DOCSLIB.ORG

Science Journals

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Science Journals SCIENCE ADVANCES | RESEARCH ARTICLE EVOLUTIONARY BIOLOGY Copyright © 2019 The Authors, some rights reserved; New skulls and skeletons of the Cretaceous legged exclusive licensee American Association snake Najash, and the evolution of the modern snake for the Advancement of Science. No claim to body plan original U.S. Government Fernando F. Garberoglio1*, Sebastián Apesteguía1, Tiago R. Simões2†, Alessandro Palci3,4, Raúl O. Gómez5, Works. Distributed 6 7 3,4 2,8 under a Creative Randall L. Nydam , Hans C. E. Larsson , Michael S. Y. Lee , Michael W. Caldwell Commons Attribution NonCommercial Snakes represent one of the most dramatic examples of the evolutionary versatility of the vertebrate body plan, License 4.0 (CC BY-NC). including body elongation, limb loss, and skull kinesis. However, understanding the earliest steps toward the acquisition of these remarkable adaptations is hampered by the very limited fossil record of early snakes. Here, we shed light on the acquisition of the snake body plan using micro–computed tomography scans of the first three- dimensionally preserved skulls of the legged snake Najash and a new phylogenetic hypothesis. These findings elucidate the initial sequence of bone loss that gave origin to the modern snake skull. Morphological and molecular analyses including the new cranial data provide robust support for an extensive basal radiation of early snakes Downloaded from with hindlimbs and pelves, demonstrating that this intermediate morphology was not merely a transient phase between limbed and limbless body plans. INTRODUCTION intermediate conditions such as a vertically oriented quadrate. The http://advances.sciencemag.org/ Snakes are a diverse and highly modified lineage of lizards with a long new cranial data also robustly resolve the phylogenetic position of but sparse fossil record, beginning in the upper Middle Jurassic (1). this crucial snake taxon, along with other limbed snakes. Anatomical adaptations from their ancestral lizard-like skull condi- The new three-dimensional, largely uncrushed fossils are found tion include greatly increased gape size, increased skull kinesis, loss in rocks deposited in dune/interdune depositional environments (10) of temporal bones, and expansion of the attachment sites for the jaw exposed in the La Buitrera Palaeontological Area (LBPA) (9). Material adductor musculature. This highly modified skull creates difficulties from this rare Lagerstätte makes Najash the best-known Mesozoic in identifying homologies with other squamates, resulting in prob- fossil snake taxon, followed closely by similar materials and ontoge- lems reconstructing phylogeny and in understanding the evolutionary netic stages of the slightly younger (Santonian-Campanian; Upper acquisition and assembly of the snake skull and elongate body. Cretaceous) but geographically proximate fossil snake Dinilysia Despite their limited fossil record, terrestrial and marine deposited (4, 11–14). Other key undisputed Mesozoic Gondwanan snakes include sediments from Late Cretaceous Gondwana and its coastal regions several terrestrial forms, all known only from single specimens: the on November 21, 2019 preserve some of the oldest known articulated snake remains in the Maastrichtian Sanajeh (15) and Menarana (16), and, most recently, world (2–6). Here, we report eight new skulls and three articulated the Cenomanian forest-dwelling snake Xiaophis (17), as well as postcrania of the Cenomanian legged snake Najash (Patagonia, marine forms represented by articulated specimens of limbed snakes Argentina) (Figs. 1 and 2 and Supplementary Materials), previously from the Middle East, the Cenomanian simoliophiids Pachyrhachis (2), known mainly from one articulated partial postcranial skeleton and a Eupodophis (3), and Haasiophis (5). partial cranium and associated fragments (6–9). The new skull speci- mens include a new and near perfectly preserved three-dimensional skull that, by itself, clarifies several long-standing problems on the RESULTS origin of key features of the modern snake skull. These new Najash The new specimens exhibit a similar overall morphology that permits specimens reveal a mosaic of primitive lizard-like features such as a their assignation to the genus Najash; however, pending a full taxo- large triradiate jugal and absence of the crista circumfenestralis, de- nomic review and assessment of the morphological diversity and rived snake features such as the absence of the postorbital, as well as disparity, the snakes from the LBPA are here conservatively assigned to Najash sp. (see the Supplementary Materials). MPCA 500 is pre- 1CONICET, Área de Paleontología, Fundación de Historia Natural Félix de Azara, served in three dimensions, with the right side in perfect articulation CEBBAD, Universidad Maimónides, Hidalgo 775, 1405 Buenos Aires, Argentina. 