Boyer diss 2009 1046..

morphology, as well as the presence of g2 grooves, demonstrates an intratympanic route
for the internal carotid plexus of P. cookei.
Grooves on the promontorium
Compared to other plesiadapids the g2 grooves diverge from the g1 groove
unusually far proximally (Fig. 3.9): they are already distinct on the posterior septum,
rather than forming farther cranially, on the promontorium. The divergence of the two g2
grooves from one another on the promontorium is also unusual, and is not observed in
any other plesiadapid specimens described in the Chapter 2. It is unknown whether this
unusual morphology is a characteristic of P. cookei or whether it represents intraspecific
variability in the course of nerves in this area (and therefore represents a pattern that
could just as easily appear in an individual of another species such as Pronothodectes
gaoi).
Composition of bulla: sutural evidence on medial tympanic process
The medial tympanic process of P. cookei is unique among the comparative
sample of plesiadapids in exhibiting a “suture-like” line of foramina (Fig. 3.9D).
Comparative rodent specimens of Marmota and Lagostomus (Chapter 2) show
neurovasculature invading the middle ear cavity at the petrosal/ectotympanic boundary,
creating a line of foramina at the sutural boundary. This extant morphological pattern
makes it tempting to interpret the line of foramina in P. cookei as the remnant of a suture
as well. This may or may not be correct: HRxCT data does not provide any more
insights, as the boundary between the pars cochlearis of the petrosal and its medial
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