Revised classification of Pteraspididae with description of new forms from Wyoming

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FIELDIANA: GEOLOGY

A Continuation of the

GEOLOGICAL SERIES

of

FIELD MUSEUM OF NATURAL HISTORY

VOLUME 20

/.S NATURAL <</\
f**> HISTORY ^1

FIELD MUSEUM OF NATURAL HISTORY
CHICAGO, U.S.A.

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TABLE OF CONTENTS

PAGE

1. Revised Classification of Pteraspididae with Description of New Forms
from Wyoming. By Robert H. Denison 1

2. Catalogue of Type and Referred Specimens of Fossil Echinozoa (Echi-
noidea and Cyclocystoidea) in Field Museum of Natural History. By-
Julia Golden and Matthew H. Nitecki 43

3. Catalogue of Type and Referred Specimens of Echinozoa (Edrioaste-
roidea) in Field Museum of Natural History. By Julia Golden and
Matthew H. Nitecki 53

4. Catalogue of Type and Referred Specimens of Fossil Stelleroidea in
Field Museum of Natural History. By Julia Golden and Matthew H.
Nitecki 65

5. Redescription of Ischadites clrodi (S. A. Miller, 1892) a Lower De-
vonian Receptaculitid. By Matthew H. Nitecki 77

('). A Strange Arthropod from the Mazon Creek of Illinois and the Trans
Permo-Triassic Merostomoidea (Trilobitoidea.) By Frederick R. Schram. 85

^FIELDIANA
Geology

Published by Field Museum of Natural History

Volume 20, No. 1 September 18, 1970

Revised Classification of Pteraspididae
with Description of New Forms from Wyoming

Robert H. Denison

Curator of Fossil Fishes
Field Museum of Natural History

In 1967 in connection with the description of a new pteraspid
from Utah, I reviewed and revised the classification of this family.
Now, in studying extensive collections in Field Museum from the
Bighorn Mountains of Wyoming, I have felt the necessity to review
this classification again, and particularly to re-evaluate the charac-
ters which have been used to distinguish genera and species. The
classification that I have arrived at is essentially the same as that of
my 1967 paper, and I will repeat it with minor changes, additions,
and further justifications. My own studies have been largely re-
stricted to North American material, and so I have attempted no
detailed review of European forms. Most of the additions concern
the genus Protaspis and its relatives, which are the common pteras-
pids of the western United States. Important new information about
the structure of these forms has been provided by the material from
the Bighorn Mountains of Wyoming, and by a restudy of old mate-
rial from Utah and from Beartooth Butte, Wyoming. I have in-
cluded all of the genera in one family, Pteraspididae, and feel no need
to elevate it to the rank of suborder or order, as did Tarlo (1962,
p. 265), Obruchev (1964, p. 63), and Stensio (1964, p. 361), although
this is necessary if Doryaspis is placed in a family of its own. As
stated below, I feel that the purposes of classification are satisfied
equally well by isolating Doryaspis from other pteraspids in a sep-
arate subfamily, which requires only the use of another subfamily,
Pteraspidinae, to include typical pteraspids.

Library of Congress Catalog Card Number: 71-136029
Publication 1106 1

2 FIELDIANA: GEOLOGY, VOLUME 20

I have given particular attention in this study to the structure of
the branchial openings and the rostral plate. In the classifications
of Stensio (1958, 1964) and Tarlo (1961), the rostral structure has
been used as the primary character for distinguishing genera. Among
the pteraspids from the western United States there are also impor-
tant differences in the rostrum, yet, in spite of this, I feel that the
majority of the species are closely related, as indicated by their
broad, highly vaulted dorsal shields, posterior branchial openings,
and usually scale-like dorsal spines. This suggests that many rostral
characters have been independently acquired in the American species
as a result of an evolution paralleling that found in Europe. For this
reason I have given the rostral characters less weight, and have, for
example, included in the subgenus Protaspis species with rostra suf-
ficiently different to distinguish the genera of Stensio and Tarlo. The
posterior branchial openings, which particularly characterize Pro-
taspis, occur in certain European species. I have not studied these
forms, so cannot come to any definite conclusions as to whether they
are closely related to American species or the result of parallel evolu-
tion. For this reason I have provisionally kept them subgenerically
distinct.

Specimens whose catalogue numbers have the prefix PF are in the
collection of Field Museum of Natural History. The drawings have
been made by Museum staff artist, Dr. Tibor Perenyi, many from
my sketches.

Family Pteraspididae

Dorsal shield composed of rostral and pineal plates, a dorsal disc
with a dorsal spine attached to its posterior part, as well" as paired
orbital, branchial, and cornual plates, the latter occasionally reduced,
absent, or two pairs. Ventral shield formed by a large ventral disc,
variably developed paired lateral, oral, and sometimes postoral plates,
and in Doryaspis a pseud orostrum. Branchial openings more or less
posteriorly placed at or near the lateral margins of the dorsal shield,
typically at the posterior ends of the branchial plates, and commonly
bounded posteriorly by cornual plates. Two or three pairs of sensory
canals radiate from the center of ossification of the dorsal disc. Plates
and scales consist of a tangentially laminated basal layer attaining
only moderate thickness, a middle layer characterized by relatively
large chambers, and a superficial layer consisting of narrow dentine
ridges, or in some forms of tubercles.

DENISON: PTERASPIDIDAE

Subfamily Pteraspidinae

Rostral plate extending anteriorly over the mouth; no pseudo-

rostrum attached to the ventral shield.

il!

brp— J+Ul W\

1 1& /// / / \\

bro-

£&l_dd— .

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Fig. 1. Region of branchial opening of Protopteraspis primaeva (Kiaer), based
largely on PF 1078 (X 7). A, ventral view, right side; B, dorsal view, left side.
bro, branchial opening; brp, branchial plate; co, cornual plate; dd, dorsal disc.

Protopteraspis Leriche, 1924

Type species. — Protopteraspis gosseleti Leriche.

Protopteraspis Leriche, 1924, Bull. Soc. Beige Geol., Pal., Hydr., 33, p. 149
(footnote), (subgenus of Pteraspis).

Simopteraspis White, 1950, Bull. Brit. Mus. (Nat. Hist.), Geol., 1 , p. 76 (sub-
genus of Pteraspis).

Zascinaspis Stensio, 1958, Traits de Zool., 13, fasc. 1, p. 255; Tarlo, 1961,
Acta Palaeont. Polonica, 6, pp. 378-379.

Diagnosis. — Small to medium-sized pteraspids. The rostrum
short and bluntly rounded, with its ventral preoral surface short and
lacking a preoral field.1 Branchial openings well in advance of the
postero-lateral corners of the dorsal shield, and bounded by branchial
and cornual plates (fig. 1).

1 1 have adopted the following terminology for the ventral surface of the ros-
trum: Ventral preoral surface, the entire ventral surface of the rostrum anterior
to the mouth, and including in some genera the preoral field, a clearly defined area
elevated above the rest of the rostral surface and lacking ornamentation of dentine
ridges; and the ascending lamella, the posterior part of the ventral preoral surface
which rises dorsally anterior to the mouth.

4 FIELDIANA: GEOLOGY, VOLUME 20

Discussion. — Although in 1967 I followed Leriche and White in
ranking this as a subgenus, I now feel warranted in elevating it (as
well as subgenera Pteraspis and Althaspis) to generic rank. White
(1961, pp. 257-258) prefers to use Simopteraspis, and to retain Pro-
topteraspis for P. gosseleti alone because the preoral region of the
latter is unknown. However, P. gosseleti and the type species of
Simopteraspis, Pteraspis leathensis, are so similar in other respects
that at one time White (1950, p. 82) believed that they might turn
out to be conspecific, so I feel justified in placing them in the same
genus.

The species referred to Simopteraspis by White in 1950 are small,
primitive forms with blunt rostra and typical branchial openings
(fig. 1). In addition, each has a small pineal plate isolated from the
orbitals, lacks postoral plates, and has the posterior extensions of the
supraorbital canals (pineal canals of Stensio) forming a V-shaped
loop on the dorsal disc. I refer also to Protopteraspis the species
placed in Zascinaspis by Stensio in 1958 and Tarlo in 1961 (Brachi-
pteraspis heintzi Brotzen, B. grossi Brotzen, and Pteraspis carmani
Denison), which differ mainly in their larger size and in characters
correlated with size, such as the relatively larger ventral preoral
surfaces, and the wider pineal plates in contact with the orbitals.
The presence of postoral plates in P. carmani may be related to size
also. The extension of the supraorbital canals onto the dorsal disc
is not known in the species referred to Zascinaspis, and may be char-
acteristic only of small primitive species; it is retained in Althaspis
whitei (Denison, 1955, fig. 110A), and in a modified form in one speci-
men of Pteraspis rostrata (White, 1935, fig. 68).

Pteraspis Kner, 1847

Type species. — Cephalaspis rostratus Agassiz.

