2024-01-13 12:00:03
Exciting discoveries in paleontology are transforming our vision of tyrannosaurids, these impressive predators from the end of the Cretaceous. A new species, named Tyrannosaurus mcraeensis, has been identified, providing essential information on the origin and evolution of these dinosaurs.
Paleontologists have discovered fossils of a huge tyrannosaurid in the New Mexico desert. We first thought that it was the Tyrannosaurus rexbut further research has shown that it is a species different, called Tyrannosaurus mcraeensis. This discovery, published in Nature, changes our understanding of tyrannosaurids.
Tyrannosaurus mcraeensis, which lived about 73 million years ago, appeared 6 to 7 million years before T. rex. Although it was older, it was even larger in size than the famous T. rex at around 12 meters long and weighing almost 10 tonnes, compared to around 8 tonnes for the T. rex. This discovery challenges our ideas about the evolution of tyrannosaurids and their place of origin.
Dinosaurs from the Campanian-Maastrichtian Hall Lake Formation. Scale = 2 m.
Tyrannosaurids were the dominant predators in South America Nord and in Asia at the end of the Cretaceous. They descend from small ancestors. The T. rex, with its skeleton solid and his powerful jaws, was the predator the most feared of his temps. However, the exact origin of the Tyrannosaurini group, to which T. rex belongs, has until now been uncertain. Two main hypotheses existed: an origin in Asia or western North America.
The study of Tyrannosaurus mcraeensis provides answers to this question. Its unique bone structure, including postorbital, squamosal, dentary, prearticular, and articular, as well as its large size, indicate that it evolved differently from T. rex. Although these differences are subtle, they are important and show that this is a distinct branch of the tyrannosaurids.
Locality and stratigraphy of Tyrannosaurus mcraeensis gen. and sp. Nov., NMMNH P-3698.
A: type locality in Sierra County, New Mexico;
B: stratigraphy of fossils and the Hall Lake Formation;
C: skull elements recovered.
Scale = 10 cm. Map by Ron Blakey.
This discovery suggests that Tyrannosaurini evolved in southern Laramidia, western North America, not Asia. This origin is confirmed by the presence of other local dinosaurs, such as the large chasmosaur Sierraceratops and the titanosaur Alamosaurus.
The discovery of Tyrannosaurus mcraeensis in New Mexico and its classification suggest that Tyrannosaurini became giant toward the end of the Campanian. This find also raises questions about the diversification of dinosaurs, possibly influenced by variations in sea level and land space.
This study opens new perspectives on the evolution of tyrannosaurids and shows the importance of paleontological discoveries for understanding the history of life on Terre.
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