Title: Two New Pelycosaurs from the Lower Permian of Oklahoma
Author: Fox, Richard C.
Language: English
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  UNIVERSITY OF KANSAS PUBLICATIONS

  MUSEUM OF NATURAL HISTORY

  Volume 12, No. 6, pp. 297-307, 6 figs.
  May 21, 1962


  Two New Pelycosaurs from the Lower Permian
  of Oklahoma

  BY

  RICHARD C. FOX


  UNIVERSITY OF KANSAS
  LAWRENCE
  1962

  UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

  Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
  Theodore H. Eaton, Jr.


  Volume 12, No. 6, pp. 297-307, 6 figs.
  Published May 21, 1962


  UNIVERSITY OF KANSAS
  Lawrence, Kansas


  PRINTED BY
  JEAN M. NEIBARGER, STATE PRINTER
  TOPEKA, KANSAS
  1962

  29-3001



Two New Pelycosaurs from the Lower Permian of Oklahoma

BY

RICHARD C. FOX


In the course of examining material from fissure deposits of early
Permian age collected from a limestone quarry near Fort Sill, Oklahoma,
the author recovered several tooth-bearing fragments of small
pelycosaurs. The fragments were examined, compared with descriptions of
known kinds appearing in the literature, and determined to be new genera
within the Nitosauridae (Edaphosauria) and Sphenacodontidae
(Sphenacodontia).

Appreciation is expressed to Prof. Theodore H. Eaton, Jr., for
permission to examine the collections of the University of Kansas from
Fort Sill, and for the financial assistance furnished by his National
Science Foundation grant (NSF-G8624). I am grateful both to Prof. Eaton
and Mr. Dale L. Hoyt for their suggestions regarding this manuscript.
The accompanying figures have been drawn by the author.



Family NITOSAURIDAE

=Delorhynchus priscus= new genus and new species


(_delos_, Gr., evident; _rhynchos_, Gr., neuter, nostril; _priscus_, L.,
ancient. _Delorhynchus_ is masculine because of the ending that it
acquires when transliterated into Latin.)

_Type specimen._--Fragmentary left maxilla, bearing four teeth, KU
11117.

_Referred specimens._--Fragmentary right maxilla having four teeth, KU
11118; fragmentary left maxilla having four teeth, the most posterior of
which has been broken, KU 11119.

_Horizon and locality._--A fissure deposit in the Arbuckle limestone at
the Dolese Brothers Limestone Quarry, approximately six miles north of
Fort Sill, in sec. 31, T. 4 N, R. 11 W, Comanche County, Oklahoma. These
sediments are of early Permian age, possibly equivalent to the Arroyo
formation, Lower Clear Fork Group of Texas (Vaughn, 1958: 981).

_Diagnosis._--Small; marginal teeth conical, slender and recurved at
tips; marginal tooth-row without caniniform enlargement; narial opening
enlarged and bordered dorsally, posteriorly and ventrally by maxilla;
maxilla with foramen opening laterally at posteroventral corner of
naris.

_Description_ (based on 3 maxillary fragments, see Table 1).--Each of
the maxillary fragments bears four thecodont teeth. These are conical,
slender and sharply pointed; in their distal third they are slightly
recurved, laterally compressed, and have anterior and posterior
non-serrated cutting edges. In medial aspect at their bases, the teeth
are longitudinally striated. The bases of the teeth are circular in
cross-section and are slightly bulbous. There is no caniniform
enlargement of any of the teeth, the longest tooth of each fragment
being differently placed in the series of teeth and little longer than
the others. There is no swelling on either the internal or external
surfaces of the maxillae. The teeth are in a continuous series; no
diastema or maxillary step is evident.

[Illustration: FIGURES 1-3. _Delorhynchus priscus_, lower Permian, 6
miles north of Fort Sill, Comanche County, Oklahoma. All × 3.