Pteraspis Kner, 1847, Haidinger's Naturw. Abh., 1 , p. 165.

Scaphaspis Lankester, 1865, Rept. Brit. Assoc. Adv. Sci., Trans. Sect., 1864,

p. 58 (in part).
Podolaspis Zych, 1931, Fauna Ryb Dewonu i Downtonu Podola, p. 89.
Brachipteraspis Brotzen, 1936, Ark. Zool., 28A, no. 22, pp. 31-35.
Mylopteraspis Stensio, 1958, Traits de Zool., 13, fasc. 1, p. 255.
Parapteraspis Stensio, 1958, Traits de Zool., 13, fasc. 1, p. 265.
Plesiopteraspis Stensio, 1958, Traite de Zool., 13, fasc. 1, p. 265.

Diagnosis. — Moderate-sized pteraspids. The rostrum somewhat
elongate and with a preoral field developed on at least the posterior
part of its ventral preoral surface. Branchial openings well in ad-

DENISON: PTERASPIDIDAE

brp

• ro — JL

Fig. 2. Left branchial opening of Pteraspis 1 priscillae (Denison), dorsal view,
PF 867 ( X 5). bro, branchial opening; brp, branchial plate; dd, dorsal disc.

vance of the postero-lateral corners of the dorsal shield, and bounded
by branchial and well-developed cornual plates.

Discussion. — As used here, the genus Pteraspis is restricted to the
species referred to the subgenus Pteraspis in my 1967 paper. Its
most important distinguishing feature is the presence on the ventral
surface of the rostrum of a preoral field lacking dentine ridges and
probably representing the locus of sensory organs. Its branchial
openings are basically similar to those of Protopteraspis (fig. 1).

White (1961, p. 270) has questioned the reference of Protaspis
priscillae Denison (1953, pp. 348-349, figs. 82-83) to Protaspis.
Further preparation and study of the type and only specimen has
shown that he was correct, for there appear to be slender branchial
openings (fig. 2, bro) well in advance of the posterior corners of the
shield with the usual relations of those of Pteraspis, except that dis-
tinct cornual plates cannot be identified. Little of the ventral surface

6

FIELDIANA: GEOLOGY, VOLUME 20

of the rostrum can be seen, but there is a median unornamented area
that is presumably a preoral field, so this species can be referred to
Pteraspis or possibly to Rhinopteraspis. It shows resemblances to
another elongate, slender species, Pteraspis dewalquei Fraipont, as
figured by White (1960, fig. 3), though the ventral surface of the
rostrum of the latter is unknown, and its generic reference is also
uncertain.

Althaspis Zych, 1931

Type species. — Pteraspis elongata Zych (non Alth) = Althaspis
samsonowiczi Tarlo.

Podolaspis (Althaspis) Zych, 1931, Fauna Ryb Dewonu i Downtonu Podola,

p. 89.
Brotzenaspis Stensio, 1958, Traite de Zool., 13, fasc. 1, pp. 265, 272.
Pseudopteraspis Stensio, 1958, Traite de Zool., 13, fasc. 1, p. 254.
Pteraspis (Cymripteraspis) White, 1960, Bull. Inst. Roy. Sci. Nat. Belg., 36,

no. 6, p. 8 (footnote).
Loricopteraspis Tarlo, 1961, Acta Palaeont. Polonica, 6, p. 382.

Diagnosis. — Mostly moderate-sized or rather large pteraspids.
The rostrum more or less elongate, but lacking a preoral field, and

Fig. 3. Rostral plate of Althaspis whitei (Denison), ventral view, PF 1195
(X 6). dla, ventral surface of dorsal lamina, lacking basal layer and exposing
cancelli anteriorly; ifc, pores of infraorbital canal; vlr, ventro-lateral face; vps, ven-
tral preoral surface.

DENISON: PTERASPIDIDAE 7

having its ventral preoral surface covered with dentine ridges. Bran-
chial openings well in advance of the postero-lateral corners of the
dorsal shield, and bounded by branchial and cornual plates.

Discussion. — An irregular dentine ridge arrangement on the ven-
tral side of the rostrum was used by Tarlo (1961, p. 382) to distin-
guish Loricopteraspis, but this is hardly evidence that this area was
formed of a number of separate synchronomorial units as he assumed.
Pteraspis whitei (Denison, 1955, p. 450-454) may show an irregular
development of the ventral rostral ridges (fig. 3), though this is a
small species with the rostrum only slightly elongate; it may be con-
sidered a primitive species of Althaspis.

White (in Allen, Halstead, and Turner, 1968, pp. 151-152) still
maintains the generic or subgeneric distinction of Cymripteraspis,
though this differs from typical Althaspis only in the presence of a
small plate with concentric ridges on the preoral border. Halstead
(in Allen, Halstead, and Turner, 1968, p. 145) has attempted to ex-
plain this as an oral plate appressed to the preoral border, an expla-
nation denied by White. In any case, it appears at present to be a
rather insecure basis for the erection of a distinct genus or subgenus.

Brotzenaspis pteraspidoides Stensio (1958, fig. 152B) is a small
form with a rostrum of only moderate length. Stensio's figure shows
the ventral surface of the rostrum to be covered with more or less
transverse ridges, which indicates a relationship to Althaspis. Tarlo
(1961, p. 378) referred it to Zascinaspis (Protopteraspis of this paper),
but that seems to be incorrect.

Rhinopteraspis Jaekel, 1919

Type species. — Palaeoteuthis dunensis Roemer, 1855.
(For synonymy, see Tarlo, 1961, pp. 368-370.)

Diagnosis. — Moderate-sized to large pteraspids. The rostrum
much elongated, with a preoral field formed by a separate plate.
Branchial openings in advance of the postero-lateral corners of the
dorsal shield, but the cornual plates reduced or absent.

Discussion. — The International Commission on Zoological No-
menclature (1957, p. 43) placed Rhinopteraspis Jaekel on the official
list, and rejected the earlier names, Archaeoteuthis Roemer and Palae-
oteuthis Roemer, as invalid. The type species was designated as
Palaeoteuthis dunensis Roemer, and it was also placed on the official
list. Since this decision, Tarlo (1961, p. 370) has indicated that
Rhinopteraspis dunensis is a synonym of the earlier name, Stegano-

8 FIELDIANA: GEOLOGY, VOLUME 20

dictyum cornubicum M'Coy, 1851, as already claimed by Lankester in
1868. Since cornubicum was the type species of Steganodictyum,
strict adherence to the law of priority would require the use of
M'Coy's name for the genus and species. However, Steganodictyum
would appear to qualify as a nomen oblitum, as defined in Article 23b
of the International Code of Zoological Nomenclature, though this is
not true of the specific name. If Lankester and Tarlo are correct,
we may then refer to the genus as Rhinopteraspis, and its best known
species as R. cornubica (M'Coy), but the type species remains Palaeo-
teuthis dunensis Roemer, here accepted as a synonym of R. cornubica.
As I suggested in 1967 (p. 34), Belgicaspis Zych, whose type spe-
cies is Pteraspis crouchi Lankester, may belong to Rhinopteraspis or
be closely related. Its preoral field is formed by a separate plate, as
indicated by White (1960, p. 8 footnote), its rostrum is long and
slender, though variable in shape (White, 1961, pi. 36, figs. 4-11),
and its cornual plates are reduced or absent. As noted above (p. 6),
Protaspis priscillae Denison may belong to Rhinopteraspis.

Protaspis Bryant, 1933

Type species. — Pteraspis bucheri Bryant, 1932.

Diagnosis. — Moderate-sized to large pteraspids with the dorsal
shield rather broad or highly vaulted. The rostrum very short to
moderate in length, with the development of its ventral preoral sur-
face dependent on the rostral length. The branchial plates long, the
cornual plates reduced or absent, and the branchial openings at the
postero-lateral corners of the shield. The dorsal spine usually small,
recumbent, and scale-like.

Discussion. — Glossoidaspis Branson and Mehl, 1931 predates Pro-
taspis Bryant, but was based only on a dorsal disc which shows no
generically diagnostic characters, so it must remain incertae sedis.

As used here, the genus Protaspis is restricted to those species in
which the branchial openings are at the postero-lateral corners of the
shield. This requires the removal of certain species formerly re-
ferred to Protaspis in which the branchial openings have a more
anterior position. I have not given the ventral preoral surface much
weight in classifying Protaspis because its development is clearly
related to the length of the rostrum. Thus, in species with a short,
broad rostrum (figs. 14, 19) the ventral preoral surface is small, as in
Protopteraspis, while in species with longer rostra (fig. 9) the ventral
preoral surface may be considerable and a preoral field may be devel-
oped, as in Pteraspis. The genus Protaspis has been subdivided into

DENISON: PTERASPIDIDAE 9

a number of subgenera, based largely on differences in ornamentation,
on details of the structure of the external gill openings, and, in one
case, on the aberrant development of the dorsal spine and orbital
plates.

