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id="toc-Subdivisions-sublist" class="vector-toc-list"> <li id="toc-ICS_(global)_subdivisions" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#ICS_(global)_subdivisions"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>ICS (global) subdivisions</span> </div> </a> <ul id="toc-ICS_(global)_subdivisions-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Global/regional_correlation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Global/regional_correlation"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Global/regional correlation</span> </div> </a> <ul id="toc-Global/regional_correlation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-British_stages_and_ages" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#British_stages_and_ages"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>British stages and ages</span> </div> </a> <ul id="toc-British_stages_and_ages-sublist" class="vector-toc-list"> <li id="toc-Ashgill" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Ashgill"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3.1</span> <span>Ashgill</span> </div> </a> <ul id="toc-Ashgill-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Paleogeography_and_tectonics" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Paleogeography_and_tectonics"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Paleogeography and tectonics</span> </div> </a> <button aria-controls="toc-Paleogeography_and_tectonics-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Paleogeography and tectonics subsection</span> </button> <ul id="toc-Paleogeography_and_tectonics-sublist" class="vector-toc-list"> <li id="toc-Ordovician_meteor_event" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Ordovician_meteor_event"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Ordovician meteor event</span> </div> </a> <ul id="toc-Ordovician_meteor_event-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Geochemistry" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Geochemistry"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Geochemistry</span> </div> </a> <ul id="toc-Geochemistry-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Climate_and_sea_level" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Climate_and_sea_level"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Climate and sea level</span> </div> </a> <ul id="toc-Climate_and_sea_level-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Life" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Life"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Life</span> </div> </a> <button aria-controls="toc-Life-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Life subsection</span> </button> <ul id="toc-Life-sublist" class="vector-toc-list"> <li id="toc-Fauna" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Fauna"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Fauna</span> </div> </a> <ul id="toc-Fauna-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Flora" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Flora"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Flora</span> </div> </a> <ul id="toc-Flora-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Microbiota" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Microbiota"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Microbiota</span> </div> </a> <ul id="toc-Microbiota-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-End_of_the_period" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#End_of_the_period"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>End of the period</span> </div> </a> <ul id="toc-End_of_the_period-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Ordovician</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 84 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-84" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">84 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Ordovisium" title="Ordovisium – Afrikaans" lang="af" hreflang="af" data-title="Ordovisium" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-als mw-list-item"><a href="https://als.wikipedia.org/wiki/Ordovizium" title="Ordovizium – Alemannic" lang="gsw" hreflang="gsw" data-title="Ordovizium" data-language-autonym="Alemannisch" data-language-local-name="Alemannic" class="interlanguage-link-target"><span>Alemannisch</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%A7%D9%84%D8%B9%D8%B5%D8%B1_%D8%A7%D9%84%D8%A3%D9%88%D8%B1%D8%AF%D9%88%D9%81%D9%8A%D8%B4%D9%8A" title="العصر الأوردوفيشي – Arabic" lang="ar" hreflang="ar" data-title="العصر الأوردوفيشي" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Ordov%C3%ADcicu" title="Ordovícicu – Asturian" lang="ast" hreflang="ast" data-title="Ordovícicu" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Ordovik_d%C3%B6vr%C3%BC" title="Ordovik dövrü – Azerbaijani" lang="az" hreflang="az" data-title="Ordovik dövrü" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%85%E0%A6%B0%E0%A7%8D%E0%A6%A1%E0%A7%8B%E0%A6%AD%E0%A6%BF%E0%A6%B6%E0%A6%BF%E0%A6%AF%E0%A6%BC%E0%A6%BE%E0%A6%A8" title="অর্ডোভিশিয়ান – Bangla" lang="bn" hreflang="bn" data-title="অর্ডোভিশিয়ান" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-zh-min-nan mw-list-item"><a href="https://zh-min-nan.wikipedia.org/wiki/Ordovices-k%C3%AD" title="Ordovices-kí – Minnan" lang="nan" hreflang="nan" data-title="Ordovices-kí" data-language-autonym="閩南語 / Bân-lâm-gú" data-language-local-name="Minnan" class="interlanguage-link-target"><span>閩南語 / Bân-lâm-gú</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%90%D1%80%D0%B4%D0%BE%D0%B2%D1%96%D0%BA%D1%81%D0%BA%D1%96_%D0%BF%D0%B5%D1%80%D1%8B%D1%8F%D0%B4" title="Ардовікскі перыяд – Belarusian" lang="be" hreflang="be" data-title="Ардовікскі перыяд" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%90%D1%80%D0%B4%D0%BE%D0%B2%D1%96%D0%BA" title="Ардовік – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Ардовік" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9E%D1%80%D0%B4%D0%BE%D0%B2%D0%B8%D0%BA" title="Ордовик – Bulgarian" lang="bg" hreflang="bg" data-title="Ордовик" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Ordovicij" title="Ordovicij – Bosnian" lang="bs" hreflang="bs" data-title="Ordovicij" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-br mw-list-item"><a href="https://br.wikipedia.org/wiki/Ordovisian" title="Ordovisian – Breton" lang="br" hreflang="br" data-title="Ordovisian" data-language-autonym="Brezhoneg" data-language-local-name="Breton" class="interlanguage-link-target"><span>Brezhoneg</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Ordovici%C3%A0" title="Ordovicià – Catalan" lang="ca" hreflang="ca" data-title="Ordovicià" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Ordovik" title="Ordovik – Czech" lang="cs" hreflang="cs" data-title="Ordovik" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Ordofigaidd" title="Ordofigaidd – Welsh" lang="cy" hreflang="cy" data-title="Ordofigaidd" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Ordovicium" title="Ordovicium – Danish" lang="da" hreflang="da" data-title="Ordovicium" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Ordovizium" title="Ordovizium – German" lang="de" hreflang="de" data-title="Ordovizium" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Ordoviitsium" title="Ordoviitsium – Estonian" lang="et" hreflang="et" data-title="Ordoviitsium" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%9F%CF%81%CE%B4%CE%BF%CE%B2%CE%AF%CE%BA%CE%B9%CE%B1_%CF%80%CE%B5%CF%81%CE%AF%CE%BF%CE%B4%CE%BF%CF%82" title="Ορδοβίκια περίοδος – Greek" lang="el" hreflang="el" data-title="Ορδοβίκια περίοδος" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Ordov%C3%ADcico" title="Ordovícico – Spanish" lang="es" hreflang="es" data-title="Ordovícico" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Ordovicio" title="Ordovicio – Esperanto" lang="eo" hreflang="eo" data-title="Ordovicio" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Ordoviziar" title="Ordoviziar – Basque" lang="eu" hreflang="eu" data-title="Ordoviziar" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%A7%D8%B1%D8%AF%D9%88%DB%8C%D8%B3%DB%8C%D9%86" title="اردویسین – Persian" lang="fa" hreflang="fa" data-title="اردویسین" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Ordovicien" title="Ordovicien – French" lang="fr" hreflang="fr" data-title="Ordovicien" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Ordov%C3%ADcico" title="Ordovícico – Galician" lang="gl" hreflang="gl" data-title="Ordovícico" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%98%A4%EB%A5%B4%EB%8F%84%EB%B9%84%EC%8A%A4%EA%B8%B0" title="오르도비스기 – Korean" lang="ko" hreflang="ko" data-title="오르도비스기" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%95%D6%80%D5%A4%D5%B8%D5%BE%D5%AB%D5%AF%D5%AB_%D5%AA%D5%A1%D5%B4%D5%A1%D5%B6%D5%A1%D5%AF%D5%A1%D5%B7%D6%80%D5%BB%D5%A1%D5%B6" title="Օրդովիկի ժամանակաշրջան – Armenian" lang="hy" hreflang="hy" data-title="Օրդովիկի ժամանակաշրջան" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%93%E0%A4%B0%E0%A5%8D%E0%A4%A1%E0%A5%8B%E0%A4%B5%E0%A4%BF%E0%A4%B6%E0%A5%80_%E0%A4%95%E0%A4%B2%E0%A5%8D%E0%A4%AA" title="ओर्डोविशी कल्प – Hindi" lang="hi" hreflang="hi" data-title="ओर्डोविशी कल्प" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Ordovicij" title="Ordovicij – Croatian" lang="hr" hreflang="hr" data-title="Ordovicij" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Ordovisium" title="Ordovisium – Indonesian" lang="id" hreflang="id" data-title="Ordovisium" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/Ord%C3%B3vis%C3%ADumt%C3%ADmabili%C3%B0" title="Ordóvisíumtímabilið – Icelandic" lang="is" hreflang="is" data-title="Ordóvisíumtímabilið" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Ordoviciano" title="Ordoviciano – Italian" lang="it" hreflang="it" data-title="Ordoviciano" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%90%D7%95%D7%A8%D7%93%D7%95%D7%91%D7%99%D7%A7" title="אורדוביק – Hebrew" lang="he" hreflang="he" data-title="אורדוביק" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%9D%E1%83%A0%E1%83%93%E1%83%9D%E1%83%95%E1%83%98%E1%83%AA%E1%83%98%E1%83%A3%E1%83%9A%E1%83%98_%E1%83%A1%E1%83%98%E1%83%A1%E1%83%A2%E1%83%94%E1%83%9B%E1%83%90" title="ორდოვიციული სისტემა – Georgian" lang="ka" hreflang="ka" data-title="ორდოვიციული სისტემა" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9E%D1%80%D0%B4%D0%BE%D0%B2%D0%B8%D0%BA_%D0%BA%D0%B5%D0%B7%D0%B5%D2%A3%D1%96" title="Ордовик кезеңі – Kazakh" lang="kk" hreflang="kk" data-title="Ордовик кезеңі" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%9E%D1%80%D0%B4%D0%BE%D0%B2%D0%B8%D0%BA_%D0%BC%D0%B5%D0%B7%D0%B3%D0%B8%D0%BB%D0%B8" title="Ордовик мезгили – Kyrgyz" lang="ky" hreflang="ky" data-title="Ордовик мезгили" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Ordovicium" title="Ordovicium – Latin" lang="la" hreflang="la" data-title="Ordovicium" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Ordoviks" title="Ordoviks – Latvian" lang="lv" hreflang="lv" data-title="Ordoviks" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Ordovizium" title="Ordovizium – Luxembourgish" lang="lb" hreflang="lb" data-title="Ordovizium" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Ordovikas" title="Ordovikas – Lithuanian" lang="lt" hreflang="lt" data-title="Ordovikas" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-li mw-list-item"><a href="https://li.wikipedia.org/wiki/Ordovicium" title="Ordovicium – Limburgish" lang="li" hreflang="li" data-title="Ordovicium" data-language-autonym="Limburgs" data-language-local-name="Limburgish" class="interlanguage-link-target"><span>Limburgs</span></a></li><li class="interlanguage-link interwiki-lfn mw-list-item"><a href="https://lfn.wikipedia.org/wiki/Ordovician" title="Ordovician – Lingua Franca Nova" lang="lfn" hreflang="lfn" data-title="Ordovician" data-language-autonym="Lingua Franca Nova" data-language-local-name="Lingua Franca Nova" class="interlanguage-link-target"><span>Lingua Franca Nova</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Ordov%C3%ADcium" title="Ordovícium – Hungarian" lang="hu" hreflang="hu" data-title="Ordovícium" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%9E%D1%80%D0%B4%D0%BE%D0%B2%D0%B8%D0%BA" title="Ордовик – Macedonian" lang="mk" hreflang="mk" data-title="Ордовик" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-mzn mw-list-item"><a href="https://mzn.wikipedia.org/wiki/%D8%A7%D9%88%D8%B1%D8%AF%D9%88%DB%8C%D8%B3%DB%8C%D9%86" title="اوردویسین – Mazanderani" lang="mzn" hreflang="mzn" data-title="اوردویسین" data-language-autonym="مازِرونی" data-language-local-name="Mazanderani" class="interlanguage-link-target"><span>مازِرونی</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Ordovisi" title="Ordovisi – Malay" lang="ms" hreflang="ms" data-title="Ordovisi" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-cdo mw-list-item"><a href="https://cdo.wikipedia.org/wiki/%C3%93%CC%A4-d%C3%B2%CC%A4-g%C4%AB" title="Ó̤-dò̤-gī – Mindong" lang="cdo" hreflang="cdo" data-title="Ó̤-dò̤-gī" data-language-autonym="閩東語 / Mìng-dĕ̤ng-ngṳ̄" data-language-local-name="Mindong" class="interlanguage-link-target"><span>閩東語 / Mìng-dĕ̤ng-ngṳ̄</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Ordovicium" title="Ordovicium – Dutch" lang="nl" hreflang="nl" data-title="Ordovicium" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ne mw-list-item"><a href="https://ne.wikipedia.org/wiki/%E0%A4%85%E0%A4%B5%E0%A4%B0%E0%A4%AA%E0%A5%8D%E0%A4%B0%E0%A4%B5%E0%A4%BE%E0%A4%B2_%E0%A4%AF%E0%A5%81%E0%A4%97" title="अवरप्रवाल युग – Nepali" lang="ne" hreflang="ne" data-title="अवरप्रवाल युग" data-language-autonym="नेपाली" data-language-local-name="Nepali" class="interlanguage-link-target"><span>नेपाली</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%82%AA%E3%83%AB%E3%83%89%E3%83%93%E3%82%B9%E7%B4%80" title="オルドビス紀 – Japanese" lang="ja" hreflang="ja" data-title="オルドビス紀" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-frr mw-list-item"><a href="https://frr.wikipedia.org/wiki/Ordovizium" title="Ordovizium – Northern Frisian" lang="frr" hreflang="frr" data-title="Ordovizium" data-language-autonym="Nordfriisk" data-language-local-name="Northern Frisian" class="interlanguage-link-target"><span>Nordfriisk</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Ordovicium" title="Ordovicium – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Ordovicium" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Ordovicium" title="Ordovicium – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Ordovicium" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Ordovician" title="Ordovician – Occitan" lang="oc" hreflang="oc" data-title="Ordovician" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Ordovik_sistemasi" title="Ordovik sistemasi – Uzbek" lang="uz" hreflang="uz" data-title="Ordovik sistemasi" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D8%A7%D9%88%D8%B1%DA%88%D9%88%D9%88%DB%8C%D8%B4%DB%8C%D9%86" title="اورڈوویشین – Western Punjabi" lang="pnb" hreflang="pnb" data-title="اورڈوویشین" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target"><span>پنجابی</span></a></li><li class="interlanguage-link interwiki-pms mw-list-item"><a href="https://pms.wikipedia.org/wiki/Ordovician" title="Ordovician – Piedmontese" lang="pms" hreflang="pms" data-title="Ordovician" data-language-autonym="Piemontèis" data-language-local-name="Piedmontese" class="interlanguage-link-target"><span>Piemontèis</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Ordowik" title="Ordowik – Polish" lang="pl" hreflang="pl" data-title="Ordowik" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Ordoviciano" title="Ordoviciano – Portuguese" lang="pt" hreflang="pt" data-title="Ordoviciano" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Ordovician" title="Ordovician – Romanian" lang="ro" hreflang="ro" data-title="Ordovician" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9E%D1%80%D0%B4%D0%BE%D0%B2%D0%B8%D0%BA%D1%81%D0%BA%D0%B8%D0%B9_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4" title="Ордовикский период – Russian" lang="ru" hreflang="ru" data-title="Ордовикский период" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-si mw-list-item"><a href="https://si.wikipedia.org/wiki/Ordovician" title="Ordovician – Sinhala" lang="si" hreflang="si" data-title="Ordovician" data-language-autonym="සිංහල" data-language-local-name="Sinhala" class="interlanguage-link-target"><span>සිංහල</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Ordovician" title="Ordovician – Simple English" lang="en-simple" hreflang="en-simple" data-title="Ordovician" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Ordovik" title="Ordovik – Slovak" lang="sk" hreflang="sk" data-title="Ordovik" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Ordovicij" title="Ordovicij – Slovenian" lang="sl" hreflang="sl" data-title="Ordovicij" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-so mw-list-item"><a href="https://so.wikipedia.org/wiki/Ordofisiyaan" title="Ordofisiyaan – Somali" lang="so" hreflang="so" data-title="Ordofisiyaan" data-language-autonym="Soomaaliga" data-language-local-name="Somali" class="interlanguage-link-target"><span>Soomaaliga</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9E%D1%80%D0%B4%D0%BE%D0%B2%D0%B8%D1%86%D0%B8%D1%98%D1%83%D0%BC" title="Ордовицијум – Serbian" lang="sr" hreflang="sr" data-title="Ордовицијум" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Ordovicij" title="Ordovicij – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Ordovicij" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Ordovikikausi" title="Ordovikikausi – Finnish" lang="fi" hreflang="fi" data-title="Ordovikikausi" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Ordovicium" title="Ordovicium – Swedish" lang="sv" hreflang="sv" data-title="Ordovicium" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/Ordovician" title="Ordovician – Tagalog" lang="tl" hreflang="tl" data-title="Ordovician" data-language-autonym="Tagalog" data-language-local-name="Tagalog" class="interlanguage-link-target"><span>Tagalog</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%93%E0%AE%B0%E0%AF%8D%E0%AE%9F%E0%AF%8B%E0%AE%B5%E0%AE%BF%E0%AE%9A%E0%AE%BF%E0%AE%AF%E0%AE%95%E0%AF%8D_%E0%AE%95%E0%AE%BE%E0%AE%B2%E0%AE%AE%E0%AF%8D" title="ஓர்டோவிசியக் காலம் – Tamil" lang="ta" hreflang="ta" data-title="ஓர்டோவிசியக் காலம்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%A2%E0%B8%B8%E0%B8%84%E0%B8%AD%E0%B8%AD%E0%B8%A3%E0%B9%8C%E0%B9%82%E0%B8%94%E0%B8%A7%E0%B8%B4%E0%B9%80%E0%B8%8A%E0%B8%B5%E0%B8%A2%E0%B8%99" title="ยุคออร์โดวิเชียน – Thai" lang="th" hreflang="th" data-title="ยุคออร์โดวิเชียน" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Ordovisiyen" title="Ordovisiyen – Turkish" lang="tr" hreflang="tr" data-title="Ordovisiyen" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%9E%D1%80%D0%B4%D0%BE%D0%B2%D0%B8%D1%86%D1%8C%D0%BA%D0%B8%D0%B9_%D0%BF%D0%B5%D1%80%D1%96%D0%BE%D0%B4" title="Ордовицький період – Ukrainian" lang="uk" hreflang="uk" data-title="Ордовицький період" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D8%A2%D8%B1%D8%AF%D9%88_%D9%88%DB%8C%D8%B3%DB%8C_%D8%AF%D9%88%D8%B1" title="آردو ویسی دور – Urdu" lang="ur" hreflang="ur" data-title="آردو ویسی دور" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/K%E1%BB%B7_Ordovic" title="Kỷ Ordovic – Vietnamese" lang="vi" hreflang="vi" data-title="Kỷ Ordovic" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-vo mw-list-item"><a href="https://vo.wikipedia.org/wiki/Lordovig" title="Lordovig – Volapük" lang="vo" hreflang="vo" data-title="Lordovig" data-language-autonym="Volapük" data-language-local-name="Volapük" class="interlanguage-link-target"><span>Volapük</span></a></li><li class="interlanguage-link interwiki-zh-classical mw-list-item"><a href="https://zh-classical.wikipedia.org/wiki/%E5%A5%A7%E9%99%B6%E7%B4%80" title="奧陶紀 – Literary Chinese" lang="lzh" hreflang="lzh" data-title="奧陶紀" data-language-autonym="文言" data-language-local-name="Literary Chinese" class="interlanguage-link-target"><span>文言</span></a></li><li class="interlanguage-link interwiki-war mw-list-item"><a href="https://war.wikipedia.org/wiki/Ordovician" title="Ordovician – Waray" lang="war" hreflang="war" data-title="Ordovician" data-language-autonym="Winaray" data-language-local-name="Waray" class="interlanguage-link-target"><span>Winaray</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E5%A5%A5%E9%99%B6%E7%BA%AA" title="奥陶纪 – Wu" lang="wuu" hreflang="wuu" data-title="奥陶纪" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-yo mw-list-item"><a href="https://yo.wikipedia.org/wiki/%C3%8Cgb%C3%A0_%E1%BB%8C%CC%80rd%C3%B2f%C3%ADs%C3%AD%C3%A0" title="Ìgbà Ọ̀rdòfísíà – Yoruba" lang="yo" hreflang="yo" data-title="Ìgbà Ọ̀rdòfísíà" data-language-autonym="Yorùbá" data-language-local-name="Yoruba" class="interlanguage-link-target"><span>Yorùbá</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E5%A5%A7%E9%99%B6%E7%B4%80" title="奧陶紀 – Cantonese" lang="yue" hreflang="yue" data-title="奧陶紀" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E5%A5%A5%E9%99%B6%E7%BA%AA" title="奥陶纪 – Chinese" lang="zh" hreflang="zh" data-title="奥陶纪" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q62100#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div 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.infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox" style="width:23em;"><tbody><tr><th colspan="2" class="infobox-above" style="padding:0.25em 0.33em 0.33em;line-height:1.2em;font-size:1.25em;background:rgb(0,146,112);">Ordovician</th></tr><tr><td colspan="2" class="infobox-subheader"><span class="noprint"><span style="display:inline-block;"></span><span style="display:inline-block;">485.4 ± 1.9 – 443.8 ± 1.5 <a href="/wiki/Year#SI_prefix_multipliers" title="Year">Ma</a></span> <span style="display:inline-block;"></span><div id="Timeline-row" style="margin: 4px auto 0; clear:both; width:220px; padding:0px; height:18px; overflow:visible; white-space:nowrap; border:1px #666; border-style:solid none; position:relative; z-index:0; font-size:97%;"> <div style="position:absolute; height:100%; left:0px; width:207.23076923077px; padding-left:5px; text-align:left; background-color:rgb(254,217,106); background-image: linear-gradient(to right, rgba(255,255,255,1), rgba(254,217,106,1) 15%, rgba(254,217,106,1));"><a href="/wiki/Precambrian" title="Precambrian">PreꞒ</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(127,160,86); left:37.636923076923px; width:18.073846153846px;"><a href="/wiki/Cambrian" title="Cambrian">Ꞓ</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(0,146,112); left:55.710769230769px; width:14.08px;"><a class="mw-selflink selflink">O</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(179,225,182); left:69.790769230769px; width:8.3261538461539px;"><a href="/wiki/Silurian" title="Silurian">S</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(203,140,55); left:78.116923076923px; width:20.409230769231px;"><a href="/wiki/Devonian" title="Devonian">D</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(103,165,153); left:98.526153846154px; width:20.307692307692px;"><a href="/wiki/Carboniferous" title="Carboniferous">C</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(240,64,40); left:118.83384615385px; width:15.907015384615px;"><a href="/wiki/Permian" title="Permian">P</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(129,43,146); left:134.74086153846px; width:17.092984615385px;"><a href="/wiki/Triassic" title="Triassic">T</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(52,178,201); left:151.83384615385px; width:19.089230769231px;"><a href="/wiki/Jurassic" title="Jurassic">J</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(127,198,78); left:170.92307692308px; width:26.738461538462px;"><a href="/wiki/Cretaceous" title="Cretaceous">K</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(253,154,82); left:197.66153846154px; width:14.543692307692px;"><a href="/wiki/Paleogene" title="Paleogene">Pg</a></div> <div style="position:absolute; height:100%; text-align:center; background-color:rgb(255,230,25); left:212.20523076923px; width:6.9215384615385px;"><a href="/wiki/Neogene" title="Neogene">N</a></div> <div id="end-border" style="position:absolute; height:100%; background-color:#666; width:1px; left:219px"></div><div style="margin:0 auto; line-height:0; clear:both; width:220px; padding:0px; height:8px; overflow:visible; background-color:transparent; position:relative; top:-4px; z-index:100;"><div style="position:absolute; height:8px; left:55.710769230769px; width:14.08px; background-color:#360; opacity:0.42;"></div> <div style="position:absolute; height:8px; left:55.710769230769px; width:14.08px; background-color:#360; opacity:1;"></div> <div style="position:absolute; height:6px; top:1px; left:56.710769230769px; width:12.08px; background-color:#6c3;"></div> </div> </div></span></td></tr><tr><td colspan="2" class="infobox-image"><span typeof="mw:File"><a href="/wiki/File:Mollweide_Paleographic_Map_of_Earth,_465_Ma_(Darriwilian_Age).png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Mollweide_Paleographic_Map_of_Earth%2C_465_Ma_%28Darriwilian_Age%29.png/250px-Mollweide_Paleographic_Map_of_Earth%2C_465_Ma_%28Darriwilian_Age%29.png" decoding="async" width="250" height="125" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Mollweide_Paleographic_Map_of_Earth%2C_465_Ma_%28Darriwilian_Age%29.png/375px-Mollweide_Paleographic_Map_of_Earth%2C_465_Ma_%28Darriwilian_Age%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Mollweide_Paleographic_Map_of_Earth%2C_465_Ma_%28Darriwilian_Age%29.png/500px-Mollweide_Paleographic_Map_of_Earth%2C_465_Ma_%28Darriwilian_Age%29.png 2x" data-file-width="3610" data-file-height="1810" /></a></span><div class="infobox-caption">A map of Earth as it appeared 465 million years ago during the Middle Ordovician Epoch</div></td></tr><tr><th colspan="2" class="infobox-header" style="background:#ededed;">Chronology</th></tr><tr><td colspan="2" class="infobox-full-data"><div style="font-size:14px"><table id="Container" role="presentation" class="toccolours searchaux" style="text-align:left;padding:0 0.5em;border-style:none;margin:auto;overflow:hidden;min-width:23.65em"><tbody><tr style="vertical-align:top"><td id="Scale" style="padding:0;margin:0.7em 0 0.7em 0;width:4.2em;position:relative;float:left;font-size:100%;height:32em;border-right:1px solid #242020"><div style="float:right;position:absolute;right:-1px;top:29.95em;transform:translateY(-50%)"><span style="font-size:90%">−485 —</span></div><div style="float:right;position:absolute;right:-1px;top:28.24em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:26.53em;transform:translateY(-50%)"><span style="font-size:90%">−480 —</span></div><div style="float:right;position:absolute;right:-1px;top:24.82em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:23.11em;transform:translateY(-50%)"><span style="font-size:90%">−475 —</span></div><div style="float:right;position:absolute;right:-1px;top:21.40em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:19.69em;transform:translateY(-50%)"><span style="font-size:90%">−470 —</span></div><div style="float:right;position:absolute;right:-1px;top:17.98em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:16.27em;transform:translateY(-50%)"><span style="font-size:90%">−465 —</span></div><div style="float:right;position:absolute;right:-1px;top:14.56em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:12.85em;transform:translateY(-50%)"><span style="font-size:90%">−460 —</span></div><div style="float:right;position:absolute;right:-1px;top:11.15em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:9.44em;transform:translateY(-50%)"><span style="font-size:90%">−455 —</span></div><div style="float:right;position:absolute;right:-1px;top:7.73em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:6.02em;transform:translateY(-50%)"><span style="font-size:90%">−450 —</span></div><div style="float:right;position:absolute;right:-1px;top:4.31em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div><div style="float:right;position:absolute;right:-1px;top:2.60em;transform:translateY(-50%)"><span style="font-size:90%">−445 —</span></div><div style="float:right;position:absolute;right:-1px;top:0.89em;transform:translateY(-50%)"><span style="font-size:90%">–</span></div></td><td id="Timeline" class="toccolours notheme" style="padding:0px;margin:0.7em 0 0.7em 0;position:relative;font-size:100%;width:7.5em;height:32em;float:left;border:none;background-color:#000000"><div class="notheme" style="font-size:100%;background-color:rgb(153,192,141);border-style:none none;position:absolute;text-align:center;margin:0;padding:0;top:0.000em;height:32.000em;left:0.000em;width:0.750em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-16.000em;transform:translateY(-50%);z-index:5"><span style="line-height:16px;display:block;"><b><a href="/wiki/Paleozoic" title="Paleozoic"> P <br /> a <br /> l <br /> e <br /> o <br /> z <br /> o <br /> i <br /> c </a></b></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(127,160,86);border-width:0em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:30.222em;height:1.778em;left:0.825em;width:6.675em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-0.889em;transform:translateY(-50%);z-index:5"><b><a href="/wiki/Cambrian" title="Cambrian">Cambrian</a></b></div></div><div class="notheme" style="font-size:100%;background-color:rgb(0,146,112);border-width:0.05em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:1.778em;height:28.344em;left:0.825em;width:0.825em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-14.172em;transform:translateY(-50%);z-index:5"><span style="line-height:14px;display:block;"><b><a class="mw-selflink selflink">O<br />r<br />d<br />o<br />v<br />i<br />c<br />i<br />a<br />n</a></b></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(179,225,182);border-width:0em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:0.000em;height:1.778em;left:0.825em;width:6.675em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-0.889em;transform:translateY(-50%);z-index:5"><b><a href="/wiki/Silurian" title="Silurian">Silurian</a></b></div></div><div class="notheme" style="font-size:100%;border-style:none none;position:absolute;text-align:center;margin:0;padding:0;top:0.000em;height:32.000em;left:0.000em;width:7.500em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-16.000em;transform:translateY(-50%);z-index:5"></div></div><div class="notheme" style="font-size:100%;background-color:rgb(26,157,111);border-width:0.05em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:19.692em;height:10.430em;left:1.725em;width:0.825em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-5.215em;transform:translateY(-50%);z-index:5"><span style="line-height:14px;display:block;"><a href="/wiki/Early_Ordovician" title="Early Ordovician">E<br />a<br />r<br />l<br />y</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(77,180,126);border-width:0em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:11.761em;height:7.932em;left:1.725em;width:0.825em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-3.966em;transform:translateY(-50%);z-index:5"><span style="line-height:14px;display:block;"><a href="/wiki/Middle_Ordovician" class="mw-redirect" title="Middle Ordovician">M<br />i<br />d<br />d<br />l<br />e</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(127,202,147);border-width:0.05em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:1.778em;height:9.883em;left:1.725em;width:0.825em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-4.941em;transform:translateY(-50%);z-index:5"><span style="line-height:14px;display:block;"><a href="/wiki/Late_Ordovician" title="Late Ordovician">L<br />a<br />t<br />e</a></span></div></div><div class="notheme" style="font-size:100%;border-style:none none;position:absolute;text-align:center;margin:0;padding:0;top:0.000em;height:32.000em;left:0.000em;width:7.500em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-16.000em;transform:translateY(-50%);z-index:5"></div></div><div class="notheme" style="font-size:100%;background-color:rgb(51,169,126);border-width:0em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:24.957em;height:5.265em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-2.632em;transform:translateY(-50%);z-index:5"><span style="font-size:80%"><a href="/wiki/Tremadocian" title="Tremadocian">Tremadocian</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(65,176,135);border-width:0.05em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:19.692em;height:5.165em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-2.582em;transform:translateY(-50%);z-index:5"><span style="font-size:90%"><a href="/wiki/Floian" title="Floian">Floian</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(102,192,146);border-width:0em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:17.846em;height:1.846em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-0.923em;transform:translateY(-50%);z-index:5"><span style="font-size:90%"><a href="/wiki/Dapingian" title="Dapingian">Dapingian</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(116,198,156);border-width:0em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:11.761em;height:6.085em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-3.043em;transform:translateY(-50%);z-index:5"><span style="font-size:90%"><a href="/wiki/Darriwilian" title="Darriwilian">Darriwilian</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(140,208,148);border-width:0.05em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:8.068em;height:3.592em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-1.796em;transform:translateY(-50%);z-index:5"><span style="font-size:90%"><a href="/wiki/Sandbian" title="Sandbian">Sandbian</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(153,214,159);border-width:0em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:2.735em;height:5.333em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-2.667em;transform:translateY(-50%);z-index:5"><span style="font-size:90%"><a href="/wiki/Katian" title="Katian">Katian</a></span></div></div><div class="notheme" style="font-size:100%;background-color:rgb(166,219,171);border-width:0.05em;border-style:solid none;position:absolute;text-align:center;margin:0;padding:0;top:1.778em;height:0.857em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-0.429em;transform:translateY(-50%);z-index:5"><span style="font-size:90%"><a href="/wiki/Hirnantian" title="Hirnantian">Hirnantian</a></span></div></div><div class="notheme" style="font-size:100%;background-color:#000000;border-style:none none;position:absolute;text-align:center;margin:0;padding:0;top:0.000em;height:32.000em;left:7.425em;width:0.075em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-16.000em;transform:translateY(-50%);z-index:5"> </div></div><div class="notheme" style="font-size:100%;background-color:#000000;border-style:none none;position:absolute;text-align:center;margin:0;padding:0;top:30.222em;height:0.068em;left:0.825em;width:6.675em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-0.034em;transform:translateY(-50%);z-index:5"> </div></div><div class="notheme" style="font-size:100%;background-color:#000000;border-style:none none;position:absolute;text-align:center;margin:0;padding:0;top:17.778em;height:0.068em;left:2.625em;width:4.875em"><div class="notheme" style="position:relative;text-align:center;vertical-align:middle;display:block;bottom:-0.034em;transform:translateY(-50%);z-index:5"> </div></div></td><td id="Annotations" style="padding:0;margin:0.7em 0 0.7em 0;float:left;position:relative;width:10.25em;height:32em"><table role="presentation" style="position:absolute;z-index:15;top:16.957em;left:0em;transform:translateY(-50%);padding:0;margin:0;font-size:100%"><tbody><tr><td style="padding:0;text-align:left;vertical-align:middle"><span style="color:var( --color-base, #000)">←</span></td><td style="padding:0;text-align:left;vertical-align:middle"><div class="annot-nudge" style="font-size:100%;float:left;position:relative;top:0em"><div style="z-index:10;font-size:75%;color:var( --color-base, #000);display:block;line-height:105%;bottom:0"><span style="line-height:10px;display:block;">First <a href="/wiki/Land_plant" class="mw-redirect" title="Land plant">land plant</a> <a href="/wiki/Spores" class="mw-redirect" title="Spores">spores</a><sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></span></div></div></td></tr></tbody></table><table role="presentation" style="position:absolute;z-index:15;top:17.983em;left:0em;transform:translateY(-50%);padding:0;margin:0;font-size:100%"><tbody><tr><td style="padding:0;text-align:left;vertical-align:middle"><span style="color:var( --color-base, #000)">←</span></td><td style="padding:0;text-align:left;vertical-align:middle"><div class="annot-nudge" style="font-size:100%;float:left;position:relative;top:0.5em"><div style="z-index:10;font-size:75%;color:var( --color-base, #000);display:block;line-height:105%;bottom:0"><span style="line-height:10px;display:block;"><a href="/wiki/Ordovician_meteor_event" title="Ordovician meteor event">Ordovician meteor event</a><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></span></div></div></td></tr></tbody></table></td></tr><tr><td id="Caption" colspan="3" style="padding:0;margin:0 0.2em 0.7em 0.2em"><div id="Caption" class="toccolours" style="margin:0 auto;float:left;border-style:none;clear:both;text-align:center;width:20.5em"><b>Subdivision of the Ordovician according to the <a href="/wiki/International_Commission_on_Stratigraphy" title="International Commission on Stratigraphy">ICS</a>, as of 2023.