Possible air sacs in theropod dinosaurs?

Yes, plenty of theropod dinosaurs (and sauropods!) have clear indications of air-spaces in their bones.  The reason that this was widely reported when it was discovered in Majungatholus is that this animal is a member of rather a primitive theropod group, whereas air-spaces are much more often seen in more advanced theropods, including spinosauroids, allosauroids, and many coelurosaurs.

What's more interesting is that, because similar air-spaces are found in the vertebrae of sauropods, it seems likely that they were produced by the same mechanism in both groups.  This suggests that the air-sacs in the soft-tissue that carry air to the hollow bones in birds (and other theropods) were in place at the time of the sauropod-theropod split.  And the presence of those air-sacs in turn suggests that even the most primitive sauropods and theropods (and their common ancestor) likely had a bird-style respiratory system, with a flow-through lung.  Now isn't that an impressive amount of conjecture to get from a few holes in some bones?  :-)

Last edited by Mike Taylor (2nd Mar 2007 09:07:06)