DOCSLIB.ORG

Temnospondyli: Dissorophoidea) from Richards Spur, Oklahoma

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Temnospondyli: Dissorophoidea) from Richards Spur, Oklahoma A New Lower Permian Trematopid (Temnospondyli: Dissorophoidea) from Richards Spur, Oklahoma by Brendan Polley A thesis submitted in conformity with the requirements for the degree of Master of Science Department of Ecology and Evolutionary Biology University of Toronto © Copyright by Brendan Polley 2009 A new Lower Permian trematopid (Temnospondyli: Dissorophoidea) from Richards Spur, Oklahoma Brendan Polley Master of Science Department of Ecology and Evolutionary Biology University of Toronto 2009 Abstract A new trematopid amphibian, Acheloma dunni, is reported based on excellently preserved cranial and postcranial elements recovered from the Lower Permian fissure fill deposits of the Dolese Brothers Co. limestone quarry near Richards Spur, Oklahoma. The new taxon is characterized by distinct lateral exposures of the palatine (l.e.p.) and ectopterygoid (l.e.e.) completely enclosed within the suborbital elements. This large, terrestrial adapted carnivore may represent the top predator of the Richards Spur assemblage. A phylogenetic analysis including 11 ingroup taxa and 54 cranial characters yielded a single most parsimonious tree, placing A. dunni within the monophyletic Trematopidae as the sister taxon to Acheloma cumminsi. Furthermore, the analysis supports including the enigmatic Ecolsonia and Actiobates within Trematopidae, forming a clade with the Upper Pennsylvanian Anconastes and the Lower Permian Tambachia. The study is the first to comprehensively analyze all valid and aberrant forms of Trematopidae within the context of broader dissorophoid phylogeny. ii Acknowledgments I am indebted to the many individuals whose support and guidance truly enriched this challenging and rewarding year. Thank you to my supervisor, R. Reisz for being an unwavering source of encouragement and direction. As you did for me, I will be sure to have faith in my own students, treat them with respect, and push them to realize their potential. I am grateful to D. Scott for her invaluable technical training, for photographing specimens, and for, of course, her friendship. Thank you to my friends in the Reisz lab, N. Campione, J. Fröbisch, N. Fröbisch, J. Hawthorn, D. Mazierski, and N. Wong Ken for all their advice and support. Also, many thanks to my advisors D. Evans and D. Walsh for your guidance and constructive feedback. Special thanks to B. Dunn and M. Feese for their continuing efforts to collect fossils from Richards Spur. This project, among countless others, would not have been made possible without their generous donations to the Sam Noble Oklahoma Museum of Natural History. I am grateful to D. Berman of the Carnegie Museum of Natural History, Pittsburgh, PA; R. Ethington of the University of Missouri, Columbia, MO; M. Norell of the American Museum of Natural History, New York, NY; and M. Ryan of the Cleveland Museum of Natural History, Cleveland, OH for allowing me access to various trematopid specimens for study. Finally, thank you to my family, friends, and especially J. Cawaling for their unconditional love and support throughout the course of this project and beyond. iii Table of Contents Acknowledgments.......................................................................................................................... iii Table of Contents........................................................................................................................... iv List of Figures................................................................................................................................ vi List of Appendices ....................................................................................................................... viii 1 Introduction................................................................................................................................ 1 2 Materials..................................................................................................................................... 4 3 Abbreviations ............................................................................................................................. 6 3.1 Institutional Abbreviations.................................................................................................. 6 3.2 Anatomical Abbreviations .................................................................................................. 6 4 Systematic Paleontology ............................................................................................................ 7 4.1 Type Specimen.................................................................................................................... 7 4.2 Referred Specimens ............................................................................................................ 8 4.3 Diagnosis............................................................................................................................. 8 4.4 Occurrence .......................................................................................................................... 8 4.5 Etymology........................................................................................................................... 8 5 Description ................................................................................................................................. 8 5.1 General................................................................................................................................ 