DOCSLIB.ORG

Two New Archosaur Reptiles from the Late Triassic Of

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

TWO NEW ARCHOSAUR REPTILES FROM THE LATE TRIASSIC OF TEXAS by MOMCHIL NIKOLAEV ATANASSOV, M.S. A DISSERTATION IN GEOSCIENCE Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Approved Chairperson of the Qbmmittee Accepted Dean of the Graduate School August, 2002 Copyright 2002, Momchil Nikolaev Atanassov ACKNOWLEDGMENTS I would like to thank the members of my committee. Dr. James Barrick, Dr. Thomas Lehman, Dr. Richard Strauss, and the committee chairman. Dr. Sankar Chatterjee for their guidance, help, and support during the completion of this dissertation. In particular, I would like to express my gratitude to my dissertation advisor Sankar Chatterjee, who invited me to come to Texas Tech University, offered his generous hospitality, and provided valuable advice and guidance throughout this project. I also wish to thank my fellow students and colleagues Alan Coulson, Axel Hungerbiihler, Richard Kissel, Jeffrey Martz, Kyle McQuilkin, Bill Mueller, Eric Simpson, Jonathan Wagner, and Jonathan Weinbaum for many useful discussions and their help in the field and in the lab. A special thanks goes to Mariana Ivanova for her help in the field and especially for her skillful preparation of a significant amotmt of material from the Dockum Group, a tedious and time-consuming task. Bill Mueller from the Museum of Texas Tech University took most photographs with great skill and patience. I theink the Museum of Texas Tech University for allowing unlimited access to the fossil collections and the museum facilities, and the Department of Geosciences at Texas Tech University for the material support throughout my studies. I also wish to thank all the individuals who helped me during my various stays at their institutions. I thank Silvio Renesto from Dipartimento di Scienze della Terra, Universita degli Studi in Milan; Ana Paganoni and the staff at Museo Civico di Scienze Naturali in Bergamo; and Guiseppe Muscio and Fabio Dalla Vecchia from Museo Friulano di Storia Naturale in Udine for their generous hospitality and help, which made my stay in Italy enjoyable and productive. I also thank Tim Rowe, Pamela Owen, Wann Langston, Jr., Ernest Lundelius, Jr., and Ron Tykoski at the Vertebrate Paleontology Lab of University of Texas, Austin, who allowed unlimited access to their Late Triassic collections and were very helpful with information and discussions. Peter Reser from the New Mexico Museum of Natural History and Science in Albuquerque provided access to the fossil collections of the museum. The staff at Institute de Geologia at Universidad Nacional Autonoma de Mexico in Mexico City also provided unlimited access to the material of the Early Jurassic pterosaur Dimorphodon weintraubi under their care. ni TABLE OF CONTENTS ACKNOWLEDGMENTS ii ABSTRACT v LIST OF TABLES vii LIST OF FIGURES viii CHAPTER I. INTRODUCTION 1 II. GEOLOGIC SETTING 5 III. DESCRIPTION OF THE NEW ARCHOSAUR PTEROMIMIMUS 17 IV. DESCRIPTION OF THE NEW ARCnOS,A\]R PROCOELOSAURUS ....65 V. PHYLOGENETIC ANALYSIS 118 REFERENCES 147 APPENDIX A. LIST OF CHARACTERS USED IN PREVIOUS PHYLOGENETIC ANALYSES OF ARCHOSAUROMORPHA 157 B. CHARACTER MATRIX USED IN PHYLOGENETIC ANALYSIS 346 C. PHOTOGRAPHS OF PTEROMIMUS LONGICOLLIS AND PROCOELOSAURUS BREVICOLLIS 352 IV ABSTRACT Two new basal archosaurs, Pteromimus longicollis and Procoelosaurus brevicollis are described from the Tecovas Formation (late Camian) and the Cooper Canyon Formation (early Norian) of the Dockum Group of West Texas. Pteromimus is based on an incomplete skull and associated and isolated skull and vertebral elements. The skull is high, with narrow snout, large orbit and naris, pneumatized maxilla and premaxilla, large inflated frontal, short parietal, plate-like supraoccipital, and reduced post-temporal openings. The dentition is thecodont and consists of conical teeth with fluted apices. The premaxillary teeth are long and slightly recurved, and the maxillary teeth are short and more laterally compressed. The vertebrae of both Pteromimus and Procoelosaurus £ire with procoelous and hollow centra, with large cavities for the interspinal ligament, well-developed epipophyses, and long and low neural arches carrying long neural processes v«th spine tables. Pteromimus is distinguished by low neural processes with weakly developed spine tables and ornamentation, while Procoelosaurus is characterized by higher neural processes that expand into wide spine tables with distinctive sculpturing. The cervical vertebrae of Pteromimus are elongate, dorsoventrally compressed, and bear unusual rib articulations consisting of a large posterior depression and a small anterior process. Procoelosaurus is represented by an association of vertebrae, pelvis, hindlimb and skull