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Grey-brown tyrannosaurid Gorgosaurus walking in side view beside a small human silhouette
Life reconstruction of Gorgosaurus libratus with a human for scale.Image credit: Leoomas, CC BY-SA 4.0, via Wikimedia Commons (unmodified except resizing)CC BY-SA 4.0 (unmodified)Source (opens in a new tab)

Gorgosaurus libratus

Pronounced GOR-goh-SORE-us lih-BRAH-tus

Coelurosauria · Tyrannosauridae

An 8 to 9 m tyrannosaur from the Late Cretaceous of Alberta and Montana, the best-represented tyrannosaurid in the fossil record. A juvenile found with two young feathered dinosaurs in its stomach shows how its diet changed as it grew.

  • Bipedal
  • Apex predator
Compare
Period
Cretaceous· Campanian
Diet
Carnivore
Length
8–9 m
Mass
2,000–3,000 kg
Location
Alberta, Canada

Quick answers

How big was Gorgosaurus libratus?
Gorgosaurus libratus was about 8–9 m long. It stood about 2.3–2.8 m tall at the hips. It weighed about 2–3 t. (Wikipedia: Gorgosaurus 2026; Currie 2003)
When did Gorgosaurus libratus live?
Gorgosaurus libratus lived during the Late Cretaceous, about 76.5–73 million years ago. (Paleobiology Database: Gorgosaurus libratus t… 2026; Therrien et al. 2023)
Where have Gorgosaurus libratus fossils been found?
Fossils of Gorgosaurus libratus have been found in Dinosaur Park Formation (Alberta) and Canada. (Lambe 1914; Currie 2003)
What did Gorgosaurus libratus eat?
Gorgosaurus libratus was a carnivore. (Lambe 1914; Currie 2003)
Who named Gorgosaurus libratus, and when?
Gorgosaurus libratus was described by Lawrence M. Lambe in 1914. (Lambe 1914; Paleobiology Database: Gorgosaurus libratus t… 2026)

On this page

GOR-goh-SORE-us lih-BRAH-tus

Period
Cretaceous76.5–73 Ma
Diet
Carnivore
Length
8–9 m
Mass
2–3 t
Location
Canada
Classification
Coelurosauria · Tyrannosauridae
Described
1914, Lawrence M. Lambe

Overview

Gorgosaurus libratus lived about 75 million years ago on the coastal floodplains of the Dinosaur Park Formation in Alberta, Canada, and in Montana. Charles M. Sternberg found a nearly complete skeleton on the Red Deer River in 1913, and Lawrence Lambe named it in 1914; it was the first tyrannosaurid found with a complete hand.

It was a close relative of Albertosaurus, lighter built than Tyrannosaurus, with long legs and tiny two-fingered arms. Dozens of skeletons of all ages make it the best-known tyrannosaurid, and some researchers treat it as a species of Albertosaurus.

A juvenile, 5 to 7 years old and about 335 kg, preserves the hind legs of two yearling Citipes, small oviraptorosaurs, in its stomach (Therrien et al. 2023). Young Gorgosaurus hunted small, young dinosaurs and only later switched to large herbivores such as hadrosaurs and ceratopsians.

Name meaning

"Fierce lizard", from Greek gorgos ("terrible, fierce") and sauros; libratus, Latin for "balanced" (Lambe 1914).

Biology & evidence

What scientists think about how this animal lived, and how strong the evidence for each idea is.

Feeding

  • Young Gorgosaurus hunted small, young dinosaurs before switching to large herbivores.

    Evidence level: Strong evidence

    A juvenile's stomach holds only the legs of two yearling feathered theropods; the shift to megaherbivores probably began as individuals approached about 600 kg.

    Evidence for / against · 1
    Evidence for

    • Specimen · Juvenile Gorgosaurus with Citipes stomach contents

      Two dismembered yearling caenagnathids eaten in two separate meals by a 5-7-year-old, 335 kg Gorgosaurus.

      Specimen: TMP 2009.12.14

Growth

  • Gorgosaurus changed body proportions as it grew.

    Evidence level: Strong evidence

    Juveniles had narrow skulls, blade-like teeth and long slender legs; adults were more robust.

    Evidence for / against · 1
    Evidence for

    • Specimen · Gorgosaurus growth series

      Dozens of skeletons from juveniles to adults, the most complete growth series of any tyrannosaurid.

Juvenile Gorgosaurus TMP 2009.12.14 preserving the hind limbs of two young Citipes in its stomach region (Therrien et al. 2023).Image credit: Therrien, F.; Zelenitsky, D. K.; Tanaka, K.; Voris, J. T.; Erickson, G. M.; Currie, P. J.; DeBuhr, C. L.; Kobayashi, Y., CC BY 4.0, via Wikimedia CommonsCC BY 4.0Source (opens in a new tab)

Size

Length
8–9 m

(29.5 ft)

Height
2.5 mpublished range 2.3–2.8 m

(8.2 ft)

Based on large adults (femur c. 1.0 m)

Mass
2,000–3,000 kg
Gorgosaurus libratus was about 9 m (29.5 ft) long, roughly 5 times the height of a 1.8 m adult human.

Timeline

Lived from about 76.5 to 73 million years ago (Ma), within the Mesozoic era (252–66 Ma).

Periods: Campanian (83.6–72.1 Ma), Late Cretaceous (100.5–66 Ma)

About 76.5-73 Ma for the genus (Wikipedia); the Dinosaur Park Formation juvenile is about 75.3 Ma (Therrien et al. 2023). PBDB bins the type collection as late Campanian (83.6-72.2 Ma).

Location

Formations

Map data: Natural Earth (public domain). Modern positions, not where the continents were then.

