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Bulletin of the American Museum of Natural History NESBITT ET AL.: Scientific Publications of the American Museum of Natural History American Museum Novitates POSTCRANIAL OSTEOLOGY OF AZENDOHSAURUS Bulletin of the American Museum of Natural History Anthropological Papers of the American Museum of Natural History MADAGASKARENSIS (?MIDDLE TO UPPER TRIASSIC, Publications Committee ISALO GROUP, MADAGASCAR) AND ITS SYSTEMATIC Robert S. Voss, Chair AZENDOHSAURUS MADAGASKARENSIS POSITION AMONG STEM ARCHOSAUR REPTILES Board of Editors Jin Meng, Paleontology Lorenzo Prendini, Invertebrate Zoology Robert S. Voss, Vertebrate Zoology STERLING J. NESBITT, JOHN J. FLYNN, Peter M. Whiteley, Anthropology ADAM C. PRITCHARD, J. MICHAEL PARRISH, Managing Editor Mary Knight LOVASOA RANIVOHARIMANANA, AND ANDRÉ R. WYSS Submission procedures can be found at http://research.amnh.org/scipubs All issues of Novitates and Bulletin are available on the web (http://digitallibrary.amnh. org/dspace). Order printed copies on the web from: http://shop.amnh.org/a701/shop-by-category/books/scientific-publications.html or via standard mail from: American Museum of Natural History—Scientific Publications Central Park West at 79th Street New York, NY 10024 This paper meets the requirements of ANSI/NISO Z39.48-1992 (permanence of paper). AMNH BULLETIN 398 On the cover: Reconstruction of Azendohsaurus madagaskarensis from the ?Middle to Upper Triassic, Isalo 2015 group, Madagascar. Drawing by Matth Celeskey. BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY POSTCRANIAL OSTEOLOGY OF AZENDOHSAURUS MADAGASKARENSIS (?MIDDLE TO UPPER TRIASSIC, ISALO GROUP, MADAGASCAR) AND ITS SYSTEMATIC POSITION AMONG STEM ARCHOSAUR REPTILES STERLING J. NESBITT Center for Integrative Research, Field Museum of Natural History; Division of Paleontology, American Museum of Natural History; Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg JOHN J. FLYNN Richard Gilder Graduate School and Division of Paleontology American Museum of Natural History ADAM C. PRITCHARD Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York J. MICHAEL PARRISH College of Science, San Jose State University, San Jose, California LOVASOA RANIVOHARIMANANA De´partment de Pale´ontologie et d’Anthropologie Biologique, Universite´ d’Antananarivo, Madagascar ANDRE´ R. WYSS Department of Geological Sciences, University of California at Santa Barbara; Division of Paleontology, American Museum of Natural History BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Number 398, 126 pp., 81 figures, 12 tables Issued December 7, 2015 Copyright E American Museum of Natural History 2015 ISSN 0003-0090 CONTENTS Abstract.......................................................... 4 Introduction . ...................................................... 4 Institutionalacronyms................................................ 5 Methods.......................................................... 6 Geologicalcontext................................................... 7 Systematicpaleontology............................................... 9 Archosauromorpha ................................................. 9 Allokotosauria.................................................... 9 Azendohsaurus ................................................... 10 Azendohsaurus madagaskarensis ....................................... 10 Holotype..................................................... 10 Paratypes ..................................................... 10 ReferredMaterial............................................... 10 Locality...................................................... 10 Revised Diagnosis ............................................... 11 Description....................................................... 11 AxialSkeleton................................................... 11 Vertebralcolumn(general)........................................ 11 Cervicalvertebrae.............................................. 13 Trunkvertebrae............................................... 21 Sacral vertebrae. ............................................... 25 Caudal vertebrae ............................................... 27 Ribs........................................................ 31 Gastralia.................................................... 33 Chevrons.................................................... 33 Pectoral girdle .................................................. 35 Clavicle . .................................................... 35 Interclavicle.................................................. 36 Scapula . .................................................... 37 Coracoid.................................................... 39 Forelimb...................................................... 40 Humerus .................................................... 40 Radius...................................................... 42 Ulna....................................................... 43 Manus...................................................... 44 Radiale.................................................... 47 Intermedium................................................ 48 Ulnare.................................................... 50 Lateralcentrale.............................................. 51 Medial centrale .............................................. 51 First–fourthdistalcarpals....................................... 51 Metacarpals................................................ 53 Manualdigits............................................... 54 Terminal phalanges ........................................... 55 Pelvicgirdle.................................................... 57 Ilium....................................................... 57 Pubis....................................................... 60 Ischium . .................................................... 61 Hindlimb..................................................... 62 Femur...................................................... 62 2 Tibia....................................................... 64 Fibula...................................................... 65 Pes......................................................... 66 Astragalus.................................................. 68 Calcaneum................................................. 73 Distaltarsals................................................ 75 Metatarsals................................................. 76 Pedaldigits................................................. 78 Phylogenetic analysis . ............................................ 79 Taxonandcharactersampling....................................... 79 Treesearchstrategy.............................................. 81 Results and Discussion . ............................................ 81 Allokotosauria: tree topology and clade support .......................... 84 Allokotosauria + Archosauriformes.................................. 84 Allokotosauria ................................................ 85 Azendohsauridae + Trilophosauridae ................................ 86 Azendohsauridae............................................... 86 Trilophosauridae . ............................................ 87 Trilophosaurus................................................. 88 Implications for the divergence of Archosauromorpha ...................... 92 ConvergenceandtheprevalenceofherbivoryinTriassicArchosauromorpha...... 93 Conclusions and perspective .......................................... 96 Acknowledgments................................................. 97 References....................................................... 97 Appendix 1. Referred material of Azendohsaurus madagaskarensis................ 106 Appendix 2. The manus of Trilophosaurus buettneri.......................... 108 Appendix 3. Extended description of newly added terminal taxa in thephylogeneticanalysis........................................... 111 Appendix 4. Phylogenetic characters .................................... 113 Appendix5.Characterscores......................................... 124 3 4 BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY NO. 398 ABSTRACT During the Triassic, archosauromorphs became one of the first groups of diapsid reptiles to diversify in terms of body size and morphological disparity in both terrestrial and marine ecosystems across Pangaea. This seemingly rapid divergence, and the numerous unique body plans stemming from it, concomitantly has confounded reconstructions of archosauromorph relationships. Teasing apart homology from homoplasy of anatomical characters in this broad suite of body types remains an enormous challenge with the current sample of taxa. Here, we present the postcranial anatomy of Azendohsaurus madagaskarensis, an early archosauromorph from ?Middle to Upper Triassic strata of Madagascar. Azendohsaurus madagaskarensis is known from nearly the entire skeleton in an ontogenetically variable sample. The holotype locality consists of a monotypic bone bed; preservation ranges from complete but disarticulated bones to articulated sections of the skeleton. Azendohsaurus madagaskarensis embodies an aberrant constellation of archosauromorph features, including an elongated neck, a short, stocky tail, robust limbs, and unexpectedly short digits terminating in large recurved unguals on the manus and pes. Together with the cranium, the postcrania reveal A. madagaskarensis to be another representative of a growing coterie of highly apomorphic and bizarre Triassic archosaur- omorphs. At the same time, recovery and description of the full anatomy
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