New tyrannosaur fossil is most complete found in Southwestern US

A remarkable new fossilized skeleton of a tyrannosaur discovered in the Bureau of Land Management's Grand Staircase-Escalante National Monument (GSENM) in southern Utah was airlifted by helicopter Sunday, Oct 15, from a remote field site, and delivered to the Natural History Museum of Utah where it will be uncovered, prepared, and studied. The fossil is approximately 76 million years old and is most likely an individual of the species Teratophoneus curriei, one of Utah's ferocious tyrannosaurs that walked western North America between 66 and 90 million years ago during the Late Cretaceous Period.

Toe bones, the upper jaw and snout of the fossilized remains of a tyrannosaur skeleton found in Grand Staircase Escalante 
National Monument. The skeleton is the most complete of its kind found in the Southwest United States 
[Credit: Mark Johnston/NHMU]

"With at least 75 percent of its bones preserved, this is the most complete skeleton of a tyrannosaur ever discovered in the southwestern US," said Dr. Randall Irmis, curator of paleontology at the Museum and associate professor in the Department of Geology and Geophysics at the University of Utah. "We are eager to get a closer look at this fossil to learn more about the southern tyrannosaur's anatomy, biology, and evolution."

GSENM Paleontologist Dr. Alan Titus discovered the fossil in July 2015 in the Kaiparowits Formation, part of the central plateau region of the monument. Particularly notable is that the fossil includes a nearly complete skull. Scientists hypothesize that this tyrannosaur was buried either in a river channel or by a flooding event on the floodplain, keeping the skeleton intact.

"The monument is a complex mix of topography -- from high desert to badlands -- and most of the surface area is exposed rock, making it rich grounds for new discoveries, said Titus. "And we're not just finding dinosaurs, but also crocodiles, turtles, mammals, amphibians, fish, invertebrates, and plant fossils -- remains of a unique ecosystem not found anywhere else in the world," said Titus.

Although many tyrannosaur fossils have been found over the last one hundred years in the northern Great Plains region of the northern US and Canada, until relatively recently, little was known about them in the southern US. This discovery, and the resulting research, will continue to cement the monument as a key place for understanding the group's southern history, which appears to have followed a different path than that of their northern counterparts.