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RE: Neovenatoridae and Megaraptora: now it can be told!



Mickey Mortimer wrote:

> First=2C even if it is a megaraptoran (which hasn't been
> shown AFAIK) =2C Ra=
> ptor is different from Australovenator. Hocknull et al.
> wrote "The Mc I of =
> Australovenator wintonensis is larger than to that of the
> Rapator ornithole=
> stoides holotype=3B is missing the prominent caudomedial
> process projecting=
>  proximo-dorsally=3B possesses more subequal distal
> condyles=3B a flat prox=
> imal articular surface compared to the concave surface in
> R. ornitholestoid=
> es=3B and a straight distal lateral condyle compared to a
> disto-laterally p=
> rojecting distal lateral condyle in R. ornitholestoides."
> Furthermore=2C Ra=
> ptor has not been shown to be identical to any other
> theropod species=2C so=
>  is not a nomen dubium.  It may just be a metacarpal
> I=2C but it's a distin=
> ctive metacarpal I.  That posteromedial process in
> particular has been sugg=
> ested to be diagnostic=2C though Gishlick and Gauthier
> (2007) did suggest a=
>  similar structure was diagnostic of compsognathids. 
> Salisbury et al. (200=
> 7) compared Rapator to Nqwebasaurus=2C which has the
> compsognathid-style pr=
> ocess if I recall correctly=2C indicating a direction for
> future research.



OK, so I'm willing to give _Rapator_ a fair shake as a potentially valid genus. 
 However, I'm not going to dwell too much on this, because the _Rapator_ 
holotype has been examined very recently, and I don't want to give anything 
away.  But you have to wonder how many differences in the exact shape of Mc I 
are attributable to individual variation...


As for the Mc I of compsognathids: if I'm interpreting their paper correctly, 
Gishlick and Gauthier (2007) actually use the morphology of Mc I to *define* 
Compsognathidae.  Interestingly, as discussed elsewhere (including Holtz in 
Dinosauria II, from memory), the peculiar morphology of the compsognathid first 
digit might represent the kind of template from which the even more bizarre 
first digit of alvarezsaurids evolved. 


Cheers

Tim