Boyer diss 2009 1046..

that plesiadapiforms are “callitrichid-like” or “squirrel-like” arborealists (Bloch and
Boyer, 2007; Boyer and Bloch, 2008). This is true with the exception of P. insignis,
which appears to have been most similar to terrestrial or scansorial taxa, as suggested by
Gingerich (1976). It must, however, be acknowledged that the variance in body segment
proportions of the comparative sample does not necessarily correspond to “behavioral
groups.” This is revealed by the position of more terrestrially adapted cercopithecoid
euprimates, which plot in the midst of more arboreal taxa in Figure 4.50C. Even so,
suspensory taxa (including Cynocephalus volans, sloths and apes) plot close to each other
in a region not overlapping the position of P. cookei. This could be considered more
evidence against the suggestion of Bloch and Boyer (2007) and Boyer and Bloch (2008)
that P. cookei had “suspensory tendencies.” In this regard, limb proportions are
consistent with evidence from vertebral proportions and analysis of joint mobility. That
is, the vertebral column exhibits a short neck and a long tail – features not typical of
suspensory taxa (Stafford, 1999). Consideration of joint mobility suggests sprawled limbs
and dorsiflexed hands and feet (see above), quite the opposite of the medially
approximated limbs and ventriflexed hands and feet expected for suspensory animals.
More phylogenetically focused comparisons of body segment lengths could be
interpreted as supporting the hypothesis of suspensory tendencies for P. cookei.
Suspensory taxa are characterized by higher brachial and intermembral indices than
quadrupedal arboreal taxa, for instance (Boyer and Bloch, 2008). P. cookei has a greater
brachial index and intermembral index than other plesiadapids. Furthermore, the longer,
more gracile humerus and femur of P. cookei, as compared to those of P. tricuspidens,
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