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FIELDIANA • GEOLOGY

Published by
FIELD MUSEUM OF NATURAL HISTORY

Volume 16 February 28, 1967 No.

Two New Species of Broiliellus (Amphibians)
from the Permian of Texas

Robert E. DeMar

Assistant Professor of Geoumjy, University op Illinois

Chicago Circle Campus

INTRODUCTION

The genus Broiliellus has been based entirely on the genotype,
Broiliellus texensis, which was described (Williston, 1914, pp. 49-56)
from two well-preserved specimens from Mitchell Creek of the Clyde
Formation, Permian, of Texas. Langston (1953, p. 380) gave the
genus considerable temporal dimensions by suggesting that Aspido-
sauras novomexicanus (Case and Williston, 1913, pp. 7-9) from the
early Permian Abo Formation of New Mexico was in reality a species
of Broiliellus.

Undescribed specimens, some from the Arroyo Formation, others
from a horizon that is probably earlier than the Clyde add informa-
tion to the nature of the genus.

Acknowledgements. — This paper is one of several to result from a
study of dissorophid amphibians initiated at the suggestion of E. C.
Olson. I am grateful to him for his advice during all phases of this
study. The illustrations were made by Mrs. Jane Hubby. Funds
for the illustrations were provided by the University of Illinois
Research Board.

Abbreviations. — Any abbreviations are explained in the figure cap-
tions except for the names of the museums from which the specimens
were obtained. Thus, FMNH means Field Museum of Natural
History and UT means the University of Texas.

Library of Congress Catalog Card Number: 66-30665

No. 1020 117

RT/y /w>w . .^_

118 FIELDIANA: GEOLOGY, VOLUME 16

HISTORY OF THE STUDY OF BROILIELLUS

A family of amphibians with dorsal dermal armor, the Dissoroph-
idae, has been recognized since the early 20th century (Boulenger,
1902, p. 383). However, the first study of reasonably comprehensive
nature dates from the description of Broiliellus by Williston. In 1914
(p. 56) he constructed the following diagnosis of the genus: "Shields
much broader than the vertebrae, not imbricated and not V-shaped;
free from slender neural spines; skull spinose." This diagnosis was
intended to separate Broiliellus from Aspidosaurus and Alegeino-
saurus which were believed to be its closest relatives. Together these
genera were placed in a new subfamily, the Aspidosaurinae, while the
other known genera of dissorophids (Dissorophus and Cacops) were
placed in another subfamily, the Dissorophinae.

These subfamilies were largely based on the number of armor seg-
ments for each vertebral segment. For each vertebral segment there
were supposed to be two armored segments in the Dissorophinae and
only one in the Aspidosaurinae.

DeMar (1966b) has shown that the number of armored segments
per vertebral segment has no taxonomic value at the subfamily level,
and that genera that are closely related have different numbers of
armored segments per vertebral segment. Broiliellus is closely re-
lated to Dissorophus, whereas Aspidosaurus, Cacops, and Alegeino-
saurus fall into another supergeneric group.

The earlier dissorophids, including some new ones, have been
studied by Carroll (1964) and when this information is available
a formal revision of Broiliellus will be possible. Until that ttme the
two new species described here add to the known dimensions of the
genus and give some evidence on the evolution of the genus.

Before the new species are described it should be pointed out that
Romer (1947, p. 160) suggested that Broiliellus was in reality a syno-
nym of Tersomius of the Belle Plains Formation. Tersomius texensis,
the only described species, had originally been described by Case
(1911, p. 51; 1946, p. 387) as a trimerorhachid, but Romer noted
that the posterior part of the skull is broken and it actually should
be interpreted as a dissorophid. :

As Romer observed, the skull of Tersomius differs from that of
Broiliellus in that it is very small, has open sutures, and does not
have the exostoses and dermal pitting of Broiliellus. These are the
characters of immature individuals, and thus, allowing for change of

DeMAR: new species OF BROILIELLUS 119

form with growth, Romer concluded that the two genera were one.
As he mentioned, the name Tersomius holds priority.

