Strangely enough, this dinosaur is known only from portions of the skull: no postcranial remains have been found, meaning most of its body information comes from other closely related species. The skull is much larger than other related species, suggesting it stood as tall as 1.5 m high (with it's head leaning forward), a length of 4.5 m, and weighing 450 kg. Pachycephalosaurus has a very distinctive skull that makes this dinosaur famous. As mentioned previously, it had an extremely thick skull (up to 25 cm) that had a smooth dome-shape to it. At the back of the skull were several bony spikes and knobs, which are also found around the sides and even on its face. Like other pachycephalosaurids, it had sharp leaf-shaped teeth that would have been successful at eating tough fibrous plants, insects, and seeds.
|Artists impression of Pachycephalosaurus by Nobu Tamura|
So what about pachycephalosaurids from Alberta? First of all, a nearly complete specimen of Stegoceras was found in southern Alberta, and is actually housed at the University of Alberta. It was much smaller than Pachycephalosaurus, at 2 m long and weighing only an estimated 60 kg. Another possible Albertan pachycephalosaurid is Stygimoloch, which is found primarily in the US with a possible find in Alberta. It is smaller than Pachycephalosaurus, and has much pointier spikes sticking off of its skull. Some authors believe that Stygimoloch, along with another pachycephalosaur Dracorex (which has a species named after the Hogwarts castle from Harry Potter) actually represent a growth series with Pachycephalosaurus being the adult . In fact, some of you may remember Dr. Jack Horner talking about this 2 summers ago at Jurassic Forest!
I hope you enjoyed learning about this interesting dinosaur. Next week, we'll be on Q, which will bring us another non-Albertan dinosaur.
Other 'P' dinosaurs from Alberta:
Prismatoolithus - a dinosaur egg genus
Prosaurolophus - a hadrosaur
Parasaurolophus - a hadrosaur
Pachyrhinosaurus - a ceratopsian
Prenoceratops - a ceratopsian
Panoplosaurus - an ankylosaur
1. Ryan, M.J., and Russell, A.P. 2001. Dinosaurs of Alberta. In D.H. Tanke and K. Carpenter eds. Mesozoic Vertebrate Life. Indiana University Press.
2. Carpenter, K. 1997. Agonistic behaviour in pachycephalosaurs (Ornithischia, Dinosauria); a new look at head-butting behaviour. Rocky Mountain Geology 32: 19-25.
3. Snively, E., and Cox, A. 2008. Structural mechanics of pachycephalosaur crania permitted head-butting behaviour. Palaeontologia Electronica 11: 3A. Freely downloadable here
4. Horner, J.R., and Goodwin, M.B. 2009. Extreme cranial ontogeny in the Upper Cretaceous dinosaur Pachycephalosaurus. PLoS ONE 4: e7626. Freely downloadable here