Subgenus Protaspis Bryant, 1933

Type species. — Pteraspis bucheri Bryant, 1932.

Diagnosis. — Dorsal shield of moderate breadth. Ornamentation
consisting of ridges of dentine arranged approximately parallel to
lines of growth. Branchial openings facing posteriorly or postero-
dorsally, and bounded externally by the branchial plates and some-
times by the dorsal disc, with cornual plates absent or poorly de-
veloped.

Protaspis (Protaspis) bucheri (Bryant), 1932

Pteraspis bucheri Bryant, 1932, Proc. Amer. Phil. Soc, 71 , pp. 232-238, text-
fig. 1; pi. 1; pi. 2, fig. 1; pi. 3, figs. 1-2.

Protaspis bucheri Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 294-296, text-
fig. 1A; pi. 1; pi. 2, figs. 1-2; pi. 5, fig. 1; 1934, Proc. Amer. Phil. Soc, 73,
p. 152, pi. 22; pi. 26, fig. 2; 1935, Proc. Amer. Phil. Soc, 75, p. 122, pi. 13,
fig. 1; White, 1935, Phil. Trans. Roy. Soc. London (B), 225, p. 438; Deni-
son, 1953, Fieldiana: Geol., 11, p. 334.

Protaspis brevirostris Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 297-298,
pi. 8, figs. 1-2; 1935, Proc. Amer. Phil. Soc, 75, p. 123, pi. 15; Denison,
1953, Fieldiana: Geol., 11, p. 334.

Occurrence. — Lower Devonian, Beartooth Butte formation, Bear-
tooth Butte, Park County, Wyoming.

Diagnosis. — Rostrum short (RL/TL= 0.11-0.19) • and broadly
rounded anteriorly. Ornamentation coarse with 4.5 to 6.5 ridges
per millimeter.

Discussion. — Certain of Bryant's figures (1932, pi. 1; 1933, pi. 1;
1935, pi. 15), as well as one specimen in Field Museum (PF 2168),
show that the branchial plates extend to the postero-lateral corners
of the dorsal shield, where they are simply terminated and usually
truncate. The branchial openings must have been at their poste-
rior ends.

1 The measurements used in determining rostral ratios are: RL, length of
rostral plate measured in the midline; RW, maximum width of rostral plate; and
TL, total length of dorsal shield, measured in midline, but excluding the dorsal
spine.

10

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 4. Dorsal shield of type specimen of Protaspis (Protaspis) mcgrewi,
n. sp., PF4337 (X 3/4).

Protaspis (Protaspis) dorfi (Bryant), 1932

Pleraspis dorfi Bryant, 1932, Proc. Amer. Phil. Soc, 71, pp. 238-240, text-fig.

3; pi. 2, fig. 2; pi. 4.
Protaspis dorfi Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 296-297, text-fig.

IB; pi. 3; pi. 5, fig. 2; pis. 6-7; 1934, Proc. Amer. Phil. Soc, 73, pp. 152-

153, pi. 23; pi. 24, fig. 1; Denison, 1953, Fieldiana: Geol., 11 , pp. 324, 334,

fig. 74.

Occurrence. — Lower Devonian, Beartooth Butte formation, Bear-
tooth Butte, Park County, Wyoming.

Diagnosis. — Rostrum short (RL/TL= 0.14-0.18) and narrowly
rounded anteriorly. Ornamentation very fine with 8 to 12 ridges
per millimeter.

DENISON: PTERASPIDIDAE
prp

11

Fig. 5. Rostral plate of Protaspis (Protaspis) mcgrewi, n. sp., ventral view
restored from PF 4763 (about X 2). al, ascending lamella; dla, ventral surface
of dorsal lamina; prp, median preoral wall; vlr, ventro-lateral face; vps, ventral pre-
oral surface.

Discussion. — Bryant's figure of the type specimen (1932, pi. 4)
indicates that the branchial plates and openings were developed as
in Protaspis bucheri.

Protaspis (Protaspis) mcgrewi,1 new species

Type. — Field Museum, PF 4337, a dorsal shield, complete except
for its right postero-lateral corner (figs. 4, 6A, 7A).

Referred specimens. — Dorsal shields, PF 4758-9, 4763 (figs. 5,
6B), 4914, 4917, 4356, and part of 4911; incomplete juvenile dorsal
shield, PF 4491; ventral disc, PF 4361; rostral plates, PF 5265, 5267,
5269, 5278, 5284-5, 5288, 5295.

Occurrence. — Lower Devonian, Beartooth Butte formation, Cot-
tonwood Canyon, east of Lovell, NE H, sec. 4, T56N, R93W, Big-
horn County, Wyoming.

Diagnosis. — Dorsal shield broader or more highly vaulted than in
P. bucheri and P. dorfi. Rostrum of moderate length and broadly
rounded anteriorly, longer relatively than in P. bucheri or P. dorfi

1 After Dr. Paul O. McGrew who first called my attention to the rich occur-
rence of fossil fishes in Cottonwood Canyon.

12

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 6. Region of branchial opening of Protaspis (Protaspis) mcgrewi, n. sp.
(about XI). A, dorsal view of PF 4337; B, ventral view of PF 4763. bro, bran-
chial opening; brp, branchial plate; dd, dorsal disc.

(RL/TL= 0.22-0.23). Dorsal spine relatively long and projecting.
Ornamentation coarse with about 5.5 ridges per millimeter in the
midline of the dorsal disc. Length of the dorsal disc (excluding the
dorsal spine) as much as 137 millimeters.

Description. — The dentine ridges (fig. 7A) typically have a smooth,
gently convex crest, but locally may be flat-crested or tuberculate.
There is a tendency for them to be grouped in bands separated by
what are probably growth lines, and in some bands the ridges may
be irregularly arranged, or rarely transverse or diagonal within the
bands. In the central area of the dorsal disc the ridges, where un-
worn, are finer, more convex, tuberculate, and with crenulate mar-
gins. The rostrum has a well-developed ventral preoral surface (fig.
5, vps), covered medially with short to elongate, crested dentine
ridges with prominent lateral projections, reminiscent of those of
Traquairaspis; this area is bounded laterally by borders with rela-
tively broad dentine ridges, or in the figured specimen, with bands of
transverse or diagonal ridges similar to those of subgenus Cosmaspis.
Ascending lamellae mark the posterior edge of the ventral preoral
surface, while medially there is a preoral wall (fig. 5, prp) connecting
the ventral preoral surface with the dorsal lamina of the rostral plate;
this structure will be described more fully in Protaspis (Protaspis)
brevispina. The pineal plate usually contacts the orbitals, and dis-
tinct suborbital plates are probably not present below the orbitals

Fig. 7. Ornament of dorsal shield (X 6). A, P. (Protaspis) mcgrewi, n. sp.,
PF4337; B, P. (Protaspis) brevispina, n. sp., PF4343; C, P. (Cyrtaspidichthys)
ovata (Bryant), PF 1523; D, Lampraspis tuberculata, n. sp., PF 4913; E, P. (Cos-
maspis) transversa, n. sp., PF 4334; F, P. (Cosmaspis) sp., PF 951.

13

14

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 8. Dorsal shield of type specimen of Protaspis (Protaspis) brevispina,
n. sp., PF4343 (X 3/4).

and between the rostral and branchial plates. In all specimens the
postero-lateral corners of the dorsal disc form the medial margins of
the branchial openings, which are directed postero-medio-dorsally
(fig. 6, bro).

Protaspis mcgrewi resembles P. bucheri in its ornament and rostral
shape, but differs in its broader (or more vaulted) dorsal shield, in
the greater length of the rostrum, and possibly in the greater length
of the dorsal spine. Its closest relative is Protaspis (Cosmaspis)
transversa (p. 21), which it resembles in many features, most espe-
cially in the occasional occurrence of bands of transverse or diagonal
ridges. However, this is rare in mcgrewi, but characteristic of trans-
versa, which also differs distinctly in the structure of its branchial
openings.

DENISON: PTERASPIDIDAE

15

Protaspis (Protaspis) brevispina, new species

Type. — Field Museum, PF 4343, a dorsal shield crushed on the
left side (figs. 7B, 8, 11A).

Referred specimens.— Dorsal shields, PF 4340, 4344, 4346-8, 4352,
4762, 4764, 4766, 4768, 4770, 4910, 4912, 4918, 4929-30, 4933-5,
4940; associated dorsal and ventral discs, PF 4345, 4365, 4923;
dorsal discs, PF 4372, 4388, 4937, 4939, 4986-7, 4989, 4991, 4999,
5062; ventral discs, PF4360, 4368, 4779, 4785, 4947; rostral plates,
PF 5274 (fig. 10A), 5279-80, 5296 (fig. 10B-C), 5298, 5299 (fig. 9);
branchial plates, PF 4376-7, 4380-1, 5314, 5322 (fig. 11B); incom-
plete articulated juvenile individual, PF 4959.

