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Evolution of the Mammal-Like Reptiles

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The Origin and Evolution of Mammals This page intentionally left blank The Origin and Evolution of Mammals T. S. Kemp Oxford University 1 1 Great Clarendon Street, Oxford OX2 6DP Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Bangkok Buenos Aires Cape Town Chennai Dar es Salaam Delhi Hong Kong Istanbul Karachi Kolkata Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi São Paulo Shanghai Taipei Tokyo Toronto Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York © Oxford University Press, 2005 The moral rights of the author have been asserted Database right Oxford University Press (maker) First published 2005 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this book in any other binding or cover and you must impose this same condition on any acquirer A catalogue record for this title is available from the British Library Library of Congress Cataloging in Publication Data (Data available) ISBN 0 19 850760 7 (hbk) ISBN 0 19 850761 5 (pbk) 10987654321 Typeset by Newgen Imaging Systems (P) Ltd., Chennai, India Printed in Great Britain on acid-free paper by Antony Rowe, Chippenham Preface This book arose from twin aims: to update my 1982 book on the origin of mammals in relation to the steady stream of new fossils that have been found or re-described in the last two decades; and to elaborate at a similar level the story of what happened next – the radiation of mammals after the end of the Cretaceous. In the latter case even more than in the former, constraints of space and time have meant severely limiting this enormous field and even then I have been able to do little more than point to the most important fossils, outline the ideas, and give guidance to appropriate recent literature for the details. The whole corresponds to a twelve lecture option I give to Oxford Honour students, and I am very grateful to all those who have, over the years, attended in encouraging numbers and stimulated me with their interest, despite the alternative, fashionable attractions on offer in the biological sciences. I hope they will find this volume helpful. I am particularly grateful to Professor Zofia Kielan-Jaworowska who read and very help- fully commented on Chapter 5, and was generous enough to allow me access to the manu- script of her joint new book Mammals from the age of dinosaurs: origins, evolution, and structure, a magnificent, comprehensive work which will be the standard account of Mesozoic mam- mals for the foreseeable future. I should also like to take the opportunity of thanking Fernando Abdala for reading Chapter 3, and to Sam Turvey for reading Chapters 6 and 7; both made extremely helpful suggestions for improving the manuscript. I am grateful to Kuba Kopycinski for his helpful advice on electronic preparation of figures. Acknowledgements are due to the following publishers and journals for kindly giving permission to reproduce illustrations. Acta Palaeontologica Polonica; American Journal of Science; Bernard Price Institute for Paleontological Research; C.N.R.S., Paris; California University Press; Cambridge University Press; Carnegie Museum of Natural History; Columbia University Press; Elsevier Ltd; Evolution; Geological Society of America; Indiana University Press; John Wiley and Sons; Journal of Morphology; Kluwer Academic Press; Monash University, Melbourne; Musée Nationale d’Histoire Naturelle, Paris; Museum of Comparative Zoology, Harvard; Museum of Northern Arizona Press; National Academy of Sciences, U.S.A.; National Geographic Society; National Museum of Bloemfontein; National Research Council of Canada; Natural History Museum, London; Nature; Oxford University Press; Paleobiology; Paleontologicheskii Zhurnal; Prentice Hall; Royal Society of Edinburgh; Royal Society of London; Royal Zoological Society of New South Wales; Science; Selbstverlag Fachbereich Geowissenschaften; Serviços Geológicos de Portugal; Smithsonian Institution Press; Society for the Study of Mammalian Evolution; Society of Vertebrate Paleontology; South African Museum; Springer-Verlag; University of Michigan; University of Wyoming Department of Geology and Geophysics; W. H. Freeman; Zoological Journal of the Linnean Society. University Museum and St John’s College Oxford This page intentionally left blank For Mal/gosia with love and thanks This page intentionally left blank Contents 1 Introduction The definition of Mammalia 1 A sketch of the plot 3 Palaeobiological questions 4 2 Time and classification The geological timescale 6 Classification 9 3 Evolution of the mammal-like reptiles The vertebrate conquest of land: origin of the Amniota 14 Pelycosauria: the basal synapsid radiation 19 The origin and early radiation of the Therapsida 26 Biarmosuchia 31 Dinocephalia 33 Anomodontia 39 Gorgonopsia 52 Therocephalia 56 Cynodontia 60 Interrelationships of Cynodontia and the phylogenetic position of Mammalia 75 Overview of the interrelationships and evolution of the Therapsida 78 The palaeoecology and evolution of Synapsida 80 4 Evolution of mammalian biology Feeding 90 Locomotion 101 Sense organs and brain 113 Growth and development 120 Temperature physiology 121 An integrated view of the origin of mammalian biology 129 The significance of miniaturisation 135 5 The Mesozoic mammals The diversity of the Mesozoic mammals 138 An overview of the interrelationships and evolution 180 The general biology of the Mesozoic mammals 183 End of the era: the K/T mass extinction and its aftermath 186 x CONTENTS 6 Living and fossil marsupials Living marsupials and their interrelationships 191 The fossil record of marsupials 196 An overview of marsupial evolution 216 7 Living and fossil placentals Living placentals and their interrelationships 222 Cretaceous fossils 226 Palaeocene fossils: the archaic placentals 230 The origin and radiation of the modern orders 250 Overview of placental evolution 274 References 291 Index 325 CHAPTER 1 Introduction There are about 4,600 species of animals today that Haemothermia concept, including the beta-globin are called mammals because, despite an astonishing gene and 18S rRNA. Gardiner’s view briefly became diversity of form and habitat, they all share a long a cause célèbre in part for its sheer heterodoxy, but all list of characters not found in any other organisms, concerned have since rejected it on the grounds that such as the presence of mammary glands, the single a careful, comprehensive analysis of the characters bone in the lower jaw, and the neocortex of the fore- supports the traditional view (Kemp 1988b), particu- brain. This makes them unambiguously distinct larly if the characters of the relevant fossils are from their closest living relatives, and their unique taken into account (Gauthier, Kluge, and Rowe characters together define a monophyletic taxon, 1988). Nor does it receive any significant support at the class Mammalia. Three subgroups are readily all from the mass of nucleotide sequence data now distinguished amongst the living mammals. The available. Monotremata are the egg-laying mammals of Australasia, consisting only of two species of The definition of Mammalia echidna and a single platypus species; for all their primitive reproductive biology, monotremes are The formal definition of Mammalia is simple as far fully mammalian in their general structure and as the living mammals are concerned, because of biology. The Marsupialia, or Metatheria are the the large number of unique characters they possess. pouched mammals, whose approximately 260 However, the fossil record makes the situation a species dominate the mammalian fauna of Australia, good deal less clear-cut. The first part of this book and also occur as part of the indigenous fauna of the is about the extraordinarily good fossil record of Americas. By far the largest group of living mam- animals that were, to varying degrees, intermediate mals are the Placentalia, or Eutheria with about 4,350 in grade between the modern mammals and the species divided into usually eighteen recent orders. last common ancestor between them and their It is virtually unanimously accepted that the clos- living sister group. They are known informally as est living relatives, the sister group, of mammals the ‘mammal-like reptiles’, and more formally as consists of the reptiles and the birds. The only seri- the non-mammalian Synapsida. By definition, a ous dissent from this view in recent years was that of mammal-like reptile possesses some, but not all the Gardiner (1982) who advocated that the birds alone characters that define living mammals. A semantic and mammals were sister groups, the two constitut- difficulty arises about defining a mammal because ing a taxon Haemothermia, defined among other a decision has to be taken on which, if any of the characters by the endothermic (‘warm-blooded’) mammal-like reptiles should be included. The ear-
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