Paleontologists have long known that sauropod bones were pneumatic (hollow and air-filled).
But as researcher Matt Wedel (here with a single C8 sauropod vertebrae) cautions in his collection paper, the pneumatic function of sauropod bones may not have started out exactly purposeful.
Although an untested hypothesis at this point, Wedel thinks that the sauropods’ pneumatic tail bones evolved randomly, much like humans sinuses, our own version of pneumaticity whose function remains unknown.
The haphazard location of holes along the tail furthers the notion they may have been selectively neutral. At some point, however, enough variation in tail pneumaticity likely existed for natural selection to pick up on the advantage of a lighter tail, just as it would favor a lighter and thus longer neck.