Dedman College of Humanities and Sciences Dedman College Research Earth Sciences Faculty News

Oldest Fossil of Sea Reptile Dating Back 94 Million Years Found in Utah


I knew right away we had something special, especially considering it was so old,” said Michael Polcyn, a vertebrate paleontologist and mosasaur expert at the Southern Methodist University in Dallas.

The discovery of the oldest fossil of a marine reptile, dating back 94 million years, is shedding new light on the evolution of animals that would later dominate the oceans.

The fossil of the mosasaur, a predatory sea creature equipped with powerful jaws and teeth designed for cutting prey, was first found in the Kaiparowits—a rock formation in the gray shale badlands of Utah—11 years ago.

Only when examining the fossil more closely, however, did researchers realize its true significance, and its record-breaking age.

They named it Sarabosaurus dahli, or “Dahl’s reptile of the mirage,” in honor of Steve Dahl, the longest-serving volunteer working on the project, and to reflect the find’s origins. “Mirage” alludes both to the vast, ancient seaway that once covered most of the middle of North America, and in which the animal swam, and the mirages that accompany the area’s extreme summer heat.

Mosasaurs were marine reptiles that lived in the Late Cretaceous period, between 84 million and 95 million years ago. They could grow up to 56 feet in length, but many didn’t exceed the size of a porpoise. They had a long, thin body, not unlike that of a snake, and a long snout.

The oldest of these creatures typically didn’t grow larger than 3 to 5 feet long. Later, when they evolved, they became gigantic, apex predators.

The Utah fossil, consisting of skull fragments and vertebrae, was found by Scott Richardson, a trained volunteer working with Barry Albright of the University of North Florida. They were both working to uncover some scattered fragments, the Bureau of Land Management (BLM) said in a statement.

Taking the fossilized remains to the lab, they realized that this was the oldest mosasaur ever found.

Read the full article