). However, the earliest members of the Pteraspidinae, the genus
Protopteraspis, have in all cases well-developed cornual plates, and on functional grounds it also
seems more likely that an outgrowth of the dorsal shield, initially developed as a control surface,
would be retained and developed into separate plates. Such outgrowths have developed independently
in the Cyathaspididae, Listraspis and Ctenaspis showing well-developed lateral laminae, and have
been reported in the Traquairaspididae (Broad 1971).

Enclosed orbits are not a normal feature in the Cyathaspididae though they are present in the
Ctenaspidinae and in Listraspis, a feature explained by Denison (1964) as being the result of fusion of
a suborbital plate. Such plates have been described in articulated cyathaspidids by Kiaer (1932) and
Dineley and Loeflier (1976). In A. crenulata disruption of the ornamentation below the orbit may be
due to the incorporation of a suborbital plate or to the growth of the orbital plate down and around
the orbit.

The pineal area in the advanced Cyathaspidinae probably remained naked longer than adjacent
areas of the shield (Dineley and Loeffler 1976), thus the pineal plate of pteraspidids could have
developed as a new centre of ossification in the postrostral field of cyathaspidids. Listraspis has
a large pineal prominence and the members of the Anchipteraspidinae also have large pineal areas
covered by separate plates.

The dorsal spine is a separate element in the Pteraspidinae and its development has been attributed
(White 1935; Denison 1960, 1964) to the attachment of a dorsal ridge scale to the posterior margin of
the dorsal disc and its gradual incorporation into the disc. The particularly scale-like dorsal spines of
Pteraspis rostrata (White 1935) and P. carmani (Denison 1960) have been cited as evidence to support
this view. Scale-like dorsal spines seem, however, to have been developed for functional reasons in
flat-bodied forms, particularly protaspids, which may have been bottom dwellers and as such may
not have required strongly functional keels. For this reason scale-like dorsal spines are seen as a
later development in the Pteraspidinae, a view supported by the fact that the early members of the
subfamily possess well-developed dorsal spines as do the Anchipteraspidinae.

In the Cyathaspididae a scale-like dorsal spine has been identified in Ariaspis (Denison 1964;
Dineley and Loeffler 1976). In the specimen illustrated by Dineley and Loeflier the scale is less
obviously demarcated from the rest of the shield and appears to be part of a band of scale-like
elements forming the posterior margin of the dorsal shield. A similar band is present in a specimen of
Archegonaspis cf. A . schmidti illustrated by Loeffler and Jones ( 1 976). If these elements are scales they
appear to have been totally incorporated into the shield and there is no evidence to suggest that they
would retain their identity within the shield to the extent of developing as separate plates.

The crest on the central epitegum in Cyathaspis has been described as a real dorsal spine

ELLIOTT: PTERASPIDS PROM ARCTIC CANADA

193

comparable with that of Pteraspis (Kiaer 1932). Similar crests are developed in Ctenaspis and
Listraspis among the cyathaspidids, and erect dorsal spines are also present in two traquairaspidids
described by Broad (1971). In none of these forms is there any indication that the spine was anything
more than a development of the dorsal disc.

In the Anchipteraspidinae the dorsal spine is a discrete element, separated from the dorsal disc. In
several specimens the anterior margin is obscured by the development of short, irregular ridges which
may indicate that the process of total separation of the spine was not yet complete. This suggests that
the first stage in the development of the pteraspidid dorsal spine was not the attachment of a scale
to the posterior margin of the dorsal shield but the development of a posterior median crest, an
adaptation of functional value to the animal. Once the crest had developed it would have separated to
form a discrete element by the development of a new centre of growth and as part of the process of
separate development of the epitegal areas taking place in the Cyathaspidinae at this time (Dineley
and Loeffler 1976, pp. 104-107).

3. The microstructure of the shield of the Anchipteraspidinae is too poorly preserved to shed any
light on the closeness of its relationship to the Cyathaspidinae and Pteraspidinae.

4. The lateral line canal system of Pteraspididae is easily derivable by minor modification of the
simple pattern of cyathaspidids (Denison 1964, p. 465), though Broad (1971) and Dineley and
Loeffler (1976) have suggested that this is more easily derived from that of certain traquairaspidids. In
the Anchipteraspidinae the system is similar in all respects to that found in Protopteraspis; however,
in Anchipteraspis crenulata the system still displays a rectangular appearance strongly reminiscent of
the cyathaspidid type, normally an almost diagrammatically simple combination of longitudinal
canals and transverse commissures. However, Kiaer and Heintz (1935) have noted an evolutionary
trend towards a more regular and complete dorsal pattern in Poraspis. The anchipteraspidinid-
pteraspidinid type of canal system could be developed from the basic cyathaspidid system by a
process of fusion, and just such a system is found in Ctenaspis, a specialized cyathaspidid thought
(Denison 1964) to have been derived from the Cyathaspidinae. In fact the resemblance is strong
enough to have led Kiaer (1930) to suggest that the pteraspidids were derived from Ctenaspis.

5. The dentine ridges of pteraspidids are typically narrow crested and crenulate. This type of ridge
is also found in Listraspis and is characteristic of the Anchipteraspidinae. It is not considered that the
traquairaspidid type of ornament could easily give rise to the pteraspidid ridge as suggested by
Broad (1971).

6. The narrow ornamented pre-oral surface typical of Protopteraspis is found in a primitive
condition in the maxillary brim of Listraspis (Denison 1964) and other cyathaspidids. The
Anchipteraspidinae also show this feature, A. crenulata bears only a narrow ornamented area but in
U. truncata it is well developed. No feature of this type has been reported in the Traquairaspididae.

Interpretations of the relationships of the most well-known heterostracan groups, the
Pteraspididae, Cyathaspididae, Psammosteida, and Traquairaspididae, has been dependent to a very
great extent on views on the way in which the dermal shield developed. The Lepidomorial Theory of
0rvig (1951) though originally based on the development of elasmobranch scales was applied by
Stensio (1958) to growth in the Heterostraci and provided support for the evolutionary development
of the shield by a process of fusion. This view was embodied in the evolutionary scheme of Halstead
(1973), which begins with the fully tessellated Eriptychius and Tesseraspis and leads to two major
groupings of heterostracans which progress from partially tessellate to non-tessellate forms. One
group passes through the partially tessellated Kallostrakon, Corvaspis, and Cardipeltis to produce
the non-tessellated Cyathaspididae and Amphiaspididae; the other progresses via Weigeltaspis, the
Psammosteida, and the Traquairaspididae to produce the non-tessellate Pteraspididae. However, as
noted by Janvier (1981), the recent discoveries of lower Ordovician remains (Ritchie and Gilbert-
Tomlinson 1977), showing no indication of tesserae, make this scheme less than satisfactory, and
the independent derivation of the Pteraspididae and Cyathaspididae is unlikely as the shape and
distribution of the dermal plates in both groups is similar.

Halstead (1973) considers the psammosteids to be ancestral to the pteraspidids; however, there is
much stronger evidence to suggest that the reverse is true (Obruchev 1947, 1967; Westoll 1967). The

194

PALAEONTOLOGY, VOLUME 27

main plates of the early psammosteids are homologous with those of pteraspidids, though an
additional postorbital plate is present and the large plates are separated by a scale mosaic. This latter
innovation may demonstrate a further advantage in growth, permitting a longer growth period in this
family. Young stages of early forms such as Drepanaspis are very pteraspidid in appearance (Gross
1963) and show most similarity to the dorsoventrally depressed early Devonian pteraspidids such as
Protaspis in which the cornuals are small and the branchial plates are large and have posterior
branchial openings (Miles 1971 ). It was probably from among these forms that the drepanaspids were
evolved.

It seems that more complex processes than simple fusion or subdivision may have been at work in
the development of the shield (Obruchev 1943; Denison 1964; Westoll 1967) and evolutionary
advancement within the Heterostraci should not be gauged automatically by the degree to which
fusion of the shield has progressed.

E F

G

H

TEXT-FIG. 10. Stages in the development of the heterostracan dorsal shield from the Cyathaspididae to the
Pteraspididae. a, cyathaspidid with undivided dorsal shield and separate branchial plate, b, c, cyathaspidinid
with dorsal shield divided into epitega. d, e, cyathaspidinid in which the lateral epitega are developed to form
laminae, the orbit is enclosed, the branchial plate fused, and the dorsal spine developed as an outgrowth of the
dorsal disc, f, anchipteraspidinid in which separate growth centres initiated in pineal and dorsal spine areas, and
development of shield occurs before maturity, g, h, pteraspidinid in which peripheral growth of plates continues
through ontogeny. For explanation of abbreviations see text-hg. 2.

ELLIOTT: PTERASPIDS PROM ARCTIC CANADA

195

CONCLUSIONS

It is proposed here that the Pteraspidinae evolved from the Cyathaspidinae during the Pridolian via
the new subfamily Anchipteraspidinae. This may have been a rapidly occurring event in a restricted
area as there have been no other reports of forms attributable to the Anchipteraspidinae though
Protopteraspis, the earliest pteraspidinid, has a wide distribution (Blieek 1981; Elliott and Dineley
1983).

The processes taking place in the dorsal shield are initially the development of rostral, dorsal, and
lateral epitega in a cyathaspidinid (text-fig. 10a-c). Growth would be initiated at maturity from
separate growth centres in the epitega and fuse peripherally on contact, though the branchial plate
would remain separate. Pionaspis is an example of this stage (Dineley and Loeffler 1976).
Subsequently the lateral epitega would be developed to form lateral laminae and the orbit would be
enclosed by the fusion of a sub-orbital plate (text-fig. IOd, e). The dorsal spine would be developed as
an extension of the dorsal disc and fusion of the branchial plate would take place; however, growth of
the shield would still be initiated at maturity. L. canadensis is an example of this stage (Denison 1964).
The next stage is that reached in the Anchipteraspidinae and requires merely the initiation of growth
centres in the pineal area and at the dorsal spine, and the initation of shield development before
maturity to allow limited growth before the final fusion (text-fig. IOf). The final stage, embodied in
Protopteraspis, requires shield growth to be initiated early allowing separate development of the
plates by peripheral growth through ontogeny with fusion occurring at maturity (text-fig. IOg, h).

Acknowledgements. The field-work and research were carried out during the tenure of a grant from the Natural
Environment Research Council and assistance and logistic aid at Resolute, Cornwallis Island, was provided by
the Polar Continental Shelf Project. The support of both these bodies is gratefully acknowledged. Assistance in
the field was provided by Dr. M. J. Gibling and I have benefited much from discussion and correspondence with
Dr. R. H. Denison, Professor D. L. Dineley, Dr. E. J. Loeffler, and Dr. R. Thorsteinsson. The photographic
illustrations are the work of R. Godwin (Bristol) and J. Q. Brown (Flagstaff).

REFERENCES

BLIECK, A. 1981. Le genre Protopteraspis Leriche (Vertebres Heterostraces) due Devonien inferieur Nord-
Atlantique. Palaeontograpliica, A113, 141-159.

BROAD, D. s. 1971. Upper Silurian and Lower Devonian Heterostraci from Yukon and Northwest Territories,
Canada. Ph.D. thesis (unpublished). University of Bristol, 239 pp.

1973. Amphiaspidiformes (Heterostraci) from the Silurian of the Canadian arctic archipelago. Bull. geol.

Surv. Can. 222, 35-50.

and DINELEY, D. L. 1973. Torpedaspis, a new Upper Silurian and Lower Devonian genus of Cyathaspididae

(Ostracodermi) from arctic Canada. Ibid. 53-90.

and LENZ, A. c. 1972. A new Upper Silurian species of Vernonaspis (Heterostraci) from Yukon Territory,

Canada. J. Paleont. 46, 415-420.

DENISON, R. H. 1960. Fishes of the Devonian Holland Quarry Shale of Ohio. Fieldiana, Geol. 11 (10), 555 -613.

1963. New Silurian Heterostraci from Southeastern Yukon. Ibid. 14(7), 105-141.

1964. The Cyathaspididae: a family of Silurian and Devonian jawless vertebrates. Ibid. 13 (5), 309-473.

1970. Revised classification of Pteraspididae with description of new forms from Wyoming. Ibid. 20 ( I ),

1-41.

1973. Growth and wear of the shield in the Pteraspididae (Agnatha). Palaeontograpliica, A143, 1-10.

DINELEY, D. L. 1964. New Specimens of Traquairaspis from Canada. Palaeontology, 7, 210-219.

- — 1968. Osteostraci from Somerset Island. Bull. geol. Surv. Can. 165, 49-63.

— 1976. The species of Ctenaspis (Ostracodermi) from the Devonian of Arctic Canada. In churcher, c. s.
(ed.). Athlon: Essays on Palaeontology in Honour of Loris Shano Russell.

and LOEFFLER, E. J. 1976. Ostracoderm faunas of the Delorme and associated Siluro-Devonian Formations,

Northwest Territories, Canada. Spec. Pap. Palaeontology. 18, 218 pp.

ELLIOTT, D. K. 1983. New Pteraspididae (Agnatha, Heterostraci) from the Lower Devonian of Northwest
Territories, Canada. J. Vert. Paleont. 2 (4), 389-406.

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PALAEONTOLOGY, VOLUME 27

ELLIOTT, D. K. and DINELEY, D. L. 1983. Ncw spccies of Protopteraspis (Agnatha, Heterostraci) from the Lower
Devonian of Northwest Territories, Canada. J. Paleont. 56, 2.

FORTIER, Y. o. et al. 1963. Geology of the north central part of the Arctic archipelago. Northwest Territories
(Operations Franklin). Geol. Surv. Canada, Mem. 320, 117-129.

GROSS, w. 1963. Drepanaspis gemuendenensis Schliiter. Neuuntersuchung. Palaeontographica, A121, 133-155.

HALSTEAD, L. B. 1973. The Heterostracan fishes. Biol. Rev. 48, 279-332.

HEiNTZ, A. 1973. Uber die altesten bekannten Wirbeltiere. Naturwiss. 26, 49-58.

JANVIER, p. 1981. The phylogeny of the Craniata with particular reference to the significance of fossil
‘Agnathans’. J. Vert. Paleont. 1 (2), 121-159.

JONES, B. and dixon, o. a. 1977. Stratigraphy and sediraentology of upper Silurian rocks, northern Somerset
Island, Arctic Canada. Can. J. Earth Sci. 14, 1427-1452.

KIAER, J. 1930. Ctenaspis, a new genus of Cyathaspidian fishes. Skr. Svalbard Ishavet. 33, 1-7.

1932. The Downtownian and Dittonian vertebrates of Spitsbergen. IV. Suborder Cyathaspida. Ibid. 52,

1-26.

and HEINTZ, A. 1935. The Downtownian and Dittonian vertebrates of Spitsbergen. Suborder Cyathaspida.

Part 1. Family Poraspidae Kiaer. Ibid. 40, 1-138.

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Northwest Territories, Canada. Palaeontology, 20, 661-674.

and DINELEY, D. L. 1976. A new species of Corvaspis (Agnatha, Heterostraci) from the upper Silurian to

lower or middle Devonian of the Northwest Territories, Canada. Ibid. 19, 757-766.

and JONES, b. 1976. An ostracoderm fauna from the Leopold Formation (Silurian to Devonian) of Somerset

Island, Northwest Territories. Ibid. 1-15.

MiALL, A. D. 1970. Continental marine transition in the Devonian of Prince of Wales Island, Northwest
Territories. Can. J. Earth Sci. 7, 125-144.

and KERR, J. w. 1977. Phanerozoic stratigraphy and sedimentology of Somerset Island and northeastern

Boothia Peninsula. Geol. Surv. Can. Paper 11-\K, 99-106.

and GiBLiNG, M. R. 1978. The Somerset Island Formation; an Upper Silurian to ?Lower Devonian

intertidal/supratidal succession, Boothia Uplift region, Arctic Canada. Can. J. Earth Sci. 15, 81-189.

MILES, R. s. 1971. Palaeozoic fishes. Chapman and Hall, London, 259 pp.

MOY-THOMAS, J. A. 1939. Ibid. 1-149.

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268-71.

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1947. Vertebrata. In Atlas of the guide forms of the fossil faunas of the USSR. Vol. 3. Devonian, 191 -206.

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104, 13-29.

0RVIG, I. 1951. Histologic studies of Placoderms and fossil Elasmobranchs. 1. The endoskeleton, with remarks
on the hard tissues of lower vertebrates in general. Ark. Zool. 2, 321-454.

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STENSio, E. A. 1958. Les cyclostomes fossiles ou Ostracodermes. In grasse, p. p. (ed.). Trade de Zoologie, 13 (i),
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TARLO, L. B. 1962. The classification and evolution of the Heterostraci. Acta palaeont. pol. 7, 249-290.

1967. The tessellated pattern of dermal armour in the Heterostraci. J. Linn Soc. {Zool.), 47, 45-54.

THORSTEINSSON, R. 1967. Preliminary note on Silurian and Devonian ostracoderms from Cornwallis and
Somerset Islands, Canadian Arctic Archipelago. Collogues int. Cent. natn. Rech. scient. 163, 45-47.

1980. Stratigraphy and Conodonts of Upper Silurian and Lower Devonian rocks in the Environs of the

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292, 1-38.

and TOZER, w. 1963. Geology of northern Prince of Wales Island and northwestern Somerset Island. In

FORTIER, Y. et al. Geology of the north central part of the Arctic archipelago. Northwest Territories (Operation
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TOOMBS, H. A. and RixoN, A. E. 1950. The use of plastics in the ‘Transfer Method’ of preparing fossils. Museums J.
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1950. Vertebrate faunas of the Lower Old Red Sandstone of the Welsh Borders. Bull. Brit. Mas. (Nat. Hist.)

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ZYCH, w. 1931. Fauna ryh Devonii i Downtoni Podola. Lwow, 91 pp.

DAVID K. ELLIOTT

Department of Geology
Box 6030

Northern Arizona University

Typescript received 26 March 1983 Flagstaff, AZ 8601 1, USA

THE LOWER JAW OF

SUNOSUCHUS THAILANDICUS, A MESOSUCHIAN
CROCODILIAN FROM THE JURASSIC OF

THAILAND

/)JERIC BUFFETAUT RUCHA INGAVAT

Abstract. A nearly complete lower jaw is described of the longirostrine mesosuchian crocodilian Simosuchiis
thailandicus Buffetaut and Ingavat (1980), from the Phu Kradung Formation (early Jurassic) of north-eastern
Thailand, and the affinities of the genus are discussed. The jaw is large and robust, with a long symphysis,
and each dentary contains about thirty teeth. Despite the unusually elongated mandibular symphysis the genus
is referred to the Goniopholididae rather than to the Pholidosauridae, on the basis of the skull characters
present in the Chinese species 5. m/«o/ Young (1948). Sunosiiciws, however, is in some respects morphologically
intermediate between the Goniopholididae and the Pholidosauridae.

In 1979 the posterior part of the right ramus of the lower jaw of a large crocodilian was collected
from the Jurassic Phu Kradung Formation by Mr. Nares Sattayarak (Department of Mineral
Resources, Bangkok), near the town of Nong Bua Lam Phu in north-eastern Thailand. The
specimen was subsequently described by us (Buffetaut and Ingavat 1980) and referred to a new
species of the genus Sunosuchus Young 1948, S. thailandicus. In November 1980 a Thai-French
party visited the locality under the guidance of Mr. Sattayarak, and could excavate most of the
remaining parts of the mandible of the same individual. The purpose of this paper is to describe
the lower jaw of S. thailandicus on the basis of the nearly complete specimen now available, and
to discuss the affinities of Sunosuchus more fully than was possible in 1980.

GEOLOGICAL SETTING

The specimen was found in a road-cut at km 80-1-800 on the highway between Udon Thani and
Nong Bua Lam Phu. It was embedded in a reddish claystone containing calcareous nodules which
give it a conglomeratic appearance, belonging to the Phu Kradung Formation. The Phu Kradung
Formation belongs to the lower part of the Khorat Group (see Ramingwong 1978, for a review
of the Khorat Group). Although it was first considered to be largely Triassic (Ward and Bunnag
1964), the Phu Kradung Formation is now usually referred to the early Jurassic (Hahn 1982),
which is in accordance with recent magnetostratigraphic data (Bunopas 1981; Maranate 1982).
Recent discoveries of land vertebrates in the Khorat Group (Buffetaut 1982r/) have allowed a better
dating of its formations, and these biostratigraphic data are in agreement with an early Jurassic
age for the Phu Kradung Formation (Buffetaut and Ingavat, in press), although very few vertebrate
fossils have been found in this formation itself. The best specimen discovered so far is the crocodilian
jaw described in this paper, and it does not provide accurate biostratigraphic information (except
that it has to be younger than the Triassic). At the moment, it is still impossible to refer the Phu
Kradung Formation to any definite stage of the early Jurassic.

The Khorat Group, which occupies a vast area of north-eastern Thailand, is interpreted as an
essentially freshwater molasse deposit resulting from the erosion of mountains created by the
eollision of the Thai-Chan, Indochina, and South China blocks (Indosinian orogeny) sometime in
the middle or late Triassic (Bunopas 1981). The Phu Kradung Formation, which contains

I Palaeontology, Vol. 27, Part I, 1984, pp. 199-206, pi. 25.|

200

PALAEONTOLOGY, VOLUME 27

non-marine bivalves, is supposed to have been deposited in a fluvio-lacustrine environment (Hahn
1982). Teeth from this formation which have been referred to marine reptiles (Kobayashi et al.
1963; Ward and Bunnag 1964) in all likelihood actually belong to crocodilians (Buflfetaut and
Inga vat 1980), and cannot be used as evidence of marine influences.

PRESERVATION OE THE SPECIMEN

The lower jaw of S. thailandicus from Nong Bua Lam Phu is kept in the collections of the
Department of Mineral Resources, Bangkok, under no. TF 1370. When found, the specimen was
already broken within the sediment, and had been further damaged by roots, especially in its
posterior parts. The dentaries were separated along the symphyseal suture. Many teeth are missing,
and their alveoli are filled with matrix; in some of them the tips of replacement teeth are visible.
All the erupted teeth still preserved in their alveoli are broken; a number of tooth fragments were
found in the sediment around the jaw, but only a few could be fitted back to it. The edges of the
alveolar openings are often poorly preserved, so that in some parts of the dentaries it is diflficult
to count the alveoli. The left ramus of the mandible is broken at the level of the most posterior
teeth, and roots have damaged this region, which is now difficult to reconstruct. On the right side,
a section comprising the back part of the symphysis (posterior to the seventeenth tooth) and the
anterior part of the ramus could not be found (see PI. 25) despite a thorough search of the outcrop,
which also failed to reveal any other skeletal elements of this crocodilian.

DESCRIPTION

The mandibular symphysis is long, reaching the level of the twenty-fifth tooth, and represents about 42% of
the total length of the lower jaw, but it is also robust and relatively wide, with an anterior spoon-shaped
expansion followed by a constriction (PI. 25, figs. 1, 2). More posteriorly, the sides of the symphysis diverge only
slightly towards the rear. In lateral view (PI. 25, fig. 3) the toothed part of the jaw is seen to be slightly curved, its
dorsal side being concave and its ventral side convex. Posterior to the symphysis, the mandibular rami diverge
gradually. The medial side of the left ramus makes an angle of 30° with the longitudinal axis of the symphysis.
The fenestra mandihularis externa is elongated and both its ends are pointed.

Measurements

Total length of lower jaw (as reconstructed) 1 140 mm

Length of symphysis (dorsally) 475 mm

Maximum height of symphysis (at the level of the twenty-second tooth) 56 mm

Maximum width of left dentary (at the level of the fourth tooth) 80 mm

Length of splenial symphysis 170 mm

Dentary. The dentaries are elongated and joined together at the symphysis for a considerable part
of their length. Twenty-eight alveoli are visible on the left dentary, the posterior part of which is damaged,
and it is likely that there were actually thirty teeth in each dentary. Anteriorly, the dentaries are widened to
form the above-mentioned spoon-shaped expansion, the dorsal surface of which is slightly concave
transversally and convex longitudinally. The maximum width of the symphysis is at the level of the fourth
alveoli, the edges of which are projecting laterally. Posterior to the expansion, the jaw becomes narrower up

EXPLANATION OF PLATE 25

Figs. 1-5. Lower jaw of Swwsuchus thailandicus Buffetaut and Ingavat 1980, from the early Jurassic Phu
Kradung Formation near Nong Bua Lam Phu, north-eastern Thailand, Collection of the Department ot
Mineral Resources, Bangkok, no. TF 1370 (holotype). 1, dorsal view. 2, ventral view of symphysis and left
ramus. 3, left lateral view. 4, lateral view of anterior part of right dentary. 5, medial view of anterior part of left
dentary. All figs. xL Photographs by C. Abrial.

PLATE 25

BUFFETAUT and INGAVAT, Sunosuchus

202

PALAEONTOLOGY, VOLUME 27

to the level of the seventh tooth, the symphysis being narrowest at the level of the interval between the seventh
and eighth teeth. Further posteriorly, the symphysis becomes slightly wider again. The two most anterior
alveoli (with diameters of 12 and 15 mm respectively) open upwards and towards the front. At this level, the
anterior edge of the symphysis is regularly rounded. The third and fourth alveoli are very large (diameters:
20 and 23 mm) and contiguous; they open upwards and outwards. The hfth alveolus is much smaller (diameter:
10 mm) and separated from the fourth by a fairly long space (20 mm). More posteriorly, the diameters of
the alveoli are difficult to measure accurately because their edges are not perfectly preserved. Up to the ninth
alveolus, the alveoli are small, with diameters between 10 and 13 mm, and separated by short spaces (5 to
10 mm). The lateral edges of the alveoli protrude in dorsal view, more so on the right side than on the left,
a condition which may well be abnormal. Further posteriorly, the alveoli are almost contiguous, separated
by spaces only a few millimetres long. Posterior to the end of the symphysis, the walls between the alveoli
are not very distinct, which gives the impression that the teeth were set in a groove. The diameter of the teeth
does not seem to decrease much towards the rear. In lateral view, on the left side (PI. 25, fig. 3), the lateral
edge of the alveolar row is regularly curved, with the concavity facing upwards. On the right side (PI. 25, fig.
4), the outline is more irregular. Medial to the tooth rows, the buccal floor is nearly flat, sloping only slightly
from the midline towards the sides. There is no sagittal ridge, and only slight longitudinal depressions on
both sides. From the level of the seventeenth alveolus rearwards, a weak ridge is visible immediately medial
to the tooth rows. At the level of the sixteenth alveolus on the right side, and medial to it, there is a distinct
rounded pit, with no symmetrical depression on the left side. Generally speaking, the teeth on the right side
show a more irregular implantation, which may be pathological. The medial face of the dentaries is a sutural
surface (PI. 25, fig. 5) longitudinally crossed by the Meckelian canal, which ends anteriorly at the level of the
sixth tooth. Grooves and ridges diverge on both sides of this canal. The ventrolateral surfaces of the dentaries
are ornamented with irregular deep grooves, which become more loosely arranged anteriorly, where their
longitudinal orientation disappears. Just below the tooth rows, a series of vascular foramina is visible.

The teeth are poorly preserved. They are strong, conical, and slightly recurved. There are very stout recurved
fangs in the third and fourth alveoli. The apex of the teeth is rarely preserved. However, in the seventeenth
alveolus of the left dentary, the rounded tip of an unworn replacement tooth is visible, with irregular ridges
and wrinkled carinae. The teeth bear numerous fine ridges, separated by grooves with a concave floor. The
carinae are poorly marked.

Splenial. The splenials taper to a point between the dentaries, thus taking part in the mandibular symphysis.
Ventrally, the right splenial is seen to reach the level of the thirteenth tooth. Dorsally, the splenial was
apparently somewhat shorter; to judge from the poorly preserved anterodorsal end of the left splenial, it
reached the level of the seventeenth or eighteenth tooth. In posterior view, the left splenial shows a deep pit
overhung by the posterodorsal part of the bone. Posteriorly, in the jaw rami, each splenial forms a kind of
low ridge medial to the tooth row. Still further back, the splenial becomes a relatively thin bony plate adhering
to the more lateral bones of the jaw and reaching the anterior extremity of the fenestra mandihularis externa,
but these regions are poorly preserved and few details can be seen.

Mandibular rami. In the posterior parts of the mandibular rami, the sutures between the bones are usually
difficult to trace, so that it is not convenient to describe each bone separately. On the lateral surface, the
dentary is fork-shaped posteriorly and thus forms the anterior border of the fenestra mandihularis externa.
Along the ventral edge of this opening, it tapers to an elongated point. More ventrally, the anterior end of
the angular also forms a point, below the posterior end of the dentary. Above the fenestra mandibularis
externa, the suture line between the surangular and the dentary is poorly visible. The fenestra mandibularis
externa is roofed over by the surangular, which forms a smooth bony plate, convex dorsally and concave
ventrally. The ventral limit of the fenestra is a more robust bony bar formed by the angular; its ventrolateral
surface is covered with grooves, while the medial and the concave dorsal surfaces are smooth. Posterior to
the fenestra mandihularis externa, the surangular and the angular meet along a hardly discernible suture to
form, on the lateral side, a vast bony surface ornamented with deep irregular pits separated by strong ridges.
This surface is limited dorsally by a distinct ridge borne by the surangular. This bone does not take part in
the glenoid surface for articulation with the quadrate. The glenoid surface is formed by the articular alone;
it is large, tongue-shaped, with a strong rounded medial expansion, which overhangs the medial surface of
the bone. The retroarticular process is moderately long (170 mm on the left side), not much recurved, with
a slight upward concavity. It is built mainly by the articular, the angular and the surangular being included
in it along part of its length only, on the lateral side.

BUFFETAUT AND INGAVAT: JURASSIC CROCODILE FROM THAILAND

203

TEXT-FIG. 1 . Reconstruction of the lower jaw of Simosuchus ihailaiuiiciis, based on
specimen TF 1370 (holotype), in the collection of the Department of Mineral
Resources, Bangkok. Dorsal view. Abbreviations: an, angular; ar, articular; d,
dentary; s, splenial; sa, surangular. x

204

PALAEONTOLOGY, VOLUME 27

AFFINITIES OF SUNOSUCHUS THAILANDICUS

The additional data now available about the mandible of the Nong Bua Lam Phu croeodilian
justify a further diseussion of its affinities (Buffetaut and Ingavat 1980).

Affinities with Sunosuchus miaoi. The type species of the genus Sunosuchus is S. miaoi Young
1948, based on various remains including an incomplete skull and lower jaw from the Jurassic
Hokou series of Kansu, in north-central China (see Young 1948, Buffetaut and Ingavat 1980).
Comparisons between S. miaoi and S. thailandicus are relatively difficult, because most of the
mandibular symphysis (the anterior part) of the Chinese specimen is missing, while nothing is
known about the skull of the Thai form. However, the parts known in both specimens are very
similar. The resemblances in the general shape of the mandibular rami and of the fenestra
mandihidaris externa, and in the morphology of the teeth, have already been mentioned in our
previous paper. It now appears that the posterior part of the symphysis is also similar in both
forms, but so little is preserved of the symphyseal region in the Chinese fossil that this comparison
is not very revealing. In any case, knowledge of the complete lower jaw of the Thai crocodilian
by no means precludes its inclusion in the genus Sunosuchus. Distinction from the Chinese form
at the species level is justified by size and proportional differences (Buffetaut and Ingavat 1980).

Affinities of the genus Sunosuchus. The discovery that S. thailandicus is a very long-snouted
crocodilian prompts a new discussion of the systematic position of the genus Sunosuchus. Young
(1948) classified S. miaoi among the Pholidosauridae because he assumed that its snout was long
and relatively narrow. Although this was not exactly obvious on the basis of the Chinese specimen,
the discovery of the jaw from Thailand now shows that Young was right in considering Sunosuchus
as a longirostrine crocodilian. In 1980 we defended the view that Sunosuchus should be included
in the Goniopholididae, because of several features of the skull of S. miaoi, viz. small supratemporal
fenestrae, anterior palatal openings, and the possible presence of maxillary depressions. Although,
as we already pointed out, some Goniopholididae had relatively long snouts, the very long
mandibular symphysis of S. thailandicus is at first sight more reminiscent of the consistently
long-snouted Pholidosauridae (although it is rather different from Pholidosaurus itself, in which
the jaws are much more slender). As mentioned above, the mandibular symphysis of Y. thailandicus
reaches the level of the twenty-fifth tooth, while it reaches the level of the sixth or seventh alveoli
in Goniopholis, and that of the eleventh tooth in Vectisuchus leptognathus, a relatively long-snouted
goniopholidid from the Wealden of England (Buffetaut and Hutt 1981). The shape of the symphysis
of S. thailandicus, and especially of its anterior end, is also reminiscent of some pholidosaurids,
notably the very large Sarcosuchus, from the lower Cretaceous of Niger and Brazil (see Buffetaut
and Taquet 1977) in which, incidentally, the symphysis reaches at least the level of the twenty-third
tooth. Although the rather conspicuous constriction at the level of the interval between the seventh
and eighth teeth in 5. thailandicus is not so marked in Sarcosuchus, in both instances there is
a noticeable anterior expansion, the widest part of which corresponds to the large third and fourth
alveoli. However, some short-snouted Goniopholididae, such as Goniopholis crassidens from the
Purbeck and Wealden of England, are also very similar to S. thailandicus in this respect, although
they have a short symphysis (see the lower jaw figured by Owen 1878, pi. I). The main difficulty
about assessing the affinities and systematic position of Sunosuchus is that the Goniopholididae
and the Pholidosauridae are two closely related mesosuchian families. Actually, the question is
whether Sunosuchus should be considered as a primitive pholidosaurid, with small supratemporal
fenestrae, or as a specialized long-snouted goniopholidid, and in this respect the length of the
symphysis is probably not of prime importance, all the more so that elongation of the jaws is
known to have occurred independently in many crocodilian lineages. There remains the already
mentioned skull characters that we used (Buffetaut and Ingavat 1980) to support the inclusion of
Sunosuchus in the family Goniopholididae. The presence of a maxillary depression in the posterior
part of the maxillae (about the definition and significance of this feature, see Buffetaut 1982fi)
would be important evidence in favour of this inclusion, but it needs to be checked on the actual

BUFFETAUT AND INGAVAT: JURASSIC CROCODILE EROM THAILAND

205

specimen whether the depression shown on Young’s figures is really natural, and not an artefact
of preservation. Maxillary depressions are known only in the Goniopholididae. Anterior palatal
openings in the palatines and maxillae, like those of S. niiaoi, have been reported only in some
North American Goniopholididae (Mook 1967; Langston 1973) of the late Jurassic, and this may
also be a character restricted to some goniopholidids. However, these openings may actually
represent a primitive condition retained from Triassic crocodilians in which the palate was not as
well developed as in the Mesosuchia (Buffetaut 1982/)). In this case they may have also been present
in primitive representatives of several mesosuchian families, including possibly the Pholidosauridae.
The problem cannot be solved at the moment for lack of relevant evidence (it should be remembered
that extremely little is known about the early representatives of most families of freshwater or
terrestrial Mesosuchia prior to the late Jurassic; see Bufl'etaut 1982/)). As to the small size of
the supratemporal fossae, it is also a primitive feature for all Mesosuchia. The question is
whether a pholidosaurid-like crocodilian with small supratemporal fossae should be included in
the Pholidosauridae.

In the absence of data about some crucial parts of the skull, such as the premaxillae, which are
hook-shaped in the Pholidosauridae (Buffetaut 1982/>), it is obviously difficult to reach a definite
conclusion about the systematic position of Sunosuchus. We think the best attitude at the moment
is to consider it as a long-snouted, specialized goniopholidid, while keeping in mind that the
Pholidosauridae probably have their origin among the Goniopholididae (Buffetaut 19826), and
that Sunosuchus is in some ways morphologically intermediate between these two families.

A NOTE ON PALAEOBIOGEOGRAPHY

There is little to add to the remarks on the palaeobiogeographical significance of S. lhailandicus
which were made in our 1980 paper. On the basis of its morphology and of the depositional
environment of both the Phu Kradung Formation in Thailand and the Hokou series in China,
Sunosuchus can be considered as a presumably piscivorous freshwater crocodilian, which should
be used as a continental faunal element in palaeobiogeographical reconstructions. In the context
of the hypothesis of the northward drift of South-East Asia and its subsequent collision with
mainland Asia (see Ridd 1980), the occurrence of the genus Sunosuchus in Thailand and in China
(and, so far, nowhere else) does suggest that in the Jurassic the fauna of north-eastern Thailand
already had Laurasian affinities. Recent palaeontological discoveries in Thailand actually indicate
that colonization of north-eastern Thailand by Laurasian continental vertebrates had already taken
place earlier: the late Triassic, probably Norian, vertebrate fauna from the Huai Hin Lat Formation,
which includes lungfishes, stegocephalian amphibians, turtles, and phytosaurs, shows striking
Laurasian affinities (review in Buffetaut 1982a). This in turn indicates that collision of the Indochina
block (which includes north-eastern Thailand) with South China occurred no later than the late
Triassic.

Acknowledgements. We thank our Thai and French colleagues who helped in the excavation of the Sunosuchus
jaw: Leonard Ginsburg, Philippe Janvier, Michel Martin (Paris), and Nares Sattayarak (Bangkok).

REFERENCES

BUFFETAUT, E. 1 982o. Mesozoic vertebrates from Thailand and their palaeobiological significance. Terra cognita,
2 (1), 27-34.

19826. Radiation evolutive, paleoecologie et biogeographie des Crocodiliens Mesosuchiens. Man. Soc.

geol. Fr. N.s. 60 (142), 1-88.

and HUTT, s. 1980. Vectisuchus leptognathus, n.g. n. sp., a slender-snouted goniopholid crocodilian from the

Wealden of the Isle of Wight. Neites Jh. Geol. Palaont. Mh. 7, 385-390.

and INGAVAT, R. 1980. A new crocodilian from the Jurassic of Thailand, Sunosuchus thailandicus n. sp.

(Mesosuchia, Goniopholididae), and the palaeogeographical history of South-East Asia in the Mesozoic.
Geohios, 13 (6), 879-889.

206

PALAEONTOLOGY, VOLUME 27

BUFFETAUT, E. and INGAVAT, R. (in prcss). Fossil vertebrates from the Jurassic of Thailand. CCOP Bulletin.

and TAQUET, p. 1977. The giant crocodilian Sarcosuchus in the early Cretaceous of Brazil and Niger.

Palaeontology, 20, 203-208.

BUNOPAS, s. 1981. Paleogeographic history of western Thailand and adjacent parts of South-East Asia. A plate
tectonics interpretation. Ph.D. thesis, Victoria University of Wellington, New Zealand. Reprinted 1982,
Geological Survey Paper, no. 5, Department of Mineral Resources, Bangkok.

HAHN, L. 1982. Stratigraphy and marine ingressions of the Mesozoic Khorat Group in northeastern Thailand.
Geol. Jh. B, 43, 7-35.

ROBAYASHi, T., TAKAi, F. and HAYAMi, I. 1963. On some Mesozoic fossils from the Khorat series of East Thailand
and a note on the Khorat series. Jap. J. Geol. Geogr. 34, 2-4, 181-192.

LANGSTON, w. 1973. The crocodilian skull in historical perspective. In gans, c. and parsons, t. s. (eds.). Biology
of the Reptilia, 4, Morphology D. Academic Press, London and New York, 263-284.

MARANATE, s. 1982. Paleonuignetism of the Khorat Group in Northeast Thailand. Geological Survey Division,
Department of Mineral Resources, Bangkok, 1-40.

MOOR, c. c. 1967. Preliminary description of a new goniopholid crocodilian. Kirtlandia, 2, 1-10.

OWEN, R. 1878. Monograph on the fossil Reptilia of the Wealden and Purbeck formations. Supplement no. 8.

Crocodilia (Goniopholis, Petrosuchus, and Suchosaurus). Palaeontogr. Soc. [Monogr.], 1-15.

RAMiNGWONG, T. 1978. A review of the Khorat Group of Thailand. In nutayala, p. (ed.). Geology and mineral
resources of Southeast Asia. Proc. 3rd Reg. Conf. Geol. Min. Res. SE Asia. Bangkok, 763-774.

RiDD, M. F. 1980. Possible Palaeozoic drift of SE Asia and Triassic collision with China. J. geol. Soc. Lond. 137,
635-640.

WARD, D. E. and BUNNAG, D. 1964. Stratigraphy of the Mesozoic Khorat Group in northeastern Thailand. Rep.
Invest. Dep. Min. Res. Thailand, 6, 1-95.

YOUNG, c. c. 1948. Eossil crocodiles in China, with notes on dinosaurian remains associated with the Kansu
crocodiles. Bull. geol. Soc. China, 28, 255-288.

ERIC BUFFETAUT

E.R.A. 963 du C.N.R.S.
Laboratoire de Paleontologie des Vertebres
Universite Paris VI
4 place Jussieu
75230 Paris Cedex 05
France

RUCHA INGAVAT
Geological Survey Division
Department of Mineral Resources
Rama VI Road
Bangkok 10 400
Thailand

Typescript received 25 April 1983

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NOTES FOR AUTHORS

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Palaeontology

VOLUME 27 • PART 1

CONTENTS

The Diploporita of the Oslo region, Norway

J. FREDRIK BOCKELIE 1

Permineralized ovulate cones of Lebachia from Late Palaeozoic
limestones of Kansas

G. MAPES and G. w. rothwell 69

The Dinantian Taphrognathus transatlanticus conodont Range
Zone of Great Britain and Atlantic Canada

PETER H. VON BITTER and RONALD L. AUSTIN 95

Patterns of stromatoporoid growth in level-bottom environ-
ments

STEPHEN KERSHAW 113

A late upper Triassic sphenosuchid crocodilian from Wales

P. J. CRUSH 131

The affinities of the Cretaceous ammonite Neosaynoceras
Breistroffer, 1947

W. J. KENNEDY and C. W. WRIGHT 159

A new subfamily of the Pteraspididae (Agnatha, Heterostraci)
from the upper Silurian and lower Devonian of Arctic Canada
D. K. ELLIOTT 169

The lower jaw of Sunosuchus thailandicus, a mesosuchian
crocodilian from the Jurassic of Thailand

ERIC BUFFETAUT and RUCHA INGAVAT 199

Printed in Great Britain at the University Press, Oxford

ISSN 003 1-0239

Palaeontology

VOLUME 27 PART 2 MAY 1984

?I55'

NnV

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Dr. A. W. Owen, Dundee

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Australia: Professor B. D. Webby, Department of Geology, The University, Sydney, N.S.W., 2006
Canada: Dr. B. S. Norford, Institute of Sedimentarv and Petroleum Geology, 3303-33rd Street NW., Calgary, Alberta
Japan: Dr. I. Hayami. University Museum, University of Tokyo, Hongo 7-3-1, Bunkyo-Ku, Tokyo
New Zealand: Dr. G. R. Stevens. New Zealand Geological Survey. P.O. Box 30368. Lower Hutt
U.S.A.: Dr. R. Cuffey. Department of Geology, Pennsylvania State University, Pennsylvania
Professor A. J. Rowell, Department of Geology, University of Kansas, Lawrence, Kansas 66045
Professor N. M. Savage, Department of Geology, University of Oregon, Eugene, Oregon 97403 „

South America: Dr. O. A. Reig, Departamento de Ecologia, Universidad Simon Bolivar, Caracas 108. Venezuela

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Cover: The Coralline Crag (Pliocene) bryozoan Cribrilina sp. showing a group of ten feeding zooids each with an ovicell and
paired adventitious avicularia on either side of the orifice. This specimen was figured as Lepralia punctata Hassall in G. Busk’s
Palaeontographical Society monograph of Crag Polyzoa (1859, pi. 4, fig. 1 ). It is reillustrated here by means of a new technique,
scanning electron microscopy of the uncoated specimen using back-scattered electrons, x 75.

CONSTRUCTIONAL MORPHOLOGY OF BIVALVES:
EVOLUTIONARY PATHWAYS IN PRIMARY
VERSUS SECONDARY SOFT-BOTTOM DWELLERS

by A. SEILACHER

(Twenty-fourth annual address, delivered 10 March 1983)

o.

V

/

0

Abstract. In contrast to the minor within-habitat improvements in shell shape and sculpture of primary
soft-bottom dwellers, the transition of fixosessile rock dwellers back to soft substrates has resulted in fast and
drastic morphological changes. They were facilitated by the available ecologic stepping stones that caused
morphogenetic programmes — first to ‘derail’ (rock habitats), then to be shortened (to fit the size of dead shell
habitats), and finally to extend again (in order to increase mechanical stability on soft bottoms). The third step
allows only a limited number of adaptational strategies (flat, outriggered, and edgewise recliners; mud stickers;
‘pickabacks’) that led to convergent shell forms in different groups of bivalves. Within groups, however,
phylogenetic and morphogenetic constraints, as well as the adaptational landscape, channel evolution to such a
degree that it becomes difficult, at least in the fossil record, to resolve the multitude of parallel and iterative
lineages.

Evolutionary discussions in modern times have often been discussed in terms of theoretical
models, with the result that they become more and more detached from the everyday experience of
palaeontologists engaged in stratigraphical and morphological problems. This development has
forced us into divided camps: neutralists versus adaptationists, gradualists versus punctuationalists,
and so on. This appears unneccessary to me. The present study builds on the conviction that
evolution is an ecological process and that it is basically opportunistic. Thus I do not expect evolution
to subscribe to any particular principle, but to follow the one or the other as fits the situation. In order
to understand a given situation in morphological evolution, we must learn the licences, i.e. the
options and constraints that are imposed on established bauplans by morphogenetic mechanisms in
their approximation of an appropriate functional design, or paradigm. This is the approach of
constructional morphology. We consider it as a method of research rather than a theoretical
framework, so that it makes sense only if applied to a certain group of organisms. Nevertheless the
resulting case histories are not irrelevant for theoretical evolutionary considerations. By extending
our view from specific cases to larger groups, we can expect to find general patterns— not in the sense
of built-in rules (because the steps are stochastic in principle), but as a reflection of the adaptive
landscape and its changes in time, by which evolution is ultimately moulded.

In this approach our curiosity focuses on the familiar phenomena of convergence (if we deal with
disparate origins) and of parallelism and iteration (within one group). Classical convergences, such
as aberrant ‘coralliform’ types— including top-shaped rudist bivalves, richthofeniid brachiopods,
hipponicid gastropods — are not randomly distributed in ecospace, but are concentrated in an
ecological group that is here called ‘secondary soft-bottom dwellers’. By this we understand forms
that acquired a sedentary mode of life, usually attached to hard substrates, in a previous evolutionary
step and have secondarily switched to life on areas of marine soft bottoms (sands and muds). In this
new habitat they found enough food as suspension feeders, but faced the critical problem of their
inherited immobility. Only very few groups, such as the swimming pectinids and limids (perhaps
similarly some strophomenacean brachiopods), the burrowing actinians, and some corals managed
to develop a new mode of mobility, sufficient to escape from predators and to reorient themselves.

I Palaeontology, Vol. 27, Part 2, 1984, pp. 207-237.]

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PALAEONTOLOGY, VOLUME 27

Others went into ‘pickaback’ symbiosis with a mobile partner such as a hermit crab. But the vast
majority solved the problem by stabilizing themselves through stable shapes and/or heavy and
commonly oversized skeletons.

From the different phyla and classes included in the project, I select here the bivalves, because they
are well-known and have made the transition from soft to hard substrates and back several times
during their long history, such that we can hope to sample most of the different solutions. Bivalves
also allow us to compare form changes in secondary soft-bottom dwellers with those in primary ones,
particularly with changes that improved the ability to burrow.

This project (D 60, ‘Substratwechsel im marinen Benthos’) is part of the Tubingen special research group (SFB
53) supported by the Deutsche Forschungsgeineinschaft. The contribution largely draws upon published results
of temporary members of the group and discussions with them through the years, in particular A. Hoffmann
(Madison, Wise.), H. Roder (Seeliberg), H. Schmalfuss (Stuttgart), P. Signor (Davis), E. Savazzi (Uppsala),
G. McGhee (New Brunswick). Figured specimens are deposited in the collections of the Institut fiir Geologie
und Palaontologie of the Tubingen University under the catalogue numbers GPIT 1604/1-42. This is Nr. 163 of
the series ’Konstruktionsmorphologie’ (Nr. 162 see: Hemleben and Spindler, Utrecht Micropal. Bull., in press).

PRIMARY SOFT-BOTTOM DWELLERS

Molluscs probably had their origin on hard bottoms, where they could crawl in a limpet-like fashion
with a broad-soled foot and protect themselves by pressing the dorsal shell against the substrate.
From such ancestors, bivalved forms evolved probably with the transition to soft substrates, where
the gills needed an extra protection (Vogel and Gutmann 1980). The change from a univalved to a
bivalved state required only a minor change in the ontogenetic programme of calcification (Bayer
1978). Since the univalved ancestors in this case had not lost their mobility, the foot could become
adjusted in the new habitat to become an effective burrowing organ. Thus, bivalves as a group can be
considered primary soft-bottom dwellers that largely use the gills as a food-filter and have therefore
lost typical mollusc attributes such as primary eyes and the radula.

In the molluscs, bivalved form has evolved more than once (rostroconchs, bertheliniid gastropods,
bivalves); but in each case (as also in bivalved arthropods) the two valves remained connected by a
less-calcified zone that acts as an elastic ligament. This is in marked contrast to the brachiopod valves,
whose articulation probably evolved secondarily from two separate shells protecting the gills of a
worm-like ancestor (Vogel and Gutmann 1980). Since this option has led to a crucial constraint in the
further modification of the bivalve bauplan, we must first discuss the properties and modifications of
the bivalve ligament.

Ligaments

As an antagonist of the adductor muscles, the ligament elegantly serves the function of opening the
valves. This problem could not be solved by hydraulics alone, because for such a function the mantle
sac would have to remain closed in the open-valve position, which is incompatible with feeding. The
alternative, namely opening the valves by diductor muscles, was secondarily achieved by the pholads.
In this group the valves have become drilling devices, while their protective function is taken over by
the hard substrate in which they bore (Roder 1977). Therefore it was possible to attach part of the
anterior adductor muscle on the outside of the hinge, where it could act as a diductor and control the
complicated movements of the valves much better than a lifeless ligament, which has become obsolete
in this case.

The other major group in which the ligament has become reduced or lost are the rudists. Flere the
delegation of the opening function to parts of the adductors seems to have been attained through
tooth-like projection of the myophores, with the advantage that the diductor parts remained inside
the shell. This construction would approach that of articulate brachiopods, but its functional details
and the possible pathways into it are not yet clear.

Returning to the structure and properties of the ligament, it should be remembered that we deal
with a less calcified part of the shell that grows primarily in a similar way, i.e. with an outer layer

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

209

(apart from the periostracum) formed near the margin and an inner layer thickening the ostracum
from the inside. The structure of the two layers corresponds to the stress to which they are exposed; it
is fibrous (or prismatic) on the compressive and lamellar (or nacreous) on the tensional side, with the
expected inversion in the ligament versus the shell. But the ideal design, in which the two layers should
have corresponding thicknesses throughout the shell so that their boundary remains in the neutral
zone, is impossible to produce in a growing structure, in which only the inner layer can be secondarily
thickened. In the calcified shell, this defect can be compensated by overdesigning. In the ligament,
however, it becomes critical. A second constraint stems from the fact that the ligament consists of
non-living material. Thus its elastic properties do not change with the dimensions of the growing shell
and they may also deteriorate by ageing.

Text-fig. 1 shows ways in which the two constraints are coped with in various types of ligaments.
Major ‘tricks’ are (1) the breaking of the outer layers, with fresh material being continuously
produced in the functional zone and (2) the regular introduction, or maintenance, of separate
generative zones for the outer layer apart from the outer shell margin. Text-fig. 1 also demonstrates
that the new generative zones do not grow as predicted by the model of spiral shell growth (text-fig.
li-K), but in ways that allow to maintain, at all stages, the same absolute distances between them
along the hinge line. We assume that these distances are optimized against the constant elastic
properties of the two ligament materials. The ligament also imposes strong constraints on shell
geometry. For instance, /u/r/ ligaments limit not only the secondary thickening of the shells, but also

^ not existent

Fold Ligaments c

Ligaments ~

Q.

amphidetic

opisthodetic

TEXT-FIG. 1. Only fold ligaments remain functional throughout their
lengths; in break ligaments the functional parts of the two layers alternate
along the hinge. Note that seemingly straightforward solutions (c, G, H)
are not represented because of geometrical or mechanical constraints
(from Seilacher 1981, modified).

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PALAEONTOLOGY, VOLUME 27

shell curvature. In the theoretically simplest case, in which this type of ligament would extend
amphidetically on both sides of the umbo (text-fig. Ic), shell curvature would be reduced to zero. It is
therefore not represented. Also, the evolution of inequilateral, prosogyre shells in this group has
probably as much to do with the space conflict between the two umbones in the case of a
non-expandable ligament, as with an endobenthic, burrowing mode of life.

It should be noted that seemingly non-breaking ligaments are nevertheless affected by growth
deformation. This is most obvious in modern Pinna (text-fig. 8), where the cross-sectional angle of
the hinge becomes widened beyond the yield of the ligament during ontogeny. As a result the ligament
is broken in the apical part of all specimens and the separated apices become scissored in a regular
way (the left apex always slips dorsally over the right one), with internal flexible septae compensating
for the inevitable damage. In this case the ligament will start to break from the inside— an interesting
analogue to the rostroconch hinge. It would be interesting to study whether in this case the animal is
able to repair the damage by deposition of new ligament material from the inside.

BURROWING SCULPTURES

Technical Paradigm Divaricate Patterns

TEXT-FIG. 2. Ratchetted sculptures reduce back slippage while the shell acts as a penetration anchor for the
probing foot. Deviations from the paradigm of the cross-country ski reflect the rocking and opening of the valves
(c-e) and their pivoting in f. In horizontal borrowers (e) burrowing sculptures are stronger on the upper valve to
compensate for reduced resistance of the sediment layer on top (a from Trueman and Ansell 1969, c-f from

Seilacher 1972, modified).

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

211

Break ligaments, on the other hand, are split from the outside. They not only allow, but require a
certain amount of shell thickening and also permit the growth of highly vaulted valves. Nevertheless
inequivalvity is common, because it reduces the space problem of the opposed umbones and because
it agrees with the pleurothetic mode of life, which is common in epibenthic species. Inequivalves are
also limited by the requirement that an equal amount of ligament should break on both valves.
Another way out of the umbonal space problem is the transition, during ontogeny, from convex to
concave curvature in the flatter valve of inequivalves such as Gryphaea.

An obviously successful compromise is the ligament design found in many heterodonts (text-
fig. 1h). Here the two ligament layers are widely separated for increased lever on both sides of the
hinge axis and breakage is not excessive. The resulting limitation of shell curvature also agrees with
the streamlining required by a burrowing mode of life, while umbonal collision can be avoided by a
prosogyrous growth programme. Another possibility to avoid this collision is an ontogenetic switch to
higher curvatures in both valves after a flattened umbo has been produced in the early stages [Circe).

We shall come back to ligamental problems in our discussion of secondary soft-bottom dwellers.

Shell adaptations to burrowing

On soft bottoms the ability to burrow has a major bonus, because it reduces predation pressure, while
allowing for various modes of nutrition such as suspension feeding, epistratal and intrastratal
sediment feeding, and even carnivorous habits. The mechanical principles of soft-substrate
burrowing have been analysed by Trueman and Ansell (1969). The most effective design is
represented by worm-like organisms. As primary soft-bottom dwellers in the strictest sense they have
evolved a cylindrical hydraulic body that combines ideal streamlining with the possibility to glide
through the sediment almost as easily as along its top. Here, the peristaltic thickening and contraction
of body sections transform the push-and-pull action into a seemingly continuous process. In bivalve
burrowing, however, functions are divided between the different parts of the body (text-fig. 2). The
foot, as a hydraulic structure, alternatively thins into a probe and thickens into a protraction anchor.
Correspondingly, the shell is expanded as a penetration anchor during the probing of the foot and
becomes partly closed when it is pulled behind. In this phase friction can be further reduced by the
ejection of water from the front end and the resulting fluidization of the sediment around the shell.

This mode of burrowing was so successful that it has been maintained by all bivalves that remained
in soft substrates. They also have never reduced the shell, because it serves not only for protection, but
also supports the necessary filter chamber. In boring bivalves, however, these two functions were
taken over by the hard substrate, so that the shell could be transformed into a boring instrument
without being constrained by additional tasks (Roder 1977).

In burrowing bivalves evolutionary trends in shell morphology are thus limited to minor
modifications that improve the burrowing function. For instance, shell geometry tends to become
more streamlined and elongated as species burrow deeper and reach more compacted sediment
(Stanley 1970).

Another common trend is the evolution of burrowing sculptures (Jefferies et al. 1981; Savazzi et al.
1982) in shallow burrowers (text-fig. 3). Like the profiles of cross-country skis, they reduce back
slippage of the shell while it serves as a penetration anchor and produce minimal friction while it is
being pulled forward. The effectiveness of such ribs obviously depends on their profile, which should
be ratchetted. But experiments (Savazzi 19816) have shown that their dimensioning is also important.
If the ribs are too low, sediment grains will be little affected; if they are too high, grains in the grooves
will slip as a whole against the outside sediment, so that effectivity diminishes again.

On this basis one can formulate the paradigm for burrowing ribs in the following way (Seilacher
1973):

1. They should be ratchetted with the gentle slopes in burrowing direction.

2. Their strike should be at right angles to burrowing direction.

3. Their height should correspond to the grain size of the burrowed sediment.

4. In highly vaulted bodies the profile may be smoothened in the most projecting surfaces, where
forward friction is most critical.

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PALAEONTOLOGY, VOLUME 27

The approximation of this paradigm has been studied in many groups of burrowers (bivalves,
gastropods, crustaceans, trilobites, lingulid brachiopods, calcichordates; see Jefferies et al. 1981 for a
summary). In the view of constructional morphology, these examples are interesting not only because
of their palaeobiological and palaeoenvironmental implications. They may, by significant deviations
from the physical paradigm, also reveal the constraints imposed by a particular bauplan or
morphogenetic program.

In bivalves the major constraint is implied in their accretionary mode of shell growth. In the
theoretical model of spiral shells (Raup 1966), growth conformable sculptures are either radial or
concentric. None of the two can have the same strike relative to burrowing direction all over the shell.
This dilemma can be lessened by emphasizing radial or concentric ribs, or both, in the parts of the
shell, in which they happen to run in the right direction (Seilacher 1973, fig. 2). More difficult is the
task to maintain the same rib dimensions during growth.

Thus it is not surprising that many bivalves programme their burrowing ribs with a principle
( Waddington and Cowe 1969; Meinhardt, in preparation) that is dependent on a time function rather
than being dictated by the geometry of spiral growth (text-fig. 3). This ‘divaricate principle’ (Seilacher
1972), familiarly expressed in mollusc colour patterns, but also in arcoid ligaments, is better suited for
the task at hand. First, it provides not only one, but two coordinate strike directions in a V-shaped
fashion. Secondly, the asymmetry is also provided, as seen in corresponding colour patterns. Thirdly,

TEXT-FIG. 3. Shell outline and divaricate rib pattern oi' Strigilla pisiformis from Miami (Florida) correspond to
the DivaricellaTypc (text-tig. 2c). The regular fashion in which traumatic gaps in the pattern regenerate indicates
that this pattern is formed by a diffusive inhibitor/activator system (SEM photos by H. Hiittemann).

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

213

the spacing (and consequently rib height) is largely growth-independent, so that a near-optimal scale
can be maintained with less difficulty. Thus the alternative, but less efficient solution of allometrically
reducing the height of the ribs relative to their distance (Savazzi 1981 a, 1982r/, h) is not necessary in
this case.

In spite of their fabricational flexibility, actual divaricate burrowing ribs deviate in significant ways
from the cross-country ski paradigm. The rib distance, for instance, is negatively allometric, but still
increases with growth in absolute measure (Seilacher 1972, fig. 6). This indicates that the underlying
morphogenetic principle is not completely growth-independent. More surprising is the fact that these
ribs do rarely run truly perpendicular to burrowing direction. This has to do with the fact that bivalve
shells are not used like cross-country skis. Shells with a rounded outline {Divaricella type, text-
fig. 2c), perform a rocking movement (Stanley 1969), which is also reflected in their V-shaped rib
pattern. The dividing line between the two sets of ribs, however, does not run in burrowing direction,
but is rotated from it counter-clockwise in left view. An analogous rotation is observed in the more
elongated shells of the Yoldia type (text-fig. 2d), in which only one set of divaricate ribs is developed.
This rotation makes sense, if we consider the opening of the valves during the probing phase: the
observed rib direction corresponds to the resultant of the opening and the backslippage vector. A
third group {Macoma type, text-fig. 2e) resembles the previous one in outline and rib pattern, but is
sculpturally inequivalve. It comprises species that burrow along horizontally in a flat position as they
graze the sediment surface with their ingestion siphons. Their reduction or omission of burrowing
sculptures on the lower valve compensates for the higher friction exerted by the sediment below the
shell as compared to the thin and less compacted sediment cover on top of it.

The occurrence of divaricate burrowing ribs in most groups of endobenthic bivalves indicates that
the underlying morphogenetic principle is generally available. All the more it is surprising that not all
burrowing species make use of this possibility. Instead, we find smooth, radially or concentrically
ribbed and tuberculated forms in the same niche. Obviously, there are alternative solutions to the
adaptational problem as well as constraints related to other functions that exclude one standard
interpretation.

It might be mentioned that the case of divaricate burrowing ribs has been repeatedly cited by modern
neutralists (e.g. Gould and Lewontin 1979) in their critique of the traditional adaptationist camp. In fact, I am
still inclined to believe that most divaricate colour patterns are primarily neutral, or non-functional features in
the sense that any other arrangement would do as well. This is suggested by the fact that in life the patterns
remain hidden in the sediment or under a thick periostracum and that they are extremely variable in contrast to
the few species, in which such patterns demonstrably have a mimetic function. A similar evolutionary
relationship was assumed in the sculptural expression of divaricate morphogenetic programmes. I see this
switching into a more rigorously selected function of a pre-existing, or pre-disposed structure as an interesting
mechanism, but not as a general or even predominating mode of evolutionary change.

SECONDARY SOFT-BOTTOM DWELLERS

Bivalves were extremely successful as soft-bottom filter feeders. Nevertheless, many groups have left
the soft bottom to become hard-bottom dwellers again; but since the burrowing foot could not evolve
back into a crawling sole, they became sedentary. The pathway into a fixosessile niche was wide open
to bivalves due to their mode of nutrition and the general presence of byssus as an organ for larval
attachment (Stanley 1972). The paedomorphic retention of this attachment (and in some instances its
replacement by cementation of the shell to the hard substrate) throughout life led to the reduction
of the foot. It also led to the high intraspecific variability in shell shape that is characteristic of
oyster-like, cemented forms and for species whose byssal attachment to rocky substrates is similarly
rigid.

It is the evolution of such fixosessile rock dwellers back to soft-bottom habitats that I address here.
This step is particularly interesting for a number of reasons:

I . The major adaptational problem implied is straightforward: to make up for the inherited loss of
the foot in an environment devoid of adequate anchoring ground.

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PALAEONTOLOGY, VOLUME 27

2. This evolutionary habitat change has happened in so many instances among bivalves as well as
in other sessile groups, that we have a good chance to do comparative studies and to sample a wide
variety of possible pathways.

3. It is in this group (for which we use the terms ‘secondary soft-bottom dwellers’) that we find the
largest number of bizzare forms — quite in contrast to the primary soft-bottom dwellers discussed in
the previous paragraph.

Thus our first question will be, what allowed the extreme and rapid changes of established bauplans
in this particular situation? This question is relatively easy to answer. It has primarily to do with the
ecological stepping stones that facilitate this change. Corresponding to the rule that an established
system tends to adapt to changing conditions first by developing a cover under which the old
functions can continue, the pioneer species will attach to hard substrates that are available on soft
bottoms, i.e. to dead shells of other organisms. The only morphological change (the ‘cover’) necessary
is progenetic reduction of adult size by shortening the life cycle (‘miniaturization stage’). This
stepping stone remains to be used during early ontogenetic stages by most of the species that do
become independent of such anchoring grounds as they grow up. This makes it difficult, in the fossil
record, to distinguish the miniaturized pioneers from juvenile stages of secondary soft-bottom
dwellers in the strict sense.

The miniaturization stage is critical, because the following evolutionary step implies a considerable
change of selection pressure and also a switch from an r- to a K-strategy. Independence from an
adequate anchoring ground can be gained in three different ways;

1 . By developing a new mode of mobility, such as the ability to swim up (pectinids, limids, and
possibly some Strophomenacea), to crawl (certain corals and bryozoans), and to burrow
(soft-bottom sea anemones; Penicillus, fig. 1 1). Among the pelecypods, only attached Arcacea seem
to have been able to re-activate the foot for this purpose (Thomas 1976).

2. By establishing symbiotic ‘pickaback’ relationship with a mobile partner. The shelter-building
associates of hermit crabs and of some worms are familiar examples.

3. By mechanically stabilizing the body by shape, weight, and size.

Among bivalves the third solution has been the one predominantly used. Therefore we will focus
our discussions on this ‘strategy’. In doing so, we first deal with the forms that were originally
cemented, then discuss byssally attached forms, and finally borers.

CEMENTED STOCKS AND THEIR SOFT-BOTTOM DERIVATIVES

Most cemented bivalves are monomyarian (oysters, spondylids, Placunopsis, plicatulids); but the
dimyarian Chamacea, Rudists, and fresh-water ‘oysters’ {Etheria) show that this is not a necessary
relationship. We shall here use the Ostreacea for reference, because this is the most varied group.
Thus the principal adaptational strategies can be discussed in oyster examples and analogous
adaptations in other groups be listed as convergences.

Morphogenetic consequences of cementation

Since cementation is the task of the growing mantle edge, the commissure has to fit snugly to the
substrate. This means that the relief of the substrate is moulded on the outside not only of the
attached valve (‘immuration’, Voigt 1968), but also of the free valve— in this case as a positive
transformed by the spiral growth geometry (‘xenomorphism’). The eontrol of substrate topography
on growth is also expressed in the outlines of cemented shells, which tend to be irregular and highly
variable. This ecotypic ‘derailment’ of a regular growth programme may facilitate a subsequent
switch to novel programmes.

Cemented growth may continue in this fashion throughout life; but in many eases the commissure
will eventually lift-off the substrate in order to faeilitate water circulation, to widen the shell cavity,
and to defend against overgrowth. This is also the case in the miniaturized soft-bottom pioneers
growing on other shells. The mode in which the attached valve lifts the commissure, predetermines

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

215

the general geometry of growth during subsequent soft-bottom adaptations (text-fig. 4). Thus
elevation of the posterior margin induces an helicospiral exogyrid form, of the ventral margin the
planispiral gryphaeid growth, and of the whole shell including the hinge the saccostreid cone shape.
Other modifications during the lift-off include the alectryoniid plication of the commissure and
retarded calcification giving the free valve a higher flexibility.

These differences can be observed in juvenile stages of advanced forms, but also in minute ancestral
forms. It is probably no coincidence that small and thin-shelled epizoic versions appear strati-
graphically below the large free forms in Lopha (Middle Triassic; Seilacher 1954) and in Exogyra
(Lower Toarcian; Seilacher 1982u). The same is true for Plicalula (P. spiiwsa; Domerian).
A systematic search should also document the miniaturized epizoic ancestors of other groups such as
rudists.

Recliners versus 'mud stickers'

Among the possible strategies of mechanical stabilization two groups should be distinguished,
although they may be not sharply separated. In the first and more common case (‘recliners’ =
Liegeformen; Dacque 1921) the animal essentially rests on the substrate; in the second the shell itself
acts as an anchor in the sediment. In the absence of active burrowing, anchorage inside the sediment
must be acquired passively and will therefore evolve preferentially in quiet environments with a
relatively high sedimentation rate (‘mud stickers’). The difference between the two life forms is
expressed in shell shapes and opening mechanisms, but also in shell structures. Only the recliners
follow the strategy of heavyweight structures that is so much in contrast to the lightweight skeletons
of mobile organisms.

The strategy of ‘mud (or sand) stickers’, being a response to sedimentation is also valid for living
substrates. Therefore it is not surprising to find related forms living in mud and in sponge or coral
colonies {Streptopinna, text-fig. 9; Vermicularia; Pyrgoma).

Cup-shaped recliners

Probably no invertebrate has received as much attention in terms of functional morphology and
evolution as Gryphaea (Hallam 1982). The geometrical inequivalvedness is induced in the juvenile
stage, when the attached valve starts to grow up from the initial anchoring ground into a cup, inside
which the free right valve nests with a flexible shell margin— a relationship which may also be
expressed in adult {orm^ [Cuhitostrea), whose left valve shows regular radial ribs, while the right valve
remains smooth. The resulting gryphaeid curvature of the left valve allows excessive deposition of
dense shell material in the umbonal region, which serves as a balance to keep the animal in the right
position. The inequivalvedness also permits the umbo of the left valve to expand without getting in
conflict with the opposed umbo. The umbonal problem can be even better avoided in the helicospiral
exogyrid version, but nevertheless the excessive thickening of the lower valve is maintained.

Convergences. As shown by Stenzel (1971), gryphaeid shells have evolved repeatedly from attached
oyster stocks. Similar growth forms can also be observed in other cemented groups, such as Spondylus
and Chama. In all of them it is the attached valve that forms the cup. This is in marked contrast by
byssally attached groups (bakevelliids, inoceramids, anomiids), in which it is the valve originally
facing the substrate that becomes the lid in cup-shaped recliners (see below).

Boulder-shaped recliners

Extreme shell thickening in both valves is characteristic for several species of Crassostrea (text-fig. 4)
in the upper Cretaceous and the Tertiary. During the later part of their lives they continue to thicken
the shell without further growth of the soft body, so that the shell cavity is only a small fraction of the
whole shell volume. For geometrical reasons, the ligament must also continue to grow during this
stage, resulting in a high ligament area with nearly parallel sides. In addition to the excessive shell
thickening and unusual size (up to 25 cm in diameter), a very dense shell structure contributes to
increase the stabilizing weight of the oysters.

It may be more than coincidence, that the most spectacular ‘storm tells’ (Seilacher 1983), some of

recliners (heavyweight)

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outriggered fan shaped boulder shaped

stick shaped spoon shaped coneshaped

cup shaped

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

217

them reaching 20 m in thickness (Bender 1968) have accumulated through event condensation during
regressive intervals from this type of oyster.

Convergences. Although this seems to be a straightforward strategy, no comparable adaptations can
be quoted from other pelecypod groups, which probably could not match the oyster’s rate of shell and
ligament production.

Fan-shaped recliners

Another possibility to stabilize the shell is its expansion into a flat fan shape. Adhesion to the
sediment may be further increased by strong sculptures (radial ribs, spines, foliate concentric ribs). In

TEXT-FIG. 4. Evolution of a wide range of adaptational strategies in soft-bottom oysters was facilitated by a
sequence of ecological steps:

(а) The ‘derailing’ of morphogenetic programmes in fully cemented rock-dwelling oysters.

(б) The progenetic miniaturization in soft-bottom pioneers that used dead shells as stepping stones into the
new habitat.

(c) True soft-bottom dwellers use shell substrates only in their early growth stages and become stabilized by
size increase, shell thickening, or mud sticking as adults.

Arctostrea sp. (Lower Cretaceous, East Africa; GPIT 1604/1 ). Horseshoe-shaped elongation stabilizes the shell
with the inhaling convex flank facing upcurrent. It is on this anterior side that the zigzag commissure is most
pronounced. Since the left valve is excessively thickened and bears lateral outrigger spines in another species
(A. cohihrina ricordeana', see Carter 1968) this was probably the preferred resting surface.

Lopha marshi (Middle Bajocian, Aalen, southern Germany; GPIT 1604/2). After a relatively long encrusting
stage that bears the xenomorphic sculpture of pelecypod or ammonite substrates, the shell became fan-shaped,
plicate, and very thick, particularly after cessation of radial growth. Epizoans indicate that the species could
recline on either valve.

Crassostrea sp. (Upper Eocene, Oriz, Vic Basin, southern Spain; GPIT 1604/3). This large species grew rather
irregular throughout life; but the large ligament area, small body cavity, and excessively thick valves as well as a
dense shell structure indicate that shell growth had the main purpose of making the animal heavier and
continued long after the soft parts had reached their ultimate size.

Exogyra sp. (Upper Cretaceous, Kansas; GPIT 1604/4). Prosogyrous spiral growth was established already in
miniaturized epizoic species of the Lower Toarcian. In later reclining species it allowed the umbo of the left valve
to become a heavy bottom weight, while the right valve formed a thinner lid. Stabilization was also improved by
a gradual evolutionary increase in adult size.

Gryphaea ura/utu (Lower Sinemurian, southern Germany; GPIT 1604/5). The almost planispiral growth of this
genus is also derived from the way in which epizoic ancestors and juveniles lift off the substrate. It allowed the
lower left valve to become even heavier compared to the upper. Narrow species such as this one may also have
been passively righted by the principle shown in text-fig. 12.

Saccostrea sp.; East Africa (GPIT 1 604/6; reconstructed after specimen courtesy of Dr. D. Nations, Flagstaff).
Cone-shaped growth of the lower valve, convergent to rudists and richthofeniid brachiopods, might appear the
simplest way to transform a cemented bivalve into a mud sticker, but it creates problems in forms that maintain a
functional break ligament with very unequal attachment areas.

Pkitygena asiatica (Upper Eocene, U.S.S.R.). In this genus a mud-sticking mode of life with the umbones down
is documented by held evidence (section of colony, from Hecker 1956). Its valves are relatively thin and very flat.
Most charateristic is the internal view (from Treatise Inv. Pal. N 1 147) with lateral areas of regressive growth
lines. They transform the umbonal part of the body cavity into a narrow handle and may have assisted the
ligament to open the valves and keep the sediment from entering, if they were provided with flexible brims.
Konhostrea konho (Upper Cretaceous, Japan; after Chinzei 1982, and in prep, and GPIT 1604/7). Early
ontogenetic replacement of the ligament function by the elastic bending of the flat and thin right valve allowed
this species to develop a stick-shaped shell, in which the body cavity is restricted to the uppermost part. The rest
of the gutter-like left valve is filled with chalky layers, whose upper end forms the fulcrum for the flexible left
valve (compare Lithiotis in text-fig. 5).

All scales = 1 cm.

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contrast to the previous types, however, there is no preference for lying on either the right or left valve.
This is indicated by equivalve shell thickness and can be tested by the statistical distribution of
epizoans.

Zigzag folding of the commissure, exemplified by reclining species of Lopha, corresponds
particularly well to his mode of life. As shown by Rudwick (1964) for brachiopods, it reduces the
danger of sediment intake. On the other hand it guarantees that in either position one side of the
folded commissure is well above the sediment level. Also it eventually results in the anchoring
ribs.

Less sculptured flat oysters may also belong to this type {Deltoideum delta in the Upper Jurassic),
but their attribution is less certain, because spoon-shaped mud stickers may have similar shapes.
Therefore additional evidence (epizoan distribution and slope orientation; observation of life
positions in the field) is desirable in these cases.

Convergences. This adaptational strategy is found in Tertiary species of Plicatula, an originally
cemented recliner, but also in byssal stocks such as many pectinids, the limid Ctenostreon, and the
anomiids Placuna, Carolia, and Hiiyella.

Oiitriggered recliners

In this case a large resting surface is acquired by deviation from the rounded outline. This can be done
by wing-like expansion of the hinge, by finger-like extension of radial ribs, or by elongation of the
whole shell into a curved, crescentic outline. The oysters have made use of all three possibilities.
Rastellum forms a long auricle on the posterior side (much like reclining Isognomon isogonum,
text-fig. 5). Lopha quadriplicata lacks auricles, but in the adult stage it produces strong outriggered
ribs by local expansions of the commissure, very much like in the isognomid genus Mulletia (text-
fig. 5). More common is the third solution {Arctostrea, text-fig. 4), combined with a zigzag
commissure line. Its curved outline also improves the separation of the inhaling and exhaling currents
because the convex inhaling side faces up-current in the hydrodynamically stable position. As in the
previous type it makes no difference for outriggered recliners which valve is up; but in Arctostrea from
the Chalk additional outrigger spines are developed only in the left valve, which must have been down
in life position (Carter 1968).

Convergences. Because of the broader range of possibilities, outriggered recliners are more common
in some byssate groups (see below), but also among brachiopods.

Cone-shaped '’mud stickers'

The morphogenetic strategy in which the attached valve grows up into a slender cone while the other
forms a lid, is well known from rudists as well as richthofeniid brachiopods and seems to be the
simplest answer to a rising sediment level. A Saccostrea from the East African coast (text-fig. 4)
resembles rudists not only in shape, but also by the thin-vaulted septa that obstruct the lower part of
the cone as the soft parts move up. But its ‘mud-sticking’ mode of life is only inferred and needs to be
verified by field observations.

In bivalves, however, this mode of growth poses a major problem. In a break ligament the two
ligament areas should be of corresponding dimensions, because a break in the middle invalidates
equal areas on both valves. Thus the extreme disproportion of ligament attachment on the two valves
of Saccostrea (text-fig. 4) required a drastic rearrangement in ligament structure, which would
deserve a detailed study. In rudists this problem was bypassed by reduction of the ligament and its
probable functional replacement by a diductor.

Convergences. Although cone-shaped rudists are commonly referred to as reef-builders (which they
may secondarily have become in some cases), their morphology suggests that they originated as
‘mud stickers’. This seems also to be the case with the brachiopod Richthofenia and other
‘coralliform’ species, such as the gastropods Rothpletzia, in which the operculum, and Vermicularia,
in which the shell has become tube-like. All these had at some time been cemented to hard substrates.
To what extent cone-shaped corals and sponges conform to this model remains to be studied.

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219

Sponges obviously can be ‘mud sticking’ only with a defunct basal portion, so that the living parts
remain washed by water from all sides.

It is probably no coincidence that no cone-shaped forms seem to have evolved from non-cemented
bivalves, because they would have no reason to grow up from the substrate by elongation of only one
valve.

Spoon-shaped ‘'mud stickers'

In this type the ligament remains submerged in the sediment. It thus acts against sediment pressure
and needs either to be very strong or supplemented in its action by other elastic structures, such as
uncalcified shell margins that also keep the sediment from laterally entering the mantle cavity in the
open position. The modern Crassostrea virginica represents this mode of life, approaching stick- or
club-shaped ‘mud stickers’ with its elongate outline. More characteristic is the Tertiary Platygena
(text-fig. 4), in which the umbonal part of the body cavity becomes secondarily narrowed to a
handle-shaped apsis flanked by broad areas of regressive growth lines. Field evidence (Hecker 1956)
shows that they stuck in the sediment as colonies that opened like the pages of a book. Corresponding
shell shape suggests a similar mode of life for the extremely fiat Upper Jurassic oyster Deltoideum
delta, although this species has not yet been recorded in life position.

Convergences. So far only the Jurassic genus Lithioperna can be quoted as a direct analogue (text-
fig. 5). It is quite variable in shape, ranging from inequivalve, cup-shaped recliners with thick shells to
fiat, equivalve forms. In the Calcari Grigi of northern Italy, some beds consist almost solely of these
fiat forms, whose imbrication superficially resembles current-induced post-mortem accumulations.
But since in these beds all specimens are double-valved, have their umbones pointing downwards,
and are unusually elongated, they must be considered as dense beds of ‘mud stickers’.

