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CaTI, ad···a • Functional Morphology and Phylogeny of Keichousaurus hui (Sauropterygia, Reptilia) Kebang Lin Department of Biology McGill University, Montreal • July, 1994 A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Doctor of Philosophy. <!l Kebang Lin, 1994 • National Ubrary Bibliothèque nationale 1+1 of Canada du Canada Acquisitions and Direction des acquisitions et Bibliographie Services Branch des services bibliographiques 395 Wellingloo Sireet 395, rue Wellingtoo OUawa, Ontario Ottawa (Onlario) K1A ON4 K1A ON4 YOCJ( "'D Votre tél6~ Our hie Noue ffJl6,-,nctt THE AUTHOR RAS GRANTED AN L'AUTEUR A ACCORDE UNE LICENCE IRREVOCABLE NON-EXCLUSIVE IRREVOCABLE ET NON EXCLUSIVE LICENCE ALLOWING THE NATIONAL PERMETTANT A LA BffiLIOTHEQUE LffiRARY OF CANADA 1'0 NATIONALE DU CANADA DE REPRODUCE, LOAN, DISTRmUTE OR REPRODUIRE, PRETER, DISTRIBUER SELL COPIES OF mS/HER THESIS BY OU VENDRE DES COPIES DE SA ANY MEANS AND IN ANY FORM OR THESE DE QUELQUE MANIERE ET FORMAT, MAKING TffiS THESIS SOUS QUELQUE FORME QUE CE SOlT AVAILABLE 1'0 INTERESTED POUR METTRE DES EXEMPLAIRES DE PERSONS. CETTE THESE A LA DISPOSITION DES PERSONNE INTERESSEES. THE AUTHOR RETAlNS OWNERSlllP L'AUTEUR CONSERVE LA PROPRIETE OF THE COPYRIGHT IN mS/HER DU DROIT D'AUTEUR QUI PROTEGE THESIS. NEITHER THE THESIS NOR SA THESE. NI LA THESE NI DES SUBSTANTIAL EXTRACTS FROM 11' EXTRAITS SUBSTANTIELS DE CELLE­ MAY BE PRINTED OR OTHERWISE CI NE DOIVENT ETRE IMPRIMES OU REPRODUCED WITHOUT mS/HER AUTREMENT REPRODUITS SANS SON PERMISSION. AUTORISATION, ISBN 0-612-00110-5 Canadti • PREFACE This thesis is a description of the osteology, ontogeny and functional a.Jatomy of the Middle Triassic Chinese pachypleurosaurid reptile Keichousaurus hui. The preliminary description published soon after its discovery (Young, 1958) was sketchy in nature and based on a small number of incomplete1y prepared specimens. More thorough preparation of sorne of the original specimens, as weil as further discoveries and preparations of new specimens from the same locality, made it possible for me to completely ilIustrate and redescribe the species. An embryo of Keichousaurus hui was described for the tirst time. The ontogenetic changes of Keichousaurus hui from embryo, through juvenile, subadult to adult stages were detailed. A functional analysis • concerning the locomotion pattern of Keichousaurus hui was carried out, and although literature is used to obtain background data, the conclusions drawn were original unless explicitly stated otherwise. The musculature reconstructions of the locomotive apparatus of Keichousaurus hui were presented, also for the tirst time. After a review of the literature, original conclusions are given. It is hcped that this study will provide a more complete picture of morphology, life history and phylogeny of Keichousaurus hui. The text of this thesis was prepared for submission to the Philosophical Transactions ofthe Royal Society ofLondon B., which has published several papers on nothosaurs, and follows the format of that journal. • j • UNIQUE CONTRIBUTIONS This study is the tirst detailed description of skeletal morphology of Keichousaurus hui Young, 1958, the Chinese member of the Family Pachypleurosauridae of diapsid reptiles. Sexual dimorphism of KeichousGurus hui was described. The growth pattern of Keichousaurus hui was studied by comparing the specimens of different developmental stages. Both morphologica! changes and the proportional changes were described. Statistical procedures were used in the study of the proportional changes. • Functional analysis was carried Oùt to detelmine the functions of limbs, the neck and the tail in the aquatic locomotion of Keichousaurus hui. 1t was shown that, unlike the European pachypleurosaurs, Keichousaurlls hui was an underwater rowing swimmer, using the foreJimbs for propulsion. Musculature reconstruction of the limbs was attempted, based on the marks on the bones and the proposed swimming pattern of the animal. A phylogenetic analysis was also carried out. This study documents the diversity both in the morphology and in the locomotion pattern among pachypleurosaw·ids. • ii • TABLE OF CONTENTS Preface . Umque·Contn'b'utlOns Il.. Table of Contents iii • LIst· 0 fF'Igures.............................................. Vil.. Listing of Tables ix Abstract x Résumé xi Acknowledgements xiii .) iii • Introduction . Systematic Paleontology ...................................... .. 