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3 x Re: flight stroke (pretty short)



----- Original Message -----
From: "Waylon Rowley" <whte_rbt_obj@yahoo.com>
Sent: Monday, May 06, 2002 1:59 AM

> The elongate femoral feathers may prove to
> be gliding surfaces in Jehol Deinonychosaurs, though.

Would require the ability to sprawl.

> > I don't think so. Moving the wings downwards or
> > upwards _once_, or tucking them in,

Just a little, I meant, so that not so much lift is produced in front of the
cg. But I was thinking too much of an animal with a full patagium, like a
gliding squirrel, which is out of place here :-)

> If anything, raising or lowering the arms (and leaving
> them in that position) will just slow you down, and
> intensify the stall effect. Repetitive flapping is the
> only way to get your body level and keep it that way
> if you're gliding with a big heavy tail. At least
> that's how I see it.

I remember having read somewhere that "Ulla Norberg (1985) has shown how
slow flaps might overcome the problem" of the glide-fly transition, "but
there is no living animal that glide-flaps this way" or something like that,
I'll look up the refs. Maybe you are reinventing that :-) -- my prime
objection is: how does the animal get the idea (consciously, by instinct,
however) of flapping?

---------------------------
No idea how much lift (or drag, for that matter) Archie's tail could
produce. Certainly easy to test, but I don't know if anyone has done it.
---------------------------

----- Original Message -----
From: "Graydon" <graydon@dsl.ca>
Sent: Monday, May 06, 2002 9:48 PM

> You're assuming that gliding was the initial phase.
>
> This isn't parsimonious in a couple of ways.
>
> One is that in living birds, the good gliders are all highly derived
> forms; the basic bird wing, as per the bracket between tiamous and
> chickens, is a high output system for energetic flight.  This is not
> something one would expect a glider to evolve into.

To add some comments about the basic bird wing (as opposed to the basic
neornithine wing), I wonder why there are no real remiges on the upper arms,
just tertials to fill in the gap between the remiges and the body. Such a
gap is not seen in any certain glider I know of. It's not sure whether
*Archaeopteryx* or *Caudipteryx* even had tertials. The Confuciusornithidae
seem to have been flutterers incapable of slow flight, difficult manoeuvres
and soaring, because of their short wings (short arms, not feathers, that
is) and lack of an alula. The more basal, but probably more derived
*Sapeornis* looks sort of like a gull and, I trust the authors, is just as
specialized for soaring.

Same for the lack of climbing adaptations in early birds and near-birds --
well, the elongated grasping 3rd finger of Confuciusornithidae might count,
but no other well enough known dinosaur (ignoring the aye-aye dino) has such
a thing.