Boyer diss 2009 1046..

the thigh (Gambaryan, 1974). The hamstrings were probably not well developed, as
surmised from the narrow dimensions of the ischial tuberosity. Furthermore the fact that
the ischium does not display any retroflexion suggests vertical leaping was not used
(Fleagle and Anapol, 1992). Finally, the inferior position and narrow dimensions of the
pubic symphysis are not typical of highly active, hind limb driven animals (Boyer and
Bloch, 2008). The cranial buttressing of the acetabulum may indicate the use of
orthograde postures in which body weight was directed through the cranial part of the
lunate facet, as suggested by other authors (Beard, 1989).
Comparison.—The innominate of P. cookei does not appear to differ drastically
from that of other plesiadapids for which it is known. These specimens are not very
complete. However, a couple of points can be made from the available material. The
known innominate fragments of P. tricuspidens are larger than those of P. cookei (Table
4.16). This is interesting considering that most of the known forelimb elements are
roughly the same size in the two species, with P. cookei usually exhibiting greater
proximodistal lengths. The acetabula of all specimens show some cranial buttressing.
The acetabula of N. gidleyi appear to be more elliptical and less circular in outline
(although they exhibit damage that makes them techniquely unmeasurable) than those of
P. tricuspidens and P. cookei. Another point of interest is the much farther distal
positioning of the ischial spine in three innominates of N. gidleyi, relative to the
acetabular dimensions (Table 4.16: IspV). Thus, in these smaller forms, the obturator
internus muscle had a greater component of force inferiorly directed and this muscle
could therefore contribute to flexion of the limb more than it could in the larger taxa.
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