elements, and by a large number of isolated vertebrae. The maxilla and dentary of Procoelosaurus bear numerous teeth with thecodont implantation and crowns that are recurved, laterally compressed, and serrated. Procoelosaurus has at least three sacral vertebrae, large plate-like ischium, and ilium with a low blade, reduced preacetabular process, and a long, tapering postacetabular process. The femur appears similar to those of pterosaurs with anteriorly bowed shaft, well developed condyles, and an intumed head. The ankle and foot of Procoelosaurus are similar to those of early pterosaurs with an advanced mesotarsal tarsus, hooked fifth metatarsal, and closely appressed metatarsals I-IV subequal in length and indicating a plantigrade pes. A phylogenetic analysis of Archosauromorpha indicates that the two new reptiles and pterosaurs are omithodiran archosaurs and form a monophyletic clade that is the sister-group to Scleromochlus + Dinosauromorpha. Pteromimus is the sister- group of pterosaurs, and Procoelosaurus is the sister-group to the clade Pteromimus + Pterosauria. VI LIST OF TABLES 1. Measurements of the vertebrae of Pteromimus longicollis 45 2. Measurements of the vertebrae of Procoelosaurus brevicollis 93 3. Ratios of iliac blade height to acetabulum height in basal archosauriforms 107 4. Character matrix used in phylogenetic analysis 347 Vll LIST OF FIGURES 1. Generalized geologic map of the southern High Plains region of West Texas and eastern New Mexico, showing distribution of the Upper Triassic Dockum Group 14 2. Detailed geologic map of the Dockum Group in the upper Brazos and Colorado River Valleys in West Texas, showing the fossil localities 15 3. Stratigraphy of the Dockum Group at the Post Quarry, Garza County, and the Kirkpatrick Quarry, Crosby County, Texas 16 4. Quarry map of the type material (skull association) of Pteromimus longicollis at Post Quarry 48 5. Lateral view of skull reconstruction of Pteromimus longicollis 49 6. Dorsal view of skull restorations of P/erow/wM5'/o«g/co//w 50 7. Posterior view of skull restoration of Pteromimus longicollis 51 8. Lateral, medial, anterior and posterior view of premaxilla of Pteromimus longicollis 52 9. Lateral and medial view of the maxillae of Pteromimus longicollis 53 10. Dorsal and ventral view of nasal of Pteromimus longicollis 54 U. Lateral view of partially preserved skull of Pteromimus longicollis 55 12. Anterior view of partially preserved skull of Pteromimus longicollis 56 viii 13. Dorsolateral view of prefrontal-postfrontal association of Pteromimus longicollis 57 14. Lateral and medial views of postorbital of Pteromimus longicollis 58 15. Medial and lateroposterior views of the right quadrate of Pteromimus longicollis with fragments of the quadratojugal and squamosal attached 59 16. Dorsal and ventral views of reconstructed palate of Pteromimus longicollis 60 17. Lateral and medial views of anterior dentary of Pteromimus longicollis 61 18. Dorsal, lateral, anterior and posterior views of the mid-cervical vertebra TTUP 10081/2 of Pteromimus longicollis 62 19. Lateral, dorsal, anterior and posterior views of the anterior cervical vertebra TTUP 10088 of Pteromimus longicollis 63 20. Lateral, anterior, posterior, and oblique views of the large cervical vertebra of Pteromimus longicollis 64 21. Lateral and medial views of the maxilla of Procoelosaurus brevicollis 108 22. Lateral and medial view of dentary of Procoelosaurus brevicollis 109 23. Anterior cervical of Procoelosaurus brevicollis in all views 110 24. Dorsal vertebra of Procoelosaurus brevicollis in all views Ill 25. Lateral and medial view of ilium of Pracoe/o5flMrw5 6revzco//w 112 ix 26. Lateral view of two ischia (TTUP 10108/3 and 10109) of Procoelosaurus brevicollis 113 27, Anterior and posterior view of femur of Procoelosaurus brevicollis 114 28. Anterior wievi of i\h\didcndif\h\x\di of Procoelosaurus brevicollis 115 29. Proximal and distal views of astragalus and calcaneum of Procoelosaurus brevicollis 116 30. Anterior and posterior views of pes of Procoelosaurus brevicollis 117 31. Majority-rule consensus tree of Archosauromorpha with Lepidosauromorpha as an outgroup 146 CHAPTER I INTRODUCTION General Background of Study The continental red beds of the Late Triassic Dockum Group are widely exposed along the foot of the Caprock Escarpment of the Southern High Plains in western Texas, through the Canadian River Valley in Texas and eastern New Mexico, and along the Pecos River Valley in New Mexico and southward into Texas. The Dockum Group rests unconformably on Permian strata, and is unconformably overlain by Cretaceous, Tertiary, or Quaternary strata. The Triassic deposits have been studied by stratigraphers, sedimentologists, and paleontologists
Recommended publications
  • First Record of Mesozoic Terrestrial Vertebrates from Lithuania

