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

Tim Williams wrote-

> 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. 
> 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_.

Oh, thrilled to bits indeed. ;)  Especially after Novas et al. (2004) found 
that Indosuchus/Indosaurus differed from other abelisaurs (though they may be 
synonymous with each other) in having an anteriorly placed frontonasal suture.  
And yeah, Walker (1964) made the scutes the type of Lametasaurus, so it's not 
going to be a senior synonym of Rajasaurus.  Btw, Mendez et al. (2010) 
described a Rahiolisaurus humerus before the official description of the taxon 
was out.  Depending on which paper gets published in hard copy first, that 
could lead to a published nomen nudum or more complicated citation for the 
name.  Now that we have all of these well preserved abelisaurs 
(Ekrixinatosaurus, Rahiolisaurus, Skorpiovenator, Aucasaurus, Majungasaurus, 
Rajasaurus, Carnotaurus) of which multiple specimens are known for 
Majungasaurus and Rahiolisaurus, it would be interesting to actually compare 
all the fragmentary species to them and see just how diagnostic they are.

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.

Note also that Novas et al. (2004) made Compsosuchus a nomen dubium because its 
axis (the only known element) didn't differ from what was later named 
Rahiolisaurus.  There was no mention as to how much it differs from other 
abelisaurids (e.g. Carnotaurus, Majungasaurus, Aucasaurus) though.  If it does 
end up differing from other abelisaurids, this could make Compsosuchus a senior 
synonym of Rahiolisaurus too.

Seriously, older paleontologists seem to have had so much more respect for 
priority.  I've been looking at ex-theropod Tanystropheus lately.  It was 
originally based on isolated cervicals (thought to be theropod caudals from 
1887-1930) named in 1852.  In 1886, Bassani described a poorly preserved 
partial skeleton as the possible pterosaur Tribelesodon longobardicus.  Then in 
1930 and 1931, Peyer described a new complete skeleton that showed Tribelesodon 
was really Tanystropheus and for the first time indicated the taxon was a 
Protorosaurus-grade reptile.  He went with the earliest genus name and referred 
his new complete specimen to the more incompletely known previously named 
species, leading to the combination Tanystropheus longobardicus.  I bet a 
version of Peyer living today would simply declare Tanystropheus and 
Tribelesodon nomina dubia and give his complete skeleton a new name, because 
hey it's better to have a name based on a complete specimen.  What's sad is 
that Peyer's proper taxonomic decision has led to him being overlooked in the 
species' citation.  Paleofile incorrectly states longobardicus is the type 
species of Tanystropheus and gives no author for the combination, while the 
Pterosaur Species List has Wild, 1973 credited for Tanystropheus 
longobardicus.  Sure Wild published a huge paper on T. longobardicus in 1973, 
but come on, Peyer even included the genus species combination in the titles of 
both of his articles!

References- Peyer, 1930. Tanystropheus longobardicus Bass. sp. Centralblatt für 
Mineralogie Abteilung B. 1930, 336-337. 

Peyer, 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner 
Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft. 50, 5-110. 

Novas, Agnolin and Bandyopadhyay, 2004. Cretaceous theropods from India: A 
  of specimens described by Huene and Matley (1933). Rev. Mus. Argentino Cienc. 
Nat., n.s. 6(1): 67-103. 

Mendez, Novas and Chatterjee, 2010. An abelisaurid humerus from the Upper 
  of India. Paläontologische Zeitschrift. DOI 10.1007/s12542-010-0055-z

Mickey Mortimer