Re:Stego plates!!!

[morgan@montereybay.com (Morgan Family)]

>>This is just my humble opinion, but if stegosaurs had wanted to evolve a 
>>radiator, wouldn't it be easier to evolve a skin structure rather than a 
>>bone one?

>Not if the "bone ones" were already in place as a series of protective
>parasagittal spines. The earliest stegosaurs didn't have the thin, flat
>plates of _Stegosaurus_.

>>All modern radiators, mammalian or otherwise, are made of skin
>>and/or cartilage (correct me if I'm wrong.) =;:>__/. Plus, even if the 
>>plates *had* been radiators, wouldn't you expect them to be more rounded
>>and  not so narrow front to back(the stegosaur's front to back, not the 
>>plates') at the base? The plates also appear to have been *widened* a bit 
>>side to side, much like an artichoke leaf. I'm looking at a photo I took
>>at the Smithosian and, though I'm no expert, these widened areas look like 
>>the attachment sites for skin muscles. I think that the idea of the plates 
>>being a sort of mobile, keratin-covered armor is far more compatible with
>>their structure. Any comments?

>A typical advanced stegosaur plate stood on a broad, elliptical base that
>really doesn't admit of much movement when it is visualized as imbedded in
>the animal's thick skin. In life, the plates were probably passively movable,
>because they weren't physically attached to the skeleton, 

Maybe they could just waggle them from side to side by shifting their weight 
around - probably a good ploy for intimidating rivals and predators - and 
nifty addition to that spiked tail if they were ever threatened by a 
theropod. I wonder if they could rattle them against each other for an 
especially threatening effect...

>but there is no
>sign of any system of dermal musculature of the kind possessed by crocs (for
>example) connected to the plates. The plates did not contact one another;
>each plate was separate from its neighbors. The plates' rough appearance is
>due to their extreme vascularity: the bone of each plate was spongy-textured
>from the intricate network of blood vessels it contained. Presumably the
>blood passed through the plate for cooling (or warming) via this spongiose
>network.

>The shapes and arrangement of the plates were tested for cooling properties
>in wind-tunnel experiments in the 1970s, and it was found that the
>arrangement in which the plates alternated from side to side along the back
>did the best job of cooling the animal. This nicely accounts for this unusual
>arrangement in the Morrison stegosaurs and probably all the other advanced
>stegosaurs (family Stegosauridae), too.

So they were probably secondarily employed as radiators, like an elephant's 
ears, but I doubt that was their primary function.



Susie "Whaddaya mean the Mesozoic is over?" Morgan




"Actually, the mammals were responsible for the extinction of the dinosaurs
- The great archosaurs died laughing when our fuzzball predecessors began
distrubuting Jehovah's-witnessesque brochures on how the end of the Mesozoic
was coming."

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