2 from the quadrate to the fragmentary premaxilla; the left side of the Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, skull is broken away and lost, revealing internal and medial aspects Canada. 3College of Science and Engineering, Flinders University, Adelaide, SA 5042, Australia. 4Earth Sciences Section, South Australian Museum, North Terrace, of the right nasal, vomer, septomaxilla, and frontal; the parabasi- Adelaide, SA 5000, Australia. 5CONICET, Departamento de Biodiversidad y Biología sphenoid rostrum; and the parietal (Figs. 1 and 2 and fig. S1). Experimental/Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas For a detailed analysis of its skull anatomy, in addition to standard y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires, Argentina. 6Arizona College of Osteopathic Medicine, Midwestern University, light microscopy studies, we performed high-resolution computed 19555 N. 59th Ave., Glendale, AZ 85383, USA. 7Redpath Museum, McGill University, tomography (CT) scanning of the best-preserved skull (MPCA 500), 859 Sherbrooke Street W., Montreal, Quebec H3A 0C4, Canada. 8Department of Earth revealing substantial new anatomical data on the early evolution of and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada. the snake skull (Fig. 2 and fig. S1). On the basis of morphology and *Corresponding author. Email: [email protected] †Present address: Department of Organismic and Evolutionary Biology, Museum of topology (18), MPCA 500 unequivocally has a large jugal bone, similar Comparative Zoology, Harvard University, Cambridge, MA 02138, USA. to that found in many non-ophidian lizards and consistent with Garberoglio et al., Sci. Adv. 2019; 5 : eaax5833 20 November 2019 1 of 8 SCIENCE ADVANCES | RESEARCH ARTICLE Downloaded from http://advances.sciencemag.org/ Fig. 1. Najash specimens from LBPA. (A) MPCA 500, skull with atlas-axis in right lateral view. (B) MPCA 591, partial skull with articulated vertebrae in right lateral view. (C) MPCA 581, partial skull with atlas in left lateral view. (D) MPCA 564, articulated specimen with partial skull and postcranium in ventral view. (E) MPCA 419, dentary and associated vertebrae and ribs. (F) MPCA 480, partial skull with atlas in dorsal view. (G) MPCA 536, partial skull in ventral view. (H) MPCA 386, partial skull in ventral view. bo, basioccipital; ti, tibia. primary homologies proposed for other early fossil snakes such as Nearly all extant snakes have a crista circumfenestralis, enclosing Pachyrhachis, Eupodophis, Yurlunggur, and Dinilysia (19). The un- a unique bony chamber around the fenestra ovalis and lateral aperture on November 21, 2019 ambiguous homology of the bone in MPCA 500 confirms the pri- of the recessus scalae tympani (20–22). The full crista circumfenestralis mary homology hypothesis in other fossil and modern snakes that is composed of three cristae (tuberalis, interfenestralis, and prootica) this circumorbital bone is the jugal, not the postorbital. The jugal of that connect, or sometimes fuse, to form a chamber, the juxtastapedial Najash, like the triradiate element found in many lizards, has three recess, for an expanded perilymphatic sac that emerges from the major processes: an anterior ramus framing the ventrolateral margin recessus scalae tympani and surrounds the stapedial footplate (20). of the orbit, superior to the maxilla, and contacting the prefrontal Arguments for a full crista circumfenestralis (6, 7, 12) versus in- on the anteroventral orbital margin; a superior ramus framing the complete, separate cristae (4, 9, 11, 20, 21) have been made in Najash posterior margin of the orbit and contacting the posterior margin of and Dinilysia. MPCA 500, and all other Najash cranial specimens the postfrontal and the parietal; and a short but robust posteroventral preserving the otic capsular region of the otoocciput (Figs. 1 and 2 ramus contacting the ectopterygoid at the ectopterygoid-maxillary and fig. S1), indicates that a full crista circumfenestralis is absent but joint. This latter process presumably also served as a point of attach- that at least two of the cristae are present: the crista interfenestralis, ment for the quadratomaxillary ligament extending across the ventral which separates the fenestra ovalis from the fenestra rotunda, and margin of the lower temporal fenestra from the jugal-maxilla- the crista tuberalis, which separates the vagus foramen from the ectopterygoid to the quadrate (19). fenestra rotunda (thus subdividing the original metotic fissure). MPCA 500 and two more fragmentary skulls, MPCA 480 and However, a crista
