For LungFish see for instance:
http://whfreeman.com/life4gif/ch41/4111_1.gif
http://whfreeman.com/life4gif/ch41/4111_2.gif
The idea is that the mammalian lung evolved from the swim bladder.
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From: Donald Howes[SMTP:dhowes@ansc.une.edu.au]
Sent: Wednesday, August 05, 1998 4:25 PM
To: evolution@calvin.edu
Subject: lungs
I have a question, how did different types of lungs and other breathing
stuff evolve? I don't see how it could be an advantage to have a partly
developed breathing system? A bird for example has an extremely complex
system that allows it to breath while flying, how could something like that
evolve? And the change from gills to lungs, how did it happen?