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Re: A Whole Bunch Of Questions



On Mon, 31 Mar 2003 17:59:02  
 Jaime A. Headden wrote:
>Ivan Kwan (dino_rampage@hotmail.com) wrote:
>
><2) Is Tarascosaurus salluvicus considered an abelisaur?>
>
>  Though it is certainly a ceratosaur based on the proximal femoral
>anatomy, thew mis-named [see note] *Tarascosaurus* has distinct dorsal
>vetrebrae that are, upon inspection, still closer to abelisaurids than
>they are to ceratosaurs in general, which are "plesiomorphic". Abelisaurid
>posterior dorsals have a distinctive centrodiapophyseal lamina "wing-like"
>arrangement of the diapophysis and parapophysis which persist into the
>sacral series, maintaining double rib heads to the very last dorsal and
>into the sacral series (thought the heads have merged with the apophyses
>of the centrum and there is no longer an apse between them). Other than
>that, the animal is largely defined by its location, the first
>"abelisaurid-type" from France. 

The holotype is a poorly preserved proximal end of a femur.  The vertebrae 
Jaime are referring to are equally poorly preserved and scrappy, and no records 
exist to show that they were positively associated with the holotype.

Regardless, even if the vertebrae belong to the holotype, there still isn't 
much that suggests that this form is an abelisauroid/abelisaurid, in my 
opinion.  Jaime's vertebral similarities are significant, but in-depth work on 
abelisauroid vertebrae is still lacking.  Perhaps these similarities will turn 
out to be bona fide synapomorphies after later work, and abelisauroids seem to 
be turning up in bunches, so I'm hopeful.

Additionally, as an addendum to my earlier post, Allain and Pereda Suberbiola's 
soon-to-be released Comptes Rendus Palevol review of French dinosaurs lists 
_Tarascosaurus_ as a nomen dubium due to its lack of diagnostic characters.  
But, it also mentions an additional specimen from France that has unique 
cnemial morphology, much like _Genusaurus_.  I hadn't heard of this specimen 
before, but that doesn't necessarily mean it is anything new.

Steve

---
******************************************************
Stephen Brusatte
Geophysical Sciences
University of Chicago
Dino Land Paleontology-http://www.geocities.com/stegob
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