    First Record of Mesozoic Terrestrial Vertebrates from Lithuania

    Edinburgh Research Explorer First record of Mesozoic terrestrial vertebrates from Lithuania Citation for published version: Brusatte, SL, Butler, RJ, Niedwiedzki, G, Sulej, T, Bronowicz, R & Nas, JS 2013, 'First record of Mesozoic terrestrial vertebrates from Lithuania: Phytosaurs (Diapsida: Archosauriformes) of probable Late Triassic age, with a review of phytosaur biogeography', Geological Magazine, vol. 150, no. 1, pp. 110-122. https://doi.org/10.1017/S0016756812000428 Digital Object Identifier (DOI): 10.1017/S0016756812000428 Link: Link to publication record in Edinburgh Research Explorer Document Version: Publisher's PDF, also known as Version of record Published In: Geological Magazine Publisher Rights Statement: Final Published Version by Cambridge University Press (2013) can be made available on Institutional Repository 12 months after publication date. General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 23. Sep. 2021 Geol. Mag. 150 (1), 2013, pp. 110–122. c Cambridge University Press 2012 110 doi:10.1017/S0016756812000428 First record of Mesozoic terrestrial vertebrates from Lithuania: phytosaurs (Diapsida: Archosauriformes) of probable Late Triassic age, with a review of phytosaur biogeography ∗ STEPHEN L.
  • An Evaluation of the Phylogenetic Relationships of the Pterosaurs Among Archosauromorph Reptiles

    An Evaluation of the Phylogenetic Relationships of the Pterosaurs Among Archosauromorph Reptiles

