RE: Family Nemegtosauridae

[<TWILLIAMS@canr1.cag.uconn.edu>]

Adam Yates wrote:

> Might Op. be the
> ultimate expression of this trend? If so the intermediate would have
> opisthocoelous anterior cadauls joined to procoelous posterior cadals via a
> biconvex vertebrae (or perhaps a short transtion zone somewhere in th
> midlength of the tail).

Except that procoely in titanosaurid evolution BEGAN at the anterior 
end of the tail, then progressed more posteriorly to include the mid-
caudals too.  If I understand you correctly, what you're suggesting 
is some sort of tug-of-war between the anterior caudals 
(opisthocoelous) and the posterior caudals (procoelous) over what the 
entire tail should be.



Tim


> I can imagine this transformation being acheived by the extension of the
> affect of some Hox gene (one that turns on the machinery that grows large
> convexities on the anterior faces of the centra)  further and further back
> along the antero-posterior axis of sauropod embryos. I can't test this idea
> yet, but I know how to, anyone got the money to send me to central Asia to
> look for the immediate outgroups of Opisthocoelocaudia? ;-)     
> 
> Adam Yates
>