8 5.2 Skull Roof ........................................................................................................................... 9 5.3 Palate................................................................................................................................. 13 5.4 Braincase........................................................................................................................... 15 5.5 Lower Jaw......................................................................................................................... 16 5.6 Axial Skeleton................................................................................................................... 17 5.7 Appendicular Skeleton...................................................................................................... 18 6 Discussion ................................................................................................................................ 20 iv 6.1 Phylogenetic Analysis....................................................................................................... 20 6.2 Habits and Lifestyle .......................................................................................................... 23 References..................................................................................................................................... 26 Figures and Captions..................................................................................................................... 35 Appendix 1.................................................................................................................................... 65 Appendix 2.................................................................................................................................... 67 v List of Figures Figure 1. Reconstruction of skull of Acheloma dunni in A, dorsal view; B, ventral view; C, right lateral view. Scale = 50 mm Figure 2. Skull of Acheloma dunni, holotype (OMNH 73281) in dorsal view. Scale = 50 mm Figure 3. Skull of Acheloma dunni, holotype (OMNH 73281) in right lateral view. Scale = 50 mm Figure 4. Acheloma dunni, referred specimen (BMRP2007.3.4) in left lateral view. Scale = 10 mm Figure 5. Acheloma dunni, referred specimen (BMRP2007.3.1) in right lateral view. Scale = 10 mm Figure 6. Acheloma dunni, referred specimen (OMNH 52365). Partial right upper jaw articulation in dorsal view. Scale = 10 mm Figure 7. Skull of Acheloma dunni, holotype (OMNH 73281) in ventral view. Scale = 50 mm Figure 8. Skull of Acheloma dunni, holotype (OMNH 73281) in occipital view. Scale = 50 mm Figure 9. Partial left lower jaw of Acheloma dunni, holotype (OMNH 73281) in A, lateral view; B, medial view; C, dorsal view; D, ventral view. Scale = 10 mm Figure 10. Partial right lower jaw of Acheloma dunni, holotype (OMNH 73281) in A, lateral view; B, medial view; C, dorsal view; D, ventral view. Scale = 10 mm Figure 11. Acheloma dunni, referred specimen (OMNH 52365). Partial right lower jaw articulation in A, lateral view; B, posterior view. Scale = 10 mm Figure 12. Atlas-axis complex and associated cervical vertebrae of Acheloma dunni, holotype (OMNH 73281) in A, right lateral view; B, left lateral view; C, anterior view. Scale = 10 mm vi Figure 13. Acheloma dunni, referred specimen (OMNH 52545). Right humerus in A, posterior view; B, extensor view; C, anterior view; D, flexor view; E, proximal view; F, distal view. Scale = 50 mm Figure 14. Acheloma dunni, referred specimen (OMNH 73514). Partial pelvic girdle and hindlimb. Scale = 5 mm. Illustration by Heidi Richter. Figure 15. Single most parsimonious tree of dissorophoid relationships derived from cladistic analysis using PAUP 4.0b10 with A, relevant synapomorphies mapped on (* indicates a synapomorphy that supports the clade, but appears elsewhere in the tree); B, bootstrap (bold) and Bremer decay (italics) values calculated for the analysis; TL, tree length; CI, consistency index; RC, rescaled consistency index vii List of Appendices Appendix
Load more

Recommended publications
  • Dissorophus Cope
    DISSOROPHUS COPE S. W. WILLISTON The University of Chicago The material herein described and figured was collected by the writer from the upper or Clear Fork Division of the Texas Red-beds on Coffee Creek, in August, 1909. It comprises a nearly complete skull, but little distorted, the two scapulae with attached cleithra, neither complete, but the two supplementing each other nearly per- fectly; the two complete clavicles attached to the incomplete inter- clavicle; the two humeri, one complete save for the capitellar angle, the other with the distal part quite complete and the proximal portion missing; two attached proximal carpals, several vertebrae and frag- ments of ribs, the nearly complete carapace, a broken and somewhat distorted pelvis, a femur, and fragments of epipodial bones. For the most part, the surface of the skull is unimpaired, showing deep, almost circular pits, with narrow, reticulating ridges between them. The pittings seem to be most pronounced in the upper pos- terior part. There are no indications of mucous grooves, and I am convinced that, were they originally present, evidences of them would be apparent. Nor, as in the case of the skulls of Cacops, can I distinguish the sutures. The skull is very broad posteriorly, with a rounded, obtuse muzzle. The orbits are situated about midway in its length, they are rather small, nearly circular in outline, and broadly separated. The table of the cranium, back of the orbits, is rather broader than long, a little wider anteriorly, with a broad emargination behind; it is nearly plane, with its margins elevated. The parietal foramen is situated a little back of a line drawn through the posterior margin of the orbits.
