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Re: Whatever prima



At 01:19 PM 4/13/97 -0600, Jeffrey Martz wrote:
>      I also find the "its all covergence" argument a little puzzling.  To
>a certain extent its probably true; ornithomimids superficially look an
>awful lot like ostriches, and if the troodonts and dromeosaurs are really
>not that closely united among maniraptors then a lot of the birdlike
>features of the braincase, teeth and jaws of troodonts may be due to
>convergence as well.  However, even if there are a lot more dinosaur-bird
>convergences then we think, it seems a little odd to say that a group that
>shows a REALLY frequent tendancy to evolve birdlike traits would be LESS
>lkely to evolve a bona-fide bird.

   My understanding of convergence is that convergence occurs when
dissimilar animals lead similar lifestyles (my shorthand for "similar
evolutionary pressures").  What I have yet to see is a really thorough
explanation of what aspects of dromaeosaurid/avian lifestyle would be alike
enough to cause convergence when it seems like dromaeosaurids and birds were
leading extremely different lifestyles. 

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