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Re: Did Osborn Goof? [was Re: Dinosaur FAQ #8]



  Jaw mechanics are not clear in oviraptorids. Barsbold (1977)
has been the only comparative analysis of the skull and
braincase relationships, Smith's 1992 analysis in _Neues
Jarbuch_ is based on the holotype but that skull has a much more
poorly preserved braincase and eroded palatal surfaces than does
the specimens Barsbold had at his disposal. If anyone is
interested, I can make this paper (Barsbold, 1977) available to
scrutiny, but it is in Russian.

  Presently, Barsbold's analysis (unlike Smith's) states that
the jaws were over-built for crushing matter, and would be
capable, on the mean, of crushing much harder shells than
typical eggs would have. This is one of the reasons he (as in
the _Dinosauria_ chapter and in _Encyclopedia of Dinosaurs_)
holds them as mulloscivores, not eggeaters. However, volumetric
and FEA (Finite Element Analysis) tests have not been performed
on these skulls, and hopefully I can get into the hallowed halls
of the AMNH specimen vaults to examine various specimens under
their care. Then comes Mongolia.... It should be noted that the
lower jaw, unlike in Disney's _Dinosaur_, is very wide in the
middle. Similarly, propalinal construction of the articular
permits mechanics similar in other animals which feed by
propalinal palate grating, including rodents. A detailed
analysis, which I am presently working on, will help clarify the
style of feeding, probably diet, and max-size volume object that
can be ingested.

  There are some preliminary observations I hope to present at
SVP this, probably as just a poster, but this is better (now)
before a oral presentation, which will probably follow detailed
examination.

  As such, I am not posting any of these observations, but only
what has been previously presented. One morphological detail
published includes the form of the posteroventral maxillary
prongs, which likely provided a precise region of puncture for a
shell. The jaws appear to be _built_ for crushing shell -- clam
or egg -- whereas crustacean shell is not as hard and bone
requires more precise holding mechanics (as evidenced by hyenas)
than the jaw of oviraptorids preovide. I don't hold anything to
be true in this case, and need to test mine, Barsbold's, and
Smith's hypotheses. 


=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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