Dental topography and diets of platyrrhine primates

Abstract

More than half a century ago, Percy Butler (1963: 4) wrote that we "need to study the functions of teeth more thoroughly so as to be in a position to assess the adaptive significance of observed variations and their possible selective value". There have been many advances in the study of dental functional morphology since that time. Here we review the various approaches to characterizing and comparing occlusal form that have been developed, especially dental topographic analysis. We also report on a new study of dental topography of platyrrhine primates (n = 341 individuals representing 16 species) with known differences in both dietary preferences and other food items eaten. Results indicate frugivores, gummivores, folivores, and seed eaters each have a unique combination of slope, relief, angularity, sharpness, and occlusal patch size and count values. Likewise, among frugivores, those that supplement their diets with hard objects, insects, leaves, and seeds, also each have a distinctive suite of topographic features. We conclude that both primary and secondary diet choices select for occlusal form, and that functional morphology more reflects the types of foods and mechanical challenges they pose rather than the frequencies in which they are eaten.

The case of the grass‐eating suids in the Plio‐Pleistocene Turkana Basin: 3D dental topography in relation to diet in extant and fossil pigs

“…Angularity is the second derivative of elevation (or slope of the slope, Figure 4a; Ungar et al, ). Angularity measures surface jaggedness, as Ungar and M'Kirera () described, the difference between slope and angularity is “analogous to the difference between the sharpness of a knife and its serratedness.” Higher angularity has been associated with insectivore primates when compared to folivores and seed eaters (Ungar et al, ; Winchester et al, ).…”

“…MSS is measured as the average degree of vertical descend over the tooth surface. As the tooth wears down, MSS usually gets lower (Ungar et al, ). Primate species that consume fruits and especially seeds tend to have less sloping crowns while folivores have steeper MSS (Ungar et al, ).…”

“…The natural breaks method divides the surface slopes into three categories, which have as small as possible variation within the groups and as high as possible variance between the groups. The relative proportion of the highest slope category is the sharpness index (Karme, ; Ungar et al, ). Seed eaters tend to have low sharpness index (Ungar et al, ).…”

“…The relative proportion of the highest slope category is the sharpness index (Karme, ; Ungar et al, ). Seed eaters tend to have low sharpness index (Ungar et al, ).…”

“…Geographic information systems‐tools consider tooth surfaces analogous to three‐dimensional landscapes (Hunter & Jernvall, ; Reed, ; Ungar & Williamson, ; Zucotti, Williamson, Limp, & Ungar, ), allowing measurements from the whole occlusal surface, making it independent of landmarks, unlike geometric morphometrics (Ungar & Williamson, ; Evans, ). Most GIS‐based dental topography studies to date have been focused on primates (Boyer, ; Bunn & Ungar, ; Dennis, Ungar, Teaford, & Glander, ; M'Kirera & Ungar, ; Pampush et al, ; Ungar, Healy, Karme, Teaford, & Fortelius, ; Ungar & M'Kirera, ; Winchester et al, ; Yamashita et al, ). However, orientation patch count (OPC, and orientation patch count rotated [OPCR]) analysis, which is based on geographical orientation of patches on the tooth surface, has also been applied to other animal groups (Evans & Janis, ; Evans & Jernvall, ; Evans, Wilson, Fortelius, & Jernvall, ; Santana, Strait, & Dumont, ; Smits & Evans, ; Wilson et al, ).…”