NM Fossil IDd as New Tyrannosaur

Thirty years ago, a Las Cruces family boating at Elephant Butte Reservoir found a massive jaw bone on the water’s eastern shore and turned it over to New Mexico scientists. Now, a team of researchers, including one of the state’s leading paleontologists, have identified the fossil as a previously unknown species of Tyrannosaur. The findings were published Jan. 11 in Scientific Reports and announced in a news conference in Albuquerque the same day.

The lead author of the paper, Montana State University doctoral candidate Sebastian Dalman, began researching the fossils in the New Mexico Museum of Natural History collection in 2013 and noticed differences between it and the teeth from known species of Tyrannosaur. In the paper, he and eight co-authors make the case for the new species they’ve dubbed T.mcraeensis as a direct ancestor of the T.rex, pre-dating it by approximately 5 to 7 million years.

While T.rex gnashed its way through the last days of dinosaurs approximately 66 to 68 million years ago, the jaw bone and other parts of skull from New Mexico indicate T. mcraeensis dates to 72 to 73 million years ago, the paper concludes. The older animal was roughly the same size—about 40 feet long and 12 feet high—but lacks a bone ridge found near the T. rex eye and has a narrower jaw.

Co-author Spencer Lucas, paleontology curator at New Mexico Museum of Natural History, said scientists derived the dinosaur’s name from the fossil’s location in the McRae rock formation, which carries the name of Civil War Gen. William McRae. After the original find in 1983, museum staff returned to the reservoir shore to recover more of the fossil and then did so again in the 1990s.

“What we knew about Tyrannosaurus rex in the 1980s was very small compared to what we know about T. rex now,” Lucas said at the press conference. “So looking at it again, as Sebastian did and then a whole group did, we’re looking at it through new eyes through a lot more knowledge than was available in the 80s.”

In addition to NMMNHS, researchers on the project included scientists from the University of Bath (UK), University of Utah, George Washington University, Harrisburg University, Penn State Lehigh Valley and the University of Alberta in Canada.

Paleontologist and evolutionary biologist Nicholas R. Longrich traveled from the Department of Biology and Biochemistry at the University of Bath to conduct a thorough examination of the fossils at the museum early last year. The conclusions of the paper, which also relied on radiometric analysis conducted by geology faculty and students at New Mexico State University, give the scientific community a new idea about the evolution of Tyrannosaurs, he said during the press conference, which was live-streamed on Zoom.

“The evidence points towards an older age” than previously known, said Longrich, noting the new evidence also disrupts previous theories that pegged the origins of Tyrannosaur in modern-day Canada and Montana. Instead, scientists conducted, the American Southwest appears to be “kind of epicenter of Tyrannosaur evolution.”

The partial skull of the Tyrannosaurus mcraeensis is now on view at the museum.

Anthony Fiorillo, museum executive director and a paper co-author, said during Thursday’s morning news conference of the original discovery “science is a process. With each new discovery, it forces us to go back and test and challenge what we thought we knew. And that’s the story. The core story of this project is that it took 30 years, but it’s part of the process of moving forward with new interpretations.”

“New Mexicans have always known our state is special, now we know that New Mexico has been a special place for tens of millions of years,” Fiorillo said in a written statement issued by the state Department of Cultural Affairs. “This study delivers on the mission of this museum through the science-based investigation of the history of life on our planet.”