    Journal of Systematic Palaeontology 5 (4): 465–469 Issued 19 November 2007 doi:10.1017/S1477201907002064 Printed in the United Kingdom C The Natural History Museum An evaluation of the phylogenetic relationships of the pterosaurs among archosauromorph reptiles David W. E. Hone∗ Department of Earth Sciences, University of Bristol, Queens Road, Bristol, BS8 1RJ, UK Michael J. Benton Department of Earth Sciences, University of Bristol, Queens Road, Bristol, BS8 1RJ, UK SYNOPSIS The phylogenetic position of pterosaurs among the diapsids has long been a contentious issue. Some recent phylogenetic analyses have deepened the controversy by drawing the pterosaurs down the diapsid tree from their generally recognised position as the sister group of the dinosaur- omorphs, to lie close to the base of Archosauria or to be the sister group of the protorosaurs. Critical evaluation of the analyses that produced these results suggests that the orthodox position retains far greater support and no close link can be established between pterosaurs and protorosaurs. KEY WORDS Pterosauria, Prolacertiformes, Archosauria, Archosauromorpha, Ornithodira Contents Introduction 465 Methods and Results 466 Discussion 467 Re-analysis of Bennett (1996) 467 Re-analysis of Peters (2000) 467 Conclusions 469 Acknowledgements 469 References 469 Introduction tained). Muller¨ (2003, 2004) also suggested that the prolacer- tiforms were not a valid clade, with Trilophosaurus splitting The basal archosaurs and their phylogenetic positions relative his two prolacertiform taxa (Prolacerta and Tanystropheus). to one another within the larger clade Archosauromorpha The analysis performed by Senter (2004) also found the pro- have been a source of controversy among palaeontologists lacertiforms to be paraphyletic, although here he removed the for decades.
  • 8. Archosaur Phylogeny and the Relationships of the Crocodylia

    8. Archosaur Phylogeny and the Relationships of the Crocodylia

    8. Archosaur phylogeny and the relationships of the Crocodylia MICHAEL J. BENTON Department of Geology, The Queen's University of Belfast, Belfast, UK JAMES M. CLARK* Department of Anatomy, University of Chicago, Chicago, Illinois, USA Abstract The Archosauria include the living crocodilians and birds, as well as the fossil dinosaurs, pterosaurs, and basal 'thecodontians'. Cladograms of the basal archosaurs and of the crocodylomorphs are given in this paper. There are three primitive archosaur groups, the Proterosuchidae, the Erythrosuchidae, and the Proterochampsidae, which fall outside the crown-group (crocodilian line plus bird line), and these have been defined as plesions to a restricted Archosauria by Gauthier. The Early Triassic Euparkeria may also fall outside this crown-group, or it may lie on the bird line. The crown-group of archosaurs divides into the Ornithosuchia (the 'bird line': Orn- ithosuchidae, Lagosuchidae, Pterosauria, Dinosauria) and the Croco- dylotarsi nov. (the 'crocodilian line': Phytosauridae, Crocodylo- morpha, Stagonolepididae, Rauisuchidae, and Poposauridae). The latter three families may form a clade (Pseudosuchia s.str.), or the Poposauridae may pair off with Crocodylomorpha. The Crocodylomorpha includes all crocodilians, as well as crocodi- lian-like Triassic and Jurassic terrestrial forms. The Crocodyliformes include the traditional 'Protosuchia', 'Mesosuchia', and Eusuchia, and they are defined by a large number of synapomorphies, particularly of the braincase and occipital regions. The 'protosuchians' (mainly Early *Present address: Department of Zoology, Storer Hall, University of California, Davis, Cali- fornia, USA. The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds (ed. M.J. Benton), Systematics Association Special Volume 35A . pp. 295-338. Clarendon Press, Oxford, 1988.
  • New Permian Fauna from Tropical Gondwana