Load more

Recommended publications
  • The Skull of the Upper Cretaceous Snake Dinilysia Patagonica Smith-Woodward, 1901, and Its Phylogenetic Position Revisited
    Zoological Journal of the Linnean Society, 2012, 164, 194–238. With 24 figures The skull of the Upper Cretaceous snake Dinilysia patagonica Smith-Woodward, 1901, and its phylogenetic position revisited HUSSAM ZAHER1* and CARLOS AGUSTÍN SCANFERLA2 1Museu de Zoologia da Universidade de São Paulo, Avenida Nazaré 481, Ipiranga, 04263-000, São Paulo, SP, Brasil 2Laboratorio de Anatomía Comparada y Evolución de los Vertebrados. Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. Angel Gallardo 470 (1405), Buenos Aires, Argentina Received 23 April 2010; revised 5 April 2011; accepted for publication 18 April 2011 The cranial anatomy of Dinilysia patagonica, a terrestrial snake from the Upper Cretaceous of Argentina, is redescribed and illustrated, based on high-resolution X-ray computed tomography and better preparations made on previously known specimens, including the holotype. Previously unreported characters reinforce the intriguing mosaic nature of the skull of Dinilysia, with a suite of plesiomorphic and apomorphic characters with respect to extant snakes. Newly recognized plesiomorphies are the absence of the medial vertical flange of the nasal, lateral position of the prefrontal, lizard-like contact between vomer and palatine, floor of the recessus scalae tympani formed by the basioccipital, posterolateral corners of the basisphenoid strongly ventrolaterally projected, and absence of a medial parietal pillar separating the telencephalon and mesencephalon, amongst others. We also reinterpreted the structures forming the otic region of Dinilysia, confirming the presence of a crista circumfenes- tralis, which represents an important derived ophidian synapomorphy. Both plesiomorphic and apomorphic traits of Dinilysia are treated in detail and illustrated accordingly. Results of a phylogenetic analysis support a basal position of Dinilysia, as the sister-taxon to all extant snakes.
    [Show full text]
  • Snakes of the Siwalik Group (Miocene of Pakistan): Systematics and Relationship to Environmental Change
    Palaeontologia Electronica http://palaeo-electronica.org SNAKES OF THE SIWALIK GROUP (MIOCENE OF PAKISTAN): SYSTEMATICS AND RELATIONSHIP TO ENVIRONMENTAL CHANGE Jason J. Head ABSTRACT The lower and middle Siwalik Group of the Potwar Plateau, Pakistan (Miocene, approximately 18 to 3.5 Ma) is a continuous fluvial sequence that preserves a dense fossil record of snakes. The record consists of approximately 1,500 vertebrae derived from surface-collection and screen-washing of bulk matrix. This record represents 12 identifiable taxa and morphotypes, including Python sp., Acrochordus dehmi, Ganso- phis potwarensis gen. et sp. nov., Bungarus sp., Chotaophis padhriensis, gen. et sp. nov., and Sivaophis downsi gen. et sp. nov. The record is dominated by Acrochordus dehmi, a fully-aquatic taxon, but diversity increases among terrestrial and semi-aquatic taxa beginning at approximately 10 Ma, roughly coeval with proxy data indicating the inception of the Asian monsoons and increasing seasonality on the Potwar Plateau. Taxonomic differences between the Siwalik Group and coeval European faunas indi- cate that South Asia was a distinct biogeographic theater from Europe by the middle Miocene. Differences between the Siwalik Group and extant snake faunas indicate sig- nificant environmental changes on the Plateau after the last fossil snake occurrences in the Siwalik section. Jason J. Head. Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, DC 20013-7012, USA. [email protected] School of Biological Sciences, Queen Mary, University of London, London, E1 4NS, United Kingdom. KEY WORDS: Snakes, faunal change, Siwalik Group, Miocene, Acrochordus. PE Article Number: 8.1.18A Copyright: Society of Vertebrate Paleontology May 2005 Submission: 3 August 2004.
