Where to find corals

Frequently asked questions

How do I identify a fossil coral?

Fossil corals preserve the calcium carbonate skeleton secreted by coral polyps. There are three main groups to recognize. Rugose corals (Ordovician to Permian) occur as solitary horn-shaped or conical forms — often called horn corals — with a deep cup (calyx) at the top and radial septa (dividing walls) visible in cross-section; colonial rugose forms make irregular masses. Tabulate corals (Ordovician to Permian) are always colonial, forming low mats with tube-like corallites and horizontal dividing plates (tabulae) inside each tube rather than vertical septa; Favosites (honeycomb coral) and Halysites (chain coral) are the classic examples. Modern-style scleractinian corals appear from the Triassic onward and have septa arranged in multiples of six. If you find a honeycomb-textured rock with clear cell boundaries and tube structures, it is almost certainly a colonial tabulate or rugose coral.

Where can I find fossil corals?

Devonian and Carboniferous limestone exposures are the most productive sites. Mineral Wells Fossil Park in Texas (Pennsylvanian, free) produces rugose corals alongside crinoids and brachiopods. Caesar Creek State Park in Ohio (Ordovician, Army Corps spillway) produces both rugose and tabulate corals. Wenlock Edge in Shropshire and Wren's Nest Hill in Dudley, UK, expose Silurian reef limestone with abundant tabulate corals including Favosites and Halysites. The Devonian limestones around Torquay in south Devon produce well-preserved colonial and solitary Devonian corals. Faxe Quarry in Denmark (Paleocene, approximately 59 Ma) is notable for producing post-Cretaceous scleractinian reef material accessible to visitors with landowner permission.

Are fossil corals different from modern corals?

Yes, significantly. The two dominant Paleozoic coral groups — rugose and tabulate — went extinct in the end-Permian mass extinction (approximately 252 Ma) and have no living representatives. Modern coral reefs are built by scleractinian corals, which first appeared in the Triassic and belong to an entirely separate evolutionary lineage. The structural similarity between Paleozoic and modern corals is an example of convergent evolution — similar reef-building functions selected for similar skeletal forms. The Cretaceous mass extinction (66 Ma) also devastated scleractinian reefs, and present-day reef diversity represents their subsequent recovery. Fossil corals commonly found in UK Silurian and Devonian limestones — including Favosites (honeycomb coral) and Heliophyllum — are not ancestral to any modern reef coral.