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Re: croc foramina
Looks like I erred in a couple of points in a recent post. Here are
some clarifications/corrections that Larry Witmer sent to me, and
graciously allowed me to post to the group:
Witmer, Larry wrote:
> One of my grad students alerted me to the thread on lips, and your messages
> to the dino net. I just wanted to point out, should it come up again, that
> the foramina don't transmit branches of the facial nerve but rather branches
> of the maxillary division of the trigeminal nerve, a nerve that is purely
> sensory in all known life forms. Perhaps not a big point, but since it is
> the facial nerve that supplies the true labial musculature of mammals, it
> could be confusing.
[side point - I should have known this, since my old comparative anatomy
notes clearly indicate it. Mea culpa.]
> Your next post on the facial musculature of crocs might also be a tad
> confusing. The term "facial muscules" is usually restricted to the muscles
> innervated by CN VII, since there are other muscles (e.g., orbital,
> adductor) muscles that are on the "face." The narial musculature of
> crocodilians is not innervated by the facial nerve, but rather by
> sympathetic nerves originating in the superior cervical ganglion.
> Crocodilians and birds do have "facial muscles" in the strict sense,
> although they topographically are not located on the "face." The muscles
> are the depressor mandibulae, stapedius, and sphincter colli (pars cranialis
> only in crocs).
Larry is correct about the confusing nature of my terminology. To me,
the "face" is more or less the surface of the rostrum - anything in
front of the orbits. Hence, "facial muscles" are "muscles on the face,"
and nothing more. The muscles moving the eyeballs, which are innervated
by the third cranial (oculomotor), would not be "facial muscles" in the
skewed world that is my terminology.
This same kind of confusion can arise when discussing the palate, which
is why I distinguish "palatal" structures (things on or in the palate)
from the "palatine," which is a bone. Sensibly, "rostral" should
replace "facial" in the manner used above.
Christopher A. Brochu
Department of Geology
Field Museum of Natural History
Roosevelt Road at Lake Shore Drive
Chicago, IL 60605
voice: 312-665-7633 (NEW)
fax: 312-665-7641 (NEW)