Re: Pachycephalosaurs & head-butting

[Philip Kelso <kelso33@comcast.net>]

Cranial histology of pachycephalosaurs (Ornithischia:Marginocephalia) 
reveals transitory structures inconsistent with head-butting behavior

Mark B. Goodwin and John R. Horner Paleobiology, 30(2), 2004, pp. 
253-267

Abstract.-Modern histological techniques allow paleontologists to 
investigate the internal microstructureof bone tissue. We apply high 
resolution images of histological thin sections from an 
ontogeneticseries (not conspecific) of pachycephalosaurid frontoparietal 
domes to test the hypothesis that these Late Cretaceous dinosaurs used 
their heads as battering rams, analogous to the behaviorof the bighorn 
sheep, Ovis canadensis, or as a thermoregulatory device. Our analysis 
reveals that the internal structure of the pachycephalosaur dome is a 
dynamic tissue that reflects the changeable expansion and vascularity of 
the dome throughout ontogeny. The radiating structures within the 
frontoparietal dome, used previously to support ''head-butting'' 
hypotheses, are unexpectedly transitory, diminishing in mature 
individuals and nearly absent in adult skulls where head-butting 
behavior is presumed to occur. The unique architecture of the 
pachycephalosaurid dome is dividable into three distinct Zones. We 
demonstrate that the relative vascularity, associated tissue structures, 
and orientation and density of Sharpey's fibers within these Zones are 
modified during growth. Evidence for an external dome covering in vivo 
precludes the determination of the final shape of the pachycephalosaur 
skull. On the basis of these new observations, we propose that cranial 
display in support of species recognition and communication is a more 
parsimonious interpretation of the function of the pachycephalosaurid 
dome. Sexual display behaviors were probably secondary.

----- Original Message ----- 
From: <hammeris1@bellsouth.net>
To: <dinosaur@usc.edu>
Sent: Wednesday, April 02, 2008 3:48 AM
Subject: Pachycephalosaurs & head-butting


> I thought I've read recent conclusions that their bony-skull tops were 
> far too thin to support this activity?
>
> Brian