Re: Dinosaurs with Pygostyles

["Jaime A. Headden" <qilongia@yahoo.com>]

Ralph W. Miller III wrote:

<What is known of the caudal series of other
oviraptorosaur specimens?

  If the "_National Geographic_ specimen" (pardon the
vernacular) is the norm, then secondary flightlessness
can be considered as a possibility.  If, on the other
hand, other oviraptorosaur specimens are known to have
distal caudal vertebrae which do not terminate in a
"pygostyle," wouldn't this argue for convergence with
protobirds, as -- barring a reversal -- the ancestral
oviraptorosaur would not exhibit this character?>

  I am aware that there are a few oviraptorosaur
specimens out there, most of them just recently
collected by the Mongolian-AMNH-team, as well as one
or two by the Polish-Mongolian-team, but of them all,
only one (well, two, but for this purpose, one)
specimen has been published, and not even in a
description. Psihoyos and Knobbler (1996) [or is this
just Psihoyos, 1996?] published one of Psihoyos'
Mongolian photographs of an oviraptorosaur skeleton as
*Oviraptor*; however, it is not, based on the hand,
pelvis, and foot. This skeleton is more web-ascesible
at the Dino-Nakasato Website under "Ingenia", which
shows more expansive veiws of the skeleton and a
rotatable view of the skull, which does not belong to
the skeleton, per Norell (pers. comm.).

  Anyway, this skeleton perserves a near perfect tail
of approximately 30 caudal vertebrae, probably at a
maximum of only 31-32 caudal verts, with
extraordinarily deed chevrons cranially. In Gauthier
(1986) and Holtz (1994, 1996) phylogenies, reduced
caudal vertebrae in Maniraptoriformes (Holtz, 1995a)
Maniraptora is indicative of a disassociation of the
hindlegs/tail locomotor as described by Gatesy and
Dial (1996), and other Gatesy papers. However, unlike
the dromaeosaurs, Archie, and other avialian and
bird-like dinosaurs and dinosaur-like birds,
oviraptorosaurs do not have reduced transverse
processes or elongate zygapophyseal contacts distally
in the tail, and in fact lack a definite transition
point in the tail, short neural spines distally,
shorter chevrons than the depth of the centra
distally, etc. This specimen does reflect that, and
may be key to the new oviraptorosaur "pygostyle."

  Whether or not there's a reversal or convergence
depends on the rest of the oviraptorosaurs, resolution
on *Caudipteryx* phylogenetic position, anatomy of the
tail of *Avimimus* when described, resolution on
*Microvenator* and more material, etc. My own personal
views on the pygostyle will have to wait until I
actually read the paper. That and Elzanowski's,
finally out after 5 years or so of "in press"
citations.


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

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

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