Oligocene
Americanadjective
noun
adjective
noun
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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.
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See Chart at geologic time
Other Word Forms
Etymology
Origin of Oligocene
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
It started with a period of glaciation that must have been a chilly change from the greenhouse-like Oligocene, and ended with a prolonged period of glaciation, too.
From Salon ● Feb. 17, 2025
It represents a segment of a population tracing its ancestry back to the widespread Oligocene ancestor, approximately 28 million years ago, in the Philippines.
From Science Daily ● Sep. 19, 2023
As the Eocene gave way to the Oligocene, tectonic forces dealt a final blow to Gondwana, cleaving apart Australia, South America and Antarctica.
From Scientific American ● Mar. 14, 2023
Based on the location and age of the rocks surrounding the ant hills, the researchers estimate that the fossils are from the late Eocene and early Oligocene epochs.
From New York Times ● Jul. 1, 2022
The most noteworthy exceptions are perhaps the Oligocene fish-bed of Glarus, the Eocene nummulitic beds in Calabria, and the Aptychus beds of Waidhofen.
From Encyclopaedia Britannica, 11th Edition, Volume 10, Slice 5 "Fleury, Claude" to "Foraker" by Various
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
