DOCSLIB.ORG

11 Evolution of the Mammalian Nose

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
11 Evolution of the Mammalian Nose 11 Evolution of the Mammalian Nose A. W. Crompton,' Catherine Musinsky, · and Tomasz Owerkowicz' Introduction Endothermy requires an integrated set of morphological and physiological features (Kemp 2006) that evolved independently in birds and mammals (Ruben i996). Morphologic evidence for the evolution of endothermy has partially been based upon the presence of the intranarial respiratory turbinals or conchae that act as temporal countercurrent exchange sites (Bennett and Ruben i986). Since endo­ therms have a higher respiratory rate than ectotherms, evolution of the temporal countercurrent exchange mechanism allowed them to control the temperature of expired air when at rest and during mild exercise, and afforded them significant savings of heat and water (Owerkowicz et al., this volume). Birds achieved this by evolving cartilaginous nasal conchae (Bang i961; Geist 2000) , while mammals de­ veloped ossified maxillary turbinals (Macrini 2012; Rowe et al. 2005). Both mecha­ nisms warm and humidify inhaled air, and cool exhaled air (Schmidt-Nielsen i981), and both require a firm temporary seal between the nasal cavity and the trachea, so that inspired and expired air passes through the nose and bypasses the oral * Museum of Comparative Zoology, and Department of Organismic and Evolutionary Biology, Harvard University t Department of Organismic and Evolutionary Biology, Harvard University :j: Department of Biology, California State University, San Bernardino Monotremata Marsupialia P lacentalia 60 mya i f In the gesting t mroughou To un nasal cap essary to 140 mya by them Haldl10do11 j MAMMALIA to the s M orgal ucodon sal caps 200 mya Probai1rgnathus Masset[1ath11s J MAMMALIAFORMES J 1hri11J_xodon 240 mya L CYNODONTIA Dimr rodon 300 mya I I SYNAPSIDA FIG . 11 .1 Relationships and timeline of the specimens discussed in this chapter cavity. Conchae and maxilloturbinals also provide sites the three-boned middle ear, precise dental occlusion, for evaporative cooling during exercise and high ambi­ determinate growth, and an enlarged braincase-are ent temperatures (Taylor 1977). well documented. The evolution of the mammalian nose, Evolution of these countercurrent exchange sites however, remains relatively uncertain. Hillenius (1992, was likely gradual and probably involved considerable 1994), Hillenius and Ruben (2004), Ruben (1996), and reorganization of the skull skeleton. In this chapter, Ruben et al. (2012) have pointed to ridges found on the we focus on the evolutionary changes to the synapsid inner surface of the nasal and maxillary bones to sug­ skull, which may have housed the incipient respiratory gest that ossified turbinates were present in nonmam­ turbinates. malian therapsids. On the basis of these characters-the Within the nonmammalian therapsids (mammal­ purported maxillary ridges, the presence of a bony like reptiles) spanning more than 100 million years from secondary palate, and an enlarged nasal respiratory the mid-Permian to the Early Jurassic (fig. 11.1) (Kemp chamber-the authors concluded that several groups of 1982; Rowe and Gauthier 1992), some of the progressive nonmammalian therapsids were either partially or fully FIG. changes leading to the mammalian skull-for example, endothermic. of th 190 A . W . CRO MPTO N , CATHERINE M US INSKY, A ND T O MASZ OWERKOWI CZ In extant mammals the embryonic cartilaginous Jurassic mammaliaforms, and review important steps nasal capsule ossifies to form the mesethmoid and in the development of the mammalian nose. ethmoid bones. The latter include ossified maxi!lotur­ binals. But such ossifications have never been found Reptiles: Squamata in the nasal region of nonmammalian synapsids, sug­ gesting that the nasal capsule remained cartilaginous Olfaction is the primary function of the reptilian nose: throughout life. olfactory nerves enter the posterodorsal region that lies To understand the structure of the cartilaginous above the flow of air through the nasal capsule. In typi­ nasal capsule of nonmammalian synapsids, it is nec­ cal living reptiles (Bellairs and Kamal 1981; Malan 1946; essary to determine the shape of the space enclosed Parsons 1959; Pratt 1948), a cartilaginous nasal cavity by the membrane bones that would have surrounded opens directly into the oral cavity through primary it. MicroCT scans contribute new insights