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forwarded from Jim C...



I'm posting this for Jim Cunningham, at his request. I guess he's having
computer problems...

>To all,
My mail has been bouncing, and I don't know if this made it to the list or
not.
If it has, I apologise for sending it twice.
JimC

> > Krzic wrote:
> >
> > > I have just been notified about the new site devoted to Archaeopteryx.
> > > Looks quite good:
> >
> > snipped
> >
> > I quote from the website:
> >
> >     "Thomas points out that fossils of Caudipteryx, a primitive
> >      feathered cousin of Archaeopteryx, have symmetrical
> >      feathers, which could provide enough drag to stabilize a
> >      short fall. But the ground-up and tree-down theories require
> >      the first birds to have evolved asymmetrical feathers, which
> >      can generate lift."
> >
A question to all.   Where did this concept first originate?  Symmetrical
feathers are perfectly capable of generating as much lift as an
asymmetrical feather.  They just require a bit more mass in the shaft
(and/or a larger shaft diameter) to resist the torsional pitching moments
generated about the symmetrically located shaft.  The extra weight
required in the shaft of the symmetrical feather isn't enough to affect
the flight mechanics or power required to fly, but might well be enough to
substantially impact the biological cost of the molt, which may have been
related to the eventual development of the asymmetrical flight feather.
However, don't expect the first flying birds to have asymmetrical feathers
(though they may have), and I'd recommend against rejecting any
possibility of flight in an animal simply because it lacks asymmetrical
feathers.  Asymmetric feathers are not a prerequisite for either the
trees-down or ground-up scenario, or any other hypothesis of flight
origins that I'm aware of.
Jim