Eocene Epoch | Climate, Flora & Fauna

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Restoration painting by Charles R. Knight, 1898." height="50" /> </a> <a href="https://cdn.britannica.com/94/111794-050-10213FE5/Map-age-regions-ocean-floor-measurements-analysis.jpg" data-href="/media/1/189322/158607" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/94/111794-004-3B1D2191/Map-age-regions-ocean-floor-measurements-analysis.jpg" alt="seafloor spreading" height="50" /> </a> <a href="https://cdn.britannica.com/67/73167-050-C66534D1/chart.jpg" data-href="/media/1/189322/66800" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/67/73167-004-106002DC/chart.jpg" alt="geologic time" height="50" /> </a> <a href="https://cdn.britannica.com/77/131677-050-D0B85EE4/Paleogene-Period-subdivisions.jpg" data-href="/media/1/189322/157358" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/77/131677-004-2C3C5A32/Paleogene-Period-subdivisions.jpg" alt="Paleogene Period in geologic time" height="50" /> </a> </div> <button disabled class="prev-button js-prev-button position-absolute btn btn-circle shadow btn-blue " aria-label="Previous"> <span class="material-icons md-24" data-icon="keyboard_arrow_left"></span> </button> <button disabled class="next-button js-next-button position-absolute btn btn-circle shadow btn-blue " aria-label="Next"> <span class="material-icons md-24" data-icon="keyboard_arrow_right"></span> </button> </div> </div> <div class="mb-30 tlr-read-next"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> Read Next </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/story/do-fossil-fuels-really-come-from-fossils"> <img loading="lazy" src="https://cdn.britannica.com/24/196924-131-6F4BE1BD/Skeleton-fossil-record-reptiles-stone.jpg?w=200&h=200&c=crop" alt="Skeleton fossil record of ancient reptiles in stone." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/story/do-fossil-fuels-really-come-from-fossils" >Do Fossil Fuels Really Come from Fossils?</a> </div> </div> </div> <div class="mb-30 tlr-discover"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> Discover </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/list/the-fastest-animals-on-earth"> <img loading="lazy" src="https://cdn.britannica.com/00/152300-131-FEE1926E/Cheetah-Maasai-Mara-National-Reserve-Kenya.jpg?w=200&h=200&c=crop" alt="Cheetah (Acinonyx jubatus) standing on rock, side view, Masai Mara National Reserve, Kenya" width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/list/the-fastest-animals-on-earth" >The Fastest Animals on Earth</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/list/9-of-the-worlds-deadliest-mammals"> <img loading="lazy" src="https://cdn.britannica.com/56/174256-131-DE02B70C/Ruminant-Deer-Red-deer-Antlers-Cervus-elaphus.jpg?w=200&h=200&c=crop" alt="Ruminant. 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Restoration painting by Charles R. Knight, 1898." loading="eager" /> </picture> <button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"> <em class="material-icons link-blue" data-icon="zoom_in"></em> </button> </a> </div> <figcaption class="card-body"> <div class="md-assembly-caption text-muted font-14 font-serif line-clamp"> <span> <a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" href="https://cdn.britannica.com/65/12665-004-5CACDC60/Coryphodon-mammals-deposits-Late-Paleocene-Early-Eocene-1898.jpg" data-href="/media/1/189322/95219"></a> <span><span><em>Coryphodon</em>, a genus of primitive hoofed mammals known from Late Paleocene and Early Eocene deposits. Restoration painting by Charles R. Knight, 1898. </span></span> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"> <span class="link-blue">(more)</span> </button> </span> </div> </figcaption> </figure> </div><div class="topic-header"> <div class="d-flex align-items-top justify-content-between"> <div class="d-flex flex-column"> <div> <div> <h1>Eocene Epoch</h1></div> </div> <div class="topic-identifier font-16 font-md-20">geochronology</div> </div> </div> <div class="d-none d-sm-flex flex-row"> <div class="mr-10 mb-15"> <button class="ai-ask-button btn border-2 btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400"> Ask the Chatbot a Question </button> </div> <div class="d-none d-sm-block md-topic-tools qa-action-buttons mb-15" data-topic-id="189322"> <button class="js-tooltip btn btn-sm btn-outline-blue border pr-10 border-2" > <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="more_vert"></em> More Actions </button> <div class="md-more-popover popover popover-sm p-0 font-14 z-1"> <div> <a class="js-modal btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" href="/print/article/189322" target="_blank" > <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="print"></em> Print </a> </div> <div> <button class="js-modal qa-cite-modal-button btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal="[data-topic-id=189322] .md-cite-modal"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="verified"></em> Cite </button> <div class="md-cite-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif d-flex align-items-center pb-15 border-bottom mb-15"> <em class="material-icons text-blue mr-10">verified</em>Cite </div> <div class="font-serif"> While every effort has been made to follow citation style rules, there may be some discrepancies. 