The tyrannosaurs (Tyrannosauridae, meaning “tyrant lizards,” is considered a family of coelurosaurian theropod dinosaurs) were extremely large, carnivorous dinosaurs that lived during the Cretaceous. These dinosaurs, including the well-known Tyrannosaurus rex, were the dominant predators of the time, growing close to 50 feet (15 meters) long. They were characterized by long, muscular tails, tiny arms, beady eyes, short, deep jaws, and long legs.

At one time, the tyrannosaurs were placed in the carnosaur group. After all, this group included the large, bipedal, carnivorous dinosaurs, and the Tyrannosaurus rex certainly fit all those criteria. However, modern cladistic analysis has shown that the tyrannosaurs are more closely related to the coelurosaurs than the carnosaurs, so they are now placed in the former group.