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LIBRARY
SEP 6 19F

HARVARD
UNIVERSITY

POSTILLA

PEABODY MUSEUM
YALE UNIVERSITY

NUMBER 121. 29 JULY 1968.

A NEW DINOCEPHALIAN FROM
THE CISURALIAN REGION (REP-
TILIA, THERAPSIDA; UPPER PER-
MIAN).

P. K. TCHUDINOV

POSTILLA

Published by the Peabody Museum of Natural History, Yale University

Postilla includes results of original research on systematic, evolution-
ary, morphological, and ecological biology, including paleontology.
Syntheses and other theoretical papers based on research are also
welcomed. Postilla is intended primarily for papers by the staff of
the Peabody Museum or on research using material in this Museum.

Editors: Jeanne E. Remington and Nancy A. Ahlstrom

Postilla is published at frequent but irregular intervals. Manuscripts,

orders for publications, and all correspondence concerning publications
should be directed to:

Publications Office
Peabody Museum of Natural History
New Haven, Conn., 06520, U.S.A.

Lists of the publications of the Museum are available from the above
office. These include Postilla, Bulletin, Discovery, special publications,
and available back numbers of the discontinued journal, Bulletin of the
Bingham Oceanographic Collection. All except Discovery are available
in exchange for relevant publications of other scientific institutions
anywhere in the world.

A NEW DINOCEPHALIAN FROM THE CISURALIAN
REGION (REPTILIA, THERAPSIDA; UPPER PER-
MIAN)

P. K. TCHUDINOV

Paleontological Institute of the Academy
of Sciences of the U.S.S.R., Moscow

ABSTRACT

A new genus and species of dinocephalian is described, based on
a skull, teeth, and lower jaw fragment from the Upper Permian
of south Cisuralian U.S.S.R. The new dinocephalian belongs to a
group of carnivorous brithopodids which are widespread in the
Cisuralian region. On the basis of morphological characteristics
it is concluded that the new genus is closely related to Syodon
and Titanophoneus, representatives of one of the late stages of
development of the dinocephalian faunas of the U.S.S.R.

MUS, COMP. ZOOL.
LIBRARY.

SEP 6 1968

HARVARD
UNIVERSITY,

POSTILLA 121: 20 p. 29 JULY 1968.

2 POSTILLA

INTRODUCTION

In the spring of 1963 A. K. Gusev, Senior Scientist at the Uni-
versity of Kazan, transmitted to the Paleontological Institute of
the Academy of Sciences of the USSR the remains of vertebrates
from three localities north-northwest of Aktyubinsk. In one of
these localities was found the skull and teeth of a carnivorous
dinocephalian. In addition to this, the author had at his disposal
a lower jaw fragment, also of a large carnivorous dinocephalian,
which had previously been sent to the Paleontological Institute
from the University of Saratov by V. G. Ochev from the Permian
deposits in the Orenburg oblast.

The skull and teeth from the Zhaksy-Karagala River bank near
Aktyubinsk belong to a carnivorous dinocephalian of the Britho-
podidae, representatives of which are fairly common in the more
northern parts of the western Cisuralian region. Study of these
remains has shown that they belong to a new genus closely related
to the genus Syodon, which is well known in the dinocephalian
fauna of the area of the village of Isheyevo (Middle Volga).
Interestingly enough, some aspects of the skull structure (its large
size, the borders of the temporal cavity, the massiveness of the
zygomatic and the postorbital arches, the development of a parietal
protuberance stronger than that of Syodon, and the development
of a separate shoulder on the lingual sides of the precanine teeth)
nay be suggestive of specializations characteristic of a later geo-
logic age. But in this instance the time interval between the faunas
of these localities, if there was one, cannot have been very long.
Thus, according to the preliminary data, the fauna of the Zhaksy-
Karagala locality is a later grouping of the Isheyevo type and
marks the southern limit of the geographic range of the Cisuralian
dinocephalian fauna. (See section on Geology, below).

Study of the lower jaw fragment of the carnivorous dino-
cephalian from the Orenburg region has shown that it belongs to
a late brithopodid fauna of the Isheyevo type, whose Early
Tatarian age is accepted by most investigators. The morphological
features of the lower jaw structure (its size, its general massive-
ness, and the small number of marginal teeth) indicate that it
belongs to the same genus as the Aktyubinsk brithopodid from
the Zhaksy-Karagala locality and that these two localities are of
the same age. The discrepancy between the systematic position

A NEW DINOCEPHALIAN 3

of the remains from the Donguz locality and their stratigraphic
position in the Upper Tatarian substage is due, in Ochev’s opin-
ion, to their redeposition after the erosion of the Lower Tatarian
deposits. In my view, this discrepancy may be owing in equal
measure to incorrect correlation of the local stratigraphic section
with the Malyy Kinel’ or the Northern Dvina suites, which are
characterized by a Late Tatarian faunal assemblage.

