Originally Posted by Thralni

Well of course you're right, but I'm not suggesting there's a straight line here. I realize my wording could have been mistaken to literally mean that.

I'm looking at the basic plan of the snake lung, and whether general patterns of expression of several key genes in mammalian lung development are also expressed in similar locations in snakes. If this is the case, one can presume evolutionary conservation of some function of these genes. If not, it'd be interesting to know how their patterns of expression might have changed, for it might be at the basis of subsequent evolution to a branching tree, from a blind ended sack, as is common in non-archosaur reptiles. Indeed, next steps would be to also include birds, crocodiles, etc, for a full evolutionary study.