Sheddable armour: identification of osteoderms in the integument of Geckolepis maculata (Gekkota)

Osteoderms are bony deposits that form within the dermal layer of skin in vertebrates. Within geckos, osteoderms are uncommon, only described in Gekko gecko and the genus Tarentola. A previous report of osteoderms in the Afro-Malagasy gekkonid genus Geckolepis has been questioned due to the extreme skin fragility and regional integumentary loss within the group. We re-evaluated the integument anatomy of Geckolepis maculata using µCT scanning, histology, and clearing and staining to verify the presence or absence of osteoderms and, if present, to characterise and compare their morphology to the osteoderms of Gekko gecko and Tarentola, as well as osteoderm diversity within squamates. Osteoderms were confirmed present in Geckolepis maculata; however, these osteoderms are compound, imbricating, squamous elements that are morphologically similar to the dermal ossifications observed in scincids and gerrhosaurids, while G. gecko and Tarentola possess plate-like and granular osteoderms. Our results suggest that osteoderms have independently evolved at least three times within the Gekkota and that epidermal anatomy may be a better predictor of osteoderm morphology than ancestral history. Further research is required to investigate the regenerative capability of Geckolepis osteoderms following skin autotomy.