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Re: birds scales
>Then the real question here is which feathers came first. Are there any
>feathers which may represent the earliest type? I hope no one is suggesting
>that the flight feather was the first to appear!
Well, I don't see why not - the earliest fossil feather known, a single
imprint (from Australia?) appears to be one. I do not think that the
asymmetrical nature of the feather came forst, but the general shape and
structure may well have.
If anything, the flight
>feather is the most derived of the bunch.
I disagree. Yes, it is a highly derived structure but I suspect that we
lack the stages it was derived from. I suspect down and other feather types
to have been derived from it. The multiplumed nature of down is what I
would expect if a pinnate structure like a flight feather were to become
modified for insulation - otherwise I would expect that if its insulating
function evolved first down would be a single-branched structure like hair -
after all that is what we find on every other animal evolving such things
(mammals. pterosaurs, bees and other insects).
The point I am entertaining is
>the fact that down appears to be the most underived, this *suggests* that it
>came first (although I'd be willing to consider any alternate ideas).
As noted, I do not see this. Underived from what? As we have no idea what
an ancestral feather looked like it is impossible to determine what the
underived state is - but if it is anything like, say, the long scales on
Longisquama (and I'm not saying it is!) then I think the most obvious
derivation from such a thing would be a pinnate feather with a central
supporting rachis, not a tuft of down. For these reasons I suspect down to
>feathers appeared as an unique adaption to the problems of thermoregulation
>(being a highly derived hair-like structure), then the finest, and simplest
>feathers would represent the first ones to appear.
Down is NOT simple! If it evolved first as an insulating structure why
doesn't it look more like hair?
Besides, is there any
>evidence to suggest that a feature (once formed) becomes less complex through
>the life of the group? It seems to me that the opposite is true.
There are many such characters in nature. Consider the shell of
cephalopods, for example - complex, chambered and multilayered in
nautiloids, greatly reduced or missing in the later, derived squids and
octopuses. Many of the features of parasites become "simplified" as the
parasite becomes more highly-adapted to life inside another organism. Etc,
Ronald I. Orenstein Phone: (905) 820-7886 (home)
International Wildlife Coalition Fax/Modem: (905) 569-0116 (home)
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