A contemporary of Cladoselache, below, Dunkleosteus was one of the largest prehistoric fish
in the history of the planet, full-grown adults measuring about 30 feet from head to tail and weighing three to four tons. Sadly, though, the Dunkleosteus species discovered in Ohio were the runts of the litter, only about as big as a tuna! More about Dunkleosteus
The most famous prehistoric shark
to be discovered in Ohio's Cleveland Shale, Cladoselache was a bit of an oddball: this Devonian
predator mostly lacked scales, and it didn't possess the "claspers" that modern sharks use to reproduce. Cladoselache's teeth were also smooth and blunt, a clue that it swallowed fish whole rather than chewing them first.
Ohio is famous for its lepospondyls, prehistoric amphibians characterized by their small size and (often) weird appearance. The dozen or so lepospondyl genera discovered in this state include the tiny, snakelike Phlegethontia
and the strange-looking Diploceraspis, which possessed an oversized head shaped like a boomerang. More about prehistoric amphibians
The most common invertebrates on earth hundreds of millions of years ago, trilobites
were three-segmented arthropods covered by hard shells (which tend to preserve well in the fossil record). The trilobites of Ohio date from the Devonian period, when these ocean-dwellers coexisted with vertebrates like Cladoselache and Dunkleosteus (above).