The North Sulphur River was created by nature as a small, slow-moving river descending at a rate of between 5 and 6 inches per mile. In 1929, as a result of the need for irrigation for agricultural land within Texas the North Sulphur River was straightened and a channel added to increase the depth. This produced a fast-flowing river descending at a rate of between 5 and 6 feet per mile, the erosion of the banks of the river produced a basin around 50 feet deep along the banks of the North Sulphur River. Within the basin and riverbed, fossils are uncovered following heavy rain, which removes surface soil. The North Sulphur River merges into the Red River, before merging again with the Mississippi and flowing into the Gulf of Mexico.
Older fossils uncovered along the North Sulphur River can date back to over 70 million years ago, according to Fossils Galore. These include varieties of marine-based dinosaurs such as the mosasaur, a marine reptile that grew to lengths of around 40 feet and was equipped with razor-sharp teeth. Other dinosaur fossils include giant oysters or exogyra ponderosa, ammonities, various types of fish and shark bones and teeth.
Younger fossils that have been discovered along the North Sulphur River have been dated to the last ice age to cover the Earth. The species of animals that have been uncovered include a giant bison with straight horns that was around twice the average size of bison roaming the Earth in 2011. A species of ground-dwelling sloth bones have been uncovered, along with the remains of giant beavers. The full skeleton of a species of giant armadillo also was discovered along the river.
A large number of the fossils discovered along the North Sulphur River are marine species from the cretaceous period of history. These fossils include cephalopods, such as cuttlefish, squid and octopus. Other marine fossils have included horn coral and certain types of turtle shell.