However, my own observations would seem to suggest that Broili-
ellus is actually a valid genus. Specimen FMNH UC 41, from the
Clyde Formation of the Permian of Texas, is a skull about 5 cm. in
length (compared to about 3.5 cm. for that of Tersomius), and is in
every way like the skull of Broiliellus texensis. Thus, its skull roof-
ing bones are firmly co-ossified, and it has a characteristic pattern of
ridges and valleys on the skull roof. Since the size difference between
this skull and that of Tersomius is not serious, they would appear to
be from animals of comparable maturity. This would appear to sup-
port the concept that the two genera are distinct.

In addition, there are certain other differences between the skulls
of these two genera that are not readily explained by differential
growth. The anterior margin of the otic notch of the skull of Ter-
somius is rounded, whereas that of Broiliellus, including the smaller
specimen, is a slanted, nearly straight shelf, facing dorsally and pos-
teriorly. Moreover, the external nares of Tersomius are small and
round, while those of Broiliellus, even in the small specimen, are elon-
gate and fairly large. Since openings in the skull tend to become
proportionately smaller with age, not larger, all this data would seem
to establish Broiliellus and Tersomius as distinct genera.

SYSTEMATICS

Class Amphibia

Order Rhachitomi

Family Dissorophidae Boulenger, 1902

Genus Broiliellus Williston, 1914

Broiliellus arroyoensis, new species

Holotype. — FMNH UR 431, from the Arroyo Formation at East
Coffee Creek, Lower Permian, Baylor County, Texas. This speci-
men is from Olson's Broiliellus pocket (DeMar, 1966a). It consists of
the anterior two-thirds of a skull, including the entire skull roof to a
point just posterior to the orbits, and the complete upper and lower
jaws to the articulation on the right side.

Referred Material. — Five specimens from the same locality as the
holotype. FMNH UR 808, a sacral rib and five articulated verte-
brae; FMNH UR 809, part of the anterior portion of the skull and
the sphenethmoid ; FMNH UR 810, a nearly complete armor cara-

120 FIELDIANA: GEOLOGY, VOLUME 16

pace; FMNH UR 811, the posterior part of the skull and braincase;
FMNH UR 812, part of the shoulder girdle and carapace.

Diagnosis. — The skull is, from a dorsal aspect, roughly triangular
with nearly straight maxillary margins, and with a sharply rounded
snout. The skull is low, but somewhat deeper than that of Broiliellus
texensis, and rises gradually from the snout posteriorly. The skull
roof sculpture is sharp and has higher relief than that of any other
Broiliellus species.

Description and Discussion. — The skull of Broiliellus arroyoensis
is represented by three previously undescribed specimens from the
Broiliellus pocket. Only one of these specimens, FMNH UR 431,
is relatively complete and that specimen does not have a preserved
braincase.

The skull roof is best represented on FMNH UR 431. This speci-
men shows that the skull is about 9.6 cm. long, and is in the shape of
an isosceles triangle from a dorsal aspect. The triangle has as its
base the posterior part of the skull (8 cm.) and, as its equal sides, the
maxillary-jugal-quadratojugal margin (9.5 cm.). The only strong
interruption to the resemblance to an isosceles triangle is the fact
that the snout is rounded, though more sharply than in the other
species of Broiliellus.

The external nares are very much like those of Broiliellus texensis
and are large, marginal, and anterior. They are directed more later-
ally than vertically or anteriorly. The orbits are directed laterally
and dorsally, and are in the shape of an irregular oval that is elon-
gated parallel to the lateral margin of the skull. Unlike the situation
in Broiliellus texensis, the anterior margin is almost flat.

It is impossible to describe the otic notch accurately, as the mate-
rial is incomplete. As seen in specimen FMNH UR 811, from Olson's
Broiliellus pocket, it is deep and has the ventrally directed half-moon-
shaped flange on the dorsal margin (DeMar, 1966a) that is charac-
teristic of the dissorophid otic notch.

The sutures between the skull roofing bones cannot be made out,
but they must be like those of Broiliellus texensis (Romer, 1947,
p. 160). Also they are no doubt like those of Broiliellus olsoni (illus-
trated in Figure 2).

