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Re: Senter 2006, Confuciusornis, and humeral mobility



I am merely suggesting that some of these things are possible, but they
are not my preferred hypothesis. They can all be tested experimentally and
rejected or supported.

If Dr. Senter's observations about limited humeral mobility are correct,
there is still this rotational possibility for the flight stroke, yes.

I am not suggesting anything about other basal avialae at this point.

And, of course, bats as large as flying foxes fly just fine with short
sterna, small sternal keels, and humeral elevations around 25 degrees. We
could expect that, around the origin of the avialae, all sorts of unique
flight strokes and morphologies could have arisen, however briefly.
There's more than one way to fly.

To be frank I have trouble seeing Confuciusornis as a glider, incapable of
powered flight, for the following reasons:

1) No extant glider that I can think of has a wing with such a high aspect
ratio and pointed tip

2) No extant glider with a  mass within an order of magnitude of 180 grams
functions without a drag - providing tail

3) No extant glider I can think of feeds on fish

4) No extant glider has such elongated distal elements of the pectoral
limb. The pattern in gliders is to elongate the proximal elements of the
limb, not the distal ones.

Instead, to me, the shape of the wing alone suggests high aerodynamic
efficiency.

Again, I'd love to see someone like Kenny Breuer put a model of one in a
wind tunnel.

> Thanks Jason for a very comprehensive and thought-provoking response.
>
> If I'm understanding you correctly, you're saying that the short
> sternum, puny keel, prominent deltopectoral crest, and minimal dorsal
> excursion by the humerus were all part of a unique kind of flight
> stroke?  The kinematics of this flight stroke were found in basal
> birds like _Confuciusornis_, which (according to your interpretation)
> were limited to low-amplitude flapping.
>
>
> Cheers
>
> Tim