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Re: Whatever prima



>    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. 

     I'm not certain if the term "convergence" can apply to just
morphological similarity, or only to similarity of form as a direct result
of function.  I used it in the formed context, since there is no way to be
certain if birds and troodonts evolved thier birdlike characters for the
same reason (assuming it WAS convergence).  
     As far as the similarity between dromeosaurs and _Archaeopteryx_ are
concerned, if they did get thier features from a common ancestor it
still doesn't entirely solve your dilemma; they are different animals
with different lifestyles.  For what sort of lifestyle did those traits
originally evolve, and for whom are they holdovers (or preadaptive for
something else)? I am starting to wonder if there might be something to
the case that dromeosaurs are secondarily flightless descendants of
_Archaeopteryx_ (or something really close) after all.

LN Jeff
O-