The discovery of Permian vertebrates in the Orenburg-Aktyu-
binsk area of the Cisuralian region opens up new prospects for
paleontological explorations and excavations and is of considerable
interest for stratigraphy and correlation, since the localities in the
Aktyubinsk area are evidently of the same age and together
embrace a large interval of the Upper Permian section correspond-
ing to the time during which the dinocephalian fauna was in
existence. Efremov and V’yushkov (1955) also mention the dis-
covery of vertebrates in the Lower Permian deposits of the Sogur-
Say ravine (Tabantal River) south of Aktyubinsk. But these
authors’ conclusion regarding their age now seems doubtful, inas-
much as the finds were lost before they could be studied in detail,
and the lithologically similar sandstone and conglomerate deposits
with limestone gravels and algal nodules along the Tabantal River
in the vicinity of the village of Kyzyl-Tu have been considered by
Gusev to be part of the Blagodarnoye suite.

DESCRIPTION OF NEW GENUS

SUBORDER DINOCEPHALIA
Family Brithopodidae Efremov, 1954
Genus Notosyodon, gen. n.

The generic name is derived from that of the existing genus Syodon
and the Greek word Notos, “south wind.”

TYPE SPECIES: N. gusevi sp. n.

SPECIES INCLUDED: The type species only.

DIAGNOSIS: Medium-sized, carnivorous, possibly omnivorous, dino-
cephalian with a massive, heavy skull. The orbits are large, slightly
oval in shape longitudinally, and almost vertical. The edge of the

orbits are thickened. The preorbital area has a step-like bend
between the dorsal and the lateral sides of the roof of the skull.

4 POSTILLA

The temporal cavities are large and converge sharply in the dor-
somedial area. The zygomatic arch is high. The rcof of the skull
is very thick in the interorbital and the parietal areas. The inter-
orbital portion is flat and straight and lacks a median ridge. The
frontals do not enter into the formation of the transverse crests
which border the anterodorsal sections of the temporal cavities.
The parietal foramen is large and slightly oval longitudinally and
is not surrounded by a bony ridge. The parietal boss is high and
unusually massive. The upper part of the occipital region is con-
siderably inclined downward and rearward. The posterior branches
of the pterygoid are long and narrow. The ventral and dorsal sur-
faces of the basisphenoid are thoroughly ossified, and its posterior
portion is wide, high, and massive. The occipital condyle is very
large. The lower jaw is high and has a massive symphysis and a
small number of teeth. The dental formula of the lower jaw is
14 Cl PC6.

COMPARISON WITH RELATED GENERA: In its general overall con-
figuration, the position of its orbits and its temporal cavities, the
skull of Notosyodon very strongly resembles that of Syodon, trom
which it differs, however, in its considerably larger size and the
much greater massiveness of its component elements. In addition,
the new genus differs in the following: the interorbital part of the
skull is wide and straight and lacks a sagittal crest; the edges ‘of
ihe orbits are wide and thickened along their whole perimeter; the
parietal boss and the occipital condyle are unusually large; the
occipital region is relatively narrow and the upper part of the
occiput is strongly slanted upward and forward; the posterior rami
of the pterygoids diverge at a small angle and the basisphenoid,
whose posterior section is very high and wide, is well ossified.
These characteristics also distinguish the new genus from
another similar and closely related genus, Titanophoneus, which
despite its large size differs from Notosyodon in its elongated skull,
its almost vertical temporal cavities, and the structure of the dorsal
surface of the pterygoids. In the thick roof of its skull, the borders
of its parietal boss, and the upper parts of its temporal cavities
Notosyodon closely resembles the genus Doliosauriscus, which was
described by Orlov (1958). It should be noted, however, that the
range of the remaining differences between these two genera is
much wider than between the new genus on the one hand and

A NEW DINOCEPHALIAN S)

Syodon and Titanophoneus on the other. In a number of characters
(thickness of the parietal area, the massiveness of the skull, the
structure of the precanine teeth and others) the new genus is close
to an earlier representative of the same family, the genus Archaeo-
syodon. But here, too, the new genus shows significant differences
in the hypertrophied parietal boss, the basisphenoid area and the
occipital condyle.