    [Show full text]
  • 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.
    [Show full text]
  • Ontogenetic Change in the Temporal Region of the Early Permian Parareptile Delorhynchus Cifellii and the Implications for Closure of the Temporal Fenestra in Amniotes
    RESEARCH ARTICLE Ontogenetic Change in the Temporal Region of the Early Permian Parareptile Delorhynchus cifellii and the Implications for Closure of the Temporal Fenestra in Amniotes Yara Haridy*, Mark J. Macdougall, Diane Scott, Robert R. Reisz Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada * [email protected] a11111 Abstract A juvenile specimen of Delorhynchus cifellii, collected from the Early Permian fissure-fill deposits of Richards Spur, Oklahoma, permits the first detailed study of cranial ontogeny in this parareptile. The specimen, consisting of a partially articulated skull and mandible, exhib- OPEN ACCESS its several features that identify it as juvenile. The dermal tuberosities that ornament the dor- Citation: Haridy Y, Macdougall MJ, Scott D, Reisz sal side and lateral edges of the largest skull of D. cifellii specimens, are less prominent in RR (2016) Ontogenetic Change in the Temporal the intermediate sized holotype, and are absent in the new specimen. This indicates that the Region of the Early Permian Parareptile new specimen represents an earlier ontogenetic stage than all previously described mem- Delorhynchus cifellii and the Implications for bers of this species. In addition, the incomplete interdigitation of the sutures, most notably Closure of the Temporal Fenestra in Amniotes. PLoS ONE 11(12): e0166819. doi:10.1371/journal. along the fronto-nasal contact, plus the proportionally larger sizes of the orbit and temporal pone.0166819 fenestrae further support an early ontogenetic stage for this specimen. Comparisons Editor: Thierry Smith, Royal Belgian Institute of between this juvenile and previously described specimens reveal that the size and shape of Natural Sciences, BELGIUM the temporal fenestra in Delorhynchus appear to vary through ontogeny, due to changes in Received: July 18, 2016 the shape and size of the bordering cranial elements.
    [Show full text]
  • Stuttgarter Beiträge Zur Naturkunde
    S^5 ( © Biodiversity Heritage Library, http://www.biodiversitylibrary.org/; www.zobodat.at Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) Herausgeber: Staatliches Museum für Naturkunde, Rosenstein 1, D-70191 Stuttgart Stuttgarter Beitr. Naturk. Ser. B Nr. 278 175 pp., 4pls., 54figs. Stuttgart, 30. 12. 1999 Comparative osteology oi Mastodonsaurus giganteus (Jaeger, 1828) from the Middle Triassic (Lettenkeuper: Longobardian) of Germany (Baden-Württemberg, Bayern, Thüringen) By Rainer R. Schoch, Stuttgart With 4 plates and 54 textfigures Abstract Mastodonsaurus giganteus, the most abundant and giant amphibian of the German Letten- keuper, is revised. The study is based on the excellently preserved and very rieh material which was excavated during road construction in 1977 near Kupferzeil, Northern Baden- Württemberg. It is shown that there exists only one diagnosable species of Mastodonsaurus, to which all Lettenkeuper material can be attributed. All finds from other horizons must be referred to as Mastodonsauridae gen. et sp. indet. because of their fragmentary Status. A sec- ond, definitely diagnostic genus of this family is Heptasaurus from the higher Middle and Upper Buntsandstein. Finally a diagnosis of the family Mastodonsauridae is provided. Ä detailed osteological description of Mastodonsaurus giganteus reveals numerous un- known or formerly inadequately understood features, yielding data on various hitherto poor- ly known regions of the skeleton. The sutures of the skull roof, which could be studied in de- tail, are significantly different from the schemes presented by previous authors. The endocra- nium and mandible are further points of particular interest. The palatoquadrate contributes a significant part to the formation of the endocranium by an extensive and complicated epi- pterygoid.
