Paleogene Period | Climate Change, Mammal Evolution & Mass Extinction

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data-href="/media/1/439462/146756">Eocene paleogeography</a> <span><span>Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the middle of the Eocene Epoch of the Paleogene Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.</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>Paleogene Period</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="439462"> <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/439462" 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=439462] .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. Please refer to the appropriate style manual or other sources if you have any questions. </div> <div class="label mt-20 mb-10">Select Citation Style</div> <select class="js-citation-format-select form-select"> <option selected value="mla">MLA</option> <option value="apa">APA</option> <option value="chicago">Chicago Manual of Style</option> </select> <div class="citation font-serif border rounded p-15 mt-20" data-authors="The Editors of Encyclopaedia Britannica" data-title="Paleogene Period" data-published-date="15 Oct. 2024" data-url="https://www.britannica.com/science/Paleogene-Period" > <div class="citation-text"></div> </div> <button class="js-copy-citation-button mt-20 btn btn-xs btn-outline-blue border shadow-sm pr-10" > <em class="material-icons md-icon ml-n10 my-n5 mr-5" data-icon="file_copy"></em> <span class="js-citation-status-text">Copy Citation</span> </button> </div> </div> </div> <div> <button class="js-share-modal-button js-modal btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal="[data-topic-id=439462] .md-share-modal"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="share"></em> Share </button> <div class="md-share-modal size-lg d-none qa-share-modal"> <div class="md-modal-body"> <div class="h2 font-serif d-flex align-items-center pb-15 border-bottom"> <em class="material-icons text-blue mr-10" data-icon="share"></em> Share </div> <div class="label my-20">Share to social media</div> <div class="md-social-toolbar-circle d-flex align-items-start inverted" data-value="share" title="Paleogene Period" data-url="https://www.britannica.com/science/Paleogene-Period" > <a class="social-icon facebook justify-content-center d-flex align-items-center align-self-center" data-provider="facebook" href="https://www.facebook.com/BRITANNICA/" target="_blank" rel="noopener"><span>Facebook</span></a> <a class="social-icon x justify-content-center d-flex align-items-center align-self-center" data-provider="x" href="https://x.com/britannica" target="_blank" rel="noopener"><span>X</span></a> </div> <div class="label pt-20 mt-20 mb-5 border-top">URL</div> <a class="font-serif text-truncate d-inline-block" href="https://www.britannica.com/science/Paleogene-Period">https://www.britannica.com/science/Paleogene-Period</a> </div> </div> </div> <div> <button class="js-feedback-modal-button js-modal btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal=".md-feedback-modal"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="message"></em> Feedback </button> </div> <div> <button class="qa-external-website-modal-button js-modal btn btn-sm btn-link gtm-topic-tool font-weight-bold btn-link" data-modal="[data-topic-id=439462] .md-websites-modal"> <em class="material-icons md-icon ml-n10 mr-5" data-icon="link"></em> External Websites </button> </div> </div> <div class="md-feedback-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif pb-15 border-bottom"> Feedback </div> <form method="post" action="/submission/feedback/439462"> <div class="my-20"> Corrections? 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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"> <span class="text-gray-700"> Last Updated: <time datetime="2024-10-15T00:00:00CDT" >Oct 15, 2024</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/science/Paleogene-Period/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>Also spelled: </dt> <dd>Palaeogene Period</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> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/Oligocene-Epoch" topicid="427570">Oligocene Epoch</a></dd> <dd><a href="/science/Eocene-Epoch" topicid="189322">Eocene Epoch</a></dd> <dd><a href="/science/Paleocene-Epoch" topicid="439414">Paleocene Epoch</a></dd> <dd><a href="/science/Paleocene-Eocene-Thermal-Maximum" topicid="1419455">Paleocene-Eocene Thermal Maximum</a></dd> <dd><a href="/science/early-Eocene-Epoch" topicid="175801">early 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/Paleogene-Period"> 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><div class="assemblies multiple medialist slider js-slider position-relative d-inline-flex align-items-center mw-100" data-type="other"><div class="slider-container js-slider-container overflow-hidden d-flex"><div class="rw-track d-flex align-items-center"><div class="position-relative rw-slide col-100 px-20 "><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="66800" data-asm-type="image"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/67/73167-050-C66534D1/chart.