</b><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><br />Vertical axis scale: Millions of years ago<br /></div></td></tr></tbody></table></div></td></tr><tr><th colspan="2" class="infobox-header" style="background:#ededed;">Etymology</th></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Name formality</th><td class="infobox-data">Formal</td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Name ratified</th><td class="infobox-data">1960</td></tr><tr><th colspan="2" class="infobox-header" style="background:#ededed;">Usage information</th></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Celestial body</th><td class="infobox-data"><a href="/wiki/Geological_history_of_Earth" title="Geological history of Earth">Earth</a></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Regional usage</th><td class="infobox-data">Global (<a href="/wiki/International_Commission_on_Stratigraphy" title="International Commission on Stratigraphy">ICS</a>)</td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Time scale(s) used</th><td class="infobox-data">ICS Time Scale</td></tr><tr><th colspan="2" class="infobox-header" style="background:#ededed;">Definition</th></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Chronological unit</th><td class="infobox-data"><a href="/wiki/Geological_period" class="mw-redirect" title="Geological period">Period</a></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Stratigraphic unit</th><td class="infobox-data"><a href="/wiki/System_(stratigraphy)" title="System (stratigraphy)">System</a></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">First proposed by</th><td class="infobox-data"><a href="/wiki/Charles_Lapworth" title="Charles Lapworth">Charles Lapworth</a>, 1879</td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Time span formality</th><td class="infobox-data">Formal</td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Lower boundary definition</th><td class="infobox-data"><a href="/wiki/First_appearance_datum" title="First appearance datum">FAD</a> of the <a href="/wiki/Conodont" title="Conodont">Conodont</a> <i><a href="/wiki/Iapetognathus_fluctivagus" title="Iapetognathus fluctivagus">Iapetognathus fluctivagus</a></i></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Lower boundary GSSP</th><td class="infobox-data">Greenpoint section, <a href="/wiki/Green_Point,_Newfoundland" class="mw-redirect" title="Green Point, Newfoundland">Green Point</a>, <a href="/wiki/Newfoundland" class="mw-redirect" title="Newfoundland">Newfoundland</a>, <a href="/wiki/Canada" title="Canada">Canada</a><br /><span class="geo-inline"><style data-mw-deduplicate="TemplateStyles:r1156832818">.mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct,.mw-parser-output .geo-inline-hidden{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap}</style><span class="plainlinks nourlexpansion"><a class="external text" href="https://geohack.toolforge.org/geohack.php?pagename=Ordovician&params=49.6829_N_57.9653_W_"><span class="geo-nondefault"><span class="geo-dms" title="Maps, aerial photos, and other data for this location"><span class="latitude">49°40′58″N</span> <span class="longitude">57°57′55″W</span></span></span><span class="geo-multi-punct"> / </span><span class="geo-default"><span class="geo-dec" title="Maps, aerial photos, and other data for this location">49.6829°N 57.9653°W</span><span style="display:none"> / <span class="geo">49.6829; -57.9653</span></span></span></a></span></span></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Lower GSSP ratified</th><td class="infobox-data">2000<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Upper boundary definition</th><td class="infobox-data">FAD of the <a href="/wiki/Graptolite" title="Graptolite">Graptolite</a> <i><a href="/w/index.php?title=Akidograptus_ascensus&action=edit&redlink=1" class="new" title="Akidograptus ascensus (page does not exist)">Akidograptus ascensus</a></i></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Upper boundary GSSP</th><td class="infobox-data"><a href="/wiki/Dob%27s_Linn" title="Dob's Linn">Dob's Linn</a>, <a href="/wiki/Moffat" title="Moffat">Moffat</a>, <a href="/wiki/United_Kingdom" title="United Kingdom">U.K.</a><br /><span class="geo-inline"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1156832818"><span class="plainlinks nourlexpansion"><a class="external text" href="https://geohack.toolforge.org/geohack.php?pagename=Ordovician&params=55.4400_N_3.2700_W_"><span class="geo-nondefault"><span class="geo-dms" title="Maps, aerial photos, and other data for this location"><span class="latitude">55°26′24″N</span> <span class="longitude">3°16′12″W</span></span></span><span class="geo-multi-punct"> / </span><span class="geo-default"><span class="geo-dec" title="Maps, aerial photos, and other data for this location">55.4400°N 3.2700°W</span><span style="display:none"> / <span class="geo">55.4400; -3.2700</span></span></span></a></span></span></td></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Upper GSSP ratified</th><td class="infobox-data">1984<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup></td></tr><tr><th colspan="2" class="infobox-header" style="background:#ededed;">Atmospheric and climatic data</th></tr><tr><th scope="row" class="infobox-label" style="width:10em;">Sea level above present day</th><td class="infobox-data">180 m; rising to 220 m in Caradoc and falling sharply to 140 m in end-Ordovician glaciations<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup></td></tr></tbody></table> <p>The <b>Ordovician</b> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ɔːr/: 'ar' in 'war'">ɔːr</span><span title="'d' in 'dye'">d</span><span title="/ə/: 'a' in 'about'">ə</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="'v' in 'vie'">v</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="/ʃ/: 'sh' in 'shy'">ʃ</span><span title="/i/: 'y' in 'happy'">i</span><span title="/./: syllable break">.</span><span title="/ə/: 'a' in 'about'">ə</span><span title="'n' in 'nigh'">n</span></span>,<span class="wrap"> </span>-<span style="border-bottom:1px dotted"><span title="'d' in 'dye'">d</span><span title="/oʊ/: 'o' in 'code'">oʊ</span></span>-,<span class="wrap"> </span>-<span style="border-bottom:1px dotted"><span title="/ˈ/: primary stress follows">ˈ</span><span title="'v' in 'vie'">v</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="/ʃ/: 'sh' in 'shy'">ʃ</span><span title="/ən/: 'on' in 'button'">ən</span></span>/</a></span></span> <a href="/wiki/Help:Pronunciation_respelling_key" title="Help:Pronunciation respelling key"><i title="English pronunciation respelling">or-də-<span style="font-size:90%">VISH</span>-ee-ən, -⁠doh-, -⁠<span style="font-size:90%">VISH</span>-ən</i></a>)<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> is a <a href="/wiki/Geologic_period" class="mw-redirect" title="Geologic period">geologic period</a> and <a href="/wiki/System_(geology)" class="mw-redirect" title="System (geology)">system</a>, the second of six periods of the <a href="/wiki/Paleozoic" title="Paleozoic">Paleozoic</a> <a href="/wiki/Era_(geology)" class="mw-redirect" title="Era (geology)">Era</a>, and the second of twelve periods of the <a href="/wiki/Phanerozoic" title="Phanerozoic">Phanerozoic</a> <a href="/wiki/Eon_(geology)" class="mw-redirect" title="Eon (geology)">Eon</a>. The Ordovician spans 41.6 million years from the end of the <a href="/wiki/Cambrian" title="Cambrian">Cambrian</a> Period 485.4 <a href="/wiki/Megaannum" class="mw-redirect" title="Megaannum">Ma</a> (million years ago) to the start of the <a href="/wiki/Silurian" title="Silurian">Silurian</a> Period 443.8 Ma.<sup id="cite_ref-ICS2015_10-0" class="reference"><a href="#cite_note-ICS2015-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>The Ordovician, named after the <a href="/wiki/Celtic_Britons" title="Celtic Britons">Welsh</a> tribe of the <a href="/wiki/Ordovices" title="Ordovices">Ordovices</a>, was defined by <a href="/wiki/Charles_Lapworth" title="Charles Lapworth">Charles Lapworth</a> in 1879 to resolve a dispute between followers of <a href="/wiki/Adam_Sedgwick" title="Adam Sedgwick">Adam Sedgwick</a> and <a href="/wiki/Roderick_Murchison" title="Roderick Murchison">Roderick Murchison</a>, who were placing the same <a href="/wiki/Rock_(geology)" title="Rock (geology)">rock</a> beds in <a href="/wiki/North_Wales" title="North Wales">North Wales</a> in the Cambrian and Silurian systems, respectively.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> Lapworth recognized that the <a href="/wiki/Fossil" title="Fossil">fossil</a> <a href="/wiki/Fauna" title="Fauna">fauna</a> in the disputed <a href="/wiki/Stratum" title="Stratum">strata</a> were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the <a href="/wiki/International_Union_of_Geological_Sciences" title="International Union of Geological Sciences">International Geological Congress</a>. </p><p>Life continued to flourish during the Ordovician as it had in the earlier Cambrian Period, although the end of the period was marked by the <a href="/wiki/Ordovician%E2%80%93Silurian_extinction_events" class="mw-redirect" title="Ordovician–Silurian extinction events">Ordovician–Silurian extinction events</a>. Invertebrates, namely <a href="/wiki/Mollusca" title="Mollusca">molluscs</a> and <a href="/wiki/Arthropod" title="Arthropod">arthropods</a>, dominated the oceans, with members of the latter group probably starting their establishment on land during this time, becoming fully established by the <a href="/wiki/Devonian" title="Devonian">Devonian</a>. The first <a href="/wiki/Land_plants" class="mw-redirect" title="Land plants">land plants</a> are known from this period. The <a href="/wiki/Great_Ordovician_Biodiversification_Event" title="Great Ordovician Biodiversification Event">Great Ordovician Biodiversification Event</a> considerably increased the diversity of life. <a href="/wiki/Fish" title="Fish">Fish</a>, the world's first true <a href="/wiki/Vertebrate" title="Vertebrate">vertebrates</a>, continued to evolve, and <a href="/wiki/Gnathostomata" title="Gnathostomata">those with jaws</a> may have first appeared late in the period. About 100 times as many meteorites struck the Earth per year during the Ordovician compared with today in a period known as the <a href="/wiki/Ordovician_meteor_event" title="Ordovician meteor event">Ordovician meteor event</a>.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> It has been theorized that this increase in impacts may originate from <a href="/wiki/Rings_of_Earth" title="Rings of Earth">a ring system</a> that formed around Earth at the time.<sup id="cite_ref-:0_13-0" class="reference"><a href="#cite_note-:0-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Subdivisions">Subdivisions<span class="anchor" id="Subdivisions"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=1" title="Edit section: Subdivisions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><span class="anchor" id="Tremadocian"></span> In 2008, the <a href="/wiki/International_Classification_for_Standards" title="International Classification for Standards">ICS</a> erected a formal international system of subdivisions for the Ordovician Period and System.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> Pre-existing Baltoscandic, British, Siberian, North American, Australian, Chinese, Mediterranean and North-<a href="/wiki/Gondwana" title="Gondwana">Gondwanan</a> regional stratigraphic schemes are also used locally.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="ICS_(global)_subdivisions"><span id="ICS_.28global.29_subdivisions"></span>ICS (global) subdivisions</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=2" title="Edit section: ICS (global) subdivisions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table class="wikitable" width="37%" rules="all" cellpadding="1" style="margin-left:20px; font-size:95%;"> <caption>The Ordovician subdivisions with "<a href="/wiki/GSSP" class="mw-redirect" title="GSSP">golden spikes</a>" according to <a href="/wiki/IUGS" class="mw-redirect" title="IUGS">IUGS</a>:<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </caption> <tbody><tr> <th>System </th> <th>Series </th> <th>Stage/age </th> <th>Lower boundary (<a href="/wiki/Annum" class="mw-redirect" title="Annum">Ma</a>) </th></tr> <tr> <td style="background-color: rgb(179,225,182)"><small><a href="/wiki/Silurian" title="Silurian">Silurian</a></small> </td> <td style="background-color: rgb(153,215,179)"><small><a href="/wiki/Llandovery_Epoch" title="Llandovery Epoch">Llandovery</a></small> </td> <td style="background-color: rgb(166,220,181)"><small><a href="/wiki/Rhuddanian" title="Rhuddanian">Rhuddanian</a></small> </td> <td style="background-color: rgb(166,220,181)" align="center"><small>443.8±1.5</small> </td></tr> <tr> <td rowspan="7" style="background-color: rgb(0,146,112)"><b>Ordovician</b> </td> <td rowspan="3" style="background-color: rgb(127,202,147)"><a href="/wiki/Upper_Ordovician" class="mw-redirect" title="Upper Ordovician">Upper Ordovician</a> </td> <td style="background-color: rgb(166,219,171)"><a href="/wiki/Hirnantian" title="Hirnantian">Hirnantian</a> </td> <td style="background-color: rgb(166,219,171)"><span typeof="mw:File"><a href="/wiki/File:Clavo_dorado.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/10px-Clavo_dorado.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/15px-Clavo_dorado.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/20px-Clavo_dorado.svg.png 2x" data-file-width="37" data-file-height="59" /></a></span>445.2±1.4 </td></tr> <tr> <td style="background-color: rgb(153,214,159)"><a href="/wiki/Katian" title="Katian">Katian</a> </td> <td style="background-color: rgb(153,214,159)"><span typeof="mw:File"><a href="/wiki/File:Clavo_dorado.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/10px-Clavo_dorado.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/15px-Clavo_dorado.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/20px-Clavo_dorado.svg.png 2x" data-file-width="37" data-file-height="59" /></a></span>453.0±0.7 </td></tr> <tr> <td style="background-color: rgb(140,208,148)"><a href="/wiki/Sandbian" title="Sandbian">Sandbian</a> </td> <td style="background-color: rgb(140,208,148)"><span typeof="mw:File"><a href="/wiki/File:Clavo_dorado.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/10px-Clavo_dorado.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/15px-Clavo_dorado.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/20px-Clavo_dorado.svg.png 2x" data-file-width="37" data-file-height="59" /></a></span>458.4±0.9 </td></tr> <tr> <td rowspan="2" style="background-color: rgb(77,180,126)"><b>Middle Ordovician</b> </td> <td style="background-color: rgb(116,198,156)"><a href="/wiki/Darriwilian" title="Darriwilian">Darriwilian</a> </td> <td style="background-color: rgb(116,198,156)"><span typeof="mw:File"><a href="/wiki/File:Clavo_dorado.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/10px-Clavo_dorado.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/15px-Clavo_dorado.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/20px-Clavo_dorado.svg.png 2x" data-file-width="37" data-file-height="59" /></a></span>467.3±1.1 </td></tr> <tr> <td style="background-color: rgb(102,192,146)"><a href="/wiki/Dapingian" title="Dapingian">Dapingian</a> </td> <td style="background-color: rgb(102,192,146)"><span typeof="mw:File"><a href="/wiki/File:Clavo_dorado.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/10px-Clavo_dorado.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/15px-Clavo_dorado.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/20px-Clavo_dorado.svg.png 2x" data-file-width="37" data-file-height="59" /></a></span>470.0±1.4 </td></tr> <tr> <td rowspan="2" style="background-color: rgb(26,157,111)"><a href="/wiki/Lower_Ordovician" class="mw-redirect" title="Lower Ordovician">Lower Ordovician</a> </td> <td style="background-color: rgb(65,176,135)"><a href="/wiki/Floian" title="Floian">Floian</a> </td> <td style="background-color: rgb(65,176,135)"><span typeof="mw:File"><a href="/wiki/File:Clavo_dorado.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/10px-Clavo_dorado.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/15px-Clavo_dorado.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/20px-Clavo_dorado.svg.png 2x" data-file-width="37" data-file-height="59" /></a></span>477.7±1.4 </td></tr> <tr> <td style="background-color: rgb(51,169,126)"><a href="/wiki/Tremadocian" title="Tremadocian">Tremadocian</a> </td> <td style="background-color: rgb(51,169,126)"><span typeof="mw:File"><a href="/wiki/File:Clavo_dorado.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/10px-Clavo_dorado.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/15px-Clavo_dorado.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Clavo_dorado.svg/20px-Clavo_dorado.svg.png 2x" data-file-width="37" data-file-height="59" /></a></span>485.4±1.9 </td></tr> <tr> <td style="background-color: rgb(127,160,86)"><small><a href="/wiki/Cambrian" title="Cambrian">Cambrian</a></small> </td> <td style="background-color: #b6dcad;"><small><a href="/wiki/Furongian" title="Furongian">Furongian</a></small> </td> <td style="background-color: rgb(230,245,201)"><small><a href="/wiki/Cambrian_Stage_10" title="Cambrian Stage 10">Stage 10</a></small> </td> <td style="background-color: rgb(230,245,201)" align="center"><small><b>older</b></small> </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Global/regional_correlation"><span id="Global.2Fregional_correlation"></span>Global/regional correlation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=3" title="Edit section: Global/regional correlation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table class="wikitable"> <caption>Approximate correlation of Ordovician regional series and stages<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </caption> <tbody><tr> <th><a href="/wiki/Series_(stratigraphy)" title="Series (stratigraphy)">ICS series</a></th> <th><a href="/wiki/Stage_(stratigraphy)" title="Stage (stratigraphy)">ICS stage</a></th> <th>British series</th> <th>British stage</th> <th>North American series</th> <th>North American stage</th> <th>Australian stage</th> <th>Chinese stage </th></tr> <tr> <td rowspan="10"><a href="/wiki/Upper_Ordovician" class="mw-redirect" title="Upper Ordovician">Upper Ordovician</a></td> <td><a href="/wiki/Hirnantian" title="Hirnantian">Hirnantian</a></td> <td rowspan="4"><a href="/w/index.php?title=Ashgill_series&action=edit&redlink=1" class="new" title="Ashgill series (page does not exist)">Ashgill</a></td> <td><a href="/wiki/Hirnantian" title="Hirnantian">Hirnantian</a></td> <td rowspan="5">Cincinnatian</td> <td>Gamachian</td> <td rowspan="3">Bolindian</td> <td><a href="/wiki/Hirnantian" title="Hirnantian">Hirnantian</a> </td></tr> <tr> <td rowspan="5"><a href="/wiki/Katian" title="Katian">Katian</a></td> <td>Rawtheyan</td> <td rowspan="2">Richmondian</td> <td rowspan="2">Chientangkiangian </td></tr> <tr> <td>Cautleyan </td></tr> <tr> <td>Pusgillian</td> <td>Maysvillian </td> <td rowspan="3">Eastonian </td> <td rowspan="7">Neichianshanian </td></tr> <tr> <td rowspan="6"><a href="/wiki/Caradoc_series" class="mw-redirect" title="Caradoc series">Caradoc</a></td> <td>Streffordian</td> <td>Edenian </td></tr> <tr> <td>Cheneyan </td> <td rowspan="4">Mohawkian </td> <td rowspan="2">Chatfieldian </td></tr> <tr> <td rowspan="4"><a href="/wiki/Sandbian" title="Sandbian">Sandbian</a></td> <td rowspan="2">Burrellian</td> <td rowspan="4">Gisbornian </td></tr> <tr> <td rowspan="2">Turinian </td></tr> <tr> <td rowspan="2">Aurelucian </td></tr> <tr> <td rowspan="6"><a href="/wiki/Whiterockian" class="mw-redirect" title="Whiterockian">Whiterockian</a> </td> <td rowspan="5"> </td></tr> <tr> <td rowspan="5"><a href="/wiki/Middle_Ordovician" class="mw-redirect" title="Middle Ordovician">Middle Ordovician</a></td> <td rowspan="3"><a href="/wiki/Darriwilian" title="Darriwilian">Darriwilian</a></td> <td rowspan="2"><a href="/wiki/Llanvirn" class="mw-redirect" title="Llanvirn">Llanvirn</a></td> <td>Llandeilo</td> <td rowspan="3"><a href="/wiki/Darriwilian" title="Darriwilian">Darriwilian</a> </td> <td rowspan="3"><a href="/wiki/Darriwilian" title="Darriwilian">Darriwilian</a> </td></tr> <tr> <td>Abereiddian </td></tr> <tr> <td rowspan="7"><a href="/wiki/Arenig" title="Arenig">Arenig</a></td> <td rowspan="2">Fennian </td></tr> <tr> <td rowspan="2"><a href="/wiki/Dapingian" title="Dapingian">Dapingian</a> </td> <td>Yapeenian </td> <td rowspan="2"><a href="/wiki/Dapingian" title="Dapingian">Dapingian</a> </td></tr> <tr> <td rowspan="3">Whitlandian </td> <td>Rangerian </td> <td>Castlemainian </td></tr> <tr> <td rowspan="9"><a href="/wiki/Lower_Ordovician" class="mw-redirect" title="Lower Ordovician">Lower Ordovician</a> </td> <td rowspan="4"><a href="/wiki/Floian" title="Floian">Floian</a> </td> <td rowspan="9">Ibexian </td> <td rowspan="3">Blackhillsian</td> <td>Chewtonian </td> <td rowspan="4">Yiyangian </td></tr> <tr> <td rowspan="2">Bendigonian </td></tr> <tr> <td rowspan="2">Moridunian </td></tr> <tr> <td rowspan="2">Tulean </td> <td rowspan="5">Lancefieldian </td></tr> <tr> <td rowspan="5"><a href="/wiki/Tremadocian" title="Tremadocian">Tremadocian</a></td> <td rowspan="5"><a href="/wiki/Tremadocian" title="Tremadocian">Tremadoc</a></td> <td rowspan="2">Migneintian</td> <td rowspan="5">Xinchangian </td></tr> <tr> <td rowspan="2">Stairsian </td></tr> <tr> <td rowspan="3">Cressagian </td></tr> <tr> <td rowspan="2">Skullrockian </td></tr> <tr> <td>Warendan </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="British_stages_and_ages">British stages and ages</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=4" title="Edit section: British stages and