 The eye-sockets of Tyrannosaurus are positioned so that the eyes would point forward, giving them binocular vision slightly better than that of modern hawks. Jack Horner also pointed out that the tyrannosaur lineage had a history of steadily improving binocular vision. It is hard to see how natural selection would have favored this long-term trend if tyrannosaurs had been pure scavengers, which would not have needed the advanced depth perception that stereoscopic vision provides. In modern animals, binocular vision is found mainly in predators (the principal exceptions are primates, which need it for leaping from branch to branch). Unlike Tyrannosaurus, Tarbosaurus had a narrower skull more typical of other tyrannosaurids in which the eyes faced primarily sideways. All of this suggests that Tarbosaurus relied more on its senses of smell and hearing than on its eyesight. In Gorgosaurus specimens, the eye socket was circular rather than oval or keyhole-shaped as in other tyrannosaurid genera. In Daspletosaurus, this was a tall oval, somewhere in between the circular shape seen in Gorgosaurus and the 'keyhole' shape of Tyrannosaurus.