The teeth of Broiliellus arroyoensis are well preserved on FMNH
UR 431, except for those on the premaxillary bones. The marginal
teeth are all slender and pointed. The most anterior teeth are about
3 mm. long and are slightly curved internally and posteriorly. Toward

i

DeMAR: new species OF BROILIELLUS

121

Fig. 1. A, dorsal view of the skull of Broiliellus arroyoensis, n. sp., FMNH
UR 431; B, lateral view of the same specimen. Both figures X 1.

the back of the tooth row the teeth gradually decrease in size so that
the most posterior maxillary teeth are 1 mm. in length. There are
about 45 teeth on each side.

The exostoses, or tubercules, ridges and depressions of the skull
roof of Broiliellus arroyoensis reach the known extreme size for any
dissorophid and, as a consequence, are exceptionally well defined.

122 FIELDIANA: GEOLOGY, VOLUME 16

Most of them may be discerned by examining Figure 1. In addition,
FMNH specimen UR 811 possesses a very large tubercule on each
postparietal, a moderately large tubercule on the posteriormost por-
tion of each tabular, and a ridge of variable proportions along the
dorsal margin of the otic notch. All of the tubercular development,
except for the greater size and relief, is very much like the situation in
other species of Broiliellus, and in Dissorophus.

The palate of Broiliellus arroyoensis is not well preserved on any
specimen, but can best be seen on FMNH specimens UR 431 and
UR 811. No palatal teeth are preserved, but they were almost cer-
tainly present since they have been described for Broiliellus novo-
mexicanus (Langston, 1953, p. 381) and for other members of the
family. The vacuities are large and the palate is firmly fused to the
braincase.

The braincase is not well preserved in the holotype, except for a
part of the cultriform process and sphenethmoid region, but FMNH
specimen UR 811, from Olson's Broiliellus pocket, has a fairly well-
exposed braincase from the pituitary fossa posteriorly. Specimen
UR 809, from the same locality, has parts of the sphenethmoid re-
gion and the cultriform process.

The braincase is well ossified, except for parts of the pro-otic, and
is very much like that of other rhachitomes, such as Eryops (Sawin,
1941, pp. 431-44), and Trematops (Olson, 1941, p. 165). Thus, only
brief comments are necessary. The parasphenoid is standard in ap-
pearance with somewhat enlarged posteriorly directed flanges for
ventral neck musculature. The fenestra ovalis is poorly preserved,
but is apparently round, and occurs just posterior and dorsal to the
parasphenoid flanges, as in Eryops. The pro-otic incisure appears
just anterior to the parasphenoid flange, on the lateral surface of the
braincase.

Twin foramina for the carotid arteries are present just posterior
to the cultriform process and pass dorsally into the pituitary fossa
The braincase is immovably fused to the palate by the firmly ossified
basipterygoid processes. Anteriorly the cultriform process of the para-
sphenoid is a slender rod ventral to the well-ossified sphenethmoid.
The sphenethmoid does not expand anteriorly, as it does in Eryops
(Sawin, 1941, pi, 3), but is approximately the same width through-
out, a condition that is universal in the dissorophids and trematopsids.

Specimen FMNH UR 808, which was found in association with
specimens of Broiliellus arroyoensis, Trematops sp., and Longiscitula
houghae, consists of a partial vertebral column and attached sacra

DeMAR: new species OF BROILIELLUS 123

rib. On the basis of size it would appear to be most reasonably-
assigned to Broiliellus arroyoensis, though this is not certain. It is
described here because its form can be compared significantly with
the form of the sacral rib in other dissorophids.

The specimen, FMNH UR 808, consists of five articulated verte-
brae, the most anterior of which probably articulated with the some-
what displaced sacral rib as it is significantly larger than its neighbors.
The sacral rib has an enlarged articular head with an oval face for the
transverse process and the intercentrum. The lateral face of the trans-
verse process is correspondingly enlarged for the reception of this
sacral articulation.

The sacral rib narrows distally to a neck, oval in cross-section,
and then expands into a blade-like rib with unfinished bone at the
extremities for articulation with the ilium. No direct observation of
the nature of the articulation can be made, but it appears that the
rib must have extended directly from the vertebra to the ilium with-
out the downward flexed distal portion that exists in Dissorophus.
Moreover, the rib is structurally similar to those of rhachitomes in
general. This rib certainly more nearly resembles that of Dissoro-
phus than those of Cacops.