    New Permian Fauna from Tropical Gondwana

    ARTICLE Received 18 Jun 2015 | Accepted 18 Sep 2015 | Published 5 Nov 2015 DOI: 10.1038/ncomms9676 OPEN New Permian fauna from tropical Gondwana Juan C. Cisneros1,2, Claudia Marsicano3, Kenneth D. Angielczyk4, Roger M. H. Smith5,6, Martha Richter7, Jo¨rg Fro¨bisch8,9, Christian F. Kammerer8 & Rudyard W. Sadleir4,10 Terrestrial vertebrates are first known to colonize high-latitude regions during the middle Permian (Guadalupian) about 270 million years ago, following the Pennsylvanian Gondwanan continental glaciation. However, despite over 150 years of study in these areas, the bio- geographic origins of these rich communities of land-dwelling vertebrates remain obscure. Here we report on a new early Permian continental tetrapod fauna from South America in tropical Western Gondwana that sheds new light on patterns of tetrapod distribution. Northeastern Brazil hosted an extensive lacustrine system inhabited by a unique community of temnospondyl amphibians and reptiles that considerably expand the known temporal and geographic ranges of key subgroups. Our findings demonstrate that tetrapod groups common in later Permian and Triassic temperate communities were already present in tropical Gondwana by the early Permian (Cisuralian). This new fauna constitutes a new biogeographic province with North American affinities and clearly demonstrates that tetrapod dispersal into Gondwana was already underway at the beginning of the Permian. 1 Centro de Cieˆncias da Natureza, Universidade Federal do Piauı´, 64049-550 Teresina, Brazil. 2 Programa de Po´s-Graduac¸a˜o em Geocieˆncias, Departamento de Geologia, Universidade Federal de Pernambuco, 50740-533 Recife, Brazil. 3 Departamento de Cs. Geologicas, FCEN, Universidad de Buenos Aires, IDEAN- CONICET, C1428EHA Ciudad Auto´noma de Buenos Aires, Argentina.
  • Studies on Continental Late Triassic Tetrapod Biochronology. I. the Type Locality of Saturnalia Tupiniquim and the Faunal Succession in South Brazil

    Studies on Continental Late Triassic Tetrapod Biochronology. I. the Type Locality of Saturnalia Tupiniquim and the Faunal Succession in South Brazil

    Journal of South American Earth Sciences 19 (2005) 205–218 www.elsevier.com/locate/jsames Studies on continental Late Triassic tetrapod biochronology. I. The type locality of Saturnalia tupiniquim and the faunal succession in south Brazil Max Cardoso Langer* Departamento de Biologia, FFCLRP, Universidade de Sa˜o Paulo (USP), Av. Bandeirantes 3900, 14040-901 Ribeira˜o Preto, SP, Brazil Received 1 November 2003; accepted 1 January 2005 Abstract Late Triassic deposits of the Parana´ Basin, Rio Grande do Sul, Brazil, encompass a single third-order, tetrapod-bearing sedimentary sequence that includes parts of the Alemoa Member (Santa Maria Formation) and the Caturrita Formation. A rich, diverse succession of terrestrial tetrapod communities is recorded in these sediments, which can be divided into at least three faunal associations. The stem- sauropodomorph Saturnalia tupiniquim was collected in the locality known as ‘Waldsanga’ near the city of Santa Maria. In that area, the deposits of the Alemoa Member yield the ‘Alemoa local fauna,’ which typifies the first association; includes the rhynchosaur Hyperodapedon, aetosaurs, and basal dinosaurs; and is coeval with the lower fauna of the Ischigualasto Formation, Bermejo Basin, NW Argentina. The second association is recorded in deposits of both the Alemoa Member and the Caturrita Formation, characterized by the rhynchosaur ‘Scaphonyx’ sulcognathus and the cynodont Exaeretodon, and correlated with the upper fauna of the Ischigualasto Formation. Various isolated outcrops of the Caturrita Formation yield tetrapod fossils that correspond to post-Ischigualastian faunas but might not belong to a single faunal association. The record of the dicynodont Jachaleria suggests correlations with the lower part of the Los Colorados Formation, NW Argentina, whereas remains of derived tritheledontid cynodonts indicate younger ages.
  • Tetrapod Biostratigraphy and Biochronology of the Triassic–Jurassic Transition on the Southern Colorado Plateau, USA

    Tetrapod Biostratigraphy and Biochronology of the Triassic–Jurassic Transition on the Southern Colorado Plateau, USA

