The Dinosaurs and Prehistoric Animals of Ohio

Isotelus maximus Ohio

Daderot/Wikimedia Commons/CC0


First, the good news: A huge number of fossils have been discovered in the state of Ohio, many of which are spectacularly preserved. Now, the bad news: virtually none of these fossils were laid down during the Mesozoic or Cenozoic eras, meaning that not only have no dinosaurs ever been discovered in Ohio, but neither have any prehistoric birds, pterosaurs, or megafauna mammals.

Discouraged? Don't be. Let's discover the most notable prehistoric animals to have lived in the Buckeye State.

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Cladoselache fyleri (fossil shark)

James St. John/Flickr/CC BY 2.0


The most famous fossil bed in Ohio is the Cleveland Shale, which harbors creatures dating back to the Devonian period, about 400 million years ago. The most famous prehistoric shark to be discovered in this formation, Cladoselache was a bit of an oddball: This six-foot-long predator mostly lacked scales, and it didn't possess the "claspers" that modern male sharks use to hold on to the opposite sex during mating. Cladoselache's teeth were also smooth and blunt, an indication that it swallowed fish whole rather than chewing them first.

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Dunkleosteus terrelli (fossil fish)

 James St John/Flickr/CC BY 2.0

A contemporary of Cladoselache, Dunkleosteus was one of the largest prehistoric fish in the history of the planet, the full-grown adults of some species measuring 30 feet from head to tail and weighing three to four tons. As big as it was, Dunkleosteus (along with the other "placoderms" of the Devonian period) was covered with armor plating. Unfortunately, the Dunkleosteus specimens discovered in Ohio are the runts of the litter, only about as big as modern tuna!

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Prehistoric Amphibians

Phlegethontia, a prehistoric animal of Ohio

Smokeybjb/Wikimedia Commons/CC BY-SA 3.0


Ohio is famous for its lepospondyls, prehistoric amphibians of the Carboniferous and Permian periods characterized by their small size and (often) weird appearance. The dozen or so lepospondyl genera discovered in the Buckeye State include the tiny, snakelike Phlegethontia and the strange-looking Diploceraspis, which possessed an oversized head shaped like a boomerang (which was likely an adaptation meant to deter predators from swallowing it whole).

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Isotelus maximus Ohio

Daderot/Wikimedia Commons/CC0


The official state fossil of Ohio, Isotelus was discovered in the southwestern part of the state in the late 1840s. One of the largest trilobites (a family of ancient arthropods related to crabs, lobsters, and insects) ever identified, Isotelus was a marine-dwelling, bottom-feeding invertebrate of a type very common during the Paleozoic Era. The largest specimen, unfortunately, was excavated outside Ohio: a two-foot-long behemoth from Canada named Isotelus rex.

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Your Citation
Strauss, Bob. "The Dinosaurs and Prehistoric Animals of Ohio." ThoughtCo, Aug. 28, 2020, Strauss, Bob. (2020, August 28). The Dinosaurs and Prehistoric Animals of Ohio. Retrieved from Strauss, Bob. "The Dinosaurs and Prehistoric Animals of Ohio." ThoughtCo. (accessed June 5, 2023).