    [Show full text]
  • A Redescription and Phylogenetic Analysis of the Cretaceous Fossil Lizard Polyglyphanodon Sternbergi Gilmore, 1940
    A Redescription and Phylogenetic Analysis of the Cretaceous Fossil Lizard Polyglyphanodon sternbergi Gilmore, 1940 by Meredith Austin Fontana B.S. in Biology, May 2011, The University of Texas at Austin A Thesis submitted to The Faculty of The Columbian College of Arts and Sciences of The George Washington University in partial fulfillment of the requirements for the degree of Master of Science August 31, 2014 Thesis directed by James M. Clark Ronald Weintraub Professor of Biology © Copyright 2014 by Meredith Austin Fontana All rights reserved ii This thesis is dedicated to the memory of my grandmother, Lee Landsman Zelikow – my single greatest inspiration, whose brilliant mind and unconditional love has profoundly shaped and continues to shape the person I am today. iii ACKNOWLEDGEMENTS I am deeply grateful to my graduate advisor Dr. James Clark for his support and guidance throughout the completion of this thesis. This work would not have been possible without his invaluable assistance and commitment to my success, and it has been a privilege to be his student. I would also like to express my appreciation to the additional members of my Master’s examination committee, Dr. Alexander Pyron and Dr. Hans-Dieter Sues, for generously contributing their knowledge and time toward this project and for providing useful comments on the manuscript of this thesis. I am especially grateful to Dr. Sues for allowing me access to the exquisite collection of Polyglyphanodon sternbergi specimens at the National Museum of Natural History. I am also extremely thankful to the many faculty members, colleagues and friends at the George Washington University who have shared their wisdom and given me persistent encouragement.
    [Show full text]
  • Naracoorte Caves National Park
    Department for Environment and Heritage Naracoorte Caves National Park Australian Fossil Mammal Site World Heritage Area www.environment.sa.gov.au Naracoorte Caves Vegetation Wonambi Fossil Centre National Par The vegetation is predominantly Brown Stringybark Step through the doors of the Wonambi Fossil Australian Fossil Mammal Site on the limestone ridge, with River Red Gum lining the Centre into an ancient world where megafauna World Heritage Area banks of the Mosquito Creek. The understorey on the once roamed. The display in the Wonambi Fossil ridge is bracken fern over a diverse array of orchids Centre ‘brings to life’ the megafauna fossils found in the Naracoorte Caves. The self-guided walk Naracoorte Caves National Park covers that flower during spring. through the simulated forest and swampland is approximately 600 hectares of limestone wheelchair accessible and suitable for all ages. ranges and is situated in the Some of the park was cleared for pine forests in the south-east of South Australia, mid 1800s, with other exotic species planted around The Flinders University Gallery has information 10 km south of Naracoorte. the caves. Many of the pines have now been cleared and areas revegetated with endemic species. The panels depicting the various sciences studied at Naracoorte, and touch screen computers to answer The area was first gardens now consist of native plants although a few questions you may have relating to the Wonambi dedicated a forestry of the historic trees remain. Fossil Centre and the fossils of Naracoorte Caves. reserve in 1882, with Fauna the first caretaker Southern employed to look Bentwing Bat The National Parks Code after the caves in The most common marsupial seen at Naracoorte is the Western Grey Kangaroo.
