Boyer diss 2009 1046..

CHAPTER 1:
INTRODUCTION
Plesiadapiformes are a paraphyletic or polyphyletic taxon also referred to as “early
primates” or “archaic primates” (e.g., Simons, 1964, 1967, 1972; Gingerich, 1975a, 1976;
Szalay et al., 1987; Bloch et al., 2007). Plesiadapids (Trouessart, 1897) are an extinct,
diverse group (Fig. 1.1) of “plesiadapiforms” that existed mainly in North America and
Europe during the Paleogene (Gingerich, 1976). They are the focus of this study.
Questionable records of the group’s existence also come from Asia (Thewissen et al.,
2001; Fu et al., 2002). Plesiadapids comprise one of the few mammalian groups from the
Paleogene for which species-level evolution has been extensively documented by studies
of large samples of dental and gnathic remains: they appear to have evolved rapidly
(Gingerich, 1973, 1975a, b, 1976). The primary stratigraphic sections in which this
pattern of evolution was established lie in several structural basins in the western interior
of North America: the Clark’s Fork Basin of northern Wyoming, the Crazy Mountains
Basin of south-central Montana, the Wind River Basin of southwestern Wyoming, and
the Bison Basin of central Wyoming. Specifically, the Clark’s Fork Basin has sections
that document the beginning and end of plesiadapid evolution, the Crazy Mountains
Basin documents the beginning and middle portions, and the Bison and Wind River
basins document only the middle portion.
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