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Re: Oviraptorid mandibular symphysis



Nick Gardner (ratites637@hotmail.com) wrote:

<I was going over Maryanska et al., 2002 this morning, and I noticed that
oviraptorids are coded as having a tightly sutured mandibular symphysis as
 opposed to a fused one.  Correct me if I am wrong, but does not 
oviraptorids, caenagnathids (which are coded correctly), and Caudipteryx
have a fused mandibular symphysis?>

  Only *Chirostenotes* and its complex of species appear to have fused
symphyses regularly. Some oviraptorid specimens, rather than species, have
unfused versus fused symphyses, but many of the taxa that the authors of
the cited paper are in fact "crestless" or "ingeniine" oviraptorids, and
these with large orbits, large dentaries, large external nares, simple
lachrymals, and small infratemporal fenestrae, are paedomorphic even when
obviously adult, as in *Conchoraptor* (and not included, *Khaan*). The
types of many of these species may be juveniles, but no one has really
surveyed oviraptorid specimens in keeping with taxa to date, their
phylogeny, and so forth, except to some degree Clark and the rest fo the
MAE team working on the material, which remains unpublished; the Polish
team have dealt primarily with the materials published in the 70's and
80's as part of the Polish-Mongolian Paleo Expeditions of the 60's and
70's ... either their immedate publications (materials pertaining to a few
species, most of these "ingeniine," and some to the Mongolian
collections). One must also note that the holotype of *Oviraptor
philoceratops* does not have a fused symphysis, though *Citipati* does.

  *Caudipteryx* does not have a fused symphysis. Every specimen I have
seen have both mandibular rami quite separate, including the paratype, and
all other referred specimens with jaws that have been published (okay,
grand total of _4_ specimens of the 6 published). The symphyseal platform
is very similar to that of oviraptorids but the sutural facet is lightly
rugose and wrinkled as opposed to heavily rugose and porous, indicating
sutural contact. Nonetheless, the symphysis was likely not as mobile as in
*Tyrannosaurus* or *Deinonychus*, in which the region is relatively
smooth. The more rugose, the tighter the fit, and in *Caudipteryx*, the
mandibles were likely relatively immobile with some minute give.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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