    [Show full text]
  • The Lower Permian Abo Formation in the Fra Cristobal and Caballo Mountains, Sierra County, New Mexico Spencer G
    New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/63 The Lower Permian Abo Formation in the Fra Cristobal and Caballo Mountains, Sierra County, New Mexico Spencer G. Lucas, Karl Krainer, Dan S. Chaney, William A. DiMichele, Sebastian Voigt, David S. Berman, and Amy C. Henrici, 2012, pp. 345-376 in: Geology of the Warm Springs Region, Lucas, Spencer G.; McLemore, Virginia T.; Lueth, Virgil W.; Spielmann, Justin A.; Krainer, Karl, New Mexico Geological Society 63rd Annual Fall Field Conference Guidebook, 580 p. This is one of many related papers that were included in the 2012 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download.
    [Show full text]
  • Cacopsamphibiala373bolt.Pdf
    v UNIVtRSlT Cp ILLINOIS I 5RARY AT URBANA-CHAMPAIGN L IOLOGY CO CO /&£^<-*x~*yw FIELDIANA Geology Published by Field Museum of Natural History Volume 37, No. 3 June 30, 1977 Cacops (Amphibia: Labyrinthodontia) From the Fort Sill Locality, Lower Permian of Oklahoma the The Library of John R. Bolt Assistant Curator, Fossil Reptiles and Amphibians 1978 Field Museum of Natural History MRRU ABSTRACT at Urbana-ChamP«* The armored dissorophid (Super family Dissorophoidea ) labyrinthodont amphi- bian Cacops aspidephorus is unusual in having a large otic notch closed posteriorly by the tabular. Cacops was previously known only from the "Cacops Bone Bed," Lower Permian of Texas. Poor preservation makes this material difficult to study. Excellently preserved, though disarticulated, Cacops material has now been recov- ered from the Fort Sill fissure fills, which are probably very close in age to the "Ca- cops Bone Bed." Identification of the Fort Sill material as Cacops is based on pala- tines (primarily), armor scutes, and quadrates; the latter are here described for the first time from Fort Sill. The Cacops quadrate resembles that of other dissorophoids in having a posterodorsal process, which is unusual in the marked anterior expan- sion of its dorsal end. Comparison with other dissorophoids having a closed otic notch shows that Cacops is not unique in this anterior expansion of the process. Orientation of the process can apparently be used to distinguish trematopsids with a slit-like, closed (by the tabular) otic notch, from dissorophids. At least one such trematopsid occurs at Fort Sill, and resembles Cacops in anterior expansion of the process.
    [Show full text]
  • Phylogeny and Evolution of the Dissorophoid Temnospondyls
    Journal of Paleontology, 93(1), 2019, p. 137–156 Copyright © 2018, The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/ licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. 0022-3360/15/0088-0906 doi: 10.1017/jpa.2018.67 The putative lissamphibian stem-group: phylogeny and evolution of the dissorophoid temnospondyls Rainer R. Schoch Staatliches Museum für Naturkunde, Rosenstein 1, D-70191 Stuttgart, Germany 〈[email protected]〉 Abstract.—Dissorophoid temnospondyls are widely considered to have given rise to some or all modern amphibians (Lissamphibia), but their ingroup relationships still bear major unresolved questions. An inclusive phylogenetic ana- lysis of dissorophoids gives new insights into the large-scale topology of relationships. Based on a TNT 1.5 analysis (33 taxa, 108 characters), the enigmatic taxon Perryella is found to nest just outside Dissorophoidea (phylogenetic defintion), but shares a range of synapomorphies with this clade. The dissorophoids proper are found to encompass a first dichotomy between the largely paedomorphic Micromelerpetidae and all other taxa (Xerodromes). Within the latter, there is a basal dichotomy between the large, heavily ossified Olsoniformes (Dissorophidae + Trematopidae) and the small salamander-like Amphibamiformes (new taxon), which include four clades: (1) Micropholidae (Tersomius, Pasawioops, Micropholis); (2) Amphibamidae sensu stricto (Doleserpeton, Amphibamus); (3) Branchiosaur- idae (Branchiosaurus, Apateon, Leptorophus, Schoenfelderpeton); and (4) Lissamphibia. The genera Platyrhinops and Eos- copus are here found to nest at the base of Amphibamiformes. Represented by their basal-most stem-taxa (Triadobatrachus, Karaurus, Eocaecilia), lissamphibians nest with Gerobatrachus rather than Amphibamidae, as repeatedly found by former analyses.
