Temporal range: Upper Cretaceous 92–66 mya
|Cast of a Pachycephalosaurus skull, Oxford University Museum of Natural History|
In some species, the skull roof is domed and several inches thick; in others it is flat or wedge-shaped.The flat-headed pachycephalosaurs are usually regarded as distinct species or even families, but they may be juveniles of dome-headed adults. The domes were often surrounded by nodes and/or spikes.
There is evidence of head-butting in pachycephalosaurs. Of 100 domes studied, 20 percent showed signs of healed injuries. The pathologies included pitting where the bone had become infected from wounds that originated in the skin. These findings suggest that pachycephalosaurids may have been using their heads for both display and defence as many modern animals do.
Competition for mates is the usual reason why adult males fight. Competition for territory is another possibility. There are many examples of both in mammalian fighting. And the head could be used as defence against predators.
Incidentally, these thick head shields are called the parietosquamosal shelf.
Family Pachycephalosauridae Edit
Tribe Pachycephalosaurini Edit
- Sullivan R.M. 2006. A taxonomic review of the Pachycephalosauridae (Dinosauria: Ornithischia). New Mexico Museum of Natural History and Science Bulletin 30 (35): 347–365.
- Longrich N.R; Sankey J. & Tanke D. 2010. Texacephale langstoni, a new genus of pachycephalosaurid (Dinosauria: Ornithischia) from the upper Campanian Aguja Formation, southern Texas, USA. Cretaceous Research 31 (2): 274.
- Maryańska, Teresa; Chapman, Ralph E. & Weishampel, David B. 2004. Pachycephalosauria. In Weishampel, David B; Dodson, Peter & Osmólska, Halszka (eds) The Dinosauria. 2nd ed, Berkeley: University of California Press. pp. 464–477. ISBN 0-520-24209-2.
- NBC News: "Boneheaded dinosaurs butted heads"