A slightly different version seems to be represented by stacks of the anomiid Carolia that T. Aigner
found in the Eocene of Egypt. In these stacks, only the first individual closes the byssal notch during
ontogeny in the usual fashion. The other ones attach with exactly the same orientation to the convex
left valve of their neighbour and secrete on it a calcareous plug that upon retraction of the byssus
snugly fits into the persisting byssal notch. These stacks, consisting of up to six individuals, were
found in various positions in the rock. They are likely to have been reworked as an aggregate and
buried alive during catastrophic events such as storms, while they originally lived in an inclined
position similar to Lithioperna, with the weight of the byssal plugs adding to keep the umbonal side
lowermost.

Club-shaped 'mud stickers'

Konbostrea konbo (Chinzei 1982) from Upper Cretaceous mud-fiats (text-fig. 4) represents the most
extreme deviation from the oyster bauplan. Its elongation, combined with a documented
‘mud-sticking’ mode of life, was made possible through the early ontogenetic replacement of the
ligament function by elastic bending of the right valve, which accordingly remained very thin and
completely fiat. The left valve, attached only in the juvenile stage, grew in a gutter-like fashion; but its
cavity became successively filled by chalky shell material as an alternative to light-weight obstruction
by septae, which is possible only in cone-shaped valves. In this way the body and the shifting ‘hinge’
zone with its fulcrum could move up like an elevator to compensate for the accumulation of mud
between the individuals of a colony.

Convergences. The genus Lithiotis (text-fig. 5), characterizing a shallow-marine limestone facies in the
Lower Jurassic Tethyan realm (Geyer 1977) was convincingly shown to have grown and functioned
in an analogous way (Chinzei 1982). This is also true for the associated genus Cochlearites, in which it
is not the right, but the left valve that provided the fulcrum. Also the fulcral area has a diflferent
structure (text-fig. 5). Therefore, Chinzei concluded that the two genera evolved independently, but
probably from related stocks. Their taxonomic relationship is still uncertain. Most probably they
belong to the bakevelliid stock {Mytiloperna, Gervilleioperna, Lithioperna', text-fig. 5), which shows
an unusual radiation in the Lithiotis facies. These genera are characterized by a broad-tooth plate

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PALAEONTOLOGY, VOLUME 27

outriggered recliners edgewise recliners

stick shaped spoon shaped cup shaped

mud stickers recliners

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

221

(broken lines in text-fig. 5) that could have evolved into fulcral areas in the elongated forms. Both
genera, however, seem to have been cemented to shelly substrates during early ontogenetic stages,
Lithiotis with the right and Coclilearites with the left valve (Chinzei 1982), in contrast to the byssal
attachment of other bakevelliids. In fact, cementation might have been necessary to induce their
extreme inequivalvedness.

BYSSATE STOCKS AND THEIR SOFT-BOTTOM DERIVATIVES

The adaptational history of byssate bivalves has been treated extensively by Stanley (1972). While I
agree with most of his interpretations in terms of functional morphology, I am not so certain about
his assumption that most epibyssate forms have evolved, without habitat change, in soft-bottom
environments and with the endobyssate stage as an initial step. Stratigraphical evidence does not
always support such a sequence (for instance are the first representatives of the bakevelliids and

TEXT-FIG. 5. Secondary soft-bottom dwellers derived from byssate stocks are commonly edgewise recliners that
maintain weak byssal attachment in addition to stabilization by shape and weight. Other strategies resemble
those in cemented stocks (text-fig. 4); but it should be noted that no cone or stick-shaped mud stickers have
evolved from non-cemented rock dwellers.

Modern rock-dwelling isognomonids (Isognomon (Isogonion) sp.; Langun, Malaysia; GPIT 1604/8) are much
more firmly attached than mangrove species (I. (/.) ephippium, Philippines; GPIT 1604/9). Therefore they show
extreme variability (‘morphogenetic derailing’) that helped them to evolve extravagant shapes in soft-bottom
descendants.

I. (/.) isognomwn (Philippines; GPIT 1604/9) is a V-shaped recliner lying either on the right or left valve. It
further develops the ventral elongation of rock-dwelling ancestors plus long posterior auricles as outriggers.
Increased shell thickness and size also improve stabilization.

Mulletia mulleti (Lower Cretaceous, England, from Treatise Inv. Pal. N 325) outriggers by toe-like expansions
of the commissure.

Hippochaeta sandhergeri (Oligocene, Weinheim, Germany; GPIT 1604/10) could have been either a flat or an
edgewise recliner; but similar forms from the Jurassic (Fiirsich 1980) have been found in edgewise life position
(see text-fig. 8).

Mytiloperna sp. (Calcari Grigi, Lower Jurassic; Vajo dell Anguilla, Verona, northern Italy; GPIT 1604/1 1). Like
the following forms, it has a broad tooth plate (broken outline) that indicates affiliation with the Bakevelliidae
rather than the Isognomonidae. Triangular cross-section and extreme shell thickening as well as reduced height
(compare Tanchintongia, text-fig. 8) are typical for edgewise recliners. The posterior gape, the marginal position
of the posterior adductor, and the lack of marked growth lines indicate that the shell was originally covered by a
less calcified outer layer that formed a flexible flap on the posterior side, much like in the following forms. Note
that this is the only edgewise recliner in the bakevelliids. This indicates evolution via mud stickers.
Gervilleioperna sp. (Calari Grigi, Lower J urassic; locality as before; GPIT 1 604/ 12) represents the gryphaeid type
of cup-shaped recliners.

Lithioperna (Calcari Grigi, Lower Jurassic; same locality) occurs in two morphotypes. As isolated recliner, it is
found in flat position, with a roundish outline and commonly with very thick and cup-shaped cross-section
(GPIT 1 604/13). In crowded, book-like colonies, the shells remain flat and thinner-shelled and grow much longer
(left specimen, from Accrosi-Benini 1978). If the ventral flexible flange extended to the anterior and posterior
sides, it could have prevented lateral penetration of the surrounding sediment when the valves were open
(compare similar regressive growth line areas in Platygena, text-fig. 4).

Lithiotis and Coclilearites (after Chinzei 1982) are perfect homeomorphs of Konbostrea (text-fig. 4), though they
are certainly not oysters. They are here tentatively affiliated with the bakevelliids, with which they are associated
in the Calcari Grigi, but from which they differ by being monomyarian and cemented as juveniles. Note also
that the thin and flat flexible valve is not the same in the two Liassic genera, indicating parallel evolution
(asterisk = right valve).

All scales = 1 cm.

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inoceramids not modiomorph endobyssates?). One should also bear in mind that by their higher
fossilization potential ‘mud stickers’ tend to be well represented compared to rock-dwelling forms,
which I would prefer as the initial stage. The main difficulty, however, is the reduction of the foot,
which in soft sediments would not have become redundant by the maintenance of byssal attachment
throughout life. Certainly, evolutionary pathways between endo- and epibyssate forms may have
been passable in either direction and one should study each case separately. Still I prefer to consider
the majority of byssate ‘mud stickers’ and recliners as secondary soft-bottom dwellers in the strict
sense, i.e. as the result of an evolutionary habitat change from soft to hard bottoms and back again.

As a reference group for byssate bivalves we select here the forms with a multivincular ligament,
because they have evolved a great diversity of soft-bottom dwellers both in the Mesozoic and the
Recent. In current taxonomy they are grouped under the families of Bakevelliidae and Isogno-
monidae, which differ in shell structure and in the form of the hinge.

While the mechanical principles of stabilization are the same in cemented and byssate stocks, some
general differences should be noted. First, byssate recliners need not be as morphologically stable and
thick-shelled as cemented ones, because the byssus may provide an additional means of stabilization
throughout life. Secondly, byssate stocks had no access to pathways such as cone-shaped ‘mud
stickers’, but commonly evolved into edgewise recliners, which are conspicuously absent in byssate
stocks.

Outriggered recliners

Compared to cemented stocks, outrigger production differs significantly in byssate forms, because
their long hinge lends itself to prolongation into a narrow auricle, which may have had a stabiliz-
ing function already in rock-dwelling ancestors (Stanley 1972). In truly multivincular species
{Isognomon, Mulletia; text-fig. 5), an auricle forms only on the anterior side, assisted by elongation of
the ventral margin at an acute angle.

Convergences. Malleus, closely related to Isognomon in spite of its alivincular ligament, is the
prototype of an outriggered recliner (text-fig. 6); but since it evolved an anterior auricle in addition to
the posterior one, elongation of the ventral shell margin proceeds at a right angle to the hinge.
Secondary shell thickening separates the auricles in later growth stages of M. albus (text-fig. 6), so that
only the ventral margin can proceed to grow. This also allows the zigzag undulation of the
commissure to develop in a more regular fashion with an overlap of the margins at the bends, which
keeps the shell from gaping more widely at these points. Epizoan overgrowth shows that Malleus
reclines ambivalently on the right or left valve (Seilacher 1982/?) and is no ‘mud sticker’ as commonly

TEXT-FIG. 6. Although being closely related, the Malleids differ from the isognomonids (top part of text-fig. 5) by
having an alivincular ligament and by being byssally attached at the umbo rather than at the anterior flank of the
shell. Accordingly they were able to evolve outriggered recliners (not mud stickers, as commonly believed) by
developing long auricles on the posterior as well as on the anterior sides of the elongate shell.

The ancestral situation is illustrated by Malleus regains (Cebu, Philippines; GPIT 1604/14) that lives firmly
attached to rocks and is relatively small, thin shelled, and highly variable in shape.

Similar stages, first with round outline and then with orimental auricles are also found in the two reclining
species; but they are very much reduced in size, indicating that evolution went through a miniaturized stepping
stone adaptation. Only in an ontogenetically following outrigger stage does the shell grow hammer shaped,
thick, and very large. It also develops a zigzag commissure, in which the absence of secondary shell broadening
allows the flanges to overlap and thus to equalize shell gape.

Note also that in comparison to M. malleus (Cebu, Philippines; GPIT 1604/15), M. alhus (Cebu, Philippines;
GPIT 1 604/ 1 6- 1 7) is the more advanced species. It inhabits deeper and finer mud bottoms, is more regular in
shape, and has a fourth growth stage, in which only the ventral edge of the shell continues to grow. This is
because in this stage the right and left valve auricles become separated and the mantle recedes from them
(recessive growth lines on inside of auricles!) in order to allow secondary shell thickening (all specimens drawn to
same scale, with the anterior side to the left; from Seilacher 19826).

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believed (Yonge 1968). The Pteriacea have probably evolved many pleurothetic recliners, some with
pronounced outriggers (Oxytoma), but few except the pearl oyster {Meleagrina) show extensive shell
thickening and excessive sizes.

Edgewise recliners

In equivalved, but thick-shelled species of a generalized outline, such as Hippochaeta (text-fig. 5), one
might argue whether a pleurothetic or an orthothetic attitude would be most stable — depending on
whether or not a byssus was maintained as an additional anchor. In this case, we must rely on field
observations, which in the case of Jurassic Isognomon species have corroborated an orthothetic life
position (Fiirsich 1980). Life position is less ambiguous in Mytiloperna, whose extremely thickened
shell and triangular cross-section provides a stable base on the anteroventral side (text-fig. 5).

Convergences, (a) Ambonychiacea (text-fig. 7). Analogous forms have evolved among the Palaeozoic
Myalinidae. Orthomyalina from the Pennsylvanian, comparable to Hippochaeta (text-fig. 5) in
outline and shell thickening, may be used to illustrate the difficulties of palaeoecological reasoning.
Shell geometry and weighting clearly correpond to a mytiliform edgewise recliner resting on the
broad and byssus-bearing anterior surface. On the other hand, a significant inequivalved form with
respect to external sculpture and to the inclination of the ligamental area suggests that they were
pleurothethic recliners with the more coarsely sculptured left valve facing the sediment (Newell 1942).
Field observations clearly support the orthothetic model, but introduce another problem; it is not the
byssus-down, but the mechanically less stable hinge-down edgewise position that clearly pre-
dominates. A similar dilemma has been recorded by Fursich (1980) in homeomorph species of
Isognomon from the Jurassic. He concluded that the morphological evidence is misleading and
reconstructed a ‘mud sticker’ in an apex-down position. As an alternative I suggest that the ‘life
positions’ record a response of the animals when being smothered. By the pull of the byssus they
would rotate the shell into an unnatural dying position most likely to be preserved.

The less ambiguous Mytiloperna type is represented in the Ambonychiacea by the giant and
thick-shelled Tanchintongia that according to Yancey and Boyd (1983) has a myalinid ligament. This
genus and other alaticonchiids thrived during the Permian in a facies and climatic zone that seems to
correspond to the Lithiotis facies in the Jurassic and the rudist facies in the Cretaceous.

(b) Mytilacea. Congeria, a thick-shelled relative of the epibyssate fresh-water mussle Dreissenia, is
broader than Hippochaeta, but not as elongate as Mytiloperna, with shell-weighting on the recessed
anteroventral side. Similar shell thickening is observed in the Jurassic species "Mytilns' mirabilis
(lc\l-hg. 9) that occurs together with bakevelliid recliners of the Lithiotis facies (text-fig. 5).

All orthothetic recliners discussed so far have probably evolved directly from epibyssate ancestors.
The upper Jurassic large- and thick-shelled genera Trichites and Stegoconcha, however, are derived
from endobyssate ‘mud stickers’ like Pinna (text-fig. 9). This derivation is indicated by the fibrous
shell structure in both genera and the retention, in Stegoconcha, of a keel corresponding to the
functional pseudoligament in mud-sticking ancestors (Chinzei et al. 1982). The necessity for a
thick-shelled pinnid to transform the folding into a breaking ligament may explain why this
adaptational pathway has not been used more often in the long history of the pinnids. Derivation
from endobyssate ancestors is also indicated for Jurassic Mytilids, in which a square triangular
cross-section {Falcimytilns, Arcomyti/us; text-fig. 8) is combined with a rudimentary anterior
extension, like in Modiolus. A similar cross-section is also found in a Rhaetic species of Modiolus
(Seilacher 1972, fig. 5b), which was a deep mud sticker with an extremely elongated shell and
divaricate, but non-ratchetted rib pattern. Available specimens unfortunately come from rocks in
which only the thin calcitic outer layer is preserved, so that the original amount of shell thickening
remains uncertain.

Edgewise recliners are also ambiguous because similar forms, even with an extreme triangular cross-section,
may have evolved directly from burrowing ancestors and would thus not be secondary soft-bottom dwellers in an
evolutionary sense. Examples are the modern cardiid genus Corciilum, whose shell acts as a light collector for
photosymbiotic algae as well as the Jurassic astartiid Opisoma (Accorsi Benini 1981) and the Triassic veneroid
genus Dicerocardiiim, for which a similar mode of life has been suggested.

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BYSSATE

BAKEVELLIIDAE

mud stickers

twisted recliners

TEXT-FIG. 7. Compared to their more heteromorph derivatives (text-tig. 5), standard bakevelliid genera appear
relatively thin-shelled, even if they are not diagenetically reduced to the calcitic outer layer. This indicates that
byssal attachment remained an important factor in the stabilization of members living in soft-bottom habitats.
Posterior elongation is a general tendency in the group. Because of the possibility of parallel and iterative
evolution within the group, no evolutionary pathways can as yet be suggested. Note that mytiliform recliners are
not represented except in Mytiloperna (text-hg. 5). This and the common occurrence of inequivalvedness
indicates pleurothetically attached hard substrate epibyssates as the ancestral stock.

Pendant epibyssate attachment to hard substrates is documented in the saber-shaped Gervillia lanceoluta of
the Lower Toarcian Posidonia Shales {a: from Seilacher I982u). This species lived attached to live ammonites
and became characteristically oriented when their host died, sank to the bottom, and tipped over in a stagnant
basin. By analogy, a similar (but not necessarily pseudoplanktonic) mode of life is assumed for other
saber-shaped species (G. olifex Quenstedt, Sinemurian oil shales, Dusslingen, GPIT 1604/18; G. angiilaii
Quenstedt, Upper Hettangian sandstone, Goppingen, GPIT 1604/19; G. sp., Carnian, Lower Liming Farm,
Pilot Mountains. Nevada, GPIT 1604/20).

Endobyssate mud stickers may be either modiolid in shape (Agtiilerella pemoides. Lower Aalenian dark shales,
Sondelhngen; GPIT 1604/21-22; compare text-fig. 9) or lance-shaped (Gervillella aviculoides, Kimmeridgian
limestones, Malagoszcz, Poland; GPIT 1604/23). Note, however, that the hinge is much longer than in similarly
elongated epibyssate forms, because the ligament must act against the sediment pressure.

Flatly reclining forms are recognized by various degrees of inequivalvedness and twisting of the commissural
plane. All figured species rested on the left valve, which is always more convex and bears stronger sculpture to
increase adhesion to the sediment (Bakevellia suhcostata, Trigonodus Dolomite, Middle Triassic, Schwieber-
dingen, GPIT 1604/24; Costigervillia cra.ssicosta, Bathonian, England, from Treatise Inv. Pal. N 307). More
elongated forms (Hoernesia tortuosa, Aalenian, Gundershofen; internal view from Aalen; GPIT 1604/25-26)
have the possibility to grow in a twisted manner, thereby keeping the anterior end in an almost vertical position
for endobyssate attachment, while the posterior part reclines flatly on the sediment (see series of cross-sections).
A very large undescribed form (H. sp., Sinemurian Limestones, Cerritos Bayos, Chile; GPIT 1 604/27) combines
twisting by about 30° with divaricate adhesion ribs on the lower valve.

226

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 8. The Ambonychiacea, differing from the isognomonids and the
bakeveliids mainly by their ligament pattern, have evolved similar forms of
recliners, but seemingly with a narrower range of strategies (no pleurothetic
recliners).

In the Permian genus Tanchitongia (from Yancey and Boyd, 1983) an edgewise
reclining stage is clearly indicated by broad triangular cross-section, extreme shell
thickening, and giant size (compare Mytiloperna, text-fig. 5).

In Orthomyalina slocomi (Upper Pennsylvanian Vinland Shales, Atchinson Co.,
Kansas) the evidence is more conflicting. Its marked inequivalvity with respect to
sculpture (even more pronounced in Septimyalina; GPIT 1604/29) and to the dip of
the ligament areas (outside views and cross-section in posterior view; GPIT
1604/28) would suggest reclining on the more strongly sculptured left valve
(asterisk position). Field measurements (with the kind help of Ron West,
Manhattan, Kansas) of isolated bivalved specimens, however, clearly speak for an
edgewise attitude — but with the ligament rather than with the byssus side down, as
the shell outline and cross-section (GPIT 1604/30) would suggest (arrowed
position). The dilemma is solved if we assume that upon irritation the byssus could
pull the shell partly into the sediment and rotate it to what would become the
preferred burial position.

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

227

Cup-shaped recluiers

While it is the attached valve that develops into the cup in recliners derived from oysters and other
cemented groups (Spondyliis, Chama, Hinnites), the relationship is reversed in pleurothetic
epibyssates. Here the valve originally facing the hard substrate remains flat and the stronger
curvature of the exposed valve (usually the left one) determines the cup of the recliners. If this
succession applies also to ontogeny an inversion of the life position is needed. Excessive thickening of
the cup-shaped valve, as observed in Gervilleiopema (text-fig. 5), may faeilitate this change. It is also
interesting that Lithiopema, which is mostly found as a thin and elongated ‘mud sticker’, occurs
occasionally in a cup-shaped and much thicker shelled ecophenotype (text-fig. 5).

Convergences. Gervilleiopema and Litliioperna, as well as truly isognomonid recliners, maintain the
deep recess on the anterior side, in which the byssus was originally loeated. In malleids, in contrast,
the byssus leaves the shell in an umbonal direction through a notch on the anterior side of the
ligament area. It was probably this detail, plus the alivincular ligament, that allowed them not only to
develop an anterior auricle {Malleus', text-fig. 6), but also rather symmetrical gryphaeid shapes
without an anterior recess {Gryphaeligmus', Lewy 1982). Cup-shaped forms, but without excessive
shell thickening and with a long hinge, have evolved in a number of other pteriomorph epibyssate
families {Cassianella, Rhaetavicula).

Twisted recliners

Shell torsion is another deviation from the standard bivalve bauplan that has received considerable
attention recently (MeGhee 1978u, Savazzi 1981u, 1982a, h, and in press a, b). It is restricted to
groups that are endobyssate in principle and twist the plane of the commissure in the emerging
posterior part of the shell in such a way that is more or less parallel to the sediment surface. The twist
is counter-clockwise (i.e. in a right-hand screw) in the arcid genus Trisidos (McGhee 1978a) and
elockwise, but less extensive, in species of Barbatia (Savazzi 1981a). Similarly backevelliid species
(text-fig. 7) may twist either clockwise (Hoernesia socialis', H. tortuoscp McGhee 1978a, b) or
counter-clockwise (Pseudoptera', Savazzi, in press b), while twisting of the present-day mytilid
Modiolus americanus is ecophenotypieally determined and may go in either direction (Savazzi, in
press a).

All twisted bivalves have in common that they are relatively thin-shelled (particularly if only the
calcitic outer layer is preserved), have two adductors, and that the byssus leaves the shell in a ventral
or anteroventral direction. Most show also a slight marginal overlap of their more convex valve,
which facilitates the development of radial or divaricate ribs in this valve that are suppressed in the
other. Since the more convex valve is usually the one that through the twist comes to face the
sediment, its inequivalve sculpture may help to stabilize the shell on the mud (text-fig. 7).

Endobyssate "mud stickers'

‘Mud stickers’ are much more common in byssate than in cemented stocks of secondary soft-bottom
dwellers, probably because a byssal anchor can also be used to pull the shell deeper into the substrate
if growth proceeds faster than sedimentation and if the animal is irritated. I prefer to see the
endobyssate state in most cases as a seeondary step, following epibyssate adaptation to rocky
substrates. This view is also supported by the fact that the forms sticking more deeply in the sediment
usually show more derived features than shallower endobyssates.

The most striking example is the genus Pinna. Its mode of life is commonly modelled after the
sand-living Mediterranean species P. nobilis, in which only the anterior third of the shell is buried.
The vast majority of tropical Pinna and Atrina species, however, live in mud with the truncated
posterior margin level to the sediment surface (text-fig. 9). In this situation, opening of the shell
becomes a major problem. It has been solved by making the outer shell layer flexible through a high
organic content (therefore it has commonly disappeared during fossilization) and by retarding its
enforcement with a nacreous inner layer. The elasticity of this shell aids the ligament in opening the
valves in sueh a way that gaping is restricted to the exposed posterior margin, while the buried ventral

228 PALAEONTOLOGY, VOLUME 27

part of the commissure remains closed. Such a shell can be closed by the strong posterior adductor
through elastic deformation.

The genus Pinna, which appears in the lower Carboniferous, has gone one step further. Here the
valves become actively broken along a line that then forms a median carina at some distance from the
growing edge. This carina heals on the inside by an elastic shell layer and is not covered by the more
rigid nacreous layer except near the umbones. Thus it can act as a pseudoligament that in conjunction
with the ligament restores the squarish cross-section after it has been deformed into a rhomb by the
adductor (text-fig. 9).

Convergences. While the functional adaptation of Pinna seems to have been unique, similarly
elongated ‘mud stickers’ with a near-terminal umbo have evolved in several byssate groups such as
the bakevelliids (text-fig. 7). In these cases, however, the shell was only half buried and equipped
with a relatively long ligament strong enough to open the valves.

Among the mytilids, a very elongate Modiolus from Rhaetian mudstones of the northern Alps
(Seilacher 1972, fig. 5b) bears a dense pattern of divaricate ribs that are not ratchetted. This sculpture
is similar to that of the borer Lithophaga (text-fig. 9) and suggests that this derived species was
sticking more deeply in the mud than the Modiolus stock.

Swimming bivalves

Although we will not go into the details of bivalve swimming in this context (Thayer 1 972) it should be
remembered that this secondary mode of mobility has evolved independently in two groups of living
bivalves. Both are monomyarian and have an alivincular hinge and both are primarly epibyssate, but
with different orientations.

The limids attach to hard substrates in an orthothetic attitude, which they also maintain while

Rock Dwellers Mud Stickers

Edgewise Recliners

Streptopinna

Trichites

'Lithophaga

Modiolus

.Falcimytilus

Pickabacks

Lithophaga

lessepsianai

Fungiacava

y Mytilus
mirabilis

MYTILOIDA

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

229

swimming with the umbo ahead. The pectinids, in contrast, are pleurothetically attached and swim
accordingly, but in the direction of the ventral margin. Nevertheless the ability to swim is not
universal in either group, nor is it unequivocally expressed in shell morphology.

Limidae. Plagiostoma lineata from the Lower Muschelkalk is much more highly vaulted than limid
swimmers today and has a broad anterior base for reclining. This shape, the common slope-oriented
overgrowth by other organisms (Seilacher 1 954), the nestling of juveniles in the byssal recess of adults
(Jefferies 1960) as well as the common preservation in life position suggest that it was essentially an
edgewise recliner. Similarly, the Lower Jurassic Plagiostoma gigantea is much too big and
thick-shelled to have been an effective swimmer in spite of its flatter shape and smooth surface. Still it
can not be excluded that these species were able to swim. An immobile mode of life can be safely
assumed, however, for forms like the Middle Jurassic Cteiiostreon, whose thick shell and anchoring
spines suggest a heavy and possibly pleurothetic recliner.

Pectinidae. Similar difficulties arise with the interpretation of fossil scallops. Pleuroneclites laevigatas
from the Upper Muschelkalk was probably not a swimmer. Its left valve is more convex and more
commonly overgrown than the right one. Thus the geometry is the opposite of what we find in

TEXT-FIG. 9. The origin of the Mytiloida is here placed in a rocky habitat in order to explain the loss of a
burrowing foot. From forms like Mytilus eduHs they evolved— either directly or via mud stickers — into the niche
of edgewise recliners, but also back into the growing rocky substrate of reef corals. Another interesting lineage
leads to rock borers and from there to commensalism with corals that had themselves become secondary soft-
bottom dwellers.

^ Mytilus' mirabUis (Calcari Grigi, Lower Jurassic, Vajo dell Anguilla, northern Italy; GPIT 1604/31) occurs in
association with the recliners Mylilopermi and GerviUeioperna (text-hg. 5). It became stabilized by differential
shell thickening and triangular cross-section.

Modiolus umericanus (New Jersey; GPIT 1604/32) represents the adaptation of the mytilid shell shape to mud
sticking.

Falcimytilus (Upper Jurassic; from Treatise Inv. Pal. N 277; cross-section from AreomytUus pectwatus\ GPIT
1604/33) is stabilized mainly by its square cross-section, with some shell thickening in the lower parts of
the calcitic outer layer that is only preserved. A vestigial anterior lobe indicates derivation from modiolid
ancestors.

Pinna diversicolor (Mindoro, Philippines; modified from Chinzei et at. 1982; GPIT 1604/34) is a perfect mud
sticker. The opening function of its long and curved ligament is supplemented by the elasticity of the shell, in
particular by the pseudoligament (Chinzei et al. 1982). This forms on the inside the median carina, where the shell
becomes actively broken and is not covered by the internal shell layer. While the series of arrowed cross-sections
was made from a plaster cast to show the secondary deformation, the one with a star is drawn from a saw cut
through a fresh shell, whose pre-stressing deformed the posterior (broken line) and the anterior side of the cut in
the opposite sense.

Trichites giganteus (Upper Jurassic, Schnaitheim, southern Germany; GPIT 1604/35) is one of the rare pinnids
that have become edgewise recliners stabilized by triangular cross-section, extreme shell thickening, and giant
size.

Streptopinna saccata (Okinawa; GPIT 1604/36) starts its life as a byssate nestler in the crevices of living coral
colonies. It then becomes inevitably enclosed by the coral and continues to grow atop of the host. In this stage the
two valves become united into a flat tube that can no more be closed. Accordingly, the posterior adductor
remains in its juvenile (circle) position to where the soft parts are retracted in defence. On the other hand the loss
of bivalvedness allows the tube to grow in a tortuous manner.

Lithophaga lithophaga (Adriatic; GPIT 1604/37) penetrates into calcareous rocks as a chemical borer. This is
expressed by the elongate and almost cylindrical shell and fine divaricate ribbing.

L. lessepsiana and Fungiacava eilatensis (from Savazzi 1982r/) transfer this habit to live corals. These have
themselves become secondary soft-bottom dwellers, either pickabacking with a sipunculid worm (left) or as
disk-shaped recliners (right).

All scales = I cm.

230

PALAEONTOLOGY, VOLUME 27

modern Pecten jacohaeus, where the right valve is convex to allow easy take-off and sinking back in
the right orientation, while the left valve is flat or slightly concave. Still an inverse life position in
Pleuronectites is unlikely, because preserved colour bands are restricted to the left valve, like in many
modern Pecten and Chlamys species.

Two pectinid lineages have become sessile again by cementation. The spondylids retain the eyes
along the mantle margin (Yonge 1968), while the shell grows thick and irregular as in oysters and
allows the introduction of an isodont hinge. Spondylids that became free recliners again in later stages
of their ontogeny have already been mentioned as homeomorphs of Gryphaea.

More unusual is the life history of Hinnites giganleus from the California coast. Here, transition to
the cemented state does not occur in early growth stages, but later in ontogeny. Pliocene species went
even a step further by becoming soft-bottom dwellers again. Accordingly, their shells record an
ontogenetic succession of three adaptational stages (text-fig. 10). The epibyssate and swimming

PECTINIDAE

epibyssate stage | | cemented stage free lying stage

TEXT-FIG. 10. The double strategy of byssal attachment (with the right valve facing the substrate) and free
swimming has enabled the scallops to become very efficient secondary soft-bottom dwellers (Chlamys sp., Peru;
GPIT 1604/38). The return to a rocky substrate in Hinnites giganteiis (California; GPIT 1604/39) is marked by
the transition, after a juvenile Chlamys stage (black), to oyster-like cementation and irregular shell growth. Other
species (H. crispus. Pliocene, N. Italy; GPIT 1604/40, courtesy of E. Savazzi) have again become recliners by-
adding a third stage, in which the shell grows very large and thick (shaded part). Note that in this stage growth
becomes also more regular and that anchorage in the sediment is provided by a new kind of scaly spines.

B

<

UJ

O

<

o

<

o

z

Q.

SURVIVAL STRATEGY

PERMANENT HABIT

TEREDINIDAE

I wood decay

Kuphus

OBLIGATORY FACULTATIVE BORING PERMANENT TUBE DWELLING

BORING OR TUBE DWELLING

TEXT-FIG. 1 1. Tube dwelling pelecypods. This unique adaptation to secondary soft-bottom dwelling has evolved
only in borers, but independently in three groups and in difTerent genera within them. The two valves remain
either free within the bag-like cyst (Gastrochaenacea and Teredinidae), or they become incorporated
( Pholadidae, Clavagellacea). Through the tubelets at the lower end of Clavagellacean cysts water can be expelled

for piston-burrowing (from Savazzi 1982c).

232

PALAEONTOLOGY, VOLUME 27

Chlamys stage has a regular shape, while growth becomes irregular and xenomorphic in the following
oyster stage. In comparison with the modern, rock-dwelling species, these two stages are reduced in
size and relatively thin-shelled in the soft-bottom dwellers in order to fit the unstable substrate of
available dead shells. Their third growth stage, in contrast, reflects the mode of life of an immobile
recliner, i.e. the shell now grows large and thick for increased stabilization. This evolution transition
may have occurred more than once, because one of the two studied species (text-fig. 10) is an
ambivalent recliner, while the other (from the Pliocene of New Zealand) is consistently inequivalve
with the attached right valve becoming thicker-shelled and cup-shaped in the reclining stage. It is also
noteworthy that with the return to a more regular growth in this stage the sculpture does not continue
in the Chlamys-stage fashion, but attains a new character.

STOCKS BORING IN HARD SUBSTRATES

The comprehensive studies of Enrico Savazzi (1982c, d) have shown how boring bivalves returned
to soft bottoms. In three groups (Pholadacea, Gastrochaenacea, Clavagellacea) we observe the
convergent development of calcareous crypts (with or without inclusion of the valves). These become
tube-shaped because further growth is restricted to one or both ends of the closed cylinder (text-
fig. 11).

TEXT-FIG. 12. Horn-shaped growth provides secondary soft-bottom dwellers with the possibility to passively
become righted-up and replanted in the sediment.

The ‘Savazzi effect’ (from Savazzi 1982c) implies that a washed-out horn-shaped body comes to rest on the
sediment in a lateral position with the convex side facing the current and that it then tips into the erosional
depression forming on the upcurrent side. This mechanism may be enhanced by differential weighting of the
skeleton on the convex side and near the apex. Complete burial may be avoided by expanding structures that
keep the open end at the surface like a snow shoe.

The crypt of Cucwbituki cymhiiim (Malaysia; GPIT 1604/41 ) lacks differential weighting, but the presence of
soft-bodied snow shoe expansions (dotted) is suggested by accessory perforations on the concave side near the
siphonal opening.

Gryphiiea arcuata (Lower Jurassic, southern Germany; GPIT 1604/5), unlike more dilatate species, is most
perfectly adapted to the Savazzi effect by its rounded cross-section and weight distribution.

The sessile gastropod Maoricrypta /W/am (Miocene, Waipara Gorge, New Zealand; GPIT 1604/42; courtesy
of D. Mackinnon, Christchurch) resembles Gryphaea in shape and excessive shell thickness in the apical part.
Still it is doubtful whether it had a similar life position on the soft bottom, because the differential weighting of
the apical part is on the concave rather than on the convex side and because soft-bottom species of the related
genus Crepidula tend to form horn-shaped colonies, to whose stabilization the shell thickening would have also
contributed.

In horn-shaped species of Hippwites (Gosau, Upper Cretaceous; Reichenhall, Inst. hist. Geol. Pal., Munich;
courtesy of R. F. Hofling) the internal pillars of the right valve are situated on the convex side for differential
weighting. Tabulate fill structures (shaded, in the studied specimen recrystallized) provide additional weight to
the apical part. Horn corals provide many good examples.

In Phaulactis {‘dhev Wedekind 1927) differential weighting is obtained by secondary thickening of septa in the
apical and convex part of the calyx.

In Archaeocyathid sponges (after Treatise) this explanation is more problematic, because the buried parts of
the body would be excluded from active feeding. It should be tested whether the horn shape in some figured
species is a regular feature.

In the lepadomorph barnacle Euscalpelhon (Senonian, Waipara Gorge, New Zealand; reconstruc-

tion from Tubingen material) the flexible pedicle is transformed into a solid calcareous body with regular horn
shape and root-like scales concentrated on the apical and convex surfaces. The belemnite-like cross-section
shows that the central cavity is always excentric, thus providing differential weighting of the convex side.

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

233

HORN SHAPED
RECLINERS

SAVAZZI

Hippurites

234

PALAEONTOLOGY, VOLUME 27

Tube dwellers

The multiple parallel evolution of crypts between and within the three groups (text-fig. 11) becomes
understandable if we consider the evolutionary constraints and options involved. All tube dwellers
seem to be derived from ancestors that bored in biogenic materials, such as shell, coral, or wood. Such
materials, smaller pieces of which are also available on the soft bottoms of low energy environments,
favour the formation of calcareous linings that seal the borehole against a porous substrate and allow
repair when this substrate has rotted or broken away. Thus cyst formation can be viewed as an
extension of former emergency strategies (Savazzi 1982c).

Such tubes could lie simply at the surface; but some species have evolved special mechanisms that
allow them to become planted in the way of ‘mud stickers’. The most spectacular adaptation is found
in some clavagellids, such as Penicillus, whose crypt grows only at the posterior (siphonal) end. This
allows the lower part of the crypt to develop into an expanded chamber with an elaborate system of
perforations and tubelets, through which water can be expelled into the sediment to produce a
piston-boring effect (Savazzi 1982c, fig. 15). The gastrochaenid genus Cucurbitula, in contrast,
becomes passively buried. Its tubes grow consistently in a curved fashion. Exposed to a current, such
a horn-shaped cyst will come to rest on its side and orient itself with the convex side upcurrent. In this
position eddies will carve out the sediment in front of it, so that the body automatically tumbles into
the depression (Savazzi 1982c, fig. 5). This principle which has so far only been tested in the flume
(Savazzi 1982c), can also be applied to fossil horn corals, to Gryphaea, to horn-shaped rudists, and to
the Cretaceous cirriped Euscalpellum zelandicwn (Withers 1951), in which the convex side of the horn
is additionally weighted to facilitate the planting process (text-fig. 12).

Commensals

Another pathway into the soft-bottom habitat is commensal association. For boring bivalves it is
favoured by the tendency of other secondary soft-bottom dwellers to develop massive skeletons. If
the hosts are molluscs, no special adaptations are necessary other than the selective settlement of the
larvae and an adequate miniaturization of the adults. But in the fossil state it may be difficult to
distinguish commensal borings from those made in dead shells, except by callus formation and the
avoidance of surfaces that were covered by soft parts while the host was alive. Not so in solitary
corals, in most species of which the skeleton is covered by living tissue and can grow on the whole
external surface. Their infestation requires the ability to penetrate living tissue and to cope with
substrate growth and is therefore likely to be more host-specific. Modern (and some fossil) examples,
as reviewed by Savazzi (1982^/), all involve mytilid borers. Since the mytilid bauplan does not allow
the formation of long siphons, this group was not only excluded from the tube-dwelling strategy
discussed in the previous paragraph. In a growing coral skeleton, mytilid borers are also forced to
keep in contact with the surface by boring backwards and filling the evacuated anterior part of the
bore hole with calcareous deposits or septa recognizable in the fossil state.

Mytilid coral borers, which make their excavations mainly by chemical means, also maintain
special attitudes and positions with reference to the host. In their horizontal bore holes they lie with
the umbones lowermost, so that the inhaling current keeps clear of the sediment. Fungiacava eilatensis
(text-fig. 8) always settles in the gastrocoel of large mushroom corals so that it can participate (a
parasite rather than a commensal) in the host’s meals (Savazzi 1982^/, figs. 19-20). Botida cordata
bores Eocene trochiform corals (Savazzi 1982r/, figs. 17, 18) from the outside wall, but the opening of
its borehole follows the upward growth of the ‘mud sticking’ host. Lithophaga lessepsiana (text-
fig. 8) has a similar position on Heteropsammia. In this case the host itself has established a symbiotic
relationship with a mobile sipunculid worm (Aspidosiphon), for which it builds a shelter and in return
is held in an upright position and carried around. ‘Pickaback’ strategies like the last example are
much more common and more highly developed in associations of encrusting sponges, hydrozoans,
actinians, corals, and bryozoans with hermit crabs.

SEILACHER: BIVALVE CONSTRUCTIONAL MORPHOLOGY

235

CONCLUSIONS

1. In contrast to one current view that evolution, being a stochastic process, can produce virtually
anything, actual lineages are strongly channelled into a limited number of pathways by the
constraints derived from inherited bauplans, fabricational principles, and the adaptive landscape. As
a result, adaptational histories appear quasi-deterministic, with convergent, iterative, and parallel
evolutions being the rule rather than the exception. This sets a limit to the cladistic analysis within
bivalve groups.

2. Tempo and degree of evolutionary change depend largely on the ecological circumstances.
While shell forms in the large group of burrowing bivalves have remained conservative (apart from
the introduction of burrowing sculptures in some species), they show rapid and sometimes bizarre
modification in the small group of secondary soft-bottom dwellers.

3. In the latter group, rapid change was necessary to cope with the problem of passive stabilization
on a mobile substrate. It was also facilitated by the ‘morphogenetic shunting’ induced by
miniaturizing stepping stones that pave the way for sessile rock dwellers into the soft-bottom habitat
and the following trend towards gigantism for autonomous stabilization.

4. Constructional morphology, if applied to larger groups and used in a comparative way, is a
valid tool in evolutionary studies, because it leads to an understanding of evolutionary pathways and
thus complements the cladistic reconstruction of phylogenetic relationships.

Acknowledgements. This project was started in 1979 during a sabbatical semester granted by the Tubingen
university. Several trips have been supported by the SFB 53; others were provided by a professorship of the
University of Kansas (1979) and the invitation as a ‘German National Fellow’ by the New Zealand Universities
(1982). During the years, many colleagues have contributed in the field with their special knowledge of modern
and fossil organisms, in particular Dr. B. Resell (University of the Philippines, Manila), Dr. K. Chinzei
(University of Tokyo), Dra. C. Broglio-Loriga (University of Ferrara), Dr. A. Sasekumar (University of
Malaya, Kuala Lumpur), Dr. G. Chong-Diaz (University del Norte, Antofagasta, Chile), Dr. H. Wanless
(University of Florida, Miami), Dr. R. West (Kansas State University, Manhattan). Others mentioned in the
text have kindly loaned specimens from their collections. Without their elforts this study would have been
impossible. I thank also my Tubingen colleagues. Earlier versions of the manuscript have been critically read by
Dr. W. E. Reif (Tubingen) and Dr. R. Thomas (Lancaster, Pennsylvania). Typing was done by Mrs. H. Worner,
photographic work by Mr. W. Wetzel. I also thank the Palaeontological Association, for committing me,
through its annual lecture 1983, to write and draft this paper.

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237

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A. SEILACHliR

Geologisches Institut
der Universitat Tubingen
Sigwartstrasse 10

Typescript accepted 9 September 1983 D-7400 Tiibingen, Germany

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SILURIAN ODONTOPLEURID TRILOBITES
FROM GOTLAND

by LARS RAMSKOLD

ABSTRACT. Trilobites of the family Odontopleuridae are described from the Silurian of Gotland, Sweden. Twelve
species and subspecies (nine named, of which four are new) are assigned to four genera. Anacaenaspis
gotlamlensis Bruton, 1967 is considered to be a junior subjective synonym of Acidaspis pectinata Angelin, 1854,
which is therefore the type species of the genus. Primaspis ( Taemasaspis) Chatterton, 197 1 is regarded as a junior
subjective synonym of Dudleyaspis, which in addition to the nominate subgenus includes D. (Siwderaspis)
subgen. nov. Ceratocephala harrandii (Fletcher in Salter, 1853), A. pectinata, Leonaspis coronata (Salter, 1853)
and L. crenata (Emmrich, 1844) are also known outside Gotland. New species and subspecies described are
D. (Dudleyaspis) hamrensis, D. {Dudleyaspis) uncifera, D. (Snoderaspis) krausi, and Leonaspis coronata hiifo.

The first odontopleurid trilobite described from Gotland was Odontopleura crenata Emmrich, 1 844,
which is now referred to as Leonaspis. Angelin (1851, 1854) included a number of additional species in
his monograph of Scandinavian trilobites. Lindstrom (1885 ) discussed these, but no new species were
described by him or other workers until Bruton (1967) revised the Gotland odontopleurids, and gave
a modern description of previously known and new species. Since Bruton’s study, a wealth of new
material has come to light, some from old collections, but most through recent collecting. This
material includes previously unknown taxa and more complete specimens of most of the known
species. It also provides information for a more satisfactory definition of the genera Anacaenaspis,
Dudleyaspis, and Primaspis.

STRATIGRAPHY AND LOCALITIES

The stratigraphical distribution of the species as plotted in text-fig. 1 follows the same scheme as that
in Ramskold (1983). Again it must be emphasized that this distribution does not necessarily reflect the
chronological appearance and disappearance of the various taxa. Locality names followed by
numbers are defined in Laufeld (19746), Larsson (1979), and Ramskold (1983). Two new localities
are described here in conformity with this system. DJUPVIKSVAGEN 1, 635572 164170 (CJ 5512
2873), Eksta parish, c. 3950 m SSW of Frojel church. Topographical map sheet 6 I Visby SO.
Geological map sheet Aa 164 Elemse. Ditch exposure along north side of road, from the forest edge
and 20 m south-east, c. 1100 m north-west of the intersection of road 140 with the road to Djupvik.
Mulde Beds, undifferentiated. VALVE 2, 637352 164018 (CJ 7299 2859), Eskelhem parish, c. 2800 m
NNW of Vastergarn church. Topographical map sheet 6 I Visby SO. Geological map sheet Aa 160
Klintehamn. Exposure in ditch running south-east from road, then curving first north then south into
the forest. The road/ditch intersection is c. 225 m south-east of the house at Valve. Slite Beds, Slite
Marl.

For other localities twelve figure grid references are given according to the Swedish National Grid
(Rikets nat) system whenever possible.

SYSTEMATIC PALAEONTOLOGY

The terminology employed here is essentially that of Harrington et al. {in Moore 1959). Lateral
glabellar lobes and furrows are labelled following Jaanusson ( 1956, p. 37). Terms for the orientation
used during photography are those of Whittington and Evitt (1954, p. 1 1 ). Specimens are deposited in

IPalac'onloloHV, Vol. 27, Pari 2, 1984, pp. 239-264, pis. 26-31.]

240

PALAEONTOLOGY, VOLUME 27

Naturhistoriska Riksmuseet, Stockholm (prefixed Ar), in the Type Collection of the Geological
Survey of Sweden (SGU), and in the Royal Scottish Museum, Edinburgh (RSM). Unless stated
otherwise, illustrations in the plates are of external surfaces of exoskeletons. All specimens were
painted with matt black opaque and coated lightly with ammonium chloride prior to photography.
Most specimens with numbers beginning Ar51 were collected by the author; other collectors are
indicated in the plate explanations when known.

SUNDRE

undifferentiated M-U
undifferentiated L-M

HAMRA

Upper c
Middle b
Lower a

o

_l

Q

3

BURGSVIK

Upper

Lower

EKE

Upper

Lower

base

HEMSE

Marl, top
e

Marl, SE part

d

c

Marl, NW part
b

Marl

f

KLINTEBERG d
c
b
a

MULDE

Upper

undifferentiated

Lower

o

o

UJ

HALLA

undifferentiated

b

a

SLITE

Siltstone

P. gotlandicus beds
9

Marl, undifferentiated
f

Marl, NW part

e

d

c

b

a

TOFTA

LL

HOGKLINT

U VISBY
L VISBY

SW facies

d

c

undifferentiated M-U
b

TEXT-FIG. 1 . Occurrence of Odontopleuridae in the different stratigraphical
units of Gotland. Solid squares represent specimens assigned definitely to a
taxon and open squares represent compared forms. A square with a question
mark indicates that the horizon is uncertain. The stratigraphical column is a
practical way of illustrating the distribution of the species within the mapped
units, and is not necessarily a reflection of the chronological appearance and
disappearance of various taxa. Diagram modified from Laufeld (1974a,

p. 124).

RAMSKOLD: SILURIAN ODONTOPLEU RI D TRILOBITES

241

Family odontopleuridae Burmeister, 1843
Subfamily odontopleurinae Burmeister, 1843

Discussion. A re-evaluation of the genera Anacaenaspis, Dudleyaspis, and Primaspis is necessary on
the basis of the Gotland material described here (for summary of previous concepts see Chatterton et
al. 1979, p. 828, and Thomas 1981, pp. 83, 85). When Chatterton (1971) erected Taemasaspis as a
subgenus of Primaspis he noted its close similarity and possible relationship to Dudleyaspis (as
diagnosed by Bruton 1968). After transferring Odontopleura portlockii Hawle and Corda, 1847
(included by Bruton in Dudleyaspis) to Taemasaspis, Chatterton considered that the subgenus fitted
best within Primaspis. However, several features indicate that Taemasaspis is closer to Dudleyaspis
than to Primaspis, including the straight-eye ridge, the shape, size, and position of the genal spine, the
wide thoracic axis, the insignificant fulcral swellings, and the disposition and relative sizes of the
pygidial border spines. The widely separated eyes, set in a horizontal plane well below LI and never
overhanging the posterior border furrow due to their rather forward position, are also indicative of
affinities with Dudleyaspis. Thomas (1981) noted these similarities and regarded Taemasaspis as a
junior synonym of Dudleyaspis', this study confirms these similarities, and Thomas is followed here.
A second subgenus of Dudleyaspis, Snoderaspis, is erected here. When Bruton (1967) erected
Anaeaenaspis, he selected as holotype of the type A. gotlandensis a specimen that is recognized

here as belonging to Angelin’s (1854) species pectinata. The type species therefore becomes
A. pectinata. This species belongs to a distinct and homogenous group of Silurian odontopleurines,
which in addition includes Acidaspis callipareosThomson, 1857, Anacaenaspis gigantea Snajdr, 1978,
A. phasganis Thomas, 1981, and Primaspis kruegeri Schrank, 1969. Generic status for this group
seems justified, and Anacaenaspis is therefore recognized here. The genus is close to Primaspis Richter
and Richter, 1917. Primaspis species fall into two morphological groups; the type species
P. primordialis (Barrande, 1846), from the Bohemian Caradoc, and the remainder. Pfibyl and Vanek
(1965) erected the subgenera P. {Primaspis) and P. (Meadowtownella), respectively, for the groups.
These subgenera have rarely been used by subsequent workers. The Meadowtownella group is very
coherent, and seems in many respects to be related, and perhaps ancestral to Dudleyaspis. P.
primordialis, on the other hand, is similar in some features to Anacaenaspis, e.g. in the lengthened
occipital ring and the overall shape of the pygidium. However, the free cheek of primordialis (figured
Snajdr 1956, pi. 2 (33), fig. 10) is not of Anacaenaspis type, but is similar to other Primaspis (i.e. the
Meadowtownella group). Known primordialis specimens are not well preserved, but the available
material seems to justify retaining Primaspis and Anacaenaspis as separate genera.

Genus anacaenaspis Bruton, 1967

Type species. Emended here; Acidaspis pectinata Angelin, 1 854, from the uppermost Llandovery and Wenlock of
Gotland (Lower Visby to Halla Beds), the Upper Llandovery of Scotland, and the Wenlock of Estonia.

Diagnosis. Occipital ring long (exsag.). Longitudinal furrow distinct. Antennal notch marked. Eye
ridges curved, eye set close to posterior border furrow, level with LI . Genal spines very long, reaching
behind thorax, base not raised markedly above lateral border. Ten to twelve long and stout cephalic
border spines, the posteriormost the largest and at right angles to genal spine. Fulcral swellings large.
Pygidium with major border spines much longer and stouter than, separated from, and set above the
plane of, secondary border spines.

Remarks. Anacaenaspis is a clearly defined genus, although Bruton’s (1967) concept of it was partly
different from mine, because of the restricted amount of material available to him. Apart from the
holotype of A. gotlandensis, all specimens assigned by Bruton to that species are referred here to
Dudleyaspis {Snoderaspis) krausi sp. nov. The second species originally included, A. emarginata
(Schmidt, 1885), is regarded here as a junior subjective synonym of pectinata.

The relationship of Anacaenaspis to Primaspis is discussed above. The genus is also close to
Acidaspis Murchison, 1839, the major difference being the large median occipital spine in the latter.

242

PALAEONTOLOGY, VOLUME 27

1851
V* 1854
. 1885
. 1885
1889

1896
1949
V. 1967
V. 1967

. 1967

1969

1973

1978
V. 1979
V. 1979

1979
1981
1981

. 1981

. 1982

Anacaenaspis pectinata (Angelin, 1854)

Plate 26, figs. 1-13; Plate 27, figs. 1-10; text-fig. 2

Angelin, pi. 21, fig. 5 [illustration only, without name].

Acidaspis pectinata Angelin, p. 33 [referring to 1851 figure].

Acidaspis pectinata Angelin; Lindstrdm, p. 55.

Acidaspis emarginata Schmidt, p. 23, pi. 1, fig. 1.

Acidaspis pectinata Angelin ? = Odontopleura ovata Emmrich; Jaekel, p. 711 [non Emmrich,
1839].

Acidaspis pectinata Angelin; Lake, p. 243.

Acanthaloma pectinata (Angelin); Prantl and Pfibyl, p. 139.

Acidaspis pectinata Angelin; Bruton, p. 234, pi. 35, figs. 3, 5, 6.

Anacaenaspis gotlandensis Bruton, p. 236, pi. 36, figs. 2-4, non pi. 35, fig. 10, pi. 36, fig. 5
[ = Dudleyaspis (Snoderaspis) krausi sp. nov.].

Anacaenaspis emarginata (Schmidt, 1885); Bruton, p. 237, pi. 35, fig. 14, pi. 36, fig. 1 [with
synonymy list].

Primaspis gotlandensis (Bruton); Schrank, p. 722 [pars].

Primaspis (Meadowtownella) gotlandensis (Bruton); Pfibyl and Vanek, p. 303.

Anacaenaspis gotlandensis Bruton; Snajdr, p. 31 [jHirs].

Acidaspis pectinata Angelin; Bruton in Jaanusson et al., p. 116.

Anacaenaspis sp.; Bruton in Jaanusson et al., p. 116.

Anacaenaspis gotlandensis Bruton; Chatterton et al., p. 828 [jKirs].

Acidaspis pectinata Angelin; Thomas, p. 81.

Anacaenaspis gotlandensis Bruton; Thomas, p. 85 [pars].

Anacaenaspis dealgach (Lamont, 1978); Clarkson and Howells, p. 529, pi. 81, fig. 2, pi. 82, figs. 1-4
[with synonymy list].

Anacaenaspis dealgach (Lamont, 1978); Howells, p. 58, pi. 15, figs. 10, 15.

Lectotype. Selected here; Ar30867, incomplete cephalon, Plate 26, fig. \2a-c, used for the composite figure of
Angelin 1851; refigured Bruton 1967, pi. 35, fig. 6; almost certainly from Hogklint Beds, Visby area.

Bruton (1967, p. 234) thought that this specimen may be one of Angelin’s (1851, 1854) syntypes. The shape of
the genal spine, faithfully depicted by Angelin, is due to a postdepositional fracture and secondary rotation of the
spine, a deformation unlikely to be exactly similar in any other specimen. In addition, the specimen (then largely
embedded in matrix) was broken at some time into three pieces. None of the fractures reveals the presence of
occipital spines, but it is obvious from the pieces that the cephalon must be broken across the occipital ring, as
stated by Angelin, and lacking the left half. All these factors indicate that this is the specimen used by Angelin for
his reconstruction of the cephalon. Additional preparation has now revealed the shape of the occipital ring.

EXPLANATION OF PLATE 26

Figs. 1-13. Anacaenaspis pectinata (Angelin, 1854). Upper Visby Beds (9). Hogklint Beds, unit a (2, 3), unit b?
(12), unit d (5, 8). Slite Beds, Slite Marl (1,4, 10, 11, 13). Halla Beds, unit b (6). Horsne kanal (6), Ireviken 1
(2, 3), Ronnklint (9), Valbytte 1 (1, 10, 1 1, 13), Vattenfallsprofilen 1 (5, 8), Visby (12), shore of Eketrask (4),
Jaani Stage, Paramaja pank, Saarema, Estonia (7). \a-c, Ar51358, cephalon, anterior, anterolateral, and
exterior views, x 3. 2, Ar51629, partial cephalon with complete spine fringe and genal spine, interior view,
x2-5. 3a-c, Ar51630, cephalon, exterior, lateral, and anterolateral views, x2-5. 4, SGU 1446, partial
cephalon, anterolateral view, note dense tuberculation, x4-5 (coll. G. Liljevall). 5, SGU 1448, flattened
exoskeleton lacking pygidium, ventral view, note displaced hypostome, x4 (coll. O. W. Wennersten 1890).
6, SGU 1447, small cephalon, exterior and anterolateral views, x9 (coll. G. Liljevall 1910). 7, Ar51750,
hypostome, exterior view, x 8 (coll. V. Jaanusson 1939). 8, Ar49890, small pygidium, x 10. 9a, Ar51709,

slightly distorted transitory pygidium, dorsal and ventral views, x 18. 10, Ar51350, genal spine showing
thorn-like tubercles with pore-openings, x 8. lla-c, Ar51354, large hypostome, exterior, posterior, and
lateral views, x 6. 12o-c, lectotype Ar30867, partial cephalon, figured Angelin 1851, pi. 21, fig. 5, refigured
Bruton 1967, pi. 35, fig. 6, anterior, anterolateral, and exterior views, x3. 13, Ar51351, partial thoracic
segment, x 2.

PLATE 26

RAMSKOLD, Anacaenaspis

244

PALAEONTOLOGY, VOLUME 27

which (together with other features) necessitates a removal from Acidaspis. The pygidium figured by Angelin
cannot be identified with certainty.

Additional material. The Scottish material from the Pentland Hills is of late Llandovery age (Clarkson and
Howells 1 98 1 ; see under ‘Discussion’ below). Estonian specimens are known from Koguva saar, Island of Muhu,
and Paramaja pank, Saarema, both Jaani Stage (upper Wenlock; Bruton 1967). On Gotland this species ranges
from the uppermost Llandovery to the upper Wenlock.

Localities. Lower and Upper Visby Beds: Lummelunda parish — Ronnklint (641181 165698). Upper Visby Beds:
Vasterhejde parish— Fridhem (638860 164375). Hogklint Beds, unit a: Stenkyrka parish— Ireviken 1. Unit b:
Visby parish— dump at Visby harbour (639275 164800), Vasterhejde parish— Fridhem (638885 164425). Units
b-d: Visby parish— Vattenfallsprofilen 1. Slite Beds, Slite Marl: Eskelhem parish— Valve 2, Faro parish —
Haganas 1; the southern shore of Eketrask, Othem parish— Slite, Sanda parish— Valbytte 1. Slite Beds, unit g:
Othem parish— Slite. Halla Beds, unit b: Horsne parish— Horsne kanal (638493 166725). The holotype of
A. gotlandensis Bruton, 1967, is stated to be from the Hemse Marl at Petesvik, Hablingbo parish (a now
overgrown locality) but this is questionable since this species is not known otherwise from Ludlow strata. One
fragment from Bolarve 1, Hejdeby parish, Slite Marl, north-western part, may also belong to this species. Some
cheek fragments (Ar5 1536-5 1538) from the Mulde Beds, lower part, at Djupvik, Eksta parish, are similar in
most respects to A. pectinata, but differ slightly in having several very large tubercles on the lateral border. A
definite assignment cannot be made until more complete specimens are known.

Diagnosis. Two paired, short, blunt spines posterolaterally on occipital ring. Six or seven tubercle
pairs on glabella. Ten or eleven stout, nearly cylindrical, cephalic border spines. Axial rings with two
paired posterolateral and one median tubercle. Very coarse cephalic tuberculation, also on
hypostome. Pygidium coarsely tuberculated except on pleural field.

Description. This species has been described recently by a number of authors (see synonymy), so that only new or
important features are noted here. Occipital ring with sharply defined occipital lobes (PI. 27, fig. 9), short median
spine with occipital organ, posterior margin with two paired spines. Anterior branch of facial suture indicated by
a discrete ridge running from eye towards antennal notch (PI. 26, figs. 6b, \2b), posterior branch indicated by a
strong ridge running from eye to genal angle. Genal spine very long, curved downwards distally. Border spines
slightly spatulate, with serrated tips (PI. 26, fig. 2). Lateral margin (but not posterior) slightly incurved at base of
genal spine. Six pairs of conspicuous tubercles (and possibly an anterior small pair) present on median lobe of

TEXT-FIG. 2. Anacaenaspis pectinata (Angelin, 1854). a, reconstruction of cephalon, based mainly on Ar30867,
Ar51358, and Ar51630, about x 3. b, reconstruction of pygidium, based on Ar51348, Ar51352, and Ar51573,

about X 3.

RAMSKOLD: SILURIAN ODONTOPLEU RI D TRILOBITES

245

glabella. Lateral border with three conspicuous tubercles decreasing in size forwards, situated above border
spines 3-4, 5-6, and 7-8 (numbered from rear forwards). Genal spine with thorn-like tubercles with a
pore-opening distally at their base (PI. 26, fig. 10).

Rostral plate unknown. Hypostome (PI. 26, figs. 7, 1 \a-c, PI. 27, fig. la-c) with oval, gently inflated middle
body. Very faint middle furrow possibly present laterally just in front of conspicuous lateral tubercle. Maculae
indicated by two smooth, oval areas. Anterior border unbroken medially, though very short, defined by wide
furrow. Lateral border with blunt, subtriangular anterior wing and prominent shoulder. On the inner edge of the
doublure underlying the shoulder is a small posterior wing (PI. 27, fig. 7c). Border behind shoulder wider (tr.),
confluent with equally wide (sag.) posterior border. Posterior margin has flattened, densely tuberculated
subtriangular area medially (PI. 26, fig. 11/5, PI. 27, fig. 7c). Middle body with pair of prominent tubercles
laterally. Small specimens with a few additional tubercles, large specimens have middle body densely
tuberculated. Ventral surface (except maculae) densely granulated.

Thorax with ten segments. Anterior and posterior pleural spines very short on first segment, progressively
larger posteriorly, anterior spine blade-like to bluntly cylindrical. Axis with paired tubercles. Posterior pleural
ridge with prominent tubercle at fulcrum and one at mid length.

Axial furrow in pygidium very deep except anteriorly and overhung by second axial ring and terminal piece.
Pleural areas depressed, with reticulate pattern of ridges and depressions (through differentiated skeletal
thickness, mostly not visible ventrally). Posteriorly are two pairs of secondary spines, laterally are three similar
pairs, the anteriormost smaller and merged with articulating process (PI. 27, fig. 2). Secondary spines situated at
slightly lower level than major spines; these curve slightly inwards and upwards distally. Paired tubercles on axial
rings and terminal piece. Posterior border with major tubercle above each spine-base. Tubercles on main body of
pygidium and proximal part of spines elongated, with slightly bulbous tips wider than at bases.

Ontogeny. The only known transitory pygidium (PI. 26, fig. 9a, h) is 1-20 mm wide and slightly distorted. It is
similar to a late transitory pygidium of Primaspis ascitus described by Whittington ( 1956/), pi. 2, fig. 9) in having
large, paired axial tubercles, a feature lost later in ascitus but retained in adult stages of pectinata. The prominent
tubercle on the posterior pleural ridge, a characteristic pectinata feature, is also present.

In the holaspid cephalon, L 1 and L2 change during growth from a more equal size to L2 being much smaller, a
change accompanied by a relative widening of the median glabellar lobe, and a reduction of eye size. The paired
glabellar tubercles are retained also in large specimens, although less obvious than in small ones. The hypostome
becomes relatively wider during growth, and the middle body becomes more tuberculated, while the tuberculate
area on the posterior margin becomes smaller. The shape of the pygidium is fairly stable, the shortening of the
secondary spines being the only marked change.

Discussion. The holotype of Anacaencispis gotkmdensis Bruton, 1967, has been examined, and no
differences between it and A. pectinata have been found. The occipital ring of the specimen is heavily
worn, with no spines preserved, but the shape of what remains does not preclude their original
presence. In addition, on the anterior axial rings of the thorax there are remains of one anteromedian
and two posterolateral tubercles. Since these rings commonly have tubercles repeating the spine
pattern of the occipital ring, corresponding occipital spines are to be expected (the tubercles on the
axis are also preserved on a specimen from the Pentland Hills, Scotland, PI. 27, fig. 10, and on
unfigured Gotland material). The holotype has only the bases of the border spines preserved, and
they cannot therefore be seen in dorsal view, a fact considered diagnostic by Bruton (but see PI. 26, fig.
2 for length of complete spines). Other features typical of A. pectinata are all present, such as the
strong posterior sutural ridge, the shape of the cheek border, carrying the same number of spines, and
the tubercle pattern on the cheek and pleurae.

Bruton (1967) described and figured the holotype of Acidaspis emarginata Schmidt, 1885, from the
upper Wenlock of Estonia, and listed the features distinguishing it from A. gotlandensis ( = A.
pectinata). The only known emarginata cephalon is similar to pectinata in all observable features, and
the Estonian hypostome (PI. 26, fig. 7) is identical to the large Gotland hypostome (PI. 26, fig. 1 \a-c).
A. emarginata is regarded here as a junior subjective synonym of A. pectinata. A. dealgacli (Lamont,
1978; see Clarkson and Howells 1981, and PI. 27, fig. 10 here), from the Upper Llandovery of
Scotland, is identical to the Gotland material and is also considered to be a junior subjective synonym
of pectinata. A. callipareos (Thomson, 1857; see Howells 1982), from the Lower Llandovery of
Girvan, Scotland, is distinguished from pectinata mainly in lacking occipital spines and paired
tubercles on the glabella, in the indented posterior margin, weak furrows and smooth surface of the

246

PALAEONTOLOGY, VOLUME 27

hypostome, in the granulate rather than tuberculate cephalon, and in the functional facial sutures. As
so far known, these differences also apply to the Bohemian Llandovery A. gigantea Snajdr, 1978,
which is also distinguished by having seventeen to nineteen marginal spines in the pygidium.
A. kniegeri (Schrank, 1969), from a late Wenlock erratic from Neu Niekohr, DDR, differs from
pectinata mainly in lacking occipital spines and in having eighteen rather than twelve pygidial border
spines. The differences listed by Schrank (1969, p. 722) refer largely to the specimens included here in
Dudleyaspis (Snoderaspis) krausi sp. nov. The British Wenlock A. phasganis Thomas, 1981, is closer
to pectinata than recorded by Thomas (1981, p. 85), differing mainly in lacking occipital spines and in
having a more adaxially placed eye.

As with the transitory pygidium (see above), the hypostomes assigned here to A. pectinata bear
some resemblance to that of the American Middle Ordovician Primaspis ascitus Whittington, \9S6b
(pi. 1, figs. 18-21; note the tuberculate, flat area on the posterior margin) and indicates the close
relationship between these genera. It also shows similarities to the hypostome of A. cincinattiensis
Meek, 1873, also from the Middle Ordovician of North America (see Whittington 1956a, pi. 59,
figs. 3, 6).

Genus dudleyaspis Prantl and Pfibyl, 1949

Discussion. Two subgenera are recognized here (see discussion under Odontopleurinae and respective
subgenus). They both have the occipital ring at least five times as broad as long; occipital lobes
present; eye lobe set at a level below LI, not in contact with posterior border furrow, transverse width
between palpebral lobes at least one and one-third the length of glabella; anterior and posterior
branches of (nonfunctional ) facial suture run on sutural ridges; genal spine slim, not exceeding length
of glabella; posterior border incurved at base of genal spine; thorax with ten segments, axis wide,
fulcral swelling small; pygidium with two pairs of spines between major spines, all spines evenly
spaced, at about the same level, zl. harbor ti Richter and Richter, 1926, may belong to Dudleyaspis, but
is not known well enough to be definitely assigned.

EXPLANATION OF PLATE 27

Figs. 1-10. Anacaenaspis pectinata (Angelin, 1854). Upper Visby Beds (4, 7-9), Hogklint Beds, unit b (1, 3), Slite
Beds, Slite Marl (2, 6), Halla Beds, unit b (5). Fridhem (3), Horsne kanal (5), Ronnklint (4, 7-9), Valbytte 1 (6),
Valve 2 (2), dump at Visby harbour (1), Wether Law Linn Formation (Upper Llandovery), Pentland Hills,
Scotland ( 10). 1, Ar5 1348, pygidium, major spine deformed distally, x3. 2, Ar5 1573, pygidium, x 3. 3,
SGU 1449, pygidium, ventral view, x 4 (coll. J. G. Andersson). 4, Ar5 1647, partial thoracic segment, x 6. 5,
SGU 1 450, partial thoracic segment, x 1 0 (coll. G. Holm). 6a, b, Ar5 1352, partial large pygidium, dorsal and
ventral views, x 3. la-c, Ar51645, small hypostome, exterior, interior, and posterior views, x 12. 8,
Ar51644, partial small cephalon, exterior view, x 12. 9, Ar51643, occipital ring with complete spines
and median organ, x 12. 10, RSM GY 1983.18.1, latex cast of external mould of exoskeleton lacking
pygidium, x 4.

Figs. 1 1-18. Dudleyaspis {Dudleyaspis) hamrensis sp. nov. Hamra Beds, unit a (1 1-17), unit b (18). Gisle 2(11,
12, 14, 16), Kiittelviken 1 (13, 15, 17), Majstre 1(18). II, Ar51550,* pygidium, x 6. 12, Ar51545,* partial
thoracic segment, x4. 13a, b, Ar51618,* pygidium, dorsal and ventral views, x 6. 14, Ar51549,* small
pygidium, ventral view, x9. 15, Ar51616,* partial cephalon, anterolateral view, x 5. 16, Ar5 1544,* partial
thoracic segment, x4. \la-d, holotype Ar51568, cephalon, exterior, lateral, anterior, and antero-lateral
views, a X 4, b-d x 3. 18, Ar51637,* partial cephalon, anterolateral view, x 6.

Fig. 19. Dudleyaspis (Dudleyaspis) hamrensis sp. nov.? Ar51638, partial cephalon, anterolateral view, Gannor 1,
Eke Beds, lower part, x 6.

* Paratypes.

PLATE 27

S pjf^

\ wk mJ '

■ rr-

t.

jt ' y ■ ■

g«f^7i]5!

/ft

Rk:1

^1

|p|^\

RAMSKOLD, Anacaenaspis, Dudleyaspis

248

PALAEONTOLOGY, VOLUME 27

Subgenus dudleyaspis (dudleyaspis) Prantl and Pfibyl, 1949

Subjective synonym: Primaspis (Taemasaspis) Chatterton, 1971

Type species. Acidaspis quinquespinosa Lake, 1896, from the Much Wenlock Limestone Formation, Dudley,
West Midlands, and Sedgley, Staffordshire, Great Britain.

Diagnosis. Cephalon wide and short; width to length 2-3 : 1 -3-2 ; 1 . Eye set closer to axial furrow than
to lateral border furrow. Facial suture with posterior branches diverging backwards at 120-180°.
Genal spine directed obliquely outwards.

Dudleyaspis {Dudleyaspis) hamrensis sp. nov.

Plate 27, figs. 11-18

Name. From the type stratigraphical unit.

Holotype. Ar51568, cephalon, PI. 27, figs, \la-d, from Kattelviken 1, Vamlingbo parish, Hamra Beds, unit a.

Paratypes. From the type locality, Ar51588, Ar51615-51619. From Gisle 2, Oja parish (Flamra Beds, unit a),
Ar51541-5 1 550. From Hamra Beds, unit b, Sundre parish: Majstre 1, Ar51637; north of Hoburgen, Ar51551. In
total seven partial cephala, seven thoracic segments, and six pygidia. A partial cephalon, Ar51638, from the
lower Eke Beds at Gannor 1, Lau parish, may also belong to this species.

Diagnosis. Posterior cephalic margin with five very small spine pairs plus equally small median spine.
Eyes set wide apart opposite anterior half of LI. Pygidium with six pairs of spines.

Description. Cephalon subtrapezoidal, highly vaulted in anterior view (PI. 27, fig. 17r). Occipital ring occupying
half of cephalic width (excluding spines). Occipital lobes very weakly defined. L3 elongate, directed at about
45° to sagittal line, with slightly bulbous tip. Longitudinal furrow wide, shallow. Axial furrow very weak. Eye
ridge merging anteriorly with lateral extension of frontal lobe. Eye set exactly mid-way between axial and
lateral border furrow. Cheek area between eye ridge/palpebral lobe and axial furrow large. Anterior branch of
facial suture indicated by indistinct ridge, posterior branch not visible close to eye; a fairly strong sutural ridge
appears near genal angle. Lateral border with eleven almost vertical spines (a twelfth knob-like anteriormost
spine may be present), cylindrical, straight, blunt, the posteriormost slightly less than normal to genal spine.
Three stout, elongated tubercles present on border, above border spines 1-2, 3-4, and 5-6 (counted from
rear forwards), increasing in size backwards. Entire cephalon except deepest parts of furrows with a fine,
spiny tuberculation. Six or seven pairs of slightly larger tubercles are barely discernible on median lobe of
glabella.

Rostral plate and hypostome unknown. Thoracic segments (PI. 27, figs. 12, 16) with axis over one-third of
width between fulcra. Anterior pleural ridge widening (exsag.) distal to fulcrum into large, blade-like anterior
spine. Posterior ridge produced into proximally downward-flexed, laterally more horizontal spine. On a
presumed anterior segment the spine is transverse or curved slightly anteriorly, on probable posterior segments
it curves backwards through 90°. Axial ring and posterior pleural ridge with three to four large, elongated
tubercles each.

Pygidium (PI. 27, figs. 11, 13, 14) with second axial ring bounded by wide (sag.) anterior and distinct posterior
furrows. Terminal piece merging with border posteriorly. Pleural areas strongly depressed. Posterior to
articulating process and a diminutive spine are two secondary border spines, followed by major spine and two
further secondary spines. Axial rings and terminal piece each with a pair of spinose tubercles; conspicuous
tubercles also at bases of all border spines.

Di.scussion. This species has a pygidium almost identical to that of D. {D.) quinquespinosa, but diflTers
in its more vaulted cephalon, the number and size of spines on the posterior cephalic margin, the more
anterolaterally situated eyes, and the only partly developed sutural ridges. It is more similar to the
American upper Wenlock or lower Ludlow D. (D.) desolator Campbell, 1967, but is distinguished by
the number and size of the posterior cephalic spines, and the slightly more abaxially set eyes. The
American D. (D.) vanliornei (Weller, 1907), from the Niagaran dolomites, is clearly related to the
above species, but is not sufficiently well known to permit a detailed comparison. These four species
form a fairly tight group within D. (Dudleyaspis). The remaining species referred here to the

RAMSKOLD; SILURIAN ODONTOPLEURID TRILOBITES

249

subgenus; Primaspis {Taemasaspis) camphelli Chatterton, 1971 (Australian Emsian or Eifelian),
Odontopleura howningensis Etheridge and Mitchell, 1896 (Australian Ludlow), Odontopleura
Portlockii Hawle and Corda, 1847 (Bohemian and British Wenlock), and D. (D.) uncifera sp. nov.
(see below), all differ from D. {D.) hamrensis (and its allies) by having a non-spinose occipital ring,
genal spine projecting sublaterally, base level with lateral border anterior to strong anteriorward
flexure of posterior margin, weak sutural ridges, and major spines on pygidium considerably larger
than secondary spines. Taemasaspis Uandoveryana Snajdr, 1975 (see Snajdr 1978 for complete
description), from the Bohemian Llandovery, does not show close similarities to the above species,
and cannot be included in Dudleyaspis, but seems to be morphologically (and stratigraphically)
intermediate between Primaspis and Odontopleura.

Dudleyaspis {Dudleyaspis) uncifera sp. nov.

Plate 28, figs. 1-11; Plate 30, fig. 17

V. J979 Dudleyaspisl sp. indet; Bruton in Jaanusson el al., p. 116.

Name. The name uncifera (Latin for ‘hook-bearing’) was used on a label written by G. Lindstrom, but it has
never been published.

Holotype. Ar51652, cephalon with four articulated thoracic segments, Plate 28, fig. la~d, from the small point
south of Kopparsvik, Visby, Upper Visby Beds.

Paratvpes. ?Lower Visby Beds; Stenkyrka parish— south-west of Balsklint, 0-2 m a.s.l. (SGU 1453), Visby
parish— Norderstrand (Ar5074). Upper Visby Beds: Lummelunda parish— Ronnklint (641181 165698)
(Ar51640a-k; parts of cephalon, thorax and pygidium from one individual, Ar5 1641 -51642). Vasterhejde
parish — Hogklint (SGU 1451). Visby parish— Vattenfallsprofilen I, 1-7-1-9 m a.s.l. (SGU 1452). Several
fragments from the Lower Visby Beds at Ronnkling may also belong to this species.

Diagnosis. Cephalon very wide and short; width to length 3-2:1 -0. Axial furrow almost effaced along
glabella. Lateral glabellar furrows shallow, with an additional furrow on LI. L2 and L3 ridge-shaped.
Posteriormost border spine straight and blunt, subparallel to short genal spine. Cephalon with fine
granulation of low relief. Posterior pleural spines on thorax very stout, short, barbed. Pygidium with
shallow axial and inter-ring furrows, seven pairs of spines, major spine stout, blunt.

Description. Cephalon subtrapezoidal. Occipital ring with occipital organ (PI. 28, fig. Ic/). Occipital lobes large.
L 1 twice as long (exsag.) as wide, divided into two parts by shallow furrow starting at inner end of S 1 and curving
laterally and posteriorly to join axial furrow. L2 small, elongated, defined faintly laterally. L3 similar in shape to
L2 but smaller and almost transverse. Longitudinal furrow barely visible. Eye ridges straight, diverging at about
110°. Eyes set wide apart opposite posterior half of L 1 . Facial suture fused, anterior branch indicated by a faint
ridge, posterior branch indicated by a short, weak ridge near genal angle. Field of cheek with reticulate pattern
(of genal caecae?). Ventrally on lateral border are ten (and possibly a small eleventh) pointed, strongly curved
spines, except the posteriormost which is cylindrical with an abrupt, blunt end. Genal spine small, proximally
directed transversely (in dorsal view) and downwards. Median lobe of glabella carries seven obvious pairs of
tubercles (PI. 28, figs. \b, 1 1), major tubercles on fixed cheek and eye ridge arranged symmetrically. Field of cheek
smooth or with very sparse, fine granulation, cephalon otherwise very finely and densely granulated. Rostral
plate and hypostome not known.

Thoracic segments with pleural ridges of low relief. Anterior pleural spine straight to curved backwards,
cylindrical to slightly flattened, pointed, with barbed anterior and posterior edges. Posterior spine stout, barbed,
almost transverse on anterior segments, posterior to this curved backwards, flexed strongly down at fulcrum.
Pleurae with a few very small tubercles, spines densely and coarsely granulated.

Pygidium with ankylosed articulating half ring in anterior inter-ring furrow, second ring indistinctly separated
from subtriangular terminal piece. Seven pairs of border spines, the fourth the major, anteriormost spine very
small (PI. 28, figs. 2, 8). Major spine thickest at about mid length, gently curved upwards and inwards distally.
Secondary spines pointed, less than half the length of major spines. Tuberculation fairly sparse, no obvious
paired tubercles on axis. Secondary spines with two rows of small tubercles. Spines densely granulated, surface
between tubercles otherwise almost smooth.

250

PALAEONTOLOGY, VOLUME 27

Discussion. This species is easily distinguished from all other Dudleyaspis by the almost effaced axial
and lateral glabellar furrows, and the shape of the posterior pleural spines in the thorax. A unique
feature is the furrow dividing LI. The closest species appears to be D. {D.) hamrensis sp. nov. (ef.
PI. 27, fig. \ la with PI. 28, fig. Ic), although that species belongs to the closely knit group around the
type species (see p. 248).

Subgenus dudleyaspis (snoderaspis) subgen. nov.

Name. From the type locality of the type species, and Greek aspis, shield.

Type species. Dudleyaspis (Snoderaspis) krausi sp. nov., from the Hemse and Eke Beds (lower-middle Ludlow),
Gotland.

Diagnosis. Cephalon very close to semicircular, width to length 2:1. Eye set very anterolaterally,
opposite anterior half of LI, three-quarters way from axial to lateral border furrow. Eye ridges
diverging at 1 10-120°. Facial suture with posterior branches diverging at elose to 90°. Genal spine
eurved backwards in horizontal plane. Anterior pleural spine on thoracie segments needle-like,
posterior spine long, slender, barbed.

Discussion. This subgenus is similar to previously known Dudleyaspis in having a straight eye ridge
and a lateral eye position, in the incurvation of the posterior border at the base of the fairly small
genal spine, the shape, size, and number of both cephalic and pygidial border spines, and the fine
surface tuberculation. However, the course of the (non-functional) facial suture and the extreme eye
position in the semicircular cephalon are features suffieiently different to warrant a new, as yet
monotypic, subgenus.

Dudleyaspis (Snoderaspis) krausi sp. nov.

Plate 29, figs, f, 2, 4, 8-10, 12, text-fig. 3
. 1895 Acidaspis n. sp. Lindstrom, p. 11.

v. 1967 Anacaenaspis gotlandensis Bruton, p. 236 pi. 35, fig. 10, pi. 36, fig. 5, non figs. 1-4

[ = Anacaenaspis pectinata (Angelin, 1854)].
v. 1967 Anacaenaspis aff. gotlandensis Bruton, p. 237 pi. 35, figs. 7-9.