ages"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Ordovician Period in Britain was traditionally broken into Early (Tremadocian and <a href="/wiki/Arenig" title="Arenig">Arenig</a>), Middle (<a href="/w/index.php?title=Llanvirn_Series&action=edit&redlink=1" class="new" title="Llanvirn Series (page does not exist)">Llanvirn</a> (subdivided into Abereiddian and Llandeilian) and <a href="/wiki/Llandeilo_Group" title="Llandeilo Group">Llandeilo</a>) and Late (<a href="/wiki/Caradoc_Series" title="Caradoc Series">Caradoc</a> and Ashgill) epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, or Upper part of the column. </p><p>The Tremadoc corresponds to the ICS's Tremadocian. The Arenig corresponds to the Floian, all of the Dapingian and the early Darriwilian. The Llanvirn corresponds to the late Darriwilian. The Caradoc covers the Sandbian and the first half of the Katian. The Ashgill represents the second half of the Katian, plus the <a href="/wiki/Hirnantian" title="Hirnantian">Hirnantian</a>. </p> <div class="mw-heading mw-heading4"><h4 id="Ashgill">Ashgill</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=5" title="Edit section: Ashgill"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Ashgill Epoch, the last epoch of the British Ordovician, is made of four ages: the Hirnantian Age, the Rawtheyan Age, the <b>Cautleyan</b> Age, and the Pusgillian Age. These ages make up the time period from c. 450 Ma to c. 443 Ma. </p><p>The Rawtheyan, the second last of the Ashgill ages, was from c. 449 Ma to c. 445 Ma. It is in the Katian Age of the ICS's <a href="/wiki/Geologic_Time_Scale" class="mw-redirect" title="Geologic Time Scale">Geologic Time Scale</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Paleogeography_and_tectonics">Paleogeography and tectonics</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=6" title="Edit section: Paleogeography and tectonics"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Earth_Paleogeography_480_Ma_(Early_Ordovician,_Tremadocian).png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Earth_Paleogeography_480_Ma_%28Early_Ordovician%2C_Tremadocian%29.png/220px-Earth_Paleogeography_480_Ma_%28Early_Ordovician%2C_Tremadocian%29.png" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Earth_Paleogeography_480_Ma_%28Early_Ordovician%2C_Tremadocian%29.png/330px-Earth_Paleogeography_480_Ma_%28Early_Ordovician%2C_Tremadocian%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Earth_Paleogeography_480_Ma_%28Early_Ordovician%2C_Tremadocian%29.png/440px-Earth_Paleogeography_480_Ma_%28Early_Ordovician%2C_Tremadocian%29.png 2x" data-file-width="4000" data-file-height="2250" /></a><figcaption>Paleogeographic map of the Earth in the early Ordovician, 480 million years ago</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Earth_Paleogeography_470_Ma_(Early-Middle_Ordovician,_Dapingian).png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Earth_Paleogeography_470_Ma_%28Early-Middle_Ordovician%2C_Dapingian%29.png/220px-Earth_Paleogeography_470_Ma_%28Early-Middle_Ordovician%2C_Dapingian%29.png" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Earth_Paleogeography_470_Ma_%28Early-Middle_Ordovician%2C_Dapingian%29.png/330px-Earth_Paleogeography_470_Ma_%28Early-Middle_Ordovician%2C_Dapingian%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Earth_Paleogeography_470_Ma_%28Early-Middle_Ordovician%2C_Dapingian%29.png/440px-Earth_Paleogeography_470_Ma_%28Early-Middle_Ordovician%2C_Dapingian%29.png 2x" data-file-width="4000" data-file-height="2250" /></a><figcaption>Paleogeographic map of the Earth in the middle Ordovician, 470 million years ago</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Earth_Paleogeography_450_Ma_(Late_Ordovician,_Katian).png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Earth_Paleogeography_450_Ma_%28Late_Ordovician%2C_Katian%29.png/220px-Earth_Paleogeography_450_Ma_%28Late_Ordovician%2C_Katian%29.png" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Earth_Paleogeography_450_Ma_%28Late_Ordovician%2C_Katian%29.png/330px-Earth_Paleogeography_450_Ma_%28Late_Ordovician%2C_Katian%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Earth_Paleogeography_450_Ma_%28Late_Ordovician%2C_Katian%29.png/440px-Earth_Paleogeography_450_Ma_%28Late_Ordovician%2C_Katian%29.png 2x" data-file-width="4000" data-file-height="2254" /></a><figcaption>Paleogeographic map of the Earth in the late Ordovician, 450 million years ago</figcaption></figure> <p>During the Ordovician, the southern continents were assembled into <a href="/wiki/Gondwana" title="Gondwana">Gondwana</a>, which reached from north of the <a href="/wiki/Equator" title="Equator">equator</a> to the <a href="/wiki/South_Pole" title="South Pole">South Pole</a>. The Panthalassic Ocean, centered in the northern hemisphere, covered over half the globe.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> At the start of the period, the continents of <a href="/wiki/Laurentia" title="Laurentia">Laurentia</a> (in present-day <a href="/wiki/North_America" title="North America">North America</a>), <a href="/wiki/Siberia_(continent)" title="Siberia (continent)">Siberia</a>, and <a href="/wiki/Baltica" title="Baltica">Baltica</a> (present-day northern Europe) were separated from Gondwana by over 5,000 kilometres (3,100 mi) of ocean. These smaller continents were also sufficiently widely separated from each other to develop distinct communities of benthic organisms.<sup id="cite_ref-FOOTNOTETorsvikCocks2017102_19-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> The small continent of <a href="/wiki/Avalonia" title="Avalonia">Avalonia</a> had just rifted from Gondwana and began to move north towards Baltica and Laurentia, opening the <a href="/wiki/Rheic_Ocean" title="Rheic Ocean">Rheic Ocean</a> between Gondwana and Avalonia.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-FOOTNOTETorsvikCocks2017103_22-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017103-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Avalonia collided with Baltica towards the end of Ordovician.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-FOOTNOTETorsvikCocks2017112_24-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017112-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>Other geographic features of the Ordovician world included the <a href="/wiki/Tornquist_Sea" title="Tornquist Sea">Tornquist Sea</a>, which separated Avalonia from Baltica;<sup id="cite_ref-FOOTNOTETorsvikCocks2017102_19-1" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> the Aegir Ocean, which separated Baltica from Siberia;<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> and an oceanic area between Siberia, Baltica, and Gondwana which expanded to become the Paleoasian Ocean in Carboniferous time. The <a href="/wiki/Mongol-Okhotsk_Ocean" title="Mongol-Okhotsk Ocean">Mongol-Okhotsk Ocean</a> formed a deep embayment between Siberia and the Central Mongolian <a href="/wiki/Terrane" title="Terrane">terranes</a>. Most of the terranes of central Asia were part of an equatorial archipelago whose geometry is poorly constrained by the available evidence.<sup id="cite_ref-FOOTNOTETorsvikCocks2017102,_106_26-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102,_106-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p><p>The period was one of extensive, widespread tectonism and volcanism. However, <a href="/wiki/Orogenesis" class="mw-redirect" title="Orogenesis">orogenesis</a> (mountain-building) was not primarily due to continent-continent collisions. Instead, mountains arose along active continental margins during accretion of arc terranes or ribbon microcontinents. Accretion of new crust was limited to the Iapetus margin of Laurentia; elsewhere, the pattern was of rifting in back-arc basins followed by remerger. This reflected episodic switching from extension to compression. The initiation of new subduction reflected a global reorganization of tectonic plates centered on the amalgamation of Gondwana.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-FOOTNOTETorsvikCocks2017102_19-2" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Taconic_orogeny" title="Taconic orogeny">Taconic orogeny</a>, a major mountain-building episode, was well under way in Cambrian times.<sup id="cite_ref-FOOTNOTETorsvikCocks201793–94_28-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks201793–94-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> This continued into the Ordovician, when at least two <a href="/wiki/Volcanic_arc" title="Volcanic arc">volcanic island arcs</a> collided with Laurentia to form the <a href="/wiki/Appalachian_Mountains" title="Appalachian Mountains">Appalachian Mountains</a>. Laurentia was otherwise tectonically stable. An island arc accreted to South China during the period, while subduction along north China (Sulinheer) resulted in the emplacement of ophiolites.<sup id="cite_ref-FOOTNOTETorsvikCocks2017106–109_29-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017106–109-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Ash_fall" class="mw-redirect" title="Ash fall">ash fall</a> of the Millburg/Big Bentonite bed, at about 454 Ma, was the largest in the last 590 million years. This had a <a href="/wiki/Dense_rock_equivalent" class="mw-redirect" title="Dense rock equivalent">dense rock equivalent</a> volume of as much as 1,140 cubic kilometres (270 cu mi). Remarkably, this appears to have had little impact on life.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p><p>There was vigorous tectonic activity along northwest margin of Gondwana during the Floian, 478 Ma, recorded in the Central Iberian Zone of Spain. The activity reached as far as Turkey by the end of Ordovician. The opposite margin of Gondwana, in Australia, faced a set of island arcs.<sup id="cite_ref-FOOTNOTETorsvikCocks2017102_19-3" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> The accretion of these arcs to the eastern margin of Gondwana was responsible for the Benambran Orogeny of eastern Australia.<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-FOOTNOTETorsvikCocks2017105_32-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017105-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> Subduction also took place along what is now Argentina (Famatinian Orogeny) at 450 Ma.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> This involved significant back arc rifting.<sup id="cite_ref-FOOTNOTETorsvikCocks2017102_19-4" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> The interior of Gondwana was tectonically quiet until the <a href="/wiki/Triassic" title="Triassic">Triassic</a>.<sup id="cite_ref-FOOTNOTETorsvikCocks2017102_19-5" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>Towards the end of the period, Gondwana began to drift across the South Pole. This contributed to the Hibernian glaciation and the associated extinction event.<sup id="cite_ref-FOOTNOTETorsvikCocks2017103–105_34-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017103–105-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Ordovician_meteor_event">Ordovician meteor event</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=7" title="Edit section: Ordovician meteor event"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Ordovician_meteor_event" title="Ordovician meteor event">Ordovician meteor event</a> is a proposed shower of meteors that occurred during the Middle Ordovician Epoch, about 467.5 ± 0.28 million years ago, due to the break-up of the <a href="/wiki/L_chondrite" title="L chondrite">L chondrite</a> parent body.<sup id="cite_ref-Lindskog_35-0" class="reference"><a href="#cite_note-Lindskog-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> It is not associated with any major extinction event.<sup id="cite_ref-Nature1_36-0" class="reference"><a href="#cite_note-Nature1-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> A 2024 study found that craters from this event cluster in a distinct band around the Earth, and that the breakup of the parent body may have formed a <a href="/wiki/Ring_system" title="Ring system">ring system</a> for a period of about 40 million years, with frequent falling debris causing these craters.<sup id="cite_ref-:0_13-1" class="reference"><a href="#cite_note-:0-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Geochemistry">Geochemistry</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=8" title="Edit section: Geochemistry"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Anomalodonta_gigantea_Waynesville_Franklin_Co_IN.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/af/Anomalodonta_gigantea_Waynesville_Franklin_Co_IN.JPG/220px-Anomalodonta_gigantea_Waynesville_Franklin_Co_IN.JPG" decoding="async" width="220" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/af/Anomalodonta_gigantea_Waynesville_Franklin_Co_IN.JPG/330px-Anomalodonta_gigantea_Waynesville_Franklin_Co_IN.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/af/Anomalodonta_gigantea_Waynesville_Franklin_Co_IN.JPG/440px-Anomalodonta_gigantea_Waynesville_Franklin_Co_IN.JPG 2x" data-file-width="3872" data-file-height="2592" /></a><figcaption>External mold of Ordovician <a href="/wiki/Bivalvia" title="Bivalvia">bivalve</a> showing that the original <a href="/wiki/Aragonite" title="Aragonite">aragonite</a> shell dissolved on the sea floor, leaving a cemented mold for biological encrustation (<a href="/wiki/Waynesville_Formation" title="Waynesville Formation">Waynesville Formation</a> of Franklin County, Indiana).</figcaption></figure> <p>The Ordovician was a time of <a href="/wiki/Calcite_sea" title="Calcite sea">calcite sea</a> geochemistry in which low-magnesium <a href="/wiki/Calcite" title="Calcite">calcite</a> was the primary inorganic marine precipitate of <a href="/wiki/Calcium_carbonate" title="Calcium carbonate">calcium carbonate</a>.<sup id="cite_ref-JonesEtAl2019_39-0" class="reference"><a href="#cite_note-JonesEtAl2019-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Carbonate_hardgrounds" title="Carbonate hardgrounds">Carbonate hardgrounds</a> were thus very common, along with calcitic <a href="/wiki/Ooid" title="Ooid">ooids</a>, calcitic cements, and invertebrate faunas with dominantly calcitic skeletons. Biogenic <a href="/wiki/Aragonite" title="Aragonite">aragonite</a>, like that composing the shells of most <a href="/wiki/Mollusca" title="Mollusca">molluscs</a>, dissolved rapidly on the sea floor after death.<sup id="cite_ref-Stanley1998_40-0" class="reference"><a href="#cite_note-Stanley1998-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Stanley1999_41-0" class="reference"><a href="#cite_note-Stanley1999-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> </p><p>Unlike Cambrian times, when calcite production was dominated by microbial and non-biological processes, animals (and macroalgae) became a dominant source of calcareous material in Ordovician deposits.<sup id="cite_ref-Munnecke2010_42-0" class="reference"><a href="#cite_note-Munnecke2010-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Climate_and_sea_level">Climate and sea level</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=9" title="Edit section: Climate and sea level"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Early Ordovician climate was very hot,<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> with intense <a href="/wiki/Greenhouse_and_icehouse_Earth" title="Greenhouse and icehouse Earth">greenhouse</a> conditions and <a href="/wiki/Sea_surface_temperature" title="Sea surface temperature">sea surface temperatures</a> comparable to those during the Early Eocene Climatic Optimum.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Carbon_dioxide" title="Carbon dioxide">Carbon dioxide</a> levels were very high at the Ordovician period's beginning.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> By the late Early Ordovician, the Earth cooled,<sup id="cite_ref-MayaElrick_46-0" class="reference"><a href="#cite_note-MayaElrick-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> giving way to a more temperate climate in the Middle Ordovician,<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> with the Earth likely entering the <a href="/wiki/Late_Ordovician_glaciation" class="mw-redirect" title="Late Ordovician glaciation">Early Palaeozoic Ice Age</a> during the Sandbian,<sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> and possibly as early as the Darriwilian<sup id="cite_ref-EPIA_50-0" class="reference"><a href="#cite_note-EPIA-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> or even the Floian.<sup id="cite_ref-MayaElrick_46-1" class="reference"><a href="#cite_note-MayaElrick-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> The Dapingian and Sandbian saw major humidification events evidenced by trace metal concentrations in Baltoscandia from this time.<sup id="cite_ref-HumidClimaticEvents_51-0" class="reference"><a href="#cite_note-HumidClimaticEvents-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> Evidence suggests that global temperatures rose briefly in the early Katian (Boda Event), depositing bioherms and radiating fauna across Europe.<sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup> The early Katian also witnessed yet another humidification event.<sup id="cite_ref-HumidClimaticEvents_51-1" class="reference"><a href="#cite_note-HumidClimaticEvents-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> Further cooling during the Hirnantian, at the end of the Ordovician, led to the <a href="/wiki/Late_Ordovician_glaciation" class="mw-redirect" title="Late Ordovician glaciation">Late Ordovician glaciation</a>.<sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup> </p><p>The Ordovician saw the highest sea levels of the Paleozoic, and the low relief of the continents led to many shelf deposits being formed under hundreds of metres of water.<sup id="cite_ref-Munnecke2010_42-1" class="reference"><a href="#cite_note-Munnecke2010-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> The sea level rose more or less continuously throughout the Early Ordovician, leveling off somewhat during the middle of the period.<sup id="cite_ref-Munnecke2010_42-2" class="reference"><a href="#cite_note-Munnecke2010-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> Locally, some regressions occurred, but the sea level rise continued in the beginning of the Late Ordovician. Sea levels fell steadily due to the cooling temperatures for about 3 million years leading up to the Hirnantian glaciation. During this icy stage, sea level seems to have risen and dropped somewhat. Despite much study, the details remain unresolved.<sup id="cite_ref-Munnecke2010_42-3" class="reference"><a href="#cite_note-Munnecke2010-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> In particular, some researches interpret the fluctuations in sea level as pre-Hibernian glaciation,<sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> but sedimentary evidence of glaciation is lacking until the end of the period.