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Titanosaurian Nemegtosaurs, Batman! (Was: Caudipteryx and sauropod embryos)



> Date: Thu, 03 Feb 2005 14:18:54 -0600
> From: Tim Williams <twilliams_alpha@hotmail.com>
> 
> The sauropod embryo paper (Salgado et al., 2005) [...]  includes a
> figure that compares an embryo titanosaur skull to an adult
> titanosaur skull (_Nemegtosaurus_), next to a comparison of a
> juvenile prosauropd skull (_Mussaurus_) to the skull of an adult
> prosauropod (_Plateosaurus_).  I have no doubt that _Nemegtosaurus_
> is a true titanosaur; but according to Yates (2000), _Mussaurus_ is
> probably not a prosauropod.

And _Nemegtosaurus_ (along with _Quaesitosaurus_) still falls out as a
basal diplodocoid in the analysis of Upchurch, Barrett and Dodson 2004
in _The Dinosauria_, 2nd edition.  I spoke to Paul Upchurch at the
SVPCA last year, and he said that he does now accept titanosaurian
nemegtosaurids, but that he'd not managed to get a cladistic analysis
to show this position.  Go figure.  Mind you, the cladogram doesn't
show _Rapetosaurus_ as an OTU, so maybe when that's introduced into
the matrix it will change everything.

Other oddities in the Upchurch et al. 2005 cladogram:
_Haplocanthosaurus_ comes out as a macronarian closer to titanosaurs
than _Camarasaurus_ is; and Euhelopodidae comes out as a paraphyletic
sequence of outgroups to Neosauropoda, similar to Wilson 2002, except
that here Euhelopus is non-neosauropodan rather than titanosauriform.
I mistrust paraphyletic euhelopodids (even when they bear gifts) on
palaegeographical grounds.  Since Upchurch also does palaegeography
work, I am surprised he's not making more of a fuss about this.

 _/|_    _______________________________________________________________
/o ) \/  Mike Taylor  <mike@indexdata.com>  http://www.miketaylor.org.uk
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