The biogeographic origins of primates and euprimates: East, west, north, or South of Eden?

Abstract

The place of origin of Primates is a subject that has received surprisingly little treatment in the literature. Part of the difficulty in considering this question is terminological. Until recently, the order Primates had usually been considered to include both euprimates sensu Hoffstetter, 1977, which are clearly related to modern members of the order, and the more archaic “plesiadapiforms” (e.g., Simpson, 1945; Hoffstetter, 1977; Szalay and Delson, 1979; MacPhee et al., 1983; Szalay et al., 1987; note that “plesiadapiforms” is placed in quotation marks to signify that it is likely a non-monophyletic group; Gunnell, 1989; Silcox, 2001). Since the very influential publication of two papers back-to-back in Nature in 1990 (Beard, 1990; Kay et al., 1990), which suggested paromomyid “plesiadapiforms” were more closely related to dermopterans than to euprimates, it has become common practice for authors to exclude “plesiadapiforms” from the order Primates (e.g., Beard, 1998a; Hartwig, 2002; Tavaré et al., 2002; Soligo and Martin, 2006). In this case the taxon name Primates was equivalent in meaning to Euprimates (see also Martin, 1968, 1986; Cartmill, 1972, 1974; Wible and Covert, 1987). This paper seeks to consider, therefore, two distinct but interrelated questions: the place of origin of Primates, and that of Euprimates. The first of these two questions is probably of greater relevance to those interested in the general patterns of mammalian evolution, in that it marks the point at which primates became a lineage distinct from other mammalian orders. The latter question may be of greater relevance to primate specialists, in that it is at this evolutionary transition that characteristic primate features such as convergent orbits and postcranial traits for leaping appear to have arisen (Silcox et al., 2007), although the process by which these features were acquired is not currently documented in the fossil record.