Boyer diss 2009 1046..

subarcuate fossa. They are well preserved and measurements are recorded in Silcox et al.
(in press). Although a fragment of ectotympanic (Fig. 2.6) is preserved, it is not enough
to permit any significant description.
Finally a fourth petrosal, UALVP 46687 from the DW-2 locality, has most of the
diagnostic morphology of the other three specimens, plus some additional features (Table
2.3; Fig. 2.7). Like UALVP 49105, the fenestra vestibuli and pars cochlearis are
measureable and yield measurements similar to the other specimens. It preserves g1-5. It
is also similar to UALVP 49105 in preserving a groove that arises on the medial aspect of
the promontorium and intersects g3. g1 is represented by two parallel grooves. Unlike,
UALVP 49105, in the present specimen, g2 is also represented by a set of two parallel
grooves. It preserves a foramen related to the tympanic canaliculus. Unfortunately
preservation of the septa is not as good as in other specimens: s1 and s3 are not visible.
While posterior septum is preserved toward its anterior margin, the posterior wall of the
bulla is crushed dorsally onto the roof of the tympanic cavity. Thus posterior septum is
broken here and internal carotid canal is obliterated. Still, the piece of bullar posterior
wall that has been pushed into the tympanic cavity is not too distorted. The posterior
carotid foramen is visible (although not measureable) on this fragment (Fig. 2.7). The
semicircular canals are preserved and their measurements are reported in Silcox et al. (in
press).
Ectotympanic.—The external auditory meatus (eam) and crista tympanica (the
raised ridge-like attachment point for the tympanic membrane that encircles the internal
aspect of the eam) are preserved in UALVP 46685 on the right side. They are both likely
to represent ectotympanic bone. The ectotympanic is thus visible on the dorsal view of
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