Oviraptors + Therizinosaurs

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

Mickey Mortimer wrote:

<I assume you mean Microvenator lacks caudal
pleurocoels.  Avimimus may have double cervical
pleurocoels, as seen in the figure in The Dinosauria
(a small secondary pleurocoel being placed directly
ventral to the neural spine).  Microvenator does have
double cervical peurocoels and the relevant data of
Caudipteryx is unpublished.>

  I'll leave *Caudipteryx* alone since my comments
were based on personal observation, and I do admit I
hadn't seen the bones in person. Additionally, a few
relevant papers have turned up missing, and so I have
to go off a limited literature. *Microvenator*,
however, possesses, according to Makovicky and Sues
(1997) has a single axial pleurocoel, and a posterior
cervical with three depressions, or invaginations,
which are not pleurocoels, and one of which may not be
a depression, but a product of preservation.
*Microvenator* is probably a subadult specimen, so
invagination of the centra probably did not complete
at the age stage preserved in the holotype compared to
other taxa, generally adult specimens due to
neural-arch/central fusion.

  *Avimimus*, I admit, may have two pleurocoels on one
midcervical, now that I compare the figures in
Dinosauria (Norman, 1990), but I can't find my copy of
Kurzanov, 1981, so.... There is a ventral central hole
illustrated that may be a second pleurocoel, near the
bottom, but Norman states (p. 284): "A pleurocoel
foramen is found on the lateral surface of the
centrum, just behind the cranial articular surface,
and in some vertebrae there may be two foramina, one
above the other." The operative term is may, and this
is too vague for me to be certain of its disribution.

  As such, cervical pleurocoely is not diagnostic,
double pleurocoels may be (I took it off my character
list because the condition is not definite on some
taxa), and extensive caudal pleurocoels are no longer
diagnostic unless *Achillobator* is an oviraptorosaur
... :). Sacral pleurocoels are known in many
maniraptoriformes, and full sacral pluerocoely is
described only in caenagnathids (Sues, 1998) and
*Ornithodesmus*? [I cannot recall, and the relevant
paper has disappeared].

  More once I can find these papers.

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