FIG. 1. KU 11117 (type specimen), lateral view of left maxilla.
FIG. 2. KU 11118, lateral view of right maxilla.
FIG. 3. KU 11119, lateral view of left maxilla.]

The fragments have been broken along similar lines of fracture, and each
is approximately rhomboidal in shape. The maxilla encircles the
posterior border of the naris and extends dorsally above the naris to an
extent sufficient to indicate the probable exclusion of the lacrimal
bone from the narial border. At the posteroventral corner of the naris a
foramen opens onto the lateral surface of the maxilla. The opening is
the entrance to a canal that runs posteriorly above the tooth-row
throughout the length of each specimen. Beneath the naris the maxilla
extends as a broad tapering shelf, the ventral surface of which
articulates with the premaxilla. The narial rim is wide, but wider
ventrally than dorsally. The plane of the narial rim is oblique to the
lateral surface of the maxilla. The external surface of each fragment is
grooved and pitted. The ossification of each fragment appears to have
been complete.

TABLE 1.--DIMENSIONS, IN MILLIMETERS, OF THREE MAXILLARY FRAGMENTS OF
DELORHYNCHUS PRISCUS

Key:

A. Anterior height of fragment
B. Posterior height of fragment
C. Length of fragment at tooth-row
D. Dorsal length of fragment
E. Mean length of teeth
F. Anterior width of naris

============================================================
CATALOGUE NUMBER |  A.  |  B.  |  C.  |  D.  |  E.  |  F.
AND MEAN         |      |      |      |      |      |
-----------------+------+------+------+------+------+------
KU 11117         | 6.0  |  8.0 |  6.0 |  8.0 |  3.0 |  3.0
KU 11118         | 6.0  |  6.0 |  9.0 |  8.0 |  2.0 |  3.0
KU 11119         | 6.6  |  8.0 | 10.0 | 11.0 |   ?  |  4.6
-----------------+------+------+------+------+------+------
Mean             | 6.2  |  7.3 |  8.3 |  9.0 |  2.5 |  4.5
-----------------+------+------+------+------+------+------

_Discussion._--The Nitosauridae are small primitive edaphosaurs with a
moderately elongate face, sharp subisodont teeth, little development of
canines and few specializations. The jaw is of a primitive type and
articulates on a level with the tooth-row. The palatal dentition is
primitive (Romer, 1956:280). The nitosaurids are thought to be related
to the later Caseidae, and the most obvious structural similarities are
found in the postcranial skeleton (Vaughn, 1958:989). Cranial
resemblances between the families are fewer, but nevertheless indicate
that a nitosaurid-caseid relationship exists.

Vaughn (1958) described a small pelycosaur, _Colobomycter pholeter_
(Eothyrididae, Ophiacodontia) that structurally resembles the Caseidae.
This individual also was obtained from the Fort Sill locality. In
Vaughn's opinion the features of _Colobomycter_ indicate a close
relationship between eothyridids and caseids and the possibility that
the caseids may well have been of eothyridid rather than nitosaurid
derivation.

In view of this historical uncertainty of the relationships between the
Nitosauridae, the Eothyrididae and the Caseidae, it is well to consider
how the maxillary fragments described above differ from and resemble
representatives of each of these three families as reported in the
literature.

_Delorhynchus_ resembles _Colobomycter_ in size. The mean
extra-maxillary length of the undamaged teeth of the three fragments is
2.5 mm., equal to that reported by Vaughn (1958:985) for teeth about
midway in the postcanine series of _Colobomycter_. None of the teeth of
_Delorhynchus_ extends beyond the maxillary rim as far as does the
canine of _Colobomycter_ (3.5 mm.).

The teeth in both genera are conical and sharply pointed. The naris in
each is enlarged, and the lacrimal is excluded from the narial margin in
each (by inference in _Delorhynchus_.)

