Morphological correlates of the secondarily symmetrical pes of gekkotan lizards

Gekkotan lizards, belonging to the family Gekkonidae, especially those that bear subdigital adhesive pads, tend to exhibit a pes that is symmetrical in appearance, rather than the asymmetrical configuration of lizards in general. Such a symmetrical morphology is reminiscent of that of primitive tetrapods, but is secondarily derived within lizards, as shown by way of qualitative assessments and quantitative comparisons of length and angular measurements of the pedal skeleton. The results reveal that trends towards secondary symmetry of the pes, including spreading of the metatarsal rays, relative shortening of the metatarsals, especially the fourth, and of the digits are already present in primitive gekkotans. It thus appears that such trends are precursors to the bearing of subdigital adhesive pads and not modifications to this end. The configuration of subdigital adhesive pads in gekkonoids appears to have resulted from exapting a syndrome of morphological modifications already present in the basal gekkotan stock.