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Re: four winged Archaeopteryx
On Wed, Sep 27, 2006 at 05:05:20PM -0700, Jaime A. Headden scripsit:
> But even so, lack of evidence cannot be used to propose a function. We CAN
> argue that Archie had such muscles and ligaments, but it becomes empty
> speculation without primary data to support it. Do any other long, bony-tailed
> animals possess muscles and ligaments which are used to motivate the
> in the fashion suggested? I have not seen any, and mammals, which also evolved
> their tail musculature from the same amphibian-like root-stock as did
> (and specifically here, birds), do not possess nearly the same integument that
> would be shape-adaptable save for, say, porcupines or maybe cats and
> though these muscles are dermal in nature.
Feathers started as insulative structures, not aerodynamic structures.
All known birds can fluff their insulative feathers, and it's very
hard to see how a non-mobile insulative structure could survive
selection pressure, so the least hypothesis is that the proto-feather
could move. Not a lot, but there would have to be some mechanism to
raise and lower it to control the amount of trapped air.
So, in the pre-Archie proto-bird, the one that didn't have aerodynamic
feathers yet, the defeault case is a mobile feather, no matter where it
Since an _immobile_ aerodynamic feather doesn't make sense from an
aerodynamic standpoint, evolving from a mobile insulative feather to an
immobile aerodynamic feather is a very strong claim.
What the mobility mechanism was we don't know, and probably cannot know,
but the idea that there necessarily wasn't one at all is an awfully