Ozraptor (was Re: Reflections on Recent "Dromaeosaurs")

["Timothy Williams" <twilliams_alpha@hotmail.com>]

Jaime Headden wrote:

>   As previously commented on, *Ozraptor* Long and
> Molnar, 1999, is a Western Australian Jurassic form
> that has a tibial form and depression for the
> astragalar ascending process (which conforms very
> closely to the actual ascending process in other
> theropods) that are remarkably similar to
> *Deinonychus* and *Velociraptor*, as inspected using
> Norell and Makovicky, 1997, and Ostrom, 1990.
> Similarly, the shape is also similar to *Utahraptor*
> Kirkland et al., 1993. I would then suggest that the
> animal is a basal dromie,

If Jaime is right, this would make _Ozraptor_ one of the earliest known 
coelurosaurs - and perhaps THE earliest.  Long and Molnar (1998) give 
_Ozraptor_'s age as Bajocian, which makes it at least a few million years 
older than either _Gasosaurus_ or _Proceratosaurus_ (both of which have been 
touted on this list as possible coelurosaurs).

The only coelurosaur that is older is that therizinosaur lower jaw from 
Yunnan, China, of Early Jurassic (Sinemurian) age.  But this specimen is 
said by some to belong to a prosauropod, not a therizinosaur.

The oblong-shaped astragalar facet of _Ozraptor_ does resemble that of 
_Deinonychus_, but _Ozraptor_ has something not reported (to my knowledge) 
in any other theropod: a central ridge (running proximodistally) in the 
middle of the facet, that sort of subdivides the facet into medial and 
lateral portions. Long and Molnar suggest the ridge was used to "lock" the 
ascending process (which presumably had a corresponding groove) even more 
securely in place.


Tim
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