Notosyodon, in contrast to the other known brithopodids, is
also characterized by a smaller number of marginal teeth; this,
like the general massiveness of the skull and its much greater
degree of ossification, is probably a sign of its later geologic age.

The morphology of Notosyodon shows that the later brithopodids
included not only light and highly mobile predators (like Syodon
and Titanophoneus) and gigantic predators who represent the so-
called titanosuchian adaptation (Doliosauriscus, Admetophoneus),
but also moderate sized, heavily built and relatively non-mobile,
possibly omnivorous dinocephalians such as Notosyodon.

DESCRIPTION OF NEW SPECIES
Notosyodon gusevi, sp. 0.

HOLOTYPE: PIN No. 2505/1, Paleontological Institute collection,
Academy of Sciences of the U.S.S.R., Moscow.

The preorbital part of the skull anterior to the transverse
processes of the pterygoids are not preserved (fig. 1). The inter-
orbital and a small part of the preorbital areas with a stepwise
curvature between the dorsal and the lateral surfaces of the skull
roof are represented by an internal mold with impressions of the
frontals and the prefrontals. The base of the skull with the occipital
condyle and the posterior rami of the pterygoids are well pre-
served. The skull is slightly deformed dorsoventrally and laterally
in such a manner that the anterior part of the base of the skull
is somewhat displaced to the right. The brain case is not fully
preserved and lacks the sphenethmoid.

JUGALS: The anterior portion of the zygomatic arch and its con-
tact with the lacrimal and the maxillae have been lost, but on the
internal surface, at the level of the anterior edge of the orbit, there
is a small fragment of the lacrimal, which lies like a scale upon
the jugal. Directly below the contact with the lacrimal, the jugal

6 POSTILLA

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gives rise to a anteriorly directed projection which fits behind the
inner edge of the mandible. The jugal is high and has a thickened
orbital edge. Its postorbital process is covered to a considerable
extent on the outside by the postorbital. The jugal is completely
covered laterally by the anterior process of the squamosal but,
to judge from its length, reached as far back as in the typical
brithopodids.

PREFRONTALS: Impressions on the internal mold show that these
bones occupied the usual brithopodid position, but differed in
their somewhat thicker orbital edges. At the boundary with the
nasals they took part in the formation of the nasoturbinal crest.

FRONTALS: Their anterior portions are narrow and show the
maximal thickness along the sagittal suture. The orbital edge is

A NEW DINOCEPHALIAN 7

wide but thinner. There is no median longitudinal crest on the
dorsal side; the ventral side preserves the usual shallow groove
bordered by ridges along its sides. They grade forward without any
separation into the nascturbinal ridge of the nasals; in the poste-
rior portion they are less distinct and join the lateral wall of the
brain case at the anterior edge of the sphenethmoid. The boundary
between the braincase and the sphenethmoid is at the level of the
dorsal suture of the prefrontals. The dorsal surfaces of the frontals
along the suture with the postfrontals are smooth and, in contrast
to Syodon and Titanophoneus, have no transverse ridges bordering
the anterodorsal areas of the temporal cavities. From the level of
the posterior edge of the orbit to the contact with the parietal,
the frontal descends smoothly and steeply, becoming twice as
thick, and contributes to the formation of the massive parietal
boss.

POSTFRONTALS: These bones are small in size and fairly narrow,
reaching their greatest width and thickness at the orbital rim.
The postfrontal has a sharp transverse ridge which runs medially
from the edge of the orbit and then bends smoothly to the rear,
disappearing at the contact with the parietal bone. Posterior to
this contact the postfrontal overlaps the parietal, forming part of
the perpendicular wall of the parietal boss, and outlines the
mediodorsal boundary of the temporal cavity.

PARIETALS: These small but very thick and massive bones make
up the greater part of the high parietal boss. The anterior slope
of the boss descends quite steeply and merges smoothly into the
roof of the skull; the posterior slope is vertical above the posterior
surface of the ccciput. The parietal boss lacks the bony ridge that
is possessed by the majority of representatives of this family. The
parietal foramen is large and slightly oval longitudinally.

POSTORBITALS: These very massive and large bones overlap the
postfrontals and the parietals in the upper part of the temporal
cavity.

