A huge number of dinosaurs and prehistoric animals have been discovered in the state of Colorado, so many that it's easier to list them by type than by genus. See this list of the most notable dinosaurs of Colorado.

Photograph of Camptosaurus: Carnegie Museum of Natural History

The shortest period of the Paleozoic Era, the Silurian marks the time when the first plants and animals colonized dry land. Here's a look at the prehistoric life that could be found on earth during the Silurian period.

Illustration of Psarolepis: Nobu Tamura

Leviathan was a 50-foot-long, 50-ton sperm whale that prowled the waters of Miocene South America. Megalodon was a comparably sized prehistoric shark that occasionally ventured into Leviathan's territory. Who wins in a battle between these two undersea titans?

Illustration of Megalodon and Leviathan: Megalodon (left), Alex Brennan Kearns; Leviathan (right), C. Letenneur

No dinosaurs have ever been discovered in Ohio, but that doesn't mean this state was totally bereft of prehistoric life. Read more about the prehistoric animals that have been discovered in Ohio.

Illustration of Dunkleosteus: Nobu Tamura