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Re: Osteological Question
I have a question about the processes bordering the temporal fenestra of a
synapsid. I teaching myself osteology so I hope I can explain myself
The temporal fenestra is bordered by three bones; the postorbital, the
jugal and the quadratojugal. Looking at the fenestra in lateral view the
jugal looks like an upside down T (triradiate) the >anterior process is the
'suborbital process', the posterior process is the 'subtemporal process'
and the dorsal process is the 'postorbital ramus' (I assume 'ramus' because
it helps separate the orbit >from the temporal fenestra). The postorbital
looks like a T and the quadratojugal a backwards facing c. My questions
Do any of the following have specific names
1) What is the ventral process of the postorbital, which together with the
postorbital ramus of the jugal forms the postorbital bar, called?
Standard anatomical practice these days -- sadly, contrary to what one
often sees in the literature -- is to refer to various processes of skull
bones with respect to the bones with which they articulate. This means that
there are NO "ventral process," "dorsal process," etc. Instead, the process
you mention above would be called the "jugal process" because it articulates
with the jugal. This avoids (a) problems of orientation (for example,
depending on the posture one reconstructs for a skull, one person's "ventral
process" could be someone else's "caudal process" or "caudoventral
process"), and (b) problems of homology (for example, in your question 3
below, would the homologous process of the quadratojugal be considered
"subtemporal" in something that doesn't have an infratemporal fenestra?).
There are some instances where a bone sends off multiple processes that
articulate with the same bone; the names given to these can be emended with
directional terms (e.g., "dorsal postorbital process" and "ventral
postorbital process," although this does re-introduce the directional
problem, but to a lesser extent).
2) What is the posterior process of the postobital, the process that
sutures to the quadratojugal, called?
The quadratojugal process.
3) Do the dorsal or ventral processes of the quadratojugal have special
names? I would guess that the ventral process would be called the
'subtemporal process of the quadratojugal' and together >with the
subtemporal process of the jugal form the 'subtemporal bar'.
If I am correctly understanding what you are asking, they would be the
postorbital and jugal processes, respectively.
Jerry D. Harris
Director of Paleontology
Dixie State College
225 South 700 East
St. George, UT 84770 USA
Phone: (435) 652-7758
Fax: (435) 656-4022
"Actually, it's a bacteria-run planet, but
mammals are better at public relations."
-- Dave Unwin