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Re: Stegosaurus




On Sat, 10 Jun 1995, James Shields wrote:

> >Does anyone know how the stegosaur plates are arranged? Is it paired,
> >alternating or flapped outward or possibly double rowed? I think
> >that they are alternating but can be flapped outward by muscles in
> >it's skin.
> 
> The honest answer is "No, nobody does for certain."
> 
> The problem is that the plates were held on to the bone by muscle and
> cartilege. When these rotted away, the plates just fell away. There doesn't
> seem to be a lot of agreement about exactly how they were attached (other
> than they were attached to the spine).
> 
> I think we have a better picture of "Spiky" stegosaurs such as Kentrosaurus.
> All the reconstructions I've seen show two rows of spikes (does anyone know
> the reason for this? Are the spines more firmly attached). This is possibly
> the reasonigy behind reconstructions of Stegosaurus with two rows of plates.
> 
> Personally I kind of favour the single row, just because it looks better
> (very scientific, eh?).
> 
> James Shields  -  jshields@iol.ie  -  http://www.iol.ie/~jshields
> -------------------------------------------------------------------------------
> And when the ark was finished Noah said unto Elvis, "What do you reckin?"
> And Elvis checked out his own cabin and shook his head saying "poky".
> And so did they knock several walls through and install a jaccuzzi.
> And when it was all done Noah scratched his beard and said, "We don't have
> room for all the animals now."
> And Elvis perused the livestock list and in his wisdom said, "Lose the
> dinosaurs."
>         -Robert Rankin, The Suburban Book of the Dead
> 
> 

James -

        We _do_ know the arrangement of _Stegosaurus_ plates, for sure, 
now!  Tahnks to the 85% complete specimen we of the Denver Museum found 
in '92, articulated with the plates in the correct positions, we know 
that _Stegosaurus_ had two rows of alternating plates.  The plates in the 
new specimen partially overlap:  if there were two parallel rows, they'd 
entirely overlap, and if there was only one row, they would only barely 
or not at all overlap.  Second, there is a great deal of matrix between 
the plates in the new specimen, indicating that in life they were 
separated by a span of space.  If the animal had only one alternating 
row, the plates would overlap only slightly, and not have such a space 
between them.  Thus, the only solution left is that they had two 
alternating rows!

        Apologies to all others on messages to which I haven't responded; 
my modem was recently "zotted" by lightning, and is being repaired!  I'm 
on another, yucky (!) non-SLIP/PPP terminal at the moment.  Be back in a 
couple of days!

Jerry D. Harris
Denver Museum of Natural History