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Re: Resolving the Digit Loss Debate?



In a message dated 6/8/01 2:23:48 AM EST, qilongia@yahoo.com writes:

<< George proposes that the wing was selected for early in dinosaur
 evolution, and that this is what drove manal digit reduction.
 This can be tested in examining the limbs of basal dinosaurs and
 their closest outgroups. >>

You must remember that the earliest dinosaur wings retained the plesiomorphic 
grasping function and did so at least to the common ancestor of the 
ceratosaurians. The flying function evolved gradually and incrementally on 
top of the already present grasping function, so the earliest wings would not 
have anatomically resembled the highly modified forelimbs that birds possess 
today and certainly would not have functioned like them. There are no 
forelimbs like these in extant animals that I know of; it is perhaps our job 
to reconstruct what these forelimbs were like from the fossil record of early 
theropod descendants of these dinobirds.