to the find­ choanae, or internal nares (fig. 11.2.A, B); thus all air ings of Hillenius (1994), Ruben (1996), and Ruben et al. breathed through the nose must also pass through the (2012). Based on such scans, we offer suggestions as oral cavity. The route of air through the nasal capsule to the structure and function of some cartilaginous na­ between the nares and the primary choana is short (as sal capsules of Triassic nonmammalian cynodonts and indicated by the arrow in fig. 11.2C), limiting the space intern as al septum A B concha pnmary choana cartilaginous nasal capsule primary Varner ~ choana Pterygoid Palatine Maxilla FI G. 11.2 Nasal region of an exta nt Amblyrhynchus cristatus (A- C) and an extinct Dimetrodon limbotus (D). A, Transverse section; B, ventral view of the palate; C, sagittal section; D, sagittal section through the nasal region. EVOLU T I O N OF THE M A MMAL I A N NOSE 191 for structures that might support respiratory epithe­ advanced nonmammalian therapsids suckled their lium. A tall, cartilaginous intemasal septum between young, possessed hair, and were endothermic. How­ the vomer and the nasal roof separates the two sides of ever, this conclusion invites reexamination because the nasal cavity (fig. 11.2A). nonmammalian therocephalians had multiple genera­ tions of tooth replacement throughout life, rather than the diphyodont dentition of mammals, which correlates Early Nonmammalian Synapsids with rapid growth and early dependence on maternal In primitive nonmammalian synapsids, such as the milk for nourishment (Hopson 1973)· pelycosaur Dimetrodon (fig. 11.2D), the nasal capsule re­ mained cartilaginous. As in reptiles, the primary choa­ Nonmammalian Cynodonts nae open directly into the oral cavity (Hillenius 1992; Hillenius 1994; Romer and Price 1940), which limits the The description of the nasal capsule of nonmammalian space available to house structures supporting respira­ cynodonts given here is based upon MicroCT scans of tory epithelium. The posterior extent of a cartilaginous Massetognathus and Probainognathus the description nasal capsule is constrained by the presphenoid bone. of the skull of Thrinaxodon upon a reconstruction from The presphenoid is Y-shaped in cross-section, its ven­ serial grinding (Fourie 1974); and that of several cyno­ tral keel forms an interorbital septum and its expanded donts upon manually prepared cynodont skulls (Brink dorsal area (Kemp 1980) encloses the olfactory nerves. 1955; Estes 1961; Hillenius 1992; Kemp 1980; Sues 1986). The dorsal edge of the tall pte1ygoid bone probably Advanced nonmammalian synapsids, such as the marks the ventral extent of the cartilaginous nasal cynodont Massetognathus, possess a fully ossified sec­ capsule. Given these volumetric constraints, the nasal ondary palate (fig. 1i.3B-E). The earliest presence of capsule of Dimetrodon was long, narrow, and, relative a hard palate in nonmammalian therapsids occurs in to the skull height, shallow. Several authors have sug­ Early Triassic nonmammalian cynodonts (Procynosu­ gested (see Hillenius 1992; Ruben et al. 2012) that ridges chus; Kemp 1979), and consists of medial projections of on the inner smiace of the intramembranous bones an­ the premaxilla, maxilla, and palatine that do not meet terior to the presphenoid supported ossified olfactory in the midline. Thomason and Russell (1986) suggest turbinals. these played a mechanical function in resisting the It is generally accepted that pelycosaurs were ec­ forces of mastication that probably arose with more tothermic (Hopson 2012; Kemp 2006). Therocephalian complex postcanine teeth. The median gap in the hard therapsids were more advanced than pelycosaurs in palate was probably occupied by soft tissue. that the dental row differentiated into well-defined inci­ The acquisition of a complete secondary palate co­ sors, canines, and small simple postcanines; however, incided with a major reorganization of the nasal region. their primary choanae did not increase much in rela­ In Massetognathus, the secondary palate formed the tive size and still opened directly into the oral cavity. floor of a nasopharyngeal duct. Primary choanae (dot­ Nonmammalian basal therocephalians lacked a hard ted lines in fig. 1L3B-D) opened into this nasopharyn­ palate, although Maier et al. (1996) claimed that ridges geal duct rather than straight into the oral cavity as in on the maxilla and palatine parallel to the postcanine reptiles and early nonmammalian