{"id":19711,"date":"2020-03-24T22:49:25","date_gmt":"2020-03-24T22:49:25","guid":{"rendered":"https:\/\/www.bgs.ac.uk\/?page_id=19711"},"modified":"2021-08-20T11:59:36","modified_gmt":"2021-08-20T11:59:36","slug":"corals","status":"publish","type":"page","link":"https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/corals\/","title":{"rendered":"Corals"},"content":{"rendered":"\t\t\t<section class=\"hero-section hero-section-with-social\">\n\t\t\t\t\t\t\t\t<div class=\"hero-info-wrap\">\n\t\t\t\t\t<div class=\"container\">\n\t\t\t\t\t\t<div class=\"row\">\n\t\t\t\t\t\t\t<div class=\"col-12\">\n\t\t\t\t\t\t\t\t<div class=\"hero-info\">\n\t\t\t\t\t\t\t\t\t<h1>Corals<\/h1>\n\t\t\t\t\t\t\t\t\t<p>Discovering Geology &mdash; Fossils and geological time<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\n\t\t\t<div class=\"social-wrap social-wrap-inline-them\">\n\t\t\t\t<div class=\"sea-background-f\">\n\t\t\t\t\t<span>Share this article<\/span><a target=\"_blank\"  href=\"https:\/\/www.facebook.com\/sharer\/sharer.php?u=https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/corals\/\"><span class=\"icon-facebook\"><span class=\"hidden\">Facebook<\/span><\/span><\/a><a target=\"_blank\"  href=\"https:\/\/twitter.com\/intent\/tweet?text=Corals&#038;url=https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/corals\/\"><span class=\"icon-twitter\"><span class=\"hidden\">Twitter<\/span><\/span><\/a><a   onclick=\"javascript:void( (function() {var e=document.createElement('script' );e.setAttribute('type','text\/javascript' );e.setAttribute('charset','UTF-8' );e.setAttribute('src','\/\/assets.pinterest.com\/js\/pinmarklet.js?r='+Math.random()*99999999);document.body.appendChild(e)})());\"  href=\"javascript:void(0);\"><span class=\"icon-pinterest\"><span class=\"hidden\">Pinterest<\/span><\/span><\/a><a target=\"_blank\"  href=\"https:\/\/wa.me?text=https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/corals\/\"><span class=\"icon-whatsapp\"><span class=\"hidden\">WhatsApp<\/span><\/span><\/a><a   href=\"mailto:?subject=Corals&#038;body=%20(https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/corals\/)\"><span class=\"icon-mail\"><span class=\"hidden\">Email<\/span><\/span><\/a><a href=\"#\" data-copy=\"https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/corals\/\" class=\"copy-url-on-click\"><span class=\"icon-link\"><span class=\"hidden\">Copy Link<\/span><\/span><\/a><\/div><\/div>\t\t\t\t\t\t\t<\/section>\n\t\t\t\n\n\n<section class=\"wp-block-bgs-blocks-content-container content-section\"><div class=\"container\"><div class=\"row\"><div class=\"col-12\">\n<p>Corals (or more formally, Zoantharia) are marine animals related sea anemones that lack a free-swimming (medusoid) stage. They have mobile larvae that become sessile (fixed to one place) after a few days.<\/p>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef019639257_1332x690.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;Colony of living coral, &lt;em&gt;Tubastrea&lt;\/em&gt; sp. (&lt;a href=&quot;https:\/\/photolib.noaa.gov\/About&quot; target=&quot;_blank&quot; rel=&quot;noopener&quot;&gt;Public domain&lt;\/a&gt;; photo collection of Dr James P McVey, NOAA Sea Grant Program.)&lt;\/p&gt;\n\" data-gallery=\"gallery_76923\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef019639257_1332x690-150x150.jpg\" class=\"lazy-blur\" alt=\"Colony of living coral, Tubastrea sp.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef019639257_1332x690-960x497.jpg\" \/><\/a><figcaption class=\"caption \">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p>Colony of living coral, <em>Tubastrea<\/em> sp. (<a href=\"https:\/\/photolib.noaa.gov\/About\" target=\"_blank\" rel=\"noopener\">Public domain<\/a>; photo collection of Dr James P McVey, NOAA Sea Grant Program.)<\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef019639257_1332x690.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;Colony of living coral, &lt;em&gt;Tubastrea&lt;\/em&gt; sp. (&lt;a href=&quot;https:\/\/photolib.noaa.gov\/About&quot; target=&quot;_blank&quot; rel=&quot;noopener&quot;&gt;Public domain&lt;\/a&gt;; photo collection of Dr James P McVey, NOAA Sea Grant Program.)