Re: pneumatization

[Dinogeorge@aol.com]

In a message dated 9/3/99 10:14:43 AM EST, jwillson@harper.cc.il.us writes:

<< The only known groups of tetrapods with pneumatization are:
 
 1) Birds
 2) Pterosaurs
 3) Sauropods
 4) Theropods
 
 - right? 
 
 No mammals, no non-archosaurian reptiles? >>

You can add small prosauropods to this list. Marsh described Anchisaurus as 
having hollow vertebrae and limb bones. I think Ammosaurus also, if memory 
serves me. I think dinosaurs originated as small animals with some degree of 
skeletal pneumaticization that was subsequently lost in the larger 
prosauropods and ornithischians (a possible apomorphy uniting the two groups) 
but developed more extensively in sauropods and theropods independently.