synapsids. Air pass­ dentition supported choanal soft tissue folds that did ing through the nose could now bypass the oral cavity not meet in the midline. When their free edges were en route to or from the larynx. pressed against the ventral surface of the vomer, a sec­ It is now possible to reconstruct the space that ondary palate was created that continued posteriorly would have contained the cartilaginous nasal capsule in the form of a mammalian muscular soft palate. This (fig. 11.4; fig. 11.sA, B). Unlike the long fiat bone presem would have allowed uninterrupted activity in the mouth in extant reptiles and nonmammalian pelycosaurs, the cavity without interfering with breathing. Based upon vomer in Massetognathus extends dorsally
Load more

Recommended publications
  • Reptile-Like Physiology in Early Jurassic Stem-Mammals
    bioRxiv preprint doi: https://doi.org/10.1101/785360; this version posted October 10, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Title: Reptile-like physiology in Early Jurassic stem-mammals Authors: Elis Newham1*, Pamela G. Gill2,3*, Philippa Brewer3, Michael J. Benton2, Vincent Fernandez4,5, Neil J. Gostling6, David Haberthür7, Jukka Jernvall8, Tuomas Kankanpää9, Aki 5 Kallonen10, Charles Navarro2, Alexandra Pacureanu5, Berit Zeller-Plumhoff11, Kelly Richards12, Kate Robson-Brown13, Philipp Schneider14, Heikki Suhonen10, Paul Tafforeau5, Katherine Williams14, & Ian J. Corfe8*. Affiliations: 10 1School of Physiology, Pharmacology & Neuroscience, University of Bristol, Bristol, UK. 2School of Earth Sciences, University of Bristol, Bristol, UK. 3Earth Science Department, The Natural History Museum, London, UK. 4Core Research Laboratories, The Natural History Museum, London, UK. 5European Synchrotron Radiation Facility, Grenoble, France. 15 6School of Biological Sciences, University of Southampton, Southampton, UK. 7Institute of Anatomy, University of Bern, Bern, Switzerland. 8Institute of Biotechnology, University of Helsinki, Helsinki, Finland. 9Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland. 10Department of Physics, University of Helsinki, Helsinki, Finland. 20 11Helmholtz-Zentrum Geesthacht, Zentrum für Material-und Küstenforschung GmbH Germany. 12Oxford University Museum of Natural History, Oxford, OX1 3PW, UK. 1 bioRxiv preprint doi: https://doi.org/10.1101/785360; this version posted October 10, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 13Department of Anthropology and Archaeology, University of Bristol, Bristol, UK. 14Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK.
    [Show full text]
  • Amphibians 1) Transition to Land A) Life on Terrestrial Earth Is a Major
    Amphibians 1) Transition to land a) Life on terrestrial earth is a major theme for all non-fish vertebrates also known as Tetrapoda b) Of Tetrapoda there are two major groups Amphibians and amniotes c) The movement form water to land is one of the most complicated and dramatic events of the evolution of animals i) Land is physically hazardous for an animal that evolved in water, is made mostly of water, and all cellular activities occur in water. ii) Plants, snails, and many arthropods made the transition before vertebrates, which provided a plentiful food source. iii) With the transition to land, vertebrates had to adapt every organ system. d) Oxygen on land i) Atmospheric air contains 20 times more oxygen than water and diffuses more rapidly through air than water. ii) By the Devonian period (400+ million years ago) fish had diversified greatly. Some of these adaptations became useful for a terrestrial life (1) Fish had evolved an air sack within their body called a swim bladder. This would allow a space for gas exchange between an organism and air (a) These early fishes were most likely freshwater. Freshwater systems are more likely to evaporate or deoxygenate compares to salt water habitats. So having a vascularized swim bladder or lung would be beneficial. (b) To this day scientist still debate heavily on whether the swim bladder evolved for buoyancy control or lung first. (2) Fish also had evolved external nares for chemoreception. In a terrestrial environment these nares can be used to draw in air to the swim bladder/lung (3) Both of these structures show great examples of evolution utilizing existing structures to turn into something new and more adapted e) However both of the characteristics are shared among fishes and tetrapods, the big shift came in the bone structure of the limbs.