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They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <a class="byline-edit-history" href="https://www.britannica.com/science/Eocene-Epoch/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/fossil" topicid="214511">fossil</a></dd> <dd><a href="/animal/adapiform" topicid="1929550">adapiform</a></dd> <dd><a href="/science/late-Eocene-Epoch" topicid="331300">late Eocene Epoch</a></dd> <dd><a href="/science/early-Eocene-Epoch" topicid="175801">early Eocene Epoch</a></dd> <dd><a href="/science/middle-Eocene-Epoch" topicid="381314">middle Eocene Epoch</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/Eocene-Epoch"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref44390"></span>Eocene Epoch</strong>, second of three major <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="worldwide" href="https://www.britannica.com/dictionary/worldwide" data-type="EB">worldwide</a> divisions of the <a href="https://www.britannica.com/science/Paleogene-Period" class="md-crosslink " data-show-preview="true">Paleogene Period</a> (66 million to 23 million years ago) that began 56 million years ago and ended 33.9 million years ago. It follows the <a href="https://www.britannica.com/science/Paleocene-Epoch" class="md-crosslink " data-show-preview="true">Paleocene Epoch</a> and precedes the <a href="https://www.britannica.com/science/Oligocene-Epoch" class="md-crosslink " data-show-preview="true">Oligocene Epoch</a>. The Eocene is often divided into <span id="ref44391"></span><a href="https://www.britannica.com/science/early-Eocene-Epoch" class="md-crosslink ">Early</a> (56 million to 47.8 million years ago), <span id="ref44392"></span><a href="https://www.britannica.com/science/middle-Eocene-Epoch" class="md-crosslink ">Middle</a> (47.8 million to 38 million years ago), and <span id="ref44393"></span><a href="https://www.britannica.com/science/late-Eocene-Epoch" class="md-crosslink ">Late</a> (38 million to 33.9 million years ago) epochs. The name Eocene is derived from the Greek <em>eos</em>, for “dawn,” referring to the appearance and diversification of many modern groups of organisms, especially <a href="https://www.britannica.com/animal/mammal" class="md-crosslink " data-show-preview="true">mammals</a> and <a href="https://www.britannica.com/animal/mollusk" class="md-crosslink " data-show-preview="true">mollusks</a>.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">Eocene rocks have a worldwide distribution. The International <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="Commission" href="https://www.britannica.com/dictionary/Commission" data-type="EB">Commission</a> on Stratigraphy (ICS) has recognized several stages and their temporal equivalents (ages) on the basis of characteristic rocks and fossils; they are, from earliest to latest, the <a href="https://www.britannica.com/science/Ypresian-Stage" class="md-crosslink " data-show-preview="true">Ypresian</a>, <a href="https://www.britannica.com/science/Lutetian-Stage" class="md-crosslink " data-show-preview="true">Lutetian</a>, <a href="https://www.britannica.com/science/Bartonian-Stage" class="md-crosslink " data-show-preview="true">Bartonian</a>, and the <a href="https://www.britannica.com/science/Priabonian-Stage" class="md-crosslink " data-show-preview="true">Priabonian</a>. Lower Eocene assemblages are poorly represented in both England and the Patagonian region of South America. Later Eocene vertebrate faunas are somewhat better developed in areas outside of <a href="https://www.britannica.com/place/North-America" class="md-crosslink " data-show-preview="true">North America</a>; however, it is in North America, especially the western <a href="https://www.britannica.com/place/United-States" class="md-crosslink " data-show-preview="true">United States</a>, that the most abundant and extensive Eocene terrestrial vertebrate record exists. Eocene rocks were deposited in much the same regions as those of the preceding Paleocene Epoch. During the Eocene, climates were warm and humid—temperate and subtropical forests were widespread, whereas grasslands were of limited extent. For example, the Eocene forests of <a href="https://www.britannica.com/place/Oregon-state" class="md-crosslink " data-show-preview="true">Oregon</a> were made up of trees and plants similar or identical to those now found in Central and <a href="https://www.britannica.com/place/South-America" class="md-crosslink " data-show-preview="true">South America</a>.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">During the Eocene, the vertebrates of North America and <a href="https://www.britannica.com/place/Europe" class="md-crosslink " data-show-preview="true">Europe</a> were very similar; many genera existed in both regions, indicating that an interchange between the regions was possible. Early Eocene faunas mirrored those of the preceding Paleocene with the addition of newer types; however, the <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="archaic" href="https://www.merriam-webster.com/dictionary/archaic" data-type="MW">archaic</a> Paleocene groups gradually became extinct.