<sup id="cite_ref-FOOTNOTETorsvikCocks2017112_24-1" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017112-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> There is evidence of <a href="/wiki/Glacier" title="Glacier">glaciers</a> during the Hirnantian on the <a href="/wiki/Gondwana" title="Gondwana">land we now know</a> as Africa and South America, which were near the <a href="/wiki/South_Pole" title="South Pole">South Pole</a> at the time, facilitating the formation of the <a href="/wiki/Ice_cap" title="Ice cap">ice caps</a> of the Hirnantian glaciation. </p><p>As with <a href="/wiki/North_America" title="North America">North America</a> and <a href="/wiki/Europe" title="Europe">Europe</a>, <a href="/wiki/Gondwana" title="Gondwana">Gondwana</a> was largely covered with shallow seas during the Ordovician. Shallow clear waters over continental shelves encouraged the growth of organisms that deposit calcium carbonates in their shells and hard parts. The <a href="/wiki/Panthalassic_Ocean" class="mw-redirect" title="Panthalassic Ocean">Panthalassic Ocean</a> covered much of the <a href="/wiki/Northern_Hemisphere" title="Northern Hemisphere">Northern Hemisphere</a>, and other minor oceans included <a href="/wiki/Proto-Tethys_Ocean" title="Proto-Tethys Ocean">Proto-Tethys</a>, <a href="/wiki/Paleo-Tethys_Ocean" title="Paleo-Tethys Ocean">Paleo-Tethys</a>, <a href="/wiki/Khanty_Ocean" title="Khanty Ocean">Khanty Ocean</a>, which was closed off by the Late Ordovician, <a href="/wiki/Iapetus_Ocean" title="Iapetus Ocean">Iapetus Ocean</a>, and the new <a href="/wiki/Rheic_Ocean" title="Rheic Ocean">Rheic Ocean</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Life">Life</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=10" title="Edit section: Life"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Nmnh_fg09.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Nmnh_fg09.jpg/220px-Nmnh_fg09.jpg" decoding="async" width="220" height="147" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Nmnh_fg09.jpg/330px-Nmnh_fg09.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0a/Nmnh_fg09.jpg/440px-Nmnh_fg09.jpg 2x" data-file-width="1000" data-file-height="669" /></a><figcaption>A <a href="/wiki/Diorama" title="Diorama">diorama</a> depicting Ordovician flora and fauna</figcaption></figure> <p>For most of the Late Ordovician life continued to flourish, but at and near the end of the period there were <a href="/wiki/Ordovician%E2%80%93Silurian_extinction_events" class="mw-redirect" title="Ordovician–Silurian extinction events">mass-extinction events</a> that seriously affected <a href="/wiki/Conodont" title="Conodont">conodonts</a> and <a href="/wiki/Plankton" title="Plankton">planktonic</a> forms like <a href="/wiki/Graptolithina" class="mw-redirect" title="Graptolithina">graptolites</a>. The <a href="/wiki/Trilobite" title="Trilobite">trilobites</a> <a href="/wiki/Agnostida" title="Agnostida">Agnostida</a> and <a href="/wiki/Ptychopariida" title="Ptychopariida">Ptychopariida</a> completely died out, and the <a href="/wiki/Asaphida" title="Asaphida">Asaphida</a> were much reduced. <a href="/wiki/Brachiopod" title="Brachiopod">Brachiopods</a>, <a href="/wiki/Bryozoa" title="Bryozoa">bryozoans</a> and <a href="/wiki/Echinoderm" title="Echinoderm">echinoderms</a> were also heavily affected, and the <a href="/wiki/Endocerid" class="mw-redirect" title="Endocerid">endocerid</a> <a href="/wiki/Cephalopod" title="Cephalopod">cephalopods</a> died out completely, except for possible rare Silurian forms. The Ordovician–Silurian extinction events may have been caused by an ice age that occurred at the end of the Ordovician Period, due to the expansion of the <a href="/wiki/Moss#Geological_history" title="Moss">first terrestrial plants</a>,<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup> as the end of the Late Ordovician was one of the coldest times in the last 600 million years of Earth's history. </p> <div class="mw-heading mw-heading3"><h3 id="Fauna">Fauna</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=11" title="Edit section: Fauna"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Endoceras_life_restoration.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Endoceras_life_restoration.png/190px-Endoceras_life_restoration.png" decoding="async" width="190" height="570" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Endoceras_life_restoration.png/285px-Endoceras_life_restoration.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Endoceras_life_restoration.png/380px-Endoceras_life_restoration.png 2x" data-file-width="2000" data-file-height="6000" /></a><figcaption><i><a href="/wiki/Endoceras" title="Endoceras">Endoceras</a></i>, one of the largest predators of the Ordovician</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:LibertyFormationSlab092313.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/LibertyFormationSlab092313.jpg/220px-LibertyFormationSlab092313.jpg" decoding="async" width="220" height="182" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/LibertyFormationSlab092313.jpg/330px-LibertyFormationSlab092313.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/67/LibertyFormationSlab092313.jpg/440px-LibertyFormationSlab092313.jpg 2x" data-file-width="2872" data-file-height="2376" /></a><figcaption><a href="/wiki/Fossiliferous_limestone" title="Fossiliferous limestone">Fossiliferous limestone</a> slab from the Liberty Formation (Upper Ordovician) of Caesar Creek State Park near Waynesville, Ohio.</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Isotelus_trilobite_from_Wisconsin.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9b/Isotelus_trilobite_from_Wisconsin.jpg/220px-Isotelus_trilobite_from_Wisconsin.jpg" decoding="async" width="220" height="302" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9b/Isotelus_trilobite_from_Wisconsin.jpg/330px-Isotelus_trilobite_from_Wisconsin.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9b/Isotelus_trilobite_from_Wisconsin.jpg/440px-Isotelus_trilobite_from_Wisconsin.jpg 2x" data-file-width="3588" data-file-height="4928" /></a><figcaption>The trilobite <i><a href="/wiki/Isotelus" title="Isotelus">Isotelus</a></i> from <a href="/wiki/Wisconsin" title="Wisconsin">Wisconsin</a></figcaption></figure><p> On the whole, the fauna that emerged in the Ordovician were the template for the remainder of the Palaeozoic. The fauna was dominated by tiered communities of suspension feeders, mainly with short food chains. The ecological system reached a new grade of complexity far beyond that of the Cambrian fauna, which has persisted until the present day.<sup id="cite_ref-Munnecke2010_42-4" class="reference"><a href="#cite_note-Munnecke2010-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> Though less famous than the <a href="/wiki/Cambrian_explosion" title="Cambrian explosion">Cambrian explosion</a>, the <a href="/wiki/Ordovician_radiation" class="mw-redirect" title="Ordovician radiation">Ordovician radiation</a> (also known as the Great Ordovician Biodiversification Event)<sup id="cite_ref-FOOTNOTETorsvikCocks2017102_19-6" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017102-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> was no less remarkable; marine faunal <a href="/wiki/Genus" title="Genus">genera</a> increased fourfold, resulting in 12% of all known <a href="/wiki/Phanerozoic" title="Phanerozoic">Phanerozoic</a> marine fauna.<sup id="cite_ref-Dixon2001_56-0" class="reference"><a href="#cite_note-Dixon2001-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> Several animals also went through a miniaturization process, becoming much smaller than their Cambrian counterparts.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (September 2023)">citation needed</span></a></i>]</sup> Another change in the fauna was the strong increase in <a href="/wiki/Filter_feeder" title="Filter feeder">filter-feeding</a> organisms.<sup id="cite_ref-57" class="reference"><a href="#cite_note-57"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup> The trilobite, inarticulate brachiopod, <a href="/wiki/Archaeocyatha" title="Archaeocyatha">archaeocyathid</a>, and <a href="/wiki/Eocrinoidea" title="Eocrinoidea">eocrinoid</a> faunas of the Cambrian were succeeded by those that dominated the rest of the Paleozoic, such as articulate brachiopods, <a href="/wiki/Cephalopod" title="Cephalopod">cephalopods</a>, and <a href="/wiki/Crinoid" title="Crinoid">crinoids</a>. Articulate brachiopods, in particular, largely replaced trilobites in <a href="/wiki/Continental_shelf" title="Continental shelf">shelf</a> communities. Their success epitomizes the greatly increased diversity of <a href="/wiki/Calcium_carbonate" title="Calcium carbonate">carbonate</a> shell-secreting organisms in the Ordovician compared to the Cambrian.<sup id="cite_ref-Cooper1986_58-0" class="reference"><a href="#cite_note-Cooper1986-58"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup></p><figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:20191205_Aegirocassis_benmoulai_Aegirocassis_benmoulae.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/92/20191205_Aegirocassis_benmoulai_Aegirocassis_benmoulae.png/220px-20191205_Aegirocassis_benmoulai_Aegirocassis_benmoulae.png" decoding="async" width="220" height="81" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/92/20191205_Aegirocassis_benmoulai_Aegirocassis_benmoulae.png/330px-20191205_Aegirocassis_benmoulai_Aegirocassis_benmoulae.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/92/20191205_Aegirocassis_benmoulai_Aegirocassis_benmoulae.png/440px-20191205_Aegirocassis_benmoulai_Aegirocassis_benmoulae.png 2x" data-file-width="1900" data-file-height="700" /></a><figcaption><i><a href="/wiki/Aegirocassis" title="Aegirocassis">Aegirocassis</a></i>, a large filter-feeding <a href="/wiki/Hurdiidae" title="Hurdiidae">hurdiid</a> <a href="/wiki/Radiodonta" title="Radiodonta">radiodont</a> from <a href="/wiki/Morocco" title="Morocco">Morocco</a> </figcaption></figure> <p>Ordovician geography had its effect on the diversity of fauna; Ordovician invertebrates displayed a very high degree of provincialism.<sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup> The widely separated continents of Laurentia and Baltica, then positioned close to the tropics and boasting many shallow seas rich in life, developed distinct trilobite faunas from the trilobite fauna of Gondwana,<sup id="cite_ref-60" class="reference"><a href="#cite_note-60"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup> and Gondwana developed distinct fauna in its tropical and temperature zones.<sup id="cite_ref-61" class="reference"><a href="#cite_note-61"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> The Tien Shan terrane maintained a biogeographic affinity with Gondwana,<sup id="cite_ref-62" class="reference"><a href="#cite_note-62"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup> and the Alborz margin of Gondwana was linked biogeographically to South China.<sup id="cite_ref-63" class="reference"><a href="#cite_note-63"><span class="cite-bracket">[</span>63<span class="cite-bracket">]</span></a></sup> Southeast Asia's fauna also maintained strong affinities to Gondwana's.<sup id="cite_ref-64" class="reference"><a href="#cite_note-64"><span class="cite-bracket">[</span>64<span class="cite-bracket">]</span></a></sup> North China was biogeographically connected to Laurentia and the Argentinian margin of Gondwana.<sup id="cite_ref-65" class="reference"><a href="#cite_note-65"><span class="cite-bracket">[</span>65<span class="cite-bracket">]</span></a></sup> A Celtic biogeographic province also existed, separate from the Laurentian and Baltican ones.<sup id="cite_ref-66" class="reference"><a href="#cite_note-66"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup> However, tropical articulate brachiopods had a more <a href="/wiki/Cosmopolitan_distribution" title="Cosmopolitan distribution">cosmopolitan distribution</a>, with less diversity on different continents. During the Middle Ordovician, beta diversity began a significant decline as marine taxa began to disperse widely across space.<sup id="cite_ref-67" class="reference"><a href="#cite_note-67"><span class="cite-bracket">[</span>67<span class="cite-bracket">]</span></a></sup> Faunas become less provincial later in the Ordovician, partly due to the narrowing of the Iapetus Ocean,<sup id="cite_ref-68" class="reference"><a href="#cite_note-68"><span class="cite-bracket">[</span>68<span class="cite-bracket">]</span></a></sup> though they were still distinguishable into the late Ordovician.<sup id="cite_ref-FOOTNOTETorsvikCocks2017112-113_69-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017112-113-69"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Eurypterids_Pentecopterus_Vertical.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/84/Eurypterids_Pentecopterus_Vertical.jpg/220px-Eurypterids_Pentecopterus_Vertical.jpg" decoding="async" width="220" height="285" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/84/Eurypterids_Pentecopterus_Vertical.jpg/330px-Eurypterids_Pentecopterus_Vertical.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/84/Eurypterids_Pentecopterus_Vertical.jpg/440px-Eurypterids_Pentecopterus_Vertical.jpg 2x" data-file-width="1545" data-file-height="2000" /></a><figcaption><i><a href="/wiki/Pentecopterus" title="Pentecopterus">Pentecopterus</a></i>, the earliest known eurypterid, and found in <a href="/wiki/Iowa" title="Iowa">Iowa</a></figcaption></figure> <p><a href="/wiki/Trilobite" title="Trilobite">Trilobites</a> in particular were rich and diverse, and experienced rapid diversification in many regions.<sup id="cite_ref-70" class="reference"><a href="#cite_note-70"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup> Trilobites in the Ordovician were very different from their predecessors in the Cambrian. Many trilobites developed bizarre spines and nodules to defend against predators such as primitive <a href="/wiki/Eurypterid" title="Eurypterid">eurypterids</a> and nautiloids while other trilobites such as <i>Aeglina prisca</i> evolved to become swimming forms. Some trilobites even developed shovel-like snouts for ploughing through muddy sea bottoms. Another unusual clade of trilobites known as the trinucleids developed a broad pitted margin around their head shields.<sup id="cite_ref-Palaeos.com_71-0" class="reference"><a href="#cite_note-Palaeos.com-71"><span class="cite-bracket">[</span>71<span class="cite-bracket">]</span></a></sup> Some trilobites such as <i>Asaphus kowalewski</i> evolved long eyestalks to assist in detecting predators whereas other trilobite eyes in contrast disappeared completely.<sup id="cite_ref-72" class="reference"><a href="#cite_note-72"><span class="cite-bracket">[</span>72<span class="cite-bracket">]</span></a></sup> Molecular clock analyses suggest that early arachnids started living on land by the end of the Ordovician.<sup id="cite_ref-73" class="reference"><a href="#cite_note-73"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup> Although solitary <a href="/wiki/Coral" title="Coral">corals</a> date back to at least the <a href="/wiki/Cambrian" title="Cambrian">Cambrian</a>, <a href="/wiki/Coral_reef" title="Coral reef">reef</a>-forming corals appeared in the early Ordovician, including the earliest known <a href="/wiki/Octocorallia" title="Octocorallia">octocorals</a>,<sup id="cite_ref-Taylor2013Pywackia_74-0" class="reference"><a href="#cite_note-Taylor2013Pywackia-74"><span class="cite-bracket">[</span>74<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-75" class="reference"><a href="#cite_note-75"><span class="cite-bracket">[</span>75<span class="cite-bracket">]</span></a></sup> corresponding to an increase in the stability of carbonate and thus a new abundance of calcifying animals.<sup id="cite_ref-Munnecke2010_42-5" class="reference"><a href="#cite_note-Munnecke2010-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> Brachiopods surged in diversity, adapting to almost every type of marine environment.<sup id="cite_ref-76" class="reference"><a href="#cite_note-76"><span class="cite-bracket">[</span>76<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-77" class="reference"><a href="#cite_note-77"><span class="cite-bracket">[</span>77<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-78" class="reference"><a href="#cite_note-78"><span class="cite-bracket">[</span>78<span class="cite-bracket">]</span></a></sup> Even after GOBE, there is evidence suggesting that Ordovician brachiopods maintained elevated rates of speciation.<sup id="cite_ref-79" class="reference"><a href="#cite_note-79"><span class="cite-bracket">[</span>79<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Mollusca" title="Mollusca">Molluscs</a>, which appeared during the Cambrian or even the <a href="/wiki/Ediacaran" title="Ediacaran">Ediacaran</a>, became common and varied, especially <a href="/wiki/Bivalvia" title="Bivalvia">bivalves</a>, <a href="/wiki/Gastropoda" title="Gastropoda">gastropods</a>, and <a href="/wiki/Nautiloid" title="Nautiloid">nautiloid</a> cephalopods.<sup id="cite_ref-Novack-GottshallMiller2003_80-0" class="reference"><a href="#cite_note-Novack-GottshallMiller2003-80"><span class="cite-bracket">[</span>80<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-RexCrick_81-0" class="reference"><a href="#cite_note-RexCrick-81"><span class="cite-bracket">[</span>81<span class="cite-bracket">]</span></a></sup> Cephalopods diversified from shallow marine tropical environments to dominate almost all marine environments.<sup id="cite_ref-KrögerAndYun-Bai2009_82-0" class="reference"><a href="#cite_note-KrögerAndYun-Bai2009-82"><span class="cite-bracket">[</span>82<span class="cite-bracket">]</span></a></sup> Graptolites, which evolved in the preceding Cambrian period, thrived in the oceans.<sup id="cite_ref-83" class="reference"><a href="#cite_note-83"><span class="cite-bracket">[</span>83<span class="cite-bracket">]</span></a></sup> This includes the distinctive <i>Nemagraptus gracilis</i> graptolite fauna, which was distributed widely during peak sea levels in the Sandbian.<sup id="cite_ref-FinneyAndBergström1986_84-0" class="reference"><a href="#cite_note-FinneyAndBergström1986-84"><span class="cite-bracket">[</span>84<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-FOOTNOTETorsvikCocks2017112_24-2" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017112-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> Some new cystoids and crinoids appeared. It was long thought that the first true <a href="/wiki/Vertebrata" class="mw-redirect" title="Vertebrata">vertebrates</a> (fish — <a href="/wiki/Ostracoderm" title="Ostracoderm">Ostracoderms</a>) appeared in the Ordovician, but recent discoveries in <a href="/wiki/China" title="China">China</a> reveal that they probably originated in the Early <a href="/wiki/Cambrian" title="Cambrian">Cambrian</a>.<sup id="cite_ref-85" class="reference"><a href="#cite_note-85"><span class="cite-bracket">[</span>85<span class="cite-bracket">]</span></a></sup> The first <a href="/wiki/Gnathostomata" title="Gnathostomata">gnathostome</a> (jawed fish) may have appeared in the <a href="/wiki/Late_Ordovician_glaciation" class="mw-redirect" title="Late Ordovician glaciation">Late Ordovician</a> epoch.<sup id="cite_ref-Brazeau-Friedman-2015_86-0" class="reference"><a href="#cite_note-Brazeau-Friedman-2015-86"><span class="cite-bracket">[</span>86<span class="cite-bracket">]</span></a></sup> Chitinozoans, which first appeared late in the Wuliuan, exploded in diversity during the Tremadocian, quickly becoming globally widespread.<sup id="cite_ref-NõlvakLiangHints2019PPP_87-0" class="reference"><a href="#cite_note-NõlvakLiangHints2019PPP-87"><span class="cite-bracket">[</span>87<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-LiangEtAl2017PPP_88-0" class="reference"><a href="#cite_note-LiangEtAl2017PPP-88"><span class="cite-bracket">[</span>88<span class="cite-bracket">]</span></a></sup> Several groups of endobiotic symbionts appeared in the Ordovician.