Riojasaurus

[tidwell@ix.netcom.com (Virginia Tidwell )]

  A couple of weeks ago someone (I think it was Tom Holtz) recommended 
a paper by Jose Bonaparte on Riojasaurus. While studying the basal 
sauropoda I got sidetracked into the prosaurpods, so it caught my eye. 
The paper does have an excellent figure of the skull, although the text 
is a little hard to follow, being in spanish.  What characters 
designate this skull as primitive when compared to Plateosaurus?  
Also, is there any prosauropod material known from the southwestern 
U.S.?

               Virginia Tidwell