INTERPARIETAL: Not fully preserved. Its lateral parts are thin and
plate-like; the upper lateral part overlaps the parietal bone and the
lower part of the interparietal covers the edge of the supraoc-
cipital. The interparietal was evidently not greatly thickened in
the area of the sagittal crest. In any case, the formation of the

8 POSTILLA

upper part of this crest on the occipital surface involves the poste-
rior parts of the parietals, which are also wedged into the inter-
parietal in the form of a crest; the lower part of this crest is
to a considerable extent formed by the ascending process of the
supraoccipital. A fracture in the bone has exposed the contact of
the interparietal with the prootic along the lower parts of the sides
of the sagittal crest.

TABULARS: These have been preserved in the area of the lateral
occipital crest, where they partially cover the posterior surface of
the lateral processes of the parietals and also the postorbitals. In
the lower occipital area they combine wih the squamosals to form
a continuation of the lateral occipital crest which commonly occurs
in the brithopodids.

SQUAMOSALS: These large bones are markedly thickened along the
posterior edge of the temporal cavity. This posterior edge repeats
the line of the curvature of the posterior wall of the orbit. In the
upper portion, along the lateral occipital crest, they overlap the
postorbitals for a considerable distance. The jugal process of the
squamosal, which is equal in height to the squamosal process on
the jugal, almost completely overlaps the latter and terminates at
the level of the inner edge of the posterior wall of the orbit.
From the lower posterior angle of the temporal cavity the squa-
mosal, which here becomes much thicker, grades smoothly into the
occipital surface, where it is bordered at the contact with the
tabular by the lateral occipital crest. The boundary of the squa-
mosal in the temporal cavity and its contacts with the quadrate
complex are unclear. The occipital surface of the squamosal along
the edge of the temporal cavity has rough corrugations.

PTERYGOIDS: The massive flanks of the transverse processes reach
their greatest height laterally and are oriented mainly perpendicular
to the axial line of the skull (fig. 2). The lower lateral parts of
the transverse processes are slightly curved downward and back-
ward. The medial part of the pterygoids directly behind the trans-
verse processes give rise to posteriorly projecting, converging crests
which form a double ventral keel on the ventral surface in front
of the basisphenoid (fig. 2b). On the dorsal side (fig. 2a) lateral
to the sagittal axis, the pterygoid forms two thin longitudinal
septa which have wide bases and are inclined forward and upward.

A NEW DINOCEPHALIAN

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10 POSTILLA

Further to the rear the septa diverge somewhat, taking on the out-
line of a compressed figure X in dorsal view. The anterior parts
of the septal bases are thickened by accumulations of bony tissue
separated laterally from the corpus of the bone by the appearance
of a suture. The posterior halves of the bases of these septa also
give rise to similar but much wider bony growths separated from
the medial parts of the bones by small and evidently fully enclosed
cavities. These cavities have a length of 10 mm, a width at the
front of 1 mm and at the rear of 3 mm, and an overall height of
2 mm. The bottoms of these cavities are inclined downward and
forward; their posterior walls at the contact with the basisphenoid
are very thin and only slightly ossified. A similar structure in the
dorsal portion of the pterygoids, and which has not previously
been noted in the Brithopodidae, is also characteristic of Titano-
phoneus and appears to be typical of the later representatives of
this family. (Of the existing skulls of Syodon, Titanophoneus and
Doliosauriscus, the dorsal part of the pterygoid is preserved only
in the second of these genera.) It is quite likely that these bony
growths and their accompanying enclosed cavities in the centra!
portions of the pterygoids originated independently and represent
an ossification of the anterior processes of the cartilaginous pala-
toquadrate.

The posterior rami of the pterygoids are high. Their ventral
edges are thickened for one third of their length, are massive and
relatively low; the middle and posterior parts are thinner and
higher and descend ventrally with ridges that curve inward slightly.
Highly characteristic of Notosyodon is the small angle of diver-
gence of the posterior rami of the pterygoids — not more than 36°.
In Titanophoneus and Syodon these angles are 70° and 80
respectively.

EPIPTERYGOIDS: From the side these have the appearance of
plates that are wide at the bottom and narrow toward the top,
their bases overlying the mediodorsal parts of the posterior rami
of the pterygoids. The anterior parts of the bases give rise to in-
ward curving medial projections which contact the dorsal surface
of the basipterygoid processes by distinct sutures. The anterior
edges of the epipterygoid are thickened and rounded along their
entire length. The lower halves of the epipterygoids, a fraction of a
millimeter in thickness and the posterior edges were evidently not

A NEW DINOCEPHALIAN 1]

ossified at all. The upper rod-like parts have wedge-shaped cross
sections with anterior edges thickened to | mm. Above their bases
the epipterygoids converge smoothly and their dorsal edges fit into
small longitudinal depressions along the ventral edges of the
parietal and just barely outside the crests which mark the lateral
walls of the brain case.

