Reptile” Diversity and Evolution George A

Total Page：16

File Type：pdf, Size：1020Kb

“Reptile” Diversity and Evolution George A. Lozano Department of Biology University of Ottawa Summary Sauropsids Turtles Diapsids/Saurians Plesiosaurs † and ichthyosaurs † Lepidosaurs Tuatara Squamates (snakes, geckos, iguanas, monitors ) Archosaurs (crocodiles, dinosaurs, pterosaurs ) Dinosaurs 2 George A. Lozano Amniota Synapsida Sauropsida Diapsida Turtles Ancestral amniotes & Turtles Turtles - Testudina 250 species Carapace (vertebrae and ribs) Appendicular girdles INSIDE the shell Beak, no teeth (along with aves) Ear ossicle columella (ind?) 4 George A. Lozano Sauropsida Diapsida/Sauria Turtles 250 Archosaurs Ichthyosaurs† Lepidosaurs Plesiosaurs† 9.1K 7K Ear ossicle collumella, 3 rd ind. evol.) Lepidosaurs “scaly” reptiles 6700 species : 4000 lizards, 2700 snakes Tuatara: ancestral diapsid skull Squamata: derived diapsid skull, hemipenes Iguanas Geckos Snakes Skinks Gila monsters, monitor lizards, Komodo dragon 6 George A. Lozano Tuatara Turtles Squamates Modified Euryapsid: Aves diapsid Plesiosaur Ichthyosaur Snakes 8 George A. Lozano Sauropsida Diapsida Turtles Archosaurs Crocodiles Dinosaurs Pterosaurs† Dinosaurs Ornithischians† Saurischians •Ceratopsids •Duck-billed dino Sauropods† Theropods •Stegosaurus •Ankylosaurus Dinosaurs Ornithischians† Saurischians •-ceratops (uni, tri…) •Duck-billed dino Sauropods† Theropods •Stegosaurus •Diplodocus •Ankylosaurus •Brachiosaurus T. rex † Velociraptor † Birds 12 George A. Lozano Sauropod and ornithischian (ankylosaurus) 13 George A. Lozano 14 George A. Lozano Dinosaurs Ornithischians† Saurischians •Ceratops (uni,tri…) •Duck-billed dino Sauropods† Theropods •Stegosaurus •Diplodocus •Ankylosaurus •Brachiosaurus T. rex † Velociraptor † Birds 9.1K 16 George A. Lozano 17 George A. Lozano You know what a bird is, but… Extant dinosaurs Feathers Flight Extensive bone fusion No teeth Long flexible neck Hollow bones Extremely high metabolism 18 George A. Lozano 19 George A. Lozano 20 George A. Lozano Sauropsida Diapsida Turtles ArchosaursIchthyosaurs† Lepidosaurs Plesiosaurs† Crocs Dinos Pterosaurs† Squamata Tuatara 23 2 Ornithischchians† Saurischchians Sauropods† Theropods Birds T. rex † Velociraptor † 9.1K Turtles (testudina) Tuatara Monitor lizzards Iguanas Geckos Squamata Lepidosauria Snakes Plesiosauria † Ichthyosauria † Crocodilia Sauropsida Diapsida Pterosaurus † Ornithischians † Sauropods † T. rex † Archosaurs Archosaurs † Dinosaurs Dinosaurs Velociraptor Saurischians Theropods Birds (aves) Caecilians Salamader Frogs Amphibia Sailback synapsids † Monotremata Metatheria Mammalia Synapsida Synapsida Eutheria Turtles (testudina) Tuatara Monitor lizzards Iguanas Geckos Squamata Theria Batrachian Lepidosauria Tetrapods Snakes Plesiosauria † Amniotes Ichthyosauria † Crocodilia Sauropsida Diapsida Pterosaurus † Ornithischians † Sauropods † T. rex † Archosaurs † Dinosaurs Velociraptor Saurischians Saurischians Theropods Theropods Birds (aves) © George A. Lozano 24 George A. Lozano.

