Major division of the Tertiary Period , from 54.
8 to 33.7 million years ago. It follows the Paleocene Epoch and precedes the Oligocene Epoch . The name, derived from the Greek eos ("dawn"), refers to the dawn of recent life; during the Eocene, all the major divisions, or orders, of modern mammals appeared, as well as many essentially modern bird orders. Climates were warm and humid. Temperate and subtropical forests were widespread, but grasslands were limited.