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Re: FEATHERS



In a message dated 96-10-07 17:33:59 EDT, znc14@ttacs1.ttu.edu (Jonathan R.
Wagner) writes (quoting moi):

> >understanding the evolution of insulation; the problem is understanding
> >specifically the evolution of structured feathers. This is where the BADD
> >theory goes _ad hoc_ on us.
>
>         As if evolution does not *always* go ad hoc?  Or are your arms still
> planning on turning into wings, senor Olshevsky?  ;)>>

Feduccia gives excellent evidence in support of the thesis that feathers
evolved for flight, and that contour feathers are modified flight feathers
rather than vice versa. Yes, the evidence includes _Longisquama_ and its
"pre-feathers." For example, there's the central rachis of the feather. Why
is it there? To stiffen the feather, for one thing. And why stiffen the
feather, if all you really need is insulatory fluff? To support the animal
aloft. And, since contour feathers are not for flying, why do they have a
rachis? Because they retain it from when the feathers first formed for
flight. Etc., etc. Much of Feduccia's work strongly supports BCF (that's one
reason I keep citing it).
 
> >It has begun to look as if avian ancestors (and other
> >dinosaurs) were active >ectotherms<, not endotherms after all. If this
> >turns
>
>         I would disaggree, oh jumper-on of bandwagons.  We simply have a
> debate once again... we have a profusion of evidence that dinosaurs were
>active creatures, and some decent arguments as well.  It hardly looks like
>there is a conclusion in sight.

Active I would agree, but that doesn't imply endothermy--just a good
circulation with a quadricameral heart. As far as jumping on bandwagons, I
wrote about dinos and avian ancestors as possible active ectotherms in both
previous printings of _Mesozoic Meanderings_, viz., that dinosaurs had some
kind of intermediate physiology, neither fully ectothermic nor fully
endothermic, and that endothermy must have evolved in stages rather than
springing up suddenly overnight.