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RE: Combined answer Archaeopteryx running...



Jim Cunningham wrot: 

> > However, at a certain point (probably early in the Pygostylia) it
> > became advantageous to dedicate the manus and carpus to flight, so
> > both were absorbed into the wing.
>
> Then why did pterosaurs retain the manus all the way to the K/T?

The long fingers of pterosaurs supported the wing.  Also, we don't have the
pterosaur equivalent of _Archaeopteryx_ to establish what changes the manus
did go through in early pterosaur evolution.  Did the immediate ancestors of
the Pterosauria retain a prehensile manus, or was it absorbed into the
flight surface from the get-go?  

> I would agree that they are inferior to SOME pygostylians.  

I would say _Archaeopteryx_ was aerodynamically inferior to MOST
pygostylians - living and extinct.  I don't even think Archie's flight
capabilities were adequate even for hunting on the wing.

> But I suspect they were quite adequate for the use the animals actually
> put them to.  

Definitely.  Although Archie looks ungainly and primitive compared to modern
birds, it was a marvel of evolution - and not just from a teleological
context.  The development of wings opened up a universe of possibilities for
small coelurosaurian hunters.

> And some pygosylians have flight capabilities inferior to 
> archaeopteryx.

Agreed.  

>This is the point I've been trying to make, with the exception that I
>don't believe archie's anatomy was particularly conservative.

I DO believe Archie's anatomy was conservative - at least osteologically.
Again, I think Ostrom is spot-on.  Stripped of its feathers, one would be
hard put recognizing _Archaeopteryx_ as a flighted bird.  The skeleton of
Archie is that of a rather unspecialized maniraptoran.  The feathers, of
course, are a whole different story...

> And the lack of a hand precluded the later pygostylians from some
> grasping maneuvers.  One life style is not inherently 'better' than the 
> other.

Agreed - and I was careful to include both these points in my last post
(though I think you expressed it much better than me).  


Tim




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

Timothy J. Williams 

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

Phone: 515 294 9233 
Fax:   515 294 3163