Boyer diss 2009 1046..

lateral trochleae is usually larger, or projects farther distally than the other. Typically this
larger trochlea is on the opposite side of that sporting the larger, blunt proximal tubercle.
As can be seen in lateral and dorsal views, the distal articular surface has its largest radius
of curvature on its ventral aspect, a narrower one distally, and almost no expression of the
distal articular surface on its dorsal aspect. The lateral aspects of the distal end are pitted
for collateral ligaments.
Lateral proximal phalanx function.—The shape of the proximal articular surface
of the proximal phalanx and its orientation with respect to the shaft, combined with
articulating metacarpals in which the distal articular surfaces are spherical and oriented
dorsally, suggest a metacarpophalangeal joint that was (1) mobile in abduction-adduction,
axial rotation, and flexion-extension; and (2) was most stable in a dorsiflexed position,
where the greatest overlap in corresponding joint surface area is formed. The orientation
of the distal articular surface of the proximal phalanx, its differential radius of curvature,
and the presence of extensive flexor sheath ridges suggest habitual ventroflexion of the
proximal interphalangeal joints.
Lateral proximal phalanges comparions.—Compared to other plesiadapids, P.
cookei cannot be demonstrated to differ strongly in any easily quantifiable fashion.
Smaller Nannodectes species seem to exhibit less pronounced lateral trochleae on the
distal articular surfaces and to have proportionally slightly wider shafts. Some of the
proximal phalanges from the French Berru locality have prominent ventrally projecting
flexor sheath ridges (e.g., MNHN R 503; MNHN unnumbered Divers coll. specimen: see
Table 4.13). Although they are identified as plesidapids, this noted morphologic
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