Spanning 11 million years, from 34 to 23 million years ago, the Oligocene is the third and final epoch of the Paleogene period of the Cenozoic era. The Oligocene saw a major shift toward a cooler, more modern Earth.
The name Oligocene is derived from the Greek oligos, meaning "few," and kainos, meaning "new." A few new, more modern, creatures appear in the Oligocene fossil record. As Antarctica froze and the Circumpolar Current developed, giant mammals evolved to live on vast grasslands — including the hornless, rhinoceros-like Paraceratherium, the largest land mammal known to have ever lived. There were also early cats, elephants, and ancestors of modern dogs and bears. During this epoch, the foundations of modern ecosystems were laid.