The occipital region of Notosyodon’s skull is wide and high. Its
maximum width at the level of the occipital condyle amounts to
about 150 mm. The upper part of the occipital area from the level
of the upper edge of the occipital foramen is concave and strongly
inclined posteroventrally. The angle between the oblique upper
occipital crests, which separate the occiput from the temporal
depressions, is 90°. The occipital condyle, which lies in the zone
of curvature of the occipital surface, projects sharply poster-
oventrally. Its lower segment, which makes up the greater part of
the condyle, is bounded by an are of 120° and its spherical artic-
ulating surface has an anteroventral orientation. The lateral seg-
ments of the condyle are more highly developed than in Syodon
and Titanophoneus and are bordered by arcs of 60°. The articular
surfaces of the lateral segments are quite distinct and well ossified.
But the three segments as a whole do not form a single spherical
surface: the lateral segments are elongated dorsolaterally, while
the ventral segment is displaced slightly forward relative to the
lateral segments.

BASIOCCIPITAL: This has a normal brithopodid position and struc-
ture, but differs in its very large size. Together with the exoc-
cipitals, the basioccipital forms the massive occipital condyle
which in Notosyodon is twice as large as in Syodon and is only
a little smaller than the occipital condyle of the much larger skull
of Titanophoneus. The sagittal suture between the exoccipitals on
the surface of the occipital condyle is not crested. The processes
for the proatlas, which are located at about the middle of the
height of the occipital foramen magnum, rise dorsoposteriorly
in the form of short rods with rounded articular facets. The pair
of foramina for the twelfth nerve occupy the usual positions in the
base of the lateral parts of the exoccipitals, whence they continue
upward medially and emerge into the cranial cavity near the
occipital foramen in a large canal about 1.5 mm in diameter. The
jugular foramen which is about 2.5 mm across, is located below

2 POSTILLA

the lateral processes of the exoccipital at the contact with the
opisthotic and passes into the brain case almost parallel to the
canal for the twelfth nerve.

SUPRAOCCIPITAL: These are not completely preserved. Their
boundaries with the tabular, the opisthotic and the exoccipital on
the occipital surface are not distinct. The anterodorsal sections of
the supraoccipital are separated by a deep sagittal incisure that
opens posteriorly, while the thin lower lateral parts are inserted
like scales between the prootic and parietal. At the boundary
with the parietal the anterodorsal parts of the supraoccipital have
small, slightly ossified areas directed toward the apices of the
epipterygoids.

oPIstHoTIC: Their anterior, upper and lateral outlines are indis-
tinct; the boundaries with the exoccipital, the basioocipital, the
stapes and the basisphenoid on the ventral side of the skull for the
most part are the same as in Syodon and Titanophoneus.
The anteromedial parts of the opisthotic in the area of the basiooc-
cipital and the basisphenoid are thickened and widened antero-
posteriorly. The area of the contact with the stapes and the
basisphenoid is indistinct because of its slight ossification. The
contact of the opisthotic with the basisphenoid evidently lies not
at the level of the anterior edge of the proximal end of the stapes
as in Syodon and Titanophoneus, but at the level of its posterior
edge—that is, it occupies a smaller area.

PROOTICS: These bones are short anteroposteriorly, high and mas-
sive. They are connected anteriorly by a distinct transverse suture
with the basisphenoid, and in their upper lateral parts with the
supraoccipital, whose anterior double lobes at the top overlie the
medial portions of the prootics. The suture connecting them with
the opisthotics is apparently overgrown. The prootics, which are
connected to the basisphenoid at the end of its deep longitudinal
groove, form high and wide medial tabular processes which con-
verge in the sagittal suture. In their location these processes cor-
respond to the false spine of the sella turcica described by Ta-
tarinov (1965) in the tapinocephalian Moschops. The upper ant-
erior parts of the prootic have the usual brithopodid semi-oval
incisure for the exit of the vein and the trigeminal nerve.