    [Show full text]
  • The Sclerotic Ring: Evolutionary Trends in Squamates
    The sclerotic ring: Evolutionary trends in squamates by Jade Atkins A Thesis Submitted to Saint Mary’s University, Halifax, Nova Scotia in Partial Fulfillment of the Requirements for the Degree of Master of Science in Applied Science July, 2014, Halifax Nova Scotia © Jade Atkins, 2014 Approved: Dr. Tamara Franz-Odendaal Supervisor Approved: Dr. Matthew Vickaryous External Examiner Approved: Dr. Tim Fedak Supervisory Committee Member Approved: Dr. Ron Russell Supervisory Committee Member Submitted: July 30, 2014 Dedication This thesis is dedicated to my family, friends, and mentors who helped me get to where I am today. Thank you. ! ii Table of Contents Title page ........................................................................................................................ i Dedication ...................................................................................................................... ii List of figures ................................................................................................................. v List of tables ................................................................................................................ vii Abstract .......................................................................................................................... x List of abbreviations and definitions ............................................................................ xi Acknowledgements ....................................................................................................
    [Show full text]
  • A Morphological Model and Ct Assessment of the Skull of Pachyrhachis Problematicus (Squamata, Serpentes), a 98 Million Year Old Snake with Legs from the Middle East
    Palaeontologia Electronica http://palaeo-electronica.org A MORPHOLOGICAL MODEL AND CT ASSESSMENT OF THE SKULL OF PACHYRHACHIS PROBLEMATICUS (SQUAMATA, SERPENTES), A 98 MILLION YEAR OLD SNAKE WITH LEGS FROM THE MIDDLE EAST Michael J. Polcyn, Louis L. Jacobs, and Annat Haber ABSTRACT Pachyrhachis problematicus is a snake with well-developed hind limbs known from two specimens from the Cenomanian of the Middle East. One specimen has a complete and articulated, albeit crushed skull. The second specimen has a disarticu- lated skull crushed beneath the body. Pachyrhachis has recently been at the center of a debate on the origins and relationships of snakes, specifically whether Pachyrhachis is the sister taxon to all other snakes, or alternatively, a relatively advanced snake allied with boids and pythonids. Workers using the same specimens arrived at different interpretations of the morphology underlying the alternative hypotheses. The most complete skull was resin-embedded and acid-prepared for its original study nearly three decades ago, rendering the dorsal surface difficult to view using optical tech- niques, and thus significantly hampering later studies. This study utilizes CT scanning and computer reconstruction to test conflicting interpretations of morphology and thus provides a method to falsify alternative phylogenetic hypotheses. Pachyrhachis is found to possess an inclined quadrate with a well-developed stylohyal process and lacking a suprastapedial process, no squamosal, and a single mental foramen. The separation of exoccipitals above the foramen magnum cannot be demonstrated. There is no jugal. Confirmed morphology best supports the phylogenetic hypothesis that Pachyrhachis is a basal macrostomatan snake. Limb retention in a basal macrostoma- tan snake implies that loss of hind limbs occurred multiple times within Serpentes.
    [Show full text]
  • Human Origins
    HUMAN ORIGINS Methodology and History in Anthropology Series Editors: David Parkin, Fellow of All Souls College, University of Oxford David Gellner, Fellow of All Souls College, University of Oxford Volume 1 Volume 17 Marcel Mauss: A Centenary Tribute Learning Religion: Anthropological Approaches Edited by Wendy James and N.J. Allen Edited by David Berliner and Ramon Sarró Volume 2 Volume 18 Franz Baerman Steiner: Selected Writings Ways of Knowing: New Approaches in the Anthropology of Volume I: Taboo, Truth and Religion. Knowledge and Learning Franz B. Steiner Edited by Mark Harris Edited by Jeremy Adler and Richard Fardon Volume 19 Volume 3 Difficult Folk? A Political History of Social Anthropology Franz Baerman Steiner. Selected Writings By David Mills Volume II: Orientpolitik, Value, and Civilisation. Volume 20 Franz B. Steiner Human Nature as Capacity: Transcending Discourse and Edited by Jeremy Adler and Richard Fardon Classification Volume 4 Edited by Nigel Rapport The Problem of Context Volume 21 Edited by Roy Dilley The Life of Property: House, Family and Inheritance in Volume 5 Béarn, South-West France Religion in English Everyday Life By Timothy Jenkins By Timothy Jenkins Volume 22 Volume 6 Out of the Study and Into the Field: Ethnographic Theory Hunting the Gatherers: Ethnographic Collectors, Agents and Practice in French Anthropology and Agency in Melanesia, 1870s–1930s Edited by Robert Parkin and Anna de Sales Edited by Michael O’Hanlon and Robert L. Welsh Volume 23 Volume 7 The Scope of Anthropology: Maurice Godelier’s Work in Anthropologists in a Wider World: Essays on Field Context Research Edited by Laurent Dousset and Serge Tcherkézoff Edited by Paul Dresch, Wendy James, and David Parkin Volume 24 Volume 8 Anyone: The Cosmopolitan Subject of Anthropology Categories and Classifications: Maussian Reflections on By Nigel Rapport the Social Volume 25 By N.J.
