pholidosis: an R package to compare biological surface patterns

Atop the heads of many lizards and snakes sit complex patterns of flattened scales, differing in their sizes, shapes, colors, textures, and inter-relationships. These patterns of head scalation–called “pholidosis” – are often diagnostic to species or genera and therefore of great importance to reptile taxonomy, yet they have never been investigated in a detailed comparative context. Similar patterns can be seen in the scutes of turtle shells and the “cells” of insect wings; these each consist of a surface pattern made up of discrete units that can be considered homologous between individuals, populations, and species. Here, I describe an R package, pholidosis , designed to analyze these patterns as networks, providing tools for their construction, analysis, and visualization, and comparative analysis via an edit distance metric.