1969 Priniaspis gotlandensis (Bruton, 1967); Schrank, p. 722 [pars].

1978 Anacaenaspis gotlandensis Bruton; Snajdr, p. 31 [/R/r^j.

1981 Anacaenaspis gotlandensis Bruton, 1967; Thomas, p. 85 [pars].

1982 Anacaenaspis gotlandensis Bruton, 1967; Howells, p. 58 [pars].

EXPLANATION OF PLATE 28

Figs. 1-11. Dudleyaspis (Dudleyaspis) uncifera sp. nov. ?Lower Visby Beds (8), Upper Visby Beds (1-7, 9-1 1).
Point south of Kopparsvik, Visby (1), Hogklint (4), Ronnklint (2, 3, 5, 7, 9-11), Vattenfallsprofilen 1 (6), coast
south west of Balsklint (8). \a-ck holotype Ar51652, cephalon with four thoracic segments, anterolateral,
anterior, and exterior views, and enlargement showing granulation and median occipital organ, a-c x2, d
X 13 (coll. G. Lindstrom 1897). 2a-c. Ar51640k,* pygidium, dorsal, posterior, and ventral views, x 5.
3, Ar5 164 L* partial small pygidium, x 9 (coll. V. Jaanusson 1981). 4, SGU 1451,* eight (seven articulated)
thoracic segments and pygidium, x 2-5 (coll. H. Hedstrom 1921). 5, Ar51640c,* cheek fragment with genal
spine and part of spine fringe, all spines complete, interior view, x 5. 6, SGU 1452,* partial distorted
cephalon, anterolateral view, x 3 (coll. G. Liljevall 1908). 7, Ar51640b,* partial cephalon, exterior view, x4.
8, SGU 1453,* small pygidium, ventral view, x 9 (coll. G. Liljevall 1911). 9, Ar51640F h,* partial thoracic
segments, anterior pleural spine intact on middle specimen, x 5. lOu, b, Ar51640e,* three (one displaced)
thoracic segments, anterolateral and dorsal views, x 5. II, Ar5 1640a,* cephalic fragment showing paired
tubercles on glabella, x 5.

* Paralypes.

PLATE 28

RAMSKOLD, DucUeyaspis

252

PALAEONTOLOGY, VOLUME 27

Name. After Mr Werner Kraus, who collected the holotype.

Holotype. Ar51757, cephalon, Plate 29, fig. Aa-d, from Snoder 2, Silte parish, Hemse Marl, north-western part,
Hemse Beds (lower Ludlow).

Paratypes. From the Hemse Marl, north-western part: Silte parish— Snoder 1 (Ar51566), Snoder 2 (Ar51349,
Ar51611). Hablingo parish — Hemmungs 1 (Ar51796), Petesvik (Ar30871, figured Bruton 1967, pi. 36, fig. 5,
correct magnification x 4). Hemse Marl, top: Lau parish — Lau kanal ( = Gannor; Ar30806u-Z?, figured Bruton
1967, pi. 35, fig. 10). Unknown locality, probably Hemse Beds (Ar3081 1, Ar308 17— figured Bruton 1967, pi. 35,
figs. 7-9, correct magnification figs. 7, 8 x 2). Eke Beds, upper part: Lau parish— Lau Backar 1 (Ar51598,
Ar51599, Ar5161 1-51614). In total four complete and seven partial cephala, one hypostome, some thoracic
segments, and three pygidia.

Diagnosis. As for subgenus.

Description. Occipital ring with faint occipital lobes, posterior margin slightly concave medially. Median
occipital organ present (PI. 29, fig. Ad). Median lobe of glabella parallel-sided, rather convex (tr., sag.).
Longitudinal furrow deep. L3 small, distinct. Eye ridge running from just in front of L3 to small palpebral lobe.
Area bounded by eye ridge/palpebral lobe and axial furrow very large, S-shaped in transverse profile, convex
(exsag.). Eye situated at a level much below LI (PI. 29, fig. 4c). No palpebral furrow. Anterior branch of facial
suture indicated by indistinct ridge on cheek, then curves across lateral border to antennal notch, posterior
branch indicated by narrow ridge running straight from eye towards genal angle. Genal spine as long as glabella.
Lateral border bearing row of twelve to thirteen gently curved, pointed spines ventrally (the number can vary
even in the same individual, see PI. 29, fig. 4c), the posteriormost at an angle of about 60° to border and genal
spine. Posterior margin strongly incurved at base of genal spine. Antennal notch distinct. Entire cephalon except
doublure with dense, fine, and even tuberculation.

Rostral plate unknown. The available hypostome (PI. 29, fig. Ic) is distorted, slightly wider than long. Middle
body as long as wide, inflated, extremely weak middle furrow possibly present at about mid length, maculae
indicated by lack of tuberculation and darker colour. Anterior wing fairly large, lateral border narrow (tr.), with
weak shoulder. Lateral border furrow narrow, distinct. Posterior border not preserved. Entire hypostome except
anterior wing and maculae with dense, spiny tuberculation.

Thoracic segments with pleural ridges inflated, fulcral swellings faint. Posterior spine close to transverse
proximally, curving gently backwards distally. Anterior spine straight, subparallel to posterior spine. Spines on
first segment shortened (PI. 29, fig. \b), reaching full size on third segment. Pleural ridges with approximately two
rows of spinose tubercles, tuberculation also on axis, posterior flange, spines, and in pleural furrow.

EXPLANATION OF PLATE 29

Figs. 1, 2, 4, 8-10, 12. Dudleyaspis (Snoderaspis) krausi sp. nov. Hemse Marl, north-western part, Hemse Beds
(1,4, 8, 9, 12), Eke Beds, upper part (2, 10). Petesvik (8), Snoder 1 (1), Snoder 2 (4, 9, 12), Lau Backar 1 (2, 10).
la-c, Ar51566,* partial cephalon with displaced hypostome and two articulated thoracic segments, ventral
view, enlargement of pleural spines (tips lost), and oblique view of hypostome lacking posterior border, u x 2,
b x5,c x5-5. 2, Ar5 161 L* partial cephalon, exterior view, x 3. 4o-r/, holotype Ar5 1757, cephalon, dorsal,
anterolateral, and anterior views, and enlargement of median occipital organ, a-c x2,dx 10 (coll. W. Kraus
1981). 8, Ar30871,* pygidium, figured Bruton 1967, pi. 36, fig. 5, x4 (coll. G. Lindstrom). 9, partial
cephalon belonging to Mr W. Kraus, Niedernhausen, dorsolateral view, x 2. 10a, b, Ar51614,* partial
pygidium, ventral and dorsal views, x 4. 12a, b, Ar5 1 349,* partial thoracic segment, dorsal and dorsolateral
views, X 5.

Figs. 3, 5-7, 1 1. Leonaspis crenata (Emmrich, 1844) angelini (Prantl and Pfibyl, 1949). ?Halla Beds (6), Mulde
Beds, lower part (1 1), undifferentiated (3, 5, 7). Blahall 1(11), Djupviksvagen 1 (3), Lilia Karlso (6), Nordervik
(5, 7). 3a, b, Ar5 1 368b, cranidium, anterior and exterior views, x 6-5. 5a, b, Ar5 1 653, cranidium, exterior and
anterior views, x 5. 6a-c, holotype Ar30859, complete specimen, figured Angelin 1854, pi. 22, fig. 14,
refigured Bruton 1967, pi. 34, figs. 4-6, enlargement of pygidium, enlargement of pleurae, and posterior view,
a, b x6,c x3. 7, Ar5 1654, partly disarticulated thorax and pygidium, oblique dorsolateral view, x 3. 11,
Ar5 1369b, partial thoracic segment, note granulation on anterior pleural ridge, x 7.

* Paratypes.

PLATE 29

RAMSKOLD, Dudleyaspis, Leonaspis

254

PALAEONTOLOGY, VOLUME 27

B

TEXT-FIG. 3. DiuUeyaspis (Snoderaspis) kraiisi subgen. and sp. nov. A, reconstruction of cephalon and part of
thorax, based on Ar30817, Ar51566, and Ar51757, x 3. b, reconstruction of pygidium, based on Ar30817 and

Ar30871, x 3.

Pygidium (PI. 29, figs. 8, 10) with anterior axial ring continuous with pleural ridges and together with these
forming a semicircle. Second ring half as wide (tr.), indistinctly separated from subtriangular terminal piece.
Axial furrow very deep alongside terminal piece and second ring, indistinct anteriorly. Pleural areas strongly
depressed. Two slender secondary spines on each side of only slightly stouter major border spines, which are of
unknown length. Doublure (PI. 29, fig. lOu) raised medially into spinose, transverse ridge. Entire pygidium with
rather fine, sparse tuberculation, densest on axis, anterior border, and spines. No paired tubercles on axis or
major tubercles at bases of spines.

Genus leonaspis Richter and Richter, 1917

Type species. Odoiitopleiira Leonhardi Barrande, 1846; from the Kopanina Formation (Ludlow), Kolednik,
Beroun, Czechoslovakia.

Discussion. The diagnosis of Whittington (1956Z), p. 206) is followed here. Bruton (1967) described
and discussed four Leonaspis species from Gotland, all from the Mulde Beds or from probable
corresponding beds on the Karlso islands. These species present difficulties in interpretation because
all four type specimens either lack important structures, or come from localities that are either known
imprecisely or are inaccessible for re-collecting. Most of the described material consists of water-worn
specimens, although often complete individuals, from the harbour at Djupvik, Eksta parish, where
collecting is no longer possible. New material from slightly higher horizons in the Mulde Beds have
supplied additional information on these species, and they are in part reinterpreted here.

Leonaspis crenata crenata (Emmrich, 1844)

Plate 30, figs. 5, 7; text-fig. 4

* 1844 Odontoplewa crenata Emmrich, p. 17.

V. 1967 Leonaspis crenata (Emmrich, 1844); Bruton, p. 224, pi. 32, figs. 3-8, pi. 33, figs. 1, 2, 5, pi. 34,
figs. 1, 2 [with synonymy list].

. 1969 Leonaspis crenata (Emmrich, 1844); Schrank, p. 710.

. 1977 L. crenata (Emmrich); Campbell, p. 113.

. 1978 L. crenata (Emmrich); Snajdr, p. 35.

. 1981 L. crenata crenata (Emmrich, 1844); Thomas, p. 92.

RAMSKOLD: SILURIAN ODONTOPLEU RID TRILOBITES

255

Lectotvpe. Selected Bruton, 1967, p. 224; specimen in the Geological-Paleontological Museum, Humboldt
University, East Berlin, HU MB 1963/29/1, incomplete cephalon with part of thorax, one of two syntypes
from the Emmrich Collection, figured Bruton 1967, pi. 32, fig. 3, from Djupvik, Eksta parish, Mulde Beds,
lower part.

Other material. Over a hundred more-or-less complete, enrolled specimens, plus some disarticulated material,
are known from the harbour at Djupvik. The only other known locality is Mulde Tegelbruk 1, Eksta parish
(Mulde Beds, undifferentiated). Washed marls from that locality have yielded several fragments, mainly of
cheeks and pygidia.

Diagnosis. Occipital ring smooth except for short, stout, blunt median spine. Anterior border with
row of about fourteen to sixteen tubercles. Free cheek with indistinct, shallow border furrow and
weakly convex to flat border. Twelve border spines, the ten anterior short, rectangular. Genal spine
long, slender, without secondary spines on dorsal surface. Cephalon finely tuberculated. Thoracic
axis and anterior pleural ridges smooth. Pygidium with short secondary spines. Second axial ring well
defined posteriorly. Pleural ridges with pair of small tubercles, pygidium otherwise smooth, major
spines granulated.

Discussion. This taxon was described comprehensively and figured by Bruton ( 1967). The term ‘bifid
spine’ should not be applied to the anterolateral corner of the pygidium since there is no spine, but
merely a process carrying the articulating facet. I have prepared unworn cranidia, and there is no
trace of occipital spines besides the median one; this is the main feature distinguishing the subspecies.
A comparison between the three subspecies of L. crenata is given in text-fig. 4.

THXT-FIG. 4. Comparison of some morphological features in the three subspecies of Leomispis crenata (Emmrich,
1844). The different elements are not drawn at the same scale. The distal part of the genal spine and major

pygidial spines are omitted.

256

PALAEONTOLOGY, VOLUME 27

V. 1851
. 1854
. 1885
. 1885
. 1896
V* 1949
V. 1967
. 1969

, 1975
. 1978
V. non 1979

. 1981
. 1981
. non 1982

Leonaspis crenata angelini (Prantl and Pfibyl, 1949)

Plate 29, figs. 3, 5-7, 11, Plate 30, figs. 1-4, 8-13, text-fig. 4

Angelin, pi. 22, fig. 14 [illustration only, without name].

Acidaspis harnmdei Angelin, p. 38 [referring to 1851 figure].

Odontoplenra Ban andei Angelin; Roemer, p. 219 (376), pi. 10, fig. 9 [fide Schrank 1969].
Acidaspis harrandei Angelin; Lindstrom, p. 53.

Acidaspis Banandei Ang.; Lake, p. 240.

Acanthalonia angelini Prantl and Pfibyl, p. 159, pi. 10, figs. 1 1, 12.

Leonaspis angelini (Prantl and Pfibyl, 1949); Bruton, p. 228, pi. 34, figs. 3-6.

Leonaspis angelini (Prantl and Pfibyl, 1949) (?); Schrank, p. 71 7, pi. 6, fig. 9, pi. 7, figs. 1 -8, pi. 8,
figs. 1, 2.

L. angelini (Prantl et Pfibyl); Snajdr, p. 315.

L. angelini Prantl and Pfibyl; Snajdr, p. 35.

Leonaspis angelini (Prantl and Pfibyl); Bruton in Jaanusson et al., p. 1 16 [ = L. sp. A of this
paper].

L. angelini (Prantl and Pfibyl); Clarkson and Howells, p. 529.

L. crenata angelini (Prantl and Pfibyl, 1949); Thomas, p. 88.

Leonaspis cf. L. crenata angelini (Prant\ and Pfibyl, 1949); Howells, p. 54, pi. 14, figs. 22, 23 [non
L. crenata angelini (Prantl and Pfibyl, 1949)].

Holotype. By monotypy; Ar30859, almost complete specimen, figured Angelin 1851, pi. 22, fig. 14; refigured
Prantl and Pfibyl 1949, pi. 10, figs. 11, 12; refigured Bruton 1967, pi. 34, figs. 4-6; refigured here Plate 29, fig.
6u-c; from Lilia Karlso, possible Halla Beds equivalents.

Other material. Apart from the holotype, only a fragmentary free cheek (Ar47407, figured Bruton 1967, pi. 34,
fig. 3) has previously been known from Gotland. I have collected abundant new material at Djupviksvagen 1 and
Nordervik (635350 163845), both Eksta parish, Mulde Beds, undilTerentiated but higher than the horizon
yielding L. crenata crenata. L. crenata angelini is also known from 'Graptolithengestein' erratics of a slightly
younger age (see Schrank 1969).

Diagnosis. Occipital ring with stout, short, blunt, vertical median spine bearing occipital organ,
flanked by pair of slender, pointed spines. Anterior border with row of about fourteen to eighteen
tubercles. Free cheek with deep border furrow and convex (tr.) border. All twelve border spines round
in section, the anterior four or five with swollen tips, the posterior pointed. Cephalon densely
tubercLilate. Thoracic axial rings with pair of pointed spines, decreasing in size backwards,
anteromedian tubercle, and several symmetrically arranged smaller tubercles. Pygidium with long
secondary spines. Second axial ring poorly defined posteriorly. Paired tubercles on axial rings, large
tubercle on each pleural ridge, and additional tubercles on axis and anterolateral pleural areas.

Discussion. There are slight differences in coarseness and density of tuberculation between specimens
from the three localities in the Mulde Beds: Blahall 1, Djupviksvagen 1, and Nordervik. The
stratigraphically lowest material, from Blahall 1 (PI. 30, fig. 3c/), is very similar to the holotype.
Specimens from Djupviksvagen 1 (PI. 29, fig. 3h) have a more sparse, coarser tuberculation;
specimens from Nordervik (PI. 29, fig. 5a) are even coarser and slightly more densely tuberculated.
These differences are small but consistent, but are not regarded here as being of taxonomic
importance above the population level.

Thomas (1981, p. 92) regarded the differences between crenata crenata and angelini to be of
subspecific rank only, an approach followed here. Practically all differences between these are due to
the strong ornamentation of angelini, and from an evolutionary point of view, only a very minor
genetic change would be required to produce that effect. Present data suggest that angelini is very
slightly younger than crenata crenata, and so is likely to be its descendant. The material described by
Schrank ( 1969) as L. angelini {'!) is indistinguishable from Gotland specimens. Thomas ( 1981 ) erected
L. crenata briitoni for British Wenlock specimens differing slightly both from crenata crenata and
crenata angelini. Differences between brutoni and the Gotland subspecies were listed by Thomas, all

RAMSKOLD: SILURIAN ODONTOPLEURID TRILOBITES

257

of which are valid except the notion of angelini and brutoni lacking an anterolateral ‘bifid’ spine in the
pygidium; this structure is similar in all three subspecies. A comparison between these subspecies is
made in text-fig. 4.

Howells (1982, p. 54, pi. 14, figs. 22, 23) figured and described Scottish Llandovery material as ‘cf.’
(in description) or ‘aff.’ (in plate explanation) L. crenata angelini. The figured pygidium is very wide
relative to its length, and has a very small second axial ring, and is on the whole more similar to
L. deflexa (Lake, 1896). The figured thorax differs from crenata crenata in the extremely long pleural
spines.

Leonaspis coronata bufo subsp. nov.

Plate 30, figs. 6, 14-16; Plate 31, figs. 1-6

. 1969 Leonaspis marklini (Angelin, 1854); Schrank, p. 714, pi. 4, figs. 9, 10, pi. 5, figs. 1-6, pi. 6, figs.

1, 2, 4-7.

Name. Latin bufo, toad; referring to the wart-like appearance of the surface sculpture.

Holotype. Ar51664, incomplete cephalon with nine thoracic segments, Plate 30, fig. \Aa-d, from Djupviksvagen
1, Eksta parish, Mulde Beds, undifferentiated.

Paratypes. All from Eksta parish. From the type locality (Ar51363-51365, Ar51665-51684). From Blahall 1,
Mulde Beds, lower part (Ar51685, free cheek). From Nordervik (635350 163845), Mulde Beds, undifferentiated
( Ar5 1 686-5 1 708). In total about twelve cranidia, sixteen free cheeks, three hypostomes, some thoracic segments,
and seventeen pygidia.

Diagnosis. Genal spines very long, reaching about seventh thoracic segment. Thoracic segments with
slender, pointed posterior pleural spines, longest on sixth segment, short on anterior three segments,
but markedly shortened on anteriormost segment only. Pygidium with major pair of spines directed
exsagittally or slightly divergent backwards, secondary spines slender, pointed. Cranidium, base of
genal spine, axis, and pygidium coarsely tuberculate.

Discussion. British coro«am material (see Thomas 1981 ) and Gotland specimens are of approximately
the same age, and are regarded here as geographical subspecies of L. coronata. The material from
German ‘Graptolithengestein’ erratics described by Schrank (1969) as L. marklini is similar in all
features to bufo, except possibly a greater range of variation.

None of the previously described or figured Gotland specimens referred to L. marklini (Angelin,
1854) are included in L. coronata bufo. L. marklini is regarded here as a nomen dubium. The holotype
(see Bruton 1967, pi. 30, fig. 7), a worn external mould of an incomplete exoskeleton, is not
identifiable since it lacks important morphological features. The shape and length of the genal spines,
the lateral border and border furrow, and the main part of the cranidium, are unknown. No topotype
material is known, and the type locality is inaccessible for recollecting. The free cheeks referred by
Bruton (1967, pi. 30, fig. 8, pi. 31, figs. 1 , 2) to marklini assigned here questionably to L. muldensis
(see below). Of the other marklini material described by Bruton (1967), the pygidia (ibid., pi. 30,
figs. 3, 5) may belong to L. coronata bufo, or perhaps to L. muldensis, the pygidium of which is poorly
known, but seems to be similar to that of bufo. The cranidia from Lilia and Stora Karlso (Bruton
1967, pi. 30, fig. 4, pi. 31, fig. 3) have a very narrow median glabellar lobe, especially between the basal
lobes, and seem not to belong either to bufo or muldensis', they cannot be compared with the holotype
of marklini, which lacks most of the cranidium. The fairly complete specimen figured by Lindstrom
(1885, pi. 13, fig. 1 5, refigured Bruton 1967, pi. 30, fig. 6) lacks free cheeks and has a median glabellar
lobe similar to bufo and muldensis, but has coarsely tuberculate spines on the thorax and pygidium,
and cannot be referred with certainty to either taxon, at least until muldensis is better known. The
material discussed above cannot be determined specifically; with regard to Leonaspis species, the
availability of either well-preserved articulated specimens or a complete ‘set’ of exoskeletal parts from
a single locality is a necessity for specific determination.

258

PALAEONTOLOGY, VOLUME 27

Two aberrant specimens of L. coronata hufo are known. One pygidium (PI. 31, fig. 5) has an
extra, median border spine, probably a genetically determined feature. The pygidium is slightly
asymmetrical. One cranidium (PI. 3 1 , fig. I ) shows a pathological left L2, with the entire cranidium in
front of LI bent sideways. The defect is probably a result of damage during the preceding moult stage.

Leonaspis miildensis Bruton, 1967
V* 1967 Leonaspis miildensis Bruton, p. 227, pi. 33, figs. 3, 4, 6, 7.

V? 1967 Leonaspis nuirklini (Angelin, 1854); Bruton, p. 219, pi. 30, fig. 8, pi. 31, figs. 1, 2 [free cheeks
only],

. 1978 L. miildensis Bruton; Snajdr, p. 35.

Holotype. Ar30826, enrolled specimen lacking pygidium, figured Bruton 1967, pi. 33, figs. 3, 4, from the harbour
at Djupvik (635602 164128), Eksta parish, Mulde Beds, lower part.

Other material, diagnosis, and description. See Bruton 1967, p. 227.

Discussion. Only the three specimens already described by Bruton are known. They are all severely
water-worn, lack genal spines and surface sculpture, and only one has the pygidium attached, which
is badly worn. From the locality yielding these specimens are also several isolated free cheeks. These
were assigned by Bruton ( 1 967) to L. marklini, but it seems more likely that they are conspecific with
the enrolled specimens from the same beds. This view is neither contradicted nor supported by the
morphology of the specimens, since the free cheeks of the enrolled specimens are poorly preserved.
On the assumption that L. miildensis should be retained as a valid taxon it can easily be distinguished
from other Leonaspis by the shape of the free cheeks, if these belong to miildensis, but is otherwise very
similar to L. coronata and L. miitica (Emmrich, 1844).

L. miildensis occurs together with, and is strongly outnumbered by, L. crenata crenata. Similarly,
L. coronata hufo is always accompanied by, and outnumbered by, L. crenata angelini. This occurrence
of two Leonaspis forms together is common, and has been discussed by several authors (see Campbell
1977, p. 1 13), and the forms are sometimes referred to as morphs of the same species. In the Gotland
examples the forms are assigned to separate species, since the differences are so profound.

EXPLANATION OF PLATE 30

Figs. 1-4, 8-13. Leonaspis crenata (Emmrich, 1844) angelini (Prantl and Pfibyl, 1949). Mulde Beds, lower part
(3), Mulde Beds, undifferentiated ( 1, 2, 4, 8-13). Blahall 1 (3), Djupviksvagen 1 (9), Nordervik (2, 4, 8, 10-13),
shore south of Djupvik ( 1 ). 1 , displaced hypostome of complete specimen belonging to K. and W. Amelang,
Aachen, exterior view, x 10. 2, Ar5 1655, free cheek, dorsolateral view, x 5. 3a, 6, Ar5 1369a, cranidium with
dense tuberculation, exterior and anterior views, x 5. 4, Ar51656, small hypostome, exterior view, x 20.
8, Ar51657, disarticulated thorax and pygidium of small holaspis, x 8. 9, Ar51367, free cheek with sparse
tuberculation, dorsolateral view, x6. 10, Ar51658, pygidium, x 6. II, Ar51659, pygidium, x 6-5. 12,
Ar5 1 660, pygidium, x 5. 13, Ar5 1661, pygidium, x 8.

Figs. 5, 7. Leonaspis crenata crenata (Emmrich, 1844). Mulde Beds, lower part, Djupvik. 5, Ar30840,
hypostome, exterior view, x 12. 7, Ar308 12, pygidium, x 7.

Figs. 6, 14-16. Leonaspis coronata (Salter, 1 853) hufo subsp. nov. Mulde Beds, undifferentiated. Djupviksvagen
1 (14-16), Nordervik (6). 6a, b, Ar51686,* free cheek, dorsolateral and dorsal views, x 5. \Aa-d, holotype
Ar51664, partly disarticulated specimen lacking pygidium, thorax, oblique anterolateral, anterior, and
exterior views, x 5. 1 5, Ar5 1665,* hypostome, exterior view, x9. 1 6, Ar51 363,* hypostome, exterior view,

X 10.

Fig. 17. Diidleyaspis (DiuHeyaspis) iincifera sp. nov. Ar51710,* earliest? holaspid pygidium, dorsal and ventral
views, Ronnklint, Upper Visby Beds, x 22.

* Paratypes.

PLATE 30

RAMSKOLD, Leonaspis, Dudleyaspis

260

PALAEONTOLOGY, VOLUME 27

Leonaspis sp. A

Plate 31, figs. 7-11, 13

V. 1979 Leonaspis angelini (Prantl and Pfibyl); Bruton in Jaanusson et al., p. 116, non Prantl and Pfibyl,
1949.

Material. All specimens are from Visby parish. Hogklint Beds, unit b: Vattenfallsprofilen 1, 20T-20-2 m a.s.l.
(SGU 1454-1456). Dump at Visby harbour (639275 164800) (Ar51347). Hogklint Beds, undifferentiated: ‘Visby’
(Ar30878, Ar30879).

Discussion. These specimens may well represent a new species, but more and better-preserved
material is needed before it can be established formally. The main distinguishing features are as
follows: occipital ring with a stout median spine flanked by a pair of slender spines; median glabellar
lobe narrow (tr.), parallel-sided; LI confluent with cheek laterally due to elfaced axial furrow;
anterior border with a row of tubercles; anterior margin convex forwards; paired tubercles on
glabella; close to facial suture is a spine dorsally on genal spine, but not on posterior margin of
cranidium; free cheek with thirteen border spines; genal spine very long, slender; pygidium fairly
similar to that of L. crenata angelini, but with narrower axis, very large tubercle-pair on pleural
ridges, and with a tubercle-pair above bases of posterior border spines.

L. sp. A is closest to L. crenata angelini, although the differences are quite marked, especially in the
shape of the glabellar lobes. Bohemian Ludlow specimens assigned by Pfibyl and Vanek (1966,
p. 295, pi. 2, fig. 1, pi. 3, figs. 3, 4) to L. geinitziana (Hawle and Corda, 1847; regarded as a synonym of
L. leonhardi (Barrande, 1846) by Bruton 1968, p. 20), show some similarity to L. sp. A, both in the
shape of the glabellar lobes and in the pygidium (if the associated parts of each species really belong
together). It differs, however, e.g. in the shape of the occipital ring and the axial furrow, and perhaps
in the number of pygidial spines. No close comparison can be made until both species are better
known.

EXPLANATION OF PLATE 31

Figs. 1-6. Leonaspis coronata (Salter, 1853) bufo subsp. nov. Mulde Beds, undifferentiated. Djupviksvagen 1
(1, 2, 4, 5), Nordervik (3, 6). 1, Ar5 1368a,* cranidium showing pathological asymmetry, x7. 2, Ar51365,*
pygidium, x 6. 3, Ar51688,* latex cast of external mould of pygidium with part of thorax, x 4. 4a, b,
Ar51364,* cranidium, exterior and lateral views, x 4. 5, Ar51684,* pygidium with extra (median) spine, note
slight asymmetry, x 7. 6, Ar5 1687,* pygidium, x 6.

Figs. 7-11, 13. Leonaspis sp. A. Hogklint Beds, unit b (7, 9-11), undifferentiated (8, 13). Dump at Visby harbour
( 10), Vattenfallsprofilen 1, 20- 1-20-2 m a.s.l. (7, 9, 1 1, coll. G. Liljevall 1908), Visby (8, 13). 7, SGU 1454, worn
pygidium, x 7. 8, Ar30878, small cranidium, exterior view, x 7. 9, SGU 1455, free cheek, dorsolateral view,
X 7. 10, Ar5 1347, partial free cheek, dorsolateral view, X 6. 1 1, SGU 1456, pygidium, x 7. 13a, 6, Ar30879,
cranidium, exterior and anterolateral views, x 6.

Figs. 12, 15-18. Ceratocephala barrandii (Fletcher in Salter, 1853). Hogklint Beds, middle-upper part (15, 17),
Halla Beds, unit b (16, 18), undifferentiated (12). Horsne kanal (16, 18), Ireviken (17), Lilia Karlso (12), south
of Visby cement factory (15). 12, Ar30792, internal mould of partial cranidium, exterior view, x 4 (coll. A.
Florin 1891). 15a, b, SGU 1457, partial tborax and pygidium, exterior view and dorsal view of pygidium,
a X 2-5, 6x3 (coll. G. Liljevall). 16, SGU 1458, anteriormosf? thoracic segment, x 2 (coll. G. Liljevall 1909).
17, mainly internal mould of partial cranidium, belonging to K. and W. Amelang, Aachen, exterior view, x 2.
18a, b, SGU 1459, partly exfoliated cephalon, exterior and anterolateral views, x 2 (coll. G. Liljevall 1909).

Fig. 14. Ceratocephala sp. Ar51626, small pygidium, dorsal and ventral views, Ronnklint -1-7-5 m, Lower Visby
Beds, X 13 (coll. V. Jaanusson 1981).

* Paratypes.

PLATE 31

RAMSKOLD, Leonaspis, Ceratocephala

262

PALAEONTOLOGY, VOLUME 27

A few pygidia of coroiiata type are also stated (on the labels) to be from the Hogklint Beds, and a
second species may thus be present. However, these specimens come from old collections with locality
stated only as ‘Visby’, and a large number of Mulde Beds specimens mislabelled ‘Visby’ are known, so
that the locality quoted must be regarded with caution.

Leonaspis sp.

Material. Ar5 1758-5 1765, small fragments of cranidia, free cheeks, thoracic segments and pygidia, from the
Lower Visby Beds at Ronnklint (641181 165698), Lummelunda parish.

Discussion. The material is very fragmentary, but may represent a new species. The free cheeks have a
very weak lateral border and border furrow, similar to L. crenata crenata, but have a secondary spine
dorsally on the genal spine, similar to L. sp. A described above. An incomplete pygidium has two
secondary spines between the major spines. The species is fairly common in the Lower Visby Beds at
Ronnklint, and new material will hopefully make a specific assignment possible.

Subfamily miraspidinae Richter and Richter, 1917
Genus ceratocephala Warder, 1838

Type species. By monotypy; Ceratocephala goniata Warder, 1838, from the middle Silurian, Springfield, Ohio.

Ceratocephala harrandii (Fletcher in Salter, 1853)

Plate 31, figs. 12, 15-18

v. 1851 Angelin, pi. 21, fig. 7 [illustration only, without name].

* 1853 Acidaspis Barrandii Fletcher in Salter, pi. 6, p. 6.

V. 1854 Trapelocera hicuspis Angelin, p. 31 [referring to 1851 figure].

V. 1933 Ceratocephala hicuspis (Angelin); Warburg, p. 13.

V. 1967 Ceratocephala hicuspis (Angelin, 1854); Bruton, p. 241, pi. 36, fig. 11 [with synonymy list].

1981 Ceratocephala harrandii {¥\etc\\&r in 1853); Thomas, p. 94, pi. 24, figs. 11-14, 18-23, pi. 25,

figs. 1-7 [with synonymy list].

Material. From Visby, most probably Hogklint Beds, units b and c; Ar2184, partial cephalon, holotype of
T. hicuspis Angelin; Ar6152, partial thoracic segment; SGU 1457, partial thorax and pygidium. From Horsne
kanal (638493 166725), Horsne parish, Halla Beds, unit b; SGU 1458-1459, cephalon and partial thoracic
segment (the two specimens discussed by Warburg 1933, p. 13). From Lilia Karlso, ?Halla Beds; Ar30792, partial
cranidium.

Discussion. This species was described recently by Thomas (1981). The Gotland material is identical
to British specimens and T. hicuspis Angelin, 1854 is accordingly considered to be a junior subjective
synonym of A. barrandii Fletcher in Salter, 1853. The few Gotland specimens do not add any new
information on the morphology of the species.

Ceratocephala sp.

Plate 31, fig. 14

Material. Ar51626 (small pygidium), Ar51751-51756 (fragments of thoracic segments and pygidia), all from the
Lower Visby Beds at Ronnklint (641181 165698), Lummelunda parish.

Discussion. One incomplete large and one small pygidium (PI. 31, fig. 14) both have only three
marginal spines. This is a feature unique among Silurian Ceratocephala, and the material almost
certainly represents a new species. It may be related to C. harrandii since one fragment is probably a
free distal part of the tenth thoracic segment, indicating the presence of a structure similar to that
described by Thomas (1981, p. 94) for harrandii. Several Ordovician species also have three-spined
pygidia and sutures on the tenth thoracic segment, but the Gotland specimens seem distinct from each
of these, although a comparison is not meaningful without more material.

RAMSKOLD: SILURIAN ODONTOPLEURID TRILOBITES

263

Acknowledgements. I am grateful to Professor Valdar Jaanusson for advice and encouragement throughout this
study, and to Dr Michael Bassett for useful discussions at several stages. In addition, preliminary drafts of the
manuscript were read critically by Dr David Bruton and Dr Alan Thomas. Dr Sven Laufeld arranged the loan of
specimens from the Museum of the Geological Survey of Sweden. Mr Werner Kraus and Mr Wilfried Amelang
kindly supplied specimens from their private collections, and Dr Euan Clarkson supplied a latex cast of a
Scottish specimen. The drawings were made by Mr Bo Bergman and Mr Bertil Bliicher at the Section of
Palaeozoology, Swedish Museum of Natural History. Field work was sponsored by the Swedish Natural Science
Research Council (NFR) and the Swedish Museum of Natural History. This paper is a contribution to IGCP
Project 53 (Ecostratigraphy).

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LAUFELD, s. 1974fl. Silurian Chitinozoa from Gotland. Ibid. 5, 130 pp.

19746. Reference localities for palaeontology and geology in the Silurian of Gotland. Sver. geol. Unders.

C705, 172 pp.

LINDSTROM, G. 1885. Forteckning pa Gotland siluriska crustaceer. Ofvers. K. Vetensk.-Akad. Fork. 6, 37-100,
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1895. Remains of a Cyathaspis from the Silurian strata of Gotland. Bih. K. svenska Veten.sk. -Akad. Hand!.

21 (4), no. 3, 14 pp., 2 pis.

MEEK, F. B. 1873. Descriptions of invertebrate fossils of the Silurian and Devonian systems. Kept. geol. Surv.
1 (2), 1-243, pis. 1-23.

264

PALAEONTOLOGY, VOLUME 27

MOORE, R. c. (ed.) 1959. Treatise on invertebrate palaeontology. Part O, Arthropoda 1. Geol. Soc. Amer. and Univ.
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MURCHISON, R. I. 1839. The Silurian System, xxxii + 768 pp., 40 pis. London.

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PRIBYL, A. and VANEK, I. 1965. Neue Trilobiten des bohmischen Ordoviziums. VTst. (Jstf. Ust. geol. 40, 277-282.

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1973. liber Hypostome von Odontopleuriden (Trilobita) und ihrer Systematik. Cas. min. geol. 18,

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RAMSKOLD, L. 1983. Silurian cheirurid trilobites from Gotland. Palaeontology, 26, 175-210, pis. 19-28.

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LARS RAMSKOLD
Sektionen for Paleozoologi
Naturhistoriska Riksmuseet

Typescript received 27 April 1983 3ox 50007

Revised typescript received 30 June 1983 S-104 05 Stockholm, Sweden

RHYNIOPHYTINA AND TRIMEROPHYTINA FROM
THE EARLY LAND FLORA OF VICTORIA.

AUSTRALIA

by J. D. TIMS and T. c. chambers

ABSTRACT. New rccords of northern hemisphere plani genera are described from the Lower Plant Assemblage
(Late Silurian, Ludlovian) and the Wilson Creek Shale (Early Devonian, Pragian/Siegenian) of Victoria,
Australia. The genera, the rhyniophyte Salopella of which there are two new species S. ausiralis and
S. caespitosa, and Dawsonites, represented by D. subarcuatus sp. nov., which is the first recording of a
trimerophyte in Victoria and probably in the Southern Hemisphere, were found associated with Baragwamithia
and are new additions to the Baragwamithia flora.

Since the work of Lang and Cookson (1930, 1935) and Cookson (1935, 1949) no formal studies
have been made on the Baragwanathia flora of the Lower Devonian of Victoria, Australia. For many
years this flora was regarded as Silurian, the oldest vascular land plant flora in the world. Elies (in
Lang and Cookson 1935) had identified the associated graptolite as Monograptiis imc iiia t us TnUherg
(an Early Ludlow species), which often occurred on the same bedding plane as specimens of
B. Lang and Cookson. Investigations by Jaeger commencing in 1959 (see Jaeger 1966) led to

the description of this as a new species, M. thomasi Jaeger. Associated with M. thomasi and slightly
higher is M. aeqiiabilis notoaequabilis Jaeger and Stein. The range of this latter species in other parts
of the world is Pragian. M. thomasi has since been identified from Malaya (Jaeger 1 970) and as M. afl’.
thomasi in Russia (Koren' 1971) in rocks believed to be Pragian. Jaeger considers that the evidence
suggests the Baragwanathia flora as described by Lang and Cookson (1930, 1935) is Pragian, a view
with which Koren' concurs. However, the precise age range of M. thomasi is still uncertain. The range
of Baragwanathia itself extends above that of M. aeqiiabilis notoaequabilis and, in Victoria, below
that of M. thomasi.

Garratt (1978) reported two distinct Baragwanathia floras from the Yea district: the Upper and
Lower Plant Assemblages. The Upper Plant Assemblage is equivalent in age to the flora described by
Lang and Cookson. The 1929 collecting party (Harris and Thomas 1941) obtained plant fossil
material from the Upper and Lower Plant Assemblages in the Yea district. The Lower Plant
Assemblage material was collected from a road cutting about 30 m from the Limestone Road locality
described here. None of this material had been included in Lang and Cookson’s papers on the
Baragwanathia flora. The Upper Plant Assemblage material illustrated by Lang and Cookson (1935)
was collected from Killingworth Road, Yea.

Separating the two assemblages is 1,700 m of virtually unfossiliferous sandstone. The Lower Plant
Assemblage contains the oldest known Baragwanathia and is regarded, somewhat controversially, as
being of Ludlovian age (Edwards et al. 1979; Garratt 1981). The dating, based initially on field
evidence, is now on the basis of associated graptolites (Rickards 1982, pers. comm.). While no new
species have been added to the Barag^r/mathia flora in the intervening years since the 1930s, when the
late Dr. Isabel Cookson did her pioneering work, it is clear from the new records reported here,
together with others still under investigation, that the Baragwanathia floras are more diverse than
have been recognized.

[Palaeontology, Vol. 27, Part 2, 1984, pp. 265-279, pis. 32-34.]

266

PALAEONTOLOGY, VOLUME 27

LOCALITIES AND MATERIALS

Locality 1 . Frenchman Spur; roadside exposure on the fire access track known as Frenchman Spur
Road about 10 km west of Matlock (Grid reference 077-656. Matlock: Australia Sheet 8122— IV,
1 : 50,000) (text-fig. 1 ).

The exposed strata are near the top of the 150 m thick Wilson Creek Shale which outcrops in the
area at a number of localities that have yielded Baragwanathia. The unit comprises a fossiliferous
shale interbedded with thick siltstones. Sediments at Frenchman Spur when fresh are hard and
grey-black; they are almost impossible to split along bedding planes. The weathered material, which
is buff coloured, splits easily and was the source of most of the specimens. Preservation of the plant
fossils varies from compressions with considerable amounts of fragmentary mineral to pink-stained
impressions. The Wilson Creek Shale has been subjected to at least one generation of folding which
appears to have fragmented the mineral remains of the plant into microscopically small pieces, often
arranged in two diagonal rows with the space in between filled with secondary silica. Most of the plant
detail and cellular structure has been lost. Maceration with Schulze’s solution yielded no fragments or
spores; cellulose acetate film pulls failed to show any structure or in situ spores in either fresh or
weathered rock.

Age ami correlation. Early Pragian (= Siegenian); M. thomasi is sometimes found on the same
bedding plane as plants, but more frequently in dense clusters on different planes. M. aequabilis
notoaeqiiahilis is not present, but has been recorded at nearby localities in the Wilson Creek Shale.

TEXT-FIG. 1. Locality map showing location of the Melbourne Trough and the two collection sites.

TIMS AND CHAMBERS: EARLY LAND PLANTS FROM AUSTRALIA 267

The only other animal fossils are eurypterid fragments. The flora, therefore, is at the same
stratigraphic level as the Upper Plant Graptolite Horizon (Couper 1965; Garratt 1978; Jaeger 1966)
and is of Early Devonian age.

Flora. Rhyniophytina: Salopella aiistrali.s sp. nov., S. caespitosa sp. nov., Yarravia ohlonga Lang and
Cookson, Fledeia spp. Zosterophyllophytina; Zosterophyllum sp., other undescribed zosterophylls.
Lycophytina: B. longifolia Lang and Cookson, B. sp., other lycopods, fragmentary but not
Baragwamithia. Trimerophytina: Dawsonites suharcuatus sp. nov.

The site has been mentioned as a Pachy theca locality (Moore 1965) but this identification has not
been substantiated.

Locality 2. Limestone Road, Yea: a recently widened road cutting 2 km south-east of Yea. (Grid
reference 466-088. Yea: Australia Sheet 7923 — 1, 1 : 50,000.) This locality was cited by Harris and
Thomas (1941) as Brackley’s Cutting, Geological Survey locality 4, by Couper (1965) as locality 62,
and by Garratt (1978) as locality 4 (text-fig. 1).

The plant-bearing strata are thin brown to grey claystones near the top of the Yea Lormation (see
stratigraphic section in Garratt 1978), and occur immediately below the Rice Hill Sandstone member.
The horizon is some 1,700 m stratigraphically below that of the main Baragwanathia floras (Upper
Plant Graptolite Horizon). Preservation is very poor; often only a depression in the plane of the rock
to indicate the outline (e.g. PI. 32, fig. 5). Some remains are of a white mineral and others of a brown
deposit, occasionally occurring together (PI. 32, fig. 6). No cellular structure or spores have been
found.

Age and correlation. Ludlow Series; Garratt (1978, 1981) considers the assemblage to be of Late
Silurian (Ludlow) age. He bases this on detailed geological mapping in this region, together with
evidence from the associated fauna and lithological affinities and especially on the presence of several
graptolite species known only from Ludlow strata elsewhere. These are Pristiograptus dubius and
Bohemograptns sp. M. aflf. uncinatus uncinatus has not been recorded at Yea, but occurs together
with these two species and Baragwanathia, some 3 km to the north (Garratt 1978, locality 1). The
Limestone Road assemblage also contains undescribed gastropods, orthocerids, Hyolithes spp.,
Neckiania (bivalve), and Maoristrophia banks! (brachiopod).

The relatively large size of the axes, up to 400 mm, suggests either that they have not been
transported far or had been transported gently. Garratt (pers. comm.) believes that the plants came
from the south.

Flora. Rhyniophytina: Salopella australis sp. nov., Hedeia sp. Zosterophyllophytina: At least one
zosterophyll (report in preparation), two other probable zosterophylls. Lycophytina: Bara-
gwanathia longifolia, at least one other lycophyte.

SYSTEMATIC PALAEONTOLOGY

Three new species have been erected. All material (except that on PI. 32, figs. 5, 6) housed at the National
Museum of Victoria.

Subdivision rhyniophytina Banks 1968
Lamily rhyniaceae Kidston and Lang 1920
Genus salopella Edwards and Richardson 1974

Type species. S. allenii.

Salopella australis sp. nov.

Plate 32, figs. 1-6; Plate 34, figs. 4, 5; text-fig. 2a-c

Diagnosis. Axes with at least two dichotomies, 0'9-2-4 mm wide with central line. Plant at least
145 mm high. No obvious branching at the base of the sporangia. Sporangia 6-5~-14 0 mm long and

268

PALAEONTOLOGY, VOLUME 27

1- 3-2 0 mm wide, with parallel sides in the lower two-thirds of the presumed fertile portion. Sterile
sporangial apex tapering to a point in the upper third. Spore characters unknown.

Range. Late Silurian (Ludlovian)-Early Devonian (Pragian).

Type locality. Frenchman Spur.

Horizon. Wilson Creek Shale (Pragian).

Holotype. NMV part and counterpart, P50,008. Plate 32, figs. 1, 2.

Derivation of specific name, ‘australis’ — southern.

Description. More than twenty specimens have been collected from two sites, Limestone Road (Ludlovian) and
Frenchman Spur (Pragian). Most are compressions (sensu Schopf 1975) but some are so weathered that they
have been reduced to impressions. Preservation varies from a pink stain on a buff-coloured matrix to a finely
divided material of coaly appearance, as seen in specimens from Frenchman Spur, and red-brown and white
minerals on similar coloured background from Limestone Road. One Limestone Road specimen (PI. 32, fig. 3) is
white on a blue-grey matrix, with its ultimate branches on different planes in the rock. The majority of specimens
have had some covering matrix removed.

The specimens show the remains of a possible vascular trace, 0-22 mm wide, in some cases as a faint dark line in
the centre of the stem (PI. 32, fig. 1) and in others, a central ridge (PI. 32, fig. 3). The ridge branches with the axis.

The maximum total length of axes is 145 mm. Eleven of the specimens are dichotomously branched (another
possibly so) and of these, four have two dichotomies. Of the remaining six specimens, one is an isolated axis apex
and the others are of axis lengths up to 40 mm. Axis width decreases with successive branching but remains
constant between nodes. Maximum width is 2-4 mm and the minimum 0-9 mm. Average widths for the lowest
branch are 21 mm (range L8-2-4 mm), the intermediate 1-8 mm (LO-2-2 mm) and the ultimate branch 1-4
(0-9-1-7 mm).

Each axis terminates in a single presumed sporangium. In the better-preserved specimens an oval-shaped area
of dark mineral is present a few millimetres below the apex. These areas are presumed to be sporogenous,
although no spores could be isolated from them. The junction between axis and sporangium could not be clearly
defined, as many axes show an increase in diameter 2-3 mm below the presumed spore mass. Measurement of the
sporangia was taken from the base of the dark area or the remaining outline. Where there was no increase in the
axis diameter below the sporangium the sporangial width was the same as that of its axis. Average length of
twenty-six sporangia is 10-2 mm (range 6-5- 14 0 mm). The average width of the sporangia is 1-8 mm (1-3-

2- 9 mm). The presumed spore-containing area where visible averaged 5-7 mm in length (4-4-7-5 mm). The
sporangia are of acute convex shape in the presumed sterile upper portion. In half the specimens there is evidence
of a slight indentation where the sterile tips connect with the fertile area (e.g. PI. 32, fig. 5). The maximum widths
of the sporangia coincide with those of the presumed fertile areas. The sporangia are parallel-sided for at least
half their length.

EXPLANATION OF PLATE 32

Figs. 1-6. Salopella australis sp. nov. 1,2, NMVP50,008 part and counterpart; holotype showing the sterile apex
of the sporangium, the dark presumed sporogenous region and dichotomous branching; Frenchman Spur;
fig. 1, x3-8,fig.2, X 2-2. 3, NMV P50,011; plant remains preserved as a white mineral on a steel-blue coloured
matrix; the two branches with eight sporangia are most likely from the one plant (see reconstruction, text-
fig. 2c); central ridge on the lower part of the plant is the probable remains of the vascular trace; Limestone
Road, X 1-8. 4, NMV P50,014; an axis with a dichotomy just below the sporangia; this specimen has the
longest sporangia and is unusual in branching just below the dark spore masses; Frenchman Spur, x IT.
5, one of the longest specimens (123 mm) from Limestone Road; although it cannot be seen from this
illustration using a unilateral light source, the two sporangia on the left both have a dark area, the remains of a
presumed spore mass; remains of the vascular trace are visible in the lower part of the axis (arrow); x 1 (this
specimen is from Dr. J. Douglas’s private collection). 6, the extreme left-hand sporangium of fig. 5, showing
the large dark presumed spore mass; photograph was taken using overhead light and high contrast film and
paper; remainder of the specimen is not visible using this technique; x 1-5.

PLATE 32

TIMS and CHAMBERS, Salopella

270

PALAEONTOLOGY, VOLUME 27

Angles of the ultimate branches average 38° (25-60°), while the lower branching angle is wider at 60° (48-70°).
The specimen illustrated on Plate 32, fig. 5 and text-fig. 2b has at first glance a much broader angle. If the angle is
examined 1 mm from the dichotomy, it can be seen that the angle is 70° and the further spreading of the branches
may be an artefact of deposition. In most examples, the branch axes curve in together until they become almost
parallel.

As may be seen in Plate 32, fig. 1, naked axes of similar widths often occur on the same bedding planes as the
specimens referred to as Salopella. Some of these naked axes are up to 200 mm long and often curved. There is
little direct evidence of the habit of Salopella, but if the long axes are portions of this species, it is possible that the
plant was partially prostrate. It is unlikely that such slender axes would exceed this height, although this would
depend to some extent on stem anatomy.

In conclusion, the Victorian specimens are part of a small, open-branched plant, at least 145 mm high with
slender naked axes terminating in elongate sporangia. Axes dichotomize at least twice, with successive planes of
dichotomy, probably at 90°. The specimen illustrated in Plate 32, fig. 3 and text-fig. 2c demonstrates this and has
dift'erent orders of branches on different planes in the rock. No spores could be isolated from the sporangia and
no cell detail was present in any of the remains. The basal parts of the plant are unknown.

Discussion. Edwards and Richardson (1974) erected the form genus Salopella to distinguish
compression fossils having Rhynia-WkQ sporangial shape and naked dichotomizing axes from the
much better-preserved plants from the Rhynie Chert. It is clear that this new species belongs in the
form genus, but there are differences from the type species S. allenii, and from Rhynia. There are other
characters which are common to both the new Salopella and other members of the Rhyniaceae.

There are seven genera in the family Rhyniaceae {sensu Banks 1975). Of these, five have sporangia
with height exceeding the width. Rhynia and Salopella are in this group, as are Horneophyton lignieri
(Kidston and Lang) Barghoorn and Darrah, Steganotheca striata Edwards, and Eogaspesiea gracilis
Daber.

Eogaspesiea from the Gaspe Peninsula, Quebec is a gregarious plant with small oval sporangia
(Daber 1960). The narrow axes rarely branch and its bushy habit readily distinguishes it from
Salopella australis. Horneophyton lignieri has small cylindrical sporangia with a distinct columella.
There is no indication of such tissue preserved in Salopella. Steganotheca striata Edwards (1970) has
truncated fusiform sporangia and a branching habit whereby the tips of the branches are parallel, a
branching pattern (see Edwards 1970, PI. 84, fig. 1.2) closely resembling the branching illustrated for
Salopella australis in Plate 32, figs. 1-5. Steganotheca striata also has axes which gently taper to
increase in diameter below the sporangia so that the sporangial bases are not clearly defined; the
sporangia are small (1-8 mm) and cup shaped.

The dimensions of the sporangia and axis width of the new Salopella are almost exactly the same as
those of Rhynia major. R. gwynne-vaughani has smaller sporangia which abcise, protuberances on the
axes and an adventitious branching system. From the descriptions of Kidston and Lang (1917 and
1920), it appears that R. major not only does not branch as frequently as Salopella, but also has axes
tapered from 6 mm at their bases to 1-5 mm below the sporangia. Both Rhynia species have clearly
defined sporangial bases and although R. major has some sterile tissue at the apex of the sporangium
(Kidston and Lang 1917, PI. 9, fig. 62), it is not extensive. Although it is difficult to compare
impression fossils with petrifications, R. major appears to have the broadest part of its sporangium
about one-third its length from the base, the upper two-thirds tapering slightly to a rounded apex.

The sporangia of S. allenii also differ from those of the new species. Although the dimensions of the
sporangia are the same, S. allenii has true fusiform sporangia, compared to the parallel-sided ones of
the new Salopella. S. allenii sporangia lack the defined spore area as seen on most specimens of S.
australis; the sporangial bases of S. allenii are more clearly defined and their axes dichotomize directly
below the sporangia. This character was observed only once (PI. 32, fig. 4) in the Victorian specimens.

The new Salopella is a larger plant in terms of axis length and does not dichotomize as frequently as
S. allenii, although it is important to note that S. allenii is known from only one specimen.

Another genus with terminal oval sporangia which is known in Victoria is Sporogonites. Halle
(1916), in his diagnosis of Sporogonites, described the sporangium as ‘a capsule obovoid or clavate’
with a slender rigid stalk. The stem broadens to form the basal region of the capsule. Sporogonites has
a possible central horizontal line of dehiscence, longitudinal ridges, and is not regarded as being a

TIMS AND CHAMBERS: EARLY LAND PLANTS PROM AUSTRALIA

271

vascular plant (Andrews 1960). A Victorian species, S. chapmani, is known from the late Early
Devonian (Emsian) Walhalla Group (Lang and Cookson 1930). Cookson (1949) reported S. sp. from
the Ruddock Siltstone which may be equivalent to, or slightly younger than the Wilson Creek Shale.
Sporogonites has not been reported from the Wilson Creek Shale, and S. chapmani is quite distinct
when compared with SalopeUa australis in terms of axis width and sporangial shape and size.

Edwards and Richardson (1974) comment on the similarity of S. allenii sporangial shape to that of
another Victorian genus, Hedeia corymbosa (Cookson 1935). They point out that H. corymbosa has
a more compact fructification, with up to four orders of branching in a comparatively short length
of axis.

A period of at least 20 million years probably separates the two deposits in which S. australis is
found, but there is no evidence at present to suggest that changes have occurred in the species over this
interval. Specimens collected from the older beds at Limestone Road tend to have longer axes.
Although the plant remains at Frenchman Spur have been further fragmented by the close jointing
pattern at the site, they were probably of shorter lengths than those at Limestone Road at the time of
deposition.

While no anatomy is preserved in the new SalopeUa, from the gross morphology it would appear
that the fertile portion of S. australis may be little more than a zone of the shoot apex in which spores
develop, and it therefore lacks an organ that could be clearly defined as sporangium. If this proves to
be so, it may represent the most primitive sporangial condition known amongst the early land plants.
The small indentation noted in some specimens may indicate a position where the apex breaks off" to
release the spores. From the faint lines and ridges in two specimens it is presumed that this plant was
vascularized.

Because of the small differences in branching and sporangial shape, and the geographical
separation between this species and S. allenii, it seems advisable to erect a new species with the specific
name ^australis' for the southern hemisphere plant.

SalopeUa caespitosa sp. nov.

Plate 33, figs. 1-4; Plate 34, fig. 3; text-fig. 2d

Diagnosis. Tufted plant at least 85 mm high of slender naked axes 1-2 mm wide, bearing ovate to
fusiform sporangia averaging 4-5 mm long and 1-7 mm wide. There are up to three orders of
branching, the ultimate dichotomy normally at least 25 mm below the sporangia, but occasionally at
the sporangial base.

Range. Pragian.

Type locality. Frenchman Spur.

Horizon. Wilson Creek Shale.

Holotype. NMV P50,016. Plate 33, figs. 1-4; Plate 34, fig. 3.

Derivation of specific name, ‘caespitosa’— tufted.

Description. The diagnosis is based on one specimen, part and counterpart. Preservation is poor, with little
mineral remaining except on some sporangia and an occasional fine line along the centre of the axis. A brittle film
of almost transparent mineral is all that remains of most of the axes and the exterior part of the sporangia.

The plant consists of a number of axes, in excess of 20. The axes do not taper but after each dichotomy decrease
in diameter. They cross each other and disappear into the matrix, making it impossible to follow fertile axes to
the bottom of the specimen, and axes from the lower parts to their apices. The broadest axis on the specimen
measures 1-9 mm, while the lowest portion of axis known to terminate in sporangia (sporangia 1-3, see PI. 33,
figs. 1, 2) has a width of 1 -7 mm. After three orders of branching, this width decreases to 1 ■ I mm. When axes can
be traced to termination, all appear to be fertile. Many axes show a fine central line 0-2 mm wide, presumably the
remains of the vascular trace. The angles of branching are narrow (10-45°), although the extremes of this range
may be an artefact of preservation.

There are twenty-six sporangia visible in the part and counterpart (see PI. 33, fig. 1 ), although some of these are

272

PALAEONTOLOGY, VOLUME 27

incomplete. The sporangia range from ovate to fusiform in shape, the larger being more fusiform and the smaller
ovate. The size ranges from 3-2-6-0 mm (average 4-5 mm) in length and T3-2-0 mm (average T7 mm) at the
widest point. The longest sporangia are not always the broadest. Three axes probably have more than one
sporangium at their apices (PI. 33, figs. 3, 4). Sporangium 13, illustrated in Plate 33, fig. 3, appears to have two
sporangia, partially superimposed. The tops of them have been broken away but Plate 33, fig. 4, illustrating the
counterpart, has the apices visible. Sporangium 14 is also broader than other single sporangia. The presumed
vascular trace of the axis of sporangium 15 appears to divide at the base of the sporangium. The preservation is
not good enough to determine whether the trace actually goes to two presumed spore bodies, or even three.
Sporangia 13, 14, and 15 are all in close proximity, although their axes do not appear connected. These are the
only axes which appear to divide so close to the base of their sporangia.

Of the intact axes, none was seen to terminate in a sterile tip. Variation in sporangial shape could be due to the
stage of maturity of the sporangia, the longer and more fusiform (e.g. sporangia 6~9) possibly being less mature.
It is recognized also that sporangia 13-15 could be the result of the manner of preservation, either in compression
to give a broader appearance to a single sporangium, or by superimposition, as shown by the axes of sporangia
5 and 6. However, the axes of sporangia 1 3 and 14 remain as one for their entire length, so it appears unlikely that
superimposition has occurred. Similarly, it seems unlikely that squashing and spreading should only happen to
these sporangia. It is also possible that they are at a stage of dehiscence, with the sporangial wall breaking away
(see especially sporangium 14; PI. 33, fig. 1). As the axes of these sporangia are broader (1-6, T5, and 1-5 mm
respectively) just below the sporangial base than any other axis at the same point, it appears that each axis
supports two sporangia.

Surrounding most of the dark spore bodies is a deposit of the semi-transparent mineral (e.g. sporangia 1 -3, 7,
8, and 10). No spores could be isolated from the presumed spore bodies, nor could any line of dehiscence be seen.
Basal parts of this plant are unknown and the tufted habit is assumed on the basis of the orientation of the axes as
preserved.

Discussion. It may be inferred from this specimen of semi-aligned axes that they are all from the one
plant, arising perhaps from a rhizome or gametophyte. Fragments of axes of comparable diameter
from the Wilson Creek Shale are rare. It appears that this species was either more delicate and hence
unable to survive a long period of immersion, or that the plant was less abundant than other Vietorian
rhyniophytes.

The points made in the discussion on Salopella australis are also relevant here. In habit the plant
resembles several northern hemisphere Early Devonian plants — Steganotlieca striata, Renalia
hueberi Gensel, and Eogaspesiea gracilis. Hicklingia edwardii Kidston and Lang from the Middle
Devonian is also similar in appearance. Hicklingia is considered a zosterophyll on the basis of its
sporangial arrangement (Edwards 1976). Gensel (1976) considers Renalia to be intermediate between
the Rhyniophytina and the Zosterophyllophytina. Eogaspesiea has few fertile axes and the sporangia
are elliptical rather than ovate; the axes rarely dichotomize and the genus is thought by Hoeg (1967)
and Gensel (1976) to be non-vascular.

Rhynia gwynne-vaughanihas sporangia only slightly smaller and of similar shape to the tufted plant
we have described as Salopella caespitosa. The habit of R. gwynne-vaughani (see Edwards 1980) is
distinct, with adventitious branching. As is the case with 5. australis, S. caespitosa cannot be
eompared adequately with the well-described genus Rhynia, and is more appropriately placed in the
form genus Salopella.

More is known of the habit of S. caespitosa than of the type species S. allenii. They both differ from
S. australis in sporangial size and in having a definite base to the sporangium. S. australis axes are

EXPLANATION OF PLATE 33

Figs. 1-4. Salopella caespitosa sp. nov.; holotype; NMV P50,016. 1, complete specimen (part) showing
numbered sporangia (refer to text); Frenchman Spur; x 1. 2, branching in S. caespitosa; stems bearing
sporangia nos. 4-7 (part); see also text-fig. 2d; x I T. 3 and 4, part and counterpart of sporangium 13; fig. 3
shows the stem with the remains of the presumed vascular trace; this sporangium gives the appearance of being
double; however, the counterpart (fig. 4) does not show this nearly as well; x 10.

PLATE 33

TIMS and CHAMBERS, Salopella

274

PALAEONTOLOGY, VOLUME 27

c

TEXT-FIG. 2. A, Salopella australis, diagram of holotype,
X 1 T . B, S. australis, diagram of large branched specimen
illustrated in PI. 32, fig. 5, x 0-5. c, S. australis, possible
branch structure of specimen illustrated in PI. 32, fig. 3. D,
Salopella caespitosa, branching of axis bearing sporangia
4-7. E, Dawsonites subarcuatus, reconstruction.

broader, have wider branch angles, and the fragmentary nature of the remains suggests that it may
not have been a gregarious plant.

The possible development of two sporangia terminating the one axis as in S. caespitosa may
indicate a higher level of organization towards more complex Rhyniophytina with multisporangiate
terminal fructifications, such as Yarravia and Hedeia. Y. oblonga is found with both species of
Australian Salopella at Frenchman Spur. However, an as yet undescribed Hedeia is present in the
Ludlovian Lower Plant Assemblage. If the organization seen in Hedeia evolved from the simpler
organization of Salopella, this must have occurred earlier than the Ludlovian.

Subdivision trimerophytina Banks 1968
Genus dawsonites Halle 1916

Type species. D. arcuatus.

Dawsonites subarcuatus sp. nov.

Plate 34, figs. 1, 2; text-fig. 2e

Diagnosis. Dichotomizing branch system with sympodially formed main axis due to dominance of the
leading branch. Ultimate branches tapering, and bearing at the apex of each dichotomy narrow,
straight, lanceolate sporangia, 3-4 mm long.

EXPLANATION OF PLATE 34

Figs. 1, 2. Dawsonites subarcuatus', NMV P33,215; part and counterpart. Specimen with one pseudomonopodial
branch near the base and ultimate dichotomous branching; at least four sporangia are present on the left
branch (fig. 2) and six on the right; counterpart shows the central line down the axis, the presumed vascular
trace (arrow); Frenchman Spur; x4-5.

Fig. 3. Salopella caespitosa', NMV P50,016; sporangia 8 (right) and 9; sporangium 9 shows the clear delineation
of the sporangial wall; x 15.

Figs. 4, 5. NMV P50,013; Salopella australis; counterpart and part; part shows the dark presumed sporogenous
area, whilst the counterpart has no such dark area; Frenchman Spur; x 1-7.

PLATE 34

TIMS and CHAMBERS, Dawsonites and Salopella

276

PALAEONTOLOGY, VOLUME 27

Range. Early Devonian (Pragian).

Type locality. Frenchman Spur.

Horizon. Wilson Creek Shale.

Holotype. NMV P33,215a and b. Plate 34, figs. 1, 2.

Derivation of specific name, ‘subarcuatus’: ‘sub’ — somewhat or almost, ‘arcuatus’— curved like a bow.

Description. This is based on a single specimen from Frenchman Spur, part and counterpart of a plant of a form
not previously recorded from Australia but closely resembling D. arcuatus Flalle. Overall the specimen measures
1 8 mm in length . The naked axis branches at four levels, the first unequally 1 • 5 mm from the base of the specimen,
at an angle of almost 90°. A further 9 mm up the axis is a dichotomy with a 70° angle between the forks. The axis
itself is 1 mm broad at the base and narrows to 0-7 mm at the dichotomous branching. A further branching
occurs on one fork of the dichotomy (the right fork of P33,215a, shown in PI. 34, fig. 1, shows this best), to give
two groups of sporangia (see also text-fig. 2e). Because of the manner of preservation the actual point of
branching cannot be seen. The fourth level of branching takes place 0-7 mm below the sporangia. The stem has
a central strand, about 0-2 mm wide, visible as a ridge of thicker carbon in P33,215a and a corresponding
depression in the counterpart. The ridge branches with the axis and is the presumed remains of the vascular
trace.

All the branches terminate in elongate fusiform sporangia which point to the left of the axis (right in the
counterpart). This is probably a depositional effect and in life the sporangia may have been semi-pendent. Each
branch divides to carry at least three sporangia on separate stalks, except for one which bears two sporangia on
the one stalk. Whole sporangia are 3 -4 mm long and 0-4-0-7 mm broad. Sporangia of the first branch are absent
from the counterpart. No obvious lines of sporangial dehiscence are shown. Cellulose acetate film pulls of the
sporangia yielded no spores.

Discussion. When Halle (1916) erected the genus Dciwsonites for fragments of branched axes with
terminal recurved pairs or groups of sporangia, he was aware of their close similarity to sporangia
assigned to Psilophyton princeps by Dawson (1859, 1871). However, because of the lack of physical
connection between the spiny axes and the terminal sporangia of the northern hemisphere species,
P. princeps, Halle considered a new genus was justified for the specimens he found in Norway. The
two taxa, D. arcuatus and P. princeps, have been proved by Hueber and Banks (1967) to be
conspecific. However, in the intervening period Dawsonites has become a form genus for fragmen-
tary axes bearing terminal sporangia. Banks et al. (1975) state that Dawsonites should be used in
Halle’s restricted sense rather than that of Hoeg (1967), who cited eight species and widened the
concept of the genus. The Wilson Creek Shale specimen fits into the original description of the
genus.

The resemblance of specimen P33,215 to Halle’s original D. arcuatus is quite apparent. There are,
however, a number of minor differences. The sporangia of P33,215 do not droop from recurved
branches but hang, probably semi-pendently, from straight branches which dichotomize at a wider
angle than those of D. arcuatus. Also, the sporangial shape differs slightly, most sporangia being more
elongate in the ’Victorian specimen. There are no ridges on the stem, although this feature may have
been lost in preservation. Spines, which are a characteristic of P. princeps and also of the lower
portions of some of the specimens identified as D. arcuatus in the Northern Hemisphere, are absent
from the Victorian specimen. This may be because the specimen is such a small fragment and spines
could have been present further down the axis. Spiny axes are rare in the Victorian Lower Devonian.
Cookson (1935) recorded some non-fertile spiny axes from the Mt. Pleasant Sandstone and we have
collected some recently from the Frenchman Spur locality.

Psilophyton axes also have pseudomonopodial branching, and a few specimens of naked axes from
other Early Devonian strata of Victoria have been found with branching of this type. At present,
however, there is no evidence that the fertile specimen and the axes are related.

It is recognized that if more material comes to hand this specimen may be reassigned to another
genus. The specimen resembles D. arcuatus in size and overall form extremely closely. It fits well into
Halle’s diagnosis for Dawsonites, ‘sporangium bearing branch systems, dividing dichotomously, or
differentiated into a sympodially formed main axis and bifurcating lateral branches. Ultimate

TIMS AND CHAMBERS: EARLY LAND PLANTS FROM AUSTRALIA

277

branches slender and curved, bearing terminal capsules of a narrowly obovoid or short fusiform
shape and usually 3-5 mm long.’ It is the only representative of the subdivision Trimerophytina
yet found in the Victorian early land flora. This record of a trimerophyte in the Victorian
Siegenian is contemporaneous with the first appearance of the group in the Northern Hemi-
sphere.

The geographic separation of Halle’s species from Norway and those in south-eastern Australia,
together with their minor differences mentioned above, have led to the designation of this specimen as
a new species, D. subarcuatus.

GENERAL CONCLUSIONS

The Lower Plant Assemblage

The Lower Plant Assemblage contains, in addition to Salopella australis, Baragwanathia longifolia,
a new species of Hedeia, a new genus from the Zosterophyllophytina, and other unidentified
fragmentary remains. Only three species, S. australis, B. longifolia, and the new Hedeia are common
to both the Lower Plant Assemblage and the Wilson Creek Shale. The Wilson Creek Shale contains
other species as mentioned previously. In other words, the floras are quite distinct, having a minority
of species in common. Even in B. longifolia, there are some small differences in form— this will be
discussed fully elsewhere.

We recognize that the dating of the Lower Plant Assemblage as Ludlovian is controversial, and has
already been questioned (Edwards et al. 1979; Hueber 1983). We also acknowledge our own caution
as to the age. The two pre-Devonian floras of Wales (Edwards 1979; Edwards and Rogerson 1979)
and Podolia (Obrhel 1962) from the Northern Hemisphere consist of simple, tiny plants in
comparison. There is, however, mounting evidence on the associated graptolites that the Lower Plant
Assemblage is indeed Ludlovian. Recent studies (Rickards and Garratt, pers. comm.) have shown
there are two Ludlovian genera of graptolites.

Palaeogeographic maps of the Early Devonian (Smith et al. 1973; Heckel and Witzke 1979) show
Europe and Australia in equatorial regions on opposite sides of the globe. Is it possible that the flora
could have developed in isolation 20,000 km from the Cooksonia floras of Wales and Podolia?
Cooksonia-iype plants were present in the Wenlockian in Ireland (Edwards and Feehan 1980) but
little development in vascular plant form seems to have occurred in Europe until the beginning of the
Devonian. Did a period of rapid evolution occur in the flora of the Melbourne Trough, and was it
contained there until the Early Devonian? The only possible vascular plants older than the Lower
Plant Assemblage currently known in Victoria are found as Hostinella-type chaff about 180 m
stratigraphically below the Lower Plant Assemblage and in the same district. There is no sign of
Baragwanathia in the chaff, despite the fact that Baragwanathia is easily recognized even in small
fragments.

The Early Devonian

The three new species described here are from genera previously recorded only from the Northern
Hemisphere. Edwards (1973) considers that there were two contrasting floras in the Early Devonian,
one being that of the Northern Hemisphere and Australia, and the other restricted to the southern
hemisphere continents: South America, southern Africa, and Antarctica. While it must be
remembered that Salopella and Dawsonites are form genera only and may not be genetically related to
their northern hemisphere counterparts, they come, with Zosterophyllum, from three separate
subdivisions. The presumed non-vascular Sporogonites and Pachytheca are common to both the
Northern Hemisphere and Australia. Baragwanathia is very similar to the northern hemisphere
genus Drepanophycus and, indeed, a new species of Baragwanathia from Canada has been described
by Hueber (1983). These records must be considered as strong evidence to support the link between
the floras of Australia and the Northern Hemisphere during Early Devonian times. This evidence also
suggests that some mixing of the floras had occurred before the Pragian.

278

PALAEONTOLOGY, VOLUME 27

Acknowledgements. We thank Dr. J. Douglas, Dr. M. Garratt, and Mr. P. Van den Berg of the Victorian
Department of Minerals and Energy, Geological Survey for their interest and cooperation throughout this
project; members of the Palaeontological Section of the National Museum of Victoria for assistance and access
to the collections, and Dr. Dianne Edwards for helpful comments. One of us (J.D.T.) was in receipt of a
Commonwealth Postgraduate Research Award. The overall project was supported by University of Melbourne
research grants.

REFERENCES

ANDREWS, H. N. 1960. Notcs On Belgian specimens of Sporogonites. Palaeobotanist, 7, 85-89.

BANKS, H. p. 1968. Early history of land plants. In drake, e. t. (ed.). Evolution and Environment. Yale Univ. Press,
Newhaven. Pp. 73-107.

1975. Reclassification of Psilophyta. Taxon, 24, 401-413.

LECLERCQ, s. and HUEBER, F. M. 1975. Anatomy and morphology of Psilophyton dawsonii sp. n. from the

late Lower Devonian of Quebec (Gaspe) and Ontario, Canada. Palaeontogr. am. 8, 11 -Ml.

COOKSON, I. c. 1935. On plant remains from the Silurian of Victoria, Australia, that extend and connect floras
hitherto described. Phil. Trans. R. Soc., Ser. B, 225, 127-148.

1949. Yeringian (Lower Devonian) plant remains from Lilydale, Victoria, with notes on a collection from a

new locality in the Siluro-Devonian sequence. Mem. natn. Mas. Viet. 16, 1 17-131.

COUPER, j. 1965. Late Silurian to Early Devonian stratigraphy of the Yea-Molesworth district, Victoria. Proc. R.
Soc. Viet. 79, 1-8.

DABER, R. 1960. Eogaspesiea gracilis n.g., n.sp. Geologic, 9, 418-425.

DAWSON, J. w. 1859. On fossil plants from the Devonian rocks of Canada. Q. Jl geol. Soc. Lond. 15, 477-488.

1871. The fossil plants of the Devonian and Upper Silurian formations of Canada. Geological Survey of

Canada. 92 pp.

EDWARDS, D. 1970. Fertile Rhyniophytina from the Lower Devonian of Britain. Palaeontology, 13, 451-461.

1973. Devonian Floras. In hallam, a. (ed.). Atlas of Palaeobiogeographv. Elsevier, Amsterdam. Pp.

105-115.

1976. The systematic position of Hicklingia edwardii Kidston and Lang. New Phytol. 76, 173-181.

1979. A Late Silurian flora from the Lower Old Red Sandstone of south-west Dyfed. Palaeontology, 22,

23-52.

BASSETT, M. G. and ROGERSON, E. c. w. 1979. The earliest vascular land plants: continuing the search for

proof. Lethaia, 12, 313-324.

and FEEHAN, J. 1980. Records of Cooksonia-typs sporangia from late Wenlock strata in Ireland. Nature,

287, 41-42.

and RICHARDSON, J. B. 1974. Lower Devonian (Dittonian) plants from the Welsh borderland. Palaeonto-
logy, 17, 311-324.

and ROGERSON, E. c. w. 1979. New records of fertile Rhyniophytina from the Late Silurian of Wales. Geol.

Mag. 116, 93-98.

EDWARDS, D. s. 1980. Evidence for the sporophytic status of the Lower Devonian plant Rhynia gwynne-vaughani
Kidston and Lang. Rev. Palaeobot. Palynol. 29, 177-188.

GARRATT, M. J. 1978. New evidence for a Silurian (Ludlow) age for the earliest Baragwanathia flora. Alcheringa,!,
217-224.

1981. The earliest vascular land plants. Comment on the age of the oldest Baragwanathia flora. Lethaia,

14, 8.

GENSEL, p. G. 1976. Renalia hueberi, a new plant from the Lower Devonian of Gaspe. Rev. Palaeobot. Palynol.
22, 19-37.

HALLE, T. G. 1916. Lower Devonian plants from Roragen in Norway. K. svenska VetenskAkad. Handl. 57, 1-46.
HARRIS, w. J. and thomas, d. e. 1941. Notes on the Silurian rocks of the Yea district. Min. geol. J. Viet. 2,
302-304.

HECKEL, p. H. and wiTZKE, B. J. 1979. Devonian world palaeogeography determined from distribution of
carbonates and related lithic palaeoclimatic indicators. In house, m. r., scrutton, c. t., and bassett, m. g.
(eds.). The Devonian System. Spec. Pap. Palaeont. 23, 99-123.

HOEG, o. A. 1967. Psilophyta. In boureau, f. (ed.). Trade de Paleobotanique. Masson et Cie, Paris.

HUEBER, F. M. 1983. A new species of Baragwanathia from the Sextant Formation (Emsian) Northern Ontario,
Canada. J. Linn. Soc. (Bot.), 86, 57-79.

and BANKS, H. p. 1967. Psilophyton princeps: the search for organic connection. Taxon, 16, 81-85.

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JAEGER, H. 1966. Two late Monograptus species from Victoria, Australia and their significance for dating the
Baragwanathia flora. Proc. R. Soc. Viet. 79, 393-413.

1970. Remarks on the stratigraphy and morphology of Pragian and probably younger monograptids.

Lethaia, 3, 173-182.

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, 761-784.

1920. On Old Red Sandstone plants showing structure, from the Rhynie chert bed, Aberdeenshire.

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, 603-627.
koren', t. n. 1971. The zones of Monograptus hercynicus and Monograptus falcarius in Pai-Khoi. Lethaia, 4,

LANG, w. H. and COOKSON, I. c. 1930. Some fossil plants of Early Devonian type from the Walhalla Series,
Victoria, Australia. Phil. Trans. R. Soc. Loud., Ser. B., 219, 133-163.

1935. On a flora, including vascular land plants, associated with Monograptus, in rocks of Silurian age,

from Victoria, Australia. Ibid. 224, 421-449.

MOORE, B. R. 1965. The geology of the Upper Yarra region, central Victoria. Proc. R. Soc. Viet. 78, 221-239.
OBRHEL, J. 1962. Die Flora der Pridoli Schichten (Budnany-Stufe) des mittelbdhmischen Silurs. Geologic, 11,
83-97.

SCHOPF, J. M. 1975. Modes of fossil preservation. Rev. Palaeobot. Palynol. 20, 27-53.

SMITH, G., BRiDEN, J. c. and DREWRY, G. E. 1973. Phanerozoic World Maps. In hughes, n. f. (ed.). Organisms and
Continents through Time. Spec. Pap. Palaeont. 12, 1-42.

235-248.

Typescript received 28 December 1982
Revised typescript received 28 August 1983

J. D. TIMS
T. C. CHAMBERS

Botany School
University of Melbourne
Parkville
Victoria 3052
Australia

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THE CRETACEOUS AMMONITE
AMMONITES REQUIENIANUS D’ORBIGNY, 1841

by w. J. KENNEDY and C. W. WRIGHT

Abstract. Coilopoceras requienianum (d’Orbigny, 1841 ) is revised on the basis of the types and other material. It
shows wide intraspecific variation and dimorphism of the type demonstrated in North American species of the
genus. Similar dimorphism is shown in other Old World species, especially Nigerian forms, with Glebosoceras
Reyment, 1954, a strongly ornamented genus which is treated as a synonym of Coilopoceras Hyatt, 1903. The
Coilopoceras from Algeria described by Pervinquiere (1910) and said to be of Cenomanian age are confirmed as
members of the genus, but they are shown to be upper Turonian; so this occurrence does not contradict previous
views that the genus arose during the Turonian via Hoplitoides von Koenen, 1898.

American species of the late Cretaceous ammonite genus Coilopoceras Hyatt, 1903, as well as
the genus and family, have recently been reviewed by Cobban and Hook (1980), but Ammonites
requienianus d’Orbigny, 1841, the first described species of the genus and its chief Old World
representative, is poorly known. Restudy of d’Orbigny’s types and other material in early collections
allows us to give a reasonably full description of the ontogenetic development, variation, and
dimorphism in the species. These accord with that shown by American species, and lead to an
examination of other problematic Old World forms.

SYSTEMATIC PALAEONTOLOGY

Repositories of specimens. BM(NH), British Museum (Natural History), London; EMP, Ecole des Mines, Paris,
Collections now housed in the Universite Claude-Bernard, Lyon; FSL, Faculte des Sciences, Universite
Claude-Bernard, Lyon; MNHP, Museum National d’Histoire Naturelle, Paris; SP, Collections of the Sorbonne,
now housed in the Universite Pierre et Marie Curie, Paris.

