DOCSLIB.ORG

An Investigation Into Ichthyosaur Ontogeny, Sexual Dimorphism and Body Size Evolution

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
An Investigation Into Ichthyosaur Ontogeny, Sexual Dimorphism and Body Size Evolution AN INVESTIGATION INTO ICHTHYOSAUR ONTOGENY, SEXUAL DIMORPHISM AND BODY SIZE EVOLUTION SAMUEL PATRICK BENNETT Thesis submitted for the degree of Doctor of Philosophy Royal Holloway College 1 Declaration of Authorship I, Samuel Patrick Bennett, hereby declare that this thesis and the work presented in it is entirely my own. Where I have consulted the work of others, this is always clearly stated Signed: Date: 2 ABSTRACT Ichthyosaurs are an extinct group of diapsid marine reptiles that existed from the Olenekian (251Ma) to end Cenomanian (93.9Ma). Morphometric data (length measurements) and meristic data (counts of repeated elements) were collected for Lower and Middle Jurassic taxa from several museums in England and one in Germany. Additional morphometric data were collected from the published record. Principal Components Analysis (PCA), Principal Coordinate Analysis (PCO) and Reduced Major Axis Regression (RMA) were used to analyse morphometric data relating to ontogeny. Linear Regression, also known as Ordinary Least Squares (OLS) was used to analyse meristic data relating to ontogeny as well as body size evolution. Sexual dimorphism was analysed using the Mann-Whitney test as well as Discriminant Analysis. The analysis of ichthyosaur ontogeny showed that neonate and juvenile ichthyosaurs had significantly larger skulls and eyes compared to body length. Once maturity is reached growth becomes isometric, and no other features varied with relative age. The numbers of repeated elements in ichthyosaurs remain stable throughout life, with the exception of post- flexural caudal vertebrae, where the numbers increase with the size of the tail, and therefore, age. Investigation of sexual dimorphism indicated that inferred males are isometrically larger than pregnant females. However, the age at which maturity is reached cannot currently be identified in individual specimens. Furthermore, the gender of an individual cannot currently be determined, with the exception of pregnant females. The study of body size evolution was not conclusive and no statistically significant trends were identified. Due to the nature of the fossil record, only 53% of the taxa examined could be used in the analysis. More taxa, particularly from the Triassic and Cretaceous, need to be included to improve the understanding of ichthyosaur body size evolution. 3 CONTENTS Abstract . 3 Contents . 4 Contents: Figures . 13 Contents: Tables . 19 Acknowledgements . 20 1: Ichthyosaur ontogeny, sexual dimorphism and body size evolution: an introduction . 21 1.1: Introduction to ichthyosaurs . 21 1.2: Introduction to ontogeny . 24 1.3: Introduction to sexual dimorphism . 25 1.4: Introduction to body size evolution . 26 1.5: Aims . 27 1.6: Thesis overview . 28 2: Methodology . 30 2.1: Introduction . 30 2.1.1: Overview . 30 2.2: Materials . .31 2.2.1: Institutions . 31 2.2.2: Genera . 31 2.2.3: Taxonomy of the Lower Jurassic ichthyosaur taxa used in this study .32 2.2.4: Key implications for the thesis . 59 4 2.3: Morphometric data . 59 2.4: Meristic (counted) data . 61 2.5 Multivariate analysis . 62 2.5.1: Principal Components Analysis (PCA) . 62 2.5.2: Principal Coordinate Analysis (PCO) . 66 2.5.3: Reduced Major Axis Regression (RMA) . 67 2.5.3.1: Bootstrap test . 68 2.5.3.2: Pearson’s R Correlation . 69 2.5.3.3: Discriminant Analysis . 69 3: Investigating ichthyosaur growth: a morphometric approach . 74 3.1: Overview . 74 3.2: Definitions: ontogeny, heterochrony and allometry . 