Ruminant mandibular tooth mesowear: a new scheme for increasing paleoecological sample sizes

Abstract

AbstractExtension of the mesowear method to include the lower cheek teeth of ruminants will dramatically increase sample sizes and thus the statistical power of paleodietary inferences. However, the mesowear method of Fortelius and Solounias, which was designed for application to the upper molars, does not effectively separate ruminant species by diet when applied to the lower teeth. Upper and lower mesowear scores have sometimes been compared among non‐analogous cusps (i.e. the buccal cusps of the maxillary teeth, which experience incursion and the buccal cusps of the mandibular teeth, which experience excursion during the chewing stroke). We therefore compare mesowear scores between the buccal cusps of maxillary cheek teeth and the lingual cusps of mandibular cheek for a large sample of ruminants because both cusps experience incursion during the chewing stroke. Using the original mesowear scoring method, we find dietary signal in both the maxillary and mandibular cheek teeth and a high correlation between them using both non‐phylogenetic and phylogenetic comparative methods. Noting unique patterns of mesowear among the mandibular teeth, we also propose a new scoring method with additional wear categories that improves dietary inference when applied to the lower teeth and is highly repeatable. We also find that mandibular mesowear scores are consistently lower than for their maxillary counterparts. Although differential wear among the upper and lower teeth is much less apparent when applying our new scoring method, wear differences might relate to anisodonty (i.e. mandibular cheek teeth are narrower). Overall, we recommend our new scoring method for application to the lingual cusps of the lower second molars of fossil ruminants.