Dimensions. Dimensions are given in millimetres, in the following order; diameter (D), whorl breadth (Wb),
whorl height (Wh), and breadth of umbilicus (U); c = costal, ic = intercostal. Figures in parentheses refer to
dimensions as a percentage of diameter.

Suture terminology. The suture terminology of Wedekind (1916; see Kullman and Wiedmann 1970) is followed
here; I = Internal lobe, U = Umbilical lobe, L = Lateral lobe, E = External lobe.

Superfamily acanthocerataceae de Grossouvre, 1894
Family coilopoceratidae Hyatt, 1903

[= Hoplitoidinae Wright, 1952, nom. correct, ex Hoplitoidines H. Douville, 1912]

Genus coilopoceras Hyatt, 1903, p. 91
Synonyms. Namadoceras Vredenberg, 1907; Glebosoceras Reyment, 1954.

Type species. Coilopoceras colled Hyatt, 1903, p. 91, pi. 10, figs. 5-21; pi. 11, fig. I.

Diagnosis. Large, up to 800 mm in diameter; involute, compressed to inflated, lanceolate to cordate in
section, with more or less sharp venter; variable broad low ribs may or may not persist; in inflated
forms (Glebosoceras) they are raised into large bulges on the inner part of the flank on outer whorls;

[Palaeontology, Vol. 27, Part 2, 1984, pp. 281-293, pis. 35-37.]

282

PALAEONTOLOGY, VOLUME 27

in some such forms ribs may strengthen into ventrolateral nodes. Suture variable; accessory saddle
may exceed in size the second lateral saddle, with auxiliary saddles tending to become entire in
outline. Dimorphic: one member of pair compressed and feebly ornamented, the other more inflated
and ribbed.

Discussion. Cobban and Hook (1980) provided a detailed account of the type species and other North
American Coilopoceras. They demonstrated convincingly the succession from Hoplitoides sando-
valensis Cobban and Hook, 1980, in the lower part of the upper Turonian Prionocyclus hyatti Zone,
to C. springeri Hyatt, 1903 in the upper part of the same Zone. C. springeri and H. sandovalensis are
indistinguishable when adult, and only the acute venter of the early stages of the former and the
tabulate venter of the early stages of the latter serve to distinguish them. C. springeri gave rise to
C. colleti Hyatt, 1903, of the succeeding P. macombi Zone. This species develops distinctive
ventrolateral tubercles when adult (see Cobban and Hook 1980, text-fig. 9). Juveniles have only
incipient tubercles, with the ends of the ribs projecting and accentuated. They also differ in sutural
characteristics: in C. colleti L/U2 is asymmetrically bifid; in C. springeri the three divisions of the
ventral half of this lobe enlarge so that there are five large lobules rather than two. The youngest
American species is C. inflatum Cobban and Hook, 1980. This is very inflated indeed and also
develops tubercles (see Cobban and Hook 1980, text-fig. 14). In all these species Cobban and Hook
demonstrated the presence of both slender, feebly ornamented and stout, strongly ribbed forms
which they regard as dimorphs, a view followed here. They were unable to show a size difference
between adults of the two forms, so that the two morphs cannot yet be identified as microconch
and macroconch. As is shown below under the systematic description of C. requienianum,
the same variation and dimorphism can be demonstrated in this Old World member of the
genus.

Occurrence. Upper Turonian of France, Germany, North and West Africa, Madagascar, Israel, Lebanon,
Baluchistan, Colorado, Wyoming, Texas, New Mexico, Mexico, Trinidad, Ecuador, Colombia, and Peru.

Coilopoceras requienianum (d’Orbigny, 1841)

Plates 35, 36; text-figs. 1-5

1841 Ammonites Requienianus d’Orbigny, p. 315, pi. 93, figs. 1-4.

1894 Sphenodiscus Requieni d’Orbigny sp.; de Grossouvre, p. 140, text-fig. 59.

71896-1897 Sphenodiscus Requieni (d’Orbigny); Peron, p. 34, pi. 17(4), figs. 2, 3; pi. 11(17), fig. 4.

1903 Coilopoceras requienianum (d’Orbigny); Hyatt, p. 99.

1903 Coilopocerasl grossouvrei n. sp. Hyatt, p. 100, pi. 12, fig. 7.

1 904 Sphenodiscus Requieni d’Orb; Solger, text-fig. 74 (pars) (after de Grossouvre).

1907 Sphenodiscus Requieni d’Orbigny; Pervinquiere, p. 221, text-fig. 90.

1907 Sphenodiscus Requienianus (d’Orbigny); Boule, Lemoine and Thevenin, text-fig. 27b (copy of de
Grossouvre).

71912 Coilopoceras Requiem d’Orbigny; Douville, p. 308, text-figs. 36-38, 68.

1913 Coilopoceras Requienianum d’Orbigny; Roman and Mazeran, p. 28, pi. 3, fig. 5; text-figs. 5, 6.
1938 Coelopoceras (sic) Requieni (d’Orbigny); Roman, p. 499, pi. 5 1 , figs. 477, Alla (copy of d’Orbigny).
71941 Coelopoceras (sic) requieni (d’Orbigny); Chiplonkar, p. 274, text-fig. 6 (indeterminate).

1952 Coilopoceras requienianum (d’Orbigny); Basse, p. 665, fig. 30 (copy of d’Orbigny).

1958 Coilopoceras requienianum (d’Orbigny); Luppov and Drushchits, p. 130, text-fig. 103</ (copy of
Roman 1938).

71965 Coilopoceras requieni d’Orb.; Collignon, p. 24, pi. 385, fig. 1658 (indeterminate from figure).
71975 Coilopoceras cf. requieni (d’Orbigny); Dassarma and Sinha, p. 70, pi. 9, fig. 6; pi. 12, fig. 5
(indeterminate).

1976 Coilopoceras requienianum (d’Orbigny); Lommerzheim, p. 231, pi. 2, fig. 4; text-fig. lOa-c.
non 1977 Coilopoceras requieni (d’Orbigny); Gonzalez- Arreola, p. 170, fig. 2d, e.

71981 Coilopoceras requieni d’Orbigny; Obata, Kanie, Ranaivoson and Ratsimba, pi. 1 (indeterminate
from figures).

KENNEDY AND WRIGHT; CRETACEOUS AMMONITE

283

TEXT-FIG. 1. Ammonites requienianus d’Orbigny, 1841 (pi. 93). Copy of d’Orbigny’s original figures.

Types. D’Orbigny must have had a series of specimens before him when erecting this species, for in his
explanation of the plate (1841, p. 317), which is reproduced here in text-fig. 1, he states as follows: ‘PI. 93, fig. 1,
Individu reduite de moitie, vu de cote. De la collection de M. Requien et de la mienne. Fig. 2. Le meme, vue de
cote de la bouche, montrant le dessus d’une cloisone. Fig. 3. Un jeune de la variete ondulee. Fig. 4. Une cloisone
de grandeur naturelle, calquee par moi sur la nature.’ The larger specimen in the Requien Collection was
re-illustrated by Roman and Mazeran (1913, text-fig. 5) and referred to as the ‘type’; this is not, however, a valid
lectotype designation. The posthumous catalogue of the d’Orbigny Collection lists thirteen specimens from
Uchaux, Vaucluse, and fourteen are in the collections under the number 6775. All of these specimens rank as
syntypes; the Requien specimen refigured by Roman and Mazeran is here designated lectotype; the
paralectotypes are all rather poorly preserved and none demonstrably agree with d’Orbigny’s pi. 93, fig. 3.
A selection of the better specimens are refigured in text-fig. 2.

Material. We have studied nearly fifty specimens in the EMP, FSL, MNHP, SP, Universite de Marseilles, and
other French collections, all from localities in the Uchaux Massif, and variously labelled ‘Colline de Boncavail’,
‘Uchaux’, or ‘Mondragon’. One specimen in the SP collections is from the Tuffeau Jaune de Touraine of
Courtinot, Touraine (Hebert Collection); Oxford University Museum no. KZ15177 and specimens in J. M.
Hancock’s Collection are from the Tuffeau Jaune at Vreigne, near Francueil, Indre-et-Loire.

Description. The material occurs either as silicified nuclei, some of which retain the silicified dorsal shell layer and
traces of the internal suture, or as sandstone moulds. The largest specimen we have seen is 200 mm in diameter.

Two forms of the species occur. At one extreme are smooth oxycones with a lanceolate whorl section and
sharp venter (text-figs. 3, 4a). At the other are ribbed individuals which are generally stouter and a little more
evolute (text-fig. 4b). Juveniles of the latter show pairs of low broad rounded primary ribs that are best developed
on the inner flank but may also be accentuated on the ventrolateral shoulder before declining, while shorter
intercalated ribs are also present. The largest ribbed variant is shown in Plate 36, fig. 12. There are six strong

284

PALAEONTOLOGY, VOLUME 27

umbilical bulges per whorl, which give rise to pairs of coarse broad primary ribs, and single shorter intercalated
ribs. These strengthen before terminating abruptly, and there is a smooth zone on either side of the venter, which
is acutely fastigiate. The siphuncle is very large. The suture line is shown by relatively few specimens (text-fig. 5).
E is broad and shallow; L very broad, open, and symmetrically bifid. The saddle E/L is squat, with broad
rounded frills, as is L/U2 and the minor saddles on the umbilical lobe.

Dimensions

D

Wb

Wh

Wb:Wh

U

FSL 14.200d

23-9(100)

6-4(26.8)

13-3(55.6)

0-48

-(— )

FSL 14.200c

26-5(100)

8-0(30-1)

15-2(51-4)

0-53

1 -0(3-7)

FSL 14.200a

64-0(100)

14-6(22-8)

36-3(56-7)

0-42

2-3(3-6)

FSL 14.201

51-0(100)

16-0(31-4)

27-6(54-1)

0-58

2-8(5-5)

FSL 14.200e

79-0(100)

19-8(25-0)

44-6(56-5)

0-45

2-l(2-7)

FSL 14.202

94-4(100)

22-1(23-4)

50-5(53-5)

0-44

— (~)

SP Pervinquiere Coll.

93-7(100)

24-0(25-6)

52-4(55-9)

0-46

2-8(3-0)

SP Toucas Coll.

136-0(100)

31-8(23-4)

72-1(53-0)

0-44

-(-)

SP ‘Mondragon’ c

165-0(100)

38-0(23-0)

74-5(45-1)

0-51

18-0(10-9)

ic

165-0(100)

42-0(25-5)

74-5(45-1)

0.56

18-0(10-9)

FSL 14.210

170-0(100)

40-0(23-5)

94-5(55-6)

0.42

8-5(50)

TEXT-FIG. 2. Ammonites reqiiiemcmus d’Orbigny, 1841. MNEIP 6775 (d’Orbigny Collection), seven of the better
preserved paralectotypes, all of which are silicified and from Uchaux (Vaucluse). All x 1.

KENNEDY AND WRIGHT: CRETACEOUS AMMONITE

285

Discussion. C. requienianum is best known from the Uchaux region, but has been recorded from
Touraine by several authors. The specimens we have seen include both ribbed and smooth individuals
and have similar sutures. Hyatt (1903, p. 100) renamed the specimen from Usseau (Vienne), of which
de Grossouvre (1894, text-fig. 59) illustrated the suture line, C.? grossouvrei because of differences in
detail from the suture figured by d’Orbigny. Comparison of d’Orbigny’s figure with the lectotype and
other Uchaux specimens shows d’Orbigny’s figure to be highly misleading with its very long narrow
elements.

The presence of ribbed and smooth forms within Coilopoceras species has already been described in
both the type species, C. colleti Hyatt, 1903, and the slightly later C. springeri Hyatt, 1903 and
C. inflatum Cobban and Hook, 1980 (see Cobban and Hook 1980 for a full review of these species),
and treated as dimorphism; the proportions of the two morphs are variable. As yet it is not known
whether this difference in ornament is accompanied by a size difference. C. requienianum can be
distinguished from these American species chiefly on the basis of the suture line (text-fig. 5); in
C. colleti E/L is narrower and much more deeply incised, with elongate rather than squat frills, as well
as asymmetrically bifid, while the inner lobes and saddles are also more incised. In C. springeri the
saddles are even more incised with narrow stems, while E/L is very broad and asymmetrically trifid.
C. inflatum Cobban and Hook, 1980 (p. 19, pi. 1, figs. 9-1 1; pi. 11, fig. 2; pis. 12-17; pi. 18, figs. 1-3,
11-13; pis. 20, 21; text-figs. 14, 15) has similarly distinctive sutures, is far more inflated than any
known C. requienianum, and develops ventrolateral tubercles.

The above species and C. requienianum are the only ones in which a reasonable number of
specimens has been described. As Cobban and Hook (1980) noted, at least twenty-seven species in
addition to the American forms have been described. We agree with them that the groups of species
described from single horizons and localities and separated on details of suture and ornament
probably represent no more than single variable species. Particularly relevant to this issue is
C. requienianum altesellata Collignon, 1965 (p. 62, pi. 403, figs. 1688, 1689; p. 64, pis. 404, 405) from
the upper Turonian of Madagascar. Collignon referred a series of smooth forms to this ‘variety’,
which he differentiated from the nominate form on the basis of the saddle E/L; this is narrow, deeply
incised, and like that of the American forms noted above. It appears to be a distinct species and,
interestingly, occurs with stouter ribbed specimens identified as Glebosoceras glebosum Reyment,
1954 (Collignon 1965, p. 60, pi. 402, figs. 1686, 1687). These have the same sutural peculiarity, and we
again take them to be a dimorphic pair. G. glebosum Reyment, 1954 (p. 161, pi. 2, fig. 3; pi. 4, fig. 1;
text-fig. 5; Reyment 1955, p. 75, text-fig. 35) from Nigeria has a similar suture line to C. discoideum
Barber, 1957 (p. 55, pi. 2, fig. 1; pi. 3, figs. 1,2; pi. 25, figs. 1-4) according to Barber, and they may be a
further pair. Certainly, Glebosoeeras is no more than an inflated Coilopoceras.

Occurrence. The type material is from the Uchaux Massif, where it is an upper Turonian Subprionocyclus neptuni
Zone species. It is also known from scattered localities in the upper Turonian Tuffeau Jaune of Touraine,
occurring at Usseau (Vienne) (de Grossouvre 1894), Courtinot (Touraine), and Vreigne, near Francueil
(Indre-et-Loire). Lommerzheim (1976) has recorded a fragment from the condensed Turonian of Mulheim
(Westphalia) that may belong here. The North African material whose sutures were illustrated by Douville
(1912) are only doubtfully referable to the species.

DISCUSSION

Observations on C. requienianum show that compressed feebly ornamented and more inflated ribbed
forms occur side by side, as in the North American type species and wherever Coilopoceras occurs.
Cobban and Hook (1980, p. 5) accepted Glebosoceras as a distinct genus on the grounds that the ribs
bend sharply forward on the outer part of the flank. A re-examination of the holotype, BM(NH)
C47336, shows that this is a pathological condition. The forward projection is shown only by the third
and fourth ribs of the figured side of the specimen (Reyment 1 954, pi. 4, fig. 1 ) and is not a criterion for
separation from Coilopoceras.

286

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 3. Coilopoceras
requienianum (d’Orbigny,
1841). FSL 14.210, large
specimen of compressed
form from Uchaux,
Vaucluse; 175 mm in
diameter.

B

TEXT-FIG. 4. Coilopoceras requienianum
(d’Orbigny, 1841). Whorl sections, a,
compressed form, based on FSL 14.210
from Uchaux, Vaucluse. b, inflated
form, based on an unregistered Sor-
bonne specimen from Mondragon,
Vaucluse.

EXPLANATION OF PLATE 35

Figs. 1-6. Coilopoceras requienianum (d’Orbigny, 1841). 1-3, FSL 14.202, ribbed juvenile from the environs of
Bollene (Vaucluse) (Sayn Collection). 4-6, a more compressed, feebly ribbed juvenile, Sorbonne Collections,
labelled ‘Mondragon ?’ (Pervinquiere Collection). All x 1.

PLATE 35

KENNEDY and WRIGHT, Coilopoceras

288

PALAEONTOLOGY, VOLUME 27

Cobban and Hook (1980) made it quite clear that Hoplitoides occurs in New Mexico in association
with Collignoniceras woollgari (Mantell, 1822), that the earliest Coilopoceras in that area occurs with
Prionocyclus liyatti (Stanton, 1894), and that later forms of Coilopoceras occur with P. macombi
Meek, 1876 and P. wyomingensis Meek, 1876. This dating does not agree with the general recording
of Hoplitoides as lower Turonian, and in particular Reyment’s (1954, 1955) and Barber’s (1957)
records from Nigeria of Hoplitoides as ‘lower Turonian’ and Coilopoceras as ‘lower Turonian
{Paravascoceras horizon)’ or even earlier (Barber 1957, p. 59). Careful reading of these papers,
however, shows remarkably few cases of actual associations of specimens of either genus with other
genera; neither appears in the only measured section, at Pindiga (Barber 1957, p. 60). The only
definite reference appears to be to the occurrence in ‘the limestone near Makurdi’ of various
Hoplitoides and C.(?) sp. with Mammites mutabilis Reyment, 1955, Benueites, and Kamerunoceras
jacobsoni Reyment, 1955. None of these are yet known to entail any definite horizon within the
Turonian. Otherwise, all the records of Hoplitoides, Glebosoceras, and Coilopoceras in Nigeria are
from imprecise horizons which may cover several zones.

TEXT-FIG. 5. Coilopoceras requienianum (d’Orbigny, 1841). External sutures from an unregistered specimen,

Sorbonne Collections {ex Pervinquiere Collection).

EXPLANATION OF PLATE 36

Figs. 1-12. Coilopoceras requienianum {d'Orhigny, 1841). 1-3, FSL 14.200b, almost smooth juvenile. 4-6, FSL
14.201, a more inflated, ribbed juvenile, the original of Roman and Mazeran (1913, pi. 3, fig. 5). 7, 8, FSL
14.200c. 9-11, FSL 14.200d, smooth nuclei. 12, the most strongly ornamented specimen seen, Sorbonne
Collections. 1-11 are labelled ‘Uchaux’, 12 ‘Mondragon’, both in Vaucluse. All x 1.

PLATE 36

KENNEDY and WRIGHT, Coilopoceras

290

PALAEONTOLOGY, VOLUME 27

In Peru (Benavides-Caceres 1956), Coilopoceras is recorded as common. One new species, C. Jenksi,
is said to be the commonest species in the Conor Formation (ibid., p. 473), though is not listed among
the fossils of that formation on p. 384. However, the Conor Formation may be up to 200 m thick and,
despite a statement (ibid., p. 473) that C.jenksi ‘is usually associated with Hoplitoides inca, Mammites
nodosoides afer, Pseudaspidoceras reesidei, Thomasites fischeri, Broggiiceras olssoni, and B. hum-
boldti', we cannot see here any hard evidence for its relative dating; the ‘associated’ species cover
Paravascoceras and M. nodosoides zones and, since they comprise all the ammonites listed from the
whole Conor Formation (ibid., p. 384), the biostratigraphic information is weak. Etayo-Serna (1979)
included in his zonation of central Colombia a ''Mammites nodosoides appelatus-Franciscoites suarezi
Assemblage Zone’ in which Hoplitoides occurs, but this Zone could in fact cover the whole Turonian.
Abundant Coilopoceras, including Glebosoceras-\ike forms, in collections before us from Colombia
(University of California Collection), are never associated with species of other genera.

A similar situation is found on close investigation of the many references to the occurrence of
Hoplitoides or Coilopoceras in the lower Turonian or earlier. In the case of the Coilopoceras described
from the Cenomanian of North Africa by Pervinquiere (1910), Reyment (1955, p. 75) suggested that
they were schloenbachiids. However, Cobban and Hook (1980, p. 12) pointed out that the sutures of
the Algerian species resemble those of true Coilopoceras in the general appearance of the first lateral
lobe, but that the rest of the suture has only two or three lateral lobes. Part of the type material of both
C. africanum Pervinquiere, 1910, and C. haugi Pervinquiere, 1910 is refigured here (PI. 37, figs. 1-12);
they are not schloenbachiids. C. africanum has a broadly bifid first lateral lobe (but with a third
subsidiary lobule) and C. haugi a trifid one, but in our view they belong to a single variable species.
The more strongly ornamented specimens compare well with small specimens of C. inflatum (e.g.
Cobban and Hook 1980, pi. 18, figs. 1, 2, 8) and we believe them to be true Coilopoceras, showing the
same range in ornament and whorl section as other species. We doubt, however, the dating of this
material. C. africanum is based on eight specimens and fragments said to be from the middle
Cenomanian of Djebel Guessa and Berrouaghia, collected by Thomas and Peron; C. haugi on three
complete specimens and a dozen fragments also said to be from the middle Cenomanian of
Berrouaghia, also collected by Thomas and Peron. The " Acanthoceras cf. Ac. Newboldi Kossmat’ of
Pervinquiere (1910, p. 45, pi. 13, fig. 37) was also collected by Thomas and is in the Peron Collection;
it was said to be from the ‘2® zone, moyenne’ of Berrouaghia, but is a juvenile Romaniceras
(Romaniceras) deverianum (d’Orbigny, 1841) (Kennedy et al. 1980, p. 330, pi. 39, figs. 7-10), a high
Turonian species commonly associated with Coilopoceras. This suggests that the Coilopoceras too are
misdated, while we have independent unpublished evidence that limonitic Turonian ammonites
occur in the Berrouaghia-Aumale area of Algeria.

We are thus led to conclude that there is no strong evidence for the occurrence of Hoplitoides or
Coilopoceras before the middle Turonian, although it is possible that the former’s occurrences in
West Africa are in rocks that are datable, at least in part, to the upper part of the lower Turonian. On
this basis there is no longer any difficulty in accepting the evolution of Coilopoceras from Hoplitoides
(Wright 1957, p. L425; Cobban and Hook 1980, p. 13).

EXPLANATION OF PLATE 37

Figs. 1, 2, 8-12. Coilopoceras africanum Pervinquiere, 1910. ‘Cotypes’ from Djebel Guessa, Algeria, Sorbonne
Collections.

Figs. 3-7. Coilopoceras haugi Pervinquiere, 1910. ‘Cotypes’ from Berrouaghia, Algeria, Sorbonne Collections.
All x2.

PLATE 37

KENNEDY and WRIGHT, Coilopoceras

292

PALAEONTOLOGY, VOLUME 27

Acknowledgements. We thank D. Phillips, D. Pajaud, J. Sornay, A. Prieur, and R. Busnardo for allowing us to
study specimens in their care. Drs. J. M. Hancock and W. A. Cobban provided valuable advice. We gratefully
acknowledge the technical assistance of the staff of the Geological Collections, Oxford University Museum, and
financial support from NERC and Wolfson College, Oxford.

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Typescript received 11 January 1983
Revised typescript received 2 June 1983

W. J. KENNEDY
C. W. WRIGHT

Geological Collections
University Museum
Parks Road, Oxford 0X1 3PW
and

Wolfson College, Oxford 0X2 6UP

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NEW POROCHARACEAE FROM THE BATHONIAN
OF EUROPE: PHYLOGENY AND PALAEOECOLOG Y

by MONIQUE FEIST aucl NICOLE G R A M B AST-FESS A R D

Abstract. The anatomical characters of some European Bathonian charophyte gyrogonites have been studied.
The presence of a multipartite basal plate in representatives of the Porocharaceae/Porocharoideae justifies the
creation of a new genus, Musacchiella gen. nov., represented by three new species: M. douzensis, M. pcdmeri,
M. sp. A. No clear relationship has been demonstrated with extant and fossil Characeae/Nitelloideae in which a
multipartite basal plate is also to be found. On the other hand, the outline of the apical pore suggests
relationships with the family Raskyellaceae. A possible link is suggested between the unusual ‘Y calcification’ in
the spiral wall cells of these species and a brackish water habitat.

I N the long history of the charophytes, the Middle Jurassic represents one of the intervals that is still
practically uninvestigated. Thus, from the Bajocian to the Oxfordian, the only known species are the
three described by Peck (1957) from Montana and Wyoming, U.S.A., and the seven studied by Bhatia
and Mannikeri (1977) from the Callovian of Western India. Other than in these two publications,
only undetermined forms or unattributed species of genus Porochara Madler have been cited. The
present study is part of a comprehensive work on the charophyte flora from the Middle Jurassic. It is
based mainly on our own collecting in the Bathonian of the ‘Gausses’ (Southern France) and also on
material from contemporaneous deposits of other regions: those from the English Midlands were
found by Dr. T. Palmer, University of Wales, and those from Eastern Sardinia by Dr. I. Dieni,
University of Padua. Amongst these Bathonian floras we have restricted ourselves in the present
study to those representatives of the family Porocharaceae Grambast which possess a gyrogonite
with a segmented basal plate (genus Musacchiella gen nov.). This is because of the great phylogenetic
importance of this structure and its relative rarity amongst fossil forms.

The abundance and the excellent state of preservation of these fossils has permitted new
observations on the apical opening of the gyrogonite, suggesting a direct relationship with a family
first known in the Upper Cretaceous. The presence of a special structure in the calcified gyrogonite
wall of the three described species is also noted and discussed with relation to the original
environmental conditions.

THE SEGMENTED BASAL PLATE
Occurrence of a divided basal plate amongst the Charophyta

Grambast ( 1 956b) first pointed out that, amongst the fossil Charophyta, there existed representatives
with a divided basal plate, and he assigned these to the genus Tolypella (Characeae Nitelloideae). This
structure corresponds to the assemblage of calcified sister cells of the oosphere = sterile oogonial
cells. These true Tolypella (with a multipartite plate) were first noted from the Lutetian (Grambast
1958; Cl 20, Pont Bernard, unpublished material). Only one pre-Tertiary example is known:
T. grambasti Musacchio (Uliana and Musacchio 1978) from the late Cretaceous of Argentina.

Amongst the extant forms, those which possess several sterile oogonial cells all belong to the
non-calcified Nitelloideae: genus Nitella and genus Tolypella section Tolypella. Daily (1969) and
Sawa and Frame (1974) have in fact pointed out that the calcified Tolypella (section Rothia R. D.
Wood) possess an undivided plate, resulting from the calcification of a single sterile cell.

[Palaeontology, Vol. 27, Part 2, 1984, pp. 295-305.]

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PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 1 . Multipartite basal plates, a, Musacchiella palmeri sp. nov., inside view of the gyrogonite, x 455.
B, M. palmeri sp. nov., external view, x 273. c, M. douzensis sp. nov., external view, x 455. D, M. douzensis

sp. nov., external view.

With regard to the representatives of the three subfamilies of the Porocharaceae, all of which are
fossil, often no mention has been made of the existence of a basal plug. When it does exist the
illustration does not always allow its presence to be seen (e.g. Madler 1952, pi. B, fig. 28). In other
cases, only a single plate has been described or illustrated, e.g. some species from the Upper Jurassic
of Mongolia (Kyansep-Romashkina 1975, pi. I, fig. 3) and the Upper Cretaceous of China (Wang
1978, pi. 3, figs. 9-14 and 31-34). In the case of Porochara gildemeisteri Koch and Blissenbach from
the Upper Cretaceous of Peru, the section given by Grambast {in Grambast et al. 1967, pi. I, fig. 14)
appears to show a vertical wall crossing the middle of the plate. However, in sections at this level it is
generally extremely difficult to distinguish true cell walls from fractures or crystal faces. On the other
hand, Grambast (1964, p. 72) mentions, without giving any information on the age or origin of the
material, the existence of Porocharaceae with a segmented plate. It is on the basis of this reference
alone that Soulie-Marsche (\919a) formulated her hypothesis concerning the origin of extant forms
with three sterile oogonial cells.

The observations described herein provide the first unequivocal evidence for the coexistence,
within the family Porocharaceae, of two types of basal plate.

FEIST AND GRAMBAST-FESSARD: BATHONIAN CHAROPHYTES FROM EUROPE 297

The divided basal plate in the Bathonian Porocharaceae

In the specimens studied the diflferent parts of the basal plate are especially conspicuous in internal
views of hollow unrecrystallized gyrogonites. In such cases, the number of parts observed is always
two. They are small sized, and one is pentagonal, the other smaller, triangular or nearly rectangular
(text-fig. 1a). From the exterior, observation is generally more difficult, because the partition wall is
often hidden by the ends of the spiral cells or reduced by wear or by the presence of sedimentary
particles. This is the aspect shown by the basal view of Musacchiella palmeri sp. nov. (text-fig. 1b). In
certain cases, however, the partition may appear rather more clearly, as in M. douzensis sp. nov.
(text-fig. Ic) or as in an internal pyritized mould of M. sp. A from Sardinia (text-fig. Id).

The presence of two components at the basal plate level is also conspicuous in longitudinal axial
sections of M. douzensis sp. nov. (text-fig. 2a, b) and of M. palmeri sp. nov. In a section of a pyritized
internal mould of M. sp. A (text-fig. 2c) the presence of three cavities is visible at the gyrogonite base
and these cavities might represent the location of the three sterile oogonial cells. The three
corresponding calcified pieces appear to be present again in the section of M. sp. A where the calcite
shell is preserved (text-fig. 2f).

Comparison with the other known occurrences of multipartite based plates

The only variation in all known cases is in the number of components observed. There are generally
two in the Bathonian Musacchiella described here, as well as in T. grambasti Musacchio from the
Maastrichtian and in a Tolypella species from the Upper Eocene of the Paris Basin illustrated by
Soulie-Marsche (1979fi, pi. 45, fig. 7). In T. pumila Grambast from the Lower Oligocene of Belgium,
two components are also seen in a basal exterior view (Grambast in Stockmans 1960, fig. 39a).
However, the same species from the Paris Basin shows a tripartite basal plate in situ in an inner side
view of the gyrogonite and Grambast (19566, 1958) mentions that the number and arrangement of
the plate elements are here variable. In the Bathonian Musacchiella, a bipartite basal plate seems to be
the norm, but in M. sp. A this seems to vary according to the angle of observation, and the elements
may appear to be two (text-fig. 2f) or three (text-fig. 2c). It must be noted that amongst the extant
species possessing several sterile oogonial cells, the number of these cells is controversial. According
to Sawa and Frame (1974), and contrary to the views of other authors like Maier (1973), the third cell
ought always to be present and, if it is not observed, it is probably due to its small development. In the
present state of knowledge of extant as well as fossil forms, no particular significance is attached here
to the biological (reproductive cycle) or phyletic nature of the number of components (2 or 3), but
only to the fact that the basal plate is multipartite.

Multipartite basal plate and phylogeny

Other than in the Bathonian Porocharaceae, multipartite plates are known only amongst the
Characeae/Nitelloideae and naturally it is with this group that affinities are to be sought. Although we
now have evidence that forms with a divided plate have existed since the Middle Jurassic, it is only at
the end of the Cretaceous that another species with this character {T. grambasti Musacchio) is to be
found. These represent two widely spaced steps which do not for the moment allow the reconstruction
of a direct lineage exhibiting no anatomical particularity other than the basal plate. The genera
Musacchiella and Tolypella clearly belong, on account of their apical structure, to two markedly
distinct groups. We shall see later on that in M. douzensis sp. nov. the other anatomical characters of
the gyrogonite (apical opening, wall of spiral cells) suggest multiple relationships, without apparent
connections with the demonstrated affinities of the Nitelloideae. We consider for this reason that the
Bathonian Porocharaceae with a segmented basal plate may belong to the ancestral stock of the
Nitelloideae, but we cannot state that they represent their direct ancestor. It is, therefore, difficult to
agree with the phylogenetic diagram drawn by Soulie-Marsche (1979c7) in which the origin of the
extant genera of Characeae goes back to the Jurassic or even, for some, to the basal Trias. Indeed, as
a result of the successive allocations of all the Triassic species to the family Porocharaceae (Grambast
1962; Sai'dakovsky 1971), it appears that no true representative of the Characeae is to be found before

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PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 2. Longitudinal sections of the gyrogonite. a, Musacchiella douzensis sp. nov., x 70. B, Same,
detail of the basal pole, x 200; 1, 2, the two parts of the basal plate, c, M. sp. A, x 250; 1, 2, 3, location of
the three basal cells, d, M. douzensis sp. nov., x 300, detail of the wall of the spiral cells, e, M. palmeri sp.
nov., X 300, detail of the wall of the spiral cells, f, M. sp. A, x 370, detail of the basal pole; b.p., site of the
multipartite basal plate. G, Lamprothamnium priscum Castel and Grambast (topotype), x 300, detail of

the wall of the spiral cells.

FEIST AND GRAMBAST-FESSARD: BATHONIAN CHAROPHYTES FROM EUROPE 299

the Middle or even the Upper Jurassic. Moreover, the basal plate morphology in the Jurassic species
is in no case typical of the Nitelloideae genera: Sphaerochara (plate undivided, thick, visible at outer
surface level), Tolypella and Nitella (segmented plate).

Taxonomic implications of the presence of a segmented plate

In the classification of fossil Charophyta (Grambast 1962, 1974) and more particularly of the order
Charales to which all the post-Palaeozoic species belong, the apical structure of the gyrogonite is
considered to be of primary importance. The species studied here, in which the apical pore is always
open, but not lying at the top of a neck, belong, without any doubt, to the Porocharaceae/
Porocharoideae. Within this subfamily, there coexist species with a single basal plate and others, first
described here, with a divided one. The systematic value of this character can be argued. Grambast
(19566) has shown that, in the Tertiary Characeae, the basal plate constitutes an important diagnostic
character and the presence of a segmented basal plate justifies the inclusion of a species in a special
subfamily. In the present case, the described species are quite closely related to each other, both on
account of their morphology and chronological isolation in the Middle Jurassic. So it seems to us that
they naturally fall into a single new genus. It is possible, however, that in the future a higher rank
division may have to be considered, particularly if other ancient forms with a segmented plate are
discovered.

THE APICAL OPENING OE THE GYROGONITE

In the Porocharaceae/Porocharoideae the apical pore of the gyrogonite is always open and is often
somewhat sunken, with a small diameter and with a more or less rounded pentagonal shape. Some
specimens of Musacchiella gen. nov. show a somewhat different form. In M. douzensis sp. nov. for
example (text-fig. 3a, b) the shape and arrangement of the spiral cell ends are seen very distinctly: the
central part of these cells outlines a rounded recess limited by the forwardly tapering intercellular
sutures which form tooth-shaped projections. The whole shape is that of a rose and looks like the
opening left by the loss of the calcified operculum in the family Raskyellaceae, as seen for example in
Rantzieniella nitida Grambast (text-fig. 3c). Such a form differs fundamentally from the cog-wheel
shape (‘roue dentee’ in Grambast 1956a) evident in a dehiscent gyrogonite of the family Characeae,
shown here in Gyrogona lamarcki Grambast (text-fig. 3e). In this case, dehiscence takes place through
the breakage of the spiral cell ends and not through the loss of special opercular cells (text-fig. 3d)
such as occurs in the Raskyellaceae (Grambast 1957; Feist in Anadon and Feist 1981).

From a biological point of view the shape of the apical opening in Musacchiella suggests the
possibility in the Porocharoideae of closure by means of an operculum made of five apical cells which,
in the Middle Jurassic, would not have been calcified. Moreover, the Porocharoideae and
Raskyellaceae exhibit other similar features in the fructifications. They are often ovoidal in shape,
with a thick lime-shell and basal plate, and a small apical pore compared to the general diameter of
the gyrogonite. As for Musacchiella this combination of characters implies even more affinities with
the Raskyellaceae than with the Nitelloideae which, however, have in common with the Jurassic
forms the peculiarities of the basal plate as discussed above. The evolution of the Porocharoideae to
the Raskyellaceae may have taken place by the calcification of the operculum, most probably
amongst forms with an undivided basal plate, in the Upper Cretaceous, i.e. not long before the
extinction of the Porocharaceae, near the Cretaceous-Tertiary boundary (Feist 1979).

The apical structure of Musacchiella also shows an inclination of the ends of the cells into the centre
of the somewhat sunken apex. This bending is commonly observed within the genus Porochara, for
example in P. globosa Grambast and Gutierrez (1977, pi. I, fig. 8). The distinction of the genus
Euaclistochara Wang, Huang and Wang, 1976, which depends upon this feature alone, is thereby
questionable. As no segmented plate has been described in the species attributed to Euaclistochara,
we consider all of them as belonging to the genus Porochara Madler. In fact, the four species of Peck
(1957) attributed by Wang et al. (1976) to Euaclistochara were previously ascribed to this genus.

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PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 3. Apical structures of the gyrogonite. a, Musacchiella douzensis sp. nov. (Porocharaceae),
X 155. B, Same, paratype, CF2098-4, apical view, x 60. c, Rantzieniella nitida Gramb. (Raskyellaceae),
(topotype— Aquitanian), dehiscent summit, x95. d, Raskyella vadaszi Gramb. (Raskyellaceae),
(Laguarres, prov. Huesca, Spain; Upper Eocene; from Anadon and Feist 1981, pi. 2, fig. 2), entire summit,
X 1 10. E, Gyrogona lamarcki Gramb. (Characeae), (Nogent I’Artaud, Aisne, France; Upper Eocene; from
Grambast and Grambast-Fessard 1981, pi. 1, fig. 7), dehiscent summit, x 30. f, Psilochara aff. repanda
Gramb. (Characeae), (La Debruge, Vaucluse, France; Upper Eocene; from Eeist-Castel 1 977, pi. 5, fig. 6),

entire summit, x 50.

THE CELL WALL STRUCTURE

Description. The Bathonian Musacchiella species studied here exhibit in longitudinal sections
(text-fig. 2a, d, e, f) a peculiar aspect of the calcified wall of the spiral cells, that is quite different from
that generally observed. A system of radial convergent lines is found here in addition to the usual
parallel lamination first described by Migula (1897, p. 49). These lines depart from the suture and
from the adaxial wall, going towards the median part of the spiral cell. At a low magnification, the
limit of these radial stripes outlines, in the middle of the cell, a letter ‘Y’, the fork of which is directed
towards the centre of the gyrogonite.

This structure strongly recalls that described by Soulie-Marsche (1979/?, pi. 9; 1982) in the extant
species of the genus Lamprothamnium, under the name of ‘structure en eventaif (fan-shaped).
However, in this case, the laminae depart only from the intercellular sutures and form divergent

FEIST AND GRAMBAST-FESSARD: BATHONIAN CHAROPHYTES EROM EUROPE 301

bunches, the junction of which again delimits a Y at the cell centre. The same aspect can be seen, less
distinctly, in the fossil species Lamprothamnium priscum Castel and Grambast from the Eocene
(text-fig. 2g). a similar structure is also present in one species of Porocharaceae/Stellatocharoideae;
Stellatochara sellingii (Horn af Rantzien 1954, pi. 2, figs. 4, 5) from the Trias of Sweden.

Phylogenetic relationships. It is tempting to search for relationships between the forms with the ‘Y’
calcification wall structure, but it seems that this character alone cannot be used to demonstrate
natural affinities. On the one hand, the genera Stellatochara and Musacchiella belong to distinct
subfamilies, Stellatocharoideae and Porocharoideae, which, separate since the Permian, apparently
correspond to distinct phyla (Saldakovsky and Shajkin 1976). On the other hand, we have shown
above, on the grounds of the anatomical characters of the base and apex of the gyrogonite, that the
likely affinities of Musacchiella lie with the Nitelloideae and Raskyellaceae, and not with the
Charoideae, to which Lamprothamnium belongs. Thus, although this peculiar ‘Y’ calcification
appears to be characteristic of some genera, these are not necessarily linked through a direct line. The
most we can say is that they may have possessed a remote common ancestor.

Ecological relationships. The question also arises as to whether the presence of the ‘Y’ calcification of
the spiral cells is related to the life conditions of the studied Musacchiella. The extant representatives
of the genus Lamprothamnium live in lagoons and may tolerate high salinity (Burne et al. 1980).
Likewise, L. priscum from the Eocene comes from a brackish facies (Castel and Grambast 1969).
However, other Characeae species found in the same outcrop that yields L. priscum, such as
Nitellopsis (Tectochara) thaleri Eeist-Castel, do not have the same wall structure. Horn af Rantzien
(1954, p. 20) does not provide any precise information on the habitat of Stellatochara sellingii.

With regard to the outcrops yielding Musacchiella, some information on the primary environ-
mental conditions, especially the salinity, is provided by the ostracod faunas. According to Palmer
(1979, p. 194), at Wood Eaton ‘the ostracod fauna is predominantly brackish’ and ‘the abundance of
charophytes also suggests the influence of fresh water’. Eurthermore, he states that the absence of
vegetative fragments implies that the fructifications were transported from lakes upstream. It may be
noted, however, that several living and fossil species have been reported, herein and elsewhere, from
brackish lagoons. Moreover, not all charophytes possess a calcified thallus. It is thus quite likely that
M. palmeri shared the same environment as the ostracods. Dr. Palmer (pers. comm. 1982)
acknowledges this as being quite compatible with his own palaeoecological analysis of the basal part
of the Hampen Marly Eormation at Wood Eaton.

The ostracods associated with M. douzensis at the southern Erance locality (E. Depeche, pers.
comm.) are mainly freshwater species, but may have been transported as suggested by the poor state
of preservation of the shells. In addition, there is one euryhaline species, Klieana levis Oertli. As
communicated by Dr. I. Dieni (pers. comm.), this latter species is predominant at the Sardinian
locality and indicates there a brackish environment. Thus it seems to be true that the forms showing a
‘Y’ calcification are found preferentially in somewhat saline environments, but it cannot be said that
there is a causal relationship between these two facts.

SYSTEMATIC PALAEONTOLOGY

Division charophyta
Order charales

Eamily porocharaceae Grambast 1962
Subfamily poroceiaraoideae
Genus musacchiella nov.

Type species. Musacchiella douzensis sp. nov.

Derivation of name. The genus is named in honour of Dr. E. Musacchio, Buenos Aires, for his work on fossil
charophytes.

Occurrence. Middle Jurassic (Bathonian) of Oxfordshire, England; Gausses, southern France; eastern Sardinia.

302 PALAEONTOLOGY, VOLUME 27

Diagnosis. Gyrogonite of Porocharoideae with a small apical pore, ovoidal shape, and segmented
basal plate.

A ffinities. The new genus bears most resemblance to Porochara Madler amongst the Porocharoideae
(characterized by an apical opening not lying at the top of a neck), in its general ovoidal to ellipsoidal
shape and in the morphology of the somewhat sunken apical opening which may occasionally possess
a ‘rose’ outline. It dilfers in the particular character of a divided basal plate. We limit, therefore, the
genus Porochara to forms with an undivided, or unknown, basal plate. In practice, of course, it will
not always be possible to recognize the new genus, since the basal plate structure will not always be
visible.

Musacchiella douzensis sp. nov.

Types. Holotype (text-fig. 4a), CF2038-1. Paratypes (text-figs. 4b, c; 3b), CF2038-2 to 5. Coll. M. Feist,
Universite des Sciences et Techniques du Languedoc, Montpellier, France.

Type horizon and locality. Lignitic marls from the Bathonian, Middle Jurassic; Les Douzes, commune of
Mures-la-Parade, Lozere, France.

Material. About 300 specimens.

Derivation of name. From the name of the type locality.

TEXT-FIG. 4u-c, Musacchiella douzensis sp. nov., x 60. a, holotype, CF2098-1, profile. B, paratype
CF2098-2, profile, c, paratype, CF2098-3, base, d, e, M. palmeri sp. nov., x 60. d, holotype, C 1094-1,
profile. E, paratype Cl 094-2, profile. F, M. sp. A, specimen CF 1598-1, profile, x 60.

FEIST AND GRAMBAST-FESSARD: BATHONIAN CHAROPHYTES EROM EUROPE 303

Diagnosis. Gyrogonite of Musacchiella, the largest diameter being at mid height. Segmented basal
plate, visible from the outer side at the bottom of a shallow pit bordered by the truncation of the spiral
cells. Dimensions: 625-975 fMm long, 500-550 |um wide; 10-13 convolutions; L/W ratio varying from
M to 1-4.

Remark. The spiral cells are frequently concave, but even when they are plane or slightly convex in the
middle part of the gyrogonite, they become more hollow at its base where the sutures are always
prominent.

Affinities. Other than in plate characters, M. douzensis differs from the Porochara present in the same
bed in its distinctly larger dimensions and its widened outline at the equator of the gyrogonite. In this
latter character the new species is reminiscent of Porochara rotunda (Peck) Shajkin from the Middle
Jurassic of U.S.A., the basal plate of which is unknown; however the dimensions and the number of
convolutions are distinctly smaller in the latter species (Peck 1957). Similarly, {S.) raoi Bhatia and
Mannikeri 1977, from the Callovian of India, is rather enlarged at the equator of the gyrogonite but is
smaller overall and apparently has an undivided basal plate. According to the divisions established by
Grambast (1962), the features of the apex, which is open and not drawn into a neck, lead us to ascribe
this species to the Porocharoideae, and more precisely to the genus Porochara Madler, with regard to
its general shape and apical morphology.

Musacchiella palmeri sp. nov.

Types. Holotype (text-fig. 4d), C1094-1. Paratypes (text-fig. 4e), C1094-2 to 5. Coll. Grambast, Universite des
Sciences et Techniques du Languedoc, Montpellier, France.

Type horizon and locality. Lignitic marls of the Bathonian, Middle Jurassic; Wood Eaton, 5 miles north-east of
Oxford, Oxfordshire, England (Palmer 1973).

Material. About 250 specimens.

Derivation of name. The species is named after Dr. T. J. Palmer, who collected the material at Wood Eaton and
sent it for study to the late Dr. L. Grambast in 1970.

Diagnosis. Gyrogonite of Musacchiella, most often ellipsoidal, tapering near the apical and basal
ends. Segmented basal plate nearly on a level with the basal pore. Dimensions: 275 650 p.m long,
250-500 pm wide, 7-9 (exceptionally 6-10) convolutions; L/W ratio varying from 108 to 1-36.

Remarks. In the Wood Eaton outcrop, only representatives of the genus Musacchiella are found, as
confirmed by the examination of basal plates. In histograms of the dimensions, the specimens are
divided in two sets with bimodal peaks interfering for lengths 400-450 pm and widths 350 pm. As the
characters, other than the convexity or concavity of the spiral cells, do not vary significantly, we
assign the whole population to a single species.

Affinities. M. palmeri differs from M. douzensis by its more dumpy shape, its smaller dimensions, and
the conformation of the basal region. However, the two species have in common two characters: the
variability of the cell relief (concave to convex) as well as the salient features of the lime-shell, these
peculiarities being also found in M. sp. A from Sardinia. On the other hand, the largest specimens
with concave cells look somewhat like P. sublaevis (Peck) Grambast in Saldakovsky (1966, p. 132)
from the Middle Jurassic of Montana, U.S.A., of which the basal plate has not been described. The
specimens with large dimensions may also be compared with ‘5.’ sahnii and 'S.' jaisalmerensis both
described by Bhatia and Mannikeri (1977). Their number of convolutions is however higher and there
is no mention of the basal plate. These two taxa seem to us to belong to only one species with various
degrees of calcification. Their apical morphology leads us to conclude that they must be ascribed,
together with ‘5.’ raoi, to the genus Porochara.

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PALAEONTOLOGY, VOLUME 27

Musacchiella sp. A
Text-fig. 4f

Occurrence. Funtana sa Mela, near Siniscola, Nuoro province, Sardinia; Bathonian, Middle Jurassic (specimens
collected by Dr. I. Dieni).

Description. Gyrogonite ellipsoidal, with concave spiral cells; basal plate apparently made of three
pieces, which have been observed in longitudinal section (text-fig. 2c). Basal plate not visible from the
outer side of the gyrogonite.

Remark. The small number of specimens and the often rather poor state of preservation do not allow
the creation of a new species, so we are leaving the described form in open nomenclature. However, it
would appear that, on the basis of their morphology and in spite of the deformations observed, the
specimens from Sardinia cannot be assigned to either of the two former species of Musacchiella.

CONCLUSIONS

Within the present work on Bathonian charophytes, we have described a new genus, Musacchiella,
which includes Porocharaceae/Porocharoideae species combining an unusual assemblage of
characters in the gyrogonite: the apical opening recalling the family Raskyellaceae (Upper
Cretaceous-Lower Miocene), the divided basal plate of the Characeae/Nitelloideae type (Upper
Cretaceous- Recent), and the ‘Y’ calcification of the wall resembling that in Lamprothamnium
(Characeae/Charoideae, Upper Cretaceous-Recent). Furthermore, this particular calcification
appears to be related to a brackish habitat. Thus a great diversity of valuable characters is present
amongst forms which are rather unspectacular at first sight: small-sized gyrogonites without any
ornamentation. One may see in this contrast the expression of an evolutionary potential amongst
these Porocharaceae from the Middle Jurassic. It has been previously suggested (Grambast 1962,
1974) that the Porocharaceae constitute the common stock from which the families Raskyellaceae
and Characeae, which comprise nearly all the Tertiary forms, are derived. The example of
Musacchiella lends support to this point of view. In addition, the genus Musacchiella has a wide
geographical distribution in Western Europe: England, France, Sardinia. Also associated with this
genus are species now ascribed to Porochara which are currently being investigated.

Acknowledgements. We wish to thank Dr. J. Mattei, Montpellier, for information on Jurassic stratigraphy; Dr.
I. Dieni, Padua, and Dr. T. J. Palmer, Aberystwyth, for the specimens they entrusted to us and Mme Depeche,
Paris, for studying the ostracod fauna. We are indebted to Mr. J. Guiraud for his skill in preparing the thin
sections of gyrogonites used in this study. We are also particularly grateful to E. N. K. and C. Clarkson for
improving the English text. The SEM pictures were made at the ‘Laboratoire de Microscopie electronique’ of the
University of Montpellier. The specimens are lodged in the Charophyte reference collections in the
Palaeobotany Department of the University of Montpellier.

REFERENCES

ANADON, p. and FEIST, M. 1981. Charophytes et biostratigraphie du Paleogene inferieur du bassin de FEbre
oriental. Palaeontographica, 178 B, 143-168.

BHATiA, s. B. and MANNiKERi, M. s. 1977. Callovian Charophyta from Jaisalmer, Western India. Geologica et
Palaeontologica, 11, 187-196.

BURNE, R. V., BAULD, J. and DE DEKKER, p. 1980. Saline lake charophytes and their geological significance. J.
sediment. Petrol. 50, 281-293.

CASTEL, M. and GRAMBAST, L. 1969. Charophytes de FEocene des Corbieres. Bull. Soc. geol. France (7e s.), 11,
936-943.

DAILY, F. K. 1969. Some late glacial charophytes compared to modern species. Proc. Indiana Acad. S'cl (1968), 78,
406-412.

FEiST-CASTEL, M. 1977. Etude floristique et biostratigraphique des charophytes dans les series du Paleogene de
Provence. Geol. medit. 4, 109-138.

FEIST AND GRAMBAST-FESSARD: BATHONIAN CHAROPHYTES FROM EUROPE 305

FEIST, M. 1979. Charophytes at the Cretaceous/Tertiary boundary. New data and present state of knowledge.

Cretaceous-Tertiary boundary events symposium, Copenhagen, II Proc. 88-94.

GRAMBAST, L. 1956u. Sur la dehiscence de I’oospore chez Chara vulgaris L. et la systematique de certaines
Characeae fossiles. Rev. gen. Bot. 63, 331-336.

19566. La plaque basale des Characees. C.R. Acad. Sci. Paris, 242, 2585-2587.

1957. Ornementation de la gyrogonite et systematique chez les Charophytes fossiles. Rev. gen. Bot. 64,

339-362.

1958. Etude sur les charophytes tertiaires d’Europe occidentale et leurs rapports avec les formes actuelles.

These Paris, 286 pp. Unpubl.

1962. Classification de I’embranchement des charophytes. Naturalia monspel. Bot. 14, 63-86.

1964. Precisions nouvelles sur la phylogenie des charophytes. Ibid. 16, 71-77.

1974. Phylogeny of the Charophyta. Taxon, 23, 463-481.

and GRAMBAST-FESSARD, N. 1981. Etude sur les charophytes tertiaires d’Europe occidentale. Ill Le genre

Gyrogona. Paleobiol. contin. 12, 1-35.

and GUTIERREZ, G. 1977. Especes nouvelles de Charophytes du Cretace superieur terminal de la province

de Cuenca. Ibid. 8, 1-34.

MARTINEZ, M., MATTAUER, M. and THALER, L. 1967. Perutherium altiplanense nov. gen., nov. sp., premier

Mammifere mesozoi'que d’Amerique du Sud. C.R. Acad. Sci. Paris D, 264, 707-710.

HORN AF RANTZiEN, H. 1954. Middle Triassic Charophyta of South Sweden. Opera bot. 1, 1-83.
KYANSEP-ROMASHKINA, N. p. 1975. Nekotorye pozdneyurskye i melovye kharofity Mongolii. Iskop. fauna flora
Mongol. Sovmestnaya 50v. mong paleontol. ehksped Tr. 2, 181-204. [In Russian: Some Charophyta from the
Upper Jurassic and the Cretaceous of Mongolia.]

MADLER, K. 1952. Charophytcn aus dem Nordwestdeutschen Kimmeridge. Geol. Jb. 67, 1-46.

MAIER, E. X. 1973. The female gametangium of Tolypella nidifica A. Br.: a misinterpretation. Acta bot. neerland.
22, 463-466.

MIGULA, w. 1897. Die Characeen. E. Kummer, Leipzig. [765 pp.]

PALMER, T. j. 1973. Field meeting in the Great Oolite of Oxfordshire: report by the director. Proc. geol. Assoc.
84, 53-64.

1979. The Hampen Marly and White Limestone Formations: Florida-type carbonate lagoons in the

Jurassic of Central England. Palaeontology, 22, 189-228.

PECK, R. E. 1957. North American mesozoic Charophyta. Geol. Survey prof, paper, 294 A, 1-44.
saIdakovsky, l. y. 1966. Biostratigrafiya triasovykh otlozhenil yuga russkol platformy. br. Iskopaemye
kharofity SSSR. Trudy geol. Inst. 143, 93-144. [In Russian: Biostratigraphy of the Triassic deposits in the
South of the Russian platform.]

1971. Novy rod triasovykh kharofitov. Geol. Zh. U.S.S.R. 31, 121-122. [In Russian: New genus of

Charophyte from the Trias.]

and SHAJKiN, I. M. 1976. Stratigraficheskoye znachenie iskopaemykh kharofitov Ukrainy. Tekton. i Stratigr.

U.S.S.R. 11, 74-86. [In Russian: Stratigraphical importance of the fossil Charophyta from Ukraine.]
SAWA, T. and frame, p. w. 1974. Comparative anatomy of Charophyta: I. Oogonia and oospores of Tolypella
with special reference to the sterile oogonial cell. Bull. Torrey Bot. Club, 101, 136-144.

SOULIE-MARSCHE, I. 1979u. Origine et evolution des genres actuels des Characeae. Bull. Centre rech. explor. prod.
Elf Aquitaine, 3, 821-831.

19796. Etude comparee de gyrogonites de charophytes actuelles et fossiles et phylogenie des genres actuels.

These Montpellier, 320 pp. Unpubl.

1982. Charophytes in Le Shati, lac pleistocene du Fezzan (Lybie). 80 -84, edit. C.N.R.S., Paris.

STOCKMANS, F. 1960. Initiation a la paleobotanique stratigraphique de la Belgique. Bruxelles. [222 pp.]

ULIANA, M. A. and MUSACCHio, E. A. 1978. Microfosiles calcareos no-marinos del Cretacico superior en Zampal,
provincia de Mendoza, Argentina. Ameghiniana, 15, 111-135.

WANG, z. 1978. Cretaceous charophytes from the Yangtze-Han river basin with a note on the classification of
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HUANG, R. j. and WANG, s. 1976. Mesozoic and Cenozoic Charophyta from Yunnan province. Mesozoic

fossils of Yunnan, 1, 65-86. [In Chinese.]

MONIQUE FEIST
NICOLE GRAMBAST-FESSARD

Laboratoire de Paleobotanique
Institut des Sciences de I’Evolution (L.A. 327 du CNRS)
Universite des Sciences et Techniques du Languedoc
34060 Montpellier, France

Original typescript received 9 February 1983
Revised typescript received 4 August 1983

ADAPTIVE SIGNIFICANCE OF SHELL TORSION
IN MYTILID BIVALVES

by ENRICO SAVAZZI

Abstract. A twisted commissure plane is a common feature in several species of the mytilid genus Modiolus.
Observations on a semi-infaunal population of M. americamis in Bermuda suggests that the twisted shell
morphology maximizes the length of posterior commissure raised above the sediment surface while keeping its
profile low, with minimum risk of accidental damage. Thus, the shell morphology in the twisted Mytilidae
represents adaptive convergence with the twisted Arcidae and Bakevelliidae. In these two families, however, the
torsional direction is genetically fixed, while in the Mytilidae both the direction and the amount of torsion seem
to develop as a phenotypic response to the shell orientation relative to the substrate.

Several infaunal or semi-infaunal representatives of the bivalve families Arcidae and Bakevelliidae
possess a twisted commissure plane (McGhee 1978; Savazzi 1981). The twisted Arcidae (Trisidos and
at least one species of Barhatia) are typically endobyssate soft-bottom dwellers, although some of the
less-twisted species can live facultatively as epibyssate dwellers on solid substrates (McGhee 1978;
Savazzi 1981 ). Trisidos is a sluggish burrower (Tevesz and Carter 1979). The twisted commissure lifts
the posterior region of the shell above the surface of the sediment and aligns it roughly horizontally
(text-fig. 1a). This allows the inhalant and exhalant mantle regions to be widely spaced (McGhee
1978). The twisted Bakevelliidae {Hoernesia, GerviUia) were similarly soft-bottom dwellers. They are
not likely to have been active burrowers, and lived partly buried in the sediment resting on one valve.
The anchoring function of the byssus was supplemented by selective thickening of the lowermost
valve (with the possible exception of the Cretaceous Pseudoptera). This adaptation facilitated passive
re-orientation of the organism by waves or water currents after accidental disturbance of the life
position (text-fig. 1b). Shell torsion offers the additional advantage that the posterior commissure,
emerging from the sediment roughly horizontally, offers less resistance to water currents and is less
likely to be accidentally damaged by objects rolling on the bottom (McGhee 1978; Savazzi 1981 ).

The torsional direction is defined as the direction of twisting of the proximal part of the shell with
respect to the distal one, orienting the shell with the hinge parallel to the line of sight. Both clockwise
and counter-clockwise torsion is known to occur in the Arcidae and Bakevelliidae (McGhee 1978;
Savazzi 1981 and unpublished data). In all instances, however, the torsional direction is constant at
the generic or specific level, and therefore appears to be genetically fixed. Evidence suggests that the
twisted shell morphology evolved repeatedly within both families. It is therefore reasonable to expect
that shell torsion also evolved convergently in other similarly pre-adapted bivalve groups. Further
examples of shell torsion in different taxonomic groups would provide an opportunity for indirectly
checking the ideas on the adaptive value and evolution of the twisted-shell morphology in the Arcidae
and Bakevelliidae (cf. Savazzi 1983).

Infaunal representatives of the Mytilidae are the most likely candidates for this search, since they
have life habits comparable with those of the twisted Arcidae and Bakevelliidae and, lacking siphons,
they similarly need to leave a consistent length of the posterior commissure exposed above the surface
of the sediment, in order to avoid fouling by sediment particles and mixing of the inhalant and
exhalant currents. In addition, since the Mytilidae belong to the superfamily Pteriomorphia together
with the Arcidae and Bakevelliidae, they possess relatively close anatomical affinities. In fact, a
survey of Recent mytilids showed that several species of Modiolus are often noticeably twisted about
the hinge axis in a manner closely comparable with the twisted Arcidae. Singularly enough, no

IPalaeontology, Vol. 27, Part 2, 1984, pp. 307-314.]

308

PALAEONTOLOGY, VOLUME 27

mention of shell torsion was found in the literature on these species. A number of other mytilid
species often display a wavy or otherwise irregular commissure. Although these irregularities do
result in a non-planar commissure, they do not conform to the definition of shell torsion (McGhee
1978) and are therefore excluded from the present discussion. Since the twisting in Modiolus is always
greatest between the antero-ventral and the posterior shell regions, as in the twisted Arcidae and
Bakevelliidae, it seemed possible that the shell torsion could be similarly adaptive. However, the
degree of twisting turns out to be extremely variable within a single species, and only some of the
individuals display torsion at all. Furthermore, it was found that both clockwise and counter-
clockwise torsion normally occur side by side within the same species. It was therefore felt that
the functional interpretation of the twisted-shell morphology would remain questionable in this
specific case, unless direct observations could be carried out on twisted mytilids in their natural
environment.

Trisidos (Arcidae)

Hoernesia (Bakevelliidae)

TEXT-FIG. 1. Schematic illustration
of twisted bivalves in life position.
A, Trisidos yongei Iredale, Recent,
East Indies, b, Hoernesia socialis
(Schlotheim), Middle Triassic,
southern West Germany. The trans-
verse section shows the characteristic
thickening of the lowermost valve.
C, Modiolus anwricanus Leach,
Recent, Bermuda.

SAVAZZl: SHELL TORSION IN MYTILIDS

309

MATERIAL AND METHODS

Modiolus americanus Leach, one of the mytilids exhibiting shell torsion, is a large species living in the
West Indies. Stanley (1970) described it as occurring in clear sand or in subtidal grass flats, mostly or
totally buried in the sediment and byssally attached to the roots of seaweeds or to coarse sediment
particles. The writer located a population of this species living at a depth of 1 -2 m along the south-
eastern coast of Harrington Sound, Bermuda, in August 1982. The bivalves were living in coarse,
muddy sand mixed with sandstone pebbles deriving from a nearby overhanging rocky cliff. The thick
byssus was always found to be anchored to a fairly large amount of coarse sediment particles,
requiring considerable physical effort to dislodge the shell. Roughly one-third of the shell surface was
exposed and heavily overgrown by algae and encrusting organisms. The life position was initially
recorded by marking the exposed parts before dislodging the shell, but it was subsequently found that
the distribution of epibionts is a fairly reliable indicator of the exposed shell regions. Only thirty-one
individuals could be located, since their distribution was patchy, and the sediment type rapidly
changed to barren muddy sand, unsuitable for M. americanus, a few metres away. Dead shells and
isolated live individuals were collected elsewhere in Bermuda, but no other population was found. A
total of forty-one individuals was observed in the living position.

The angle of shell torsion was measured by projection on to a plane perpendicular to the hinge axis.
The inclination of the posterior commissure relative to the surface of the sediment could not be
reliably measured because of irregularities in the substrate. For most individuals, it was estimated at
30° to 60°. Only two individuals were found lying with the commissure plane approximately vertical.

RESULTS

The data relative to live M. americanus (text-fig. 2a) show an almost perfect association between the
direction of shell torsion and the lateral inclination of the commissure plane in the living position.
With a single exception, possibly due to a previous disturbance, the direction of shell torsion is such as
to maximize the length of posterior commissure raised above the surface of the sediment, as found in
other twisted bivalves (text-fig. Ic). Lateral asymmetries (other than twisting about the hinge axis)
were not noticed in the anatomy of the soft parts, nor in the distribution of the periostracal hairs on
the outer surface of the shell. The two specimens with a vertically oriented commissure showed
negligible torsion. Otherwise, the lack of information on inclination of the commissure relative to the
substrate precludes detection of any correlation between torsional angle and obliquity of shell
insertion in the sediment.

The histogram in text-fig. 2b shows the degree of twisting of the commissure plane for the living
individuals of M. americanus collected for this study. The torsional angle of counter-clockwise
twisted individuals is arbitrarily given a negative sign. When the absolute value of the torsional angle
is displayed, the distribution becomes unimodal (text-fig. 2c). Together with the comparable number
of clockwise and counter-clockwise twisted individuals, this suggests that the direction of shell
torsion is determined by a stochastic process.

The bimodal distribution in text-fig. 2b contrasts with those obtained from dead shells of M.
americanus and other Recent species from museum collections (text-fig. 3). This discrepancy can be
explained by the fact that species in museum collections are usually represented by several shell-lots
from different localities and environments. According to the functional interpretation of shell torsion
as a facultative adaptation to life in soft sediments, the twisted-shell morphology should be expected
to occur only in populations living infaunally or semi-infaunally. M. americanus, for instance, occurs
as an epibyssate dweller on rocky bottoms in North Carolina (Van Dover and Kirby-Smith 1979). In
such a case, shell torsion would not be expected. Environmental data are usually absent in museum
material, so that the above hypothesis cannot be tested. None the less, it is interesting to note that the
percentage of twisted individuals in museum collections was found to be extremely variable among
shell-lots of the same species but from different localities.

310

PALAEONTOLOGY, VOLUME 27

DISCUSSION

The relatively small number of individuals of M. americanus and the other twisted mytilids available
for this study does not allow an effective statistical treatment. However, the approximately equal
number of clockwise and counter-clockwise twisted individuals (with the exception of M. auriculatus,
which is represented by a beach collecting and could therefore be biased by sorting) suggests that the
direction of shell torsion in Modiolus is not genetically determined, but rather develops as a
phenotypic response to the shell orientation relative to the substrate. The twisted Arcidae and
Bakevelliidae are usually found in loose, essentially homogeneous sediments. The correct life
orientation can be assumed by the settling veliger and/or be subsequently established by active or
passive means. Therefore, a genetically fixed direction of torsion does not decrease the adaptiveness
of the organism. A fixed torsional direction probably simplifies the introduction of other coadaptive
inequivalve characters (differential valve weighting in the Bakevelliidae, different valve overlap in the
Arcidae, functional inequivalve shell sculpture in representatives of both families: McGhee 1978;
Savazzi 1981) in the morphogenetic programme of the shell.

M. americanus as observed during the present study, on the other hand, is better described as a
byssally anchored semi-infaunal nestler among sediment-covered pebbles, rather than as a true soft-
sediment dweller. The local topography of the substrate, rather than a preference of the veliger, seems

LIFE POSITION

left valve
uppermost

commissure

vertical

right valve
uppermost

number of
individuals

/ TORSION
! DIRECTION

23

-

1

clockwise

-

2

-

no torsion

-

-

15

counter-

clockwise

A

Modiolus americanus
Bermuda

TEXT-FIG. 2. Occurrence of shell torsion in Modiolus americanus from Bermuda, a, relationship between life
position and direction of shell torsion, b, distribution of the amount of shell torsion. Counter-clockwise and
clockwise torsion are given negative and positive values, respectively, c, distribution of the absolute value of the

amount of shell torsion.

SAVAZZI: SHELL TORSION IN MYTILIDS

31 1

TEXT-FIG. 3. Occurrence of shell torsion in Recent mytilid species. See preceding figure for explanation.

to be the most likely factor determining which valve will happen to lie uppermost. The possibility of
developing either direction of torsion would therefore considerably increase the adaptiveness of the
organism and, since apparently not associated with other inequivalve characters, it would not require
a particularly complex morphogenetic programme. The alternative hypothesis, i.e. that the direction
of torsion is genetically fixed and that the organisms assume a life position compatible with the
anticipated torsion direction, would require a considerably more complex morphogenetic and
behavioural programme. Since the possible shell orientation is highly constrained by the substrate
morphology, only a proportion of the settling veligers would be in the condition of taking advantage
of the shell twisting.

Other characters indicate that the adaptive strategy of M. americamis is rather different from that
of both twisted Bakevelliidae and Arcidae. In these two families, the torsional angle reaches its
maximum value between the posterior commissure line and the byssal gape. In M. americamis and in
other twisted mytilids, on the other hand, the maximum torsional angle, relative to the posterior
commissure, is often found slightly anterior to the byssal gape. When M. americamis is feeding
normally, the shell gapes all around, and the long and slender pedal retractor muscles are contracted,
pulling the byssus anteriorly. As a result, the shell is pushed backwards and upwards about half a
centimetre, thus elevating the posterior commissure clear of the sediment surface and the
surrounding algae. The torsion in the shell region anterior to the byssal gape causes the shell to rotate
slightly as it is pushed backwards, further elevating the posterior commissure. When the mollusc
adopts the feeding position, a cavity forms between the buried shell surfaces and the surrounding
sediment, allowing the growth of interstitial cemented epibionts on the shell (text-fig. Ic). Since the
shell surfaces exposed above the substratum are heavily overgrown by algae, the encrusting red algae

312

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 4. Twisted bivalves, a-b, Trisidos semitorla (Lamarck), Recent, Philippines; left lateral
and ventral views, x 0-75, NRS (NRS = Naturhistoriska Riksmuseet Stockholm), c-d, Tr.
tortuosa (Linnaeus), Recent Philippines; left lateral and ventral views, x 0-75, NRS. Note the corals
attached to the posterior region of the left valve, which is exposed in life position (compare with
text-fig. I a), e, Hoernesia socialis (Sch\othe'\m), Middle Triassic, Wurttemberg(West Germany); left
lateral view, x L5, Paleontologiska Institutionen Uppsala, f-g. Modiolus americanus Leach,
Recent, Bermuda; left lateral and ventral views, x 0-75. h, M. philippinarum. Recent, Bali; ventral
view, X 2, NRS. Note that the specimens in G and h are counter-clockwise and clockwise twisted,

respectively.

SAVAZZI: SHELL TORSION IN MYTILIDS

313

and worm tubes are often more frequently found on the buried shell regions, where they face little
spatial competition. In other twisted mytilids, in contrast, the exposed parts are more heavily
overgrown by calcareous algae than the buried parts. Therefore, the distribution of cemented
epibionts would be of little use as an indicator of the life habits of fossil mytilids.

Repaired minor damage to the posterior commissure is a common feature in the twisted Arcidae
and Bakevelliidae and in most twisted Modiolus (text-fig. 4). Such damage is probably the result of
the impact of objects rolled on the sea floor by waves or water currents. Traces clearly referable to
the attack by shell-chipping predators are uncommon. In the twisted Arcidae and Bakevelliidae, the
anterior and ventral commissure is generally immune from damage, since these parts are buried. In
M. americanus, on the other hand, repaired damage to the shell margin is often also observed in the
byssal region (text-fig. 4f). This is explained by the fact that Modiolus, unlike the other twisted
bivalves, is byssally attached to, and surrounded by, buried rock fragments. When the posterior end
of the shell is moved, the shell surface exerts a leverage against these solid bodies, the byssus acting as
a fulcrum. A closely similar breakage pattern is often observed in epibyssate bivalves (e.g. Mytilus,
Area). Thus, it may be difficult to infer the life habits of fossil Modiolus from either the distribution of
epibionts or the patterns of repaired marginal fractures. Shell torsion, on the other hand, is an easily
recognizable feature and therefore a useful tool in autecological analysis, since it should be expected
to occur only in those individuals living semi-infaunally and lying on one valve. As shown by the
records in the literature, the life habits of single species can vary in different localities, resulting in a
variable percentage of twisted individuals.

It was not possible to assess the frequency of occurrence of shell torsion in fossil mytilids. However,
a late Caenozoic mould of a Modiolus species from the West Indies, closely related to M. americanus
(Paleontologiska Institutionen Uppsala Nr. lb 6007) shows pronounced shell twisting.

The principal adaptive advantages of shell torsion in the Arcidae and Bakevelliidae, i.e. leaving a
suitable length of the posterior commissure clear of the sediment, to facilitate the respiratory and
feeding current exchanges, and aligning it approximately horizontally, so that it would be less likely
to be accidentally damaged (McGhee 1978; Savazzi 1981), apply to the twisted Mytilidae as well. The
frequency of repaired damage to the posterior commissure in all twisted bivalves attests to the
vulnerability of this exposed shell region. Other bivalves living in similar environments with part or
all of the commissure exposed rely on several protective mechanisms. The shell margins are very thick

TEXT-FIG. 5. An idealized comparison of life positions with the commissure plane vertical (A) and inclined (B)
shows that the latter reduces the height of the portion of the shell projecting above the surface of the substratum
(h). The length of exposed posterior commissure is the same in both cases. Shell torsion coupled with a reclining
position on one side (B) allows the byssus to be buried at a suitable depth within the substratum {d) to provide

firm anchorage.

314

PALAEONTOLOGY, VOLUME 27

(e.g. epibyssate arks; some oysters), or the mollusc relies on extensive repair capabilities (e.g. Pinna\
Yonge 1953). Alternatively, thick periostracal bristles or flexible and frilled shell margins may act as
elastic shock absorbers {Pteria, Isognomon, some mytilids). Text-fig. 5 shows how shell torsion in
Modiolus significantly reduces the height and vulnerability of the parts of the shell projecting above
the surface of the sediment, while at the same time it allows the byssus to be buried at a suitable depth
to ensure a reliable anchorage. A nearly horizontal posterior commissure, moreover, allows feeding
on the particle-rich bottom layer of water.

According to McGhee (1978), evolution of the twisted morphology in the Arcidae and
Bakevelliidae was rendered possible when a morphogenetic programme supplemented or substituted
the interference of the byssus with the mantle margins in determining the shape of the byssal gape.
The byssal gape is a weakly controlled region of the shell also in the Mytilidae, as shown by its greatly
variable shape and extension. Therefore, McGhee’s explanation can be applied to this family as well.

CONCLUSIONS

The twisted-shell morphology in Modiolus represents an adaptation to a semi-infaunal life habit with
the commissure plane lying on one side, and constitutes therefore a functional convergence with the
twisted Arcidae and Bakevelliidae. While the potential for shell torsion is present in several species of
Modiolus, its expression is dependent upon life habits and environmental conditions. It is significant
that shell torsion in Modiolus was observed solely in species possessing a relatively unspecialized shell
shape. Very streamlined and elongated species, adapted to burrowing at a high angle to the sediment
surface, and Mytilus-Wke, species with a broad flat ventral region, suitable for epibyssate attachment,
were never found to be twisted. Similarly, shell torsion was not found in the mytilinid genus
Brachidontes, whose infaunal representatives burrow at a high angle to the sediment surface (Stanley
1970).

Acknowledgements. R. Reyment and S. Bengtson read and commented on drafts of this paper. Recent mytilid
shells were supplied by Stockholm Naturhistoriska Riksmuseet and H. Mutvei. Field-work in Bermuda was
defrayed by a grant from the Bermuda Biological Station for Research, Inc., supplied by Exxon Corporation. A
Guest Scholarship from the Swedish Institute at the Paleontologiska Institutionen, Uppsala, is gratefully
acknowledged.

This paper is Contribution No. 960, Bermuda Biological Station for Research, Inc., and Konstruktions-
Morphologie No. 170 of the Sonderforschungsbereich 53 ‘Palokologie’, Tubingen, West Germany.

REFERENCES

MCGHEE, J. R. 1978. Analysis of the shell torsion phenomenon in the Bivalvia. Lethaia, 11, 315-329.

SAVAZZi, E. 1981. Barbatia mytiloides and the evolution of shell torsion in arcid pelecypods. Ibid. 14, 143-150.

1983. Aspects of the functional morphology of fossil and living invertebrates (bivalves and decapods).

Acta Univ. Upsaliensis. Abstr. Uppsala Diss. Fac. Sci. 680, 1-21.

STANLEY, s. M. 1970. Relation of shell form to life habits of the Bivalvia (Mollusca). Geol. Soc. Amer. Mem. 125,
1-296.

TEVESZ, M. J. s. and carter, j. g. 1979. Form and function in Trisidos (Bivalvia) and a comparison with other
burrowing arcoids. Malacologia, 19, 77-85.

VAN DOVER, c. and KiRBY-SMiTH, w. w. 1979. Field guide to common marine invertebrates of Beaufort, North
Carolina. Part I: Gastropoda, Bivalvia, Amphipoda, Decapoda and Ecliinodermata. Duke University Marine
Laboratory, Beaufort, North Carolina, 78 pp.

YONGE, c. M. 1953. Form and habit in Pinna carnea. R. Soc. Fond. Phil. Trans, ser. B, 237, 335-374.

ENRICO SAVAZZI
Uppsala Universitet
Paleontologiska Institutionen
Box 558

S-751 22 Uppsala
Sweden

Original typescript received 18 March 1983
Revised typescript received 17 July 1983

EARLY ORDOVICIAN TRILOBITES
NORA FORMATION, CENTRAL AUSTRALIA

by RICHARD A. FORTEY and JOHN H. SHERGOLD

Abstract. This is the first detailed account of the trilobites from the platformal carbonate/clastic Nora
Formation of central Australia. The fauna records a remarkable, endemic radiation of the Family Asaphidae,
producing forms with inflated, tuberculate frontal glabellar lobes unlike any other asaphids, but with a general
resemblance to certain unrelated trilobites which lived in former epeiric habitats. The fauna is probably of
mid-late Arenig age. The generic composition indicates that Australia lay in equatorial latitudes during the early
Ordovician, attached or close to the Gondwanaland of the time and well-removed from other continents
spanning the palaeoequator. The fauna includes eighteen species, of which four are left under open
nomenclature. The concept of the Leiostegiidae is reviewed to include Aimamitella, formerly regarded as a
bathyurid. The classification of trinucleine trilobites is briefly reviewed. The peculiar blind trilobite Prosopiscus,
hitherto considered an aberrant cheiruracean, is reclassified in the Phacopina, and for its reception a separate
family, Prosopiscidae nov., is proposed. The following new taxa are described: Aimamitella strigifrons, A.
hrachvops', Norasaphus, N. (Norasaplms) skalis, Norasapliites, Norasaplms (Norasaphites) moiiroeae, N. (N.)
vesiculosus; Lycophron, L. rex\ Fitzroyaspis irritaus, Hungioides acutlnasus, Nambeetella embolion, Gogoella
brevis, and Prosopiscus praecox. On the basis of the trilobite fauna two assemblage zones are defined in the Nora
Formation.

The trilobites described here were collected from the Nora Formation during 1976. Although the
formation has a wide geographic distribution (text-fig. 1 ) extending over at least a 300 km east-west
belt, we have restricted our present investigations to the faunas of the Toko and Toomba Ranges,
respectively the eastern and western limbs of the Toko Syncline. This area has been more thoroughly
documented by members of the Australian Bureau of Mineral Resources Georgina Basin Project
than the sequences of either the Tarlton or Dulcie Ranges to the west; the formation is thought to be
most completely developed in the Toko Syncline where its stratigraphic relationships are better
known, and the trilobite faunas are more prolific.

During the Arenig the continental interior of Australia was immersed beneath a shallow, tropical
sea, which supported a rich fauna of trilobites, brachiopods, and molluscs. Outcrops of rocks of this
age are widely distributed in the Georgina and Amadeus Basins, but their inaccessibility has meant
that the faunas have only recently been studied in any detail. Platform faunas of this kind are relevant
to the assessment of the paleogeographic position of Australia during the early Ordovician. This
paper describes the trilobite fauna of the Nora Formation, which crops out along the southern
margin of the Georgina Basin, central Australia. The fauna is of particular interest because it records
endemic morphologies arising within what was evidently a short time; probably no better example
exists of the adaptability of the trilobite exoskeleton in the epeiric habitat.

Type material described here is prefixed CPC, and is deposited in the Commonwealth
Palaeontological Collection, Bureau of Mineral Resources, Canberra, Australia. A representative
non-type suite of material is deposited in the British Museum (Natural Flistory), London, and is
prefixed BM It. R. A. F. contributed pp. 318-360, although joint responsibility is accepted for the
scientific content of the paper.

STRATIGRAPHIC SYNOPSIS

The Nora Formation was named by Casey {in Smith 1963a, p. 10, table 1) for the informally
designated rock unit 01-8 of Pritchard (1960, pp. 112-113). Originally referred to the Toko Series
(Whitehouse 1936) or Toko Beds (Casey 1959; Pritchard 1960), the Nora Formation is now

[Palaeontology, Vol. 27, Part 2, 1984, pp. 315-366, pis. .38-46.]

