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Lameta abelisauroids



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

This is an extensive paper, so I can't be as thorough as with
Unquillosaurus.  Novas et al. describe most of the ISI material described by
Huene and Matley, though much has been lost.  The latter include the
holotypes of Indosuchus and Indosaurus, as well as the referred skull roofs.
Indosuchus resembles Abelisaurus and is distinguished from other
abelisaurids by its rostrally placed nasofrontal suture.  Other sutures
indicate it might be immature.  Indosaurus is very damaged, and does not
preserve Carnotaurus-like horns, or any other differences from Indosuchus
that cannot be attributed to individual variation.  It cannot be determined
if it possesses Indosuchus' unique frontonasal suture position.  Now the
question becomes "is Indosaurus differentiable from other abelisaurids?".
Once this is determined, we can either synonymize it or make it a nomen
dubium.  This may be difficult with only drawings to go off of.  Novas et
al. leave it as valid, but state the "anatomical distinctions between
Indosuchus and Indosaurus are doubtful, at least".  There are two kinds of
basioccipitals preserved, one of which resembles abelisaurids and the other
which has some unique characters.  There are two types of premaxillae, one
basically identical to Majungatholus (Sampson et al., 1996), and one that
lacks lateral sculpture, unlike abelisaurids.  There are two kinds of jugal,
one with an odd texture on the lateral dorsal process, the other with a
marked concavity on the posteroventral edge of the dorsal process.  The
preserved quadrate is not fused to the quadratojugal, unlike abelisaurids.
Compsosuchus preserves two pairs of pleurocoels and other abelisaurid
characters.  It's supposedly basically identical to an axis-atlas referred
by Chatterjee and Rudra to Indosaurus.  Novas et al. say because of this,
it's a nomen dubium.  However, there's no reason to assign Chatterjee and
Rudra's specimen to Indosaurus.  So I say, if it's differentiable from other
abelisaurs, keep its validity and refer Chatterjee and Rudra's specimen to
Compsosuchus.  All but one specimen of Laevisuchus is lost.  The remaining
cervical is noasaurid, and differentiable from Noasaurus and Masiakasaurus.
Ornithomimoides mobilis, O? barasimilis and Dryptosauroides are based on
caudals which cannot be distinguished from Majungatholus.  On the other
hand, Jubbulpuria, two specimens of Coeluroides and AMNH 1957 are all caudal
vertebrae with a unique morphology, resembling Ligabueino.  There are two
kinds of sacrum, one resembling Carnotaurus, another resembling
Masiakasaurus, Rajasaurus and Lametasaurus.  There are two kinds of femora,
slender and robust.  Both resemble abelisaurids.  None of the tibiae could
be located, and only one is illustrated, a robust specimen resembling
Lametasaurus and Pycnonemosaurus.  Novas et al. say it probably belongs to
Lametasaurus, which they believe may be a senior synonym of Rajasaurus.  A
fibula resembles Rajasaurus, and there are a whole ton of pedal elements,
which can be divided into robust abelisaurid and gracile noasaurid
morphotypes.  Many elements were misidentified by Huene and Matley
("lacrimal", "postorbital", "astragalus" = jugal, jugal, quadrate).  I'll
have to look this paper over carefully to decide what taxa to refer various
elements to.

I'll be scanning this paper too, for those who want it.

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html