There are really two mystery elements here, both commonly invoked in dinosaur books: the particular puzzle faced each time new findings must be interpreted and put together, and the larger unanswered question of why the dinosaurs died. But within this mystery framework, Cobb integrates a sprightly, conversational introduction to some of the better-known dinosaurs with a picture of science as an ongoing process of question, speculation, and adjustment. Starting with a huge skull that had its 18th-century discoverers baffled, then sketching in how paleontologists find clues in fossils and rock layers, she focuses on ""The Detective Work: Putting the Pieces Together."" Thus ""some flat teeth, a spike that looked like a horn, and some toe bones"" (all pictured) yield on the next page an early, mistaken reconstruction, and then a very different revised model, of iguanadon. Brachiosaurus is considered in terms of changing explanations of its high nostrils, and stegosaurus for changing views of its spinal plates. A discussion of tyrannosaurus ends suggestively, ""Perhaps it was a warm-blooded animal."" Citing the current asteroid explanation as the ""most popular theory"" for the dinosaurs' sudden extinction, and noting that ""perhaps"" today's birds are the dinosaurs' descendants, she concludes that ""There is still lots of detective work to be done."" Again, it's an almost universal dinosaur-book ending, but Cobbs' whole approach makes that last line more than a token.