    [Show full text]
  • 2. Bilateral Cleft Anatomy 19
    BILATERAL CLEFT ANATOMY IS ATTACHED TO THE SINGLE CLEFT THE PREMAXILLA NORMALLY ROTATED OUTWARD MAXILLA ON ONE SIDE AND THIS ENTIRE COMPONENT IS THE CLEFT SIDE MAXILLA IN AN VARYING DEGREES FROM ASYMMETRICAL DIFFERENT DISTORTION DOUBLE CLEFTS PRESENT AN ENTIRELY CONFIGURA TION IN THE COMPLETE BILATERAL CLEFT THE PREMAXILLA IS UNATTACHED THREE WHICH TO EITHER MAXILLA THUS THERE ARE SEPARATE COMPONENTS IN THEIR DISTORTION THE MAXILLAE ARE MORE OR LESS SYMMETRICAL TWO WHILE THE ARE USUALLY EQUAL TO EACH OTHER IN SIZE AND POSITION FORWARD ITS IN CENTRAL PREMAXILLARY ELEMENT PROCEEDS ON OWN WITHIN ITSELF FOR DIFFERENT DEGREES BUT WITH SYMMETRY EXCEPT IJI POSSIBLE DEVIATION FRONTONASAL THE COMPLETE SEPARATION OF THE CENTRAL COMPONENT OF PROLABIUM AND PREMAXILLA FROM THE LATERAL MAXILLARY SEGMENTS THE VASCULAR ABNORMALLY INFLUENCES NOSE PHILTRUM MUSCULATURE AND OF ALL THREE ELEMENTS ITY NERVE SUPPLY GROWTH DEVELOPMENT WHERE THE CLEFT IS INCOMPLETE ON BOTH SIDES THE DEFORMITY IS LESS AND IS STILL SYMMETRICAL IN SUCH CASE THERE IS USUALLY MORE OR LESS INTACT ALVEOLUS AND LITTLE OR NO PROTRUSION OF THE PRE THE MAXILLA THE COLUMELLA IS LIKELY TO BE LONGER THAN IN COMPLETE CLEFT BUT NOT OF NORMAL LENGTH SOMETIMES SOMETIMES THE DEGREE OF CLEFT VARIES ON EACH SIDE SIDE THE INCOMPLETENESS SHOWS AS ONLY THE SLIGHTEST NOTCH ON ONE SIDE OR THERE CLEFT ON THE OPPOSITE AND HALFWAY OR THREEQUARTER ON THE CLEFT ONE SIDE AND AN INCOMPLETE ONE CAN BE COMPLETE ON OF THE EXASPERATING ASPECT OTHER WHICH CONDITION EXAGGERATES THE ROTATION OF THE IN THE AND NOSE
    [Show full text]
  • O Esqueleto Pós-Craniano De Exaeretodon Riograndensis Abdala Et Al
    Rev. bras. paleontol. 10(2):79-94, Maio/Agosto 2007 © 2007 by the Sociedade Brasileira de Paleontologia O ESQUELETO PÓS-CRANIANO DE EXAERETODON RIOGRANDENSIS ABDALA ET AL. (CYNODONTIA, TRAVERSODONTIDAE), TRIÁSSICO DO BRASIL TÉO VEIGA DE OLIVEIRA, CESAR LEANDRO SCHULTZ & MARINA BENTO SOARES Instituto de Geociências, UFRGS, Avenida Bento Gonçalves, 9500, 91501-970, Porto Alegre, RS, Brasil. [email protected], [email protected], [email protected] RESUMO – Pela primeira vez, elementos pós-cranianos de Exaeretodon riograndensis, um cinodonte traversodontídeo da Cenozona de Rhynchosauria da Formação Santa Maria, Neotriássico do sul do Brasil, são descritos e comparados com E. frenguellii e outros cinodontes não-mamalianos. O material inclui parte da coluna vertebral, radio, ulna e elementos da cintura pélvica. As diferenças mais significativas em relação a E. frenguellii estão na morfologia e nas dimensões do arco neural do atlas, na presença de intercentros em vértebras cervicais posteriores ao áxis e na ausência da dilatação do ápice do espinho neural das vértebras truncais. A morfologia da região sacral da coluna, do rádio, da ulna e da cintura pélvica são concordantes com o observado em E. frenguellii. A comparação com outros táxons de cinodontes não-mamalianos permite a observação da nítida evolução em mosaico do esqueleto pós-craniano destes animais: E. riograndensis mostra alguns caracteres similares a outros Cynognathia (grupo ao qual pertence), enquanto outros são mais próximos aos observados em alguns Probainognathia (incluindo mamíferos), como a natureza mais avançada do complexo atlas-áxis. Palavras-chave: Triássico, Brasil, Formação Santa Maria, Traversodontidae, Exaeretodon riograndensis, pós-crânio. ABSTRACT – THE POSTCRANIAL SKELETON OF EXAERETODON RIOGRANDENSIS ABDALA ET AL.
