Re: Ornithodira, breathing with long necks

["David Marjanovic" <david.marjanovic@gmx.at>]

> What is actively transported that would keep these air sacs inflated?
> Oxygen? Nitrogen?  Carbon dioxide?

I'm sure active transport of such gases (except maybe carbon dioxide, but
this is rare in air) is neither possible nor necessary -- diffusion of air
through tissue is a very slow process. About how the air sacs were
inflated -- I don't know either, but since birds can do it...