Scientists Uncover Fossils Belonging to New Reptile Species in Central Wyoming

By Shen Wu Tan

Special to the Wyoming Truth

This story has been corrected as of 10:33 a.m. MT on April 27, 2023.

Is it a crocodile? A bird?

Technically, it’s a species of rhynchosaur, a distant relative of modern birds and crocodiles with a beak-like mouth that existed over 200 million years ago – the fossils of which scientists unearthed from the exposed rocks of the Popo Agie Formation tucked in the northern Rocky Mountains in central Wyoming. 

A study released earlier this month in the journal Diversity definitively describes the rhynchosaur species for the first time. The species was given a name from the Northern Arapaho Tribal Historic Preservation Office: Beesiiwo cooowuse, meaning “big lizard from the Alcova area.”

The study’s researchers, who hail from Virginia Tech and the University of Wisconsin-Madison (UW-Madison), discovered 12 different specimens from the rhynchosaur family, of which three “isolated maxillary tooth plates” belonged to the Beesiiwo cooowuse, the report states. The researchers estimate the species roamed the earth 237 to 227 million years ago.

“Beesiiwo [cooowuse] belongs to a group, Hyperodapedontinae, that only exists in a very specific time in Earth history, a window of about ten million years,” Adam Fitch, the study’s lead author and a master’s student at Virginia Tech’s Department of Geosciences, told the Wyoming Truth. “This 10-million-year period is notable as seeing the origin of the modern fauna, seeing the earliest modern mammals, earliest feathered bird ancestors and earliest shelled turtles, among other present-day forms.”

Dave Lovelace, a scientist at the University of Wisconsin Geology Museum and one of the study’s authors, said the presence of rhynchosaurs, specifically the Beesiiwo cooowuse, helps “constrain the age of the rocks that they are found in” to the Carnian (late Triassic) time period.

“The big reason that becomes important is because within that time interval the very first dinosaurs evolved,” said Lovelace. “It means that these rocks in Wyoming have the potential to preserve part of the fossil record that is otherwise not preserved in North America. It makes it a unique window into the evolution of dinosaurs.”

A collaboration between scientists and Native American tribes

Although the species existed during the age of the dinosaurs, it was not a dinosaur, Lovelace clarified. Beesiiwo cooowuse is an archosaur, a subclass that includes dinosaurs, flying reptiles and animals that are related to crocodiles and birds mostly from the Triassic period.

From the small fragments of fossils, Lovelace said scientists have a general idea of what the species looks like: about two to three feet long, squat and short-legged. The researchers uncovered the first fossils in July 2013 in a chunk of rock in a campground; the last piece was found in July 2018.

Beesiiwo cooowuse is the first Western-science species to be assigned a name from the language of the Arapaho people, an article published by the University of Wisconsin-Madison claims. The fossils originated from the ancestral lands of these Native Americans.

“Beesiiwo cooowuse, a name of the Arapaho language given by our Northern Arapaho tribal elder coauthors, is distinctly of this region of the world, both in actuality and in the care taken by our coauthors and partners in giving it a name that reflects its place and story,” Fitch said. “This represents part of the beginning of an ongoing partnership between members of the Northern Arapaho tribe and members or alumni of the UW-Madison paleontological research group.”

Two other species will be assigned names from the Eastern Shoshone language when researchers release studies about them.

Lovelace, who grew up in Wyoming, helps conduct excavations on public lands that originally belonged to many First Nations, including the Eastern Shoshone and Northern Arapaho. He and Fitch, along with UW-Madison students, have collaborated with representatives of both tribes and Fort Washakie schools on the Wind River Reservation.

“There’s not the inclusivity and representation that is needed in things like naming new animals or new plants,” Lovelace told the Wyoming Truth. “And so, working with the communities, it’s very, very important to me – and I think it should be important to other scientists working in communities around the world – to actually have those community members involved in the scientific process and sharing their knowledge.”

Will the team find more fossils belonging to this new reptile species? Only time will tell.

“Of course, we hope that we’ll be able to find a complete specimen,” Lovelace said. “That could be next season or three decades from now. Or it could be never. We just don’t know. But that’s part of the thrill and excitement of vertebrate paleontology. You never really know what you’re going to find.”

The Northern Arapaho Tribal Historic Preservation Office could not be reached for comment.