Copy Link

Recommended publications

A Phylogenomic Analysis of Turtles ⇑ Nicholas G
Molecular Phylogenetics and Evolution 83 (2015) 250–257 Contents lists available at ScienceDirect Molecular Phylogenetics and Evolution journal homepage: www.elsevier.com/locate/ympev A phylogenomic analysis of turtles ⇑ Nicholas G. Crawford a,b,1, James F. Parham c, ,1, Anna B. Sellas a, Brant C. Faircloth d, Travis C. Glenn e, Theodore J. Papenfuss f, James B. Henderson a, Madison H. Hansen a,g, W. Brian Simison a a Center for Comparative Genomics, California Academy of Sciences, 55 Music Concourse Drive, San Francisco, CA 94118, USA b Department of Genetics, University of Pennsylvania, Philadelphia, PA 19104, USA c John D. Cooper Archaeological and Paleontological Center, Department of Geological Sciences, California State University, Fullerton, CA 92834, USA d Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA e Department of Environmental Health Science, University of Georgia, Athens, GA 30602, USA f Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720, USA g Mathematical and Computational Biology Department, Harvey Mudd College, 301 Platt Boulevard, Claremont, CA 9171, USA article info abstract Article history: Molecular analyses of turtle relationships have overturned prevailing morphological hypotheses and Received 11 July 2014 prompted the development of a new taxonomy. Here we provide the ﬁrst genome-scale analysis of turtle Revised 16 October 2014 phylogeny. We sequenced 2381 ultraconserved element (UCE) loci representing a total of 1,718,154 bp of Accepted 28 October 2014 aligned sequence. Our sampling includes 32 turtle taxa representing all 14 recognized turtle families and Available online 4 November 2014 an additional six outgroups. Maximum likelihood, Bayesian, and species tree methods produce a single resolved phylogeny.
[Show full text]
Reptiles A. Cladistics 1. Many Groups of Organisms
Reptiles A. Cladistics 1. Many groups of organisms are “polyphyletic” a. This means that the group combines 2 or more lineages - example=fish 2. Cladistics follows only pure lineages going back in time - example Osteichthys B. Reptile Classifiecation - looks like a polyphyletic group 1. Dry skin - no loss of water through skin like amphibians 2. Aminotic egg - an egg that can survive on dry land - in contrast with the amphibian egg C. Mammals and Birds are derived from different lineages of reptiles (We will see below) D. Stem Reptiles 1. Different lineages based on the temporal region of their skulls - number of holes (or bars) a. These holes are necessary to accommodate large jaw muscles b. Anapsid Skull - no holes in temporal - jaws can move fast, but with little force 1. Muscles that move the jaw are small 2. There is no good paleotological evidence for the transition between amphibians and reptiles - no fossil intermediates a. Fossil amphibians have lots of dermal bones in skull b. Amphibians have no temporal openings in skull 1. (Aside) both fossil amphibians and primitive reptiles have a parietal “eye” that senses light and dark (“third” eye in middle of head) c. Reptile skull is higher than amphibian to accomodate larger jaw muscles d. Of the modern reptiles only turtles are anapsids 2. Diapsid Skull - has holes in the temporal region a. Diapsid reptiles gave rise to lizards and snakes - they have a diapsid skull 1. Also Tuatara, crocodiles, dinosaurs and pterydactyls Reptiles b. One group of diapsids also had a pre-orbital hole in the skull in front of eye - this hole is still preserved in the birds - this anatomy suggests strongly that the birds are derived from the diapsid reptiles 3.
