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RE: Evidence For a Feathered Velociraptor...



Tim Williams (twilliams_alpha@hotmail.com) wrote:

<IMHO, the fact that _Velociraptor_ has quill knobs and clearly did *not* fly,
adds an element of doubt to the idea that _Rahonavis_ was capable of powered
flight because it had quill knobs too.  (I know the presence of quill knobs is
not the only evidence in support of powered flight in _Rahonavis_, but it is
one of the most compelling).  Also, the quill knobs of _Velociraptor_ (and
maybe _Rahonavis_ too) may be associated with the need to securely anchor the
forelimb feathers during prey capture.  In this case, the "external pressure"
mentioned by Michael would be the struggling prey (e.g., _Protoceratops_).>

  In addition, the fact that features such as this appear and that some
features of obviously nonflying animals show up optimized in animals that can
fly, even ancestrally, does not mean the features ARE flight-related. Thus, an
animal that retained features of an ancestor who was exapted for, say, WAIR
that had other descendant forms that became volant does NOT mean that animal
was secondarily flightless.

  And the phylogeny seems to support this. It looks as if *Archaeopteryx* is a
descendant of a nonvolant taxon which also gave rise to dromaeosaurids, but
this ancestor was not a flyer. The features that ancestor possesses that were
exapted by *Archaeopteryx* and birds (maybe on the same lineage, maybe
separately) were also present in the earliest dromaeosaurs, namely
Microraptoria and Unenlagiinae. The latter may even have used these features to
develop flight on their own. If insects can do it, why can't theropods?

  Of course, the reverse is also possible: You can get a singular lineage of
volant theropods that continuously lost flight, and this may also explain the
evidence, but doesn't tell us how quill knobs show up in a non flyer when
ancestral taxa (including a volant taxon like *Archaeopteryx*!) lack them. How
else do you explain ratites and other such phenomena? Except, of course,
functionality, which works the other way as easily.

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


       
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