Brief introductions to a dozen extinct giants, not just dinosaurs but birds, insects, a lizard, and some early mammals. With her usual finesse, Selsam explains how we know about them and links her information into a coherent whole, concluding with a definition of ""extinct"" and a plea to give the animals of the present a chance to survive. The naturalist-artist's full-color illustrations are attractive, informative, and unsensational.