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Re: Quaesitosaurus and Nemegtosaurus



In a message dated 96-12-09 17:52:40 EST,
T.Williams@cclru.randwick.unsw.edu.au (Tim Williams) writes:

> It's worth noting that Upchurch's cladistic analysis regarded
> _Opisthocoelicaudia_ not as camarasaur or even a diplodocoid, but as
> a titanosaur.  The postcranial skeleton of _O._ has a close OVERALL
> similarity to camarasaurids, but when it comes down to the nitty-
> gritty, there's not too many synapomorphies linking the two
> together. 

Alas, I disagree with Upchurch's self-admittedly debatable placement of _O._
among the titanosauroids. It's no more a titanosauroid than segnosaurs are
theropods. Cladists tend to dwell too much on subjective morphological
minutiae of dubious significance and lose sight of the forest for the trees.
Not one titanosauroid is known with bifid dorsal neural spines, but _O._ has
a whole series of them. All titanosauroids have at least a few procoelous
caudals and never any opisthocoelous caudals, but those of _O._ are
opisthocoelous (hence the generic name!).