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 in the 1980s, is estimated to be about 74 million years old, placing it in the Late Campanian. It is also believed to be a close relative of Tyrannosaurus. The bone's size, shape, and weight estimate puts it at around 4,700 kilograms (about 5.2 tons) or more than 10,000 pounds. The discovery hints at the origins of Tyrannosaurs, although it remains unclear as to where they originated.