The armor of this species has been described in another paper
(DeMar, 1966b), so here it is only necessary to point out that it is
identical in every observed detail to that of Broiliellus texensis. For-
tunately, it has been possible to examine the ventral surface of the
armor and to ascertain that each segment has a ventrally directed
flange that must have fit between the neural spines. This is like the
situation in the internal series (DeMar, 1966b) of Dissorophus.

Broiliellus olsoni new species

Holotype. — UT 3189-8, consisting of two-thirds of a skull, includ-
ing the almost complete anterior portion, and part of the posterior
portion on one side, from the Thaxton Ranch locality, Wichita Group
(probably the lower part), Lower Permian, Clay County, Texas.

Referred Material. — UT 3189-8, consisting of a ventral posterior
lateral part of a skull, including part of the maxillary, posterior part
of the lower jaw, and the ventral part of the otic notch, from the same
locality as the holotype.

Diagnosis. — The skull is roughly triangular. From a dorsal aspect
it has a broadly rounded snout, and a curved maxillary margin. The
skull is broad, with the postorbital part of the skull relatively shorter

124

FIELDIANA: GEOLOGY, VOLUME 16

Fig. 2. A, dorsal view of the skull of Broiliellus olsoni, n. sp., UT 3189-8. X 1.
B, lateral view of the skull of Broiliellus olsoni, n. sp., UT 3189-8. X 1.

than in other species. External nares are large and nearly circular.
The skull is relatively high and with nearly the same depth from a
point just posterior to the nares to the posterior margin. In connec-
tion with this form and depth, the anterior and lateral margins of the
skull are sharply rounded downward. The anterior margin of the
otic notch is steeper than in the other species.

DeMAR: new species OF BROILIELLUS 125

Description and Discussion. — The only material currently repre-
sentative of this new species is one partial skull, and another small
fragment of a skull and lower jaw. The material is a part of a large
collection of fragmentary Seymouria, miscellaneous reptiles, and frag-
ments of amphibian skeletal material from Thaxton Ranch. More
of this material may belong to B. olsoni, but this is impossible to
determine. A careful search of all the material has revealed no armor.

At least two individuals are included in the available material, and
since armor is easily preserved, it would appear that there is some
possibility that this species is not armored. If this is ever demon-
strated to be so, it would be best to elevate this species to a new genus.

The best preserved skull is UT 3189-8. This specimen shows that
the skull is almost the same as B. texensis in size and in the form and
sculpture of the dermal skull bones. In dorsal aspect the skull is
shaped almost like an equilateral triangle, except that the lateral and
anterior margins are broadly rounded. The posterior margin is not
preserved. In lateral aspect, beginning anteriorly, the skull roof rises
sharply at about a 45° angle to a point just posterior to the nares,
where the skull rounds off and increases only slightly in depth to the
posterior extremity. The skull is very deep, compared with the other
species of Broiliellus.

In addition to the great depth of the skull, the postorbital length
of the skull is relatively short compared with that of Broiliellus texen-
sis or B. arroyoensis. This, incidentally, seems to be characteristic
of a number of Early Permian and Late Pennsylvanian dissorophids,
including Amphibamus grandiceps (Gregory, 1950, p. 844) and Broili-
ellus novomexicanus (Langston, 1953, p. 380).

The external nares are lateral and anterior, and are directed for-
ward, upward and laterally about equally. The nares are nearly
circular, unlike those of most other dissorophoids.

The orbits are large, nearly circular, and are directed upward and
laterally. As has been mentioned, the skull is shorter, posteriorly,
than in most dissorophids, consequently the orbits occupy a slightly
more posterior position than usual.

The otic notch is incompletely preserved, making it impossible to
know the exact nature of the tabular, and whether the tabular joins
the quadrate, thus closing the otic notch behind. At present, the
otic notch can be described thus: The dorsal margin is horizontal,
and about 2-3 mm. posterior to the squamosal-postparietal contact
it curves downward, and partly backward, so that the anterior mar-

126 FIELDIANA: GEOLOGY, VOLUME 16

gin slopes 60° posteriorly, to a point just dorsal to the jaw articula-
tion, where it becomes sharply horizontal. The steep slope of the
anterior ventral face of the otic notch is no doubt connected with
the shortness and great depth of the skull table.

