In a groundbreaking discovery, researchers from several universities and the New Mexico Museum of Natural History and Science have identified a new subspecies of tyrannosaur, believed to be an older and more primitive relative of the iconic Tyrannosaurus rex. The findings were unveiled on Thursday at a gathering at the museum, where the team presented fossil evidence and published their study in the journal Scientific Reports.

The research was based on a partial skull that was first discovered in the 1980s by boaters on the shore of New Mexico's largest reservoir. The fragile specimen, which includes a massive jaw bone and pointy teeth, was meticulously reexamined over the years, leading to the identification of the new subspecies, named Tyrannosaurus mcraeensis.

The differences between T. rex and Tyrannosaurus mcraeensis are subtle, as is often the case with closely related species. The team analyzed the specimen bone by bone, noting variations in numerous features compared to those synonymous with T. rex. According to Nick Longrich, a co-author from the Milner Centre for Evolution at the University of Bath in the United Kingdom, these differences are the result of evolution slowly causing mutations to accumulate over millions of years.

The analysis suggests that Tyrannosaurus mcraeensis was a side-branch in the species' evolution, rather than a direct ancestor of T. rex. It is believed to have predated T. rex by up to 7 million years, indicating that tyrannosaurs were present in North America much earlier than previously thought. The new subspecies is estimated to have been roughly the same size as T. rex, measuring up to 40 feet long and 12 feet high. Like its well-known relative, T. mcraeensis was also a carnivorous predator.

The significance of this discovery goes beyond the identification of a new subspecies. Thomas Richard Holtz, a paleontologist at the University of Maryland who was not involved in the study, pointed out that T. rex's closest relatives were primarily from southern North America, with the exception of Mongolian Tarbosaurus and Chinese Zhuchengtyrannus. This raises the question of whether these Asian dinosaurs were immigrants from North America or if the new subspecies and other large tyrannosaurs were immigrants from Asia. Holtz emphasized the need for more fossils from the Hall Lake Formation in southern New Mexico to provide further insights into this question.

The researchers involved in the study believe that their findings challenge existing notions about the origins of T. rex in North America. The discovery of Tyrannosaurus mcraeensis as its earliest known relative on the continent reshapes our understanding of how this iconic dinosaur came to dominate the end of the age of the dinosaurs. Anthony Fiorillo, a co-author of the study and the executive director of the New Mexico Museum of Natural History and Science, stated, "New Mexicans have always known our state is special; now we know that New Mexico has been a special place for tens of millions of years."

This groundbreaking research not only sheds light on the evolutionary history of the Tyrannosaurus rex but also highlights the importance of continued exploration and discovery in the field of paleontology. With each new finding, scientists are forced to reevaluate and challenge existing knowledge, pushing the boundaries of our understanding of the ancient world.