National Library Bibliothèque nationale 1+1 01 Canada du Canada Acquisitions and Direction des acquisitions et Bibliographie services Branch des services bibliographiques 39S Wellington Slrecl 395. rue Wellington Ottawa.Onlano Onaw3 (Onl<1OO) K1AON4 K1AON4

NOTICE AVIS

The quality of this microform is La qualité de cette microforme heavily dependent upon the dépend grandement de la qualité quality of the original thesis de la thèse soumise au submitted for microfilming. microfilmage. Nous avons tout Every effort has been made to fait pour assurer une qualité ensure the highest quality of supérieure de reproduction. reproduction possible.

If pages are missing, contact the S'il manque des pages, veuillez university which granted the communiquer avec l'université degree. qui a conféré le grade.

Sorne pages may have indistinct La qualité d'impression de print especially if the original certaines pages peut laisser à pages were typad with a poor désirer, surtout si les pages typewriter ribbon or if the ·originalos ont été university sent us an inferior dactylographiées à l'aide d'un photocopy. ruban usé ou si l'université nous a fait parvenir une photocopie de qualité inférieure.

Reproduction in full or in part of La reproduction, même partielle, this microform is governed by de cette microforme est soumise the Canadian Copyright Act, à la Loi canadienne sur le droit R.S.C. 1970, c. C-30, and d'auteur, SRC 1970, c. C·30, et subsequent amendments. ses amendements subséquents.

Canada • THE PROCOLOPHONIDBARASAURUS AND THE PHYLOGENY OF EARLYAMNIOTES

DIRK MECKERT BIOLOGY DEPARTMENT McGILL UNIVERSITY, MONTREAL QUEBEC,CANADA

A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

• © DIRK MECKERT, 1995. National Ubra:y Bibliothèque nationale 1+1 of Canada du Canada Acquisitions and Direction des acquisitions et Bibliographie Services Branch des services bibliographiques 395 Wellington Street 395. rue Wellington Ottawa, Qnlario Ottawa (Ontario) K1A QN4 K1A QN4

The author has granted an L'auteur a accordé une licence irrevocable non·exclusive licence irrévocable et non exclusive allowing the National Library of permettant à la Bibliothèque Canada to reproduce, loan, nationale du Canada de distribute or sell copies of reproduire, prêter, distribuer ou hisjher thesis by any means and vendre des copies de sa thèse in any form or format, making de quelque manière et sous this thesis available to interested quelque forme que ce soit pour persons. mettre des exemplaires de cette thèse à la disposition des personnes intéressées.

The author retains ownership of L'auteur conserve la propriété du the copyright in hisjher thesis, droit d'auteur qui protège sa Neither the thesis nor substantial thèse. Ni la thèse ni des extraits extracts from it may be printed or substantiels de celle-ci ne otherwise reproduced without doivent être imprimés ou hisjher permission. autrement reproduits sans son autorisation.

ISBN 0-612-12435-5

Canada • PREFACE This thesis is centered around an anatomicai study of the osteoiogy of Barasaurus besairiei, a procoiophonoid from the Upper Permian of Madagascar. Barasaurus had been described in a preiiminary fashion in 191)5 hy Piveteau. This study is hased on the original material as weil as a large number of new specimens. 1 examined ail the specimens. My description is ail original and presents for the l'irst time a complete picture of the anatomy of Barasaurus in ail aspects. With this wealth in information 1 reconstructed the skull as weil as the postcranial skeleton. This provided me with a sound hasis for further study and comparison with other genera. My detailed description ofB(zrasaurus permitted the compilation of a data matrix that 1 used in a large scale analysis of amniote relationships. My analysis led to a reassessment of the phylogeny of sorne major lineages of early amniotes. 1 demonstrated Amniota to he a mOl1ophyletic group. Sauropsida, which can he divided into Palaeosauropsida and Eusauropsida, was introduced to replace Reptilia. Turtles were found to he the sister-group of pareiasaurs, refuting the hypothesis of procolophonids (Laurin & Reisz 1995) as the sister-group. Although the pareiasaur-turtle sister-group relationship was proposed by Lee (1995) my result differs significantly. This difference is due to my focus on procolophonoids rather than pareiasaurs. Although 1 made use of the literature to ohtain background data, ail conclusions drawn are original unless explicitly stated otherwise. • 1 • ACKNOWLEDGME."ITS This study owes its existence to the su?ervision of Dr. Robert L. Carroll who critically read and edited several drnfts of this manuscript. 1 am greatly indebted for his interest, encouragement, suggestions and his unlimited patiel1ce. Furthermore it is a pleasure to acknowledge Dr. R. Bolmes, Dr. D. Dilkes, Dr. Kebang Lin, Dr. J. Boy (Mainz, Germanyl, Dr. D. Goujet (Paris, France), Dr. P.Y. Gagnier (Paris, France), Victor Reynoso and Ed Hitchcock for stimulating discussion concerning the origin and interrelationships of early amniotps and turtles. 1 have particularly benefitted l'rom Victor Reynoso's and Dr. David Dilkes' knowledge of PAUP and McClade software packages. My thanks are also due to Pamela Gaskill for drawing most of the specimens; Dr. R. Reisz (University of Toronto) for letting me study material in his lab; Dr. E.S. Gaffney for lending a specimen of Owenetta; Dr. M. S. Lee for providing manuscripts of his work and vital information about pareiasaurs. In addition, 1 have received considerable assistance trom Ingrid Birker and my "accountant" Marie La Ricca, both part of the staff at the Redpath Museum. Finally 1 would like to thank Mark Bendit, Hans Feve Beckmann and Thomas Lindenbaum for being friends; my wife Barbara Kelly for the French translation of the abstract, editing, accepting my many moods and taking care of our sons Caddaric (who still believes 1 am playing "Prince of Persia" ail night) and Sheridan ( who is most intrigued by my screensaver • II programJ. • This research was made possible by financial support from the Natural Sciences and Engineering Research Council of Canada Grants ta Dr. R. L. CarroI!.

• III • TABLE OF CONTENTS Preface...... 1 Acknowledgments...... II List of Illustrations...... VI List of Tables...... VII Abstract...... VIII Résumé...... X

Introduction...... 1 History of the Classification of "Reptiles" 3

Materials and Methods...... 20 List of specimens...... 23 Barasaurus besairiei...... 25 8ystematic Palaeontology...... 25 Description...... 27 8kull...... 27 Braincase 40 Vertebrae...... 41 Ribs...... 51 Pectoral girdle 53 Pelvic girdle...... 71 Analysis...... 84 Results...... 102 Discussion...... 120 Conclusions...... 128 References...... 129 • IV Appendix 1: List of characters...... 141 • Appendix II: Data matrix.. 144 Appendix III: Shortest tree and apomorphy list...... 145 Appendix IV: List of abbreviations...... 148

• V • LIST OF ILLUSTRATIONS Figure Page 1 Skeletal reconstructions of early amniotes...... 5 2 Temporal distribution of early amniotes...... 14 3 Cladograms illustrating possible sister-group relationships of turtles...... 17 4 Map of Madagascar and map of the Ranohira region showing the distribution of the Lower Sakamena Formation...... 22 5 Barasaurus besairiei, composite reconstruction of the entire skeleton...... 26 6 Reconstructed skulls of owenettids, dorsal view...... 28 7 Reconstructed skulls of owenettids, lateral view...... 29 8 Reconstructed skulls of owenettids, ventral view...... 30 9 Reconstructed skulls of owenettids, occipital view..... 31 10 Barasaurus besairiei, Holotype specimen P 1, dorsal. 34 11 Barasaurus besairiei, Holotype specimen P 1, ventral 35 12 Barasaurus besairiei, specimen P 8, dorsal view...... 36 13 Barasaurus besairiei, specimen P 6, ventral view...... 37 14 Barasaurus besairiei, specimen P 9, dorsal view...... 38 15 The atlas-axis complex ofBarasaurus besairiei, in comparison with the atlas-axis complex in other tetrapods...... 42 16 Barasaurus besairiei, specimen P 7, dorsal view...... 45 17 Barasaurus besairiei, specimen CM 47517, dorsal view 46 • VI 18 BaraSallrUS besairiei, specimen CM 47518, dorsal view 49 tg BarasaurllS besairiei, specimen CM 47518,ventral view 50

• ~ Barasaurus besairiei, specimen CM 47512, dorsal view 54 21 Barasaurus besairiei, specimen CM 47512,ventral view 55 22 Barasaurus besairiei, specimen CM 47514,ventral view 58 Z3 Barasaurus besairiei, specimen PlO, ventral view..... 59 24 Barasaurus besairiei, specimen P 5, dorsal view...... 62

25 Barasallrus besairiei, specimen P 3, dorsaL...... 70

26 Barasaurus besairiei, reconstruction of manus and pes 81 27 Skulls of batrachosaurs in dorsal view...... 86

28 Skulls of batrachosaurs in lateral view...... 88 29 Skulls of batrachosaurs in ventral view...... 90 30 Skulls of batrachosaurs in occipital view...... 92 31 Amniote phylogeny used in this study...... 104

LIST OF TABLES Table Page 1 Simplified outlines of classifications of reptiles, after Zittel (1890), Osborn (1903), Watson (1917) and Williston (1925)...... 7 2 Simplified outlines ofclassifications of reptiles, aftel' OIson (1947) and Romer (1956)...... 12

• VII • AB8TRACT The procolophonid amniote Barasaurus /:'csairici Pivl'teau 1955 is l\dly described and restored for the first time with emphasis placed on the postcranial skeleton, which is only poorly known in most of the other taxa of early amniotes. The study focuses on testing a hypothesis of relationships, namely whether procolophonids are the sister-group of Testudines as proposed by Reisz & Laurin (1991). The description provides a sound basis for a new phylogenetic study of early amniotes. Using 13 taxa and 68 characters, the analysis indicates that synapsids are the sister-group of ail other known amniotes, named Sauropsida. The Sauropsida are divided into Palaeosauropsida and Eusauropsida. Palaeosauropsida comprise Millerettidae as the sister-group of Procolophoniformes. The Procolophoniformes contain Procolophonia and Testudinomorpha as sister-groups. Testudines are the sistt'r-group of Pareiasauria within the Testudinomorpha. Within Procolophonia, the family Owenettidae, including Barasaurus and Owenetta, is the sister-group of the family Procolophonidae. Eusauropsida include captorhinids, Palaeothyris and diapsids. AlI of the three major amniote clades have extant taxa: Synapsida ­ m:lI:lmals; Palaeosauropsida - turtles; Eusauropsida - diapsids including birds. The terms "Reptilia" and "Parareptilia" are omitted from systematics. Parareptilia for a misleading name and Reptilia in general because ofits historical burden. • VIII The new tree IS strong ln supporting Proeolophonia and • Testudinomorpha (sister-group of Pareiasauria and Testudines). lt is not very firm in establishing eusauropsids and diadeetomorphs beeause they were outside the main foeus of the anaiysis. Mesosauria is the only group of Palaeozoie amniotes nût included in this study.

• IX RÉsUMÉ • Le procolophonid amniote Barasallrus bcsairici Pivetenu (1955) l'st complètement décrit et se rétablit pour la première fois. Le squelette post­ craniaux, qui est peu connu dans la plupartdes autres taxa d'amniotes anciens, est souligné ici. L'étude est centré sur une analysis de l' hypothèse des lien de parentages procolophonids, a savoir s'ils sont les soeurs des Testudines (Reisz & Laurin 1991). La déscription fournit une base solide pour une nouvelle étude phylogénétique des amniotes anciens. En utilisant 13 taxa et 68 caractères, l'analyse indiques que les synapsids sont soeurs de tout les amniotes connus. Elles sont appelés Sauropsida. Le Sauropsida se divise en Paleosauropsida et Eusauropsida. Le Palaeosuuropsida comprend le Millerettidae qui sont soeurs des PI·ocoluphoniformes. Procolophoniformes a Procolophonia et Testudinomorpha comme soeurs. Testudines sont la soeur de Pareiasaura a l'intérieur de Testudinomorpha. A l'intérieur de Procolophonia , la famille d' Owenettidae, compris Barasaurus et Owenetta, est la soeur de la Procolophonidae. Eusauropsida inclus captorhinids, Palaeathyris et diapsids. Tous les trois amniotes clades proéminentes ont taxa existants: Synapsida- les mammifères; Palaeosauropsida- les tortues; Eusauropsida- diapsids (inclus les oiseaux). Les termes "Reptilia" et "Parareptilia" sont omis de les systématiques. Parareptilia est un nom trompeur. Reptilia en géneral comporte un fardeau historique.

• x Le nouveau arbre soutient bien Procolophonia et Testudinomorpha qui • sont soeurs de Pareiasauria et Testudines. Cela établit fermement eusauropsids et diadectomorphs parce qu'ils sont a l'extérieur du foyer principal de cette analyse. Mesosauria est le seul groupe des palaeozoic amniotes qui n'est pas inclus dans cette étude.

• XI • INTRODUCTION During the past 30 years, there has been a revolution in the theOl'y and practice of classification as a result of the work of Hennig (1951, 1966) and his foIlowers. Hennig's system of phylogenetic systematics can be applied to aIl organisms, fossil and living, but has had a particularly strong influence on the study offossil vertebrates. One of the most frequently cited examples of the difference between phylogenetic systematics and earlier methods of systematics is the classification of the group commonly termed reptiles. The group Reptilia dates from a time before evolution was even considered as a scientific theory and for most biologists, reptiles are still classified as they were before the time of Darwin, concentrating on differences from living birds and mammals with little or no consideration of their fossil history or more general relationships. A prime example for this pre-evolutionary classification where a group has not changed its position in centuries is one of the major reptiliomorph groups, the turtles. As customarily used, the Reptilia not only include the extant turtles, crocodiles, !izards and snakes but also the ancestors of birds and mammals. Furthermore the transition from non-amniote to amniote, the amphibian-reptile transition, is still only poorly understood. This means that the animaIs termed "reptiles" have to be redefined in terms of both their ancestry and relationships to other living amniotes. The turtles may be one of the earliest groups to have evolved from the cornmon ancestry of modern reptiles, birds, and mammals, and are very important to the • classification of aIl these amniote lineages. 1 If there are problems in classifying reptiles in the modern fauna, these • pro1JIems are magnified several fold when looked at from the palaeontological viewpoint. There is a considerable and significant record of fossil vertebrates in the Palaeozoic. It poses no problem to put most of them in a broad framework of relationships of major groups that eventually lead to the modern fauna. However, looked at in more detail, many of the answers do not seem to be very convincing and weIl founded. In addition to taxa that can be allied with living amniotes, there are several enigmatic groups that show no resemblance to any of the modern forms and whose affinities remain unclear. These groups include the mesosaurs, the millerosaurs, the pareiasaurs, and procolophonids. It is this enigmatic assemblage of early amniotes termed Parareptilia which has been repeatedly postulated to be close to the ancestry of turtles. Thus they are a key to the broader problem of the classification of aIl amniotes and they will be intensively discussed here This thesis focuses on the origin of amniotes! reptiles, the relationships of turtles with other amniotes and more specifie, the relationship to sorne of the so called "Parareptilia".

• 2 • mSTORY OF THE CLASSIFICATION OF "REIYfILES" It seems to be in the nature of humans that they try tu describe and categorize anything they see, be it living or dead. Carl von Linné introduced binary nomenclature into the biological sciences in the eighteenth century. This system is still in use today. At the time when this system was introduced it was commonly accepted that Gad created the earth and aIl living things. Problems of relationships were unknown because everything was created individuaIly to inhabit a certain place on earth. In Linné's time anything that crawled on the ground and had a "slimy" appearance was considered bad, and usuaIly allied with the underworld. It is not surprising that Linné (1758) did not spend much time in distinguishing these creatures from one another but united amphibians and reptiles in one group, in the same manner used by Ray (1698) in his Svnopsis Methodica Animalium Quadrupedum et Serpentin;i, based on the simple structure of the heart. The actual c:lass Reptilia was erected by Laurenti in 1768. Nevertheless it was not until 1816 before Blainville proposed a division between the "Batrachians" and the "Sauropsides". This division was confirmed a few years later by Merrem (1820). Around that time this classification did not pose much of a problem since aIl the living forms cciuld be easily put into a few major groups, lizards, snakes, crocodiles, and turtles, based on skeletal and physiological characters. By the early nineteenth century the first fossil species had been , described, often as "curiosities", but with thenroper Linnean procedure of naming. By the middle of the last century had the number of fossil species increased dramatically and it became apparent that there were many • among them that did not show close affinities to any living taxon. Since 3 palaeontologists are iimited to studying the skeietai morphoiogy of an organism, it olten proves difficuit to give definite answers. The concept of a • reptiiian versus an amphibian ievei of organization was originally based on modern forms before the idea of evoiution. It is not difficuit to distinguish modern forms on the basis of the presence or absence of gills for exampie. What works on extant forms does not necessarily apply to fossiis. Therefore, it is no surprise that large temnospondyl amphibians were once mistaken for reptiles because of their general crocodilomorph appearance (von Meyer 1858). This illustrates very weIl the problem that scientists had to deal with up to the beginning of this century. Evolution was not discussed until the middle of last century and was not generally accepted until decades later; species were based on being created differently and not on being related in a phylogenetic way. One should not forget thnt well into this century evolutionary strategies and predetermination played a large role in evolutionary theory. Laws that are intrinsic factors guiding processes, formulated as Cope's or Haeckel's law nt the turn of the century, can still he found in the work of Hennig (1966) when he talks about the "living universe following it's own innermost laws in it's travel through time". Owen (1860) was one of the first to attempt a classification of reptiles including both recent and extinct groups. He correctly classified many fossils with modern groups, and erected six extinct orders of reptiles -plesiosaurs, ichthyosaurs, thecodonts, dinosaurs, pterosaurs- all of which are still recognized today. The sixth group he termed Anomodontia, which included mammal-like reptiles and some forms that could not he • classified anywhere else. 4 •

Fig. 1. Skeletal reconstructions of early amniotes, drawn not to scnle. A:Hylonomus, the earliest known amniote after Carroll (1982); B: Haptodus, a synapsid after Currie (1979); C: Eocaptorhinus after Heaton & Reisz (1980); D: Milleretta after Gow (1972); E: Pareiasaurus after Gregory (1946).

• 5 •

• In 1880, Cope described a fragmented skull of Diadcctcs. a large bodied • reptiliomorph animal with close affinities to the reptiles. He misinterpreted a missing basioccipital in one of the specimen. Based on this error he erected a new group: the Cotylosauria. In later publications (1889, 1896 a,b), he redefined this group putting the emphasis on the "roofed character" of the skull, meaning the lack of fenestration. Later the term anapsid has come to be used as ifit meant stem as in stem-reptile The next important attempt at a classification of reptiles including fossil forms was undertaken by Zittel (1890) in his "Handbuch der Palaeontologie". He placed reptiles in nine differcnt orders (table 1). Like Owen, he put turtles in a separate order but more primitive forms were placed into several different orders. This is partly due to the recognition of Sphenodon as a primitive basal reptile for which the order Rhynchocephalia was erected including ail animais that were believed to be close to the ancestry of modern reptiles. In contrast to the work of Owen the emphasis here is not on the "roofed nature" of the primitive reptilian skull, but on the "two arched" character of the Sphenodon skull. This included the suborder Progancsauria in which are placed diverse reptiles like pelycosaurs (mammal-like) and Mesosaurus, an enigmatic aquatic reptile from the Permian. Most of the other primitive reptilian groups were included in the Theromorpha. The latter include the suborders Anomodontia - including sorne mammal-like reptiles, Placodontia • a Triassic aquatic group, and Pareiasauria - where we not only find pareiasaurs but also Procolophon and Diadectes; based on tooth morphology, distribution ofteeth on the palate and stout limbs. In figure 1 • sorne of these early amniotes are pictured. 6 •

Table 1. Simplified outlines of classifications of reptiles, to show distribution of palaeosauropsids and diadectomorphs; the problematic mesosaurs are highlighted by italics. Palaeosauropsids are in bold typeface; diadectomorphs are underlined. A: Zittel (1890); B: Osborn (1903); C: Watson (1917); D: Williston (1925).

• 7 Order Iehtyosauria A Supl~rorrlcr Cntylusauria B Order Sauropterygia Pnrcinsnuriu • Order Testudines DindpdicllW Order Theromorpha Supcrordcr Annmodonti" Suborder Anomodontia Theriodontia Suborder Plaeodontia Dieynodontin Suborder Pareiasauria Placodontin Suborder Procolophonidae Superorder Testudinntn Diadeetidae Superorder Sauropterygin Suborder Theriodonta Superorder Dinptosaurin Suborder Rhynchocephalia Protorosnurin Suborder Pelyeosauria Pelycosnurin Suborder Rhynehoeephalia Rhynehosnurin Mesosauria Procolophonia Mesosauria

Superorder Cotylosauria c Subclass Annpsidn D Order Seymouriamorpha Order Cotylosnurin Order Diadeetomorpha Dindectjdne Djadeetidae Ljmnoscoljdnc Pareiasauridae Pareiasauridne Procolophonidae Procolophonidae Order Captorhinomorpha Order Eunotosnurin Captorhinidae Order Testudinata LjrnuQscelidae Subclnss Synnpsidn Pantylidae Order Theromorphn Superorder Anomodontia Order Thernpsidn Superorder Testudinata Subclnss Synnptosuuriu Superorder Archosauria Order Snuropterygin Mesosauria Order Plneodontia Subelass Parnpsidn Mesosauria • 8 With the start of this century, a new era began in the classification of reptiles with the publication of Osborn's "The reptilian subclasses

