T he Cenozoic Era began with the extinction of the dinosaurs about 65 million years ago and is still in session. It is often referred to as the Age of Mammals.
Scientists divide eras into periods.
The Cenozoic Era has so far been divided into two periods, the Tertiary and Quaternary. The Tertiary Period is further divided into five epochs the Paleocene, Eocene, Oligocene and Miocene. The Quaternary Period is not yet finished. The Pleistocene and Holocene are the beginning of the Quaternary Period. The Paleocene through Pliocene epochs make up the Tertiary Period.