PALEOGENE PERIOD

also spelled Palaeogene Period older of the two stratigraphic divisions of the Cenozoic Era (the Cenozoic Era began about 66.4 million years ago and extends to the present). The Paleogene, whose beginning coincides with that of the Cenozoic Era, ended 23.7 million years ago and was followed by the Neogene Period. The Paleogene, which means ancient-born, includes the Paleocene (Palaeocene), Eocene, and Oligocene epochs. The term Paleogene was devised in Europe to emphasize the similarity of marine fossils found in rocks of the first three Cenozoic epochs, as opposed to the later fossils of the Neogene Period. In North America the designations Paleogene and Neogene have not gained wide usage, and the Cenozoic is divided only into the Tertiary Period (about 66.4 million to 1.6 million years ago) and the Quaternary Period (about 1.6 million years ago to the present). Thus, the Paleogene Period may also be considered to be roughly equivalent to the first two-thirds of the Tertiary Period.