Occurrence. — Lower Devonian, Beartooth Butte formation, Cot-
tonwood Canyon, east of Lovell, NE yA, sec. 4, T56N, R93W, Big-
horn County, Wyoming.

Diagnosis. — Shield moderately slender. Rostrum of moderate
length (RL/TL= 0.20-0.24), narrowly rounded anteriorly, and with
a well-developed preoral field covered with a fine reticular ornament.

vir

na

Fig. 9. Rostral plate of Protaspis (Protaspis) brevispina, n. sp., ventral view,
restored largely from PF 5299 ( X 2}4). al, ascending lamella; dla, ventral surface
of dorsal lamina; na, possible narial notch; pf, preoral field; prp, median preoral
wall; spr, outline of paired rostral space, based on dissection of PF 5298; vlr, ven-
trolateral face.

16 FIELDIANA: GEOLOGY, VOLUME 20

Dorsal spine short, projecting little or not at all. Ornament rather
fine with 6 to 8 ridges per millimeter near the midline of the dorsal
disc. Dorsal shield estimated to have attained a length of 175 mil-
limeters.

Description. — This species differs from P. mcgrewi in its narrower
proportions, longer and more narrowly rounded rostrum, short dorsal
spine, and usually by its finer dentine ridges. From P. dorfi it may
be distinguished by its coarser ridges and relatively longer rostrum.

The more or less complete dorsal shields referred to this species
have a length of 107-142 millimeters. The largest specimen referred
here, PF 4365, is estimated to have had a dorsal shield 175 milli-
meters long on the basis of the length of its ventral disc, which is
140 millimeters. The dentine ridges (fig. 7B) are usually smooth
with flat or gently convex crowns and crenulate margins, but in some
specimens the crests may be slightly tuberculate. Near the center of
the dorsal disc the ridges may be similar, but sometimes their crests
are cut by cross grooves which give the ridges the appearance of a
row of overlapping pointed scales.

The rostrum is somewhat variable in shape and proportions, but
ventrally has a long preoral surface (fig. 9, pf) with fine reticular,
probably non-dentinous ornament, comparable to the preoral field
of Pteraspis. The posterior edge of the preoral field has a slight,
rounded median process, bounded on either side by an ascending
lamella (fig. 9, al). In many specimens there is a rostral space
(fig. IOC, spr), widely open posteriorly, between the dorsal and ven-
tral laminae of the rostrum. This is the usual condition in pteraspids
with somewhat elongate rostra, and has been figured by Stensio
(1964, figs. 46B-C, 91A-C). In other specimens of Protaspis brevi-
spina, especially PF 5299, there is a nearly vertical preoral wall
(fig. 9, prp) in the midline at the posterior edge of the ventral lamina
of the rostrum, and connecting it with the dorsal lamina. A longi-
tudinal section of another specimen (PF 5274) shows that in the
midline where the preoral wall is developed (fig. 10 A, prp), the rostral
space is absent and the rostrum is filled with spongy bone. On either
side of the preoral wall the rostral space is present (fig. 10B, spr) ;
its extent has been determined by dissection of another specimen
(PF 5298) and indicated on Figure 9 (spr). This is important in the
interpretation of pteraspid structure since it indicates the presence
of a pair of pockets extending anteriorly from the oral cavity, and
occupied in life by paired structures. These structures were prob-
ably nasal sacs, and they could have opened posteriorly into the

DENISON: PTERASPIDIDAE

17

die

dla

Fig. 10. Vertical longitudinal sections through rostral plates of Protaspis
(Protaspis) brevispina, n. sp. ( X 3). A, sagittal section of PF 5274; B, parasagittal
section of same rostrum; C, approximately sagittal section of PF 5296. dla, dorsal
lamina; pf, preoral field; prp, median preoral wall; spr, rostral space.

buccal cavity, or perhaps postero-laterally to the exterior at the cor-
ners of the mouth, where notches are sometimes seen in the rostral
plate (figs. 9, 19, na) . A preoral wall has also been found in Protaspis
(Protaspis) megrewi and Protaspis (Cosmaspis) transversa. Its ab-
sence in other species and in some specimens of Protaspis brevispina
suggests that it formed only at maturity, perhaps as a part of the
rostral plate itself, or perhaps as a distinct plate.

The pineal plate of Protaspis brevispina contacts the orbitals, and
usually there are separate suborbital plates separating the branchial
and rostral plates. The branchial openings (fig. 11, bro) are similar
to those of P. megrewi with their medial margins formed dorsally by
the postero-lateral corners of the dorsal disc. Below this, one or
more small platelets, possibly cornuals (fig. 11,? co), line the medial
side of the branchial duct in some specimens.

Subgenus Europrotaspis White, 1961

Type species. — Protaspis (Europrotaspis) crenulata White, 1961.

Europrotaspis White, 1961, Bull. Brit. Mus. (Nat. Hist.), Geol., 5, pp. 268-
270 (new subgenus).

18

FIELDIANA: GEOLOGY, VOLUME 20

I. i

.' brp--

FlG. 11. Region of external branchial opening of Protaspis (Protaspis) brevi-
spina, n. sp. (about X 2). A, dorsal view, PF4343; B, ventral view, PF 5322.
bro, branchial opening; brp, branchial plate; ? co, possible cornual plates; dd, dor-
sal disc.

Diagnosis. — Similar to subgenus Protaspis except that each bran-
chial opening is bounded medially by a small narrow cornual plate
at the postero-lateral corners of the dorsal disc.

Discussion. — When White (1961, p. 268) erected the subgenus
Europrotaspis, the structure of the branchial openings of the typical
Protaspis was unknown. It now appears that the branchial openings
are very similar in the two subgenera. In typical Protaspis, where
cornual plates are known, they are small elements lying in the medial
walls of the posterior ends of the branchial ducts, but they do not
appear on the dorsal surface of the shield. In Europrotaspis (fig. 12,
co), especially in P. (Europrotaspis) arnelli from Podolia (Brotzen,
1936, fig. 3), they differ only in extending to the dorsal surface of the
shield, where they lie against the postero-lateral corners of the dorsal
disc and form the medial edges of the branchial openings.

White used other characters to distinguish Europrotaspis. One
was the large, flat preoral field of P. (Europrotaspis) crenulata, which
he contrasted with the very narrow ventral preoral surface of "Pro-
taspis cf. bucheri" (of Denison, 1953, fig. 78, here referred on p. 29
to Oreaspis dunklei n. gen., n. sp.). However, a well-developed pre-
oral field may occur in those species of Protaspis which have a ros-
trum of moderate length, as P. brevispina (fig. 9) . White also mentions
the very large ridge scales of Europrotaspis, but all of his scales are

DENISON: PTERASPIDIDAE

19

\, \

Fig. 12. Region of external branchial opening of Protaspis (Europrotaspis)
crenulala White, after White, 1961. bro, branchial opening; brp, branchial plate;
co, cornual plate; dd, dorsal disc.

isolated and their relative size uncertain; moreover, the ridge scales
of Protaspis dorfi and P. (Cosmaspis) transversa are known to be rela-
tively large. The asymmetrical ridge scales of P. (Europrotaspis) cren-
ulata described by White can hardly be accepted as sufficient evidence
for the presence of lateral keels, for they are isolated, and lateral keels
are unknown in other pteraspids.

I conclude that Europrotaspis, as far as it is known, differs only
in minor ways from the subgenus Protaspis.

Subgenus Gigantaspis N. Heintz, 1962

Type species. — Gigantaspis isachseni N. Heintz, 1962.

Giganthaspis A. Heintz, 1937, Skr. Svalbard og Ishavet, nr. 72, p. 18 (nomen
nudum); F0yn and Heintz, 1943, Skr. Svalbard og Ishavet, nr. 85, p. 14
(nomen nudum); Dineley, 1960, Geol. Mag., 97, pp. 18, 20, 22-23, 30 (no-
men nudum).

Gigantaspis N. Heintz, 1962, Norsk Polarinst., Arbok 1960, pp. 23-24.

Diagnosis. — Similar to the subgenus Protaspis, from which it is
distinguished by the very slight vaulting of the dorsal disc, the up-
right dorsal spine, the relatively longer rostral plate, and by the slit-
like branchial openings facing upward between the posterior ends of
the branchial plates and the dorsal disc.

Discussion. — Gigantaspis, the characteristic pteraspid of the Kapp
Kjeldsen division of the Wood Bay series of Spitsbergen, was recog-
nized as a close relative of Protaspis by N. Heintz. She gave it
generic rank, but I find that it fits well in the genus Protaspis as used

20 FIELDIANA: GEOLOGY, VOLUME 20

here, and differs from the subgenus Protaspis only in relatively minor
characters that certainly warrant no more than subgeneric distinc-
tion. The branchial openings are fundamentally the same in both
subgenera; in both there are no visible cornual plates (except possibly
for small platelets in Protaspis brevispina) , but in Gigantaspis the
openings face more dorsally and are more slit-like. The dentine
ridges of subgenus Protaspis may be "fine, smooth and entire," as
described for Gigantaspis. The rostal plate is relatively longer than
in any known species of subgenus Protaspis; based on the restoration
of P. (Gigantaspis) bocki (N. Heintz, 1982, fig. 1A), RL/TL=0.30,
compared to 0.11 to 0.24 in species of subgenus Protaspis. An up-
right dorsal spine is unknown in subgenus Protaspis, though it occurs
in Eucyclaspis and doubtfully in P. (Europrotaspis) arnelli.

