Re: diplodocid radiation

["Tim Williams" <T.Williams@cclru.randwick.unsw.edu.au>]

> Is there any strong evidence of diplodocids present in Asia?  I am 
> belonging more and more convinced that Asian sauropods considered to be 
> diplodocids are now being placed within the Euhelopodids or some other 
> family (similar to diplodocids) as yet to be named.

There were certainly diplodocOIDs in Asia, at least in the 
Cretaceous - like _Nemegtosaurus_ and _Quaesitosaurus_ (both of the 
family Nemegtosauridae) and _Mongolosaurus_ (_incertae sedis_).  

_Mamenchisaurus_ is now considered to be related to other Asian 
sauropods like _Euhelopus_ and _Omeisaurus_, so it is certainly a 
euhelopodid.

> 
> P.S. this goes for Camarasaurids also.

_Euhelopus_ is (usually) no longer considered to be a camarasaurid. 

For _Tienshanosaurus_, the material is too incomplete to be sure what 
it is (one account says the hip-bones of _Tienshano_ are rather 
diplodocid-like).  Same goes for _Chiayusaurus_.

For _Opisthocoelicaudia_ - well, it depends on who you ask.  A recent 
review (by Paul Upchurch) allies it with the titanosaurids.  But, the 
caudal vertebrae of _O_ are opisthicoelous (the name probably gives 
that away), compared to the procoelous caudals of titanosaurids (the 
complete opposite).  

There seems to be some genuine titanosaurids in Asia during the 
Cretaceous - mostly "_Antarctosaurus_" species.  (As opposed to the 
type species for _Antarcto_, which is some form of diplodocoid, not 
titanosaurid.)

There's no proof that _O_ is the same sauropod as _Nemegtosaurus_ 
though.  The body-plan of _O_ is very camarasaurid-like (except for 
the tail), but it's synapomorphies that count in the end, and the 
affinities of _O_ are very difficult to pin down.

 > ---John Schneiderman (dino@revelation.unomaha.edu)