    [Show full text]
  • Micheli Stefanello
    UNIVERSIDADE FEDERAL DE SANTA MARIA CENTRO DE CIÊNCIAS NATURAIS E EXATAS PROGRAMA DE PÓS-GRADUAÇÃO EM BIODIVERSIDADE ANIMAL Micheli Stefanello DESCRIÇÃO E FILOGENIA DE UM NOVO ESPÉCIME DE CINODONTE PROBAINOGNÁTIO DO TRIÁSSICO SUL-BRASILEIRO Santa Maria, RS 2018 Micheli Stefanello DESCRIÇÃO E FILOGENIA DE UM NOVO ESPÉCIME DE CINODONTE PROBAINOGNÁTIO DO TRIÁSSICO SUL-BRASILEIRO Dissertação apresentada ao Curso de Mestrado do Programa de Pós-Graduação em Biodiversidade Animal, Área de Concentração em Sistemática e Biologia Evolutiva, da Universidade Federal de Santa Maria (UFSM, RS), como requisito parcial para obtenção do grau de Mestre em Ciências Biológicas – Área Biodiversidade Animal. Orientador: Prof. Dr. Sérgio Dias da Silva Santa Maria, RS 2018 Micheli Stefanello DESCRIÇÃO E FILOGENIA DE UM NOVO ESPÉCIME DE CINODONTE PROBAINOGNÁTIO DO TRIÁSSICO SUL-BRASILEIRO Dissertação apresentada ao Curso de Mestrado do Programa de Pós-Graduação em Biodiversidade Animal, Área de Concentração em Sistemática e Biologia Evolutiva, da Universidade Federal de Santa Maria (UFSM, RS), como requisito parcial para obtenção do grau de Mestre em Ciências Biológicas – Área Biodiversidade Animal. Aprovada em 28 de fevereiro de 2018: Santa Maria, RS 2018 AGRADECIMENTOS Ao meu orientador, Dr. Sérgio Dias da Silva, pela orientação, por todo o tempo despendido ao longo desse mestrado e por possibilitar meu aprimoramento na área a qual tenho apreço. Aos colegas do Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia da Universidade Federal de Santa Maria (CAPPA/UFSM) e do Laboratório de Paleobiodiversidade Triássica, dessa mesma instituição, pela convivência e por terem ajudado-me de diferentes formas ao longo do mestrado. Em especial, ao colega Rodrigo Temp Müller, pela coleta do espécime (objeto de estudo dessa dissertação), por toda a ajuda com o TNT e com as figuras, e por auxiliar-me de inúmeras formas.
