Name Meaning: Alberta Lizard
Geologic Era: Late Cretaceous (83-72 million years ago)
Location Found: Eastern Montana (Judith River Group)
Size: 10 meters long (maximum)
Estimated Range: Canada, may have extended further south
Extinction Date: 72 million years ago
Albertosaurus has the distinction of being one of the best studied tyrannosaurids, with over 30 individuals of all ages being found to date. One bone bed includes the remains of 22 individuals of varying ages. This find led some to suggest that Albertosaurus was a pack hunter, and the remains were of a family unit. Other contend that the bones could have been washed together, possibly during a flash flood. Regardless of its hunting style, more is known about Albertosaurus anatomy than any other tyrannosaur. The teeth exhibit the typical banana shape of tyrannosaurids.
These teeth would not have been terribly useful for slicing flesh, but would have been much better at crunching through bone and muscle. An adult Albertosaurus would have been the apex predator of its time and area. Younger individuals would have filled intermediate spots in the predatory world. On the menu would have mainly been cerotopsians and hadrosaurs. Albertosaurs, especially younger ones, would have been able to run down most any prey.
There is some question as to what species this tooth actually belongs. There are three tyrannosaurids found in the Two Medicine formation: Albertosaurus, Dapletosaurus, and Gorgosaurus. Isolated teeth are next to impossible to identify down to the genus level, and having three closely related species in the same area further complicates matters. The tooth is definitely tyrannosaurid, and Albertosaurus is the most commonly found tyrannosaurid in this formation.
Gorgosaurus may also be the same animal as Albertosaurus, since they have many skeletal similarities. They also have enough differences that some paleontologists believe Gorgosaurus warrants its own species. Also, Albertosaurus tends to be found in more southern latitudes, while Gorgosaurus is generally found at higher latitudes. Given that our tooth is from Montana, the southernmost end of the Two Medicine formation, it is more likely to be from Albertosaurus than Gorgosaurus. All three of the above species were smaller than Tyrannosaurs rex, and generally had a lighter build.
Another interesting note about Albertosaurus fossils is that they show very little evidence of pathology compared to other species of theropods. Comparatively few Albertosaurus skeletons show evidence of bone healing and trauma, indicating that this was a relatively healthy species. They show few signs of intraspecific competition (members of same species attacking each other), compared to other theropods such as Majungasaurus. This could be an indication of cooperative pack behavior, or simply that individuals had the sense to avoid each other. It is possible that younger Albertosaurs targeted different prey than the adults, and this practice would have kept them out of the way of larger, stronger Albertosaurs.
Skeleton: “Albertosaurus sarcophagus mount” by James St. John – Albertosaurus sarcophagus (Upper Cretaceous; Alberta, western Canada) 1. Licensed under CC BY 2.0 via Commons – https://commons.wikimedia.org/wiki/File:Albertosaurus_sarcophagus_mount.jpg#/media/File:Albertosaurus_sarcophagus_mount.jpg
Life Restoration: “Albertosaurus sarcophagus copia”. Licensed under CC BY 3.0 via Commons – https://commons.wikimedia.org/wiki/File:Albertosaurus_sarcophagus_copia.jpg#/media/File:Albertosaurus_sarcophagus_copia.jpg