[Show full text]
Evolution of the Iguanine Lizards (Sauria, Iguanidae) As Determined by Osteological and Myological Characters David F
Brigham Young University Science Bulletin, Biological Series Volume 12 | Number 3 Article 1 1-1971 Evolution of the iguanine lizards (Sauria, Iguanidae) as determined by osteological and myological characters David F. Avery Department of Biology, Southern Connecticut State College, New Haven, Connecticut Wilmer W. Tanner Department of Zoology, Brigham Young University, Provo, Utah Follow this and additional works at: https://scholarsarchive.byu.edu/byuscib Part of the Anatomy Commons, Botany Commons, Physiology Commons, and the Zoology Commons Recommended Citation Avery, David F. and Tanner, Wilmer W. (1971) "Evolution of the iguanine lizards (Sauria, Iguanidae) as determined by osteological and myological characters," Brigham Young University Science Bulletin, Biological Series: Vol. 12 : No. 3 , Article 1. Available at: https://scholarsarchive.byu.edu/byuscib/vol12/iss3/1 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Brigham Young University Science Bulletin, Biological Series by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. S-^' Brigham Young University f?!AR12j97d Science Bulletin \ EVOLUTION OF THE IGUANINE LIZARDS (SAURIA, IGUANIDAE) AS DETERMINED BY OSTEOLOGICAL AND MYOLOGICAL CHARACTERS by David F. Avery and Wilmer W. Tanner BIOLOGICAL SERIES — VOLUME Xil, NUMBER 3 JANUARY 1971 Brigham Young University Science Bulletin
[Show full text]
(Diapsida: Saurosphargidae), with Implications for the Morphological Diversity and Phylogeny of the Group
Geol. Mag.: page 1 of 21. c Cambridge University Press 2013 1 doi:10.1017/S001675681300023X A new species of Largocephalosaurus (Diapsida: Saurosphargidae), with implications for the morphological diversity and phylogeny of the group ∗ CHUN LI †, DA-YONG JIANG‡, LONG CHENG§, XIAO-CHUN WU†¶ & OLIVIER RIEPPEL ∗ Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China ‡Department of Geology and Geological Museum, Peking University, Beijing 100871, PR China §Wuhan Institute of Geology and Mineral Resources, Wuhan, 430223, PR China ¶Canadian Museum of Nature, PO Box 3443, STN ‘D’, Ottawa, ON K1P 6P4, Canada Department of Geology, The Field Museum, 1400 S. Lake Shore Drive, Chicago, IL 60605-2496, USA (Received 31 July 2012; accepted 25 February 2013) Abstract – Largocephalosaurus polycarpon Cheng et al. 2012a was erected after the study of the skull and some parts of a skeleton and considered to be an eosauropterygian. Here we describe a new species of the genus, Largocephalosaurus qianensis, based on three specimens. The new species provides many anatomical details which were described only brieﬂy or not at all in the type species, and clearly indicates that Largocephalosaurus is a saurosphargid. It differs from the type species mainly in having three premaxillary teeth, a very short retroarticular process, a large pineal foramen, two sacral vertebrae, and elongated small granular osteoderms mixed with some large ones along the lateral most side of the body. With additional information from the new species, we revise the diagnosis and the phylogenetic relationships of Largocephalosaurus and clarify a set of diagnostic features for the Saurosphargidae Li et al.
[Show full text]
A Small Lepidosauromorph Reptile from the Early Triassic of Poland
A SMALL LEPIDOSAUROMORPH REPTILE FROM THE EARLY TRIASSIC OF POLAND SUSAN E. EVANS and MAGDALENA BORSUK−BIAŁYNICKA Evans, S.E. and Borsuk−Białynicka, M. 2009. A small lepidosauromorph reptile from the Early Triassic of Poland. Palaeontologia Polonica 65, 179–202. The Early Triassic karst deposits of Czatkowice quarry near Kraków, southern Poland, has yielded a diversity of fish, amphibians and small reptiles. Two of these reptiles are lepido− sauromorphs, a group otherwise very poorly represented in the Triassic record. The smaller of them, Sophineta cracoviensis gen. et sp. n., is described here. In Sophineta the unspecial− ised vertebral column is associated with the fairly derived skull structure, including the tall facial process of the maxilla, reduced lacrimal, and pleurodonty, that all resemble those of early crown−group lepidosaurs rather then stem−taxa. Cladistic analysis places this new ge− nus as the sister group of Lepidosauria, displacing the relictual Middle Jurassic genus Marmoretta and bringing the origins of Lepidosauria closer to a realistic time frame. Key words: Reptilia, Lepidosauria, Triassic, phylogeny, Czatkowice, Poland. Susan E. Evans [[email protected]], Department of Cell and Developmental Biology, Uni− versity College London, Gower Street, London, WC1E 6BT, UK. Magdalena Borsuk−Białynicka [[email protected]], Institut Paleobiologii PAN, Twarda 51/55, PL−00−818 Warszawa, Poland. Received 8 March 2006, accepted 9 January 2007 180 SUSAN E. EVANS and MAGDALENA BORSUK−BIAŁYNICKA INTRODUCTION Amongst living reptiles, lepidosaurs (snakes, lizards, amphisbaenians, and tuatara) form the largest and most successful group with more than 7 000 widely distributed species. The two main lepidosaurian clades are Rhynchocephalia (the living Sphenodon and its extinct relatives) and Squamata (lizards, snakes and amphisbaenians).
