It’s come up here a few times already–it’s hard to talk about sauropod vertebrae without bringing it up–but now it’s time to get it out in the open. In almost all sauropods, and certainly in all the ones you learned about as a kid, at least some of the vertebrae were pneumatic (air-filled). Now, this is a very strange thing. Most bones are filled with marrow, so if we find a bone that is filled with air, somebody’s got some ‘splainin’ to do.