By Will Dunham
WASHINGTON (Reuters) – T. rex still reigns as king of the dinosaurs, scientists say who on Monday argued against a controversial hypothesis put forward this year that the mighty meat-eater Tyrannosaurus should be recognized as three species, not just one. .
Seven research paleontologists https://link.springer.com/article/10.1007/s11692-022-09573-1 published Monday said a March study offered insufficient evidence to show there were three species of Tyrannosaurus based on fossils from the world’s most famous dinosaur, citing inappropriate statistical methods, limited comparative samples and faulty measurements.
T. rex is the only recognized species of the genus Tyrannosaurus since the dinosaur was first described in 1905. A genus is a larger grouping of related organisms than a species.
Three other researchers said in the previous study https://link.springer.com/article/10.1007/s11692-022-09561-5 published in the same journal that three species should be recognized based on variation in thickness of femurs and shape of lower front teeth among about three dozen Tyrannosaurus specimens.
“The evidence must be compelling, and suddenly dividing such an iconic animal as T. rex, known for over a hundred years, into different species requires a high burden of proof. It is true that there are variations 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, 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 tremendous bite force, walked on two strong legs, and had puny arms with only two fingers.
The new study examined intra-species variation in femur thickness in four other carnivorous dinosaurs and 112 species of living birds, descendants of small feathered theropods, and found that variations in Tyrannosaurus were not exceptional.
“It’s normal for any species to vary in size and shape. Just look at the range in height, waistline and toothy smiles among people today, who are all members of a single species. Thus, the differences between the bones and teeth of T. rex are so minor that they do not support the division of T. rex into multiple species,” Brusatte said.
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 .
“Tyrannosaurus rex remains the only true king of the dinosaurs. It was the only species of giant apex predator dinosaur that lived in late Cretaceous North America,” Brusatte added.
In addition to the species T. rex, meaning “tyrant lizard king”, Baltimore-based freelance paleontologist and paleoartist Gregory Paul and two colleagues have proposed two additional species: T. imperator, meaning “tyrant lizard emperor”, and T. regina, meaning “tyrant lizard queen.”
Paul criticized the new work as being hastily done and “not a proper scientific study”.
“This comes across as paleopropaganda that appears to be structured to defend T. rex, rather than seriously exploring the possibilities that fossil specimens of the genus Tyrannosaurus contain more than one species than the genus certainly has,” Paul said.
“There is something about the beloved T. rex that makes people restless to a degree never seen with other paleotaxes (ancient organisms). If our article had focused on the species of, say, the gigantic theropod Argentinian Giganotosaurus, there most likely wouldn’t have been so much fuss and hassle,” Paul added.
Perhaps the largest known tyrannosaur is a specimen named Sue at the Field Museum in Chicago, measuring 12.3 meters in length.
“We are open to the idea 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 a consistent way to divide Tyrannosaurus into multiple species based on clear, easy differences. to be defined and consistent.”
(Reporting by Will Dunham; Editing by Lisa Shumaker)