<sup id="cite_ref-VinnMotus2012_89-0" class="reference"><a href="#cite_note-VinnMotus2012-89"><span class="cite-bracket">[</span>89<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-VinnWilsonMotusToom2014_90-0" class="reference"><a href="#cite_note-VinnWilsonMotusToom2014-90"><span class="cite-bracket">[</span>90<span class="cite-bracket">]</span></a></sup> </p><p>In the Early Ordovician, trilobites were joined by many new types of organisms, including <a href="/wiki/Tabulata" title="Tabulata">tabulate</a> corals, <a href="/wiki/Strophomenida" title="Strophomenida">strophomenid</a>, <a href="/wiki/Rhynchonellida" title="Rhynchonellida">rhynchonellid</a>, and many new <a href="/wiki/Orthida" title="Orthida">orthid</a> brachiopods, bryozoans, planktonic graptolites and conodonts, and many types of molluscs and echinoderms, including the ophiuroids ("brittle stars") and the first <a href="/wiki/Starfish" title="Starfish">sea stars</a>. Nevertheless, the arthropods remained abundant; all the Late Cambrian orders continued, and were joined by the new group <a href="/wiki/Phacopida" title="Phacopida">Phacopida</a>. The first evidence of land plants also appeared (see <a href="/wiki/Evolutionary_history_of_life" class="mw-redirect" title="Evolutionary history of life">evolutionary history of life</a>). </p><p>In the Middle Ordovician, the trilobite-dominated Early Ordovician communities were replaced by generally more mixed ecosystems, in which brachiopods, bryozoans, molluscs, <a href="/wiki/Cornulitida" title="Cornulitida">cornulitids</a>, <a href="/wiki/Tentaculites" title="Tentaculites">tentaculitids</a> and echinoderms all flourished, tabulate corals diversified and the first <a href="/wiki/Rugosa" title="Rugosa">rugose corals</a> appeared. The planktonic graptolites remained diverse, with the Diplograptina making their appearance. One of the earliest known armoured <a href="/wiki/Agnatha" title="Agnatha">agnathan</a> ("<a href="/wiki/Ostracoderm" title="Ostracoderm">ostracoderm</a>") vertebrates, <i><a href="/wiki/Arandaspis" title="Arandaspis">Arandaspis</a></i>, dates from the Middle Ordovician.<sup id="cite_ref-RitchieGilbert-Tomlinson1976_91-0" class="reference"><a href="#cite_note-RitchieGilbert-Tomlinson1976-91"><span class="cite-bracket">[</span>91<span class="cite-bracket">]</span></a></sup> During the Middle Ordovician there was a large increase in the intensity and diversity of bioeroding organisms. This is known as the Ordovician Bioerosion Revolution.<sup id="cite_ref-WilsonPalmer2006_92-0" class="reference"><a href="#cite_note-WilsonPalmer2006-92"><span class="cite-bracket">[</span>92<span class="cite-bracket">]</span></a></sup> It is marked by a sudden abundance of hard substrate trace fossils such as <i><a href="/wiki/Trypanites" title="Trypanites">Trypanites</a></i>, <i>Palaeosabella</i>, <i><a href="/wiki/Petroxestes" title="Petroxestes">Petroxestes</a></i> and <i><a href="/wiki/Osprioneides" title="Osprioneides">Osprioneides</a></i>. <a href="/wiki/Bioerosion" title="Bioerosion">Bioerosion</a> became an important process, particularly in the thick calcitic skeletons of corals, bryozoans and brachiopods, and on the extensive <a href="/wiki/Carbonate_hardgrounds" title="Carbonate hardgrounds">carbonate hardgrounds</a> that appear in abundance at this time. </p> <ul class="gallery mw-gallery-traditional"> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:OrdovicianEdrio.jpg" class="mw-file-description" title="Upper Ordovician edrioasteroid Cystaster stellatus on a cobble from the Kope Formation in northern Kentucky with the cyclostome bryozoan Corynotrypa in the background"><img alt="Upper Ordovician edrioasteroid Cystaster stellatus on a cobble from the Kope Formation in northern Kentucky with the cyclostome bryozoan Corynotrypa in the background" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/OrdovicianEdrio.jpg/120px-OrdovicianEdrio.jpg" decoding="async" width="120" height="91" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/OrdovicianEdrio.jpg/180px-OrdovicianEdrio.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5c/OrdovicianEdrio.jpg/240px-OrdovicianEdrio.jpg 2x" data-file-width="900" data-file-height="680" /></a></span></div> <div class="gallerytext">Upper Ordovician <a href="/wiki/Edrioasteroid" class="mw-redirect" title="Edrioasteroid">edrioasteroid</a> <i>Cystaster stellatus</i> on a cobble from the Kope Formation in northern Kentucky with the cyclostome <a href="/wiki/Bryozoan" class="mw-redirect" title="Bryozoan">bryozoan</a> <i>Corynotrypa</i> in the background</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:FossilMtnUT.jpg" class="mw-file-description" title="Middle Ordovician fossiliferous shales and limestones at Fossil Mountain, west-central Utah"><img alt="Middle Ordovician fossiliferous shales and limestones at Fossil Mountain, west-central Utah" src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/FossilMtnUT.jpg/120px-FossilMtnUT.jpg" decoding="async" width="120" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/FossilMtnUT.jpg/180px-FossilMtnUT.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f2/FossilMtnUT.jpg/240px-FossilMtnUT.jpg 2x" data-file-width="1500" data-file-height="1125" /></a></span></div> <div class="gallerytext">Middle Ordovician fossiliferous shales and limestones at Fossil Mountain, west-central Utah</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Outcrop_of_Upper_Ordovician_rubbly_limestone_and_shale,_southern_Indiana.jpg" class="mw-file-description" title="Outcrop of Upper Ordovician rubbly limestone and shale, southern Indiana"><img alt="Outcrop of Upper Ordovician rubbly limestone and shale, southern Indiana" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Outcrop_of_Upper_Ordovician_rubbly_limestone_and_shale%2C_southern_Indiana.jpg/120px-Outcrop_of_Upper_Ordovician_rubbly_limestone_and_shale%2C_southern_Indiana.jpg" decoding="async" width="120" height="81" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Outcrop_of_Upper_Ordovician_rubbly_limestone_and_shale%2C_southern_Indiana.jpg/180px-Outcrop_of_Upper_Ordovician_rubbly_limestone_and_shale%2C_southern_Indiana.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Outcrop_of_Upper_Ordovician_rubbly_limestone_and_shale%2C_southern_Indiana.jpg/240px-Outcrop_of_Upper_Ordovician_rubbly_limestone_and_shale%2C_southern_Indiana.jpg 2x" data-file-width="700" data-file-height="472" /></a></span></div> <div class="gallerytext">Outcrop of Upper Ordovician rubbly limestone and shale, southern Indiana</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:OrdOutcropTN.JPG" class="mw-file-description" title="Outcrop of Upper Ordovician limestone and minor shale, central Tennessee"><img alt="Outcrop of Upper Ordovician limestone and minor shale, central Tennessee" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/42/OrdOutcropTN.JPG/103px-OrdOutcropTN.JPG" decoding="async" width="103" height="120" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/42/OrdOutcropTN.JPG/154px-OrdOutcropTN.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/42/OrdOutcropTN.JPG/205px-OrdOutcropTN.JPG 2x" data-file-width="700" data-file-height="818" /></a></span></div> <div class="gallerytext">Outcrop of Upper Ordovician limestone and minor shale, central Tennessee</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:LibertyBorings.jpg" class="mw-file-description" title="Trypanites borings in an Ordovician hardground, southeastern Indiana[93]"><img alt="Trypanites borings in an Ordovician hardground, southeastern Indiana[93]" src="//upload.wikimedia.org/wikipedia/commons/thumb/2/27/LibertyBorings.jpg/120px-LibertyBorings.jpg" decoding="async" width="120" height="80" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/27/LibertyBorings.jpg/180px-LibertyBorings.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/27/LibertyBorings.jpg/240px-LibertyBorings.jpg 2x" data-file-width="300" data-file-height="200" /></a></span></div> <div class="gallerytext"><i><a href="/wiki/Trypanites" title="Trypanites">Trypanites</a></i> borings in an Ordovician <a href="/wiki/Hardground" class="mw-redirect" title="Hardground">hardground</a>, southeastern Indiana<sup id="cite_ref-WilsonPalmer2001_93-0" class="reference"><a href="#cite_note-WilsonPalmer2001-93"><span class="cite-bracket">[</span>93<span class="cite-bracket">]</span></a></sup></div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Petroxestes_borings_Ordovician.jpg" class="mw-file-description" title="Petroxestes borings in an Ordovician hardground, southern Ohio[92]"><img alt="Petroxestes borings in an Ordovician hardground, southern Ohio[92]" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Petroxestes_borings_Ordovician.jpg/82px-Petroxestes_borings_Ordovician.jpg" decoding="async" width="82" height="120" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Petroxestes_borings_Ordovician.jpg/123px-Petroxestes_borings_Ordovician.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Petroxestes_borings_Ordovician.jpg/164px-Petroxestes_borings_Ordovician.jpg 2x" data-file-width="536" data-file-height="786" /></a></span></div> <div class="gallerytext"><i><a href="/wiki/Petroxestes" title="Petroxestes">Petroxestes</a></i> borings in an Ordovician <a href="/wiki/Hardground" class="mw-redirect" title="Hardground">hardground</a>, southern Ohio<sup id="cite_ref-WilsonPalmer2006_92-1" class="reference"><a href="#cite_note-WilsonPalmer2006-92"><span class="cite-bracket">[</span>92<span class="cite-bracket">]</span></a></sup></div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:OilShaleEstonia.jpg" class="mw-file-description" title="Outcrop of Ordovician kukersite oil shale, northern Estonia"><img alt="Outcrop of Ordovician kukersite oil shale, northern Estonia" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e3/OilShaleEstonia.jpg/120px-OilShaleEstonia.jpg" decoding="async" width="120" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e3/OilShaleEstonia.jpg/180px-OilShaleEstonia.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e3/OilShaleEstonia.jpg/240px-OilShaleEstonia.jpg 2x" data-file-width="700" data-file-height="525" /></a></span></div> <div class="gallerytext">Outcrop of Ordovician kukersite <a href="/wiki/Oil_shale" title="Oil shale">oil shale</a>, northern <a href="/wiki/Estonia" title="Estonia">Estonia</a></div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:OilShaleFossilsEstonia.jpg" class="mw-file-description" title="Bryozoan fossils in Ordovician kukersite oil shale, northern Estonia"><img alt="Bryozoan fossils in Ordovician kukersite oil shale, northern Estonia" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/OilShaleFossilsEstonia.jpg/120px-OilShaleFossilsEstonia.jpg" decoding="async" width="120" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/OilShaleFossilsEstonia.jpg/180px-OilShaleFossilsEstonia.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/12/OilShaleFossilsEstonia.jpg/240px-OilShaleFossilsEstonia.jpg 2x" data-file-width="700" data-file-height="525" /></a></span></div> <div class="gallerytext">Bryozoan fossils in Ordovician <a href="/wiki/Kukersite" title="Kukersite">kukersite</a> oil shale, northern <a href="/wiki/Estonia" title="Estonia">Estonia</a></div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:OrdFossilsMN.JPG" class="mw-file-description" title="Brachiopods and bryozoans in an Ordovician limestone, southern Minnesota"><img alt="Brachiopods and bryozoans in an Ordovician limestone, southern Minnesota" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/eb/OrdFossilsMN.JPG/120px-OrdFossilsMN.JPG" decoding="async" width="120" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/eb/OrdFossilsMN.JPG/180px-OrdFossilsMN.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/eb/OrdFossilsMN.JPG/240px-OrdFossilsMN.JPG 2x" data-file-width="1600" data-file-height="1200" /></a></span></div> <div class="gallerytext"><a href="/wiki/Brachiopod" title="Brachiopod">Brachiopods</a> and <a href="/wiki/Bryozoa" title="Bryozoa">bryozoans</a> in an Ordovician limestone, southern Minnesota</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:PlatystrophiaOrdovician.jpg" class="mw-file-description" title="Vinlandostrophia ponderosa, Maysvillian (Upper Ordovician) near Madison, Indiana (scale bar is 5.0 mm)"><img alt="Vinlandostrophia ponderosa, Maysvillian (Upper Ordovician) near Madison, Indiana (scale bar is 5.0 mm)" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/PlatystrophiaOrdovician.jpg/120px-PlatystrophiaOrdovician.jpg" decoding="async" width="120" height="94" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/PlatystrophiaOrdovician.jpg/180px-PlatystrophiaOrdovician.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/71/PlatystrophiaOrdovician.jpg/240px-PlatystrophiaOrdovician.jpg 2x" data-file-width="1844" data-file-height="1452" /></a></span></div> <div class="gallerytext"><i>Vinlandostrophia ponderosa</i>, Maysvillian (Upper Ordovician) near Madison, Indiana (scale bar is 5.0 mm)</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Echinosphaerites.JPG" class="mw-file-description" title="The Ordovician cystoid Echinosphaerites (an extinct echinoderm) from northeastern Estonia; approximately 5 cm in diameter"><img alt="The Ordovician cystoid Echinosphaerites (an extinct echinoderm) from northeastern Estonia; approximately 5 cm in diameter" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Echinosphaerites.JPG/120px-Echinosphaerites.JPG" decoding="async" width="120" height="113" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Echinosphaerites.JPG/180px-Echinosphaerites.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Echinosphaerites.JPG/240px-Echinosphaerites.JPG 2x" data-file-width="1648" data-file-height="1548" /></a></span></div> <div class="gallerytext">The Ordovician cystoid <i><a href="/wiki/Echinosphaerites" title="Echinosphaerites">Echinosphaerites</a></i> (an extinct <a href="/wiki/Echinoderm" title="Echinoderm">echinoderm</a>) from northeastern Estonia; approximately 5 cm in diameter</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Prasopora.JPG" class="mw-file-description" title="Prasopora, a trepostome bryozoan from the Ordovician of Iowa"><img alt="Prasopora, a trepostome bryozoan from the Ordovician of Iowa" src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Prasopora.JPG/120px-Prasopora.JPG" decoding="async" width="120" height="73" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Prasopora.JPG/180px-Prasopora.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Prasopora.JPG/240px-Prasopora.JPG 2x" data-file-width="750" data-file-height="454" /></a></span></div> <div class="gallerytext"><i>Prasopora</i>, a trepostome <a href="/wiki/Bryozoan" class="mw-redirect" title="Bryozoan">bryozoan</a> from the Ordovician of Iowa</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:EncrustedStroph.JPG" class="mw-file-description" title="An Ordovician strophomenid brachiopod with encrusting inarticulate brachiopods and a bryozoan"><img alt="An Ordovician strophomenid brachiopod with encrusting inarticulate brachiopods and a bryozoan" src="//upload.wikimedia.org/wikipedia/commons/thumb/a/ab/EncrustedStroph.JPG/120px-EncrustedStroph.JPG" decoding="async" width="120" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/ab/EncrustedStroph.JPG/180px-EncrustedStroph.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/ab/EncrustedStroph.JPG/240px-EncrustedStroph.JPG 2x" data-file-width="1600" data-file-height="1200" /></a></span></div> <div class="gallerytext">An Ordovician strophomenid brachiopod with encrusting inarticulate brachiopods and a bryozoan</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:Protaraea.jpg" class="mw-file-description" title="The heliolitid coral Protaraea richmondensis encrusting a gastropod; Cincinnatian (Upper Ordovician) of southeastern Indiana"><img alt="The heliolitid coral Protaraea richmondensis encrusting a gastropod; Cincinnatian (Upper Ordovician) of southeastern Indiana" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/46/Protaraea.jpg/120px-Protaraea.jpg" decoding="async" width="120" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/46/Protaraea.jpg/180px-Protaraea.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/46/Protaraea.jpg/240px-Protaraea.jpg 2x" data-file-width="1788" data-file-height="1348" /></a></span></div> <div class="gallerytext">The heliolitid coral <i>Protaraea richmondensis</i> encrusting a gastropod; Cincinnatian (Upper Ordovician) of southeastern Indiana</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:ZygospiraAttached.jpg" class="mw-file-description" title="Zygospira modesta, atrypid brachiopods, preserved in their original positions on a trepostome bryozoan from the Cincinnatian (Upper Ordovician) of southeastern Indiana"><img alt="Zygospira modesta, atrypid brachiopods, preserved in their original positions on a trepostome bryozoan from the Cincinnatian (Upper Ordovician) of southeastern Indiana" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/ZygospiraAttached.jpg/84px-ZygospiraAttached.jpg" decoding="async" width="84" height="120" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/71/ZygospiraAttached.jpg/127px-ZygospiraAttached.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/71/ZygospiraAttached.jpg/169px-ZygospiraAttached.jpg 2x" data-file-width="1116" data-file-height="1584" /></a></span></div> <div class="gallerytext"><i>Zygospira modesta</i>, atrypid brachiopods, preserved in their original positions on a trepostome bryozoan from the Cincinnatian (Upper Ordovician) of southeastern Indiana</div> </li> <li class="gallerybox" style="width: 155px"> <div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"><a href="/wiki/File:DiplograptusCaneySprings.jpg" class="mw-file-description" title="Graptolites (Amplexograptus) from the Ordovician near Caney Springs, Tennessee"><img alt="Graptolites (Amplexograptus) from the Ordovician near Caney Springs, Tennessee" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/dd/DiplograptusCaneySprings.jpg/120px-DiplograptusCaneySprings.jpg" decoding="async" width="120" height="91" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/dd/DiplograptusCaneySprings.jpg/180px-DiplograptusCaneySprings.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/dd/DiplograptusCaneySprings.jpg/240px-DiplograptusCaneySprings.jpg 2x" data-file-width="1989" data-file-height="1515" /></a></span></div> <div class="gallerytext">Graptolites (<i>Amplexograptus</i>) from the Ordovician near Caney Springs, Tennessee </div> </li> </ul> <div class="mw-heading mw-heading3"><h3 id="Flora">Flora</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=12" title="Edit section: Flora"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Green_algae" title="Green algae">Green algae</a> were common in the Late Cambrian (perhaps earlier) and in the Ordovician. Terrestrial plants probably evolved from green algae, first appearing as tiny non-<a href="/wiki/Vascular_plants" class="mw-redirect" title="Vascular plants">vascular</a> forms resembling <a href="/wiki/Marchantiophyta" title="Marchantiophyta">liverworts</a>, in the middle to late Ordovician.<sup id="cite_ref-Porado-etal-2016_94-0" class="reference"><a href="#cite_note-Porado-etal-2016-94"><span class="cite-bracket">[</span>94<span class="cite-bracket">]</span></a></sup> Fossil spores found in Ordovician sedimentary rock are typical of bryophytes.<sup id="cite_ref-95" class="reference"><a href="#cite_note-95"><span class="cite-bracket">[</span>95<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Ordovician_Land_Scene.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/05/Ordovician_Land_Scene.jpg/220px-Ordovician_Land_Scene.jpg" decoding="async" width="220" height="338" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/05/Ordovician_Land_Scene.jpg/330px-Ordovician_Land_Scene.