75 3.3: The importance of understanding ontogeny . 77 3.4: Approaches to studying diapsid ontogeny in the fossil record . 78 3.4.1: An introduction to ichthyosaur ontogeny . .79 3.4.2: Size independent criteria . 80 3.4.3: Bone histology . 82 3.4.4: Tooth loss . 85 3.4.5: Ossification patterns . 86 3.4.6: Other ontogenetic differences . 88 3.4.7: Discussion of ichthyosaur ontogeny . 88 3.4.8: Summary of current knowledge of ichthyosaur ontogeny . 90 5 3.5: Ontogeny of other diapsids: Sauropterygia . 64 3.5.1: Plesiosaurs . 91 3.5.2: Pachypleurosaurs . 92 3.5.2.1: Inferred embryos . 93 3.5.2.2: Inferred juveniles . 94 3.5.2.3: Inferred adults . 95 3.5.2.4: Bone histology . 95 3.5.2.5: Sexual dimorphism in pachypleurosaurs . 96 3.5.2.6: Pachypleurosaur summary . 96 3.6: Ontogeny of other diapsids: Crocodylia . 97 3.6.1: Bone fusion . 97 3.6.2: Other ontogenetic features . 98 3.7: Ontogeny of other diapsids: Dinosauria . 99 3.7.1: Triceratops . 99 3.8: Summary of evidence for ontogeny . 100 3.9: Implications for ichthyosaur ontogeny . 101 3.10: Materials and methods . 101 3.11: Results and interpretation . 102 3.11.1: Multivariate analysis: PCA . 102 3.11.1.1: PCA analysis: humerus . 103 3.11.1.2: PCA Analysis: femur . 108 3.11.1.3: PCA Analysis: skull . 113 3.11.1.4: PCA analysis of all measurements . 118 6 3.11.2: Multivariate analysis: PCO . 119 3.11.2.1: PCO analysis: humerus . 119 3.11.2.2: PCO Analysis: femur . 120 3.11.2.3: PCO Analysis: skull . 122 3.11.3: Bivariate analysis: RMA . 123 3.11.3.1: All measurements vs. total body length . 124 3.11.3.2: Humerus length vs. humerus width . 131 3.11.3.3: Femur length vs. femur width . 132 3.11.3.4: Skull length vs. jaw length . 133 3.11.3.5: Length of longest digit vs. width of paddle . 134 3.11.3.6: Total body length vs. skull length . 135 3.11.3.7: Skull length vs. external diameter of the sclerotic ring . 136 3.12: Discussion . 137 3.12.1: Limitations of the data . 137 3.12.2: Significance of results . ..
Load more

Recommended publications
  • Resetting the Evolution of Marine Reptiles at the Triassic-Jurassic Boundary
    Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary Philippa M. Thorne, Marcello Ruta, and Michael J. Benton1 School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom Edited by Neil Shubin, University of Chicago, Chicago, IL, and accepted by the Editorial Board March 30, 2011 (received for review December 18, 2010) Ichthyosaurs were important marine predators in the Early Jurassic, life, swimming with lateral undulations of the tail and steering and an abundant and diverse component of Mesozoic marine with elongate fore paddles and producing live young at sea. ecosystems. Despite their ecological importance, however, the After the Tr-J bottleneck, ichthyosaurs apparently did not Early Jurassic species represent a reduced remnant of their former achieve such diversity of form but nonetheless recovered suffi- significance in the Triassic. Ichthyosaurs passed through an evolu- ciently to be the dominant marine predators of the Early Ju- tionary bottleneck at, or close to, the Triassic-Jurassic boundary, rassic, after which they dwindled in diversity through the Middle which reduced their diversity to as few as three or four lineages. and Late Jurassic and much of the Cretaceous until they dis- Diversity bounced back to some extent in the aftermath of the appeared at the end of the Cenomanian, ∼100 Ma, after having end-Triassic mass extinction, but disparity remained at less than had a significant role in Mesozoic seas for 150 Myr. one-tenth of pre-extinction levels, and never recovered. The group In this study, we concentrate on disparity (morphological fi remained at low diversity and disparity for its nal 100 Myr.