• 1). Diapsida and Synapsida" in 1903 (table In it the emphasis is put on the configuration of the temporal region as a key character in classification. In contrast to later classifications, he used the temporal arches instead of the actual openings. At that time, it was believed that these arches could "fuse" and thus produce the different pattern found in the various groups. Even though he revolutionized the classification of reptiles, he oversimplified the problem by putting ail animais in just two groups - one arched Synapsida and two arched Diapsida. He put Cotylosauria, the stem reptiles of Cope and Testudinata into the subclass Synapsida along with Anomodontia, which still included the placodonts as weil as mammal-like reptiles. Nevertheless, he put the truly non-diapsid Pelycosauria and Procolophonia as orders within the Diapsida. In 1911, Case gave a definition ofthe Cotylosauria that was accepted for many decades. In it he included ail early reptiles with closed skulls and therein the suborders Diadectosauria, Pareiasauria, Pantylosauria. Pantylosauria, after the small microsaurian amphibian Pantylus, and Procolophonia, the latter being distinguished by a posteriorly enlarged orbit and three sacral ribs amongst other characters. A very interesting attempt to solve the problem of relationships was carried out by Goodrich (1916). He proposecl a basic division between sauropsids- including turtles, Sphenodon, squamates, and crocodiles on 'J one side and theropsids (the synapsids of other authors) on the other. This division was based on the difference in the arrangement of tht;! aortic arches in these two groups. In his opinion, this fundamental division • appeared so early in fetaI development that it must have occurred on the 9 amphibian level. Of course, this can not be veritied in the fossil rccord. '1'0 • support his argument Goodrich chose a morphologicnl charnctcr thnt seemed to solve the problem. A hooked fifth metntarsal was common to nll living sauropsids bd never occurred in nny of the then known theropsids. Watson (1917) made the next attempt to provide a system of relationships (table 1). He stated that there are clenr limits to the procedure of using primitive characters as means of uniting groups since it neglects the use of advanced characters found in these animaIs. Nevertheless Watson concludes that it is best to keep the primitive groups of Goodrich and Osborn as a way to illustrate the origin of more advnnced modern taxa. Watson (1917) l'l'tains the superorder Cotylosauria as erected by Cope. Nevertheless, he felt uncomfortable mentioning that it was merely a dumping ground for lessel' known taxa. Within the Cotylosauria, he erected three orders, the Seymouriamorpha, animaIs with generally primitive characters resembling those of anthracosaurian amphibians; the Diadectomorpha, animais with an exaggerated lateral otic notch and vertical tabulars; and the Captorhinomorpha, showing an obliterated otic notch. The main dichotomy lay between the Diadectomorpha and the Captorhinomorpha. In the Diadectomorpha, he grouped the diadectids, the pareiasaurs and the procolophonids. They are united by having an otic notch, except for pareiasaurs in which it is assumed to have been secondarily obliterated. This led tu the belief that the Diadectomorpha evolved directly from anthracosaurian ancestors. The Captorhinomorpha on the other hand were distinguished by possessing an obliterated otic notch , "primarily" in Watson's sense, justifying the inclusion of • Limnoscelis. Limnoscelis is a large-bodied animal that exhibits a mixture 10 of reptilian (transverse flange of the pterygoid) and amphibian (iateralline • canal) features. Williston's classification, worked out in the first two decades of this

century, was published posthumously in 1925 (table 1). Like Osborn he also put the emphasis on using the temporal arches as a key character in classification. He was the first one to recognize that the absence of any arches, meaning the "solid roof' condition, is the actual primitive condition for reptiles. Consequently, he included the orders Cotylosauria and Testudinata in the Anapsida, recognizing the "primitive" character of the skull of turtles. In his Synapsida, he only included pelycosaurs and therapsids, primitive and advanced mammal-like reptiles, removing the aquatic plesiosaurs and placodonts to form their own subclass the Synaptosauria. Based on the great increase in data over the following decades but using arguments similar to those ofWatson (1917), OIson (1947) proposed another hypothesis of relationships (table 2). Within the Class Reptilia, he distinguished between the Subclasses Parareptilia and Eureptilia. He suggested that these subclasses had separatp. ancestries from a technically amphibian leveI. Within the Pa!"areptilip., he grouped aIl animaIs with a clear otic notch whilst aIl the Eureptilia lacked it. He gave detailed arguments for inclusion of the seymouriamorphs in the Parareptilia. Even though they showed clear amphibian characteristics, they can be seen as technically reptilian in sorne characteristics like the toe-count and the stemmed interclavicle. The other groups he inc1uded within the Parareptilia were the diadectomorphs, procolophonids, pareiasaurs, and • turtles. 11 Subc1ass Parareptilia A Sllbclass Anapsida B • arder Diadecta Order Cutylusnuria Suborder Seymouriamorpha Procolophonidlle Suborder Diadectomorpha Pnrcillsnuridnc Suborder Procolophonomorpha Dind(,'cUdjw Suborder Pareiasauria Li mnnHc('lidne arder Testudinata arder Tcstudinllta Subc1ass Eureptilia Subclass Lepidosllllrin Infrac1ass Captorhina Subclass Archosnuria Limnoscelidae Subc1nss unccrtnin Infrac1ass Synapsida Order Mesosouria Infrac1ass Paral'sida Subclnss lchtyoplerygin Infraclass Euryapsida Suhclnss EurYllpsidll Infraclass Diapsida SubcillSS SYllapsida

Table 2. Simplified outlines of classifications of reptiles, to show distribution of palaeosauropsids and diadectomorphs; the problematic mesosaurs are highlighted by italics. Palaeosauropsids are in bold typeface; diadectomorphs are underlined. A: OIson (1947); B: Romer (1956). • 12 Watson summed up his various attempts at classifying reptiles in 1954. • In reevaluating the hypothesis of Goodrieh (1916), he states that there was a basal diehotomy between sauropsids and theropsids; theropsids being mammals and their aneestors and sauropsids ineluding ail other reptiles plus birds. Watson (1954) faeed the problem arising from new data aeeumulated sinee the time of Goodrieh whieh showed that none of the oldest known reptiles had a hooked fifth metatarsa1. Nevertheless, Watson thought he had found evidenee in the differenees of the hearing apparatus and espeeially in the stapes and quadrate to support the division into theropsids and sauropsids. In 1956 Romer's Osteology of the Reptiles (table 2) was published. One ehapter is dedieated ta the history and trends in reptilian classification. In his own classification he used the framework of Williston (1925). Here the subclass Anapsida includes the orders Cotylosauria and Chelonia. Anapsids he saw as reptiles in which no temporal opening was developed. Other characters mentioned like sprawling gait and "modified" otic notch only serve to obscure the original idea (using temporal openings). Consiàering this broad definition which uses such a very variable assemblage of characters, it is no surprise to find seymouriamorphs alongside with diadeetids, procolophonids, pareiasaurs, and eaptorhinomorphs. Romer included within the captorhinomorphs, which have a broad skull table and no or only little development of an otic notch­ Limnoscelis, romeriids (which include the oldest known reptiles) and captorhinids. The aquatic mesosaurs one might have expected to see within the anapsids, but Romer placed them as an order within an • uncertain subclass by themselves. 13 •

Fig. 2. Temporal distribution of early amniotes, hinting at their relationships Cafter Carroll 1988).

• 14 • 1 l~· ... rudlll.~I.1 111------,------î---

~ è

•

;;1

- , <~I , ~~ ~ ! ~l" l \ ~ "" , Z,' ,, 1 1 ~. '\ \ \ 1 4':. " \ 1 =: " \ , :.:.: \ ,1 '- ",, \ Ttl dinu\,1.ur... "nKudilC". <\ \\ "nd hird:o; ',\, \

., . • The following years saw the description of an assemblage of primitive • anapsids and the protorothyrids by Carroll (1964,1969 a,b). These had been previously been worked on by Dawson (1860) and Price (1937). Carroll started with the redescription of Hylonomus (1964) and continued further in a number of other publications (1982, 1987, 1991). In those publications he devoted a great deaI of attention to early reptilian phylogeny. He proposed that protorothyridids, which are the earliest known anapsid stock, were ancestral to aIl other lineages. Captorhinids, mesosaurs, pareiasaurs, procolophonids and the small lizard-like millerosaurs he considers as captorhinomorphs, basically anapsids with uncertain affinities. SeymouriCL and Limnoscelis are removed from the Reptilia, since they were much more primitive than protorothyrids. The work of Reisz (1972) on early pelycosaurs shed more light on the early dichotomy between anapsids and synapsids. Turtles were seen by Carroll as anapsids as weIl, directly derived from the primitive reptilian stock. This was supported in 1979 by Gaffney & McKenna who discovered several characters shared between captorhinids and turtles. Gaffney & McKenna (1979) were probably the tirst scientists ta attempt a limited cladistic analysis to solve the problem of relationships among early reptiles. Heaton (1980) argued that the Cot,ylosauria are an order including the suborders Seymouriamorpha and Diadectomorpha, but excluding captorhinomorphs and procolophonids. He detined cotylosaurs as having akinetic skulls and reduccd or lost post-temporal fenestra. Heaton also came to the conclusion that. the Limnoscelidae, which ware long included in the Captorhinomorpha (Romer 1946, 1964) also belong to the • Diadectomorpha. 15 In 1986 Heaton & Reisz challenged Carrol!'s view that protorothyridids • are ancestral to al! subsequent lineages of amniotes. They suggesteà that Palaeothyris is derived in sharing with diapsids several characters like keeled pleurocentra and a short postorbital region of the skull, thus precluding affinities to any other lineage. Gauthier et al. (1988) used data from the literature to attempt the first large scale cladistic analysis of amniotes to support a new hypothesis of relationships amongst tetrapods. Synapsids appear as the most primitive clade, a view which was also supported by CarroI! (1982) and Heaton & Reisz (1986). Furthermore two new groups appear, one of which Gauthier et al. (1988) termed parareptiles, including pareiasaurs, millerosaurs, procolophonids, and the other mesosaurs. AlI other reptiles, including turtles, were included in a restricted Reptilia. This is in contrast to OIson (1947) who included the turtles in his definition ofParareptilia. Gauthier et al. admitted however, that this node (Parareptilia) might not withstand further testing since it was not weIl defined. The node is based merely on the loss of the maxillary caniniform and the loss of the supraglenoid foramen, both of which are prone to convergence. The notion of Heaton & Reisz (1986) that palaeothyrids were more closely related to the diapsids than to the captorhinids was also supported by Gauthier et al. (1988). Recently there have been several other attempts in solving reptilian versus parareptilian relationships One was undertaken by Reisz & Laurin (1991). On the basis of the redescription of the procolophonid Owenetta, they proposed a sister-group relationship with the earliest known turtle Proganochelys on the basis of ten shared derived characters, and denied a • relationship to captorhinids as proposed by Gaffney & McKenna (1979). 16 •

Fig. 3. Cladograms illustrating possible sister-group relationships of turtles. A: Gauthier et al.. (1988); B: Laurin & Reisz (1995).

• 17 • A

Syn:wsid3 Pareiasauria Millerettldae ~ Mesosauriœe TeSludines C3ptortlinldae PaJeoU1yri$ Aracosc.elicla Sauna

Ao'lAPSIOA

REFT1LIA

w B w lJl w 8" W W W W W W C Z " ::;; W C " C " 0 0. .. ë: " a: :il z ). w li. ::> ;:: U r! 1- 0 ::> lJl W ..J § ï: U 0 U lJl " li: li: i: 0 ~ :.; w 0 f 0 lJl :1 0 0 Cl C Z iii" w U " lJl ,. .. ..J 0 e- l- UJ W Z w ::;; 2 li: ..J 0 lJl !il 0. ... ::> lJl "ë ::; > li: W li: Ul 0. :â 0. ::;; .. U 0 " e- 0. " ,. " '" "

• This would make turtles extant members of the "Parareptilia". In 199:; • they expanded and redeveloped this hypothesis in a lengthy publication about early amniote phylogeny. The notable difference is that OwclIctfa is excluded l'rom this analysis. Still they argue for a strong support of a sister-group relationship between turtles and procolophonids. These two, together with millerettids and pareiasaurs form the monophyletic group Parareptilia. The Eureptilia include captorhinids and palaeothyrids. Furthermore synapsids including mammals are presented as n monophyletic group as weil. The relationship that creates the most controversy, the turtle-procolophonid sister-group is weil supported in their study. Lee (1993) picked up an idea that was briefly discussed by Gregory (1946). Lee proposed a close relationship between pareiasaurs and turtles. More recent publications (1993,1995) use data that was won through restudying and reinterpreting pareiasaur materia1. The result is that pareiasaurs and procolophonids are successive sister-groups of the tm'tles within the Parareptilia, Several recent publications by Berman, Sumida, and Lombard dealt with the atlas-axis complex in the amphibian to amniote transition and the special position of the Diadectomorpha. Berman et al. (1992) included the Diadectomorpha within the Amniota, whereas Sumida et al. (1991) placed them as the primitive sister-group to the Amniota. However, later Sumida et al,(1992) acknowledged that characters of the atlas-axis complex are not sufficient to include the Diadectomorpha within the Amniota without the addition of other characters. The latest published attempt to include turtles in a working system of • relationships was undertaken by Rieppel (1993). He proposed a possible 18 sister-group relationship with diapsids on the basis of restudying diapsid • materia1. An interesting aspect of the work is that turtles share a number of characters with "moderately" advanced diapsids whilest only one character is shared with the more primitive areoscelids. This appears to be due to the fact that a data matrix compiled to study diapsids was applied instead of a comparative study with turtles. Of ail the outstanding problems in early tetrapod evolution, the parareptiles demand special attention. Do they have their ancestry somewhere else within the Amphibia, making the Amniota a paraphyletic group? This requires the study of early reptiliomorph groups to acquire a character set that can be used in an analysis to determine ifthere is only a single monophyletic Amniota. This is accomplished on the basis of the redescription of the procolophonid Barasaurus besairiei.

19 • MATERIALSAND METHODS In the 1920's, Piveteau (1926) wrote preliminary descriptions 01' various reptiliomorph amniotes from Madagascar that were found by geologists working for French exploration companies. Much attention has been paid ta some of the species, including Hovasallrlls (ClIITie 1981). Others like Barasallrus (Piveteau 1955) did not attract much attention for decades. This is surprising due ta the unique nature of the fauna found in the Permian of Madagascar. In the Permian Madagascar was still part of the African mainland, but the breakup of the super continent pangea was clearly on the horizon. The fauna found in the sediments of the Sakamena Formation on Madagascar (fig. 4) are clearly different from the Karoo fauna of south eastern Africa (Piveteau 1926, Currie 1981). The Karoo essentially was a basin that was filled over time while the sediments in Madagascar reflect those of a rift valley with a large number of small basins between ridges (Anderson & Anderson (1970, 1978). Thus the fauna found in Madagascar is mainly that of drier uplands as compared ta that of the wet lowlands of the Karoo. The procolophonid Barasaurus is the only reptiliomorph member of the fauna that has an equally abundant counterpart in the Karoo: Owenetta. AlI the specimens at hand come from two sources. One is the former Germain collection, now housed in the Carnegie Museum, Pittsburgh and on loan ta the Redpath Museum, Montreal. AlI the other specimens are in the collection of the Natural History Museum in Paris, France. These specimens comprise the original material that Piveteau (1955) used in his preliminary description and new material that recently was given ta the • Museum as part of a University collection. The latter were cast by Dr. P.Y. 20 Gagnier. Additionally, a specimen of Ou:enetta from the South African • Museum was available for study from Dr. E. Gaffney, American Museum, New York. The specimens of Barasaurus are ail preserved in silty limestone nodules. Those nodules first formed around the decomposing body and in many cases the nodule forming process ceased before the whole skeleton was encased. That is the reason why many specimens are missing the skulI. The skulls were probably preserved in the soft silt stone surrounding the nodules but overlooked when the nodules were coIlected. The nodules frequently contain pebbles, plant debris, and in sorne cases fish scales which often obscure parts of the skeleton. The bone usuaIly breaks when the nodules are split, since it is softer than the material of the nodule. Using a brush and a needle the bone can easily be removed, resulting in a natural mold. From the molds latex casts are made resulting in most cases in high quality three-dimensional reproductions of the skeletons. Aimost aIl skeletons have been drawn, and the drawings together with the casts were used in the reconstruction of the entire animal.

• 21 •

Fig. 4. Map showing Madagascar in outline. Enlarged the distribution of the Upper Permian Sakamena Formation in the region of Ranohira. Altered from Currie (1981).

• 22 • ----500 Ok

..-+-=~=~=---:300

51JL.- SaIcamena Fonnation ~ MiddIe& ~ Saka",""a • • LIST OF SPECIMENS The following specimens are housed at the Carnegie l\'!lISelllll. Pitt"bllrgh:

CM47512 One adult and one juvenile skeleton in one nodule. bath missing skull. CM 47513 Same specimen as CM 47512 but ventral view. CM47514 Complete skeleton. CM47517 Almost complete skeleton with Skllll, pectoral girdle and pelvic girdle. CM47518 Pelvic region and hind limb. CM 47519 Pelvic region and part of the pectoral girdle. CM47520 Trunk Region. CM47521 Complete skeleton, except for tai! and distal limb elements.

The following specimens are housed at the National Museum of Natural History in Paris, France. No collection numbers have been assigned yet. Therefore they are numbered P 1 through P 10

Pl Complete specimen, except for distal limb elements; dorsal and ventral view. P2 Complete skeleton, except for tai! and skull; dorsal view. P3 Hind limb and tail region; dorsal view. P4 Anterior part ofskeleton with pectoral girdle and occiput. P5 Trunk vertebrae and front limb; dorsal view P6 Anterior part ofskeleton, with shoulder girdle and skull; • ventral view 23 P7 Anterior part of skeleton with skull; dorsal view. • P8 Skull; dorsal view. P9 Skull; dorsal view. PlO Anterior part ofskeleton with shoulder girdle and part of skull; ventral view.

The following specimen is housed at the South African Museum and was available through Dr. E. Gafi'ney, New York.

K7582 Owenetta, complete skull.

• 24 BARASAURUS BESAIRIEI • SYSTEMATIC PALAEONTOLOGY BarasaunlS

Type species: Barasaurus besairiei Piveteau 1955 Etymology: Saurus from Greek Sauros (1izard). Diagnosis: A procolophonoid differing from ail others in having the following unique features: Narrow lacrimal borders naris and QI·bit; prefrontal borders naris; quadratojugal narrow dorsoventrally; no palatal teeth or denticles are present; no contact between postfrontal and supratemporal.

Barasaurus besairiei

Holotype: P 1: Natural mold of entire skeleton except tai! and distal limb elements in dorsal view. Anterior part of the skeleton as a natural mold in ventral view. • Locality: Ranohira, Madagascar. Stratigraphie Position: Lower Sakamena Formation. Age: Upper Permian. Etymology: In honor ofH. Besairie the collector ofthe first specimen. Diagnosis: As for genus.

• 25 •

Fig. 5. Barasaurus besairiei. Composite reconstruction of entire skeleton in lateral view, altered from Carroll (1982). Outline ofthe lower jaw redrawn from Reisz & Laurin (1991).

• 26 •

• DESCRIPrION • General features Considering the generally well- preserved condition of the postcranial skeleton in the majority of the specimens, it is interesting to note that all the cranial parts preserved are crushed. The skull also tends to be more disarticulated than the postcranial skeleton if present. Many of the specimens at hand are completely articulated but the skull is missing for no apparent reason. However, two explanations are possible. Considering the strong postcranial skeleton, the skull is very small in proportion. Approximately 2cm skull length versus a snout vent length of about 13 cm in most specimens. The bOlles of the skull are very thin and fragile and therefore easily crushed in the course of sedimentation. Ali specimens come from silty nodules that formed around the decaying body. This nodule formation excluded the head in many cases. In sorne cases, it is obvious that the head was present but when the nodules were collected the bones outside of the nodule were overlooked or crumbled away.

Skull The skull of Barasaurus is very lightly built. The narial openings are greatly enlarged for an unknown purpose. This underlines the posterior embayment of the orbit and lets the skull appear frog-like. The squamosal and quadratojugal are displaced in al! the specimens and a certain mobility cannot be ruled out. The nasal is roughly rectangular in outline as in most other early amniotes and Diadectes except Procolophon where it is irregularly shaped. • Anteriorly, the nasal is slanted to meet the premaxilla. Posteriorly, it is 27 •

Fig. 6. Reconstructed skulls of owenettids. A, Barasaurus besairiei. Composite reconstruction of the skull in dorsal view. B Owenetta. Skull reconstructed after K 7582, dorsal view. A list of abbreviations can be found on page 148.

• 28 CT III - •

E o Q, III

Q, Q,

1cm -

o e III Q, Q, Q, •

Fig. 7. Reconstructed skulls of owenettids. A, Barasaurus besa.iriei. Composite reconstruction of the skull in lateral view. B Owenetta. Skul\ reconstructed after K 7582, lateral view.

29 • A pp

ex pm

pt q

1cm

B pp

so

ex pm

pt • •

Fig. 8. Reconstructed skulls of owenettids. A, Barasaurus besairiei.· Composite reconstruction of the skull in ventral view. B Owenetta. Skull reconstructed after K 7582, ventral view.

30 •

E Co o oC

1cm

B -

E Co o oC

• •

Fig. 9. Reconstructed skulls of owenettids. A, Barasaurus besairiei. Composite reconstruction of the skull in occipital view. B Owenetta. Skull reconstructed after K 7582, occipital view.

31 A • pp p

sq

qJ

pt

1cm

B

pp p

sq

qJ

pt

• concave. Laterally, the nasal fOl"mS about three quarters of the length of • the narial opening. The dorsal maI'gin of the naris is very peculiarly constructed (P 9, fig. 14). There is no simple rim br r the bOl1l' l'caches down and is recessed. A similar feature is also present in Oll'cllctta and Procolophon but to a much lesser degree. The prefrontal is about two times as long as it is wide, like in Diadcctcs and Eocaptorhinlls. In other early amniotes, the i-Il"efrontal is severnl times as long as it is wide. In Barasallrlls, the prefrontal reaches the naris and is downturned and recessed in the same way as the nasal. In no other early amniote c:" diadectomorph does the prefrontal reach the nari"l. Internally, visible through the orbit, the prefrontal passesses a !lange t!:dt almost re9.ches the midline (fig 7). Procolophon and Owcnctta show a similar structure. The frontals are the largest bones of the skull table. They are about live times as long as wide. The frontals generally look the samo in ail other early amniotes. Only inDiadectes and pareiasaurs the frontals aI'e ruther short and in bath cases they do not participate in the orbit. In BaraSalll"ltS, the postfrontal is an elongate, narrow bon.. that does not extend beyond the frontal and does nùt border the supratemporal. lt contacts the supratemporal in Owenetta. In Procolophon a massive parietal reaches the postorbital. The parietal forms the major part of the posterior border of the skull table. In Diadectes, Palaeothyris and pareiasaurs it does not reach the occiput. Only in Procolophon does the parietal also reach the orbit. At the medial posterior end of the parietals very small rounded postparietals (CM • 47517, fig. 17) are present, as in Owenetta. In other early amniotes the 32 (loHtparietals are about as wide as the parietals and rectangular in shape. • No (lostparietals are present in Eocaptorhinus and Procolophon. The lateral corners of the skull table are formed by the supratemporals like in Diadectes, Procolophon, and Palaeothyris. In Eocaptorhinlls and

pareiasaur~, the tabulars take this position. There is no tabulaI' in Barasallrlls, Procolophon and Owenetta, whilst it is present in ail other carly amniotes. The postorbital is generally similar to that in other early amniotes. Except, as in the postfrontal, it is elongated due to the orbital embayment. The squamosal is square in outline very much like in Owenetta and Procolop,'wn. In contrast to Owenetta, the otic notch is not as strongly developed. As mentioned above, a regular dislocation of the bone indicates a somewhat loose connection to the skull roof. In other early amniotes and Diadectes, the squamosal is larger and appears to be better integrated with the surrounding bones. The am:!r!.or border of the quadratojugal is

rounded and was obviously not attached to the jugal (P 9, fig. 14). Amongst other early amniotes, this situation is only equaled to this degree by Owcnctta. In other procolophonids, this area is also concave but not as deep. The jugal forms the whole ventral margin of the orbit. In Diadcctcs, Palcothyris and Mil/crctta (Gow 1972), the jugal does not reach the anterior border of the orbit thus allowing a participation of the maxilla in the orbital margin. The lacrimal is a smail short bone that borders both the orbit and the naris like in most other early amniotes and Diadectes. Only in Owcnctta and Procolophon does the maxilla extend upward posterior to the naris thus reaching the nasal, excluding the lacrimal from the naris.

33 •

Fig. 10. Barasaurus besairiei. Holotype Pl in dorsal view.

•

• 34 • pm

p r f . ~"fflj,<:t J

po

q

h

ect gr

ul

• lem , •

Fig. 11. BarasaurlU>' besairiei. Holotype Pl in ventral view.

• 35 •

rad-... --.

ul

• lem •

Fig. 12. Barasaurus besairiei. Specimen P 8, dorsal view of skull.

• 36 •

po . '"

atn '<:' ;'" ex I-atp? l'...... , l ' : ,,', ", f ,"/', ~i~. • 1 . .1 .. "::-' .. ) \.#_"'. .... \.-: ",-.' ...... cl

lem •

Fig. 13. Barasaurus besairiei. Specimen P 6, ventral view of palate and shoulder girdle.

• 37 • pal sp

sa

ar _.-'oP prot

op at le

lem •

Fig. 14. Barasaurus besairiei. Specimen P 9, dorsal view of skull.

• 38 •

sq qJ

cap '=-~it>.

ax

lem • , • The premaxilla shows no difference ta the one l'Hllld in otl1l'r early amniotes and Diodeetes. It is not downturned as in eaptorhinids. 'l'hl' maxilla and the premaxilla have nllmerous peglike t.el'th li' G, lig. 1:;), Though there might be a canine present, il. is barely Im'ger t.han t.lll' surrounding teeth. There is sllrely no canine region as in synapsids (CUl'rie 1979) Or Palacothyris (Carroll 1969), No pattel'l1 of t.oot.h replacement is apparent. No septomaxilla is present.

