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RE: Archaeopteryx running



 
Jim Cunningham wrote:

> I didn't take any offense.  I just assumed you meant I wasn't
> interested in overall function.  I am.  All flying animals did other 
> things than fly, and most of those other things are equally important 
> to the welfare of the animal.  

And still are important.  However, at the earliest stages certain abilities
of theropods conflicted with the demands of flight and perching.  These
include grasping prey with the hands, and running easily over the ground
with the aid of a long tail and cursorial pes (including a short &
"out-of-the-way" hallux).  I think _Archaeopteryx_ endeavored to retain all
these skeletal traits and, at the same time, dedicate its integument to
aerial flight.  Modern birds took a different approach: they sacrificed
their ancestral grasping and cursorial abilities to focus on aerodynamics.  

However, the question which I've been dwelling on a lot lately is to what
degree did the anatomy and behavior of little theropods help or hinder (a)
the development of the wing and (b) the decoupling of the forelimb from
predation - (a) and (b) being closely associated.


> However, I do prefer that the 
> assumptions made about flying animals actually be consistent with the 
> ability to fly -- note that I'm not saying that your thoughts are 
> inconsistent with flight ability, indeed, just the opposite
> -- but I have noticed occasional assumptions by others that would make
> flight far more difficult than it actually appears to be.

If the earliest stages of aerial flight simply involved the predator leaping
into the air (either from an elevated site or as the culmination of a short
sprint), do we really need to be too concerned with aerodynamics?  I'm not
saying aerodynamics were not important - God forbid!  Quite the opposite.
Aerodynamics came up whenever the predator tried to make its leaps higher or
longer or more precise - such as for snatching prey.  BUT - I think
_Archaeopteryx_'s "mosaic" anatomy (feathers vs skeleton) tells us that the
first birds were prepared to "hold back" on improved flight abilities in
order to retain the superb ground-running and prey-catching abilities given
to them by their maniraptoran ancestors.

As I said, later birds took a very different path - and the world is a much
better place for it.



Tim

------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163