Table Of ContentThe invasion of land M W h e n t h e I n va s I o n
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by ocean-dwelling plants and animals was one of the most G
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revolutionary events in the evolution of life on Earth, yet the animal invasion almost e
failed—twice—because of the twin mass extinctions of the Late Devonian Epoch.
Some 359 to 375 million years ago, these catastrophic events dealt our ancestors a o f L a n d fa I L e d
blow that almost drove them back into the sea. If those extinctions had been just a W
bit more severe, spiders and insects—instead of vertebrates—might have become the h
ecologically dominant forms of animal life on land. E
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This book examines T
h The Legacy of the Devonian Extinctions
the profound evolutionary consequences of the Late
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Devonian extinctions and the various theories proposed to explain their occurrence.
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Only one group of four-limbed vertebrates exists on Earth, while other tetrapod-like n
v George R. McGhee Jr.
fishes are extinct. This gap is why the idea of “fish with feet” seems so peculiar to
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us, yet such animals were once a vital part of our world. If the Devonian extinctions s
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had not happened, members of these species, like the famous Acanthostega and o
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Ichthyostega, might have continued to live in our rivers and lakes. Synthesizing
decades of research and including a wealth of new discoveries, this accessible, o
f
comprehensive text explores the causes of the Devonian extinctions, the reasons
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vertebrates were so severely affected, and the potential evolution of the modern a
world if the extinctions had never taken place. n
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“McGhee
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is able to organize a vast literature into a coherent evolutionary story a
that is quite unique. From the origin of plants and animals through the Devonian IL
era, this book is a marvelous read. It is important for a wide variety of geologists and E
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biologists and for any readers interested in paleontology and environmental change.”
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—PEtEr ShEEhan, curatOr, MILwaukEE PubLIc MuSEuM he
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George R. McGhee Jr. cy
is Distinguished Professor of Paleobiology at rutgers of th
university and a Member of the konrad Lorenz Institute for Evolution and e
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cognition research in klosterneuburg, austria. he has held research positions at ev
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the university of tübingen, the Field Museum of natural history, and the american ia
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Museum of natural history. Ex
tin
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Critical Moments and Perspectives in Earth history and Paleobiology tio
n
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cover art: kalliopi Monoyios
cover design: Milenda nan Ok Lee
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CoLUMBIa UnIvERsITY PREss | nEW YoRK o
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cup.columbia.edu bia
PRInted In the U.s.a.
When the Invasion of Land Failed
Critical Moments and Perspectives in Earth History and Paleobiology
CrItICaL MoMents and PersPeCtIves In
earth hIstory and PaLeobIoLogy
david J. bottjer, richard K. bambach, and hans-dieter sues, editors
Mark a. s. McMenamin and dianna L. s. McMenamin, The Emergence of Animals: The
Cambrian Breakthrough
anthony hallam, Phanerozoic Sea-Level Changes
douglas h. erwin, The Great Paleozoic Crisis: Life and Death in the Permian
betsey dexter dyer and robert alan obar, Tracing the History of Eukaryotic Cells: The
Enigmatic Smile
donald r. Prothero, The Eocene-Oligocene Transition: Paradise Lost
george r. Mcghee Jr., The Late Devonian Mass Extinction: The Frasnian/Famennian
Crisis
J. david archibald, Dinosaur Extinction and the End of an Era: What the Fossils Say
ronald e. Martin, One Long Experiment: Scale and Process in Earth History
Judith totman Parrish, Interpreting Pre-Quaternary Climate from the Geologic Record
george r. Mcghee Jr., Theoretical Morphology: The Concept and Its Applications
Thomas M. Cronin, Principles of Paleoclimatology
andrey yu. Zhuravlev and robert riding, editors, The Ecology of the Cambrian Radiation
Patricia g. gensel and dianne edwards, editors, Plants Invade the Land: Evolutionary
and Environmental Perspectives
david J. bottjer, Walter etter, James W. hagadorn, and Carol M. tang, editors, Excep-
tional Fossil Preservation: A Unique View on the Evolution of Marine Life
barry d. Webby, Florentin Paris, Mary L. droser, and Ian g. Percival, editors, The Great
Ordovician Biodiversification Event
Frank K. McKinney, The Northern Adriatic Ecosystem: Deep Time in a Shallow Sea
hans-dieter sues and nicholas d. Fraser, Triassic Life on Land: The Great Transition
When the Invasion
of Land Failed
The Legacy of the Devonian Extinctions
George R. McGhee Jr.
Columbia university Press new york
Columbia University Press
Publishers Since 1893
new york Chichester, West sussex
cup.columbia.edu
Copyright © 2013 Columbia University Press
all rights reserved
Library of Congress Cataloging-in-Publication data
Mcghee, george r.
When the invasion of land failed : The legacy of the devonian extinctions /
george r. Mcghee Jr.
p. cm. — (Critical moments and perspectives in earth history
and paleobiology)
Includes bibliographical references and index.
Isbn 978-0-231-16056-8 (cloth : alk. paper) —
Isbn 978-0-231-16057-5 (pbk. : alk. paper) —
Isbn 978-0-231-53636-3 (ebook)
1. extinction (biology) 2. Paleontology—devonian.
3. Catastrophes (geology) I. title. II. series: Critical moments and
perspectives in earth history and paleobiology series.
Qe721.2.e97M393 2013
560’.174—dc23
2013011766
Columbia University Press books are printed on permanent and durable acid-free paper.
This book is printed on paper with recycled content.
Printed in the United states of america
c 10 9 8 7 6 5 4 3 2 1
p 10 9 8 7 6 5 4 3 2 1
cover art: Kalliopi Monoyios
cover design: Milenda nan ok Lee
references to websites (UrLs) were accurate at the time of writing. neither the author nor
Columbia University Press is responsible for UrLs that may have expired or changed since
the manuscript was prepared.
For Marae
Is gràdhaich leam thu.
Contents
Preface ix
CHAPTER 1 The evolution of Life on Land 1
CHAPTER 2 The Plants establish a beachhead 27
CHAPTER 3 The First animal Invasion 53
CHAPTER 4 The First Catastrophe and retreat 99
CHAPTER 5 The second animal Invasion 159
CHAPTER 6 The second Catastrophe and retreat 179
CHAPTER 7 victory at Last 213
CHAPTER 8 The Legacy of the devonian extinctions 263
notes 277
references 295
Index 313
Color plates insert between pages 98 and 99
Preface
This book is about the profound evolutionary consequences of the twin
extinction events that occurred in the Late devonian period of geologic
time, some 375 and 359 million years ago, for the evolution of terrestrial
animal life on earth. our ancestors, the first vertebrates on land, were
dealt a severe blow in their infancy by those catastrophic events, one
that almost drove them back into the sea. If those extinctions had been
just a bit more severe, spiders and insects might well have become the
ecologically dominant forms of animal life on land—we, the vertebrates,
would have remained in the oceans.
We know that five catastrophic losses of biological diversity have
occurred in the history of life on earth since the evolution of animals more
than 600 million years ago. each of these biodiversity crises, commonly
called the "big Five," changed the direction and pattern of the evolution
of life on earth and had consequences that extend to our present world.
The most recent of these biodiversity crises is the end-Cretaceous
extinction, which occurred 65 million years ago. The environmental
catastrophe that triggered the end-Cretaceous extinction destroyed the
dinosaurian ecosystem, a highly successful terrestrial ecosystem that
had persisted for 150 million years. We mammals owe our current eco-
logical dominance to that event. It was only after the destruction of the
dinosaurian ecosystem that mammals, in a classic example of ecological
