Gorgosaurus libratus
Gorgosaurus libratus was a tyrannosaurid roughly eight to nine metres long that roamed western North America about 76.6 to 75.1 million years ago. Its build was classic tyrannosaurid: a deep, powerful skull set on a short muscular neck, a horizontal backbone counterbalanced by a long stiffened tail, tiny two-fingered arms and long, striding hind legs.
Gorgosaurus
Gorgosaurus libratus
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Weight
2000–2900 kg
Length
8–9 m
Diet
Carnivore
Period
Cretaceous
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2000–2900 kg
8–9 m
Cretaceous
Bipedal
2.4–3 m
35 km/h
Carnivore
15 recorded fossil finds in Canada and United States. Most in Alberta and Montana. First described in 1914 by Lambe.
Sites and counts from the Paleobiology Database
The timeline shows the whole age of dinosaurs – and how much time has passed since. The glowing part is when Gorgosaurus lived.
million years ago
Lived 76.6–75.1 million years ago
If the whole age of dinosaurs were a single day, Gorgosaurus lived at 22:44.
Chapter • Meet the dinosaur
Gorgosaurus libratus was a tyrannosaurid roughly eight to nine metres long that roamed western North America about 76.6 to 75.1 million years ago. Its build was classic tyrannosaurid: a deep, powerful skull set on a short muscular neck, a horizontal backbone counterbalanced by a long stiffened tail, tiny two-fingered arms and long, striding hind legs. The skull was somewhat lighter and narrower than that of Tyrannosaurus, with small angular hornlets in front of the eyes. Its blade-like, serrated teeth were built for slicing rather than the bone-crushing work done by the more robust teeth of later tyrannosaurs.
Chapter • Where it lived
Gorgosaurus lived during the Late Cretaceous (Campanian) on the coastal lowlands west of the Western Interior Seaway, in what is now Alberta, Canada, and Montana, USA. The landscape was a mosaic of broad floodplains, meandering rivers, swampy forests and brackish lagoons under a warm, humid and strongly seasonal climate. Most specimens come from the Dinosaur Park Formation of Dinosaur Provincial Park, one of the richest dinosaur localities in the world, with additional material from the Judith River Formation of Montana. There it shared its world with horned dinosaurs such as Centrosaurus and Chasmosaurus, hadrosaurs including Corythosaurus and Lambeosaurus, armoured ankylosaurs, small feathered theropods, and a second, more heavily built tyrannosaurid, Daspletosaurus.
Chapter • Wild behavior
Cathemeral
Whether Gorgosaurus was social remains unresolved. Its close relative Albertosaurus is known from a bonebed containing at least a dozen individuals of different ages, often interpreted as a group or at least a temporary aggregation, but no comparable monodominant assemblage has been found for Gorgosaurus, whose specimens usually occur singly. Marked differences between juvenile and adult jaws and limb proportions suggest that age classes targeted different prey, reducing competition within the species regardless of whether the animals travelled together. Face-biting scars on tyrannosaurid skulls indicate that encounters between individuals could turn violent, perhaps during territorial or courtship disputes.
The name means roughly 'fierce lizard'; it was coined by Canadian palaeontologist Lawrence Lambe in 1914.
Gorgosaurus is among the best-represented large predatory dinosaurs on Earth, with dozens of skeletons from Alberta, several almost complete.
A juvenile described in 2023 preserved the hind limbs of two young bird-like dinosaurs (Citipes) inside its rib cage — rare direct evidence of a tyrannosaurid's last meals.
Young Gorgosaurus had slender jaws and long lower legs and almost certainly hunted different prey than the bulky adults.
Bone growth rings show the fastest growth came in the teenage years, and the oldest known individuals reached about 22 years.
One famous specimen shows healed rib fractures, an infected jaw and a broken fibula — life at the top of the food chain was rough.
For a time the species was placed in Albertosaurus as A. libratus; most researchers now keep Gorgosaurus separate.
The arms were only about a metre long on a nine-metre animal and could not reach the mouth.
Chapter • Scientific place
Journal of Vertebrate Paleontology
Reviewed: 9/5/2026
Peer-reviewed paper that explicitly places Gorgosaurus libratus within Tyrannosauridae: Albertosaurinae, supporting the stored lineage from Theropoda through Tyrannosauroidea.
Open sourcePaleobiology Database
Reviewed: 9/5/2026
PBDB taxon page listing the recorded fossil collections, North American localities and Campanian stratigraphic range of Gorgosaurus libratus.
Open sourceSedimentary Geology (Elsevier)
Reviewed: 9/5/2026
Sedimentological reconstruction of the Dinosaur Park Formation's meandering rivers, floodplains and coastal-plain setting west of the Western Interior Seaway, the habitat in which Gorgosaurus lived.
Open sourceScience Advances
Reviewed: 9/5/2026
Reports preserved stomach contents in a juvenile Gorgosaurus libratus, giving direct evidence of its carnivorous diet and an ontogenetic dietary shift.
Open sourceCanadian Journal of Earth Sciences
Reviewed: 9/5/2026
Extinct taxon; conservation status NE
Open sourceActa Palaeontologica Polonica
Reviewed: 9/5/2026
Open-access peer-reviewed overview of Gorgosaurus libratus anatomy, growth and distinguishing features relative to other Albertan tyrannosaurids, used as the general description source for all language versions.
Open sourceActa Palaeontologica Polonica
Reviewed: 9/5/2026
Open-access peer-reviewed overview of Gorgosaurus libratus anatomy, growth and distinguishing features relative to other Albertan tyrannosaurids, used as the general description source for all language versions.
Open sourceActa Palaeontologica Polonica
Reviewed: 9/5/2026
Open-access peer-reviewed overview of Gorgosaurus libratus anatomy, growth and distinguishing features relative to other Albertan tyrannosaurids, used as the general description source for all language versions.
Open sourceActa Palaeontologica Polonica
Reviewed: 9/5/2026
Open-access peer-reviewed overview of Gorgosaurus libratus anatomy, growth and distinguishing features relative to other Albertan tyrannosaurids, used as the general description source for all language versions.
Open source