Trochlea & Condyli

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

Caleb Lewis wrote:

<I was reading a paper that was describing Dromaeosaurus,>

  A very good complement to this paper (I assume you have Colbert and
Russell, 1969, A.M.Novitates) is Currie's 1995 paper in _Journal of
Vertebrate Paleontology_ (15: 576-591), which revises the cranial
material and description of *Dromaeosaurus.*

<and when the second digit on the foot came up, the term trochlea was
mentioned several times. I have tried to look it up but have been thus
far unsuccessful, and was wondering if someone would be kind enough to
give me a quick definition off list. Thank you all very much.>

  Here's two terms that require clarification. Hopefully when Mike
Keesey's glossary is up, this will become a great resource.

  Trochlea: A structure of a hinge articulation bearing two condyli
(below) that form a semicircle or great arc for the purpose of allowing
a structure to swing about a transverse axis centered on the trochlea.
This trochlea usually bears a groove that differentiates condyli, and
the flexor or extensor extents of these condyli are distinctive; when
both extensor and flexor condyli project beyond the base of the shaft
bearing the trochlea, this is called a ginglymoid articulation, or a
ginglymus.

  Condyle: one of the cylindrical or toroidal (structure as cut from a
section of a torus) parts of a trochlea. The plural is "condyli." The
opposite, concave structure on the other end of the articulation is a
contyle, pl. "cotyli."

  Hope this clarifies.

=====
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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