Boyer diss 2009 1046..

which abuts the ectocuneiform, is notched. The medial two-thirds of the distal surface
itself is shallowly dorsoventrally concave, for MT IV; the lateral third, where MT V fits,
is shallowly convex.
Function.—The orientation of the proximal and distal facets indicate habitual
abduction of the foot with respect to the proximal tarsus: the cuboid facet on the
calcaneum is medially rotated by ~15°, but subtracting the ~60° angle between the
proximal and distal cuboid facets reveals that the metatarsal facet would have faced 45°
laterally with respect to the axis of the calcanaeum. Manipulation of the articulated
calcaneum and cuboid reveal that they do not rotate very extensively, contrary to Szalay
and Decker (1974) and Beard’s (1989) description of the nature of movements at this
joint in other plesiadapids and plesiadapiforms. There is much more mobility in
abduction and adduction of the cuboid on the calcaneum, thereby reducing or increasing
the 45° of abduction that occurs in the closest packed position. It is interesting to note
that, in an inverted foot position, mobility in abduction-adduction of the foot translates to
plantarflexion-dorsiflexion relative to the more proximal limb elements (e.g., tibia
proximodistal axis).
Comparison.—Compared to other plesiadapids, P .cookei differs in having a
proportionally broader peroneus longus groove (PgV: Table 4.22). This supports
functional inferences regarding morphological differences between the upper ankle bones
of P. cookei and other plesiadapids (see above). That is, a larger peroneous longus
tendon groove may equate to more forceful control over eversion of the foot.
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