Paleontologists have discovered a new species of Tyrannosaurus, the “Tyrannosaurus mcraeensis,” which lived seven million years before the arrival of the famous T-Rex in the southern United States.
Twelve meters long, powerful jaws capable of shattering bones, a robust skeleton… Everything led us to believe that the fossil was actually that of a Tyrannosaurus Rex (T-Rex). Contrary to all expectations, after re-examining the bones, American paleontologists discovered that it was in fact a new species of Tyrannosaurus, which they are presenting to the public this Thursday, January 11, under the name Tyrannosaurus mcraeensis. This emerges from a study published in the journal Scientific Reports. The large animal was found to be older than the T-Rex, seven million years older, and was its closest relative. An important discovery that allows us to learn a little more about the Tyrannosaurus lineage.
“Relatively subtle” deviations
The fossil, discovered in the heart of the Hall Lake Formation, a paleontological site known for preserving ancient fauna in New Mexico, USA, was “previously called a T-Rex,” the team of nine researchers wrote from various American universities, led by Nicholas R. Longrich, paleontologist at the University of Bath, United Kingdom. At first glance, the two species might be confused. In addition to being the same size, both have similar teeth, one of the essential elements that allow paleontologists to distinguish dinosaurs. But the “recently collected” new bones, this time located at skull level, made it possible to highlight their “relatively subtle” differences such as the shape and articulation between bones.
Real new species or simple variant of Tyrannosaurus Rex? French paleontologist Ronan Allain, a leading dinosaur specialist at the Natural History Museum, notes with Libération “quite a few similarities” between the two species. Researchers dispel possible doubts: the T-Rex is one of the best-studied specimens with “a high degree of variation”. However, the discovered fossil “does not resemble any other specimen associated with T. rex,” and paleontologists point out that “differences between species are often relatively subtle,” such as between cousins Alioramus and Daspletosaurus the case is the tyrannosaur.
Another notable difference: The two dinosaur species would not have lived at exactly the same time. Thanks to radiometric dating – which includes the famous carbon-14 dating – researchers estimate that Tyrannosaurus mcraeensis lived 70.9 to 72.7 million years ago, “that is, 5 to 7 million years before Tyrannosaurus rex.” On this point, Ronan Allain is “a little more convinced, in the sense that their animal seems very outdated and older than the Tyrannosaurus Rex”. “If there had only been the anatomical arguments, I would have been very cautious, but here I would be more inclined to accept the emergence of this new species,” adds the French specialist.
Reconstruction of ancestry
Although the origins of the tyrannosaur lineage are still unknown, this new species allows us to find out more. In their study, dinosaur specialists recall that the T-Rex appeared “suddenly” in North America without any potential ancestors being found in the region. The closest dinosaur species to the T-Rex once came from what is now Mongolia in Asia. But the discovery of Tyrannosaurus mcraeensis now suggests that tyrannosaurs may have appeared in the south of what was then the island continent of Laramidia, particularly extending across what is now the state of New Mexico in the United States. A clue that allows us to slowly reconstruct the lineage of this impressive dinosaur.
“Beyond the simple “new Tyrannosaurus”, what is interesting is that this discovery contradicts certain, somewhat questionable models,” emphasizes Ronan Allain about this study. As the paleontologist recalls, researchers confirmed in 2021 that the diversity of dinosaurs had been declining long before the fatal fall of the giant meteorite and that the dinosaurs were indeed doomed to extinction. Not so sure. “The discovery of a dinosaur other than the T-Rex increases the diversity of these animals at a time that is ultimately not yet well known,” says Ronan Allain. And finally: “Their results are important because we need this kind of discovery to be sure of what we say about the extinction of the dinosaurs.”
Tyrannosaurs were the most important predators of the dinosaur world – “and perhaps of all time,” American paleontologists add – in North America and Asia at the end of the Cretaceous period, a period that ended with the extinction of these fascinating creatures 66 million years ago.