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Re: mass, momentum, & misc.




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> From: ngear@gvtc.com
> To: dinosaur@usc.edu
> Subject: mass, momentum, & misc.
> Date: Wednesday, February 11, 1998 5:26 PM
> 
>   I've been crawling around the Tyrrell Museum website (nice site, by the
> way) and find myself once again vexed with questions about dinosaur
physics.
>   While I'm going on about dinosaur physics, the Tyrrell had some
displays
> on pachycephalosaurs which I found curious.  
> At  http://tyrrell.magtech.ab.ca/tour/stegocer.html we see a scene
described
> as "A male stegoceras prepares to butt a rival in the ribs."  I have
often
> heard pachycephalosaurs described as head-butters, much like bighorn
sheep.
> Does this strike anyone else as peculiar?  Look at that flexible curved
> spine.  If the impact force decelerating that head is great enough to
> require such a thick skull (far thicker in proportion than the bighorns
seem
> to need) wouldn't the momentum of the body following the head fold up
that
> spine like a wet soda straw?  I don't know.  If someone handed me a club
> that was round and blunt on the end, but with knobs and spikes
surrounding
> the end, I think I would be more inclined to swing that club than thrust
> it--particularly if the handle was flexible.  (But then, I like to do
things
> the easy way.)
>From what I know, the spine was not all that flexible in pacycephalosaurs,
with some sort of interlocking mechanism to prevent twisting. Also no
cervical vertebrae are known from any sort of pacycephalosaur, so the neck
isjust a highly educated guess(as far as I know, I may have missed
something.) Also, are you suggesting that when pachycephalosaurs fought
intraspecially, they swung the sides of their heads together (I tried to
draw a liitle diagram at the bottom, its pretty bad.sorry.) or am I reading
too much into your mail?Thats interesting, but  the fact that the skull is
thickened on top as opposed the sides  seems to argue against this.

             Head-swinging Pachycephalosaurs
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                                                                 BHR