Palate

The configuration of vomer, palatine and pterygoid (P 6, lig. 13) is virtually identical in Eocaptorhinus, Procolophon, Owenetta and Barasaurus. In contrast with Eocaptorhinus the other three species ail have an ectopterygoid. Since ail the skulls ofBarasalt/'us are qllite crushed nothing l'an be said about the orientation of the basicmnial articulation. As a whole the palate is virtually identical in Owcnctta (Reisz & Lalll'in 1991) and Barasaurus except for being edentulous in the latter.

Quadrate The quadrate, due 1.0 its orientation in the skull, is completely broken in

aIl the specimens. The parts of the quadrate (P 1, fig. 10; P 6, fig. 13) that

are reconstructable are similar 1.0 those in Owcnctta. Both are not 1.00 far removed l'rom the condition described for Eocaptorhinus (Heaton 1979).

The condition in Procolophon appears 1.0 be rather different. The elongate articulation surface is more obliquely oriented and quite narrow. It also seems that the surface is l'ven whilst there is a groove partitioning il. in the • other species. 39 The quadrate did not extend posteriorly beyond the quadratojugal in either • Barasaurus or Owenetta. Brainca , Again, the braincases of Barasaurus and Owenetta are virtually identical. Except that the exoccipitals seem to meet at the midline in Owenetta which is cIearly not the case in Barasaurus.. The exocci}Jitals are slender in both genera as is the case in Eocaptorhinus, while they are stubby in Procolophon. The supraoccipital (P 8, fig. 12) in Barasaurus, Owenetta and Procolophon only attaches via a narrow median ridge to the skull roof. In Eocaptorhinus, the supraoccipital attaches to the skull roof along its whole length. The opisthotics are flattened dorsoventrally in Barasaurus and Owenetta and do not attach to the cheek. The lateral ends of the bones are rough indicating a layer of cartilage. In Procolophon the opisthotic is attached to the supratemporals. In contrast to this the opisthotic of Eocaptorhinus reaches towards the squamosal and was also capped by cartilage CHeaton 1979). The basioccipital of Eocaptorhinus provides the whole area of the occipital condyle. In Barasaurus, Owenetta and Procolophon the exoccipitals participate in the condyle as weIl. Another striking difference between Eocaptorhinus and the other three species exists. The cultrifonn

process (P 6, fig. 13) is about 1.5 times as long as the main body of the parasphenoid in Eocaptorhinus, as compared. to 0.5 in the latter species. The other bones of the braincase are n'Jt visible or crushed beyond recognition. In most specimens which show the palatal surface, a weIl ossified hyoid apparatus is present. The copula is shaped as in Procolophon

40 (Carroll & Lindsay 1985), a thin pinte that is strongly recesserl posterioriy • and slightly wider than long. It is accompanierl by paired. rorl likL' ceratobranchials. Carroll & L~~say (1985) mention similar dements !ilI' pareiasaurs and turtles but neither Gaffney (1990) nor Lee (1993, 1995) mention it. Vertebral' The atlas-axis complex consists of sever. bones as in ail early amniotes a paired proatlas, an atlas intercentrum, a paired atlantal neural Ill'ch, an element built through the fusion of the atlas pleurocentl'llll1 and axis intercentrum, and the axis itself. None of the specimens show these

elements in full articulation (P 9, fig. 14; P 7, fig 16). The reconstruction is therefore based on several different specimen. The smooth, rounded, lateral face of the proatlas bears no distinct feature. It is most closely comparable to that of Palacothyris (Carroll 1969). The atlas intercentrum, visible in ventral view in specimen P 6, is a very large bone relative to the other atlas-axis elements. It is much larger than that of Captorhinus, Paleothyris, Procolophon or Pctrolacosaurus but similar in size to that ofDimetrodon and Ophiacodon. It bears a faint mid ventral sagittal ridge, but it is not distinctly keeled. Anteroventrally, it extends weil under the edge of the occipital condyle. The robust parapophyseal articulations for the atlantal ribs project posterolaterally, as in Dimetrodon (Romer & Price 1940) and Diadcctcs (Sumida & Lombard 1991). In other early amniotes, including Captorhinus, Palcothyris, and Petrolacosaurus, the parapophyses are highly reduced. The atlantal neural arch is narrow and subrectangular in lateral outline. Although comparable in shape to that of Diadectcs (Sumida & • Lombard 1991), it is not as robust, resembling the slender arch of 4J •

Fig. 15. The atlas-axis complex of Barasaurus besairiei in comparison with the atlas-axis complex in other tetrapods. A, composite reconstruction of the atlas axis complex of Barasaurus besairiei; B, Proterogyrinus after Holmes (1984); C, Seymouria ; D, Limnoscelis ; E, Diadectes C,D,E after Sumida et al. (1992); F, Ophiacodon after Romer & Price (1940); G, Captorhinus after Sumida (1990); H, Palaeothyris after Carroll (1969). B-H not drawn to scale.

• 42 • A

lem

c D B

E F G H

• Captorhinus

43 The axis is the largest of the cervical vertebrae. Neverthelet't' the • combined centrum and spine appear to be rather t'lender and tall, comparable in outline with Diadectes (Sumida & Lombard 1991). Gnly in mature specimens is the neural arch fused to the centrum, the only aspect of the whole complex that seems to be similar to the configuration in Procolophon. In other early amniotes, including Captorhilll/s. Paleothyris, and Petrolacosallrlls the neural arch is greatly expanded antel'oposteriorly. In Captorhinlls (Sumida 1987) and Pa1eothyris (Carroll 1969), the elements are fused early in ontogeny. The axis centrum it'

amphicoelous with slightly thickened margins. In vent,'al view (P 6), a distinct longitudinal keel is vi"ible. The transverse processes are positioned rather low anteriorly and protrude only slightly fi'mu the surface surrounding it. No other early amniote resembles this specitic condition The base of the neural arch is wider than that of Diadectes (Sumida & Lombard 1991) but it is not swollen. It sweeps smoothly up into a thin spine. The dorsal end of the arch is round, describing almost a half-circle anteroposteriorly. The oval prezygapophyses are tilted anterolaterally and the more dorsally placed postzygapophyses are angled posterodorsally. In dorsal view (CM 47514), the dorsal rim of the spine thickenR gently thus giving the dorsal margin a blunt look. There is no variation in spine thickness anteroposteriorly as in Diadectes {Sumida & Lombard 1991). No unique characters of the atlas axis complex are shared with Proganochelys (Gaffney 1990, Fig.1l2). The structure of the remaining vertebrae is generally similar to that of other comparable sized early amniotes, such as protorothyrids and • captorhinids. Complete presacral series, comprising 27 segments, can be 44

, '\ •

Fig. 16. Barasaurus besairiei. Specimen P 7 in dorsal. The only specimen known to the author that shows sclerotic elements.

45 •

. . 1

• lem •

Fig. 17. Barasaurus besairiei. Specimen CM 47517 in dorsal view.

,

46 •

• lem seen In CM 47512, CM 47514 and P 1. This is two more than the typical • procolophonid number (Colbert 1946). The column can be divided into four regions; the cervicals, dorsals, sacraIs, and caudals. Cervical and dorsal vertebrae can be distinguished on the basis of rib morphology. Ribs associated with the four cervicals are short and very robust compared to those of the dorsals. The intercentra persist throughout the dorsal series, unlike the situation in more derived procolophonids in which these elements are lost. The centra appear much as in captorhinomorphs in being deeply amphiroelous. They are slightly wider than high. The anterior and posterior ends of the centra are slightly beveled ventrally to accommodate the intercentra. Longitudinal reinforcing ridges pass between the ends of the centra. The most prominent of these is median in position and projects slightly ventral to the edge of the centrum; it shows slight longitudinal striation, typical for early amniotes. The parapophysis is fused to the hypapophysis; together they form the transverse process. Unlike the primitive amniote condition, the capitulum does not articulate with the intercentrum but with the centrum proper just dorsal to the intercentrum. The transverse processes extend from the centrum approximately the same distance as do the prezygapophyses. The process has it's anterior extremity half way up the anterior margin of the centrum. It continues posteroventrally, ending on the neural arch beneath and slightly posterior to the prezygapophyses. The thin, straight, anteroposteriorly tilted articulating surface is about three times as long as wide. The sides are subparallel. A slight constriction occurs at, or dorsal to, the middle of the arti!'ulation surface. This character is subject tG • regional variation, becoming less pronounced posteriorly. 47 The neural arches exhibit transverse expansion (CM 47517. lig. 17) • approaching that of later procolophonids but to a lesser degree [han [hnt nC Procolophon. In procolophonids, the swelling is restricted to the nrea nI' the spine and is not as extreme as in Captorhilllls (Heaton & Reisz 1986). The pre- and postzygapophyses are low, wide and merlially inclined. The neural arch is a very low, rounded structure. From the anterior base of the neural arch, low ridges diverge anteriorly toward the inner margins oC the prezygapophyses. The postzygapophyses appear to be the same width m; the prezygapophyses. The neural arches and centra are fused throughout the whole length oC their contact in mature specimen. The neural arch is typically 1.8 times the length of the centrum. The posterior third, approximately t'rom the apex of the neural arch posteriad, extends beyond the posterior end of the centrum, such that each postzygapophysis overlaps a quarter to a thin( Dt' the su.ccessive centrum. There are a few notable differences when compared to Eocaptorhînus (Heaton & Reisz 1980). The ventral ridge between the anterior and posterior margin of the centrum is more pronounced, the transverse p''lcess is shorter, more robust, and straighter and the division between capitular and tubercular surfaces is less clearly marked than in Eocaptorhînus. The neural arches are lower, and the neural spine is shorter. The zygapophyses, while of comparable height, are more widely expanded than those ofEocaptorhinus. These descriptions are based upon a typical mid· dorsal vertebra. In contrast ta Captorhinus (Heaton & Reisz 1986) Barasaurus shows no alternation in spine height or shape, neither do Palaeothyris, pelycosaurs and millerosaurs.

48 •

Fig. 18. Barasaurus besairiei. Specimen CM 47518, pelvic region in dorsal view.

,

49 •

dt I-IV

1cm • •

Fig. 19. Barasaurus besairiei. Specimen CM 47518, pelvic region in ventral view.

,

50 •

1cm • The three sacral vertebrae are best visible in CM 47518 (fig. 18). They do not • otl"er any special features when compared to the last dorsal vertebrae, except that the sacraIs are of slightly stronger build. The fïrst few caudal vertebrae show no notable difference when compared to the dorsal series, except that the rib articulation is round and fairly large. From the fifth caudal on the intercentra are expressed as hemal arches. The centra become progressively shorter caudally, which leads to the narrowing of the neural arches to a rod-like structure. Caudal autotomy is not present in Barasaurus.

Ribs Although facets for the articulation of an atlas rib are present, the rib itself is not visible in any of the specimens. The first preserved rib is associated with the axis. It is short, (0.3 cm) barely longer than the centrum and rapidly tapering. The ribs associatfj!d with the third and fourth vertebrae increase gradually in length but are distinctly shorter than the rib that articulates with the fifth vertebra. These ribs are not sharply curved posteriorily as in Eocaptorhinus, but are relatively ôtraight and projected posü,;rolaterally at an angle of approximately 60·. The rib-head appears to be quite bulbous and the area of articulation with the transverse process is dorsoventrally elongated. The middle of the head is slightly constricted. The curvature of the rib is greatly reduced near the proximal end of the rib, especially on the posterior margin. The ribs from the fifth vertebrae back to the last presacral comprise the dorsals cP 7, fig. 16). There is no pronounced regional differentiation apart from graduaI change in length and arc of the rib shaft. The ribs increase • in length rather rapidly but uniformly until the -tenth vertebra and 51 thereaftcr decrease gradually in length. The shafts curve pr()gTessi\"l'I~· more caudally up to the fifteenth dorsal vertebrn; thereafter the ribs become progressively less curved. Ali dorsal vertebral' boar ribs. The rib heads are slender and flattened anteroposteriorly. Ali appoar to be holocephalous, although the dorsal and ventral ends are slightly bulbous. The capitulum divf)rges trom the ventral mm'gin of the shaft at a more oblique angi':J tl: .n does the tuberculum. The shaft of the rib is gently curved ventrally and slightly posteriorly, describing about a seventh of the arc of a ch·cle. In cross-section, the shaft is subcircular. Shallow ridges that begin at the articulating heads extend almost to the end of the shaft. The ribs are less robust than in Procolopholl or pelycosaurs and are more closely comparable to those of Eocapthorhinus, Palaeothyris and millerosaurs. This is probably a size related feature. There are three pair of sacral ribs (CM 47518, fig. 18), a diagnostic feature of procolophonids. They are roughly of equivalent length. The tirst two look similar to those of Eocaptorhinus, but are slightly more robust. The proximal, and in particular, distal ends are widely expanded. The .~ proximal articulation surfaces are almost circular in outline. In dorsal view, the anterior margin of the distal expansion expands more evenly and markedly. The anterior expansion starts at about one third orthe length of the shaft, while the posterior expansion approximately begins at two thirds the length of the shaft and curves more abruptly. The first and second sacral ribs are approximately equally robust; the distal expansion being 70% and 73% of the total length of the element respectively. The third is of considerably lighter build. It's distal expansion • accounts for about 40% of the length. Much of the expansion of the third 52 sacral rir is formed by the divergence of the anterior margin. • Consequently this element appears to bend anteriorly. The distal articulating surf<.1ces of the three ribs coalesce to form a continuous surface for the articulation with the pelvic girdle. The first four caudal vertebl'ae bear ribs that are not fused to the centra. These ribs are fiat, short, horizontal and turned backward. From the fifth caudal vertebrae on it is ur.sure whether ribs are fused to the centra or whether elongated transverse !,rocesses are present. Posteriorly the ribs or transverse processes become progressively smaller.

Pectoral girdle The pectoral girdle of Barasaurus exhibits the generalized primitive amniote pattern with minor changes. Most of the procolophonid characters expressed in Barasaurus are alterations in proportion which are less pronounced than in later forms such as Procolophon. A cleithrum is not exposed in any specimen. Procolophon was reconstructed by Colbert & Kitching (1975) as lacking it. Restorations ofthe early procolophonid Nyctiphruretus (Ivachnenko 1979) clearly show a long slender cleithrum about equal in length to the dorsal expansion of the clavicle. As in primitive amniotes the clavicle consists of a slender vertical blade and a ventral expansion which turns medially to reach nearly to the midline. The transition between the vertical and the ventral portion is not as abrupt in Barasaurus as in Eocaptorhinus. The medial margins of th,~ segments produce an angle of about lOS· in Eocaptorhinus and 114· in Protorothyris (Clark & Carroll 1973). That in Barasaurus 133·, is • considerably larger. This may refiect a difference in gait. 53 Fig. 20. Barasaurus besairiei. Specimen CM 47512, entire skeleton without skull in dorsal view. Note partial skeleton of a juvenile at the bottom.

, :,.

• 54 •

• . 1 JoiCID , t •

Fig. 21. Barasaurus besairiei. Specimen CM 47512, entire skeleton without skull in ventral view. Note partial skeleton ofa juvenile at bottom.

