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Re: Anchiornis huxleyi
On Fri, Sep 25, 2009 at 02:24:59PM -0700, Erik Boehm scripsit:
> Are we sure its a Troodontid?
> If its feathers were symmetrical and it was a troodont, then that
> means asymmetry in feathers evolved twice, as Microraptor and birds
> had/have asymmetrical feathers.
Asymmetry in feathers is not a stable character; any kind of aerodynamic
load produces it, absence of aerodynamic load means it goes away, it's
obviously plastic under selection.
You can postulate that the developmental machinery to produce asymmetry
is a significant character, but we can't find that in a fossil.