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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
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