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Re: bird evolution



In a message dated 3/18/99 12:43:04 PM EST, tkeese1@gl.umbc.edu writes:

<< There's a very clear transition in the fossil record from the basal
 dinosaurs/dinosauriforms to basal birds. Basal dinosaurs had five manual
 digits, then primitive theropods like coelophysoids had only four, and no
 claw on the fourth. Advanced theropods (tetanurans) lost the fourth digit
 as well, leaving them with three digits, like birds today. >>

I think the questioner was more concerned with the transition from small,
relatively dysfunctional or grasping forelimbs to large wings, not with the
transition from five-digit hands to three-digit hands (which is quite
straightforward and amply documented in the fossil record). This is a major
problem for the "ground up" theory of bird origins.