Boyer diss 2009 1046..

portion of the bulla medial to the annular component of the ectotympanic, where an
ectotympanic suture is most likely to have been (given the results of more recent studies).
Specifically, descriptions of paromomyid plesiadapiform basicrania (Kay et al., 1992;
Bloch and Silcox, 2001) that do preserve the portion of the bulla medial to the annular
component of the ectotympanic are interpreted as having an ectotympanic/entotympanic
suture located in this portion. MacPhee and Cartmill (1986: fig. 17) also showed a
radiograph of the Pellouin skull, which reveals the presence of extensive “cellules”
inferred to communicate with the tympanic cavity. They suggested that presence of these
“cellules,” as a consequence of tympanic cavity pneumatic expansion, is further
indication that previously noted (e.g., Gingerich, 1976) similarities between plesiadapids
and modern lemuriforms are convergences. Finally, they documented a specific example
of an animal convergent on plesiadapids and lemuriforms: the chinchillid Lagostomus
maximus has a similarly constructed annular component to its external auditory meatus,
and an obliterated suture between the ectotympanic bulla and pars cochlearis of the
petrosal.
Szalay et al. (1987: figs. 1, 2) provided a detailed description, stereophotographs
(the same as those provided by Szalay [1972: figs. 7-9]) and a reconstruction of MNHN
CR 7377, a cranial fragment of Plesiadapis tricuspidens. They suggested that it
represents a young individual because sutures between the squamosal and petrosal are
“clearly visible,” as well as sutures between the petrosal and the ectotympanic. The
former are clearly illustrated. While the suture between the mastoid part (pars
canalicularis) of the petrosal and the ectotympanic is visible, it is not clear whether these
represent the “clearly visible” structures to which the authors refer. They pointed out
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