Subgenus Cyrtaspidichthys Whitley, 1940
Type species. — Cyrtaspis ovatus Bryant, 1932.

Cyrtaspis Bryant, 1932 (not of Fischer, 1853), Proc. Amer. Phil. Soc, 71,

p. 241; 1933, Proc. Amer. Phil. Soc, 72, p. 304; White, 1935, Phil. Trans.

Roy. Soc. London (B), 225, p 438.
Cyrtaspidichthys Whitley, May 1940, Australian Nat., 10, p. 243; Denison,

1953, Fieldiana: Geol., 11, p. 318.
Eucyrtaspis White and Moy Thomas, June 1940, Ann. Mag. Nat. Hist. (11),

5, p. 507.

Diagnosis. — Dorsal shield broad or highly vaulted. Ornamenta-
tion consisting of oval dentine tubercles arranged in rows approxi-
mately parallel to the lines of growth (fig. 7C). Branchial openings
directed postero-medially at the posterior ends of the branchial
plates.

Protaspis (Cyrtaspidichthys) ovata (Bryant), 1932

Cyrtaspis ovatus Bryant 1932, Proc. Amer. Phil. Soc, 71 , pp. 242-243, text-fig.

4, pi. 6, fig. 1; 1933, Proc Amer. Phil. Soc, 72, pp. 304-305, text-fig. 5;

pi. 5, fig. 3; pi. 14, figs. 1-2; 1935, Proc. Amer. Phil. Soc, 75, pp. 123-124,

pi. 11, fig. 2, pi. 16.

Cyrtaspis papillatus Bryant, 1933, Proc. Amer. Phil. Soc, 72, p. 306, pi. 15,

figs. 1-2; 1934, Proc. Amer. Phil. Soc, 73, pp. 153-154, pi. 25.
Cyrtaspis falcatus Bryant, 1933, Proc. Amer. Phil. Soc, 72, p. 307, pi. 17, fig. 1.
Protaspis (Cyrtaspidichthys) ovatus Denison, 1953, Fieldiana: Geol., 11 , p. 336.
Occurrence. — Lower Devonian, Beartooth Butte formation, Bear-
tooth Butte, Park County, Wyoming.

Diagnosis. — Shield very broad (or highly vaulted). Rostrum of
moderate length (RL/TL=0.25 to 0.28) and rather sharply rounded
anteriorly.

DENISON: PTERASPIDIDAE 21

Discussion. — Specimens figured by Bryant (1933, pi. 14, fig. 2;
1935, pi. 16). as well as those in Field Museum (PF 1523, 1601. 2170).
show that the branchial openings were fundamentally as in the sub-
genus Protaspis. The branchial plates are very broad and their
posterior ends extend slightly beyond the postero-lateral corners of
the dorsal disc, with the result that the branchial openings must
have opened medially as well as posteriorly.

Protaspis (Cyrtaspidichthys) sculpta (Bryant), 1933

Cyrlaspis sculptus Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 306-307, pi. 16,

figs. 1-2.
Protaspis (Cyrtaspidichthys) sculptus Denison, 1953, Fieldiana: Geol., 11,

p. 336.

Occurrence. — Lower Devonian, Beartooth Butte formation, Bear-
tooth Butte, Park County, Wyoming.

Diagnosis. — Shield less broad (or less vaulted) than in P. (C.)
ovata. Rostrum relatively shorter (RL/TL=0.20) and bluntly
rounded.

Subgenus Cosmaspis,1 new subgenus

Type species. — Protaspis (Cosmaspis) transversa, new species.

Diagnosis. — Dorsal shield broad or highly vaulted. Ornamenta-
tion mostly arranged in bands more or less parallel to lines of growth,
while within the bands the individual dentine ridges are arranged
diagonally, or sometimes transversely or irregularly with respect to
the bands. Branchial openings behind the dorsal disc at the poste-
rior tips of the branchial plates.

Protaspis (Cosmaspis) transversa, new species

Type. — Field Museum, PF 4334, a nearly complete dorsal shield
(figs. 7E, 13, 16).

Referred specimens.— Dorsal shields, PF 4335-6, 4338-9, 4349,
part of 4352 (fig. 15), 4355, 4755, 4757, 4760, 4915, 4924, 4926, 4931-
2, 4944, 5497; dorsal discs (juvenile), PF4375, 4394, 4403, 4408,
4412, 4416, 4772-4, 4974, 4977, 4981, 4984, 5020, 5050-1, 5059, 5077;
ventral discs, PF 4362-3, 4780, 4936; ventral discs (juvenile), PF
4450-1, 4453-4, 4486, 4994, 5016, 5122, 5148-9, 5175, 5177-8, 5180,
5184; dorsal and ventral discs, PF4369; rostral plates, PF 4942,
5262, 5268, 5276-7, 5281 (fig. 14), 5291-4; orbital plates, PF 5211,

1 From kocthos, ornament; and aains, shield.

22

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 13. Dorsal shield of type specimen of Protaspis (Cosmaspis) transversa,
n. subgen., n. sp., PF 4334 (X 3/4).

5215, 5221, 5233-4, 5237, 5243, 5252, 5259, 5260; branchial plates,
PF4382, 4384, 5300, 5307, 5311, 5315-6, 5319, 5324; dorsal spine,
PF 5349; more or less articulated specimens, PF 4389 (fig. 17),
4390-1; juvenile articulated or associated specimens, PF 4490, 4492,
4494, 4496, 4953, 4969.

Occurrence. — Lower Devonian, Beartooth Butte formation, Cot-
tonwood Canyon, east of Lovell, NE }4, sec. 4, T56N, R93W, Big-
horn County, Wyoming.

Diagnosis. — As for genus. Dorsal shield attaining a length of
140 millimeters.

Description. — The ornament of bands of cross ridges is particu-
larly characteristic of the subgenus Cosmaspis. In P. (C.) transversa

DENISON: PTERASPIDIDAE

23

Fig. 14. Rostral plate of Protaspis (Cosmaspis) transversa, n. sp., ventral view,
PF 5281 (about X 2). dla, ventral surface of dorsal lamina; ma, matrix; prp,
median preoral wall; vps, ventral preoral surface.

(fig. 7E) the individual cross ridges are more commonly arranged
diagonally than transversely within the bands, and are typically
gently convex and smooth-topped with crenulate margins. The
bands are approximately 1.5 to 2.5 millimeters wide, while the indi-
vidual ridges within the bands are 4.5 to 5.5 per millimeter. In the
central or juvenile area of the dorsal disc the ornament is different
and resembles that of typical pteraspids, for the ridges are not ar-
ranged in bands, but are concentric and parallel to lines of growth.
They are finer, 6 to 8 per millimeter, and where unworn are sharp-
crested or tuberculate. Outside of this zone is an intermediate zone
where the ridges may occur diagonally in bands, where they are of
intermediate coarseness, and where they grade from tuberculate into
smooth crests.

The rostrum, though variable in proportions, may be described
as of moderate length (RL/TL=0.20 to 0.27), broad (RW/RL=
1.75 to 2.38), and broadly rounded anteriorly. Ventrally, it has a
narrow preoral surface (fig. 14, vps) covered with irregularly-shaped,
serrate tubercles, arranged in patches posteriorly, irregularly ante-
iorly, and in rows laterally. Dorsally, the posterior border of the
rostral plate is usually (though not in the type) deeply indented at
each side to receive the prominent anterior process of each orbital
plate. Beneath each orbital plate there may be a separate suborbital

24

FIELDIANA: GEOLOGY, VOLUME 20

A B

Fig. 15. Region of branchial opening of Protaspis (Cosmaspis) transversa,

n. sp., PF 4352 (X 1M)> A, dorsal view; B, ventral view, bro, branchial opening;
brp, branchial plate; dd, dorsal disc.

plate separating the rostral and branchial plates (PF 4334, 4338,
4775) ; in others (PF 4391, 4924) this space is occupied by a ventral
process of the orbital plate. The pineal and orbital plates may or
may not contact each other. The dorsal spine is long, projecting,
and recumbent.

