Smithsonian.com

The skull of Stegoceras. Image from Wikipedia.

The thick, dome-shaped skulls of the pachychephalosaurs immediately raise the question, “What were those things for?” Like many other bizarre structures sported by dinosaurs—from crests to sails to spikes—the reinforced skulls of dinosaurs such as Pachycephalosaurus and Stegoceras have puzzled paleontologists. The bony domes look like they would be well-suited for absorbing impact, much like the skulls of big horn sheep today, but were these dinosaurs really capable of head-on combat? A new PLoS One paper by Eric Snively and Jessica Theodor suggests that they were.

Snively and Theodor compared the skulls of the dome-headed dinosaurs Stegoceras and Prenocephale with several head-butting mammals, including elk, duiker and musk ox. These comparisons were carried out through CT scans—which allowed the scientists to look at the internal structure of the skulls—and computer models of the dinosaur heads to investigate the stresses and strains the skulls were capable of withstanding.

In terms of overall anatomy, the domes of the dinosaurs most closely resembled the skulls of the musk ox and duiker, and the thick skulls of the pachycephalosaurs appeared to be well-suited to dissipating the stresses which would have been involved in head-butting. From a mechanical perspective, Stegoceras was capable of direct head strikes in competition between members of the same species. With the discovery of addition pachycephalosaur skulls and future analyses, the peculiar anatomy of these dinosaurs should reveal a clearer picture of how they may have been behaving.

References:

Snively, E.; Theodor, J. (2011). Common Functional Correlates of Head-Strike Behavior in the Pachycephalosaur Stegoceras validum (Ornithischia, Dinosauria) and Combative Artiodactyls PLoS One, 6 (6) DOI: 10.1371/journal.pone.0021422