A new analysis of a shinbone from the oldest known giant tyrannosaur in North America suggests that the 'king of dinosaurs ,' Tyrannosaurus rex , may have had an unusually large ancestor. The fossil, found at the Kirtland Foundation in New Mexico, US, in the 1980s, is about 74 million years old, placing this gigantic tyrannosaur in the Late Campanian . That's a fair bit earlier than most T. rex fossils, which typically date to the very end of the dinosaurs' rule, in the late Maastrichtian ,