    [Show full text]
  • Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha)
    Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha) by Richard Kissel A thesis submitted in conformity with the requirements for the degree of doctor of philosophy Graduate Department of Ecology & Evolutionary Biology University of Toronto © Copyright by Richard Kissel 2010 Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha) Richard Kissel Doctor of Philosophy Graduate Department of Ecology & Evolutionary Biology University of Toronto 2010 Abstract Based on dental, cranial, and postcranial anatomy, members of the Permo-Carboniferous clade Diadectidae are generally regarded as the earliest tetrapods capable of processing high-fiber plant material; presented here is a review of diadectid morphology, phylogeny, taxonomy, and paleozoogeography. Phylogenetic analyses support the monophyly of Diadectidae within Diadectomorpha, the sister-group to Amniota, with Limnoscelis as the sister-taxon to Tseajaia + Diadectidae. Analysis of diadectid interrelationships of all known taxa for which adequate specimens and information are known—the first of its kind conducted—positions Ambedus pusillus as the sister-taxon to all other forms, with Diadectes sanmiguelensis, Orobates pabsti, Desmatodon hesperis, Diadectes absitus, and (Diadectes sideropelicus + Diadectes tenuitectes + Diasparactus zenos) representing progressively more derived taxa in a series of nested clades. In light of these results, it is recommended herein that the species Diadectes sanmiguelensis be referred to the new genus
    [Show full text]
  • Early Tetrapod Relationships Revisited
    Biol. Rev. (2003), 78, pp. 251–345. f Cambridge Philosophical Society 251 DOI: 10.1017/S1464793102006103 Printed in the United Kingdom Early tetrapod relationships revisited MARCELLO RUTA1*, MICHAEL I. COATES1 and DONALD L. J. QUICKE2 1 The Department of Organismal Biology and Anatomy, The University of Chicago, 1027 East 57th Street, Chicago, IL 60637-1508, USA ([email protected]; [email protected]) 2 Department of Biology, Imperial College at Silwood Park, Ascot, Berkshire SL57PY, UK and Department of Entomology, The Natural History Museum, Cromwell Road, London SW75BD, UK ([email protected]) (Received 29 November 2001; revised 28 August 2002; accepted 2 September 2002) ABSTRACT In an attempt to investigate differences between the most widely discussed hypotheses of early tetrapod relation- ships, we assembled a new data matrix including 90 taxa coded for 319 cranial and postcranial characters. We have incorporated, where possible, original observations of numerous taxa spread throughout the major tetrapod clades. A stem-based (total-group) definition of Tetrapoda is preferred over apomorphy- and node-based (crown-group) definitions. This definition is operational, since it is based on a formal character analysis. A PAUP* search using a recently implemented version of the parsimony ratchet method yields 64 shortest trees. Differ- ences between these trees concern: (1) the internal relationships of aı¨stopods, the three selected species of which form a trichotomy; (2) the internal relationships of embolomeres, with Archeria
    [Show full text]
  • A Juvenile Skeleton of the Nectridean Amphibian
    Lucas, S.G. and Zeigler, K.E., eds., 2005, The Nonmarine Permian, New Mexico Museum of Natural Histoiy and Science Bulletin No. 30. 39 A JUVENILE SKELETON OF THE NECTRIDEAN AMPHIBIAN DIPLOCAULUS AND ASSOCIATED FLORA AND FAUNA FROM THE MITCHELL CREEK FLATS LOCALITY (UPPER WAGGONER RANCH FORMATION; EARLY PERMIAN), BAYLOR COUNTY, NORTH- CENTRAL TEXAS, USA DAN S. CHANEY, HANS-DIETER SUES AND WILLIAM A. DIMICHELE Department of Paleobiology MRC-121, National Museum of Natural History, PC Box 37012, Washington, D.C. 20013-7021 Abstract—A well-preserved skeleton of a tiny individual of the nectridean amphibian Diplocaulus was found in association with other Early Permian animal remains and a flora in a gray mudstone at a site called Mitchell Creek Flats in Baylor County, north-central Texas. The locality has the sedimentological attributes of a pond deposit. The skeleton of Diplocaulus sp. is noteworthy for its completeness and small size, and appears to represent a juvenile individual. The associated plant material is beautifully preserved and comprises the sphe- nopsids Annularia and Calamites, the conifer IBrachyphyllum, possible cycads represented by one or possibly two forms of Taeniopteris, three gigantopterids - Delnortea, Cathaysiopteris, and Gigantopteridium — and three unidentified callipterids. Several unidentified narrow trunks were found at the base of the deposit, appar- ently washed up against the northern margin of the pond. Other faunal material from the deposit comprises myalinid bivalves, conchostracans, a tooth of a xenacanthid shark, and a palaeonisciform fish. INTRODUCTION Wchita Rver T ^ Coinage i ^ 1 t Complete skeletons of Early Permian vertebrates are rare in north- FwmatJon Grcyp c central Texas, where much collecting has been done for about 150 years c c (Fig.
