Eocene landscape (56 to 34 million years ago). The second oldest of the five major worldwide divisions (epochs) of the Tertiary Period (Cenozoic Era), the interval of time (epoch) extending from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The diversification of life seen in the Paleocene continued in the Eocene, a reflection of the poleward expansion of the tropics, particularly during early Eocene time. Middle and late Eocene time witnessed the development of extensive endemic animal evolution. Bats, flying lemurs, creodont carnivores, artiodactyls (cloven-hoof mammals, such as cattle, deer, and camels) and perissodactyls (odd-toed, hoofed mammals, such as rhinoceroses and horses). Illustration originally captioned: Eocene landscape by Franz Unger, 1916.