New paper on pachycephalosaur behavior

["Andrew A. Farke" <andyfarke@hotmail.com>]

Hi all,

This is in the latest issue of Paleobiology--quite relevant to some of the
discussions of the past week. At any rate, I don't think I've seen it
mentioned on-list.

GOODWIN, M. B., AND J. R. HORNER. 2004. Cranial histology of
pachycephalosaurs (Ornithischia: Marginocephalia) reveals transitory
structures inconsistent with head-butting behavior. Paleobiology,
30(2):253-267.

To quickly summarize, Goodwin and Horner argue (?demonstrate?) that the
famous radial bone structure of pachycephalosaur domes is just a factor of
ontogeny related to building a big dome in a short period of time. That is,
the largest Pachycephalosaurus skull they sectioned didn't display the
radial architecture--it's pretty much a solid lump of bone. They use an
"ontogenetic series" pieced together from several taxa to infer the way dome
histology changes through ontogeny, and also to suggest that a specimen from
the Two Medicine Formation is a previously unrecognized taxon. They also
claim that the "sexual dimorphism" recognized in Stegoceras is actually due
to differences between subadults and adults. The bottom line is that they
say this pretty much lays to rest the "headbutting" idea, and that the domes
evolved for species recognition and communication. 

I'm not sure if I totally agree with all of their conclusions. . .the
histology is definitely a great leap forward, in showing that adult domes
aren't that "spongy" after all. I'd be greatly interested to see a true
ontogenetic series for a single taxon, or even for several taxa. I suspect
there may be some developmental differences between the various species that
led to the variation in dome size and shape (i.e., do you see the same three
histological zones in the same proportions in all taxa?). If so, this means
that the data presented in Goodwin and Horner's paper aren't as easy to
interpret.

And as for what this all *really* means for behavior, who knows. . .are
there really so many sympatric species of Pachycephalosaur as to need to
evolve domes just for species recognition? This will really require more
work with extant taxa. And a pachycephalosaur bonebed.

Andy

________________________________
Andrew A. Farke, Graduate Student
Department of Anatomical Sciences
Stony Brook University
T8 040 Health Sciences Center
Stony Brook, NY  11794-8081
 
Phone: 631-444-7364