• 55 •

~~~.di ~

• lem ~~ --_.~----- ··10'__ The ventral part of the c1avic1e is slender in comparison \Vith that of • Eocaptorhinus. Typically, the c1avic1e of Barasallrlls articulates \Vith the interc1avic1e in a more or less transverse plane, the pattern also seen in Nyctiphruretus and Procolophon. As in Procolophon, Nyctiph1'llrctlls, and most protorothyrids the clavic1es approach one another medially but appear not to touch. The c1avic1es of Eocaptorhinus and Palacot.hyris meet at the midline. As in other procolophonids, a pronounced median ridge l'uns the entire

length of the stem of the interc1avic1e, comprising the bulk of it (P 6, fig. 13). The stem flattens gradually towards the anterior end to become the thickened basal portion of the crossbar. Lateral to this ridge the bone extends as a thin lamina whose edge c10sely follows the outline of the coracoid plate, but does not overlap it. The width of the ridge remains constant while the lamina gradually widens toward the midpoint of the stem, posterior to which it narrows again, converging toward the ddge near its posterior end. At the distal ends of the crossbar, the ridge turns posteriorly to present an anterolateral facet for articulation with the anterior portion of the c1avicle. The configuration of ihis structure is consistent throughout the procolophonids, and is not present in any other early ammote. The dorsal surface of the interc1avicle is not exposed in any specimen. There is little evidence of muscle scars on the interclavicle. The robust ridge, however, suggests a large and extensive M. pectoralis major. This insertion is corroborated by the robust deltopectoral crest of the humerus. Given that the clavicles do not meet medially, it is probable that the omohyoideus muscle inserted directly on the interclavicle. There is a small depression where the processes meet with the medial stem which

56 might have accommodated such musculature. If this is the case, it • contrasts with the situation found in Captorhinus where the omohyoideus originates exclusively on the clavicles. The endochondral pectoral girdles of early synapsids show three

distinct centers of ossification (P 6, fig. 13), the scapula, anterior and posterior coracoid, whilst Pala.eothyris and other early amniotes only show one coracoid. In Barasaurus three elements are present and contribute to the glenoid cavity. The coracoids comprise the coracoid plate, make up the bulk of the ventral, horizontally oriented portion of the pectoral girdle. The pectoral girdle extends weil antenor and slightly posterior to the glenoid cavity. The scapu1a is relatively short dorsoventrally. It is oriented more or less straight vertically as in other early amniotes. The dorsal edge of the scapula looks unfinished and porous, indicating the presence of a cartilaginous suprascapula of unknown extent. The posterior border is defined by a prominent ridge that bifurcates at the narrowest portion of the bone which is at about half of it's height. The lateral branch turns outward in a posteroventral direction. The medial branch turns sharply posteriad. The two ridges form, respectively, the anterior and the posterior margin of the triangular supraglenoid buttress. The buttress, absent in Procolophon, is a comparatively large structure, but does not show the deep indentation seen in Eocaptorhinuf'. It is consideràbly smaller than that of Captorhinus (Holmes 1977). The supraglenoid foramen, present in Eocaptorhinus and Protorothyris (Clark & Carroll 1973) and primitive pelycosaurs (Currie 1979) is absent in Barasaurus, and other procolophonids.

57 •

Fig. 22. Barasaurus besairiei. Specimen CM 47514, skeleton in ventral view with skull elements obscured by fish scales.

• 58 •

lem • 1• •

Fig. 23. Barasaurus besairiei. Specimen PlO, pectoral region and skull elements in ventral view.

• 59 •

'-,

• lem The anterior margin of the anterior coracoid can be seen in specimens P 4, CM 47514. It r;.ms posterodorsally from it's anteriormost point, giving the scapula the appearance of a slight posterior tilt. The lateral edge of the scapula above the glenoid cavity bears two shallow depressions one above the other, indicating the origins of the large scapulodeltoideus and scapulohumeralis Musculature respectively as reconstructed for Captorhinus by Holmes (1977).

The coracoids are preserved ln various stages of ontogenetic development. This ranges from smail distinct elements in specimen CM 47512 to the large fully ossified condition of P 5. In adults the anterior coracoid and the scapula coossifY indistinguishably, but in aIl specimens the suture between the antllrior coracoid and the posterior coracoid is visible. The anterior coracoid apparently contributes about one quarter of the glenoid cavity, from the coracoid foramen, which in immature specimen appears to be confluent with the glenoid cavity, forward to the anterior margin of the glenoid. The situation is not unlike that in early pelycosaurs except that the foramina are farther anterior. The smoothly rounded edge of the anterior coracoid turns ventromedially, paralleling the contours of the interclavicle. No anterior coracoid foramen is present. The posterior coracoid comprises somewhat less than half of the coracoid plate. It makes up the posterior half of the glenoid, from the .posterior edge of the supraglenoid buttress to the posterior end. It is a relatively flat bone, slightly concave in ventral view. It curves dorsally .>.- behind the glenoid cavity presenting a dorsolateral facet for the origin of the triceps medialis.

The coracoid plate in adult specimens is almost 2 cm long (P 11,84 cm). • It is narrowest at the intercoracoid suture. As in Procolophon early 60 pelycosaurs and Palaeothyris, but not Eocaptorh ill liS. the corncoid plate is • considerably shorter than the interclavicle. The anterior edge of the glenoid, just anterior to the glenoid convexity, is the most prominent feature on the lateral surface of the scapulocoracoid. Three ridges radiate from this point: 1. dOl'sally, to where the anterior margin of the supraglenoid buttress becomes confluent \\ ith the dorsal margin of the scapula, 2. anterodorsally, the least conspicuous ridge, and 3. anteroventrally, toward the anteriormost corner, the most prominent ridge. It is inferred from the skeletal similarities to Eocaptorhinus that this genus provides an adequate mod~l upon which to restore the musculature of this region in Barasaurus. Dorsal to ridge two lies the origin of the scapulohumeralis muscle. Between ridge two and three and beyond ridge three the anterior coracoid is heavily scarred, indicative of the origin of a large, possibly tendinous scapulocoracoideus. The areas of insertion of the coracobrachialis brevis and biceps can easily be discerned in FI. It lies on the ventral surface medial and distal to the edge of the coracoid foramen, and extends posteriorly to the end ofthe coracoid plate. A few major differences to Eocaptorhinus should be noted, however. Due to the restricted expansion of the clavicle, the episternohyoideus would be expected to be much reduced from that figured by Holmes (1977) for Captorhinus. Holmes (1977) identifies the cleithrum as the area of insertion of the levator scapulae inferior. Since Barasaurus lacks a cleithrum, the insertion is to be expected on the anterior margin of the scapula. The large supraglenoid buttress possesses a small scar near it's posterior extremity. This could indicate a tendinous insertion of the subcoracoscapularis.

61 •

Fig. 24. Barasaurus besairiei. Specimen P 5, anterior vertebrae and manus in dorsal view

,

62 •

.''''.'' v'~,", " • 1cm Humerus • The tetrahedral configuration of the primitive tetrapod humerus is retained in procolophonids but to a lesser degree than in captorhinids (Holmes 1977). In keeping with the generally robust nature of the posteraniai skeleton of Barasaurus, the humerus is stout with a comparatively thick shaft and greatly enlarged proximal and distal

expansions (P 5, fig. 24). The proximal articulating surface retains the strap shaped appearance common in primitive amniotes, although it is somewhat shorter and deeper than in Captorhinus (Holmes 1977), and comparatively more of the articulating surface is concentrated in the anteroventral edge of the head. The shorter articulating surface and more ventral orientation may indicate an abbreviated power stroke and less rotation around the longitudinal axis. In cross-section the proximal head of the humerus in Barasaurus is triangular, compared to the rectangular shape found in captorhinids. This is attributable largely to the ventral location of the prominent deltopectoral crest. The deltopectoral crest of Barasaurus, while being short proximodistally, is markedly expanded laterally. A prominent scar marks the insertion of the deltoideus and pectoralis. Both of these prominences are located posteroventrally on the proximal expansion. The deltopectoral crest is located more ventrally than that in captorhinids, in a position more comparable to that of pareiasaurs (Boonstra 1932) and pelycosaurs (Romer & Price 1940). The remainder of the proximal posteroventral surface is covered by the coracobrachialis brevis. The • coracobrachialis brevis insertion is separated from the insertion of the 63 brachialis inferior by a stout ridge extending distally fi'om the deltopeetoral • crest, turning b'radually into the entepicondyle. Most of the anterodorsal surface is occupied by a large triangulaI'

depression, the apex being near the ventral constriction. It is bordered proximally by the deltopectoral crest. Scarring in this area suggests that

the insertion of the triceps lateralis is larger than in Captorhilllls (Hol mes 1977), thus restricting the insertion of the scapulohumeralis to the opposite side of the ridge that delimits the subcoracoscapularis insertion. A distinct low ridge extends from the proximal anterior surface toward the medial constriction to the level of the processus latissimus dOl'si, which is more conspicuous than in captorhinids. It is located closer to the

proximal head of the humerus, 22.3% of the total length in BamsallrllS

and 35.5% in Captorhinlls. Anterior to this ridge the surface is (lriented somewhat more parallel to the body surface than is the case in

Captorhinlls, suggesting that the subscapulocoracoiàeus was difTerently oriented. The anteroventral surface provides a large area for insertion of the supracoracoideus, whilst the ventral insertion of this muscle seems to be

restricted in comparison with Captorhinlls..

The distal expansion of the humerus is less pronounced in Barasallrlls

than in Captorhinus, and differs more profoundly from the latter than does the proximal expansion. This results in part from the smaller size of the entepicondyle, as found in other procolophonids. The average width of the distal expansion is 37.7% of the humerallength compared to 40~% for

Captorhinus (Holmes 1977). The supinator process is not a distinct structure but it is incorporated into the ectepicondyle. The ectepicondylar • foramen is present as· a notch through which the radial nerve and blood 64 vessel presumably passed (Romer (1956), much as in Petrolacosaurus • (Reisz 1972). The foramen is never closed in bone but may have been bridged over by cartilage. The distance between the trochlear notch and the ectepicondyle is almost equal to the distance between the trochlear notch and the entepicondyle in Barasaurus, whereas in Captorhinus it is 0.6 times the length of the latter. The entepiconriylar foramen is absent in Barasaurus as is in Owenetta (Reisz & La.urin 1991), but is otherwise invariahly present in early amniotes, including Nyctiphruretus (Ivachnenko 1979) and Procolophon. The distal articulating surface is similar to that found in Captorhinus and pelycosaurs, although due to the lesser size of the entepicondyle it is more centrally located. In contrast with Captorhinus (Holmes 1977), the capitulum is more hemispherical than ovoid. The trochlear groove is confluent with the capitulum. The dorsal extent of the trochlear groove cannot be ascertained due to the lack of an adequate view of this area in any of the specimens.

Ulna The ulna in Barasaurus is the more robust of the two propodial

elements (P 5, fig. 24) and stouter than that of Captorhinus. The configuration of this bone is similar to that of most primitive amniotes, as well as !izards and Sphenodon. The proximal and distal ends are expanded and the shait is very narrow. Of these expansions the distal one is slightly larger in mature specimens. The expansions are asymmetrical along the longitudinal axis, the medial margin being decidedly more • concave than the lateraI. 65 In contrast to the ulna of Captorhil1l/s (Holmes 1977) the si!{moid notch • is but a shallow indentation. The olecranon process is markedly shOl·ter in Barasaurus. It equals 23% oftte totai length in Captorhil!lls (Holme3 1977\ but only 14.4% in Barasaurus, measured from the lowest point of the sigmoid notch. This suggests a lessel' function of the triceps medial head. In immature individuals the olccranon is missing and the proximal end of the ulna is finished in porous bone. The posterior surface of the ulna is slightly convex and nearly featureless. Little evidence for muscle attachment is observed except on the proximal expansion, perhaps outlining the insertion of the dorsal portion of the epitrochleoanconaeus. The proximal portion of the anterior surface has a shallow triangulaI' depression- the apex is directed distally. Laterally a distinct Hexor crest l'uns the entire length of the ulna. Specimen P2 bears a smal! îlange projecting laterally from the flexor crest. This structure is not evident in other Barasaurus specimen but can be observed in sorne specimen of Captorhinus. As in al! primitive amniotes, the distal end articulates with the intermedium, ulnare and pisiform of the carpus. This surface is

considerably broll.der than that of Captorhinus (38% versus 25% of the total length) and other early amniotes. The largest of the facets is that which articulates with the pisiform, which takes up about half of the extent of the distal expansion. The area of connection of the pisiform is distinct from that of the ulnare and intermedium, being separated from that of the ulnare and intermedium by a tiny ridge, more conspicuous on the lateral than on the medial surface. The regions of articulation with the ulnare • and intermedium are confluent. 66 Radius • The radius is a stout, cylindrical bone, the shaft of which is ovoid in crossection. The central constriction gradually expands towards both ends. The radius reaches about 94% of the length of the ulna in mature specimens. This is similar to the condition found in early protorothyrids and other early amniotes (Romer 1956). Both lateral and medial surfaces show very !ittle evidence of muscle attachment. The medial and lateral surfaces are marked by low, rounded ridges. The proximal extremity of the medial Eurface appears to be less rounded and on specimen P 3 a scar indicates the biceps is found in this area. The proximal articulating surface bears an almost circular depression, which corresponds with the hemispherical capitulum. The periphery of this depression is smooth but for the slight extension of the aforementioned ridge of the medial surface. The distal head of the radius articulates with the radial alone, and appears as a simple, slightly concave surface. In general the antebrachium of Barasaurus is somewhat shorter and considerably more robust than in the majority of early amniotes. The wna - humerus length ratio is .63 compared to .76 in Captorhinus. A comparable ratio to that of Barasaurus is present in millerosaurs (Gow 1972). Reisz (1981) reports that the ulna of Petrolacosaurus is longer than the humerus.

Carpus

The carpus is weil preserved in a number of specimens (P 5, fig 24; CM 47512, fig. 21). The radiale is the smallest of the proximal series ofcarpals, like in Palaeothyris (Carroll 1969). It is semicircular in lateral view. A • short, broad parallel sided area projects medioproximally. It bears a 67 shallow cavity for the articulation with the radius that probably allowL'd • sorne rotation on this joint. 8eparate facets fol' the distal articulat.ions arL' not evident.

The intermedium is very similar to it's counterpart 1Il Captorll i 1111.' (Holmes 1977). The largest side, the medial surface, slopes obliquely away from the ulna forming the medial periphery of the "ulnar pyramid" (Miner 1925). It's proximal extremity bears a facet for the medial port.ion of the distal articulation surface of the ulna, much like in Palacotllyris. A semi-circular notch in the medial margin of the ulnare contributes to the lateral border of the perforating foramen. A shallow trough passes obliquely from the ventral to dorsal surface, reflecting the path of the perforating nerve and vascular bundle. The remainder of the ulnare is almost circulaI' in dorsal aspect. There is only a minimal excavation laterally to accommodate the pisiform and fifth metacarpal in contrast with Captorhinus and Palaeothyris in whkry the ulnare is greatly incised laterally thus appearing "hourglass" shaped. The proximolateral corner of the lateral centrale is incised to form the distal border of the perforating foramen. On the ventral surface a shallow depression occupying the proximal half of the bone is continuous with a similar feature on the intermedium. This shallow depression delimits the origin of the extensor digitori!l communis brevis (Miner 1925). Among the carpal bones the most striking difference compared with that of Captorhinus and Palaeothyris is in the pisiform. It is considerably larger than the radiale and roughly rhomboidal in shape. The apex is directed medially, the base laterally. It articulates broadly with the ulna and ulnare. Both surfaces are closely connected, apparently precluding any substantial movement between the elements. The distal end of the

68 ventral surface is beveled sharply indicatiflg the insertion of the extensor • carpalis ulnare (Miner 1925). An important character in ail procolopl. 'Jnids is the presence of only four distal carpals as opposed to five in most other early amniotes. Only pareiasaurs share this character among early amniotes. Ali distal carpals of Barasaurus are roughly rectangular. The first is slightly larger than the second and third as in Bradysaurus, a reversai of the situation found in most other early amniotes where the distal carpal increase in size from one to four. The fourth distal carpal is conspicuously enlarged in Barasaurus, roughly the size of the radiale. Metatarsals two to five exhibit the same hourglass shape and appear to be of roughly similar size. Metatarsal one is shorter and the proximal expansion is larger than the distal one. This is due to a conspicuous medial process, similar to, but not as developed as in Procolophon (Colbert & Kitching 1975). In early amniotes only pareiasaurs seem to exhibit a similar process (Romer 1956). Barasaurus shows the general phalangeal count of the manus in early amniotes 2, 3, 4, 5, 3., but the elements are short and stubby. Only pareiasaurs show a reduced formula of 2, 3, 3, 3, 2., and Proganochelys the even more reduced formula of 2, 2, 2, 2, 2.

• 69 •

Fig. 25. Barasaurus besairiei. Specimen P 3, pelvic region and pes in dorsal view.

• 70 •

sac

• lem Pelvicgirdle • The pelvic girdle morphology in amniotes is generally consen·ati\'e. Ali three elements contribute about equally to the acetabululll. Unlike the glenoid, it is a large, deep, concave and rounded structure. The simplicity of it's outline corresponds to the relatively simple stroke cycle of the hind limb. A distinctive characteristic of the procolophonid pelvic girdle is the

attachment to the axial skeleton via three pairs of sacral ribs (P 3, fig. 25 l. This requires an expansion of the ilium in an anteroposterior plane tu accommodate the sturdy articulation. This expansion, also observable in Diadectes, pareiasaurs, and sorne derived pelycosaurs, facilitates a reinforced area for the insertion of the dorsal musculature of the l'l'mur and lower leg. In lateral view the iliac blade of Procolophon is virtually symmetrical around an axis running through the center of the acetabulum. Just dorsal to the acetabulum the blade narrows to an isthmus. Above that the anterior margin flares extensively. In contrast, in Barasaurus the anterior margin ascends straight dorsally l'rom the constriction. The blade, however, is considerably more rcbust than those seen in captorhinids. The pubic symphysis in Eocaptorhinus is very thick, about 50 mm in mature specimens, whereas the symphysis of Barasaurus appears to be l'quai throughout the entire length of the line of attachment which was probably cartilaginous until late in life. The late coossification of the bilatei'ul elements, and indeed the three elements on each side are indicative of a prolonged growth period. The pubis is the smaller of the two remaining bones. It's bulk is • concentrated in the puboischial plate. It is almost square in outline but the 71 lateral border turns dorsally about 90', contributing to the anteroventral • portion of the acetabulum. The deeply notched anterior margin bears a wide pubic tubercle laterally. The ischium is almost twice as long as the pubis. It contributes the posterior quarter to one-third of the acetabulum. In ventral view the lateral border is deeply notched for the femoralis longus muscle. The whole ventral surface of the puboischiadic plate offers little evidence of muscle scaring. A few prominent markings on the ischium may signify the attachment of the ilioischiadic ligament and the puboischiofemoralis muscle. The internai surface of the puboischiadic plate is distinctly different from the condition found in Eocaptorhinus, in which it is dominated by a massive ridge passing medioventrally from the anteromedial edge of the ilium at approximately the dorsal extremity of the acetabulum, increasing in prominence to comprise the bulk of the heavy pubic symphysis. This ridge is not apparent in any procolophonid, although a similar pattern occurs in pelycosaurs (Romer 1940). The ridge divides the internai surface of the puboischiadic plate into two portions in Captorhinus. The posterior part is comprised of the ischium and the posterior portion of the pubis. The other portion is the anterior part of the pubis. The anterior area is roughly triangular in outline, the apex being anterior. The obturator foramen perforates this surface. In captorhinids, the anterlor area provides the origin of the puboischiofemoralis internus. The corresponding surface in Barasaurus cannot be identified. In the absence of the massive ridge the internai surface appears as a simple plane. The significance of this is two fold. It suggests a reduced puboischiofemoralis, or at least a modified • origin, wrapping around the prominent anterior margin of the ilium. 72 The acetabulum does not ref1ect any of the modification" """n • elsewhere in the girdle. The maximum dimension of the acetabulum run" l'rom it's anterior extremity posteriorly and slightly dOl'sally to th" ilioischiadic junction, in contrast to most other early amniotes in which the maximum dimension is horizontal. The generalized outline and lack of information on the shape and extensiveness of the cartilaginous part of the acetabulum make it difficult to infer the stroke-~ycle, as hus been done in other primitive amniotes (Sumida 1990, 1991). As a result of the retarded ossification, the three elements of the girdle are easily discernible in the cup. The bulk of the surface is made up by the ilium. The pubis and ischium contribute little more than the ventral ridges, a condition also found in Eocaptorhinus and Procolophon. In other early amniotes like pelycosaurs or palaeothyrids the elements contribute up to one third each to the acetabulum. The apex of the acetabulum, while located ventrally on the ilium in Barasaurus is displaced posteriorly in Procolophon. The dorsal muscles which insert directly on the girdle - the longissimus dorsi and iliocostalis - constitute the only muscular attachments that also reach onto the lateral surface of the iliac blade. On the upper portion of the Eocaptorhinus iliac blade, both lateral and medial surfaces are obviously areas of origin for this muscle group. The procolophonid condition as exemplified by Barasaurus is more advanced. The ilium is expanded anteroposteriorly, restricting the insertion of the dorsal axial musculature to the medial surface. The appendicular musculature has migrated to take it's origin on the anterior surface of the ilium. The procolophonid condition seems to converge on that found in • Diadectes and sphenacodont pelycosaurs (Romel' & Price 1940). 73 The ventral musculature of modern reptiliomorph amniotes comprises • two portions, one anterior and the other posterior to the ilium. Little evidence of these divisions can be seen in fossil reptiles. According to Romer (1956) the bulk of the ventral muscles inserted on the iIiopubic ligament, which runs from the dorsal surface of the ilium to the pubic tubercle. Neither this ligament nor it's connecting musculature is reflected in scars on the bone surface in Barasaurus. The most striking difference between the Barasaurus ischio-pubic plate and that of captorhinids is the absence of the anteriorly facing surface for the origin of the puboischiofemoralis externus. It's relative significance is inferable from the large internaI trochanter of the proximal femoral head. The origin in Barasaurus is reconstructed as being located on the dorsal surface of the pubis; the muscle passed over the pubic tubercle and under the iliopubic ligament, then inserted on the tibia. Despite the difference in orientation of the origin, its basic function remains the same, although the vertical and rotational component may have been reduced due to the minimal dorsal extension of the pubis. Romer (1922) reconstructs the same structural modification for Dimetrodon but argues against the expansion of the origin of the puboischiofemoralis externus onto the puboischiadic plate. The probable area of origin of the iliofemoralis is preserved in CM 47513 and CM 47514, occupying a considerable central portion of the iliac blade. It is much larger than the corresponding area in Eocaptorhinus or Palaeothyris. In modern lizards the ventral plate supports a number of muscles, including a complex set of flexor muscles pubotibialis, puboischiotibialis, tibialis internus and externus. Their respective areas of • origin are continuous and cannot be differentiated accurately. The head of 74 the consplCUOUS puboischiofemoralis internus accu pIes the bulk of tlw • ventral plate.

