Book excerpt: If dinosaurs still walked the earth, you'd use this field guide to identify them! Photographically realistic color paintings capture 120 genera of sauruses, organized according to evolutionary relationships, in their habitats. Open the "fact file" for instant information on each creature's length and weight; physical description; diet; and more. A small sketch shows the dinosaur next to another animal--like a human or elephant--to convey its comparative size. The world map shows where they dwelt, and a timeline tells when