After the mass extinction of the dinosaurs 65 million years ago, mammals became the dominant terrestrial life form on our planet. Roaming the earth were spectacular beasts such as saber-toothed cats, giant mastodonts, immense ground sloths, and gigantic giraffe-like rhinoceroses. Here is the ultimate illustrated field guide to the lost world of the "The Princeton Field Guide to Prehistoric Mammals is a must-have for anyone interested in the fossil history of mammals, in part because works that review the whole of mammal history are otherwise virtually non-existent."---ScientificAmerican.com's Tetrapod Zoology blog