Re: Coelurosaur phylogeny

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

Steve Brusatte wrote-

> >Taxa not complete enough to be included yet, with number of characters
coded
> >for in parentheses.
> >Dromaeosauridae- Adasaurus (2), Pyroraptor (9), Variraptor (18).
>
> Interesting...so you see _Variraptor_ as valid, and you're able to code it
for double the characters you code for _Pyroraptor_??

As far as coding goes, remember my characters are only cranial, axial and
pectoral so far.  Of these areas, Variraptor contains an anterior dorsal,
last dorsal, sacrum and fifth sacral vertebra.  Pyroraptor only contains two
teeth, an undescribed dorsal vertebra and a proximal caudal vertebra.  So
more codable material is known for Variraptor than Pyroraptor.
Validity is a more complicated question.  All elements of Pyroraptor belong
to a single specimen from La Boucharde (Bouches-du-Rhone), but the situation
in Variraptor is different.  The holotype is a thirteenth dorsal and sacrum
from La Bastide Neuve (Var).  Referred material (anterior dorsal, fifth
sacral, humerus, femur) is from Roques-Hautes (Bouches-du-Rhone).  The
Variraptor material is all from the same formation, and Pyroraptor could be
as well.  Indeed, there is a possibility all material is from the same
taxon.  Allain and Taquet (2000) questioned the validity of Variraptor
because they felt the holotype was indeterminate.  Variraptor differs from
Deinonychus in the smaller dorsal pleurocoels and lower sacral count.
Velociraptor differs in lacking posterior dorsal pleurocoels, lacking
pleurocoels on sacral 1, having mid sacrals not transversely compressed.
Unenlagia has more similar dorsals, but has one more sacral as well.
Variraptor differs from Sinornithosaurus in having transversely compressed
mid sacrals (3-4), a last sacral less reduced in width compared to the
first, the first sacral the shortest (as opposed to the last two), sacral
rib 2 not contacting sacral centrum 1, and a more anteroposteriorly
compressed last dorsal.  Microraptor has no dorsal pleurocoels, more
elongate dorsal vertebrae, and much broader sacrals 2 and 3.  Achillobator
differs in having two pairs of posterior dorsal pleurocoels and shorter
dorsal neural spines which are posterodistally expanded.  Saurornitholestes
differs in having the last sacral shortest, the sacrum dorsally arched, the
mid sacrals not transversely compressed, no pleurocoels in sacral 2, and
sacral rib 4 that does not contact sacral centrum 3.  Ornithodesmus differs
in having six sacrals, a dorsally arched sacrum, mid sacrals not
transversely compressed, and sacral rib 4 that does not contact sacral
centrum 3.  Other dromaeosaurs are either too incomplete or too poorly
described to compare.  So Variraptor definitely seems distinguishable from
other related taxa, which I feel makes it valid.  For those of you demanding
distinct autapomorphies for a taxon's validity, the highly compressed third
and fourth sacral centra (transverse width <60% of first sacral centrum)
counts.  Tyrannosaurids are somewhat similar, except that their second and
third sacrals are compressed.

Mickey Mortimer