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Re: feathers, hair and Compsognathus
On Tue, 22 Oct 1996, Jeffrey Martz wrote:
> On the places where birds have feathers, thier skin is relatively
> smooth. If I am not mistaken, on birds that have lost thier feathers in
> some places (for example, the necks of living ratites), the skin there is
> also smooth (the legs? on all birds retain the scales, indicating
> that feathers were probably never present here). Birds being theropods after
> all (if you choose to call them that), it would seem strange for a secondarily
> naked skinned dinosaurs to have somehow reverted back to prominant scales
> when a smooth skin seems to do the job just fine in nekkid birds.
You could make fun of the birds because probably a third of
their evolution involves stealing features the theropods already had
(feathers, beaks, roosting on eggs, pneumatic skeleton, tridactyl pes, in
all likelihood, endothermy) and another third, reducing down features
the dinosaurs had (teeth, tail, fingers, etc.) and the remaining third is
the actual innovation and modification. (I'm being a little facetious in
saying the birds aren't original, yes, I realize they did some important
innovation and this is the pattern of evolution in general).
But if we view one of these patterns- the loss of dinosaurian
features to reduce weight- we might be able to understand where the
scutes went to, if they ever had both. It seems to me that
scutes, let alone the bone- reinforced ones, would be heavier than naked
skin or feathers, and so that, along with teeth, claws, big tails and
penises, scutes were one of the features done in with to reduce weight. So
perhaps ancestral dinosaurs did have both, just like some had both teeth
and beaks, but lost the heavy teeth over time (as did pterosaurs).
Pterosaurs- seeing as they appear to be archosaurs- almost certainlyu
would have had armor-plated ancestors, but it's no surprise we don't see
armor-plated pterosaurs either. So I'm suggesting that maybe the bird
ancestors did have scutes, only they were one more thing thrown away for
the all-important selectional pressure to reduce weight.