Rahiolisaurus vs Indosuchus (was Re: Nomen Dubium Misuse Part II- Gwyneddosaurus

[Tim Williams <tijawi@yahoo.com>]

Michael Mortimer <mickey_mortimer111@msn.com> wrote:


> Remember that post on Agnolin et al.'s paper where they
> used the term nomen dubium incorrectly for Rapator?  


I remember a thread that followed on from that post, where I argued that 
Agnolin et al. were quite correct in regarding _Rapator_ as a nomen dubium.  :-)


> Well,
> it seems Olsen has a similar issue with Gwyneddosaurus where
> he thinks it's clearly synonymous with a taxon he named
> later, and even
>  includes a diagnosic element, but wants to make it a nomen
> dubium so that his more complete specimen can be the
> name-bearer.  


In this specific case, if the two genera are stated to be synonymous, and an 
overlapping element is clearly diagnostic at the genus level, then the 
older-named genus clearly has priority (_Gwyneddosaurus_ over _Tanytrachelos_).


Returning to dinosaurs, and given your opinions regarding what is or is not a 
nomen dubium, I'm sure you'll be thrilled to bits with the latest paper by 
Novas et al. (2010).  They describe a new theropod, _Rahiolisaurus 
gujaratensis_, based on abundant abelisaurid material from the Lameta Formation 
of Rahioli, India.  This material had previously been referred to _Indosuchus 
raptorius_ by Chatterjee and Rudra (1996).  However, Novas et al. dismiss 
_Indosuchus_ as a nomen dubium, with very little fanfare.  In their words:


"It is difficult to evaluate the taxonomic status and validity of Indian 
abelisaurids, as most species have been established on the basis of fragmentary 
remains.  This is the case for the abelisaurids _Lametasaurus indicus_ (Matley, 
1923), _Indosuchus raptorius_ (Huene and Matley, 1933; Chatterjee, 1978), and 
_Indosaurus matleyi_ (Huene and Matley, 1933; Chatterjee, 1978).  These Indian 
abelisaurids have had a complex and checkered taxonomic history, already 
reviewed in several recent papers (see Wilson et al., 2003; Novas et al., 2004; 
Carrano and Sampson, 2008).  Unfortunately, the holotypic materials supporting 
each of these taxa do not offer clear autapomorphic fea
fficult (if not impossible) to refer the several isolated bones collected in 
the same quarry to any of the above mentioned species.  Moreover, many of the 
specimens originally described by Matley (1923) and Huene and Matley
 (1933) are currently lost. [snip] Because of these problems, we believe that 
_Lametasaurus indicus_, _Indosuchus raptorius_, and _Indosaurus matleyi_ must 
be considered as nomina dubia."


The citation is:

Novas, F.E., Chatterjee, S., Rudra, D.K., and Datta, P.M. (2010) _Rahiolisaurus 
gujaratensis_, n. gen. n. sp., A New Abelisaurid Theropod from the Late 
Cretaceous of India.  In: S. Bandyopadhyay (ed.), New Aspects of Mesozoic 
Biodiversity, Lecture Notes in Earth Sciences 132, DOI 
10.1007/978-3-642-10311-7_3.  Chapter 3, pp.45-62. Springer-Verlag, Berlin 
Heidelberg.


Thus, in the estimation of Novas et al. (2010), _Indosuchus_, _Indosaurus_ and 
_Lametasaurus_ are all nomina dubia.  Novas et al. recognize only two 
abelisaurid species from the Lameta Formation: the heavily built _Rajasaurus 
narmadensis_ and the slender-limbed _Rahiolisaurus gujaratensis_.


Previously, Wilson et al. (2003) noted that certain elements in the 
_Lametasaurus_ type material may be referrable to _Rajasaurus_; but they did 
not formally sink _Lametasaurus_ as a nomen dubium.  It should be noted that 
the _Lametasaurus_ type material (ilia, sacrum, tibia, scutes) is likely 
chimeric, so even if certain elements are (a) diagnostic, and (b) belong to the 
same taxon as _Rajasaurus_, then the name _Lametasaurus_ could be attached to 
non-abelisaurid material (like the scutes).  


Interestingly, the Rahioli abelisaur specimen ("Indosuchus") restored by 
Chatterjee and Rudra (1996) included forelimb elements that Novas et al. 
interpret as belonging to a juvenile titanosaur.  So no forelimb material is 
known for _Rahiolisaurus_.  The _Rahiolisaurus_ material is associated, but 
disarticulated, and from several individuals, but Novas et al. appear confident 
in assigning all the Rahioli abelisaur material to a single taxon.



Cheers

Tim