    [Show full text]
  • Morphology and Evolutionary Significance of the Atlas−Axis Complex in Varanopid Synapsids
    Morphology and evolutionary significance of the atlas−axis complex in varanopid synapsids NICOLÁS E. CAMPIONE and ROBERT R. REISZ Campione, N.E. and Reisz, R.R. 2011. Morphology and evolutionary significance of the atlas−axis complex in varanopid synapsids. Acta Palaeontologica Polonica 56 (4): 739–748. The atlas−axis complex has been described in few Palaeozoic taxa, with little effort being placed on examining variation of this structure within a small clade. Most varanopids, members of a clade of gracile synapsid predators, have well pre− served atlas−axes permitting detailed descriptions and examination of morphological variation. This study indicates that the size of the transverse processes on the axis and the shape of the axial neural spine vary among members of this clade. In particular, the small mycterosaurine varanopids possess small transverse processes that point posteroventrally, and the axial spine is dorsoventrally short, with a flattened dorsal margin in lateral view. The larger varanodontine varanopids have large transverse processes with a broad base, and a much taller axial spine with a rounded dorsal margin in lateral view. Based on outgroup comparisons, the morphology exhibited by the transverse processes is interpreted as derived in varanodontines, whereas the morphology of the axial spine is derived in mycterosaurines. The axial spine anatomy of Middle Permian South African varanopids is reviewed and our interpretation is consistent with the hypothesis that at least two varanopid taxa are present in South Africa, a region overwhelmingly dominated by therapsid synapsids and parareptiles. Key words: Synapsida, Varanopidae, Mycterosaurinae, Varanodontinae, atlas−axis complex, axial skeleton, Middle Permian, South Africa.
    [Show full text]
  • And Early Jurassic Sediments, and Patterns of the Triassic-Jurassic
    and Early Jurassic sediments, and patterns of the Triassic-Jurassic PAUL E. OLSEN AND tetrapod transition HANS-DIETER SUES Introduction parent answer was that the supposed mass extinc- The Late Triassic-Early Jurassic boundary is fre- tions in the tetrapod record were largely an artifact quently cited as one of the thirteen or so episodes of incorrect or questionable biostratigraphic corre- of major extinctions that punctuate Phanerozoic his- lations. On reexamining the problem, we have come tory (Colbert 1958; Newell 1967; Hallam 1981; Raup to realize that the kinds of patterns revealed by look- and Sepkoski 1982, 1984). These times of apparent ing at the change in taxonomic composition through decimation stand out as one class of the great events time also profoundly depend on the taxonomic levels in the history of life. and the sampling intervals examined. We address Renewed interest in the pattern of mass ex- those problems in this chapter. We have now found tinctions through time has stimulated novel and com- that there does indeed appear to be some sort of prehensive attempts to relate these patterns to other extinction event, but it cannot be examined at the terrestrial and extraterrestrial phenomena (see usual coarse levels of resolution. It requires new fine- Chapter 24). The Triassic-Jurassic boundary takes scaled documentation of specific faunal and floral on special significance in this light. First, the faunal transitions. transitions have been cited as even greater in mag- Stratigraphic correlation of geographically dis- nitude than those of the Cretaceous or the Permian junct rocks and assemblages predetermines our per- (Colbert 1958; Hallam 1981; see also Chapter 24).
    [Show full text]