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/05/Ordovician_Land_Scene.jpg/440px-Ordovician_Land_Scene.jpg 2x" data-file-width="1025" data-file-height="1575" /></a><figcaption>Colonization of land would have been limited to shorelines</figcaption></figure> <p>Among the first land <a href="/wiki/Fungi" class="mw-redirect" title="Fungi">fungi</a> may have been <a href="/wiki/Arbuscular_mycorrhiza" title="Arbuscular mycorrhiza">arbuscular mycorrhiza</a> fungi (<a href="/wiki/Glomerales" title="Glomerales">Glomerales</a>), playing a crucial role in facilitating the colonization of land by plants through <a href="/wiki/Mycorrhiza" title="Mycorrhiza">mycorrhizal symbiosis</a>, which makes mineral nutrients available to plant cells; such fossilized fungal <a href="/wiki/Hypha" title="Hypha">hyphae</a> and <a href="/wiki/Spore" title="Spore">spores</a> from the Ordovician of Wisconsin have been found with an age of about 460 million years ago, a time when the land flora most likely only consisted of plants similar to non-vascular <a href="/wiki/Bryophyte" title="Bryophyte">bryophytes</a>.<sup id="cite_ref-96" class="reference"><a href="#cite_note-96"><span class="cite-bracket">[</span>96<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Microbiota">Microbiota</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=13" title="Edit section: Microbiota"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Though stromatolites had declined from their peak in the Proterozoic, they continued to exist in localised settings.<sup id="cite_ref-97" class="reference"><a href="#cite_note-97"><span class="cite-bracket">[</span>97<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="End_of_the_period">End of the period</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=14" title="Edit section: End of the period"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Ordovician%E2%80%93Silurian_extinction_events" class="mw-redirect" title="Ordovician–Silurian extinction events">Ordovician–Silurian extinction events</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Anji_Biota.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Anji_Biota.jpg/220px-Anji_Biota.jpg" decoding="async" width="220" height="160" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Anji_Biota.jpg/330px-Anji_Biota.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Anji_Biota.jpg/440px-Anji_Biota.jpg 2x" data-file-width="4230" data-file-height="3070" /></a><figcaption>The Anji Biota (Wenchang Formation, <a href="/wiki/Zhejiang" title="Zhejiang">Zhejiang</a> Province, <a href="/wiki/China" title="China">China</a>) preserves abundant and diverse <a href="/wiki/Hexactinellid" title="Hexactinellid">glass sponges</a> and graptolites as well as rare examples of other marine animals (such as the eurypterid <a href="/wiki/Archopterus" title="Archopterus">Archopterus</a>) living at a depth of several hundred metres. It is dated to just after the <a href="/wiki/Late_Ordovician_mass_extinction" title="Late Ordovician mass extinction">Hirnantian mass extinction</a> at the end of the Ordovician period.<sup id="cite_ref-98" class="reference"><a href="#cite_note-98"><span class="cite-bracket">[</span>98<span class="cite-bracket">]</span></a></sup></figcaption></figure> <p>The Ordovician came to a close in a series of <a href="/wiki/Extinction_event" title="Extinction event">extinction events</a> that, taken together, comprise the second largest of the five major extinction events in <a href="/wiki/History_of_Earth" title="History of Earth">Earth's history</a> in terms of percentage of <a href="/wiki/Genus" title="Genus">genera</a> that became extinct. The only larger one was the <a href="/wiki/Permian%E2%80%93Triassic_extinction_event" title="Permian–Triassic extinction event">Permian–Triassic extinction event</a>. </p><p>The extinctions occurred approximately 447–444 million years ago and mark the boundary between the Ordovician and the following <a href="/wiki/Silurian" title="Silurian">Silurian</a> Period. At that time all complex multicellular organisms lived in the sea, and about 49% of genera of fauna disappeared forever; <a href="/wiki/Brachiopods" class="mw-redirect" title="Brachiopods">brachiopods</a> and <a href="/wiki/Bryozoans" class="mw-redirect" title="Bryozoans">bryozoans</a> were greatly reduced, along with many <a href="/wiki/Trilobite" title="Trilobite">trilobite</a>, <a href="/wiki/Conodont" title="Conodont">conodont</a> and <a href="/wiki/Graptolithina" class="mw-redirect" title="Graptolithina">graptolite</a> families. </p><p>The most commonly accepted theory is that these events were triggered by the onset of cold conditions in the late Katian, followed by an <a href="/wiki/Ice_age" title="Ice age">ice age</a>, in the Hirnantian faunal stage, that ended the long, stable <a href="/wiki/Greenhouse" title="Greenhouse">greenhouse</a> conditions typical of the Ordovician. </p><p>The ice age was possibly not long-lasting. Oxygen <a href="/wiki/Isotopes" class="mw-redirect" title="Isotopes">isotopes</a> in fossil brachiopods show its duration may have been only 0.5 to 1.5 million years.<sup id="cite_ref-Stanley1999b_99-0" class="reference"><a href="#cite_note-Stanley1999b-99"><span class="cite-bracket">[</span>99<span class="cite-bracket">]</span></a></sup> Other researchers (Page et al.) estimate more temperate conditions did not return until the late Silurian. </p><p>The <a href="/wiki/Late_Ordovician_glaciation" class="mw-redirect" title="Late Ordovician glaciation">late Ordovician glaciation</a> event was preceded by a fall in atmospheric carbon dioxide (from 7000 ppm to 4400 ppm).<sup id="cite_ref-Young_2010_100-0" class="reference"><a href="#cite_note-Young_2010-100"><span class="cite-bracket">[</span>100<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hecht_2010_101-0" class="reference"><a href="#cite_note-Hecht_2010-101"><span class="cite-bracket">[</span>101<span class="cite-bracket">]</span></a></sup> The dip may have been caused by a burst of volcanic activity that deposited new silicate rocks, which draw CO<sub>2</sub> out of the air as they erode.<sup id="cite_ref-Hecht_2010_101-1" class="reference"><a href="#cite_note-Hecht_2010-101"><span class="cite-bracket">[</span>101<span class="cite-bracket">]</span></a></sup> Another possibility is that <a href="/wiki/Bryophyte" title="Bryophyte">bryophytes</a> and lichens, which colonized land in the middle to late Ordovician, may have increased weathering enough to draw down CO<sub style="font-size: 80%;vertical-align: -0.35em">2</sub> levels.<sup id="cite_ref-Porado-etal-2016_94-1" class="reference"><a href="#cite_note-Porado-etal-2016-94"><span class="cite-bracket">[</span>94<span class="cite-bracket">]</span></a></sup> The drop in CO<sub style="font-size: 80%;vertical-align: -0.35em">2</sub> selectively affected the shallow seas where most organisms lived. It has also been suggested that shielding of the sun's rays from the proposed Ordovician ring system, which also caused the <a href="/wiki/Ordovician_meteor_event" title="Ordovician meteor event">Ordovician meteor event</a>, may have also led to the glaciation.<sup id="cite_ref-:0_13-2" class="reference"><a href="#cite_note-:0-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> As the southern supercontinent <a href="/wiki/Gondwana" title="Gondwana">Gondwana</a> drifted over the South Pole, ice caps formed on it, which have been detected in Upper Ordovician rock strata of <a href="/wiki/North_Africa" title="North Africa">North Africa</a> and then-adjacent northeastern South America, which were south-polar locations at the time. </p><p>As glaciers grew, the sea level dropped, and the vast shallow intra-continental Ordovician seas withdrew, which eliminated many ecological niches. When they returned, they carried diminished founder populations that lacked many whole families of organisms. They then withdrew again with the next pulse of glaciation, eliminating biological diversity with each change.<sup id="cite_ref-102" class="reference"><a href="#cite_note-102"><span class="cite-bracket">[</span>102<span class="cite-bracket">]</span></a></sup> Species limited to a single epicontinental sea on a given landmass were severely affected.<sup id="cite_ref-Stanley1999_41-1" class="reference"><a href="#cite_note-Stanley1999-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> Tropical lifeforms were hit particularly hard in the first wave of extinction, while cool-water species were hit worst in the second pulse.<sup id="cite_ref-Stanley1999_41-2" class="reference"><a href="#cite_note-Stanley1999-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> </p><p>Those species able to adapt to the changing conditions survived to fill the ecological niches left by the extinctions. For example, there is evidence the oceans became more deeply oxygenated during the glaciation, allowing unusual benthic organisms (Hirnantian fauna) to colonize the depths. These organisms were cosmopolitan in distribution and present at most latitudes.<sup id="cite_ref-FOOTNOTETorsvikCocks2017112-113_69-1" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017112-113-69"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup> </p><p>At the end of the second event, melting glaciers caused the sea level to rise and stabilise once more. The rebound of life's diversity with the permanent re-flooding of continental shelves at the onset of the Silurian saw increased biodiversity within the surviving Orders. Recovery was characterized by an unusual number of "Lazarus taxa", disappearing during the extinction and reappearing well into the Silurian, which suggests that the taxa survived in small numbers in <a href="/wiki/Refugium_(population_biology)" title="Refugium (population biology)">refugia</a>.<sup id="cite_ref-FOOTNOTETorsvikCocks2017122–123_103-0" class="reference"><a href="#cite_note-FOOTNOTETorsvikCocks2017122–123-103"><span class="cite-bracket">[</span>103<span class="cite-bracket">]</span></a></sup> </p><p>An alternate extinction hypothesis suggested that a ten-second <a href="/wiki/Gamma-ray_burst" title="Gamma-ray burst">gamma-ray burst</a> could have destroyed the <a href="/wiki/Ozone_layer" title="Ozone layer">ozone layer</a> and exposed terrestrial and marine surface-dwelling life to deadly ultraviolet <a href="/wiki/Radiation" title="Radiation">radiation</a> and initiated global cooling.<sup id="cite_ref-Melott2006_104-0" class="reference"><a href="#cite_note-Melott2006-104"><span class="cite-bracket">[</span>104<span class="cite-bracket">]</span></a></sup> </p><p>Recent work considering the <a href="/wiki/Sequence_stratigraphy" title="Sequence stratigraphy">sequence stratigraphy</a> of the Late Ordovician argues that the mass extinction was a single protracted episode lasting several hundred thousand years, with abrupt changes in water depth and sedimentation rate producing two pulses of last occurrences of species.<sup id="cite_ref-105" class="reference"><a href="#cite_note-105"><span class="cite-bracket">[</span>105<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ordovician&action=edit&section=15" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol 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.citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFWellman,_C.H.Gray,_J.2000" class="citation journal cs1">Wellman, C.H.; Gray, J. 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M.; Rasmussen, C.M.Ø.; Connelly, J. N.; Eriksson, M. E. (2017-01-24). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5286199">"Refined Ordovician timescale reveals no link between asteroid breakup and biodiversification"</a>. <i>Nature Communications</i>. <b>8</b>: 14066. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fncomms14066">10.1038/ncomms14066</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/2041-1723">2041-1723</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5286199">5286199</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/28117834">28117834</a>. <q>It has been suggested that the Middle Ordovician meteorite bombardment played a crucial role in the Great Ordovician Biodiversification Event, but this study shows that the two phenomena were unrelated</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature+Communications&rft.atitle=Refined+Ordovician+timescale+reveals+no+link+between+asteroid+breakup+and+biodiversification&rft.volume=8&rft.pages=14066&rft.date=2017-01-24&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC5286199%23id-name%3DPMC&rft.issn=2041-1723&rft_id=info%3Apmid%2F28117834&rft_id=info%3Adoi%2F10.1038%2Fncomms14066&rft.aulast=Lindskog&rft.aufirst=A.&rft.au=Costa%2C+M.+M.&rft.au=Rasmussen%2C+C.M.%C3%98.&rft.au=Connelly%2C+J.+N.&rft.au=Eriksson%2C+M.+E.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC5286199&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://stratigraphy.org/ICSchart/ChronostratChart2023-09.pdf">"International Chronostratigraphic Chart"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/International_Commission_on_Stratigraphy" title="International Commission on Stratigraphy">International Commission on Stratigraphy</a></i>. 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(June 1985). <a rel="nofollow" class="external text" href="https://timescalefoundation.org/references/Silurian1.pdf">"Series and Stages of the Silurian System"</a> <span class="cs1-format">(PDF)</span>. <i>Episodes</i>. <b>8</b> (2): 101–103. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.18814%2Fepiiugs%2F1985%2Fv8i2%2F005">10.18814/epiiugs/1985/v8i2/005</a></span>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20220119093253/https://timescalefoundation.org/references/Silurian1.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on 19 January 2022<span class="reference-accessdate">. Retrieved <span class="nowrap">11 December</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Episodes&rft.atitle=Series+and+Stages+of+the+Silurian+System&rft.volume=8&rft.issue=2&rft.pages=101-103&rft.date=1985-06&rft_id=info%3Adoi%2F10.18814%2Fepiiugs%2F1985%2Fv8i2%2F005&rft.aulast=Holland&rft.aufirst=C.&rft_id=https%3A%2F%2Ftimescalefoundation.org%2Freferences%2FSilurian1.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHaq,_B._U.Schutter2008" class="citation journal cs1">Haq, B. U.; Schutter, SR (2008). "A Chronology of Paleozoic Sea-Level Changes". <i>Science</i>. <b>322</b> (5898): 64–68. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2008Sci...322...64H">2008Sci...322...64H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.1161648">10.1126/science.1161648</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/18832639">18832639</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:206514545">206514545</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=A+Chronology+of+Paleozoic+Sea-Level+Changes&rft.volume=322&rft.issue=5898&rft.pages=64-68&rft.date=2008&rft_id=info%3Adoi%2F10.1126%2Fscience.1161648&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A206514545%23id-name%3DS2CID&rft_id=info%3Apmid%2F18832639&rft_id=info%3Abibcode%2F2008Sci...322...64H&rft.au=Haq%2C+B.+U.&rft.au=Schutter%2C+SR&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation encyclopaedia cs1"><a rel="nofollow" class="external text" href="https://www.dictionary.com/browse/Ordovician">"Ordovician"</a>. <i><a href="/wiki/Dictionary.com" title="Dictionary.com">Dictionary.com Unabridged</a></i> (Online). n.d.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Ordovician&rft.btitle=Dictionary.com+Unabridged&rft_id=https%3A%2F%2Fwww.dictionary.com%2Fbrowse%2FOrdovician&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-ICS2015-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-ICS2015_10-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.stratigraphy.org/ICSchart/ChronostratChart2015-01.pdf">"International Chronostratigraphic Chart v.2015/01"</a> <span class="cs1-format">(PDF)</span>. <a href="/wiki/International_Commission_on_Stratigraphy" title="International Commission on Stratigraphy">International Commission on Stratigraphy</a>. January 2015. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150402142607/http://stratigraphy.org/ICSchart/ChronostratChart2015-01.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on 2015-04-02<span class="reference-accessdate">. Retrieved <span class="nowrap">2015-05-30</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=International+Chronostratigraphic+Chart+v.2015%2F01&rft.pub=International+Commission+on+Stratigraphy&rft.date=2015-01&rft_id=http%3A%2F%2Fwww.stratigraphy.org%2FICSchart%2FChronostratChart2015-01.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text">Charles Lapworth (1879) <a rel="nofollow" class="external text" href="https://books.google.com/books?id=JJpZAAAYAAJ&pg=PA1">"On the Tripartite Classification of the Lower Palaeozoic Rocks"</a><sup class="noprint Inline-Template"><span style="white-space: nowrap;">[<i><a href="/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot"><span title=" Dead link tagged October 2023">permanent dead link</span></a></i><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span>]</span></sup>, <i>Geological Magazine</i>, new series, <b>6</b> : 1-15. From pp. 13-14: "North Wales itself — at all events the whole of the great Bala district where Sedgwick first worked out the physical succession among the rocks of the intermediate or so-called <i>Upper Cambrian</i> or <i>Lower Silurian</i> system; and in all probability, much of the Shelve and the Caradoc area, whence Murchison first published its distinctive fossils — lay within the territory of the Ordovices; … Here, then, have we the hint for the appropriate title for the central system of the Lower Paleozoic. It should be called the Ordovician System, after this old British tribe."</span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.sciencedaily.com/releases/2016/06/160615135230.htm">"New type of meteorite linked to ancient asteroid collision"</a>. <i>Science Daily</i>. 15 June 2016. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190403222034/https://www.sciencedaily.com/releases/2016/06/160615135230.htm">Archived</a> from the original on 3 April 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">20 June</span> 2016</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Science+Daily&rft.atitle=New+type+of+meteorite+linked+to+ancient+asteroid+collision&rft.date=2016-06-15&rft_id=https%3A%2F%2Fwww.sciencedaily.com%2Freleases%2F2016%2F06%2F160615135230.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-:0-13"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_13-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_13-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:0_13-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTomkinsMartinCawood2024" class="citation journal cs1">Tomkins, Andrew G.; Martin, Erin L.; Cawood, Peter A. (2024-11-15). <a rel="nofollow" class="external text" href="https://linkinghub.elsevier.com/retrieve/pii/S0012821X24004230">"Evidence suggesting that earth had a ring in the Ordovician"</a>. <i>Earth and Planetary Science Letters</i>. <b>646</b>: 118991. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.epsl.2024.118991">10.1016/j.epsl.2024.118991</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0012-821X">0012-821X</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Earth+and+Planetary+Science+Letters&rft.atitle=Evidence+suggesting+that+earth+had+a+ring+in+the+Ordovician&rft.volume=646&rft.pages=118991&rft.date=2024-11-15&rft_id=info%3Adoi%2F10.1016%2Fj.epsl.2024.118991&rft.issn=0012-821X&rft.aulast=Tomkins&rft.aufirst=Andrew+G.&rft.au=Martin%2C+Erin+L.&rft.au=Cawood%2C+Peter+A.&rft_id=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0012821X24004230&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text">Details on the Dapingian are available at <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWangStougeChenLi2009" class="citation journal cs1">Wang, X.; Stouge, S.; Chen, X.; Li, Z.; Wang, C. (2009). 