The discovery of the closest relative of 'Tyrannosaurus rex' illuminates the mystery of these predators

The most popular of the dinosaurs, the Tyrannosaurus rex, was the largest predator of its time and perhaps of all time, but for the scientific community it is a mystery how these animals grew to become giants. They weighed 10 tons, were 12 meters long and had enormous heads and teeth capable of crushing bones. The discovery of a new species of tyrannosaurid could clear up some of these doubts. Analysis of a skull found in New Mexico, United States, is published today in Scientific Reports and add a new familiar to the tree of the history of these dinosaurs: the Tyrannosaurus mcraeensis. It is the closest relative of the T. rex and sheds light on the diversity, origin and large size of these feared predators from the Late Cretaceous.

“In paleontology, knowledge is advanced in two ways: by finding new fossils or by restudying and reinterpreting previously found remains,” explains paleontologist Luis Alcalá, director of the Granada Science Park and unrelated to the discovery. To identify this close relative of T. rex, the second one was used. A group of New Mexico scientists used computer programs that distinguish between different bones to classify species and discovered that a skull found in Hall Lake, New Mexico, had been attributed to a T. rex, but it actually belonged to a different dinosaur. The differences in the shape and union of the bones of the fossil compared to the T. rex They are subtle, but significant, enough to distinguish it as a different animal species.

The new tyrannosaurus Mcraeensis—which is named for the McRae Formation in New Mexico, where multiple dinosaur remains have been found—could have lived between 71 and 73 million years ago, that is, between five and seven million years before the T. rex. This is suggested by the study led by paleontologist Sebastian G. Dalman of the University of Massachusetts and his colleagues, based on the location of rocks and other remains from the Hall Lake area, where the skull was originally found.

Laramidia: Home of the giant dinosaurs

“Although a lot is known about them, there are aspects that lead to still open debates about the origin of tyrannosaurids,” explains Fidel Torcida, director of the Salas de los Infantes Dinosaur Museum, who did not participate in the study. Within the controversy, one of the hypotheses that paleontologists have proposed is that these large dinosaurs emerged in Asia and moved to America, while a second theory proposes the opposite, that is, that they appeared in what is now North America and according to They increased in population, moved towards Asia, and later retraced their steps to North America.

The discovery of Tyrannosaurus mcraeensis supports the theory of origin in North America, suggesting that the evolutionary line of tyrannosaurids originated specifically in Laramidia, an island continent that existed between 100 and 66 million years ago in what is now Canada, the United States and Mexico. The researchers also detail that these dinosaurs lived in the south of the territory and were not always colossal. They went from being hunters of small species during the early cretaceous to be predators of large herbivores as they increased in size.

In a small region such as an island territory, it would not be strange for the species to be small or of a size corresponding to the place where they live. But this was not the case in Laramidia. On this island, “the temperature and the absence of competitors and predators could have caused the herbivores in the area to grow to the size of giant dinosaurs such as titanosaurs, ceratopsians or hadrosaurs,” explains Torcida. And as the herbivores increased in size, so did those who ate them. In this way, the authors suggest, they evolved towards a giant body size approximately 72 million years ago to the newly known Tyrannosaurus mcraeensis to give rise, millions of years later, to the famous T. rex.

Both Alcalá and Torcida consider it positive that a new species of tyrannosaurid has been discovered. The discovery brings diversity to the family Tyrannosaurus and opens new avenues of exploration, urging researchers to delve deeper into the mysteries of the ecosystems and relationships between predators and prey of the ancient world. Alcalá remembers that at Tyrannosaurus mcraeensis It was initially classified as T. rexand asks: “Could there be other species of tyrannosaurs?”

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