Each branchial plate extends a short distance behind the postero-
lateral corner of the dorsal disc. In this region, the medial side of
its dorsal lamina (fig. 15A) bends down to meet the inner margin
of its ventral lamina (fig. 15B), and so surrounds the branchial duct,
which opens at the posterior end of the branchial plate. The bran-
chial duct extends forward from here for some distance in a deep
groove between the dorsal and ventral laminae of the branchial plate.
For a short distance anterior to the point where the branchial plate
joins the dorsal disc, the branchial duct is bounded medially by one
or more plates of thick, spongy bone, extending from the lateral mar-
gin of the dorsal disc to the medial margin of the ventral lamina of
the branchial plate (fig. 16,? co) . This plate or plates has much of the
relations of the cornual plate of Protaspis arnelli, as figured by Brot-
zen (1936, fig. 3:1), and may be called by that name provisionally.

One large articulated specimen, PF 4389, is crushed but shows
much of the structure of the oral region and tail. At least 18 oral
plates (fig. 17, op) are exposed but considerations of symmetry indi-

brd br,Pd

brpv

Fig. 16. Oblique section through left branchial duct of Protaspis (Cosmaspis)
transversa, n. sp., PF 4334. b, breaks; brd, branchial duct; brpd, dorsal lamina of
branchial plate; brpv, ventral lamina of branchial plate; ? co, possible cornual plate;
dd, dorsal disc.

Fig. 17. Attempted restoration of the oral region of Protaspis (Cosmaspis)
transversa, n. sp., ventral view, based on PF 4389 (about X 1). brp, branchial
plate; Ip, lateral plates; ol, oral-lateral plate; op, oral plates; orp, orbital plate;
pop, postoral plates; vd, ventral disc; vps, ventral preoral surface.

25

26

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 18. Region of branchial opening of Protaspis (Eucyclaspis) erroli Deni-
son, somewhat restored from PF 3814 (about X 2 }/£). A, ventral view; B, dorsal
view; C, posterior view, bro, branchial opening; brp, branchial plate; ? co, possible
cornual plate; dd, dorsal disc.

cate that there were more originally. Between them and the ventral
disc are two rows of postoral plates (fig. 17, pop) . The posterior row
bounding the ventral disc consists of a small median plate with one
or two elongate plates bounding it on either side. The anterior row
consists of a large, subtriangular median element with a small plate
at either side. At each antero-lateral corner of the ventral disc are
two lateral plates (fig. 17, Ip).

The posterior and dorsal part of the tail is not preserved. The
median ventral edge is formed by a series of ridge scales, of which the
first is very large, the second even larger, while those behind gradu-
ally decrease in size posteriorly. The flank scales are also relatively
large anteriorly and of the usual shape found in pteraspids.

As indicated above (p. 14), Protaspis (Protaspis) mcgrewi, though
distinguished subgenerically from Protaspis (Cosmaspis) transversa,
was surely closely related. P. mcgrewi rarely and locally shows bands
of diagonal or transverse ridges, and agrees well in many other
characters.

Protaspis (Cosmaspis) sp.

Protaspis sp., representing an undescribed subgenus, Denison, 1953, Fieldiana:
Geol., 11, p. 350, fig. 84A.

DENISON: PTERASPIDIDAE 27

Occurrence. — Lower Devonian, Card member of Water Canyon
formation, Cache County, Utah.

Discussion. — The few fragments from the Water Canyon forma-
tion described by me in 1953 can now be referred to the subgenus

vlr

Fig. 19. Rostral plate of Protaspis (Eucyclaspis) erroli Denison, ventral view,
restored from PF 3814 (X 2l/Q. al, ascending lamella; dla, ventral surface of
dorsal lamina; na, possible narial notch; sla, sutural area for lateral plate; vlr, ven-
trolateral face; vps, ventral preoral surface.

Cosmaspis. They differ from P. (C.) transversa in that the cross
ridges within the bands of ornamentation are more regular and trans-
verse and have flatter crests (fig. 7F) . Also, the rostrum (PF 952)
appears to be relatively longer.

Subgenus Eucyclaspis,1 new subgenus

Type species. — Protaspis (Protaspis) erroli Denison.
Diagnosis. — A Protaspis in which the branchial ducts open poste-
riorly at the postero-lateral corners of the rather broad shield (fig. 18),
and are bounded by the branchial plates ventrally and laterally, by
the dorsal disc dorsally, and by probable cornual plates medially.
The dorsal spine is slender and erect, and each orbital plate has a
process projecting postero-laterally from its lateral margin behind
the orbit. The ornament consists of very fine ridges more or less
concentric to lines of growth.

Protaspis (Eucyclaspis) erroli Denison, 1967

Protaspis (Protaspis) erroli Denison, 1967, Jour. Linn. Soc. (Zool.), 47, pp. 34-
37, text-figs. 1-2, pi. 1.

Occurrence. — Lower Devonian, near base of Grassy Flat member
of Water Canyon formation, Logan Canyon, Cache County, Utah.

1 From tvKvicXos, well rounded; aaxis, shield.

28

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 20. Region of branchial opening of Oreaspis dunklei, n. gen., n. sp., slightly
restored from U. S. Nat. Mus. 20524 (about X 3}^). A, dorsal view; B, ventral
view, bro, branchial opening; brp, branchial plate; ? co, possible cornual plate;
dd, dorsal disc; pbr, postbranchial plate; ppb, posterior process of branchial plate.

Diagnosis. — A small species with the median length of the dorsal
shield attaining 61 millimeters. The rostral plate broad (RW/RL=
2.14), bluntly rounded anteriorly, and with a narrow ventral preoral
surface (fig. 19, vps). Ornament of sharp-crested, crenulate ridges,
about 11 to 13 per millimeter.

Discussion. — This species differs from all the other species referred
to the genus Protaspis in having projecting processes on the orbital
plates, and from all except the species of Gigantaspis in its erect
dorsal spine. These characters are considered sufficiently aberrant
to warrant subgeneric separation.

Oreaspis,1 new genus

Type species. — Oreaspis dunklei, new species.

Diagnosis. — Pteraspids with each branchial opening situated dor-
sally between the posterior part of the dorsal disc and branchial plate,
and usually bounded posteriorly by both (fig. 20, bro) . Typically a
scale-like post-branchial plate (fig. 20, pbr) is attached to a posterior
projection of each branchial plate. Dorsal shield moderately broad
or vaulted.

1 From opos, mountain; a<nn.s, shield.

DENISON: PTERASPIDIDAE

29

Oreaspis dunklei,1 new species

Protaspis (Protaspis) cf. bucheri Denison, 1953, Fieldiana: Geol., 11, pp. 338-
343, figs. 72, 77-79.

vps

Fig. 21. Rostral and lateral plates of Oreaspis dunklei, n. sp., ventral view,
somewhat restored from U. S. Nat. Mus. 20524 (X 2}4)- al, ascending lamella;
dla, ventral surface of dorsal lamina of rostral plate; lap, lateral plates; vlr, ventro-
lateral face of rostral plate; vps, ventral preoral surface.

Type. — U. S. Nat. Mus. 20524, a dorsal shield lacking the postero-
medial part (figs. 20-21).

Occurrence. — Lower Devonian, probably Card member of Water
Canyon formation, Cottonwood Canyon, north of Logan Canyon,
Cache County, Utah.

Diagnosis. — Rostrum short (RL/TL estimated to be 0.18) and
broadly rounded anteriorly. Ornament rather coarse with about six
flat-topped dentine ridges per millimeter. Total length of dorsal
shield about 70 mm.

Discussion. — Though resembling Protaspis in the broad or vaulted
dorsal shield and in the posterior position of the branchial openings,
the distinctive relations of the branchial openings (fig. 20, bro) makes
it convenient to distinguish this and related species as a separate
genus. The rostrum is short and has a narrow ventral preoral sur-
face (fig. 21, vps).

Oreaspis williamsi,2 new species

Protaspis (Protaspis) dorfi Denison, 1953, Fieldiana: Geol., 11, pp. 337-338,
figs. 75-76.

1 After Dr. David H. Dunkle of the Natural Science Museum, Cleveland, Ohio.

2 After Professor J. Stewart Williams of Utah State University, who has been
active in the study of the Devonian rocks of northern Utah.

30

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 22. Region of branchial opening of Oreaspis williamsi, n. sp., PF 868
(X 3). A, ventral view; B, dorsal view, bro, branchial opening; brp, branchial
plate; ? co, possible cornual plate; dd, dorsal disc; pbr, postbranchial plate; ppb,
posterior process of branchial plate.

Type. — Field Museum, PF 868, a flattened dorsal shield.

Occurrence. — Lower Devonian, Card member of Water Canyon
formation, Blacksmith Fork, Cache County, Utah.

Diagnosis. — Rostrum short (RL/TL=0.17) and sharply rounded
anteriorly. Ornamentation very fine with about nine dentine ridges
per millimeter in the midline of the dorsal disc. Total length of
dorsal shield 121 mm.

Discussion. — This species resembles Protaspis dorfi in the pro-
portions and shape of its rostrum and in its fine ornamentation. In
the structure of its branchial opening (fig. 22, bro) it is quite different
from P. dorfi, which was inadequately known at the time of my 1953
paper, and in this respect is closely related to Oreaspis dunklei.