&lt;\/p&gt;\n\" data-gallery=\"gallery_76923\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<p>The oldest known corals lived during the Cambrian, more than 500 million years ago, and are still found living today. Some, like octocorals (which have has eight &#8216;arms&#8217;) are soft bodied and rarely preserved as fossils, but others secrete a hard, calcarous (made of calcium carbinate) skeleton and are thus important rock-forming organisms. <\/p>\n\n\n\n<p>We focus here on the three groups, or orders, of corals that are most frequently found as fossils: <a href=\"https:\/\/www.bgs.ac.uk\/discoveringGeology\/time\/fossilfocus\/coral.html#Rugosa\">Rugosa<\/a>, <a href=\"https:\/\/www.bgs.ac.uk\/discoveringGeology\/time\/fossilfocus\/coral.html#Tabulate\">Tabulata<\/a> and <a href=\"https:\/\/www.bgs.ac.uk\/discoveringGeology\/time\/fossilfocus\/coral.html#Scleractinia\">Scleractinia<\/a>.<\/p>\n\n\n\n<ul><li><a href=\"#animal\">The animal<\/a><\/li><li><a href=\"#environment\">Environment<\/a><\/li><li><a href=\"#time\">Corals through time<\/a><\/li><li><a href=\"#3d-fossil\">3D fossil models<\/a><\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"animal\">The animal<\/h2>\n\n\n\n<p>Corals comprise a soft-bodied animal called a polyp that lives in a calcareous skeleton or corallum. Food is taken in and waste products are discharged through the mouth, which is surrounded by tentacles with poisonous stings.<\/p>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/03\/CORAL1.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;An imaginary solitary coral, partly broken away, to show the calcareous structure of the corallite and the living animal (polyp). BGS \u00a9UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_80238\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/03\/CORAL1-150x150.jpg\" class=\"lazy-blur\" alt=\"An imaginary solitary coral, partly broken away to show the calcareous structure of the corallite. BGS \u00a9UKRI. All rights reserved.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/03\/CORAL1.jpg\" \/><\/a><figcaption class=\"caption \">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p>An imaginary solitary coral, partly broken away, to show the calcareous structure of the corallite and the living animal (polyp). BGS \u00a9UKRI.<\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/03\/CORAL1.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;An imaginary solitary coral, partly broken away, to show the calcareous structure of the corallite and the living animal (polyp). BGS \u00a9UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_80238\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<p>The polyp removes calcium carbonate from the sea water to create a skeleton of calcite or aragonite, although when fossilised, aragonite often changes to calcite. The corallite in which the polyp lives is strengthened by septa (radiating plates), tabulae (corallite floors that build up one on the other) and sometimes dissepiments (small concentrically arranged plates between the septa). Corals may live alone (solitary) or in a group (colonial or compound).<\/p>\n\n\n<div  class=\"accordions\">\n\t\t\t\t<div class=\"acc-wrap\">\n\t\t\t\t\t<button class=\"acc-top secondary-background icon-arrow button no-btn\"><span class=\"button-content\" tabindex=\"-1\">Rugose corals<\/span><\/button>\n\t\t\t\t\t<div class=\"acc-body sea-background-e\">\n\t\t\t\t\t\t<p>Rugose corals are solitary or colonial types with bilateral symmetry. They have a hollow in the top surface (calice) in which the polyp sits, together with numerous tabulae, septa (the major ones being arranged in groups of four), dissepiments and, in some, a central calcareous rod (columella).<\/p>\n<figure id=\"attachment_33635\" aria-describedby=\"caption-attachment-33635\" style=\"width: 960px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33635 size-medium\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549526_1332x690px-960x497.jpg\" alt=\"&lt;em&gt;Lithostrotion basaltiformis&lt;\/em a colonial rugose coral from the Carboniferous of Derbyshire.\" width=\"960\" height=\"497\" srcset=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549526_1332x690px-960x497.jpg 960w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549526_1332x690px-768x398.jpg 768w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549526_1332x690px.jpg 1332w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/><figcaption id=\"caption-attachment-33635\" class=\"wp-caption-text\"><em>Lithostrotion basaltiformis<\/em>, a colonial rugose coral from the Carboniferous of Derbyshire. BGS \u00a9 UKRI.