Gorgosaurus (Ancient Greek for "dragon lizard") is a genus of carnivorous dinosaur that reached 7 to 8 meters (27 to 30 feet) in length, and weighed 2.5 tonnes (2.75 short tons). It was first described by paleontologist Lawrence Morris Lambe in 1914, and has been establish in western Canada and the United States. It lived concerning 70 million years ago in the late Cretaceous period.
Over 20 Gorgosaurus skeletons have been improved, making it the well-represented tyrannosaurid in the fossil record. Generally alike to Tyrannosaurus and most other large tyrannosaurids (such as Daspletosaurus, and Albertosaurus), Gorgosaurus can be described as having a massive head, large curved teeth, tiny two-fingered front limbs, and powerful legs. Compared to the other tyrannosaurids, Gorgosaurus is most similar to its very close comparative Albertosaurus.
Although it has been optional that Gorgosaurus was a scavenger, its co-existence with the similarly sized, but more robust tyrannosaurid Daspletosaurus casts doubt on this theory. Another hypothesis proposes that Gorgosaurus, which was quite lean for a tyrannosaurid, actively hunted fleet-footed animals such as duckbills and ornithomimids ("ostrich-mimic" dinosaurs). According to this proposal, the more troublesome ceratopsians and ankylosaurians (horned and heavily armoured dinosaurs) would have been left to Daspletosaurus.
For years, the species Gorgosaurus libratus (the only species of Gorgosaurus at present recognized) was assigned to the Albertosaurus genus. However, recent work done by paleontologists suggests that enough differences live between G. libratus and the other Albertosaurus species, to validate the original genus name of Gorgosaurus.