These are the places where fossils have been found, not the full area where the animal lived.

Ecosystem

Lived in: Dinosaur Park

76.5–74.4 million years ago · floodplain, coastal plain, river system

Late Campanian alluvial and coastal plains on the western shore of the Western Interior Seaway, in what is now southern Alberta.

Same ecosystem

Parasaurolophus walkeri

Cretaceous· CampanianHerbivore

Same ecosystem

Troodon formosus

Cretaceous· CampanianCarnivoreOmnivore

Same ecosystem

Styracosaurus albertensis

Cretaceous· CampanianHerbivore

Classification

  1. cladeDinosauria
  2. cladeSaurischia
  3. cladeTheropoda
  4. cladeCoelurosauria
  5. superfamilyTyrannosauroidea
  6. familyTyrannosauridae
  7. subfamilyAlbertosaurinae
  8. genusGorgosaurus
  9. speciesGorgosaurus libratus

Taxonomic status: Valid

Fossil record

Gorgosaurus libratus skeleton at the Royal Tyrrell Museum of Palaeontology, Alberta.Image credit: IJReid, CC BY 4.0, via Wikimedia Commons, Royal Tyrrell Museum of PalaeontologyCC BY 4.0Source (opens in a new tab)
Specimens
Catalog numberStatusInstitutionFound
CMN 2120HolotypeCanadian Museum of Nature (CMN)1913
TMP 2009.12.14Referred specimenRoyal Tyrrell Museum of Palaeontology (TMP)—

What has been found

Holotype: CMN 2120

  • Preserved
  • Partial
  • Reconstructed
  • Unknown / not recorded

Holotype: CMN 2120

Region by region (table)
Skeleton regions of Holotype: CMN 2120
RegionState
SkullPreserved
MandibleUnknown / not recorded
TeethUnknown / not recorded
Cervical vertebraeUnknown / not recorded
Dorsal vertebraeUnknown / not recorded
SacrumUnknown / not recorded
Caudal vertebraeUnknown / not recorded
RibsUnknown / not recorded
GastraliaUnknown / not recorded
Scapula / shoulder girdleUnknown / not recorded
HumerusUnknown / not recorded
Forearm (radius / ulna)Unknown / not recorded
Hand (manus)Preserved
PelvisUnknown / not recorded
FemurUnknown / not recorded
Tibia / fibulaUnknown / not recorded
Foot (pes)Unknown / not recorded

Referred specimen: TMP 2009.12.14

Region by region (table)
Skeleton regions of Referred specimen: TMP 2009.12.14
RegionState
SkullPreserved
MandibleUnknown / not recorded
TeethUnknown / not recorded
Cervical vertebraeUnknown / not recorded
Dorsal vertebraeUnknown / not recorded
SacrumUnknown / not recorded
Caudal vertebraeUnknown / not recorded
RibsUnknown / not recorded
GastraliaUnknown / not recorded
Scapula / shoulder girdleUnknown / not recorded
HumerusUnknown / not recorded
Forearm (radius / ulna)Unknown / not recorded
Hand (manus)Unknown / not recorded
PelvisUnknown / not recorded
FemurUnknown / not recorded
Tibia / fibulaPreserved
Foot (pes)Unknown / not recorded
Skull of the juvenile Gorgosaurus libratus TMP 1991.036.0500 from the Belly River Group, at the Royal Tyrrell Museum.Image credit: Chris Woodrich, CC BY-SA 4.0, via Wikimedia Commons (unmodified except resizing), Royal Tyrrell Museum of PalaeontologyCC BY-SA 4.0 (unmodified)Source (opens in a new tab)

All specimens

Discovery

Year described
1914
Described by
Lawrence M. Lambe
Type specimen
CMN 2120

Discovery timeline

  1. 1913 · First material found

    Charles M. Sternberg finds the Gorgosaurus holotype

    A nearly complete skeleton is found near Berry Creek on the Red Deer River.

    People: Charles M. Sternberg

  2. 1914 · Formally described

    Lambe names Gorgosaurus libratus

    Named in The Ottawa Naturalist.

    People: Lawrence M. Lambe

  3. 2023 · Major study

    Juvenile Gorgosaurus stomach contents described

    Therrien and colleagues describe the first tyrannosaur with stomach contents in place.

    People: François Therrien, Darla K. Zelenitsky

Sources

  1. (2026). Paleobiology Database: Gorgosaurus libratus type collection 11897. The Paleobiology Database (paleobiodb.org), data service 1.2, accessed 2026-09-23. https://paleobiodb.org/data1.2/colls/list.json?coll_id=11897&show=paleoloc,strat,loc,ref,geo&pgm=gplates&vocab=pbdb (opens in a new tab)
  2. (2026). Wikipedia: Gorgosaurus. Wikipedia (English), accessed 2026-09-24. https://en.wikipedia.org/wiki/Gorgosaurus (opens in a new tab)
  3. Currie, P. J. (2003). Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences 40: 651-665. doi:10.1139/e02-083 (opens in a new tab)
  4. Lambe, L. M. (1914). On the fore-limb of a carnivorous dinosaur from the Belly River Formation of Alberta, and a new genus of Ceratopsia from the same horizon, with remarks on the integument of some Cretaceous herbivorous dinosaurs. The Ottawa Naturalist 27(10): 129-135.
  5. Paul, G. S. (2016). The Princeton Field Guide to Dinosaurs (2nd edition). Princeton University Press.
  6. Therrien, F., Zelenitsky, D. K., Tanaka, K., Voris, J. T., Erickson, G. M., Currie, P. J., DeBuhr, C. L. & Kobayashi, Y. (2023). Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator. Science Advances 9: eadi0505. doi:10.1126/sciadv.adi0505 (opens in a new tab)