DENTAL-BASED BODY MASS ESTIMATION IN EARLY EOCENE PRIMATES AND PLESIADAPIFORMES; WILLWOOD FORMATION, BIGHORN BASIN, WYOMING

Body mass is a crucial variable for assessing dietary adaptations in living and extinct primates. Kay's threshold of 500 grams body weight corresponds with dietary protein utilization in extant primates. Taxa below the threshold cannot assimilate proteins derived from foliage, and those above the threshold cannot acquire sufficient amounts of animal-based proteins to survive. For extinct primates, this important dietary correlate requires estimates of body weight derived from dimensional data obtained from molar dentitions of fossil primate taxa. Using linear dimensional data of molars from early Eocene (Willwood Formation) fossil primates (Superfamily Omomyoidea; Superfamily Adapoidea) and Plesiadapiformes, we report body mass estimations using multiple established dental metric based formulae (i.e., Gingerich, Legendre). The results indicate discrepancies related to the formula employed, molar position, and taxon sampled. Based on our analyses, we suggest expanding the research on body mass estimation to determine (1) the best formula for a given taxonomic group and (2) utilizing several methodologies when reporting body mass estimations. Estimated body weights should be reported as a range of determinations, rather than means alone, in recognition of intraspecies variations common to extant taxa.