A NEW DINOCEPHALIAN 13

BASISPHENOID: The basisphenoid of Notosyodon is distinguished
for its massiveness and the great width of its posterior portion.
Its contact with the basioccipital on the ventral side is quite distinct,
although it shows some signs of incomplete ossification. The con-
tact with the opisthotic lies in a slightly ossified zone which also
extends to the posterolateral angles of the basisphenoid. On the
ventral side the basisphenoid has a deep and wide longitudinal
groove. This begins directly behind the short ventral crest which
separates the foramina for the carotid arteries at the level of their
anterior edges, then widens and becomes deeper toward the rear,
continuing into the anterior part of the basioccipital. The corpus
of the basisphenoid, which is divided by a medial groove, forms
two massive, diverging and rearward extending rounded crests,
each of which has a posterior unossified area facing the fenestra
ovalis. The basisphenoid is connected anteriorly with the medial
parts of the pterygoids by a deep stepwise suture in whose postero-
medial part, along the inner sides of the basipterygoid processes,
are the vidian canals. On the dorsal side the basisphenoid is
divided into two sections: an anterior section which is compara-
tively narrow and solid, and a posterior section that is divided
by a long, deep groove beginning just behind the canals for the
carotid arteries and terminates in the anteromedial portions of the
prootic. The anterior part of the basisphenoid is divided by a short
and shallow but wide groove which originates behind the elevated
and widened bases of the pterygoidal septa and runs back, nar-
rowing and finally terminating at the base of the dorsal process of
the basisphenoid. The vidian canals, which are separated by a very
thin bony partition, open into the anterior part of this groove. The
base of the basipterygoidal rostrum lies in front of the hypophyseal
pit and the medial canals of the carotid arteries. In plane view it
has a cross section shaped like an isosceles triangle with its
vertex forward. The basisphenoidal rostrum itself is a thin plate
which, as seen from the side, has the form of a scalene triangle
with its obtuse angle at the base of the rostrum. From the base to
the apex, the more elongated anterior edge of the rostrum rises
in a straight line upward and forward at an angle of about 60°
tc the base of the skull. The upper point of its anterior wedge-
shaped end projects far forward of the vidian canals between the
anterior ends of the pterygoidal septa. The posterior edge of the
rostrum is also straight and runs back above the hypophyseal pit

14 POSTILLA

and upward parallel to the ridge of the posterior part of the
basisphenoid; its uppermost point projects above the basisphenoid
somewhat forward of the prootic. The dorsal edge of the rostrum
was convex and may have been incompletely ossified. The canals
for the carotid arteries, which emerge on the ventral side through
two large and widely separated foramina, pass through the body
of the basisphenoid, converging upward and to the rear and emerge
dorsally in two quite large foramina separated by a thin bony
partition. Besides these basic canals, the two arterial branches
continuing dorsally give rise to five smaller foramina. The first
of these emerges to the side of the principal foramina; the other
four, which are still smaller, emerge forward along the sides of the
base of the rostrum. The lateral sides of the posterior part of the
basisphenoid have a steep lateral inclination, and their lower parts
are slightly concave. The posterior part of the basisphenoid at the
contact with the prootic is very high, and its lateral ridges at the
rear almost reach the height of the false spine of the sella turcica.
The posterior surface cannot be seen, but the dorsal contact of the
basisphenoid with the prootic and the basioccipital shows a slight
degree of ossification. In general, the basisphenoid in Notosyodon
is much more fully ossified than in Syodon and Titanophoneus.

STAPES: The left stapes, which has the form of a massive bony
column with widened ends, has been preserved in its natural
articulation. Its proximal end, which has a round cross section
and is slightly ossified, has no distinct contacts in the area of the
fenestra ovalis. The corpus of the bone is inclined posteroventrally,
is widened dorsoventrally and has an oval cross section. The distal
end is wide, cut off at an angle and well ossified in the present
specimen; its articular areas are turned toward the posterior rami
of the pterygoid. The posterior section of the distal end of the
stapes lies like a broad lead cn the anterolateral edge of the
opisthotic. The contact with the quadrate is not clear. Quite
characteristically, the stapes in Notosyodon, as in the other brith-
opodids, has no stapedial foramen.

TEETH

Along with the skull fragment were found two isolated teeth
(fig. 3) which appear to have belonged to the same skull. One
of these (PIN 2505/3) is the fourth or fifth upper left postcanine;

A NEW DINOCEPHALIAN Les)

the other (PIN 2505/2) is probably the crown of the third incisor
tooth on the right side of the lower jaw.

The upper tooth has a longitudinally oval cross section; its
crown is low, only half as long as the root. The outer side of the
crown is markedly convex and the lingual side slightly so. The
apex of the crown is somewhat displaced posteriorly relative to
the axis of the tooth; its anterior and posterior edges are sharp
and have serrated notches. The base of the crown where it merges
with the root has a slight annular neck. The surface of the root
has a concentric annular sculptured pattern which is especially
marked at the base.

