- name meaning: Alberta Lizard
- average length: 8-9m( 26-30 ft )
- maximum length: 9-10 m ( 30-33 ft )
- average weight: 2-2.5 tons
- maximum weight: 2.5-2.8 tons
- average height: 2.6 m ( 8 ft )
- maximum height: 2.8-3.3 m ( 9-10 ft )
- time period: 76.6-70.3 mya
- habitat: North America
- skull length: 90-99 cm (36-39 in )
- bite force: 5000-7300 psi
- tooth length: 15 cm ( 5 in )
Albertosaurus ( "Alberta lizard") is a genus of tyrannosaurid theropod dinosaur 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. 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 with dozens of large, sharp teeth. It may have been at the top of the food chain in its local ecosystem. Although relatively large for a theropod, Albertosaurus was much smaller than its more famous relative Tyrannosaurus, probably weighing less than 2 metric tons.
Since the first discovery in 1884, fossils of more than thirty 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. Albertosaurus was smaller than some other tyrannosaurids, such as Tarbosaurus and Tyrannosaurus. Typical adults of Albertosaurus measured up to 9 metres (30 ft) long,while rare individuals of great age could grow to over 10 metres (33 ft) in length. Several independent mass estimates, obtained by different methods, suggest that an adult Albertosaurus weighed between 1.3 tonnes (1.4 short tons) and 1.7 tonnes (1.9 tons).
All tyrannosaurids, including Albertosaurus, shared a similar body appearance. Typically for a theropod, Albertosaurus was bipedal and balanced the heavy head and torso with a long tail. However, tyrannosaurid forelimbs were extremely small for their body size and retained only two digits. The hind limbs were long and ended in a four-toed foot. The first digit, called the, was short and only the other three contacted the ground, with the third (middle) digit longer than the rest. Albertosaurus may have been able to reach walking speeds of 14−21 kilometres per hour (8−13 miles per hour) and a running speed of 60-64 kilometers per hour ( 38-40 miles per hour).
The massive skull of Albertosaurus, perched on a short, S-shaped neck, was approximately 1 metre (3.3 ft) 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 sixty-two. 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, the maximum force, by the hind teeth, reaching 7300 psi. Above the eyes were short bony crests that may have been brightly coloured in life and used in courtship to attract a mate.