A linear analysis of pliopithecoid dental morphology
Pliopithecoidea are an extinct group of catarrhine primates that occupied Eurasia during the Miocene. While their placement within the larger Primates order is well-classified, the phylogenetic and taxonomic relationships between pliopithecoid species are currently unresolved. This study sought to quantify the 2-D differences in tooth morphology between pliopithecoid species to determine whether these measurements were sufficiently able to differentiate between groups. We photographed the occlusal surface of the second (M/2) and third (M/3) lower molars from various Pliopithecoid, Propliopithecoid, and Parapithecoid species. ImageJ was used to record linear, angular, and area measurements. Variables were analyzed through a combination of univariate and multivariate statistical techniques, including principal component analyses and linear discriminate analyses (LDA) using PAST software. For both M/2 and M/3 analyses, the first two principal components accounted for approximately 85% of the total variance between specimens, largely relating to overall shape and cusp position. Species-level distinctions were observed among taxa, whereas great overlap was found at the family-level. Despite this overlap in variation, LDAs show that these 2-D dental measurements can reliably be used to classify samples into a priori groups. As such, we assert that linear measurements of pliopithecoid dentition are sufficient to elucidate morphological differences between pliopithecoid species on multiple scales. These results will assist in dental character selection which can then be used to inform pliopithecoid phylogenetic and biogeographic theory. This will ultimately broaden our comprehension of the factors that impacted Eurasian primates during the Miocene, information which will extend to our understanding of emerging hominoids.