Washington: Reevaluating a partial skull discovered in southeastern New Mexico in 1983, scientists have now concluded that the fossil signifies a novel Tyrannosaurus species predating the iconic T. rex. Previously misidentified as a T. rex skull, the subtle distinctions observed in the fossil have led researchers to designate it as a distinct species named Tyrannosaurus mcraeensis. This newly proposed species, comparable in size to T. rex, existed several million years before the renowned apex predator.

Paleontologist Anthony Fiorillo, an author of the study published in Scientific Reports, clarified that about 25% of the skull has been recovered, with significant portions, including most of the braincase and upper jaws, still missing. Notable differences from T. rex include a shallower and more curved lower jaw and lower hornlets above the eyes.

While some researchers expressed skepticism about recognizing it as a new species, citing unremarkable differences and disputing the fossil’s age of 71-73 million years, the study asserts that consistent disparities across various T. rex specimens support the distinct classification of T. mcraeensis.

The researchers argue that the variations in T. mcraeensis imply different eating habits and potential differences in mate selection compared to the more well-known T. rex. Notably, the feature above the eyes is considered crucial in sexual selection.

This discovery challenges the conventional understanding of Tyrannosaurus origins, suggesting that T. mcraeensis, larger than its contemporaries in northern North America, evolved millions of years earlier in southern North America. The existence of this species prompts a reevaluation of the timeline and evolutionary patterns of giant Tyrannosaurus relatives.

However, paleontologist Thomas Carr, who has studied T. rex variation, remains unconvinced, describing the study as “unpersuasive.” Carr argues that the observed differences are not distinct and could be attributed to relative maturity and individual variation. Moreover, he questions the fossil’s dating method, asserting that existing evidence places the appearance of Tyrannosaurus no earlier than 67 to 68 million years ago. The debate over potential additional Tyrannosaurus species continues, with differing interpretations within the scientific community.

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