© 2024 Wyoming Public Media
800-729-5897 | 307-766-4240
Wyoming Public Media is a service of the University of Wyoming
Play Live Radio
Next Up:
0:00 0:00
Available On Air Stations
Transmission & Streaming Disruptions
A regional collaboration of public media stations that serve the Rocky Mountain States of Colorado, Idaho, Nevada, New Mexico, Utah and Wyoming.

Paleontologists Find An Ancestor Of T.Rex In Utah. It's Small.

A reconstruction of North America's newest tyrannosaur, Moros intrepidus.
Jorge Gonzalez
A reconstruction of North America's newest tyrannosaur, Moros intrepidus.

Paleontologists have found a new species of tyrannosaur based on fossils in Emery County, Utah.

Lindsay Zanno found the fossilized leg bone sticking out of a grey hill in a part of Utah where landmarks get names like "Cliffs of Insanity" and "Suicide Hill."

"I knew right away it was something interesting, but we didn't know for a long time what it was," says Zanno, a paleontologist at the North Carolina Museum of Natural Sciences and NC State University. "It took a long time of sort of meticulous anatomical research to try and figure out what type of dinosaur it actually belonged to."

The tyrannosaur, dubbed 'Moros intrepidus,' is an ancestor of T-rex, with legs built for speed an a surprisingly small body.

"Moros is about the size of a large deer," says Zanno. "This is an animal that would have stood about four feet at the hip or maybe five feet at the head. Moros could have looked you directly in the eyes."

As Zanno and her colleagues write in the journal Communications Biology, the fossil suggests that tyrannosaurs in North America were quite the underdogs among dinosaurs until climate change did in the top dogs of the time, the allosaurs. Then, the deer-sized tyrannosaurs ballooned and took over, growing to be about ten times as big and ascending to the top of the food chain.

"We were surprised at how tiny of a tyrannosaur Moros is," says Zanno. "It tells us that once allosaurs went extinct on the North American continent, these tiny tyrannosaurs were able to increase their body mass by about ten times in a span of just about 10 to 15 million years. That's really short in evolutionary time. So they were obviously very sophisticated animals that were ready and primed to ascend to those top roles when given the chance."

Zanno and her colleagues captured some of the animal’s dramatic exit from its "prolonged stint as marginal predators" in the little guy’s name, Moros. It’s Greek for "the embodiment of impending doom."

This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUER in Salt Lake City and KRCC and KUNC in Colorado. 

Copyright 2021 KUNC. To see more, visit KUNC.

Rae Ellen Bichell is a reporter for NPR's Science Desk. She first came to NPR in 2013 as a Kroc fellow and has since reported Web and radio stories on biomedical research, global health, and basic science. She won a 2016 Michael E. DeBakey Journalism Award from the Foundation for Biomedical Research. After graduating from Yale University, she spent two years in Helsinki, Finland, as a freelance reporter and Fulbright grantee.
Rae Ellen Bichell
I cover the Rocky Mountain West, with a focus on land and water management, growth in the expanding west, issues facing the rural west, and western culture and heritage. I joined KUNC in January 2018 as part of a new regional collaboration between stations in Colorado, Idaho, Montana, Utah and Wyoming. Please send along your thoughts/ideas/questions!
Related Content