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RE: Abydosaurus mcintoshi, a new sauropod from the Albian of Utah
Greg Paul wrote:
<Nemegtosaurus is known from plenty of postcranial material, its known as
Opisthocoelocaudia. Funny how they often end up widely separated on cladograms.>
The reason this argument has not seen much support is that there is no way to
disprove it (there being NO overlapping material).
Both have been included in comparative titanosaur matrices. Postcranially,
however, *Opisthocoelicaudia skarzynskii* clades with the derived saltasaurs,
for which cranial material is generally unknown. Cranially, *Nemegtosaurus
mongoliensis* and *Quaesitosaurus orientalis* appear to clade along with
*Rapetosaurus krausei,* which is far more conservative in the body plan than
are derived saltasaurs. If one were to infer that the crania of nemegtosaurus
like *Rapetosaurus* or *Bonatitan* are also conservative relative to their body
plans, then it is unlikely that *Opisthocoelicaudia* represents the postcrania
of *Nemegtosaurus*. Way back in the 90s, when *Rapetosaurus* was unknown, this
was a reasonable claim to make, as there was no other evidence that might allow
one to disprove it, but know, there is a substantive wealth of data that show
that there was as much diversity among titanosaurs as among non-titanosaur
eusauropods (one reasoning for this of course being that the former were
replaced by the latter, and as such the latter filling the niches of the
former, but this is an hypothesis).
Cheers,
Jaime A. Headden
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