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Figure 5.2. Illustration of plesiadapid skulls based on character state reconstructions.
Comparison of the reconstructed skulls of basal (based on ancestral node reconstruction)
and derived (based on Plesiadapis tricuspidens) Plesiadapidae in A, ventral, and B,
dorsal views. Numbers correspond to characters listed in Table 5.3. The derived form was
reconstructed using measurements from skulls of P. tricuspidens, which are complete
enough to reveal overall cranial proportions. This reconstruction was then modified by
using all available measurements and morphology from Pronothodectes gaoi (Table 2.5),
which matches the ancestral node reconstruction in most respects (Table 5.4A-B). In
order to transform the skull of P. tricuspidens into that of Pronothodectes, all bones were
re-scaled according to nasal length, but this re-scaling could have been done using a
single dimension on any other bone that was preserved without distortion in both taxa.
Wherever there was no morphological information on basal plesiadapids, the
reconstruction was left similar to the image of the derived form. Thus, these comparisons
probably under-represent the full morphological disparity separating basal, Pr. gaoi-like
and derived, P. tricuspidens-like plesiadapids. Numbers correspond to features in which
derived P. tricuspidens (and in some cases P. cookei) differ from primitive ones (Table
5.3). C, Size comparison of reconstructed skulls of basal and derived Plesiadapidae in
dorsal view. The more derived skull is shown at 210% the size of the basal one, which
approximates the difference in size between early, Nannodectes intermedius-sized taxa
and late-occurring P. tricuspidens. The only plesiadapid that has been estimated to be
substantially larger is P. cookei (but see Table 3.3, 5.7 and Chapter 4). The only smaller
plesiadapids are Pr. matthewi and N. gazini (Gingerich, 1976). Still, most of the size
range for the family Plesiadapidae is illustrated by the two reconstructed skulls in this
figure.
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