Boyer diss 2009 1046..

plesiadapiform Ignacius graybullianus. The analysis used information on skull length
and posterior carotid foramen diameter. Functionality of the internal carotid artery in the
fossil was assessed by comparison to extant taxa with either functional or non-functional
internal carotid arteries.
Not all plesiadapids represented by cranial material preserve the posterior carotid
foramen. Even so, some of these specimens can be included in the analysis by using the
diameter of the groove for the internal carotid artery on the posterior septum where it
meets the promontorium, as demonstrated by Bloch and Silcox (2001). This is equivalent
to the diameter of the g1 groove of Chapters 2-3 (Table 2.3). This analysis also requires
information on skull length. However, because skull length can be directly measured in
only P. tricuspidens (MNHN CR 125), where it is 106 mm, skull length must be
estimated in other plesiadapid specimens. In Chapter 3, the length of the skull of P.
cookei (UM 87990) was estimated to be nearly identical to that of MNHN CR 125 using
39 different cranial measurements (Table 3.3). However, the skull of P. tricuspidens
differs from P. cookei and other North American plesiadapids with respect to a number of
features discussed in chapters 2 and 3. Therefore, using measurements from MNHN CR
125 to estimate skull length in North American specimens that are more fragmentary than
UM 87990 is likely to yield inaccurate results due to differences in shapes of various
regions of the skulls (e.g., mediolateral width of the caudal extent of the nasals). Thus,
for North American specimens where substantially fewer than 39 points of comparison
are available (e.g., there are only 14 measurements available for Nannodectes
intermedius), skull measurements of P. cookei were used to reconstruct cranial length.
This was done specifically by calculating the average of logged percentage differences
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