Oreaspis ampla (Bryant), 1933

Protaspis amplus Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 299-300, text-
fig. 3, pi. 10; 1935, Proc. Amer. Phil. Soc, 75, p. 123, pi. 14.

Protaspis nanus Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 298-299, pi. 9,
fig. 1.

DENISON: PTERASPIDIDAE

31

Fig. 23. Region of branchial opening of Oreaspis ampla (Bryant) (X l^j).
A, dorsal view, PF2167; B, ventral view, PF 2166. bro, branchial opening;
brp, branchial plate; dd, dorsal disc; pbr, postbranchial plate; ppb, posterior process
of branchial plate.

Protaspis perlatus Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 300-302, text-
fig. 4, pi. 11.

Protaspis perryi Bryant, 1933, Proc. Amer. Phil. Soc, 72, pp. 302-303, pi. 12,
figs. 1-2.

Protaspis amplus-perlatus-perryi group, Denison, 1953, Fieldiana: Geol., 11,
p. 335.

Occurrence. — Lower Devonian, Beartooth Butte formation, Bear-
tooth Butte, Park County, Wyoming.

Diagnosis. — Rostrum of moderate length, relatively longer in
larger individuals (RL/TL= 0.23-0.32) with the roundness of its an-
terior end intermediate between that of O. dunklei and O. williamsi.
Ornament coarse, with about five dentine ridges per millimeter.
Total length of dorsal shield reaching 170 mm.

Discussion. — In 1953 (p. 335) I considered Bryant's species, Pro-
taspis ampla, P. nanus, P. perlatus, and P. perryi, to be closely re-
lated, and here I go one step further and place them in synonymy.
This species differs from typical Protaspis in the structure of its gill
openings, which resembles that of Oreaspis dunklei. A Field Mu-
seum specimen, PF 2166 (fig. 23B), shows this region in ventral
view, and differs from O. dunklei and O. williamsi only in that the

32 FIELDIANA: GEOLOGY, VOLUME 20

posterior process of the branchial plate is relatively small, and the
scale-like postbranchial plate relatively large. PF 2167 (fig. 23A)
shows the dorsal side with the branchial opening in typical position,
but it differs from 0. dunklei and 0. williamsi in that the branchial
plate does not extend posteriorly to meet the dorsal disc and post-
branchial plate posterior to the branchial opening. A specimen of
0. ampla figured by Bryant (1935, pi. 14) appears to have the same
structure.

? Oreaspis sp.

A few fragmentary specimens in the Field Museum collection
from the Card member of the Water Canyon formation of Cache
County, Utah, resemble Oreaspis in the position of their branchial op-
enings; that is, they are near the posterior end of the branchial plates,
but not terminal, and open dorsally between the branchial plates and
dorsal disc. They differ from typical Oreaspis in lacking the posterior
process on the branchial plate and the scale-like postbranchial plate.
One such specimen (PF 869), figured by me in 1953 (fig. 73) as Pro-
taspis sp., has a smooth, blunt posterior termination on the branchial
plate, but two others (PF 875, 878) have a rough, concave termina-
tion to which a postbranchial plate might have attached. If this
were so, the difference from typical Oreaspis would be minor.

Lampraspis1, new genus

Type species. — Lampraspis tuberculata, new species.

Diagnosis. — Pteraspids with each branchial opening well in ad-
vance of the posterior corner of the dorsal shield, opening dorsally,
bounded anteriorly and laterally by a branchial plate, posteriorly by
a large posterior cornual plate, and medially by a small anterior
cornual plate. Dorsal shield of moderate width, and in life well
arched. The rostral plate short and broad with a narrow ventral
preoral surface. Dentine ridges typically coarse and knobby, or
subdivided into elongate tubercles.

Lampraspis tuberculata, new species

Type.— Field Museum, PF4342, a dorsal shield (figs. 24, 25A).

Referred specimens. — Associated dorsal shield and ventral disc,
PF 4754; dorsal shields, PF 4370, 4756, 4913 (fig. 7D), 4916, 4919,
4920, 4922, 4928, 5865; dorsal shields exposed ventrally, PF 4925

1 From \an*pos, splendid; a<nris, shield.

DENISON: PTERASPIDIDAE

Fig. 24. Dorsal shield of type specimen of Lampraspis tuberculata, n. gen.,
n. sp.f PF4342 (X 3/4).

(fig. 25B), 4927; parts of dorsal shields, PF4341, 4351, 4761, 4767,
4771, 4941, 4943, 5350; incomplete, partly articulated juveniles,
PF 4946, 4952, 4954-5; juvenile dorsal discs, PF 4371, 4373-4, 4393,
4400, 4407, 4417, 4432, 4436, 4776, 4972-3, 4976, 4980, 4982-3, 5019,
5046, 5064, 5068, 5078; juvenile ventral discs, PF 4141, 4440-1, 4445,
4448, 4455-7, 4459, 4462, 4464-5, 4467-8, 4470, 4479, 5023, 5095-6,
5099, 5103, 5105, 5107-8, 5111, 5116, 5118-9, 5125-9, 5131, 5134-6,
5138, 5150, 5154, 5162-3, 5170, 5172, 5174, 5182-3, 5188, 5190;
larger ventral discs, PF 4366, 4784, 4786; rostral plates, PF 5261
(fig. 26), 5263, 5270-3, 5287, 5290, 5297; orbital plates, PF 5199,
5202, 5204, 5212, 5214, 5216-7, 5222, 5225, 5229, 5230-2, 5238-9,
5240, 5244-7, 5250, 5254-5; branchial plates, PF 4385, 5306, 5317-8,
5323.

Occurrence. — Lower Devonian, Beartooth Butte formation, Cot-
tonwood Canyon, east of Lovell, NE \i, sec. 4, T56N, R93W, Big-
horn County, Wyoming.

34

FIELDIANA: GEOLOGY, VOLUME 20

Fig. 25. Region of branchial opening of Lampraspis tuberculata, n. sp., some-
what restored ( X IK). A, dorsal view, PF 4342; B, ventral view, PF 4925. aco,
anterior cornual plate; bro, branchial opening; brp, branchial plate; dd, dorsal
disc; pco, posterior cornual plate.

Diagnosis. — As for genus. Dorsal shield attaining a length of
118 mm.

Description and discussion. — At first glance, Lampraspis, with its
broad (when flattened) dorsal shield, short broad rostrum, and small
recumbent dorsal spine, would appear to be a typical Protaspis.
However, the position of the branchial openings (fig. 25A, bro) far
in advance of the postero-lateral corners of the dorsal shield distin-
guishes Lampraspis sharply from all Protaspis and Oreaspis, and
suggests a relationship to Pteraspis or Protopteraspis. In addition,
the anterior and posterior cornual plates (fig. 25, aco, pco), except for
the large size of the latter, together have precisely the relationships
of the typical single cornual plates of Pteraspis. However, two juve-
nile specimens reveal an interesting situation. The larger of these,
PF 4952, whose dorsal shield may have been about 60 mm. long, has
small scale-like posterior cornuals, and the branchial openings occupy
a much more posterior position than they do in adults. The smaller
juvenile, PF 4955, whose dorsal shield was probably about 30 mm.

DENISON: PTERASPIDIDAE 35

long, has the branchial openings nearly at the postero-lateral corners
of the shield, and the posterior cornuals as seen in ventral view are
minute plates, 3 mm. long, projecting somewhat at the corners of the
shield. These two specimens suggest that Lampraspis was derived
from a Protaspis-like pteraspid, and that the anterior position of the
branchial openings is secondary phylogenetically as well as onto-
genetically.

The ornamentation of Lampraspis (fig. 7D) consists characteris-
tically of coarse knobby ridges, with crenulate margins basally, about
five to six per millimeter. Locally, and especially in certain areas such
as the branchial and posterior cornual plates, the ridges appear to
be subdivided into elongate tubercles, much like those of Cyrtaspid-
ichthys; in some cases, however, these tubercles are united at their
bases into a ridge. Near the center of growth of the dorsal disc the
juvenile ridges, where unworn, may be nearly as coarse and knobby
as more peripheral ridges. In PF 4913 the juvenile ridges are slightly
finer, and most centrally have a continuous crest without knobs.

The dorsal shields of L. tuberculata are almost invariably flat-
tened, which makes them appear quite broad. However, the ventral
discs assigned to this species are of moderate proportions; for exam-
ple, the ventral disc on PF 4754 has a width/length ratio of 0.73.
This means that the apparent breadth of the associated dorsal shield
is the result of flattening, and in life it must have been narrower and
highly vaulted. The rostra are usually crushed or flattened so the

ma

_ ^

vps

dla

^^ ^. ■' ^.,_/

'"•■' '■••■"''

"~*^y(, vlr

iSmsSmJ

\^9&>

Fig. 26. Rostral plate of Lampraspis tuberculata, n. sp., ventral view, PF 5261
(X 3). dla, ventral surface of dorsal lamina, lacking the basal layer anteriorly;
ma, matrix; vlr, ventro-lateral face; vps, ventral preoral surface.

