There have been several juvenile presentations of the new views on dinosaurs, but Mannetti uses the revision process itself to edifying effect. Like many good children's science books, this one proceeds by posing questions which hook readers into following quite detailed arguments and explanations, and it gives readers the sense of participating in the theories' formulation. The existence of blood vessels in dinosaur bones or secondary palates in their mouths may not be of much interest as listed characteristics, but are as two of six duly explained reasons for the current belief that dinosaurs were not reptiles. The fossilized archaeopteryx discovered in 1862 is discussed in terms of the debates and dilemmas that ensued from the assumption that it had to be categorically a bird or a dinosaur--and of the uncertainties that remain. The characteristics of pterosaurs, which were not dinosaurs and not bird ancestors (the dinosaur group called coelurosaurs have that distinction), have meaning as solutions to problems solved in similar or comparable ways (white fur, swing-back wings, etc.) by bats, jet aircraft, or polar bears. A later chapter on the mystery of dinosaur extinction examines a number of hypotheses in a commonsense manner, and precedes this with a sensible explanation of just what a scientific hypothesis is. And throughout, Mannetti's manner of presentation emphasizes the tentative nature of scientific ""facts,"" reminds us that new answers raise new questions, and demonstrates the interrelationship between discovery and interpretation.