Boyer diss 2009 1046..

Various plesiadapid taxa differ from the reconstruction representing the ancestral
node for Plesiadapidae. For instance, N. gidleyi differs in having an apparently relatively
larger glenoid fossa (Table 5.4B: 30) and an internal carotid plexus route that probably
did not have an intratympanic route. However, if the posterior carotid foramen is
correctly identified in N. gidleyi (Chapter 2), the route for the internal carotid plexus was
similar to that of other plesiadapids in being relatively laterally positioned on the
basicranium. P. tricuspidens differs in a number of respects illustrated in Figure 5.2: it
exhibits a tubular external auditory meatus (Table 5.4A: 3), a narrow nasal bone (Table
5.4A: 16), a broad premaxilla/frontal contact (Table 5.4B: 27), and an annular component
to its ectotympanic that flares substantially beyond the bony struts connecting it to the
bullar wall (Table 5.4B: 28). Additionally, P. tricuspidens lacks exposure of molar tooth
roots other than the distobuccal root of M 3 (Table 5.4B: 29), has a proportionally larger
glenoid fossa (Table 5.4B: 30), and appears to have a less posteriorly projecting nuchal
crest (Table 5.4B: 31). P. cookei is similar to P. tricuspidens in the tubular form of its
external auditory meatus and in the lack of dorsal exposure of most tooth roots on its
maxilla in the orbit.
Major features shared by basal and most derived plesiadapids include a
premaxilla that contacts the frontal bone, an apparently petrosal bulla, and an internal
carotid artery that has a posterolateral entrance, is non-functional, and crosses the lateral
aspect of the promontorium (see chapters 2-3). Plesiadapids have previously been
considered to lack a lacrimal tubercle. However, as discussed in Chapter 2, the best
preserved lacrimal specimen of P. tricuspidens (MNHN CR 126) has a blunt lacrimal
tubercle.
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