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and identified it as a fragmentary ulna. It seems likely that the specimen to which they
referred as “MNHN R 549” actually corresponds to MNHN R 589, listed by Russell
(1964: p. 291) as a distal phalanx and described in more detail by Beard (1989). Despite
problems with specimen numbers, I have little doubt that these authors correctly
identified bones of P. tricuspidens for their study. Using multivariate methods, they
convincingly demonstrated that P. tricuspidens is more similar to the arboreal squirrels in
their sample than to the terrestrial ones. They analogized the lifestyle of P. tricuspidens
with that of the extant tree squirrel Ratufa (as suggested by Szalay and Dagosto, 1980).
Unlike Runestad and Ruff’s (1995) study, Youlatos and Godinot’s (2004) measurements
did not incorporate information on the “robustness” of the limbs, which certainly partly
explains why their results contrast with those of the earlier publication.
Bloch and Boyer (2007) discussed morphological and functional features of the
plesiadapid postcranium. They referred to new observations of “a skeleton of Plesiadapis
cookei… in the process of being described.” (p. 562). A layout of this skeleton in
anatomical position was provided (p. 545, fig. 3D). This is the same skeleton, UM
87990, as that referred to by Gunnell and Gingerich (1987), Gunnell (1989), Gingerich
and Gunnell (1992), Hamrick (2001) and Bloch and Boyer (2002), and which is
described in detail in this chapter. Bloch and Boyer (2007) stated that P. cookei differs
from other plesiadapids in morphology of the scapula, humerus, claws, and digital
proportions. They suggested that these differences reflect a greater tendency toward
suspensory postures in P. cookei.
Bloch et al. (2007) reiterated the points made by Bloch and Boyer (2007) and
presented the results of a cladistic analysis that included plesiadapids and other
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