\u00a0<\/figcaption><\/figure>\n<figure id=\"attachment_33710\" aria-describedby=\"caption-attachment-33710\" style=\"width: 960px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33710 size-medium\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549524_P549525_1332x690-960x497.jpg\" alt=\"&lt;em&gt;Dibunophyllum bipartitum&lt;\/em&gt; from the Carboniferous of North Wales, a solitary rugose coral (left). The cross section view (right) shows septa and dissepiments.\" width=\"960\" height=\"497\" srcset=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549524_P549525_1332x690-960x497.jpg 960w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549524_P549525_1332x690-768x398.jpg 768w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549524_P549525_1332x690.jpg 1332w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/><figcaption id=\"caption-attachment-33710\" class=\"wp-caption-text\"><em>Dibunophyllum bipartitum<\/em> from the Carboniferous of North Wales, a solitary rugose coral (left). The cross section view (right) shows septa and dissepiments. BGS \u00a9 UKRI.\u00a0<\/figcaption><\/figure>\n\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t<\/div><div  class=\"accordions\">\n\t\t\t\t<div class=\"acc-wrap\">\n\t\t\t\t\t<button class=\"acc-top secondary-background icon-arrow button no-btn\"><span class=\"button-content\" tabindex=\"-1\">Tabulate corals<\/span><\/button>\n\t\t\t\t\t<div class=\"acc-body sea-background-e\">\n\t\t\t\t\t\t<p>Tabulate corals are all colonial and have many closely spaced tabulae, but septa and dissepiments are either absent or very weak. Their fossils are often preserved as a cluster of long, slender tubes (corallites).<\/p>\n<figure id=\"attachment_33597\" aria-describedby=\"caption-attachment-33597\" style=\"width: 960px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33597 size-medium\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549521_1332x690-960x497.jpg\" alt=\"&lt;em&gt;Palaeofavosites rugosus&lt;\/em&gt; a tabulate coral from the Silurian of May Hill, Gloucestershire, England.\" width=\"960\" height=\"497\" srcset=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549521_1332x690-960x497.jpg 960w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549521_1332x690-768x398.jpg 768w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549521_1332x690.jpg 1332w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/><figcaption id=\"caption-attachment-33597\" class=\"wp-caption-text\"><em>Palaeofavosites rugosus<\/em> a tabulate coral from the Silurian of May Hill, Gloucestershire, England. BGS \u00a9 UKRI.\u00a0<\/figcaption><\/figure>\n\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t<\/div><div  class=\"accordions\">\n\t\t\t\t<div class=\"acc-wrap\">\n\t\t\t\t\t<button class=\"acc-top secondary-background icon-arrow button no-btn\"><span class=\"button-content\" tabindex=\"-1\">Scleractinian corals<\/span><\/button>\n\t\t\t\t\t<div class=\"acc-body sea-background-e\">\n\t\t\t\t\t\t<p>Scleractinian corals may be solitary or colonial. They have a very porous or spongy skeleton made of aragonite that is strengthened by radiating septa (the main ones being arranged in groups of six), dissepiments and sometimes a columella.<\/p>\n<figure id=\"attachment_21155\" aria-describedby=\"caption-attachment-21155\" style=\"width: 500px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-21155 size-full\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/03\/isatreaConybeari.jpg\" alt=\"&lt;em&gt;Isastrea conybeari&lt;\/em&gt;, a colonial scleractinian coral from the mid-Jurassic. BGS \u00a9UKRI. All rights reserved.\" width=\"500\" height=\"371\" \/><figcaption id=\"caption-attachment-21155\" class=\"wp-caption-text\"><em>Isastrea conybeari<\/em>, a colonial scleractinian coral from the mid Jurassic. BGS \u00a9 UKRI.<\/figcaption><\/figure>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-33631\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549520_1332x690-960x497.jpg\" alt=\"Flabellum woodi, a small solitary scleractinian coral\" width=\"960\" height=\"497\" srcset=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549520_1332x690-960x497.jpg 960w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549520_1332x690-768x398.jpg 768w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549520_1332x690.jpg 1332w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/><em style=\"font-size: 14px;\">Flabellum woodi<\/em><span style=\"font-size: 14px;\">, a small solitary scleractinian coral that grew to about 2 cm across. BGS \u00a9 UKRI.