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Re: Paper on Chinese sauropods



Microsoft decided not to send the reply to me, but I see in the archives
that David answered it.  So here's my late reply, with info from Zhang and
Chen (1996).

> > > *Zizhongosaurus chuanchensis* Dong et al., 1983
> >
> > Any reasons it's a "shunosaurine euhelopodid" as opposed to a more basal
> > "vulcanodontid"?
>
> No. "Material: IVPP V9067: a neural spine of a dorsal vertebra, a distal
end
> of a pubis and a fragmentary humerus." That's all. Maybe some diagnostic
> characters in there. -- There isn't any study about "Vulcanodontidae", is
> there?

Upchurch (1995) said it may be vulcanodontid based on the sauropod-like
dorsal neural arch and prosauropod-like pubis.  Of course, vulcanodontids
seem to be paraphyletic now.

> *Tienshanosaurus* therefore seems very close to *Euhelopus*. The dorsal
> vertebrae present the same characters in these two genera [no mention of
> McIntosh, 1990]. The scapula shows a similar constriction at the base of
the
> blade, as well as a very similar ventral protuberance. The humeri have the
> same proportions. The cervicals of *Tienshanosaurus*, though fragmentary,
> show a development of a lamina comparable to *Euhelopus* [no details]. A
> reexamination of the material of *Tienshanosaurus* could [ah, _could_)
lead
> to a reunion of these two specimens in one genus [not species?].
> ZHEN et al. likewise mention this great resemblance between these two
> genera."

Upchurch (1995) excluded Tienshanosaurus from the Neosauropoda because of
its amphicoelous dorsals and bridged over chevrons.  Suppose that fits with
it being related to Euhelopus, but Martin-Rolland's study does not seem
definitive enough for me to trust.

> > > Zhang and Chen (1996) refer Zigongosaurus fuxiensis to Mamenchisaurus.
> >
> > Any comments on why Martin-Rolland disagrees?
>
> That paper isn't cited.

Zhang and Chen assign Z. fuxiensis to Mamenchisaurus because the posterior
cervical and anterior dorsal neural spines are weakly bifurcated.  Also, it
supposedly comes from a stratigraphic layer between Omeisaurus junghsiensis
and Mamenchisaurus hochuanensis.  Sounds like a good reason to me.

> The above paper also says that Omeisaurus changshouensis may be referrable
> to Mamenchisaurus, unlike the type species O. junghsiensis.  Any
explanation
> for why the species are synonymized by Martin-Rolland?
>
> > The resemblances between these two species of *Omeisaurus* are numerous
and
> > the difference in the flattening of the limbs does not seem to justify
the
> > creation of a new species for the material from Shizitan [ = *O.
> > changshouensis*]. .... Therefore it
> > seems that *Omeisaurus changshouensis* can be put into synonymy with
> > *Omeisaurus junghsiensis*."
> >
> > It simply isn't compared to *Mamenchisaurus*. Martin-Rolland didn't get
the
> > idea, it seems. Apparently it's stratigraphically intermediate between
> > *Omeisaurus* and *Mamenchisaurus*...

Zhang and Chen assign O. changshuoensis to Mamemchisaurus based on the fact
its stratigraphic position is "almost the same as" M. fuxiensis and its
characters are "nearly similar" to that taxon.
I don't trust either Martin-Rolland's dependence on differences cited in the
literature, nor Zhang and Chen's stratigraphic and undefined differences.
The species is actually rather poorly known, but Dong et al. (1983) state it
differs from O. junghsiensis because of its opisthocoelous caudal centra,
more reduced deltopectoral crest, crest on humerus that "lies
posterodorsally and runs directly ventral to the condyles", pubis more
expanded proximoventrally.  The high tibiofemoral ratio is blamed on an
inaccurately reconstructed humerus.  The opisthocoelous caudals would differ
from both Omeisaurus' (amphicoelous or procoelous, depending on source) and
Mamenchisaurus' (procoelous).  As these are just the centra, they may be
dorsals instead.  This taxon is obviously in need of a good redescription,
as are all Omeisaurus species.

Mickey Mortimer