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Re: [dinosaur] Indian titanosaurs (was Re: How many end-Cretaceous dinosaur genera were there)



Some papers, such as Wilson et al. (2011) (doi:10.1111/j.1475-4983.2011.01087.x) have said that only two species of titanosaur are currently supported for the Indian subcontinent, which was the basis of my statement. That said, there seems to be a lot of variation in mid-caudals which seems to point to more, but maybe we just don't have caudal variation pinned down yet. I don't know. 

What makes you say that T. indicus and J. septentrionalis have similar caudals? The Chhota Simla Jainosaurus specimen preserves a caudal that lacks a ventral longitudinal hollow and isn't mediolaterally compressed at all, nor is it strongly waisted, which doesn't seem very much like the Titanosaurus indicus type specimen. There's less on the Jainosaurus type series caudal, but its centrum doesn't seem to be mediolaterally compressed and seems to have straight, not convex, lateral margins in anterior view--similar to the Chhota Simla Jainosaurus but not T. indicus.

Is Laplatasaurus madagascariensis from India a different nomen from Titanosaurus madagascariensis Deperet 1896? Regardless, it's part of the mid-caudal nightmare so I'm not sure what to make of it. A few complete tails from the Lameta beds would be nice.

On Mon, Dec 5, 2016 at 9:26 PM Tim Williams <tijawi@gmail.com> wrote:
John D'Angelo <assuming.dinosaur@gmail.com> wrote:

> Moreover, many of those species are likely synonyms or nomina dubina.
> Titanosaur-biased as I am, the example that sticks out to me is that
> Balochisaurus malkani, Jainosaurus septentrionalis, Khetranisaurus barkhani,
> Marisaurus jeffi, Pakisaurus balochistani, Sulaimanisaurus gingerichi,
> Titanosaurus indicus, Titanosaurus blanfordi, and Isisaurus colberti (not
> listed for whatever reason) all come from the Maastrichtian of the Indian
> subcontinent which may have as few as two species, the rest based on
> non-overlapping or dubious material.


The Lameta beds of India probably contain at least four different
kinds of titanosaurs.  This assessment is based on the different
morphologies of the mid-caudal vertebrae.  Although most of the Lameta
titanosaur species are indeterminate at the species level, the known
caudal vertebrae are distinctive enough to indicate the presence of
multiple taxa.

Only two Lameta titanosaur species are generally regarded as valid:
_Isisaurus colberti_ (originally _Titanosaurus colberti_) and
_Jainosaurus septentrionalis_ (originally _Antarctosaurus
septentrionalis_).  But the Lameta caudals named _Titanosaurus
blanfordi_ and those referred to _Titanosaurus_ (or _Laplatasaurus_)
_madagascariensis_ are different enough from both _Isisaurus_ and
_Jainosaurus_, and from each other, that they probably represent
distinct species - although neither is diagnostic (i.e., _T.
blanfordi_ and _T. magascariensis_ are nomina dubia).  The taxonomic
situation of the Indian titanosaurs is not helped by the fact that
Huene made a complete dog's breakfast of describing the Lameta
species, including his completely arbitrary criteria for sorting
material into _T. indicus_ versus _A. septentrionalis_.

_T. indicus_ (the type species for _Titanosaurus_) has been considered
a nomen dubium (e.g., Wilson & Upchurch, 2003; Wilson et al., 2009).
The _T. indicus_ type caudals seem to have come from the same site as
the _A. septentrionalis_ type material (an incomplete skeleton,
partially articulated): the 'Sauropod bed', Bara Simla, Jabalpur.  The
caudals of the two species (all from around the middle of the tail)
are strikingly similar in morphology.  So there's a very good chance
that the 'Sauropod bed' titanosaur material comes from a single
species.  Further, the 'Sauropod bed' titanosaur material is
consistent with a single individual - as noted by Wilson & Upchurch
(2003), who regarded _A. septentrionalis_ (but not _T. indicus_) as a
valid species.  But _T. indicus_ was regarded as a nomen dubium
because the type material (two mid-caudals) was non-diagnostic.

By contrast, Jain and Bandhyopadhay (1997) regarded _T. indicus_ as
valid, and regarded _A. septentrionalis_ as a junior synonym of _T.
indicus_.  (Oddly, this study suggested that one of the Bara Simla
caudals might not come from a titanosaur because it was amphicoelous,
not procoelous like the others; even though titanosaurs are perfectly
capable of having amphicoelous caudals.)

I think a case could be made to regard _T. indicus_ and _A.
septentrionalis_ as one and the same species - although I'm aware that
there are cogent reasons for abandoning the name _T. indicus_.
Hopefully, the 're-discovery' of titanosaur material in Indian museum
collections, including hitherto missing _T. indicus_ type material
(Wilson et al., 2009; Mohabey, 2013), might shed light on the taxonomy
of the original Bara Simla material.

As for Malkani's Pakistani titanosaur taxa... who knows.  Some of the
material (all very fragmentary) might be salvageable, and possibly
referable to Indian titanosaur taxa.