Femur The femur possesses fewer distinguishing features than the humerus. Romer (1922) attributed the general conformity of femoral structure throughout primitive amniotes to it's relatively simple mode of action. Whereas the humerus simultaneously performs the function of support, propulsion, and orientation of the body, the femur functions primarily in propulsion. Romer (1922) contrasts the simple "down and back" excursion of the femur with the complex action of the humerus (also Watson 1917, Miner 1925, Holmes 1977). The general impression given by the femur of Barasaurus is that of a comparatively long slender bone. Characteristically in primitive amniotes the femur is longer than the humerus. The femur of Barasaul'1ls averages 1.06 times the length of the humerus, similar to the value found by Colbert (1975) for Procolophon. The Procolophon femur is much larger and somewhat more robust, but the general structure is clearly comparable to that of Barasaurus. Romer (1956) describes the femur of Procolophon as lacking an adductor ridge and the fourth trochanter. Whilst the latter appears to be true, plaster casts at hand appear to show a faint adductor ridge. Barasaurus clearly lacks a fourth trochanter. In Barasaurus the femur exhibits the typical primitive amniote configuration. Roughly triangular proximal and distal expansions, less pronounced than those of the humerus, taper gradually toward each other and are joined by a long, slender shaft (CM 47518, fig. 18). Lines drawn • through the maximum breadth of each of these areas (through the 75 articular surface proximally; and through the anterior and posterior condyles distally) appear to be roughly in one plane. This contrasts with an

• 0 angle of about 45 reported by Fox and Bowman (1966) for Captorhinus, and the situation pictured for pareiasaurs by Gregory (1946). The dorsal surface of the proximal expansion is devoid of conspicuous

features. It resembles a triangle with the posterior margin more divergent and slightly concave. It is divided into two subequal facets by a ridge which extends distally from the proximal articulating surface to become the anterodorsal margin of the shatt. Slightly anteroventral to this ridge is the internai trochanter exposing a large dorsal surface area like in early pelycosaurs and Procolophon, considerably more than in protorothyridids or captorhinids (Heaton & Reisz 1980). Faint evidence of the puboischiofemoralis internus and ischiotrochantus can be seen near the posteromedial border. The internaI trochanter of Barasaurus.is a ,:omparatively smaU structure that extends toward the articulating surface as a narrow ridge. This contrasts with the situation in Captorhinus where the trochanter is separated by a distinct notch. Fox and Bowman (1966) identify a lappet of porous bone that projects from the articulating surface towards, and sometimes joining, the trochanter. This lappet is only minùte in Barasaurus and Procolophon. The internaI trochanter diminishes in prominence distaUy as it converges with the adductor ridge. Contrary to the condition in Captorhinus, their convergence does not clearly demarcate the distal extremity of the intertrochantic fossa, nor does their conjunction form a fourth trochanter, as is the case in pareiasaurs (Gregory 1946), which is in • contrast to all other early amniotes. 76 On the ventral surface of the shaft, as in Frocolopholl. but unlike • captorhinids and primitive pelycosaurs, the adductor ridge is short. TIll' adductor ridge arises as a direct extension of the internaI trochanter, resembling somewhat the situation of protorothyridids (Reisz 1980), but unlike Captorhinus, in which the adductor ridge finds it's origin anterior to the internaI trochanter. The adductor ridge, as in protorothYl'ids, defines the ventralmost border of the femur from the level of the distal portion of the intertrochantic fossa. It continues distal1y, decreasing gradually in prominence to the point at which the distal expansion originates. The distal head flares abruptly to produce the anteriol' condyle. The adductor ridge continues distal1y, diverging only slightly posteriad to forrn the ventral ridge ofthe posterior condyle. The dramatic broadening of the anterior border of the distal expansion gives the impression that the adductor ridge and it's extension, the ventral margin of the posterior condyle, gradually cross the femur diagonal1y from the anterior proximal edge to the posterior distal margin, as in protorothyridids (Reisz 1980). The adductor ridge in Captorhinus forms an more oblique angle with the shaft, and is not confluent with the ventral ridge of the posterior condyle but rather gradually diminishes in height distally, ending near the apex of the papiteal space. The ventral ridge of the posterior condyle and the anterior margin of the distal expansion form the posterior and anterior borders of the popliteal space, a triangulaI' area located between the condyles. Due to distortion and damage in the Barasaurus specimens it cannot be described in detaiL Posterior to the ventral ridge the posterior facet of the lateral • condyle rises ventrally, bearing a depression. 77 The condyles are divided dorsally by a conspicuollS longitudinal groove that guided the tendons of the flexor femoralis. The posterior condyle

• fu~ther projects distally than does ifs counterpart in many primitive amniotes like Captorhinus or Palaeothyris (Carroll 1969), resembling early pelycosaurs and pareiasaurs. The generalized nature of the primitive amniote femur coupled with the relative incompleteness of preservation in this element in Barasaurus prohibit a detailed interpretation of the pelvic musculature in this genus. The reduced internai trochanter implies a somewhat smaller puboischiofemoralis internus than is found in Captorhinus. The absence of a fourth trochanter suggests a highly reduced caudifemoralis similar to the condition inferred for pareiasaurs by Boonstra (1932).

TIbia and Fïbula The epipodial elements of the hind limb conform to the basic amniote structure (CM 47518, fig. 18). By comparison to the tibia and fibula of Captorhinus these elements are quite long and slender, exceeding three quarters of the length of the femur in adult specimen. The maximum width of the proximal tibial head is one third of the total length, proportions comparable to protorothyrids (Carroll 1969) and pelycosaurs (Romer 1940). It gradually tapers distally attaining a minimum width at exactly half it's length. The lateral margin of the proximal expansion diverges further from the longitudinal axis than does the media!. .The slender shaft continues distally expanding gradually towards the obliquely angled articulation surface for the astragalus. Distal to the central constriction, the dorsal surface is somewhat • flattened. The cnemial crest divides the proximal dorsal surface into 78 subequal portions, the medial being the smaller. At it's proximal • extremity it is a prominent flange inclined medially. The crest diminishes distally disappearing at approximately the level of the central constriction. Romer (1956) states that the procolophonids have lost the cneminl el'est entirely. It is clearly evident in Barasallrlls but not as strong as in pelycosaurs. Longitudinal axes drawn through the proximal and distal articulating surfaces appear to be offset at an angle of about 30". The distal articulation with the astragalum at the beginning of the power stroke is oriented transversely, whereas the proximal articulation with the femur is oriented diagonally - anteromedial to posterolatera1. This torsion is more pronounced in Captorhinus than it is in Barasallrus. The fibula is more slender than the tibia and slightly longer. Like the tibia, it is expanded at either end, and is less massive than that found in Captorhinus or Procolophon. In contrast to the tibia, however, the distal expansion is larger than the proximal. The distal articulating surface, which contacts the astragalum and calcaneum, is set obliquely to the longitudinal axis such that the lateral border appears longer than t.he medial. The medial margin is only slightly concave. In cross section the fibula is mediolaterally compressed.

Tarsus Numerous well articulated specimens present almost perfect conditions to reconstruct and describe the tarsus (CM 47518, fig. 18; CM 47512, fig. 20). The astragalo-calcaneum is a broad structure, very thin dorsoventrally. This condition, shared with protorothyrids, early synapsids and Captorhinus, appears to be primitive for amniotes. It is in

79 contrast to the astragalo-calcaneum of Procolophon which is considerably • more elaborated -the elements are closely integrated; a large perforating foramen persists. The astragalus is significantly larger than the calcaneum in contrast with Palaeothyris in which they are of roughly similar size. The astragalus and calcaneum are fused in specimen CM 47512. A suture can be seen extending from the contact with the fibula to the perforating foramen. The astragalus possesses a small but nonetheless distinct medial extension reminiscent of that ofDimetrodon (Romer 1956), that is responsible for an angle of about 90· in the articulation with distal tarsus bones to that of the tibia proximally. As in Captorhinus (Heaton & Reisz 1980) the tibial articulation is distal to that of the fibula in Barasaurus. This does not occur in either Procolophon or Nyctephuretus. The Nyctephuretus cruro-tarsal joint as reconstructed by Efremov (1940, see also Ivachnenko 1979) is oriented transversely to the long axis of the foot. In Barasaurus, a gently concave surface separates these two areas. The distal quarter of the articulation with the calcaneum is taken over by the perforating foramen. Distally the astragalus articulates with four bones, the lateral centrale and distal tarsals two, three, four. This is in contrast with other early amniotes where it articulates with the lateral centrale and the distal tarsal four. Only synapsids show a different pattern with a medial centrale present in early forms like Ophia"odon. The calcaneum is smaller than the astragalum in both longitudinal and lateral dimensions. It is roughly circular in outline as in Eocaptorhinus. Proximally an area of porous bone indicates the site of • fibular articulation. Distally a distinct facet for the articulation with the 80 •

Fig. 26. Barasaurus besairiei. A, reconstruction of the left rnanus in dorsal view. B, reconstruction of the left pes in dorsal view.

,

81 •

1cm

• large tarsal four is present. Il. is very likely that the ~ll\all di~tal tar~nl li\,<' • articulated on the same surface. Most of the dist.al ~urfacl' l'o1"111 S an articulating surface for the remaining distal tar~als.

The calcaneum is concave in dorsal aspect. Prominent ridges OCClII' in the region of the perforating foramen and the border \Vith the a~tragnlull\, the lateral border, and where it articulates \Vith the fllurth di~tal tnl·~al. The central depression is marked by a number of short, circularly oril'l1t.ed muscle scars. Distal ta the astragalocalcaneum a single centrale persists, in contrast ta sorne protorothyridids and early pelycosaurs that possess both a medial and lateral centrale (Carroll 1969). It is located directly between the mediodistal border of the astragalus and the distal tarsals. It shows the construction typical for the Captorhinus tarsus. The condition in Captorhinus and Barasaurus might indicate a fusion of the medial and lateral centrale, but there is no direct evidence ta support this. Ali centralia are lost in Procolophon. Nycteplwretus l'l'tains one but in contrast ta the situation in Barasaurus and Captorhinus il. is extremely large (lvachnenko 1979). Five distal tarsals are present in Barasaurus, which is comparable ta the primitive condition of Palaeothyris (Carroll 1969). Distal tarsal four, the most prominent of the series, is a large rectangular bonI.'. It's apex is securely lodged between the astragalus and calcaneum which obviously prohibits any movement along a metatarsal joint. This is visible ta a lesser degree in Ophiacodon. Metatarsals 2 - 5 exhibit the typical rod-like pattern. Metatarsal one has a unique shape in Barasaurus, resembling that of Procolophon. It is a short bone, considerably more robust than the other metatarsals. The

82 proximal expansIOn IS asymmetrical, the medial border exhibits a • conspicuous flange ending in a point at about one third of the bone's length. Distally from this point the medial margin is ventrally concave. Heavy scaring on both flexor and extensor surfaces indicate the insertion of tendons of the supinator and pronator musculature. The formula for the phalangeal count of the pes is 2, 3, 4, 5, 4 in early amniotes. Although the number of elements in the fifth digit cannot be verified, Barasaurus otherwise conforms to this count. Amongst early amniotes pareiasaurs show a reduced formula of 2, 3, 3, 4, 3 (Gregory 1946). This description is used as a basis for establishing a character list to test hypotheses of relationships ofearly amniotes.

• 83 ANALYSIS • The matrix used in this study comprises 13 taxa and 68 charncters. The data for the character list \Vas compiled on the basis of examinatioll of specimens and publications: Proterogyril1l1s (Holmes 1984); Eocaptorhil1l1s (Holmes 1977); Seymollria (White 1939); Lillll10scelis (Fracasso 1983); Diadectes (Carroll 1969, Berman et al. 1992); Haptodlls (CUlTie 1979); Milleretta (Gow 1972); Paraiasauria (Lee 1993, 1995); Procolophon (Carroll & Lindsay 1985); Proganochelys (Gaffney 1990); Eocaptorhinlls (Heaton 1979); Palaeothyris (Carroll 1969). Additionally, computer-based Im'ge scale analyses by Gauthier et al. (1988), Lee 0.995) and especially LaUl'in & Reisz (1995) have been reviewed. One of the main objectives of this study was to test the hypothesis of relationships as published by Reisz & Laurin (1991) -- tUl·tIes as the sister­ group of procolophonids. It was seen as useful to follow their general structure concerning the character list and discussion of results to allow better comparison. However, this proved difficult at times because their study is not description based. Quite a few characters are based on observations that are not available in publications and are thel'l'fore difficult to test or verify. Since 1 did not have the opportunity to study ail the material that was available to Laurin & Reisz sorne characters had to be omitted from this study. Those characters will have to be restudied in the future.

The characters used in this study and their expression in the taxa involved are as follows (l'valuation of characters in the systematics section and • discussion): 84 1. Narial shelf present or absent. • A narial shelf or recess is present in ail procolophonids included in this study. It is best developed in Barasaurus, whilst it is just a shallow trough in Procolophon. 2. Frontal orbital contact absent or present. Primitively the frontal is excluded from the orbit by the pre- and postfrontal. This condition is also present in Milleretta, for which only the description ofjuvenile material is published, and Proganochelys. 3. Postparietal present or absent. Primitively postparietals are rather large bones that make up a significant portion of the posterior rim of the skull table. In early procolophonids the postparietals are very smaU, rounded knobs at the end of the skuU table. The postparietal is completely lost in Procolophon and Proganochelys. 4. Prefrontal palatal contact absent or present. The contact is absent in Proterogyrinus, Limnoscelis, Haptodus and Palaeothyris which is considered primitive. AlI other forms exhibit a contact but in the case of the Barasaurus and Owenetta specimen at hand it is difficult to ascertain as to what degree the elements are in contact. 5. Prefrontal internaI medial process absent or present. Whilst most of the forms show a varying degree of prefrontal palatal contact, only procolophonids possess a process that reaches almost the midIine, partitioning the nasal cavity off from the orbit. 6. Lacrimal narial contact present or absent. The lacrimal borders the narial opening in aU forms except in Owenetta, Procolophon and Proganochelys. • 85 •

Fig. 27. Skulls of batrachosaurs in dorsal view. A, Seymouria after Laurin & Reisz (1995; B, Limnoscelis after Fracasso (1983); C, Procolophon after Carroll & Lindsay (1985), D, Proganochelys after Gaffney (1990); E, Eocaptorhinus after Heaton (1979); F, Haptodus after Currie (1979); G, Scutosaurus after Ivachnenko (1987). Drawn to no scale.

86 pD 1 • po po

qj

~ pD 1 c D pd-

qj

F

qj

st • 7. Anterior reach of the jugal. • The jugal does not extend to the anterior orbital ri!l1 in Proterog\'rillus. Seymouria, Haptodus, Milleretta, Owclletta. Barasuurus. Progullochc!ys and Palaeothyris. This condition is interpreted as primitive. Lillllloscc!is. Diadectes, Procolophon and Eocaptorhinus exhibit the advanced condition where the jugal reaches the anterior orbital rim or beyond. 8. Postorbital supratemporal contact present or absent. In Proterogyrinus, Seymouria, Barasaurus, Proganochclys, Eocaptorhinus and Palaeothyris there is no contact between the postorbital and the supratemporal. The advanced condition in which the postorbitai contacts the supratemporal is present in the other forms. 9. Intertemporal present or absent. Only Proterogyrinus and Seymouria possess an intertemporai, which is seen as primitive. Ali other forms have lost the intel'temporal. 10. Posterolateral corner of skull table formed by tabular or supratemporal. For the latest summary of the tabular versus supratemporal question sec Lee (1995). Only in Proterogyrinus and Seymouria is the tabular at the posterolateral corner of the skull table. In ail other forms the supratemporal occupies this position. 11. Tabular present or absent. Proterogyrinus, Seymouria, Limnoscelis, Diadectes and Haptodus possess tabular that is comparable in size to the parietal. In Milleretta and Palaeothyris the tabular is only a small splinter of bone. No tabular is present in pareiasaurs, procolophonids, Proganochelys and Eocaptorhinus. • 87 •

Fig. 28. Skulls of batraehosaurs in lateral view. A, Seymouria after Laurin & Reisz (1985; B, Limnoscelis after Fracasso (1983); C, Procolophon after Carroll & Lindsay (1985), D, Proganochelys after Gaffney (1990); E, Eocaptorhinus after Heaton (1979); F, Haptodus after Currïe (1979); G, Scutosaurus after Ivaehnenko (1987). Drawn to no seale.

,

88 A po ~ • Ji B nprf st .. ~

po

n

po

E prf ~ Ji

po • 12. Anterodorsal process of maxilla absent or present. • This process, which forms the posterior rim of the naris, is present in pareiasaurs, Owenetta, Procolophon and Proganochelys. It is absent in al1 the other forms. 13. Anterior maxillary foramen. Proterogyrinus, Seymouria, Limnoscelis, Diadectes, Haptodus, Eocaptorhinus and Palaeothyris show multiple foramena on the maxilla which is considered primitive. Milleretta, pareiasaurs, Owenetta, Barasaurus, and Procolophon possess one prominent foramen. No foramen is present on the maxil1a of Proganochelys. 14. Maxil1a and quadratojugal contact each other or are separated. In Haptodus, pareiasaurs, Owenetta and Barasaurus does the maxilla does not contact the quadratojugal. This is considered to be advanced. In al1 other forms the two bones contact each other. 15. Quadratojugal is narrow or dorsal1y expanded. In most early amniotes and amphibians the quadratojugal is a narrow bone dorsoventrally. Milleretta, pareiasaurs, Procolophon and Proganochelys are advanced in having the quadratojugal expanded dorsoventrally. 16. Otic emargination. No otic emargination is present in Proterogyrinus, Limnoscelis, Haptodus, Eocaptorhinus and Palaeothyris. This state is seen as primitive. In Seymouria and Diadectes an emargination is present, formed by the squamosal and supratemporal. In Milleretta, pareiasaurs, procolophonids and Proganochelys the otic emargination is formed by the • squamosal and quadratojugal. 89 •

Fig. 29. Skulls of batrachosaurs in ventral view. A, Seymollria after Laurin & Reisz (1995; B, Limnoscelis after Fracasso (1983); C, Procolophon after Carroll & Lindsay (1985), D, Proganochelys after Gaffuey (1990); E, Eocaptorhinus after Heaton (1979); F, Haptodus after Currïe (1979); G, Scutosaurus after Ivachnenko (1987). Drawn to no scale.

• 90 A •

F

• 17. Ventral margin of skull. • Primitively the skull is ventrally convex us in Protcrogyrilllls. SCYlllollria. Limnoscelis, Diadectes, Haptodlls und pureiasuurs. The ventral murgin of the skull is rectilinear in Milleretta. Progallochelys. Eocaptorhilllls and Palaeothyris. Only procolophonids exhibit A concuve ventral mm'gin of the skull. 18. Quadrate exposure. Primitively the quadrate sits medial to the squumosal und quadratojugal and is not exposed laterally. Of ail the forms involved only Diadectes and Proganochelys have a quadrate that reaches beyond the externut skull bones. 19. Anterior process of quadrate. In Proterogyrinus, Seymouria, Limnoscelis, Haptodus, Millcretta. pareiasaurs, Procolophon and Proganochelys the anterior process of the quadrate almost reaches the basicranial articulation. This is interpreted as primitive. In Diadectes, Owenetta, Barasaurus, Eocaptorhinus and Palaeothyris the anterior process of the quadrate is short, reaching maximally hall' way to the basicranial articulation. 20. Jaw articulation. Primitively, as is the case in Proterogyrinus and Scymouria, the jaw articulation is positioned weil posterior to the occiput. In Limnoscelis, Diadectes, Haptodus, Eocaptorhinus and Palaeothyris the jaw articulation is even with the occiput. In Milleretta, pareiasaurs, procolophonids and Proganochelys the jaw articulation is anterior to the occiput. • 91 •

Fig. 30. Skulls of batrachosaurs in occipital occipital view. A, Seymouria after Laurin & Reisz (1995; B, Limnoscelis after Fracasso (1983); C, Procolophon after Carroll & Lindsay (1985), D, Proganochelys after Gaffney (1990); E, Eocaptorhinus after Heaton (1979); F, Haptodus after Currie (1979); G, Scutosaurus after Ivachnenko (1987). Drawn to no scale.

• 92 • A qj

p D 21. posterior extension ofthe orbit. • The posterior extension of the orbit to accommodate the jaw adductor musculature in the sense of a pseudo temporal opening is a feature unique to procolophonids. 22. Dentition of the transverse flange of the pterygoid. In non amniotes like Proterogyrinus and Seymouria the flange is absent. In Diadectes, Owenetta and Eocaptorhinus a shagreen of denticles covers the transverse flange. In Limnoscelis, Haptodus, ,-vlilleretta, pareiasaurs and Palaeothyris a row of teeth is present. In Barasaurus, Procolophon and Proganochelys no dentition is present on the transverse flange of the pterygoid. 23. Orientation of choanae. Pareiasaurs and Proganochelys exhibit a unique condition where the posterior part of the choanae is turned medially instead of running parallel as in the other forms. 24. Ectopterygoid absent or present. Whilst the size of the ectopterygoid varies amongst the forms studied, only Proganochelys and Eocaptorhinus lost the bone entirely. 25. The ectopterygoid is toothed in Proterogyrinus, Seymouria, Limnoscelis, Diadectes, Haptodus and Palaeothyris. The ectopterygoid is edentulous in Milleretta, Owenetta, Barasaurus, Procolophon an d pareiasaurs. 26. Suborbital foramen. A suborbital foramen is primitively absent in Proterogyrinus, Seymouria, Limnoscelis, Diadectes and Haptodus. Th.. other forms involved possess a • suborbital foramen. The condition for Palaeothyris is not known. 93 27. Ventral cranial fissure. • Only Proganochelys and pareiasaurs exhibit the advanced condition Dl' li fissure between basioccipital and basisphenoid. 28. Posterior width of parasphenoid Primitively the posterior part of the parasphenoid is wider than the

