DINOSAUR TRACKS AND OTHER FOSSIL FOOTPRINTS OF THE WESTERN UNITED STATES Martin Lockley and Adrian P. Hunt artwork by Paul Koroshetz COLUMBIA UNIVERSITY PRESS NEW YORK
CONTENTS Foreword Preface Acknowledgments Abbreviations of Institutional Collections of Fossil Tracks xi xiii xviii xxi 1. An Introduction to Fossil Footprints 3 How to Observe and Record Tracks and Trackways 9 Box 1.1 Who Dun It? 11 Naming Tracks 15 How Are Tracks Preserved? 18 Where Are Tracks Preserved? 20 Box 1.2 Elite Tracks 22 Interpreting Fossil Footprints 23 Interpreting Track Assemblages 25 Tracks Through Time 26 Institutional Collections of Tracks 28 Conservation and Preservation 29
viii Contents 2. Ancient Tracks: The Paleozoic Era 33 Western Traces in the "Age of Amphibians" 34 Carboniferous Tracks: Amphibian, Reptile, or Other? 35 Box 2.1 Paleozoic Horses? 36 Tracks of the Arid Permian 39 "Stone Tracks" of the Coconino Sandstone 40 The Lyons Sandstone: Twin of the Coconino 44 Interpreting Tracks and Track Habitats 47 The Latest Big Discovery 57 3. Archosaur Ascendancy: The Triassic 65 An Overview of Triassic Trackmakers and Tracks 67 The Moenkopi Formation of the Early and Middle Triassic 69 Tracks Around the World 73 Box 3.1 Which Came First, the Dinosaur or the Track? 75 The Chinle Group of the Late Triassic 76 The Southern Colorado Plateau Region of the Chinle 77 Box 3.2 The Coelophysis Crisis 81 The Eastern Region of the Chinle 85 Box 3.3 What Do Prosauropod Tracks Look Like? 9 The Northern Colorado Plateau Region of the Chinle 93 Interpreting Chinle Tracks and Track Habitats 98 Mass Extinctions at the Triassic-Jurassic Boundary 99 4. Days of Dinosaur Dominance I: The Jurassic 109 Sand Seas of the Early Jurassic 112 Desert Trackmakers of the Wingate Formation 114 More Desert Trackmakers of the Moenave Formation 118 Kayenta Tracks and the Problem of "Provincial Taxonomy" 119 Box 4.1 Different Species? Or Different Ages? 120 An Abundance of Tracks in the Navajo Formation 129 Is It Mammaloid? 137 The Pterosaur Tracks Dispute 140 Box 4.2 What's in a Name? 144 Early Jurassic Climates and Biogeography 147
Contents ix Were Dinosaurs Mostly Meat-Eaters? 149 The Moab Megatracksite of the Middle Jurassic 150 The Real Pterosaur Tracks Story 158 Morrison Formation Tracks of the Late Jurassic: The Golden Age of Brontosaurs 164 Box 4.3 The Sauropod Straddle 175 Tracks Versus Bones 176 5. Days of Dinosaur Dominance II: The Cretaceous 181 An Overview of Early Cretaceous Tracks 183 "Swimming" Brontosaurs and the Dangers of Misinterpretation 185 Box 5.1 Problematic Potholes 191 Tracks Along the Shores of the Western Interior Seaway 192 Parallel Trackways and Dinosaur Herds 196 Box 5.2 Digging for Dinosaur Tracks 199 Box 5.3 Mama, Papa, and Baby Dinosaurs 207 The Dinosaur Freeway 209 Early Cretaceous Bird and Crocodile Tracks 211 Overview of the Late Cretaceous Environment 213 Coal Deposits of the Mesa Verde Group 216 The Case of the "Mystery Dinosaur" 217 Bird, Frog, Pterosaur(?) and Baby Dinosaur(?) Tracks 223 Underground Hazards 226 Rare Tracks of the Laramie Formation 229 Box5.4TrexTrax? 234 Raton Formation Tracks and the Cretaceous Extinctions 237 6. The Age of Birds and Mammals: The Cenozoic Era 243 Paleocene Tracks and the Survivors of the Mass Extinction 245 Box 6.1 Is the Decimal System Based on Five Fingers and Five Toes? 249 One-of-a-Kind Tracks from the Eocene 250 The Puzzle of Miocene Tracks in the Oligocene 257 Box 6.2 Big Bird Tracks Have Paleontologists All Aflutter 262 Camels, Bear-Dogs, and Other Denizens of the Miocene 265 Box 6.3 Ancient Ships of the Desert 268 Pliocene Tracks and the Camel That Died While Standing 273
x Contents Mammoths of the Pleistocene 274 Box 6.4 Linking Tracks with the Trackmakers 274 The Case of the Carson City "Man Tracks" 277 7. Tracks Galore, and What They Can Tell Us 285 Naming Tracks and Identifying Trackmakers 286 Individual Behavior 287 Groups, Populations, and Social Behavior 288 Dinosaur Biomass 289 Trampling 291 Tracks and Ancient Ecology 292 Sedimentological Controls on the Distribution of Track-Bearing Strata 296 Tracks More Common Than Bones 298 A Finite and Valuable Resource 301 Appendix: Fossil Footprint Sites and Exhibits in the Western United States 303 Annotated Bibliography 311 General Index 325 Systematic Ichnological Index 336