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

TL;DR

This study shows that preserved reptile scales retain microscopic features, enabling the discovery of a new case of convergent evolution in microtextures associated with sidewinding locomotion.

Contribution

It demonstrates that museum specimens preserve microtextures, allowing new insights into reptile evolution and the independent development of sidewinding-specific skin features.

Findings

Microtextures on preserved specimens match those on shed skins.

Confirmed a third independent evolution of sidewinding microstructure.

Identified loss of micro-spikes and emergence of micro-pits in viper scales.

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.