University of Kentucky
Revisiting Incisor Allometry and Diet (Again): New 2D and 3D Approaches to an Old Question
Institution
University of Kentucky
Faculty Advisor/ Mentor
Andrew Deane
Abstract
Among anthropoids, and hominoids in particular, incisors function in the pre-processing of food prior to ingestion. Given the unique selective pressures imposed by the mechanical loading associated with individual dietary resources, it is not surprising that incisor allometry and shape are strongly correlated with anthropoid diets. Although it has been commonly accepted that incisor row width discriminates between frugivorous and folivorous anthropoids, this conclusion has recently been questioned on the basis that dietary discrimination is likely a composite function involving several variables unrelated to incisor width (i.e. procumbency, spacing, orientation) and that, in isolation, incisor width is a relatively poor discriminator among dietary groupings. The present study addresses methodological differences among prior analyses of incisor allometry and contrasts their results with those from a similar analysis quantifying the “true” length of the parabolic incisor row for a taxonomically and ecologically diverse anthropoid sample (n=120). In addition, a supplemental analysis of the relative hominoid I1 crown surface area was completed to examine the potential for individual incisors to reliably predict diet. Results indicate that the “true” length of the parabolic incisor row is a more accurate predictor of anthropoid diet relative to the summed widths of individual incisors or the maximum distance between the distal margins of the left and right I2. Likewise, relative hominoid I1 crown surface area accurately discriminates among soft and hard object frugivores, seasonal folivores and dedicated folivores. These results pose significant implications for future dietary analyses of extant and fossil anthropoids based on incisor allometry.
Revisiting Incisor Allometry and Diet (Again): New 2D and 3D Approaches to an Old Question
Among anthropoids, and hominoids in particular, incisors function in the pre-processing of food prior to ingestion. Given the unique selective pressures imposed by the mechanical loading associated with individual dietary resources, it is not surprising that incisor allometry and shape are strongly correlated with anthropoid diets. Although it has been commonly accepted that incisor row width discriminates between frugivorous and folivorous anthropoids, this conclusion has recently been questioned on the basis that dietary discrimination is likely a composite function involving several variables unrelated to incisor width (i.e. procumbency, spacing, orientation) and that, in isolation, incisor width is a relatively poor discriminator among dietary groupings. The present study addresses methodological differences among prior analyses of incisor allometry and contrasts their results with those from a similar analysis quantifying the “true” length of the parabolic incisor row for a taxonomically and ecologically diverse anthropoid sample (n=120). In addition, a supplemental analysis of the relative hominoid I1 crown surface area was completed to examine the potential for individual incisors to reliably predict diet. Results indicate that the “true” length of the parabolic incisor row is a more accurate predictor of anthropoid diet relative to the summed widths of individual incisors or the maximum distance between the distal margins of the left and right I2. Likewise, relative hominoid I1 crown surface area accurately discriminates among soft and hard object frugivores, seasonal folivores and dedicated folivores. These results pose significant implications for future dietary analyses of extant and fossil anthropoids based on incisor allometry.