[Show full text]
Tiago Rodrigues Simões
Diapsid Phylogeny and the Origin and Early Evolution of Squamates by Tiago Rodrigues Simões A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in SYSTEMATICS AND EVOLUTION Department of Biological Sciences University of Alberta © Tiago Rodrigues Simões, 2018 ABSTRACT Squamate reptiles comprise over 10,000 living species and hundreds of fossil species of lizards, snakes and amphisbaenians, with their origins dating back at least as far back as the Middle Jurassic. Despite this enormous diversity and a long evolutionary history, numerous fundamental questions remain to be answered regarding the early evolution and origin of this major clade of tetrapods. Such long-standing issues include identifying the oldest fossil squamate, when exactly did squamates originate, and why morphological and molecular analyses of squamate evolution have strong disagreements on fundamental aspects of the squamate tree of life. Additionally, despite much debate, there is no existing consensus over the composition of the Lepidosauromorpha (the clade that includes squamates and their sister taxon, the Rhynchocephalia), making the squamate origin problem part of a broader and more complex reptile phylogeny issue. In this thesis, I provide a series of taxonomic, phylogenetic, biogeographic and morpho-functional contributions to shed light on these problems. I describe a new taxon that overwhelms previous hypothesis of iguanian biogeography and evolution in Gondwana (Gueragama sulamericana). I re-describe and assess the functional morphology of some of the oldest known articulated lizards in the world (Eichstaettisaurus schroederi and Ardeosaurus digitatellus), providing clues to the ancestry of geckoes, and the early evolution of their scansorial behaviour.
[Show full text]
Clades™ Prehistoric Card Game a Clade Is a Section of the Evolutionary Family Tree—Basically Any Branch, Including All Its Sub-Branches
CLADES™ PREHISTORIC Card Game A clade is a section of the evolutionary family tree —basically any branch, including all its sub-branches. A clade is a family of organisms, or living things, that are all more closely related to each other than they are to any other organisms. In this game you match cards according to their clades. Contents: Deck of 83 Clades Prehistoric cards. Includes 27 cards of each color and 2 bonus cards. There are also 5 animal description cards not used in play. Object: Spot matching card triples to collect the biggest animal pile! Setup Deal 1 face-down card to each player as their personal card. For now, players keep these cards face-down and don’t look at them. Deal 12 face-down shared cards to the middle of the play area. If you’re learning or teaching the game: • Before dealing, set aside the bonus cards and the cards showing only one or two animals. Play with just the cards showing three animals. • Deal 7 shared cards instead of 12. CLADESPrehistoricRules2.indd 1 10/17/17 10:15 AM All players help flip the 12 shared cards face-up. Sort the cards into three Making Triples rows according to their clades: top for Mammalia (mammals), middle for Sauropsida (sauropsids, or reptiles and birds), and bottom for Arthropoda In Clades Prehistoric, any two cards can make a triple with exactly one other (arthropods, or “bugs”). When the table is ready, each player picks up their card in the deck. personal card and looks at it.
[Show full text]
Antimicrobial Peptides in Reptiles
Pharmaceuticals 2014, 7, 723-753; doi:10.3390/ph7060723 OPEN ACCESS pharmaceuticals ISSN 1424-8247 www.mdpi.com/journal/pharmaceuticals Review Antimicrobial Peptides in Reptiles Monique L. van Hoek National Center for Biodefense and Infectious Diseases, and School of Systems Biology, George Mason University, MS1H8, 10910 University Blvd, Manassas, VA 20110, USA; E-Mail: [email protected]; Tel.: +1-703-993-4273; Fax: +1-703-993-7019. Received: 6 March 2014; in revised form: 9 May 2014 / Accepted: 12 May 2014 / Published: 10 June 2014 Abstract: Reptiles are among the oldest known amniotes and are highly diverse in their morphology and ecological niches. These animals have an evolutionarily ancient innate-immune system that is of great interest to scientists trying to identify new and useful antimicrobial peptides. Significant work in the last decade in the fields of biochemistry, proteomics and genomics has begun to reveal the complexity of reptilian antimicrobial peptides. Here, the current knowledge about antimicrobial peptides in reptiles is reviewed, with specific examples in each of the four orders: Testudines (turtles and tortosises), Sphenodontia (tuataras), Squamata (snakes and lizards), and Crocodilia (crocodilans). Examples are presented of the major classes of antimicrobial peptides expressed by reptiles including defensins, cathelicidins, liver-expressed peptides (hepcidin and LEAP-2), lysozyme, crotamine, and others. Some of these peptides have been identified and tested for their antibacterial or antiviral activity; others are only predicted as possible genes from genomic sequencing. Bioinformatic analysis of the reptile genomes is presented, revealing many predicted candidate antimicrobial peptides genes across this diverse class. The study of how these ancient creatures use antimicrobial peptides within their innate immune systems may reveal new understandings of our mammalian innate immune system and may also provide new and powerful antimicrobial peptides as scaffolds for potential therapeutic development.