316

PALAEONTOLOGY, VOLUME 27

recognized as the basal formation of the Toko Group, as revised by Draper (1980, pp. 473-474) who
also illustrates the historical development of nomenclature for these rocks. Stratigraphic relation-
ships are illustrated in text-fig. 2. The type area of the Nora Formation is in the northern continuation
of the Toomba Range, in the vicinity of Halfway Dam (text-fig. 16), 71 km south of Tobermory.
A type section has never been defined. In its type area the formation consists of brown ferruginized
coquinite at the base, succeeded by quartz sandstone and siltstone (Smith 1965). Elsewhere a basal
clastic interval of varying thickness occurs, sometimes containing pelletal or pebble skeletal
grainstone. The clastic to carbonate ratio increases as the formation is followed from north to south.

Three petroleum exploration wells and a Geological Survey of Queensland stratigraphic corehole
have penetrated the Nora Formation (text-fig. 1) which, together with surface outcrop measure-
ments, give some idea of the thickness and lithological variation within the formation in the Toko
Syncline. Drilling in the Netting Fence Anticline in the northern part of the Toko Syncline
(unpublished well completion report, Papuan Apinaipi Petroleum Co. Ltd., 1965), penetrated 1 14 m
of Nora Formation which consisted of 41 m of sandstone, shale, and coquinite, overlain by 73 m of
fine sandstone and shale. This total correlates well with a similar sequence, 119 m thick, in the
Pulatera Hills in the central portion of the Toko Range, and the approximate 100 m measured in the
type area. At the southern end of the Toomba Range, the Nora Formation is 250 m thick in AOD
Ethabuka No. 1 (unpublished well completion report. Alliance Oil Development, Australia N.L.
1975) where it is reportedly composed mainly of shale with minor amounts of dolomitic sandstone
and coquinite. Similarly, at the extreme southern end of the Toko Range, GSQ (Geological Survey of
Queensland) Mount Whelan No. 2 stratigraphic hole penetrated 235 m of Nora Formation, again
mainly composed of silty shale and sandstone with minor limestone (Green and Balfe 1980, p. 173).

riton Downs

\ Va TARLTON \
RANGE \

Marqua

^ TARLTON
' FAULT

Mt.

50 km _

GSQ Mt. Whelan 2

AOD MIrrica

AOD Ethabuka 1 ^

I h

22°30'

23°00'

McDonald

DOWNS

5953

ARAPUNGA

6053

LUCY

6153

ALGAMBA

6253

ALKEA

6353

TOBERMORY

6453

ONEIPER

5952

JINKA

6052

JERVOIS

6152

TARLTON

6252

MARQUA

6352

TOKO

6452

NEEYAMBA

HILL

6552

GLENORM-

ISTON

6652

ndex of 1 :1 00 000 scale geological series
sheets covered by this map

ADAM

6451

ABUODA

LAKES

6551

MOUNT

WHELAN

6651

TEXT-FIG. 1. Location and geographic distribution of the Nora Formation in central Australia.

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

317

Elsewhere, the Nora Formation is 70-100 m thick in the Tarlton Range (Smith 1965, 1972), where
it conformably overlies sandy carbonates and dolomites ascribed to the Kelly Creek Formation, the
Coolibah Formation not being recognized (Smith 1972, p. 128). The internal lithostratigraphy of the
Nora Formation in the Tarlton Range is similar to that in the northern Toko Range. At the eastern
end of the Dulcie Syncline, in the Huckitta district some 120 km further west. Smith (19636) has
recorded a predominantly dolomitic, coquinitic, ferruginized sequence (including oolitic ironstone)
up to 125 m thick, and conformably overlying Tomahawk Beds of late Cambrian and early
Ordovician age.

Webby (1978, 1981) has correlated the Nora Formation of the Georgina Basin with the Florn
Valley Siltstone of the Amadeus Basin, and the Willara and Gap Creek Formations of the Canning
Basin in Western Australia. On the basis of these correlations, Webby (1978, fig. 6b) has
reconstructed a palaeogeography for late early Ordovician time wherein the Nora Formation is
deposited under the influence of a warm equatorial current in a narrow, basically east-west
orientated, Farapintine Sea. Within this seaway. Draper (1977) considers the Nora Formation to
represent below wave base sediments, in part contemporaneous with sand bars (Carlo Sandstone
on his fig. 2) and lagoon bay sediments (Mithaka Formation on his fig. 2), but there is no
palaeontological evidence to confirm this relationship. As far as regional correlation of stratigraphic
units within this seaway go, the conodonts of the Horn Valley Siltstone suggest a mid-Arenig age,
within the Oepikodus evae and Baltoniodus navisIB. triangularis Biozones of the Baltic region,
according to Cooper (1981). Based on this information, and as yet unpublished conodonts from the
Georgina Basin, Cooper {op. cit.) concluded that the Horn Valley Siltstone is equivalent to the
Coolibah and basal Nora Formations of Toko Syncline, thus supporting our contention (below)
of a mid-late Arenig age for the Nora Formation. While this information does not alter the
palaeogeographic picture, it may suggest a certain diachroneity of the stratigraphic units correlated
by Webby.

TEXT-FIG. 2. Stratigraphic relationships of the Nora Formation to adjacent Formations in central Australia.

318

PALAEONTOLOGY, VOLUME 27

AGE OF THE NORA FORMATION

The Nora Formation is in places extremely fossiliferous and, collectively, a large biota has been
recorded: bivalves, nautiloids, gastropods, rostroconchs, brachiopods, ostracodes, bryozoans,
pelmatozoa, sponges, corals, conodonts, trilobites, ichnolites, and questionable foraminifera (see
Shergold and Druce 1980, p. 163). Of these groups, some actinoceratoid nautiloids have been
described by Beard {in Hill et al. 1 969) and Wade ( 1 911a, b), and these are considered to have an early
middle Ordovician age. Similarly, the conodonts illustrated by Nieper {in Hill et al. 1969) are ascribed
an early middle Ordovician age, by virtue mainly of the presence of Histiodella. This is disputed by
Druce {in Shergold and Druce 1980, p. 163) who regards the Nora conodonts as indicating an age late
in the early Ordovician (late Arenig), based on the presence of non-fibrous Scandinavian forms. The
Nora Formation has also yielded ten species of bivalves which include an ambonychiid form, a family
not known elsewhere earlier than the beginning of the middle Ordovician. Together with the other
bivalve evidence, Pojeta and Gilbert-Tomlinson (1977, pp. 4-5) suggest an age near the early/middle
Ordovician boundary. The rostroconch species Technophorus sp. and Euchasma skwarkoi described
by Pojeta et al. (1977) are not age diagnostic. The orthoid and plectambonitid brachiopods, a variety
of gastropods {ILophospira, IClathrospira, IHelicotoma, a bellerophontid), a monoplacophoran, and
the ichnolites, are yet to be described in detail, although some are illustrated by various authors in Hill
et al. (1969).

The definition of lower and middle Ordovician in the preceding discussion is that customarily
adopted by North American workers; the base of the middle Ordovician is taken at the base of the
Whiterock Stage of the North American platform sequence at a horizon approximately equivalent
to the base of the Llanvirn. Part of the apparent conflict between lower and middle Ordovician
determinations in the Nora Formation may be a reflection of the correlation problems involved with
the Whiterock Stage. Fortey (1980d) has suggested that the Whiterock is diachronous and often
underlain by an interval in which shelly fossils are rare, or a disconformity, equivalent at the least to
the upper part of the Arenig Series. Faunas of ‘Whiterock aspect’ (e.g. Wade \911a) may appear
within this interval if the appropriate facies is developed. To give one example. Hill et al. (1969,
pi. O-IV, fig. 3) figure Cacheoceras trifidum Flower, 1968 from the Nora Formation. Flower’s original
description cites the horizon as ‘certainly within Zone K of Ross (1951)’ (Flower 1968, p. 32). If the
base of the Whiterock is taken as the base of the succeeding Zone L, as is usual, then this occurrence
indicates lower, not middle, Ordovician. Correlation of Zone K with the late Arenig was suggested by
Fortey (1980u); so the cephalopod and trilobite evidence below are not greatly at odds.

The trilobite fauna described here is mostly endemic to Australia. Of the endemic genera,
Fitzroyaspis, Gogoella, and Nambeetella are all present in the Canning Basin in Arenig rocks (Legg
1976), but we have determined all our forms as new species so they cannot be used for precise
correlation. Presbynileus cf. utahensis is compared with a species from zone J of Utah (Hintze 1953)
which correlates with the middle part of the Arenig Series (Fortey 1976). Among the pelagic forms,
Carolinites genacinaca occurs in the earliest part of the Nora Formation only, the upper part having
C. cf. ekphymosus. Carolinites spp. with narrow fixed cheeks like the latter are not known outside
Australia before the late Arenig {Isograptus Zone and equivalents), while C. genacinaca is widespread
in mid-Arenig faunas over a great area (Fortey 1975). So, on the evidence of these species
comparisons, the Nora Formation is assuredly Arenig and probably belongs within the middle and
upper part of the Series (for informal definitions of lower, middle, and upper Arenig see Cooper and
Fortey 1982). If this assessment is correct, it means that several of the trilobite genera in the Nora
Formation are making their first appearances. Hungioides is elsewhere Llanvirn; Prosopiscus and
Pliorocephala have previously recorded ranges from Llanvirn to Caradoc; Annamitella is widely
distributed in rocks of late Arenig and Llanvirn age. For correlation purposes we place more
emphasis on the few, close species-level comparisons than on the generic composition as a whole.

FORTEY AND SHERGOLD; ORDOVICIAN TRILOBITES

319

Zonal subdivision

The Nora faunas divide broadly into two; since the facies is similar throughout we can recognize two
assemblage zones, with the bulk of the Formation lying in the upper Zone. The readiest zonal guides
are the extraordinary endemic asaphids of the genus Norasaphus which are also common in most
localities. The lower Zone of N. (N.) skalis is dominated by the eponymous species but also includes:
Lycophron sp. A., C. genacinaca, Annamitella strigifrons, Phorocephala cf. P. genalata Lu. The upper
Zone of N. (Norasaplntes) monroeae includes also: N. (N.) vesiciilosus (common), Lycophron rex, A.
glabra, Presbynileus cf. P. utahensis (Hintze), C. cf. C. ekphynwsus Fortey, Nambeelella embolion,
Hungioides acutinasus, G. brevis, and F. irritans. Prosopiscus spp. span both zones (text-lig. 3). The
few trilobites in common with the faunas of the Canning Basin indicate a broad correlation with
Fauna 3 of Legg (1978). Because trilobites become rare at the top of the Nora Formation it is not
possible to pick up overlap between the Nora faunas and those of the overlying Carlo Sandstone,
although sedimentation appears to have been continuous.

PRESERVATION OE THE TRILOBITES

Most of the trilobites are preserved as moulds in fine sandstones. All are fragmentary and some of the larger
pieces are broken. Some beds are full of fine trilobitic hash. The detail preserved on external moulds varies from
locality to locality, but at its best the preservation is good enough to show sculptural details. All specimens are in
full relief. A few beds in the lower part of the Nora Formation are carbonate-rich, and in these the trilobites are
preserved with their exoskeleton intact. The fragmentary nature of the fossils makes association of the different
parts especially difficult, and we have stated the reasons for making particular associations where these are not
obvious. It seems there has been post-mortem sorting of the trilobites, and it is not possible to identify
‘communities’ in the fauna. Yet the endemic character of most of the fauna indicates that the trilobites all lived in
an inshore, cratonic environment.

BIOGEOGRAPHIC ASSESSMENT OF THE NORA FORMATION FAUNA

Shallow-water cratonic faunas like that from the Nora Formation are the most sensitive indicators of
provincial affinities (Cocks and Fortey 1982), being specifically adapted to ambient temperature and
substrate conditions. It is appropriate to consider what the Nora trilobite faunas tell us about the
early Ordovician palaeogeography of Australia. Sedimentology of earlier Ordovician formations
( Radke 1981) indicates limestone deposition under tropical conditions; the occurrence in Australia of
early Ordovician cephalopods (Gilbert-Tomlinson, in Hill el cd. 1969), molluscs and conodonts
(Druce and Jones 1971 ) known elsewhere from areas lying near the palaeoequator, as well as typical
‘Pacific’ province graptolites in Victoria, all leave no reason to doubt that Australia straddled low
latitudes in the earlier part of the Ordovician. Larval dispersal doubtless varied considerably from
one group to another, and the trilobites tend towards endemicity more than, say, conodonts. This
means that the trilobites are a better guide to former continent separation than many other groups,
although concomitantly less useful in inter-regional correlation. Comparisons are considered at
generic and specific level.

In the first place there are a few elements in the Nora trilobite fauna which are familiar from North
America at a considerable distance around the equatorial great circle. These are Carolinites spp.,
a species intermediate between Goniophrys and Phorocephala ( = Carrickia), and a Presbynileus
species close to, if not identical with, one from Utah and Nevada. The first two named belong to the
pelagic family Telephinidae; their independence from facies type and continent distribution, and
their circum-equatorial distribution, has been familiar for some time (Fortey 1975). The last named is
so far unrecorded outside North America. These aside, there is little in common between faunas from
North America, or north-eastern Siberia, and that from the Nora Formation, and when apparently
similar forms appear (e.g. Lycophron gen. nov. compared with Isotelus) this is because of convergence
rather than phylogenetic continuity.

The most common trilobites in the Nora Formation, comprising about 85 per cent of the benthic

320

PALAEONTOLOGY, VOLUME 27

elements, are a group of curious endemic asaphids {Lycophron, Fitzroyaspis, Norasaphus), especially
the unique tuberculate genus Norasaphus which frequently covers entire bedding planes. Two other
genera, Gogoella and Nanibeetella, were described by Legg (1976) from the Canning Basin, north-
western Australia (but for taxonomic problems see systematic section). Well over half the benthic
forms are unknown outside Australia and include the dominant elements in the fauna.

Q 1
Eo

1

o

2

20
T 15-
“ 10-
5-

f (308/1)

128/9
128/8
1 28/7
128/6
128/5
128/4
128/3
1 28/2
128/1

SECTION 158 (308)

CL

o

-- T -- + +

2 -c

CL.

ce

5: a:

TEXT-OG. 3. Composite stratigraphic section through the Nora Formation with ranges of trilobites.

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

321

There remain a few genera which are ‘Gondwanan’ in distribution, notably Hungioides and
Prosopiscus. Both occur in southern China. Hungioides has a wide distribution through South
America ( = Argentinops Pfibyl and Vanek 1 980) to Bohemia and Thuringia. Prosopiscus occurs also
in the Himalaya (Salter 1865). Finally, the genus Annamifella is very widely distributed through
China, Kazakhstan, Vietnam, and with various occurrences off volcanic islands in Maine,
Newfoundland, and Anglesey, Wales. Although such a spread might suggest planktonic habits like
the Telephinidae there is nothing in the morphology of Annamifella to suggest that this was the case.

Only one explanation seems to us to explain the different elements combined in the Nora trilobite
faunas. An equatorial position explains the pelagic elements, the dispersal of which is not inhibited by
distance. Yet the dominance of peculiar endemics implies that platformal Australia was separated
from other cratonic areas near the Ordovician palaeoequator sufficiently to induce speciation among
available families— especially Asaphidae. A few forms {Annamifella, Presbynileus) were more widely
distributed, probably because of efficient larval dispersal. Finally, the presence of otherwise
Gondwanan elements suggests that Australia may have been attached to, or at least close to, the rest
of Ordovician Gondwanaland (as in the reconstruction of Scotese ef cd. 1979), sufficient for the
penetration of a few more eurytopic genera. Text-fig. 4 summarizes the relationships of the Nora
Formation trilobites to those of other areas.

It is interesting to note that the fauna from the Canning Basin described by Legg (1976) is the
closest to that from the Nora Formation (six genera in common), but it also includes a number of very
widely distributed benthic genera such as Triarfhrus, Ampyx, Slmmardia, and Ogygiocaris. Both the
lithologies and associated graptolites and conodonts (North Atlantic community type) indicate that
deeper water, peripheral-cratonic facies are represented in this area. These include biofacies deep
enough not to be restricted geographically in the same way as the on-craton faunas of Queensland
and the Northern Territory.

SYSTEMATIC DESCRIPTIONS

Terminology follows that of the Treafise on Invertebrafe Paleontology, Part O, Arthropoda I (Harrington,
Moore, and Stubblefield, in Moore 1959), with the addition of certain terms from Opik (1967) and Fortey (1975).
Glabella is usually understood to include the occipital ring. Systematic order is by family as they appear in the
Treatise.

SOUTHERN

EUROPE

ARGENTINA NORTH

AMERICA

SOUTHWEST

CHINA

CANNING NORA

BASIN FORMATION

20/A/I 8

TEXT-FIG. 4. Diagram to show relative resemblances at generic level of the trilobite
faunas from the Nora Formation to those of other areas. The scale ranges from six
genera in common in the Canning Basin to one only in southern Europe.

322

PALAEONTOLOGY, VOLUME 27

Family leiostegiidae Bradley, 1925

Discussion. We extend the concept of the Leiostegiidae to include a number of Ordovician genera
which have hitherto been referred to other families. In particular, we regard Annamitella (and its
three possible synonyms Bathyuriscops, Monella, and Proetiella) as belonging to a late radiation of
the leiostegiids in which the dorsal furrows are fully expressed. Species of this type have been regarded
as bathyurids (Whittington 1963). Recent revision of Canadian bathyurid genera (Fortey 1979)
shows that any resemblances to that family are misleading, and that Annamitella and related forms
are not closely comparable to either Bathyurinae or Bathyurellinae. In particular the long, anteriorly
truncate glabella (concave-sided in some species) and the straight, inward- and backward-directed IP
glabellar furrow are not bathyurid features; in the latter the IP furrows, when developed, are broadly
arched or hooked backwards. The pygidium is possibly most similar to that of Bathyurina among
bathyurids, but again the resemblance is misleading as there are twice as many axial segments in most
species of Annamitella, and the broad, convex pleural fields surrounded by a narrow, ‘rolled’ border
are leiostegiid features. It also seems likely that Agerina Tjernvik, 1956, which shares glabellar
characters with Annamitella, should be removed from the Bathyuridae. The pygidium in this genus is
much smaller than in Annamitella, however. Leiostegium itself and its close relative Lloydia are highly
eflaced genera, but since elfacement is of all trilobite characters the one most susceptible to
polyphyletic derivation, it is apparent that subdued furrows cannot be used in the definition of the
superfamily, as in the Treatise (Lockman-Balk in Moore 1959, p. 313). Of Lloydia species with
an elongate glabella like that of Annamitella we may cite L. oblonga (Billings) from the Levis
Conglomerate. There is also a tendency in Lloydia for the border to become reclined against the
glabella, a process carried to completion in Annamitella. Note also that there are strong apodemal
pits at the anterolateral corners of the glabella in L. hituberculata (Billings), pits which occur in
exaggerated form in the homologous site in Annamitella. It is also possible to see muscle insertion
areas on the glabella of L. spp., comparable in form (though more anteriorly placed) to those in
Annamitella.

Transitional forms between conventional Leiostegiidae and Annamitella occur in Tremadoc rocks.
In particular the genus Szeclmanella Lu, 1959 (type species S. szechuanensis — see Lu 1975, p. 3,
figs. 3-9) has a pygidium almost indistinguishable from that of Annamitella, while the cranidium,
although relatively effaced, clearly shows the backward-directed IP glabellar furrow, and the border
is tipped back against the front of the glabella. Co-aptative structures like those described below in
Annamitella have been described on Pagodia {Wittekindtia) variabilis by Wolfart (1970, pi. 8, fig. 5b).
Lu (1975, p. 458) also erected a new family Eucalymenidae for some Arenig-Llanvirn trilobites from
central China. Lu included two genera in the family: Eucalymene Lu, 1975 (itself a probable synonym
of Pseudocalymene Pillet, 1973) and Bathyuriscops Lisogor, in Keller and Lisogor, 1954. As discussed
below, the latter is a subjective synonym of Annamitella. The former resembles Szecliuanella and
difi'ers from Annamitella in its relatively small palpebral lobes being somewhat removed from the
glabella, and in the characters of the cranidial border. Eucalymene has strong glabellar furrows of
Annamitella type; its pygidium has interpleural furrows, and the pygidial border is almost obsolete.
These characters are scarcely of familial significance. Flence, we regard the Eucalymenidae as
synonymous with the Leiostegiidae.

Once the Leiostegiidae is extended to include forms en grande tenue, we can speculate on the
inclusion of other candidates within at least the same superfamily. When three glabellar furrows are
developed on Annamitella, they have a distinctive form, with IP steeply backward-inclined, 2P only
gently so, and 3P anteriorly directed close to 2P. The same kind of furrow arrangement is seen on the
diminutive earliest Canadian genus Missisquoia (particularly the type species M. typa, e.g. Stitt 1971,
pi. 8, fig. 2). The systematic position of Missisquoia has long been problematic; the family
Missisquoiidae Flupe, 1953, is generally regarded as of uncertain ordinal affinities, although
Shergold (1975, 1980, 1982) has consistently referred the family to the Leiostegiacea. We propose that
Missisquoia is a neotenous derivative from a leiostegiacean. Additional features suggestive of a
neotenous origin include especially the pygidium, in which the numerous segments are arranged as

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

323

if ‘ready for release’, and the extremely long, narrow glabella (which is like smaller Anmmntella).
Curiously, we have never seen leiostegiids in the same beds as Missisqiioia, and so it does not seem
probable that the small trilobite is simply a growth stage of a larger, more conventional leiostegiid.

Genus Annamitella Mansuy, 1920
Type species. Annamitella asiatica by original designation.

Revised diagnosis. Leiostegiid genus with dorsal furrows strongly expressed. Glabella long,
subparallel-sided to slightly tapering forwards, with a tendency towards a slight expansion of the
frontal lobe in some species. Two or three pairs of glabellar furrows, IP straight and strongly
backward-directed, 2P more transverse. Frontal border incorporated into glabella medially. Eyes
large, close to glabella; width of preocular cheeks correspondingly reduced. Genal spines long to
reduced. Pygidium strongly furrowed, four to nine axial rings, five or six pleural ribs. Axis extends to
near posterior margin. Pygidial border variable, usually narrow and convex, but may be almost
absent, to moderately broad and flattened.

Discussion. Dean ( 1973) and Whittington (1963) have noted that Bathyuriscops Lisogor, in Keller and
Lisogor 1954, Proetiella Harrington and Leanza, 1957, and Monella Bates, 1968 could all prove to be
synonyms of Annamitella. Our well-preserved material of Annamitella enables some clarification of
the problems involved.

The material of the type species A. asiatica Mansuy (1920, pi. 2, figs. Ict-k) is not entirely
satisfactory, being somewhat distorted internal moulds. Nevertheless, they do show the long glabella,
two pairs of glabellar furrows, and, most important, what Mansuy interpreted as a third pair of
glabellar furrows— in fact the trace on the internal mould of the lateral edge of the anterior border
(cf. PI. 38, fig. 4). The pygidium is like that of our Australian species, but with one less pleural rib
posteriorly, a narrower border, and one or two less axial rings. But these differences are scarcely of
generic standing, and we regard our assignment of the species from the Nora Formation as well-
founded. The type species of the other genera named above are also poorly preserved. Bathyuriscops,
type species i?.gra/zw/fl/ux( Weber 1948, pi. 1, figs. 22-24; also Keller and Lisogor 1954, pi. l,figs. 1-7;
Chugaeva 1958, pi. 1, figs. 1-3) from the Llandeilo of Kazakhstan, is also apparently known from
exfoliated material but, except for deeper glabellar furrows (and in some of the figured specimens
a greater median contraction of the glabella), the resemblance to our species is overwhelming;
Bathyuriscops is accordingly regarded as a subjective synonym of Annamitella. Proetiella from the
Llanvirn of Argentina is also closely similar in all major features, but one specimen of a cranidium of
the type species (P. tellecheai, see Harrington and Leanza 1 957, fig. 59, 3) shows what is probably a 3P
glabellar furrow immediately in front of 2P. The type species of Monella {M. perplexa Bates, 1968,
from the Arenig rocks of Anglesey) is very badly preserved but also shows evidence of the 3P glabellar
furrow (e.g. Bates 1968, pi. 11, fig. 18), so there may be a case for regarding the presence of the 3P
furrow as a generic discriminant. Unlike the type species of the other genera, M. perplexa has a broad
and probably flattened pygidial border. The Australian species have a broader anterior cranidial
border (vertically) than any of the species discussed so far, also well-developed co-aptative devices;
no other species have been described fully enough to be sure whether structures similar to the latter
were present or not. In any case we do not regard the presence of such structures as of generic
significance because they are found in several leiostegiids.

In summary, we incline to the view that Annamitella is the senior synonym of Bathyuriscops,
Proetiella, and Monella. Further information on P. tellecheai may possibly allow for the
discrimination of a second genus (of which Monella will be a junior synonym), but the presence of
a 3P glabellar furrow alone seems inadequate grounds for so doing at the moment. Taking the broad
view of Annctmitella advocated here the following described species may be assigned to the genus:
A. asiatica Mansuy, 1920; B. granulalus (Weber, 1948); P. tellecheai (Rusconi, 1951 ); B. kantsingensis
Chang and Fan, 1960; A. I borealis Whittington, 1963; M. perplexa Bates, 1968; A.l insulana Dean,

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PALAEONTOLOGY, VOLUME 27

1973; and guizhouensis Yin, 1978. North American and European occurrences seem to be confined
to Ordovician volcanic islands, but the Asiatic and southern hemisphere occurrences are apparently
in normal platform facies.

Annamitella strigifrons sp. nov.

Plate 38; text-fig. 5

Diagnosis. Annamitella species with granulate surface sculpture. Anterior border, incorporated into
glabella, forming a wide anterior wall on cranidium, carrying raised lines. Palpebral lobes very long,
anterior limit at or in front of 2P glabellar furrow. Pygidium with seven or eight axial rings, and
distinct, narrow convex border. Genal spines reduced to stub on large free cheeks.

Derivation of name. Latin strigifrons, ‘ridged-front’.

Holotype. Largely exfoliated cranidium, CPC 22642, from loc 071/4.

Other material. Cranidia, CPC 22643^22645, 22775, 22776; librigenae, CPC 22646-22648, 22777; pygidia, CPC
22649-22652, 22778-22782.

Occurrence. Lower part of Nora Formation, Iocs. 071/4, 126/3.

Description. Most of the material is stripped of exoskeleton, but enough remains to describe the dorsal surface of
this species. The cuticle is very thick and the internal mould retains little trace of the surface details. Since most
other species of Annamitella have been described from exfoliated material it is evident that many of the salient
details are not known from these. All furrows internally are deeper and wider.

TEXT-FIG. 5. Annamitella strigifrons sp.
nov. Reconstruction of cephalon and
pygidium, about x 2.

EXPLANATION OF PLATE 38

Figs. \-\5. Annamitella strigifrons sy>.no\. Loc. 071/4 (1-13) and loc. 126/3(14, 15). 1,2, CPC 22643, cranidium
retaining cuticle but damaged posteriorly; dorsal (1) and anterior (2) views to show incorporation of border
into frontal lobe of glabella, x 6. 3, 5, CPC 22642, holotype, well-preserved, but largely exfoliated cranidium
in dorsal (3) and anterior (5) views, x 6. 4, CPC 22644, typically preserved internal mould of cranidium, x 5.

6, CPC 22646, testate free cheek with ridges as well as tubercles, tilted forwards to show posterior margin, x 6.

7, CPC 22645, small cranidium, internal mould, x 7. 8, CPC 22647, small free cheek, internal mould showing

genal spine, x 7. 9, 10, CPC 22648, well-preserved free cheek in dorsal (9) and anterior (10) views, the latter
showing notch in border, x 7. 11, CPC 22649, lateral view of internal mould of pygidium, x6. 12,

CPC 22650, small pygidium, x 8. 13, CPC 22651, pygidium largely retaining cuticle, x 6. 14, 15, CPC 22652,
typical internal mould preservation of pygidium; dorsal view ( 1 4), and latex cast (15) from second specimen on
same rock piece photographed from anterior end to show doublure and pair of prominent prongs proving
relationship with pagodiids, x 6.

PLATE 38

FORTEY and SHERGOLD, Annamitella

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PALAEONTOLOGY, VOLUME 27

Cranidium of sagittal length about three-quarters maximum width across posterior margin. Glabella of
relatively low transverse convexity, not projecting above level of intraocular cheeks, sloping downwards steeply
over anterior half, width at mid-length a little over half maximum sagittal length (dorsal view). Glabella tapers
forwards gently, to minimum width at 2P glabellar furrows, with frontal lobe expanding in width more rapidly
towards anterolateral corners; front margin broadly rounded about mid-line. Deep occipital furrow, deepest
laterally and gently forward-arched medially, so that the occipital ring correspondingly widens medially. Two
pairs of glabellar furrows, both deep, short, and straight to very gently curved; IP opposite mid-length of
palpebral lobes, steeply inward-backward inclined, 2P about halfway between IP and anterior border (exsag.),
transverse to slightly backward inclined. No trace of 3P furrow on larger cranidia, but a small cranidium (PI. 38,
fig. 7) shows a faint pair of dimples which may be the vestiges of 3P. The small cranidium also has a narrower
glabella with less taper posteriorly. Axial furrows are hugely deepened at the anterolateral corners of the glabella
to form a pair of stout, ventrally-directed apodemes which presumably articulated with the wings of the
hypostoma. The anterior cranidial border is defined immediately in front of these pits, where it is narrow (exsag.)
and ridge-like. Adaxially the border merges with the front of the glabella, and the furrow defining it becomes
obsolete quite rapidly. The course of the border is, however, revealed by the ridges that cover its outward-facing
surface (PI. 38, fig. 2); one specimen shows a slight median dip in the height of the border.

Preocular cheeks steeply downward sloping, narrow (tr.) and convex. Gently arcuate palpebral lobe extremely
large, forward end closest to glabella, opposite or slightly in advance of outer end of glabellar furrow 2P,
posterior end at occipital furrow. Palpebral furrow deep, broadly outward-bowed, outlining a convex, relatively
narrow palpebral rim. Cheeks inside palpebral lobes are somewhat inflated. Postocular cheek triangular, width
(tr.) about two-thirds that of occipital ring, with deep transverse border furrow, and narrow, convex posterior
border which widens laterally. Sutures diverge at a high angle behind palpebral lobes; anterior divergence slight,
subparallel with anterior expansion of frontal glabellar lobe; they then appear to converge across downward
slope of border before running across edge of border to meet at mid-line. Dean (1973, pi. 7, fig. 8) seems to have
incorrectly interpreted the steep border as a rostral plate.

Surface sculpture on glabella and occipital ring of dense and posteriorly somewhat flat-topped tubercles,
stopping abruptly at fine elevated ridges on vertical part of border. Free cheek with outline in dorsal view almost
a quarter circle, genal fields broadly convex. Genal spine reduced to small stub, but still present on small cheeks
(PI. 38, fig. 8). Lateral border furrow exceedingly deep and narrow anteriorly, but shallowing abruptly and dying
out near genal angle. Major part of lateral border a steep, outward-facing ‘wall’ continuous with that on
cranidium, excavated by a deep notch at about mid-length. This notch received a prong on the pygidial doublure
during enrolment, a co-aptative device for this species. Exterior to the notch the border is less steep. Posterior
border carries a broad, backward-directed projection of about the same dimensions as the genal spine remnant;
presumably this was connected with the anterolateral articulation of the first thoracic segment. Eyes not
preserved; beneath the eye there is a deep, smooth groove. Sculpture on genal fields tuberculate like glabella. One
specimen has some of the tubercles carried on low ridges (PI. 38, fig. 6); we incline to the view that this is an
intraspecific variant, particularly as there is a tendency on the other cuticulate specimen for the tubercles to form
lines, and the cheeks agree in all other respects.

Pygidium with maximum width near anterior margin, 1-3- 1-4 times sagittal length including half-ring. Width
of axis at anterior margin equal to, or slightly exceeding, that of adjacent pleural field plus border. Axis tapers
initially very gently, becoming parallel-sided at fourth or fifth axial ring. Up to eight axial rings are present,
which become only slightly narrower (sag.) backwards, of which the first four or five are clearly defined, the
seventh and particularly the eighth (which is not discernible on some internal moulds) poorly so. Small rounded
terminal piece. Axis extends to border to which it slopes down almost vertically. Pleural fields broadly convex
(tr.). Pleural ribs flat-topped on exterior surface, separated by deep furrows of about half their width; on internal
moulds the dimensions are reversed, with furrows exceeding width of more rounded ribs. Six pairs of such ribs,
the last developed as triangular nodes adjacent to the terminal piece of axis. Border of same width as axial rings,
continuous around posterior perimeter, gently convex. Steeply downsloping triangular facets less than half
width of anterior margin. Pygidial doublure (PI. 38, fig. 15) steeply reflexed inside border and narrowing a little
medially. Anterolateral edges carry a pair of prominent, ventrally projecting prongs, visible as pits in the external
mould, which obviously served to engage with the notches in the cephalic border during enrolment. Exterior to
the prong there is a slight groove which probably received the lateral edge of the median part of cephalic border.
Small pygidium (PI. 38, fig. 13) is slightly longer, and shows only seven axial rings, with a longer terminal piece on
the axis.

Discussion. No other species of Annamitella is preserved as well as ,4. strigifrons, and comparisons are
generally difficult, although Dean (1973) showed that the exterior surface of A. insulana (Arenig-

FORTEY AND SHERGOLD; ORDOVICIAN TRILOBITES

327

Llanvirn, Newfoundland) was tuberculate, and with a comparable cranidial border (‘rostral plate’ of
Dean 1973, pi. 7, fig. 8). A. insulana is otherwise difficult to compare, being greatly distorted.
However, the palpebral lobe is assuredly shorter, and there is a genal spine in the adult of this species.
The type species (Mansuy 1920, pi. 2, figs, la-k) has a longer frontal glabellar lobe (more like our
immature specimen), the pygidial border appears to be much reduced, and there are apparently no
more than six axial rings. A. /jorcfl/w Whittington, 1963 apparently lacks tubercles externally, has the
2P glabellar furrow effaced, a narrower cephalic border, genal spines, and fewer pygidial segments
defined. A1 guizhouensis Yin, 1978 also has large eyes, but has a distinct 3P glabellar furrow, and the
pygidium has only four pairs of ribs. A. kantsingensis {C\vdng and Fan 1960, pi. 5, figs. 9-12) includes
granulate cranidia, but with the glabella expanding uniformly forwards, the one pygidium (ibid.,
fig. II) with a much broader, flattened border than in A. strigifrons. The latter character also
distinguishes A. monensis Bates, 1968 which additionally has a much narrower cranidial border,
defined faintly across the mid-part of the glabella. The pygidial proportions of A. tellecheai
(Harrington and Leanza, 1957) are closely similar to the Australian species; cranidial differences
include the probable presence of a 3P glabellar furrow, a (?) narrow cranidial border (ibid., fig. 59, 7),
and smaller palpebral lobes that fall short of the 2P glabellar furrow. The closest species to A.
strigifrons is A. gramdata from the Karakansk Formation of Kazakhstan (Keller and Lisogor 1954,
pi. 1, figs. 1-7; Chugaeva 1958, pi. 1, figs. 1-3). This species has eyes as large as A. strigifrons, and
seems to lack genal spines. Posterior forward taper of the glabella (adjacent to the IP lobe) is very
strong on the Kazakhstan species, however, and there are only four fully developed pleural ribs
on the pygidium, the fifth pair being represented by triangular remnants, as is the sixth pair on
A. strigifrons.

The very wide dispersal of a whole suite of closely similar species may lead one to wonder whether
this genus had pelagic habits. Curiously, Annann'tella does not seem to have penetrated into the
platform carbonates of either North America or north-east Siberia. It seems to be associated
particularly with clastic facies, as it is in Australia, and if this is the case then it must have spent much
of its life feeding near the bottom; but its dispersal remains wider than that of any other genus in the
Nora Formation apart from the truly pelagic Carolinites.

Annamitella brachyops sp. nov.

Plate 45, figs. 15-17

Diagnosis. Annamitella with short (exsag.) and highly curved palpebral lobes; glabella parallel-sided
and broadly rounded in front; IP glabella furrows gently curved. Sculpture of granules.

Derivation of name. Greek brachyops, ‘short-eyed’.

Holotype. Cranidium, CPC 22772, from loc. 308/1.

Material. Cranidia, CPC Tim, 22783-22785; pygidia, CPC 22774, 22786-22788; small librigena, CPC 22789.
Occurrence. Upper part of Nora Formation, Iocs. 158/4, 308/1.

Discussion. This second species of Annamitella differs in several features from A. strigifrons: (1 ) the
glabella is parallel-sided, rather than expanding at the frontal glabellar lobe which has a nearly
semicircular outline in A. brachyops’, (2) glabellar furrows, especially IP, are more transverse and
gently curved in A. brachyops’, (3) palpebral lobes are less than one-third (exsag.) length of whole
cranidium in dorsal view, compared with one-half or more in A. strigifrons’, (4) surface sculpture (but
only seen on one external) apparently of rather discrete, fine granules. The palpebral lobes are nearly
semicircular in A. brachyops. This difference makes the cranidium of A. brachyops relatively wide
compared with that of A. strigifrons, width across palpebral lobes 1-4 to 1-5 times sagittal length,
compared with 11 to 1-3 times in the latter. Pygidia of the two species are closely similar; posterior
border on A. brachyops may be slightly wider laterally, and only five pleural ribs are clearly
developed.

Of the species of Annamitella listed above only two have short palpebral lobes like A. brachyops :

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PALAEONTOLOGY, VOLUME 27

these are A. {Proetiella) tellecheai Harrington and Leanza, 1957, and the material of A.
CBathyuriscops') granulata illustrated by Weber (1948) and Chugaeva (1958). The type material in
Weber ( 1 948) of the latter has a long, narrow glabella with a strongly curved front margin, and the 1 P
glabellar furrow is certainly more oblique. The cranidium illustrated by Chugaeva (1958) from the
Kopalin Formation in Kazakhstan, of late Arenig to Llanvirn age (Fortey 1975, p. 31), is extremely
close to the Australian specimens, particularly with regard to the curved palpebral lobe symmetrically
disposed about IP, and may be conspecific. The Argentine species A. macrophthalma is also similar,
and apparently granulate (Harrington and Leanza 1957, fig. 59, 7 bottom right), and really differs
only in the distinctly truncate forward margin of the glabella, and the straight course of the IP
glabellar furrow.

Family asaphidae Burmeister, 1843
Subfamily asaphinae Burmeister, 1843
Genus Norasaphus gen. nov.

Diagnosis. Asaphine trilobites with tuberculate or smooth dorsal surfaces. IP glabellar furrows
excavated as deep pits, or uniting across glabella to cut off basal glabellar lobe. Frontal glabellar lobe
may become greatly inflated. Cephalic borders narrow but distinct. Long and narrow genal spines.
Eyes small, far back. Cephalic doublure broad under cheeks, greatly narrowing medially, with very
deep lateral marginal vincular furrow. Hypostoma with U-shaped notch, and maculae. Pygidium
relatively small, with or without narrow border, with two to five axial rings defined. Pygidial pleural
(and in some species interpleural) furrows exceptionally deeply incised.

Derivation of name. Combination of Nora (Formation) with Asaphus, to which genus the new one is related.

Discussion. This new genus includes the most extraordinary trilobites of the Nora Formation.
Looking at the most advanced species (PI. 40, fig. 1 ) it is difficult to imagine that such a P/?aco/7x-like
trilobite could be an asaphid at all. In particular, dorsal tuberculation is otherwise unknown (and
unlikely) in other asaphids, and its absence was used by Jaanusson {in Moore 1959, p. 334) as one
of the defining characters of the family. However, we are certain that we have good grounds
for assigning the closely related set of species from the Nora Formation to the Asaphidae. The
stratigraphically earliest species, N.(N.) skalis, is also the most primitive, and, if we are able to ignore
the dorsal tuberculation, is in most respects a typical asaphine, with its deep IP apodemal furrows,
well-defined occipital ring, and immediately pre-occipital glabellar tubercle. It may be compared with
a genus like Basiliella Kobayashi, for example. The hypostoma is conventionally asaphine, as is the
lateral vincular furrow on the free cheek. Subsequent evolution of the Norasaphus group produces
exaggeration of the aberrant features. The IP glabellar furrows become united across the glabella,
producing a transverse furrow which chops off a basal median glabellar lobe. The posterior lobes
adjacent to the glabella are discretely defined to become bacculae. These advanced characters are the
basis of the subgenus Norasaphus (Norasaphites).

Within Norasaphus {Norasaphites) one species {N. monroeae) loses cephalic tuberculation, acquires
stalked eyes, and a tendency towards posterior effacement, while N. (Norasphites) vesiculosus takes
the peculiarities of N. {Norasaphus) skalis further, with very dense tuberculation and exceptional
inflation of the frontal glabellar lobe, which in many specimens overhangs the anterior border, and
highly incised furrows in all parts. This species is furthest removed from conventional asaphids, and
yet we presume that all these profound anatomical modifications took place within the span of
deposition of the Nora Formation, only a part of the Arenig Series (say about 5 million years). It is an
indication of the flexibility of the external skeletal structure of the trilobites that such modifications
can occur even in a generally conservative group like the Asaphidae when circumstances permit, and
shows that caution is necessary to determine familial affinities in the face of homeomorphic
resemblance.

We considered the possibility that the new forms merited subfamilial status. Since N. {N.) skalis is
clearly an asaphine {sen.su Fortey 1980a), and the new species taken together are more closely related

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

329

to other Asaphinae than to Niobinae or Isotelinae, in a phylogenetic classification they are to be
included in the first-named subfamily, of which they are an extraordinary and probably short-lived
branch.

What circumstances may be invoked to explain their unique modifications? Most inshore asaphids
are the most highly effaced of the group, and their cuticle is not exceptionally thick (see, for example,
Isoteloides in Fortey 1979). By contrast Norasaphus has a very thick cuticle (PI. 39, fig. 1 ), but occurs
with isotelines which are not unusual in this regard. In other shallow-water faunas of about the same
age, for example the St. George (Catoche Formation) fauna of western Newfoundland, smooth
isotelines occur with other trilobites with tumid glabellar frontal lobes, elevated eyes far back, thick
cuticles, and strong tuberculate sculpture. In the St. George, the closest trilobite is Petigunis
(redescribed by Fortey 1979), an anomalous bathyurid. Petigunis also has a pygidium with strong
interpleural furrows, and a narrow border, superficially like that of Norasaphus. It is unlikely to be
coincidence that both Norasaphus and Petigurus are convergent with Phacops, which was also
adapted to carbonate facies of epeiric seas, in the Devonian. Phacopid convergence with Norasaphus
extends even to pygidial details; the pygidium of N. monroeae is strikingly like that of Eophacops. We
term this repeated morphological type the phacomorph design. Tubercles may have been partly
concerned with strengthening the cuticle, but those of some of the phacopids have sophisticated
internal structures (‘pseudo-tubercles’ of Miller 1 976) which might argue for a more specific function.
Eldredge (1971) has suggested that phacopids ‘relied more heavily on labral secretion than
appendage manipulation for ingestion’ of food, which he associated with an oesophagal expansion
housed beneath the inflated frontal glabellar lobe, like that so conspicuous on N. (Norasaphites)
vesiculosus. The basal transglabellar furrow in phacopids and Norasaphus (Norasaphites) was
presumably connected with the insertion of muscles for a powerful posterior appendage pair.

Whatever the functional explanation of phacomorph design, it was obviously one which could
arise from different phylogenetic sources at different times, and was associated with inshore, or at
least shallow-water carbonate habitats. In the case of midcontinent faunas, and both the St. George
in Newfoundland and the Nora Formation in central Australia are typical examples, there seem to
have been a limited number of potential stocks from which phacomorphs could be derived. We
assume that the opportunity to occupy the phacomorph niche (or niches) was taken by the asaphids
in Australia and the bathyurids in Newfoundland; in both cases their tenure of the niche was short-
lived. The morphological distance travelled in a comparatively short time was considerable in both
cases, which may relate to theories that the rates of evolution of inshore trilobites in warm climates
were relatively rapid (Eldredge 1974; Fortey 19806).

Subgenus Norasaphus subgen. nov.

Type species. N. (N.) skalis sp. nov.

Diagnosis. Subgenus of Norasaphus with tuberculate sculpture: glabellar furrows of normal asaphine
type. Narrow pygidial border.

Norasaphus (Norasaphus) skalis sp. nov.

Plate 39; text-fig. 6

Diagnosis. Norasaphus (Norasaphus) is monotypic; diagnosis follows that of subgenus.

Derivation of name. Greek skalis, a hoe or mattock, referring to the shape of the anterior border.

Holotype. Cranidium, CPC 22653, from red limestones near base of Nora Formation, loc. 071/4.

Other material. Cranidia, CPC 22654-22660, 22790 22793; librigenae, CPC 22664, 22665, 22801, 22802;
hypostomata, CPC 22666, 22667, 22803; pygidia, CPC 22661-22663, 22794-22800.

Occurrence. Numerous in lower Nora Formation at Iocs. 071/4, 127/2, 127/4, 127/12, 127/15.

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PALAEONTOLOGY, VOLUME 27

Description. This species is known from well-preserved material in limestone, preserving details of the external
cuticular surface. Cranidia have maximum width at posterior margin, only slightly greater than width across
palpebral lobes, and about one and a half times maximum glabellar width at frontal lobe. Sagittal cranidial
length about equal to maximum width. Glabella with maximum convexity across frontal lobe, minimum
convexity at median constriction. Frontal lobe broadly pear-shaped, well-defined all round, posterior part
enclosed by axial furrows which diverge forwards to enclose an angle of 50-70 degrees. These axial furrows
continue backwards to form powerful, broad, deepened IP apodemes. Axial furrows again shallow posteriorly
to continue as depressions between basal glabellar lobe and inflated genal lobes to meet lateral end of occipital
furrow. Basal genal lobes fusiform, inclined inwards-forwards, and greatly inflated, extending forwards to
a point near anterior edge of palpebral lobes. These basal lobes are mostly outside the area subtended by the
occipital ring, and they are of extraglabellar origin, being produced by an adaxial inflation of the genal region.
Occipital furrow transverse, and especially deep at either side; occipital ring of uniform width (sag., exsag.)
deeply downcurved laterally to meet posterior border. Presumed axial furrows passing on outside of basal lateral
glabellar lobes, diverging backwards, very shallow anteriorly and deepening to border furrow. Strong glabellar
tubercle in front of occipital furrow. Palpebral lobes elevated to about the level of frontal glabellar lobe, small
(about one-sixth glabellar length) and close to axial furrows, strongly curved to slightly more than a semicircle.
Apparently narrow palpebral rims. Postocular cheeks acutely triangular, transverse width about half that of
occipital ring, posterior border narrow (exsag.) and highly convex, as defined by a deep border furrow. Preocular
sutural divergence somewhat exceeds that of anterior section of axial furrows so that the downward-sloping
preocular cheeks, which are very narrow (tr.) in front of eyes, increase gradually in transverse width forwards.
Sutures converge across anterior border, presumably running marginally to meet at mid-line. Border abruptly
breaks downward slope of preocular cheeks, being flat to slightly concave with rounded rim. Anterior edges of
border converge towards mid-line at a large obtuse angle, but rounded medially. Border furrow broad and
diffuse; preglabellar field lacking.

TEXT-FIG. 6. Norasaphus (Norasaphus) skalis
gen. et sp. nov. Reconstruction of cephalon
and pygidium, xl.

EXPLANATION OF PLATE 39

Figs. 1-8. Norasaphus (Norasaphus) skalis gen. et sp. nov. Lower part of Nora Formation, loc. 071/4(1, 3 -8) and
loc. 127/12(2). l,CPC22653,holotype, well-preserved but slightly incomplete cranidium, x 6. 2, CPC 22654,
22655 , latex cast taken from external mould of two cranidia, x 4. 3, CPC 22664 free cheek, plan view partly
exfoliated, x4. 4, CPC 22656, latex cast from small cranidium from same bed as holotype, x 6. 5, CPC 22661,
incomplete large pygidium, showing surface sculpture, x 4. 6, CPC 22662, small pygidium, excavated to
doublure on right, x 6. 7, CPC 22666, hypostoma, exfoliated, x 6. 8, CPC 22663, large, exfoliated pygidium;
dorsal surface sculpture is not reflected on the internal surface, and more axial rings are visible, x 3.

PLATE 39

FORTEY and SHERGOLD, Norasaphus (Norasaphus)

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PALAEONTOLOGY, VOLUME 27

Surface sculpture of tubercles and granules on glabella, occipital ring, and anterior rim. Tubercles sparse but
large on posterior median lobe of glabella and occipital ring; these large tubercles reflected also on internal
moulds, but pre-occipital glabellar tubercle exceeds all in prominence. Finer tubercles on frontal glabellar lobe,
basal lobes, and fine granules on forward part of anterior border; these not reflected on internal moulds.

Free cheeks with long, slightly curved genal spine. Genal field convex (exsag.) with zone of tubercles
surrounding base of eye but not extending anteriorly or laterally. Deep posterior border furrow narrows
abruptly abaxially over region corresponding to inner margin of doublure. Lateral border continues from
cranidium narrowing round periphery of cheek and passing on to genal spine, which thereby carries a groove
down its exterior surface. Eye strip-like, slightly elevated from cheek on smooth socle. Doublure broad beneath
genal fields, recurved beneath cheek well beyond border but narrowing as the suture is approached to form
a comparatively narrow band extending anteriorly beneath cranidial border to median suture. Deep vincular
furrow about one-third length of lateral border on cheek, bounded by ridges on doublure. Terrace lines on
ventral doublural surface not reflected on its dorsal surface.

Hypostomata of type consistently found with Norasaphus, and therefore associated with some confidence.
Conventional asaphine type, similar to that of Basilicus, for example, with subcircular middle body, ill-defined,
carrying pair of forward-inclined, smooth maculae. Lateral borders wide, with maximum width at about half
hypostomal notch with shape like inverted U. Terrace lines relatively fine and transverse on middle body, parallel
to margins of borders.

Pygidium with sagittal length about twice maximum width, pleural fields convex, with steep downward slope
to border. Axis occupying less than one-third pygidial width at anterior margin, and extending to posterior
border, with rounded tip; gentle axial taper encloses angle of no more than 20 degrees. On specimens preserving
cuticle two axial rings are clearly defined, separated by deep ring furrow. Ring furrows become faint after that
defining second axial ring, definition of third and fourth rings poor, principally on flanks of axis. Internal moulds
show up to seven faint rings. Articulating half-ring of similar (sag.) length as first axial ring. Dorsal surface shows
four pairs of pleural furrows, the first of which extends to the border, the posterior three progressively shorter
and further removed from border. Interpleural furrows divide the first three ribs just anterior to centre line,
much shallower than pleural furrows, and not reflected on internal mould. Broad, triangular facet about twice
transverse width of border. Border gently downsloping laterally, becoming progressively narrower and more
steeply sloping posteriorly. Definition of border sharper on small specimens. Sculpture, mostly on axis and faint
on pleural ribs, tubercles like those on glabella; few faint scalloped terrace lines on border.

Discussion. This is the only species attributed to Norasaphus (Norasaphus). Small cranidia show that
the ‘basal glabellar lobes’ originate from an extra-glabellar position adjacent to the base of the
glabella (PI. 39, fig. 2). With increase in size they tend to migrate adaxially. In many Asaphinae the
posterior part of the glabella tends to effacement, and in these circumstances it can be difficult to
distinguish the ‘glabellar’ from the genal areas. The distinguishing asaphine feature appears to be the
deepening of the axial furrows at what we have termed the IP position at the rear end of the frontal
lobe, a feature which remains constant whatever the degree of effacement on the rest of the cranidium.

Subgenus Norasaphites subgen. nov.

Type species. N. (Norasaphites) monroeae sp. nov.

Diagnosis. Norasaphus species with smooth or tuberculate exoskeleton. IP united across glabella to
form definite transglabellar furrow. Pygidial border absent.

Derivation of name. Diminutive of Norasaphus.

Species included. N. (Norasaphites) monroeae sp. nov., N. (N.) vesicidosus sp. nov.

Norasaphus (Norasaphites) monroeae sp. nov.

Plate 40, figs. 1-4, 6 10; text-fig. 7
1980 Asaphid gen. nov.; Fortey, p. 256, fig. 2.

Diagnosis. Norasaphus (Norasaphites) species lacking surface sculpture; frontal glabellar lobe not
greatly inflated; eyes strongly stalked. Pygidium tending to effacement on posterior part of axis and
pleural lobes, with only three pairs of pleural furrows.

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

333

Derivation of name. Dedicated to Marilyn Monroe.

Holotype. Cranidium, CPC 22668, from loc. 158/9.

Other material. Cranidia, CPC 22669, 22804-22822; pygidia, CPC 22670-22672, 22833-22839; librigenae, CPC
22673, 22674; hypostomata, CPC 22675, 22676, 22843.

Occurrence. Upper part of Nora Formation, Iocs. 015/6, 122/1?, 158/4, 158/8, 158/9, 158/13, 158/15,308/1.

Description. Cranidium of relatively low transverse convexity compared with other species of Norasaphiis.
Glabella well-defined, hardly inflated, width at narrow ‘neck’ slightly less than half maximum width at
anterolateral corners. The narrowest part of glabella lies at about one-quarter length of pre-occipital glabella.
Deep axial furrows converge forward gently to this point, in front of which they diverge markedly around
forward lobe of glabella, enclosing an angle of 75-80 degrees. Front margin of glabella broadly rounded about
mid-line. Transglabellar furrow straight, less deep than occipital furrow. Occipital ring not as wide (tr.) as widest
part of glabella, and of length (sag.) only slightly less than that of posterior glabellar lobe. Axial furrows are
shallower where defining lateral ends of occipital ring. Occipital furrow narrow, deep, and straight transverse.
Inflated bacculae three times longer than wide, inclined gently inwards until cut off by forward expansion of
glabella at a point a little in front of the transglabellar furrow. Palpebral lobes greatly elevated above level of rest
of cranidium, such that the intraocular cheek is nearly vertical, and sited at about mid-cranidial length. Narrow
( tr. ) preocular cheeks also inward-inclined, with outline closely following that of forward glabella lobe. Anterior
border of cranidium acuminate, almost flat, wider medially, and at lateral edges. Posterior cranidial border
convex, pointed, extending laterally to a point just beyond that of anterior cranidial border. External surface of
cranidium lacking tubercles. Small cranidia (sag. length 0.5 cm or less) differ from the larger ones in having less
marked expansion of the frontal glabellar lobe, and the pre- and postocular sutures are also less divergent.

Free cheek generally like that of N. (N.)skalis, but lateral border furrow shallower, and thegenal spinels much
shorter, pointed, not curved. The posterior border furrow becomes completely effaced as it approaches the
doublure. The eye is borne on a distinct stalk (PI. 40, fig. 6), such that it must have projected above the level of the
rest of the trilobite.

Hypostoma rather flat, anterior width (tr.) of middle body about two-thirds maximum width across broad
wings. Lateral margins of wings converge backwards to almost pointed tips separated by wide, shallow fork.
Middle body not well-defined posteriorly, tapering to forward edge of fork, with pairs of shallow maculae.

Pygidium about two-thirds as long as wide, convex. Axis occupies more than one-third of total pygidial width
anteriorly, tapering posteriorly such that the axial furrows enclose an angle of 25-30 degrees, at the same time
becoming less convex so that its tip is not clearly defined from the postaxial field. Only two narrow axial rings are
defined across the mid-part of the axis, and the second of these is faint. Third and fourth rings faintly indicated
laterally. Flalf-ring of about same width (sag.) as first axial ring. Pleural furrows relatively narrow, first two pairs
almost reaching margin, third usually extending no more than half-way across pleural fields (very faint fourth
pair suggested on some specimens). Broad facets extend close to axis. Small pygidia relatively more transverse,
with axis better defined.

TEXT-FIG. 7. Norasaphus (Norasaphites)
nionroeae gen. et sp. nov. Reconstruction
of cephalon and pygidium, x 1 -5.

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PALAEONTOLOGY, VOLUME 27

Discussion. This species is distinguished from N. {Norasaphites) vesiculosus below. The relatively low
convexity, strongly stalked eyes and lack of surface sculpture are features which contrast with N. {N.)
skalis stratigraphically below it; if we are correct in proposing a derivation of N. {Norasaphites)
monroeae from this more generalized form, there should be a functional explanation for the changes.
One suggestion is that N. monroeae was adapted to shallow infaunal life. The relative smoothness,
and loss of convexity on the frontal glabellar lobe would have reduced sediment resistance during
burial, and the high-perched eyes would have protruded above the sediment surface even when the
rest of the animal was completely concealed. By contrast, N. {Norasaphites) vesiculosus carries the
morphological peculiarities (tuberculation, glabellar inflation) of N. {Norasaphus) skalis even further
and it was presumably a surface dweller. So in this case the speciation events producing monroeae on
the one hand and vesiculosus on the other were by niche partitioning, presumably operating
sympatrically or parapatrically.

Norasaphus {Norasaphites) vesiculosus sp. nov.

Plate 40, fig. 5; Plate 41; text-fig. 8

1969 Proetusl sp.; Gilbert-Tomlinson in Hill et al., pi. O-V, figs. 5, 6.

Diagnosis. Norasaphus {Norasaphites) species with tuberculate surface sculpture, frontal glabellar
lobe greatly inflated, often overhanging border; eyes not so elevated as N. {Norasaphites) monroeae.
Pygidium with three or four strong pleural ribs.

Derivation of name. Latin vesiculosus, ‘covered in blisters’.

Holotype. Cranidium CPC 22677, from loc. 158/8-9.

Other material. Cranidia, CPC 22678-22685, 22844-22857; pygidia, CPC 22686, 22687, 22858-22862;
librigenae, CPC 22688, 22689, 22863-22865; hypostomata, CPC 22690, 22866.

Occurrence. Higher parts of Nora Formation, Iocs. 015/6, 122/1, 122/4, 126/1-7, 126/11, 139/4, 156/1, 158/4,
158/8, 158/9, 158/10, 308/1.

Discussion. This species is best discussed briefly in relation to N. {N.) monroeae, from which it differs
in the following features: (1) The frontal lobe of the glabella is subspherical rather than wedge-
shaped. Especially in stratigraphically later examples this lobe becomes enormously inflated, often
becoming extended into an almost conical protuberance. The frontal lobe overhangs the cranidial
border, which becomes very narrow medially, forming a convex rim. (2) The anterior divergence of
the facial sutures is lower. (3) The glabella (and adocular part of the free cheek) carries a sculpture of
tubercles, which are quite coarse on some specimens; internal moulds are smooth. (4) The bacculae
do not slope inwards. (5) The palpebral lobes, although elevated, are not higher than the frontal
glabellar lobe; the eye is not stalked. (6) The free cheek is acutely triangular, with a distinct, narrow
lateral border, the border furrow continuing on to the genal spine as a groove. (7) The pygidium is
similar to that of N. {N.) monroeae in lacking a border, and only two axial rings are clearly defined, the
posterior part of the axis being smooth except for faint lateral indications of two or three segments.

EXPLANATION OF PLATE 40

Figs. 1-4, 6-10. Norasaphus {Norasaphites) monroeae subgen. et sp. nov. Loc. 158/9 (1, 2, 4, 6, 7, 9, 10), loc. 308/1
(3), and loc. 0 1 5/6 (8 ). 1 , 2, 1 0, CPC 22668, latex cast from holotype, external mould of cranidium in dorsal ( 1 ),
anterior(2), and oblique (10) views, x 6. 3, CPC 22669, internal mould of cranidium, x4. 4, CPC 22670, latex
cast from pygidium, external mould, x 6. 6, CPC 22674, latex cast from fragmentary free cheek, to show
stalked eye, x 6. 7, CPC 22675, internal mould of hypostoma probably belonging to this species, x 6. 8, CPC
22673, internal mould of free cheek, x 2. 9, CPC 22671, latex cast of external mould of pygidium, x 6.

Fig. 5. N.(N.) vesiculosus subgen. et sp. nov. CPC 22690, loc. 158, internal mould of hypostoma, x 6.

Fig. 1 1. Asaphid gen. et sp. indet. CPC 22770, lowest Nora Formation, loc. 071/4, pygidium, x 6.

PLATE 40

FORTEY and SHERGOLD, Norasaphus (Norasaphites)

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PALAEONTOLOGY, VOLUME 27

However, the tip of the axis is defined close to the posterior margin, and the pleural furrows are broad
and deep, with the first three pairs running close to the margin and the fourth to about two-thirds
the extent of the anterior pairs. There remains only a small, smooth triangular area adjacent to the
posterior part of the axis. The areas between the pleural furrows, and between the first pair of furrows
and the facets, are elevated into distinct ribs, which die out shortly before the pygidial margin. We
have not, however, detected coarse granulation on the pygidial axis.

We admit a great deal of intraspecific variation in our concept of N. {N.) vesiculosus. This
particularly relates to the development and sculpture of the anterior glabellar lobe. In some
specimens this lobe is only about one and a half times the width (tr.) of the posterior glabellar lobe, in
others fully twice as wide (PI. 40, fig. 2); the inflation of the lobe varies also, some specimens becoming
almost pointed. The coarseness of the tuberculation is variable: some specimens are coarsely
tuberculate all over the glabellar lobes, others grade into fine granulation over the mid-part of the
anterior lobe (PI. 41, fig. 9). The more finely tuberculate form is associated with a free cheek which
carries a longer, more curved genal spine than the typical form, which is that shown on the
reconstruction in text-fig. 8.

The more inflated form seems to come from higher in the Nora Formation than the granulose
form. However, there appears to be every transition between these various morphs and, for this
reason, we take a taxonomically conservative view and incorporate them within a single speeies. The
great variability is presumably another indication of the processes of endemic speciation at work, and
would repay study with larger populations than we have available.

EXPLANATION OF PLATE 41

Figs. 1-14. Norasaphus (Norasaphites) vesiculosus subgen. et sp. nov. All latex casts from external moulds.
1 , CPC 22678, loc. 308 / 1 , cranidium of morph with pointed frontal glabellar lobe, x 4. 2,5,6, CPC 22677, loc.
158/8-9, holotype in dorsal (2), anterior (5) ( x 6), and lateral (6) ( x 3) views. 3, CPC 22688, loc. 308/1, free
cheek; note sculpture around base of eye, x 4. 4, CPC 22679, loc. 308/1, cranidium of morph with especially
expanded (tr.) frontal glabellar lobe, x 6. 7, CPC 22680, loc. 122/4, cranidium of morph with relatively
subdued tuberculation, but glabellar proportions like holotype, x 3. 8, CPC 22681, loc. 126/3, small
cranidium, x 3. 9, CPC 22682, loc. 126/7, cranidium, with incomplete free cheek on left; this is the morph with
expanded frontal lobe (as fig. 4), but with frontal lobe granulate rather than tuberculate, and somewhat
elevated palpebral lobes, x 3. 10, CPC 22686, loc. 308/1, pygidium, x2. 11, CPC 22687, loc. 015/6,

incomplete pygidium, showing granulation on terminal piece of axis, x 2. 12, CPC 22689, loc. 126/7, free
cheek associated with the sparsely tuberculate morph, same locality; cast taken to show ventral surface with
doublure and vincular notch, x 3. 13, 14, CPC 22683, loc. 126/7, cranidium of sparsely tuberculate morph,
dorsal ( 1 3) and lateral ( 14) views, x 3.

PLATE 41

mm

FORTEY and SHERGOLD, Norasaphus (Norasaphites)

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PALAEONTOLOGY, VOLUME 27

Subfamily isotelinae Angelin, 1854
Genus Fitzroyaspis Legg, 1976

Type species. Priceaspis (Fitzroyaspis) guppyi Legg, 1976.

Discussion. Effaced asaphids are always a problem to classify, and the new species from the Nora
Formation, described below, is no exception. Its few distinctive characters include a well-defined
cephalic border, rounded genal angles, large medially placed eyes, and low sutural divergence behind
the eyes. The pygidium is characteristically asaphid, but with no particularly distinctive features. Few
asaphids have facial sutures that are not highly divergent behind the eyes, and of those with weakly
divergent sutures (e.g. Asaphellus) most have small eyes and long genal spines. Isotelus itself has
generally smaller eyes, the cephalic border is ill-defined, and the pygidium is characteristically
triangular in outline; any resemblance between this typically North American genus and the
Australian form is because of convergence. The same probably applies to such genera as Anataphrus
and Homotelus in which effacement has gone even further; these genera lack defined cranidial
borders altogether, although the general cranidial outline of certain species of Anataphrus is like that
of our material. Legg (1976) described the type species of Priceaspis (Fitzroyaspis) from the early
Arenig of the Canning Basin. The general cephalic structure is like our species, especially with regard
to the well-defined, but narrow cephalic border. The pygidial border is comparatively poorly defined,
a difference we do not consider of generic importance. The major point of difference lies in the more
posterior extension of the eyes in F. guppyi, with a concomitant high angle of postocular suture
divergence, and the presence in that species of distinct posterior border furrows. The cranidium of
our species is also somewhat broader in proportion to its length. We regard these differences as of
specific significance only, effectively produced by an anterior migration of the eyes compared with
F. guppyi. A similar ‘trend’ happens also in Isotelus comparing the position of the eyes and sutural
form in I. copenhagenensis Ross and Shaw (1972, pi. 2, fig. 8) with 7. gigas Dekay. Legg separated
Fitzroyaspis as a subgenus of his relatively uneffaced genus Priceaspis', with the inclusion of a second
species in Fitzroyaspis we prefer to accord it full generic status until the phylogenetic relationships of
these asaphids can be fully worked out.

Fitzroyaspis irritans sp. nov.

Plate 42, figs. 1-4, 7; text-fig. 9

Diagnosis. Highly effaced Fitzroyaspis lacking cephalic posterior border furrows; eyes smaller than in
F. guppyi', postocular sutures divergent at a low angle; pygidium with border expressed laterally.

Derivation of name. Latin irritans, ‘irritating’, referring to the problem of its generic assignment.

Holotype. Cranidium, CPC 22691, from loc. 158/10.

Other material. Cranidia, CPC 22692, 22867-22878; hypostomata, CPC 22697, 22888; librigenae, CPC 22693,
22694, 22879-22881; pygidia, CPC 22695, 22696, 22882-22887.

OccwTcncc. Through most of higher Nora Formation, Iocs. 122/4, 126/7, 158/4, 158/10, 158/15.

EXPLANATION OF PLATE 42

Figs. 1 -4, 7. Fitzroyaspis irritans sp. nov. Middle to upper Nora Formation. 1 , CPC 22697, loc. 1 58/4, latex cast
of hypostoma most probably belonging to this species, x 3-5. 2, CPC 22691, loc. 158/10, latex cast taken from
holotype, external mould of cranidium, x 2. 3, CPC 22693, latex cast taken from external mould of free cheek,
X 2. 4, CPC 22694, loc. 158/15, free cheek, prepared to show doublure and vincular furrow, x 3. 7, CPC
22695, loc. 126/7, latex cast from external mould of pygidium, x 4.

Figs. 5, 6. Preshynileus cf. P. utahensis Hintze, 1953. Upper Nora Formation. 5, CPC 22710, loc. 308/1, internal
mould of cranidium, x 3. 6, CPC 22712, loc. 158/1 1, internal mould of pygidium, x3.

PLATE 42

FORTEY and SHERGOLD, Fitzroyaspis and Preshynileiis

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PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 9. Fitzroyaspis irritans sp. nov. Reconstruction
of cephalon and pygidium, x 1 .

Description. Cranidium with width across palpebral lobes 0-85 of sagittal length on large cranidia; small cranidia
tend to be more elongate. Very low convexity across the axial region suggesting glabella forward-tapering from
prominent articulating notches at posterior margin, opposite hind ends of palpebral lobes. Steep downturn
around frontal glabellar lobe and in front of palpebral lobes on to virtually flat cranidial border, which does not
exceed one-eighth (and may be as little as one-tenth) of the total glabellar length at mid-line. Palpebral lobes
medially placed, tilted only slightly upwards, and with length (exsag.) one-third glabellar length. Facial sutures
distinctly isoteliform, diverging at a low angle (20-40 degrees) in front of the eyes, and at a scarcely higher angle
behind the eyes. The gently downsloping, triangular postocular cheeks so defined terminate acutely. Internal
moulds show prominent glabellar tubercle (not visible externally) placed at about one-quarter glabellar length.
Also some internal moulds show what are probably prominent IP muscle impressions constricting the glabella
shortly in front of the tubercle. Small cranidia of sagittal length 1 cm or less have more divergent sutures in front
of and behind the eyes, but the fixed cheeks do not become extended (tr.) in the manner of F. guppy i. We
tentatively associate a hypostoma (PI. 42, fig. 1) of typical isoteline type, which does not belong to Norasapinis,
and is from the same bed in which F. irritans is common.

Free cheek somewhat longer (exsag.) than wide in plan view, showing border becoming narrower and feebler
towards the broadly rounded genal angle. On doublure vincular furrow runs parallel to border.

Pygidium two-thirds as long as wide, with gently convex pleural fields sloping down to ill-defined, still sloping
border, which peters out around tip of axis. Pleural fields unfurrowed. Axis extends to more than two-thirds
pygidial length; on the external moulds no ring furrows are visible, but on internal moulds four (?five) rings may
be visible, of which only the first two are defined across the mid-part of the axis. Doublure broad, and concave
towards outer edge, carrying at least twenty terrace lines which are approximately parallel to the posterior
margin peripherally but slope backwards at a much more acute angle to the sagittal line near inner edge of
doublure. Lateral tip of doublure sharply downward-flexed.

Discussion. F. irritans is distinguished from F. guppyi by its smaller eyes and wider cranidium, and by
the low angle of divergence of the facial sutures behind the eyes; the pygidial border of the new
species is better defined. In addition to the genera discussed above there is a certain resemblance
between the cranidium of F. irritans and that of Ptyocephalus, especially P. accliva (Hintze 1953,
pi. 15, fig. 2). However, the important features of Ptyocephalus are outside the axial region —
a compression of the lateral pleural area resulting in laterally truncate free cheeks and pygidium.

Genus Lycophron gen. nov.

Type species. Lycophron rex sp. nov.

Diagnosis. Large, effaced isotelines with elongate, triangular cephalon and pygidium. Cephalon with

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

341

extremely narrow, acute lateral borders. Pygidium usually lacking border altogether. Hypostoma
narrow (tr.) anteriorly, with very long fork with pointed tips.

Derivation of name. After the third-century Greek philosopher Lycophron.

Discussion. This genus resembles Megistaspidella and Isotelus. It is convergent upon both, but we
believe that there is no phylogenetic connection. Megistaspidella is confined to the Baltic continent in
the early middle Ordovician, and is related to the Megistaspis plexus of species. Its pointed, unforked
hypostoma lies at the opposite morphological extreme among asaphids to that of Lycophron, and is
sufficient evidence of their separate origins. Isotelus includes some species, such as I. gigas, which are
like L. rex. These Isotelus species are much younger than the Australian genus. Early representatives
of Isotelus, such as I. liarrisi (see Shaw 1968, pi. 22), are quite different, with relatively broad cephalic
and pygidial borders, and wide lateral borders on the hypostoma. These in turn are related to the
early middle and early Ordovician genera Stegnopsis and Isoteloides which are unlike Lycophron in
almost every particular, although they are its North American contemporaries. So in our view
Isotelus species resembling Lyeophron were independently derived later in the Ordovician (see also
Lycophron sp. A below). The hypostoma of the Isotelus-Isoteloides group remains generally
conservative, with broader borders than in Lycophron, and flared tips to the fork. The pygidial border
is visible in Isotelus. The similarities between Lycophron, Isotelus, and Megistaspidella probably
indicate similar life habits in response to a comparable environment: all are found in calcareous,
epicratonic sediments.

Species included. L. rex sp. nov., Asaplms liowchini Etheridge, 1894, L. sp. A (below).

Lycophron rex sp. nov.

Plate 43, figs. 1-10; text-fig. 10

Diagnosis. As for genus.

Derivation of name. Latin rex, ‘king’, for the largest of the Nora trilobites.

Holotype. Pygidium, CPC 22698, from loc. 126/5.

Other material. Cranidium, CPC 22699; librigenae, CPC 22700, 22701, 22889-22891; hypostomata, CPC 22706,
22707, 22897, 22898; pygidia, CPC 22702-22705, 22892-22896.

Occurrence. Ranges throughout the Nora Formation except the basal part: at Iocs. 1 18/7, 122/1, 122/3, 126/1,
126/2, 126/3, 126/5, 127/7, 127/12, 152/9, 308/1.

Description. One or two large hypostomata, and pygidial fragments, indicate that this species grew to a
considerable size. Most pygidia are 1 -2 cm long, and the description is based on material of this size. Pygidia are
abundant in the Nora Formation; cranidia are distinctly rare. There does not seem any reason to doubt that the
association is correctly made. Disparity between the numbers of pygidia and cranidia preserved is rather
common among asaphids; possibly the irregularly shaped cranidium was susceptible to fracture during post-
mortem current sorting compared with the compact pygidium.

Cranidium with outline generally like isosceles triangle; relatively long and pointed anterior ‘nose’ distinctly
convex transversely, while there is a gentle downward slope on the posterior fixigenae. Glabella defined by
shallow furrows converging forwards to pass well inside palpebral lobes; anterior course of axial furrows not
well-marked, but they appear to swing out towards the posterior margin of the frontal cranidial lobe. There was
probably a faintly defined occipital ring, incompletely preserved on our material. Small palpebral lobes slightly
elevated, and in relatively forward position for an asaphid at about mid-cranidial length. Acute triangular
postocular cheeks defined by sutures which run in a nearly straight course to the posterior margin. Border furrow
relatively deep, especially near glabella. Slight tendency towards flattening of anterior, pointed part of
cranidium.

Long and acutely triangular free cheeks are assigned to this species, having the eye in the appropriate
advanced position, and lacking genal spines. There is a narrow border, having a narrow and steep exterior face,
and topped by an acute rim; border furrow at its mid-length, but fading out before the genal angle, and also
anteriorly. A sharp vincular notch truncates the outside face of the border near the genal angle, where the border
furrow fades out.

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PALAEONTOLOGY, VOLUME 27

Hypostoma remarkably long and narrow, looking like a tuning fork. Anterior margin bowed forwards. Front
part of hypostoma narrower (tr.) than width at front end of fork. The fork itself is so deep that the prolongations
on either side are more than twice, or even three times, as long as wide. Middle body does not seem to be defined
on our specimens, the whole of the posterior part of the hypostoma forming an almost flat plane. The large
examples, which almost certainly belong to this species, have a broader, less acute fork, and a pair of faint
depressions represent the maculae.

Deeply convex (tr.) pygidia are typically triangular, with an acute tip slightly rounded, and with width equal
to, or slightly exceeding, the sagittal length. There is no sign of axis or border, although the width of the former at
the front margin is indicated by a distinctly defined, fusiform half-ring occupying 0-4 of maximum pygidial
width. The broad (tr.) articulating facets are backed by convex half-ribs, and a single pair of deep but narrow
pleural furrows which do not extend to the pygidial margin. Doublure narrow for an asaphid, gutter-like. The
combination of long, triangular shape, high effacement, yet deep furrows on the anterior segment only makes
these pygidia distinctive compared with most asaphids. Some specimens (PI. 43, fig. 8), from stratigraphically
high in the range of the species, are relatively even more elongate and tend towards flattening of the posterior tip
of the pygidium. We do not have enough specimens to know whether this is a consistent difference deserving
taxonomic recognition. There is no indication of surface sculpture in this species, apart from terrace lines on
doublure and hypostoma.

Discussion. Etheridge (1 894) described Asaphus {Megalaspis) howchini from the MacDonnell Ranges,
figuring a large pygidium with attached thoracic segments, very similar to L. rex and undoubtedly
congeneric. A similar pygidium from the Nora Formation was figured by Gilbert-Tomlinson (in Hill
et al. 1969, pi. O-V, fig. 4). Etheridge’s original specimen is refigured here as text-fig. 1 1 . The pygidial
axis is defined, whereas all specimens of L. rex are completely effaced. Even small (3 mm long) pygidia

EXPLANATION OF PLATE 43

Figs. 1-10. Lycophron rex gQn. Qisp. no\ . Middle to upper Nora Formation. 1, CPC 22700, loc. 1 18/7, latex cast
from free cheek, x 3. 2, 3, CPC 22699, loc. 158/4, cranidium in dorsal (2) and lateral (3) views, x 2. 4, CPC
22702, 22703, loc. 126/2, latex cast showing two pygidia, x 2. 5, CPC 22706, latex cast of hypostoma, same
bed as holotype, x 6. 6, 10, CPC 22698, loc. 126/5, holotype, latex cast of large pygidium in dorsal (6) and
oblique lateral (10) views, x 5. 7, CPC 22704, loc. 127/7, pygidium, relatively short compared with other
examples, x 10. 8, CPC 22705, loc. 308/1, pygidium, most elongate form in which the tip shows tendency to
become spatulate, x 3. 9, CPC 22701 , loc. 1 58/4, cast from free cheek, x 2-5.

Figs. 1 1, 12. Lycophron sp. A. CPC 22708, lower Nora Formation, loc. 071/4. Pygidium in dorsal (11) and
posterior ( 12) views, x 6.

PLATE 43

FORTEY and SHERGOLD, Lycophron

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PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 1 1 . Lycophron howchini
(Etheridge), South Australian Museum
type collection, F 7104. Lectotype
thorax and pygidium, x 0-5.

of L. rex show no indication of the pygidial axis; definition of dorsal furrows in asaphids is usually
more marked in smaller specimens. So the difference between L. rex and L. howchini is real, and
unlikely to be because of a difference in preservation or size. Etheridge (1894, pi. 3, fig. 2) figured
an asaphid hypostoma, which is very likely that of L. howchini. A species which may prove to be
L. howchini occurs commonly in the Carlo and Mithaka Formations overlying the Nora Formation
in the Georgina Basin.

Lycophron sp. A
Plate 43, figs. 11,12

Material. Pygidia, CPC 22708, 22709, from loc. 071/4.

Occurrence. Lowest part of Nora Formation, loc. 071/4.

Discussion. A second species of Lycophron is represented by pygidia only, occurring stratigraphically
beneath L. rex. We cannot formally name it on the basis of this sparse material. It differs from the
type species in having a well-defined pygidial axis extending almost to the posterior margin, furrowed
pleural fields and a distinct border, but it shares the distinctive triangular shape. At least fifteen pairs
of muscle impressions are visible on the flanks of the pygidial axis, and ten or eleven segments are
expressed on the pleural fields, represented by shallow pleural and interpleural furrows which stop at
the border. Like L. rex, only the first pair of pleural furrows are deep. The pygidium is more
transverse than that of L. rex or L. howchini, and the latter also has unfurrowed pleural fields and no
border. Presumably L. sp. A shows the primitive condition in Lyco/j/iron— furrowed pleural regions
and pygidial borders are primitive for the Asaphidae as a whole. Note that this pygidium is unlike
that of Isoteloides (from which Isotelus was probably derived) and Megistaspis (a close relative, if not
the ancestor of Megistaspidella) which may be taken as evidence that any resemblance between
Lycophron and Isotelus or Megistaspidella is a matter of convergence rather than phyletic relationship.

Genus Presbynileus Hintze, 1954
Type species. Paranileus ibexensis Hintze, 1953, by original designation.

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345

Preshyirileus cf. P. ulaliensis {Hintze, 1953)

Plate 42, figs. 5, 6

Material. Cranidia, CPC 22710, 22899-22903; pygidia, CPC 22712, 22713, 22904, 22905.

Occurrence. Mid to upper parts of the Nora Formation, Iocs. 038/38, 126/7, 158/9, 158/1 1, 308/1.

