Team finds new dinosaur species

Question: What's toothy, about 73 million years old, and hails from south-central New Mexico?

The answer: A new species of dinosaur, discovered by a team of paleontologists associated with the New Mexico Museum of Natural History and Science.

The new species, known as Tyrannosaurus mcraeensis, is an older relative of the world's most famous dinosaur — the Tyrannosaurus rex. The discovery, published by a group of researchers spanning New Mexico, the U.S., Canada and England, fundamentally changes paleontologists' understanding of how tyrannosaurs first arrived in North America, museum Executive Director Anthony Fiorillo announced at a news conference Thursday.

"We're very proud of the fact that we're a museum that serves all of New Mexico, and it's really terrific to see people around the state come here to learn about and celebrate New Mexico's natural heritage," Fiorillo said. "And today we're going to talk about New Mexico's newest dinosaur."

The path to discovering the new species began about 30 years ago when Las Cruces residents found some fossil remains while boating at Elephant Butte Reservoir and reported their finding to the museum, said Spencer Lucas, paleontology curator at the museum. Paleontologists then excavated about a quarter of a fossilized dinosaur skull, which Fiorillo described as a "big toothy thing." At the time, they identified it as once belonging to a T. rex, he said.

But as time marched on — and scientists learned a lot more — they realized parts of the jaw, the teeth and the boney structures around its eyes didn't match a T. rex, although the massive dinosaurs were about the same size, paleontologist Sebastian Dalman said.

In 2013, Dalman set about studying the fossil, and he was soon joined by eight more paleontologists from institutions across New Mexico, Pennsylvania, Utah, the District of Columbia, Canada and England.

"What we knew about Tyrannosaurus rex in the 1980s was very small compared to what we know about T. rex now. ... We're looking at it through new eyes, through a lot more knowledge than was available in the '80s," Lucas said.

Based on differences in the fossil's jaw and skull, the researchers determined the fossil was not a Tyrannosaurus rex but a previously unknown close relative of T. rex that roamed what's now the American Southwest and perhaps Mexico.

Fiorillo illustrated the difference between T. rex's and T. mcraeensis' jaws using a cinematic exemplar: the moment in Jurassic Park in which a T. rex sinks its teeth into the park's sturdy safari cars.

"Tyrannosaurus [rex] is a big, bone-chewing, Jeep-crunching dinosaur from Jurassic Park," he said. "The more slender jaw here means that it [T. mcraeensis] might have been a bone-chewing, Fiat-crunching dinosaur."

Geological findings confirmed the paleontologists' analysis, Lucas said. Rock structures surrounding the fossil determined its age to be about 73 million years old — 5 million years older than T. rex.

The discovery shifts scientists' understanding of how T. rex came to be in North America. Although paleontologists have unearthed plenty of T. rexes in Montana, Wyoming, the Dakotas, Saskatchewan and Alberta, it long seemed that, lacking close relatives in North America, the famous dinosaur appeared from out of nowhere — its arrival and evolution in the continent a mystery.

This finding indicates the American Southwest or parts of central America served as the "epicenter of tyrannosaur evolution," said Nick Longrich, another paleontologist who worked on the project. It shows more primitive tyrannosaurs — like T. mcraeensis — once lived in southern North America, eventually evolving and moving north to become T. rex.

"We'd been looking in the wrong place all along," Longrich said Thursday. "The origin of these things is not up in Montana; it's down here in New Mexico and Mexico."