Taxon-related variation in palmar and plantar friction ridge patterns among Aotus infulatus, Saimiri collinsi and Sapajus spp.: Individual-level variation and implications for identification

Friction ridges play important biomechanical roles in primates, contributing to the regulation of skin moisture and increasing friction with substrates and objects during locomotion and manipulation. In this context, the present study aimed to characterize and compare level I and II dermatoglyphic patterns of the palmar and plantar surfaces of Aotus infulatus (owl monkey), Saimiri collinsi (squirrel monkey), and Sapajus spp. (capuchin monkey). Following chemical restraint, skin impressions of the hands and feet were obtained by applying a thin layer of commercial ink used for human fingerprinting. The analyses revealed a consistent pattern of differentiation among taxa. A. infulatus exhibited greater dermatoglyphic homogeneity, with a higher frequency of deltas and whorls, as well as a greater occurrence of the dot on the ridge (P-IN) minutia compared to the other groups. Additionally, no identical palmar or plantar epidermal impressions were observed among individuals within the same taxon, indicating individual-level variability in these structures. Thus, palmar and plantar friction ridge patterns may provide useful morphological markers for comparative studies of taxon-related variation in non-human primates, with potential applications in biological research, population management, and conservation strategies.