    [Show full text]
  • THE ORIGIN and EVOLUTION of SNAKE EYES Dissertation
    CONQUERING THE COLD SHUDDER: THE ORIGIN AND EVOLUTION OF SNAKE EYES Dissertation Presented in Partial Fulfillment for the Requirements for the Degree of Doctor of Philosophy in the Graduate School of The Ohio State University By Christopher L. Caprette, B.S., M.S. **** The Ohio State University 2005 Dissertation Committee: Thomas E. Hetherington, Advisor Approved by Jerry F. Downhower David L. Stetson Advisor The graduate program in Evolution, John W. Wenzel Ecology, and Organismal Biology ABSTRACT I investigated the ecological origin and diversity of snakes by examining one complex structure, the eye. First, using light and transmission electron microscopy, I contrasted the anatomy of the eyes of diurnal northern pine snakes and nocturnal brown treesnakes. While brown treesnakes have eyes of similar size for their snout-vent length as northern pine snakes, their lenses are an average of 27% larger (Mann-Whitney U test, p = 0.042). Based upon the differences in the size and position of the lens relative to the retina in these two species, I estimate that the image projected will be smaller and brighter for brown treesnakes. Northern pine snakes have a simplex, all-cone retina, in keeping with a primarily diurnal animal, while brown treesnake retinas have mostly rods with a few, scattered cones. I found microdroplets in the cone ellipsoids of northern pine snakes. In pine snakes, these droplets act as light guides. I also found microdroplets in brown treesnake rods, although these were less densely distributed and their function is unknown. Based upon the density of photoreceptors and neural layers in their retinas, and the predicted image size, brown treesnakes probably have the same visual acuity under nocturnal conditions that northern pine snakes experience under diurnal conditions.
    [Show full text]
  • Attachment J Assessment of Existing Paleontologic Data Along with Field Survey Results for the Jonah Field
    Attachment J Assessment of Existing Paleontologic Data Along with Field Survey Results for the Jonah Field June 12, 2007 ABSTRACT This is compilation of a technical analysis of existing paleontological data and a limited, selective paleontological field survey of the geologic bedrock formations that will be impacted on Federal lands by construction associated with energy development in the Jonah Field, Sublette County, Wyoming. The field survey was done on approximately 20% of the field, primarily where good bedrock was exposed or where there were existing, debris piles from recent construction. Some potentially rich areas were inaccessible due to biological restrictions. Heavily vegetated areas were not examined. All locality data are compiled in the separate confidential appendix D. Uinta Paleontological Associates Inc. was contracted to do this work through EnCana Oil & Gas Inc. In addition BP and Ultra Resources are partners in this project as they also have holdings in the Jonah Field. For this project, we reviewed a variety of geologic maps for the area (approximately 47 sections); none of maps have a scale better than 1:100,000. The Wyoming 1:500,000 geology map (Love and Christiansen, 1985) reveals two Eocene geologic formations with four members mapped within or near the Jonah Field (Wasatch – Alkali Creek and Main Body; Green River – Laney and Wilkins Peak members). In addition, Winterfeld’s 1997 paleontology report for the proposed Jonah Field II Project was reviewed carefully. After considerable review of the literature and museum data, it became obvious that the portion of the mapped Alkali Creek Member in the Jonah Field is probably misinterpreted.