    Palaeogeography, Palaeoclimatology, Palaeoecology 244 (2007) 242–256 www.elsevier.com/locate/palaeo Tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau, USA Spencer G. Lucas a,⁎, Lawrence H. Tanner b a New Mexico Museum of Natural History, 1801 Mountain Rd. N.W., Albuquerque, NM 87104-1375, USA b Department of Biology, Le Moyne College, 1419 Salt Springs Road, Syracuse, NY 13214, USA Received 15 March 2006; accepted 20 June 2006 Abstract Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups on the southern Colorado Plateau preserve tetrapod body fossils and footprints that are one of the world's most extensive tetrapod fossil records across the Triassic– Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean–Wassonian boundary approximates the Triassic–Jurassic boundary. This tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau confirms that crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic. © 2006 Elsevier B.V. All rights reserved. Keywords: Triassic–Jurassic boundary; Colorado Plateau; Chinle Group; Glen Canyon Group; Tetrapod 1. Introduction 190 Ma. On the southern Colorado Plateau, the Triassic– Jurassic transition was a time of significant changes in the The Four Corners (common boundary of Utah, composition of the terrestrial vertebrate (tetrapod) fauna.
  • 112 Appendix B Hydrogeologic and Soils Factors

    112 Appendix B Hydrogeologic and Soils Factors

    APPENDIX B HYDROGEOLOGIC AND SOILS FACTORS INFLUENCING LEAKAGE POTENTIAL FROM THE CONCHAS-HUDSON CANAL SYSTEM, ARCH HURLEY CONSERVANCY DISTRICT, QUAY AND SAN MIGUEL COUNTIES, NEW MEXICO by John W. Hawley, Senior Hydrogeologist New Mexico Water Resources Research Institute and John F. Kennedy, GIS Specialist/Hydrogeologist New Mexico Water Resources Research Institute October 2005 INTRODUCTION The following discussion of geology and soils in the Arch Hurley Conservancy District (District) study area introduces the major landscape features (landforms) and surficial geologic units of the Conchas-Hudson Canal system between Conchas Reservoir in San Miguel County and the eastern part of the Tucumcari (irrigation) Project in Quay County. Emphasis is on hydrogeologic and soils factors that influence leakage from not only the canal corridor but also the complex network of laterals, ditches and field- drainage features that characterize irrigated parts of the District. Of particular importance is the historic role played by Project operations (since 1946) in recharge of the shallow- alluvial and bedrock (Entrada Sandstone) aquifer systems of the Tucumcari Metropolitan area. The latter topic was first addressed in detail by Trauger and Bushman (1964) and is only briefly covered here. 112 The geologic setting of the entire study area is the subject of a recent comprehensive review paper that was written specifically for a general audience by Adrian Hunt (Director, New Mexico Museum of Natural History and Science; 1998). Hydrogeologic characteristics of major stratigraphic units exposed or shallowly buried along the canal corridor are summarized in Table B1, which also includes a list of supporting references. Distribution patterns and leakage potential of surficial-geologic units and soils are summarized in Tables B2-B5 in Attachment B1 to this Appendix.
  • The Origin and Early Evolution of Dinosaurs

    The Origin and Early Evolution of Dinosaurs

    Biol. Rev. (2010), 85, pp. 55–110. 55 doi:10.1111/j.1469-185X.2009.00094.x The origin and early evolution of dinosaurs Max C. Langer1∗,MartinD.Ezcurra2, Jonathas S. Bittencourt1 and Fernando E. Novas2,3 1Departamento de Biologia, FFCLRP, Universidade de S˜ao Paulo; Av. Bandeirantes 3900, Ribeir˜ao Preto-SP, Brazil 2Laboratorio de Anatomia Comparada y Evoluci´on de los Vertebrados, Museo Argentino de Ciencias Naturales ‘‘Bernardino Rivadavia’’, Avda. Angel Gallardo 470, Cdad. de Buenos Aires, Argentina 3CONICET (Consejo Nacional de Investigaciones Cient´ıficas y T´ecnicas); Avda. Rivadavia 1917 - Cdad. de Buenos Aires, Argentina (Received 28 November 2008; revised 09 July 2009; accepted 14 July 2009) ABSTRACT The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis,andPanphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as ‘‘all descendants of the most recent common ancestor of birds and Triceratops’’.
  • HOVASAURUS BOULEI, an AQUATIC EOSUCHIAN from the UPPER PERMIAN of MADAGASCAR by P.J

