Albertosaurus Almighty

Albertosaurus mount at the Royal Tyrrell Museum. Photo by Dave Anderson, via Flickr.

A hundred summers ago, an American Museum of Natural History team led by legendary fossil hunter Barnum Brown discovered a mass grave of the tyrannosaur Albertosaurus while traveling down the Red Deer River. This was, incidentally, the same scow expedition that inspired this year's sadly aborted reenactment led by Darren Tanke (which I hope will be able to be completed next year). Coinciding with this centennial, the newest issue of the Canadian Journal of Earth Sciences is dedicated to Albertosaurus.

The fossils comprising Brown and company's discovery were not the first appearance of Albertosaurus in the annals of paleontology. The first remains, a partial skull discovered in 1884, were assigned by Cope to his invalid Laelaps genus in 1892, which was changed to Marsh's Dryptosaurus in 1904 by Lawrence Lambe. Henry Fairfield Osborn gave the animal its current name the following year in an early roundup of tyrannosaurs.

In 1919, Barnum Brown wrote a piece for National Geographic describing the ground covered by his flatboat expeditions and providing a glimpse back to the Mesozoic. About Albertosaurus, he wrote:

Preying on the various herbivorous kinds were powerful flesh eaters. Albertosaurus... an active animal 30 feet long and about 15 feet high. Armed with large serrate dagger teeth and sharp, bird-like claws, it was capable of destroying any of its herb eating relatives It walked habitually on its hind legs, balanced by a long tail, while the short, reduced, front legs could have been used only in grasping its prey.

The Albertosaurus posture he describes jibes perfectly with the modern image of theropods as constructed with paleontological evidence. But it would be several decades before it was accepted that theropods held their tails off the ground, balancing the weight of their business end - you know, the one with the jaws and great gnashing teeth.

Arguably, he most significant contribution Albertosaurus has made to paleontology is the idea of some theropods as gregarious pack hunters, based mostly on the Barnum Brown bone bed. Phillip Currie of the Royal Tyrrell Museum and University of Alberta, and a main contributor to the new CJES issue, has been one of the biggest proponents of the hypothesis. He argues that Brown's site, home exclusively to about twenty Albertosaurus individuals ranging widely in age, was the result of a sudden event that killed all of the members of a pack. Currie offers the gracile, long-legged build of Albertosaurus as evidence that they were likely swift-footed predators, and pack-hunting would have been a good strategy to take down the large lambeosaurine duckbills their preyed upon. It's certainly an evocative idea. It's hard to imagine what it would feel like to watch a group of albertosaurs chase and bring down a Hypacrosaurus. Part of the allure of paleontology is this license to engage in fantasies like this, and while we'll probably never have definitive evidence of albertosaurs behaving in such a way, it's not completely implausible. All we have are hints into a lost world. Paleontology is a journey without end.