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Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

david marjanovic

> The wings, at least, may well have become large enough for flight long
> before flight started. That's because the wing feathers of birds may well
> have evolved for brooding and/or display rather than any aerodynamic
> function.

   I don't really buy this idea, and your statement "rather than any 
aerodynamic function" is why. If you look at modern flightless birds (like 
ostriches) that use their wings only for brooding and display, you will see 
that they are soft, downy structures with absolutely no aerodynamic qualities 
at all. True flight feathers are complex structures that have to be constantly 
maintained via preening. Since an animal can not evolve an organ before its 
use, I doubt these display/brooding feathers would be the kind of complex 
difficult to care for structures we see in modern birds. The idea of a dinosaur 
trying to use a display/brooding feather like this for early powered flight 
reminds me of my little brother trying to fly with a large towel. In other 
words, i think it would be a complete waste of energy on the dinosaur's part. 
Using them for running would be pointless, as it would create unnecessary drag. 
However, an animal using structures like these to break a fall (parachuting) 
 a high place would make perfect sense to me. In this early stage, the feathers 
would not have genrate lift or thrust, just a high amount of drag.


> Sure. Still, if you do that for a living, then having a few extra
> adaptations like actual grasping feet would help -- would be selected for.
> We find the opposite in the fossil record. How come?

 I think people focus way too much on Archaeopteryx as being the possible 
origin of flight in Aves. Archaeopteryx could have been on the road to 
flightlessness and even been the ancestor to the dromaeosaurids for all we 
know. I think GSP made a pretty good case for something like this. The 
ancestors of Archaeopteryx, the possible TRUE ancestors of birds, could have 
been highly arboreal animals with more obvious adaptations for climbing. The 
fact that there were few trees in Archaeopteryx's's environment could imply it 
was adapting to an increasingly cursorial, flightless lifestyle and not the 
other way around. While not the direct ancestors of birds, arboreal forms such 
as Epidendrosaurus may be closer in appearance to what the true ancestors of 
birds may have been like.