- noting or pertaining to an epoch of the Tertiary Period, occurring from 40 to 25 million years ago.
- the Oligocene Epoch or Series.
- of, denoting, or formed in the third epoch of the Tertiary period, which lasted for 10 000 000 years
- the Oligocene the Oligocene epoch or rock series
adj.1856, “pertaining to the Tertiary period between the Eocene and the Miocene,” coined in German (1854) by Heinrich Ernst von Beyrich, from oligo- “small, little, few” + -cene. So called because few modern fossils were found in Oligocene rocks.
- The third epoch of the Tertiary Period, from about 37 to 24 million years ago. During this time there was an increase in volcanic activity, and Australia and South America separated from Antarctica. The climate started to cool and a glacier started to form in Antarctica. Modern mammalian groups continued to develop, and the first cats, dogs, horses, and related mammals appeared. Artiodactyls (even-toed ungulates) took over from the perissodactyls (uneven-toed ungulates) as the dominant medium-sized herbivores. Many types of grass also first appeared at this time. See Chart at geologic time.