6 Description . II Axial skeleton . II Skull . II Lower Jaw . 23 Tooth Implantation ................................ 24 Vertebrae and Ribs ................................ 25 Gastralia . 36 Appendicular Skeleton 37 • Pectoral Girdle 37 Humerus . 41 Dina and radius . 41 Carpus and Manus . 42 Pelvic Girdle . 46 Femur . 49 Tibia and fibula ................................. 51 Tarsus and Pes . 51 Measurements and Proportions 53 • iv • Sexual Dimorphism o......................................... 57 Ontogenj o................................................ 61 Description of GXD835û02 o.............................. 61 The developmental stage of GXD835002 o..................... 64 The ontogenetic stage of V7917 o........................... 67 Subadult specimens o.................................... 69 The adults .........................................." 69 Allometric growth of Keichousaurus hui 71 Locomotion . 76 Function of the forelimbs of Keichousaurus hui o •••••••••••••••• 78 • Reconstruction of the muscular system of the shoulder girdle 84 Hindlimb and the pelvic girdle o •••••••••••••••••••••••••••• 89 Muscle reconstruction of pelvic girdle and hindlimbs . 91 The tail . 93 The neck o ••••••••••••••••••••••••••••••••••••••••••• 95 The swinuning pattern of Keichousaurus o ••••••••••••••••••••• 96 Phylogenetic Analysis o....................................... 98 Conclusions o............................................. 112 • v • References 114 Abbreviations 122 • • VI • LIST OF FIGURES Figure 1 Location of Keichousaurus hui. 8 Figure 2 Reconstruction of Keichousaurus hui. 12 Figure 3 Reconstruction of the skull of Keichousaurus hui. 13 Figure 4 The skull of Keichousaurus hui. 14 Figure 5 Palatal view of Keichousaurus hui skull, GXD838028. 22 Figure 6 Dorsal aspect of Keichousaurus hui, GXD7613. 26 Figure 7 Ventral aspect of Keichousaurus hui, GXD838028. 27 Figure 8 The atlas-axis complex of Keichousaurus hui. 30 • Figure 9 The accessory articulation complex of Keichousaurus hui. 34 Figure 10 Pectoral girdle of Keichousaurus hui. 38 Figure II Humerus of Keichousaurus hui. 43 Figure 12 Lower arm of Keichousaurus hui. 44 Figure 13 Pelvic girdle of Keichousaurus 47 Figure 14 Hindlimb of Keichousaurus hui. 50 Figure 15 An embryo of Keichousaurlls hui, GXD835002. 62 Figure 16 A juvenile specimen of Keichousaurus hui, V7917. 68 Figure 17 Swimming speeds of modern aquatic vertebrates. 81 Figure 18 Cladogram of sauropterygians. 110 • vii • LISTING OF TABLES Table 1 Measurements of Keichousaurus hui 54 Table Il Proportions of measurements of Keichousaurus hui 56 Table III AHometric coefficients 74 Table IV Character states of sauropterygians 109 • • viii • ABSTRACT Keichousaurus hui Young, 1958, from the Middle Triassic of Guizhou, China is a small sauropterygian reptile. It has short snout and elongated temporal openings resembling the European pachypleurosaurid Dactylosaurus. Unlike ail the other sauropterygians, the parietal opening is anteriorly positioned. The neck is long and flexible. The body is rigid and the bones are pachyostotic. It has two or threc sacral vertebrae. The most striking feature of Keichousaurus is its broad ulna. The entire forelimb has the outline of a paddle or an oar, and may have been functioned like one. There is noticeable sexual dimorphism, as is the case for Alpine pachypleurosaurids. • The growth of the humerus is highly positive allometric, indicating an important role of the forelimb in locomotion. The horizontal orientation ofthe pectoral girdle indicate that Keichousaurus,