RE: What're Rebbachisaurids? (was - New Nemegtosaurus paper)

[John Hunt <john.bass@ntlworld.com>]

I must admit to being puzzled by the phenomena alluded to by these posts.
The probability of remains becoming fossilised is very small, so the chances
of preservation of different parts of an animal that have been removed a few
km apart must be tiny.

John Hunt

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] On Behalf Of
Jaime A. Headden
Sent: 26 August 2005 19:08
To: dinosaur@usc.edu
Cc: twilliams_alpha@hotmail.com
Subject: RE: What're Rebbachisaurids? (was - New Nemegtosaurus paper)

Tim Williams (twilliams_alpha@hotmail.com) wrote:

<Given that _Opisthocoelicaudia_ (once considered a camarasaurid) and
_Nemegtosaurus_ (once considered a diplodocoid) have both been moved into
the
Titanosauria, based on very convincing evidence; and that the skull of
_Nemegtosaurus_ and the postcervical skeleton of _Opisthocoelicaudia_ were
found a few kilometers apart at the same stratigraphic level... this narrows
the odds that the two may be the same.  However, Wilson's point (and he is
absolutely correct) is that proof is needed - such as a specimen that
includes
both cranial and postcranial material.  I'm sure Dr Currie feels the same
way.
While it is tempting to synonymize the two, we cannot discount the
possibility
that more than one titanosaur existed at this locality.>

  And to be honest, they were found at separate localities within the Nemegt
Valley, both corresponding to the same layer (Altan Ula [Or Uul] IV and
Nemegt
Uul [or the classical Nemegtu locality] respectively above). That both were
included in one analysis (Currie-Rogers and Forster, 2001) and did not find
themselves as sister groups, prompting the use of Opisthocoelicaudinae as a
sub
group of Saltasauridae implies one phylogenetic answer; but the presence of
several sympatric species of highly similar sauropod from the Morrison
levels
indicates it _could_ happen elsewhere, and the caution of waiting for a
better
specimen with head and body (would be nice if a neck, virtually nonexistent
in
*Opisthocoelicaudia*, were also found).

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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