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Re: Evidence For a Feathered Velociraptor...



On Wed, Sep 26, 2007 at 07:39:08PM -0400, ptnorton scripsit:
> Graydon wrote:
>> But I don't think it _is_ a correlation between quill knobs and powered
>> flight.  I think it's a correlation between quill knobs and aerodynamic
>> load on retrices.
>
> Exactly right, in my opinion.

Thank you!

>> We know there are other ways to deal with feather control and
>> anchoring, because there are modern volant species as don't have
>> quill knobs
>
> Really? Which ones? (I'm just curious, not questioning.)

"Tinamiformes, Phoenicopteriformes, and taxa outside of Ornithurae all
lack quill knobs", according to  "A new bird from the Upper Cretaceous
Two Medicine Formation of Montana", David J. Varricchio, Can. J. Earth
Sci. 39: 19-26 (2002).

I believe that means tiamous and flamingos; tiamous are not good fliers,
and flamingos aren't particularly good, but both do fly.

> It's worth noting that some extinct and presumably volant species,
> such as Archeopteryx, have (at least so far) not been found to have
> quill knobs.  This has always been troubling to me, since the
> biomechanical advantage of quill knobs seems to be to transfer
> aerodynamic forces from the feathers through the skeleton to the
> animal's center of mass.

I think it's fair to say that quill knobs are the preferred
biomechanical solution for transferring forces from wing feathers to the
skeleton in extant flying birds.

This had to have evolved in stages, though, and given the extant
examples, I don't think we can go from 'no quill knobs' to 'doesn't
fly'; I think we can go from 'no quill knobs' to 'flies less well than
terns or eagles' safely enough. :)

-- Graydon