RE: Rapetosaurus stuff

[rbi <rbi@dana.ucc.nau.edu>]

>According to their analysis, Alamosaurus is a basal member of a clade also
>containing the Indian Titanosaurus colberti, South American Neuquensaurus
>and Saltasaurus, and Asian Opisthocoelicaudia.  However, I would REALLY like
>to see this analysis rerun by combining the Opisthocoelicaudia and
>Nemegtosaurus data in the matrix, and seeing how it changes the results.

I am not convinced that Opisthocoelicaudia and Nemegtosaurus are the same
taxon.  Remember that Rapetosaurus has both cranial and post-cranial material,
so that the cladogram should be pretty stable.  In their analysis, Opistho. is
significantly more derived than Rapetosaurus, and while Opistho cranial
material is not known, cranial material is known from other taxa that are
grouped with it.  Therefore through indirect comparison it is shown that
Opisthocoelicaudia and Nemegtosaurus are probably different taxa.  Of course,
if combining the two in an analysis shakes things up, then I am probably
totally wrong :)


>Lehman discusses both Asian and South American origins for Alamosaurus, but
>further suggests the possibility that Alamosaurus is the survivor of North
>American titanosaurs (as new work shows that titanosaurs were present in the
>mid-Cretaceous of the U.S.).

As you say, if this is the case, than one does not need to invoke any
migration for Alamosaurus, as everyone knows the paucity of material from the
mid-Cretaceous.  Maybe they will find a titanosaur in the Zuni Basin!

Regards,
Randall Irmis