Book excerpt: During the Mesozoic era, the southwestern US was a tropical or semitropical region of seas and lowland swamps, inhabited by reptiles of all sizes and descriptions. This introduction to dinosaurs that once inhabited what are now the western states gives a background on paleontology, the dating of fossils, the variety in types, sizes and habits, and several theories about the reasons for the disappearance of the dinosaurs. Extensively illustrated with drawings by John C. McLoughlin, this book is a readable, accurate introduction valuable to tourists, young scientists, and other readers interested in this era of southwestern history.