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Re: Anchiornis huxleyi
Wouldn't one assume with feathers forming surfaces as shown in this fossil,
that they did serve an aerodynamic function, and were under aerodynamic loads?
And by "any kind of aerodynamic load produces it, absence of aerodynamic load
means it goes away,"
Do you mean the trait goes away in species that don't experience aerodynamic
loads (obviously, an Osterich doesn't have much need for asymmetrical feathers,
and birds that fly have both symmetrical and asymmetrical feathers),
or do you mean that somehow the feather needs to be be exposed to aerodynamic
forces at the individual level to become asymmetrical - Im fairly sure flight
feathers start off asymmetrical long before exposed to aerodynamic forces, I'm
just making sure I understand your statement clearly.
--- On Fri, 9/25/09, Graydon <firstname.lastname@example.org> wrote:
> From: Graydon <email@example.com>
> Subject: Re: Anchiornis huxleyi
> To: firstname.lastname@example.org
> Date: Friday, September 25, 2009, 2:31 PM
> 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
> -- Graydon