anterior part. This condition is present in Protcrogyrilllls. SCYlIIllII ria. Limnoscelis, Diadectes and Haptodlls. In ail other forms under investigation the posterior part of the parasphenoid is narrower than the anterior part. 29. Length of cultriform process. In Proterogyrinus, Seymouria, Limnoscelis, Diadcctcs. Haptodlls. Milleretta, Eocaptorhinus and Palaeothyris the cultriform process is at least as long as the main body of the parasphenoid. In pareiasaurs, procolophonids and Proganochelys the cultriform process is shorter than the main body of the parasphenoid. which is interpreted as the advanced character state. 30. Basal tubera on basioccipita1. Amongst the forms involved only pareiasaurs, procolophonids and Proganochelys show the advanced condition with strongly developed basal tubera on the basioccipita1. 31. Occipital flange. Only procolophonids possess a distinct occipital flange formed by parietal and supratemporal. No comparable structure is present in the other forms. 32. Dorsal contact of supraoccipital. Primitively the supraoccipital is absent, or contacts the parietal with the • whole width. In Milleretta, pareiasaurs, procolophonids, Proganochelys. 94 Eocaptorhinus and Palaeothyris the contact is facilitated via a narrow • median ridge. 33. Expansion of paroccipital process. In procolophonids, Proganochelys and Eocaptorhinus the advanced character state is present where the paroccipital process is expanded anteroposteriorly instead of dorsoventrally. 34. Contact of paroccipital process. Primitively the paroccipital process contacts the tabular as is the case in Proterogyrinus, Seymouria and Limnoscelis. In Diadectes it also contacts the suprat'1mporal next to the tabular. In Haptodus it contacts the squamosal and tabular. Mil/eretta, pareiasaurs and Procolophon exhibit astate where the paroccipital process contacts the squamosal and supratempora1. In Proganochelys it contacts the squamosal and quadrate, whilst in Owenetta, Barasaurus, Eocaptorhinus and Palaeothyris the paroccipital process ends freely. 35. Size ofpostorbital foramen. Primitively the foramen is about equal in size to the foramen magnum, as is the case in Proterogyrinus, Seymouria, Diadectes and Haptodus. In Limnoscelis, Mil/eretta, pareiasaurs, procolophonids, Proganochelys, Eocaptorhinus and Palaeothyris the postorbital foramen is larger than the foramen magnum. 36. Shape ofoccipital condyle. The occipital condyle is wider than high in Proterogyrinus, Seymouria, Limnoscelis and Diadectes. AlI the other forms exhibit the advanced • condition where the occipital condyle is almost circular in outline. 95 37. Lateral flange of exoccipita1. • Only pareiasaurs and Proganochclys possess a lateral tlange of the exoccipital, which is interpreted as advanced. The condition is not known in Palaeothyris. 38. Articular surface of quadrate. Pareiasaurs, Procolophon and Proganochclys exhibit an almost tlat and rather short articular surface of the quadrate. In all othel' forms the primitive condition is present where the quadrate articular surface is convex and elongate. 39. Anterior reach of the splenia1. Primitively the splenial contributes to the symphysis. Only procolophonids and Proganochelys show the advanced state where the splenial dous not reach the symphysis. 40. Presacral count. Generally early tetrapods have a count of 25 or more vertebrae in the presacral region. Only pareiasaurs and Proganochclys show an advanced state where there are significantly less presacral vertebrae. 41. Bize of atlantal neural spine. In Proterogyrinus and Seymouria the size of the atlantal neural spine almost equals the size of the axial neural spine which is interpreted as primitive. In all the other forms the atlantal neural spine is significantly smaller than the axial neural spine. 42. Process on axial intercentrum. Only Limnoscelis and Diadectes are united by having a distinct anteroventral process on the axial intercentrum. • 96 43. Fusion of atlantal pleurocentrum with axial intercentrum. • In Proterogyrinus, Seymouria, Haptodus and pareiasaurs the atlantai pleurocentrum and the axial intercentrum remain as two separate bones, which is considered ,Jrimitive. The two elements fuse in Limnoscelis, Diadectes, Milleretta, Procolophon, Proganochelys, Eocaptorhinus and Palaeothyris. The condition in Owenetta is not known. In Barasaurus it appears that the elements do not fuse untillate in ontogeny. 44. Trunk neural arches. In Proterogyrinus, Haptodus, Milleretta, Proganochelys and Palaeothyris the neural arches are narrow. This condition is interpreted as being the primitive. The swollen neural arches with wide zygapophyseal buttresses of Seymouria, Limnoscelis, Diadectes and Eocaptorhinus are considered derived partially due to large body size. Pareiasaurs and procolophonids possess swollen neural arches with narrow zygapophyseal buttresses. 45. Ventral surface of anterior pleurocentra. This surface is rounded in Proterogyrinus, Seymouria, Limnoscelis, Diadectes, Haptodus, Milleretta, pareiasaurs and Eocaptorhinus. In Proganochelys and Palaeothyris the ventral surface is keeled. Procolophonids are unique in having two ridges. 46. Number ofsacral vertebrae. Primitively only one sacral vertebra is present as in Proterogyrinus and Seymouria. Limnoscelis, Diadectes, Haptodus, Milleretta, Proganochelys, Eocaptorhinus and Palaeothyris have two sacral ribs. Pareiasaurs and • procolophonids are further specialized in having three sacral ribs. 97 47. Transverse processes on anterior caudals. • Primitively only the anteriormost caudals carry transverse processC's :1'; i,; the case in Proterogyrinus, Seymollria, Limnoscclis. Haptodl/s. Eocaptorhinlls and Palaeothyris. In pareiasaurs, procolophonids and Proganochelys transverse processes continue beyond the tenth caudal. The situation in Diadectes and Milleretta is unknown. 48. Hemal arches. In pareiasaurs and Proganochelys the hemal arches are attached to the anterior centrum, which is considered advanced. Where the situation is known in other forms the hemal arches are wedged between the centra. There is no information available for Limnoscelis, Diadectcs and Milleretta. 49. Shape of interclavicle. In pareiasaurs and procolophonids the interclavicle is strictly T-shaped. Primitively the anterior end is diamond shaped in ail other forms under investigation including turtles (Rieppel 1994). 50. Attachrnent of clavicles to interclavicle. In Proterogyrinus, Seymouria, Limnoscelis, Diadectes, Haptodus, Milleretta, Eocaptorhinus and Palaeothyris the clavicles attach to the ventral side of the interclavicle. In pareiasaurs and procolophonids an anterior groove is present to receive the clavicles. Proganochelys is advanced in having the interclavicle integrated into the plastron. 51. Cleithrum. In the primitive state the cleithrum caps the scapula anterodorsally. This is present in Proterogyrinus, Seymouria, Limnoscelis and Diadectes. In • Haptodus, Milleretta, pareiasaurs, Eocaptorhinus and Palaeothyris the 98 cleithrum does not cap the scapula. In procolophonids and Proganochelys • the cleithrum is absent. 52. Scapulocoracoid. Only two separate ossifications are distinguishable in Proterogyrinus, Seymouria, Limnoscelis, Diadectes and Proganochelys. Milleretta , Haptodus, pareiasaurs, procolophonids, Eocaptorhinus and Palaeothyris show three ossifications in the ecapulocoracoid. 53. Supraglenoid foramen. Primitively a supraglenoid for"men is present, but in M illeretta, pareiasaurs, procolophonids and Proganochelys this foramen is absent. 54. Length ofglenoid In the advanced stüe the glenoid is distinctly less than half the length of the scapulocoracoid, namely in pareiasaurs, procolophonids and Proganochelys. In aIl the other forms under investigation the primitive elongate condition of the glenoid is present. 55. Supinator process. In the primitive state the supinator process is a distinct unit. This is exhibited by Proterogyrinus, Seymouria, Limnoscelis, Diadectes and Haptodus. In Milleretta, Proganochelys and Palaeothyris the supinator process lies paralIel to the shaft of the humerus, but is separated from it by a groove. In pareiasaurs, procolophonids and Eocaptorhinus the attachment for the supinator muscle is not a distinct unit. 56. Ectepicondylar foramen and groove. In Proterogyrinus, Seymouria, Limnoscelis, Diadectes, Haptodus and Palaeothyris only a groove is present which is considered primitive. • Milleretta and Proganochelys are united in having a foramen in addition 99 to the groove. Pareiasaurs only have a foramen present. In procolophonid" • and Eocaptorhinus neither groove nor formnen nl'e present. 57. Entepicondylar foramen. An entepicondylar foramen is present in n11 forllls except Progallochelys. 58. Phalangeal formula of manus. A high phalangeal count is primitive for tetrapods. In thi" investigation the primitive formula 2 3 4 5 3 is exhibited by most of the l'orms involved in this study except for Procolophon which has a formuln of 2 3 4 4 3 and

pareiasaurs and Proganochelys which have a formula of 2 3 3 4 3 01' less. 59. Dorsolateral process of ilium. Limnoscelis and Diadectes are unique in having a dorsolnteral pl'ocess on the ilium. There is no comparable structure in the other l'orms involved. 60. Adductor crest. An adductor crest is present on the ilium of Proganoclwlys. This is not present in any of the other forms. The condition ofMilleretta is unknown. 61. Trochanter major. Pareiasaurs and Proganochelys are united by having a trochanter major, absent in the other forros. 62. Astragalocalcaneum Primitively the astragalocalcaneum is absent. In Diadectes, Haptodus, Milleretta, Eocaptorhinus and Palaeothyris the astragal and calcaneum remain separate. In pareiasaurs, Barasaurus and Proganochelys the two elements are solidly fused. Owenetta and Procolophon are coded as advanced as weIl because the fusion is only shown by adult specimen amongst procolophonids. • 100 63. Medial pedal centrale. • This bone is present in Proterogyrinus, 8eymouria, Limnoscelis, Diadectes. and Palaeothyris. It is absent in ail other forms. 64. Number of distal tarsals. In the primitive state five distal tarsals are present. Pareiasaurs, Procolophon and Proganochelys have four or less distal tarsals, convergent with synapsids. In 8eymouria, Limnoscelis, Diadectes and Owenetta the condition is not known. 65. Length of fifth pedal digit. Only in pareiasaurs and Proganochelys is the fifth digit not longer than the first. This is considered the advanced state. 66. Metapodials. The advanced character state where the metapodials overlap is only present in pareiasaurs and Proganochelys. 67. Phalangeal formula of the peso The primitive phalangeal count of 2 3 4 5 4 is present in aH forms except pareiasaurs and Proganochelys where the formula is 2 3 3 4 3 or less. 68. Dermal ossifications. Ossifications in the dermis are only present in pareiasaurs and Proganochelys.

AU characters were treated as equal. As in Laurin & Reisz (1995), character optimization was performed using the delayed transformation (DELTRAN) algorithm of PAUP 3.1 (Swofi'ord 1993). Proterogyrinus was used as outgroup to determine character polarity. Emphasis was put on using species rather than idealized taxa. However, due to the fossil record • and the material available, this could not always be avoided. Character 101 states were not ordered in this study. The argument of Laurin & Rei~z • (1995) that morphoclines could be mnpped on shortest tn'e~ if ail t.1ll' transformations of a charncter supported it, is invnlid. It doe~ not establish a morphocline since the algorhithm produces this l'l'suit nnyway and in any further study any of those chnracters might not prove to be thnt unambiguous anymore.

RESULTS

One tree was found, requiring 139 steps. The consistency index is 0.626; excluding uninformative characters it is 0.615 (Appendix Ill). In comparison with the tree published by Laurin & Reisz (1995) there is only one notable difference, turtles show up as the sister-group of pareiasaurs and not procolophonids. Mesosaurs, because of inadequatc information, and diapsids, which could not be studied satisfactorily, were not included in my study. The restricted character list used generally supports the cladogram established by Laurin & Reisz (1995). An attempt is made therefore to follow their definitions of the major groups involved. The Batrachosauria include the last common ancestor of Seymoltria, Cotylosauria and aIl its descendants. The Cotylosauria include the last common ancestor of Limnoscelis, Diadectes and amniotes.

• 102 The hypothesis of amniote phylogeny can be described as follows: • Cotylosauria Cope 1880 Diadectomorpha Watson 1917 Amniota Haeckel 1866 Synapsida Osborn 1903 Sauropsida Huxley 1864 Palaeosauropsida new taxon Millerettidae Watson 1957 Procolophonia Seeley 1888 Pareiasauria Seeley 1888 Testudines Linnaeus 1758 Eusauropsida new taxon Captorhinidae Case 1911 Palaeothyris Carroll 1969

Character numbers and node numbers referred to in the text can be found in the appendix in short form and in the list of characters above. In cases where more than one derived condition of a character is present, the condition is given in parenthesis. Negative signs indicate reversais. Names and dates following the taxa indicate their first appearence in the literature but do not reflect the same definition. Since the Cotylosauria reflects the definition of Laurin & Reisz (1995), this group does not need to be discussed further in this study. • 103 •

Fig. 31. Amniote phylogeny used in this study. 1, Batrachosauria; 2,Cotylosauria; 3, Amniota; 4, Sauropsida; 5, Palaeosauropsida; 6, Procolophoniformes; 7, Testudinomorpha; 8, Procolophonia; 9, Eusauropsida.

104 •

7 9

8

6

5

4

3

2

1

• Diadectomorpha Watson 1917 • Definition: The last common ancestor of diadectids and limnof'ce1idf' and ail its descendants. 7 Jugal extends at least to anterior orbital rim. 42 A.xial intercentrum with anteroventral process. 43 Atlantal pleurocentrum and axial intercentrum fused 44 Trunk neural arches swollen with wide zygapophyseal buttresses. 59 Dorsolateral process on ilium present.

Laurin and Reisz (1995) used the following characters: Postparietal median: This character is also widespread among amphibians (Carroll 1987) and does not appear to be applicable at this level. Quadratojugal not reaching level of orbit: Laurin & Reisz are not sure about the polarity of the character since the distribution is somewhat conflicting. Additionally one could ask how the orbit of a procolophonid is

actually defined. Is it the "eye socket" or does it also include UV;! posterior embayment that accommodates the adductor musculature? Occipital f1ange of squamosal absent: The information used in this study concerning Diadectomorpha has been extracted from the literature, making it difficult to assess this character. However, the nature of the character distribution as described by Laurin & Reisz could indicate that there is actually more than one character involved here. Otic trough in ventral f1ange of opisthotic: Again this character could not be satisfactorily verified. Axial intercentrum with anterior process: The same as character 42 of • this study (Berman et al. 1987). 105 Humerus robust without real shaft: This is obviously an adaptation to • lar'ge size and also present convergently in pareiasaurs as Laurin and Reisz mention. This is one in a series of characters frequently used in cladistic analysis that merely reflect size. 1 doubt that any such character can resolve phylogenetic problems.

Amniota Haeckel 1866 Definition: Including the last common ancestor of mammals, testudines and diapsids (including birds) and ail its descendants. 2 Frontal orbital contact present. 22 Transverse flange of pterygoid with row of teeth. 36 Circular occipital condyle. 51 Cleithrum does not cap scapula. 52 Three centers of ossification in scapulocoracoid. 63 Medial centrale pes absent Laurin & Reisz (1995) used the following characters for describing amniotes: Frontal enters margin of orbit: Same as character 2. This condition is also present in the Diadectomorpha. Occipital flange of squamosal: See section Diadectomorpha. Transverse flange bearing t()eth: Sarne as character 22. Occipital condyle rounded: Same as character 36. Labyrinthodont infolding of enamel absent: This appears to be a size related character. Small individuals of an amphibian species might not exhibit this character, whilst it is present in adults. Since most early amniotes are small bodied it would not be surprising if the character is not • expressed accordingly. 106 A.xial centrum tilted anterodorsally: It was not clear which Cl'ntrum is • meant. If the "main" centrum, the pleurocentnml is the one in question. it does not appear to be tilted anterodorsally. Cleithrum restricted to anterior edge of scapula: Same as character 51. Presence of three scapulocoracoid ossifications: Same as charader 52.

Synapsida Osborn 1903 Definition: The last common ancestor of Haptodus and Eothy,.is and ail its descendants.

Though Haptodus was used in this study, my intention was to sec it '1S

a basal synapsid that could help to support a definition of the group Co"; a whole. 14 Maxilla and quadratojugal contact. 34(2) Paroccipital process contacts tabular and squamosal. 64 Number of distal tarsals four or less. Characters used by Laurin & Reisz (1995), who apparently excluded sphenacodonts: Maxilla contacts quadratojugal: Like character 14.In Haptodus the two elements appear to be separated. Laurin & Reisz definition is accepted in this case because of their use of an idealized early synapsid. Caniniform maxillary tooth: Palaeoreptilia lack a clearly defined caniniform. Bince a caninifbrm tooth was present in Palaeothyl'is , it i" more likely that it was lost among early members of the Palaeosauropsida. Lower temporal fenestra present: This character was omitted from this study since it did not contribute to establishing relationships among the • taxa studied. 107 Short postorbital region of skull: It is difficult to determine the length of • the postorbital region in procolophonids. Therefore the character was not uscd. Ectopterygoid absent: An ectopterygoid is c1early present in Haptodus (Currie 19?1 J. Retroarticular process dorsally concave: This character could not be verified with the material at hand. Cauùal haemal arches attached to anterior centrum: This was interpreted as not present in Haptodus, but needs direct investigation. Supraglenoid foramen absent: a supraglenoid foramen is still present in Haptoàus (Currie 1981). Humerus long and slender: As of yet it has not been demonstrated in any satisfactory wv.y that one can compare "stoutness" or "slenderness" from one species to another, let alone from one group to another in a generalized way. The character was "l,,,refore not considered to be of any use. Adductor crest absent: The adductor crest is still present in Haptodus.

Sauropsida Huxley 1864 Definition: The most recent common ancestor of testudines and diapsids, and aIl its descendants. 11 Tabular small. 17 Ventral margin of skuIl rectilinear. ~ Suborbital foramen present. 28 Parasphenoid posteriorly narrower than anterior part. • 32 Supraoccipital with median dorsal ridge. IDS 35 posttemporal fenestra large in compnrison with fornmen • magnum. 43 Atlantal pleurocentrum and axial intercentrum fused. 55 Supinator process parallel to humerus and separated by groove.

Laurin & Reisz (1995) used the following characters: Tabular small or absent: Same as character 11. Suborbital foramen present: Same as character 26. Parasphenoid recess: This character could not be studied on the material at hand. Parasphenoid wingt: absent: Same as character 28. Supraoccipital anterior crista present: This character could not be studied on the material at hand. Supraoccipital plate narrow: Corresponds to character 32. However here the width ofthe plFi:e is compared to the width of the postparietal. Post temporal fenestra large: Same as character as 35 but lacking the reference to the foramen magnum.

Palaeosauropsida new taxon Definition: Testudines and ail reptiles more closely related to them than to eusauropsids. 4 Prefrontal palatel contact absent. 13 One larger anterior maxillary foramen present. 15 Quadratojugal dorsally expanded. 16 (2) Otic emargination formed by squamosal and quadratojugal. 20 (2) Jaw articulation anterior to occiput. • 25 Ectopterygoid edentulous. 109 34 (3l Paroccipital process contacts squamosal and supratempora1. • 53 Supraglenoid foramen absent. 56 Ectepicondylar groove and foramen present.

6i Number of distal tarsals four or less (primitive state retained in BarasaurusJ.

Characters used by Laurin & Reisz (1995) in their definition of the "Parareptilia": Prefrontal palatine contact present: Same as character 4. Foramen orbito nasale: This condition could not be verified with the material at hand. Anterior lateral maxillary foramen: Same as character 13. Quadratojugal expanded dorsally: Same as character 15. Temporal emargination bordered by quadratojugal and squamosal: Same as character 16. Jaw articulation to occiput: Same as character 20. Ectopterygoid small: In this study the ectopterygoid was only coded as present or absent, since it was not clear on which basis smallness was to be defined. Ectopterygoid edentulous: Same as character 25. Stapedial dorsal process: The stapes of Barasaurus is not preserved in any of the specimen, and also not present in the specimen of Owenetta at hand. Sacral ribs slender with narrow distal contact: Again a character that uses slenderness without the possibility of comparing relative slenderness in a millerettid with that of a paraiasaur, for example. Therefore the • character was omitted. 110 Supraglenoid foramen absent: Same as character 53 . • Ectepicondylar foramen and groove present. Same as character 56. Iliac blade dorsally expanded: Whilst the ilium of paraim'aurs (Lee 1995) is significant1y dorsally expanded, the ilium of Barasa/lr/ls is not. The character was seen as an autapomorphy of paraiasuurs and therefore uninformative.

Millerettidae Definition: The most recent common ancestor of Milleretta, Milleropsis and Millerosaurus. and ail its descendants. 18 Quadrate exposed laterally Most of the other characters used by Laurin & Reisz (1995) are not convincing as they admit themselves. Furthermore, the demlal sculpturing in Barasaurus is also composed of tuberosities when present; the length of the interpterygoid vacuity is tied to the skull shape and difficult to evaluate; parasphenoid teeth are present in various groups and are primitive rather than convergent as argued by Laurin & Reisz (1995). 1 sel' the proportional differences in the metatarsal as a possible autapomorphy of millerettids. A much needed study by Gow of adult material is currently in progress (pel'. com. Dilkes).

Procolophoniformes Lee 1993 Definition: The most l'l'cent common ancestor of Procolophonia Pareiasaur:a and Testudines. The name assigned by Laurin & R"isz (1995) is not acceptable because this study reveals that testudines are the sister group of paraiasaurs and not procolophonids. The name Procolophonia • (Seeley 1888) is reserved for true procolophonids in this study. 111 11 (2) Tabular absent. • 12 Anterodorsal process of maxilla present. 29 Cultriform process shorter than main body of parasphenoid.

3J Basal tubera on basioccipital present. 47 Transverse processes on ten or more caudal vertebrae. 50 Clavicle sits in anterior groove on interclavicle. 54 Glenoid distinctly less than half the length of scapulocoracoid.

62 Astragalocalcaneum fused or sutured.

Characters used by Laurin & Reisz (1995) to define this clade: Pineal foramen: Testudines generally do not have a pineal foramen, except for a few "mutants" (Laurin & Reisz 1995). Since a pineal foramen is irregularly present in testudines, its absence cannot be used to diagnose the group. Postorbital far from occiput: This cannot be evaluated due to the posterior embayment of the orbit in procolophonids. Tabular absent: Same as character 11. Anterior maxillary foramen: This character was already used to describe Palaeosauropsida. Caniniform region: As coded in this study, this character is only significant at a more inclusive level; see discussion of Synapsida. Cranio-quadrate space large: The space does not appear to be comparatively larger or smaller in any of the species involved here. The paroccipital process in Procolophon is not parallel to the quadrate ramus of the pterygoid (Carroll & Lindsay 1985) and neither is it in Barasaurus • nor Owenetta. 112 Transverse fiange of pterygoid points anterointel'l11: This is not t111' caSl' • in Procolophon (Carroll & Lindsay 1985). Cultriform process short: Same as chal'l1cter 29. Supraoccipital plate reduced: This character is poody detincd. Paroccipital process antero-posterior1y expandcd: This is the case in

Barasaurus and Owenetta but not in Procolopholl as pictured by Carroll & Lindsay (1985). Quadrate condyle short and fiat: Not in Barasaul"lIsand Owclll'tta. This character is ambiguous in pareiasaurs (Lee 1995). Foramen intermandibularis: This could not be located in Barasallrus and l'l'mains ambiguous as Laurin & Reisz state themselves. Meckelian fossa faces dorsally: This is not the case in Barasaurus and Owenetta. Fossa meckelii short: The fossa does not appear to be much shorter in Barasaurus than it is in Eocaptorhinus (Heaton 1979). Prearticular position: This character could not be veritied with the material of Barasaurus. Trunk neural arches: This character was coded differently in this study due to using Proterogyrinus as an outgroup. The primitive state was narrow neural arches as in most smail anthracosaurs, rather than the size related wide neural arches of Seymouria. Transverse processes on caudals: Since the condition is not known for millerettids (coded ?), it might be a synapomorphy of Palaeosauropsids. T-shaped interclavicle: This is not the case in Milleretta (Gow 1972). Groove on interclavicle for clavicle attachment: Same as character 50. • Scapula narrow and high: This is not the case in Barasaurus. 113 Glenoid bipartite: Somewhat related to character 54. Laurin & Reisz • (1995) mention two facets of the glenoid, one on the scapula and one on the coracoidal part. In Barasaurus the glenoid also stretches l'rom the scapula onto the coracoidal part but it is still one surface. The character appears to be somewhat ambiguous if coded sensu Laurin & Reisz (1995). Acetabular buttress: This is not present in Barasaurus. Femoral greater trochanter: ls not present in Barasaurus and a comparable structure mentioned for Procolophon is questionable as to its homology as Laurin & Reisz state themselves. Astragalus and calcaneum sutured or fused: Same as character 62. Loss of fil'th distal tarsal: This has been coded as also present in Haptodus and Milleretta but that could be due to the difficulty of interpreting this area in both species. Dorsal dermal ossifications: AIe coded differently in this study, since there appear to be differences between the ones found in pareiasaurs and procolophonids (De Braga pers. comm.)