The crown of the third lower incisor is quite large, with an
apex that curves posteriorly. The convex outer side bears traces of
two weak facets. The inner side is slightly concave and at the
base has a small oblique cingulum formed by shoulders which
descend along the inner side to the sharp posterior edge of the
crown. From the base of the collar a few well marked ribs ascend
and converge toward the apex.

These teeth differ little from the corresponding teeth in
Archaeosyodon or Titanophoneus. It is noteworthy that the large
and massive teeth are consistent with the general massiveness of
the skull.

TYPE LOCALITY: 20 km north-northwest of the city of Aktyubinsk
and 7.8 km south of the village of Turazhol, in the lower part of

FIG. 3. Notosyodon gusevi, gen. et sp. n. A. Fourth or fifth upper left
postcanine. PIN 2505/3. Left) lateral view; right) crown view. B. Crown
of third precanine tooth on right side of lower jaw. PIN 2505/2. Left)
lateral view; right) lingual view.

16 POSTILLA

riG. 4. Notosyodon sp. PIN 2608. Fragment of lower jaw, dorsal view.

the right bank of the Zhaksy-Karagala River. Kazakhstan,
WS.S.R:

GEOLOGIC AGE AND GEOGRAPHIC RANGE: Upper Permian, Lower
Tatarian beds. Southern Cisurals region. (See also Geologic Data,
below ).

REMARKS: This species is named in honor of the geologist A. K.
Gusev.

OTHER MATERIAL

The lower jaw, specimen PIN 2608, (which is tentatively con-
sidered as part of the type species) is known only from a frag-
ment of the left dentary which has lost its incisors and canine
(fig. 4). The symphysial portion of the dentary is high and
thick. The rami of the mandible diverge at a small angle toward
the proximal end. The height of the jaw at the anterior end of

A NEW DINOCEPHALIAN 17

the tooth row is smaller than at the posterior end. The lower
edge of the mandible has no projection below the chin. The outer
side in the area of the symphysis has a network of grooves and
minute apertures for the superficial blood vessels and_ nerves.
Judging from the size of the alveoli, the first incisor was small,
the second larger and the last or fourth incisor about equal in
size to the first. The canine was somewhat larger than the third
incisor. The crowns of the teeth are damaged. The first tooth,
which is the smallest, has a very low and sharp crown and on the
iingual side is separated from the root by a slight cingulum. The
second tooth is twice the size of the first. The preserved lower
portion of its crown has a small cingulum. The third and fourth
teeth are again larger than the second and equal to each other in
size. The fifth has not been preserved. The sixth tooth, which is
the last in the series, is equal in size to the third. The preserved
lingual portion of its crown is separated from the root by a slight
cingulum and barely extends above the edge of the jaw. On the
lingual side of the tooth there is a small alveolus with a replacing
tooth whose serrated apex is inclined forward. All the teeth have
longitudinally oval sections.

TYPE LOCALITY AND GEOLOGIC AGE: Specimen PIN 2608 was
found on the right bank of the Donguz River, opposite the
Dolmatovskiy farm, in the Sol-Iletsk district of the Orenburg
oblast, U.S.S.R.

It was in a stratum of light brown shales which in the local stra-
tigraphic section are correlated by Ochev with the base of the
Malyy Kinel’ suite. In a recent summary by Ignat’yev (1962) of
the Tatarian stage and in earlier publications by Rachitskiy (1956,
1957) and other investigators, the Matyy Kinel’ suite is considered
parallel with the lower part of the Upper Tatarian substage or
the Northern Dvina horizon in the unified scheme adopted by the
Interdepartmental Stratigraphic Committee.

GEOLOGIC DATA

Specimens 2505/1, 2505/2, and 2505/3 were contained in a
sandstone lens broken open by old rock fractures. On the basis
of observations by A. K. Gusev and the present writer, who visited
the site in 1964, the following description of the fossiliferous
sandstone lens can be given. The sandstone is light gray in color,

18 POSTILLA

fine-grained aud polymictic in composition with a calcareous
cement, cross-bedded and made up of thin sandstone layers which
contain a fine shaly gravel. In the upper part are interbedded gray
shales with a multitude of impressions of stems and leaves of
large plants (?gingkos, calamites and conifers). The cross-bedded
inclined layers in the upper part of the lens contain frequent oval
and cylindrical stromatolite formations up to 6 cm across. The
fossil bones (part of the skull, and some teeth and vertebrae)
were found in the upper portion of the lens, in a clayey-calcareous
concretion. The upper part of the fossiliferous sandstone grades
along the trend into a greenish-brown cross-bedded sandstone.
The visible thickness of the fossiliferous lens is 6 m. The gray
fossiliferous sandstone is overlain by a half-meter-thick stratum
of reddish-brown sandstones and shales, separated by an inter-
layer (20-30 cm) of stromatolitic limestone bioherms.