The margin of the otic notch is smooth, has essentially no surface
irregularities, and is formed from the following bones: Tabular (not
preserved), supratemporal, squamosal or quadrate. Dorsally, the
supratemporal and a small part of the squamosal are inflected down-
ward, with a vertical external surface, so that a half-moon-shaped
obstruction decreases the size of the otic notch, as in other dissoro-
phids. Anteriorly, the squamosal is inflected inward and backward
from the margin of the otic notch in a broad shelf, which declines to
the jaw articulation, as previously described.

The internal posterior projection of the quadrate is inflected up-
ward, and is terminated by a rough, broken surface, indicating that
the otic notch was either partly closed behind, as in B. texensis, or
completely closed, as in Dissorophus. This detail, however, does not
seem very important, as it may have varied according to the age of
the animal at death.

The surface details of the skull have some importance for taxo-
nomic purposes, as in other dissorophids. One is struck by the gen-
eral similarity of the surface detail of the skull of this animal tathat
of Dissorophus, of course, and more particularly to those of the other
species of Broiliellus. The major difference is that the topography
is more subdued in B. olsoni than in either B. texensis or B. arroyoen-
sis. The surface sculpture is illustrated in Figure 2.

The sutures between the skull roofing bones are clear, and show
those bones which one would expect. There is no intertemporal.
The orbit intersects the jugal, lacrimal, prefrontal, frontal and post-
frontal bones, as in other genera with large orbits. The squamosal
is strongly indented by the otic notch. Details can be seen in the
illustrations.

The marginal teeth are not well preserved on the holotype. The
margins of the maxillary and premaxillary bones apparently have a
single row of small, pointed teeth which are continuous, except on the
extreme posterior part of the maxillary, where they are absent. There
are approximately 47-48 teeth on either side of the upper jaw in this
marginal series. They are fairly homogeneous in size, except for the
most posterior teeth, which are slightly smaller.

DeMAR: new species OF BROILIELLUS 127

The referred specimen, UT 3189-8, from Texas, has the only well-
preserved teeth. Theseareabout 2 mm. long and are pointed. They
are apparently directed somewhat inward.

The palate is similar to that of other dissorophids. The palatal
vacuities and the internal nares are large. The internal nares are
marginally placed, and elongated parallel to the margin of the jaw.
The bones of the palate are difficult to distinguish, although some
sutures can be made out. There is nothing obviously irregular, ex-
cept possibly that the cul triform process of the parasphenoid is firmly
interdigitated to the vomers.

The braincase is preserved only in the sphenethmoid region. The
sphenethmoid is well ossified, and passes throughout the known ex-
tent without variation in width, unlike Eryops, but similar to the
situation in other known dissorophids. The cultriform process is
firmly attached to the sphenethmoid.

DISCUSSION AND CONCLUSIONS

Two new species of Broiliellus, B. olsoni and B. arroyoensis, have
been described. There is little question that these two species, to-
gether with B. novomexicanus and the genotype, B. texensis, form a
closely knit group of species. However, there is also little doubt that
these species are truly distinct. There are not enough specimens to
evaluate variation properly, but all of the type specimens are of about
the same size, so that it is unlikely that the relative maturity of the
individuals can explain their differences. In addition, such growth
stages as are known indicate that there is little differentiation of skull
form with age.

Moreover, these species are all from different horizons. B. olsoni
is from the Thaxton Ranch locality, which is, most probably. Lower
Wichita, possibly the Admiral Formation, according to Romer (1958,
p. 176). B. texensis is from the Clyde Formation, and B. arroyoensis
is from the Arroyo Formation.

Broiliellus novomexicanus (Langston, 1953, p. 380) is certainly
another species of Broiliellus, and is known only from the Lower
Permian of New Mexico. This is approximately equivalent to the
Moran and Admiral Formations in Texas (Langston, 1953, p. 411),
which means that this species is about the same age as B. olsoni. This
species cannot be reviewed here thoroughly, because of the diffi-
culty of studying certain specimens. However, it can be said that

128 FIELDIANA: GEOLOGY, VOLUME 16

this species stands out from the other named species because of its
early occurrence, its generally low skull, its narrow armor (DeMar,
1966b), and its short postorbital skull length.

