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Re: CNN on Lungs and Feathers



>John R. Hutchinson wrote:
>
>> Also, Chris Brochu has previously pointed out that a posthepatic diaphragm
>> may be a valid synapomorphy for the Archosauria, which is an interesting
>> point.
>A *post*-hepatic diaphragm?!  As in a diaphragm caudal to the liver?  How
>does this work?

More or less the same way it does in us, only behind the liver.  In living
crocs, the diaphragm attaches to the pubis and, when it contracts, it yanks
the viscera back with it, like a piston.  This expands the thoracic cavity.
The functional details are different in adult birds, in whom the pubis is
immobile and backturned, but the placement and ontogenetic histories (as
far as I can tell) are the same.

BTW the original observation on this wasn't by me - it was by Jacques
Gauthier.


chris

=-=-=-=-=-=-=-=-=-=-=-=-=-=
Christopher Brochu
Department of Geological Sciences
University of Texas at Austin
Austin, TX 78712

gator@mail.utexas.edu