File:Solitary rugose corals (Columbus Limestone, Middle Devonian; abandoned quarry, Kelleys Island, Lake Erie, Ohio, USA) 32 (48644708236).jpg

Solitary rugose corals in limestone in the Devonian of Ohio, USA.

The Columbus Limestone is a significant carbonate unit in the Middle Devonian of central and northern Ohio. It's actually part of a much more widespread sheet of Devonian carbonates that extends from New York State to the Midwest. The Columbus Limestone represents deposition in a subtropical, shallow-water, carbonate platform environment. The rocks are principally micritic limestones, fossiliferous wackestones, and fossiliferous packstones. Some chert nodules are present in the unit. Fossils are typical Paleozoic shallow marine invertebrates - favositid corals, rugose corals, stromatoporoids brachiopods, crinoids, blastoids, bryozoans, trilobites, bivalves, gastropods, cephalopods, rostroconchs, and tentaculites. Microfossils include conodonts and charophyte oogonia. Other fossils in the Columbus Limestone include vertebrates (fish), land plants (rare), and trace fossils. Some fossil horizons in the Columbus Limestone are partially silicified.

This fossiliferous limestone surface has several rugose corals, commonly known as "horn corals". Rugosans are an extinct group - they only occur in Paleozoic rocks. The soft parts were sea anemone-like creatures called polyps. The polyps made calcareous hard-part skeletons. Most rugosans were solitary, but some were colonial. These specimens are solitary rugose corals - they had solid, tapering skeletons of calcite.

Classification: Animalia, Cnidaria, Anthozoa, Rugosa

Stratigraphy: Columbus Limestone, Eifelian Stage, lower Middle Devonian