Albertosaurus

Chapter • Meet the dinosaur

Overview

Albertosaurus sarcophagus was a tyrannosaurid that stalked western Canada at the end of the Cretaceous. It was smaller and more lightly built than its famous relative Tyrannosaurus rex, reaching roughly 8–10 metres in length with most published mass estimates falling between 1.3 and 2 tonnes. Its skull was close to a metre long and carried some sixty recurved, serrated teeth in powerful jaws. Short bony crests sat above the eyes, probably covered in horn or brightly coloured skin and used for display. The animal balanced on two long, muscular hind limbs, its stiffened tail held out behind it so that the body was carried horizontally — never upright with a dragging tail. The arms were famously tiny and two-fingered. Skin impressions from close relatives show small pebbly scales, but because several early tyrannosauroids bore filamentous feathers, a sparse fuzz on hatchlings and juveniles remains plausible. The long lower legs and narrow feet suggest an animal built for endurance and reasonable speed. Most biomechanical estimates cluster around 25–30 km/h at top speed, with slim juveniles far more agile than heavy adults. Endocasts reveal large olfactory lobes and well-developed balance organs, pointing to a keen sense of smell and good coordination. Growth rings in the bones show the fastest growth between about twelve and sixteen years of age, when an individual could add well over a hundred kilograms a year, and that the oldest known specimens reached about 28 years. Albertosaurus was the apex predator of its ecosystem, most likely hunting duck-billed dinosaurs such as Edmontosaurus and Hypacrosaurus, along with horned dinosaurs and smaller plant-eaters. Tooth marks on prey bones show it sliced through flesh and crushed cartilage, though it lacked the extreme bone-crushing bite of Tyrannosaurus. Like large predators today, it almost certainly combined active hunting with scavenging whatever carcasses it found. The first known skull was collected in 1884 by Canadian geologist Joseph Burr Tyrrell along the Red Deer River in Alberta. Henry Fairfield Osborn named the species in 1905, the same year the province of Alberta was created. In 1910 Barnum Brown excavated a bonebed containing many individuals, but the site was lost until Philip Currie relocated it in 1997 in Dry Island Buffalo Jump Provincial Park. At least 26 individuals of all ages have been identified there, making Albertosaurus one of the best-known large predatory dinosaurs.

Chapter • Where it lived

Habitat

Albertosaurus lived roughly 71–68 million years ago, during the Maastrichtian age of the Late Cretaceous, in what is now Alberta, Canada. Its fossils come chiefly from the Horseshoe Canyon Formation along the Red Deer River, a warm, humid coastal plain on the western shore of the Western Interior Seaway that then split North America in two. The landscape was a mosaic of meandering rivers, swamps, peat mires and forests of conifers, ginkgoes and early flowering trees, under a strongly seasonal climate. The richest sites are the bonebed in Dry Island Buffalo Jump Provincial Park and numerous localities around Drumheller.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy