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. This book is an illustrated field guide to the lost world of these prehistoric creatures. It covers all the main groups of fossil mammals, discussing taxonomy and evolutionary history, and providing concise accounts of the better-known genera and species as well as an up-to-date family tree for each group. Illustrated throughout with full-color reconstructions and photographs of fossils from around the world.