Physical characteristics

Most geckos are relatively small (1.2-3.5 in, or 30-90 mm) with short, somewhat flattened bodies; large heads; large eyes; and well-developed limbs. Eublepharines have movable eyelids, but they have been replaced by a transparent spectacle (eye cover) in other members of the subfamily. The smallest geckos are the sphaeros of the West Indies; the Jaragua sphaero (Sphaerodactylus ariasae) averages only 0.63 in (16 mm) in snout-vent length. At the other end of the spectrum is the New Caledonian giant gecko (Rhacodactylus leachianus), the largest living species at more than 10 in (250 mm). The recently extinct Delcourt's giant gecko (Hoplodactylus delcourti) of New Zealand, however, was much larger still at 14.6 in (370 mm) in snout-vent length.

The feet are one of the most striking and varying aspects of the morphologic characteristics of the gecko. Eublephar-ines and some gekkonines and diplodactylines have slender digits with well-developed claws, but many species have expanded pads on the base and or tips of the toes that permit adhesion to smooth surfaces. These pads may be distal (at the tips of the toes) and fan- (Ptyodactylus) or leaf-shaped (Phyllo-dactylus), or they may be basal (at the base of the toes) and arranged in single (Gekko) or divided (Hemidactylus) rows. The

A white-striped gecko (Gekko vittatus) demonstrates the toes and climbing ability of geckos. A. Underside of each foot has specialized toe pads; B. Overlapping scales on each toe; C. Each scale is made up of thousands of hair-like setae; D. Each seta is divided into microscopic filaments. (Illustration by Patricia Ferrer)

A white-striped gecko (Gekko vittatus) demonstrates the toes and climbing ability of geckos. A. Underside of each foot has specialized toe pads; B. Overlapping scales on each toe; C. Each scale is made up of thousands of hair-like setae; D. Each seta is divided into microscopic filaments. (Illustration by Patricia Ferrer)

first digit of the hands and feet may be reduced in size, but it is never lost entirely.

Pygopods have features that are an exception to the typical gecko body plan. In this lineage the forelimbs have been lost entirely, whereas the hind limbs are reduced to small flaps lying lateral to the vent. Pygopods also have smaller heads and much more elongate bodies (and especially tails) than other members of the family. Pygopods are covered with smooth, imbricating (overlapping) scales. Such scaling is extremely rare among geckos, which usually are covered with small granules, with or without larger keeled tubercles (enlarged scales with a raised ridge) intermixed.

Most geckos are drab in color, in keeping with their nocturnal habits. Browns and grays are the most common colors, and diffuse patterns of chevrons or crossbars characterize many species; in diurnal forms, such as the Malagasy day gecko (Phelsuma), bright greens, yellows, reds, and blues may be encountered. The males of many species of geckos possess a series of precloacal glands or femoral pores, or both, on the ventral surface of the groin and thighs.

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