Boyer diss 2009 1046..

Figure 3.9. Right promontorium of Plesiadapis cookei (UM 87990): A,
stereophotographic ventral view. B, HRxCT ventral view reconstruction shown without
parallax. C, HRxCT ventromedial view reconstruction – fragment of tympanic process
(37) has been digitally removed to show continuation of foramina lined groove that may
represent a suture. D, close-up of promontorium in same view as part C. E,
stereophotographic lateral view (ventral to right, anterior to top). F, same view as E.
Hatches indicate broken surfaces, thick red line represents main course of internal carotid
plexus while thin red lines represent branches stemming from the internal carotid plexus.
Yellow lines represent components of the tympanic plexus. Fine dashed line – g3
groove. Numbers and abbreviations: 37 – tympanic processes of auditory bulla, 40 –
tubular external auditory meatus, 41 – crista tympanica; Boc – basioccipital; Bul –
auditory bulla; Eoc – exoccipital; Ptr – petrosal; Sq – squamosal; ac – aperture for
cochlear fenestra; av – aperture for fenestra vestibuli; bs – bullar suture; cc – cochlear
canaliculus; g1 – groove with lateral route that likely holds internal carotid plexus and
possibly remnant of internal carotid artery; g2 – groove with slightly more medial route
that may hold internal carotid plexus fibers that approach s1; g3 – groove that leads to s2,
which likely contains contributions from tympanic plexus, but was mainly responsible for
transmitting a small vein; g4 – frequently present alternative or additional groove for
tympanic plexus fibers to reach routes 1-3; g5 – frequently present groove that leads from
point ventral to vestibular fenestra dorsolaterally, toward epitympanic crest; ps –
posterior septum; s1 – first (anterior) septum: most lateral septum extending anteriorly
from promontorium (tubal canal forms between s1 and epitympanic crest); s2 – second
septum: forms medial to s1, projects anteromedially from promontorium., tca – tympanic
canaliculus; tng – tympanic nerve groove.
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