A distinguishing feature of Pongo upper molars and its implications for the taxonomic identification of isolated hominid teeth from the Pleistocene of Asia

Abstract

Objectives: The taxonomic status of isolated hominoid teeth from the Asian Pleistocene has long been controversial due to difficulties distinguishing between pongine and hominin molars given their high degree of morphometrical variation and overlap.Here, we combine nonmetric and geometric morphometric data to document a dental pattern that appears to be taxonomically diagnostic among Pongo. We focus on the protoconule, a cuspule of well-documented evolutionary history, as well as on shape differences of the mesial fovea of the upper molars. Materials and methods:We examined 469 upper molars of eight hominid genera (Australopithecus, Paranthropus, Homo, Meganthropus, Sivapithecus, Pan, Gorilla, and Pongo), including representatives of Homo erectus and extinct and recent Pongo. Analyses were conducted at the enamel-dentine junction to overcome the limitations introduced by dental wear.

A deep‐learning‐based workflow to assess taxonomic affinity of hominid teeth with a test on discriminating Pongo and Homo upper molars

“…In addition to the spatio‐temporal overlap between Pongo and Homo , they experienced a similar reduction trend of the dentition, associated with a convergence in molar morphology (Smith, Olejniczak, et al, 2009). Both orangutans and hominins have variably wrinkled molars with low cuspal relief and oval occlusal outline (Ortiz et al, 2019). In addition, molars of both taxa overlap for a number of quantitative variables, including enamel thickness, daily secretion rate, crown formation time, 2D geometric morphometric analyses of the EDJ (Martin, 1985; Olejniczak, Tafforeau, Feeney, & Martin, 2008; Smith, 2016; Smith et al, 2011; Smith et al, 2018).…”

“…However, CNN can also be applied to partial EDJ card and if the features recorded on the remaining parts are enough to identify a specific taxon for a given sample, then it would be worth exploiting the potential of incomplete EDJ cards. For example, Ortiz et al (2019) have demonstrated that the shape of EDJ mesial fovea of upper molar is a distinguishing feature that capable of separating Pongo from Homo . In this case, only partial information is needed, supporting the potential of incomplete EDJ card.…”

Comparative Morphological Analysis of Enamel and Dentin Surfaces’ Reconstructions by Means of Automated Digital Odontometry

“…Thus shape analysis, previously applied exceptionally to studies of external surface of dental enamel (Robinson et al, 2002), has been successfully applied to studies of dentin surface. Moreover, comparatively small morphological details can be studied using geometric morphometric analysis (Ortiz et al, 2019). However today high resolution reconstructions obtained through microcomputed tomography are widely used in studies of external and internal morphological structures.…”

Orientation vs. Orientation: Image Processing for Studies of Dental Morphology

“…In addition, volume and surface area assessments technically feasible on 3d reconstructions become essential parts of studies of enamel thickness research avoiding application of invasive and destructive techniques (Olejniczak, 2008;Suwa et al, 2009). Significantly more detailed research becomes possible in odontology in general and including geometric morphometric analysis as well (Ortiz et al, 2019).…”