Discussion. This highly eflfaced asaphid is quite frequent in the higher part of the Nora Formation;
cranidia are immediately distinguishable from those of Fitzroyaspis irritcms in lacking a border. The
cranidium has medially placed palpebral lobes and very short (tr.) postocular cheeks, defined by
distinctly curved sutures. The pygidium assigned here also lacks all traces of a border. Preshyuileus
includes several species from the early Ordovician of Utah which agree with the Nora material in their
salient features; only one of these, P. iitcihensis, has convex postocular sutures and narrow cheeks like
our species. Hintze’s (1953, pi. 13, fig. 2) cranidia are only about 0.5 cm long, whereas we have
specimens up to 2 cm long. We can see no points of difference between the type cranidium and that
illustrated on Plate 42, fig. 6, other than slightly shorter palpebral lobes in the Nora form (which
could well be accounted for by difference in growth stage). Pygidia are of similar dimensions,
although the axis of the Nora form is wider. We have not recovered a hypostoma from the Nora
Formation. The similarities between material from these widely separated localities are sufficient to
suggest conspecificity. We retain a qualification to cover the pygidial difference, and because we have
not yet recovered the distinctive hypostoma from Australia.

Asaphid gen. et sp. indet.

Plate 40, fig. 1 1

Material. Pygidium, CPC 2271 1.

Discussion. One or more asaphids additional to those described above occur in the Nora Formation;
they are fragmentary and difficult to associate, and no formal nomenclature is possible. The pygidium
illustrated is from the lower Nora Formation at 071/4. It is similar to that of a species described
by Legg (1976) as lAsaphellus pricensis from the Canning Basin, except that the pygidial axis is
somewhat longer in our form.

Family dikelokephalinidae Kobayashi, 1936
Genus Hungioides Kobayashi, 1936

Synonymy. Argentinops Pfibyl and Vanek, 1980, p. 38, fig. 1 1.

Type species. Dikelokephalina bohemica Perner, in Novak and Perner 1918, by original designation.

Discussion. Lu (1975, p. 357) has discussed the definition of genera in the Dikelokephalinidae. He
cites the presence of two pairs of pygidial spines as diagnostic of Hungioides. Material from the Nora
Formation should be placed in Hungioides on the basis of this character. However, Lu also regards
a ‘bell-shaped glabella with rounded frontal lobe’ as typical, whereas the Australian material shows
a conical forward part of the glabella, in this respect resembling certain Asaphopsis species, or
Asaphopsoides. In the family as a whole there appears to be a good deal of variation in glabellar shape
between species, as there is in incision of glabellar furrows, and we regard the pygidial structure as the
better generic discriminant in this case. Pfibyl and Vanek (1980) distinguished the genus Argentinops
(based on Asaphopsis intermedia Harrington and Leanza) on the basis of its more slender exterior pair
of pygidial spines. This is scarcely adequate for generic discrimination, and may be subject to
ontogenetic variation as well; hence we regard Argentinops as a subjective synonym of Hungioides.

Hungioides acutinasus sp. nov.

Plate 44

Diagnosis. Hungioides with conical glabellar front; highly divergent preocular facial sutures;

346 PALAEONTOLOGY, VOLUME 27

palpebral lobes half glabellar length (including occipital ring). Pygidial spines relatively slender
compared with other species.

Derivation of name. Latin acutinasus, ‘sharp-nose’, referring to the shape of the glabella.

Holotype. Cranidium, CPC 22714, from loc. 126/3.

Other material. Cranidia, CPC 22715, 22716, 22906-22908; pygidia, CPC 22717-22720, 22909-22915; probable
librigenal fragment, CPC 22721.

Occurrence. Lower to upper Nora Formation, Iocs. 071/4, 122/1, 126/1, 126/3, 126/4, 126/5, 126/11, 152/9,
158/4, 308/1.

Description. This species must have attained a large size. Cranidia probably attained a length of about 4 cm and
a width of at least 6 cm; pygidia were over 4-5 cm long (including spines); complete specimens probably exceeded
12 cm in length. The well-preserved cranidia are all small, 2 cm long or less, and the description is mostly based
on these. The general convexity of this species is remarkably low; the highest parts of the cranidium are the
glabellar mid-line and the palpebral lobes, the latter being quite elevated, which would result in the visual
surfaces on the free cheeks being higher than most of the rest of the exoskeleton. Glabella with maximum width
at occipital ring, being 0-7 sag. length. Gentle forward taper increases greatly at level of 3P glabellar furrows,
such that the front part is broadly conical, although rounded medially. Occipital ring well-defined, furrow
shallower medially, deepened slightly on line with inner ends of glabellar furrows. Three pairs of glabellar
furrows, isolated as pits within glabella: IP forked at inner end, the posterior branch of fork especially strong; 2P
and 3P close together, broadly oval (tr.), 3P placed opposite forward end of palpebral lobe. Distance between
2P and 3P approximately half that between 2P and IP and between IP and the occipital furrow. Furrow
circumscribing glabella uniformly narrow and shallow. Prominent ‘alae’ are here semicircular, depressed areas
about half as long as the palpebral lobes and with hind ends adjacent to the occipital furrow. Palpebral lobes
large (measured exsag. about half total glabellar length), and posteriorly placed such that the posterior ends are
behind the occipital furrow; hence the postocular cheeks are reduced to very narrow strips. Divergent anterior
sections of the facial sutures are broadly sigmoidal, mid-section making an angle of 45-60 degrees with sag. line
on smaller cranidia; on a large, fragmentary specimen this angle has increased to more than 80 degrees, resulting
in an extremely wide (tr.) preglabellar area. Paradoublural line meets the preocular suture at about its mid-
length. This line serves to divide posterior depressed area from the very gently convex preglabellar/anterolateral
held, which widens towards the exsagittal part of glabella. Broad, depressed border furrow separates this convex
area from narrow, distinctly upturned brim.

As far as preserved, the cuticle on this large species was very thin. The biggest specimen preserves traces of
some terrace lines running approximately parallel with the anterior margin across the preglabellar held and
border.

Pygidia are mostly fragmentary, but several prove the existence of two pairs of marginal spines. The narrow
axis tapers uniformly backwards to more than half pygidial length, and is continued into a postaxial ridge which
does not extend on to the border (the exact tip of the axis is thus hard to discern). Up to seven axial rings are
present, of which the hrst four are well-dehned. Ribs number six, adaxial parts sloping progressively backwards
posteriorly; they fade out on inner part of concave border, which had terrace lines like those on the cephalic
border. On large pygidia the marginal spines are slender, and the exterior pair are about as long as the pygidial
axis. A well-preserved, small pygidium (PI. 44, hg. 6), which is probably referable to H. acutinasus, shows a
relatively broad (tr.) outer pair of spines, and it seems likely that these became more slender during later
ontogeny.

Discussion. The type species (Novak and Perner 1918, pi. 1, figs. 4, 6; Marek, in Horny and Basil 1970,
pi. 5, fig. 7) from the Llanvirn Sarka Formation of Bohemia, has a pygidium with at least eleven axial

EXPLANATION OF PLATE 44

Figs. \-l . Hungioides acutinasus syi.noM. 1, CPC 22715, loc. 126/3, fragment of large exfoliated cranidium, x2.
2, CPC 22714, loc. 126/3, holotype cranidium, internal mould, x 3. 3, CPC 22716, latex cast of small
cranidium, same bed as holotype, x 3. 4, CPC 22721, locality as holotype, incomplete free cheek probably
belonging here, internal mould, x 3. 5, CPC 22717, loc. 126/5, latex cast from incomplete, large pygidium,
X 2. 6, 7, CPC 22718, loc. 071/4, latex cast from well-preserved smaller pygidium (6), x 6; and sculptural
detail (7), x 12.

PLATE 44

FORTEY and SHERGOLD, Hungioides

348

PALAEONTOLOGY, VOLUME 27

rings, and a more prominent, stubbier interior pair of marginal spines. If the cranidium of H.
bohemicus (Novak and Perner 1918, pi. 1, fig. 6) is correctly assigned, it has a more uniformly
parabolic glabella and eyes further forward than in H. acutinasus. H. graphicus Richter and Richter,
1954, is generally similar to H. bohemicus, and differs from our species in the same pygidial features.
Kobayashi (1936) separated the original pygidium of Novak and Perner (1918, pi. 18, fig. 5) as H.
novaki; the marginal spines of this species are subequal in length, short and wide, and conjoined at
their bases. The same kind of pygidial structure is shown by H. mirus Lu (1975, pi. 29, figs. 8-15).
Both differ from H. acutinasus in the prominent development of the interior pair of spines, and the
broad bases of the exterior ones. Cephalic characters of the Chinese species show that the eyes are in
a similar posterior position to those of our species, but the anterior branches of the facial sutures are
less divergent, and there is apparently no cranidial border. Another species described by Lu (1975),
H. constrictus from the Tremadoc, has a truncate glabella, smaller eyes, less divergent sutures, and an
ill-defined border compared with H. acutinasus. ' Asaphopsis' intermedia Harrington and Leanza,
1957, from the Llanvirn of Argentina also shows a small inner pair of pygidial spines, and is better
referred to Hungioides. As in H. acutinasus the outer pair of spines are slender, but originate more
adaxially. Apart from being more convex, the Argentine species has a pygidium with eleven axial
rings and seven or eight pleural ribs. Pfibyl and Vanek (1980) erected a new genus, Argentinops, based
on this species, which we consider to be a junior subjective synonym of Hungioides. The new species is
thus readily distinguished from all others, but differences concerning sutural divergence and pygidial
spines are not of generic significance.

Hungioides has a curious distribution. It extends from that part of Europe which was part of the
Selenopeltis (high latitude) province through central and south-western China (also South America)
to platform Australia, which as we have discussed was probably near the palaeoequator in the earlier
Ordovician. Its thin cuticle, fiattened form, and large size argues for benthic habits. This distribution
is the only one known to us which shows independence of palaeolatitude at the generic level. The
distribution does, however, appear to be peri-Gondwanan, but the genus is only at all common on the
eastern part of its geographic range.

Family telephinidae Marek, 1952

Discussion. We follow here the expanded concept of the Family Telephinidae introduced by Fortey
(1975). The family includes five genera which had pelagic habits: Carolinites Kobayashi, Telephina
Marek, Goniophrys Ross, Oopsites Fortey, and Phorocephala Lu (= Carrickia Tripp, 1965, see
below).

Genus Phorocephala Lu, 1965
Type species. Phorocephala typa Lu, 1965, by original designation.

Discussion. The generic name Phorocephala has publication priority over Carrickia Tripp, 1965 (see
Tripp 1976, p. 423). The type species of both genera are so similar that it is likely that both should be
referred to the same genus, Phorocephala. Phorocephala species are distinguished from those of
Goniophrys by their long (tr.) anterior cranidial borders, and relatively gently curved palpebral lobes
(Fortey 1976, fig. 1 1 ). The species from the Nora Formation is an early one, and retains a few features
suggestive of derivation from Goniophrys.

Phorocephala sp. alf. P. genalata Lu, 1975
Plate 45, figs. 1-6

Material. Cranidia, CPC 22722-22724; pygidium, CPC 22725.

Occurrence. Lower part of Nora Formation, Iocs. 071/4, 127/3?.

Description. Glabella highly vaulted above fixed cheeks, maximum width being half that of cranidium measured
transversely at back end of palpebral lobes. The glabellar outline is broadly parabolic, much like that of Oopsites
or Goniophrys. Muscle impressions are lacking, except for a vague indication of IP isolated within the glabella
opposite hind part of palpebral lobes. Occipital ring about one-fifth total glabellar length. Axial and preglabellar

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

349

furrows uniformly deep around perimeter of glabella, but deepened into a pit anteromedially. Preglabellar field
short, hardly downward sloping, merging without a sharp break into flat or gently concave border, the two
together having about the same length (sag.) as that of the occipital ring when viewed dorsally. Lateral part of the
preocular fixed cheeks steeply declined, so that the front edge of the cranidium is broadly upward-arched about
the mid-line. Palpebral lobes of length 0-4 that of glabella (sag.), narrow and slightly convex, forward two-thirds
curving gently inward-forward, posterior third curved inward-backwards. Palpebral furrow follows change of
curvature of palpebral lobe with a somewhat angulate bend. Palpebral furrow is deep but at anterior end it
terminates at a poorly defined eye ridge. Intraocular cheek very slightly convex. Posterior border not clearly
preserved on available material. Glabella smooth, scattered punctae on cheeks.

Small, wide pygidium is attributed to this species. Wide axis tapers posteriorly and terminal piece merges with
a deep, steeply downsloping posterior border, the outline of which is transverse medially. Two axial rings are
completely defined, a third faintly. Similarly, two segments are defined on the narrow (tr.) pleural fields, with
pleural and interpleural furrows about equally incised, with a short, faint pleural furrow of a third segment.

Discussion. This species differs from the type species of Pliorocephala, P. typa Lu, 1965 (pi. 123,
fig. 14; 1975, pi. 34, fig. 13) in its parabolic glabella and punctate (rather than pustulose) surface
sculpture; the palpebral lobes of P. typa are less curved. Our species has a glabellar form like that of
G. prima Ross, 1951 (pi. 18, fig. 17), which is primitive for the Telephinidae. The curvature of the
palpebral lobes is also reminiscent of Goniophrys. On the other hand, the wide, transverse cranidial
anterior border precludes its inclusion in that genus and elearly allies it with Phorocephala. The
glabella and palpebral lobes are primitive characters retained from a Goniophrys-\\k& ancestor, which
is in accord with the early stratigraphic occurrence of our species compared with that of other
described Phorocephala ( = Carrickia) spp. The closest comparison is with P. genalata Lu, 1 975 from
a late Arenig occurrence in south-west China, which has a similar glabella. Unfortunately it is
described from poor material: the preglabellar field appears to be longer, and the intraocular cheeks
are wider than in our species. Goniophris (sic.) venustus Ancigin, 1977 (pp. 70-71, pi. 1, figs. 14-20,
24), from the early Ordovician, Karakol-Mikailov Formation of the southern Urals, differs from our
species in its very wide glabella, and broad, flattened border on the pygidium. Although ours is
therefore apparently a new species, the material is insufficient to name it as such— hence our
comparative referenee to P. genalata. One Llanvirn species with punctate sculpture is that referred by
Whittington (1965) to Goniophrys brevicepsl (Billings) from the Llanvirn of Newfoundland; this
species is also referable to Phorocephala. The very long palpebral lobes and convex cranidial border
immediately distinguish it from our species.

Genus Carolinites Kobayashi, 1940
Type species. Carolinites btilbosus Kobayashi, 1940, by original designation.

Discussion. The morphology of Carolinites is now well-known from a number of species, and the
stratigraphic importance of the genus is established. It is unfortunate that the type species, C.
hulbosus, has not been redescribed from topotype collections. As interpreted by Legg (1976) from
Canning Basin material, C. bulbosus would be the senior synonym of the widespread species C.
genacinaca Ross, 1951. Legg’s specimens are undoubtedly conspecific with the species from North
America, but it is less clear that this applies also to the type material of C. bulbosus. The width of the
fixed cheek (Kobayashi 1940, pi. 12, fig. 6) adjacent to the baccula, for example, is less than in typical
specimens of C. g. genacinaca, and belongs to the range of overlap between that species and C.
ekphymosus Fortey, 1975 (text-fig. 14; pi. 39, figs. 4, 10), a species which is probably a senior synonym
of C. pardensis Legg, 1976. However, the pygidium, possibly incorrectly assigned to C. bulbosus by
Kobayashi, is unlike that of any other Carolinites species, being relatively transverse, and with
a flattened border. In view of these uncertainties we prefer to compare our material with previously
described species for which cranidium, pygidium and free cheek are known.

Carolinites genacinaca Ross, 1951 (s.l.)

Plate 45, figs. 7-10

Synonymy. Synonymy of this species, and its two subspecies, was given by Fortey (1975; 1980u, pp. 103, 104).

350

PALAEONTOLOGY, VOLUME 27

Material. Cranidia, CPC 22728, 22729; pygidia, CPC 22726, 22727.

Occurrence. Basal Nora Formation, loc. 071/4.

Discussion. The species is divided into two subspecies: C. g. genacinaca Ross, 1951, and C. g. nevadensis
Hintze, 1953, both known from silicified material. Detailed comparative discussion of these sub-
species was given by Fortey ( 1 975). A crucial point of distinction is the presence of a marked subocular
ridge in C. g. nevadensis. We do not have a free cheek from the Nora Formation which might show
this feature, and so we prefer to identify the species sensu lato. That apart, the relative size of the
bacculae adjacent to the base of the glabella, and the clear definition of the third pygidial axial ring
shown by the Australian material, are features of the subspecies C. g. genacinaca, a mid-Arenig form.

The type specimen of C. minor (Sun, 1931) was re-illustrated by Lu (1975, pi. 2, fig. 20); it is very like
cranidia of C. genacinaca of the same small size. C. minor may prove to be the senior synonym both of
C. genacinaca and C. bidhosus, but in view of the uncertainty surrounding the identity of the type
species, we employ the well-characterized species C. genacinaca here.

Carolinites cf. C. ekphymosiis Fortey, 1975
Plate 45, figs. 1 1-14

Material. Cranidia, CPC 22732-22740, 22916-22930; librigenae, CPC 22748-22750; pygidia, CPC 22741-
221 Al, 22931-22942.

Occurrence. Ranges through much of the higher part of the Nora Formation, Iocs. 1 18/7, 122/4, 126/3, 126/4,
158/4, 308/1.

Discussion. This species of Carolinites with narrow fixed cheeks is mostly represented by poorly
preserved external moulds, but a few good specimens allow comparison with previously described
species. Narrow-cheeked Carolinites include C. sihiricus Chugaeva, 1964 (= C. angustagena Ross,
1967) and C. ekphymosus Fortey, 1975 ( = C. pardensis Legg, 1976, see Fortey 1980u, p. 104). The
former has the genal spine reduced to a small stub, whereas the Nora species has a well-developed and
curved genal spine. This is like C. ekphymosus from the late Arenig of Spitsbergen (Fortey 1975,
pi. 39, fig. 2). Well-preserved Nora cranidia are also very like those of C. ekphymosus (compare PI. 45,
fig. 1 1 with Fortey 1975, pi. 39, fig. 3). One of the characteristics of C. ekphymosus vs. a finely granulate
surface sculpture, and none of the Australian material is well enough preserved to show this. The
pygidia of C. ekphymosus from Spitsbergen show a faintly defined fourth axial ring on the pygidium.

EXPLANATION OF PLATE 45

Figs. 1-6. Phorocephala sp. aff. P. genalata Lu, 1975. All from Nora Formation, loc. 071/4. 1-3, CPC 22722,
exfoliated cranidium in dorsal ( 1), lateral (2), and anterior (3) views, x8. 4, CPC 22723, cranidium, x8. 5,6,
CPC 22725, pygidium, dorsal (5) and posterior (6) views, x 8.

Figs. 7-10. Carolinites genacinaca Ross, 1951 (s.l.). All from lowest Nora Formation, loc. 071/4. 7, CPC 22726,
pygidium, x 6. 8, CPC 22727, pygidium, x 6. 9, CPC 22728, incomplete cranidium, x 6. 10, CPC 22729,
small cranidium with well-preserved cheek on right side showing relatively great width compared with C. cf
ekphymosus, x 6.

Figs. \ \-\A. Carolinites ci. C. ekphymosus¥oxX.Qy,\915. 1 1, CPC 22732, loc. 1 18/7, cast of cranidium, x 6. 12,
CPC 22733, loc. 308/1, cast of cranidium with narrowest cheeks, x 7. 13, CPC 22741, loc. 308/1, cast of
pygidium, x 6. 14, CPC 22748, loc. 308/1, free cheek, latex cast, x 6.

Figs. 15-17. Annaniitella brachyops sp. nov. 15, CPC 22773, loc. 308/1, latex cast of incomplete cranidium
showing granulose sculpture, x4. 16, CPC 22774, loc. 308/1, pygidium, x 6. 17, CPC 22772, loc. 308/1,
holotype, internal mould of cranidium in typical preservation, x 6.

Figs. 1 8-22. Namheetella emholion sp. nov. 18, CPC 22757, loc. 126/7, pygidium, internal mould, x 6. 19, CPC
22755, loc. 126/3, cephalic doublure with median spine, same bed as holotype, x 6. 20-22, CPC 22751, loc.
126/3, holotype, latex cast of external mould of cranidium, in anterior (20), lateral (21), and dorsal (22)
views, X 6.

PLATE 45

■ ■ j

FORTEY and SHERGOLD, Nora Formation trilobites

352

PALAEONTOLOGY, VOLUME 27

which we have not seen on Australian specimens. These small differences could be because of
preservation, but it is preferable to retain a qualification in the determination. Narrowest-cheeked
specimens from the Nora Formation (PI. 45, fig. 12) are like C. sibiricus, but no associated free cheek
that we have prepared has the genal spine reduced, and the fourth pygidial axial ring is clearly defined
on C. sibiricus. Regardless of specific identity no Carolinites with large bacculae but narrow fixed
cheeks is known elsewhere before the later Arenig.

Family alsataspididae Turner, 1940

Emended diagnosis. Trinucleine trilobites in which the median cephalic spine originates from the
cephalic doublure. Eyes present primitively; later forms blind. Some forms tend to multiplication of
thoracic segments (probably to as many as thirty in Seleneceme).

Discussion. Fortey ( 1 975, p. 92) noted the difficulties in an objective definition of this family. We now
believe that the presence of a long anterior spine, originating from the cephalic doublure (rather than
the glabella as in raphiophorids), is a shared, derived character unusual enough to indicate a
monophyletic group. As thus recognized, the Alsataspididae would include Seleneceme, Falanaspis,
Nambeetella {helow), and "Hapcdopleura' longicornis Harrington and Leanza, 1957. As Fortey noted,
the reconstructions of the first- and last-named given in the Treatise (Moore 1959) are incorrect in
showing what appears to be a dorsal origin for the frontal spine. Whittard (1958) clearly observed the
ventral origin of the frontal spine in Seleneceme, while Fortey noted that specimens of ‘//’ longicornis
lacking free cheeks also lacked the frontal spine, which was present on entire specimens. This early
Tremadoc species also has small eyes. The implication is that the alsataspids became blind
subsequently. Presumably all trinucleine groups were primitively sighted, and blindness could be
polyphyletically derived. Seleneceme shows another tendency widespread in raphiophorid-like
trilobites— the multiplication of post-cephalic segments. We regard this as an adaptation for life in
poorly oxygenated environments (Fortey 1975, p. 93; Fortey and Owens 1978, p. 239), and not of
high level taxonomic significance. In support of this is the fact that such highly segmented forms are
developed at different times in different groups (Hapalopleura in the Tremadoc; Edmundsonia, a
middle Ordovician raphiophorid; and Seleneceme, an alsataspidid).

If this phylogenetic view is correct, there are no grounds for separating the Hapalopleuridae from
the Orometopidae (Henningsmoen 1959, p. 170) and the latter family name would take precedence.
The extended Orometopidae would embrace primitively sighted genera including the ancestors of
raphiophorines and endymioniines. Rushton (1982) has shown the origin of Mv»?f/n-like forms from
orometopids (in our sense) resembling Araiopleura, ih.\s shows that Myinda (and Myindella), hitherto
regarded as comprising a separate family, should be included as a subfamily of Orometopidae.

In summary, we would classify the Trinucleina into the following families: Trinucleidae;
Dionididae (syn. Tongxinaspididae Zhou, 1981); Orometopidae (syn. Hapalopleuridae), including
Subfamily Myindinae; Alsataspididae; Raphiophoridae (Subfamilies Raphiophorinae,
Endymioniinae, and possibly Ampyxinellinae). We are inclined to regard Eotrinucleus, the only
genus ascribed to the Eotrinucleidae Zhou and Zhang, 1978, as a harpedid.

Genus Nambeetella Legg, 1976

Type species. N amheetella fitzroyensis Legg, 1976, by original designation.

Diagnosis. Alsataspidids with convex, flask-shaped glabella not overhanging cranidial margin.
Triangular pygidium with one or two pairs of pleural furrows.

Discussion. The use here of Legg’s genus Nambeetella requires some justification. Legg did not
describe the free cheeks of the type species, and the free cheeks include the critical alsataspidid feature
of the anteromedian spine. The cranidium alone is extremely like that of Globarnpyx trinucleoides
Eortey (1975, pi. 29, fig. 1) from the Arenig of Spitsbergen, but this is a raphiophorine entirely lacking
a frontal median spine. Legg (1976) compared Nambeetella with Mendolaspis, but again this genus
appears to have an anterior tubercle on the glabella homologous with the anterior spine ot

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

353

raphiophorines (Fortey 1975, pi. 30, fig. 8). On our analysis both Glohampyx and Memhlaspis are
raphiophorids, and any resemblance to the alsataspidid from the Nora Formation is a matter of
convergence. We have made the assumption, however, that the Nora material and that from the
Canning ^as\n {N.fitzroyensis) is congeneric. In view of the other genera in common between the two
areas (Fitzroyaspis, Gogoella, Prosopiscus, etc.), and the endemic character of the fauna as a whole,
this does not seem an unreasonable assumption. But it requires the discovery of the cephalic doublure
of the type species before it can be proven. If the anteromedian spine proved to be lacking on N.
fitzroyensis, Nambeetella would become a junior subjective synonym of Glohampyx, and a new
generic name would be required for the species described below.

As understood here, Nambeetella is distinguished from other genera of the Alsataspididae by its
narrow, vaulted glabella and relatively large pygidium; it is the most raphiophorid-like of the family.
We regard the presence of the median spine on the doublure as the more reliable indicator of its
affinities.

Nambeetella embolion sp. nov.

Plate 45, figs. 18-22

Diagnosis. Nambeetella with steeply sloping and somewhat tumid preglabellar field; lateral tips of
fixed cheeks extended into spine-like projections. Pygidium about twice as wide as long, with axis
occupying about one-third transverse pygidial width at front margin.

Derivation of name. Greek embolion, ‘javelin’, referring to the frontal spine.

Holotype. Cranidium, CPC 22751, from loc. 126/3.

Other material. Cranidia, CPC 22752-22754, 22952, 22953; librigenae, CPC 22755, 22756; pygidium,
CPC 22757.

Occurrence. Lower part of Nora Formation, Iocs. 126/3, 126/4, 126/5, 126/6, 126/7, 127/7.

Description. Cranidia, free cheeks, and pygidium are all from a short stratigraphic interval in which no other
trinucleines occur, so their association is made with confidence. Cranidium twice as wide as long, glabella even at
maximum width occupying a third cranidial width, or less. T ransverse glabellar vaulting increases forwards from
quite low near the occipital ring to a maximum at about two-thirds length in dorsal view, in front of which there
is a decrease in convexity to the preglabellar furrow. One might expect a tubercle on the anterior high point of the
glabella but none is visible— probably the preservation is too coarse to see it. For the same reason no sculptural
details are preserved. Two pairs of subcircular muscle impressions on narrow, posterior part of glabella. Fixed
cheeks curve downwards progressively forwards, running into the preglabellar field, which protrudes slightly
forwards, slopes steeply downwards, and is gently inflated. Axial furrows are quite broad posteriorly but there is
no indication of inflated ‘alae’ within. Short (sag., tr.) anterior cranidial border weakly indicated at mid-part of
preglabellar field. Well-defined posterior border becomes wider and steeply forwards inclined away from
glabella. The most distinctive feature of the cranidium is the prolongation of the borders, and narrow, triangular
slivers of the fixed cheeks in front, into curious spine-like projections at the posterolateral corners of the
cranidium.

We have two examples of the cephalic doublure bearing the median spine; all that remains of the dorsal part of
the free cheeks is a narrow strip running around the anterior margin of the cranidium. The doublure itself is
divided along its length with a somewhat ventrally depressed posterior band, and its inner edge is turned
upwards and embayed about the mid-line. The frontal spine tapers from a stout base to reach a length possibly
exceeding that of the cranidium; the underside of the spine is flattened near its base, but the cross-section is nearly
circular distally. It was probably slightly downward-declined. A curious feature of both specimens is the lack of
genal spines. All trinucleines have genal spines, and it seems unlikely that they were absent in Nambeetella, but it
is difficult to see why they should have been broken off when the anteromedian spine is preserved, particularly in
so symmetrical a fashion.

Pygidium twice as wide as long, with steeply downturned posterior border which is not arched up about the
mid-line. Gently convex axis occupies about one-third of the pygidial width at the front margin, tapering gently
posteriorly, and extends as far as border, but preservation is not good enough to see whether it encroached on to
the border in the manner of some raphiophorids. Four narrow axial rings appear to be defined. On the pleural
fields only the first pair of pleural furrows are deeply defined. The pygidium is an internal mould, and it is
possible that an additional pair of furrows could have been expressed dorsally.

354

PALAEONTOLOGY, VOLUME 27

Discussion. The reasons for assigning the species from the Nora Formation to Nanibeetella have been
discussed above. N. fitzroyensis, the type and only other species, has a narrower preglabellar field,
and Legg (1976) does not mention the distinctive, pointed extensions of the posterolateral angles of
the fixed cheeks which are a feature of N. embolion. The pygidium assigned to N. fitzroyensis is
relatively much wider than that of N. embolion, with a proportionately narrow axis; a second pleural
furrow is defined.

Family pliomeridae Raymond, 1913
Genus Gogoella Legg, 1976

Type species. Gogoella wadei Legg, 1976, by original designation.

Gogoella brevis sp. nov.

Plate 46, figs. 11-14; text-fig. 12

Diagnosis. Gogoella with glabella wider than long, forward-expanding; fixed cheeks narrow (tr.).
Pygidial ribs broad (tr.), steeply downturned, with somewhat truncate spinose tips.

Derivation of name. Latin brevis, ‘short’.

Holotype. Cranidium, CPC 22758, from loc. 308/1.

Other material. Cranidia, CPC 22954-22956; pygidia, CPC 221 59-121 6\, 22957-22960.

Occurrence. Upper part of Nora Formation, Iocs. 308/1, 158/4.

Description. A small species, cranidium not exceeding 5 mm in length, but transversely convex. Cranidium with
postocular cheeks steeply downturned, glabella squat and flat-topped. Glabella expands forwards so that
maximum width is at 3P lobes, this exceeding its sagittal length. Front glabellar margin gently rounded about

TEXT-FIG. 12. Comparative recon-
structions of Gogoella wadei Legg
(left), from the Canning Basin (re-
constructed from Legg 1976), and
G. brevis sp. nov. (right) from the
Nora Formation, both about x 2.

EXPLANATION OF PLATE 46

Figs. 1-6, 9. Prosopiscus praecox sp. nov. 1, 2, CPC 22762, lower Nora Formation, loc. 071/4, holotype, well-
preserved, but broken testate cranidium in dorsal (1) and oblique anterior (2) views, x 4. 3, 5, CPC 22764,
loc. 158, latex cast from well-preserved pygidium, dorsal (3) and oblique posterior (5) views, x 3. 4, CPC
22765, loc. 1 58/9, latex cast from smaller pygidium, x 3. 6, CPC 22766, loc. 158/4, latex cast from pygidium,
X 5. 9, CPC 22763, loc. 071/4, incomplete cranidium from same bed as holotype, x 6.

Figs. 7,8,1 0. Prosopiscus sp. A. 7, CPC 22767, loc. 07 1 /4, cast from fragmentary, but well-preserved cranidium,
X 8. 8, CPC 22768, loc. 308/1, small cranidium, imperfect internal mould, x 8. 10, CPC 22769, loc. 158/9,
latex cast from the pygidium most likely to belong here, dorsal view, x 3.

Figs. 11-14. Gogoella brevis sp. nov. 1 1, CPC 22760, loc. 308/1, pygidium, latex cast, showing all five ribs, x 6.
1 2, CPC 22758, loc. 308/ 1 , holotype cranidium, internal mould, x 8. 13,14, CPC 22759, loc. 1 58/4, latex cast
from external mould of pygidium, shown in dorsal (13) and posterior (14) views, x 6.

PLATE 46

FORTEY and SHERGOLD, Prosopiscus and Gogoella

356

PALAEONTOLOGY, VOLUME 27

mid-line. Glabellar expansion is less marked on small cranidia, and the frontal lobe is more broadly rounded.
Glabellar furrows short, extending less than one-quarter of transverse glabellar width. IP deepest, conhning
narrow (exsag.) IP lobe; 2P and 3P lobes are progressively longer (exsag.). 2P furrow is directed slightly
forwards, approaching axial furrow near its anterior end; 3P directed strongly forwards, finishing well inside the
preglabellar furrow. Occipital ring deeply defined, and curving forwards medially. Axial furrows very deep and
wide, like posterior border furrow. Because most of our specimens are internal moulds we do not know the
dorsal expression of glabellar and other furrows. If they follow the usual pliomerid pattern (pliomerids usually
have a very thick cuticle) furrows would have been narrower, but still deep on the dorsal surface. Intraocular
cheeks very narrow (tr.) not exceeding one-quarter maximum glabellar width. Palpebral lobes are far back,
centred on the IP glabellar furrow, thereby constricting a narrow (exsag.) and short (tr.) postocular cheek.
Anterior border not well-preserved on available material.

Pygidium almost twice as wide as long, pleural ribs deeply downward-curved peripherally. Axis tapers
backwards gently and uniformly, the five axial rings decreasing greatly in convexity in the process. The fifth axial
ring is incompletely defined posterolaterally. No distinct terminal piece is developed. The pleural ribs are
relatively short for a pliomerid, swollen and sausage-shaped, terminating on a line as somewhat truncate-tipped
spines.

Discussion. Legg (1976, p. 20) briefly distinguished the type species from other pliomerids; the
inclusion of G. brevis in the genus modifies the original diagnosis. G. brevis differs from G. wadei in its
forward-expanding and relatively wide glabella, with concomitantly shorter glabellar furrows, 3P
being closer to the mid-line in the new species. G. brevis has more swollen pygidial pleural ribs than G.
wadei. Both species share: very narrow fixed cheeks, with the palpebral lobes further back than in any
other pliomerid; glabellar furrows similarly disposed, apart from the more adaxial 3P in G. brevis \
wide pygidium with short ribs (steeply inclined distally, but not extended into long vertical spines).
These characters are regarded as important in distinguishing Gogoella from other pliomerids. Legg
emphasized a small median glabellar indentation on the type species, but this is a character which is
widespread in pliomerids— although most strongly expressed in Pliomera. Inclusion of G. brevis in
Gogoella means that a ‘subelliptical glabella . . . with anterior furrow approximately at anterolateral
angle of glabella’ (Legg 1976, p. 19) cannot be used to distinguish the genus from Pliomera. The type
species of that genus, P. fischeri (e.g. Neben and Krueger 1975, pi. 10, figs. 18-20), is more like G.
brevis than G. wadei, but in P. fischeri the median cephalic indentation is developed as strongly as the
(very short) 3P glabellar furrows, the palpebral lobes are further forward, and, as Legg pointed out,
the structure of the cranidial anterior border is quite different from that in G. wadei. The long (sag.)
pygidium of P. fischeri is unlike that of Gogoella. We regard the cephalic similarities between Gogoella
and Pliomera to be the result of convergence. Similarly, on Pliomerops canadensis (see Shaw 1968, pi.
1, fig. 4) the 3P glabellar furrows are far forwards, as in G. brevis, but the structure of the pygidium,
with long, downturned spines, is quite different from the Australian forms. It seems that the anterior,
adaxial migration of the 3P glabellar furrows is an evolutionary trend in pliomerids that was attained
independently several times.

Legg (1976) reported only ten thoracic segments on G. wadei, the smallest number of any pliomerid
known to us. The structure of the anterior border of this species is also unusual in the Pliomeridae,
being thin and almost tucked beneath the frontal glabellar lobe. We lack information on the border
structure of G. brevis, however.

Family prosopiscidae fam. nov.

Diagnosis. Blind Phacopina with broad, convex fixed cheeks covered with pitting. Glabella typically
tapering in later species, but primitively subparallel sided. Broad anterior cranidial border, often
sloping back towards glabella. Eye ridges running immediately forward from 3P glabellar furrow to
margin on primitive forms. Pygidium with six to eight segments, equally developed pleural and
interpleural furrows; posterior pleural bands tending to fuse with border.

Discussion. Prosopiscus is the only genus assigned to the new family; it has hitherto been placed with
the Encrinuridae or Cheiruridae. Our reasons for regarding it as a separate family are given with
a discussion of its affinities in the following paragraphs.

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

357

Genus Prosopiscus Salter, 1865

Type species. Prosopiscus mimus Salter, 1 865, by original designation.

Discussion. The Nora Formation has yielded good material of this most extraordinary trilobite. The
genus has hitherto been recorded from rocks of Llanvirn to Caradoc age; our species are therefore by
far the oldest, and are appropriate for a consideration of the affinities of the genus. Lu (1975)
discussed Prosopiscus at some length, and described well-preserved cephalic shields of three Chinese
species. He concluded that the genus should be assigned to the Family Cheiruridae, Subfamily
Areiinae Prantl and Pfibyl. Lu and Chang (1974) figured a complete specimen of P. latus. We have
also attributed the pygidium here, and this rules out any possibility of cheirurid affinities for
Prosopiscus because the pygidium has up to eight segments, and an entire margin. The resemblance to
Areia must be a matter of convergence. However, several features, particularly the pitted sculpture on
the fixed cheeks and the form of the glabellar furrows, show that whatever its closest relatives
Prosopiscus belongs to the Order Phacopida. The genus had a history extending through much of the
Ordovician, and its earliest representatives are as old as any dalmanitacean, for example. In view of
its curious combination of characters, and this long independent history, we regard Prosopiscus as
belonging to a distinct family.

To which of the major groups of Phacopida is Prosopiscus most closely allied? We presume that the
Cheirurina can be excluded, because of the entire pygidial margin of Prosopiscus, with the pleural ribs
bisected by long, deep pleural furrows. This leaves two possibilities (a and b in text-fig. 13);
Prosopiscus is more closely related to the Phacopina than the Calymenina, or vice versa. Blindness
as a character is irrelevant, because it is capable of polyphyletic development. Later species of
Prosopiscus have a markedly forward-tapering glabella, but this is not the primitive condition; our
early species has a parallel-sided glabella, or even with slight expansion at the 3P glabellar lobe, and it
is this form which must be compared with phacopines and calymenines. The ocular ridge is strongly
defined, running forwards from the 3P glabellar furrow to the cranidial margin. The anterolateral
view of the specimen of P. praecox on Plate 46, fig. 2, shows that there was room for a minute,
triangular free cheek adjacent to the cranidial anterior border. However, the fact that no palpebral
lobe is developed makes it very unlikely that there was even a rudimentary eye. The interpretation of
the facial suture presents several problems. If a free cheek were present, then what appears to be the
edge of the lateral cranidial border is interpretable as a suture which may run some way towards the
genal angle. In support of this interpretation is the fact that the anterior cranidial border is distinctly
rolled back into the doublure, whereas the ‘border’ on the fixed cheek is much narrower, not rolled
and sharply truncated at its edge. The free cheek would then consist of the outer part of the border
plus doublure. However, on species with broad lateral cranidial borders (PI. 46, fig. 7, and those in Lu
1975) the suture has presumably retreated to a completely marginal position, and this applies to all
the younger species.

Of derived characters which might indicate calymenine affinities, one only is considered important:
the structure of the anterior cranidial border, which is robust, convex-forwards, and increases in
width (tr.) away from the glabella. It may be compared with the structure of the preglabellar area of
such early calymenids as Neseuretus. Although the tapering glabellae of calymenines and most

TEXT-HG. 13. The two competing
hypotheses for the closest related
taxa to the peculiar trilobite
Prosopiscus, as discussed in text.

358

PALAEONTOLOGY, VOLUME 27

Prosopiscus spp. are similar, this is clearly a secondary character in the latter, the primitive glabellar
form being parallel-sided. The pygidium cannot be closely matched among calymenids, although
some Platycalymene species are not dissimilar in general structure.

Derived characters which might indicate Phacopina are as follows: (1) The finely pitted surface
sculpture on the fixed cheeks; such a sculptural type is present on many early Phacopina (Destombes
1972, pi. 4, fig. 1; Henry 1980, pi. 28, fig. 5b), while calymenids are apparently primitively granulate.
(2) The form of the 3P glabellar furrow is typically phacopinoid, showing gently sigmoidal curvature
and much greater forward inclination than the 2P furrow, making the 3L glabellar lobe longest
(exsag.). (3) The pygidium is most like that of Eudolatites among phacopines (see E. (Bcmilatites) aff.
dubius figured by Destombes 1972, pi. 4, fig. 7) with regard to the development of pleural and
interpleural furrows, and the retention of relict half-rings on the pygidial axis.

We conclude that more derived characters indicate the common ancestry of Prosopiscus and
Phacopina than Calymenina. Pygidial details show that the Dalmanitidae include the closest forms.
Since both Prosopiscus and Dalmanitidae are found in the Arenig, their common ancestor is of
Tremadoc age or older but we know of no suitable candidate. The early origin and subsequent history
of Prosopiscus indicates that its familial status is justified.

Note that other phacopids became blind: Typhloiuscus is a Devonian genus which is homoeo-
morphic in some respects with Prosopiscus (Rennie 1930, pi. 10, fig. 12). In its glabellar furrows and
pygidial features Typhloniscus is clearly a phacopid derivative, and there is no question of classifying
it with Prosopiscus. It is interesting to observe, though, that the manner of eye loss appears to have
been similar in both genera: forward migration of the facial sutures and (presumably) eventual
elimination of the ocular part of the fixed cheek. Areia in the Cheiruridae may have lost its eyes in the
same way.

Prosopiscus praecox sp. nov.

Plate 46, figs. 1-6, 9; text-fig. 14

Diagnosis. Prosopiscus with glabella nearly parallel-sided; remnant eye ridges present; lateral border
narrower than other species. Genal pitting very dense.

Derivation of name. Latin praecox, ‘Spring’, referring to its early appearance in the Nora Formation.

Holotype. Cranidium, CPC 22762, from loc. 071/4.

TEXT-FIG. 14. Prosopiscus praecox sp. nov.
Reconstruction of cephalon and pygidium,
about X 2.

FORTEY AND SHERGOLD: ORDOVICIAN TRILOBITES

359

TEXT-MG. 15. Prosopiscits mimus Salter. Reconstruc-
tion of the cephalon of the type species of Prosopiscus,
based on fragments in the type collection in the British
Museum (Natural History), about x 2.

Other material. Cranidium, CPC 22763; pygidia, CPC 22764-22766, 22961 .

Oeciirrence. Throughout most of Nora Formation, from Iocs. 071/4, 158/4, 158/9, 158/1 1.

Description. Cranidium deeply vaulted transversely, with lateral parts of cheeks steeply downsloping, and broad
arch about the mid-line. Cheeks about one and a half times the maximum width of glabella, which is elevated
above the cheeks rather than sunk between them, as in species such as P. rugosus Lu. Glabella almost parallel-
sided, though with a tendency for the 3L lobe to bulge outwards slightly into axial furrow; frontal lobe with
semicircular outline. First pair of furrows on glabella interpreted as lateral parts of occipital furrow, very shallow
over mid-part of axis. Lateral glabellar furrows likewise extend far into glabella, dehning a median glabellar lobe
only about one-quarter width of glabella. IP and 2P transverse (inner end of IP deepened into an apodeme),
glabellar lobe 2L slightly shorter (exsag.) than IL. 3L is longer than either, adjacent to axial furrow, slightly
inflated, delimited by 3P furrow which slopes inwards quite strongly, and is gently sigmoidal. Axial and
preglabellar furrows nowhere deep, except for hypostomal pit, but there are four or hve pits in the preglabellar
furrow. Eye ridge almost continuing line of 3P glabellar furrow, furrow defining its posterior edge much the
deeper, and continuing without a break into lateral border furrow. Although the eye ridge is slightly wider where
it joins the border there is no palpebral lobe. Area in front of eye ridge continuous with cranidial anterior border
(although the posterior part may well have a genal origin), which is narrowest medially and broadly ‘rolled'.
Anterior view shows a short section (PI. 46, fig. 2) of the presumed facial suture terminating the anterolateral
edge of the border. The question of whether a free cheek was present, and its probable extent, has been touched
upon above. Lateral border narrow, no wider than the eye ridge; posterior border about twice as wide as lateral;
genal angle rounded. Borders appear to lack the dense granulation that occurs everywhere else. Cheeks alone are
densely pitted; the largest pits are concentrated in a line of about fifteen pits a little in front of the very narrow
posterior border furrow.

Pygidia assigned here are two-thirds as long as wide, with slightly elevated axis, and distal part of pleural fields
deeply downsloping. External mould shows seven segments clearly defined, and an eighth only indicated. Axis
tapers gently almost to border, with seven rings and a small terminal piece. Long, narrow pleural furrows divide
each segment into anterior and posterior bands, of which the anterior only merges with the slightly convex
border. Posterior bands are sharply marked off from border by deep furrows. Narrow border widens and
becomes more rounded where arched upward about mid-line. Internal moulds show that doublure was ventrally
correspondent with border, forming marginal tube, widest posteriorly.

Discussion. The type species of Prosopiscus, P. mimus, was redescribed by Reed (1912); the type
material is fragmentary. We have used it as the basis for a new reconstruction shown in text-fig. 15.
Compared with P. praecox, the borders are much wider and the glabella tapers strongly, differences
which also apply to the several younger species figured by Lu (1975). The closest species is P.
edgurensis Legg, 1976 (pi. 6, figs. 30, 35) from the early Llanvirn of the Canning Basin, north-western
Australia. The specimens used to found this species are small and flattened, hence comparison is
difficult with our material, but several differences are shown, not all accountable to preservation or
size. The posterior border furrow of P. edgurensis is comparatively deep and wide, while the genal
pitting is coarse. No lateral border is shown on the cranidia figured by Legg and according to him the
border on this species is entirely librigenal: free cheeks ‘narrow (tr.) and almost entirely consist of
border only’ (ibid., p. 23). P. lulus Lu, in Lu and Chang 1974 from the late Arenig of south-west
China, has a broad lateral cephalic border, and an acutely triangular pygidium with feeble
interpleural furrows.

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PALAEONTOLOGY, VOLUME 27

Our assignment of the pygidium to P. praecox is based on the following assumptions: having
matched other pygidia and cranidia in the fauna, we were left with two kinds of Prosopiscus cranidia,
and two types of pygidia, in approximately equal abundance scattered through the Nora Formation;
the assumption that they belonged together seems reasonable. On morphology the assignment is
consistent: low axial convexity is matched by glabella and pygidial axis, P. praecox has nearly
horizontal fixigenal areas adaxially, distally turning downwards steeply, a profile which must have
been reflected in the thorax, and which is shown also on the pygidium we assign to P. praecox. Note
also that the axial arch along the mid-line is similar on cranidium and pygidium of P. praecox, and
that the ‘thickened’ appearance of the anterior cranidial border is matched also by the adaxial part of
the pygidial border. The longer of the two types of pygidia was assigned to P. praecox because of its
convexity and relatively narrow border; the wider type of pygidium was matched with P. sp. A
(below), which is less convex, and with broad borders. Both are also generally similar to the pygidium
in the complete specimen of P. latus Lu, in Lu and Chang 1974 (pi. 51, fig. 10).

Prosopiscus sp. A
Plate 46, figs. 7, 8, 10

Material. Cephalic shields, CPC 22767, 22768, 22962, 22963; pygidia, CPC 22769-22771, 22964-22966.
Occurrence. Nora Formation, Iocs. 071/4, 158/9, 308/1.

Discussion. Cephalic material of this species is insufficient to formally name it as new. It obviously
differs from P. praecox in the following respects: (1) Lateral cephalic border is very broad; there is no
question here of a narrow librigenal strip appearing dorsally and if there were any librigenal remnant
it would have to be wholly ventral; overall cephalic convexity is lower than that of P. praecox.
(2) Fixigenal pitting has about half the density of that on P. praecox ■, pits become large and sparse
near lateral border. (3) Length (exsag.) of 2P glabellar lobe is relatively short in relation to IP and 3P.
(4) The pygidium is much more transverse and less convex than that assigned to P. praecox', only
four (faint fifth) axial rings are present; pygidial pleural regions are greatly effaced compared with
P. praecox and only the anterior segment is clearly defined. None the less the basic similarity of
construction of the pygidia of the two species is apparent in the form of the borders and axial rings;
internal moulds of pygidia of P. sp. A show similar pleural morphology to that observed on P.
praecox dorsally.

LOCALITY INFORMATION

Material described here has been collected from both single samples and measured sections, principally on the
Toko, Abudda Lakes, and Mount Whelan 1: 100 000 Geological Series Sheets, numbers 6452, 6551, and 6651,
respectively. These sheets form portions of the Tobermory and Mount Whelan 1:250 000 Geological Series
Sheets, SF/53-12 and SF/54-13, respectively. Localities are given grid references from the 1: 100 000 scale series,
and additional geographic references for location where only 1 : 250 000 scale sheets are available. They are listed
numerically.

Locality 015/6: this refers to Stop 15 on the 1976 International Geological Congress field Excursion 4C
(Shergold et al. 1976, p. 25, fig. 13), and is referred to more fully under Section 158 below. Samples numbered
015/6, 158/4, and 308/1 are all from the same layer.

Locality 038/38: specimens prefixed 038 are from spot sampling on the Toko and Neeyamba Hill 1:100 000
Geological Sheets 6452 and 6552, respectively. Sample 038/38 (text-fig. 16) is on the Toko Sheet at grid reference
79950 74563, geographic coordinates lat. 22°58'24" S. and long. 137°55'10" E., 6 km ESE of Burnt Well and
1-5 km SSE of The Gap Outstation. Brachiopods, bivalves, and gastropods occur with Presbynileus cf P.
utahensis in quartz sandstones from the upper part of the Nora Eormation.

Section 071: Syncline (text-fig. 17), 14-5 km WSW of Rocky Waterhole, and 7-5 km due N. of Cravens
Peak Homestead, Mount Whelan 1; 100000 Sheet, grid reference 25500 74256, geographic coordinates lat.
23° 1 5' 34" S., long. 1 38° 36' 19" E., containing a short sequence at the boundary between Coolibah Limestone
and Nora Eormation. At this loeality the basal Nora Formation comprises poorly outcropping coarse pebbly

137°45' n7"50' 137°55' 138 00'

TEXT-FIG. 16. Detailed locality map for the Nora Formation in the Toko syncline.
For key see text-fig. 1 7 below.

Alluvium, sand sheets and dunes
Undifferentiated Mesozoic
Ethabuka Sandstone
Mithaka Formation
Carlo Sandstone
Nora Formation
Coolibah Formation
Withillindarma Dolomite
Kelly Creek Formation
Ninmaroo Formation
Arrinthrunga Formation

Nora Formation

23"30'

TEXT-FIG. 17. Detailed locality map for the Nora Formation in the Carlo-Cravens Peak district.

362

PALAEONTOLOGY, VOLUME 27

skeletal grainstone layers, interbedded with fine sandstone and siltstone, and generally concealed below
alluvium. The following trilobite fauna occurs with gastropods, rostroconchs, bivalves, nautiloids, ostracodes,
and an eocrinoid: Annamitella strigifrons, Carolinites genacinaca, Prosopiscus praecox, P. sp. A., Norasaphus
(Norasaphus) skciHs, Lycophron sp. A., Plwrocephala sp. alT. P. gemilata, and Himgioides acutinasus.

Section 1 18: 25 m sequence of fossiliferous grainstone overlain by fine-grained sandstone, 2 km N. of Halfway
Dam, Toko Range 1 : 100000 Sheet area. Horizon 1 18/7: sandstone containing L. rex, C. cf. ekphymosus (text-
fig. 16), lying 21-5 m above base of section at geographic coordinates lat. 22°51'28" S., long. 137°48'46" E., lower
part of Nora Formation.

Localities 122/1, 122/3, and 122/4 (text-fig. 16) refer to spot samples taken in the vicinity of Halfway Dam on the
Toko 1 : 100000 Sheet (text-fig. 16). 122/1 is 110 km ENE of Halfway Dam at grid reference 78980 74672,
and geographic coordinates lat. 22°52'37" S., long. 137°49'29" E. 122/3 is T7 km N. of Halfway Dam at
78960 74679, lat. 22°52'23" S., long. 137°49'2" E. 122/4 is 1-8 km N. of Halfway Dam at 78920 74679, lat.
22°52'28" S., long. 137°48'42" E. Fine-grained sandstones occur at all three localities in the lower part of the
Nora Formation, and these contain brachiopods, gastropods, nautiloids, and bivalves, together with L. rex
(122/1, 122/3), Fitzroyaspis irritans (122/4), N. (Norasaphites) monroeae (122/1?), N. (N.) vesiculosus (122/1,
122/4), and H. acutinasus (122/1).

Section 126: this section (text-fig. 17) is located 10.5 km SE of Carlo Homestead, at grid reference 271 10 73999
and geographic coordinates lat. 23°29'31" S., long. 138°45'20" E., on the Mount Whelan 1 : 100000 Sheet. Some
20 m of varicoloured siltstone and sandstone layers are separated by intervals of no outcrop. Stratigraphically,
the section is thought to fie slightly above that exposed at 071. Nautiloids, bivalves, brachiopods, ostracodes,
and ichnofossils are associated with L. rc.\ ( 126/1, 126/2, 126/3, 126/5), H. acutinasus {\26l\, 126/3, 126/4, 126/5,
126/1 \), A. strigifrons (126/3), C. cf. C. ekphymosus (126/3, 126/4), Nambeetella embolion (126/3, 126/4, 126/5,
126/6, 126/7), Presbvnileuscf. P. utahensis {\26ll), F. irritans {\26P), and Norasaphus (Norasaphites) vesiculosus
(126/1, 126/2, 126/3, 126/4, 126/5, 126/6, 126/7, 126/11).

Localities prefixed 127 refer to spot samples collected along the length of the Toomba Range and western
portion of the Toko Syncline.

127/2: spot sample located immediately S. of Lake Namabooka, 3 km SE of Carlo Homestead, Mount
Whelan 1:100000 Sheet area, grid reference 2645074040, geographic coordinates lat. 23°27'30" S., long.
138°41'42" E. Fine-grained sandstone has yielded bivalves and N. (Norasaphus) skalis.

127/3: sample collected on eastern side of Lake Namabooka, 1 -9 km NE of Carlo Homestead, Mount Whelan
I : 100000 Sheet area, grid reference 2637074070, geographic coordinates lat. 23°25'45" S., long. 138 41 '8" E.
Fine-grained sandstone contains ichnofossils and Plwrocephala sp. alf. P. genalata.

127/4: locality situated approximately 3 km N. of Carlo Homestead, Mount Whelan 1: 100 000 Sheet area,
grid reference 261 1074090, geographic coordinates lat. 23°16'30" S., long. 138 39'55" E. Fine-grained sandstone
contains ichnofossils and N. (N.) skalis.

127/7: a spot sample 4-4 km NE of Cravens Peak Homestead, Mount Whelan 1 : 100000 Sheet area, at grid
reference 25700 74200, geographic coordinates lat. 23°I8'35" S., long. 138°37'22" E. The locality contains
a sequence of sandstone with calcareous lenses in the lower part of the Nora Formation. Ostracodes and bivalves
occur with L. rex and Nambeetella embolion, and the conodonts Trigonodus and Drepanoistodus spp.

127/12: this locality is adjacent to 1 32/ 10 at the southern end of the synclinal structure 1 km S. of section 071, at
grid reference 2550074250, geographic coordinates lat. 23°16T8" S., long. 138°36'30" E. (text-fig. 17), Mount
Whelan 1:100 000 Sheet area. Varyingly indurated, lateritized sandstone, siltstone, and carbonate occurs at
these localities. Nautiloids and a bivalve are associated with L. rex and Norasaphus (Norasaphus) skalis.

127/15: spot sample at S. end of Ilanama Swamp, 21-5 km NW of Cravens Peak Homestead, Mount Whelan
1: 100 000 Sheet area, grid reference 24520 74387, geographic coordinates lat. 23°8'22" S., long. 138°30'41" E.
Fine-grained standstone contains ichnofossils, brachiopods, nautiloids, and N. (N.) skalis.

Locality 132/10: see 127/12 (above).

Locality 1 39/4: this locality lies at the SE corner of Ilanama Swamp, 22-3 km NN W of Cravens Peak Homestead,
Mount Whelan 1 : 100 000 Sheet area, at grid reference 24550 74394, geographic coordinates lat. 23°8'0" S., long.
138°30'55" E. A skeletal, peloidal clast grainstone sequence about 10 m thick, contains brachiopods, bivalves,
and N. (Norasaphites) vesiculosus.

Section 1 52: this is a long and discontinuous line of section running from the top of the Kelly Creek Formation
( 152/1 ) into the lower Nora Formation (152/10), commencing 7-5 km due east of Cravens Peak outstation and
terminating 4-2 km from the same (text-fig. 17), on the Mount Whelan 1:100 000 Sheet, grid reference
2605074192 to 2577074180, geographic coordinates for 152/9, lat. 23°19'37" S., long. 138°37'55" E. Locality

FORTEY AND SHERGOLD; ORDOVICIAN TRILOBITES

363

152/9 comprises varyingly indurated micaceous sandstone containing bivalves, nautiloids, and brachiopods
associated with L. rex and H. acutinasus, and two species of the conodont Trigonodus.

Section 156; this section line runs from the Coolibah to the Nora Formation, commencing 7-5 km WSW of
Mount Harriet on the Abudda Lakes 1: 100 000 Sheet area, grid references 20350 74176 to 20280 74177, and
geographic coordinates approximately lat. 23°19'23" S., long. 1 38°5'40" E. to lat. 23°I9'28" S., long. 1 38°6'4" E.
Nora Eormation comprises some 42 m of quartz sandstone and skeletal pelletal grainstone yielding brachiopods
and N. (N.) vesiculosus throughout.

Section 1 58: this section (text-fig. 1 6) was initially spot sampled and the numbers 308/ 1 , 308/2, and 015 also refer
to it. Section 158 is located 5 km NNW of Burnt Well, and 8-5 km NW of The Gap outstation in the Toko
1: 100 000 Sheet area, grid references 79180 74625 to 79420 74625, and geographic coordinates lat. 22°55'8" S.,
long. 137°50'43" E. to lat. 22°55'5" S., long. 1 37°51 '2'' E. The section (see also Shergold cG//. 1976, p. 25, fig. 13)
exposes some 26 m of resistant ferruginized carbonate layers significantly devoid of trilobites, overlain by
a further 30-40 m of flaggy bedded sandstone and siltstone with occasionally more calcareous interlayers,
now decalcified, which contain the richest faunas (e.g. horizon 158/4, = 308/1, = 015/6). These sandstones
represent the lower portion of the upper Nora Eormation. A variety of molluscs, bivalves, gastropods, a
rostroconch, and brachiopods occur on section 158. Trilobites, occurring in the interval between 26-40 m,
include A. hrachvops, C. cf. C. ekphymosiis, F. irritans, Gogoella brevis, H. acutiuasus, L. rex, N. (N.) numroeae,
N.(N.) vesiculosus, Preshynileus cf. P. utahensis, Prosopiscus praecox, and P. sp. A.

Localities 308/1 and 308/2: see section 158 (text-fig. 16) above.

Acknowledgements . The authors acknowledge the assistance given during field work by former members of the
Bureau of Mineral Resources Georgina Basin Project, particularly Dr. E. C. Druce and Mr. J. J. Draper who
guided us to suitable collecting localities and provided lithostratigraphic documentation. Dr. B. J. Cooper,
Geological Survey of South Australia, kindly reviewed the available conodont information. J. H. Shergold
publishes with the approval of the Director, Bureau of Mineral Resources, Canberra.

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RICHARD A. FORTEY

JOHN H. SHERGOLD

British Museum (Natural History)
Cromwell Road, South Kensington
London SW7 5BD

Typescript received 3 June 1983

Revised typescript received 28 September 1983

Division of Continental Geology
Bureau of Mineral Resources
PO Box 378

Canberra, ACT 2601, Australia

THE UPPER CARBONIFEROUS TETRAPOD
ASSEMBLAGE FROM
NEWSHAM, NORTHUMBERLAND

by M. J. BOYD

Abstract. The Upper Carboniferous amphibians from Newsham in Northumberland constitute one of only
five large, compact tetrapod assemblages known from the Westphalian of Europe and North America. The
environment in which the Newsham tetrapods were preserved appears to have been a large and deep freshwater
lake occupying a stretch of abandoned river channel. The lake was apparently surrounded by swamp-forest
dominated by arborescent lycopods; sphenopsids, including Calamites, probably grew around its shoreline.

A revised list of the (eight) Newsham tetrapods which are certainly determinate at least to family level is
presented. Specimens probably representing three additional species, including a colosteid temnospondyl, are
described. A census of tetrapod specimens from the site facilitates distinction of the abundant endemic species
from those representing erratics from environments other than that in which they were preserved. The eogyrinid
embolomere Eogyrimis attheyi Watson, the loxommatid Megalocephalus pachycephalus (Barkas) and the
keraterpetontid nectridean Batrachiderpeton reticulatum (Hancock & Atthey) seem to have been endemic in life
to the Newsham lake. The aistopod Ophiderpeton nanum Hancock and Atthey, a lysorophid and a urocordylid
nectridean are each represented by only a single specimen and are regarded as possible erratics from water bodies
smaller and shallower than the Newsham lake. The colosteid specimen is probably also derived from a shallow-
water/swamp-lake environment, as may be the material representative of the medium-sized eogyrinid Pteroplax
cornutus Hancock and Atthey. The only Newsham tetrapod which appears to represent an erratic from a
terrestrial/marginal environment is the anthracosaurid embolomere Anthracosaurus russelli Huxley.

The structure of the, fish-dominated, open-water/lacustrine community which includes the three endemic
Newsham tetrapod species is briefly discussed. Finally, the Newsham assemblage is compared with the only
other large, compact tetrapod assemblage of Westphalian B age known, that from Joggins in Nova Scotia. In
direct contrast to those known from Newsham, the Joggins tetrapods appear to represent only the more
terrestrial elements of the Westphalian B lowland tetrapod fauna of the southern margin of Laurasia. It is
therefore suggested that, in view of their close contemparaneity, the assemblages from Newsham and Joggins
may be regarded as complementary.

Tetrapod fossils of Carboniferous age are of rare occurrence and have so far been recorded only
from Europe and North America. Within the Westphalian stage of the Upper Carboniferous, only
five large, compact tetrapod assemblages are known (A. R. Milner 1980^). Two, those from Linton,
Ohio, and Nyrany in Czechoslovakia, are of upper Westphalian D age. The assemblage from Jarrow,
Eire, is from the middle Westphalian A and the remaining two, from Joggins, Nova Scotia, and
Newsham, Northumberland, are both lower Westphalian B in age (data from Rayner 1971, which
see for further stratigraphic and palaeoenvironmental details). The Newsham amphibians are of
particular importance as constituting the largest taxonomically diverse assemblage of well-preserved
tetrapods yet yielded by the Westphalian Coal Measures of the north-west European paralic belt.

Tetrapod specimens from Newsham were first recorded by Kirkby and Atthey (1864), who figured
(as " Rhizodus lanciformis') a skull fragment of the loxommatid amphibian Megalocephalus. Further
tetrapod material was described by Hancock and Atthey (1868, 1869a, b, 1870a, b, 1871a), Barkas
(1873), Embleton and Atthey (1874), Atthey (1876, 1877, 1884) and Embleton (1889). Much of the
loxommatid and eogyrinid material was described by Watson (1912, 1926), who also gave a detailed
account of the Newsham keraterpetontid nectridean Batrachiderpeton (Watson 1913). With the
exception of a short description of the sole recorded Newsham aistopod specimen by Steen (1938),

IPalaeontology, Vol. 27, Part 2, 1984, pp. 367-392.|

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PALAEONTOLOGY, VOLUME 27

subsequent work on the tetrapods from the site has been confined to the past two decades. The
eogyrinid embolomeres have been restudied by Panchen (1964, 1966, 1970, 1972) and Boyd (1978,
1980fl), Megalocephalus by Beaumont (1971, 1977), the keraterpetontid material by A. C. Milner
(1978, 1980) and the ai'stopod by Boyd (1982a). Specimens representing three taxa hitherto
unrecorded from the site have also recently been described. These comprise a lysorophid
‘lepospondyf (Boyd 19806), the anthracosaurid embolomere Anthracosaurus (Panchen 1981 ), and a
urocordylid nectridean (Boyd 19826).

Most previous publications on the Newsham tetrapods have been morphological and taxonomic
studies of individual taxa. Comparison with other Westphalian tetrapod assemblages has been
hampered by the fact that the Newsham assemblage has never been reviewed in detail as a single
entity and no precise information as to the relative frequency of the species represented has been
published. In the present paper the nature of the palaeoenvironment in which the Newsham
tetrapods were preserved is considered and the, hitherto unpublished, plant and invertebrate material
from the site is briefly described. A revised list of the tetrapod taxa so far recorded from Newsham is
given and specimens probably representing three further amphibian taxa are described. A census of
Newsham tetrapod specimens follows and an attempt is made to identify ecological associations
within the assemblage, employing the methods used by A. R. Milner (19806) in his study of the
Nyfany tetrapods. Finally, the Newsham assemblage is compared with the only other large, compact
assemblage of Westphalian B tetrapods known, that from Joggins in Nova Scotia.

The following abbreviations are used for institutions and organizations in this work; BRM,
Bradford Museums; bm[nh], British Museum (Natural History); IGS, Institute of Geological
Sciences; NCB, National Coal Board; RSM, Royal Scottish Museum, Edinburgh. All specimens
referred to by museum registration numbers without one of the above institutional prefixes are in the
Hancock Museum, Newcastle upon Tyne.

PALAEOENVIRONMENT

The Newsham tetrapod assemblage was collected entirely from the workings of Hannah Pit,
Newsham Colliery (NZ 306791), which was situated at South Newsham, approximately 1 km south
of Blyth in Northumberland. Hannah Pit was sunk in 1860 and remained operational until 1914;
however, most of the vertebrate specimens known from the site were collected prior to 1880, by the
amateur palaeontologist Thomas Atthey. All are from a bed of black shale immediately overlying
the Northumberland Low Main Seam. This horizon lies within the upper Modiolaris non-marine
lamellibranch zone of the Middle Coal Measures (Land 1974) and is lower Westphalian B in age.
During the Westphalian the Newsham area formed a small part of the Pennine depositional province,
itself a part of the north-west European paralic belt (Calver 1969).

The shale in which the Newsham tetrapods are preserved is a highly carbonaceous sediment,
always well bedded and having, according to Atthey ( 1 877), a thickness of between 7-5 cm and 10 cm.
Pyrite is abundant in the shale and is often closely associated with the vertebrate specimens. The
presence of pyrite and the high organic content of the shale suggest deposition as an anaerobic
sapropel, either in the centre of a lake or during a period of low input of inorganic detritus. As
Panchen (1970, p. 66) has noted, the presence of xenacanth and other sharks at Newsham suggests
that the surface waters, at least, were adequately oxygenated and the lake may have been thermally
stratified, with a warm aerobic epilimnium and a cooler anaerobic hypolimnium.

The lateral extent of the highly fossiliferous area of the black shale worked at Newsham is not
certainly known. However, a clue to the nature and extent of the lake in which it was deposited may
be afforded by the presence, in the Newsham area, of a linear trough-like ‘swelly’ of thick coal within
the Low Main Seam. The recorded length of this structure, which ranges between approximately
1 20 m and 1 85 m in width, extends some 8 km southward from Newsham to the vicinity of Backworth
(text-fig. 16). The ‘swelly’ appears to terminate at its northern end in the Newsham area, but its
southern end has not been explored. The structure of the ‘swelly’ will be apparent from text-figure Ic.
About 0-8 km west of the structure the seam, here between 1 -2 m and 1 -8 m thick, splits. The lower leaf

BOYD; CARBONIFEROUS TETRAPOD ASSEMBLAGE

369

thins out completely before reaching the ‘swelly’. The upper leaf also thins, to between 0-4 m and
0-9 m, before thickening into the ‘swelly’ itself (data from Land 1974, p. 59). The ‘swelly’ has been
described by Hurst (1860), who pointed out that strata above and below it are not affected and
attributed it to penecontemporaneous deformation, and by Land (1974). The latter, although
arriving at no firm conclusion as to the origin of the structure, noted that its direction is in line
with that of contemporary depositional currents. Interestingly, Elliot (1965) has described almost
precisely similar ‘swilleys’ within seams in the Modiolaris and Similis-pulchra zones of the

o

b

TEXT-FIG. 1. Location and structure of ‘swelly’ in Northumberland Low Main Seam, a. Map of north-east
England showing area (B) covered by text-fig. 1b. b. Map of the Newsham area showing recorded course of
‘swelly’ and site of Hannah Pit shaft. Line X-Y indicates course of split in seam to west of ‘swelly’ (after Land
1974). c. Section through ‘swelly’ between points A and B on text-fig. 1b. Double lines represent faults (after
Hurst 1860). NLM, Northumberland Low Main Seam.

370

PALAEONTOLOGY, VOLUME 27

Nottinghamshire Coal Measures. These are convincingly demonstrated by Elliot to represent river
courses which became established and were abandoned within the period of deposition of the seams
concerned. It seems very likely that the Newsham ‘swelly’ originated in this manner and that, after
reflooding (presumably due to local subsidence) of the old channel to submerge the peat which had
accumulated therein since its abandonment, the linear lake thus formed was the environment of
preservation of the Newsham tetrapods. It is particularly interesting to note that in the
Nottinghamshire Abdy Seam ‘swilley’ described by Elliot (1965) the thick coal of the ‘swilley’ trough
is roofed by a dark pyritic shale containing fish and lamellibranch fragments. That the trough coal of
the Newsham ‘swelly’ was, at least in certain areas, also roofed by a black shale is evidenced by the
strata recorded in the shafts of A and B Pits, Seaton Delaval Colliery (NZ 299 763), which were sunk
to the Low Main Seam where it forms the western slope of the ‘swelly’ trough (Borings and Sinkings
1878-1910, no. 1691).

Unfortunately, it is not certain that the Newsham vertebrates were collected from the roofing shale
associated with the thick coal of the ‘swelly’ trough. The 1893 Abandonment Plan (NCB No. 8566)
of the Newsham Colliery Low Main Seam workings indicates that Hannah Pit did work the ‘swelly’
coal, but the writer has been unable to trace any documentary or other evidence linking the ‘swelly’
and the vertebrate material. Mining in the area has now ceased, precluding the possibility of
examining the ‘swelly’ underground. However, the occurrence within the workings of one small
colliery of a large assemblage of (mostly aquatic) vertebrates and a structure interpretable as an
abandoned stretch of river channel is a very remarkable coincidence if the two were not directly
associated.

As Panchen (1970) and A. R. Milner (1980fi) have pointed out, the presence at Newsham of the
large embolomere Eogyrinus and of crossopterygians up to 6 m long implies a lake large and open
enough to sustain the biomass required for the support of such large ultimate consumers. The size of
some of the, apparently endemic, vertebrates and the presumed thermal stratification also suggest a
water-body of some depth. It will therefore be assumed in the present study that the Newsham
vertebrates were preserved in the bottom sediments of a single large lake. However, as Hannah Pit
worked approximately the northernmost 1 -5 km of the ‘swelly’s’ recorded length it is conceivable that
two or more adjacent lakes may have been involved.

Invertebrates. The only invertebrate specimens from the Newsham black shale which are known to
the writer pertain to ostracods and the bivalve genus Naiadites. All are preserved on two small shale
slabs, in the Hancock Museum. G 162.46 bears several fragmentary Naiadites specimens and
ostracods representing two species of Carbonita; all are too poorly preserved for specific
identification. G 162.47 bears a single specimen of Carbonita cf. humilis (Jones and Kirkby) and a
second ostracod referable to Geisina. The presence of Carbonita is of some importance as an indicator
of the salinity of the Newsham lake. Whereas Geisina is known to have been tolerant of very brackish
(and occasionally marine) conditions within the Coal Measures (Calver 1968), Carbonita species
appear to have been oligohaline, tolerating only fresh to slightly brackish water (Pollard 1966).
Naiadites species seem to have been euryhaline and Calver (1968) has suggested that the members of
this genus may have lived by byssal attachment to floating vegetation. Their presence in the area of
deposition of the Newsham black shale, even as living individuals, is thus not necessarily ruled out by
the presumed low oxygen tension of the bottom sediments and hypolimnium. None of the, several
hundred, specimens of the Newsham black shale examined by the writer shows any convincing
evidence of the activity of benthonic invertebrates. In view of the nature of the sediment it
is likely that this absence reflects a genuine scarcity of benthonic animal life in the area of its
deposition.

Plants. The Atthey collection in the Hancock Museum includes a suite of undescribed plant
specimens from the Newsham black shale. Of the seventy specimens examined by the writer, fifty-one
are determinate at least to generic level. The high proportion of well-preserved, and hence
determinate, specimens in the sample may, however, merely reflect collector bias. The taxa present
are listed below; the values in brackets indicate the number of specimens present.

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

371

LYCOPSIDA

Sigillaria tessellata ( 1 )
Sigillaria sp. (3)
Lepidophloios acerosus (3)
Lepidodendron aculeatimi (3)
Lepidodendron sp. (3)
Lepidostrohus sp. (23)

SPHENOPSIDA
Calamites cisti ( 1 )
Calamites sp. ( 1 1 )

PTERIDOSPERMS
Trigonocarpus sp. (3)

With the exception of three Calamites specimens (notably G 162.45) preserved as pith-casts in a
micaceous siltstone, all are compression fossils. The lycopod material, apart from the well-preserved
and usually entire strobili, consists of leafy shoots and fragments of large branches. The Calamites
specimens all represent lengths, mostly less than 10 cm, of stem or branch.

Scott (1977, 1979, 1980) has emphasized the need to relate fossil plant assemblages to depositional
environments, and to consider the possible transport history of specimens, before attempting
interpretation of the assemblages in terms of the communities they derive from. In the case of the
known Newsham plant material it seems likely that most of the specimens represent the flora of the
lake margins and have undergone minimal transport. This is suggested by:

1 . The well-preserved nature and large size of many of the plant fragments.

2. The relatively large number of intact lycopod strobili.

3. The paucity of taxa represented.

There is, moreover, much evidence to suggest that arborescent lycopods comprised the dominant
flora of Westphalian swamp-forests and that Calamites grew around the margins of lakes (Scott 1 979,
1980).

Nonetheless, the Calamites specimens preserved as siltstone pith-casts embedded in the black shale
were presumably transported some distance. The same may apply to the pteridosperm seeds; only
three are present in the sample and these were probably the parts of the plants in question best suited
to surviving transport in a recognizable form. In addition, Scott (1980) has noted that pteridosperms
appear to have been characteristic inhabitants of river flood-plains and levee banks in the
Westphalian. A swamp-forest or lake margin origin for the Newsham Trigonocarpus specimens thus
appears unlikely.

The nature of the small lenticular structures from Newsham, described by Hancock and Atthey
(1869c) as fungi (Archagaricon spp.), is uncertain and the material needs re-study.

Fishes. Most of the known Newsham vertebrate material pertains to fishes, which dominate the total
assemblage from the site in terms of both number of specimens and number of species represented.
Much of the Newsham fish assemblage needs re-study, but a list of twenty-five of the twenty-eight
species so far reported from the site has been given by Dr. S. M. Andrews [in Land 1974, p. 61);
the remaining three species, all haplolepid actinopterygians, were described by Westoll (1944). In
addition to the haplolepids, the fish assemblage includes palaeoniscoid and platysomoid palaeo-
niscids, dipnoans (currently being studied by Dr. T. R. Smithson (University of Newcastle upon
Tyne)), rhizodontid and osteolepid crossopterygians, the coelacanth Rhabdoderma, climatiid and
ischnacanthid acanthodians and a number of elasmobranch genera.

In summary, the environment of preservation of the Newsham tetrapods appears to have been
a large and deep freshwater lake of linear shape (but unknown length), occupying a stretch of
abandoned river channel in which peat had previously accumulated. Many species of fish inhabited
the lake, as did ostracods and, possibly, the bivalve Naiadites. The lake was probably surrounded by
swamp-forest, composed largely of arborescent lycopods and sphenopsids; the latter may have been
especially abundant around the shoreline.

372

PALAEONTOLOGY, VOLUME 27

THE TETRAPOD ASSEMBLAGE

Eight tetrapod species, all amphibians, have so far been described from Newsham:

Order temnospondyli

Loxommatidae; Megalocephalus pachycephalus {Barkas, 1873)

Note. The above ‘traditional’ classification of the Loxommatidae as a family of the Order Temnospondyli is
for convenience of listing only, and should not be taken to indicate disagreement with the recent suggestions of
Panchen (1980) and Smithson (1982) that the Loxommatoidea as a whole should be removed from this order.
Order batrachosauria {sensu Panchen 1980)

Eogyrinidae; Pteropla.x conmtus Hancock and Atthey, 1868
Eogyrinus attheyiV^atson, 1926
Anthracosauridae: Anthracosaurus raxic/// Huxley, 1863

Order nectridea

Keraterpetontidae: Batrachiderpeton reticulatum (Hancock and Atthey, 1869)

Urocordylidae: Urocordylid gen. et sp. indet.

Order aistopoda

Ophiderpetontidae; Ophiderpeton nanum Hancock and Atthey, 1868
Order lysorophia

Lysorophidae: Lysorophid gen. et sp. indet.

However, three further amphibian species from Newsham appear to be represented, each by a single specimen,
in the collections of the Hancock Museum. Although none is strictly determinate, even to family level, they will
now be described for the sake of completeness.

Order temnospondyli
?Colosteidae: colosteid gen. et sp. indet.

Specimen G24.98 consists of an incomplete interclavicle preserved with its ventral surface exposed on a small
slab of shale (text-fig. 2a). The anterior, posterior and right lateral extremities of the element are absent. The
form of the posterior part is, however, apparent from an impression in the matrix and the right lateral extremity
may confidently be restored as the mirror-image of the left. Except on the clearly defined, anterolateral, areas of
clavicular overlap and on the narrower posterolateral marginal areas, the interclavicle bears a well-developed
ornament of pits and ridges radiating from the presumed centre of ossification of the bone. Near the ossification
centre, the pits are circular or oval and completely enclosed. Towards the margins of the element, however, the
pits become more elongate and are deepest mesially, becoming shallower at their, open, distal ends. Bystrow
(1935) has noted that differential growth of ornamented dermal bones produces elongation of the pits in the
direction of the greatest growth rate. In G24.98, as preserved, the degree of elongation of the pits is greatest
anterior to the centre of ossification, suggesting that the complete bone originally extended further in this
direction than posteriorly.

G24.98 does not appear referable to any of the eight previously described Newsham amphibians which are
determinate at least to family level. Its size is such that it could only have been derived from a very small juvenile
of Eogyrinus, Pteropla.x, Anthracosaurus or Megalocephalus. However, the nature of the ventral ornament would
seem to preclude reference of G24.98 to any of the embolomeres. No certainly associated interclavicle has been
described for Megalocephalus, but the ornament of G24.98 does not resemble the ‘honeycomb’ pit and ridge
ornament characteristic of much of the dermal skull roof in this genus (Beaumont 1977, fig. 6). In addition, the
well-ossified nature of the interclavicle and its well-developed ornament do not suggest that it derives from a very
young animal. Nor is it likely that the specimen pertains to any of the four ‘lepospondyl’ species recorded from

TEXT-EiG. 2. Isolated skeletal elements of Newsham tetrapods. a-b. Interclavicle G24.98: a. As preserved.
Stippling represents matrix; b. Restoration. Stippling represents area actually preserved (ornament omitted).
c-D, neural arch G25.03 as preserved: c. Anterior view; d, posterior view, e-f. Interclavicle G94.65. e. As
preserved. Stippling indicates area preserved as impression only, f. Restoration. All scale bars graduated in
centimetres. Cross-hatching indicates broken bone surface.

