page_title: Albertosaurus
section_title: Skull and teeth
hierarchical_section_title: Albertosaurus / Description / Skull and teeth
caption_attribution_description: Albertosaurus skull cast (specimen TMP 1981.010.0001) at the Geological Museum in Copenhagen.
context_page_description: Albertosaurus is a genus of tyrannosaurid theropod dinosaurs that lived in western North America during the Late Cretaceous Period, about 70 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 has been discovered in the Corral de Enmedio and Packard Formations in Mexico. 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 nine to ten meters long and possibly weighing 2.5 metric tons or less.
  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.
context_section_description: The massive skull of Albertosaurus, which was perched on a short, S-shaped neck, was about 1 metre (3.3 feet) long in the largest adults. Wide openings in the skull (fenestrae) reduced the weight of the head while also providing space for muscle attachment and sensory organs. Its long jaws contained, both sides combined, 58 or more banana-shaped teeth; larger tyrannosaurids possessed fewer teeth, Gorgosaurus at least 62. Unlike most theropods, Albertosaurus and other tyrannosaurids were heterodont, with teeth of different forms depending on their position in the mouth. The premaxillary teeth at the tip of the upper jaw, four per side, were much smaller than the rest, more closely packed, and D-shaped in cross section. Like with Tyrannosaurus, the maxillary (cheek) teeth of Albertosaurus were adapted in general form to resist lateral forces exerted by a struggling prey. The bite force of Albertosaurus was less formidable, however, with the maximum force, by the hind teeth, reaching 3,413 Newtons. Above the eyes were short bony crests that may have been brightly coloured in life and used in courtship to attract a mate.
  William Abler observed in 2001 that Albertosaurus tooth serrations resemble a crack in the tooth ending in a round void called an ampulla. Tyrannosaurid teeth were used as holdfasts for pulling flesh off a body, so when a tyrannosaur pulled back on a piece of meat, the tension could cause a purely crack-like serration to spread through the tooth. However, the presence of the ampulla distributed these forces over a larger surface area, and lessened the risk of damage to the tooth under strain. The presence of incisions ending in voids has parallels in human engineering. Guitar makers use incisions ending in voids to, as Abler describes, "impart alternating regions of flexibility and rigidity" to wood they work. The use of a drill to create an "ampulla" of sorts and prevent the propagation of cracks through material is also used to protect aircraft surfaces. Abler demonstrated that a plexiglass bar with incisions called "kerfs" and drilled holes was more than 25% stronger than one with only regularly placed incisions. Unlike tyrannosaurs, ancient predators like phytosaurs and Dimetrodon had no adaptations to prevent the crack-like serrations of their teeth from spreading when subjected to the forces of feeding.
caption: Skull cast at the Geological Museum in Copenhagen
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