Testudinomorpha Laurin & Reisz 1995 Definition: The MOSt recent common ancestor of Pareiasauria and Testudines and aIl its descendants.

:?3 Posterior end of choana angled mediaIly. 'Z7 Ventral cranial fissure absent. ~ Lateral flange of exoccipital present. 38 Quadrate articular surface almost flat, and short 40 Presacral vertebral count twenty or less. • 48 Caudal hemal arches attached to anterior centrum. 114 61 Greater trochanter of femur present. • 65 Fifth pedal digit not longer than tirst digit. 66 Metapodials overlapping. m Phalangeal formula of pes 2 3 3 43 or less. 68 Dermal ossifications present.

Due to the mounting discrepancies in the interpretation of the cladograms and the differing sister-group relationships of testudines between this study and the study of Laurin & Reisz, it seems more

appropriate to present the arguments concerning the remaining taxa 111 the discussion.

Pareiasauria Seeley 1888 Definition: The most recent common ancestor of Anthodon, Bradysaurus, Deltavjatia, Elginia, Embrithosallrus, Na.noparia., Parasallrus, Pareiasaurus, Scutosaurlls and Shihtienfenia and al! its descendants.

7 Jugal extends to anterior orbital rim. 14 Maxilla and quadratojugal separated. 17 (-0) Ventral margin of skull convex. 43 (-0) Atlantal pleurocentrum and axial intercentrum separate. 44 (2) Trunk neural arches swollen with narrow zygapophyseal buttresses. 46 (2) Three or more sacral vertebrae. • 49 Interclavicle T-shaped. 115 55 (2) Supinator process of humerus parallel to shaft, not separated by • groove. 56 (2) Only ectepicondylar foramen present. 58 (2) Phalangeal formula of manus 2 3 3 3 3 or less.

Testudinata Linnaeus 1758 Definition: The last common ancestor of Proganochelys and modern turtles and ail its descendants.

2 (-0) Frontal does not form margin of orbit. 3 Postparietal absent 8 (-0) Postorbital supratemporal contact absent. 13(2) Lateral anterior maxillary foramen absent 18 Quadrate exposed laterally. 22(2) Trans·!p.rse flange of pterygoid edentulous. 2A Ectopterygoid absent. 33 Paroccipital process expanded anteroposteriorly. 34(4) Paroccipital process contacts squamosal and quadrate. 39 Splenial does not reach symphysis. 45 Ventral surface of anterior centra keeled. 50(2) Interclavicle fused iuto plastron. 51(2) Cleithrum is absent. 52 (-0) Two scapulocoracoid ossifications. 57 Entepicondylar foramen absent. 00 Adductor crest absent. • 116 Procolophonin Seeley 1888 • Definition: The most recent common nncestor of 011'<'11 <,fla, Procolophonidae and Sclerosauridae and n\l its descendants.

1 Narial shelf present. 5 InternaI medial process of prefrontnl present. 17 (2) Ventral margin of skull concave. 21 Posterior extension of orbit present. 22 (2) Transverse flange of pterygoid edentulous. 31 Occipital flange of parietal and supratempornl present. 33 Paroccipital process expanded anterioposteriorly. 39 Splenial does not reach symphysis. 44 (2) Trunk neural arches swollen with nnrrow zygapophysenl buttresses. 45 (2) Ventral surface of anterior centra bears two ridges. 46 (2) Three or more sacral vertebrae. 49 Interclavicle T-shaped. 51 (2) Cleithrum is absent. 55 (2) Supinator process parallel to shaft not separated by groove. 56 (3) No ectepicondylar foramen or groove present.

Owenettidae Broom 1939 Definition: The most recent common ancestor of Owenetta and Barasaurus and aIl its descendants.

14 Maxilla and quadratojugal separated. • 15 (-0) Quadratojugal narrow. 117 19 Anterior process of quadrate short. • 34 (5) Paroccipital process ends freely.

Procolophonidae Lydekker 1890 Definition: The most recent corn mon ancestor of Anomoidon, Burtensia, Candelaria, Contritosaurus, Eumetabolodon, Hypsognathus, Kapes, Koikilosaurus, Leptopleuron, Macrophon, Microphon, Microthelodon, Myocephalus, Neoprocolophon, Orenburgia, Paoteodon, Procolophon and Telegnathus and ail its descendants.

3 Postparietal absent. 6 Lacrimal narial contact absent. 7 Jugal extends at least to anterinr orbital rim. 38 Quadrate articular surface almost fiat, and short. 58 Phalangeal formula of manus 2 3 4 4 3.

Eusauropsida new taxon Definition: Diapsids and ail amniotes related more closely to them than to testudines.

8 (-0) Postorbital supratemporal contact absent. 19 Anterior process of quadrate short. 34(5) Paroccipital process ends freely. • 118 Captorhinidae Case 1911 • Definition: The last common ancestor of Captorhill/ls. Captorhilli/i"". Captorhinoides, Eoeaptorhi/l/ls. Heca togolll ph i /1", 1\a li /leria.

Labidosauri/ws, Labidosa /1 rus, 111oradi"a /1 r/l", Protoea ptorh i /l/l .'. Rhiodentieulatus. Romeria. and Rothia/lise/ls and ail its descendants.

4 Prefrontal palatal contact present. 7 Jugal extends at least to anterior orbital rim. 11 (2) Tabular absent. 22 (-0) Transverse flange of pterygoid carries shagreen of denticles. 24 Ectopterygoid absent. 33 Paroccipital process expanded anteroposterior1y. 44 Trunk neural arches swollen with wide zygnpophysenl buttresses. 55 (2) Supinator parallel to shaft not separated by groove. 56 (3) Ectepicondylar groove and foramen absent.

Palaeothyris Carroll 1969 45 Ventral surface of anterior centra keeled. 63 (-0) Medial pedal centrale present,

The Eusauropsida are not very well supported in this study since they were not at the center of attention. Only three additional steps break up this clade. The Captorhinidae are fairly well established, since they possess several autapomorphies. "Ancestor" type taxa like Palaeothyris pose special difficulties in cladistics hecause they are only definahle by the • absence of autapomorphies, Characters 45 and 63 are primitive for 119 amniotes as are the characters used by Laurin & Reisz (1995): presence of • parasphenoid teeth, trunk neural arches narrow and postorbital far from occiput The long and slender humerus is again not quantifiable. Gauthier

et al. (1988), Rieppel (1993) and Laurin & Reisz (1995) accept Palaeothy,.i~ as the sister group of diapsids. l cannot comment on that because diapsidi.' were not included in my study.

DISCUSSION

Recent years have seen a number of publications on the subject of early amniote phylogeny (Gauthier et al. 1988, Heaton & Reisz 1986, Lee 1995, Rieppel 1993, Laurin & Reisz 1995). Up to the publication by Gauthier et al. (1988) ail large scale phylogenies were "handmade" without the sUPllort of computer mediated analysis. It is no surprise therefore that the handmade, pre-cladistic phylogenies only appeared in t.extbooks such as Romer's Osteology of the Reptiles (1956) or Carroll's Vertebrate Paleontology and Evolution (1988) because of the time consuming nature. Even though completely reworked from Romer's original text, the latter still followed a generally conservative approach to the problem of phylogenetic relationships. Since the English publication of Hennig's (1966) groundbreaking work on cladistic phylogenetics, this procedure ha.3 completely changed the face of systematics. A great number of publications appeared using this method on a small scale since the count (If characters still had·ln be done by "hand~'. This changed with the arrivaI of the PC and the computer • based algorithms of programs like PAUP and McClade. Only their arrivai 12û allowed Gauthier et al. (1988) their tirst ail inclusive study of early amnill!l' • phyJogeny. Based solely on data extructed l'rom the literature, il. is 1111 surprise that the study contain,~d some major tlaw,;. In particular, the resurrected Parareptilia of Oison (1947) posed many problems becausl' virtually ail the groups involved had been lleg!ectoJd fOI' decades and most of the descriptions were outdated. Inspired by the wOi'k of Gauthier et al. (1988), other scientists went tu work on early amniote phylogeny to test their hypothesis. It was ubvioUH that the long neglected "Parareptilia" actually were a key to tiguring out relationships among amniotes. 1991 saw the arrivai of another groundbreaking publication in the field: Reisz & Laut'in proposed a sister­ group relationship between the procolophonid Owenetta. and tut'tles. TurtIes were long seen as a problem with their ancient appearance and being the only group of extant amniotes that defied any close linkage to allY of the basal groups. In their last publication on the subject, Laurin & Reisz (1995) altered the initial sister-group relationship between procolophonids and turtIes considerably. Owenetta was omitted from their study altogether but they claimed that the sister-group relationship (procolophonids • turtIes) is better supported than before -- seventeen instead of ten synapomorphies.

The description of Barasaurus offers a good insight as 1.0 why Owenetta, Barasaurus, and the Russian procolophonoids pose a problem. Many of

the characters used 1.0 demonstrate a turtIe-procolophonid sister-group relationship are simply not expressed in the early procolophonoids, sueh as characters concerning the meckelian fossa, the paroccipital process • and the palate, to name a few, 121 Laurin & Reisz's (1995) suggestion of a taxon Cotylosauria comprising • the sistp.r-groups Diadectomorpha and Amniota is supported here. Diadectomorphs lack the amniote characters named above. Berman et al. (1991) suggested a sister-group relationship of diadectomorphs with synapsids but thei:- characters are not convincing. Many early amniotes possess a large supratemporal at the lateral corner of the skull table. The other character used, "otic trough" is problematic also and appears to be convergent (Currie 1981, Laurin & Reisz 1995). Mesosaurs were excluded from my study, because no satisfactory descriptions have yet been published. Laurin and Reisz (1995) see mesosaurs as a sister-group of aIl reptiles within a clade caIled Sauropsida. However, they admit that only one further step coIlapses this node and makes l''lesosaurs the sister-group of palaeosauropsids. Working through the publication it becomes appearant that numerous characters are shared between mesosaurs and palaeosauropsids but appear as convergences due to the autapomorphies that force the appearance of this animal on a different level in the cladogram. It is proposed here that the taxon comprising the most recent ancestor of testudines and diapsids and aIl its descendants be called Sauropsida. The term Reptilia should be omitted from systematics altogether because it describes an organizational level rather than a clade. In the form of "reptiliomorph" this term will serve a better purpose. The next node splits the Sauropsida into Palaeosauropsida and Eusauropsida. Palaeosauropsida is introduced here to replace the doubtful term "Parareptilia". The use of this name in recent literature is awkward because aIl authors included them in the Amniota (Gauthier et al. 1988) or • even within the "Reptilia", Lee (1993) and Laurin & Reisz (1995). OIson 122 (1947) believed that the reptilian condition hadevolved severnl times -- once • in the "Eureptilia" and at least once in the "Parareptilia" since the btter included the Seymouriamorpha which he believed to be below the level of reptiles. Considering this definition, para (belonging to but Ilot quite) makes sense, but not as it is misused in modern literature. "Palaeo" was chosen because of the distance in time between those groups and modern sauropsids. Turtles, the extant members of this group have not changed their gestalt since the Triassic.

The Eusauropsida equal the "Eureptilia" of Laurin & Reisz (1995). Since this group was not the main focus of the thesis and there is consensus between the two studies, the subject should best be left for a separate investigation t(\ come up with a more satisfactory set of apomorphies. The Procolophonia, as defined in this study, contain aIl advanced forms of the Triassic -- the Procolophonidae as weIl aR the more conservative appearing Owenettididae. The intensive ~tudy of the latter did not reveal any character that would preclude t.' .em from being a member of the Procolophonia. A preliminary examinatiun of Nyctiphruretus (Ivachnenkû 1979) revealed sorne problems concerning its affinities. As

suggested by Laurin & Reisz (1995), the Russian material should be described in detail before conclusions are drawn. The acceptance of the Owenettidae significantly changes the pattern in which characters link turtlcs tu either pareiasaurs or procolophonids. 1 agree with Lee (1995) that most similarities between Barasaurus and Oweneita are primitive and hence the clade is not weIl defined. lnitially Reisz & Laurin (1991) used Oi.,:i.etta to support their turtle - procolopho~d sister-group relationship. Owenetta was excluded from their 19:95 • publication because many characters coded for the Procolophonidae are 123 not supported by it. 1 venture as far as to suggest that without this omission there would have been no case to support a sister-group

• proc~lophonids. relationship between turtles and However, since the Procolophonia are the successive sister-group to the Testudinomorpha they are ultimately linked to the "ancestry" of turtles. Laurin & Reisz (1995) claim that there are seventeen synapomorphies, fourteen of which are unambiguous, uniting procolophonids with turtles. Postparietal absent: both Owenr·:ta and Barasaurus have postparietals, while later procolophonids lack them. Strong prefrontal palatal contact: as far as 1 could verify this character, the contact is not very strong in owenettids, compared to Procolophon (Carroll & Lindsay 1985) or pareiasaurs (Lee 1995). Wide prefrontal medial flange: this is an autapomorphy of the Procolophonia. Gaffney's (1990) description of Proganochelys.mentions this process, but it appears that it is not as developed as it is in proeolophonids. Laerimal does not reaeh naris: The laerimal does reaeh the naris in Barasaurus. Anterodorsal proeess of maxilla: this proeess is also present in pareiasaurs (Lee 1993) but not in Barasaurus. The expression of this eharaeter seems to be closely linked to the previous one. Olleipital flange of the squamosal: sueh f1anges are present in pareiasaurs (Lee 1993) as weil as in proeolophonids. However, in pareiasaurs, this eharaeter is somewhat "obstrueted" by the paroeeipital proeess of the opistothie . Transverse flange of pterygoid edentulous: this is true for a11 • prol;olophonids and turtles. Nyctiphruretus (Ivaehnenko 1979) has teeth on 124 the transverse t1ange, but only a detailed redescription can ascl'rtain • procolophonoid affinities (or disprove them). Basal tubera on basisphenoid: these are also present in pareiasaurs. but admittedly, it is not clear whether the structures are homologous. Slender imperfomte stapes : a stapes couId not be found in Barasartrrts. Though the stapes seems to be imperforate in Pl'Ocolophon, it still has a footplate. Gaffney (1990) does not picture a stapes ofProganochclys but the det :ription does not match that of Procolophon. The character was therefore not included. Accessory lateral shelf of surangular: not weil eno'..Igh pl'esel'ved in Barasaurus to be described and eva1.uated. Number of bones forming retroarticu~al' process: it appears that more than one bone participates in forming the retroarticular process in both Barasaurus and Owenetta, but the evidence was not clear enough to include this character in the analysis. High coronoid process: the coronoid process is not high in owenettids. Splenial excluded from symphysis: This is the case in procolophonidR and turtles. Cleithrum lost: the cleithrum is lost in various amniote groups. It is included in this study as well but appears as a character that is prone to convergence. Olecranon small: the olecranon of Barasaurus is l'ully developed. Femoral articulation short and wide. The coding of this character is inadequately described. In owenettids, the proximal articulation surface shows no specialization. Metapodials overlapping: The metapodials of owenettids do not overlap, but • they do in pareiasaurs (Lee 1995). 125 The Testudinomorpha comprising turtles and pareiasaurs are • supported by the eleven characters listed above. These characters suggest that there is a strong evidence supporting this node but one has to be cautious since many of the characters are not as unambiguous as they might look. Character 23, concerning the posterior end of the choana, seems to be weil supported. The absence of the ventral cranial fissure might be related to the degree of ossification: many of the other taxa in question were coded on the basis of descriptions of immature specimens. These will obviously exhibit a non­ coosified ventral cranial fissure. The lateral flange of the exoccipital is anoth:ar unambiguous cha.racter. The shape of the articular surface of the quadrate is a convergence between turtles and procolophonids. Turtles and pareiasaurs were the only amniotes under inv':\stigation that have a significantly reduced vertebral count. The num~cJr 20 is of course arbitrarily chosen. It is not clear whether the reduction of the phalangeal and pedal count reaIly is homologous. Laurin & Reisz (1995) claim that the loss of elements in turtles is related to their adaptation to swim and dig, while pareiasaurs reduced their count to achieve a somewhat elephantine foot for better support of their large body weight. Gaffney (1990) does not accept the dermal ossifications of par· 1asaurs as homologous with those of turtles nor do Laurin & Reisz (1995). 1 suggest that since no one is able to convincingly explain the initial formation of the turtle-sheIl, this character might as weIl be included in an analysis. Dermal ossifications were also found to be present in procolophonids • (Laurin & Reisz 1995) but are not described yet. 126 Other characters used by Lee (1993, 1995), such as the alTomion proccss • were not used because they were not accepted as homologies in pareiasaurs and turtles. Yet others, like the count of caudal vertebnll' with transverse processes, appear on other levels in my phylogeny. This cou Id be related to coding, objective of the study, or the simple reason that the definitions of taxa do not necessarily follow the apomorphy list in Lee's publications (Lee 1993, 1995). Due to the unambiguous nature in which the characters uniting turt\es and pareiasaurs were coded, this node is the best supported on the tree. It. still stands when aIl the other nodes on the tree have collapsed. 'l'hirteen additional steps are neccessary to let Procolophon uppenr as the sister­ group of turtles. 'l'he Procolophoniformes comprising Procolophonia and Testudinomorpha is very strong as weil. Here eight step arc necessary to let the group collapse. The millerettids are only supported by one character but they seem to be weIl established in the Palaeosauropsida. Even fifteen additional steps do not change their position. The study generally reflects the results ofLaurin & Reisz (1995) and Lee (1995), as weIl as supporting Lee's notion of a sister-group relal;ionship between turtles and pareiasaurs.

• 127 • CONCLUSIONS Barasaurus besairiei is a procolophonoid from the Upper Permian of Madagascar. It is most closely related to the South African procolophonoid Owenetta. Together they comprise the family Owenettidae. The Owenettidae are the sister-group of the Procolophonidae. Together they comprise the Procolophonia. Testudines are the sister-group of Pareiasauria. Together they comprise the Testudinomorpha. The clade uniting Testudinomorpha and Procolophonia is named Procolophoniformes. The term "Reptilia" should be omitted from systematics. 1 suggest the use of Sauropsida instead since it carries less historical burden. Though "Reptiliomorph" might be accepted as an organizational level. Because of the syHable "para" it is misleading to continue use of the term "Parareptilia". The term Palaeosauropsida is introduced here instead. Consequently "Eureptilia" are renamed Eusauropsida. Synapsida and Sauropsida form the Amniota. This study offers a new hypothesis of relationships amongst early amniotes, but it is limited, as are aH other studies quoted above, by its focus. Further studies and descriptions of Palaeosauropsida and related, or possibly related taxa are needed before any further analysis can take place. • 128 • REFERENCES Anderson H.M., Anderson J.M. 1970: A preliminary review of the biostratigraphy of the uppermost Permian, Triassic and lowermost Jurassic of Gondwanaland. Palaeontologica Africana 13 (suppl.) 1 - 22. Anderson H.M., Anderson J.M., Cruickshank A.R.!. 1978. The biostratigraphy of the Permian and the Triassic. Pr,rt 5. A review of the classification and distribution of Permo-Triassic tetrapods. Palaeontologica Africana 21: 15 - 44 Berman D.S., Martens T. 1993. First occurence of Seymouria (Amphibia: Batrachosauria) in the Lower Permian Rotliegend of central Germany. Annals of the Carnegie Museum of Natural History 62: 63-79. Berman D.S., Reisz RR 1986. Captorhinid reptiles from the Early Permian of New Mexico, with description of a new genus and species. Annals ofthe Carnegie Museum of Natural History 55: 1-28. Berman D.S., Reisz RR, Eberth DA. 1987. Seymouria sanjuanensis (Amphibia, Batrachosauria) from the Lower Permian Cutler Formation of north-central New Mexico and the occurence of sexual dimorphism in that genus questioned. Canadian Journal of Earth Sciences 24: 1769-1784. Berman D.S., Sumida S.S.. 1990. A new species of Limnoscelis (Amphibia, Diadectomorpha) from the Late Pennsylvanian Sangre de Cristo Formation of central Colorado. Annals of the Carnegie Museum ofNatural History 59: 303-341. Berman D.S., 8umida 8.8., Lombard RE. 1992. Reinterpretation of the temporal and occipital region in Diarkctes and the relationships of • diadectomorphs. Journal of Paleontology 66: 481-499. 129 Boonstra L.D. 1930. A contribution of the cranial osteology of Pareiasaurus • serridens (Owen). Annale van die Universiteit van Stellenbosch 8: 1-18 Boonstra L.D. 1932a. Pareiasaurian studies. Part VII. On the hind limb of the two little-known pareiasaurian genera: Anthedon and Pareiasaurus. Annals of the South AfricaJ1 Museum 28: 429-435. Boonstra L.D. 1932b. Pareiasaurian studies. Part VIII. The osteology and mythology of the locomotor apparatus. B Fore limb. Annals of the South African Museum 28: 437-503. Boonstra L.D. 1934a. Pareiasaurian studies. Part X. The Dermal Armour. Annals of the South African Museum. 31: 39-48. Boonstra L.D. 1934b. Pareiansaurian studies. Part IX. The Cranial Osteology. Annals of the South African Museum 31: 1-38. Boonstra L.D. 1935. On a pareiasaurian reptile from South Africa. Bradyasurus whaitsi. American Museum Novitates 770: 1-4. Boy J.A. 1991. Ein neues captorhinomorphes Repti! aus dem thüringischen Rotliegend (Unter-Perm; Ost Deutschland). Palaeontologische Zeitschrift 65: 363 -389. Brlnkman D. 1988. Size-dependent criteria for estimating relative age in Ophiacodon and Dimetrodon (Reptilia, Pelycosauria) from the AdmiraI and Lower Belle Plains formations ofwest-central Texas. Journal ofVertebrate Paleontology 8: 172-180. Broom R. 1924. On the classification ofthe reptiles. Bulletin ofthe American Museum ofNatural History 51: 39-65. Carroll R.L. 1964. The earliest reptiles. Zoological Journal ofthe Linnean Society 45: 61·83. • 130 Carroll RL. 1969a. A Middle Pennsylvanian captorhinomorph and the • interrelationships of primitive reptiles. Journal of Paleontology 43: 151­ 170. Carroll R.L. 1969b. Problems of the origin of reptiles. Biological Review 44: 393 - 432. Carroll RL. 1981. Plesiosaur ancestors from the Upper Perrnian of Madagascar. Philosophical Transactions of the Royal Society B293: 315­ 383. Carroll R.L. 1982. Early evolution of reptiles. Annual Revue of Ecology and Systematics 13: 87-109. Carroll R.L. 1987. Vertebrate Paleotology and Evolution. New York: W. H. Freeman. Carroll R.L. 1991. The origin ofreptiles. In: Schultze H-P, Trueb L, eds. Origin of the Higher Group of Tetrapods Controversy And Consensus. Ithaca: Comstock Publishing Associates. 331-353. Carroll RL., Currïe P.J. 1991. The early radiation of diap!lid reptiles. In: Schultze H.-P., Trueb L., eds. Origins ofthe Higher Group of Tetrapods Controversy and Consensus. Ithaca: Comstock Publishing Associates, 354-424. Carroll RL., Lindsey W. 1985. Cranial anatomy of the primitive reptile Procolophon . Canadian Journal ofEarth Sciences 22: 1571-1587. Case E.C. 1907. Restortion ofDiadectes . Journal ofGeology 15: 556-559 Case E.C. 1911. A revision of the Cotylosauria of North America. Carnegie Institution ofWashington Publication 145: 1-122. Clark J., Carroll R.L. 1973. Romeriid Reptiles from the Lower Permian. • Bulletin ofthe Museum ofComparative Zoololgy 144: 353-407. 