[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Pachycephalosaurs & head-butting
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.
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 -----
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?