Albertosaurus

**Albertosaurus** (/ælˌbɜːrtəˈsɔːrəs/; meaning "Alberta lizard") 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. Scientists disagree on the content of the genus, with some recognizing Gorgosaurus libratus as a second species. Many noting the similarities between the two genus.

## Description

Albertosaurus was smaller than some other tyrannosaurids, such as Tarbosaurus and Tyrannosaurus. Typical Albertosaurus adults measured up to 9 m (30 ft) long, while rare individuals of great age could grow to be over 10 metres (33 feet) long. Several independent mass estimates, obtained by different methods, suggest that an adult Albertosaurus weighed between 1.3 tonnes and 1.7 tonnes (1.9 tons).

Albertosaurus shared a similar body appearance with all other tyrannosaurids. 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 on which the first digit, called the hallux, was short and did not reach the ground. The third digit was longer than the rest. Albertosaurus may have been able to reach walking speeds of 14−21 km/hour (8−13 mi/hour). At least for the younger individuals, a high running speed is plausible. This was probably to chase or pursue after tough prey, or to be nimble when confrontation.

Two skin impressions from Albertosaurus are known, both showing scales. One patch is found with some gastralic ribs and the impression of a long, unknown bone, indicating that the patch is from the belly. The scales are pebbly and gradually become larger and somewhat hexagonal in shape. Also preserved are two larger feature scales, placed 4,5 cm apart from each other. Another skin impression is from an unknown part of the body. These scales are small, diamond-shaped and arranged in rows

## Discovery and naming

Although the small flesh-eating dinosaurs were diverse and dangerous, Cretaceous Alberta was ruled by members of the family tyrannosauridae.

All tyrannosaurs had hind legs that were long and powerful, with each hind foot having three toes ending in enormous claws. The two-fingered front limbs were small, not much larger than a mature human arm. The function of the front limbs is not known.

*Albertosaurus*, the "lizard from Alberta," was among the most fearsome predators in Cretaceous Alberta. 9 meters long and 3 meters high at the hip, it was the most common of the large carnivores found here. Smaller but longer-limbed than *T. rex*, *Albertosaurus* would have been a mobile hunter. Like modern carnivores, it probably fed on the carcasses of already dead animals as well.

*Albertosaurus* weighed up to 3 tons yet may have been capable of attaining speeds of more than 40 mph. This fleetness, combined with obvious physical strength, would have made *Albertosaurus* a fierce hunter, but less than the more massive *T. rex*. *Albertosaurus* neck was strong and muscular, supporting a large but lightly built head. The teeth were long and recurved with saw-like edges, perfect for tearing flesh. They were not adapted for chewing, making it likely than *Albertosaurus* swallowed flesh in large chunks.

*Albertosaurus* bones were among the earliest dinosaur remains collected in Alberta. A skull found by J.B. Tyrrell in 1884 was the first important dinosaur fossil to be discovered along the Red Deer River. It was named in 1905, the same year that Alberta became a province. Since then, many *Albertosaurus* fossils have been discovered. the smallest documented *Albertosaurus*, a juvenile less than a quarter of the size of a full grown adult, was collected from Sandy Point on the South Saskatchewan River in 1986. [1]

J.B. Tyrrell spent most of his long career as a geologist, explorer and entrepreneur on the Canadian Shield. However, in 1884 his first field work was in Cretaceous strata along the Red Deer River where his discovery of a skull of the tyrannosaur *Albertosaurus* provided a name to the paleontological museum in Drumheller. At the time, several discoveries were made to what was 10 Albetosaurus species (Gorgosaurus, Deinodon, Tarbosaurus, Alectrosaurus, Dryptosaurus, Dinotyrannus/Tyrannosaurus) ; including the Nanotyrannus, Jane, by courtesy of von Huene, Riabinin, and most noticeably Gilmore, Matthew, Kuhn, Paul and Russell. But recent research proved that the other species were sperate genus, and there being only one genus of Albertosaurus.

## Paleoecology

The Albertosaurus lived in the northern Canadian regions as its name suggests. It likely shared its environment with other carnivores, and much herbivores. One specific paleo-art, a painting shows an Albertosaurus pursuing after a juvenile Edmontosaurus in the Northern regions of Alberta. It probably shared its environment with Pachyrhinosaurus, Edmontosaurus, Troodon, and all sorts of Pterosaurs.