Dental microwear texture reflects dietary tendencies in extant Lepidosauria despite their limited use of oral food processing

Abstract

Lepidosauria show a large diversity in dietary adaptations, both among extant and extinct tetrapods. Unlike mammals, Lepidosauria do not engage in sophisticated mastication of their food and most species have continuous tooth replacement, further reducing the wear of individual teeth. However, dietary tendency estimation of extinct lepidosaurs usually rely on tooth shape and body size, which allows only for broad distinction between faunivores and herbivores. Microscopic wear features on teeth have long been successfully applied to reconstruct the diet of mammals and allow for subtle discrimination of feeding strategies and food abrasiveness. Here, we present, to our knowledge, the first detailed analysis of dental microwear texture on extant lepidosaurs using a combination of 46 surface texture parameters to establish a framework for dietary tendency estimation of fossil reptilian taxa. We measured dental surface textures of 77 specimens, belonging to herbivorous, algaevorous, frugivorous, carnivorous, ovivorous, insectivorous, molluscivorous, as well as omnivorous species. Carnivores show low density and shallow depth of furrows, whereas frugivores are characterized by the highest density of furrows. Molluscivores show the deepest wear features and highest roughness, herbivores have lower surface roughness and shallower furrows compared to insectivores and omnivores, which overlap in all parameters. Our study shows that despite short food–tooth interaction, dental surface texture parameters enable discrimination of several feeding strategies in lepidosaurs. This result opens new research avenues to assess diet in a broad variety of extant and extinct non-mammalian taxa including dinosaurs and early synapsids.

Multiple evolutionary origins and losses of tooth complexity in squamates

“…In contrast with tooth complexity ancestral states reconstructions, extant data allow the formulation of informed hypotheses on possible dietary transitions in squamates. Insects are an important food resource for the juveniles of many squamate species, and several extant species of plant consumers show an ontogenetic dietary shift from insectivorous juveniles to omnivorous or herbivorous adults 36,64,81,82 . Moreover, extant data show that predatory squamates may rely on plant material depending on environmental conditions 34,64,83-85 .…”

“…However, selective pressures on squamate teeth may not be as intense as for mammals. Most plant-eating squamates still consume insects 36 , suggesting that, unlike in Mammalia, no hyper-specialist ratchet operated 37,38 .…”

Elevated activity levels do not influence extrinsic fiber attachment morphology on the surface of muscle‐attachment sites

“…Motif analysis refers to the application of automated pattern‐recognition algorithms to quantify structures on material surfaces. Developed in the engineering field for machining purposes, this technique has been used to assess a wide range of surface textures from geological features to tooth wear (review: Bernardos & Vosniakos, ; tooth wear: Schulz et al ; Puech & Pinilla, ; Böhm et al ; Winkler et al ). In this case, the motif analysis was customized in MountainsMap to identify the borders of EF insertion sites, the bony pit‐like morphology left behind at the point of EF attachment after rendering the surface anorganic.…”

Dust and grit matter: abrasives of different size lead to opposing dental microwear textures in experimentally fed sheep (Ovis aries)

“…Tooth surfaces of browsers, in contrast, generally show flatter surfaces with lower peaks. Microwear and DMTA have been applied to several non-mammalian taxa, including reptiles (Winkler et al, 2019b) and fish (Purnell et al, 2012), but for the most part these methods have been applied to mammals (Ungar et al, 2007;Schubert et al, 2010;Merceron et al, 2014;Brent Jones and Desantis, 2017;Aiba et al, 2019), including extinct humans (Pérez-Pérez et al, 2003).…”