Bones of a King! Measuring 40ft (12m) in length and weighing upwards of 14 tons, Tyrannosaurus rex was one of the largest and most powerful terrestrial predators in history. The most advanced in an 80 million-year chain of tyrannosaurid evolution, T. rex had heavy, deep skulls reinforced with sutures, lightened by hollow chambers. This specimen is a fragment of Tyrannosaurus rex bone recovered on private land in South Dakota from the Hell Creek Formation.