Figure 3. An unambiguous gain of adhesive toepads in house geckos (Hemidactylus).

Maximum likelihood tree of included Hemidactylus species and their close relatives, the padless “naked-toed” geckos and the Cyrtodactylus + Geckoella clade. Circles at nodes indicate bootstrap support. Bayesian posterior probabilities of the presence of toepads are shown for two key nodes. Selected morphological components that comprise the digital adhesive mechanism are illustrated for each major clade. All three clades share spinules on the subdigital epidermis although only in Hemidactylus are they fully elaborated as setae. In the Cyrtodactylus + Hemidactylus clade: the subdigital lamellae are broadened; the antepenultimate phalanx of the digit (in blue) is reduced and, together with the penultimate phalanx and the claw, forms a raised arc; and the dorsal (extensor) musculature is expanded distally along the digit. The transition to fully functional toepads occurs in Hemidactylus, which incorporate the tendinous system that controls individual scansors, and possesses epdidermal spinules that are of increased length and that are multi-spatulate, enhancing functional adhesive surface area. These are recognizable as setae.