Boyer diss 2009 1046..

elationships of the group, given the elevated significance assigned to this region of the
basicranium by students of primate systematics (e.g., MacPhee, 1981; MacPhee et al.,
1983; MacPhee and Cartmill, 1986; Bloch and Silcox, 2001).
In addition to providing additional descriptive information, I assess previous
anatomical interpretations of the plesiadapid cranium using the new fossil and new
comparative data. Specifically, I reevaluate the following features: (1) the position of the
posterior carotid foramen, (2) the presence of an intratympanic route for the internal
carotid plexus, (3) the presence of a foramen rotundum and (4) the bony composition of
the auditory bulla. The position of the posterior carotid foramen has previously been
tentatively considered as “posteromedial” (Bloch and Silcox, 2006), as mentioned above.
Whether or not the internal carotid plexus had an intratympanic route has been
considered ambiguous (MacPhee and Cartmill, 1986; Bloch and Silcox, 2001, 2006;
Bloch et al., 2007). The foramen rotundum has been considered present in Plesiadapis
tricuspidens by some (e.g., Russell, 1964; Bloch and Silcox, 2006) and absent by others
(Kay et al., 1992). The bulla has likewise been considered petrosal by some (Russell,
1964; Gingerich, 1976; Bloch and Silcox, 2006) and non-petrosal by others (MacPhee et
al., 1983; MacPhee and Cartmill, 1986; Kay et al., 1992; Beard, 1993). The same authors
who consider the plesiadapid bulla as non-petrosal favor the hypothesis that euprimates
are united by a common ancestor whose auditory bulla was comprised of only the
petrosal, unlike that in any other studied modern mammalian group (e.g., MacPhee,
1981). A non-petrosal bulla has been documented in paromomyid plesiadapiforms
(Bloch and Silcox, 2001), but claims (Kay et al., 1992) that the plesiadapid bulla is
entotympanic remains unsubstantiated. The hypothesis that plesiadapids have a non-
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