The differences between the maxillae of _Colobomycter_ and
_Delorhynchus_ are most striking in the lack of canines in the latter
and the correlated absence of modifications of the maxillary for support
of canines. Additionally, _Delorhynchus_ bears an infraorbital canal in
contrast to the groove in similar position in _Colobomycter_. The
recurvature of the four teeth present in the fragments of _Delorhynchus_
differs from that in the teeth of _Colobomycter_ in which only the
canine and precanine are recurved. Vaughn implies that anterior and
posterior cutting edges extend the length of the teeth in
_Colobomycter_; these are restricted to the distal third of the teeth in
_Delorhynchus_. The external surfaces of the maxillae of _Delorhynchus_
are pitted and ridged; Vaughn was unable to discern sculpturing of the
corresponding surfaces in _Colobomycter_.

_Delorhynchus_ resembles the nitosaurids in size, the shape and
sharpness of the teeth, their recurvature and the slight enlargement of
their bases, the exclusion of the lacrimal bone from the narial margin
(in _Mycterosaurus_) and the apparent lack of a special canine pair of
teeth. Resemblances to the caseids are to be noted in the enlargement of
the naris (4.5 mm. in height as opposed to 1.7 mm. in _Colobomycter_),
lack of development of canines, presence of an infraorbital canal (in
_Cotylorhynchus_) and absence of many replacement gaps in the marginal
row of teeth.

The absence of caniniform enlargement and the extension of the maxilla
dorsad of the naris exclude _Delorhynchus_ from the Eothyrididae
(Ophiacodontia) but are no bar to its inclusion in the Nitosauridae
(Edaphosauria). The marginal teeth of _Delorhynchus_ are simple and
primitive, being much like those of the nitosaurids that are described
in the literature.

The large narial opening and its posterior, dorsal and ventral enclosure
by the maxilla, the infraorbital canal, and the sculptured external
surfaces of the maxillary fragments indicate that _Delorhynchus_, in
these features at least, is close to achieving the caseid grade.



Family SPHENACODONTIDAE

=Thrausmosaurus serratidens= new genus and new species


(_Thrausmosaurus_ is formed from the neuter Greek noun, _thrausma_,
meaning fragment, and the masculine Greek noun, _sauros_, meaning
reptile. The specific name, _serratidens_, is formed from the Latin
_serratus_, meaning serrate, and the masculine Latin noun, _dens_,
meaning tooth. The specific name is used as a substantive in apposition
with the generic name.)

_Type specimen._--Fragmentary left dentary, bearing five teeth, the
most posterior of which is broken at the base, KU 11120.

_Referred specimens._--Fragmentary ?left maxilla, having two teeth, KU
11121; fragmentary left dentary having two teeth, KU 11122.

_Horizon and locality._--From the early Permian fissure deposits in the
Arbuckle limestone of the Dolese Brothers Limestone Quarry,
approximately 6 miles north of Fort Sill, in sec. 31, T. 4N, R. 11 W,
Comanche County, Oklahoma.

_Diagnosis._--Small; teeth thecodont, compressed laterally, recurved
distally, and bearing anterior and posterior cutting edges; anterior
serrations limited to recurved portions of teeth, posterior serrations
extending nearly entire length of teeth; lateral compression of teeth
more pronounced medially than laterally; bases of teeth expanded.

_Description._--The type specimen is 16 mm. long. It bears five teeth
that are implanted in a straight row. Empty sockets are present between
the first and second teeth, and the third and fourth teeth. The first
tooth is 3.0 mm. long, the middle two are each 2.5 mm. long, and the
fourth tooth is 2.0 mm. long. The fifth tooth is broken off at its base.

The empty sockets are large. The mouth of each is circular and
approximately 2.0 mm. in diameter. Both sockets are 1.25 mm. deep. The
bases of the teeth are expanded to fill the sockets, although the blades
of the teeth arise from only the lateral portions of the bases. The edge
of the dentary rises above the bases of the teeth medially, thereby
producing a small depression at the junction of each base with the
dentary bone.

