Boyer diss 2009 1046..

the pars cochlearis, and rostral processes, while broken, are more visible and intact than
on the right side.
The broken edges of the bullar walls just ventral to the ectotympanic ring and
medial to the pars cochlearis of the petrosal on the right side are clearly comprised of two
layers of bone (Fig. 2.30E-G). Figure 2.30 also shows the double layer near the
ectotympanic ring. The outer (more superficial) layer is generally thinner near the
ectotympanic and of a deeper amber color than the deep layer. On the medial bullar wall,
the superficial layer is thicker than the deep layer.
Morphology suggesting against a petrosal composition to the bulla (contrary to
the evidence above – see discussion) is that the left ear has a distinct color change
between the edge of the pars cochlearis and the posterior septum as well as between the
pars cochlearis and the very base of the medial tympanic process. Associated with this
color change is what also looks like a groove that begs interpretation as a sutural margin
or bone boundary (Fig. 2.28E: 131). However, closer inspection of this juncture reveals
the presence of a thin crack at its posterior end that accentuates the distinction between
these two regions of the petrosal.
Plesiadapis tricuspidens MNHN CR 126
Cranial sutures.— This specimen shows convincing evidence of frontal/maxilla
contact in the orbit. The sutures are generally sinuous (or convoluted) here. There are
two anteroposteriorly running discontinuities along the medial orbital wall. The more
dorsally positioned one is clearly a suture given its sinuous form (Fig. 2.31: 132). It
appears to separate the maxilla and frontal. The second discontinuity (Fig. 2.31: 133),
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