Re: (LONG) THOUGHTS ON BIRDS etc.

[TomHopp@aol.com]

Greg Paul wrote a lengthy, and very illuminating dissertation on the dangers
of dogmatic interpretations in cladistic and phylogenetic relationships among
birds and dinosaurs.  I enjoyed it and strongly agree.  However, I would like
to pick at a small point.
   There may be a bit of dogma creeping in on the issue of certain of the
characters you describe as "flight-related," such as folding arms, robust
sterna, furculae and other "breast-strengthening" measures that occurred among
bird-like theopods and early birds.  Perhaps it is risky even to associate
these with flight, although the temptation to do so is understandable.
    As I have broached on this list recently, there is another cause that
might be responsible for these characters -- brooding.  As Mark Orsen and I
presented at Dinofest, brooding is a critical function for the wings of modern
birds that does not involve flying, and yet it DOES force certain anatomical
requirements on its practitioners.  A case can be made, as we have (our
manuscript for the Dinofest symposium volume can be considered in press) that
folded arms, strong sterna and breast musculature are required for any animal
that carries around a long set of arm feathers, even if flight is not at all
in the picture.  Our manuscript includes some photos of birds doing amazing
stunts with their wings to cover their babies.  Why assume this is a modern
invention?  It is just as likely to be the most ancient of reasons to have
long arm feathers. Furthermore, the practice must have brought some problems
along with it, such as stepping on your own feathers, dragging them in the
dirt, being blown away in a wind storm.  The response to such pressures
against brooding would have been to develop the characters you listed --
folding arms, strong chests, furculae -- long before flight was an issue.
        Where I see the above ideas being neglected is in the area of secondary
flightlessness.  As you said, parsimony should drive arguments as much as
possible, but multiple evolution of flight and flightlessness is not very
parsimonious.  If we try applying some brooding-came-first logic, then much of
the confusion goes away.  Your concept of "intense mosaic evolution" may be
right, but may not need to include secondary flightlessness, if most of the
traits you are calling "flight-related" are actually "brooding-related."
Since we can be pretty sure that secondarily-broodless animals would leave no
progeny, the animals unearthed to date may be telling a story of body forms
that all somehow relate to a basic "brooding-wing" that indeed is very bird-
like, but MAY OR MAY NOT have been of sufficient size and shape to permit
flight.
    Any thoughts?