Evolution of bird lungs from reptile lungs impossible?

My memory is a little sketchy about all of this but one thing I do remember is that reptiles are polyphylogenic - that is they do not have a recent common ancestor. They are kind of a catch-all group with some of the grouping based on derived rather than acquired characters. In other words, it is not particularly helpful to talk about birds evolving from reptiles - which reptile? Furthermore, it is not clear how closely related dinosaurs were to current extant reptiles. Furthermore, this whole discussion seems to be veering into the logical fallacy of "argument from ignorance" - if we can't logically explain it, it didn't happen. Lungs and circulatory systems are soft body parts - they don't fossilize well. So it is difficult to extrapolate much about lung morphology of extinct ancestors/relatives. I would think about the best we could do is use DNA analysis to establish the closest extant relatives (presumably some "reptile") of birds and go from there.

That should rock the socks of the "no transitional species" crowd.

In my opinion convergent evolution is the biggest problem the creationists (and fellow travelor IDers)have. As soon as it can be shown that a problem (in this case sustained flight) can be solved in more than one way, it makes the irreducible complexity idea all the more untenable.