    [Show full text]
  • Study Guide Medical Terminology by Thea Liza Batan About the Author
    Study Guide Medical Terminology By Thea Liza Batan About the Author Thea Liza Batan earned a Master of Science in Nursing Administration in 2007 from Xavier University in Cincinnati, Ohio. She has worked as a staff nurse, nurse instructor, and level department head. She currently works as a simulation coordinator and a free- lance writer specializing in nursing and healthcare. All terms mentioned in this text that are known to be trademarks or service marks have been appropriately capitalized. Use of a term in this text shouldn’t be regarded as affecting the validity of any trademark or service mark. Copyright © 2017 by Penn Foster, Inc. All rights reserved. No part of the material protected by this copyright may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the copyright owner. Requests for permission to make copies of any part of the work should be mailed to Copyright Permissions, Penn Foster, 925 Oak Street, Scranton, Pennsylvania 18515. Printed in the United States of America CONTENTS INSTRUCTIONS 1 READING ASSIGNMENTS 3 LESSON 1: THE FUNDAMENTALS OF MEDICAL TERMINOLOGY 5 LESSON 2: DIAGNOSIS, INTERVENTION, AND HUMAN BODY TERMS 28 LESSON 3: MUSCULOSKELETAL, CIRCULATORY, AND RESPIRATORY SYSTEM TERMS 44 LESSON 4: DIGESTIVE, URINARY, AND REPRODUCTIVE SYSTEM TERMS 69 LESSON 5: INTEGUMENTARY, NERVOUS, AND ENDOCRINE S YSTEM TERMS 96 SELF-CHECK ANSWERS 134 © PENN FOSTER, INC. 2017 MEDICAL TERMINOLOGY PAGE III Contents INSTRUCTIONS INTRODUCTION Welcome to your course on medical terminology. You’re taking this course because you’re most likely interested in pursuing a health and science career, which entails ­proficiency­in­communicating­with­healthcare­professionals­such­as­physicians,­nurses,­ or dentists.
    [Show full text]
  • Mammalian Origins Major Groups of Synapsida
    Mammalogy 4764 9/16/2009 Chapter 4 “Reptile” Mammalian Origins Early mammal Carnivore Amniota Herbivore Feldhamer Table 4.1 Savage and Long 1986 Major Fig. 3.2, Vaughn, Fig. 4.1, Feldhamer groups Mammalian Origins of Dimetrodon Overview Synapsida Synapsids Pelycosaurs and Therapsids First Mammals Mesozoic Era appear Feldhamer Fig. 4.2 Cenozoic Era radiate Savage and Long 1986 Pelycosaur Skull, jaw musculature, and teeth Cynodontia -- Advanced, predaceous therapsids Pelycosaur Scymnognathus Cynognathus Therapsid Early Cynodont Derived Therapsid/Mammal Primitive Late Cynodont Fig. 3.2, Vaughn Thrinaxodon Fig 4.3 & 4, Feldhamer 1 Mammalogy 4764 9/16/2009 Skeletal transition Extinction of Cynodonts Possibly competition from dinosaurs Pelycosaur Early Cynodonts were dog-size, last surviving were squirrel sized Fig. 4.15 Mammals that survived while Cynodonts went extinct (contemporary) were mouse-sized. Cynodont Thrinaxodon Modern Mammal Fig. 3.5, Vaughn Fig. 4.16c, Early Cynodont Early mammals Changes in land masses Feldhamer 4.11 200 - 250 million years ago Derived characters: Dentary/squamosal jaw articulation Diphyodont dentition 200 MYA 180 MYA Mammary glands Secondary palate Early Mid- Viviparity (loss of eggshell) When? Jurassic Jurassic 65 MYA 135 MYA Early Early Cretaceous Cenozoic Feldhamer 4.5, 4.9 Skull and teeth of mammals 2 Mammalogy 4764 9/16/2009 Teeth and Dentition of Mammals Teeth Heterodont teeth with different functions Differentiated on the basis of function, resulting in increased One of the major keys efficiency acquiring and digesting food. to success of mammals Teeth occur in 3 bones of skull: Teeth of mammals are premaxilla, maxilla, dentary extremely variable with different diets -- more than other taxa Feldhamer et al.