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href="https://hdl.handle.net/1808%2F9204">1808/9204</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:13124815">13124815</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=Did+a+gamma-ray+burst+initiate+the+late+Ordovician+mass+extinction%3F&rft.volume=3&rft.issue=1&rft.pages=55-61&rft.date=2004&rft_id=info%3Ahdl%2F1808%2F9204&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A13124815%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2004IJAsB...3...55M&rft_id=info%3Aarxiv%2Fastro-ph%2F0309415&rft_id=info%3Adoi%2F10.1017%2FS1473550404001910&rft.aulast=Melott&rft.aufirst=Adrian&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></span> </li> <li id="cite_note-105"><span class="mw-cite-backlink"><b><a 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class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/57px-Wikisource-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/76px-Wikisource-logo.svg.png 2x" data-file-width="410" data-file-height="430" /></span></span></div> <div class="side-box-text plainlist"><a href="/wiki/Wikisource" title="Wikisource">Wikisource</a> has the text of the <a href="/wiki/Encyclop%C3%A6dia_Britannica_Eleventh_Edition" title="Encyclopædia Britannica Eleventh Edition">1911 <i>Encyclopædia Britannica</i></a> article "<span style="font-weight:bold;"><a href="https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Ordovician_System" class="extiw" title="wikisource:1911 Encyclopædia Britannica/Ordovician System">Ordovician System</a></span>".</div></div> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1235681985"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237033735"><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Ordovician" class="extiw" title="commons:Category:Ordovician">Ordovician</a></span>.</div></div> </div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOgg2004" class="citation web cs1">Ogg, Jim (June 2004). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20060423084018/http://www.stratigraphy.org/gssp.htm">"Overview of Global Boundary Stratotype Sections and Points (GSSP's)"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.stratigraphy.org/gssp.htm">the original</a> on 2006-04-23<span class="reference-accessdate">. Retrieved <span class="nowrap">2006-04-30</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Overview+of+Global+Boundary+Stratotype+Sections+and+Points+%28GSSP%27s%29&rft.date=2004-06&rft.aulast=Ogg&rft.aufirst=Jim&rft_id=http%3A%2F%2Fwww.stratigraphy.org%2Fgssp.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMehrtens" class="citation web cs1">Mehrtens, Charlotte. <a rel="nofollow" class="external text" href="http://www.anr.state.vt.us/dec/geo/chazytxt.htm">"Chazy Reef at Isle La Motte"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160306233902/http://www.anr.state.vt.us/dec/geo/chazytxt.htm">Archived</a> from the original on 2016-03-06<span class="reference-accessdate">. Retrieved <span class="nowrap">2006-12-27</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Chazy+Reef+at+Isle+La+Motte&rft.aulast=Mehrtens&rft.aufirst=Charlotte&rft_id=http%3A%2F%2Fwww.anr.state.vt.us%2Fdec%2Fgeo%2Fchazytxt.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AOrdovician" class="Z3988"></span> An Ordovician reef in Vermont.</li> <li><a rel="nofollow" class="external text" href="http://members.wri.com/jeffb/Fossils">Ordovician fossils of the famous Cincinnatian Group</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090103233229/http://members.wri.com/jeffb/Fossils/">Archived</a> 2009-01-03 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><a rel="nofollow" class="external text" href="https://ghkclass.com/ghkC.html?ordovician">Ordovician (chronostratigraphy scale)</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20221006184657/https://ghkclass.com/ghkC.html?ordovician">Archived</a> 2022-10-06 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist 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.navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Ordovician_Period" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse 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href="/wiki/Special:EditPage/Template:Ordovician_footer" title="Special:EditPage/Template:Ordovician footer"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Ordovician_Period" style="font-size:114%;margin:0 4em"><a class="mw-selflink selflink">Ordovician Period</a></div></th></tr><tr><td colspan="2" class="navbox-list navbox-off hlist" style="width:100%;padding:0;border: none;;background:transparent;color:inherit;"><div style="padding:0px"><table class="navbox-columns-table" style="border-spacing: 0px; text-align:left;width:100%;border-collapse: collapse;"><tbody><tr><td class="navbox-abovebelow" style="font-weight:bold;background-color: #ffffff; border-style:solid; border-width: 0 3px 3px 3px; border-color:rgb(0,146,112); text-align:center;">Lower/Early Ordovician</td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;background-color: #ffffff; border-style:solid; border-width: 0 3px 3px 3px; border-color:rgb(0,146,112); text-align:center;">Middle Ordovician</td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;background-color: #ffffff; border-style:solid; border-width: 0 3px 3px 3px; border-color:rgb(0,146,112); text-align:center;">Upper/Late Ordovician</td></tr><tr style="vertical-align:top"><td class="navbox-list" style="padding:0px;background-color: #ffffff; border-style:solid; border-width: 3px 0 0 0; border-color:rgb(0,146,112); text-align:center;width:33.33333%;"><div> <ul><li><a href="/wiki/Tremadocian" title="Tremadocian">Tremadocian</a></li> <li><a href="/wiki/Floian" title="Floian">Floian</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;background-color: #ffffff; border-style:solid; border-width: 3px 0 0 0; border-color:rgb(0,146,112); text-align:center;width:33.33333%;"><div> <ul><li><a href="/wiki/Dapingian" title="Dapingian">Dapingian</a></li> <li><a href="/wiki/Darriwilian" title="Darriwilian">Darriwilian</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;background-color: #ffffff; border-style:solid; border-width: 3px 0 0 0; border-color:rgb(0,146,112); text-align:center;width:33.33333%;"><div> <ul><li><a href="/wiki/Sandbian" title="Sandbian">Sandbian</a></li> <li><a href="/wiki/Katian" title="Katian">Katian</a></li> <li><a href="/wiki/Hirnantian" title="Hirnantian">Hirnantian</a></li></ul> </div></td></tr></tbody></table></div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"><style data-mw-deduplicate="TemplateStyles:r886047488">.mw-parser-output .nobold{font-weight:normal}</style><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886047488"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886047488"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886047488"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886047488"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886047488"></div><div role="navigation" class="navbox" aria-labelledby="Geological_history_of_Earth" style="padding:3px"><table class="nowraplinks mw-collapsible mw-collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Geological_history_of_Earth" title="Template:Geological history of Earth"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Geological_history_of_Earth" title="Template talk:Geological history of Earth"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Geological_history_of_Earth" title="Special:EditPage/Template:Geological history of Earth"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Geological_history_of_Earth" style="font-size:114%;margin:0 4em"><a href="/wiki/Geological_history_of_Earth" title="Geological history of Earth">Geological history of Earth</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Cenozoic" title="Cenozoic">Cenozoic Era<br /><span class="nobold">(present–66.0 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Quaternary" title="Quaternary">Quaternary <span class="nobold">(present–2.58 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Holocene" title="Holocene">Holocene (present–11.7 ka)</a></li> <li><a href="/wiki/Pleistocene" title="Pleistocene">Pleistocene (11.7 ka–2.58 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Neogene" title="Neogene">Neogene <span class="nobold">(2.58–23.0 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pliocene" title="Pliocene">Pliocene (2.59–5.33 Ma)</a></li> <li><a href="/wiki/Miocene" title="Miocene">Miocene (5.33–23.0 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Paleogene" title="Paleogene">Paleogene <span class="nobold">(23.0–66.0 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Oligocene" title="Oligocene">Oligocene (23.0–33.9 Ma)</a></li> <li><a href="/wiki/Eocene" title="Eocene">Eocene (33.9–56.0 Ma)</a></li> <li><a href="/wiki/Paleocene" title="Paleocene">Paleocene (56.0–66.0 Ma)</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Mesozoic" title="Mesozoic">Mesozoic Era<br /><span class="nobold">(66.0–252 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Cretaceous" title="Cretaceous">Cretaceous <span class="nobold">(66.0–145 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Late_Cretaceous" title="Late Cretaceous">Late (66.0–100 Ma)</a></li> <li><a href="/wiki/Early_Cretaceous" title="Early Cretaceous">Early (100–145 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Jurassic" title="Jurassic">Jurassic <span class="nobold">(145–201 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Late_Jurassic" title="Late Jurassic">Late (145–164 Ma)</a></li> <li><a href="/wiki/Middle_Jurassic" title="Middle Jurassic">Middle (164–174 Ma)</a></li> <li><a href="/wiki/Early_Jurassic" title="Early Jurassic">Early (174–201 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Triassic" title="Triassic">Triassic <span class="nobold">(201–252 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Late_Triassic" title="Late Triassic">Late (201–237 Ma)</a></li> <li><a href="/wiki/Middle_Triassic" title="Middle Triassic">Middle (237–247 Ma)</a></li> <li><a href="/wiki/Early_Triassic" title="Early Triassic">Early (247–252 Ma)</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Paleozoic" title="Paleozoic">Paleozoic Era<br /><span class="nobold">(252–539 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Permian" title="Permian">Permian <span class="nobold">(252–299 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Lopingian" title="Lopingian">Lopingian (252–260 Ma)</a></li> <li><a href="/wiki/Guadalupian" title="Guadalupian">Guadalupian (260–272 Ma)</a></li> <li><a href="/wiki/Cisuralian" title="Cisuralian">Cisuralian (272–299 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Carboniferous" title="Carboniferous">Carboniferous <span class="nobold">(299–359 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pennsylvanian_(geology)" title="Pennsylvanian (geology)">Pennsylvanian (299–323 Ma)</a></li> <li><a href="/wiki/Mississippian_(geology)" title="Mississippian (geology)">Mississippian (323–359 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Devonian" title="Devonian">Devonian <span class="nobold">(359–419 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Late_Devonian" class="mw-redirect" title="Late Devonian">Late (359–383 Ma)</a></li> <li><a href="/wiki/Middle_Devonian" title="Middle Devonian">Middle (383–393 Ma)</a></li> <li><a href="/wiki/Early_Devonian" title="Early Devonian">Early (393–419 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Silurian" title="Silurian">Silurian <span class="nobold">(419–444 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pridoli_Epoch" title="Pridoli Epoch">Pridoli (419–423 Ma)</a></li> <li><a href="/wiki/Ludlow_Epoch" title="Ludlow Epoch">Ludlow (423–427 Ma)</a></li> <li><a href="/wiki/Wenlock_Epoch" title="Wenlock Epoch">Wenlock (427–433 Ma)</a></li> <li><a href="/wiki/Llandovery_Epoch" title="Llandovery Epoch">Llandovery (433–444 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a class="mw-selflink selflink">Ordovician <span class="nobold">(444–485 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Late_Ordovician" title="Late Ordovician">Late (444–458 Ma)</a></li> <li><a href="/wiki/Middle_Ordovician" class="mw-redirect" title="Middle Ordovician">Middle (458–470 Ma)</a></li> <li><a href="/wiki/Early_Ordovician" title="Early Ordovician">Early (470–485 Ma)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Cambrian" title="Cambrian">Cambrian <span class="nobold">(485–539 Ma)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Furongian" title="Furongian">Furongian (485–497 Ma)</a></li> <li><a href="/wiki/Miaolingian" title="Miaolingian">Miaolingian (497–509 Ma)</a></li> <li><a href="/wiki/Cambrian_Series_2" title="Cambrian Series 2">Series 2 (509–521 Ma)</a></li> <li><a href="/wiki/Terreneuvian" title="Terreneuvian">Terreneuvian (521–539 Ma)</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Proterozoic" title="Proterozoic">Proterozoic Eon<br /><span class="nobold">(539 Ma–2.5 Ga)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Neoproterozoic" title="Neoproterozoic">Neoproterozoic <span class="nobold">(539 Ma–1 Ga)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ediacaran" title="Ediacaran">Ediacaran (539–635 Ma)</a></li> <li><a href="/wiki/Cryogenian" title="Cryogenian">Cryogenian (635–720 Ma)</a></li> <li><a href="/wiki/Tonian" title="Tonian">Tonian (720 Ma–1 Ga)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Mesoproterozoic" title="Mesoproterozoic">Mesoproterozoic <span class="nobold">(1–1.6 Ga)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Stenian" title="Stenian">Stenian (1–1.2 Ga)</a></li> <li><a href="/wiki/Ectasian" title="Ectasian">Ectasian (1.2–1.4 Ga)</a></li> <li><a href="/wiki/Calymmian" title="Calymmian">Calymmian (1.4–1.6 Ga)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:26ch"><a href="/wiki/Paleoproterozoic" title="Paleoproterozoic">Paleoproterozoic <span class="nobold">(1.6–2.5 Ga)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Statherian" title="Statherian">Statherian (1.6–1.8 Ga)</a></li> <li><a href="/wiki/Orosirian" title="Orosirian">Orosirian (1.8–2.05 Ga)</a></li> <li><a href="/wiki/Rhyacian" title="Rhyacian">Rhyacian (2.05–2.3 Ga)</a></li> <li><a href="/wiki/Siderian" title="Siderian">Siderian (2.3–2.5 Ga)</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Archean" title="Archean">Archean Eon <span class="nobold">(2.5–4 Ga)</span></a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Neoarchean" title="Neoarchean">Neoarchean (2.5–2.8 Ga)</a></li> <li><a href="/wiki/Mesoarchean" title="Mesoarchean">Mesoarchean (2.8–3.2 Ga)</a></li> <li><a href="/wiki/Paleoarchean" title="Paleoarchean">Paleoarchean (3.2–3.6 Ga)</a></li> <li><a href="/wiki/Eoarchean" title="Eoarchean">Eoarchean (3.6–4 Ga)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hadean" title="Hadean">Hadean Eon <span class="nobold">(4–4.6 Ga)</span></a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div><a href="/wiki/Year#SI_prefix_multipliers" title="Year">ka</a> = kiloannum (thousand years ago); <a href="/wiki/Year#SI_prefix_multipliers" title="Year">Ma</a> = megaannum (million years ago); <a href="/wiki/Year#SI_prefix_multipliers" title="Year">Ga</a> = gigaannum (billion years ago).<br /> <i>See also:</i> <a href="/wiki/Geologic_time_scale" title="Geologic time scale">Geologic time scale</a>  •  <span class="nowrap"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:WikiProject_Geology.svg" class="mw-file-description"><img alt="icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/WikiProject_Geology.svg/16px-WikiProject_Geology.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/WikiProject_Geology.svg/24px-WikiProject_Geology.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e7/WikiProject_Geology.svg/32px-WikiProject_Geology.svg.png 2x" data-file-width="327" data-file-height="328" /></a></span> </span><a href="/wiki/Portal:Geology" title="Portal:Geology">Geology portal</a>  •  <span class="nowrap"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:The_Earth_seen_from_Apollo_17.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/97/The_Earth_seen_from_Apollo_17.jpg/16px-The_Earth_seen_from_Apollo_17.jpg" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/97/The_Earth_seen_from_Apollo_17.jpg/24px-The_Earth_seen_from_Apollo_17.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/97/The_Earth_seen_from_Apollo_17.jpg/32px-The_Earth_seen_from_Apollo_17.jpg 2x" data-file-width="3000" data-file-height="3002" /></a></span> </span><a href="/wiki/Portal:World" title="Portal:World">World portal</a></div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"><style data-mw-deduplicate="TemplateStyles:r1038841319">.mw-parser-output .tooltip-dotted{border-bottom:1px dotted;cursor:help}</style><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1038841319"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1038841319"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1038841319"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1038841319"></div><div role="navigation" class="navbox authority-control" aria-labelledby="Authority_control_databases_frameless&#124;text-top&#124;10px&#124;alt=Edit_this_at_Wikidata&#124;link=https&#58;//www.wikidata.org/wiki/Q62100#identifiers&#124;class=noprint&#124;Edit_this_at_Wikidata" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Authority_control_databases_frameless&#124;text-top&#124;10px&#124;alt=Edit_this_at_Wikidata&#124;link=https&#58;//www.wikidata.org/wiki/Q62100#identifiers&#124;class=noprint&#124;Edit_this_at_Wikidata" style="font-size:114%;margin:0 4em"><a href="/wiki/Help:Authority_control" title="Help:Authority control">Authority control databases</a> <span class="mw-valign-text-top noprint" typeof="mw:File/Frameless"><a href="https://www.wikidata.org/wiki/Q62100#identifiers" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" src="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" decoding="async" width="10" height="10" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/15px-OOjs_UI_icon_edit-ltr-progressive.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/20px-OOjs_UI_icon_edit-ltr-progressive.svg.png 2x" data-file-width="20" data-file-height="20" /></a></span></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">International</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"><ul><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="Ordovician Geologic Period"><a rel="nofollow" class="external text" href="http://id.worldcat.org/fast/1353916/">FAST</a></span></span></li></ul></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">National</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"><ul><li><span class="uid"><a rel="nofollow" class="external text" href="https://d-nb.info/gnd/4172743-5">Germany</a></span></li><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="Paleoecology--Ordovician"><a rel="nofollow" class="external text" href="https://id.loc.gov/authorities/sh95010914">United States</a></span></span></li><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="Ordovicien"><a rel="nofollow" class="external text" href="https://catalogue.bnf.fr/ark:/12148/cb119442931">France</a></span></span></li><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="Ordovicien"><a rel="nofollow" class="external text" href="https://data.bnf.fr/ark:/12148/cb119442931">BnF data</a></span></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="https://id.ndl.go.jp/auth/ndlna/00568938">Japan</a></span></li><li><span class="uid"><span class="rt-commentedText tooltip tooltip-dotted" title="ordovik"><a rel="nofollow" class="external text" href="https://aleph.nkp.cz/F/?func=find-c&local_base=aut&ccl_term=ica=ph117302&CON_LNG=ENG">Czech Republic</a></span></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="http://olduli.nli.org.il/F/?func=find-b&local_base=NLX10&find_code=UID&request=987007537114305171">Israel</a></span></li></ul></div></td></tr></tbody></table></div>    </div><noscript><img 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