Horse Environments - Keys to Cenozoic Fauna Eocene (55.8-33.9 MYA) Return. Oligocene (33.9-23 MYA) Return. Miocene (23-5.3 MYA) Return. Pliocene (5.3-2.6 MYA) Return. Pleistocene (2.6 MYA-10,000 YA) Return. Original art by: Xavier Moss
