HOW DINOSAURS CAME TO BE

The dinosaurs didn't just appear out of nowhere. They, like humans, had relatives. Lauber (Fur, Feathers, and Flippers, 1994, etc.) helps readers put together a sort of family tree describing the creatures that preceded dinosaurs and mammals. The book begins with a look at the large amphibians that were alive during the Permian period, 286 million years ago, when the continents were connected in larger land masses, e.g., the Pangaea. Lauber explains how later, during the Middle Triassic period, the therapsids—a cross between reptiles and mammals—became the dominant life form. But instead of proliferating, they died out, leaving another group, the thecodonts, to branch off into the direct ancestors of dinosaurs. This history isn't covered well in other children's books. Lauber not only names names, she puts the creatures into an evolutionary context. Henderson's illustrations are superb, conveying real information as well as conjuring an active picture of these beasts in readers' imaginations. The book has dull moments—lists of multisyllabic names of creatures and their barely known attributes can get tedious to all but fanatics on the subject—but it's otherwise an exquisite prelude to the rest of the dinosaur canon. (charts, diagrams, chronology, index) (Nonfiction. 9-12)