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Re: Abydosaurus mcintoshi, a new sauropod from the Albian of Utah
GSP1954@aol.com <GSP1954@aol.com> wrote:
> Nemegtosaurus is known from plenty of postcranial material,
> its known as Opisthocoelocaudia.
Although _Nemegtosaurus_ and _Opisthocoelocaudia_ were both found in the Nemegt
Formation of southern Mongolia, they were found at separate sites that are
several kilometers apart (Nemegt Uul and Altan Uul IV, respectively).
The skull of _Quaesitosaurus_ (another titanosaur) was also found in the Nemegt
Formation of southern Mongolia, at a third site. I know there is some talk
that _Quaesitosaurus_ might be the same as _Nemegtosaurus_, but Wilson (2005)
found enough cranial differences to separate the two. There is also
potentially a fourth sauropod taxon from the Nemegt Formation, known from a
dorsal series (mentioned in Wilson, 2005).
So at this stage it seems premature to combine _Nemegtosaurus_ and
_Opisthocoelocaudia_ into a single taxon. This will have to await the
discovery of associated cranial and postcranial material that can confirm or
refute this hypothesis. Until that happens, it's probably very dangerous to
treat _Nemegtosaurus_ and _Opisthocoelocaudia_ as the same OTU.
> Funny how they often end up widely separated on cladograms.
This is only funny (and then only mildly so) if _Nemegtosaurus_ and
_Opisthocoelocaudia_ turn out to be the same titanosaur. But this synonymy has
yet to be demonstrated at the moment. It does not seem unreasonable that
multiple species of derived titanosaur could have been roaming around southern
Mongolia at the same time.