Relative dental eruption and mechanically challenging diets in colobines and cercopithecines

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The Ohio State University

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The present study examines the potential relationship between relative dental eruption and diet in Colobus angolensis, Colobus polykomos, Colobus satanas, Piliocolobus badius, Procolobus verus, Cercocebus torquatus, Cercocebus atys, Cercocebus lunulatus, Lophocebus aterrimus, and Lophocebus albigena. These species were selected to examine predictions of the Food Processing Hypothesis (FPH), which suggests that species whose weanlings must process hard or tough foods will have accelerated rates of dental growth and development, as their permanent teeth—particularly their molars—are required to process these mechanically challenging foods (Godfrey, 2001). FPH predicts that folivorous weanlings that are reliant on tough foods require more advanced dental eruption than frugivorous weanlings that are adapted to processing softer foods (Godfrey, 2001). Based on FPH, it was hypothesized that there would be relatively earlier second and third molar, as well as fourth premolar eruption in species that are hard object feeders in comparison to what is used as the baseline dental eruption sequence of the Cercopithecoidea. Hypothesis 1 addresses whether it is possible to replicate Harvati’s (2000) results of eruption sequence differences between Colobus and Piliocolobus. It is hypothesized that with the addition of Colobus satanas, these genus level differences would persist. Given its softer diet and close phylogenetic relationship to P. badius (Oates, 1988), Procolobus verus was expected to be similar to Piliocolobus badius and follow a relative eruption sequence more similar to the baseline than Colobus (Harvati, 2000). Hypothesis 2 explores whether there are differences in relative dental eruption within the Colobus genus related to seed-eating. It is hypothesized that the hard-object feeding Colobus species show early relative molar eruption when compared to their counterparts. Hypothesis 3 addresses whether hard-object feeding cercopithecoid species outside of the colobine clade exhibit evidence of advanced relative eruption of molars. Under FPH, relatively advanced dental eruption would be expected. In this study dental eruption sequences were scored in a manner similar to that of Harvati (2000). Sample sizes were limited because only the dental remains of juveniles with mixed dentitions could be scored, precluding statistical analysis. Results are displayed in bar charts showing the frequencies of differences from the baseline eruption sequence. Hypothesis 1 and Hypothesis 2 were supported. Hypothesis 3 was not supported, with low frequencies of early molar eruption in Cercocebus and Lophocebus. With respect to FPH, it seems that hard-object feeding is associated with advanced relative molar eruption in colobines but not in cercopithecines. Reasons for this difference, especially concerning the effect of brain size on growth and development in primates, will be discussed.



Dental eruption, dental development, Colobines, diet