T-Rex's "Great Uncle" Unveiled at Utah Natural History Museum

Nov 7, 2013

Dr. Randall Irmis speaks at a press conference at the Natural History Museum of Utah on November 6, 2013. Irmis and his team announced the discovery of a previously unknown dinosaur species. A skeletal model of the dinosaur stands behind Irmis.

Researchers announced the discovery of a new dinosaur species at the Natural History Museum of Utah on Wednesday.

The specimen was found in southern Utah in November 2009, and it is a rare ancestor to the well-known Tyrannosaurus rex.

Four years ago, paleoentological technician Scott Richardson went on a walk in the desert. Then he saw something sticking out of the ground that caught his eye: a leg bone.

"Then I stopped, because that was so obvious, and I looked around and realized I had just walked through bone that was laying there, and I should have been paying more attention, but good thing that leg bone was there, because I might have walked right through it," Richardson said.

After taking a closer look, Richardson started to suspect that he had stumbled upon something special. He called paleontologist Dr. Alan Titus.

"Told him the story of the last four days, how boring it was, then said, 'Oh and by the way I'm probably sitting on top of an associated theropod, you probably ought to come out here tomorrow and look at this, this is pretty cool,'" Richardson said. "He just paused and for a second and said, 'No you're not.' I said, 'yeah, I really am.'"

Titus came out the next day to inspect Richardson’s find, and sure enough, it was a tyrannosaur—a meat-eating relative to the Tyrannosaurus rex.

Giddy with the news, Titus called Dr. Mark Loewen, who would become the lead author of Wednesday’s study, and Dr. Randall Irmis.

"Randy and I are sitting at Big Ed's, having a burger, and we get a phone call from Alan Titus, and he's like, 'I've got a nasal. I think it's a tyrannosaur.' And you know, sometimes you're skeptical. People get a little giddy in the field when they find things, but he sent us a picture and I was like, 'Absolutely. That nasal right there can only come from a tyrannosaur,'" Loewen said. "As soon as we saw it, there are little features on the nasal that suggest it's unique."  

Loewen was right: this was a unique dinosaur. So unique, in fact, that Loewen and his team eventually determined that it was a brand new species of tyrannosaur. And as Titus emphatically points out, finding a new tyrannosaur is a pretty rare occurrence.

"This was very improbable," Titus said. "Tyrannosaurs as a rule are very unusual because they're predators and their number is relative to the prey animals are low, so for every hundred hadrosaurs (duck-billed) or ceratops and horned dinosaurs that you'd find, you might find a chunk of one of these," Titus said. "The formation it came from is not especially fossiliferious, and they're rare to begin with so this was a very rare and remarkable find."

They’re calling it Lythronax argestes, which means “gore king of the Southwest.” Its beastly name is perhaps earned through relation alone: the new species is only a common ancestor away from the T-rex. As Irmis puts it, you could think of the Lythronax as a “great uncle” to the T-rex.

Irmis said this discovery is significant not just because it’s a new species, but because it teaches us more about the evolution of dinosaurs.

"Really, the story of these tyrannosaurs is not just about a new species, but it's actually about the evolution of ecosystems on land 80- and 70-million years ago, showing us that changes of sea level, global events actually had an effect on all the different types of dinosaurs and other organisms that we find," Irmis said. "It really provides insights into why we're finding so many new dinosaur species here in Utah and other places throughout western North America."

This likely won’t be the last discovery in Grand Staircase-Escalante National Monument. Titus said of the one million acres at the site where the Lythronax was found, only 10 percent has been explored.