Stegosaur plates as heat exchangers

[Joshua Dyal <j-dyal@geocities.com>]

One thing that bothers me about the idea of Stegosaurus using his plates
as heat exchangers are the plates of closely related genera.  Maybe
someone on this list can help me clear it up, or settle it in my mind at
least.

OK.  Stegosaurus stenops does have very broad, large plates with a lot
of surface area that could have worked well as heat exchangers. 
However, S. ungulatis has much narrower and smaller plates that wouldn't
have worked nearly as well.  Huayangosaurus, another setgosaur, had very
thin, pointed plates, that resembled spikes more than solar panels.  And
finally, Dacentrurus, another stegosaur, had no plates at all-- just
spikes all the way up his back.

So S. stenops had plates that could have made good heat exchangers, but
the examples I gave got progressively worse until Dacentrurus, who
couldn't have used his spikes for anything other than defense.  If all
of these genera are supposedly closely related, wouldn't it be extremely
odd that the plates (or spikes in Dacentrurus' case) would be used for
such diverse functions as defense in one genus and heat exchange in
another?  To me, this seems like very strong indirect evidence that even
big plated stegosaurs like S. stenops must have used the plates for
defense, but it seems most paleontologists preach the heat exchanger
doctrine.  This doctrine seems (to me, at least) to use S. stenops as
its model while ignoring other stegosaurs that would have been quite
inefficient at heat exchange with their narrow plates, that had very
little surface area relative to big plated stegosaurs.

Anyway, I've said my piece.  Now its up to everyone else here to show me
why I'm wrong.  I do want to know why it is that experts keep saying
that the heat exchanger idea is the preferable one, but I can't for the
life of me, buy into it.

Joshua Dyal
j-dyal@geocities.com