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Titanosaurus (was RE: Some Comments Re: Antarctosaurus)



Jaime Headden wrote:

> The braincase is that of a nemegtosaurid and possibly
> scapula as well, the caudals (and maybe the limbs) that of a
> pellegrinisaurid or saltasaurid 

I wasn't aware that Pelligrinisauridae had been officially named.

> (which already may supplant Titanosauridae), 

It may be possible to have both Saltasauridae and Titanosauridae.  More on
this below...


> Without being an expert on titanosaur mid-caudal veriation and
> distribution of features, I would not discount *Titanosaurus indicus*
> just yet. 

AFAIK, the species _T. indicus_ has *never* been officially diagnosed - with
the possible exception of Lydekker's original description, which is now
obsolete.  Several authors (McIntosh, 1990; Jain and Bandyopadhay, 1997)
have drawn attention to the flat-sided, laterally compressed mid-caudals of
_T. indicus_ as features that may distinguish this taxon from other
titanosaurs, when put in combination with the strongly procoelous caudals.
But no author to my knowledge has gone so far as to offer a diagnosis for
the species.  Jain and Bandyopadhay (1997) provided a new diagnosis for the
genus _Titanosaurus_; but the proposed characters were (1) mostly drawn from
_T. colberti_ and (2) general titanosaur or titanosaurid characters.

Huene and Matley (1933) referred Lameta material to _T. indicus_, and
regarded these elements as deriving from the same horizon that yielded the
type caudals of _T. indicus_ (named and described by Lydekker [1887]).
Interestingly, Huene and Matley's material includes an *amphicoelous*
caudal, which apart from being cupped on both anterior and posterior
articular faces (and hence strongly amphicoelous) resembles the procoelous
mid-caudals of the type series, and the other caudals referred to _T.
indicus_ (and _A. septentrionalis_) by Huene and Matley (1933).

Jain and Bandyopadhay (1997) provisionally removed this amphicoelous caudal
from _T. indicus_, and even doubted whether it came from a titanosaurid.
This is curious, since a combination of strongly procoelous and strongly
amphicoelous caudals are known for other titanosaurs, and have been
described by LeLoeuff (Europe) and Bonaparte (Sth America).

If Lydekker's type caudals for _T. indicus_ and the putative topotypic
material described by Huene and Matley (1933) all belong to a single
species, then there is probably enough elements to diagnose a species.  This
species would bear the name _T. indicus_, and _A. septentrionalis_ would
become a subjective junior synonym of _T. indicus_.  This species lacks a
number of derived features seen in _Saltasaurus_ and its closest relatives
(e.g. dorsoventrally compressed caudals) and appears to lie outside the
Saltasauridae.  Thus Titanosauridae may be retained for a subset of
non-saltasaurid titanosaurians, as advocated by Powell (though he accorded
this group the rank of subfmily, and his Titanosaurinae was possibly
paraphyletic).


> No one has proven the likelihood of synonymy with any other taxon,
> and so far, it does possess unique features (Jain and Bandyopadhyay,
> 1997)

Actually, Jain and Bandyopadhay (1997) compared _T. indicus_ and _A.
septentrionalis_, and regarded the two species as one and the same, based on
the comparable morphology of the caudals and limb elements.  They also
supported the referral of sauropod material described by Swinton in the
1940's to _T. indicus_.  This material also comes from the Lameta Beds; but
not from the same horizon as the _T. indicus_ and _A. septentrionalis_ type
material.  Swinton (1947) did not describe the caudals (!), only the limb
elements.  Thus, this referral is very uncertain.


> that permit some comparison to the majority of Titanosauriformes, and
> this may still be enough to save the taxon, just not the referral of
> countless species to it.

Agreed.  The genus _Titanosaurus_ should be limited to the type species, _T.
indicus_.  Other species should be re-assigned to different genera (in the
works for _T. colberti_) or regarded as _nomina dubia_ (definitely _T.
raholiensis_; probably _T madagascariensis_, _T. blanfordi_).  It's worth
mentioning that the type caudals of _T. blanfordi_ resemble those of
_Pelligrinisaurus_ in their elongated, cylindrical shape; but I'm not sure
how diagnostic this character is.



Tim