Skeleton of Albertosaurus libratus. Albertosaurus lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species was restricted in range to the modern-day Canadian province of Alberta, after which the genus is named. As a tyrannosaurid, Albertosaurus was a bipedal predator with two-fingered hands and a massive head with dozens of large, sharp teeth. Although relatively large for a theropod, Albertosaurus was much smaller than its more famous relative Tyrannosaurus, probably weighing less than 2 metric tons. 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 22 individuals at one site provides evidence of pack behavior. Royal Tyrrell Museum, Drumheller, Alberta, Canada