    [Show full text]
  • Checklist of Helminths from Lizards and Amphisbaenians (Reptilia, Squamata) of South America Ticle R A
    The Journal of Venomous Animals and Toxins including Tropical Diseases ISSN 1678-9199 | 2010 | volume 16 | issue 4 | pages 543-572 Checklist of helminths from lizards and amphisbaenians (Reptilia, Squamata) of South America TICLE R A Ávila RW (1), Silva RJ (1) EVIEW R (1) Department of Parasitology, Botucatu Biosciences Institute, São Paulo State University (UNESP – Univ Estadual Paulista), Botucatu, São Paulo State, Brazil. Abstract: A comprehensive and up to date summary of the literature on the helminth parasites of lizards and amphisbaenians from South America is herein presented. One-hundred eighteen lizard species from twelve countries were reported in the literature harboring a total of 155 helminth species, being none acanthocephalans, 15 cestodes, 20 trematodes and 111 nematodes. Of these, one record was from Chile and French Guiana, three from Colombia, three from Uruguay, eight from Bolivia, nine from Surinam, 13 from Paraguay, 12 from Venezuela, 27 from Ecuador, 17 from Argentina, 39 from Peru and 103 from Brazil. The present list provides host, geographical distribution (with the respective biome, when possible), site of infection and references from the parasites. A systematic parasite-host list is also provided. Key words: Cestoda, Nematoda, Trematoda, Squamata, neotropical. INTRODUCTION The present checklist summarizes the diversity of helminths from lizards and amphisbaenians Parasitological studies on helminths that of South America, providing a host-parasite list infect squamates (particularly lizards) in South with localities and biomes. America had recent increased in the past few years, with many new records of hosts and/or STUDIED REGIONS localities and description of several new species (1-3).
    [Show full text]
  • A Mysterious Giant Ichthyosaur from the Lowermost Jurassic of Wales
    A mysterious giant ichthyosaur from the lowermost Jurassic of Wales JEREMY E. MARTIN, PEGGY VINCENT, GUILLAUME SUAN, TOM SHARPE, PETER HODGES, MATT WILLIAMS, CINDY HOWELLS, and VALENTIN FISCHER Ichthyosaurs rapidly diversified and colonised a wide range vians may challenge our understanding of their evolutionary of ecological niches during the Early and Middle Triassic history. period, but experienced a major decline in diversity near the Here we describe a radius of exceptional size, collected at end of the Triassic. Timing and causes of this demise and the Penarth on the coast of south Wales near Cardiff, UK. This subsequent rapid radiation of the diverse, but less disparate, specimen is comparable in morphology and size to the radius parvipelvian ichthyosaurs are still unknown, notably be- of shastasaurids, and it is likely that it comes from a strati- cause of inadequate sampling in strata of latest Triassic age. graphic horizon considerably younger than the last definite Here, we describe an exceptionally large radius from Lower occurrence of this family, the middle Norian (Motani 2005), Jurassic deposits at Penarth near Cardiff, south Wales (UK) although remains attributable to shastasaurid-like forms from the morphology of which places it within the giant Triassic the Rhaetian of France were mentioned by Bardet et al. (1999) shastasaurids. A tentative total body size estimate, based on and very recently by Fischer et al. (2014). a regression analysis of various complete ichthyosaur skele- Institutional abbreviations.—BRLSI, Bath Royal Literary tons, yields a value of 12–15 m. The specimen is substantially and Scientific Institution, Bath, UK; NHM, Natural History younger than any previously reported last known occur- Museum, London, UK; NMW, National Museum of Wales, rences of shastasaurids and implies a Lazarus range in the Cardiff, UK; SMNS, Staatliches Museum für Naturkunde, lowermost Jurassic for this ichthyosaur morphotype.
