Brian Switek reports on a study that investigated bony features correlated with lung morphology in birds and crocodiles, to see how much dinosaur lungs resembled birds: “Dinosaurs Had Birdlike Lungs”. Birds have pretty efficient lungs, and while researchers already knew that many dinosaurs had air sacs similar to those of birds, that didn’t fully answer the question about the lung morphology.
The bottom line is that dinosaurs probably had lungs that were similar in morphology and function to those of living birds.
This doesn’t mean that all dinosaurs were just big birds. (Very non-bird like dinosaurs like Triceratops were part of this study, as well as those closely related to the origin of birds.) Rather, as the anatomists point out, the results indicate that the ancestral condition for dinosaurs was “a dorsally immobile lung, strongly partitioned into gas-exchanging and ventilatory regions.” Modifications from that basic setup - perhaps kept conservative in ornithischian dinosaurs and highly modified with air sac systems in saurischians - allowed for the respiratory diversity that paleontologists are now assessing and studying.
This is one of those anatomical observations that is very difficult to examine with the kind of evidence left from dinosaurs, and yet to most people it probably seems like it should be obvious.
I’m reading today about Neanderthal ribcage morphology, and that’s another issue that many people have written about in the past, but the evidence from most fossils just does not provide enough evidence to be sure about the overall shape and function of the anatomical structure.
It’s great when scientists can put together a more synthetic view that draws upon a broad spectrum of evidence.