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Re: Notes on Rebbachisaurs and Tehuelchesaurus (less longish)
Dann Pigdon wrote:
This is interesting, since the Australian Mid-Jurassic sauropod
been suggested as being euhelopodid. With Austrosaurus now considered by
a titanosauriform, perhaps the authors may have a vested interest in
another Gondwanan Mid to Late Jurassic euhelopodid?
It may depend on how you define/diagnose the Euhelopodidae. Two different
phylogenetic schemes (that of Wilson and Sereno and that of Upchurch) have
put forward very different affinities for _Euhelopus_, even though they
agreed in most other aspects of sauropod phylogeny:
Upchurch unites _Euhelopus_ with _Omeisaurus_ and _Mamenchisaurus_ as a
clade of basal neosauropods (Euhelopodidae). Wilson and Sereno regard
_Euhelopus_ as a derived titanosauriform, as the sister taxon to the
Titanosauria, and a long way from _Omeisaurus_.
_Rhoetosaurus_ has been linked to _Shunosaurus_ and _Omeisaurus_ (the
shunosaurines of McIntosh). _Rhoetosaurus_ reportedly does have forked
("skid-like") chevrons, although Upchurch rejected Macintosh's placement of
_Rhoetosaurus_ in the Shunosaurinae (euhelopodids in Upchurch's
classification) and cast doubt on its possesion of forked chevrons. At any
rate, Wilson and Sereno claim that forked chevrons have a wider distribution
among sauropods than just the shunosaurines and diplodocoids. Apart from
this character, I can't think of one character to link _Rhoetosaurus_ with
the shunosaurines/euhelopodids. If I'm wrong, feel free to fire away!
The classification of
Austrosaurus and Rhoetosaurus would suddenly make sense,
_Austrosaurus_ seems fairly comfortable in the Titanosauriformes. Based on
characters in the femur and vertebrae it appears to be close to the
Titanosauria. I don't think the same can be said for _Rhoetosaurus_.
Australia abelisaurs, any one?
Ralph Molnar once put _Rapator_ among the abelisaurs. With only a single
metacarpal to base his assessment on, I'm not at all sure why he did this.
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