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Re: Bird lips and dinosaur jaws

Matti Aumala (mjaumala@nettilinja.fi) wrote:

<But when and how did this change from reptilian mouths with
fold-away skin to avian mouths with lips happen?

Some dinosaurs, most notably oviraptorids, actually look very
strange with the classic reptilian mouths, but seem much more
"ordinary" when restored with avian mouths. I've seen some
maniraptorans reconstructed with avian-like mouths, as well as
birds with reptilian mouths>

  There's a very good reason to restore the jaws of oviraptorids
(for instance) and most other oviraptorosaurs with the extensive
lateral skin, and this is primarily the result of the position
of the coronoid eminence. This process attaches the primary
adducting (m. psuedotemporalis) muscle to the supratemporal, but
also provides the anchor for the deep adductors, which attach at
the inner coronoid or below it, but at that level. Presently I
am involved in mechanics of the oviraptorid jaw, so pardon for a
lack of clarification. Several other adductors, including the
retractor (m. pterygoideus) muscle, attach very much anterior to
the position they normally do in other maniraptoriform
theropods. These result in the extensive anterior position of
the "reptilian cheek" restored by artists, including Greg Paul,
and force the jaw to be restored this way. There is no way to
restore the musculature any other way. As of the level of the
coronoid, anything behind it was muscle, and skin.

Jaime A. Headden

  Where the Wind Comes Sweeping Down the Pampas!!!!

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