131 Colhert E.H. 1946. llypsognathus, a Triassic reptile from New Jersey. Bulletin of the American Museum of Natural History P-6: 379 - 466. • Colbert E.H., Kitching JW. 1975. The Triassic Reptile Procolophon in Antarctica. American Museum Novitates 2566: 1-23. Cope E.D. 1880. The skull ofEmpedocles. American Naturalist 14: 304­ 304. Cope E.D. 1896a. The ancestry of the Testudinata. American Naturalist 30: 398-400. Currie P.J. 1981. Hovasaurus boulei, an acquatic cosuchian from the Upper Permian of Madagascar. Paleontologicia Africania 24: 99-168. Dawson J.W. 1860. On a terrestrial mollusk, a chilognathus myriapod, and some new species of reptiles from the Coal-Formation of Nova Scotia. Journal of Geological Sciences 16: 268 - 277. Dilkes D.W., Reisz RR. 1986. The axial skeleton of the Early Permian reptile F;!Jc=pt!)rhinus laticeps (Williston). Canadian Journal of Earth Sciences 23: 1288-1296. Efremov J.A. 1940: Die Mesen Fauna der permischen Reptilien. Neues Jahrbuch für Mineralogie, Beilagenband 84: 379 - 466. Fox R.C., Bowman MC. 1966. Osteology and relationships of Captorhinus aguti (Cope) (Reptilia: Captorhinomorpha). Paleontological Contributions. University ofKansas 11: 1-79. Fracasso M.A. 1983. Cranial Osteology, FunctionaI Morphology, Systematics and Paleoenvironment ofLimnoscelis paludis (Williston). Ph.D. thesis, Yale, 1-624. Gaffney E.S. 1979. Comparative craniaI morphology ofrecent and fossil turtles. Bulletin ofthe American Museum of NaturaI History 164: 65­ • 376. 132 Gaffney E.S. 1980. Phlyogenetic relationships of the major groups of • amniotes. In: Panchen AL, ed. The Terrestrial Environment and the Origin of Land Vertebrates. London: Academic Press, 593-610. Gaffney E.S. 1990. The comparative osteology of the Triassic turtle Proganochelys . Bulletin of the American Museum of Natural History 164: 1-263. Gaffney E.S., Hutchinson JH, Jenkins FA, Jr, Meeker LJ. 1987. Modnrn turtle origins: The oldest known cryptodire. Science 237: 289-291. Gaffney E.S., McKenna MC. 1979. A late Permian captorhinid from Rhodesia. American Museum Novitats 2688: 1-15. Gaffney E.S., Meylan PA. 1988. A phylngeny of turtles. In: Benton MJ, ed. The Phylogeny and Classification of the Tetrapods. Oxford: Clarendon Press, 157-219. Gaffney E.S., Meylan PA, Wyss AR. 1991. A computer assisted analysis of the relationships of the higher categories ofturtles. Cladistics 7:313-335 Gao K. 1989. Pareiasaurus from the Upper Permian of North China. Canadian Journal ofEarth Sciences. 26: 1231-1240. Gauthier J., Kluge A.G., Rowe T. 1988. The early evolution of the Amniota. In: Benton M.J., ed. The Phylogeny and Classification of the Tetrapods. Oxford: Clarendon Press, 103-155. Goodrich E.S. 1916. On the classification of the Reptilia. Proceedings of the Royal Society (London) 89: 261 • 276. Gow C.E. 1972. The osteology and relationships ofthe Millerettidae (Reptilia: Cotlyosauria). Journal ofZoology (London) 167: 219·264 Gow C.E. 1977. Owenetta in perspective. Palaeontologica Africana 20: 115· • 118. 133 Gregory W.K. 1946. Pareiasaurs versus placodonts as near ancestors to • turtles.Bulletin of the American Museum of Natural History 86: 275­ 326. Haeckel E. 1866. Generelle Morphologie Der Organismen. Berlin: Reimer. Heaton M.J. 1979. Cranial anatomy of primitive captorhinid reptiles from Late Pennsylvanian and Early Permian Oklahomaand Texas. Bulletin of the Oklahoma Geological Survey.127: 1-84. Heaton M.J.1980. The Cotylosauria: A Reconsideration of a Group of ArchaicTetrapods. In: PanchenAL, ed. The Terrestrial Environment and the Origin ofLand Vertebrates. London: Academic Press, 497-551. Heaton M.J, Reisz R.R. 1980. A skeletal reconstn\ctic.a ofthe Early Permian captorhinid reptile Eocaptorhinus laticeps (Wiiliston). Journal ofPaleontology 54: 136-143. Heaton M.J., Reisz R.R. 1986. Phylogenetic relationships of captorhinomorph reptiles. Canadian Journal of Earth Sciences 23: 402­ 418. Hennig W. 1951. Grundzüge einer theorie der phylogenetischen Systematik. Berlin. Hennig W. 1966. Phylogenetic systematics. Urbana. Holmes R. 1977. The osteology and musculature of the pect::>rallimb of small captorhinids. Journal ofMorphology 152: 101-140. Holmes R. 1984. The Carboniferous amphibian Proterogyrinus scheeli Romer, and the early evolution ofktrapods. Philosophical Transactions of the Royal Society (London) B, 306: 431 - 527. Huene F. von 1941. Osteologie und systematische Ste!lung von Mesosaurus . Paleotographica. Abteilung A. Paleczoologie­ • Stratigraphie 92: 45-58. 134 Huxley T.H. 1864. Lectures on the Elements of Comparative Anatomy. • London, J. Churchill. lvachnenko M.F. 1979. Pernùan and Triassic procolophonids of the Russian platform. Akademiya Nauk SSSR 164: 1-80 (in Russianl. lvaclmenko M.F. 1987. Permian parareptiles of D.S.S.R. Akademia Nauk SSSR 223: 1-159 (in Russianl. Kemp T.S. 1974. The braincase and associated structures of the cotylosaur reptile Procolophon trigoniceps Owen. Annals of the South African Museum 64: 11-26. Kemp T.S. 1985. Synapsid reptiles and the origin ofhigher taxa. Special Papers in Paleontology 33: 175-184. Kluge A.G. 1985. Ontogeny and phylogenetic systematics. Cladistics 1: 13 ­ 27. Kuhn O. 1969. Cotylosauria. Handbuch der Palaeoherpetologie, Part 6. Stuttgart. Laurin M., Reisz R.R. 1992. A reassessment of the Pennsylvanain tetrapod Romeriscus. Journal ofVertebrate Paleontology. 12: 524-527. Laurin M., Reisz RR 1995. A reevaluation of early amniote phylogeny. Zoological Journal of the Linnean Society 113: 165 - 223. Lee M.S.Y. 1993. The origin of the turtle body plan: bridging the morphological gap. Science 261: 1716·1720. Lee M.S.Y. 1995. Historical burden in systematics and the interrelationships of "parareptiles". Biological Review, Manuscript. 75 pp. Linnaeus C. 1758. Systema Naturae. 10 ed. Stockholm. Lydekker R 1888. Catalogue OfThe Fossil Reptilia And Amphibia In The • British Museum (Natural History), Part l, Containing The Orders 135 Orinthosauria, Crocodilia, Dinosauria, Squamata, Rhynchocephalia • And Proterosauria. London: British Museum Natural History. Lydekker R. 1889. Catalogue Of The Fossil Reptilia And Amphibia In The British Museum (Natural History), Part II. Containing The Orders Itchthyopterygia And Sauropterygia. London: British Museum Natural History. Maddison W.P., Maddson D.R. 1992. Macclade: Analysis Ofphylogeny and character evolution. Version 3.0. Sunderland. Massachusetts: Sinauer Associates. Meyer H. von 1858. Nachtrag zu den Reptilien aus der Steinkohlenformation in Deutschland, insbesondere Archegosaurus latirostris. Palaeontographica 6: 219 - 220. OIson E.C. 1936. Notes on the Skull ofYoungina capensis Broom. Journal of GeoIogy 44: 523-533. OIson E.C. 1947. The family Diadectidae and its bearing on the classification of reptiles. Fieldiana Geology 11: 1-53. OIson E.C. 1950. The temporal region ofthe Permain reptile Diadectes. Fieldiana Geology 10: 63-77. OIson E.C. 1950. Parallelism in the evolution of the Permian reptilian faunas ofthe old and new wurld. Fieldiana: Zoology 37: 385 - 401. OIson E.C. 1965. Relationships ofSeymouria, Diadectes, and Chelonia . The American Zoologist 5: 295-307. OIson E.C. 1966. Relationships ofDiadectes . Fieldiana Geology 14: 199-227 OIson E.C. 1968. The family Caseidae. Fieldiana Geology 17: 225-349. Osborn H.F. 1903. The reptilian subclasses Diapsid and Synapsida and the early history of the Diaptosauria. Memoirs from the American • Museum ofNatural History 1: 265-270. 136 Owen IL 1860: Palaeontology; or, a systematic summary of extinct animaIs • and their geological remains. Edinburgh. Piveteau J. 1926. Paléontologie de Madagascar. XIII. Amphibiens et reptiles Permiens. ArmaIs de paléotologie 15: 53-180. Piveteau J. 1955. Existence d'un Reptile du groupe Procolophonides ,i Madagascar. Conséquences stratgraphiques et paléontologiques. Comptes rendus :lebdomadaires des séances de l'Académi~ des sciences 241: 1325· 1327. Reisz RR 1972. Pelycosaurian reptiles from the Middle Pennsylvanian of North America. Bulletin of the Museum of Comparative Zoology 144: 27 ·62. Reisz RR 1980. A protorothyrid captorhinomorph reptile from the Lower Permian of Oklahoma. Sciences Contributions Royal Ontario Museum 121: 1- 16. Reisz RR, Laurin M. 1991. Owenetta and the origin of turtles. Nature 349: 324-326. Rieppel O. 1988. Fundamentals ofcomparative Biology. Basel. Rieppel O. 1993a. Euryapsid relationships: A preliminary analysis. Neun Jahrbuch für Geologie und PaHiontologie, Abhandlungen 188:241-264. Romer A.S. 1922. The locomotor apparatus ofcertain primitive and mammal-like reptiles. Bulletin of the American Museum of Natural History 46: 517 - 606. Romer A.S. 1946. The primitive reptile Limnoscelis restudied. American Journal ofScience 244: 149-188. Romer A.S. 1956. Osteology of the reptiles. Chicago: The University of • Chicago Press. 137 Romer A 3. 1966. Vertebrate paleontology 3rd ed. Chicago: The University • of Chicage Press. Romer A.S, PriCë L.I. 1940. Review of the Pelycosauria. Vol. 28. Geologïcal Society of America, Special Papers. New York: Arno Press. Seeley H.G. 1888. Researches on the structure, organisation, and classification of the fossi! Reptilia.Vi. On the anomodont Reptilia and their allies. Proceedings ofthe Royal Society of London. 44:381-383. Smithson T.R 1989. The earliest known reptile. Nature 342: 676-678. Surnida S.S. 1987. Two different vertebral forms in the axial column of Labidosaurus Captorhinomorpha: Captorhinidae. Journal of Paleotology 61: 155-167. Sumida S.S. 1989. The appendicular skeleton of the Early Permian genus (Reptilia, Captorhinomorpha,Captorhinidae) and the hind limb musculature of captorhinid reptiles. Journal of Vertebrate Paleontology 9: 295-313. Sumida S.S., Lombard RE. 1991. The atlas-axis complex in the Late Paleozoic genus Diadectes and the characteristics of the atlas -axis complex across the amphibian to amniote transition. Journal of Paleontology 65: 973 - 983. Sumida S.S., Lombard E.R, Berman D.S. 1992. Morphology of the atlas axis complex of the late Palaeozoic tetrapod suborders Diadectomorpha and Seymouriamorpha. Philosophical Transaction of the Royal Society (London) 336: 259 - 273. Swofford D.L. 1993. PAUP: Phylogenetic Analysis using Parsimony. Version 3.1. Champaign: Illinois Natural History Survey. Thommasen H., Carroll RL. 1981. Broomia. the oldest known millerettid • reptile. Palaeontology 24: 379 - 390. 138 Vaughn P.P. 1966. Seymouria from the Lower Permian of Southeastern • Utah, and possible sexual dimorphism in that genus. Journal of Paleontology 40: 603 - 612. Watson D.M.S. 1914. Procolophon trigoniceps. a cotylosaurian reptile from South Africa. Proceedings of the Zoological Society of London, 1914: n5­ 747. Watson D.M.S. 1917. A sketch classification of the pre jurassic tetrapod vertebrates. Proceedings of the Zoological Society ofLondon, 1917: 167­ 186. Watson D.M.S. 1918. On Seymouria, the most primitive known reptile. Journal ofZoology iLondon) 2: 267 - 301. Watson D.M.S. 1954. On Bolosaurus and the origÎn and classification of reptiles. Bulletin ofthe Museum ofComparative Zoology 111: 299 - 449. Watson D.M.S. 1957. On Millerosaurus and the early history ofthe sauropsid reptiles. Philosophical Transactions of the Royal Society B240: 325 - 400. White T.E. 1939. Osteology ofSeymouria baylorensis Broili. Bulletin of the Museum of Comparative Zoology 85: 325 - 409. Wild R. 1985. Ein Schadelrest von Parasaurus geinitzi H. von Meyer (heptilia, Cotylosauria) aus dem Kupferschiefer, (Perm) von Richelsdorf (Hessen). Geologische Blatter mr Nordost Bayern und angrenzende Gebiete 34135: 879 - 920. Wiley. E.O. 1981. Phylogenetics. New York. Williston S.W. 1911. A new family ofreptiles from the Permian of New Mexico. American Journal of Science 31: 378 - 398. Williston S.W. 1912. Restoration ofLimnoscelis, a cotylosaur reptile from • New Mexico. American Journal ofScience 34: 457 - 468. 139 Williston S.W. 1917. The phylogeny and classification ofreptiles. • Contributions from the Walker Museum 2: 61 - 71. WillistoI'. S.W. 1925. The Osteology of the Reptiles. Cambridge Harvard Univ.:'!rsity Press. Wu X.C. 1991. The comparative anatomy and Systematics of Mesozoic Sphenodontidans. McGill University Ph.D. thesis. 1 - 229 + XV. Zittel K.A. 1887 - 1890. Handbuch der Palaeontologie. 1. Abteilung III. Band Vertebrata (Pisces, Amphibia, Reptilia, Aves). MÜllchen und Leipzig.

• 140 APPENDIXI Listofcharacters • 1. Narial shelfpresent 0; absent 1. 2. Frontal orbital contact absent 0; present 1. 3. Postparietal present 0; absent 1. 4. prefrontal palatal contact absent 0; present 1. 5. prefrontal, internaI medial process absent 0; present 1. 6. Lacrimal narial contact present 0; absent 1. 7. Jugal does not extend to anterior rbital rim 0; extends at least to anterior orbital rim. 8. Postorbital supratemporal contact absent 0; present 1. 9. Intertemporal present 0; absent 1. 10. posterolateral corner of skull table formed by tabular 0; supratemporal 1. 11. Tabular roughly equal in size to tabular 0; less than half the size of the parietal 1; absent 2. 12. anterodorsal process ofmaxilla absent 0; present 1. 13. multiple lateral anterior maxiUary foramen 0; one larger foramen 1; foramen absent 2. 14. Maxilla and quadratojugal in contact 0; separated 1. 15. Quadratojugal. narrow; dorsally expanded 1. 16. Otic emargination absent 0; formed by squamosal and supratemporal 1; formed by squamosal and quadratojugal 2. 17. Ventral margin ofpostorbital skull convex 0; rectilinear 1; concave 2. 18. Quadrate not exposed laterally 0; exposed laterally 1. 19. Anterior process of quadrate long 0; short 1. 20. Jaw articulation posterior to occiput 0; even with occiput 1; anterior to occiput 2. 21. Posterior extension oforbit absent 0; present 1. 22. Transverse flange ofpterygoid: shagreen of denticles 0; row of teeth 1; only ridge present 2. 23. Choana parallel to maxilla 0; posterior end of maxilla angled medially 1. 24. Ectopterygoid present 0; absent 1. 25. Ectopterygoid toothed 0; edentulous 1. • 26. Suborbital foramen absent 0; present 1. 141 27. Ventral cranial fissure present 0; absent 1. 28. Parasphencid posteriorly wider than anterior part 0; narrower than • anterior part 1. 29. Cultriform process longer than main body of parasphenoid 0; shorter than main body of parasphenoid 1. 30. Basal tubera on basioccipital absent 0; present 1. 31. No occipital flange 0; occipital flange formed by parietal and supratemporal 1. 32. Supraoccipital broad contact dorsally 0; has a dorsal ridge 1. 33. Paroccipital process expanded dorsoventrally 0; expanded anteroposteriorly 1. 34. Paroccipital process contacts tabular 0; supratemporal and tabular 1; tabular and squamosal 2; squamosal and supratemporal 3; squamosal and quadrate 4; ends freely 5. 35. Posttemporal fenestra in comparison with foramen magnum: small 0; large 1. 36. Occipital condyle broad 0; circular 1. 37. Lateral fIange of exoccipital absent 0; present 1. 38. Quadrate articular surface convex and elongate 0; almost fiat, and short 1. 39. Splenial contributes to symphysis 0; does not reach 1. 40. Presacral vertebral count more than twenty 0; twenty or less 1. 41. Atlantal neural spine almost size ofaxial spine 0; spine very small1. 42. Axial intercentrum rounded anteroventrally 0; with anteroventral process 1. 43. Atlantal pleurocentrum and axial intercentrum separate elements 0; fused 1. 44. Trunk neural arches narrow with wide zygapophyseal buttreslles 0; swollen with wide zygapophyseal buttresses 1; swollen with narrow zygapophyseal buttresses 2; 45. Ventral surface of anterior pleurocentra rounded 0; keeled 1; two ridges 2. 46. One sacral vertebrae 0; two 1; three or more 2. 47. Transverse process~s or ribs oIÙY on anterior caudals 0; on ten or more • caudals 1. 142 48. Caudal hemal arches wedged between centra 0; attached to anterior centrum 1. • 49. Interclavicle with diamond shaped head 0; T-shaped 1. 50. Interclavicle attachment for clavicle ventral area 0; anterior grollve 1; fused into plastron 2. 51. Cleithrum caps scapula anterodorsal1y 0; does not cap scapula 1; is absent 2. 52. Scapulocoracoid ossifications two 0; three 1. 53. Supraglenoid foramen present 0; absent 1. 54. Glenoid long anteroposteriorly 0; distinctly less than half the length of the scapulocoracoid 1. 55. Supinator process pointing away from shaft 0; paral1el to shaft and separated from it by a groove 1; paral1el to shaft not separated by groove 2. 56. Ectepicondylar foramen and groove: orny groove present 0; groove and foramen present 1; orny foramen present 2; both absent 3. 57. Entepicondylar foramen present 0; absent 1. 58. PhalangeaI formula ofmanus: 2 3 453 0; 2 3 4 4 3 1; 2 3 3 3 3 or less 2. 59. Dorsolateral process on ilium absent 0; present 1. 60. Adductor crest present 0; absent 1. 61. Greater trochanter offemur absent 0; present 1. 62. Astragalus and calcaneum separate 0; fuscd or sutured 1. 63. Medial pedaI centrale present 0; absent 1. 64. Number ofdistal tarsals five 0; four or less 1. 65. Fifth pedaI digit longer than first digit 0; not longer than first digit 1. 66. Metapodials not overlapping 0; overlapping 1. 67. PhalangeaI formula ofpes 2 3 4 5 4 0; 2 3 343 or less1. 68. Dermal ossification" absent 0; present 1.

• 143 APPENDIXll Data Matrix , TAXA 1 1 1 2 1 3 • 5 1 6 1 7 1 & • 1 Q 1 1 ,2 1 31141,51,61,7 1 1 1 1 1 1 1 1 1 1 1 Proloroavrinua Q 1 Q 1 Q 0 0 0 010 0 0 0 0 0 0 0 0 0 2 Seymour•• 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 1 0 , limnollcolis O· 0 U 0 0 0 1 1 1 1 1 0 0 0 0 0 o 1 0 • • Dladoclo$ 0 1 0 1 0 0 1 1 1 1 0 0 0 0 0 1 0 5 Haptodu& 0 1 0 0 0 0 0 1 1 1 0 0 0 1 0 0 0 6 Miller.lIa 0 1 0 1 0 0 0 1 1 1 1 0 1 0 1 2 1 7 P'fuiosaun8 0 1 0 1 0 0 1 1 1 1 2 1 1 1 1 2 0 & Owonolla 1 1 0 1 1 1 0 , 1 1 2 1 1 1 0 2 2 1 0 1 , , 0 1 1 0 2 2 • B.rasaurui 1 0 0 0 1 2 10 Procolophon 1 1 1 1 1 1 1 1 1 1 2 1 1 0 1 2 2 11 Proganochelvs 0 0 1 1 0 .. 0 0 1 1 2 1 2 0 1 2 1 EOC3Plorhinus 1 , 12 0 1 1 0 0 0 1 0 , 2 0 0 0 0 0 1 13 Pllloothyris 0 1 1 0 0 0 0 0 0 1 1 1 0 0 0 0 0 1

2 ,.1,. 20 211 .. 123 .. 126 26 27 2& 2. 30131 32 133 134 1 1 1 1 1 1 PrOlotOoyrinus 0 0 0 0 o 1 0 0 0 0 0 0 0 0 0 0 0 1 0 2 Sovmouria 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ?? 0 3 Limnoscolis t 0 1 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 • Diadecles 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 5 Haplodus 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 2 6 Millorolta 1 0 2 0 1 0 0 1 1 0 1 0 0 0 1 0 3 7 Paroins8utia 0 0 2 0 1 1 0 1 1 1 1 1 1 0 1 0 3 0 Owonotla 0 1 2 1 0 0 0 1 1 0 1 1 1 1 1 1 5 81uaSDutus 0 1 2 1 2 0 0 1 1 0 , 1 1 1 1 1 5 10• Procolophon 0 0 2 1 2 0 0 1 , 0 1 1 1 1 1 1 3 1 1 Prooonocholvs 1 0 2 0 2 1 1 ? 1 1 1 1 1 0 1 1 • 12 EocoPlorhlnus 0 1 1 0 0 0 1 ? 1 0 , 0 0 0 1 1 5 '3 Pllloothyris 0 1 1 0 1 0 0 0 ? 0 1 0 0 0 1 0 5

3 35 36 37 3 &1,. 40 141 .2 • 3 •• 4S .6 '7 .& .. 50 6' 1 1 1 Pro1erogYrinua 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 Seymourl. 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 3 L1mnolcolls 1 0 0 0 0 0 1 1 1 1 0 1 0 ? 0 0 0 • Dladecles 0 0 0 0 0 0 1 1 1 1 0 1 ?? 0 0 0 6 HOlllodu. 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 6 MllleroUa 1 1 0 0 0 0 1 0 1 0 0 1 ?? 0 0 1 7 ParelaSDuria 1 1 1 1 0 1 1 0 0 2 0 2 1 1 1 1 1 & Owenella 1 1 0 0 1 0 1 0 ? 2 2 2 1 0 1 1 2 • 9arasBurus 1 1 0 0 1 0 1 0 ? 2 2 2 1 0 1 1 2 1 0 Procolophon 1 1 0 1 1 0 1 0 1 2 2 2 1 0 1 1 2 11 Prooanochelva 1 1 1 1 1 1 1 0 1 0 1 1 1 1 0 2 2 12 EOCDolorhlnus 1 1 0 0 0 0 1 0 1 1 0 1 0 0 0 0 1 13 Pal.othyrls 1 1 ? 0 0 0 1 0 1 0 1 1 0 0 0 0 1

• 52 63 5' 55 56 57 5& 5' 6016, 62 63 6. 6. •• 1.71.& 1 1 1 1 Proteroovrlnus 0 0 0 0 0 0 0 0 0 0 ? 0 0 0 0 0 0 2 Sevmourl. 0 0 0 0 0 0 0 0 0 0 ? 0 ? 0 0 0 0 3 - L!m~':!~e~lls 0 0 0 0 0 0 0 1 0 0 ? 0 ? 0 0 0 0 • Olodecle' 0 0 0 0 0 0 0 1 0 0 0 0 ? 0 0 0 0 5 Haotodus 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 6 Millerelta 1 1 0 1 1 0 0 0 ? 0 0 1 l 0 0 0 0 7 ParollS.url. 1 1 1 2 2 0 2 0 0 1 1 1 1 1 1 1 1 & Owen_na , 1 1 2 3 0 0 0 0 0 1 1 .1 0 0 0 0 • Bar••aurus 1 1 1 2 3 0 0 0 0 0 1 1 0 0 0 0 0 '0 ProcolODhon 1 , 1 2 3 0 1 0 0 0 1 1 1 0 0 0 0 ,, Prooanochelva 0 1 1 1 1 1 0 0 1 1 1 1 1 1 , 1 1 '2 Eocaptorhlnua 1 0 0 2 3 0 0 0 0 0 0 , 0 0 0 0 0 • 13 Paleothvrls 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 144 APPENDIX III ShortestTree and ApoIilorphy Lista

3~anch-and-bound search sêttings: • Initial upp.:r bound: unkno....n (corrpute vi,] stcpWi.s~) Addition sequence: furthest Initial MAXTREES setting = 100 Branches having ~;~ length =ero collapsed to yi~ld polJ~omiûs Topological constraints not enforced Tr~as are unrooteè.

Branch-and-bound search completed:

Shortest tree found = 139 Number of trees retained = 1 Time used = 25.88 sec

Tree d~scription:

Unrooted tree(s) rooted using outgroup method Character-state optimizatlon: Delayed transformation (DELTRANl

Tree number 1 (rooted using default outgroup) :

Tree length = 139 Consistency index (CI) = 0.626 Homoplasy index (HI) = 0.374 CI excluding uninformative characters = 0.615 HI excluding uninformative characters = 0.385 Retention index (RI) = 0.733 Rescaled consistency index (RC) = 0.459

J------..------Prot~rogyrinus 1 + ------__'e_ ---'.------_-_-___ SeYtOOuria 1 1 1------­ tJ.mnoscolis 24 1------14 1 1 \------Diadectes 1 1 1 1 1------··----- Haptodus \-----23 1 1 1 1------Milleretta 1 1 1 1 1 1 1------PareiasiJuria \------22 1------19 1------15 1 1 1 1 \------Proganochelyn 1 1 1 1 1 1 \-----18 1------CMenetta 1 1 1 1-----16 \-----21 1 1 \------Barasaurus 1 \------17 1 \------Procolophon 1 1 1------Ebcaptorhinus \------20 \------Paloe~Oyris Apomorphy lists:

Branch Charactar 5teps CI Change

node_24 --> Seymouria 4 1 0.250 0 --> 1 • 16 1 0.667 0 ==> 1 145 ,11. l O. ·100 0 --> l i.1j'Jn_24 ncdn-23 8 l 0.250 a ==;;. l 9 l 1.OGO 0 ==;;. 10 l 1.000 0 ==> l 20 l 1. 000 0 =::;;. l .n l 1. 000 a ==> l ·16 l 0./567 0) ==> l nodû_2J :'.orI.-~_1·\ 7 l 0).250 a ==:> ·12 J. l.OOO a ==> l ·13 l 0.333 a --> l • 4·1 l O. ·100 a --> l 59 l 1. 000 0 :::=> l noc!c!_l·i --:. Li:nno~-;celi:; 22 l 0.333 0 --> l 35 l 0.500 ,; ==> l nodQ_l<1 --:. Diadcctas 2 l 0.333 a --:> l ·1 l 0.250 a --'> l 16 l 0.667 a ==> l 18 l 0.333 0 =:::> l 19 l 0.333 0 ==> l 3·1 0.833 0 ==> l noda_23 --> node 00 2 l 0.333 0 --> l --- 22 1 0.333 0 --> l 36 l 1. 000 0 ::::::> l 51 1 0.667 0 ==> 1 52 l 0.500 0 ==> l 63 1 0.500 0 ==> 1 node_22 --> Haptodus 14 1 0.333 0 :::=> 1 34 1 0.833 a --> 2 64 1 0.500 0 --> l node_22 --> node_:n 11 l 0.667 0 ==> l 17 1 0.667 0 ==> l 26 1 1.000 0 ==> 1 28 1 1.000 0 ::::=> l 32 1 1.000 0 :::=> l 35 l 0.500 0 :::=> l 43 1 0.333 0 --> 1 55 1 0.500 0 ==> l nocle_2l --> node_19 4 1 0.250 0 --> 1 13 1 1.000 0 ==> 1 15 1 0.500 0 ==> 1 16 1 0.667 0 ==> 2 20 1 1.000 1 :::=> 2 25 1 1.000 0 ==> 1 34 1 0.833 0 --> 3 53 1 1.000 0 ==> 1 56 1 0.750 0 ==> 1 64 1 0.500 0 --> 1 node_19 --> Milleretta 18 1 0.333 0 ==> 1 node_19 --> node_18 11 1 0.667 1 --> 2 12 1 0.500 0 ==> 1 29 1 1.000 0 ==> 1 30 1 1.000 0 ==> 1 47 1 1.000 --> 1 50 1 1.000 0 ==> 1 54 1 1.000 0 ==> 1 62 1 1.000 0 ==> 1 node_la --> node_15 23 1 1.000 0 ==> 1 27 1 1.000 0 ==> 1 31 1 1.000 0 ==> 1 38 1 0.500 0 --> 1 40 1 1.000 0 ==> 1 48 1 1.000 0 ==> 1 61 1 1.000 0 ==> 1 65 1 1.000 0 ==> 1 66 1 1.000 0 ==> 1 61 1 1.000 0 ==> 1 68 1 1.000 0 ==> 1 node_l~ --> Pareiasauria 1 .1 0.250 0 ==> 1 14 1 0.333 0 ==> 1 17 1 0.667 1 ==::.- 0 43 1 0.333 1 ==> 0 • 44 1 0.400 0 --> 2 146 46 1 0.667 1 --> ~ 49 1 0.500 a --> 1 55 1 0.500 1 --~ ~ 56 1 0.750 1 ==':> ~ SB 1 1.000 a ==> :l • node_15 --> Proganochelys :l 1 0.333 ==> 1 a 3 1 0.500 a ::::::> 1 6 1 0.333 a --> 1 B 1 0.:::50 l ==> 0 13 1 1. 000 l ==> ~ lB 1 0.333 a ==> l 22 1 0.333 1 --> ~ 2·1 1 0.500 a ==> 1 33 1 0.333 a --> 1 34 1 0.B33 3 ==> 4 39 l 0.500 0 --:-- 1 45 1 0.667 a ==> l 50 1 1.000 1 ==> :l 51 1 0.667 l --> ~ 52 1 0.500 l ==> a 57 1 1. 000 a ==> 1 60 1 1. 000 0 ==> 1 node_la --> r:.ode_17 1 1 1.000 a ==> 1 5 1 1. 000 a ==> 1 17 l 0.667 1 ==> 2 21 1 1. 000 a ==> 1 22 1 0.333 1 --> 2 31 l 1. 000 a :::;::> 1 33 1 0.333 a --> 1 39 1 0.500 a --> 1 44 1 0.400 a --> :l 45 1 0.667 a :::;> 2 .46 1 0.667 1 --> 2 ·\9 1 0.500 a --> 1 51 1 0.667 1 --> 2 55 1 0.500 l --> ~ 56 1 0.750 1 ==> 3 noàe_17 --> noda_lo:' 14 l 0.333 a ==> 1 15 1 0.500 1 ==> a 1~ l 0.333 a ==> l 34 l 0.B33 3 ==> 5 node_16 --> Dwenetta 6 1 0.500 a --, 1 22 1 0.333 2 ==> a node_16 --> Barasaurus B 1 0.250 1 ==> a 12 1 0.500 1 ==> a 64 1 0.333 1 a node_17 --, --> Procolophon 3 1 0.500 a ==> 1 6 1 0.500 a --, 1 7 1 0.250 a ==> 1 3B 1 0.500 a --, 1 SB 1 1.000 0 ==> 1 node_21 --> nocle_20 B 1 0.250 1 ==> 0 19 1 0.333 0 ==> 1 34 1 0.B33 0 --, 5 node_20 --> Eocaptorhinus 4 1 0.250 0 --, 1 7 1 0.250 0 ==> 1 11 1 0.667 1 --> 2 22 1 0.333 1 ==> 0 24 1 0.500 0 ==> 1 33 1 0.333 a aa> 1 44 1 0.400 0 .a> 1 55 l 0.500 l --> 2 56 l 0.750 0 ..> 3 node_20 --> Palaothyris 45 l o 667 0 -=> l • 63 l 0.500 l ==> 0 147 APPENDIXIV Listofabbreviations • ar articular ascal astragalocalcaneurn atic atlas intercentrum atn atlas neural arch ax axis pleurocentrurn andneural arch axi-atp axis intercentrum-atlas pleurocentrum ID basioccipital cbr ceratobranchial œn centrale ci clavicle cop copula cr caudal rib cul cultriform process de distal carpals d distal tarsals ec ectopterygoid ectgr ectepicondylar groove ex: exoccipital f frontal il femur fi fibula gl glenoid h humerus ha hemal arch ic intercentrum ici interclavicle il ilium int intermedium is ischium it intertemporal j jugal 1 lacrimal lac lateral centrale manus m maxilla mt metatarsal n nasal 01 olecranon cp opisthotic p parietal pal palatine Ii postfrontal Ii pisiform pm premaxilla ID postorbital Al postparietal • p:f prefrontal 148 ..-0 pro-atlas prot prootic ps parasphenoid • It pterygoid q quadrate

•

149