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CHAPTER 6:
SUMMARY AND CONCLUSIONS
This section serves to summarize and emphasize major contributions and
conclusions of the foregoing chapters.
New crania of plesiadapids and reassessment of cranial stucture
Chapter 2 provides the first description of crania referred to a member of the
genus Pronothodectes (Fox, 1990). Furthermore, it provides the most extensive and
detailed documentation and description of plesiadapid cranial morphology heretofore
available. Finally, it examines a larger sample of better preserved cranial material, with
more advanced visualization techniques than any other study on plesiadapid crania. The
fossil and analytical resources of this work allowed me to describe distinctive features of
taxa traditionally thought to represent basal plesiadapids (such as Pronothodectes and
Nannodectes) and more derived plesiadapids (such as Plesiadapis tricuspidens), as well
as similarities shared by them. These new observations revealed the morphology of basal
plesiadapids to be different from previous perceptions in some ways (e.g., Russell, 1964;
Bloch et al., 2007). Major findings include the following: (1) the bony composition of
the plesiadapid tympanic bulla is uncertain, but best interpreted as petrosal in origin given
available evidence (including that presented here); (2) all known plesiadapids other than
P. tricuspidens appear to have nasals that exhibit a slight lateral flaring at their caudal
extent (as compared to the mediolateral width of either the rostrocaudal midpoint or the
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