[_ Old Earth _] One-way ventilation preceded birds and possibly even dinosaurs.

[Barbarian]

It turns out that monitor lizards breathe mostly by a one-way airflown in the lungs, depending on pores in the lung segments similar to the Pores of Kohn, found in mammals. This "collateral ventilation" occurs in humans if the bronchi are obstructed, but in monitor lizards, happens as the usual pathway. It is intermediate between human ventilation and that found in birds and some dinosaurs.

http://www.livescience.com/41881-lizard-breathing-evolution.html