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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.

Stephan Perry is one of the world's foremost authorities on septate lung
morphology.  His papers are definately worth reading.  However, don't
mistake the context of his statement.  In this section of the paper he is
trying to explain how it is possible to go from an unmodified (i.e.,
reptilian) septate lung to a highly modified (i.e., modern bird)
parabronchial lung-air sac system.  He is NOT referring to how these lungs
are ventilated; this is a completly different issue.
>
>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.

Birds do not have a postpulmonary diaphragm--a diaphragm is generally
regarded as an active structure.  They have a horizontal septum that
originated from the postpulmonary septum (found in lizards, turtles, etc. as
well), which itself originated from the transverse septum (see Dunker,H-R.
1978. General morphological princples of amniotic lungs.  Pp. 2-15, in
Respiratory function in birds, adult and embryonic [J. Piiper, ed.] and
references therein) .  The horizontal septum in birds (who have a
non-expansible parabronchial lung) is very different form the active
diaphragm in crocodilians.

>
>                       --John R. Hutchinson
>
>
>
TDJ
:-{)>
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    Terry D. Jones                             Voice:  541/737-6120     
    Oregon State University              Fax:      541/737-0501          
    Dept. of Zoology                         JONEST@bcc.orst.edu
    3029 Cordley Hall
    Corvallis, OR  97331-2914
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