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33658 size-medium\" style=\"font-size: 14px;\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549517_1332x690-960x497.jpg\" alt=\"&lt;em&gt;Acropora&lt;\/em&gt;, a modern scleractinian coral from the latest Quaternary of the Pacific showing the spongy aragonite skeleton.\" width=\"960\" height=\"497\" srcset=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549517_1332x690-960x497.jpg 960w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549517_1332x690-768x398.jpg 768w, https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P549517_1332x690.jpg 1332w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/><em style=\"font-size: 14px;\">Acropora<\/em><span style=\"font-size: 14px;\">, a modern scleractinian coral from the latest Quaternary of the Pacific showing the spongy aragonite skeleton. BGS \u00a9 UKRI.<\/span><\/p>\n\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t<\/div>\n\n\n<h2 class=\"wp-block-heading\" id=\"environment\">Environment <\/h2>\n\n\n\n<p>Corals live in marine water, at most depths and latitudes. They have been found in water 6000 m deep, but are most common at depths of less than 500 m. At these depths, the water temperature may be close to 0\u00b0C, but corals are most common between 5\u00b0 and 10\u00b0C. Deeper water corals are mainly solitary, although some, such as <em>Lophelia<\/em>, are colonial and form thickets and banks.<\/p>\n\n\n\n<p>Corals reefs on the other hand, are restricted to the warmer regions of the world&#8217;s oceans such as the Seychelles, in the Indian Ocean, and Australia. They gradually add skeletal calcium carbonate to the existing reefs to build huge structures in well-lit, warm, tropical waters, clear of land-derived sediment. Reef-building corals favour water depths of less than 10\u201320&nbsp;m and temperatures between 25\u00b0 and 29\u00b0C.<\/p>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef255886274_1332x690px.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;A living coral reef in the Florida Keys National Marine Sanctuary. \u00a9Public domain. NOOA, Mike White, Florida Keys National Marine Sanctuary. &lt;\/p&gt;\n\" data-gallery=\"gallery_70918\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef255886274_1332x690px-150x150.jpg\" class=\"lazy-blur\" alt=\"A living coral reef in the Florida Keys National Marine Sanctuary.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef255886274_1332x690px-960x497.jpg\" \/><\/a><figcaption class=\"caption \">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p>A living coral reef in the Florida Keys National Marine Sanctuary. \u00a9Public domain. NOOA, Mike White, Florida Keys National Marine Sanctuary. <\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/reef255886274_1332x690px.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;A living coral reef in the Florida Keys National Marine Sanctuary. \u00a9Public domain. NOOA, Mike White, Florida Keys National Marine Sanctuary. &lt;\/p&gt;\n\" data-gallery=\"gallery_70918\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<h3 class=\"wp-block-heading\">Ancient coral reefs<\/h3>\n\n\n\n<p>Tabulate and rugose corals built mounds and thickets during the Palaeozoic, contributing to reef building, and fossils are commonly seen in Silurian to Carboniferous rocks of Britain. On a worldwide scale, they seem to have lived in equatorial latitudes, similar to modern forms. Since the Triassic, scleractinian corals have become reef builders. Coral reefs range in size from a few metres to hundreds of kilometres, but they fall into three main types.<\/p>\n\n\n\n<ul><li>Fringing reef: forms when coral reefs grow in warm, shallow-coastal waters. Sudden changes of sea level, such as during the last ice age, kill the coral, but where sea level rises (or the land sinks) at a slow rate, coral growth can keep pace. This can happen around an island formed by a volcano as the land subsides after volcanic activity stops.