In the rocky gray shales of southern Utah, scientists discovered the remains of a mosasaur that once roamed a thriving sea 94 million years ago. According to a new study published in the journal Cretaceous SurveyThe toothy reptile is a never-before-seen species and is the oldest mosasaur fossil ever found in North America.

Mosasaurs were a group of marine reptiles that dominated the seas during the Cretaceous period (145 to 66 million years ago). At that time, this area of ​​Utah was part of the Western Inland Seaway, an ancient sea that stretched from the Gulf of Mexico to the Arctic Circle and bisects modern North America.

Many mosasaurs that lived at the same time as dinosaurs had long tails and shovel-like appendages to chase their prey. According to a 2014 study in the Proceedings of the Institute of Zoology of the Russian Academy of Sciences, some individuals likely grew to be 56 feet (17 meters) tall.

“During the deposition of tropical shales about 94 million years ago, mosasaurs were still very small (about 0.9 meters), primitive, and fully adapted to marine conditions in the early stages of evolution,” said study co-author Barry Albright. A paleontologist at the University of North Florida. “For these reasons, their fossils are extremely rare and hard to find.”

In 2012, scientists discovered the first piece of a mosasaur fossil, then recovered nearly half of the individual over the next two field seasons, eventually allowing them to classify it as a new species.

“The fossil was found in several pieces and weathered on the surface for many years,” said study author Michael Polsin, a paleontologist at Southern Methodist University in Texas and Utrecht University in the Netherlands. “So it wasn’t in the old state. Numerous detailed comparisons have been made to study the entire anatomy and understand its connections.”

They named the new species Sarabosaurus dahli – translated as “desert mirage lizard” – after Steve Dahl, one of the team’s volunteers, and as “a tribute to the mirages often seen in hot deserts in summer.”

Early mosasaur species were similar to lizards in appearance and had relatively primitive limbs compared to later mosasaur species that dominated the seas with their streamlined bodies. However, the fact that S. dahli’s brain was different from other early mosasaur forms in circulation may have helped it better adapt to its marine environment.