Physiology LocomotionĪdhesive pads enable geckos to climb vertically.Īside from legless lizards, most lizards are quadrupedal and move using gaits with alternating movement of the right and left limbs with substantial body bending. In addition, the toes of chameleons are divided into two opposed groups on each foot ( zygodactyly), enabling them to perch on branches as birds do. The pads are composed of millions of tiny setae (hair-like structures) which fit closely to the substrate to adhere using van der Waals forces no liquid adhesive is needed. Three lineages, the geckos, anoles, and chameleons, have modified the scales under their toes to form adhesive pads, highly prominent in the first two groups. Chameleons have very long sticky tongues which can be extended rapidly to catch their insect prey. In geckos, the tongue is used to lick the eyes clean: they have no eyelids. In the beaded lizards, whiptails and monitor lizards, the tongue is forked and used mainly or exclusively to sense the environment, continually flicking out to sample the environment, and back to transfer molecules to the vomeronasal organ responsible for chemosensation, analogous to but different from smell or taste. The tongue can be extended outside the mouth, and is often long. Most species are pleurodont, though agamids and chameleons are acrodont. Species typically have uniform teeth suited to their diet, but several species have variable teeth, such as cutting teeth in the front of the jaws and crushing teeth in the rear. The dentitions of lizards reflect their wide range of diets, including carnivorous, insectivorous, omnivorous, herbivorous, nectivorous, and molluscivorous. Red tegu ( Tupinambis rufescens) skull, showing teeth of differing types The scales may be modified into spines for display or protection, and some species have bone osteoderms underneath the scales. Unlike snakes which shed the skin in a single piece, lizards slough their skin in several pieces. The skin is tough and leathery, and is shed (sloughed) as the animal grows. This adaptation enables lizards to thrive in some of the driest deserts on earth. This provides protection from the environment and reduces water loss through evaporation. Īs in other reptiles, the skin of lizards is covered in overlapping scales made of keratin. Some lizards such as chameleons have prehensile tails, assisting them in climbing among vegetation. Lizards and snakes share a movable quadrate bone, distinguishing them from the rhynchocephalians, which have more rigid diapsid skulls. Lizards typically have rounded torsos, elevated heads on short necks, four limbs and long tails, although some are legless. Most lizards are fairly small animals.Ī young Mediterranean house gecko in the process of moulting. The adult length of species within the suborder ranges from a few centimeters for chameleons such as Brookesia micra and geckos such as Sphaerodactylus ariasae to nearly 3 m (10 ft) in the case of the largest living varanid lizard, the Komodo dragon.
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