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Re: Velociraptorinae and Dromaeosaurinae 2

Filip Milovanovic wrote-

> I can only say that there seems to be no satisfactory character or set of
> characters that would differ Velociraptorinae from Dromaeosaurinae (and
> vice versa) in enough precise way.
> Am I right?

Basically every reference you'll see divides dromaeosaurs into
Velociraptorinae (Velociraptor, Deinonychus, Saurornitholestes,
Sinornithosaurus?, Bambiraptor?) and Dromaeosaurinae (Dromaeosaurus,
Adasaurus?, Utahraptor?, Achillobator?).  As Matias wrote, this is largely
due to the larger distal denticles vs. smaller mesial denticles on the teeth
(this is termed a high DSDI- Denticle Size Disparity Index).  Matias also
pointed out that 'velociraptorines' have pointed denticles hooked towards
the tooth tip, while 'dromaeosaurines' have a more generalized theropod
condition of rectangular denticles that are perpendicular to the tooth tip.
In addition, there are other characters suggested by Paul (1988), Currie
(1995) and other authors to defend this division.  See my discussion of
Currie's characters here http://dml.cmnh.org/2003May/msg00427.html , though
that's a bit outdated.  As you can see, the characters are problematic,
especially so since both the Theropod Working Group (e.g. Xu and Zhang,
2005) and Senter et al. (2004) have found 'velociraptorine'-like
Sinornithosaurus to be outside the Velociraptor+Dromaeosaurus group (in a
clade with Microraptor termed Microraptoria).  So many 'velociraptorine'
characters are probably primitive.

I should note that Velociraptorinae is defined as all taxa more closely
related to Velociraptor mongoliensis than to Dromaeosaurus albertensis,
while Dromaeosaurinae consists of taxa closer to D. albertensis than V.

Both Xu and Zhang (2005) and Currie and Varricchio (2004) have recovered a
Velociraptorinae including
Deinonychus and Saurornitholestes in their cladistic analyses.  In addition,
Xu and Zhang's Velociraptorinae includes Unenlagia and Adasaurus, while
Currie and Varricchio's includes Bambiraptor and Atrociraptor.  Xu and
Zhang's also placed Utahraptor in the Dromaeosaurinae, but couldn't place
Achillobator in either subfamily.  Notably, Currie and Varricchio's analysis
was rather small and included no postcranial characters or microraptorians.
And Xu and Zhang's analysis recovered the subfamilies with low support (only
present in 54-59% of the most parsimonious trees).

Senter et al. (2004) recovered an odd topology with Adasaurus, Deinonychus
and Saurornitholestes as primitive dromaeosaurines, and Dromaeosaurus,
Utahraptor and Achillobator as being derived dromaeosaurines.  In his tree,
Bambiraptor is a microraptorian and Unenlagia isn't a member of the
Dromaeosaurus+Velociraptor group.  So in Senter's tree, the
'velociraptorine' tooth morphology is primitive for dromaeosaurs.

My own analyses get results closer to Senter's, so I support his view that
no there are no known velociraptorines besides Velociraptor, and that other
dromaeosaurs with 'velociraptorine'-type teeth are either more closely
related to Dromaeosaurus or more primitive than either.

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html