    [Show full text]
  • The Strawberry Bank Lagerstätte Reveals Insights Into Early Jurassic Lifematt Williams, Michael J
    XXX10.1144/jgs2014-144M. Williams et al.Early Jurassic Strawberry Bank Lagerstätte 2015 Downloaded from http://jgs.lyellcollection.org/ by guest on September 27, 2021 2014-144review-articleReview focus10.1144/jgs2014-144The Strawberry Bank Lagerstätte reveals insights into Early Jurassic lifeMatt Williams, Michael J. Benton &, Andrew Ross Review focus Journal of the Geological Society Published Online First doi:10.1144/jgs2014-144 The Strawberry Bank Lagerstätte reveals insights into Early Jurassic life Matt Williams1, Michael J. Benton2* & Andrew Ross3 1 Bath Royal Literary and Scientific Institution, 16–18 Queen Square, Bath BA1 2HN, UK 2 School of Earth Sciences, University of Bristol, Bristol BS8 2BU, UK 3 National Museum of Scotland, Chambers Street, Edinburgh EH1 1JF, UK * Correspondence: [email protected] Abstract: The Strawberry Bank Lagerstätte provides a rich insight into Early Jurassic marine vertebrate life, revealing exquisite anatomical detail of marine reptiles and large pachycormid fishes thanks to exceptional preservation, and especially the uncrushed, 3D nature of the fossils. The site documents a fauna of Early Jurassic nektonic marine animals (five species of fishes, one species of marine crocodilian, two species of ichthyosaurs, cephalopods and crustaceans), but also over 20 spe- cies of insects. Unlike other fossil sites of similar age, the 3D preservation at Strawberry Bank provides unique evidence on palatal and braincase structures in the fishes and reptiles. The age of the site is important, documenting a marine ecosystem during recovery from the end-Triassic mass extinction, but also exactly coincident with the height of the Toarcian Oceanic Anoxic Event, a further time of turmoil in evolution.
    [Show full text]
  • 71St Annual Meeting Society of Vertebrate Paleontology Paris Las Vegas Las Vegas, Nevada, USA November 2 – 5, 2011 SESSION CONCURRENT SESSION CONCURRENT
    ISSN 1937-2809 online Journal of Supplement to the November 2011 Vertebrate Paleontology Vertebrate Society of Vertebrate Paleontology Society of Vertebrate 71st Annual Meeting Paleontology Society of Vertebrate Las Vegas Paris Nevada, USA Las Vegas, November 2 – 5, 2011 Program and Abstracts Society of Vertebrate Paleontology 71st Annual Meeting Program and Abstracts COMMITTEE MEETING ROOM POSTER SESSION/ CONCURRENT CONCURRENT SESSION EXHIBITS SESSION COMMITTEE MEETING ROOMS AUCTION EVENT REGISTRATION, CONCURRENT MERCHANDISE SESSION LOUNGE, EDUCATION & OUTREACH SPEAKER READY COMMITTEE MEETING POSTER SESSION ROOM ROOM SOCIETY OF VERTEBRATE PALEONTOLOGY ABSTRACTS OF PAPERS SEVENTY-FIRST ANNUAL MEETING PARIS LAS VEGAS HOTEL LAS VEGAS, NV, USA NOVEMBER 2–5, 2011 HOST COMMITTEE Stephen Rowland, Co-Chair; Aubrey Bonde, Co-Chair; Joshua Bonde; David Elliott; Lee Hall; Jerry Harris; Andrew Milner; Eric Roberts EXECUTIVE COMMITTEE Philip Currie, President; Blaire Van Valkenburgh, Past President; Catherine Forster, Vice President; Christopher Bell, Secretary; Ted Vlamis, Treasurer; Julia Clarke, Member at Large; Kristina Curry Rogers, Member at Large; Lars Werdelin, Member at Large SYMPOSIUM CONVENORS Roger B.J. Benson, Richard J. Butler, Nadia B. Fröbisch, Hans C.E. Larsson, Mark A. Loewen, Philip D. Mannion, Jim I. Mead, Eric M. Roberts, Scott D. Sampson, Eric D. Scott, Kathleen Springer PROGRAM COMMITTEE Jonathan Bloch, Co-Chair; Anjali Goswami, Co-Chair; Jason Anderson; Paul Barrett; Brian Beatty; Kerin Claeson; Kristina Curry Rogers; Ted Daeschler; David Evans; David Fox; Nadia B. Fröbisch; Christian Kammerer; Johannes Müller; Emily Rayfield; William Sanders; Bruce Shockey; Mary Silcox; Michelle Stocker; Rebecca Terry November 2011—PROGRAM AND ABSTRACTS 1 Members and Friends of the Society of Vertebrate Paleontology, The Host Committee cordially welcomes you to the 71st Annual Meeting of the Society of Vertebrate Paleontology in Las Vegas.