The following stratigraphic subdivision (top to bottom) has been
adopted for the Permian deposits of the Aktyubinsk region by the
geologists of the University of Kazan:

Rodnikovo suite P.'*'2"4
Aktyubinsk suite Py'*t1**
Tuketsk suite Po@‘1%
Blagodarnoye suite P»** 4
Akshat suite P."t *s

In the local stratigraphic section, the lens containing the fossil
bones belongs, in Gusev’s opinion, to the upper portion of the
Lower Aktyubinsk subsuite, which on the basis of its bivalve
molluscs correlates fully with the strata of the P suite in the
Ciskazanian area — that is, with the strata which contain the
dinocephalian fauna of Isheyevo.

ACKNOWLEDGMENTS

J am deeply grateful to A. K. Gusev and V. G. Ochev for pro-
viding valuable data on the localities and for transmitting
the skeletal remains from which a new vertebrate genus has been
established. My thanks also to A. W. Crompton for his critical
review of the manuscript and to Jeanne E. Remington for editorial
help on the English version.

A NEW DINOCEPHALIAN iy

Preparation of the skull was done by M. F. Luk’yanova, the
drawings are by N. A. Yan’shinov and K. P. Meshkov and the
photographs by N. P. Finogenov.

The Russian manuscript was translated into English by Paul T.
Broneer, Senior Geologist, Scripta Technica, Inc., New York.

KEY TO ABBREVIATIONS

Bo — basioccipital

Bs — basisphenoid

cc — canal for carotid artery
cvi — vidian canal

Ep — epipterygoid

Exo — exoccipital

fj — jugular foramen

Fr — frontal

J — jugal

Pa — parietal

Po — postorbital

Poc — paroccipital (opisthotic )
Pof — postfrontal

Prf — prefrontal

Pro — prootic

Pt — pterygoid

Sq — squamosal

St — stapes
V. V3; —n. trigeminus
XII — aperiure for suborbital nerve

REFERENCES

Efremoy, I. A. and B. P. V’yushkov, 1955, Katalog mestonakhozhdeniy
permskikh i triasovykh nazemnykh pozvonochnykh na territorii SSSR
[A catalogue of Permian and Triassic vertebrate localities in the
territory of the USSR]: Trudy Paleontologicheskogo Instituta, t. 46,
p. 3-185.

Ignatyev, V. I., 1962, Tatarskiy yarus tsentral’nykh i vostochnykh oblastey
Russkoy platformy. Chast’ I [The Tatarian stage in the central and
eastern areas of the Russian platform. Part I]: Izdaniye Kazanskogo
Universiteta, p. 3-334.

Orlov, Yu. A., 1958, Khishchnyye deynotsefaly fauny Isheyeva [Predatory
dinocephalians in the Isheyevo fauna]: Trudy Paleontologicheskogo
Instituta, t. 72, p. 3-113.

20 POSTILLA

Rachitskiy, V. I., 1956, K voprosu ob ob’yéme 1 stratigrafit Tatarskogo
yarusa Kuybyshevsko-Chkalovskogo Zavolzh’ya [On the extent and
the stratigraphy of the Tatarian stage in the Kuybyshey-Chkalov
districts of the Transvolga region]: Vestnik Leningradskogo Universi-
teta, No. 18, p. 40-56.

1957, O sopostavlenii tatarskikh otlozheniy Russkoy_plat-
formy [Correlation of the Tatarian deposits on the Russian platform]:
Vestnik Leningradskogo Universiteta, No. 18, p. 61-67.

Tatarinov, L. P., 1965, Novyye dannyye ob ulemozavre [New data on
Ulemosaurus|: Paleontologicheskiy zhurnal, No. 2, p. 93-108.

Tchudinov, P. K., 1960, Verkhnepermskiye terapsidy yezhovskogo meston-

akhozhdeniya [Upper Permian therapsids of the Yezhov locality]:
Paleontologicheskiy zhurnal, No. 4, p. 81-94.

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