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Re: Comments on _Longisquama_ in _Science_.



<So again, to be consistent, feathers or feather-like structures could have
evolved more than once.>

Yes!
There was another quote from the same group that the odds against feathers
evolving twice were 'astronomical'.  And?!  Even if true, this statement
does not prohibit feathers evolving more than once.
Parsimony is asserted to be the best way to evaluate potential cladograms,
and wouldn't it be most parsimonious to say that feathers evolved once?  I
know that analysis is based on a multiplicity of characters, though I would
like to ask if any small number of characters should be considered most
diagnostic?
Is it possible that in general the fewer characters used to identify a
particular group, the more likely an error in assigning species to that
group?
Regards,
----- Original Message -----
From: "Matthew Bonnan" <mbonnan@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Tuesday, June 27, 2000 6:55 PM
Subject: Re: Comments on _Longisquama_ in _Science_.


>
> ><That's important, Ruben says, because he and most other scientists think
> >structures as specialized as feathers must have evolved only once, almost
> >certainly in some ancient member of a vast group of creatures called
> >archosaurs.>
>
> Hmmm.  But according to Ruben, Martin, Feduccia, et al. the skeleton of a
> theropod and a bird could evolve twice while looking so similar and
sharing
> so many osteo characters?  This statement about feathers evolving only
once
> would seem inconsistent with their previous statements on convergence of
> body plans.  Furthermore, one could argue (as has been done, although I
> forget the reference) that endothermy evolved only once since it is also
> very complicated and yet it appears that mammals and birds (and perhaps
> dinosaurs and pterosaurs) all developed it.  So again, to be consistent,
> feathers or feather-like structures could have evolved more than once.
>
> Matt Bonnan
>
> "... Hey mighty Brontosaurus don't you have a lesson for us? / Thought
your
> rule would always last / There were no lessons in your past / You were
built
> three stories high / They say you would not hurt a fly / If we explode the
> atom bomb / Would they say that we were dumb? / We're walking in your
> footsteps ..."
> -- The Police, "Walking in Your Footsteps"
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