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Re: Senter 2006, Confuciusornis, and humeral mobility



Do you know of any gliders that do not have a caudal source of drag? I
mean a tail, abdomen, tentacles or other structure that is positioned
posteriorly from the main glide surface(s)? The only taxa I can think of
are gliding frogs, but perhaps their pes webbing is larger and provides
more drag than that of the manus. If a glider (and now I mean man - made
gliders also) was not stabilized in this way couldn't they end up spinning
like a frisbee?

Half of Confuciusornis specimens do not have tail feathers. Has anyone
ever tried one in a wind tunnel to see if it is stable or if it pitches
wildly and spins around the long axis of its wingspan?


>
> On Mar 22, 2011, at 4:53 PM, Jason Brougham wrote:
>
>> At least half of the specimens lack aerodynamic tail feathers, which
>> suggests that any aerodynamic capabilities would be unstable, advanced,
>> types rather than gliding which would probably benefit from  a good
>> stabilizer (like the long tail of Archaeopteryx).
>
> Just as a quick note, it is a myth that the tail of modern birds is
> primarily a stabilizer; it is also a myth that unpowered flight must be
> more stable than powered flight.  The long tail of Archaeopteryx would
> tend to act as a passive stabilizer because of the specific effects on the
> drag profile it would tend to promote.  It has been suggested that taxa
> near the base of a group that later develops powered flight might benefit
> from passive stabilization, as those organisms might lack the required
> neural architecture to control unstable flight.  To the extent that those
> stem-taxa might be unpowered, then basal gliders could be expected to be
> more stable than more derived members of the group (seems to be true for
> birds).  I don't mean to suggest that you, personally, were mistaken but
> only that the terminology regarding stabilization and gliding is often
> taken to mean something it does not (in both casual conversation and in
> published works, sadly).
>
> --Mike H.
>
>
>>
>>
>
> Michael Habib
> Assistant Professor of Biology
> Chatham University
> Woodland Road, Pittsburgh PA  15232
> Buhl Hall, Room 226A
> mhabib@chatham.edu
> (443) 280-0181
>
>


Jason Brougham
Senior Principal Preparator
Department of Exhibition
American Museum of Natural History
81st Street at Central Park West
212 496 3544
jaseb@amnh.org