During the last Ice Age, there were many large, interesting mammals, like the saber-toothed cats, giant ground sloths, mastodons, and mammoths. These animals have long since gone extinct and are known mostly from fossils, from frozen, mummified carcasses, and even from ancient cave drawings. These phenomenon changed the surface of the earth, forming lakes, changing the paths of rivers, eroding land, and depositing sand, gravel, and rocks along the glaciers' paths.
Mammals are animals that have hair, are warm-blooded, and nourish their young with milk.
Mammals evolved during the Triassic period , about the same time that the first dinosaurs appeared. Some modern-day mammals include people, apes , cats, dogs, mice, elephants, whales , and horses. Synapsids include the mammals, and their ancestors, the pelycosaurs, therapsids, and cynodonts. The cynodonts led to the true mammals. Over time, the synapsid gait became more upright and tail length decreased.