Belly Ribs and air sacs

["Stephen V. Cole" <adbinc@arn.net>]

Ten years ago (the last time I bought a dinosaur book and went to 
Dinofest) Bakker was talking about finding belly ribs on a theropod 
(Trex?). Was this ever confirmed?

I'm an engineer, not a paleontologist, but as I understand it....

Mammals and reptiles have elastic lungs. Air sucked in, air spewed 
out via the same plumbing. Two way street, less efficient.

Birds have rigid lungs. Air is pulled into air sacks in the belly, 
then blow n out through different plumbing. I'm not sure if the air 
goes through the lungs on the inbound or outbound stroke, but the 
point is that air only goes one way through the lungs, which is more 
efficient and needed to fly.

Belly ribs are needed to make air sacs work. If T-rex (or raptors or 
other theropods) had belly ribs, they had air sacs, and if they have 
air sacs, they are warm blooded. Belly ribs are mostly cartillage 
(except on Sauropods due to size) and dont fossilize well, so the 
idea that theopods used bird-type lungs is controversial and not 
accepted by eveyone until proven.

In the ten years i was one, did anybody ever prove if theropods had air sacs?