Lowell Dingus is Research Associate in Vertebrate Paleontology at the American Museum of Natural History in New York and the Natural History Museum of Los Angeles County. He is the author ofHell Creek, Montana,and coauthor ofWalking on EggsandThe Mistaken Extinction.Mark A. Norell is Chair of Paleontology at the American Museum of Natural History and coauthor ofUnearthing the Dragon. Together with Eugene Gaffney, Dingus and Norell coauthoredDiscovering Dinosaurs: Evolution, Extinction, and the Lessons of Prehistory(UC Press, winner of an American Library Association Award).