Boyer diss 2009 1046..

INTRODUCTION
Among North American plesiadapids (Fig. 1.1), one of the latest occurring and
largest species is Plesiadapis cookei (Jepsen, 1930; Gingerich, 1976). The only known
skull and skeleton of P. cookei, UM 87990, was discovered in late Paleocene strata of the
Clarks Fork Basin in 1987 (Gunnell and Gingerich, 1987; Gingerich and Gunnell, 1992;
Gingerich and Gunnell, 2005). The specimen has not yet received a thorough description
or analysis despite the fact that it is arguably the most completely preserved skeleton of a
plesiadapiform yet recovered (Bloch and Boyer, 2007).
The relative completeness of the skeleton allows for documentation of inter- and
intra-limb skeletal element proportions, and assessment of likely habitual configurations
and ranges of mobility of the major joints of the limbs. Estimates of the latter two
parameters have never been made for the radiocarpal and mid-carpal joints.
An initial obstacle to study of this fossil was its preservation in a freshwater
limestone nodule along with an individual of Uintacyon, a similarly sized apparently
arboreal carnivoran (Carnivora, Miacidae): this made the process of preparation and
documentation difficult. The skeletons were prepared using acid reduction techniques
described in Bloch and Boyer (2001). Detailed records of skeletal associations were not
kept and there is thus substantial confusion as to which postcranial elements were
originally components of P. cookei and which belong to Uintacyon. This uncertainty is
becoming increasingly minor due to recent description of plesiadapiform specimens with
documented skeletal-dental associations (e.g., Beard, 1989; Bloch et al., 2007). Some
elements are easily identified as belonging to P. cookei, because they are well known
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