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Re: solnhofen



In a message dated 5/1/01 1:18:58 PM EST, graydon@dsl.ca writes:

<< 1) whenever the first bird evolved, the wing stroke had to be
 initially exapted from something; if that *isn't* a predatory grasping
 stroke, what was it?>>

A simpler wing stroke. A climbing movement. A fluttering movement. Take your 
pick; the fossil record is too poor to constrain even wild guesses. But the 
articulation of a dromaeosaurid arm and hand prohibits a >grasping< stroke.
 
<< 2) what part of a full, four phase wing beat *can* be co-opted as a
 grasping predatory stroke?  The adaptations for flight more or less
 force full extension of wings when used at or near full power; geese,
 frex, do threat displays without fully extending their wings but when
 they're trying to hit you with them have to fully extend them to
 generate any power. >>

Birds can fend off a predator by slamming it with their wings. Now imagine 
that the wing still has a set of two or three claws; >this< is where the 
dromaeosaurid/maniraptoran forelimb comes from. The wing stroke of modern 
birds is pretty much useless for anything else, so when a modern bird opts 
for secondary flightlessness, the wings usually vestigialize without function 
in its descendants.