<\/li><li>Barrier reef: as a volcanic island slowly subsides, the reef grows upwards at the same rate. In this way the reef forms a barrier reef a little way from the shore and with a lagoon behind it.<\/li><li>Atoll: continued subsidence (or a rise in sea level) causes the volcanic island to disappear below the waves. The reef, however, continues to grow, taking on a roughly circular shape (an atoll) (and enclosing a lagoon, floored by sediment and reef debris.<\/li><\/ul>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/TypesOfReefs_1332x690px_2.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;Formation of coral reefs: (a) fringing reef; (b) barrier reef and (c) atoll. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_11281\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/TypesOfReefs_1332x690px_2-150x150.jpg\" class=\"lazy-blur\" alt=\"a) A fringing reef (left) forms when coral reefs grow in warm, shallow coastal waters. Sudden changes of sea level, such as during the last Ice Age, kill the coral, but where sea level rises (or the land sinks) at a slow rate, coral growth can keep pace. b) The volcanic island has subsided slowly and the reef has grown upwards at the same rate. In this way the reef has formed a barrier reef (centre) a little way from the shore and with a lagoon behind it. c) Continued subsidence (or rise in sea level) causes the volcanic island to disappear below the waves. The reef, however, continues to grow, taking on a roughly circular shape (an atoll) (right) and enclosing a lagoon, floored by sediment and reef debris.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/TypesOfReefs_1332x690px_2-960x497.jpg\" \/><\/a><figcaption class=\"caption sm-line\">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p>Formation of coral reefs: (a) fringing reef; (b) barrier reef and (c) atoll. BGS \u00a9 UKRI.<\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/TypesOfReefs_1332x690px_2.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;Formation of coral reefs: (a) fringing reef; (b) barrier reef and (c) atoll. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_11281\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<h2 class=\"wp-block-heading\" id=\"time\">Corals through time <\/h2>\n\n\n\n<p>Rugose and tabulate corals were common in the Palaeozoic. However, a mass extinction event took place at the end of the Permian, when over 90 per cent of all invertebrates became extinct, including all tabulate and rugose corals. The reason seems to have been due to the formation of the supercontinent Pangaea and the disappearance of environmental niches. <\/p>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/coralsThroughTime.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;The distribution of corals through time. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_45844\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/coralsThroughTime-150x150.jpg\" class=\"lazy-blur\" alt=\"The distribution of corals through time.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/coralsThroughTime.jpg\" \/><\/a><figcaption class=\"caption sm-line\">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p>The distribution of corals through time. BGS \u00a9 UKRI.<\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/coralsThroughTime.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;The distribution of corals through time. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_45844\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<p>This was also a time of increased aridity, with changes in ocean currents, more competition for less space on the continental shelf, widespread occurrence of evaporite deposits, intense volcanicity and changes in sea level. Scleractinian corals, which evolved during the Triassic, replaced the extinct groups.<\/p>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/lowerCarboniferousCoralZones.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;Coral zones in the early British Carboniferous. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_36855\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/lowerCarboniferousCoralZones-150x150.jpg\" class=\"lazy-blur\" alt=\"Coral zones in the British Lower Carboniferous.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/lowerCarboniferousCoralZones.jpg\" \/><\/a><figcaption class=\"caption sm-line\">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p>Coral zones in the early British Carboniferous. BGS \u00a9 UKRI.