    HOVASAURUS BOULEI, an AQUATIC EOSUCHIAN from the UPPER PERMIAN of MADAGASCAR by P.J

    99 Palaeont. afr., 24 (1981) HOVASAURUS BOULEI, AN AQUATIC EOSUCHIAN FROM THE UPPER PERMIAN OF MADAGASCAR by P.J. Currie Provincial Museum ofAlberta, Edmonton, Alberta, T5N OM6, Canada ABSTRACT HovasauTUs is the most specialized of four known genera of tangasaurid eosuchians, and is the most common vertebrate recovered from the Lower Sakamena Formation (Upper Per­ mian, Dzulfia n Standard Stage) of Madagascar. The tail is more than double the snout-vent length, and would have been used as a powerful swimming appendage. Ribs are pachyostotic in large animals. The pectoral girdle is low, but massively developed ventrally. The front limb would have been used for swimming and for direction control when swimming. Copious amounts of pebbles were swallowed for ballast. The hind limbs would have been efficient for terrestrial locomotion at maturity. The presence of long growth series for Ho vasaurus and the more terrestrial tan~saurid ThadeosauTUs presents a unique opportunity to study differences in growth strategies in two closely related Permian genera. At birth, the limbs were relatively much shorter in Ho vasaurus, but because of differences in growth rates, the limbs of Thadeosau­ rus are relatively shorter at maturity. It is suggested that immature specimens of Ho vasauTUs spent most of their time in the water, whereas adults spent more time on land for mating, lay­ ing eggs and/or range dispersal. Specilizations in the vertebrae and carpus indicate close re­ lationship between Youngina and the tangasaurids, but eliminate tangasaurids from consider­ ation as ancestors of other aquatic eosuchians, archosaurs or sauropterygians. CONTENTS Page ABREVIATIONS . ..... ... ......... .......... ... ......... ..... ... ..... .. .... 101 INTRODUCTION .
  • A Phylogenetic Analysis of the Basal Ornithischia (Reptilia, Dinosauria)

    A Phylogenetic Analysis of the Basal Ornithischia (Reptilia, Dinosauria)

    A PHYLOGENETIC ANALYSIS OF THE BASAL ORNITHISCHIA (REPTILIA, DINOSAURIA) Marc Richard Spencer A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements of the degree of MASTER OF SCIENCE December 2007 Committee: Margaret M. Yacobucci, Advisor Don C. Steinker Daniel M. Pavuk © 2007 Marc Richard Spencer All Rights Reserved iii ABSTRACT Margaret M. Yacobucci, Advisor The placement of Lesothosaurus diagnosticus and the Heterodontosauridae within the Ornithischia has been problematic. Historically, Lesothosaurus has been regarded as a basal ornithischian dinosaur, the sister taxon to the Genasauria. Recent phylogenetic analyses, however, have placed Lesothosaurus as a more derived ornithischian within the Genasauria. The Fabrosauridae, of which Lesothosaurus was considered a member, has never been phylogenetically corroborated and has been considered a paraphyletic assemblage. Prior to recent phylogenetic analyses, the problematic Heterodontosauridae was placed within the Ornithopoda as the sister taxon to the Euornithopoda. The heterodontosaurids have also been considered as the basal member of the Cerapoda (Ornithopoda + Marginocephalia), the sister taxon to the Marginocephalia, and as the sister taxon to the Genasauria. To reevaluate the placement of these taxa, along with other basal ornithischians and more derived subclades, a phylogenetic analysis of 19 taxonomic units, including two outgroup taxa, was performed. Analysis of 97 characters and their associated character states culled, modified, and/or rescored from published literature based on published descriptions, produced four most parsimonious trees. Consistency and retention indices were calculated and a bootstrap analysis was performed to determine the relative support for the resultant phylogeny. The Ornithischia was recovered with Pisanosaurus as its basalmost member.
  • Osteology of Pseudochampsa Ischigualastensis Gen. Et Comb. Nov

