Evolution of bird lungs from reptile lungs impossible?

Recently I am stumped by a challenge posed from a creationist in my local evolution mailing list. The creationist said that bird lungs cannot evolve from reptile-lungs, due to very different designs. Reptile lungs, like our mammalian lungs, has only one air passage in which air comes in and out, while modern bird lungs has two passages, for the inflow and outflow of air. The argument mainly comes from here http://www.harunyahya.com/evolutiondeceit06.php under the heading 'Special Lungs for Birds'.Naturally I would look for some studies concerning possible evolutionary scenarios for this, but so far I've been disappointed because the only ref I found is thisRuben, John A, et al (1997). Lung Structure and Ventilation in Theropod Dinosaurs and Early Birds. Science 278(5341): 1267-1270.(Link to html version of Ruben et al 1997):
http://cas.bellarmine.edu/...structure_and_ventilation_i.htmin which the authors claim this:"Recently, conventional wisdom has held that birds are direct descendants of theropod dinosaurs. However, the apparently steadfast maintenance of hepatic-piston diaphragmatic lung ventilation in theropods throughout the Mesozoic poses fundamental problems for such a relationship. The earliest stages in the derivation of the avian abdominal air sac system from a diaphragm-ventilating ancestor would have necessitated selection for a diaphragmatic hernia in taxa transitional between theropods and birds. Such a debilitating condition would have immediately compromised the entire pulmonary ventilatory apparatus and seems unlikely to have been of any selective advantage."which adds to the difficulty because birds are now also supposed to have lost the diaphragm-ventilating condition.Also, I am not too familiar with bird anatomy so I cannot tell if the argument itself is valid. Do birds actually have that kind of lung?So should we admit defeat to creationists on this point, or does anyone know how to refute it? Please don't suggest that I use the 'lungs don't fossilise' argument, as this will only be seen as evading the challenge.This topic would go into 'Biological Evolution'.This message has been edited by Andya Primanda, 06-22-2005 05:18 AM

Thanks Mr. Jack. Somehow I get the impression (from that Harun Yahya page) that birds have two separate windpipes. Of course this is not true (I should confirm this... *slaughters a nearby pigeon*).I'll see if I can get this to my opponent.

Update from me. My opponent claimed the whole bird respiratory system is IC. But I managed to defuse his IC argument [he claimed birds cannot fly without the one-way airflow system] by pointing that bats don't have them, and they still fly. Still awaiting answer from him for that one.

Can you read Bahasa Indonesia?