Eocene

[ ee-uh-seen ]

/ ˈi əˌsin /

Geology

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adjective

noting or pertaining to an epoch of the Tertiary Period, occurring from 55 to 40 million years ago and characterized by the advent of the modern mammalian orders.

noun

the Eocene Epoch or Series.

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Origin of Eocene

First recorded in 1825–35; eo- + -cene

OTHER WORDS FROM Eocene

post-E·o·cene, adjective

Words nearby Eocene

EO, Eoanthropus, EOB, eobiont, EOC, Eocene, EOD, EOE, EOF, EOG, Eogene

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use Eocene in a sentence

Those specimens included mammals from 17 groups dating to the Paleocene and 17 to the Eocene, the epoch that spanned 55 million to 34 million years ago.
Mammals’ bodies outpaced their brains right after the dinosaurs died|Carolyn Gramling|March 31, 2022|Science News
The cathedral’s building blocks are Lutetian limestone, unique to this part of France, formed in a shallow sea during the Eocene period about 45 million years ago.
Hiking along Virginia’s Aquia Creek and finding history a stone’s throw from home|Walter Nicklin|April 2, 2021|Washington Post
The fourth area displays a very different succession of Eocene strata, and one of extreme interest.
The Principles of Stratigraphical Geology|J. E. Marr
This uplift imprisoned an enormous Eocene lake that occupied much of what is now the Colorado River basin.
Your National Parks|Enos A. Mills

The Middle Eocene is represented by the well-known “Calcaire grossier,” about 90 ft. thick.
Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 6|Various
The late Eocene flora of Europe was very similar to its descendant in modern Australasia.
Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 6|Various
Marls and limestones with fossils of an Eocene facies overlie the Cretaceous rocks on the Gabun.
Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 1 "Franciscans" to "French Language"|Various

British Dictionary definitions for Eocene

Eocene

/ (ˈiːəʊˌsiːn) /

adjective

of, denoting, or formed in the second epoch of the Tertiary period, which lasted for 20 000 000 years, during which hooved mammals appeared

noun

the Eocene the Eocene epoch or rock series

Word Origin for Eocene

C19: from eo- + -cene

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for Eocene

Eocene

[ ē′ə-sēn′ ]

The second epoch of the Tertiary Period, from about 58 to 37 million years ago. During the earliest part of this epoch, land connections existed between Antarctica and Australia, between Europe and North America, and between North America and Asia, and the climate was warm. The land connection between Antarctica and Australia disappeared in the mid-Eocene and early Oligocene, resulting in a change in the predominant oceanic currents and a cooler climate. With this change, the average size of mammals changed from less than 10 kg (22 lbs) to more than 10 kg. The Himalayas also formed during the Eocene, and most modern orders of mammals appeared. See Chart at geologic time.