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Re: Senter 2006, Confuciusornis, and humeral mobility
Powered flight must not be the null hypothesis, and I have an open mind. I've
said before that gliding is plausible.
But you are right if you think I am biased towards powered flight for
My reasons include:
The overall anatomy of the animal: the small body, short legs, huge arms, strut
like coracoid, pygostyle, and big sternum with incipient keel, are thought to
correlate with flight ability (Chiappe et al. 1999).
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).
The fish found in the crop of one specimen (though it could have been carrion
found on the beach)
Now, the new evidence from Wang, Nudds, and Dyke that the arm length to primary
feather length ratio groups with ornithurines, and does not overlap with more
> The thing is that given the orientation of the glenoid and the
> supracoracoideus it can't stabilize the arm in the socket of
> Confuciousornis; modern birds (even with a cut supracoracoideus) still
> have the modern glenoid orientation, which provides better bracing to
> the humerus during flapping motion.
Please explain. How does the modern glenoid brace a moving humeral head when
the supracoracoideus is cut?
I too prefer to restrict Aves to the crown group, but I'm cooler with calling,
say, enantiornithines birds since the latter is an informal term.
It is hard to be convinced by the impressions of anatomists, because they so
often disagree about function. Hou, Chiappe, Clarke, and Norell have looked at
the pectoral anatomy and favored powered flight. Anatomists like Senter and
yourself have looked and favored gliding. I have never closely examined a
fossil of Confuciusornis myself.
I think that you and I might agree that the real problem is designing
experiments to test the functional hypotheses.
Senior Principal Preparator
American Museum of Natural History
(212) 496 3544