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

[Tim Williams <tijawi@yahoo.com>]

Michael Mortimer <mickey_mortimer111@msn.com> wrote:


> Note that since Rahiolisaurus doesn't preserve a braincase,
> and Rajasaurus differs from Indosaurus/Indosaurus (Wilson et
> al., 2003; which would be impossible if the latter were
> nomina dubia), if there are only two Lameta abelisaurids
> then Rahiolisaurus would be Indosaurus/Indosuchus.  Not
> that I'd defend such a position because we don't know how
> many species are in that formation.  I'd say we have at
> least three valid Lameta abelisaurids (Rajasaurus,
> Indosuchus/Indosaurus and Rahiolisaurus) of which the latter
> two may be synonymous.  We won't know until we find a more
> complete specimen.


Yes, I'll go along with that.  At the moment it is unknown whether 
_Indosaurus_/_Indosuchus_ and _Rahiolisaurus_ are one and the same taxon, given 
the lack of overlapping material.  

If further cranial material is found for _Rahiolisaurus_, and this material 
shows the "anteriorly placed frontonasal suture" that Novas et al. (2004) 
considered diagnostic for _Indosuchus_, then it would seem appropriate to refer 
_Rahiolisaurus_ to _Indosaurus_.  Unless this "anteriorly placed frontonasal 
suture" is found in other abelisaurids, thereby excluding it as a genus-level 
diagnostic character.  It's a moveable feast.  The best approach at the moment 
is to regard _Rahiolisaurus_ as a valid genus, and retain _Indosuchus_ as a 
provisionally valid genus.



Cheers

Tim