<\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/07\/lowerCarboniferousCoralZones.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;Coral zones in the early British Carboniferous. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_36855\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<p>One of the most important uses of fossils is in biostratigraphy, where short-lived fossil species are used to date the rocks in which they are found. Coral species are usually too long-lived to be useful in this way, but early Carboniferous rocks of Britain can be subdivided into zones defined by the first appearance of key corals they contain. These zones can also be traced throughout western Europe.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">The coral clock<\/h3>\n\n\n\n<p>When corals are examined under a microscope, their outer surface can be seen to be made up of hundreds of ridges (about 200 per centimetre). Each ridge was formed in a single day as the coral grew. Modern corals, such as <em>Manicina<\/em> and <em>Lophelia<\/em>, have about 360 growth ridges per year on average (it varies a little as they do not grow during breeding or bad environmental conditions), but Devonian corals like <em>Heliophyllum<\/em> and <em>Eridophyllum<\/em> grew 400 ridges each year on average. This is because the Earth&#8217;s rotation has slowed down so that there are 35\u201340 fewer days in the year now compared to Devonian times.<\/p>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/04\/Annual_monthly_growth_ings.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;&lt;em&gt;Heliophyllum halli&lt;\/em&gt; (left) lived during mid Devonian times in Michigan, USA. Annual and monthly growth rings can be recognised. Daily growth rings of &lt;em&gt;Heliophyllum halli&lt;\/em&gt; (right) show there were about 400 days in the year during the Devonian period. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_72344\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/04\/Annual_monthly_growth_ings-150x150.jpg\" class=\"lazy-blur\" alt=\"Heliophyllum halli (left) lived during mid Devonian times in Michigan, USA. Annual and monthly growth rings can be recognised. Daily growth rings of Heliophyllum halli (right) show there were about 400 days in the year during the Devonian period.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/04\/Annual_monthly_growth_ings-960x497.jpg\" \/><\/a><figcaption class=\"caption \">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p><em>Heliophyllum halli<\/em> (left) lived during mid Devonian times in Michigan, USA. Annual and monthly growth rings can be recognised. Daily growth rings of <em>Heliophyllum halli<\/em> (right) show there were about 400 days in the year during the Devonian period. BGS \u00a9 UKRI.<\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/04\/Annual_monthly_growth_ings.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;&lt;em&gt;Heliophyllum halli&lt;\/em&gt; (left) lived during mid Devonian times in Michigan, USA. Annual and monthly growth rings can be recognised. Daily growth rings of &lt;em&gt;Heliophyllum halli&lt;\/em&gt; (right) show there were about 400 days in the year during the Devonian period. BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_72344\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<h2 class=\"wp-block-heading\" id=\"3d-fossil\">3D fossils models<\/h2>\n\n\n<figure  class=\"img-wrap\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P851598_1332x690.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;&lt;em&gt;Cyclolites cupuliformis (&lt;\/em&gt;Jurassic, Pliensbachian). BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_46295\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P851598_1332x690-150x150.jpg\" class=\"lazy-blur\" alt=\"Cyclolites cupuliformis. (OUM J.41497 \u2013 Holotype). Pliensbachian Age (Jurassic Period) (182.7 \u2013 190.8 Ma B.P.) See 3D fossils online.\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P851598_1332x690-960x497.jpg\" \/><\/a><figcaption class=\"caption sm-line\">\n\t\t\t\t\t<div class=\"caption-icon\">\n\t\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/info-caption.svg\" alt=\"Information icon\">\n\t\t\t\t\t<\/div>\n\t\t\t\t\t<div class=\"caption-text\"><p><em>Cyclolites cupuliformis (<\/em>Jurassic, Pliensbachian). BGS \u00a9 UKRI.