EARLY EOCENE PRIMATE DISTRIBUTION IN RELATION TO PALEOSOL MATURITY: IMPLICATIONS FOR DETERMINING MICROHABITAT PREFERENCES USING GEOLOGIC PROXIES

The Willwood Formation of the Bighorn Basin in Wyoming is characterized by vast exposures of fossiliferous paleosols (ancient soils). The relative maturities of these paleosols have been attributed to the relative proximities of the sediments to fluvial channels, and therefore may correspond to different microhabitats as well. This author has investigated a relationship between paleosol maturity and primate species distribution from the Bighorn Basin in order to find evidence of microhabitat preference in these early Eocene primates. Data from the Colorado State University Department of Anthropology fossil mammal collection was used to test this relationship. Preliminary investigations suggest that paleosol maturity may not be a reliable proxy for determining microhabitat preferences in early Eocene primates. The relative distribution of fossil primates with respect to paleosol maturities instead probably reflects increased deposition and drying that occurs through the time of deposition of the Willwood Formation. Therefore, paleosol maturity may be better utilized as a proxy for taphonomic processes and time when examined with respect to other meter levels. However, the lack of lateral variation in the distribution of these primate species may simply reflect their similar arboreal adaptations. If this is the case, niche partitioning on a small scale would not be significant enough to provide geologic resolution of these minute differences. Further research on more abundant and differentially adapted species, such as the small condylarth Hyopsodus, may be useful in resolving these possibilities.