Albertosaurus sarcophagus

Albertosaurus sarcophagus was a long-legged tyrannosaurid that lived several million years before Tyrannosaurus rex. Its narrow body, proportionally long lower legs and lighter skull distinguish it from the deeper, more massive build of later tyrannosaurines. The species is unusually informative because the Dry Island bonebed preserves at least twelve individuals of different ages in one deposit. That assemblage reveals growth and population structure, but a shared burial site alone cannot establish coordinated pack hunting or a permanent family group.

Its fossils occur between approximately 71.5 and 68.5 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull was long and relatively low, with large openings that reduced weight and powerful muscles closing the jaws. Small bony crests rose above the eyes and may have carried keratin or display tissue. Thick, serrated teeth were replaced throughout life. The arms were very short and ended in two functional fingers, while the hind limbs were long and gracile for an animal approaching nine metres. Juveniles had especially slender skulls and legs; the head deepened and the body became more robust as they matured.

• Long, low tyrannosaurid skull with strong jaw-muscle attachments
• Small paired bony crests above the eyes
• Large serrated teeth replaced throughout life
• Very short forelimbs with two functional fingers
• Long, relatively slender hind limbs and feet
• Documented growth series from juveniles to mature adults

Geologist Joseph Burr Tyrrell found the incomplete skull CMN 5600 beside Alberta's Red Deer River on 12 August 1884. Thomas Chesmer Weston collected the partial skull and skeleton CMN 5601 in 1889. Henry Fairfield Osborn named Albertosaurus sarcophagus in 1905, the same publication in which he named Tyrannosaurus rex. Barnum Brown found the Dry Island bonebed in 1910, but its position was later lost. Philip Currie relocated it in 1997 and renewed excavation, producing a growth series that helped confirm the bonebed animals belonged to the same species as the damaged type skulls.

Discovery credit: Joseph Burr Tyrrell, Thomas Chesmer Weston.

Naming authors: Henry Fairfield Osborn.

The Horseshoe Canyon Formation records river channels, floodplains, swamps and coastal lowlands near the retreating Western Interior Seaway. Alberta's climate was cool-temperate by Cretaceous standards and strongly seasonal. Albertosaurus shared the broader formation with hadrosaurs, horned dinosaurs, armoured dinosaurs, smaller theropods, turtles and crocodile-line reptiles, although not every named taxon occupied the exact same horizon.

Albertosaurus was an active carnivore able to bite and tear flesh with reinforced jaws and serrated teeth. Long lower legs suggest efficient terrestrial movement, but maximum running speed remains model-dependent. The Dry Island concentration demonstrates that many individuals died and were buried together. They may have associated before death, or carcasses may have accumulated through local environmental processes; neither explanation proves cooperative hunting. Bite marks on Albertosaurus bones can record feeding or scavenging, not necessarily fatal combat.

• Joseph Tyrrell's 1884 skull discovery eventually gave its name to Alberta's Royal Tyrrell Museum.
• Osborn named Albertosaurus and Tyrannosaurus rex in the same 1905 paper.
• The Dry Island bonebed preserves at least twelve Albertosaurus individuals of several ages.
• Adults were long but considerably lighter-built than Tyrannosaurus rex.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   Palaeobiology Collections

   Canadian Museum of Nature

   Open source
2. 02
   A taxonomic assessment of the type series of Albertosaurus sarcophagus and the identity of Tyrannosauridae in the Albertosaurus bonebed

   Thomas D. Carr · Canadian Journal of Earth Sciences 47(9) · 2010

   Open source
3. 03
   Stratigraphy, sedimentology, and taphonomy of the Albertosaurus bonebed (upper Horseshoe Canyon Formation; Maastrichtian), southern Alberta, Canada

   David A. Eberth, Philip J. Currie · Canadian Journal of Earth Sciences 47(9) · 2010

   Open source
4. 04
   Cretaceous Alberta

   Royal Tyrrell Museum

   Open source