Boyer diss 2009 1046..

more abduction could have really occured, but lateral rotation, followed by extension,
allowed the condyles to shift farther caudally. Relatively small greater and third
trochanters, and a medially projecting (rather than posteriorly projecting) lesser
trochanter are further indicative that the femur was not flexed and extended forcefully
using the gluteal musculature (Sargis, 2002b). However, the expansive trochanteric fossa
and expanded area distal to the intertrochanteric crest for the obturators and quadratus
femoris, respectively, would have given the limb a capacity for powerful abduction and
lateral rotation of a flexed, adducted thigh. The large, medially projecting lesser
trochanter would have provided a large lever arm for the iliopsoas muscle: from a
somewhat extended, abducted, medially rotated posture, iliopsoas would also have served
to flex, adduct, and laterally rotate the femur. The proximally restricted patellar groove
and distally extensive condyles suggest that full extension of the knee was infrequent or
impossible, and that a flexed knee was a habitual posture. Relatively shallow femoral
condyles suggest extension of the knee was not particularly forceful (Beard, 1989; Sargis,
2002b) when it occurred. The pattern of buttressing of the patellar groove margins are
consistent with a posture wherein the femur was habitually flexed and abducted, and the
knees were flexed (Boyer and Bloch, 2008).
Comparison.—The femur of plesiadapids does not exhibit a drastic amount of
variation in the species for which it is known. Most aspects of the description given for P.
cookei apply equally to P. tricuspidens, N. gidleyi and a newly recognized specimen of N.
intermedius (Table 4.17A-C). The description of the femoral head of P. cookei differs
from that given by Beard (1989) for other plesiadapids. He characterized the plesadapid
femoral head as being spherical, having a centrally placed fovea capitis femoris, and as
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