For Marjorie Osborne

Scientific Consultant:

RAYMOND RYE, Museum Specialist, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C.

HEIDI JOHNSON, Earth Science and Paleontology, Lowell Junior High School, Bisbee, Arizona

Education Consultant:

MELINDA MURPHY, Media Specialist, Reed Elementary School, Cypress Fairbanks Independent School District, Houston, Texas

We would also like to thank Alison Brooks at George Washington University for help with our time line; Helen McGovern at the American Museum of Natural History in New York City for her kind assistance; Paul Coughlin for his imaginative photography; and at Random House, Cathy Goldsmith for her wonderful and creative design, Joy La Brack for her long hours of photo research, Mallory Loehr for her ongoing guidance and support, and most especially, our editor, Shana Corey, for her diligence, insight, and joyful enthusiasm throughout the process of creating this book.