[Show full text]
Elachistosuchus Huenei Janensch, 1949 (Reptilia: Diapsida) from the Upper Triassic of Germany and Its Relevance for the Origin of Sauria
RESEARCH ARTICLE Anatomy of the Enigmatic Reptile Elachistosuchus huenei Janensch, 1949 (Reptilia: Diapsida) from the Upper Triassic of Germany and Its Relevance for the Origin of Sauria Gabriela Sobral1☯*, Hans-Dieter Sues2☯, Johannes Müller1☯ 1 Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany, 2 Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121, Washington, DC, United States of America ☯ These authors contributed equally to this work. * [email protected] OPEN ACCESS Citation: Sobral G, Sues H-D, Müller J (2015) Abstract Anatomy of the Enigmatic Reptile Elachistosuchus huenei Janensch, 1949 (Reptilia: Diapsida) from the The holotype and only known specimen of the enigmatic small reptile Elachistosuchus hue- Upper Triassic of Germany and Its Relevance for the nei Janensch, 1949 from the Upper Triassic (Norian) Arnstadt Formation of Saxony-Anhalt Origin of Sauria. PLoS ONE 10(9): e0135114. μ doi:10.1371/journal.pone.0135114 (Germany) is redescribed using CT scans of the material. This re-examination revealed new information on the morphology of this taxon, including previously unknown parts of the Editor: Shree Ram Singh, National Cancer Institute, UNITED STATES skeleton such as the palate, braincase, and shoulder girdle. Elachistosuchus is diagnosed especially by the presence of the posterolateral process of the frontal, the extension of the Received: January 27, 2015 maxillary tooth row to the posterior margin of the orbit, the free posterior process of the Accepted: July 19, 2015 jugal, and the notched anterior margin of the interclavicle. Phylogenetic analyses using two Published: September 9, 2015 recently published character-taxon matrices recovered conflicting results for the phyloge- Copyright: This is an open access article, free of all netic position of Elachistosuchus–either as an archosauromorph, as a lepidosauromorph or copyright, and may be freely reproduced, distributed, as a more basal, non-saurian diapsid.
[Show full text]
An Early Late Triassic Long-Necked Reptile with a Bony Pectoral Shield and Gracile Appendages
An early Late Triassic long-necked reptile with a bony pectoral shield and gracile appendages JERZY DZIK and TOMASZ SULEJ Dzik, J. and Sulej, T. 2016. An early Late Triassic long-necked reptile with a bony pectoral shield and gracile appendages. Acta Palaeontologica Polonica 61 (4): 805–823. Several partially articulated specimens and numerous isolated bones of Ozimek volans gen. et sp. nov., from the late Carnian lacustrine deposits exposed at Krasiejów in southern Poland, enable a reconstruction of most of the skeleton. The unique character of the animal is its enlarged plate-like coracoids presumably fused with sterna. Other aspects of the skeleton seem to be comparable to those of the only known specimen of Sharovipteryx mirabilis from the latest Middle Triassic of Kyrgyzstan, which supports interpretation of both forms as protorosaurians. One may expect that the pectoral girdle of S. mirabilis, probably covered by the rock matrix in its only specimen, was similar to that of O. volans gen. et sp. nov. The Krasiejów material shows sharp teeth, low crescent scapula, three sacrals in a generalized pelvis (two of the sacrals being in contact with the ilium) and curved robust metatarsal of the fifth digit in the pes, which are unknown in Sharovipteryx. Other traits are plesiomorphic and, except for the pelvic girdle and extreme elongation of appendages, do not allow to identify any close connection of the sharovipterygids within the Triassic protorosaurians. Key words: Archosauromorpha, Sharovipteryx, protorosaurs, gliding, evolution, Carnian, Poland. Jerzy Dzik [[email protected]], Instytut Paleobiologii PAN, ul. Twarda 51/55, 00-818 Warszawa, Poland and Wydział Biologii Uniwersytetu Warszawskiego, Centrum Nauk Biologiczno-Chemicznych, ul.