36 FIELDIANA: GEOLOGY, VOLUME 20

ratios of their width/length are unreliable. However, the rostral
plate is relatively short (RL/TL= 0.19-0.22), broad, and bluntly or
even squarely rounded anteriorly. As is to be expected in a short
rostrum, the ventral preoral surface (fig. 26, vps) is narrow, and has
a slight median posterior projection. This surface is mostly covered
with a fine reticular ornamentation, but anteriorly there are fine
tubercles. The pineal plate usually contacts the orbitals, though not
in PF 4754. The orbital plates have a ventral process that separates
the rostral and branchial plates. The dorsal spine is short and re-
cumbent, and projects behind the dorsal disc in most, though not in
all specimens.

Psephaspis 0rvig, 1961

Type species. — Psephaspis williamsi 0rvig.

Diagnosis. — Moderate to large-sized pteraspids with the shield
usually relatively broad, and with the ornament consisting typically
of denticles with crenulate margins. The branchial openings are at
the postero-lateral corners of the shield, at the posterior ends of the
branchial plates.

Discussion. — Psephaspis was originally referred to the Drepa-
naspida by 0rvig (1961, pp. 526-533), but was shown to be a pteras-
pid by me in 1968 (p. 270). Its known characters indicate a close
relationship to Protaspis, from which it is most clearly distinguished
by its psammosteid-like ornamentation. Additional differences may
be discovered when it is more completely known. It is the latest
pteraspid, and the only genus of the family known to survive into
the Middle Devonian.

Psephaspis williamsi 0rvig, 1961

Psephaspis williamsi 0rvig, 1961, Ark. Zool., ser. 2, 12, nr. 33, pp. 526-533,
figs. 6-10; Denison, 1968, Fieldiana: Geol., 16, p. 270, figs. 2, 7A.

Occurrence. — ? Lower Devonian, upper part of Water Canyon
formation, Cache County, Utah, and Bear Lake County, Idaho.

Diagnosis. — A species attaining a large size, and with the den-
ticles lower and less convex than in P. idahoensis.

Psephaspis idahoensis Denison, 1968

Psephaspis idahoensis Denison, 1968, Fieldiana: Geol. 16, pp. 270-279, figs.
1, 3, 7B, 8.

Occurrence. — Middle Devonian, basal unit of Jefferson formation,
Lemhi County, Idaho.

DENISON: PTERASPIDIDAE 87

Diagnosis. — A species attaining a smaller size, and having higher,
more convex denticles than P. williamsi.

Subfamily Doryaspidinae

Rostral plate truncate anteriorly, and the mouth opening antero-
dorsally between it and an elongate pseudorostrum, which is attached
to the ventral shield.

Doryaspis White, 1935

Type species. — Scaphaspis nathorsti Lankester.

Dyreaspis A. Heintz, 1934, Naturen, 58, p. 244 (nomen nudum); 1935, Ann.

Rept. Smithsonian Inst., 1934, p. 235 (nomen nudum).
Doryaspis White, 1935, Phil. Trans. Roy. Soc. London (B), 225, p. 444; F0yn

and Heintz, 1943, Skr. Norges Svalbard-og Ishavs-Unders0k.( 85, pp. 14-

15; Obruchev, 1964, Osnovy Paleontologii, 11, p. 69.
Lyktaspis N. Heintz, 1968, Proc. 4th Nobel Symp., Stockholm, 1967, p. 73.

Diagnosis. — An aberrant pteraspid with the rostral plate short
and truncate anteriorly, and underlain by a long pseudorostrum
attached to the ventral shield, and with the mouth opening antero-
dorsally between the rostrum and pseudorostrum. The cornual
plates project far laterally. The ornament consists of concentric
ridges subdivided by a system of radiating grooves.

Doryaspis nathorsti (Lankester)

Scaphaspis nathorstii Lankester, 1884, K. Svenska Vetenskapsakad. Handl.'

(n.f.), 20, no. 9, p. 5, pi. 1, figs. 1-3.
Pteraspis nathorsti Woodward, 1891, Ann. Mag. Nat. Hist., (6), 8, p. 2, pi. 2,

fig. 1.
Doryaspis nathorsti White, 1935, Phil. Trans. Roy. Soc. London, (B), 225,

p. 444, text-fig. 80, pi. 25, fig. 102; F0yn and Heintz, 1943, Skr. Norges

Svalbard-og Ishavs-Unders0k., 85, p. 14, fig. 5A; Obruchev, 1964, Osnovy

Paleontologii, 11, p. 69, fig. 44.
Lyktaspis nathorsti N. Heintz, 1968, Proc. 4th Nobel Symp., Stockholm, 1967,

pp. 73-79, figs. 1-4.

Occurrence. — Lower Devonian, Lykta Division, Wood Bay Series,
Spitsbergen.

Discussion. — According to Errol White (in litt., July 2, 1968),
Doryaspis Dejean 1835 (Coleoptera) is a nomen nudum, as are its
three species, which apparently have never been validated, so Dory-
aspis was available when used by White, in 1935. This being the

38 FIELDIANA: GEOLOGY, VOLUME 20

case, the new name, Lyktaspis, proposed by N. Heintz, was not
necessary.

Doryaspis is an aberrant genus and occupies an isolated position
with relation to other pteraspids. This has been recognized by Tarlo
(1962, p. 265) who placed it in a separate family, Doryaspididae,
and in a separate order, Doryaspidida; by Obruchev (1964, p. 69)
who used the family Doryaspididae; and by N. Heintz (1968, p. 79)
who used the family Lyktaspididae, and with reservations the sub-
order Lyktaspidida. In my own work with Heterostraci I have not
felt the need, as have some students of the group, to elevate families
to orders and to create new families, but have found that retaining
the original family rank and using subfamily divisions has been ade-
quate to express the grouping and relationships of genera. Using
this approach, Doryaspis can be placed in a subfamily, Doryaspidi-
nae, to distinguish it from all other pteraspids, which have been re-
ferred to the Pteraspidinae.

Pteraspididae incertae sedis

Two small pteraspids from the Lower Devonian, Wood Bay
Series, of Spitsbergen have been described by Natascha Heintz
(1960) as Pteraspis ? lyktensis and Pteraspis ? minor. They are
known only from isolated dorsal and ventral discs, and are distin-
guished particularly by the following: their coarse, non-crenulated
dentine ridges; the absence of a dorsal spine; the fact that the median
longitudinal sensory canals meet a loop of the supraorbital (or pineal)
canals on the dorsal disc; and the inclusion of the lateral longitudinal
sensory canals on dorsal discs as small as 14 and 18 millimeters. The
inclusion of the lateral sensory canals is no proof that these discs be-
longed to adults, for many pteraspids continue to grow long after
this stage, as has been clearly shown by White (1958, p. 230, figs.
4-8). However, the inclusion at such a small size indicates that the
adults were small, and the extension of the supraorbital canals onto
the dorsal disc is known only in small pteraspids. Pteraspis ? lykten-
sis has been referred to a new genus, Grumantaspis, by Obruchev
(1964, p. 69), and Pteraspis ? minor has placed in another new genus,
Ennosveaspis, by Stensib" (1964, p. 363). What little is known about
them hardly warrants their separation into two distinct genera, in
fact, at present they are inadequately characterized generically.
They may represent persistently primitive pteraspids, as suggested
by N. Heintz (1960, p. 11).

DENISON: PTERASPIDIDAE 39

Pteraspis dixoni White (1938, pp. 100-110, figs. 11-25) was re-
ferred to a new genus Penygaspis, by Stensio (1958, p. 292) because
of a presumably different manner of growth, as inferred from its den-
tine ridge pattern. The distinction of its ridge pattern is that the
central areas of the dorsal and ventral discs have more or less longi-
tudinal ridges, while only the peripheral parts have the usual con-
centrically arranged ridges. Stensio was probably correct in assuming
that the central areas were mineralized at one time (synchronomori-
ally), but this is also true of pteraspids with concentric central ridges,
as will be shown later. One difference is that the central areas are
relatively large, with a length on the order of 25 millimeters. The
longitudinal arrangement of the central ridges is known to occur
occasionally in other pteraspids, such as Protaspis (Europrotaspis)
crenulata White (1961, pp. 277-278, pi. 43, fig. 4), and may be con-
sidered a relic of cyathaspid ancestry. Until this species is more
completely known it must remain incertae sedis, but it is probably
primitive.

Protaspis (Protaspis) tenuistriatus Denison (1953, pp. 343-348>
figs. 80-81) does not preserve the posterior part of the shield, so the
position of the external branchial openings is uncertain. The slight
development of the branchial groove in the most posterior preserved
part of the left branchial plate suggests that the branchial openings
were posterior, but there is no way to tell whether they are the type
found in Protaspis or in Oreaspis.

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40 FIELDIANA: GEOLOGY, VOLUME 20

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DENISON: PTERASPIDIDAE 41

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