Boyer diss 2009 1046..

primates, as well as treeshrews and elephant shrews, according to MacPhee (1981). It
has also been identified in Ignacius graybullianus (Bloch and Silcox, 2001) (Fig. 2.38).
Either the s2 or s3 is equivalent to the medial secondary septum of MacPhee
(1981), while the other one cannot be analogized with morphology present in the sample
of primates and treeshrews studied by him. The hypothesis that the s2 is more nearly
equivalent to the medial secondary septum is favored here as discussed below.
The g1 groove is clearly related to the internal carotid plexus. This is supported
by its anatomical relationships and its typical morphology. Specifically, it is located on
the lateral aspect of the posterior septum and ventral apex of the pars cochlearis of the
petrosal. It thus leads directly anterior from the internal carotid canal formed in the floor
of the posterior septum. Furthermore, the fact that it often appears as a pair of grooves is
consistent with a relationship to the internal carotid plexus, because the internal carotid
plexus commonly exists as two major nerve bundles (e.g., MacPhee, 1981; Conroy and
Wible, 1978; Wible, 1993).
The g2 groove on the petrosal, which is usually present, is also interpreted as
having held contents of the internal carotid plexus. This groove begins from where g1
reaches the promontorium, and always approaches the lateral side of the anterior septum.
MacPhee (1981) and other authors (e.g., Conroy and Wible, 1978) demonstrate that the
internal carotid plexus follows the anterior septum (and thus leads towards the tubal
canal) in various lemuroid euprimates, treeshrews and macroscelidean insectivores. My
own observations reveal that the internal carotid plexus of Capra also leads towards the
tubal canal. These anatomical associations and the fact that g2 is sometimes present as a
pair of parallel grooves strongly suggest that it relates to the internal carotid plexus.
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