The second geological epoch of the Palaeogene period. It extended from the end of the Palaeocene epoch, about 55 million years ago, to the beginning of the Oligocene epoch, about 34 million years ago. The term was first proposed by Sir Charles Lyell (1797–1875) in 1833. Mammals were dominant in the Eocene: rodents, artiodactyls, carnivores, perissodactyls (including early horses), and whales were among the groups to make their first appearance.
Subjects: Biological Sciences.