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

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PALAEONTOLOGY, VOLUME 27

Newsham. The interclavicle is not known for adult specimens of Batrachiderpeton, but the interclavicle of the
juvenile figured by Watson (1913, text-fig. 1 67 (as ‘ Ceraterpeton) ) has the form of an antero-posteriorly elongate
ovoid. Moreover, the dermal skull roof ornament of adult Batrachiderpeton specimens (e.g. Watson 1913,
pi. XCVI) is very different from the ornament of G24.98. The Newsham urocordylid, represented in the study
sample by only a single vertebra, appears to be a member of the Ptyonius-group of Bossy (1976), which comprises
the described genera Ptyonius, Urocordylus, and Ctenerpeton (Boyd 19826). The interclavicles of Ptyonius (Bossy
1976, fig. 576) and Urocordylus (Bossy 1976, fig. 776) are, like those of juvenile Batrachiderpeton specimens,
ovoid in outline, tapering most acutely to their anterior ends. The ventral ornament in both cases differs from
that of G24.98. No interclavicle has been described for Ctenerpeton but there is no reason to suppose it to have
been radically different in form or ornament from those of Ptyonius and Urocordylus. Lysorophid limbs and
limb-girdles are very small in relation to body size (e.g. Sollas 1 920, fig. 1 , Carroll and Gaskill 1 978, fig. 1 32b) and
G24.98 thus seems far too large to have pertained to a lysorophid of the dimensions of the single Newsham
specimen (Boyd 19806) representative of this group. An interclavicle may have been present in Ophiderpeton
nanum (Boyd 1982a), but it seems unlikely that G24.98 could have been derived from an individual of this
species. Although the only known specimen of O. nanum may be a juvenile which could have grown to a size
compatible with the possession of an interclavicle of the dimensions of G24.98, the shape of the element
tentatively identified as an interclavicle in this form (Boyd 1982a, fig. 1 ) does not resemble that of G24.98.

Specimen G24.98 does, however, appear closely to resemble the interclavicles known for members of the
temnospondyl family Colosteidae. Colosteids have been described from the upper Visean of Scotland
(Pholidogaster: e.g. Panchen 1975), the upper Visean or lower Namurian of West Virginia, U.S.A. (Greererpeton:
e.g. Carroll 1980; Smithson 1982) and the Westphalian D of Linton, Ohio {Colosteus: e.g. Romer 1930). Their
occurrence at Newsham would thus not be unexpected from a stratigraphic point of view. Moreover, the
Westphalian A tetrapod assemblage from Jarrow, Eire, includes undescribed colosteid specimens, whose
dimensions seem roughly compatible with those of G24.98 (A. R. Milner 1980a, p. 135 and pers. comm.).

Among points of particular resemblance between described colosteid interclavicles and G24.98 may be
noted:

1 . The nature, degree of development and distribution of the ventral ornament (e.g. Carroll 1980, fig. 2).

2. The proportions of the element, partly inferred in the case of G24.98, which extends further anterior to the
point of maximum width than posterior to it (e.g. Romer 1930, fig. 8; Carroll 1980, fig. 2).

3. The distinctive shape of the posterior tip of the element, clearly indicated by an impression in the matrix in
G24.98 (e.g. Romer 1930, fig. 8). The writer would, therefore, suggest that interclavicle G24.98 probably pertains
to a colosteid temnospondyl. The restoration of the element (text-fig. 26) is based on the form of the interclavicle
in Greererpeton and Colosteus.

Order temnospondyli

Family incertae sedis

Specimen G25.03 is an isolated neural arch (text-fig. 2c-d) which, although otherwise well preserved, has suffered
severe antero-posterior compression during preservation. In the course of this compression the anterior face of
the arch has been shifted, in the morphologically vertical plane, relative to the posterior face, so that the dorsal
edge of the neural spine now slopes downward from posterior to anterior. In addition, the diapophyses have
been rotated in such a fashion that their originally antero-dorsal surfaces now face anteriorly.

The height of the neural spine, together with the form and span of the diapophyses, suggest, by comparison
with Eryops (Moulton 1974), that the arch is that of an anterior dorsal vertebra. The neural spine is a high,
narrow structure in its lateral aspect and is deeply excavated both anteriorly and posteriorly by an upwardly
tapering groove. Dorsally, the anterior and posterior grooves are linked by a canal piercing the neural spine. The
margins of the canal are irregular; whether it is entirely an artefact, produced by breakage of the very thin bone in
this region, or a genuine supra-neural canal enlarged by damage to its periphery is uncertain. In view of its small
size, the former seems the more likely explanation. The top of the neural spine is slightly expanded and
terminates in an originally dorsally-directed, concave facet, whose irregular surface suggests a covering of
cartilage in life. The facet may originally have abutted against a dermal ossification. Moulton (1974, p. 1 5) has
noted that the expanded and rugose tips of the dorsal neural spines in mature Eryops specimens probably lay in
the dermis. He points out, moreover, that in some cases their appearance suggests formation by fusion of the
original spine tips with overlying osteoderms. The zygapophyses of G25.03 are large. Unfortunately the post-
mortem compression of the specimen prevents determination of their original orientation.

Of the eight described Newsham amphibians determinate to family level, only the four iabyrinthodont’
species are large enough to have possessed neural arches of the dimensions of G25.03. The specimen is most
unlikely to pertain to any of the embolomeres. The presacral neural spines of Eogyrinus, as evidenced by the

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

375

vertebrae associated with the lectotype of E. attheyi (G 13.72), and of Pteroplax, as evidenced by the attributed
vertebrae described by Boyd (1980a), differ markedly from G25.03. They are relatively short and more massive
structures, roughly rectangular in lateral view and lacking expanded tips or dorsal facets. No certainly associated
vertebrae have been described for Anthracosaurus, but the posterior trunk vertebrae hgured by Panchen (1977,
hg. 1 2(a)) as possibly pertaining to A . msselli have neural spines resembling those of Eogyrinus. Little is known of
the vertebrae of Megalocephalus or any other loxommatid. However, Baird ( 1 957) described a series of vertebral
elements, including apparently five neural arches, associated with a skull of M. lineolatus (Cope) from Linton,
Ohio. These have been figured by Beaumont (1977, fig. \6b), who has also attributed a very similar, isolated
neural arch (G37.88) from Newsham to M. pachycephalus (Tilley (Beaumont) 1971, fig. 32). All differ markedly
from G25.03 in the possession of narrower neural spines, which appear to lack dorsal facets, and in the size and
form of the diapophyses. While it is possible that these differences merely reflect regional variation within the
vertebral column of Megalocephalus, the evidence at present available is not such as to warrant attribution of
G25.03 to this genus.

Of described amphibian neural arches, G25.03 seems most closely to resemble those of the anterior dorsal
vertebrae of Eryops as figured by Moulton (1974, fig. 2). Points of particular resemblance include the
proportions of the diapophyses and the presence, anteriorly and posteriorly, of strongly developed ridges
extending dorsally and mesially from the zygapophyses to enclose an upwardly tapering groove in the neural
spine. Nonetheless, the neural spines of Eryops appear to be somewhat higher than that of G25.03 and,
moreover, no diagnostic Eryops material of pre-Stephanian age has been described. It is, however, possible that
G25.03 pertains to an edopid, rather than eryopid, temnospondyl. Edops itself is of lower Permian age and no
certainly associated neural spine has been figured. However, edopids occur in the Westphalian D at Linton and
Nyfany (A. R. Milner 1980/?, p. 463) and the Westphalian A assemblage from Jarrow includes an EdopsAike.
form whose vertebrae, since they are apparently rhachitomous in type, may well have borne neural arches not
dissimilar to those of Eryops (A. R. Milner, pers. comm.). It is interesting to note also that two large
rhachitomous vertebrae, in many respects resembling those of Eryops, are known from the upper Visean or
lower Namurian of Greer, West Virginia (Smithson 1982, p. 30).

Order batrachosauria

Family incertae sedis

Specimen G94.65 is an incomplete interclavicle preserved with its dorsal surface uppermost on a small shale slab
(text-fig. le). The right lateral and posterior extremities of the element are absent; the shape of at least part of
the latter region is, however, apparent from a very clear impression remaining in the matrix. The impression
unfortunately terminates abruptly at the edge of the slab, making it impossible to determine with certainty
whether or not a parasternal process was originally present. It is apparent from the impression that the ventral
surface of the interclavicle bore, at least posteriorly, a weakly developed ornament of elongate shallow pits,
presumably radiating from the centre of ossification. The anterior margin of the bone is very markedly
fimbriated.

The size of G94.65 is such that, if it were to be referred to any of the eight certainly determinate Newsham
amphibians listed above, it could only pertain to a small individual of one of the four ‘labyrinthodont’ species.
No certainly associated interclavicle has been described for Megalocephalus, but the ornament of G94.65 could
hardly be more different from that of the dermal skull roof of M. pachycephalus (e.g. Beaumont 1977, fig. 6).
Moreover, the isolated Newsham interclavicle (G13.81) referred to this species by Tilley (Beaumont) (1971,
fig. 33) differs from G94.65 in shape, ornament and the absence of a distinctly fimbriated anterior margin. Although
the ornament of G94.65 suggests that the specimen pertains to a batrachosaur, rather than a temnospondyl, it is
not possible to attribute it with certainty to any of the three known Newsham embolomeres. No certainly
attributable interclavicle has been described for Eogyrinus attheyi but that present in the holotype specimen of
Pholiderpeton scutigerum Huxley, which is probably in fact at least congeneric with the former species, resembles
in form the interclavicle of the Permian embolomere Archeria as figured by Romer (1957, fig. 1) (J. A. Clack,
pers. comm.). It thus differs from G94.65 in both shape and the lack of a ‘comb-like’ anterior margin. No
certainly associated interclavicle has been described for Pteroplax or Anthracosaurus', the almost total lack of
ornament on the dermal skull bones in the latter genus (e.g. Panchen 1 977, fig. 1 ), however, makes it unlikely that
G94.65 pertains to this form. While it is just possible that G94.65 derives from a small individual of Pteroplax,
it must, in the absence of any positive evidence to support such an attribution, be regarded simply as a
batrachosaur interclavicle at present indeterminate below ordinal level. The restoration of the specimen (text-
fig. If) is based upon an assumption of bilateral symmetry and, in part, upon the impression in the matrix.

376

PALAEONTOLOGY, VOLUME 27

CENSUS OF TETRAPOD SPECIMENS

In order to assess the relative abundance of the various tetrapod species represented in the Newsham
assemblage a census of specimens from the site has been carried out. Almost all of the known tetrapod
material from Newsham is stored in the Hancock Museum (Boyd and Turner 1980), but the census
sample also includes specimens in the British Museum (Natural History).

Only specimens referable with some certainty to one of the eight Newsham tetrapod species which
are certainly determinate at least to family level have been included in the census sample. The
numerous isolated ‘labyrinthodont’ ribs from the site have thus been excluded. Moreover, the
recent recognition of cranial material of Anthracosaurus from Newsham (Panchen 1981) means that
isolated elements of large embolomerous vertebrae can no longer be attributed with any certainty
to Eogyrinus. The large numbers of isolated Megalocephalus teeth present in the two museum
collections examined for census purposes have also been excluded from the census sample, as many
may have been lost in the course of normal tooth replacement during life.

Most of the tetrapod material consists of skulls, isolated skull and postcranial elements or, at best,
incomplete articulated skeletons (Boyd and Turner 1980). The assessment of the relative abundance
of the taxa present has therefore been made employing the principle of the minimum number i.e. by
determining the minimum number of individuals of each species necessary to account for all the
specimens referable to that species in the census sample. This method compensates for possible
inaccuracies due to one species possessing more skeletal elements, or a more easily disarticulated
skeleton, than another (Ager 1963, p. 249).

The results of the census are presented in text-fig. 3; the numbers of individuals of each species
estimated to be present in the sample are given in histogram form. A card index comprising details of
all 105 tetrapod specimens in the census sample is held by the writer and a copy has been deposited in
the Hancock Museum.

IDENTIFICATION OF ASSOCIATIONS

As A. R. Milner (1980Z)) has pointed out, there are four main types of information inherent in
Westphalian tetrapod assemblages, such as that from Nyfany, which permit identification of
ecological associations within them:

1. The relative frequency of the various taxa present.

2. The size distribution and degree of articulation of the specimens.

3. The functional morphology of the animals themselves.

4. The environmental and faunal contexts in which the taxa present occur elsewhere.

TAXON

NO. OF
SPEC-
-IMENS

MINIMUM NUMBER
OF INDIVIDUALS IN
SAMPLE

Megalocephalus pachycephalus
Batrachiderpeton reticulatum
Eogyrinus attheyi
Anthracosaurus russelli
Pteroplax cornutus
Ophiderpeton nanum
Lysorophid gen. et sp. indet.
Urocordylid gen. et sp. indet.

61

21

11

3

6

1

1

1

11

9

4

2

1

1

1

1

TEXT-FIG. 3. Results of census of Newsham tetrapods.

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

377

On the basis of the above types of information, Milner recognized three associations, derived from
different environments, within the Nyfany assemblage. These associations, which were further
defined by Milner (1980/?, pp. 471-473) in terms of the most consistently occurring tetrapod families
charaeteristic of each at Nyfany and other Westphalian sites, comprised:

1. A terrestrial/marginal association, characterized by dendrerpetontid and dissorophid
temnospondyls (the latter family apparently replacing the former in post-Westphalian B localities),
gymnarthrid, hapsidopareiontid and tuditanid microsaurs, romeriid captorhinomorphs, and
ophiacodontid pelycosaurs.

2. A shallow-water/swamp-lake association, characterized by ophiderpetontid ai'stopods and
urocordylid nectrideans.

3. An open-water/lacustrine association, characterized by loxommatids and eogyrinid em-
bolomeres.

Using the four types of information listed above, the Newsham tetrapods may also be divided into
three ecological associations, derived from different environments.

1. Terrestrial I marginal association. The terrestrial/marginal ‘association’ known from Newsham
appears to include only Anthracosaurus russelli, represented in the census sample by three specimens.
The specimens comprise the incomplete left mandibular ramus (G24.35) described by Panchen
(1981), an undescribed right jugal (G24.39) noted by Boyd and Turner (1980, p. 13) and an isolated
skull table (G13.78). The skull table was originally figured by Atthey (1877, pi. XIII) as that of
Pteroplax cornntus, but was later referred by Watson (1926) to Eogyrinus attheyi\ the latter
attribution was endorsed by Panchen (1970, 1972). However, comparison of G13.78 with the skull
table of the holotype of A. russelli indicates that it actually pertains to this species (J. A. Clack, pers.
comm.). Its almost unornamented dorsal surface is thus not due, as has been suggested (Panchen
1964), to post-mortem erosion but is probably merely characteristic of Anthracosaurus (e.g. Panchen
1977, fig. 1). At least two individuals are represented by the three Newsham Anthracosaurus
specimens. The jaw ramus apparently derives from a somewhat smaller animal than is represented by
the, 40 cm long, holotype skull of A. russelli (Panchen 1981, p. 89), but the jugal and skull table are
closely similar in size to those of the holotype. They could, therefore, both be derived from one
individual.

No certainly associated post cranial remains have been described for A. russelli but several aspects
of its known cranial morphology suggest that the adults, at least, may have been largely terrestrial in
habit. Thus, the skull is massively built and reptiliomorph in appearance, with orbits facing more
laterally than is the case in Eogyrinus, and lateral line sulci are absent save for possible traees on the
jugals. Naso-labial grooves, regarded by Panchen (1967) as probably primitive for tetrapods and
serving, in conjunction with ventrally placed external nares, to keep the buccal cavity free of excess
water, are absent. The teeth are massive, roughly conical structures and are recurved to a much
lesser extent than those of the, probably largely piscivorous, Eogyrinus (data from Panchen 1977).
Moreover, the mid-point of insertion and line of action of the adductor muscles of the lower jaw were
further forward in relation to the tooth row in Anthracosaurus than in Eogyrinus, increasing the static
pressure capable of being exerted on prey items when the jaw was near closure ( Panchen 1981). Olson
(1961) has suggested that the static pressure system of jaw closure was originally developed in
tetrapods as an adaptation to terrestrial feeding, upon invertebrates such as insects and molluscs. It
seems likely, however, that adults of Anthracosaurus fed also upon other tetrapods, possibly around
the margins of lakes and rivers.

Specimens of A. russelli, the sole known member of the family Anthracosauridae, have been
described only from the Westphalian of England and Scotland (Panchen 1977); no certainly
anthracosaurid material has been reported amongst the tetrapod assemblages from Linton, Nyfany,
Jarrow, or Joggins. The absence of anthracosaurids from the Joggins assemblage, which is almost
precisely contemporary with that from Newsham and is composed primarily of terrestrial tetrapods,
is of some interest and is discussed elsewhere in the present study (see below).

In summary, the relative rarity of A. russelli specimens in the census sample and the functional

378

PALAEONTOLOGY, VOLUME 27

morphology of the animal, so far as it is known, suggest that this species was not endemic in life to the
environment of preservation of the Newsham tetrapods. It is presumed to have formed part of a
terrestrial/marginal tetrapod community, of which it is the only representative so far known from the
site (text-fig. 4). While it is possible that the Newsham /I. russelli material, which all appears to pertain
to adult animals, is derived from individuals which were visiting the lake to breed, the fragmentary
nature of the known specimens suggests rather that they are erratics, having been transported to the
site post-mortem.

2. Shallow-water I swamp-lake association. The three Newsham tetrapods regarded with some
confidence as comprising this association are the ophiderpetontid ai'stopod Ophiderpeton nanum,
a urocordylid nectridean and a lysorophid. Each is represented by only a single specimen in the
census sample. The urocordylid and the lysorophid are not certainly determinate below family
level.

The specimen of Ophiderpeton nanum consists of a poorly preserved skull and incomplete
postcranial skeleton, the latter including the most anterior forty-three vertebrae in an articulated
series (Boyd 1982a, fig. 1). The vertebral count in an entire specimen of this species is not known, but
Baird (1964, p. 6) has given a figure of 100 + for a juvenile of O. granulosum Fritsch. The first forty
vertebrae of the O. nanum specimen together measure 1 1 -2 cm; on the assumption the verebral count
of the complete animal was similar to that of O. granulosum, the total length of its vertebral column
may very roughly be estimated at somewhat in excess of 28 cm. The skull appears to have been
approximately 1 cm in length.

A restoration of the probable appearance of Ophiderpeton in life has been published by A. R.
Milner ( 1 980b, fig. 5). The body in this genus is highly elongate and snake-like, and the tail very short
(Zidek and Baird 1978). Although an interclavicle may be present in the Newsham O. nanum
specimen (Boyd 1982a), there is no convincing evidence of the presence of limbs in any described
ai'stopod (Baird 1964; Wellstead 1982). The skull of Ophiderpeton is narrow and elongate' with the
orbits placed well forward, anterior to large temporal fenestrae (Steen 1931; Thomson and Bossy
1 970). The body bears a ventral armour of elongate, needle-like gastralia arranged en chevron, and the
dorsal and lateral surfaces of both body and tail are covered by an armour of small, pebble-like
osteoderms. The latter armour also extends forward to cover the temporal fenestrae (Baird 1964).
Examination of a skull (BM(NH) R2657) of O. amphiuminum (Cope) from Linton indicates that the
small marginal teeth are not, as described by Steen (1931), merely erect and cylindrical, but possess
horizontal chisel-like edges and resemble in form those of the lower Permian embolomere Archeria
(e.g. Panchen 1970, fig. Ab). Like those of Archeria, the marginal teeth of Ophiderpeton appear to have
been closely set and of roughly uniform height over most of the length of the tooth row. As A. R.
Milner (1978) has pointed out, such a dentition provides a continuous surface for gripping, rather
than piercing, prey and it is probable that Ophiderpeton fed largely upon soft-bodied invertebrates
considerably smaller than itself. While it is clear that Ophiderpeton had a lateral undulatory
propulsive system (Lund 1978), conflicting opinions have been expressed as to the primary
environment in which the system was used. Thus, Romer (1930) considered that both phlegethontiid
and ophiderpetontid a'istopods were entirely aquatic whereas Gregory ( 1 948) argued for a burrowing
mode of life for Ophiderpeton, and Thomson and Bossy (1970) merely noted that, whether on land or
in water, a'istopods obviously ‘swam’. However, as A. R. Milner (19806) has noted, Ophiderpeton has
not been reported from any primarily terrestrial tetrapod assemblage but is of frequent occurrence at
Jarrow, Linton, and Nyfany. Furthermore, at the latter two localities this genus would appear, from
published data (Romer 1930, p. 140; A. R. Milner 1980, p. 454), to be considerably more abundant
than the phlegethontiid a'istopod Phlegethontia, which has been convincingly demonstrated by Lund
(1978) to have been primarily terrestrial. Thus, although the serpentiform body, short tail, small
orbits and heavy dermal armour of Ophiderpeton may indicate derivation from burrowing ancestors
it would seem likely that the known members of this genus were very largely, if not entirely, aquatic in
habit. Gregory’s (1948) objection to an aquatic mode of life for Ophiderpeton, on the grounds that the
caudal vertebrae lack the high neural and haemal spines seen in the tail of urocordylid nectrideans.

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

379

seems of little moment. In Ophiderpeton the trunk is very elongate and the tail short (Zidek and Baird
1978) whereas the reverse of this arrangement is exhibited by the urocordylids, in which the tail is
markedly longer than the trunk (A. C. Milner 1980) and clearly constituted the major propulsive
organ in aquatic locomotion. It is, moreover, possible that the posterior body and tail of
Ophiderpeton species bore dorsal and ventral fin-like membranes without skeletal supports, such as
are present in some (almost tailless) aquatic apodans of the family Typhlonectidae. Indeed,
Ophiderpeton species may parallel the typhlonectids in being secondarily aquatic, limbless
amphibians derived from ancestors adapted for a burrowing mode of life.

The presumed mode of life of Ophiderpeton, the presence of only a single specimen at Newsham
and the relative abundance of this genus at Jarrow, Linton, and Nyfany together suggest that O.
nanwn was not endemic in life to the environment of preservation of the Newsham tetrapods but is
to be regarded as probably an erratic derived from a shallow-water/swamp-pool environment. The
poorly preserved and incomplete nature of the specimen may indicate post-mortem transport (text-
fig. 4).

The Newsham urocordylid specimen is an isolated posterior caudal vertebra which, although
indeterminate at generic level, appears, as noted above, to pertain to a member of the Ptyonius-gronp
of Bossy (1976). Comparison with the caudal vertebrae of the Urocordylus wandesfordii holotype as
figured by Bossy (1976, fig. 73), which measures approximately 55 cm in total length, suggests that
the Newsham vertebra derives from an animal of closely similar size. Like other urocordylids, the
Ptyonius-group members were principally, if not entirely, aquatic in habit, swimming by sinusoidal
flexure of the body and long laterally compressed tail (A. C. Milner 1980). Ctenerpeton is known only
from the posterior trunk and tail, but in Urocordylus and Ptyonius the trunk was shorter than in the
Sciuroleura-gronp urocordylids {Sauropleura, Lepterpeton, and Crossotelos: Bossy 1976), having a
maximum of twenty-two vertebrae. The tail, which in Urocordylus includes over eighty vertebrae,
was particularly deep in vertical profile, being of constant depth for the anterior two-thirds of its
length and then tapering rapidly to its tip (A. C. Milner 1980, after Bossy 1976). Bossy (1976) has
suggested that Urocordylus and Ptyonius were adapted for sustained powerful swimming, although
having a lower initial acceleration than the Sauropleura-gvonp genera. The skull of Ptyonius-group
urocordylids is adequately known only in Ptyonius itself, but that of Urocordylus, as restored by
Bossy (1976), appears similar in being broader and shorter-snouted than is the case in the
Sauropleur a-group. Cranial kinesis in Ptyonius was apparently restricted to the supratemporal-
squamosal line and Bossy (1976) suggests that the jaw mechanics of this genus tended towards the
static-pressure system of Olson (1961), thus differing from the specialized type of kinetic inertial
system found in Sauropleura and its allies. The teeth of Ptyonius are smaller and more numerous than
those of Sauropleura and differ also in not being recurved. It thus seems likely that Ptyonius-group
urocordylids were adapted for feeding on relatively smaller and less vigorous prey than that of
Sauropleura-group members, and their diet may have consisted in large part of soft-bodied
invertebrates.

Although rare at Newsham, urocordylids are relatively abundant at Nyfany (at least thirty-two
specimens of Sauropleura scalar is Fritsch), Linton (many specimens of Sauropleura pectinata Cope,
at least eight specimens of Ctenerpeton remex Cope and at least fifteen specimens of Ptyonius marshii
(Cope)) and at Jarrow (four specimens of Urocordylus wandesfordii Wright and Huxley and two
specimens of Lepterpeton dobbsii Wright and Huxley) (data from A. C. Milner 1980). It is therefore
probable that, although known urocordylids were clearly largely aquatic in habit, the species
represented by the single Newsham specimen was not endemic in life to the environment in which the
Newsham tetrapods were preserved but is an erratic from a shallow-water/swamp-pool environment
(text-fig. 4). The nature of the specimen suggests that transport to the site of preservation may have
been post-mortem.

The lysorophid specimen from Newsham consists of twenty-one articulated vertebrae, apparently
from the anterior trunk region, most of which are associated with their respective rib pairs (Boyd
1980^>, fig. 1a). The vertebrae are almost identical in size with the anterior trunk vertebrae of the
Lysorophus specimen described by Sollas (1920), which has a skull length of slightly less than 2 cm.

380

PALAEONTOLOGY, VOLUME 27

Seventy-two presacral vertebrae are present in the articulated specimen of Cocytinus figured by
Carroll and Gaskill ( 1 978, fig. 1 32b). On the assumption that a similar number was originally present
in the animal represented by the Newsham specimen, the length of its presacral vertebral column may
very tentatively be estimated at approximately 35 cm, although this makes no allowance for regional
variation in centrum length. The snout-vent length of the Newsham lysorophid was thus probably
about 37 cm and, if the tail was like that of Lysorophus (Olson 1971) in being roughly one-sixth as
long as the body, the overall length would have been in the region of 43 cm.

The known lysorophids were apparently largely aquatic, although Olson (1971) has suggested that
Lysorophus may have been capable of some overland travel by wriggling. Lysorophid limb girdles
and limbs are very small relative to body size (e.g. Sollas 1920, fig. 1; Carroll and Gaskill 1978,
fig. 132b) and the latter were probably functionally insignificant in both aquatic and terrestrial
locomotion. There is little doubt that the animals were active swimmers, moving by sinusoidal fiexure
of the long body and short, laterally compressed, tail. The skull is completely open in the orbital and
temporal regions (Sollas 1920) suggesting that lysorophids were not habitual burrowers; the presence
of Lysorophus specimens preserved in aestivation burrows in the lower Permian of Oklahoma (Olson
1971) does, however, indicate some capability in this respect. As Olson (1971) has pointed out, the
ability to aestivate would also seem to suggest that, although lysorophids exhibit well-ossified
branchial arches and may have been perennibranchiate, functional lungs were also present.
Lysorophid premaxillae and maxillae were freely moveable on the rest of the skull (Carroll and
Gaskill 1978) and the teeth of Lysorophus are relatively large, few in number and slightly recurved
(Sollas 1920, fig. 38). It would thus seem likely that lysorophids were active carnivores, feeding on
relatively large and vigorous prey. Coprolites containing the bones of a small temnospondyl, a small
captorhinomorph reptile and palaeoniscid fishes, in addition to lamellibranch shells, have been
attributed to Lysorophus by Olson (1971). As Olson notes, insects and various aquatic invertebrates
doubtless also formed part of the diet of Lysorophus, which probably had a mode of life in many
respects similar to that of the extant urodele Amphiuma.

The presence of only a single, incomplete, lysorophid in the census sample and the inferred mode of
life of the members of the group together suggest that the Newsham specimen was derived from an
aquatic environment other than that in which it was preserved. Lysorophids have been reported from
few localities in the Westphalian. They do, however, occur at Linton, where the group is represented
by the genera Molgophis and Cocytinus (Steen 1931), and may also be present at Jarrow (Carroll and
Gaskill 1978, p. 187), although the poor preservation of the material from the latter site makes
identification uncertain. It thus seems likely that the Newsham lysorophid specimen represents an
erratic transported from a shallow-water/swamp-lake environment (text-fig. 4). A. R. Milner (1982,
p. 661) has suggested a similar origin for the single Cocytinus specimen recorded as part of the
Westphalian D tetrapod assemblage from Mazon Creek, Illinois.

Two further Newsham amphibian taxa may also, although less certainly, represent erratics from
shallow-water/swamp-lake environments. The first is the medium-sized, almost certainly eogyrinid,
embolomere Pteroplax cornutus, apparently represented in the census sample by six specimens. Of
these, only the isolated skull table (G15.72) designated the lectotype of P. cornutus by Romer (1963)
is certainly referable to this species. However, as the five attributed specimens could all, in theory, be
derived from the same individual as the lectotype, the slight uncertainty as to their pertaining to P.
cornutus does not affect the assessment of the minimum number of individuals represented by
the material. The attributed specimens comprise: a trunk pleurocentrum, intercentrum and one
indeterminate central element in association with two neural arches and three ribs (G83.68); seven
articulated trunk vertebrae in association with four ribs (G15.73); a caudal intercentrum (G4.83); an
isolated left pterygoid (G25.45) and a right nasal with associated premaxilla (G24.40). The last
specimen is, if correctly attributed to P. cornutus, of some importance as the premaxilla bears four
recurved teeth (Boyd 1978, fig. 10) of the shape characteristic of eogyrinid, rather than archeriid or
anthracosaurid, embolomeres (Panchen 1970). Reasons for attributing the above five specimens to P.
cornutus have been set forth elsewhere (Boyd 1978; 1980a). There can be little doubt that P. cornutus
was largely aquatic: the skull table bears well-developed lateral line sulci (Panchen 1970, fig. 14a), as

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

381

do the attributed nasal and premaxilla. The structure and mode of life of eogyrinid embolomeres
have been discussed by Panchen (1970; 1972), who regards the members of this family as aquatic
carnivores, swimming in anguilliform manner by sinusoidal flexure of the elongate body and long,
laterally compressed, tail. The teeth of P. comutus, if correctly attributed to this species, suggest a
piscivorous habit. The inferred mode of life of P. cornutus, its rarity at Newsham and the nature of the
few specimens known from the site together suggest the possibility that the species may not have
been endemic to the environment of preservation but represents an erratic from another aquatic
environment, possibly of the shallow-water/swamp-lake type. A second and, in view of the rarity of
embolomere specimens at Nyfany (A. R. Milner 1980(>) and Linton (Panchen 1977), perhaps more
likely possibility is that P. cornutus was primarily a river-dwelling species.

If the isolated amphibian interclavicle (G24.98) described above as probably that of a colosteid
temnospondyl is correctly so designated, it too may represent a transported erratic from a shallow-
water/swamp-lake environment. Described colosteids were clearly largely aquatic in habit; the skull
bore a well-developed lateral line system (e.g. Romer 1930, fig. 1 1: Smithson 1982, fig. 7) and the
vertebral column, where known, includes approximately forty presacral vertebrae (Smithson 1982,
p. 31). Colosteids have not been reported from any primarily terrestrial tetrapod assemblage, such
as that from Joggins, and in the Westphalian occur at Jarrow and Linton (A. R. Milner 1980u,
p. 1 35; Romer 1930).

As A. R. Milner (1980/7) has pointed out, the haplolepid actinopterygians known from Newsham
are probably also to be regarded as erratics from a shallow-water/swamp-lake environment.
Haplolepids are rare at Newsham: Westoll (1944) described the remains of only four individuals,
representing three species, from the site. The haplolepid-aistopod-nectridean ‘facies fauna’ of
Westoll (1944) has been equated by A. R. Milner (1980/7, p. 474) with the latter’s shallow-water/
swamp-lake association and redefined, in more precise terms, as a haplolepid-ophiderpetontid-
urocordylid association. However, the recent recognition of urocordylid material from Newsham
(Boyd 1982/7) means that, despite Milner’s more restricted definition of the haplolepid ‘facies fauna’,
Westoll’s (1944) statement that members of all three constituent groups occur as occasional
individuals at the site still holds true.

3. Open-waterllacustrine association. The three Newsham tetrapod species regarded as comprising
this association, and as having been endemic in life to the environment of their preservation, are
Megaloceplialus pachycephalus, Batrachiderpeton reticulatum, and Eogyrinus attheyi. These are the
most abundant species in the census sample, each being represented by more than ten specimens
(text-fig. 3).

Megalocephalus pachycephalus is the most frequent tetrapod in the sample studied. Sixty-one
specimens are present, representing the remains of at least eleven individuals. Interestingly, all the
Newsham material certainly referable to M. pachycephalus consists of skulls, skull fragments,
isolated cranial elements, and teeth (Boyd and Turner 1980), although a few postcranial bones from
the site have been attributed to this species. The latter comprise an isolated neural arch (G37.88), an
interclavicle (G13.81 ) and an ilium (RSM 88.33) figured by Tilley (Beaumont) (1971, figs. 32-34), and
a number of isolated centra figured in part by Panchen (1980, fig. 9d-e). In view of the relative
abundance of M. pachycephalus at Newsham, the absence of certainly associated postcranial remains
is somewhat surprising. However, a similar state of affairs has been noted by A. R. Milner (1980/7,
p. 448) at Nyfany, where many of the medium to large amphibian specimens consist only of isolated
skulls or skulls in association with disarticulated pectoral elements. Milner suggests that this is due
to the combination in the animals concerned of a large dense skull and pectoral girdle anteriorly
and a potentially autolysing hind-gut posteriorly, resulting in the bodies and tails of the corpses
disintegrating or floating away while the denser anterior ends remained stationary. The almost total
lack of even isolated postcranial material plausibly referable to M. pachycephalus at Newsham may
conceivably be due to most of the floating, headless, bodies having been carried from the lake by
excurrent streams. Alternatively, many of the ‘missing’ postcranial elements may be preserved in
areas of the Newsham black shale which have not been collected.

382

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 4. Restorations of tetrapod taxa recorded from Newsham. The animals are depicted in diagrammatic
representations of the environments they are considered to have inhabited in life. Abbreviations; M —
Megalocephalus (after A. R. Milner 1980Z?, fig. 3), B — Batrachiderpeton (postcranial proportions based on those
of Keraterpeton as figured by A. C. Milner 1980, fig. 4a). Scale bar represents 5 cm, E — Eogyrinus (after A. R.
Milner 1980(), fig. 3), L— lysorophid (proportions based upon those of Cocytinm skeleton figured by Carroll and
Gaskill 1978, fig. 132b). Scale bar represents 3 cm, U~urocordylid (restoration based upon skeleton of
Urocordylus as figured by Bossy 1976, fig. 73). Scale bar represents 6 cm. 0~Ophiderpeton (after A. R. Milner
19806, fig. 5). Scale bar represents 3 cm, A — Anthracosaurus (postcranium hypothetical). Plant symbols partly
after Scott (1979). Abbreviations; a—Calamites, h~~Lepidodendron, c — Sigillaria.

The total lengths of the Newsham M. pachycephalus skulls in which such measurement is possible
range between approximately 35 cm and 40 cm, although the dimensions of one incomplete specimen
(BM(NH) R3417) are suggestive of an even greater original length (Beaumont 1977). The presence
at the site of sub-adult individuals of the species is suggested by an isolated right jugal (G140.81)
measuring only 72 mm in length; that of the roughly 35 cm long, skull figured by Beaumont (1977,
fig. 8) measures approximately 150 mm. The skull of M. pachycephalus is crocodile-like in shape and
bears well-developed lateral line sulci, suggesting that the animal spent a considerable amount of time
in water. Such a habit is also suggested by the ventrally placed external nares, which are separated
from the jaw margin by distinct naso-labial grooves {sensu Panchen 1967, p. 413). The slender,
lanceolate marginal teeth of M. pachycephalus, the shagreen of denticles on the parasphenoid and
dermal palatal elements and the kinetic inertial system of jaw closure (Beaumont 1977) all suggest
that this species was an aquatic feeder and probably largely piscivorous. Although it is possible that.

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

383

as A. R. Milner (1980/>) has suggested, loxommatids such as Megalocephahis lived a crocodile-like
existence, entering the water to feed but otherwise resting around lake and river margins, the large
amount of M. pachycephalus material from Newsham might be taken to indicate a more thoroughly
aquatic mode of life for this species at least. Loxommatids appear to occur only rarely in tetrapod
assemblages from shallow-water/swamp-lake environments. Thus, A. R. Milner (1980/)) reported
only one specimen representative of this family, a skull of Baphetes, amongst approximately 400
tetrapod specimens from Nyfany. Beaumont (1977) listed only five loxommatid specimens from
Linton and one, a Megalocephahis skull, from Jarrow; the second Jarrow skull (BM(NH) R8465)
cited by Beaumont, and considered by her to be possibly that of a juvenile Megalocephahis specimen,
actually pertains to the aistopod Ophiderpeton (A. R. Milner, pers. comm.).

Batrachiderpeton reticiilatiim is the second most frequent tetrapod species in the census sample;
twenty-one specimens are present, representing at least nine individuals. Both adults and juveniles are
represented in the material (Boyd and Turner 1980, pp. 18-19) and there appears to be a correlation
between the size and degree of disarticulation of the specimens. The adult B. reticiilatiim material
consists almost entirely of isolated skulls, skull fragments and isolated mandibular rami and
vertebrae, although in one specimen (G25.39) part of the pectoral girdle is associated with an
incomplete skull. Of the four juvenile specimens, however, two consist of skulls in association with
much of the postcranial skeleton. This size-linked disinegration may have been a result of the larger
animals having had a greater, potentially autolysing, volume of hind gut, capable of producing more
gas before decomposition was inhibited by the anaerobic conditions on the lake bottom (A. R. Milner
1980/), p. 448). Like all other known keraterpetontid nectrideans, B. reticiilatiim was clearly largely, if
not entirely, aquatic in habit, swimming by sinusoidal flexure of the body and the long, laterally
compressed tail. The skull, which in the restoration figured by A. C. Milner ( 1980, fig. 5f) measures
approximately 5 cm in length, is short-snouted with an akinetic skull table firmly sutured to the,
relatively deep, cheek region. The marginal teeth are of moderate size and conical in form, with
incurved tips. Teeth only slightly smaller are present on the coronoids and the lateral dermal palatal
elements; in addition, the pterygoids bear a shagreen of denticles anteriorly. The mandible bears a
well-developed retroarticular process (data from A. C. Milner 1980). A. C. Milner (1978; 1980) has
suggested that the jaw mechanism of keraterpetontids tended towards the static pressure type and
that the animals were adapted for seizing and crushing small invertebrates with shells or hard
exoskeletons. B. reticulatum appears to have possessed a, probably ligamentous, connection between
the tabular horn and cleithrum on each side; these connections probably served to dampen lateral
oscillatory movements of the head during swimming and thus to facilitate a straight-line approach to
prey (A.C. Milner 1980, p. 389). It seems quite probable that, as A. R. Milner (1980/), p. 477) has
suggested, this species lived around the margins of the Newsham lake, possibly in stands of marginal
vegetation including Calamites.

The relative abundance of B. reticulatum at Newsham and the nature of the known material both
strongly suggest that this species was endemic to the site. Indeed, A. R. Milner ( 1 980/)) has suggested
that keraterpetontids should be regarded as forming part of the Westphalian open-water/lacustrine
tetrapod association, although not occurring uniformly enough with loxommatids and eogyrinid
embolomeres to be included with the latter two taxa in the familial characterization of this
association. Keraterpetontids are absent from Nyfany (A. R. Milner 1980/)) and rare at Linton (only
eight reported specimens of Diceratosaurus brevirostris (Cope): A. C. Milner 1980, p. 404). At least
twenty-four specimens of Keraterpeton galvani Wright and Huxley are known from Jarrow (A. C.
Milner 1980) but A. R. Milner (1980/), p. 473) interprets these as constituting a ‘juvenile swarm’ and,
presumably, as inhabiting a water body shallower than those preferred by the adults.

Eogyrinus attheyi is represented in the census sample by eleven specimens; these include the
remains of at least four individuals. All the specimens in the sample, with the exception of the
lectotype of E. attheyi, are skull fragments and isolated cranial elements. The lectotype consists of an
almost complete skull with both mandibular rami (Panchen 1972, fig. 2), in association with at least
twelve anterior trunk vertebrae, six ribs, a number of dermal scutes and a limb bone interpreted by
Panchen ( 1 972) as a femur. The presence of only a few anterior vertebrae with the lectotype skull and

384

PALAEONTOLOGY, VOLUME 27

the absence of associated postcranial remains with the other E. attheyi skull specimens may, as has
been suggested in the case of the Newsham loxommatid material, be due to the disintegration or
floating away of the, less dense, postcrania as a result of gas generation by hind-gut autolysis. As has
been noted above, the, fairly numerous, isolated elements of large embolomerous vertebrae from
Newsham (e.g. Boyd & Turner 1980, pp. 13-16) have been omitted from the census sample on the
grounds that some may pertain to Anthracosaurus nisselU rather than E. attheyi. The same applies to
the large isolated dermal scutes (e.g. Panchen 1972, fig. 1 5) from the site. However, even if most or all
of these vertebrae and scutes are in fact derived from E. attheyi, as is statistically likely to be the case,
they are not sufficient in number for their exclusion from the study sample to make any difference to
the assessment of the minimum number of individuals of this species based upon skull material.

E. attheyi was probably the largest of the apparently endemic Newsham tetrapods and one of the
largest vertebrates known from the site; the lectotype skull has an overall length of 41 cm and the
complete animal may have been up to 4 m long (Panchen 1972). The fact that this species is
apparently much less abundant at Newsham than are Megalocephalus and Batrachiderpeton is
consistent with its greater size and presumed status as an ultimate consumer. The skull bears well-
developed lateral line sulci and naso-labial grooves are present below the external nares; there can
thus be little doubt that E. attheyi was, as suggested by Panchen (1970), largely aquatic in habit,
swimming by sinusoidal flexure of the elongate body and long, deep, tail. The marginal teeth are of
moderate size and recurved at their tips. A row of similar teeth is present on each ectopterygoid,
which, like the palatine, bears tusks anteriorly. The form of the teeth and the shagreen of tiny
denticles on the pterygoids and coronoids are suggestive of a diet largely of fish and the presence in
E. attheyi of a kinetic inertial system of jaw closure (Panchen 1970) might be taken to indicate
that aquatic feeding was the norm for this species. Moreover, as Atthey (1876, p. 165) pointed out,
amongst the vertebrae and ribs associated with the E. attheyi lectotype are preserved a toothplate, rib,
and several scales referable to the dipnoan genus Ctenodus, which may represent gut contents. In
addition, the holotype specimen of the large eogyrinid Pholiderpeton scutigerum Huxley (BRM
NS. 1 1 1.81) is associated with two scales of the crossopterygian Megalichthys which, to judge from
their situation and eroded condition, are probably also derived from ingested prey (J. A. Clack, pers.
comm.). Although E. attheyi was probably mainly piscivorous, it seems highly likely that it fed also
upon other aquatic tetrapods; there is, however, no direct evidence for this. A. R. Milner (19806) has
suggested that eogyrinids may have been adapted for swimming and/or crawling among dense
Calamites stands around lake margins.

Eogyrinids appear to be scarce in tetrapod assemblages from shallow-water/swamp-lake environ-
ments. Only two incomplete specimens of the, doubtfully eogyrinid, embolomere Diplovertebron
punctatum Fritsch were reported by A. R. Milner (19806) from Nyfany. Panchen (1977) noted only
six specimens of Leptophractus obsoletus Cope from Linton. No precise published data are available
concerning the frequency of eogyrinids in the Jarrow assemblage; however, Panchen (1970, p. 64)
reported a mere two embolomere specimens from the site. Interestingly, the tetrapod assemblage
from Joggins, which is composed mostly of terrestrial tetrapods (see below), includes a few specimens
of the tiny, probably eogyrinid (Panchen 1970), embolomere Calligenethlon watsoni Steen. They are,
however, relatively rare components of the assemblage (Carroll 1967) and, while the mode of their
preservation suggests that they were capable of terrestrial locomotion, it is doubtful if larger
eogyrinids were habitual overland travellers.

In summary, the relative frequency of Megalocephalus, Batrachiderpeton, and Eogyrinus specimens
in the Newsham tetrapod assemblage, the nature of the material and the presumed mode of life of
the animals themselves together suggest that these taxa were endemic in life to the environment
of preservation. The scarcity of loxommatids, keraterpetontids, and eogyrinids in shallow-water/
swamp-lake tetrapod assemblages would seem to confirm that the Westphalian members of these
families were characteristic inhabitants of larger and deeper water bodies, such as the Newsham lake
(text-fig. 4).

The structure of the Newsham open-water/lacustrine community has been discussed by A. R.
Milner (19806, pp. 475-479), who suggests that the ultimate energy sources in Carboniferous open-

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

385

water bodies such as the Newsham lake were probably organic detritus and algae, the former being
fed upon by a wide range of invertebrate primary consumers and the algae, both planktonic and
encrusting, mainly by ostracods and gastropods. Milner further suggests that all the endemic fish
species at Newsham, with the possible exception of the platysomoid palaeoniscid Cliirochis, were,
like the amphibians, secondary and tertiary consumers which fed upon other vertebrates and
invertebrates. As noted elsewhere in the present paper, the only invertebrate taxa known from
Newsham are ostracods and bivalves; the other invertebrate groups noted by Milner as possible
carnivores (chelicerates) and primary consumers (palaeocarid crustaceans and gastropod molluscs)
in open-water/lacustrine communities have not been reported from the site. However, all three are
known from Westphalian non-marine deposits (e.g. Calver 1968; Schram 1976) and their absence
from the Newsham assemblage may merely be due to non-preservation or non-collection. While
generally in agreement with A. R. Milner’s (19806) conclusions with respect to the structure of
the Newsham open-water/lacustrine community, the present writer would suggest that Chirodus
(represented by a very few articulated specimens of C. striatus (Hancock and Atthey)) may not have
been the only vertebrate primary consumer at the site. Two species of dipnoan, the ctenodontid
Ctenodus cristatus Agassiz and the sagenodontid Sagenodus maequalis Owen, have been reported
from Newsham (S. M. Andrews in Land 1974, p. 61) and the latter, at least, may have been partly, if

TEXT-FIG. 5. Hypothetical food-web of the Newsham open-water/lacustrine community. The
food-web is much simplified, for the sake of clarity, and does not attempt to show all possible
interactions involving juveniles and larvae. Format based upon that employed by A. R. Milner

(19806, fig. 9).

386

PALAEONTOLOGY, VOLUME 27

not entirely, herbivorous. Unlike the tooth-plates of Ctenodus, which appear to have been specialized
for crushing, those of Sagenodus bear a reduced number of ridges and denticles and were probably
mainly sectorial in function (Moy-Thomasand Miles 1971, p. 152). It is interesting to note, moreover,
that both juveniles and adults of Neoceratodus, structurally the most primitive of the living Dipnoi,
are known to take vegetable, as well as animal food. Indeed, Gunther (1880, p. 357) noted that the
stomach of Neoceratodus specimens usually contains large quantities of leaves derived from plants
growing on river banks, which are evidently eaten after falling into the water. If one or both of the
Newsham dipnoans included significant amounts of plant material in their diet, they must have been
much more important as primary consumers than the, rare, Chirodus striatus; a cursory survey of the
extensive Newsham fish collections in the Hancock Museum suggests that the Dipnoi may be the
most abundantly represented group. Moreover, Hancock and Atthey (1871Z?, p. 197) note that
Atthey’s collection at that date included at least 400 isolated dipnoan tooth-plates from Newsham,
representing a minimum of 100 individuals. Like Neoceratodus, the juveniles of the Newsham
lungfish may have eaten filamentous algae and the adults may have taken both living and dead
vascular plant material, including, perhaps, Calamites growing around the lake margins.

Text-fig. 5 is a hypothetical food-web of the Newsham open-water/lacustrine community, which
incorporates the above suggestions.

THE JOGGINS TETRAPOD ASSEMBLAGE

As noted above, only one other large, compact tetrapod assemblage of Westphalian B age is known,
that from Joggins in Nova Scotia (text-fig. 6). All described tetrapod specimens from this site were
collected from within Division 4 {sensu Logan 1 845) of the lower Westphalian B Cumberland Group,
on the south side of Chignecto Bay at the head of the Bay of Fundy (Carroll 1967). Division 4 of the
Cumberland Group includes approximately forty horizons at which erect stumps of arborescent
lycopods, including Sigillaria, occur. All but a very few of the Joggins tetrapods were found within
these stumps. As Carroll (1967, p. 112) has pointed out, ‘the preservation of the stumps in an erect
position is apparently a result of very rapid deposition. In the cases where vertebrates are found
within the trees, it is probable that the bases of the trees were covered but most of the trunk remained
exposed. The portion of the trees remaining above the new ground level then fell over, and the centre
of the stumps (pulpy even in the living trees) rotted out. The resulting hollow cylinders served as traps
for animals living on the new land surface.’ Rayner (1971, P- 463), however, has suggested that at least
some of the Joggins tetrapods may have deliberately entered the hollow stumps in search of food. The
Joggins assemblage has been briefly reviewed by Carroll et al. (1972, pp. 64-80).

Comparison of the tetrapod assemblages from Newsham and Joggins is of some interest in view
of the fact that they are closely contemporaneous but preserved in sediments deposited in two
very different micropalaeoenvironments within broadly similar (coal-swamp basin) macropalaeo-
environments. The fact that the Joggins lycopod stump tetrapods were collected from a number of
different horizons within over 450 m of strata (Carroll et al. 1972), whereas the Newsham assemblage
derives entirely from one bed of shale no more than 10 cm thick (Atthey 1877), is probably of less
significance for such a comparison than initial consideration might suggest. The Newsham black
shale was apparently laid down during a period of very low detrital input into (at least the centre of)
the Newsham lake and sedimentation may have been very slow. Conversely, the presence at Joggins
of erect lycopod stumps up to 9 m in height is, as noted by Carroll (1967) and Rayner (1971),
indicative of very rapid sedimentation. The lengths of time represented by the tetrapod-bearing
deposits at the two localities may thus not be so widely disparate as suggested by the differing
thicknesses of strata involved. The ten valid tetrapod species so far recorded from the Joggins
lycopod stumps are listed below. Where possible, data (derived from the literature) on the frequency
of each species at the site have been included, as has an indication of size. The latter is, in most cases,
given as skull length, as many of the Joggins tetrapods are known only from disarticulated and
incomplete skeletons.

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

387

TEXT-FIG. 6. Map of Laurasia during mid-Carboniferous times to show approximate positions
of Joggins and Newsham relative to one another and to the southern margin of the continent.
Stippling indicates terrestrial hinterland; unstippled area of continent comprises shelf seas and
marginal environments (map modified from Johnson 1981, fig. 4).

Order temnospondyli

Dendrerpetontidae: Owen — ‘about 100 specimens’ (Carroll 1967,p. 111).

The largest described skull of this species from Joggins has a midline length of 102 mm and, as
restored by A. R. Milner (1980a, fig. 3d), a total length of about 120 mm.

Order batrachosauria

Eogyrinidae: Calligenethlon watsoni Steen — ‘less than a dozen specimens’ (Carroll 1967, p. 111).
Carroll (1967) estimates the skull of this species to have been between 50 mm and 75 mm in length.

Order microsauria

Tuditanidae: Asaphestera intermedia (Dawson)— twenty identifiable specimens. The larger skulls
have a total length of about 42 mm (Carroll and Gaskill 1978).

Pantylidae: Trachystegos megalodon Carroll— five identifiable specimens (Carroll and Gaskill
1978). The total length of the skull as restored by Carroll (1966, fig. 1 1b) is 53 mm.

Gymnarthridae; Leiocephalikon problematicum (Dawson) — ten identifiable specimens. The total
length of the skull appears to have been about 21 mm (Carroll and Gaskill 1978).

Gymnarthridae: Hylerpeton dawsoni Owen— fourteen identifiable specimens (Carroll and Gaskill
1978). The total length of the skull is not known but the left mandibular ramus figured by Carroll
(1966, fig. 6a) is 37 mm long.

388

PALAEONTOLOGY, VOLUME 27

Hapsidopareiontidae: Ricnodon sp.— four identifiable speeimens (Carroll and Gaskill 1978). The
total length of the skull is unknown but the isolated dentary figured by Carroll (1966, fig. 19b)
measures about 9 mm in length.

Order captorhinomorpha

Romeriidae: Hylononms lyelli Dawson— eighteen specimens (Carroll et al. 1972). The skull of the
type specimen is 33 mm in length (Carroll and Baird 1972).

Romeriidae: Archerpeton anthracos — sixteen specimens (Carroll et al. 1972). This species is known
from very incomplete remains; it is, however, clearly substantially smaller than Hylononms (Carroll
and Baird 1972).

Order pelycosauria

?Ophiacodontidae: Protoclepsydrops Impious Carroll four specimens (Reisz 1972). The skull is
not known in its entirety but the humeral length of this species is only slightly less than that of the
Westphalian D ophiacodont pelycosaur Archaeothyris florensis (Reisz 1972, fig. 1 8), which has a skull
about 92 mm in length.

All the above listed species, with the possible exception of Calligenethlon watsoni, appear to
have been largely terrestrial in habit (e.g. Carroll 1967; Carroll and Gaskill 1978; Carroll and Baird
1972; Reisz 1972) and are members of families regarded by A. R. Milner (19806) as belonging
to the Westphalian terrestrial/marginal tetrapod association. C. watsoni is, as noted above,
the smallest described embolomere and may have been more terrestrial than other known
eogyrinids.

The Eogyrinidae, represented at Joggins by C. watsoni, is the only tetrapod family common to both
this assemblage and that from Newsham. Microsaurs {sensu Carroll and Gaskill 1978), pelycosaur
and captorhinomorph reptiles and dendrerpetontid temnospondyls have not been reported from
Newsham. Loxommatids, keraterpetontid and urocordylid nectrideans, lysorophids, ophider-
petontid aistopods and anthracosaurid embolomeres are not known from the Joggins erect stumps.
The differences in the composition of the two assemblages clearly reflect their dilTering environments
of preservation. Most, if not all, of the Joggins tetrapods were primarily terrestrial forms whereas the
Newsham assemblage is composed almost entirely of amphibians which were either endemic to the
lake in whose bottom sediments they were preserved or derived from other aquatic environments.
However, a second difference exists between the tetrapod assemblages from the two sites. Whereas
the Newsham assemblage includes both small and very large amphibian species, that from Joggins
is composed only of relatively small tetrapods. The largest species reported from the erect stumps
appears to be Dendrerpeton acadianum, with a recorded skull length of up to 120 mm. A. R. Milner
(1980u, p. 126) has suggested that the known members of this genus probably grew to about one
metre in total length. The absence of larger tetrapods at Joggins is, as suggested by Carroll et al.
(1972, p. 71 ), probably due to the manner in which the assemblage was preserved; tetrapods above a
certain size would have been unlikely to fall into the, 0-9m-l-2 m diameter, hollow lycopod stumps
or, if they did so, may have been able to extricate themselves. The operation of this filter, controlling
the size of the animals preserved, may explain the absence from the Joggins assemblage of the only
terrestrial/marginal tetrapod species known from Newsham, the large anthracosaurid embolomere
Anthracosaunis russelli, or any other representative of the Anthracosauridae.

Of the seven tetrapod families represented at Joggins but not at Newsham, all but one (Pantylidae)
occur also in the Westphalian of Europe, either at Jarrow (Dendrerpetonidae: A. R. Milner 1980fl)
or at Nyfany (Tuditanidae, Gymnarthridae, Hapsidopareiontidae, Romeriidae, Ophiacodontidae;
A. R. Milner 19806, p. 453). Similarly, all but one (Anthracosauridae) of the six families occurring
at Newsham, but not Joggins, are present in the North American Westphalian at Linton, Ohio
(Loxommatidae, Keraterpetontidae, Urocordylidae, Lysorophidae, Ophiderpetontidae; Romer
1930). It thus seems likely that the constitutional differences between the tetrapod assemblages
from Joggins and Newsham are largely, if not entirely, due to the differing coal-swamp basin
micropalaeoenvironments represented by the tetrapod-bearing deposits at the two sites. The writer

BOYD; CARBONIFEROUS TETRAPOD ASSEMBLAGE

389

would, therefore, suggest that the two assemblages may be regarded as complementary, and as
together providing a more balanced and complete picture of the Westphalian B lowland tetrapod
fauna of southern Laurasia than either does alone.

Acknowledgements. Most of the amphibian specimens collected from Newsham are stored in the Hancock
Museum, Newcastle upon Tyne. My thanks are therefore due first to Mr. A. M. Tynan, Curator of that
institution, forallowingme to work on the material in his care. I am also indebted to Mrs. J. A. Clack (University
Museum of Zoology, Cambridge), Mr. and Mrs. P. L. Edwards (Kingston upon Hull Museum), Professor M. R.
House (University of Hull), Dr. A. C. Milner (British Museum (Natural History)), Dr. A. R. Milner (Birkbeck
College, University of London), Dr. A. L. Panchen (University of Newcastle upon Tyne) and Drs. J. G. O. Smart
and David Mills (IGS, Leeds) for helpful comments, discussion and information relevant to the subject of the
present paper. Finally, especial thanks are due to Dr. N. Riley (IGS, Leeds), who very kindly assisted with the
identification of the Newsham invertebrate specimens, and to the staff of the NCB Mining Records Office at
Gateshead, Tyne and Wear, for their kindness in making available mine plans and providing valuable historical
information. The manuscript of this paper was typed by Mrs. J. M. Boyd and Mrs. C. R. Edwards.

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GUNTHER, A. c. L. G. 1880. An introduction to the study of fishes, xvi-t-720 pp. Edinburgh: A. & C. Black.

HANCOCK, A. and ATTHEY, T. 1868. Notes on the remains of some reptiles and fishes from the shales of the
Northumberland coal-field. Ann. Mag. nat. Hist. (4) 1, 266-278, 346-378.

1 869a. On a new labyrinthodont amphibian from the Northumberland coal-field, and on the occurrence in

the same locality of Anthracosaurus russelli. Ibid. 4, 182-189.

\869b. Note on Anthracosaurus. Ann. Mag. nat. Hist. (4) 4, 270-271.

1869c. On some curious fossil fungi from the black shale of the Northumberland coal-field. Ibid. 221-228.

1870fl. On the occurrence of Loxomma allmanni in the Northumberland coal-field. Ibid. 5, 374-379.

18707). Description of a labyrinthodont amphibian, a new generic form, obtained in the coal-shale at

Newsham, near Newcastle upon Tyne. Ibid. 6, 56-65.

1871a. Description of a considerable portion of a mandibular ramus of Anthracosaurus russelli, with notes

on Loxomma and Archichthys. Ibid. 7, 73-83.

18717). A few remarks on Dipterus and Ctenodus, and on their relationship to Ceratodus forsteri, Krefft.

Ibid. 190-198.

HURST, T. G. 1860. On some peculiarities of the Tyne Low Main Seam. Trans. N. Engl. Instn min. Engrs, 8, 23-31.

HUXLEY, T. H. 1863. Description of Anthracosaurus russelli, a new labyrinthodont from the Lanarkshire coal
field. Q. Jl geol. Soc. Lond. 19, 56-68.

JOHNSON, G. A. L. 1981. Geographical evolution from Laurasia to Pangaea. Proc. Yorks, geol. Soc. 43, 221-252.

KiRKBY, J. w. and ATTHEY, T. 1 864. On some fish remains from the Durham and Northumberland Coal Measures.
Trans. Tyne-side Nat. Eield Club, 4, 231-235.

LAND, D. H. 1974. Geology of the Tynemouth district. Mem. geol. Surv Gt Br. 15.

LOGAN, w. E. 1 845. A section of the Nova Scotia coal measures as developed at the Joggins . . . reduced to vertical
thickness. Geol. Surv. Canada, Kept Prog., 1843, Appendix, 92-159.

LUND, R. 1978. Anatomy and relationships of the Lamily Phlegethontiidae (Amphibia, Aistopoda). Ann.
Carnegie Mus. 47 (4), 53-79.

MILNER, A. c. 1978. Carboniferous Keraterpetontidae and Scincosauridae (Nectridea: Amphibia)— a review.
Ph.D thesis, University of Newcastle upon Tyne.

1980. A review of the Nectridea (Amphibia), 377-405. In panchen, a. l. (ed.). The terrestrial environment

and the origin of land vertebrates, xii -1-633 pp. Systematics Association Special Volume No. 15. London:
Academic Press.

MILNER, a. r. 1978. A reappraisal of the early Permian amphibians Memonomenos dyscriton and Cricotillus
brachydens. Palaeontology, 21, 667-686.

1980a. The temnospondyl amphibian Dendrerpeton from the Upper Carboniferous of Ireland. Ibid. 23,

125-141.

19807). The tetrapod assemblage from Nyfany, Czechoslovakia, 439-496. In panchen, a. l. (ed.). The

terrestrial environment and the origin of land vertebrates, xii -|- 633 pp. Systematics Association Special Volume
No. 15. London: Academic Press.

1982. Small temnospondyl amphibians from the Middle Pennsylvanian of Illinois, Palaeontology, 25,

635-664.

MILNER, A. r. and PANCHEN, A. L. 1973. Geographical variation in the tetrapod faunas of the Upper
Carboniferous and Lower Permian, 353-368. In tarling, d. h. and runcorn, s. k. (eds.). Implications of
continental drift to the earth sciences, Vol. 1. London: Academic Press.

MOULTON, J. M. 1974. A description of the vertebral column of Eryops based on the notes and drawings of A. S.
Romer. Breviora, 428, 1-44.

BOYD: CARBONIFEROUS TETRAPOD ASSEMBLAGE

391

MOY-THOMAS, J. A. and MILES, R. s. 1971. Palaeozoic Fishes, 2nd edn, xi + 259 pp. London: Chapman and Hall.
OLSON, E. c. 1961. Jaw mechanisms: rhipidistians, amphibians, reptiles. Am. ZooL 1, 205 215.

1971. A skeleton of Lysorophus tricarinafus (Amphibia: Lepospondyli) from the Hennessey Formation

(Permian) of Oklahoma. J. Paleont. 45, 443-449.

PANCHEN, A. L. 1964. The cranial anatomy of two Coal Measure anthracosaurs. Phil. Trans. R. Soc. Loud. B247,
593-637.

1966. The axial skeleton of the labyrinthodont Eogyrinus attheyi. J. ZooL, Load. 150, 199-222.

1967. The nostrils of choanate fishes and early tetrapods. Biol. Rev. 42, 374-420.

1970. Ted 5a Anthracosauria. Handbiich der Paldoherpetologie. Stuttgart: Fischer.

1972. The skull and skeleton of Eogvrinus attheyi Watson (Amphibia: Labyrinthodontia). Phil. Trans. R.

Soc. Land. B263, 279-326.

1975. A new genus and species of anthracosaur amphibian from the Lower Carboniferous of Scotland and

the status of Pholidogaster pisciformis Huxley. Ibid. B269, 581-640.

1977. On Anthracosaurus riisselli Huxley (Amphibia: Labyrinthodontia) and the family Anthracosauridae.

Phil. Trans. R. Soc. Fond. 8279,447-512.

1980. The origin and relationships of the anthracosaur amphibia from the late Palaeozoic, 319-350. In

PANCHEN, A. L. (ed.). The terrestrial environment and the origin of land vertebrates, xii + 633 pp. Systematics
Association Special Volume No. 15. London: Academic Press.

1 98 1 . A jaw ramus of the Coal Measure amphibian Anthracosaurus from Northumberland. Palaeontologv,

24, 85-92.

POLLARD, J. E. 1966. A non-marine ostracod fauna from the Coal Measures of Durham and Northumberland.
Ibid. 9, 667-697.

RAYNER, D. H. 1971. Data on the environment and preservation of late Palaeozoic tetrapods. Proc. Yorks, geol.
Soc. 38, 437-495.

REisz, R. 1972. Pelycosaurian reptiles from the Middle Pennsylvanian of North America. Bull. Mus. comp. ZooL
Harv. 144, 21-62.

ROMER, A. s. 1930. The Pennsylvanian tetrapods of Linton, Ohio. Bull. Am. Mus. nat. Hist. 59, 77-147.

1957. The appendicular skeleton of the Permian embolomerous amphibian Archeria. Contr. Mus. Geol.

Univ. Mich. 13, 103-159.

1963. The larger embolomerous amphibians of the American Carboniferous. Bull. Mus. comp. ZooL Harv.

128,415-454.

SCHRAM, F. R. 1976. Crustacean assemblage from the Pennsylvanian Linton vertebrate beds of Ohio.
Palaeontology, 19,411-412.

SCOTT, A. c. 1977. A review of the ecology of Upper Carboniferous plant assemblages, with new data from
Strathclyde. Ibid. 20, 447-473.

1979. The ecology of Coal Measure floras from northern Britain. Proc. Geol. Ass. 90, 97-1 16.

1980. The ecology of some Upper Palaeozoic floras, 87-115. In. panchen, a. l. (ed.). The terrestrial

environment and the origin of land vertebrates, xii -1-633 pp. Systematics Association Special Volume No. 15.
London: Academic Press.

SMITHSON, T. R. 1982. The cranial morphology of Greererpeton burkemorani Romer (Amphibia: Temno-
spondyli). ZooL Jl Linn. Soc. Lond. 76, 29-90.

SOLLAS, w. J. 1920. On the structure of Lysorophus as exposed by serial sections. Phil. Trans. R. Soc. Lond. B209,
481-527.

STEEN, M. c. 1931. The British Museum collection of Amphibia from the Middle Coal Measures of Linton, Ohio.
Proc. zool. Soc. Lond. 1930, 849-891.

1938. On the fossil Amphibia from the Gas Coal of Nyfany and other deposits in Czechoslovakia. Ibid.

B108, 205-283.

THOMSON, K. s. and BOSSY, K. H. 1970. Adaptive trends and relationships in early Amphibia. Forma et Functio, 3,
7-31.

TILLEY [BEAUMONT], E. H. 1971. Morphology and taxonomy of the Loxommatoidea (Amphibia). Ph.D thesis.
University of Newcastle upon Tyne.

WATSON, D. M. s. 1912. The larger Coal Measure Amphibia. Mem. Proc. Manchr. lit. phil. Soc. 57, 1-14.

1913. Batrachiderpeton lineatum Hancock and Atthey, a Coal Measure stegocephalian. Proc. zool. Soc.

Lond. 1913, 949-962.

1926. Croonian Lecture. The evolution and origin of the Amphibia. Phil. Trans. R. Soc. Lond. B2I4,

189-257.

WELLSTEAD, c. F. 1982. A Lower Carboniferous aistopod amphibian from Scotland. Palaeontology, 25, 193-208.

392

PALAEONTOLOGY, VOLUME 27

WESTOLL, T. s. 1944. The Haplolepidae, a new family of late Carboniferous bony fishes. Bull. Am. Mus. nat. Hist.
83, 1-121.

ziDEK, j. and BAIRD, D. 1978. Cercariomorphus Cope, 1885, identified as the ai'stopod amphibian Ophiderpeton. J.
Paleont. 52, 561-564.

MICHAEL J. BOYD
Department of Natural History
Kingston upon Hull Museum
Queen Victoria Square, Kingston upon Hull
North Humberside
and

Department of Geology
University of Reading

Typescript received 27 April 1983 Reading, Berkshire

Revised typescript received 23 July 1983 RG6 2AB

Note added in proof. Since the present paper went to press, preparation of a hitherto enigmatic
specimen (Hancock Museum, no. G.2484) from Newsham has enabled it to be identified as the skull
table of a romeriid reptile. This new reptile forms an addition to the terrestrial/marginal tetrapod
assemblage. A full description of the material will shortly be published.

COMPUTER-BASED STORAGE AND RETRIEVAL
OF PALAEONTOLOGICAL DATA AT THE
SEDGWICK MUSEUM, CAMBRIDGE, ENGLAND

by DAVID PRICE

Abstract. The computer-based data handling system at the Sedgwick Museum is a specialized application of
the GOS program package, geared to the requirements of a targe palaeontological collection. Rigorous analysis
and careful structuring of palaeontological data facilitate the automatic production, by machine processing, of
hard-copy catalogues, labels, and a variety of indexes. The system goes beyond the capabilities of the standard
GOS package in that a number of extra programs are geared to direct access information retrieval. The
Information Retrieval System incorporates a solution to the problem of variant forms of single catalogue terms
and can be used to answer rapidly many queries about the collections which formerly would either have been
virtually impossible or have required extensive physical searches. Those aspects of the Sedgwick System of
interest and potential use to palaeontologists and biostratigraphers are described.

Many museums are using or beginning to use computer-based methods for cataloguing and the
production of collection indexes (see, for instance, Roberts and Light 1980). The computer-based
procedures described in this paper will be of particular interest to palaeontologists in that they are
geared to the documentation requirements of the Sedgwick Museum, whose large palaeontological
collections are of international scope and contain a high proportion of type, figured, and cited
specimens; many represent classic pieces of research.

HISTORICAL DEVELOPMENT

The long history of Cambridge as a centre of palaeontological and biostratigraphic research ensured
that the value of well-organized and accessible collections was appreciated at an early date (see
Rickards 1979). Such appreciation led to the development, particularly during the pioneering regime
of A. G. Brighton (Curator, 1931-1968), of a curatorial system whose outstanding characteristic
was its exceptionally high standard of collection documentation. Specimens were comprehensively
labelled, fully and systematically catalogued, and taxonomically indexed; there was also a sup-
porting Curator’s library of annotated scientific periodicals, monographs, and reprints, together
with collector’s original catalogues, notebooks, field-slips, and museum correspondence. This
Sedgwick manual system has been described elsewhere (Price 1981; see also Orna and Pettitt 1980,
pp. 152-153).

The Sedgwick Museum became a centre for the early development of ideas on computer-based
data handling in museums, through the work of J. L. Cutbill, from the mid-1960’s onwards (Cutbill
1971; Cutbill et al. 1973). Many characteristics of the Sedgwick manual system had an important
influence on those ideas. But the ‘computerization’ of the Sedgwick Museum came to be only a partial
aim of the several Sedgwick-based projects through which Cutbill’s work developed. Those projects
increased in scope to embrace a multidisciplinary approach to the analysis and recording of museum
data, and the development of a computer program package for handling museum data which was
equally flexible. While this broader approach led in 1977 to the setting up of the Museums
Documentation Association, and the subsequent release by MDA of the GOS program package,
the move of the final Sedgwick-based project team to their new MDA headquarters (Duxford,

I Palaeontology, Vol. 27, Part 2, 1984, pp. 393-405.)

394

PALAEONTOLOGY, VOLUME 27

Cambridgeshire) took place before the Sedgwick manual catalogue had been entirely transcribed to
machine-readable computer files and indeed before all the necessary procedures for maintaining and
updating a computerized catalogue had been fully developed and tested.

The gap between 1977 and the revival of the Sedgwick computerization project in 1981 only served
to emphasize differences between the MDA’s ‘all-embracing’ approach, with its broadly conceived
data standard, and the rather specialized documentation procedures used in earlier phases of work
at the Sedgwick Museum. Differences of approach have further increased during the completion and
refinement of the Sedgwick System, because the final phase had the sole aim of deriving a working
system specific to the needs of the museum. The final Sedgwick System is based on the GOS program
package (with extra programs related to the Information Retrieval System described below), but is a
specialized application of that package to a large palaeontological collection. Porter (1982) has given
a more technical overview of the general capabilities of GOS. At the time of writing, the Sedgwick
System’s computer catalogue file contains details of 451 000 specimens, representing approximately
10000 man-hours of typing and checking catalogue data.

It is not appropriate to describe here the Sedgwick System in its entirety. It is a complete working
system covering all aspects of museum documentation, including the automatic production of labels
and the recording of specimen loans. This paper attempts merely to describe those characteristics and
capabilities of the Sedgwick System which will be of interest and potential use to palaeontologists and
biostratigraphers.

GENERAL STRUCTURE OF DATA

Palaeontological data is stored in a precisely structured, machine-readable form within the computer
file which now constitutes the Sedgwick Museum catalogue. To enable manipulation by the various
programs (‘processors’) of the GOS package, each record is broken down into a large number of
discrete data-categories ox fields', each field is labelled or tagged so that it can be identified by the
programs operating on it. The nature and relationships of all the fields considered necessary to
contain the data in any Sedgwick Museum catalogue record are described by the SM Format, a
complex hierarchical arrangement of fields derived from a rigorous analysis of existing manual
catalogue entries, together with a consideration of what other kinds of data it might be useful to
record for each specimen. The SM Format is described in the Appendix.

RETRIEVAL OF DATA

Indexes

The original purpose of rigorously analysing the data in each record into tagged fields (in the way
outlined in the Appendix) was to enable the generation of collection indexes on a very large number
of keyword terms. The possible use of any of the tagged keyword terms in the format to sort and order
the records permits the construction of complex taxonomic indexes, donor indexes, collector indexes,
locality indexes, stratigraphic indexes, bibliographic indexes, and so on. The generation and use of
such indexes for data retrieval was indeed central to all thinking about data-handling in the Sedgwick
Museum up until the most recent phase of ‘computerization’. The Sedgwick System still retains the
ability to produce all these indexes, but their use in practice has involved a number of difficulties.

Most indexes have proved very unwieldy in use, particularly so when two or more large indexes are
used in conjunction. Problems of this kind can be reduced somewhat by using the great flexibility of
the GOS package to produce ‘multiple’ indexes. An example index is shown as text-fig. 1 arranged
primarily geographically, but including also basic stratigraphy and taxonomic names. Another way
of easing the problems of handling large indexes is to reduce their bulk by producing them as
microform output (COM), in our case as 127x76 mm microfiche at a 42 x reduction. Even so,
difficulties with hard copy indexes remain.

It should be emphasized at this point that much of the machine-readable catalogue at the Sedgwick
Museum was simply transcribed, word for word, from a manual catalogue which had grown

PRICE: COMPUTER-BASED DATA HANDLING

395

British Somaliland, Biyo Cora.
Eocene ,

(Fish) Cichlid (indet.);

(Sect. 1).

C. 801 31

(Fish) Ogyg iochrom is sp . ;

(Sect. 1).

C. 80 130

Lower Eocene ,

(Fish) Pycnodont;

(2628-2646 m below), (strata section

i) , 10 d 22' N. , 45 d 12' E. , loc ;
sigma 35.

C. 73 153

(Fish) Sparoid;

(2755-2781 m below top - strata

section i), 10 d 22' N.. 45 d 12'
E . , loc : sigma 42 .

C. 73157-73158

Middle Eocene,

(Fish) Odontaspis sp . ;

(I960 m. below top - strata section

i) , loc : sigma 25.

c. 73155

Tertian y.

(Fish) Aplooheilus sp . nov . ;

(922-923 m. below top of strata

section i), loc; sigma 17.

C. 761 20-761 32

(970-976 m. below top of strata
section i) , loc: sigma 18.

C. 761 33-761 34

(1179-1184 m. below top of strata
section i) , loc: phi 21.

C. 761 35

(Fish) Tilapia? sp. nov.;

(111-116 m. below top of strata

section i), loc: phi 13.

C. 76087

(210-212 m. and 271-285 m. below top
of strata section i) , loc: phi 14.

C. 76088-76096

(strata section i) , loc: phi 14.

C. 76097-76103

(270-274 m. below top of strata
section i) , loc: sigma 15.

C. 76104

(329-330 m. and 420-422 m. below top
of strata section i) , loc; phi 15.

C. 76105

(583-589 m. below top of strata
section i), loc: phi 151.

C. 76106-76108

(922-938 m. below top of strata
section i) , loc: sigma 17.

C. 76109-76115

(970-976 m. below top of strata
section i), loo; sigma 18.

C. 76116

(1179-1184 m. below top of strata
section i), loc: phi 21.

C. 76117

(1199-1203 m. below top of strata
section i) , loc: phi 23.

C. 76118

(1326-1328 m. below top of strata
section i) , loo; phi 149.

C. 76119

(1179-1184 m. below top of strata
section i) , loc: phi 21.

0. 76136-76157

(1199-1203 m. below top of strata
section i) , loo; phi 23.

C. 76158-76165

British Somaliland, Biyo Gora, Daban Corner.
Eocene ,

(Fish) Cichlid (indet.);

(Sect. 1).

C. 80129

British Somaliland, Rhabka.
Eocene ,

(Fish)

(section), 10 d 10' N., 45 d 19' E..

loc : sigma 14.

C. 73159-73161

Buckinghamshire, Brickhill.
Lower Greensand ,

(Fish) Asteracanthus sp . ;

B. 26675-26676

(Fish) "Edaphodon" sp.;

B. 58620
B. 26759

(Fish) Ischyodus townsendii (Buckland);

B. 26765-26766

(Fish) Lepidotus maximus Wagner;

B. 26549-26553

(Fish) Otothus sp . ;

B. 26790-26792

(Fish) Oxyrhina ;

B. 26639

(Fish) Pycnodus sp.;

B. 26648
B. 26637

(Fish) Pycnodus couloni Agassiz;

B. 2661 8-2661 9

(Fish) Sphenonchus sp.;

B. 26716

(Fish) Strophodus sp.;

B. 26595

Buckinghamshire, Pitstone, Upper Icknield Way.
Turonian ,

(Fish) Scapanorhynchus subulatus (Agassiz);

(pit on S. side), (600 yds. E.S.E. of

church), grid ref: 42/946147.

B. 91737 4.20

TEXT-FIG. 1. Part of ‘Fish’ Locality Index.

396

PALAEONTOLOGY, VOLUME 27

gradually over almost fifty years. Data quality is thus rather variable. Over the full range of the
catalogue, locality names may have several different spellings or differ in orthography. Geographical
information for a single locality may be given in different records in different hierarchical sequences,
in one case say ‘farm name — village — town — county’, in others ‘farm name — town — county’, or
just ‘village — county’. Such variation can cause a single locality to appear in many different places
on a single index. The same is true for stratigraphic horizons.

Because of all these difficulties with indexes, and to obviate the need for reprinting large numbers of
indexes at each updating of the catalogue, the Sedgwick Museum has now reduced the number of
routinely used indexes to just one: a taxonomically based index divided up into sections on the basis
of convenient suprageneric groups. An example of the layout and contents of part of the ‘Fish’
section of this index is shown in text-fig. 2. This taxonomic index in the form of microfiche (currently
90 fiche), together with a fiche version of the entire catalogue in alphanumeric order (117 fiche), are
the only fixed hard-copy documents which play any important part in the Sedgwick System. The
need for a variety of other indexes has been obviated by the use of an Information Retrieval System
(IR System), which is now central to all Sedgwick Museum procedures.

Acanthodes sp .

(bone-bed - conglomeratic sandstone - Bed 2), Downtonian (base); Lower Wolton Farm,

Woolhope Inlier, Herefordshire.

Listed. Gardiner, 1927, Q.J.G..S., Ixxxiii, pp.517. 527 p.527. A. 45356

Coal Measures, Carboniferous. E. 3969

Coal Measures, Carboniferous; Newcastle, Northumberland.

Identified, Traquair, R.H. E. 3970

Lancashire, 40 yds Mine, Coal Measures, Carboniferous; Bacup.

styliform, bone. E. 3971

Acanthodes mitchelli Edgerton

Mesacanthus mitchelli (Egerton)

Old Red Sandstone, Devonian; Reswallie, Forfar. H. 4465-4467

Old Red Sandstone, Devonian; Forfar. H, 4468

Acanthodes nitides A. S. Woodward

Cement Stone Group, Calciferous Sandstone Series, Carboniferous; Esk R.,

Glencartholm . Langholm, Dumfries, Scotland.

