Comparative micro-ornamentation patterns of reptile skin: Phylogeny-ecology debate and species-specific variations

The Oberhautchen cells of reptile skin possess micro-ornamentations that are complex structures with a wide diversity. The ongoing debate regarding the origin of these structures oscillates between phylogenetic and ecological drivers. The current study also contributes to this debate by examining micro-ornamentations in seven lizards from three families, one worm lizard, and four snakes from three families that have epigeal, fossorial, saxicolous, or semi-aquatic life habits. They were compared in terms of phylogeny and life habits. Additionally, the variations in different scales of the same individual and different regions of the same scale were studied. The aim of comparing phylogenetically distant species among reptiles was to understand whether micro-ornamentation morphologies evolved convergently in species with the same life habits. The results showed that there are three cell shapes, two cell borders, five cell surfaces, and three ridges as morphological character states within the studied species. These variations might also differ significantly on different scales for an individual and even change gradually on the same scale. The ancestral form possibly has polygonal cells and regular borders with a smooth surface where the ridges are absent. It is essential to consider that convergent evolution facilitates the resolution of "problems" with similar "answers," however, comparisons suggest that phylogenetic limitations are more decisive than habitat restrictions in shaping the diversity of reptile skin micro-ornamentation.