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WASHINGTON — Scientists reevaluating parts of a skull first unearthed in southeastern New Mexico in 1983 say they believe the fossil is a new species of tyrannosaurus, a fearsome apex that lived in western North America during the twilight of the dinosaur era. It was concluded that it represented a predator (predator). Rex.
The subtle differences observed in the skull from Tyrannosaurus rex warrant recognition of this dinosaur as a separate species called Tyrannosaurus macraiensis, which lived several million years earlier than Tyrannosaurus and was also larger. researchers announced Thursday. This skull was previously identified as a Tyrannosaurus rex.
Other researchers have expressed doubts that the fossil represents a new species of Tyrannosaurus, saying that the differences between this fossil and other Tyrannosaurus skulls are not significant and that the fossil is between 71 and 73 million years old. He said the study’s conclusion that there is is problematic.
Tyrannosaurus rex is the only recognized species in the genus Tyrannosaurus since the dinosaur was first described in 1905. A genus is a broader group of related organisms than a species. Tyrannosaurus fossils date back millions of years, before an asteroid hit Earth and wiped out the dinosaurs 66 million years ago.
The first part of the New Mexico skull was discovered near the base of Kettle Top Butte in 1983, and more parts have since been discovered.
Paleontologist Anthony Fiorillo, executive director of the New Mexico Museum of Natural History and Science and one of the authors of the study published in the journal Scientific Reports, said about 25% of the skulls have been collected. . Most of the braincase and upper jaw are missing.
One of the researchers, Nick Longrich, a paleontologist at the University of Bath in the UK, said: “Compared to Tyrannosaurus, the lower jaw is shallower and more curved towards the back. The blunt hornets above the eyes are lower than in Tyrannosaurus. ” he said. .
“It’s the nature of the species that the differences are subtle. What’s important is that they’re consistent. We’ve looked at a lot of different tyrannosaurs, and our animal has every bone, every known “Tyrannosaurus rex was consistently different from that of the previous one,” Longrich added.
The researchers said this difference involves important characteristics. Fiorillo pointed out that features on Tyrannosaurus’ eyes have been interpreted as important in sexual selection.
“Thus, these differences suggest that our animal may have had a different diet and chosen mates differently than the more famous tyrannosaurs,” Fiorillo said.
Tyrannosaurus had a huge head, amazing bite force, walked on two strong legs, and had slender arms. Perhaps the largest known tyrannosaurus is a specimen named Sue, housed at the Field Museum in Chicago, measuring 40.1 feet long.
Researchers said the presence of T. macraensis changes the understanding of the origins of tyrannosaurs. Researchers say Tyrannosaurus macraensis was larger than other tyrannosaurid relatives that lived in northern North America before Tyrannosaurus, and the group’s giant species could be millions larger than previously thought. This suggests that it evolved earlier in the year and came from southern North America.
Thomas Kerr, a paleontologist at Carthage College in Wisconsin who studies mutations in tyrannosaurs, called the study “not convincing.”
“The characteristics that we think make the New Mexico specimen unique are also found in other tyrannosaur fossils,” Kerr said. “The ‘differences’ are not discrete and obvious; instead, they are more like shades of gray or shapes in a cloud. I have seen this specimen myself several times, but… “We couldn’t think of anything that would make it different from other adult tyrannosaurs. Any differences could be explained by relative maturity and individual differences.”
Kerr said the fossils were dated based on the underlying rock, not the skull itself. Existing evidence indicates that tyrannosaurs appeared 67 to 68 million years ago, Carr added.
The possibility of additional Tyrannosaurus species is controversial. In 2022, some researchers argued that there were three species of tyrannosaurs, based on variations in femurs and teeth between fossils. Other researchers objected, citing insufficient evidence.