Comments on: Guest post: when pachycephalosaurs attack.

By: Mark Robinson

Mark Robinson — Sun, 17 Jul 2011 02:29:56 +0000

Interesting post, Eric. As a layperson, I share some of Zhen's frustration, altho' I understand the causes. I thought that there was a suggestion that Stygimoloch (and Dracorex) were possibly juvenile Pachycephalosaurus, and that the spikes tended to be swallowed up (resorbed?) as the dome overgrew them. If this were the case, it also suggests that the animals used their skulls differently at different life stages.

By: Eric Snively

Eric Snively — Sat, 16 Jul 2011 15:51:58 +0000

Zhen,
I agree! To be fair, there’s some decent evidence that contradicts head butting in some pachycephalosaurs. Domes of big adult Pachycephalosaurus lack cancellous bone and vascularity to feed a keratin pad, which would be bad for healing and absorbing energy (although their momentum would clobber youngsters anyway). Also, the dome of Stygimoloch is relatively small and sharp, which Ken Carpenter suggests would be good for inflicting soft tissue pain while flank-butting. Yet we’ve shown with Andy Farke that cancellous bone+a keratin pad, present in most pachycephalosaurs, would absorb energy. The whole vertebral column in front of the hips was built telescope and spring back, reducing the force of (apparently) dramatic impacts.
Eric

By: Zhen

Zhen — Sat, 16 Jul 2011 03:12:56 +0000

This is why paleontology is a pain in the rear. I remember reading a few years ago that they can’t butt heads due to some… reason that I’ve forgotten. Even then I had trouble believing that simply because it seems really hard to explain why else their skulls are so thick.