File:Gastropod internal mold (Columbus Limestone, Middle Devonian; abandoned quarry, Kelleys Island, Lake Erie, Ohio, USA) 3 (48620317702).jpg

Fossil gastropod 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.

Seen here is an internal mold of a fossil low-spired gastropod in limestone matrix on Kelleys Island in Lake Erie, Ohio. The gastropods (snails & slugs) are a group of molluscs that occupy marine, freshwater, and terrestrial environments. Most have a calcareous external shell (the snails). Some lack a shell completely, or have reduced internal shells (the slugs & sea slugs & pteropods). Most members of the Gastropoda are marine. Most marine snails are herbivores (algae grazers) or predators/carnivores.

Classification: Animalia, Mollusca, Gastropoda

Stratigraphy: Columbus Limestone, Eifelian Stage, lower Middle Devonian