Preface

Vertebrate palaeontology is always in the news: astonishing, ancient basal chordate and vertebrate fossils are announced from China; fossil hunters argue about which was the largest dinosaur of all, or the oldest dinosaur with feathers; an ancient fossil bird is announced that adds 100 million years to their history; ever-older specimens of human beings are unearthed in Africa.

When I wrote this book in 1989, I felt that there was a need for an up-to-date account of what is known about the history of vertebrates, but also for a summary of the latest of these exciting discoveries. The first edition was published in 1990. The second edition, substantially modified, appeared in 1997. It offered extensive coverage of the new discoveries of the early 1990s, as well as comprehensive cladistic coverage of the main vertebrate clades. Since 1990, the book has hopped from publisher to publisher: it was commissioned by Unwin Hyman, who were soon after acquired by Harper Collins, and their science list was in turn acquired by Chapman & Hall, so the first edition appeared under three publishers' logos, in 1990, 1991 and 1995. The second edition appeared with Chapman & Hall, but they were then taken over by Kluwer, and this book was marketed by their Stanley Thornes subsidiary for a while, before passing to Blackwell Science in 2000. I hope these wandering days are now over.

The first edition appeared in Spanish in 1995 (Paleontología y evolución de los vertebrados, Edition Perfils, Lleida) and the second in Italian in 2000 (Paleontología dei Vertebrati, Franco Lucisano Editore, Milano), and a German edition is in progress. This is a measure of the international appeal of vertebrate palaeontology and the demand from students and instructors for up-to-date information.

The story of the evolution of the vertebrates, the animals with backbones, is fascinating. There is currently an explosion of new research ideas in the field — the origin of the vertebrates, dramatic new fish specimens unlike anything now living, the adaptations required for the move on to land, the relationships of the Palaeozoic and Mesozoic tetrapods, the origins and biology of the dinosaurs, the role of mass extinctions in vertebrate evolution, new Mesozoic birds, the earliest mammals, ecology and mammalian diversification, reconstructing the tree of life and reconciling morphological and molecular evidence, the origins and evolution ofhuman beings.

I have four aims in writing this book. First, I want to present a readable narrative of the history of the vertebrates that is accessible to any interested person, whether having a professional or an amateur interest in the subject. The book broadly follows the time-sequence of major events in the sea and on land, so that it can be read as a continuous narrative, or individual chapters may be read on their own. I have tried to show the adaptations of all major extinct groups, both in words and in pictures.

The second aim is to highlight major evolutionary anatomical changes among vertebrate groups. This book is not a classic anatomy text and there is no space to give a complete account of all aspects of the hard-part and soft-part anatomy of the major groups. However, I have selected certain evolutionary anatomical topics, such as the vertebrate brain, the jaws of bony fishes, tetrapod vertebral evolution, posture and gait in archosaurs and endothermy in mammals, to present an overview of current thinking, including evolutionary and developmental aspects, where appropriate.

The third aim is to show how palaeobiological information is obtained. It is important to understand the methods and debates, and not simply to assume that all knowledge is fixed and immutable. To do this, I summarize in Chapter 2 the methods used by vertebrate palaeontologists in collecting and preparing the fossils, in using them to learn about ancient environments, biomechanics and palaeobiology, and as evidence for discovering parts of the great evolutionary tree of life. Then, throughout the text, I present short boxed thematic sections that are divided into three categories: tree of life controversies (deuterostome relationships, jawless fishes, sarcopterygians, basal tetrapods, am-niotes, dinosaurs and the origin of birds, molecular information on mammalian phylogeny, hominin relationships), exceptional fossils or faunas (basal chor-dates from China, a rich fossil deposit of early tetrapods, dramatic new discoveries of Cretaceous birds, fossil mammals with hair, new basal humans from Chad) and palaeobiology of selected unusual ancient vertebrates (biology ofa helmeted fish, jaw action and diet of dicynodonts, biology of a pack-hunting dinosaur, thermal physiology of the dinosaurs, hair in pterosaurs, horse-eating birds, the earliest whales).

The fourth aim is to survey the present state of discovery of the tree of life of vertebrates. The clado-grams are set apart from the body of the text and full lists of diagnostic characters are given. In some cases, there are controversies among palaeontologists, or between the morphological and the molecular results, and these are explored. In many cases it was a difficult task to represent current views fairly, yet incisively. Some parts of the tree appear to have been relatively stable for ten years or more, whereas others are changing rapidly— these aspects are indicated. The cladograms throughout the book may be linked to provide an overview of the vertebrate tree of life, and this is replicated in the classification (Appendix).

I am indebted to many people. I thank Roger Jones and Clem Earle of Unwin Hyman who commissioned the first edition, and Ward Cooper of Chapman & Hall who steered the second edition through. The following people read parts of the first and second editions, or made other valuable contributions: Dick Aldridge, Peter Andrews, Chris Beard, Derek Briggs, Henri Cap-petta, Bob Carroll, Luis Chiappe, Jenny Clack, Mike Coates, Liz Cook, Joel Cracraft, Eric Delson, David Dineley, Susan Evans, Jens Franzen, Nick Fraser, Brian

Gardiner, Alan Gentry, David Gower, Lance Grande, fBev Halstead, Jim Hopson, Axel Hungerbühler, Christine Janis, Philippe Janvier, Dick Jefferies, Tom Kemp, Zofia Kielan-Jaworowska, Gillian King, Liz Loeffler, John Maisey, Andrew Milner, Alec Panchen, Mike Parrish, fColin Patterson, Mark Purnell, Jeremy Rayner, Robert Reisz, Bruce Rubidge, fBob Savage, Pascal Tassy, Paul Sereno, Glen Storrs, Mike Taylor, Nigel Trewin, David Unwin, Cyril Walker, Peter Wellnhofer and Bernard Wood. For the third edition, I thank Phil Donoghue and Kevin Padian for their helpful advice on how to update the second edition, as well as Kenneth Angielczyk, David Archibald, David Berman, Jenny Clack, Mike Coates, Joel Cracraft, Phil Donoghue, Gareth Dyke, Andrzej Elzanowski, Susan Evans, David Gower, Lance Grande, Christine Janis, Philippe Janvier, Jürgen Kriwet, Adrian Lister, Luo Zhe-Xi, Sean Modesto, Kevin Padian, Kevin Peterson, Mark Purnell, Robert Reisz, Olivier Rieppel, Chris Stringer, Bernard Wood and Adam Yates who read individual chapters, and Bill Harrison and Hezy Shoshani, who volunteered valuable comments.

My special thanks go to three artists, Libby Mul-queeny (Belfast) who drew most of the diagrams for the book in a frenzy of work, John Sibbick (Bath) who prepared the spectacular chapter openers, and Debbie Maizels (Surrey) for the new computer-generated artwork. I also thank those people, who are acknowledged separately throughout the book, who supplied photographs and drawings. Finally, thanks to Ian Francis and Delia Sandford at Blackwell Publishing for commissioning the revision, Rosie Hayden and Harry Langford for their careful work on the text, and Cee Pike for design work.

Michael J. Benton March 2004

Note. I would appreciate any corrections (fax -44-117925-3385 or e-mail to [email protected]). More details at http:/www.palaeo.bris.ac.uk/

There is a dedicated website for this book at http:// www.blackwellpublishing.com/benton where you can make web connections from, view the illustrations online, and find out more.

CHAPTER l

Vertebrate Origin

1 What are the closest living relatives of vertebrates?

2 When did deuterostomes and chordates originate?

3 What are the key characters of chordates?

4 How do extraordinary new fossil discoveries from China help us understand the ancestry of vertebrates?

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