Size-driven dietary partitioning in Archaeotherium (the North American “Hell Pig”) revealed through dental microwear texture analysis

Abstract

Archaeotherium was a North American entelodont that existed ∼37–20 mya, spanning major global environmental and climatic changes. Although well represented in the fossil record, Archaeotherium paleoecology remains poorly understood. This study uses dental microwear texture analysis (DMTA) to reconstruct the paleoecology of Archaeotherium of different size classes, representing broad geographic and temporal ranges, to infer dietary strategies and ecological niches. DMTA quantifies enamel surface-texture features via complexity (Asfc), anisotropy (epLsar), and textural fill volume (Tfv). Asfc is determined by surface roughness, indicating consumption of brittle/hard items (such as bone, seeds, and woody-browse), while epLsar is determined by alignment of parallel scratches, indicating consumption of tough foods (such as flesh or grass). Tfv is determined by microwear feature depth, indicating the degree of durophagy. This dataset includes two Archaeotherium morphotypes: smaller-bodied and larger-bodied morphs. DMTA results demonstrate that Archaeotherium exhibited size-driven dietary partitioning. Smaller-bodied Archaeotherium have statistically indistinguishable Asfc values from the extinct peccaries Protherohyus and Platygonus, extant wolves, cheetahs, and brown bears, with Tfv values also being indistinguishable from cheetahs. These similarities suggest consumption of softer foods with minimal durophagy. In contrast, larger-bodied Archaeotherium exhibit significantly greater Asfc values that are statistically indistinguishable from extinct durophagous peccaries and extant bone-consuming carnivorans, including lions and hyenas, with Tfv values indistinguishable from peccaries and hyenas. These data are consistent with the consumption of harder and/or more brittle foods that could include browse, nuts, tubers, and/or bone. Integrating results from both Archaeotherium morphotypes indicates that they occupied diverse ecological niches with dietary strategies strongly influenced by body size.