When it comes to identifying fossil species, a lone leg bone isn’t much to go on. Yet a new analysis of a large fossil tibia suggests it offers a clue to the origins of Tyrannosaurus rex, the hulking, sharp-toothed apex predator that dominated the twilight of the Age of Dinosaurs.
The bone’s sheer size hints that it was a tyrannosaurid, a group that includes the most massive members of the tyrannosaur family tree, researchers claim in a study published March 12 in Scientific Reports. Tyrannosaurids lived late in the Cretaceous Period, between 83 million and 66 million years ago, and have been found only in Asia and North America.