Objectives: The premolar sub-cervical region in four non-human extant ape genera are examined to: 1) define a classification scheme for the premolar root system in order to rigorously characterize, quantify and document variation in root and canal, form, number and configuration; 2) compare this variation within and between genera; and 3) test the hypotheses that sex and size (i.e., the "size/number continuum," Shields, ) of the premolar are determinants of root/canal form and/or number.
Materials and methods: Microtomography and 3D visualization software are utilized to examine a large sample of Hylobates, Pan, Gorilla, and Pongo (n = 951 teeth). Each premolar root system is examined to ascertain the expected level of variability for each taxon. Cervical surface area (mm2 ) serves as a metric proxy for tooth size. A Chi-square test of independence is used to assess for variability differences between and within each taxon, and Mann-Whitney U tests are employed to assess the predicted relationship between tooth size and variation within each taxon.
Results: Our findings indicate that root and canal configurations, non-metric root traits and tooth size can distinguish between extant ape genera. Within the four ape taxa, premolar size variation is generally, but not always, correlated with canal/root number. Our results indicate that males and females within genera differ in tooth size but not in canal/root form and number.
Discussion: We report previously undocumented variation in the study taxa. Our results are discussed within the context of Miocene Apes as well as the developmental and systematic implications. Am J Phys Anthropol 158:209-226, 2015. © 2015 Wiley Periodicals, Inc.
Keywords: Gorilla; Hylobates; Pan; Pongo; canal; cervical size; dental anatomy; hominoid; premolar; root; taxonomy.
© 2015 Wiley Periodicals, Inc.