Dental microwear of Neogene cercopithecoids from the Turkana Basin, Kenya

Reconstructions of the diets of individual fossil species can help us better understand the adaptive radiations of higher-level primate taxa. Some researchers have posited that folivory was key to the divergence of cercopithecoids from the catarrhine stem, with bilophodonty reflecting an adaptation for leaf consumption. Others have questioned this model, suggesting that dental functional morphology and wear patterns are more consistent with frugivory and perhaps hard-object consumption. Here, we present new microwear texture data (n = 22) that might contribute to the discussion. Specimens were sampled from Buluk (∼17 Ma, Early Miocene, Noropithecus bulukensis) and Lothagam (∼8-4 Ma, Late Miocene to Early Pliocene, Parapapio lothagamensis/sp. indet and fossil Colobinae) in the Turkana Basin, Kenya, and compared with a select group of extant taxa. Point clouds were generated from high-resolution replicas of molar teeth using a white light confocal profiler and analyzed using scale-sensitive fractal analysis. Results of dental microwear texture analyses for both fossil samples align with those of extant grass (Theropithecus) and leaf (Trachypithecus) eaters and differ significantly from those of frugivores/generalists (Macaca, Papio) and hard-object specialists (Cercocebus). While both Noropithecus and Parapapio postdate the divergence of the cercopithecoid clade from other catarrhines, these results are largely consistent with previous work on the dietary ecology of the early papionin Parapapio from Lothagam and the traditional 'tough-food' model of leaves/grasses. Some previous Noropithecus dietary reconstructions indicated a diet of harder objects or fruits. Thus, the discrepancy between the microwear results and previous dietary reconstructions for N. bulukensis is unexpected. These results raise hypotheses that may help provide new context and insights into the radiation of this important superfamily of primates.