    Osteology of Pseudochampsa Ischigualastensis Gen. Et Comb. Nov

    RESEARCH ARTICLE Osteology of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae) from the Early Late Triassic Ischigualasto Formation of Northwestern Argentina M. Jimena Trotteyn1,2*, Martı´n D. Ezcurra3 1. CONICET, Consejo Nacional de Investigaciones Cientı´ficas y Te´cnicas, Ciudad Auto´noma de Buenos Aires, Buenos Aires, Argentina, 2. INGEO, Instituto de Geologı´a, Facultad de Ciencias Exactas, Fı´sicas y Naturales, Universidad Nacional de San Juan, San Juan, San Juan, Argentina, 3. School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, West Midlands, United Kingdom *[email protected] Abstract OPEN ACCESS Proterochampsids are crocodile-like, probably semi-aquatic, quadrupedal Citation: Trotteyn MJ, Ezcurra MD (2014) Osteology archosauriforms characterized by an elongated and dorsoventrally low skull. The of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae) from the group is endemic from the Middle-Late Triassic of South America. The most Early Late Triassic Ischigualasto Formation of recently erected proterochampsid species is ‘‘Chanaresuchus ischigualastensis’’, Northwestern Argentina. PLoS ONE 9(11): e111388. doi:10.1371/journal.pone.0111388 based on a single, fairly complete skeleton from the early Late Triassic Editor: Peter Dodson, University of Pennsylvania, Ischigualasto Formation of northwestern Argentina. We describe here in detail the United States of America non-braincase cranial and postcranial anatomy
  • The Shoulder Girdle and Anterior Limb of Drepanosaurus Unguicaudatus

    The Shoulder Girdle and Anterior Limb of Drepanosaurus Unguicaudatus

    <oological Journal of the Linnean Socieg (1994), Ill: 247-264. With 12 figures The shoulder girdle and anterior limb of Drepanosaurus unguicaudatus (Reptilia, Neodiapsida) from the upper Triassic (Norian) Downloaded from https://academic.oup.com/zoolinnean/article/111/3/247/2691415 by guest on 27 September 2021 of Northern Italy SILVIO RENESTO Dipartimento di Scienze della Terra, Universita degli Studi, Via Mangiagalli 34, I-20133 Milano, Italy Received January 1993, accepted for publication February 1994 A reinvestigation of the osteology of the holotype of Drepanosaurus unguicaudatus Pinna, 1980 suggests that in earlier descriptions some osteological features were misinterpreted, owing to the crushing of the bones and because taphonomic aspects were not considered. The pattern of the shoulder girdle and fore-limb was misunderstood: the supposed interclavicle is in fact the right scapula, and the bones previously identified as coracoid and scapula belong to the anterior limb. The new reconstruction of the shoulder girdle, along with the morphology of the phalanges and caudal vertebrae, leads to a new hypothesis about the mode oflife of this reptile. Drepanosaurus was probably an arboreal reptile which used its enormous claws to scrape the bark from trees, perhaps in search of insects, just as the modern pigmy anteater (Cyclopes) does. Available diagnostic characters place Drepanosaurus within the Neodiapsida Benton, but it is impossible to ascribe this genus to one or other of the two major neodiapsid lineages, the Archosauromorpha and the Lepidosauromorpha. ADDITIONAL KEY WORDS:-Functional morphology - taxonomy - taphonomy - palaeoecology . CONTENTS Introduction ................... 247 Taphonomy ..... .............. 249 Systematic palaeontology . .............. 251 Genus Drepanosaurus Pinna, 1980 .............. 252 Drepannsaurus unguicaudatus Pinna, 1980.