    [Show full text]
  • Universidad Nacional Del Comahue Centro Regional Universitario Bariloche
    Universidad Nacional del Comahue Centro Regional Universitario Bariloche Título de la Tesis Microanatomía y osteohistología del caparazón de los Testudinata del Mesozoico y Cenozoico de Argentina: Aspectos sistemáticos y paleoecológicos implicados Trabajo de Tesis para optar al Título de Doctor en Biología Tesista: Lic. en Ciencias Biológicas Juan Marcos Jannello Director: Dr. Ignacio A. Cerda Co-director: Dr. Marcelo S. de la Fuente 2018 Tesis Doctoral UNCo J. Marcos Jannello 2018 Resumen Las inusuales estructuras óseas observadas entre los vertebrados, como el cuello largo de la jirafa o el cráneo en forma de T del tiburón martillo, han interesado a los científicos desde hace mucho tiempo. Uno de estos casos es el clado Testudinata el cual representa uno de los grupos más fascinantes y enigmáticos conocidos entre de los amniotas. Su inconfundible plan corporal, que ha persistido desde el Triásico tardío hasta la actualidad, se caracteriza por la presencia del caparazón, el cual encierra a las cinturas, tanto pectoral como pélvica, dentro de la caja torácica desarrollada. Esta estructura les ha permitido a las tortugas adaptarse con éxito a diversos ambientes (por ejemplo, terrestres, acuáticos continentales, marinos costeros e incluso marinos pelágicos). Su capacidad para habitar diferentes nichos ecológicos, su importante diversidad taxonómica y su plan corporal particular hacen de los Testudinata un modelo de estudio muy atrayente dentro de los vertebrados. Una disciplina que ha demostrado ser una herramienta muy importante para abordar varios temas relacionados al caparazón de las tortugas, es la paleohistología. Esta disciplina se ha involucrado en temas diversos tales como el origen del caparazón, el origen del desarrollo y mantenimiento de la ornamentación, la paleoecología y la sistemática.
    [Show full text]
  • Investigating Sexual Dimorphism in Ceratopsid Horncores
    University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2013-01-25 Investigating Sexual Dimorphism in Ceratopsid Horncores Borkovic, Benjamin Borkovic, B. (2013). Investigating Sexual Dimorphism in Ceratopsid Horncores (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/26635 http://hdl.handle.net/11023/498 master thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY Investigating Sexual Dimorphism in Ceratopsid Horncores by Benjamin Borkovic A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE DEPARTMENT OF BIOLOGICAL SCIENCES CALGARY, ALBERTA JANUARY, 2013 © Benjamin Borkovic 2013 Abstract Evidence for sexual dimorphism was investigated in the horncores of two ceratopsid dinosaurs, Triceratops and Centrosaurus apertus. A review of studies of sexual dimorphism in the vertebrate fossil record revealed methods that were selected for use in ceratopsids. Mountain goats, bison, and pronghorn were selected as exemplar taxa for a proof of principle study that tested the selected methods, and informed and guided the investigation of sexual dimorphism in dinosaurs. Skulls of these exemplar taxa were measured in museum collections, and methods of analysing morphological variation were tested for their ability to demonstrate sexual dimorphism in their horns and horncores.
