Re: Triassic Sauropods

["Tim Williams" <twilliams_alpha@hotmail.com>]

Matt Bonnan wrote:

> Needless to say, I still have my doubts about titanosauriforms appearing so
> early based on current morphological evidence, but if they did it would be
> interesting -- such an early appearance of titanosauriformes would suggest
> that a whole line of sauropods that has numerous advanced characters
> appeared before other Neosauropod groups.

Perhaps one or two derived characters - in effect, those one or two 
characters that may place _Lapparentosaurus_ and _Volkheimeria_ among the 
titanosauriforms (or at least within the camarasauromorphs).  The evidence 
is weak, I know, and even Salgado et al. (1997) regard these two genera as 
probable basal neosauropods.


> It would imply a basal sauropod
> split much earlier than current evidence indicates,

A Diplodocimorpha/Macronaria split may have occurred close to the 
Triassic/Jurassic boundary.  To put it in perspective, the 
Ceratosauria/Tetanurae split of the Neotheropoda occurred much earlier than 
this.  And if that piece of jaw from the Early Jurassic of Lufeng really 
does belong to a therizinosauroid (and not to a prosauropod as some workers 
have suggested), then the great maniraptoran radiation probably had its 
roots very early in the Mesozoic (?Late Triassic).

(After all, Sankar Chatterjee has identified birds, ornithomimosaurs and 
pachycephalosaurs from the Late Triassic.  I'm not certain if these 
identifications have received unanimous support ...)


Tim

------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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