Fossils are defined as any remains of ancient life that has been preserved in the Earth's crust. Fossils can be from plants or animals, whether actual remains of animals or evidence of their movement, such as footprints. Fossils can be found throughout Oklahoma, especially in the Arbuckle Mountains in south-central Oklahoma.

About 490 million years ago, the land that is now Oklahoma was actually located south of the Equator and was covered by a shallow sea. Over the next 300 million years, the land drifted slowly northward and alternated between being dry and being covered by sea. By 144 million years ago, Oklahoma was in its current position but was part of a giant inland sea stretching from Texas to Canada.

While dinosaurs probably once roamed Oklahoma, erosion has removed most fossil evidence of dinosaurs. However, dinosaur bones have been found in Atoka and Cimarron counties. One of these dinosaurs was a large meat-eating dinosaur called Acrocanthosaurus atokensis that lived between 146 million and 100 million years ago. Fossil remains indicate this dinosaur could have been as much as 18 feet tall and 43 feet long.

The state fossil of Oklahoma is the Saurophaganax maximus. This carnivorous dinosaur was about 40 feet long and lived during the Jurassic period, about 150 million years ago. A group from the University of Oklahoma found skeletal remains of this dinosaur in Cimarron County in the 1930s.

Oklahoma is best know for its abundance of trilobite fossils. Trilobites were marine arthropods that lived from from 540 million to 250 million years ago.

FossilSites.com lists areas throughout Oklahoma where you may find fossils. Another option for finding fossils is to join a fossil dig expedition through the Sam Noble Museum of Oklahoma History.