    [Show full text]
  • Ichthyosaur Species Valid Taxa Acamptonectes Fischer Et Al., 2012: Acamptonectes Densus Fischer Et Al., 2012, Lower Cretaceous, Eng- Land, Germany
    Ichthyosaur species Valid taxa Acamptonectes Fischer et al., 2012: Acamptonectes densus Fischer et al., 2012, Lower Cretaceous, Eng- land, Germany. Aegirosaurus Bardet and Fernández, 2000: Aegirosaurus leptospondylus (Wagner 1853), Upper Juras- sic–Lower Cretaceous?, Germany, Austria. Arthropterygius Maxwell, 2010: Arthropterygius chrisorum (Russell, 1993), Upper Jurassic, Canada, Ar- gentina?. Athabascasaurus Druckenmiller and Maxwell, 2010: Athabascasaurus bitumineus Druckenmiller and Maxwell, 2010, Lower Cretaceous, Canada. Barracudasauroides Maisch, 2010: Barracudasauroides panxianensis (Jiang et al., 2006), Middle Triassic, China. Besanosaurus Dal Sasso and Pinna, 1996: Besanosaurus leptorhynchus Dal Sasso and Pinna, 1996, Middle Triassic, Italy, Switzerland. Brachypterygius Huene, 1922: Brachypterygius extremus (Boulenger, 1904), Upper Jurassic, Engand; Brachypterygius mordax (McGowan, 1976), Upper Jurassic, England; Brachypterygius pseudoscythius (Efimov, 1998), Upper Jurassic, Russia; Brachypterygius alekseevi (Arkhangelsky, 2001), Upper Jurassic, Russia; Brachypterygius cantabridgiensis (Lydekker, 1888a), Lower Cretaceous, England. Californosaurus Kuhn, 1934: Californosaurus perrini (Merriam, 1902), Upper Triassic USA. Callawayia Maisch and Matzke, 2000: Callawayia neoscapularis (McGowan, 1994), Upper Triassic, Can- ada. Caypullisaurus Fernández, 1997: Caypullisaurus bonapartei Fernández, 1997, Upper Jurassic, Argentina. Chaohusaurus Young and Dong, 1972: Chaohusaurus geishanensis Young and Dong, 1972, Lower Trias- sic, China.
    [Show full text]
  • Records from the Aalenian–Bajocian of Patagonia (Argentina): an Overview
    Geol. Mag.: page 1 of 11. c Cambridge University Press 2013 1 doi:10.1017/S0016756813000058 Ophthalmosaurian (Ichthyosauria) records from the Aalenian–Bajocian of Patagonia (Argentina): an overview ∗ MARTA S. FERNÁNDEZ † & MARIANELLA TALEVI‡ ∗ División Palaeontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina. CONICET ‡Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, 8332 General Roca, Río Negro, Argentina. CONICET (Received 12 September 2012; accepted 11 January 2013) Abstract – The oldest ophthalmosaurian records worldwide have been recovered from the Aalenian– Bajocian boundary of the Neuquén Basin in Central-West Argentina (Mendoza and Neuquén provinces). Although scarce, they document a poorly known period in the evolutionary history of parvipelvian ichthyosaurs. In this contribution we present updated information on these fossils, including a phylogenetic analysis, and a redescription of ‘Stenopterygius grandis’ Cabrera, 1939. Patagonian ichthyosaur occurrences indicate that during the Bajocian the Neuquén Basin palaeogulf, on the southern margins of the Palaeopacific Ocean, was inhabited by at least three morphologically discrete taxa: the slender Stenopterygius cayi, robust ophthalmosaurian Mollesaurus periallus and another indeterminate ichthyosaurian. Rib bone tissue structure indicates that rib cages of Bajocian ichthyosaurs included forms with dense rib microstructure (Mollesaurus) and forms with an ‘osteoporotic-like’ pattern (Stenopterygius cayi). Keywords: Mollesaurus,‘Stenopterygius grandis’, Middle Jurassic, Neuquén Basin, Argentina. 1. Introduction all Callovian and post-Callovian ichthyosaurs, two different Early Jurassic taxa have been proposed as Ichthyosaurs were one of the main predators in the ophthalmosaurian sister taxa: Stenopterygius (Maisch oceans all over the world during most of the Mesozoic & Matzke, 2000; Sander, 2000; Druckenmiller & (Massare, 1987).
