File:Strophomenid brachiopod (Columbus Limestone, Middle Devonian; abandoned quarry, Kelleys Island, Lake Erie, Ohio, USA) 3 (48620563887).jpg

Strophomenid brachiopod 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.

Brachiopods are sessile, benthic, filter-feeding, marine invertebrates. They first appear in Cambrian rocks and were abundant in Earth's oceans throughout the Paleozoic. They were also common in Mesozoic oceans, but are scarce in modern oceanic biotas. Brachiopods have two shells, called valves, that are usually calcareous (made of calcite - CaCO3 - calcium carbonate). Each shell of a brachiopod is bilaterally symmetrical, unlike each shell of a bivalve (clam).

Classification: Animalia, Brachiopoda, Articulata (a.k.a. Rhynchonelliformea), Strophomenida

Stratigraphy: Columbus Limestone, Eifelian Stage, lower Middle Devonian