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RE: stegosaur

        John Schneiderman (dino@revelation.unomaha.edu) asked <is
it possible that there existed a row of keeled plates...between the 
large plates>.  No, based on three specimens with armor plates preserved 
in situ rule this out.  Two of the specimens also have matrix separating 
the plates of one side from the other indicating that the plates were 
not arranged along the midline. Assuming a minimum compaction of 50% for 
the mudstones, the plates are about 30 cm or more apart.  The plates of 
all three specimens also alternate.
          <I think that the large plates were firmly attached and
did not have as much motion capabilities..> I fully agree for the 
reasons given by Buffrenil, Farlow and Ricqles (Paleobiology 
12:459-473).  In addition, there is no evidence for rearrangement of the 
epaxial muscles along the back to a perpendicular position
in order to move the plates. 
          <Although the alternating plate arrangement is
effective for thermo-regulation, I'm just not 100% convinced.>
Nor am I (sorry, Jim).  First, Stegosaurus stenops, used in the initial 
study, is unusual among stegosaurs for its large plates.  Other 
stegosaurs (e.g. Huayangosaurus, Stegosaurus armatus ) have a mass equal 
to or approaching that of S. stenops.  They must have endured similar 
levels of heat stress, yet, they have much smaller plates.  An
alternative hypothesis I propose is that the plates were used in
display and species recognition.