Re: Saltasauridae (was Re: new titanosaur paper)

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 07:09 PM 7/27/99 -0500, Tim Williams wrote:
>I wonder if anyone has thought to petition the ICZN to have _T. indicus_ 
>suppressed as the type species of _Titanosaurus_ and replaced by (say) _T. 
>colberti_ - like what Charig and Chapman (1998) have proposed for having 
>_Iguanodon anglicus_ declared a nomen dubium and making _I. bernissartensis_ 
>the type species of _Iguanodon_.  I think it was also done with 
>_Cetiosauriscus_.
>
>_T. colberti_ as described by Jain and Bandyopadhyay (1997) is based upon a 
>fairly decent, diagnostic skeleton.  _T. indicus_, on the other hand, is 
>based on two scrappy tail vertebrae.  _Titanosaurus_ is a fairly well-known 
>(popularly) and well-loved genus, and I think it should be saved.  (It would 
>also give some stability to sauropod higher taxonomy.)  Other genera which 
>were named from scrappy and often nondiagnostic type material have been 
>salvaged in this sort of way, like _Allosaurus_ and _Coelophysis_.

As George mentioned, you could always do it.  However, I suspect at least
some of the sauropod workers would write against your petition.

Unlike the cases of _Allosaurus_ and _Coelophysis_, there has not been a
relatively complete, well known, multiple specimen set of fossils referred
to _Titanosaurus_ for decades.  It was just a few years after the type of
_Allosaurus_ was discovered before much more complete fossils were found;
much longer between the naming of _Coelophysis_ and the Ghost Ranch digs
(but prior to the Ghost Ranch digs, _Coelophysis_ did not play a major role
in thinking on theropod history).

In contrast _T. colberti_ was only named two years ago, and it has yet to be
fully incorporated in almost any subsequent study: this material has not
been central to concepts titanosaurian.  (Furthermore, it has yet to be
shown convincingly that this new species is in fact closer to _T. indicus_
than to the other Indian titanosaurians).

As for stability of the name: under phylogenetic taxonomy, the traditional
kind of name stability is not an issue.  Someone could define "Titanosauria"
as "all taxa closer to wombats than to numbats": it would be a damn stupid
thing to do, but it would be legit.  I have on the record stated that, if a
larger taxon name is derived from a genus name (such as Titanosauria,
Ornithosuchia, etc.) that the eponymous genus be one of the included anchor
taxa, but that is a preference, not a rule.

On the other hand, I think that the Indian titanosaurid material needs some
good going over: it may be that _Titanosaurus_ IS a defensible taxon on
basis of morphology, but that no one has spent the time comparing the
material to better, more recent discoveries from elsewhere.

(Oh, for the record, I think that Charig & Chapman should have used
_Iguanodon aetherfieldensis_ rather than _I. bernissartensis_ for the new
type species: it would at least have still been a British type!).

                        Thomas R. Holtz, Jr.
                        Vertebrate Paleontologist
Department of Geology                   Director, Earth, Life & Time Program
University of Maryland                  College Park Scholars
College Park, MD  20742       
Webpage: http://www.geol.umd.edu        Phone:301-405-4084
Email:tholtz@geol.umd.edu               Fax:  301-314-9661