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FW: Anchiornis huxleyi

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A poor powered flyer and distance glider maybe BUT=2C I seriously doubt tha=
t asymmetric feathers would have developed under any other circumstances th=
as a purely aerodynamic function. You have to start somewhere. (Would there=
 be any other type of selective pressure that would result in asymmetrical
vanes?? I'm not aware of any). --dale
> Date: Fri=2C 25 Sep 2009 17:57:04 -0400
> From: oak@uniserve.com
> To: erikboehm07@yahoo.com
> CC: dinosaur@usc.edu
> Subject: Re: Anchiornis huxleyi
> On Fri=2C Sep 25=2C 2009 at 02:43:33PM -0700=2C Erik Boehm scripsit:
>> Wouldn't one assume with feathers forming surfaces as shown in this
>> fossil=2C that they did serve an aerodynamic function=2C and were under
>> aerodynamic loads?
> I think the absence of asymmetric remiges is a powerful argument that
> the Anchiornis huxleyi was neither a powered flier _nor_ a distance
> glider.
> Contour feathers form aerodynamic surfaces=2C in the sense of providing
> streamlining=3B I think it's perfectly plausible to suggest that a small
> theropod with the feather pattern observed in this case derived benefit
> from streamlining but not from exerting force through interacting with
> the air. (Or it benefited from a cryptic shape=2C or being able to make a
> particular display in breeding season=2C or being able to look big=2C or =
> snaggers=2C or snowshoes=2C or something of that character as well.)
>> And by "any kind of aerodynamic load produces it=2C absence of
>> aerodynamic load means it goes away=2C" Do you mean the trait goes away
>> in species that don't experience aerodynamic loads (obviously=2C an
>> Osterich doesn't have much need for asymmetrical feathers=2C and birds
>> that fly have both symmetrical and asymmetrical feathers)=2C
> This.
> Note that you need a truly flightless bird to lose the vane asymmetry in
> the remiges=3B flightless ducks will do the run-across-the-water thing=2C
> with the wings providing thrust=2C for example=2C and so keep the asymmet=
> remiges. Really flightless birds like ratites and some rails lose the
> asymmetric remiges.
> I should certainly have said "any kind of aerodynamic load on a
> thrust-producing bird wing"=2C rather than the rather hasty version I did
> write.
>> 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=2C I'm just making sure I understand your
>> statement clearly.
> Flight feathers develop with the flight asymmetry whether or not the
> bird is flying. (the Metro Zoo has a one-winged barred owl=2C and the
> feathers of the remaining wing come in entirely suitable for flight=2C fo=
> example.) So=2C no=2C didn't mean this version=3B sorry for the lack of
> clarity!
> -- Graydon                                      =0A=
Internet explorer 8 lets you browse the web faster.=0A=