A DIAPSID REPTILE FROM THE PENNSYLVANIAN OF KANSAS ROBERT R. REISZ Department of Biology Unive rsity of Toronto ErindaIe Campus Mississauga, Ontario Canada L5L lC6 SPECIAL PUBLICATION OF THE MUSEUM OF NATURAL HISTORY. UNIVERSITY OF KANSAS NUMBER 7 1981 \ UNIVERSITY OF K ANSAS M US EUM OF N ATURAL HISTORY SPECIAL P UBUCATION No. 7 FEBRU ARY 18, 1981 A Diapsid Reptile From the Pennsylvanian of Kansas BY R OBERT R. R EISZ Depart ment of Biology University of T oronto Erindale Campus Mississauga, Ontario Canada LSL 1G6 U NIVERSITY OF KA NSAS LAWHENC E 1981 . UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Editor: Joseph T. Collins Editors for this issue: E. O. Wiley and Larry D. Martin Special Publication No.7 pp. 1.74; 26 figures 1 table Published February 18, 1981 COPYRIClITED 1981 BY MUSEUM OF NATURAL HISTORY UNIVERSITY OF' KA:-:SAS LAWRE l\'CE, KANSAS 66045 U.S.A. PnL,\'Y1ill BY UNIVERSITY OF KANSAS PruNnNC SERVIa:: LAWR£,. ... CE, KANSAS ISBN , 0-89338-011-3 This is the first of a series of Special Publications honoring the contributions of Dr. Theodore H. Eaton to the fi elds of vertebrate paleontology and zoology. The series will center around the Pennsylvanian fau na of eastern Kansas, and will include papers on fi shes, amphibians and reptiles, as befits the wide-rangi ng interests Dr. Eaton has shown in his research. E. O. W ILEY LAnny D. MARTU'; 15 J UNE 1980 LAWRENCE, KANSAS CONTENTS l NTRODUCTION .. _._. 1 ACKNOW LEDCE~rENTS _._ 2 DESCIUPTIV£ AND SYSTE~ ' I ATIC H ISTORY ._...•. ______. __ .......... __ .. ________ . ___.. 2 SYSTEMATIC DESCRIPTION __________________ _ 4 Family Petrolaoosauridae Peabody, 1952 .. 4 Genus PetrolocO$(lu ru$ Lane, 1945 _ .. ____ _ 4 Petrolacos(luru$ kllnsensis Lane, 1945 ___ 4 OSTEOLOGY _______________________________________ ._ 5 SICULL ____••••• _____________•.• _____ •... ______ •• 5 Dermal Bones of the Skull Hoof _ ... ______ ... _ .. 9 Dennal Bones of the P"latc ...... ____ .... ___._. __ . ___ ... ...... _ ._ ........... 21 Ossifications of the Palatoqundrnte Cartilage ... ... ___ ................................. _..... __ .. __ 23 Ossifications of the Braincase _____.. _ ...... ,_ ............ __ .. __ . _______ ... ". __ ._. __ .. __ 24 MA;o..'DmLE ___________•••• __ .••• _ ••.• ____•.•.• _ ....... ___ . __._ .. __.. ....... _____ ._.. 26 DE1'.'TmON •... _______. 27 SCLEROTIC PLATES _. __ •. _.. ___ ..• ___ . ______._ ... __••• _._ •.•. _ .. _ ... _._. __ .... ___ 28 VERTEBRATE _ __ _ ••• _. __ ._. ___ •__ •••.••. _ •• _._. ___ .••.•••. _ .•.•••• _ .••.. __ •__ ._._ •. _. ___• ____ • 28 Cervical Vertebrae .............. _.... __ ... __ ......... _............. _._ ........ _. ___ ._ ... _.. 29 Dorsal Vertebrae _.............. _..... ............................. __ .... _... __ ._._. __ .... ____ .______________ 33 Saccal Ve,tcbmc __ . ________ ._ .. _____________ .. ____ . ___ .. _____. ___ . _______________________ . ___ . 34 Caudal Vertebrae ._ ... __.. _ .. __ . ______. ___..... __ .. _ .... ____ .____ . __. __.. __ . 35 funs _ .. __. __..• _._. .________________ . ____ . ____ .._. ______________ ._____________________ ._ 36 PECTORAL GIRDLE _ •..••• ___ 38 PELVIC GInDLE _•. _. _ .•••. 40 LD!BS ___. ___............. _ •.. _._ ...... _... _._. ___ . __ ._ ..•......_. __._._._._ ..... _... _____........ 43 PHYLOGENETIC RELATIONS HIPS OF PETROl... ACOSAURUS ..... _ ......._. 54 HVT'OTIi ESES m- RELATIO!"SHIPS ............ ._..... 57 BASIC T AXA ....___ .............. _ ... _._............ _._ .._ ..... _... _________________ . ________ .. _._. ______ . _______ 58 S UAIlED DERIVED C IlAIlAcn:ns TESTIl\'C TIlE HYPOTHESIS m- RELATIO"SHlP B ETWEE~' Pelrafacosa urus ANI) Pofeat1Jyris ..... ____... __ ._ .. 61 SIIARED DEI\IVED CuAIt.... cn:Hs TESTING TIlE HYPOTHESIS O ~- RELATIOl\""SHIP BEnV.: ~: N Petrofacosaurus Al'D )'oullgina 62 Petroiacosaurus CO~lI)AREI) WITH Araeoscelis ___.. _ ...... __ _ 64 HEARI NG IN PETROLACOSAUR US Al~D OTHEH EARLY REPTILES _.... _. 66 CONCLUSIONS ._..... _..... ___. __._ ... _.. _._.. _...... _._... _......... _.. _................. _. __ ......__ ... _ 69 SUr..1 ~' IAHY ..._. ___ .... _ ..._ .••... _.. _._._._... _.. _ ..._ .......__ .• _•.. _ ....... _ ......... _._ ......•...... 7 1 LITERATURE CITED __ ... _. ________________________________________ . ____________ . _____________ _____ . _________________ . 