A single quarry of 26 Albertosaurus hints that these tyrannosaurs lived in groups
In 1910 Barnum Brown stumbled onto a quarry beside Alberta's Red Deer River crammed with the bones of one predator species. Later counts reached 26 Albertosaurus individuals at that one site, a rare glimpse of how a tyrannosaur might have lived together and grown up.
Albertosaurus, the Alberta lizard, roamed northwestern North America about 71 million years ago in the Late Cretaceous. It had the classic tyrannosaur build: walking on two legs, balancing a massive head with a long muscular tail, and carrying tiny arms with only two working fingers. Dozens of sharp teeth, keen smell, binocular vision and a bone-crushing bite may have made it the top predator of its surroundings. Adults reached 8 to 9 metres long and weighed 1.7 to 3.0 metric tons, big for a theropod yet well short of Tyrannosaurus.
The first find came on June 9, 1884, when a Geological Survey of Canada team led by Joseph Burr Tyrrell dug out a partial skull from the Horseshoe Canyon Formation, hampered by a lack of proper tools. Henry Fairfield Osborn named the genus in 1905 in a one-page note tacked onto his description of Tyrannosaurus, the same year the province of Alberta was established.
Brown's party found the big bonebed on August 11, 1910 but lacked time to collect everything, so they took samples from each animal they could identify. More than 30 individuals are now known, giving a fuller picture of this tyrannosaur's anatomy than exists for most relatives. Oddly, no new fossils turned up between 1926 and 1972, after which finds resumed; amateur collector Maurice Stefanuk found a specimen in 1978. Two possible specimens have also surfaced in Mexico.
Naming has zigzagged. A 1928 species, A. arctunguis, has been folded into the original since 1970, and other scientists shuffled Albertosaurus into Deinodon in 1922 and 1939. Its close relative Gorgosaurus, named by Lawrence Lambe in 1914 from a skeleton found by Charles H. Sternberg, was long lumped with it, until Philip J. Currie concluded in 2003 that the two are distinct sister species.
Source: Albertosaurus
