Preserved reptile scales retain microscopic features, revealing a new instance of convergent evolution

Abstract

Small-scale structures on biological surfaces can profoundly impact how animals move, appear, and interact with their environments. Such textures may be especially important for limbless reptiles, such as snakes and legless lizards, because their skin serves as the primary interface with the world around them. Here, we examine ventral microstructures of several limbless reptiles, which are hypothesized to be highly specialized to aid locomotion via frictional interactions. Inspired by prior studies that investigated potential links between microtextures, phylogeny, habitat, and locomotion -- but that were limited by their reliance on shed skins -- we characterized the structures present on preserved museum specimens and found that they are quantitatively similar to those found on shed skins. Using this result, we confirmed a previously hypothesized -- but untested due to the lack of shed skins -- third independent evolution of sidewinding-specific isotropic microtexture. Specifically, we examined a museum-preserved \textit{Bitis peringueyi} specimen and identified a new instance of convergent evolution in sidewinding viper microstructures: the loss of micro-spikes (present on many snake species) and the appearance of micro-pits with a characteristic spacing. Our results reveal that museum-preserved specimens retain intact microtextures, greatly expanding the availability of samples for evolutionary studies.