Scientists defend the T. rex as the only species of the mighty Tyrannosaurus

WASHINGTON, July 25 (Reuters) – T. rex still reigns as king of the dinosaurs, according to scientists who argued on Monday against a controversial hypothesis advanced this year that the mighty carnivore Tyrannosaurus should be recognized as three species rather than just one. .

Seven paleontologists in research published Monday said a March study provided insufficient evidence to show there were three species of Tyrannosaurus based on fossils of the world’s most famous dinosaurs, citing improper statistical methods, limited comparison samples and measurements. wrong.

T. rex has been the only known species of the genus Tyrannosaurus since the dinosaur was first described in 1905. A genus is a broader grouping of related organisms than a species.

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Three other researchers said in the previous study published in the same journal that three species should be recognized based on the difference in the thickness of the thighs and the shape of the lower front teeth among about three dozen Tyrannosaurus specimens. Read more

“The evidence has to be convincing, and to suddenly split such an iconic animal as T. rex, which has been known for more than a hundred years, into different species requires a high burden of proof. It is true that there are differences in size and the shape of T. rex bones, but in our new study we show that this variation is minimal,” said University of Edinburgh paleontologist Steve Brusatte, a co-author of the new study published in the journal Evolutionary Biology.

Tyrannosaurus, part of a group called theropods that included all carnivorous dinosaurs, had a massive head and great bite force, walked on two strong legs, and had weak arms with only two fingers.

The new study examined within-species variation in thigh thickness in four other meat-eating dinosaurs and 112 species of living birds, descendants of small feathered theropods, finding that Tyrannosaurus’s variation was remarkable.

“It’s normal for any species to be variable in size and shape. Just look at the height and waist and toothy grins of humans today, who are all members of a single species. So the differences between the bones and teeth of T. rex are so small that they do not support splitting T. rex into multiple species,” said Brusatte.

Tyrannosaurus roamed western North America during the Cretaceous period in the twilight of the age of dinosaurs before an asteroid hit Mexico’s Yucatan Peninsula 66 million years ago, dooming the dinosaurs. Read more

“Tyrannosaurus rex remains the only true king of the dinosaurs. It is the only species of giant predatory dinosaur that lived at the end of the Cretaceous period in North America,” added Brusatte.

In addition to the species T. rex, meaning “king of tyrannical lizards,” Baltimore-based paleontologist and paleoartist Gregory Paul and two colleagues proposed two additional species: T. imperator, meaning “emperor of tyrannical lizards” and T. regina, which means. “the tyrannical lizard queen”.

Paul criticized the new work as being rushed and “not a proper scientific study”.

“It comes across as paleopropaganda that appears to be structured to protect T. rex, rather than seriously exploring the possibility that fossil specimens of the genus Tyrannosaurus contained more than one species that the genus certainly contained,” Paul said.

“There is something about the beloved T. rex that makes people concerned on a scale not seen with other paleotaxa (ancient organisms). If our paper were about the species of, say, theropod giant Argentinian Giganotosaurus out there, there probably wouldn’t have been so much fuss and concern,” added Paul.

Perhaps the best-known Tyrannosaurus is a specimen named Sue at the Field Museum in Chicago, measuring 40-1/2 feet (12.3 meters).

“We’re open-minded that there could be multiple species of Tyrannosaurus,” Brusatte said. “We just need more and better fossils. The number of fossils in their dataset is so small that it’s hard to find any consistent way to separate Tyrannosaurus into multiple species based on differences in clear, easy to define and consistent.”

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Reporting by Will Dunham; Editing by Lisa Shumaker

Our Standards: The Thomson Reuters Trust Principles.

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