Paraphalangeal elements of gekkonid lizards: A comparative survey.

Paraphalanges of gekkonid lizards are cartilaginous structures associated with interphalangeal joints. Their form and structure have been investigated by dissection, cleared-and-stained specimens, routine histoloty, and radiography. A family-wide survey revealed that paraphalangeal elements occur in at least 57 species in 16 genera of the subfamily Gekkoninae. The distribution and structure of these elements suggests multiple origins among gekkonine geckos. In most instances, they are present in species with expanded subdigital climbing pads, divided scansors, and a markedly raised penultimate phalanx that is elevated from, or free of, the pad. Thus, they seem to be associated with placement of the scansors onto the locomotor substrate. In two genera, Uroplatus and Palmatogecko, paraphalanges at the more proximal interphalangeal joints are associated with muscles that run between them. In these cases, the paraphalanges appear to be involved in grasping abilities of the foot associated with digging and climbing modifications.