The skull of a previously unidentified species of tyrannosaurus was found in the early 1980s. Not all researchers agree that it is a new species.
American the research team has concluded that a partial tyrannosaurus skull discovered more than 40 years ago belongs to a species that was previously unknown. The news agency Reuters and a US newspaper report on the matter, among others The New York Times (NOW) on Thursday.
A skull in the collections of the New Mexico Museum of Natural History was once believed to belong to the world's most famous dinosaur For Tyrannosaurus rex. However, the researchers re-evaluated the discovery, and its slight differences with the skulls of other tyrannosaurs led the researchers to conclude that it was a different species.
The newly discovered species got its name Tyrannosaurus mcraeensis. It is believed to have lived several million years before rex and to have been the same size as it, slightly less than 12 meters long. Rex lived about 66 million years ago, being one of the last ones of dinosaur species that lived.
Artist's impression of what Tyrannosaurus mcraeensis may have looked like when it was alive.
Perception is significant, because the rex that received its name in 1905 was still the only species belonging to the tyrannosaur family on Wednesday.
Mcraeensis skull was excavated in 1983, and later researchers found other bones belonging to it. The skull, which was previously thought to be a rex, was re-evaluated in 2013, NYT says.
Director of the New Mexico Museum of Natural History Anthony Fiorillo about a quarter of the skull has been found. For example, most of the cerebral cortex and upper jaw are missing.
“Compared to T. rex, [mcraeensisin] the lower jaw is lower and more curved towards the back. The blunt little horns above the eyes are lower than in Rex,” said a paleontologist who was part of the research team Nick Longrich.
According to Longrich, the differences between species are usually subtle.
“We studied several T. rexes, and our animal was consistently different from all known T. rexes, at every bone.”
According to NYT, the lower jaw of mcraeensis is smaller than the lower jaw of rex and its teeth are different.
The researchers estimate that the eating and mating behavior of mcraeensis has also been different compared to its more famous cousin. This can be seen, for example, in the difference in the skull above the eyes – in the past, researchers have estimated that this was an important factor in rex's gender selection.
Researchers mcraeensis changes the understanding of the origin of tyrannosaurs.
Based on research, it seems that
mcraeensis was larger than other tyrannosaurus relatives that lived in the present-day North American region. This would mean that large tyrannosaurs evolved millions of years earlier than previously thought and originated in southern North America.
Based on the Rex discoveries, several researchers have previously concluded, according to the NYT, that tyrannosaurs had evolved from a group that crossed a land bridge to North America from what is now Asia.
Jaw bone of Tyrannosaurus mcraeensis illustrated from two different perspectives.
All researchers have not accepted estimates that it is a new species. According to NYT, researchers have often disagreed about the alleged tyrannosaurus discoveries, because the species has been so extensively studied.
According to Reuters, for example, a paleontologist at Carthage University in Wisconsin Thomas Carr says the research has not convinced him.
“The so-called differences [T. rexiin] are not separate and obvious, but instead like different shades of gray or shapes in the clouds. I have seen [mcraeensis-] individual several times, and nothing stands out as being in any way different from other adult T. rexes,” Carr said.
In addition, Carr says that the age of a fossil is not determined by itself, but by the rock surrounding it. Carr considers the earlier estimate of the age of tyrannosaurs to be more likely.
According to the NYT, several researchers who were opposed to previous discoveries have been more sympathetic in the case of mcraeensis, as the evidence is more comprehensive than in other allegedly new tyrannosaur discoveries in recent years.
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