• synonyms


  1. 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.
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  1. the Eocene Epoch or Series.
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Origin of Eocene

First recorded in 1825–35; eo- + -cene
Related formspost-E·o·cene, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for eocene

Historical Examples of eocene

  • Prestwich, Mr., on English and French eocene formations, 328.

    On the Origin of Species by Means of Natural Selection

    Charles Darwin

  • Eocene, miocene, pliocene Tuff, Lias and Trias and that is enough.

  • The epoch following on after the Eocene is designated as the Miocene.

  • They had a place in the Eocene and Miocene forests of the old world and new.

    American Forest Trees

    Henry H. Gibson

  • But the mammals are the most interesting vertebrates of the Eocene period.

British Dictionary definitions for eocene


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

Word Origin and History for eocene



in reference to the second epoch of the Tertiary Period, coined in English 1831, from eo- + Greek kainos "new" (see recent); along with Miocene and Pliocene, by the Rev. William Whewell (1794-1866), English polymath.

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Online Etymology Dictionary, © 2010 Douglas Harper

eocene in Science


  1. 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.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.