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



I 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,>>

  and Timothy Williams wrote:
 
<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).>

  In accord with recent phylogenies of bird-like
dinosaurs, Greg Paul suggested that *Archaeopteryx*
was a predescesor of the lineage that led to
dromaeosaurs. I would place *Ozraptor* in that
lineage, and because some features of velociraptorines
compare more closely with birds than even
*Dromaeosaurus* does, the latter taxon would lie
outside the Vel+Archie clade (Eumaniraptora), but
within the Archie>Ornithom clade (Paraves). Similarly,
the Lizard of Oz would be paravian by definition, if
it shares more features with dromaeosaurs than with
ornithomimosaurs, and even several other
maniraptoriform taxa; and I also note that there is
some similarity to tyrannosaurid astragali, so this
animal may be convergent on one, or both, of these
groups, so may not even be a coelurosaur. I consider
it unlikely, but this is what you get with fragm.
material. Similarly, mononykids have short astragali
that have an interesting flange and notch dorsally and
medially, and this makes the ascending process appear
short for a supposedly maniraptoriform theropod or
strict bird.

<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.>

  A nice autapomophic feature for the taxon, and
indicative of its uniqueness. But not useful when
dealing phylogenetically, since no other theropod
shares the feature as known. Theropods for which
astragali are locked to the tibia without indication
of the underlying tibial facet, could indicate the
ridge, but not apparently.

=====
Jaime "James" A. Headden

"Come the path that leads us to our fortune."

Qilong---is temporarily out of service.
Check back soon.

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