<\/p>\n<\/div>\n\t\t\t\t\t<div class=\"expand-box expand-box-top\"><a href=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/05\/P851598_1332x690.jpg\" data-toggle=\"lightbox\" data-footer=\"&lt;p&gt;&lt;em&gt;Cyclolites cupuliformis (&lt;\/em&gt;Jurassic, Pliensbachian). BGS \u00a9 UKRI.&lt;\/p&gt;\n\" data-gallery=\"gallery_46295\"><img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/themes\/bgs\/img\/expand.svg\" alt=\"Expand icon\"><\/a><\/div>\n\t\t\t\t<\/figcaption><\/figure>\n\n\n<p>Many of the fossils in the&nbsp;<a href=\"https:\/\/www.bgs.ac.uk\/geological-data\/national-geological-repository\/palaeontology-collections\/\">BGS palaeontology collections<\/a>&nbsp;are available to view and download as 3D models. To view this fossil, or others like it, in 3D visit <a rel=\"noreferrer noopener\" href=\"http:\/\/www.3d-fossils.ac.uk\/home.html\" target=\"_blank\">GB3D Type Fossils<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Reference<\/h2>\n\n\n\n<p>Wilkinson, I P, and Scrutton, C. 2000. Corals: fossil focus. (Nottingham, UK: British Geological Survey.)<\/p>\n<\/div><\/div><\/div><\/section>\n\n\n\n\n\t\t\t\t\t<section   id=\"latest-content-2727-block_5ed532702ceae\" class=\"grid-section  primary-background   \" >\n\t\t\t\t\t\t<div class=\"container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"row header-of-section\">\n\t\t\t\t\t\t\t\t<div class=\"col-12\">\n\t\t\t\t\t\t\t\t\t<h2>You may also be interested in<\/h2>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"row grid-wrap\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"col-lg-6 col-12\">\n\t<div class=\"cards cards-orizontal-sm  cards-find-more  cards-bordered\">\n\t\t\t\t<a href=\"https:\/\/www.bgs.ac.uk\/discovering-geology\/\" class=\"media-wrap\">\n\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/04\/feature_homepage_p815563-150x150.jpg\" class=\"lazy-blur wp-post-image\" alt=\"Ammonite p815563\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2020\/04\/feature_homepage_p815563.jpg\" \/>\t\t\t\t\t<\/a>\n\t\t\t\t<div class=\"info-wrap\">\n\t\t\t<div class=\"info\">\n\t\t\t\t<h4><a href=\"https:\/\/www.bgs.ac.uk\/discovering-geology\/\">Discovering Geology<\/a><\/h4>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<p>Discovering Geology introduces a range of geoscience topics to school-age students and learners of all ages.<\/p>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t<a href=\"https:\/\/www.bgs.ac.uk\/discovering-geology\/\">Show more<\/a>\n\t\t<\/div>\n\t<\/div>\n<\/div>\n<div class=\"col-lg-6 col-12\">\n\t<div class=\"cards cards-orizontal-sm  cards-find-more  cards-bordered\">\n\t\t\t\t<a href=\"https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/\" class=\"media-wrap\">\n\t\t\t<img decoding=\"async\" src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2021\/06\/fishThroughTime-150x150.jpg\" class=\"lazy-blur wp-post-image\" alt=\"fishThroughTime\" data-src=\"https:\/\/www.bgs.ac.uk\/wp-content\/uploads\/2021\/06\/fishThroughTime.jpg\" \/>\t\t\t\t\t<\/a>\n\t\t\t\t<div class=\"info-wrap\">\n\t\t\t<div class=\"info\">\n\t\t\t\t<h4><a href=\"https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/\">Fossils and geological time<\/a><\/h4>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<p>Take a look at the history of the Earth, from its formation over four and a half billion years ago to present times.<\/p>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t<a href=\"https:\/\/www.bgs.ac.uk\/discovering-geology\/fossils-and-geological-time\/\">Show more<\/a>\n\t\t<\/div>\n\t<\/div>\n<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"row\">\n\t\t\t\t\t\t\t\t<div class=\"col-12\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/section>\n\t\t\t\t","protected":false},"excerpt":{"rendered":"","protected":false},"author":6,"featured_media":36544,"parent":16685,"menu_order":13,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"on","_relevanssi_pin_keywords":"coral, fossils","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"57656,37491,9609,17149,34330,33925","_relevanssi_noindex_reason":"","footnotes":""},"tags":[],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.3 - 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