RE: Suchosaurus, Baryonyx and Martinavis

[Tim Williams <twilliams_alpha@hotmail.com>]

Guy Leahy wrote:


> If _Spinosaurus_ is a chimera, where would that place
> the dorsal vertebrae? 

Possibly an allosauroid, close to _Acrocanthosaurus_.

> Are there any features of the
> vertebrae which unite the specimen with _Suchomimus_?
> Dr. Sereno's original description of _Suchomimus_
> doesn't mention any:
>
> http://www.projectexploration.org/suchomimus.htm
>
> An update on the original _Spinosaurus_ material
> doesn't touch on this issue either:
>
> http://www.geocities.com/stephvern/spino-newinfo.pdf

Regarding the possibly chimeric nature of the _Spinosaurus aegyptiacus_ type 
material, my solitary source for this is Rauhut.  The cranial material strongly 
suggests affinities to _Baryonyx_/_Suchomimus_, but the postcranium (says 
Rauhut) does not.  The distinctive tall-spined dorsals are quite different to 
those of _Baryonyx_/_Suchomimus_: they lack the strong pneumatization and 
additional laminae of baryonychine dorsals, and are more similar to the dorsals 
of allosauroids.  Also, the known cervical of _S. aegyptiacus_  is said by 
Rauhut to be too morphologically distinct from the _S. aegyptiacus_ dorsals to 
be referrable to the same theropod taxon.  Finally, the proximal caudal 
assigned to _S. aegyptiacus_ is said to be too big to belong to the same 
individual as the dorsals - and the morphology even suggests that the caudal 
may be ornithischian!  Nevertheless, the snout and dorsals all come from a huge 
theropod, which helps bolster the case that these (at least) come from a single
 taxon.  

BTW, this "chimeric _Spinosaurus_" idea has received very little attention, and 
even less support (to date).  I don't know enough to comment either way.  It 
may pan out (which would lead to all sorts of trouble - what element gets 
custody of the name?); or it may not.  It's a shame all the material was blown 
to Smithereens.

Reference

Rauhut, O. W. M. (2003). The interrelationships and evolution of basal theropod 
dinosaurs.  Special Papers in Palaeontology 69: 1-213.



Cheers

Tim
_________________________________________________________________
Help yourself to FREE treats served up daily at the Messenger Café. Stop by 
today.
http://www.cafemessenger.com/info/info_sweetstuff2.html?ocid=TXT_TAGLM_OctWLtagline