Re: Andrew McDonald response re: European iguanodonts

[Tim Williams <tijawi@gmail.com>]

Jaime Headden <qi_leong@hotmail.com> wrote:


>   The situation is similar to *Titanosaurus indicus*, where the holotype of 
> *Titanosaurus colberti* (read: *Isisaurus*)  comes from the same hill and 
> formation as the type species/specimen, but eas
> excluded merely for purposes of implied poor stability on the part of 
> *Titanosaurus indicus* and slight variation in the preserved caudals 
> (ignoring variation in the holotype and paratype caudals of the
> rejected taxon). We could reasonably state that *Isisaurus colberti* is a 
> junior synonym of *Titanosaurus indicus* by designating the holotype of the 
> former as the neotype of the latter.


I don't believe this is at all correct.  While it is true that the
type material for _T. indicus_ comes from Bara Simla Hill of Jabalpur,
the holotype of _T. colberti_ (now the type species for _Isisaurus_)
hails from Dongargaon.  Although both specimens were recovered from
the Lameta Formation, the sites themselves aren't even in the same
state of India.  Moreover, the type mid-caudal vertebrae of _T.
indicus_ are very different in morphology to those of _I. colberti_,
so it's highly unlikely that _T. indicus_ and _I. colberti_ could
represent the same species.


The type material of _T. indicus_ was found at the same site as the
holotype of _Antarctosaurus septentrionalis_ (now the type species for
_Jainosaurus_).  When you say _Isisaurus_, do you perhaps mean
_Jainosaurus_?  The caudals of _A. septentrionalis_ compare well to
those of _T. indicus_, and it is likely that the two represent the
same species.  Unfortunately, Huene sorted the Bara Simla sauropod
material somewhat arbitrarily into two taxa (_T. indicus_ and _A.
septentrionalis_), and here as in many other endeavors, he made a huge
mess of titanosaur taxonomy.  I think a case could be made to refer
_A. septentrionalis_ to _T. indicus_, and thereby have the latter kept
as a valid genus.  It all hinges on whether or not the Bara Simla
titanosaur material is monospecific.  The type caudals of _T. indicus_
and the caudals assigned to _A. septentrionalis_ certainly match in
terms of morphology, even allowing for the poor preservation of the
former.



Cheers

Tim