72 • INTRODUCTION AU living reptiles can be grouped into Sauropsida, and therefore diapsids, could not four orders: Chelonia, RhynchocephaHa, be derived from captorhinomorphs. Squamata and Crocodilia. The latter three Romer (1966) rejected Watson's theory of can be associated with the largest assemblage the evolution of the car and reiterated his of fossil reptiles, collectively called diapsid belief that all true reptiles ean be derived reptiles. The dinpsid condition refers to the from primitive eaptorhinomorphs. In a re­ presence of two pairs of temporal openings view of early rcptilian evolution, Romer on the skull roof behind the orbits. This con­ ( 1967 ) suggested not only that the sauropsid­ dition has been retained in a primitive form theropsid dichotomy, insofar as it exists, has in crocodilians and in the sole living rhyncho­ little phylogenetic Sign ificance, but also that cephalinn Sp llenodon pllllctatum but has been the term Sauropsida has no systematic or modified in the squamates by the progressive phylogenetic meaning. Furthermore, he em­ loss of dermal bones in the temporal region. phasized that the diapsids may not belong to Diapsid reptiles have an evolutionary his­ a single phyletic unit. He argued that two tory long thought to extend only into the late discrcte diapsid groups should be recognized, Permian. The early evolution of this assem­ the Archosauria and the Lepidosauria. He blage is not well documented in the fossil proposed that the Lepidosauria (the squa­ record. Consequently. the origins and phy­ mates, rhynchocephalians and the ancestral letic relationships of member groups have eosuchians) on the one hand, and the Archo­ been subject to dispute. sauria ( the two dinosaur orders, pterosaurs, On several occasions, Watson (1951, 1954) crocodilians and the basic Triassic group, the reiterated his belief in Goodrich's concept of thecodonts) on the other, evolved separately a basic dichotomy among reptiles. According from the ancestral captorhinomorphs. It was to th is theory, one group called the Therop­ his suggestion that the milleretid skull pattern sida led to mammals and included the mam­ represents an intcnnediate slage between the mal-like reptile orders Pelycosauria and The­ ancestral captorhinomorphs and the lepido- rapsida. The other group, the Sauropsida, saurs. also called "true" reptiles, included the diap­ In 1967 Reig set forth, and later ( 1970) sid reptiles and the turtles (Chelonia). Wat­ elaborated, a radically different hypothesis for son argued for independent origins of the the origin of archosaurs. He proposed that Theropsida and Sauropsida from anthraco­ the ancestors of archosaurs should be sought saurian amphibians via some unknown inter­ among varanopsid pelycosaurs. ~· r ost of the mediate fonns. He based this conclusion on comparable features cilcd by Reig as indica­ his theory of the evolution of the car (Wat­ tive of phylogenetic relationships are, how­ son, 1953). He discounted the possibility of ever, primitive characteristics fo und in the captorhinomorphs having given rise to the ancestral captorhinomorphs (Romer, 1971). Sauropsida and, hence, to the diapsid rep­ Cow ( 1972 ), in his reconsideration of the tiles. He actually placed the Captorhino­ millcretids. contended that this group gave morpha among the Therapsida. In 1957 Wat­ rise directly to the Squamata. He felt on the son suggested that the diapsids evolved from other hand, that the Rhynchocephalia and the seymoriamorph anthracosaurs via the Millero­ Archosauria had an entirely independent ori­ sauria. gin. Vaughn (1955 ) also accepted the saurop­ The above workers have based their theo­ sid-theropsid dichotomy and felt that the ries of the origins and early evolution of the 1 2 SPECIAL PUBLICATION MUSEUM OF NATURAL HISTORY NO.7 diapsid reptiles mainly on the meager evi­ primiti ve captorhinornorphs and to more ad· dence provided by the known Permian coty­ vanced diapsid reptiles. The problem of hear­ losaurs and on the Upper Permian and Trias­ ing in l'elro!acosauniS and other early rephles sic diapsids. Thanks mainly to the labors of forms an integral part of this study. Robert L. Carroll and the late Frank E . Pea­ body, the problem of the origins and early A CKNO\VLEDGEMENTS evolution of diapsid reptiles can be rcconsid­ J am greatly indebted to T . H. Eaton of crecl. Carroll , duri ng a period of about ten the Un;\'ersity of Ka nsas Natural History Mu­ years, dc.'icribcd and reconsidered all of the seum, at whose suggestion this study was avail able Pennsylvanian and Lower Permian undertaken and who kindly allowed me to specimens of primitive captorhinomorphs. One borrow the l'etro/a coSllllrl/S specimens at his significant conclusion became evident: the disposal. I am particularly gratcful to Dr. and described members of this group confonn to Mrs. Eaton for courtes ies extended to me a single conscn'ativc morphological pattern d uring the time spent studying the Kansas and remained sufficientl y genernlized to indi­ collection. catc that primitive captorhinomorphs could Thanks are due also to R. L. Carroll whose be ancestral to most subsequent reptilian line­ wisc guidance, fr iendliness, and unrelenting