    [Show full text]
  • The Making of Calibration Sausage Exemplified by Recalibrating the Transcriptomic Timetree of Jawed Vertebrates
    bioRxiv preprint doi: https://doi.org/10.1101/2019.12.19.882829; this version posted January 5, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-ND 4.0 International license. The making of calibration sausage exemplified by recalibrating the transcriptomic timetree of jawed vertebrates 1 David Marjanović 2 Department of Evolutionary Morphology, Science Programme “Evolution and Geoprocesses”, 3 Museum für Naturkunde – Leibniz Institute for Evolutionary and Biodiversity Research, Berlin, 4 Germany 5 ORCID: 0000-0001-9720-7726 6 Correspondence: 7 David Marjanović 8 [email protected] 9 Keywords: timetree, calibration, divergence date, Gnathostomata, Vertebrata 10 Abstract 11 Molecular divergence dating has the potential to overcome the incompleteness of the fossil record in 12 inferring when cladogenetic events (splits, divergences) happened, but needs to be calibrated by the 13 fossil record. Ideally but unrealistically, this would require practitioners to be specialists in molecular 14 evolution, in the phylogeny and the fossil record of all sampled taxa, and in the chronostratigraphy of 15 the sites the fossils were found in. Paleontologists have therefore tried to help by publishing 16 compendia of recommended calibrations, and molecular biologists unfamiliar with the fossil record 17 have made heavy use of such works (in addition to using scattered primary sources
    [Show full text]
  • Final Copy 2019 10 01 Herrera
    This electronic thesis or dissertation has been downloaded from Explore Bristol Research, http://research-information.bristol.ac.uk Author: Herrera Flores, Jorge Alfredo A Title: The macroevolution and macroecology of Mesozoic lepidosaurs General rights Access to the thesis is subject to the Creative Commons Attribution - NonCommercial-No Derivatives 4.0 International Public License. A copy of this may be found at https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode This license sets out your rights and the restrictions that apply to your access to the thesis so it is important you read this before proceeding. Take down policy Some pages of this thesis may have been removed for copyright restrictions prior to having it been deposited in Explore Bristol Research. However, if you have discovered material within the thesis that you consider to be unlawful e.g. breaches of copyright (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please contact [email protected] and include the following information in your message: •Your contact details •Bibliographic details for the item, including a URL •An outline nature of the complaint Your claim will be investigated and, where appropriate, the item in question will be removed from public view as soon as possible. This electronic thesis or dissertation has been downloaded from Explore Bristol Research, http://research-information.bristol.ac.uk Author: Herrera Flores, Jorge Alfredo A Title: The macroevolution and macroecology of Mesozoic lepidosaurs General rights Access to the thesis is subject to the Creative Commons Attribution - NonCommercial-No Derivatives 4.0 International Public License.
    [Show full text]
  • Evolution of Limblessness
    Evolution of Limblessness Evolution of Limblessness Early on in life, many people learn that lizards have four limbs whereas snakes have none. This dichotomy not only is inaccurate but also hides an exciting story of repeated evolution that is only now beginning to be understood. In fact, snakes represent only one of many natural evolutionary experiments in lizard limblessness. A similar story is also played out, though to a much smaller extent, in amphibians. The repeated evolution of snakelike tetrapods is one of the most striking examples of parallel evolution in animals. This entry discusses the evolution of limblessness in both reptiles and amphibians, with an emphasis on the living reptiles. Reptiles Based on current evidence (Wiens, Brandley, and Reeder 2006), an elongate, limb-reduced, snakelike morphology has evolved at least twenty-five times in squamates (the group containing lizards and snakes), with snakes representing only one such origin. These origins are scattered across the evolutionary tree of squamates, but they seem especially frequent in certain families. In particular, the skinks (Scincidae) contain at least half of all known origins of snakelike squamates. But many more origins within the skink family will likely be revealed as the branches of their evolutionary tree are fully resolved, given that many genera contain a range of body forms (from fully limbed to limbless) and may include multiple origins of snakelike morphology as yet unknown. These multiple origins of snakelike morphology are superficially similar in having reduced limbs and an elongate body form, but many are surprisingly different in their ecology and morphology. This multitude of snakelike lineages can be divided into two ecomorphs (a are surprisingly different in their ecology and morphology.
    [Show full text]