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Re: CNN on Lungs and Feathers



Happy New Year! More aspirin, please... thank you. On the subject of
archosaurs and air sacs: If you're eager to read more on the subject, one
paper to try is:

Perry, S.F. 1988. Functional morphology of the lungs of the Nile Crocodile,
_Crocodylus niloticus_: non-respiratory parameters. J.exp.biol. 134: 99-117.

A quote from pp.111-112:
"Furthermore, the tendency of crocodilian lung chambers to form arching,
tubular structures is reminiscent of developing avian secondary bronchi and
parabronchi.... It is possible to construct an approximation of the avian
lung-air sac system from the crocodilian structural type: sac-like cranial,
ventral, and caudal chambers become air sacs..." etc.

Not that transformational storytelling is empirical evidence, but the
similarity in developing archosaur lungs is striking. Frankly, it's silly
to compare adult morphs and try to connect them just by morphing the adults
and ignoring the fact that adults are towards one end of an ontogenetic
series. Developmental data are important, too, and the data are out there
in the literature (but not well synthesized in a phylogenetic context).
Also, Chris Brochu has previously pointed out that a posthepatic diaphragm
may be a valid synapomorphy for the Archosauria, which is an interesting
point.

                       --John R. Hutchinson