    [Show full text]
  • The Ear in Mammal-Like Reptiles and Early Mammals
    Acta Palaeontologica Polonica Vol. 28, No. 1-2 pp, 147-158 Warszawa, 1983 Second Symposium on Mesozoic T erre stial Ecosystems, Jadwisin 1981 KENNETH A. KERMACK and FRANCES MUSSETT THE EAR IN MAMMAL-LIKE REPTILES AND EARLY MAMMALS KERMACK, K . A. a nd MUSS ETT, F.: The ear in mammal-like r eptiles an d early mammals. Acta Palaeont. P olonica , 28, 1-2, 147-158, 1983. Th e early m embers of the Theropsida lacked a tympanic membrane. In the later theropslds, the Therapsid a, a tym p an ic membrane develop ed from thc skin on the lateral side of th e lower jaw. The tympanum is not homologous In the Therapsida and ' t he Sauropslda. The ther apsid ea r w as a poor receiver of airborne sound, both In hi gh frequency r esp onse and In the r ange of frequencies encompassed. With the radiation of the Sauropsida in the Triassic the large therapsids became extinct, the small therap si ds evolv ed In to the mammal s and became nocturnal. High frequency hearin g w as essen tial for the nocturn al mode of life; quadrate and arttcutar became diss ociated from the jaw hinge to become the m ammali an au di tory ossi cles . I n the Theria the cochlea became coil ed. The spiral cochlea could n ot have existed until there w as a middle ear w ith the n ec essary h ig h f re q uency r esp onse. This m ay n ot have been until the Cretace ous.
    [Show full text]
  • Width Measured at the Level of Anterior Squamosal/Parietal Suture
    Fig. 5. (A) Scaling of brain vault size (width measured at the level of anterior squamosal/parietal suture) relative to skull size (measured at the distance between the left versus right temporomandibular joints). This shows that allometry of small size of Hadrocodium, by itself, is not sufficient to account for its very large braincase. Had-rocodium's brain vault is larger (wider) than expected for the crown-group mammals with similar skull width from the allometrical regression. By contrast, all contemporaneous mammaliaforms (triangles: Sinoconodon, Morganucodon, and Haldanodon) with the postdentary trough and meckelian groove have smaller (narrower) brain vaults than those living mammal taxa (and Hadrocodium) of comparable skull size. The brain vault is narrower in nonmammaliaform cynodonts (squares: Chaliminia, Massetoganthus, Probelesodon, Probainognathus, and Yunnanodon) than in mammaliaform stem taxa and much narrower than expected for crown group mammals of similar size. The allometric equation (natural logarithmic scale) for the brain vault width (Y) to the skull width at the level of TMJ (X) for species in the mammalian crown groups (circles: 37 living and 8 fossil species): Y =0.98X -0.31 (R2 – 0.715). Data from cynodonts, mammaliaforms, and Hadrocodium are added second arily for comparison with the regression of extant and fossil species of mammalian crown group. (B) Estimated body-size distributions of mammaliaform insectivores in the Early Jurassic Lufeng fauna [following method of Gingerich (50)]. The estimated 2-g body mass of Hadrocodium is in strong contrast to its contemporary mammaliaforms of the Late Triassic and Early Jurassic, such as Sinconodon (from ~13 to ~517 g, based on skull length from 22 to 62 mm) and Morganucodon (from 27 to 89 g, based on skull length from 27 to 38 mm).
    [Show full text]
  • The Mesozoic Era Alvarez, W.(1997)
    Alles Introductory Biology: Illustrated Lecture Presentations Instructor David L. Alles Western Washington University ----------------------- Part Three: The Integration of Biological Knowledge Vertebrate Evolution in the Late Paleozoic and Mesozoic Eras ----------------------- Vertebrate Evolution in the Late Paleozoic and Mesozoic • Amphibians to Reptiles Internal Fertilization, the Amniotic Egg, and a Water-Tight Skin • The Adaptive Radiation of Reptiles from Scales to Hair and Feathers • Therapsids to Mammals • Dinosaurs to Birds Ectothermy to Endothermy The Evolution of Reptiles The Phanerozoic Eon 444 365 251 Paleozoic Era 542 m.y.a. 488 416 360 299 Camb. Ordov. Sil. Devo. Carbon. Perm. Cambrian Pikaia Fish Fish First First Explosion w/o jaws w/ jaws Amphibians Reptiles 210 65 Mesozoic Era 251 200 180 150 145 Triassic Jurassic Cretaceous First First First T. rex Dinosaurs Mammals Birds Cenozoic Era Last Ice Age 65 56 34 23 5 1.8 0.01 Paleo. Eocene Oligo. Miocene Plio. Ple. Present Early Primate First New First First Modern Cantius World Monkeys Apes Hominins Humans A modern Amphibian—the toad A modern day Reptile—a skink, note the finely outlined scales. A Comparison of Amphibian and Reptile Reproduction The oldest known reptile is Hylonomus lyelli dating to ~ 320 m.y.a.. The earliest or stem reptiles radiated into therapsids leading to mammals, and archosaurs leading to all the other reptile groups including the thecodontians, ancestors of the dinosaurs. Dimetrodon, a Mammal-like Reptile of the Early Permian Dicynodonts were a group of therapsids of the late Permian. Web Reference http://www.museums.org.za/sam/resource/palaeo/cluver/index.html Therapsids experienced an adaptive radiation during the Permian, but suffered heavy extinctions during the end Permian mass extinction.
