Re: Plate movement in Stegasaurs

[Nick Longrich <longrich@phoenix.Princeton.EDU>]

On Tue, 9 Jul 1996, Mickey Rowe wrote:

> rstephen@cswnet.com (Roger A. Stephenson) wrote:
> 
> > It would seem that without some movement [of stegosaur plates -- MR]
> > the alleged radiator effect would be lessened.
> 
> The comparison with dog hair isn't terribly appropriate.  The plates
> could easily change their radiative properties via pigment migrations
> and the selective opening and closing of the blood vessels feeding
> them.  Any flapping-mediated increase in heat transfer would be
> negligible in comparison.  Unless you propose that they spun around
> like fan blades...

        The best guess is that these were bony plates covered in horny 
material like a croc's scutes, right? Do modern animals change the color 
of horn structures in this way?
        Now, the implication that usually goes along with Stegosaurus 
using its plates for heating/cooling is that it was an ectotherm, or that 
they are radiators and not heaters, so I just have a few questions points on 
that subject:

a) are there any cold-bloods that actually use these surfaces? Not 
everything that lived in the past has a modern counterpart (rearing 
browsers seem to be an example of this) but are there ANY lizards or 
reptiles that actually use fins for heating/cooling?
b)There ARE a few endotherms that have specialized radiator fins, 
among them jackrabbits and elephants.
c)There is a variable-temperature endotherm that warms itself in the 
morning by turning its side to the sun, and cools in the day by turning 
its head to the sun, it lives in the desert, and it's called a camel.
d)I read somewhere that modern ungulates manage to dump a lot of heat 
through their horns, so if the plates are horn-covered, they'd likely 
make for pretty good radiators.
        I'm not trying to restart a debate we'll never finish, but I'd 
just like to make the point that thermoregulatory plates might be 
consistent with fully endothermic dinos, even if they are used for 
heating -we might just be dealing with a variable-temperature endotherm, 
like a camel. 
        nick L.