Mammal Fossil Collection
The first mammals emerged in the Late Triassic Period, 220 million years ago, but never gained a dominant presence and broad diversity until the Miocene Period, 15 million years ago. The warming and cooling of the earth during the Great Ice Age of the Pleistocene--2 million years ago--gave rise to the emergence of enormous land mammals. All of these impressive beasts died out during the Pleistocene Era, about 12,000 years ago.