[Show full text]
What Are Dinosaurs?
Tote Hughes, 140819 [email protected] Dinosaurs 1/20 What Are Dinosaurs? The following are not dinosaurs∗: • Things that aren’t organisms—There is no rock that is a dinosaur. • Things that existed before the Triassic period† • Pterosaurs The following are dinosaurs: • Birds (Aves) The following contain dinosaurs: • Archosaurs (X.Archosauria) • Reptiles (Reptilia) Dinosaur Overview A discussion of the important dinosaur clades. Dinosaurs are divided into two main groups: the eusaurischians‡ and ornithischians. Eusaurischians • Sauropods – Apatasaurus: diplodocoidean – Barosaurus: diplodocoidean – Brachiosaurus: macronarian – Diplodocus: diplodocoidean • Theropods – Allosaurus: carnosaurian – Archaeopteryx: maniraptor – Giganotosaurus: carnosaurian – Megalosaurus: megalosaurid – Spinosaurus: megalosaurid – Tyrannosaurus: tyrannosauroid – Velociraptor: maniraptor ∗See the Dinosaur Encyclopedia section for details on terms. †See Appendix: Time for details on geological time. ‡These are commonly called saurischians, but since almost every interesting saurischian is actually in the subclade X.Eusaurischia, I’ve taken the liberty of breaking the standard. I hope you will grow to understand and accept my decision. 1/20 Tote Hughes, 140819 [email protected] Dinosaurs 2/20 Ornithischians • Eurypodans (thyreophor) – Ankylosaurus: ankylosaurian – Stegosaurus: stegosaurian • Marginocephalians (cerapod) – Pachycephalosaurus: pachycephalosaurian – Triceratops: ceratopsian • Ornithopods (cerapod) – Hadrosaurus: hadrosauriform – Iguanodon: hadrosauriform
[Show full text]
Evolution and Homology of the Astragalus in Early Amniotes: New Fossils, New Perspectives
JOURNAL OF MORPHOLOGY 267:415–425 (2006) Evolution and Homology of the Astragalus in Early Amniotes: New Fossils, New Perspectives F. Robin O’Keefe,1* Christian A. Sidor,1 Hans C.E. Larsson,2 Abdoudaye Maga,3 and Oumarou Ide3 1Department of Anatomy, New York College of Osteopathic Medicine, Old Westbury, New York 11568 2Redpath Museum, McGill University, Montreal, Quebec H3A 2K6, Canada 3Institut de Recherches en Sciences Humaines, Niamey, Niger Republic ABSTRACT The reorganization of the ankle in basal tarsal elements are unclear, rendering the study of amniotes has long been considered a key innovation al- specific joint articulations difficult (Sumida, 1997, p. lowing the evolution of more terrestrial and cursorial be- 387). New data and new insights on the developmen- havior. Understanding how this key innovation arose is a complex problem that largely concerns the homologizing tal and evolutionary repatterning of the amniote of the amniote astragalus with the various ossifications in ankle are therefore of prime importance, for they the anamniote tarsus. Over the last century, several hy- bear on one of the key transitions in tetrapod his- potheses have been advanced homologizing the amniote tory: the attainment of full terrestriality after the astragalus with the many ossifications in the ankle of long transition from fin to limb (Clack, 2002). amphibian-grade tetrapods. There is an emerging consen- Perhaps the most important novelty within the sus that the amniote astragalus is a complex structure amniote tarsus is the astragalus, a large, complex emerging via the co-ossification of several originally sep- arate elements, but the identities of these elements re- bone comprising the primary area of articulation for main unclear.
[Show full text]