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/439462/66800"><picture><source media="(min-width: 680px)" srcset="https://cdn.britannica.com/67/73167-050-C66534D1/chart.jpg"><img src="https://cdn.britannica.com/67/73167-050-C66534D1/chart.jpg?w=300" alt="geologic time" data-width="2000" data-height="1500" loading="eager"></picture><div class="position-absolute top-10 left-10 assembly-slide-tag rounded-lg">1 of 2</div><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/67/73167-050-C66534D1/chart.jpg" data-href="/media/1/439462/66800">geologic time</a><span>The stratigraphic chart of geologic time.</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="position-relative rw-slide col-100 px-20 "><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="157358" data-asm-type="image"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/77/131677-050-D0B85EE4/Paleogene-Period-subdivisions.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/439462/157358"><picture><source media="(min-width: 680px)" srcset="https://cdn.britannica.com/77/131677-050-D0B85EE4/Paleogene-Period-subdivisions.jpg"><img src="https://cdn.britannica.com/77/131677-050-D0B85EE4/Paleogene-Period-subdivisions.jpg?w=300" alt="Paleogene Period in geologic time" data-width="1186" data-height="1600" loading="eager"></picture><div class="position-absolute top-10 left-10 assembly-slide-tag rounded-lg">2 of 2</div><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/77/131677-050-D0B85EE4/Paleogene-Period-subdivisions.jpg" data-href="/media/1/439462/157358">Paleogene Period in geologic time</a><span>The Paleogene Period and its subdivisions.</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></div><button disabled="true" class="prev-button js-prev-button position-absolute btn btn-circle shadow btn-lg btn-blue-dark m-20"><span class="material-icons" data-icon="keyboard_arrow_left"></span></button><button disabled="true" class="next-button js-next-button position-absolute btn btn-circle shadow btn-lg btn-blue-dark m-20"><span class="material-icons" data-icon="keyboard_arrow_right"></span></button></div><p class="topic-paragraph"><strong><span id="ref202828"></span>Paleogene Period</strong>, oldest of the three stratigraphic divisions of the <a href="https://www.britannica.com/science/Cenozoic-Era" class="md-crosslink " data-show-preview="true">Cenozoic Era</a> spanning the interval between 66 million and 23 million years ago. Paleogene is Greek meaning “ancient-born” and includes the <span id="ref202829"></span><a href="https://www.britannica.com/science/Paleocene-Epoch" class="md-crosslink " data-show-preview="true">Paleocene</a> (Palaeocene) <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="Epoch" href="https://www.britannica.com/dictionary/Epoch" data-type="EB">Epoch</a> (66 million to 56 million years ago), the <span id="ref202830"></span><a href="https://www.britannica.com/science/Eocene-Epoch" class="md-crosslink " data-show-preview="true">Eocene</a> Epoch (56 million to 33.9 million years ago), and the <span id="ref202831"></span><a href="https://www.britannica.com/science/Oligocene-Epoch" class="md-crosslink " data-show-preview="true">Oligocene Epoch</a> (33.9 million to 23 million years ago). The term Paleogene was devised in <a href="https://www.britannica.com/place/Europe" class="md-crosslink " data-show-preview="true">Europe</a> to emphasize the similarity of marine fossils found in rocks of the first three Cenozoic epochs, as opposed to the later fossils of the <a href="https://www.britannica.com/science/Neogene-Period" class="md-crosslink " data-show-preview="true">Neogene Period </a>(23 million to 2.6 million years ago) and the <a href="https://www.britannica.com/science/Quaternary" class="md-crosslink " data-show-preview="true">Quaternary Period</a> (2.6 million years ago to the present). In <a href="https://www.britannica.com/place/North-America" class="md-crosslink " data-show-preview="true">North America</a>, the Cenozoic has traditionally been divided only into the <a href="https://www.britannica.com/science/Tertiary-Period" class="md-crosslink " data-show-preview="true">Tertiary Period</a> (66 million to 2.6 million years ago) and the Quaternary Period; however, the notion that the Tertiary should be replaced by the <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="designations" href="https://www.merriam-webster.com/dictionary/designations" data-type="MW">designations</a> Paleogene and Neogene is becoming more widespread.</p><span class="marker MOD1 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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