    [Show full text]
  • Mammals from the Mesozoic of Mongolia
    Mammals from the Mesozoic of Mongolia Introduction and Simpson (1926) dcscrihed these as placental (eutherian) insectivores. 'l'he deltathcroids originally Mongolia produces one of the world's most extraordi- included with the insectivores, more recently have narily preserved assemblages of hlesozoic ma~nmals. t)een assigned to the Metatheria (Kielan-Jaworowska Unlike fossils at most Mesozoic sites, Inany of these and Nesov, 1990). For ahout 40 years these were the remains are skulls, and in some cases these are asso- only Mesozoic ~nanimalsknown from Mongolia. ciated with postcranial skeletons. Ry contrast, 'I'he next discoveries in Mongolia were made by the Mesozoic mammals at well-known sites in North Polish-Mongolian Palaeontological Expeditions America and other continents have produced less (1963-1971) initially led by Naydin Dovchin, then by complete material, usually incomplete jaws with den- Rinchen Barsbold on the Mongolian side, and Zofia titions, or isolated teeth. In addition to the rich Kielan-Jaworowska on the Polish side, Kazi~nierz samples of skulls and skeletons representing Late Koualski led the expedition in 1964. Late Cretaceous Cretaceous mam~nals,certain localities in Mongolia ma~nmalswere collected in three Gohi Desert regions: are also known for less well preserved, but important, Bayan Zag (Djadokhta Formation), Nenlegt and remains of Early Cretaceous mammals. The mammals Khulsan in the Nemegt Valley (Baruungoyot from hoth Early and Late Cretaceous intervals have Formation), and llcrmiin 'ISav, south-\vest of the increased our understanding of diversification and Neniegt Valley, in the Red beds of Hermiin 'rsav, morphologic variation in archaic mammals. which have heen regarded as a stratigraphic ecluivalent Potentially this new information has hearing on the of the Baruungoyot Formation (Gradzinslti r't crl., phylogenetic relationships among major branches of 1977).
    [Show full text]
  • Femur of a Morganucodontid Mammal from the Middle Jurassic of Central Russia
    Femur of a morganucodontid mammal from the Middle Jurassic of Central Russia PETR P. GAMBARYAN and ALEXANDER 0.AVERIANOV Gambaryan, P.P. & Averianov, A.O. 2001. Femur of a morganucodontid mammal from the Middle Jurassic of Central Russia. -Acta Palaeontologica Polonica 46,1,99-112. We describe a nearly complete mammalian femur from the Middle Jurassic (upper Bathonian) from Peski quarry, situated some 100 km south east of Moscow, central Rus- sia. It is similar to the femora of Morganucodontidae in having a globular femoral head, separated from the greater trochanter and reflected dorsally, fovea capitis present, both trochanters triangular and located on the same plane, distal end flat, mediolaterally expanded, and somewhat bent ventrally, and in the shape and proportions of distal condyles. It is referred to as Morganucodontidae gen. et sp. indet. It is the first representa- tive of this group of mammals in Eastern Europe from the third Mesozoic mammal local- ity discovered in Russia. Exquisite preservation of the bone surface allowed us to recon- struct partial hind limb musculature. We reconstruct m. iliopsoas as inserting on the ridge, which starts at the lesser trochanter and extends along the medial femoral margin for more than half of the femur length. On this basis we conclude that the mode of loco- motion of the Peski morganucodontid was similar to that of modern echidnas. During the propulsive phase the femur did not retract and the step elongation was provided by pronation of the femur. Key words : Mammalia, Morganucodontidae, femur, anatomy, locomotion, Jurassic, Russia. Petr P. Gambaryan [[email protected]] and Alexander 0.
    [Show full text]