Re: squamosal articulations and lamina.

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

Caleb Lewis wrote:

<Squamosal articulation...
 Lamina>

  The quadrate inserts on the squamosal bone inside the external
processes, so its hidden from view. In articulated specimens, this
makes it nearly impossible to view. One reason paleontologists like
disarticulated (but associated) braincases -- at least in some cases. A
quadrate that is holocephalous has only one articulation -- a
bicephalous articulation can vary with the second, medial articular
condyle (or head) lying on the opisthotic or prootic, and also hidden
from view. It's the condition of holocephaly that allows the quadrate
to turn on its axis and allow the jaw to open or the snout to turn up
in squamates, hadrosaurs, and birds. There are, of course, much more
complex and detailed literature on this, and one can start with _The
Skull_ (Hanken and Hall, 1993; Chicago University Press, in three
volumes).

  A lamina is a sheet of bone that extends between two points. Simply,
I believe. The laminae [plural] of the sauropod vertebrae are very
distinctive and a description of a single [neo]sauropod dorsal vertebra
will give you a working knowledge of laminae in vertebrae. Check out
Wilon's 1999 "Laminae in sauropod verts." paper in _JVP_ 19.

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

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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