A dinosaur known only from a partial skull has been dubbed Tyrannosaurus mcraensis, adding a new twist to long-running debates about putative relatives of Tyrannosaurus rex

The partial skull of a dinosaur found 40 years ago has now been identified as a new species of Tyrannosaurus, and perhaps the closest relative of Tyrannosaurus rex. The research adds a new twist to a long-running debate about how many species of tyrannosaurs there were, and could help to clarify how the iconic predator evolved.

T. rex appeared in North America around 68 million years ago, 2 million years before the mass extinction that wiped out most dinosaurs. Palaeontologists have been stumped as to the carnivore’s origins. Some have suggested that the ancestors of T. rex walked over a land bridge from prehistoric Asia, while others placed its origins in southern North America.