Tyrannosaurus rex dinosaurs. Artwork of a pair of Tyrannosaurus rex dinosaurs hunting prey in a forest. Some theories say that this dinosaur had feathers and fur, as seen here. When fully grown, this bipedal dinosaur was one of the largest ever terrestrial predators, measuring over 12 metres in length from head to tail. It is thought to have combined hunting and scavenging to feed itself. Its fossils are found in North America, and date to around 67 million years ago, during the Cretaceous period.