Albertosaurus (/ælˌbɜːrtəˈsɔːrəs/; meaning "Alberta lizard") is a genus of tyrannosaurid theropod dinosaurs that lived in western North America during the Late Cretaceous Period, about 71 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which the genus is named, although an indeterminate species ("cf. Albertosaurus sp.") has been discovered in the Corral de Enmedio and Packard Formations in Mexico.[1] Scientists disagree on the content of the genus, with some recognizing Gorgosaurus libratus as a second species.
As a tyrannosaurid, Albertosaurus was a bipedal predator with tiny, two-fingered hands and a massive head that had dozens of large, sharp teeth. It may have been at the top of the food chain in its local ecosystem. While Albertosaurus was large for a theropod, it was much smaller than its larger and more famous relative Tyrannosaurus rex, growing 8 to 10 m (26 to 33 ft) and possibly weighing 2.5 tonnes (2.8 short tons) to 4 tonnes (4.4 short tons)
Since the first discovery in 1884, fossils of more than 30 individuals have been recovered, providing scientists with a more detailed knowledge of Albertosaurus anatomy than is available for most other tyrannosaurids. The discovery of 26 individuals at one site provides evidence of pack behaviour and allows studies of ontogeny and population biology, which are impossible with lesser-known dinosaurs due to their remains being rarer and more fragmentary compared to those of Albertosaurus.
Albertosaurus was named by Henry Fairfield Osborn in a one-page note at the end of his 1905 description of Tyrannosaurus rex.[2]: 265 The name honours Alberta, the Canadian province established the same year, in which the first remains were found. The generic name also incorporates the Greek term σαυρος/sauros ("lizard"), the most common suffix in dinosaur names. The type species is Albertosaurus sarcophagus; the specific name is derived from Ancient Greek σαρκοφάγος (sarkophagos) meaning "flesh-eating" and having the same etymology as the funeral container with which it shares its name: a combination of the Greek words σαρξ/sarx ("flesh") and φαγειν/phagein ("to eat").[2] More than 30 specimens of all ages are known to science.[3][4]
The type specimen is a partial skull, collected in the summer of 1884 from an outcrop of the Horseshoe Canyon Formation alongside the Red Deer River, in Alberta. This specimen, found on June 9, 1884, was recovered by an expedition of the Geological Survey of Canada, led by the famous geologist Joseph Burr Tyrrell. Due to a lack of specialised equipment the almost complete skull could only be partially secured. In 1889, Tyrrell's colleague Thomas Chesmer Weston found an incomplete smaller skull associated with some skeletal material at a location nearby.[5] The two skulls were assigned to the preexisting species Laelaps incrassatus by Edward Drinker Cope in 1892,[6] although the name Laelaps was preoccupied by a genus of mite and had been changed to Dryptosaurus in 1877 by Othniel Charles Marsh. Cope refused to recognize the new name created by his archrival Marsh. However, Lawrence Lambe used the name Dryptosaurus incrassatus instead of Laelaps incrassatus when he described the remains in detail in 1903 and 1904,[7][8] a combination first coined by Oliver Perry Hay in 1902.[9]