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Re: Yet more on dinosaur quad climbers

On Jul 12, 2013, at 7:36 PM, Ruben Safir <ruben@mrbrklyn.com> wrote:

>> Indeed.  And in a similar sense, the early stages of shell expansion may not 
>> have been for armor, because the earliest changes in the turtle skeleton may 
>> not have conferred much protection.  Just as for feathers, a functional 
>> shift likely occurred.  Structures don't evolve for functions they'll have 
>> later.
> We are not talking about precursors and proto feathers, which were
> clearly NOT for flight.  We are talking about wings and flight feather.

Of course.  And the immediate precursor to flight feathers was presumably an 
"almost" flight feather - likely vaned, interlocking, and relatively large - 
but just short of the morphology required for aerial locomotion.  This is what 
I meant by a "precursor" in this context.  Some maniraptorans had small wings, 
but were not aerial animals in the strict sense.  Their near-flight grade 
feathers therefore presumably evolved in a non-aerial context.  This could 
still be a lift-dominated context, a drag-dominated context, or a 
non-aerodynamic context (such as display or protection).  It could also be a 
combination of any of those three.  

Regardless, there needs to be a mechanism to move from a relatively 
non-aerodynamically active feather to a highly aerodynamically active feather, 
and that is going to necessitate some morphology that is very nearly "good 
enough" for flight, but not quite.  Since an animal with such feathers wasn't 
flying, the feathers have to get at least that far without flight as a factor.


Michael Habib
Assistant Professor of Cell and Neurobiology
Keck School of Medicine of USC
University of Southern California
Bishop Research Building; Room 403
1333 San Pablo Street, Los Angeles 90089-9112
(443) 280-0181