Re: Triassic Sauropods

["Matthew Bonnan" <mbonnan@hotmail.com>]

Tim Williams wrote:

"Just a clarification: the term I used was "titanosauriform".  
Titanosauriformes = Brachiosauridae + Titanosauria.  If the sauropod 
material from the Isalo Group of Madagascar belings to some type of 
brachiosaurid (or at least shows "brachiosaurid" features") then it is 
probably basal titanosauriform."

Fine.

Tim:

"Actually, I was not referring at all to _Isanosaurus_ from Thailand.  I was 
referring to the Isalo Group of Madagascar.  (No, I'm not confusing the 
two.)

A Late Triassic age for the Isalo Group is given in :

Flynn, J.J. et al. (1999).  A Triassic fauna from Madagascar, including 
early dinosaurs.  Science 286 (5440): 763-765.

Abstract: "The discovery of a Middle to Late Triassic (apprx 225 to 230 
million years old) terrestrial vertebrate fauna from Madagascar is reported. 
This fauna documents a temporal interval not well represented by continental 
vertebrate assemblages elsewhere in the world. It contains two new 
prosauropod dinosaurs, representing some of the earliest dinosaur 
occurrences known globally. This assemblage provides information about the 
poorly understood transition to the dinosaur-dominated faunas."

Yes, I understand now what you're getting at.  I guess the e-mail thread ran 
together and I had confused your idea with the Isanosaur stuff.

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.  It would imply a basal sauropod 
split much earlier than current evidence indicates, and might suggest, on 
re-analysis of sauropod phylogeny, that many similar characters in 
diplodocids, for instance, would have been independently acquired.  For 
these reasons, I will remain skeptical of Late Triassic or Early Jurassic 
titanosauriforms until better evidence surfaces.

Matt Bonnan
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