Re: NOVA problems

[MICHAEL HABIB <habib@jhmi.edu>]

"People are doing double back flips to explain away how the rear airfoil, 
whose area at least matched and may have exceeded that of the arm wings, was 
not 
used in a fairly conventional manner with wild and convoluted postures and 
poses." 

Yes, they certainly are.  However, we need to consider what is meant here by 
"conventional".  The backflips are occurring in an attempt to make the hind 
"wings" into airfoils that support weight in a steady glide, in a fixed 
position.  As best I can tell, this just isn't plausible.  The feathers are 
unlikely to be used "backwards" as you mentioned, the hind limbs cannot be 
substantially sprawled, and the feathers are very unlikely to have oriented 
laterally from the tmt as in the C&T version.  The large area suggests that the 
hind foils had a substantial aerodynamic action, but the morphological 
constraints and shape of the effective "tip" on the hind foils mean that they 
were probably not classic wings.  Instead, there are other, perfectly simple 
ways in which such foils can be aerodynamically active and advantageous (one of 
which was already mention: redirection of thrust vectors via effects on the air 
accelerated by the forewings).

"Yet in their wind tunnel tests they concluded that the bizarre arrangement 
with the legs paralleling the tail was 
the most effective, even though the foot borne primaries are oriented so that 
the trailing edge is acting as the leading edge! Gosh, one would think that if 
the legs were being used in such an adsurd manner, at least the development 
of the feathers would have been selected for them to be at least oriented in 
the proper aerodynamic manner. Duh."

You'd think.  Although, just to play devil's advocate, developmental 
constraints could limit the orientation of hind foil feathers to those that are 
homologous with the forelimb feather arrangment.  That said, I would expect 
such a constraint to simply prevent the aforementioned bizarre position, rather 
than constrain the animal to using the feathers backwards.

Cheers,

--Mike


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu