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RE: stegosaur

 From: ornstn@hookup.net (Ronald Orenstein)
 > >          <Although the alternating plate arrangement is
 > >effective for thermo-regulation, I'm just not 100% convinced.>
 > >Nor am I (sorry, Jim).  First, Stegosaurus stenops, ...
 > >, is unusual among stegosaurs for its large plates. ..
 > >  An
 > >alternative hypothesis I propose is that the plates were used in
 > >display and species recognition.
 > >
 > Excuse me, Dr. Carpenter, but does this not assume that the other stegosaurs
 > were exposed to the same kind of climate regimes as S. stenops? 

They certainly lived in the same *area*, and more or less at the
same time.  ALL species of Stegosaurus come from the Morrison formation,
and only from it or its equivalents.

For an animal that size, there were not that many distinct habitats
available in the Morrison area.

Now, Huayangosaurus comes from a different area, and possibly a
different climate.

 >  Though I am
 > not trying to support the thermoregulation hypothesis, is it not at least
 > possible that S. stenops lived in an area (or behaved in a way) that exposed
 > it to greater degrees of heat stress than those experienced by its relatives
 > of equal mass?

Well, I suppose behavior differences could do it, but that seems
unlikely, as all stegosaurs were low browsers.  In an open, dry
habitat like the Morrison area, there are only limited amounts
of low browse.  This puts severe limits on the range of behavior
that would be viable in an animal like Stegosaurus.

Also, I will point out that the shape of the plates fits a classic
display mode - the "look how big I am" mode.  The fact is that the
plates make a Stegosaurus look *substantially* larger in lateral
profile, rather like a cat arching its back.
 > Presumably, of course, the plates could serve both functions
 > (thermoregulation and display).  Am I correct in thinking that there is
 > evidence that the skin over the plates was highly vascularized?

Yes, but that is not really as conclusive as it sounds, a display
organ might need vascularization to supply the pigment cells giving
it bright colors.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.