    [Show full text]
  • Redalyc.Comparative Studies of Supraocular Lepidosis in Squamata
    Multequina ISSN: 0327-9375 [email protected] Instituto Argentino de Investigaciones de las Zonas Áridas Argentina Cei, José M. Comparative studies of supraocular lepidosis in squamata (reptilia) and its relationships with an evolutionary taxonomy Multequina, núm. 16, 2007, pp. 1-52 Instituto Argentino de Investigaciones de las Zonas Áridas Mendoza, Argentina Disponible en: http://www.redalyc.org/articulo.oa?id=42801601 Cómo citar el artículo Número completo Sistema de Información Científica Más información del artículo Red de Revistas Científicas de América Latina, el Caribe, España y Portugal Página de la revista en redalyc.org Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto ISSN 0327-9375 COMPARATIVE STUDIES OF SUPRAOCULAR LEPIDOSIS IN SQUAMATA (REPTILIA) AND ITS RELATIONSHIPS WITH AN EVOLUTIONARY TAXONOMY ESTUDIOS COMPARATIVOS DE LA LEPIDOSIS SUPRA-OCULAR EN SQUAMATA (REPTILIA) Y SU RELACIÓN CON LA TAXONOMÍA EVOLUCIONARIA JOSÉ M. CEI † las subfamilias Leiosaurinae y RESUMEN Enyaliinae. Siempre en Iguania Observaciones morfológicas Pleurodonta se evidencian ejemplos previas sobre un gran número de como los inconfundibles patrones de especies permiten establecer una escamas supraoculares de correspondencia entre la Opluridae, Leucocephalidae, peculiaridad de los patrones Polychrotidae, Tropiduridae. A nivel sistemáticos de las escamas específico la interdependencia en supraoculares de Squamata y la Iguanidae de los géneros Iguana, posición evolutiva de cada taxón Cercosaura, Brachylophus,
    [Show full text]
  • Macropredatory Ichthyosaur from the Middle Triassic and the Origin of Modern Trophic Networks
    Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks Nadia B. Fröbischa,1, Jörg Fröbischa,1, P. Martin Sanderb,1,2, Lars Schmitzc,1,2,3, and Olivier Rieppeld aMuseum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung an der Humboldt-Universität zu Berlin, 10115 Berlin, Germany; bSteinmann Institute of Geology, Mineralogy, and Paleontology, Division of Paleontology, University of Bonn, 53115 Bonn, Germany; cDepartment of Evolution and Ecology, University of California, Davis, CA 95616; and dDepartment of Geology, The Field Museum of Natural History, Chicago, IL 60605 Edited by Neil H. Shubin, The University of Chicago, Chicago, IL, and approved December 5, 2012 (received for review October 8, 2012) The biotic recovery from Earth’s most severe extinction event at the Holotype and Only Specimen. The Field Museum of Natural His- Permian-Triassic boundary largely reestablished the preextinction tory (FMNH) contains specimen PR 3032, a partial skeleton structure of marine trophic networks, with marine reptiles assuming including most of the skull (Fig. 1) and axial skeleton, parts of the predator roles. However, the highest trophic level of today’s the pelvic girdle, and parts of the hind fins. marine ecosystems, i.e., macropredatory tetrapods that forage on prey of similar size to their own, was thus far lacking in the Paleozoic Horizon and Locality. FMNH PR 3032 was collected in 2008 from the and early Mesozoic. Here we report a top-tier tetrapod predator, middle Anisian Taylori Zone of the Fossil Hill Member of the Favret a very large (>8.6 m) ichthyosaur from the early Middle Triassic Formation at Favret Canyon, Augusta Mountains, Pershing County, (244 Ma), of Nevada.
    [Show full text]
  • First Amphibian Ichthyosaur Fossil Found
    First amphibian ichthyosaur fossil found An ancient marine reptile with seal-like flippers may have been adapted to life on the land as well as in the sea, scientists believe. The 250-million-year-old creature is the first amphibious ichthyosaur known. Its relatives were dolphin-like creatures that swam in the oceans at the time of the dinosaurs. They are thought to have had terrestrial ancestors, but previously no fossils had come to light marking the transition of ichthyosaurs from land to sea. “Now we have this fossil showing the transition,” said lead scientist Professor Ryosuke Motani, from the University of California at Davis who reported the discovery in the journal Nature. At 1.5 feet long, Cartorhynchus lenticarpus was also the smallest known ichthyosaur. Its fossil remains found in Anhui Province, China, date from the start of the Triassic period about 248 million years ago. As well as big flippers, Cartorhynchus had flexible wrists which would have been essential for movement on the ground. While most ichthyosaurs have long beak-like snouts, the new specimen possessed a short nose that may have been adapted to suction feeding. Its body also contained thicker bones than other ichthyosaurs. This supports the theory that most marine reptiles that left the land first grew heavier to help them swim through rough coastal waves. The animal lived about 4 million years after the worst mass extinction in history, shedding light on how long it took for life on Earth to recover. The Permian-Triassic extinction, known as the “Great Dying”, wiped out 96% of all species and may have been linked to global warming.
    [Show full text]