</p><a class="link-module shadow-sm d-block qa-read-more-module" href="/animal/primate-mammal/Eocene#ref876449" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/92/76392-050-88161966/apes.jpg" alt="species of apes" class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-navy-dark">More From Britannica</div> <div class="font-weight-semi-bold mt-5">primate: Eocene</div> </div> </a><span class="marker MOD3 mod-inline"></span><span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph">Among terrestrial vertebrates, the start of the Eocene is marked by the appearance of two new groups of animals: the <span id="ref44394"></span><a href="https://www.britannica.com/animal/perissodactyl" class="md-crosslink " data-show-preview="true">perissodactyls</a>, or odd-toed ungulates, and the <span id="ref44395"></span><a href="https://www.britannica.com/animal/artiodactyl" class="md-crosslink " data-show-preview="true">artiodactyls</a>, or even-toed ungulates. The perissodactyls include the <a href="https://www.britannica.com/animal/horse/Evolution-of-the-horse#ref10373" class="md-crosslink " data-show-preview="true">horses</a>, <a href="https://www.britannica.com/animal/rhinoceros-mammal" class="md-crosslink " data-show-preview="true">rhinoceroses</a>, and <a href="https://www.britannica.com/animal/tapir" class="md-crosslink " data-show-preview="true">tapirs</a>; among the artiodactyls are the <a href="https://www.britannica.com/animal/deer" class="md-crosslink " data-show-preview="true">deer</a>, <a href="https://www.britannica.com/animal/cattle-livestock" class="md-crosslink " data-show-preview="true">cattle</a>, and <a href="https://www.britannica.com/animal/domesticated-sheep" class="md-crosslink " data-show-preview="true">sheep</a>. An early horse ancestor, the <span id="ref44396"></span><a href="https://www.britannica.com/animal/dawn-horse" class="md-crosslink " data-show-preview="true">dawn horse</a>, known in North America as <em>Eohippus</em>, is among the <a href="https://www.britannica.com/science/fossil" class="md-crosslink autoxref " data-show-preview="true">fossil</a> perissodactyls found in the lower Eocene rocks of both North America and Europe. Artiodactyls, rare during the early Eocene, became abundant later in the <a href="https://www.britannica.com/science/epoch-geologic-time" class="md-crosslink autoxref " data-show-preview="true">epoch</a>.</p><span class="marker MOD4 mod-inline"></span><span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">Archaic <a href="https://www.britannica.com/animal/primate-mammal" class="md-crosslink autoxref " data-show-preview="true">primate</a> forms from the Paleocene Epoch declined during the Eocene as many of their ecological <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="niches" href="https://www.merriam-webster.com/dictionary/niches" data-type="MW">niches</a> were usurped by the more-efficient rodents. Vertebrate groups arising during the Middle Eocene were not as widespread as those of the early Eocene; the isolation that resulted allowed different evolutionary trends to occur in the <a href="https://www.britannica.com/animal/ungulate" class="md-crosslink autoxref " data-show-preview="true">ungulate</a> groups of North America and Europe. By late in the Eocene Epoch this isolation had ceased, and North American and European groups once again came into contact with one another.</p><div class="one-good-fact-module"> </div><span class="marker MOD5 mod-inline"></span><span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">The Eocene Epoch marks the first appearance in the <a href="https://www.britannica.com/science/fossil-record" class="md-crosslink autoxref " data-show-preview="true">fossil record</a> of the two completely marine mammal groups, the <span id="ref44397"></span><a href="https://www.britannica.com/animal/cetacean" class="md-crosslink " data-show-preview="true">cetaceans</a> (<a href="https://www.britannica.com/animal/whale" class="md-crosslink " data-show-preview="true">whales</a>, <a href="https://www.britannica.com/animal/porpoise" class="md-crosslink " data-show-preview="true">porpoises</a>, and <a href="https://www.britannica.com/animal/dolphin-mammal" class="md-crosslink " data-show-preview="true">dolphins</a>) and the <span id="ref44398"></span><a href="https://www.britannica.com/animal/sirenian" class="md-crosslink " data-show-preview="true">sirenians</a> (akin to the modern <a href="https://www.britannica.com/animal/manatee" class="md-crosslink " data-show-preview="true">manatees</a> and <a href="https://www.britannica.com/animal/dugong-mammal" class="md-crosslink " data-show-preview="true">dugongs</a>). Similarly, the Eocene provides the first <a href="https://www.britannica.com/animal/elephant-mammal" class="md-crosslink " data-show-preview="true">elephant-like</a> animals and the early <a href="https://www.britannica.com/animal/bat-mammal" class="md-crosslink " data-show-preview="true">bats</a>. In addition, <a href="https://www.britannica.com/animal/gastropod" class="md-crosslink " data-show-preview="true">gastropods</a> (a class of mollusks containing <a href="https://www.britannica.com/animal/snail" class="md-crosslink " data-show-preview="true">snails</a>, <a href="https://www.britannica.com/animal/slug-mollusk" class="md-crosslink " data-show-preview="true">slugs</a>, and <a href="https://www.britannica.com/animal/limpet-gastropod" class="md-crosslink " data-show-preview="true">limpets</a>) underwent great diversification, and many <a href="https://www.britannica.com/animal/bird-animal" class="md-crosslink " data-show-preview="true">bird</a> orders that were in essence modern appeared during the Eocene.</p><span class="marker MOD6 mod-inline"></span></section> <span class="md-signature">This article was most recently revised and updated by <a href="/editor/John-P-Rafferty/6747">John P. 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Eocene Epoch | Climate, Flora & Fauna | Britannica