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Re: Phylogeny of Maniraptora



'Phugoid gliding' doesn't seem to be used quite in the usual aerodynamic
sense of 'phugoid'. I took it to mean that the airspeed is allowed to
build up to some number greater than necessary by increasing the sink
rate, and then the excess speed was converted back to potential energy
by climbing, in an oscillitory manner.  I could well be wrong in my
interpretation.

Re the gliding vs. flapping thing, when gliding you become more
efficient by substantially increasing the aspect ratio to reduce induced
drag.  Which also increases the moment of inertia about the shoulder
(and wrist).  When doing incipient flapping you find that it is much
more difficult when you also have to deal with increased moment of
inertia. Which implies that incipient flapping is easier for animals
that have relatively short wings and aren't good gliders. In a way, it
seems to me to be more likely that you'd see an early, short winged bird
evolve into Diomedes exulans than that you would see Dex evolve into a
short winged bird that does rapid flapping.  As an aside, Archaeopteryx
seems to be a fair to middlin' powered flapper as far as flight
performance is concerned.  It also seems to be a truly crappy glider. 
So which way would it be more likely to spend its time?

David Marjanovic wrote:
> 
> ----- Original Message -----
> From: "Tim Williams" <twilliams_alpha@hotmail.com>
> 
> > I was under the impression that the
> > Norbergs (among others) had demonstrated that a glider could start
> flapping
> > without being detrimental to gliding.
> 
> I have never seen a discussion of this (but of course neither the original
> papers from the mid-80s). It has become common to presuppose their
> conclusions, methinks, e. g. in the recent Naturwissenschaften paper by
> Chatterjee & Templin which praises phugoid gliding.
> 
> What does phugoid gliding actually mean? Dropping oneself from a height to
> gain speed before spreading the patagia?