Boyer diss 2009 1046..

this septum is located medial to the anterior septum). A groove appears to represent g3
(Fig. 2.40).
The lateral walls of the auditory bulla (Figs. 3.5, 9: 37) have been crushed
concentrically toward the promontorium such that septa and tympanic processes have
been crushed and obscured to some degree. For instance, the posterior septum is broken
and the posterior wall of the bulla is destroyed such that no posterior carotid foramen is
visible. On the medial side, the ridge above the cochlear canaliculus (Fig. 3.9: cc) is just
barely visible. The cochlear canaliculus itself is visible with HRxCT. Additionally, as
mentioned earlier, the groove and foramen that typically sit on the ventral aspect of this
ridge, which appear to relate to the tympanic nerve, are visible. Running anteriorly and
posteriorly from the foramen of tympanic canaliculus is a distinct foramina-enervated
groove (Fig. 3.9: bs).
A fragment of the pars canalicularis is preserved on the left side. It is relatively
short anteroposteriorly. There is a deep groove that abuts the jugular process of the
exoccipital and appears to lead to the stylomastoid foramen; it may also represent the
digastric fossa (Fig. 3.5: 38). Lateral to this is a prominent tubercle that probably
buttressed the posterior aspect of the ectotympanic tube and is probably best referred to
as a mastoid process (Fig. 3.5: 39). If the pars canalicularis of the petrosal had any
posterior exposure in the pristine skull, it is not apparent from the fossil (Fig. 3.10).
Ectotympanic.— What seems likely to be the ectotympanic bone is preserved
bilaterally (Fig. 3.5). Although the right side is fragmentary, it exposes morphology not
visible on the left (Fig. 3.11). The left reveals that the external auditory meatus is narrow
compared to its mediolateral length and it can thus be described as “tubular” (Figs. 3.4, 5,
196