Re: Bone heads

["Jerry Harris" <jdharris@lust.isem.smu.edu>]

> Paul (pwillis@ozemail.com.au) writes:
> >What is the current accepted wisdom on what pachycephalosaurs used their
> >heads for? I think that the case for male to male combat holds as much
> >water as the Rainbow Warrior (No 1, not No 2). The head is better designed
> >for delivering a Liverpool Kiss to an impending predator. What is hte
> >general feeling out there?
> 
> The head-butting theory is conventional, but IMHO, not wisdom. :)
> 
> Besides the head-butting and somewhat more likely T. rex-butting 
> ideas, there is one other theory I've seen: In John McLoughlin's book,
> _Archosauria_, he suggests that pachycephalosaurs kept their heads 
> down and the bony dome pointed forward to quickly push tall, thick
> vegetation out of its way as it ran.  This seems at least somewhat
> plausible...at least until our wretched pachyceph ran into a 
> giant redwood or dosing _Euoplocephalus_ it its path! :)

     Conventional theory on the head-butting isn't wise, you are correct.  An 
examination of the domes of the pachycephalosaurine pachycephalosaurs shows that
they aren't nice and round like football helmets; instead, they're actually 
somewhat pointed, leaving extremely little surface area for which to make 
contact with another dome (imagine two cones trying to ram each other 
point-first!)  So actual head-butting is somewhat impractical.  However, the 
dome and the specializations of the cervical vertabrae indicate that they 
probably _were_ butting something!  Possibly they were butting bodies, not heads
-- this is a theory mounted in two sculpted _Stygimoloch_ statues at the Denver 
Museum's new exhibit.  
     The idea of also using the dome to crash through the underbrush is possible
-- modern cassowaries do it with their head crests -- but I don't know how that 
helps the homalocephaline pachycephalosaurs.




Jerry D. Harris
_NOW_ at:
     Schuler Museum of Paleontology
     Southern Methodist University
jdharris@lust.isem.smu.edu
(or on CompuServe:  73132,3372)

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