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Re: BCF and BADD



>Right.  However, it is highly unlikely that flight feathers are going to=
> sprout from some theropod's arms, there will have to be a few transitional=
> steps.  From this, we can deduce the existance of contour feathers. =
> Besides, contour feathers are considerably softer than flight feathers, we=
> would expect differing (or no) preservation.
>
>Rob

I do not think we can make any such deduction.  First of all, as another
correspondent pointed out, Confuciornis had contour feathers and apparently
there is some suggestion on one Archaeopteryx specimen that it, too, may
have had them.  But all this shows is that the two were both present, not
which came first or how.

Others have proposed that the transitional steps to feathers may not have
been insulating structures but stiff vane-like scales (possibly used for
gliding and/or display, but lacking specimens, who knows?).  These MAY have
resembled the peculiar structures of Longisquama, but the latter are not
placed properly to have been direct homologues of flight feathers.

In fact (in the absence of evidence) one could speculate that the unique
structure of feathers evolved as a way of lightening and softening flight
feathers while enabling them to retain their basic shape - ie  as  a direct
breakdown of a single-piece scale into a series of linked components (the
barbs and barbules).  Had they evolved primarily as insulating structures I
would have expected them to resemble the hairs of pterosaurs, mammals,
bumblebees or even some plants - basically simple single-shaft structures
forming a thick overlapping layer - rather than the complicated
barb-and-barbule arrangement of true feathers.  Derive them first as remiges
or rectrices - whatever they were for - and a further degeneration and
modification of structure could produce contour feathers, down, filoplumes
etc etc.

I don't know  how it happened, of course - but neither does anyone else, I
suspect!
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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