The lateral compression of the teeth is pronounced but asymmetrical, in
that the lateral surface of each blade is more convex than the medial
surface.

[Illustration: FIGURES 4-6. _Thrausmosaurus serratidens_, lower Permian,
6 miles north of Fort Sill, Comanche County, Oklahoma. All × 3.

FIG. 4. KU 11120 (type specimen), lateral view of left dentary.
FIG. 5. KU 11121, lateral view of ?left maxilla.
FIG. 6. KU 11122, lateral view of left dentary.]

The recurvature of the anterior cutting edges is much more severe than
that of the posterior edges, but the recurvature of both is limited to
the distal half of each tooth.

The serrations of the cutting edges are not visible to the naked eye and
are limited on the anterior edges of the teeth to those portions of the
blades that are recurved. The posterior serrations extend nearly to the
junction of the blade of each tooth with its base. The serrations tend
to be more nearly crenulate than cuspidate.

A portion of the lateral wall of the dentary surrounding the Meckelian
canal is present. The external surface of the wall is gently convex and
smooth, without sculpturing. The internal surfaces of the canal are
unmarked either by muscle scars or foramina.

The fragment is a piece from the posterior portion of the dentary, since
the decrease in height from the first tooth to the fourth is pronounced.

KU 11122, a fragment of the left dentary bearing two teeth, is 7.5 mm.
long. The anterior tooth is 3.0 mm. long; the posterior tooth is 3.5 mm.
long. The shape of the teeth and their implantation conform to the
description of the type specimen. The lateral surface of the fragment is
smooth and gently convex. What little is present of the surface
bordering the Meckelian canal is unmarked.

The ?maxillary fragment bears two teeth which are 3.0 mm. long, and
which conform in their characters to the type. The lateral, medial and
ventral surfaces of the fragment have been sheared off, so that an exact
identification of the bone is impossible. Presumably the fragment is too
deep dorsoventrally to be a piece of the dentary, and no sign of the
Meckelian canal is present.

_Discussion._--The implantation, lateral compression, recurvature and
cutting edges of the teeth borne by these fragments make clear their
sphenacodontid nature. The characters of the fragments are too few to
determine subfamilial affinities, however. That the fragments are the
remains of adult animals can be only surmised from the lack of bones or
teeth of large pelycosaurs in the extensive collections of the
University of Kansas from the Fort Sill locality.

If _Thrausmosaurus_ is, in fact, adult, the genus is an unusually small
sphenacodontid, and of significance both on that account and because of
the resemblance of the teeth presently known to those of its far larger
relatives.

_The Fort Sill Locality._--Peabody (1961) suggested that the fissures of
Fort Sill had been used as dens by predatory animals in the early
Permian, and that the unusually abundant bones in the fissures were the
remains of animals eaten there by these occupants. Evidence now known to
me affords an alternative explanation that is presented here as a
preliminary to a more complete study of the fauna and paleoecology of
these deposits currently being undertaken.

The suggestion that the skeletal material found in the fissures is the
remnant of the prey of other animals is questionable because of:

     1. The absence of tooth marks on the fossils.

     2. The recovery from the matrix of skulls and portions of
     articulated skeletons that are undamaged or damaged only by
     pressure after burial.

     3. The rarity in the deposits of animals of larger body size than
     _Captorhinus_, the exceptions being a few limb fragments and skull
     fragments of labyrinthodont or pelycosaurian nature.

     4. The absence of coprolites in the matrix.

If the fissures were the dens of predators, at least some and probably
many of the bones would show tooth marks. A predator feeding on other
animals would be expected to leave some evidence of its habits on the
bones of its prey. No such evidence is known to me, either from my own
examination of several thousand bones or from the reports in the
literature by others who have studied aspects of the early Permian fauna
of Fort Sill.

