94 million-year-old fossilized sea monster is the oldest of its kind in North America

Illustration of a lizard-like creature under the ocean along with a few fish and another animal that resembles a snail

In the rocky gray shale of southern Utah, scientists have unearthed the remains of a mosasaur that roamed a once-thriving sea 94 million years ago. The toothy reptilian is a never-before-seen species and the oldest mosasaur fossil ever found in North America, according to a new study published Monday (June 26) in the journal Cretaceous Research. 

Mosasaurs were a group of marine reptiles that dominated the seas during the Cretaceous period (145 million to 66 million years ago). At that time, this region of Utah was part of the Western Interior Seaway — an ancient sea that stretched from the Gulf of Mexico to the Arctic Circle and split what is now North America in two.