Topotype , E. 4965

Acanthodes wardi Egerton

Coal Measures, Carboniferous; Longton, Staffordshire. E. 3950

Coal Measures, Knowles Ironstone, Carboniferous; Fenton, Staffordshire.

Identified, Traquair, R.H., spine. E. 3951 -3954

Coal Measures, Carboniferous; Longton, Staffordshire.

Identified, Traquair, R.H., pectoral, spine. E. 3955

Coal Measures, Better Bed, Carboniferous; Low Moor, Yorkshire.

Identified, Traquair, R.H., spine. E. 3956-3959

Coal Measures, 40 yds Mine, Carboniferous; Bacup, Lancashire.

Identified, Traquair, R.H., spine. E. 3960-3961

Identified, Traquair, R.H., pectoral, spine. E. 3962

Coal Measures, Carboniferous; Longton, Staffordshire.

trunk. E. 3963-3965

TEXT-FIG. 2. Part of ‘Fish’ Taxonomic Index.

PRICE: COMPUTER-BASED DATA HANDLING

397

Information Retrieval System

The entire catalogue can be searched rapidly on-line using the IR System, on the basis of pre-
determined search criteria which may be very complex. The I R System responds initially by giving the
number of specimens found in all records conforming to the search criteria. It can then be asked to list
all such specimens by number, or a 'job’ can be submitted to the computer to retrieve the actual
records from a magnetic disc version of the catalogue. The job may take fifteen minutes or so to run.

Each specimen in the catalogue is indexed by a set of terms which are generated automatically
from the GOS record describing the specimen. A term has the form of an initial upper case letter
followed by a series of up to 23 lower case letters, digits, commas or full stops, but with all other
characters, including spaces, discarded e.g. ‘Ajones,o.t. 1948’, ’Roxfordclay’. The initial letter
indicates the nature of the term: ’A’, for instance, indicating authorship. The list below explains the
significance of each upper case initial and shows also from which field or fields of a record each term is
derived (field-tags, such as *al or *gn, relate to the SM Format given in the Appendix).

Term category

Example

Term derived from (see Appendix)

A = authorship

‘Abarker,r.w.l927’

first *al and *ryear in *doc in each *re

D = donor

‘Dstricklandcolf’

each *psl in *oh

F = function word

‘Fholotype’

each *fl containing ‘fig’d’ or ending in ‘type’

G = group

‘Gtrilobite’

each *gn

K = keyword

‘Kcranidium’

individual words in each *kwl

L = locality

‘Lrobinhoodsbay’

each *locl

N = informal name

‘Ngoniatite’

each *taxs with no formal taxonomic name components

O = lithology

‘Oblackshale’

each *lithl

P = preservation

‘Preplacement’

each *presl

Q = age

‘Qjurassic’

each *agel

R = rock

‘Rcornbrash’

each *rkl

S = store

‘Sxxx.n.39’

each level (between stops) in each *storel

T = genus

‘Thildoceras’

each *gen

U = species

‘Ublumenbachii’

each *spec

In addition every catalogued specimen is indexed as T’. The way in which such index terms are
generated from an actual record is illustrated by an example in the Appendix.

Within the system each term has a term number, n, which merely indicates its position within the
current index, and a frequency,!, which is the number of specimens indexed by that term. Terms are
usually printed in « — term — / order, with / in brackets, e.g.

593 = Gforaminiferan (5424)

2027 = Lperu (1921)

The simplest possible retrieval request is based on a single term. The query a-q < ’Gam-
monoid’ > asks what ammonoids there are in the collection. More complex queries combine terms
together according to the rules of Boolean logic, using the operators '&’ ( — logical and), T ( = logical
or), and ’ (= logical subtraction). Further, actual terms may be replaced in queries by the term
number, n, or by a specimen identity number, or by a range of such numbers. The query a-q
<’Gammonoid’ & ‘Qoxfordian’—[F. 1-23000] > asks for all British ammonoids of Oxfordian age
(British since all ‘foreign’ Mesozoic specimens, of which there are just over 22,000, have specimen
numbers prefixed with ‘F.’). Of course, an actual retrieval request would be more complex than this,
since not all records for ammonoids of Oxfordian age would necessarily contain ‘Oxfordian’ as an
age term, particularly if they had been transcribed from the earlier part of the manual catalogue. In
practice it would be necessary to retrieve also on rock terms such as ‘Roxfordclay’, ‘Rampthillclay’,
‘Rwestwaltonbeds’, ‘Rbrorasandstone’, etc. Similar problems arise when locality names appear in
different guises in different parts of the catalogue.

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PALAEONTOLOGY, VOLUME 27

The problem of variant forms of a single term. This is another aspect of the problem discussed earlier in
relation to the use of hard-copy indexes; only in the case of index terms in the IR System there is a
solution. The IR System has a facility for listing all index terms which show similarity to a given term.
Each term in the term index is broken into fragments of four characters and separately indexed under
all of these fragments, e.g. ‘Cambridge’ generates the fragments ‘camb’, ‘ambr’, ‘mbri’, ‘brid’, ‘ridg’,
and ‘idge’. The measure of similarity between terms is based on the number of fragments they have in
common. A list can be requested which will give similar terms in decreasing order of similarity up to
any number specified by the user. The list may either be restricted to terms of a particular category
(e.g. age terms, genus names) or may include all terms irrespective of category.

The usefulness of this ‘similar term’ facility can be illustrated by an actual example. An IR query
asking what specimens in the collections were donated by F. R. Cowper-Reed might be expected to
take the form a-q <‘Dcowperreed,f.r.’>. In fact, the submission of such a query should be
preceded by a request for similar terms. If the ten most similar donor terms are requested by a-simt
< Dcowperreed, f.r. >, the system responds with:

(cfterms)
Dcowperreed,f. r. ;

3271 = Dcowperreed, f.r. (804)

3272 = Dcowperreed,f.r.coll. (1)

3270 = Dcowperreed,!. (3)

3254 = Dcooperreed,f.r. (3)

4754 = Dreed, f.r.cowper (48)

3269 = Dcowperreed

(22)

4752 = Dreed,f.r.c.

(1225)

4753 = Dreed, f.r.c.coll.

(61)

4751 = Dreed,f.c.r.

(1)

5484 = Dwoodward,f.r.

(1)

The first nine of the above terms are indeed variations on F. R. Cowper-Reed (‘cooperreed’ is a mis-
spelling; ‘coir is an abbreviation for collection). Using term numbers, the original query could now be
replaced with a-q <3271 j 3272 | 3270 | 3254 | 4754 1 3269 | 4752 | 4753 | 4751 > . The original query
would have yielded only 804 specimens, but the more complex query now yields 2168.

The IR System can be used to answer many enquiries about the collections which would have been
virtually impossible to answer using the manual system. Enquiries which formerly could only have
been answered by physically searching the collections (exploiting a lay-out which reflects both
stratigraphy and geography) can now be answered in a minute fraction of the time such a physical
search would have taken— and much less fallibly.

DISCUSSION

Major benefits of ' computerization''

As a result of adopting computer-based data handling techniques, the Sedgwick Museum has
acquired a wide range of new capabilities. Many of these are of strictly curatorial interest in that they
are aimed at facilitating and improving management of the collections. Even here though external
users will derive some benefit; for example, from rapid automatic processing of loans. Most of the
main benefits to external users, however, are implicit in the preceding description of data retrieval,
particularly in the illustration of the great variety of queries about the collections which can now
be rapidly answered using the IR System. One major use of the IR System has been to provide
palaeontologists with what might be termed ‘specialist catalogues’: retrieving and printing-out for
instanee the records of vertebrates from the Oxford Clay, Ordovician ostracodes, British Liassic,
Callovian and Kimmeridgian corals, or Wealden reptiles from Brook on the Isle of Wight (all actual
examples).

The complete museum catalogue and the taxonomic index are both on mierofiehe, and can there-
fore be very quickly and cheaply reproduced (in whole or in part) and readily distributed. Diazo
copies from the COM fiche originals at present cost between 1 2p and 1 4p, depending on the numbers
involved. At such a rate, a copy of the entire catalogue costs approximately £ 1 6, the taxonomic index
approximately £13. Each section of the taxonomic index (e.g. ‘trilobites’, ‘graptolites’, ‘bivalves’) is
usually only a few fiches in length.

PRICE: COMPUTER-BASED DATA HANDLING

399

Specimen security and locality conservation

The possibility of easy reproduction and distribution of catalogues and indexes raises problems of
data security. At present the main concern must be with data about specimen storage. Data ‘in the
computer’ is reasonably secure because it is only accessible to those at once familiar with the general
working of the Cambridge Data Network, with the general working of GOS, and with the esoteric
command syntax for the Sedgwick System; and who, in addition, are in possession of (or able to
obtain) the passwords which safeguard access. Such data is also safe from loss because there are
duplicated magnetic tape versions of the catalogue stored separately from the primary version and, of
course, hard-copy fail-back in the form of fiche.

It is hard-copy output which potentially leads to the greatest security risk. Internal ‘working’
Museum hard-copy needs to carry storage locations; the present policy is to ensure that all hard-copy
for external use is produced from GOS files which have had the *store field stripped out. It would be
possible to strip out also detailed locality information, including grid-references or latitude and
longitude. At present we see little point in doing this since the information is usually readily available
in scientific papers and monographs, and because catalogue information is only distributed to bona
fide research workers.

Future developments

Direct access to the museum database is restricted at present to the Curators who alone decide what
information to release and to whom. It may be possible in the future to permit some form of access to
external users at other computer sites linked to the Cambridge Network, or through a dial-up link.
Such access would be via the IR System and, we envisage, would be restricted to the IR System
indexes, thus enabling external users to make full use of the fiche versions of the catalogue and
indexes while still safeguarding access to museum storage data (and any other data deemed ‘sensitive’
in the GOS database). Ideally any such arrangements would include reciprocal arrangements with
other museums.

The Sedgwick Museum has acquired a complete, working, computer-based documentation system
earlier than many other museums. It is now open to palaeontologists and palaeontological curators
elsewhere to appraise the system in relation to their own requirements. It is our strong hope at this
early stage that it might find wider application. Thoughts of a unified palaeontological database,
involving the collections of many major institutions, may seem Utopian at present but we believe
that in our work at the Sedgwick there lies one opportunity for such a future. Opposed to this
opportunity is the very real danger that soon each institution will develop its own computer-based
system, with its own data standard, and that mapping data from one system to another will become
virtually impossible. In the field of computer-based museum documentation as a whole in Britain,
it is already apparent that various factors (not least political and economic ones) have conspired
to force such a pluralistic future. Perhaps for the major palaeontological collections this can yet be
avoided.

Acknowledgements. My enormous indebtedness to Martin Porter, prime architect of the computer-based system
described in this paper, will be obvious. He, Dr. W. D. I. Rolfe, and Mr. R. H. Hughes kindly read earlier
typescripts and made useful suggestions for improvements.

REFERENCES

CUTBILL, j. L. 1973. Computer filing systems for museums and research. Sedgwick Museum, Cambridge.

HALLEN, A. J. and LEWIS, G. D. 1971. A format for the machine exchange of museum data. In cutbill, j. l.

(ed.) Data processing in biology and geology. Academic Press, London. Pp. 31 1 -320.

ORNA, L. and PETTITT, c. 1980. Information handling in museums. Bingley. 190 pp.

PORTER, M. F. 1982. GOS: a package for making catalogues. Inf. Technol. Res. Dev. I, 113-129.

PRICE, D. 1981. Collections and collectors of note. 39. The Sedgwick Museum, Cambridge. Geol. Curator, 3,
28-35.

400

PALAEONTOLOGY, VOLUME 27

RICKARDS, R. B. 1979. The physical basis of palaeontological curating. Spec. Pap. Palaeont. 23, 75-86.

ROBERTS, D. A. and LIGHT, R. B. 1980. Progress in documentation: museum documentation. J. Docwn. 36,

42-84.

DAVID PRICE
Sedgwick Museum
Department of Earth Sciences

Typescript received 6 September 1983 Downing Street

Revised typescript received 14 October 1983 Cambridge CB2 3EQ

PRICE: COMPUTER-BASED DATA HANDLING

401

APPENDIX

Details of data structure

The SM Format is a much modified version of the ‘General Index Format’ devised by J. L. Cutbill during the
early stages of work at the Sedgwick Museum. It can be visualized as an irregularly branching tree-like structure.
The main trunk represents a complete record, and this is progressively divided into increasingly restricted data
categories until the terminal branches represent basic data fields which, unlike the group data fields nearer the
trunk, cannot be divided further and contain the actual items of data making up the record, either as strings of
characters or as numeric variables. Basic fields are either keyworr/ fields containing essential data, or detail fields
containing data elaborating the keywords. If each data field is represented by its tag, the point where the trunk of
the format first divides can be represented as follows:

*rec

*rec denotes the complete record in SM Format

*id the record identity ( = specimen catalogue number)

*bcat the broad category of objects to which the specimen belongs (implicitly ‘fossil’; otherwise

‘replica’, ‘artefact’, ‘rock specimen’, or ‘inorganic’ explicitly stated)

*part a declaration that the specimen comprises two or more parts
*store the storage location

*oh the ownership history (mode of acquisition by the Sedgwick Museum, and previous ownership)

*cs a collection statement (saying by whom the specimen was collected and when)

*ps a provenance statement

*re a research event (anything from an informal identification to the designation of the specimen as
a type)

*cat cataloguer information

Of these nine data fields, * *oh, *cs, *ps, and *re contain by far the bulk of the data in the record, and are
accordingly known as the main data groups. They represent major branches of the format which are worth
following separately. First, ownership history:

*oh

*f *prt *pers *when *rn *note

*f a function word (e.g. ‘presented’, ‘exchanged’, ‘pur-
chased’)

*prt the part(s) of the specimen concerned
*pers the person or institution concerned
*when the date or a time period (range of dates)

*rn the reference number of the specimen in any previous
collection

*note a general detail field

*f and *pers are each made up of keyword and detail fields, *when contains *date denoting a single date (field
repeated for a period) and is broken further into separate fields for day, month, and year (each containing a two
digit number), with a detail field for terms like ‘circa’, ‘not later than’ etc. The collection statement field has a
similar structure;

but for this field the function (*f) word ‘collected’ is automatically

generated by the GOS ‘display’ processor rather than put in as data.

*f *prt *pers *when *rn *note

402

PALAEONTOLOGY, VOLUME 27

The provenance statement has the structure:
*ps

*geogr * *strat *ref *note

These fields have the following structure:
*geogr

*strat

*rk *zone *age *sd

*rkl *rkd *zonel *zoned *agel *aged

*ref

1

*

*

1 *t *r *v

*al *ad

1 1 1 1

*rday *rmonth *ryear *rdd

*geogr

contains geographical information

*strat

contains stratigraphical information

*ref

contains documentary information
(e.g. bibliographic references)

*loc

place names

*locl

a specific place name (keyword)

*ld

detail for *locl (e.g. ‘near’, ‘3 km NW’)

*11

latitude and longitude

*lls

text for *11

*gr

grid reference

*grs

text for *gr

*ln

locality number

*lnl

text for *ln

*gd

general geographical detail

*rk

litiwstratigraphic information

*rkl

name of rock unit (usually a forma-
tional name)

*rkd

detail for *rkl (e.g. ‘basal’)

*zone

biostratigraphic information

*zonel

name of zone or sub-zone

*zoned

detail for zonel (e.g. ‘topmost’)

*age

chronostratigraphic information

*agel

name of period, stage, etc.

*aged

detail for *agel

*sd

general stratigraphic detail

*doc

document

*a

author

*al

name of author

*ad

detail for *al

*d

date

*rday

day (as a two digit number)

*rmonth

month (as a two digit number)

*ryear

year (as a two digit number)

*rdd

any qualifying details for date

*t

title

*r

journal

* Y

volume

*rd

reference detail

*pp

page number, plate, and figure
information

PRICE: COMPUTER-BASED DATA HANDLING

403

The research event is structured thus:

*re

*f *prt *pers *when *taxon *desc *pres *lith *ref *note

In the *re field, *f contains words such ‘described’, ‘mentioned’, ‘fig’d’, ‘holotype’, ‘paratype’, etc.

*taxon taxonomic information *pres preservational information

*desc dci'cnpt/ve information (morphology) *lith /d/;o/og/ca/ information (matrix)

*pres and *lith are simply made up of keyword and detail fields; *taxon and *desc are structured as follows:

*taxon

*group *tax ’•’td

*gn *taxs

*group suprageneric classification ) arbitrary museum scheme

*gn name of suprageneric group ) only

’•'tax formal taxonomic nomenclature

*taxs full taxonomic name with author(s)

*gen genus

*sgen subgenus

*spec species

*sspec subspecies

”^gen *sgen *spec *sspec

*desc

*desct *dd

*keyw

*desct descriptive term
*keyw keyword information

*kwl actual keyword (e.g. ‘cranidium’, ‘phragmacone’)

*kwd detail for *kwl (e.g. ‘incomplete’, ‘distal end’)

*dd description detail (e.g. ‘atypically convex’, ‘shows doublure’)

*kwl *kwd

In designing the SM Format we have tried to produce a data structure which gives much scope for improved
specimen documentation; for instance, by incorporating fields for morphological, preservational, and litho-
logical data. The only major data category not catered for is biometric data, and we have considered this to be
beyond the scope of a general museum database. It would, of course, be possible to produce specialized data-
bases to contain biometric data for particular groups of organisms for which standardized measurement
schemes had been agreed.

404

PALAEONTOLOGY, VOLUME 27

The rationale of the SM Format can be illustrated by considering its application to a hypothetical specimen
from the Schloenbachia varians Zone of the lower Chalk (Cenomanian) of Burwell, Cambridgeshire, collected by
J. Bloggs in 1970, identified by him as the external mould of the right valve of the bivalve Agenus beta Smith and
presented to the Sedgwick Museum in the same year. The specimen is subsequently selected by T. Jones as the
holotype of his new species nova Jones, 1975 (Geo/. Mag. vol. 200, p. 16, pi. l,fig.3). Supposing that a

catalogue number A1 had been applied to the specimen, and that it had been stored in drawer x.t.ll4 of the
museum, then it would ultimately have a record in the computer-file catalogue with the following structure:

*rec
*id
*key
*code
*elem A
*elem2 1

*elem2 0 (this indicates a single
specimen)

*bcat fossil (implicit — data not actually
present)

*store

*storel x.t.l 14
*oh
*f

*fl presented
*pers

*psl Bloggs, J.

*when

*date

*wyear 1970
*cs
*f

*fl collected (implicit— data not
actually present)

*pers

*psl Bloggs, J.

*when

*date

*wyear 1970
*ps

*geogr

*loc

*locl Burwell
*locl Cambridge
*strat
*rk

*rkl Chalk
*rkd lower
*zone

*zonel /USchloenbachia/N
/Uvarians/N Zonef

*age

*agel Cenomanian
*agel Cretaceous

*f

*fl identified
*pers

*psl Bloggs, J.

*when

*date

*wyear 1970
*taxon
*group

*gn Bivalve
*tax

*taxs /UAgenus/N /Ubefa/N Smifht
*gen Agenus
*spec befa
*desc
*desct
*keyw

*keywl right valve

*pres

*presl external mould
*re
*f

*fl fig’d
*fl holotype
*taxon
*group

*gn Bivalve
*tax

*taxs /UAgenus/N /Unova/N Jonest
*gen Agenus
*spec nova

*ref

*doc

*a

*al Jones, T.

*d

*ryear 1975
*r Geol. Mag.

*v 200

*pp p.l6, pl.l, fig. 3
*caf

*catn Price, D.

*catd 1972

(t /U and /N are ‘flags’ conf rolling underlining)

This example illustrates an important feature of GOS-based data handling: that fields can be repeated, if
necessary many times over. For example, complicated locality descriptions can be broken down into a series of
*Ioc keywords or complicated modes of preservation described by a series of *pres keywords. This feature is of

PRICE: COMPUTER-BASED DATA HANDLING

405

particular importance in the Sedgwick System in respect to the *re (research event) field. Repetition of this field
allows a record to contain all the taxonomic names ever applied to a specimen so that the specimen could be
retrieved on any one of them. The hypothetical record with the structure illustrated above would, in fact,
generate the following catalogue entry:

A.l store: x.t. 1 14

Presented, Bloggs, J., 1970.

Collected, Bloggs, J., 1970.

Lower Chalk, Schloenhachia varians Zone, Cenomanian, Cretaceous; Burwell, Cambridgeshire.

Identified, Bloggs, J., 1970, as bivalve Agenus beta Smith; right valve, external mould.

Fig’d, Holotype, Jones, T., 1970, Geol. Mag., 200, p. 16, pi. 1, fig. 3, as bivalve Agenus nova ione?,.

[Catalogued Price, D./1972]

With respect to the Information Retrieval System, this hypothetical record would generate the following index
terms (from the fields listed on p. 397 above):

T’

‘Sx.’

‘Sx.t.’

‘Sx.t.ll4’

‘Dbloggs,j.’

‘Lburweir

‘Lcambridgeshire’

‘Rchalk'

‘Qcenomanian’

‘Qcretaceous’

‘Gbivalve’

‘Tagenus’

‘Ubeta’

‘Unova’

‘Krightvalve’
‘Pexternalmould’
‘Ffig’d’
‘Fholotype’
‘Ajones,t. 1970’

. t-

. •• -ff

■ l-J- ' > \

U

J

■}

’ ;

y) ■ ■ -s

■y. ■ ' t"? -fiiv’' >. nsr^tl 'Av>^!' '■'4*'bWy^r .- ,./

... '^,« . , ■•^■.•' -'I

►.>? .»; “r» 4'^

■ y.;: • ■'' ■ ■•'• 1

■• . i?.i- , •)

^ ^ kP'\

i'. •.•*■' ' ■ ~'h ’

■‘ -.**1

I

;r.f ■ ( '

T

•A

■J

’ >j

-.*1

• ' fj;

I

vM‘

'■'i

•5

'j:

■=iJ

i?

PTEROSAUR REMAINS FROM THE KAYENTA
FORMATION (7EARLY JURASSIC) OF ARIZONA

by KEVIN PADIAN

Abstract. Two records of pterosaurs, the earliest from the Western Hemisphere, are reported from the
Kayenta Formation (?Early Jurassic) of north-eastern Arizona. The first specimen represents a new genus and
species, Rhamphiniori jenkinsi. It consists of three pieces of a skull, including an occipital region, most of a left
jugal, and two teeth associated with a possible fragment of the dentary; it is difficult to diagnose because it is so
fragmentary and because the occipital region of early pterosaurs is not well known, but may be recognized by the
position and configuration of the orbital and antorbital borders of the jugal. The second specimen is the left-wing
(fourth) metacarpal of a rhamphorhynchoid; it is well-preserved but cannot be classified more precisely.

Over the past few years, field parties from the Museum of Comparative Zoology at Harvard
University (MCZ), the Museum of Northern Arizona (MNA), and the Museum of Paleontology of
the University of California at Berkeley (UCMP) have renewed intensive palaeontological
exploration of the Kayenta Formation of northern Arizona. The Kayenta Formation was prospected
sporadically since the 1930s, but its white to orange-red sandstones and grey-purple siltstones yielded
few specimens. The recent finds, however, have greatly increased our knowledge of the faunal
diversity of the Kayenta, which now includes large and small ornithischian and saurischian
dinosaurs ( Welles 1954; Colbert 1980; Attridge et al. MS.), several kinds of crocodilians, (Crompton
and Smith 1980), testudinates, lizards, amphibians, tritylodontid mammal-like reptiles (Lewis 1958;
Kermack 1982), and several kinds of mammals (Jenkins et al. 1983). Most remains of the smaller
vertebrates have been recovered by screen-washing sediment and hand-picking the sieved residue;
most of this work has been ably carried out by Mr. William R. Downs of the Museum of northern
Arizona. The results of these labours, in addition to an expanded faunal list, include a better under-
standing of the biostratigraphical relationships among the fossiliferous horizons of the Kayenta
and other early Mesozoic formations. While the exact age of the Kayenta Formation is not certain,
the general faunal composition and the consistent absence of Triassic marker species now appear
to argue for Early Jurassic (Olsen and Galton 1977), although difficulties with this assignment may
remain (Colbert 1980). Most Kayenta vertebrates, at the taxonomic levels so far determined, do
not permit of a precise stratigraphical correlation. Dinosaurs, testudinates, crocodilians, lizards, and
perhaps mammals are known both from Late Triassic and Early Jurassic sediments. Until the
phytogenies of the early members of these groups have been elucidated, we shall be unable to
comment on the stratigraphical and geographical distribution of certain sub-groups of each, which
may indeed be restricted and therefore diagnostic.

This note describes the first remains of pterosaurs (flying reptiles) from the Kayenta Formation.
These are the earliest known from the Western Hemisphere, but not the oldest in the world;
Eudimorphodon ranzii Zambelli 1 973 and Peteinosaurus zambellii Wild 1 978, from the Norian (Upper
Triassic) sediments of northern Italy, are older. Pterosaurs are exceptionally light-boned animals and
therefore do not preserve well. It is indeed fortunate to recover their remains from the Kayenta
Formation; pterosaurs are best preserved in low energy, fine-grained marine or lacustrine sediments,
and their record in any kind of terrestrial sediment is poor. Although the quality of the specimens at
hand is not very good, I believe there is sufficient evidence to assign them to the Order Pterosauria, as
outlined below.

(Palaeontology Vol. 27, Part 2, 1984, pp. 407-413.]

408

PALAEONTOLOGY, VOLUME 27

SYSTEMATIC PALAEONTOLOGY

Class REPTILIA
Order pterosauria
Sub-order rhamphorhynchoidea
Family Incertae sedis
Genus Rhamphinion gen. nov.

Type species. Rhamphinion jenkinsi, sp. nov.

Etymology. Rhampho-, comb, form of rhamphos, Gr., ‘beak’, used in other rhamphorhynchoid names; inion, Gr.,
‘nape of the neck’; referring to the occipital region comprising much of the present specimen.

Diagnosis. The material is diagnostic of the Order Pterosauria because of the large, long, strap-like
quadrate, the relatively small occipital condyle, the thin, laminar cranial bones, the large lower
temporal fenestra, the shape and orientation of the ascending process of the jugal, and the form of
the teeth. Without better preservation it is difficult to specify characters that diagnose the Sub-
order Rhamphorhynchoidea, although the shape of the jugal is not at all similar to those of
pterodactyloids. The genus is characterized by nearly rounded antorbital and orbital margins next to
the ascending process of the jugal. The apparent suture between the maxilla and the jugal has a long,
low sloping contact and the orbit is situated at approximately the same height above the tooth row as
is the antorbital opening.

Remarks. The shape of the quadrate is reminiscent of that of Eudimorphodon (see Wild 1978, fig. 1
and pi. 3), as is the general shape of the jugal and the participation of the lacrimal (prefrontal of Wild
1978) in the anterior margin of the orbit. The present specimen has single-cusped teeth that are
slightly recurved and tapered at both ends. Such teeth occur in juvenile Eudimorphodon (Wild 1978),
and are found in the maxillary region of Dimorphodon macronyx (Buckland) (Owen 1870; Padian,
in press) and most other rhamphorhynchoids. Family division and nomenclature among the
Pterosauria are greatly in need of revision, as is the generally accepted phytogeny of the group and its
evolutionary position with respect to other archosaurs. Hence, no family designation is given here.
The genus is generally similar to several early rhamphorhynchoids, including Eudimorphodon,
Dimorphodon, and Dorygnathus.

Rhamphinion jenkinsi, sp. nov.

Text-figs. 1-3

Etymology. Named in honour of Dr. Parish A. Jenkins Jr., who discovered the specimen and very kindly made it
available to me for description.

Material and occurrence. Holotype, MNA V 4500, consisting of four pieces: an occipital region, a left jugal
fragment, a possible mandibular fragment with two associated teeth and the impression of a third, and an
unidentifiable bone fragment. Middle Kayenta Formation (Lower Jurassic) of north-eastern Arizona, at the
locality known as ‘Foxtrot Mesa’, the southern side of Sand Mesa, along the Adeii Eechii cliffs, Ward’s Terrace,
Little Colorado River Valley. Approximate coordinates 35°4L43" N., 1 1 1°0'25” W. The remains were found in
surface float of the silty facies of the Kayenta; the horizon cannot be precisely traced. Collected by Dr. Parish
A. Jenkins Jr. and his field party from the Museum of Comparative Zoology at Harvard University and the
Museum of northern Arizona. With this material, which was given the field number 23/78A, were a few other
scraps of as yet unidentified bone, lighter in colour and more robust in structure, and not pterosaurian.

Diagnosis. As for the genus.

Description. The preserved fragment of the left jugal (text-fig. 1) is 40 mm long and 19 mm wide at its highest
point on the ascending process. The horizontal, sub-orbital portion widens posteriorly and ascends slightly. The
rounded bottom of the orbit curves more gently posteriorly, whereas the base of the antorbital opening curves
more gently anteriorly. The lower borders suggest that the antorbital opening may have been larger than the
orbit, as in most pterosaurs. Along the posterior border of the ascending process is a splint of bone identifiable as

PADIAN: PTEROSAUR FROM ARIZONA

409

TEXT-FIG. 1. Rhamphinion Jenkinsi, gen. et sp. nov. Left jugal with associated fragments. Part of
holotype, MNA V 4500. Scale = 10 mm. Abbreviations; antorb = antorbital opening;] = jugal;
lac = lacrimal; orb = orbital opening; ?pt = possible fragment of pterygoid.

the lacrimal (following Welinhofer’s (1978) terminology; Wild (1978) calls this the pre-frontal). This splint is
about 7 mm long, and it tapers as it descends.

Most of the bone has been worn away beneath the very front of the orbit, but the remaining bone seems to be
undisturbed. The lower border of the jugal appears to slope upwards and forwards, and 22 mm of the maxillary
suture is preserved. Anteriorly the bone is broken away, and posteriorly it is hidden by a support compound
applied during preparation, that might be difficult to remove without damage to the specimen. Parts of internal
skull bones can be seen within the openings, but these have been crushed beyond recognition.

The occipital fragment (text-fig. 2a) is about the same size as the jugal fragment. It preserves the occipital
condyle with part of the adjacent basioccipital and exoccipital regions, the medial part of the left paroccipital
process, an underlying fragment which may be the prootic, and two descending rami of bone that seem to be
portions of the quadrates. It is difficult to estimate the size of the complete skull from these remains, but in
relation to the other bones the occipital condyle is small, a characteristic of pterosaurs and birds (Seeley 1901;
Wellnhofer 1978). Text-fig. 2b, based on the skull of Rhamphorhynchus, shows the parts of the occipital region
represented in this specimen. A great deal of crushing and dislocation has taken place, and the identification of
many features must be regarded as tentative.

The occipital condyle is ovate in shape; it lacks some of its dorsal portion, but is otherwise fairly complete.
Portions of the left exoccipital can be seen ventral and lateral to the condyle, including the basal tubera that
connect the exoccipital with the basisphenoid and the basioccipital, and the lateral flange that meets the
opisthotic or paroccipital process. Along its lateral border there is a recess in which the most posterior cranial
foramina should be located, but no details of this region are preserved. Most of the basioccipital region is
missing, and only a few bone fragments of dubious origin remain. Lateral and dorsal to this region is the medial
portion of the left opisthotic or paroccipital process. Its dorsal and ventral borders are well-formed, and the
positions of the post-temporal foramen and the foramen magnum can be inferred from its preserved relationship
to the other bones of the occipital region. About 1 5 mm, or roughly half the length of the entire bone, appears to
have been preserved. There is no trace of the supraoccipital. A portion of another bone, perhaps displaced from
the skull roof, overlies the medial section of the opisthotic, but it has no diagnostic feature.

A wide, strap-like lamina of bone runs lateroventrally from just below and to the left of the occipital condyle,
widening until its disappearance at the lower left edge of the specimen. Medially it tapers somewhat, but this end

410

PALAEONTOLOGY, VOLUME 27

is obscured by overlying portions of the exoccipital region; it appears to be part of the left quadrate. Another
similar fragment, apparently the right quadrate, is located behind the occipital region and is mostly obscured by
compound applied in preparation. The quadrates in pterosaurs, though quite large, are light in structure; their
apparent displacement in this specimen does not facilitate identification of their major features. They
superficially resemble the basipterygoid processes, which are unusually large in pterosaurs (Wellnhofer 1978,
fig. 3). However, the structures on the specimen at hand widen as they descend from the occipital region, unlike
the basipterygoid processes, which are of fairly uniform width throughout.

In the space bounded by the paroccipital and the quadrate, and overlain by both bones, there is a small
segment of bone that, from its position, I take to be part of the prootic; however, there are no identifying features
of the bone, and no foramina are evident.

A third piece of matrix, encrusted with haematite, bears a sheet of bone with the remains of three teeth
(text-fig. 3a, b). These teeth do not appear to be in position, and so the bone cannot be positively identified as
either maxilla or dentary; its depth and general surface character, however, suggest the latter (cf. Dimorphodon
macronyx, Owen 1870, pis. XVII and XVIII). Most of two teeth and an impression of a third are preserved. No
alveoli are visible. The larger of the two preserved teeth is 6.0 mm long, missing about 0.5 mm at the tip of
its crown. It shows the slightly compressed and recurved, unserrated shape of the mid-maxillary teeth of
the approximately contemporaneous Dimorphodon (Owen 1870; Padian 1980, 1983). There are faint
longitudinal striations on the tooth, and its tip is only slightly sharper than its root. A second tooth is smaller,
with only 2-5 mm of the tip of the crown exposed. Next to this is a shallow impression about 50 mm long of most
of the main body of a third tooth, preserving some detail of the longitudinal striations. Similar teeth can be found

TEXT-FIG. 2. Rhamphinion jenkinsi, gen. et sp. nov. Occipital region, a, part of holotype, MNA V 4500. Scale =
10 mm. Abbreviations; bo = basioccipital; bs = basisphenoid; eo = exoccipital; for mag = foramen magnum;
Iq = left quadrate; oc = occipital condyle; op = opisthotic; ?p = possible fragment of parietal; ?pr = possible
fragment of prootic; rq = right quadrate, b, posteroventral view of occipital region of Rhamphorhynchus
(Carnegie Museum of Natural History CM 11434; actual breadth 32 mm), schematic diagram, bpt = basi-
pterygoid; ps = parasphenoid; so = supraoccipital; sq = squamosal. Portions represented by the corresponding

region in Rhamphinion jenkinsi are heavily outlined.

PADIAN: PTEROSAUR FROM ARIZONA

41 I

TEXT-FIG. 3. A, B, Rharnplunion jenkinsi, gen. et sp. nov. Jaw fragment with two disarticulated teeth and one tooth
impression. Part of holotype MNA V 4500. Bis an enlargement of indicated part of a. c, d, left fourth metacarpal
of a rhamphorhynchoid pterosaur, Kayenta Formation, UCMP 1 28227, in medial (c) and lateral (d) view, distal

end up. Scale bars = 10 mm.

in other archosaurs, but are normally serrated or keeled, whereas they never are in pterosaurs. The general shape
of the teeth, particularly the relative proportions and relationships of the root and crown, is indistinguishable
from that of several Jurassic pterosaurs including Dimorphodon and Campylognathoides (Wellnhofer 1974), but
is not reported in any other Lower Mesozoic.

ADDITIONAL PTEROSAUR REMAINS FROM THE KAYENTA FORMATION

In the Autumn of 1981 James M. Clark, a graduate student at the University of Chicago, discovered
two fragments of a haematite-encrusted bone that he suspected were from a pterosaur. These proved
to be the nearly complete left fourth (wing) metacarpal, about 42 mm long as reconstructed, of
a rhamphorhynchoid pterosaur (UCMP 128227). It was found at the ‘Airhead West’ locality
(V82374), not far from where the crocodilian Eopnenmatosuchus colberti was collected by an MCZ
field party in 1979 (Crompton and Smith 1980, p. 197). The horizon is near the base of the Kayenta
Formation in Coconino County, Arizona, 1 1 miles NE of Cameron between the southern two
tributaries of Five Mile Wash. The two pieces were preserved in a green siltstone with a thin
sandstone stringer; no other remains were found.

The wing-metacarpal (text-fig. 3c, d) is diagnostic of rhamphorhynchoid pterosaurs because of its
short, flattened shape and the topography of its articular surfaces. The pterodactyloid metacarpal is
relatively longer, rounded in cross-section, and lacks the pronounced ventral flange present at the
proximal end of rhamphorhynchoid metacarpals; it is often the longest, or one of the longest,
segments of the pterodactyloid wing, whereas in rhamphorhynchoids it is nearly always the shortest.

Gabon (1981) has recently described in detail a superbly preserved rhamphorhynchoid wing
metacarpal from Como Bluff, Wyoming (Brushy Basin Member of the Upper Jurassic Morrison
Formation). He named it Cornodactylus ostromi, assigning separate generic status because of its
large size and corresponding proportional differences from the metacarpals of other, smaller
rhamphorhynchoids. In pterosaurs the fourth metacarpal appears to have rotated its position
through 90° with respect to the other metacarpals, so that its distal condyles faced laterally instead of
ventrally. As such, the wing-finger flexed and extended in a horizontal plane from its articulation with
me IV, and the first three metacarpals were also arranged in a horizontal plane (Wellnhofer 1978,

412

PALAEONTOLOGY, VOLUME 27

figs. 1 1 and 12; Wild 1978, pis. 1, 2, and 9g). This adaptation has led to some confusion in the terms
used to describe orientation: the natural ‘dorsal’ face, for example, is properly regarded as ‘medial’ in
orientation.

The proximal end of UCMP 128227 is badly worn and lacks most surface detail. The groove
interpreted by Galton (1981) as for an extensor of the wing-finger is recognizable, but the ventral
(or medial, in Gallon’s sense) flange near the proximal end has been mostly worn away. As in
Comodactylus and other well-preserved metacarpals of both rhamphorhynchoid and pterodactyloid
pterosaurs, the dorsal (lateral) condyle of the distal end is the larger and is skewed away from the axis
of the shaft (see Wellnhofer 1978, fig. 12). There are deep ginglymal facets on both sides of the
distal end.

The wing metacarpal is one of the poorest indicators of wing length in pterosaurs. In fact, no
individual bone is a very good indicator because relative proportions vary among genera. However,
the relative proportions of any two wing bones (except for the metacarpals and the last phalanx of the
wing-finger) are almost without exception diagnostic to the generic level (Padian, unpublished). In
size and proportions the present specimen resembles the larger specimens of Dimorphodon in the
British Museum (Natural History), which have a wing span of approximately 1-5 m.

This specimen, and the cranial material of Rhamphinion jenkinsi described above, provide the
third and fourth (and also the earliest) records of rhamphorhynchoid pterosaurs in the Western
Hemisphere: the others are Nesodactylus hesperius Colbert 1969, from the Upper Jurassic of Cuba,
and Comodactylus ostromi, also from the Upper Jurassic.

Acknowledgements 1 thank Dr. Parish A. Jenkins Jr., who presented the Rhamphinion material to me for study;
Mr. James M. Clark, who collected the metacarpal during field work sponsored by the Museum of Paleontology,
University of California; and the National Geographic Society which funded both expeditions. Mr. William
Amaral prepared MNA V 4500, and Mr. Mark Goodwin prepared UCMP 128227 from its haematite crust.
Ms. Augusta Lucas-Andreae illustrated text-figs. 1, 2a, and 3. 1 should also like to thank Mr. Charles Schaff of
the Museum of Comparative Zoology for locality information on MNA V 4500, and Drs. A. J. Charig, Wann
Langston Jr., and John H. Ostrom for reviewing the manuscript.

REFERENCES

ATTRiDGE, J., CROMPTON, A. w. and JENKINS, F. A. Jr. MS. Common Liassic Southern African prosauropod,
Massospondyhis, discovered in North America.

COLBERT, E. H. 1969. A Jurassic pterosaur from Cuba. Am. Mus. Novit. 2246, U23.

1980. A primitive ornithischian dinosaur from the Kayenta Formation of Arizona. Bull. Mus. nth. Ariz.

53, 1-61.

CROMPTON, A. w. and SMITH, K. K. 1980. A new genus and species of crocodilian from the Kayenta Formation
(Late Triassic?) of Northern Arizona. In Jacobs, L. L. (ed.). Aspects of Vertebrate History. Museum of
Northern Arizona Press, Flagstaff, Arizona. Pp. 193-218.

GALTON, p. M. 1981. A rhamphorhynchoid pterosaur from the Upper Jurassic of North America. J. Paleont. 55,
1117-1122.

JENKINS, F. A., JR., CROMPTON, A. w. and DOWNS, w. R. 1983. Mesozoic mammals from Arizona: new evidence on
mammalian evolution. Science, 222, 1233-1235.

KERMACK, D. M. 1982. A new tritylodontid from the Kayenta Formation of Arizona. Zool. J. Linn. Soc. 76 ( 1 ),
1-17.

LEWIS, G. E. 1958. American Triassic mammal-like vertebrates. Bull. geol. Soc. Am. 69, 1735.

OLSEN, p. E., and galton, p. m. 1977. Triassic-Jurassic tetrapod extinctions: are they real? Science N.Y. 197,
986-989.

OWEN, R. 1870. A monograph of the fossil Reptilia of the Liassic Formations. III. Palaeontogr. Soc. (Monogr.),
41-81.

PADIAN, K. 1980. Studies of the structure, evolution, and flight of pterosaurs (Reptilia: Pterosauria). Ph.D.,
Thesis, Yale University. 309 + xiv pp.

1983. Description of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) in the Yale

Peabody Museum. Postilla, 189, 1-44.

PADIAN: PTEROSAUR FROM ARIZONA

413

SEELEY, H. G. 1901. Dragons of the Air: an account of extinct flying reptiles. London: Methuen & Co.

WELLES, s. p. 1954. New Jurassic dinosaur from the Kayenta Formation of Arizona. Bull. geol. Soc. Am. 65,

WELLNHOFER, p. 1978. Handhuch der Palaolierpetologie. Teil 19: Pterosauria. Stuttgart: Gustav Fischer Verlag.
WILD, R. 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene be Bergamo, Italien. Boll.
Soc. paleont. ital. 17 (2), 176-256.

ZAMBELLi, R. 1973. Eudimorphodon ranzii gen. nov., sp. nov., uno pterosauro triassico. Rc. 1st lomh. Sci. Lett. B.
107, 27-32.

591-598.

Typescript received 9 February 1983
Revised typescript received 30 August 1983

KEVIN PADIAN

Department of Paleontology
University of California
Berkeley, CA 94720

ORDOVICIAN RECEPTACULITID ALGAE

FROM BURMA

SIEGFRIED RIETSCHEL and MATTHEW H. NITECKI

Abstract. Fisherites burmensis sp. nov., is described from the Lower-Middle Ordovician Wunbye Formation in
the western part of the southern Shan State, Burma. This extends the geographic range of receptaculitids known
from North America, Europe, and Australia to south-eastern Asia, where they have hitherto been poorly
known.

Since the first publication 179 years ago (Hiipsch 1805) receptaculitids have had a vagrant history.
Like a pendulum they have swung from sponges to algae with brief pauses in a considerable variety of
animal Phyla. However, most workers preferred to banish them to a remote place of retirement
among sponges, and Raulf (1892) alone argued that they were algae. The oscillations of this
systematic pendulum have stopped only in the mid 20th century. Byrnes (1968), Rietschel (1969), and
Nitecki (1972), among others, produced new and convincing evidence that receptaculitids are plants.
However, Byrnes’s (1968) arguments that they were dasyclads and Nitecki’s (1976 and subsequent)
propositions that, although not dasyclads, they were nevertheless an independent order of green
algae within siphonous complex of Chlorophyceae, cannot any longer be maintained (Rietschel
1977). A detailed demonstration of the algal nature of receptaculitids will be presented elsewhere;
suffice it to say here that the arrangement of branches in whorls or circlets and the calcification of the
thallus are common features not only of chlorophytes, but also of certain other groups of algae.
Furthermore, since we do not know the exact nature of receptaculitid reproduction, we cannot assign
them with any degree of certainty to any specific group of thallophytes.

Receptaculitids range from Lower Ordovician to Permian but they are most abundant in the
Ordovician, particularly in North America, where they are very common and are frequently used as
index fossils. They decline rapidly in the Middle Devonian, and are known only from single localities
in the Carboniferous (Roemer 1897) and Permian (Parona 1933). Receptaculitids are known from all
continents except Antarctica.

In many North American localities receptaculitids are a major component of organic buildups
(Toomey and Nitecki 1 979). They are not well studied in South America and are known only from the
Ordovician of Argentina (Nitecki and Forney 1978) and the Devonian of Bolivia (Branisa 1965).

Although rather rare in Europe, receptaculitids have been studied there for a considerable period
of time; many taxa have been described, and their morphology is well understood. The entire
stratigraphic range of receptaculitids is represented in Europe, but the best known European ranges
are the Silurian and Devonian (Rietschel 1969).

African receptaculitids have been figured from the supposed Ordovician of Morocco (Termier and
Termier 1950) and from the Devonian of Algeria (Le Maitre 1952). In Australia, receptaculitids are
less common than in North America but considerably more abundant than in Europe. Their
stratigraphic range is more restricted than, but otherwise similar to, the North American distribution
(Byrnes 1968).

The least well-known receptaculitids are from Asia. Except for single taxa known from: ( 1 ) Soviet
Asia, particularly the Ordovician of Siberia, where receptaculitids have been described in detail
(Miagkova 1965); (2) the Ordovician of Manchuria (Endo 1932); (3) the Devonian of Iran (Eliigel
1961); and (4) the Devonian of Afghanistan (Nitecki and De Lapparent 1976), Asian receptaculitids
have either been misidentified or are poorly known. Kobayashi (1960) illustrated, but did not

[Palaeontology, Vol. 27, Part 2, 1984, pp. 415 420, pi. 47.]

416

PALAEONTOLOGY, VOLUME 27

Otherwise describe, Ordovician Receptaculites from Vietnam. He also described a sponge,
Archaeoscyphia, from Malaya (Kobayashi 1959); this last taxon is an undoubted Calathium. Thein
(1973) listed Receptaculites from the Ordovician of the southern Shan State in Burma.

The new receptaculitids from the Middle Ordovician of Burma described here are the first
receptaculitids from south-east Asia available for detailed description; they thus extend the
geographic range of these fossils and fill a gap in their global distribution.

SYSTEMATIC PALAEONTOLOGY

Class RECEPTACULITAPHYCEAE WcisS 1954
Order receptaculitales James 1885
Family receptaculitaceae Eichwald 1860
Genus fisherites Finney and Nitecki 1979

Fisherites burmensis sp. nov.

PL 47, figs. 1,2

Diagnosis. Thallus subglobular to globular; nuclear area of small and very numerous meroms;
intercalation asymmetrical, occasionally symmetrical; meroms of two distinct sizes.

Holotype. Nuclear hemisphere FMNH PP 20079.

Other material. Eight more or less incomplete specimens EMNH PP 20076 to FMNH PP 20083.

Derivation of name. From Burma.

Terminology. The terminology used in descriptions of receptaculitids was confused in the past mainly due to the
conflicting interpretations of the nature of receptaculitids. When receptaculitids were considered sponges,
sponge terminology was used (e.g. Hinde 1884); when they were believed to be dasyclads (e.g. Byrnes 1968),
dasyclad terminology was applied. Now that we can be certain that they are algae (although independent of
Dasycladales), a terminology has evolved which in many ways is unique to this group of fossils. The terminology
in this paper follows Fisher and Nitecki (1982) as modified from Rietschel (1969).

Shape and size of thalli. The specimens are preserved only as flat, incomplete discs, a very common state of
preservation of receptaculitids. They were certainly neither conical nor cylindrical and were probably
subglobular to globular in the adult stage; the small specimens (FMNH PP 20081 and PP 20083) appear to have
been globular. The diameter of the preserved thallus is between 6 cm (3 specimens) and 10 cm (1 specimen). Due
to the fragmentary nature of the specimens, maximum diameter is unknown. We assume that the adult thallus
was at least 12 cm in diameter.

Nucleus. Nuclear area is preserved only on the outer side of the intervallum (FMNH PP 20079). Although the
nucleus itself is obscure, a large number of small meroms is discernible (PI. 47, fig. 1 h). The plates in this area were
not more than 0-3 to 0-4 mm in largest dimensions.

Lacunar hemisphere. Not preserved in any specimens available.

Nuclear hemisphere. Intercalation is predominantly either dextral or sinistral and thus asymmetrical (in the
terminology of Fisher and Nitecki 1982) or Mf (in the terminology of Rietschel 1970). Occasionally, the
intercalation is in both directions, and thus symmetrical or Mf. Orthostichies are pronounced, and

explanation of plate 47

Figs. 1, 2. Nuclear hemispheres of Fisherites burmensis sp. nov.; Middle Ordovician, Wunbye Formation;
southern Shan State, Burma. 1, holotype; FMNH PP 20079; bar = 3-29 cm. 2, FMNH PP 20082;
bar = I -78 cm.

PLATE 47

RIETSCHEL and NITECKI, Fisherites

418

PALAEONTOLOGY, VOLUME 27

intercalations are clustered along them. Intercalations are thus not distributed at random, and areas of thallus
free from intercalary meroms are pronounced. In the holotype (PI. 47, fig. la) there are 29 visible asymmetrical
intercalations, 14 sinistral and 15 dextral, and thus left and right intercalations are approximately of equal
number. In FMNH PP 20082 (PI. 47, fig. 2a) there are 35 intercalary meroms of which 15 are asymmetrical
sinistral, 18 asymmetrical dextral, and 2 symmetrical.

Meroms. The size of the merom plates increases away from the nucleus and can be estimated from the positions
of merom shafts. Thus, plates range from very minute in the nuclear area to 2-5 mm in largest dimension at the
preserved edge of the thallus. Complete meroms are observed in only three specimens, and their distances from
the nucleus are unknown: (1) on the weathered outer surface of FMNH PP 20078 the height of the merom is
8-5- 10 0 mm; thickness 2 0 mm; plate size 2-5 mm; foot, largest dimension 21 to 2-2 mm; (2) on the polished
surface of FMNH PP 20081 the length of the merom is 10 mm and the thickness 1-8 mm (maximum); (3) on
FMNH PP 20080 the height of the merom is at least 3-5 mm and the thickness is greater than 2-3 mm. The sizes of
meroms do not increase greatly on individual specimens because intercalations are relatively abundant, allowing
the sizes of plates to remain relatively constant. There are about 1,100 meroms visible on FMNH PP 20082
(PI. 47, fig. 2), and about 600 on the holotype (PI. 47, fig. 1). The meroms have well-developed heads and feet;
plates are poorly preserved; and the stellate structures are stout and short.

Discussion. In the past, the criteria used in the definitions of receptaculitid taxa were: (1) the shapes
and relative ratios of length to width of meroms; (2) the outlines of plates; and (3) the general shapes
of thalli. However, these features of morphology are not sufficient, and other characters now used in
receptaculitid systematics include; (4) the intercalation pattern; (5) the morphology of stellate
structures; and (6) the relative size of meroms with respect to the size of plates. The pattern of
intercalation, which reflects morphogenesis, is now considered of prime importance.

Because our taxon agrees in all but one of these aspects (the length of meroms) with the genus
Fisherites, and it agrees in only very limited aspects with other taxa, we are assigning it to Fisherites
Finney and Nitecki 1979.

Stratigraphy and lithology. F. burmensis (sp. nov.) occurs in the Wunbye Formation (Lower-Middle Ordovician)
of the Pindaya Group (Ordovician) of the western part of the Shan Plateau region of Burma (text-fig. 1).
According to Thein ( 1973) the Wunbye Formation, the principal formation of the Pindaya Group, is distributed
extensively in the Bawsaing and Pindaya ranges, Yengan, Myogyi, and Pyaukseikpin areas at Kyaukse East, and
between Mandalay and Maymyo in the north. It consists of a succession of thick-bedded limestones, siltstones,
and dolomites. The limestones are finely crystalline, grey to bluish grey, sometimes oolitic, and with pink, buff,
or yellow silty materials in the forms of burrows, specks, pellets, or irregular and regular laminations; burrow
structure is so typical of these limestones that locally the limestone is called the Burrow Limestones. The
siltstone sub-units are thin, medium to thick-bedded, yellow to light grey, and soft to indurated. The dolomite
sub-units are usually thick-bedded, often massive, but generally with fine laminations, and with highly jointed
surfaces in criss-cross pattern; colour is usually bluish grey or grey with submetallic lustre, but dull on weathered
surfaces. They are finely crystalline although often oolitic, and do not usually extend laterally for long distances.

F. burmensis occurs in the Burrow Limestone sub-units of the Wunbye Formation. It is not abundant and is
distributed locally. The five major localities in the western part of the Shan Plateau region of Burma (text-fig. 1)
are listed below.

Specimen No. Locality No.

FMNH PP 20076, 20079, 20080, 2008 1 Xj and

FMNH PP 20077, 20078, 20083 Xj

FMNH PP 20082 X4

No specimens collected X5

F. burmensis occurs in association with Helicotoma,
Ormoceras.

Location

2-4 km due east (Xj ) and 2-8 km due south-east (X2)
of Pyaukseikpin village, east of Kyaukse town.

4-8 km south-west of Pindaya town; 2-4 km north
of Wabya village.

Just north of Yebyukan village, 5-2 km north-east
of Bawsaing.

0-8 km north-east of Kyauk-Chaw village.
Lophospira, Cyrtolites, Paurorthis, Actinoceras, and

Acknowledgements. We are grateful to the Field Museum of Natural History for financial support to Rietschel
during his 1981 tenure of Visiting Scientist position at the Geology Department of the Museum.

RIETSCHEL AND NITECKE BURMESE RECEPTACULITID ALGAE

419

TEXT-FIG. 1 . Geological map of the area south-east of Mandalay, Burma showing the geology of the western Shan
Plateau region and the localities where Fisherites bunnensis have been found.

420

PALAEONTOLOGY, VOLUME 27

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MiAGKOVA, E. I. 1965. Soanity— novaya gruppa organismov. Paleontol. Zh. 3, 16-22. [In Russian.]

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and FORNEY, G. G. 1978. Ordovician Receptaculites camacho n. sp. from Argentina. Ibid. 37, 93-1 10.

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Ibid. 35,41-82.

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Thallophyta). Ibid. 51, 429-447.

1977. Receptaculitids are calcareous algae but not dasyclads. Pp. 212-214. In flugel, e. (ed.). Fossil Algae.

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ROEMER, F. 1897. Lethaea Geognostica. 7 Theil, Lethaea Palaeozoica. Text and Atlas. 324 pp.

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geol. Maroc., Notes et Memoires, 73, 1-218.

THEiN, M. L. 1973. The Lower Paleozoic stratigraphy of western part of the Southern Shan State, Burma. Bull,
geol. Soc. Malaysia, 6, 143 163.

TOOMEY, u. E. and NITECKI, M. H. 1979. Organic buildups in the Lower Ordovician (Canadian) of Texas and
Oklahoma. Fieldiana: Geol. N.s. 2, 1-181.

S. RIETSCHEL

Landessammlungen ffir Naturkunde
D-7500 Karlsruhe
West Germany

M. H. NITECKI

Typescript received 26 March 1982
Revised typescript received 12 July 1982

Department of Geology
Field Museum of Natural History
Chicago
Illinois 60605
U.S.A.

USE OF ETHANOLAMINE THIOGLYCOLLATE
IN THE CONSERVATION OF PYRITIZED FOSSILS

by LORRAINE CORNISH and ADRIAN DOYLE

Abstract. The neutralization and removal of decay products from pyritized fossil material with ethanolamine
thioglycollate is described. Its use on a wide range of material is a significant improvement over previous
techniques which, although satisfactory, were complex and hazardous to the preparator.

The deterioration and even complete decomposition of pyritized fossils through oxidation is a
common problem in collections throughout the world. Various conservation treatments have been
described, e.g. Rixon (1976). Howie (1977u) reviewed these techniques, together with many of the
hypotheses put forward to explain the decay process, and showed that pyrite breakdown is initiated
in storage or exhibition environments solely by high relative humidity. Howie (1979a, b) also
demonstrated that where specimens incorporating reactive pyrite (i.e. with a micro-crystalline
structure) are exposed to relative humidities above 60 per cent, visible deterioration due to oxidation
may occur within a few weeks.

The practice of protecting the surface of specimens from the air by coating with lacquer or resin is
now considered ineffective as a safeguard since such coatings are permeable to both oxygen and water
vapour. This can be readily observed by studying the surface of decayed, coated specimens (text-fig.
1a). The coating will usually have been ruptured by the sulphuric acid produced during oxidation,
exposing earthy textured iron sulphate breakdown products beneath. Thus, it is advisable to remove
as much of the coating as possible to expose the specimen surface for effective re-treatment. In some
cases this may result in the specimen breaking up and care must be taken in noting where the pieces
belong for reassembly after treatment. In most instances pyrite oxidation breakdown products are
easy to identify on the surface of the specimen (Howie 1979a). In cases where the operator is unsure
whether or not pyrite breakdown has occurred, a simple test with universal indicator paper moistened
with distilled water and pressed against the affected area, will confirm this if the pH is less than or
equal to 3.

The method described here replaces the ammonia neutralization process (Rixon 1976; Howie
1979a) and morpholine treatments (Rixon 1976) hitherto used in the British Museum (Natural
History) and other laboratories. The substance now used, ethanolamine thioglycollate, is of
comparatively low toxicity and can be safely employed where calcareous material or water soluble
compounds, such as animal glue, are present.

ETHANOLAMINE THIOGLYCOLLATE

This material, originally developed for use in hair-perming preparations (see Robinson Brothers
Limited, Technical Bulletin 210868 PAL) has three important characteristics that are relevant in the
conservation of pyritic fossil material.

1. Ethanolamine is alkaline and in solution will react with and effectively wash out acidic pyrite
oxidation products (i.e. sulphuric acid).

2. Thioglycollates will react with soluble and insoluble iron compounds (though not stable pyrite)
and chelate or complex iron in solution as a violet-coloured ferrothioglycollate.

3. Ethanolamine thioglycollate is readily soluble in ethanol or propan-2-ol (isopropanol), as are
the products of its reactions with those of pyrite oxidation; thus contact of specimens with reagents
containing more than a small proportion of water, which may be damaging, can be avoided.

(Palaeontology, Vol. 27, Part 2, 1984, pp. 421 424. |

422

PALAEONTOLOGY, VOLUME 27

The chemistry of the formation of iron-thiol compounds has been described in detail (Leussing and
Tischer 1963) and thioglycollic acid is currently used as a successful technique in the preparation of
vertebrate fossils encrusted with haematite (Howie 1974). A major advantage of using ethanolamine
thioglycollate is its solubility in organic solvents which, coupled with its high pH and the ready
solubility of the violet coloured ferrothioglycollates in solvents, makes it an effective neutralization
and dry-cleaning treatment for oxidized pyrite. Ethanolamine thioglycollate is supplied com-
mercially as an aqueous solution containing 40 per cent thioglycollic acid. This material is an
alkaline, colourless to pale pink viscous liquid, miscible in all proportions with water, ethanol or
isopropanol. Despite its relatively low toxicity, precautions should be taken against the possible
hazards associated with its use. The manufacturer’s product safety data sheet should be consulted for
full specifications, but generally its corrosive action necessitates the use of PVC gloves and goggles for
eye protection. Its use should be restricted to a well ventilated area, preferably a fume cupboard.

METHOD

Actively decomposing specimens should initially be placed, together with containers and any
associated labels, in an environment of 40-50 per cent relative humidity until treatment can
commence. It may be necessary to use a desiccator for this purpose. Specimens should then be
examined and note taken of their general condition, whether they are very friable or largely intact. If a
specimen is very friable then the immersion procedure discussed below should be avoided as this may
do more harm than good.

Loose breakdown products can be removed by either gentle brushing or scraping. Sturdier
specimens can be cleaned using an ‘Airbrasive’ with sodium bicarbonate powder; however, this
should be carried out carefully to avoid damaging any surviving original surface. Old coats of varnish
and laquer can also often be removed by this process. Any wax-based adhesives or fillers should be
removed by the application of methylene chloride soaked tissues or pads (Rixon 1976; Howie
1979u) as these can impair treatment. Where the original shell is preserved, particular care is needed
to avoid damage when physical cleaning methods are used; in many such cases it is better not to carry
out initial cleaning and proceed directly to ethanolamine thioglycollate treatment.

After cleaning, each specimen is completely immersed in a solution of between 2 per cent and 5 per
cent ethanolamine thioglycollate in 95 per cent industrial methylated spirit, or alternatively absolute
ethanol or anhydrous iso-propanol. The higher concentration is used on more oxidized material. The
small quantities of water present in the final solution are not enough to endanger specimens during
treatment. Glass beakers are ideal containers for immersion as one can observe both the iron
complexing reactions and the general state of the specimen. The ethanolamine thioglycollate solution
should cover the specimen by 5-6 cm to ensure adequate dilution of the reaction products, and ideally
the specimen should not touch the side of the beaker. Each immersion should last between one and
four hours depending on how badly decayed the specimen is. The clear colourless solution will turn a
violet colour as neutralization and iron complexing occurs. The solution should be changed after a
maximum of four hours immersion to prevent the violet coloured complex ferrothioglycollate anion
from oxidizing to a brown insoluble precipitate which will coat the specimen. Treatment can be
repeated if necessary, provided the specimen is ‘washed’ in clean dry alcohol between immersions.
The specimen should be washed at least three times longer than the treatment time to ensure
removal of reaction products.

Once reaction has slowed down or ceased altogether, i.e. when little or no violet ferrothioglycollate
complex forms, the specimen should be given a final wash and allowed to dry in air. When the
specimen has dried, the surface should be carefully examined and cleaned with the ‘Airbrasive’ to
remove any remaining oxidation products. Alternatively, if the more persistent black coatings (which
are usually mixtures of microcrystalline pyrite and iron oxides) remain, a further course of treatment
using a more concentrated solution of ethanolamine thioglycollate (e.g. 10-15 per cent) may be
effective. Cleaned fragments can be reassembled and glued using Butvar B76 in acetone (1:1 by
volume) or other solvent-based cement.

CORNISH AND DOYLE: CONSERVATION OF PYRITIZED FOSSILS

423

Friable and other specimens which would be damaged by immersion can be neutralized in the
following manner. Place the specimen on a flat surface in a well-ventilated area and apply a paste
composed of 3-5 per cent ethanolamine thioglycollate in spirit added to sepiolite in about equal
portions. The area requiring treatment or the whole specimen should be covered by the paste and
then by polythene or aluminium foil to prevent rapid evaporation of the solvent and left for one to
three hours. Immersion of the sturdier specimens in clean alcohol is a recommended method of
washing. If the specimen cannot be immersed the ferrothioglycollate complex may be removed by
applications of I. M.S. /sepiolite paste until clean. Consolidation of treated but friable specimens is
often advisable although this will not offer protection against exposure to high relative humidity.
Such consolidantsas polyvinyl acetate (5- 10 per cent in ethyl methyl ketone) or polyvinyl butyral (e.g.
5-10 per cent Butvar B98 dissolved in isopropyl alcohol, or 5-10 per cent Butvar B76 dissolved in
acetone) are recommended. Thin coats should be applied and if more than one is necessary, adequate
drying time should be allowed between each coat.

Specimen containers should be replaced where possible and labels coated or wiped clean with a
tissue. Badly damaged labels can be treated by exposing to ammonia fumes or by washing in a very
dilute I per cent ethanolamine thioglycollate solution in alcohol, and subsequently coated in a
polymethyl methacrylate emulsion (Primal AC 73), or alternatively, inserted into small polythene
sachets which can be pressure or heat sealed. Storage of treated material should be in a low humidity
environment (40-55 percent relative humidity), which will help prevent further decay. Howie (I979r/)
and Thompson (1978) described methods for controlling and modifying storage and exhibition
environments using various techniques.

Conclusion

The use of enthanolamine thioglycollate in palaeontological conservation has provided a satisfactory
method of treating decaying pyritized fossils. As well as being an effective reagent for the removal of
pyrite oxidation products, without endangering calcareous structures, it is safer and easier to use than
previous techniques. It can also be readily adapted to suit the requirements of individual specimens.

Supplier of ethanolamine thioglycollate. Robinson Brothers Limited, Phoenix Street, West Bromwich, West
Midlands B70 OAH

TEXT-FIG. I . Dimorphohoplitid ammonite from the Gault Clay (Albian, lower Cretaceous;
Folkstone, Kent) preserved in pyrite. a, before treatment, showing typical areas of pyrite oxidation
speckled white, b, after removal of pyrite oxidation products with ethanolamine thioglycollate.

424

PALAEONTOLOGY, VOLUME 27

REFERENCES

HOWIE, F. M. p. 1974. Introduction of thioglycollic acid in preparation of vertebrate fossils. Curator, 17, 159-165.

1977a. Pyrite and conservation. Part 1: historical aspects. Newsl. Geol. Curators Grp, 1, 457-465.

\911b. Pyrite and conservation. Part 2. Ibid. 1, 497-512.

1979a. Physical conservation of fossils in existing collections. Ibid. 2, 269-280.

\919b. Museum climatology and the conservation of palaeontological material. Spec. Pap. Palaeont. 22,

103-125.

LEUSSiNG, D. L. and TISCHER, T. N. 1963. Iron-catalyzed autoxidation of mercaptoacetate. Adv. Chem. 37,
216-225.

RIXON, A. E. 1976. Fossil animal remains: their preparation and conservation. Athlone Press, London. 304 pp.
THOMPSON, G. 1978. The museum environment . Butterworths, London. 270 pp.

LORRAINE CORNISH
ADRIAN DOYLE

Department of Palaeontology
British Museum (Natural History)
Cromwell Road

Typescript received 10 June 1983 South Kensington

Revised typescript received 30 September 1983 London SW7 5BD

DICHOGRAPTID S YNRH ABDOSOMES
FROM THE ARENIG OF BRITAIN

by J. A. ZALASIEWICZ

Abstract. Dichograptid synrhabdosomes are reported for the first time. Synrhabdosomes of Didymograptus
aff. simidam Elies and Wood from Arenig Fawr, North Wales and Azygograptus lapworthi Nicholson from near
Keswick, Lake District, are described, both from the Arenig Series (exterisus Zone). Possible reconstructions of
synrhabdosomes of D. aff. simutans are attempted. It is suggested that synrhabdosomes acted as mechanisms to
promote rapid breeding in short-lived, highly favourable environmental conditions.

Synrhabdosomes are comparatively rare associations of graptolite rhabdosomes. Individual
rhabdosomes are generally linked at the free distal ends of their virgulae or nemata, although in one
recorded instance (Bjerreskov 1976) linkage involves the free ends of proximal virgellae. Biserial
(diplograptid) graptolites make up the bulk of known examples (e.g. Ruedemann 1947), but
synrhabdosomes have also been recorded amongst uniserial monograptids (e.g. Rickards 1975,
p. 414); possible synrhabdosomes of Dictyonema (Bulman 1927-1967, p. 27; Ruedemann 1947, pi. 2,
fig. 11), and Corynoides (Ruedemann 1947, pi. 58, fig. 25) have also been figured. Dichograptid
synrhabdosomes have not been described previously. The figured specimens are deposited in the
Sedgwick Museum, Cambridge (SM).

DESCRIPTION OF SYNRHABDOSOMES
Didymograptus aff. simulans Elies and Wood, 1901

Material. Five synrhabdosomes from three localities in the Llyfnant Member of the Carnedd lago Formation
(lower Arenig Series, extensus Zone) of Arenig Fawr, North Wales (text-fig. 1; Zalasiewicz, in press). The
Llyfnant Member is dominated by interlayered sandstones and mudstones, containing burrows, loadcasts, and a
few ripples (Zalasiewicz 1981). There is little or no grading of individual layers or evidence, such as mudcracks
and rainprints, of subaerial exposure. The environment was probably shallow marine subtidal. The only body
fossil found in situ was D. aff. simulans, which is locally abundant.

Description. D. aff. simulans from Arenig Fawr differs from the type material in having a slightly smaller angle
between the stipes. The synrhabdosomes are made up of from four to eight rhabdosomes, radially to subradially
arranged. The apices of the siculae point towards the centre of the synrhabdosome (text-fig. 2a, h, d), and give rise
to short, tangled nemata (text-fig. 2c). Nemata within synrhabdosomes are locally thickened, up to 0 036 mm
across, while nemata of unassociated rhabdosomes do not exceed 0 027 mm across. Preservation of the
synrhabdosomes is not good enough to state v/hether their constituent rhabdosomes are all at the same stage of
development.

Discussion. The difference between the nemata of unassociated rhabdosomes and those that form
part of a synrhabdosome appears to represent a functional adaptation. However, this does not
seem to have been simply a strengthening of the nemata in order to hold the synrhabdosome together,
as the thickening is only local (text-fig. 2c). In any case, it is likely that synrhabdosomes were held
together by soft tissue rather than by the nemata themselves (Rickards 1975, p. 416). Possible
reconstructions of synrhabdosomes of D. aff. simulans are shown in text-fig. 3. The major alternatives
are between an ordered (text-fig. 3u) and a disordered (text-fig. hb) structure. An ordered structure
would have been preferable if most or all D. aff. simulans rhabdosomes spent most or all of their life-
spans as members of synrhabdosomes. However, if synrhabdosomes were temporary structures, or
were not formed by all rhabdosomes of D. aff. simulans, then it may not have been neeessary to attain
an ordered structure. These general questions are addressed below.

(Palaeontology, Vol. 27, Part 2, 1984, pp. 425-429.|

426

PALAEONTOLOGY, VOLUME 27

TEXT-FIG. 1 . Location and stratigraphic position of synrhabdosomes of Didymograptus aff.
simulans Elies and Wood. Loc. A, spoil from old pits south of Hafotty Ffilltirgerig, NGR SH
8167 3844. Loc. B, 200 m south-east of Beudy Nant-y-pysgod, NGR SH 8202 3703. Loc. C,
east face of Moel Llyfnant, NGR SH 81 16 3575.

ZALASIEWICZ: GRAPTOLITE S YN RH A BDOSOM ES

427

TEXT-FIG. 2. Synrhabdosomes. a-d, Didymograptus aff, simulans Elies and Wood, a, SM A I02852n-A102860a,
loc. B. b, SM A102893Z)-A102898/i, ioc. A. c, proximal part of b. d, SM AI0297I -AI02975, loc. C. e,
Azygograptus lapworthi Nicholson, SM AI7963-A17970, Hodgson Howe Quarry, near Keswick, Cumbria./,

proximal part of e. a, b, d, e to same scale.

Azygograptus lapworthi Nicholson (ex Lapworth MS), 1875

Material. One synrhabdosome in a grey mudstone from the middle Skiddaw Slates (lower Arenig Series, extensm
Zone) of Hodgson Howe Quarry, near Keswick, Cumbria, England.

Description. At least fifteen rhabdosomes, radially arranged (text-fig. 2c). The centre of the synrhabdosome is
poorly preserved, but fragments of tangled nemata are visible (text-fig. 2/).

ABUNDANCE, EORM, AND FUNCTION OF SYNRHABDOSOMES

Synrhabdosomes are paradoxical: few species are known to form them, although these species are
nevertheless widely scattered both in time and within the graptolite orders. It is commonly implied
that this rarity is illusory. Many reconstructions of the Ordovician sea show graptolite synrhab-
dosomes in the plankton, suspended by their ‘floats’ (such ‘Boats’ are now known to be artefacts; see
Rickards 1975, p. 416). In this view, synrhabdosomes are rare due to post-mortem break-up with, in
addition, many synrhabdosomes being overlooked as ‘chance associations’. Several features suggest
that this view is probably not true. First, where synrhabdosomes have been found they tend to
be present in numbers, as in those of D. aff. simulans described above, and the examples of
synrhabdosomes figured by Ruedemann (1947, e.g. pi. 81, fig. 33). Secondly, even moderately well-
preserved synrhabdosomes are striking fossils, unlikely to be taken as chance associations. Thirdly,

428

PALAEONTOLOGY, VOLUME 27

many species appear to have been physically incapable of forming synrhabdosomes, e.g. Dicrano-
graptus, and species of Dicellograptus in which the nema is absent or embedded in the dorsal wall of
one of the two stipes; in any hypothetical Cyrtograptus synrhabdosome the individual graptolites
must have been stacked one on top of the other like pancakes~an unlikely structure. Fourthly,
any widespread occurrence of graptolites as synrhabdosomes would contradict a most marked
evolutionary trend in graptolites, that of the progressive reduction through time in the number of
stipes. It follows that synrhabdosomes were relatively rare, yet they possessed advantages that must
have overcome the ‘disadvantage’ of a marked increase in stipe number.

Consider a synrhabdosome-forming species of graptolite. In Didymograptus aflf. simulans it
appears that rhabdosomes were not members of synrhabdosomes all of the time, since unassociated
rhabdosomes have a straight slender nema, unlike the short, twisted and locally thickened nemata of
those within synrhabdosomes. It is also unlikely, for two reasons, that these unassociated
rhabdosomes were bound up in synrhabdosomes at some point in their life-cycle. First, the graptolite
would have had to discard its nema and grow another to suit its new life-style. Secondly, a numerical
argument can be applied: in the case of A. lapworthi, several hundred specimens were present on the
slabs examined, and only one synrhabdosome was discovered; in the case of D. aflf. simulans, some 1 20
specimens included five synrhabdosomes. The formation of synrhabdosomes emerges as a strategy
indulged in by only some members of a population for what must have been quite particular reasons.

Ruedemann (1895, 1947) described diplograptid synrhabdosomes that included rhabdosomes at
all stages of development. In contrast, the rhabdosomes of Rhaphidograptus toernquisti joined at their
virgellae, that make up the remarkable synrhabdosomes described by Bjerreskov (1976), were all at
the same stage of development. Previously suggested modes of development of synrhabdosomes
envisage either budding from the apical part of the original sicula (Kozlowski 1949), or the
development of a number of siculae from within a mass of extrathecal tissue (Bjerreskov 1976). These
imply that the members of any synrhabdosome were either genetically identical, as in the former
instance, or were at least kin to each other. Since the most plausible function of the synrhabdosome
was to aid sexual reproduction (Rickards 1975, p. 416), both modes of development would have
resulted in presumably disadvantageous inbreeding. This disadvantage would have arisen through a
reduction in the interchange of genetic material rather than through ‘genetic mistakes’, a few of which
could have been afforded in the likely r-selective reproductive regime of the graptolites (D. Grzywacz,
pers. comm.). However, if the members of synrhabdosomes were not genetically related, then some

TEXT-FIG. 3. Possible reconstructions of synrhabdosomes of Didymograptus aff. simulans Elies and Wood, a, an
ordered structure composed of symmetrically positioned graptolites. h, a disordered structure, with randomly

positioned graptolites.

ZALASIEWICZ: GRAPTOLITE SYNRHABDOSOMES

429

clustering together of ‘automobile’ graptolites must have occurred, perhaps under the influence of
some graptolite pheromone. Whether graptolites were capable of ‘automobility’ (Kirk 1 969) remains
in doubt (Rickards 1975).

I conclude therefore that the graptolites making up synrhabdosomes were indeed genetically
related, that the function of synrhabdosomes was to aid sexual reproduction, and that synrhabdo-
somes formed only under environmental conditions in which the joint ‘disadvantages’ of a multi-stipe
colony and inbreeding were over-ridden by special circumstances. The special circumstances might
have been short-lived, highly favourable conditions, in which synrhabdosomes acted as a mechanism
to promote rapid breeding. Given such a function, there would have been little need for
synrhabdosomes to obtain the stable ordered structure necessary for an optimum feeding strategy,
and those of D. aff. simulans would have had the disordered structure shown in text-fig. 36.

Acknowledgements. Most of this work was carried out whilst I was in receipt of a N.E.R.C. studentship at the
Sedgwick Museum, Cambridge, under the guidance of Professor H. B. Whittington. I thank Drs. R. B. Rickards,
R. A. Fortey, A. W. A. Rushton, D. Grzywacz, and W. A. Read for valuable comments on the manuscript. This
paper is published with the permission of the Director of the British Geological Survey.

BJERRESKOV, M. 1976. A new type of graptolite synrhabdosome. Bull. geol. Soc. Denm. 25, 41 -47.

BULMAN, o. M. B. 1927-1967. British dendroid graptolites. Palaeontogr. Soc. (Monogr.), lxiv-|-97 pp., 10 pis.
ELLES, G. L. and WOOD, E. M. R. 1901 . Monograph of British graptolites. Part 1. Palaeontogr. Soc. (Monogr.), 1 -54,
pis. 1-4.

KIRK, N. H. 1969. Some thoughts on the ecology, mode of life and evolution of the Graptolithina. Proc. geol. Soc.
Lond. 1659, 273-292.

KOZLOWSKi, R. 1949. Les graptolithes et quelques nouveaux groupes d’animaux du Tremadoc de la Pologne.
Palaeont. pol. 3 (for 1948), 1-235, pis. 1-42.

NICHOLSON, H. A. 1875. On a new genus and some new species of graptolites from the Skiddaw Slates. Ann. Mag.
nat. Hist. (Ser. 4), 11, 133-143.

RICKARDS, R. B. 1975. Palaeoecology of the Graptolithina, an extinct Class of the Phylum Hemichordata. Biol.
Rev. 50, 397-436, pis. 1 -4.

RUEDEMANN, R. 1895. Development and mode of growth of Diplograptus McCoy. Rep. N. Y. St. geol. Siirv. (for
1894), 217-249, pis. 1-5.

1947. Graptolites of North America. Mem. geol. Soc. Am. 19, 652 pp., 92 pis.

ZALASIEWICZ, J. A. 1981. Stratigraphy and palaeontology of the Arenig area. North Wales. Ph.D. thesis
(unpubl.), Cambridge University.

(in press). A re-examination of the type Arenig Series. Geol. J.

REFERENCES

Typescript received 18 May 1983
Revised typescript received 3 October 1983

J. A. ZALASIEWICZ
British Geological Survey
Keyworth

Nottingham NG12 5GG

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© The Palaeontological Association, 1984

Palaeontology

VOLUME 27 PART 2

CONTENTS

Constructional morphology of bivalves: evolutionary path-
ways in primary versus secondary soft-bottom dwellers
A. SEILACHER 207

Silurian odontopleurid trilobites from Gotland

LARS RAMSKOLD 239

Rhyniophytina and Trimerophytina from the early land flora
of Victoria, Australia

J. D. TIMS and T. C. CHAMBERS 265

The Cretaceous ammonite Ammonites requienianus
d’Orbigny, 1841

W. J. KENNEDY and C. W. WRIGHT 281

New Porocharaceae from the Bathonian of Europe:
phylogeny and palaeoecology

MONIQUE FEIST and NICOLE G R A MB A ST- FESS A R D 295

Adaptive significance of shell torsion in mytilid bivalves
ENRICO SAVAZZI 307

Early Ordovician trilobites, Nora Formation, central
Australia

RICHARD A. FORTEY JOHN H. SHERGOLD 315

The Upper Carboniferous tetrapod assemblage from New-
sham, Northumberland

M. J. BOYD 367

Computer-based storage and retrieval of palaeontological

data at the Sedgwick Museum, Cambridge, England

DAVID PRICE 393

Pterosaur remains from the Kayenta Formation (? Early
Jurassic) of Arizona

KEVIN PADIAN 407

Ordovician receptaculitid algae from Burma

SIEGFRIED RIETSCHEL and MATTHEW H. NITECKI 415

Use of ethanolamine thioglycollate in the conservation of
pyritized fossils

LORRAINE CORNISH and ADRIAN DOYLE 421

Dichograptid synrhabdosomes from the Arenig of Britain

J. A. ZALASIEWICZ 425

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