Re: The 5th cerebral nerve once more

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

 David Marjanovic (david.marjanovic@gmx.at) wrote:

<"Braincase, trigeminal nerve, separation of ophthalmic branch within the bone; 
0, no; 1,
incipient with trough in lateral surface of laterosphenoid; 2, complete with 
ophthalmic branch
enclosed in a tube within laterosphenoid."

As expected, *Acrocanthosaurus* and *Herrerasaurus* (the outgroup) are coded 0, 
*Fukuiraptor* and
*Sinosauropteryx* are coded ?, Dromaeosauridae 1, Ornithomimidae and 
Tyrannosauridae 2. More
surprising but already discussed onlist is 2 for *Allosaurus*, which might be a 
real convergence,
given that *Sinraptor* is coded 1. What is really surprising is the 1 rather 
than 2 for
Oviraptoridae. It contradicts everything I've read so far. Can it simply be a 
typo, or is it real?
Any clarification is appreciated. (In the cladogram this character never 
reverses, Dromaeosauridae
and Oviraptoridae come out as sister groups, birds, Troodontidae, and 
"enigmosaurs" except
Oviraptoridae are not included in the cladogram, but coelurosaur relationships 
are not the topic
of the paper.)>

  The problem here is the wording (though accurate) is not immediately 
described without having
the bone in your hand, or knowing your cranial nerve separations. The fifth 
cranial never normally
has one opening in the laterosphenoid, where all three branches separate 
outside the bone.
Incipient separation occurs with the third branch, the ophthalmic, at the base 
of the opening,
creating a "trough." This progresses deeper into the bone in other dinosaurs 
9and birds) as two
separate openings (V1-2, and V3). Oviraptorids, *Avimimus,* birds, and 
segnosaurs, as well as the
above-mentioned forms, have the two openings. There does not appear to be any 
single commonality
for theropods with both openings, but perhaps two, or one with some distinctive 
reversals.

  If a matrix codes something, check it out. Do not take a matrix at face 
value. It is GOOD to
question, to inquire, to TEST.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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