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R CARCHARODONTOSAURS CERATOSAURS?



I believe that Rudolfo Coria is saying that carcharodontosaurids are 
part of Neoceratosauria - to my knowledge the only published 
description of this hypothesis is in the Currie and Padian 
encyclopedia. I don't know off hand what characters are being used to 
support this idea.. intrinsically it seems unlikely as 
_Carcharodontosaurus_ is so much like _Acrocanthosaurus_. Jerry 
Harris' new paper, and the work of others including Tom Holtz and 
Stovall and Langston (1950), firmly supports an allosauroid position 
for these big theropods. Having examined _Neovenator_ at great length 
which, if Madsen (1976) is truly reliable, really really is very 
similar in the postcrania to _Allosaurus_, I cannot see 
_Acrocanthosaurus_ as closer to non-allosauroids than it is to 
allosauroids.

Jaime Headden wrote, regarding the possibility of a 
carcharodontosaurid-sinraptorid affinity...

>  First, the vertebrae are unique for theropods in the region
>  of the anterior dorsum, with rostrocaudally... [snip] 

You can only describe a position as 'rostral' if it is in the skull 
where, obviously, the directional term 'cranial' is not particularly 
useful.

>  Anyway, there are several other features of Giganoto that point 
> towards the abelisaurs, including the cnemic crest of the tibia, 
> which is very pronounced and superficially similar to ceratosaurs, 
> but it should be noted that abelisaurs and carnosaurs share a 
> similar knee and this this is not diagnostic.

Tetanurans (allosauroids + coelurosaurs) primitively have a prominent 
cnemial crest that, viewed proximally, curves laterally towards the 
fibula. They also have a well-developed sharp-ridged fibular 
crest. Neoceratosaurs share this design of cnemial crest (well 
figured for _Ceratosaurus_ (e.g. Gilmore 1920), _Xenotarsosaurus_ 
(Martinez et al. 1986) and _Carnotaurus_ (Bonaparte et al. 1990)) 
with tetanurans. Coelophysoids have a short, stout cnemial crest that 
does not curve laterally when viewed proximally. I believe this to be 
the primitive state for dinosauromorphs because it's seen in 
_Marasuchus_ and _Herrerasaurus_. Neoceratosaurs, like coelophysoids, 
do not have a sharp-ridged fibular crest, so this is a tetanuran 
character.

This cnemial crest morphology can thus either be interpreted as (1) a 
convergence between neoceratosaurs and tetanurans, or (2) as a 
derived character of the ?clade Neoceratosauria + Tetanurae. In 
numerous other characters (e.g. number of sacral verts, lesser 
trochanter morphology, extensor groove on distal femur, cranial 
proportions etc. etc.), neoceratosaurs are far more like tetanurans 
than they are like coelophysoids, and in some respects are 
intermediate, if you like, between coelophysoids and tetanurans. Add 
to this the fact that Ceratosauria sensu Gauthier 1986 and Rowe and 
Gauthier 1990 is based on characters like pelvic and tarsal fusion.. 
I, for one, am agreeing with people with Brooks Britt and Phil Currie 
that Ceratosauria is paraphyletic and Neoceratosauria (_Ceratosaurus_ 
+ Abelisauroidea) is the sister-taxon to Tetanurae. 

_Elaphrosaurus_,  BTW, is not an abelisauroid. Oh, and it's not a 
coelophysoid either. Oh yes.. and it's not an ornithomimosaur.

I bet you didn't know Pete had a sister.

DARREN NAISH
darren.naish@port.ac.uk