If the predators were larger than _Captorhinus_ and occupied the
fissures for a long enough time to account for the accumulation of the
tremendous numbers of individuals that are represented, a considerable
amount of the skeletal material of the larger animals would be present
in the fissure deposits. Even if for some reason the predators died in
areas other than within the fissures, thereby accounting for the absence
of large bones, coprolites should appear in the deposits if, in fact,
the fissures were feeding places. In view of the nearly undamaged
condition of many of the bones recovered from the fissures, it is
reasonable to expect that fecal material would be preserved.

The character of the matrix of the deposits varies from a homogeneous
clay to clay interrupted by layers of soft, limey, conglomeratic rock,
to a hard, well-cemented, calcareous conglomerate. In general the bone
in each kind of matrix is colored characteristically and exhibits a
characteristic degree of wear. The bones entrapped in the homogeneous
clay are relatively few, black, usually disarticulated, little worn and
not unduly fragmented; consequently the discovery of undamaged limb
bones, for example, from this kind of matrix is not unusual. The bones
found in the stratified portion of the matrix are more numerous within
the layers of conglomerate than between. The bones are black, brown or
white, highly fragmented and waterworn to a variable degree. The
fragments recovered from the hard, calcareous matrix are numerous, range
in color from white through various shades of brown, to black, are
highly fragmented, and are usually worn by water.

These categories for bone and matrix, however, are not mutually
exclusive, since bones of any of these colors and exhibiting any degree
of wear and fragmentation are found in any of the kinds of matrix
described above. That water was the agent of wear is suggested by the
highly polished appearance of the worn bones and pebbles that are found
in the matrix.

The variability of the matrix and of the color and condition of the
bones indicates that the agencies of burial and fossilization differed
from time to time and that the agency of transportation of the bones
from the site of burial to the fissures was running water. One can
easily visualize a stream coursing the early Permian landscape that was
subject to periodic flooding and droughts. Along the banks of the stream
and in its pools lived a variety of microsaurs, captorhinids, small
labyrinthodonts and small pelycosaurs. Some of the animals, after they
died, were either buried near the site of their death or were swept
along and buried in sediments further downstream. Burial was for a
length of time sufficient to impart a color to the bones characteristic
of the site in which they were buried. Later floods reexposed the sites
of burial, picked up the bones and carried them to the openings into the
fissures. Presumably, too, a proportion of the bones was carried to the
fissures without previous burial.

The differences in wear exhibited by different bones within the same
block of matrix is attributable to differences in distance that the
bones were transported before final deposition. The final sites of
deposition, the fissures, were inundated occasionally by floods alone,
or because of changes in location of the channel of the stream at the
time of flooding. The periodicity of deposition of the sediments within
portions of the fissures is indicated by the stratification of the bone
conglomerate mentioned earlier.

In summary, it seems that there is little or no evidence beyond the
numbers of bones involved to support the hypothesis that the
concentration of bones in the fissures of Fort Sill represents the
remains of food of predators, and that the fissures were used as dens by
their predatory occupants. On the contrary, the evidence indicates that
the deposition of the bones in the fissures was secondary and that the
agency of transportation, deposition and accumulation of the bones was
an early Permian stream characterized by periodic flooding.



LITERATURE CITED


PEABODY, F. E.
   1961. Annual growth zones in living and fossil
         vertebrates. Jour. Morph. 108 (1): 11-62, 69 figs., January.

ROMER, A. S.
   1956. Osteology of the reptiles. The University of Chicago
         Press, Chicago, xxi + 772 pp., 248 figs.

ROMER, A. S., and PRICE, L. I.
   1940. Review of the Pelycosauria. Geol.
         Soc. America, Spec. Pap., 28: x + 538 pp., 71 figs., 46 pls.,
         8 tables, December 6.

VAUGHN, P. P.
   1958. On a new pelycosaur from the lower Permian of
         Oklahoma, and the origin of the family Caseidae. Jour. Paleont.,
         32:981-991, 1 fig., September.

_Transmitted March 15, 1962._





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