Thus Broiliellus is one of the most diverse and long-lived of Per-
mian amphibian species. We cannot be sure of the phylogeny, be-
cause of the scarcity of specimens, but we can recognize certain
evolutionary trends. There is a gradual development in the armor
from the early, lightly armored B. novomexicanus, or possible lightly
armored B. olsoni, to the heavily armored B. texensis and B. arroyo-
ensis. In addition, there appears to be a progressive development of
greater relief and sharpness in the skull roof topography, and of more
complete closure of the sutures between the skull roofing bones. All
of these features can be interpreted together as causing a general in-
crease in the strength of the skull.

In general, dissorophids of Arroyo age and later (B. arroyoensis,
Dissorophus multicinctus and Cacops aspidephorus, especially) have
firmly constructed skulls, and are well ossified with good articula-
tions. This has been interpreted (DeMar, 1966a) as evidence that
the dissorophids were becoming more completely adapted to terres-
trial life. From this point of view, it would be preferable that the
species of Broiliellus represent a single phyletic ramus.

On the other hand, there is the possibility (with continuous^er-
mutations with the previous one) that the species of Broiliellus pro-
vide an all-too-dim look at the adaptive radiation of the genus. In
this case, these four species would be related only by having a com-
mon ancestor. The terrestrial adaptations would be interpreted in the
same way as before, but there would be no record of a gradual devel-
opment toward a more terrestrial state.

Another paper will deal with the distribution and general adapta-
tion of the dissorophids, but it can be pointed out here that none of
these species is found associated with the common aquatic or semi-
aquatic species of the Permian. Instead, they are found with reptiles
or terrestrial-appearing amphibians. This would suggest that Broili-
ellus avoided aquatic environments, and lived in the more upland
portions of the Permian depositional area.

Note: Since this paper was submitted in 1964, new material has been published
by Carroll. Since the main purpose of the present paper is to describe new spe-
cies of Broiliellus, this information is not discussed here.

DeMAR: new species OF BROILIELLUS 129

References

boulenger, g. a.

1902. Amphibia. Encyclopedia Britannica, 10th ed., pp. 381-384.

Case, E. C.

1911. Revision of the Amphibia and Pisces of the Permian of North America.
Carnegie Inst. Wash., Pub. 146, pp. 1-148.

1946. A census of the determinable genera of the Stegocephalia. Trans. Am.
Phil. Soc, n.s., 35, pp. 325-420.

Case, E. C, and S. W. Williston

1913. A description of Aspidosaurus novomexicanus. Carnegie Inst. Wash.,
Pub. 181, pp. 7-9.

Carroll, R.

1964. The early evolution of the dissorophid amphibians. Bull. Mus. Comp.
Zool., 131, pp. 161-250.

DeMar, R. E.

1966a. Longiscitula houghae: a new dissorophid amphibian from the Permian
of Texas. Fieldiana: Geology, 16, pp. 45-53.

1966b. The functional and phylogenetic significance of the armor of dissorophid
amphibians. Fieldiana: Geology, 16, pp. 55-88.

Gregory, J. T.

1950. Tetrapods of the Pennsylvanian nodules from Mazon Creek, Illinois.
Am. Jour. Sci., ser. 5, 249, pp. 833-873.

Langston, W.

1953. Permian amphibians from New Mexico. Bull. California Univ. Dept.
Geol. Sci., 29, pp. 349-416.

Olson, E. C.

1941. The family Trematopsidae. Jour. Geol., 49, pp. 149-176.

ROMER, A. S.

1947. Review of the Labyrinthodontia. Bull. Mus. Comp. Zool., 99, pp. 1-368.

Sawin, H. J.

1941. The cranial anatomy of Eryops megacephalus. Bull. Mus. Comp. Zool.,
88, pp. 407-466.

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1914. Broiliellus, a new genus of amphibians from the Permian of Texas. Jour.
Geol., 22, pp. 49-56.