Lizard is the common name used for all squamate reptiles other than snakes (and to a lesser extent amphisbaenians or "worm lizards"), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The grouping is paraphyletic as some lizards are more closely related to snakes than they are to other lizards. Living lizards range in size from chameleons and geckos a few centimeters long to the 3-meter-long Komodo dragon.
Most lizards are quadrupedal, running with a strong side-to-side motion. Some lineages (known as "legless lizards") have secondarily lost their legs, and have long snake-like bodies. Some lizards, such as the forest-dwelling Draco, are able to glide. They are often territorial, the males fighting off other males and signalling, often with bright colours, to attract mates and to intimidate rivals. Lizards are mainly carnivorous, often being sit-and-wait predators; many smaller species eat insects, while the Komodo eats mammals as big as water buffalo.
Lizards make use of a variety of antipredator adaptations, including venom, camouflage, reflex bleeding, and the ability to sacrifice and regrow their tails.
Snakes are descended from lizards, so cladistic classification systems often regard "lizard" as a paraphyletic group (a group with a shared evolutionary origin, but excluding some descendant groups, in this case snakes). In order to regard lizards as a monophyletic clade (a group with a single origin and no descendants excluded), one would have to classify snakes as a type of lizard. This would also make lizards and squamates equivalent terms.
Anatomy
Largest and smallest
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 in the case of the largest living varanid lizard, the Komodo dragon. Most lizards are fairly small animals.
Distinguishing features
thumb|right|A young [[Mediterranean house gecko in the process of moulting.|300px]]
Lizards typically have rounded torsos, elevated heads on short necks, four limbs and long tails, although some are legless. Lizards and snakes share a movable quadrate bone, distinguishing them from the rhynchocephalians, which have more rigid diapsid skulls. Some lizards such as chameleons have prehensile tails, assisting them in climbing among vegetation.
thumb|Red tegu ([[Tupinambis rufescens) skull, showing teeth of differing types]]
The dentitions of lizards reflect their wide range of diets, including carnivorous, insectivorous, omnivorous, herbivorous, nectivorous, and molluscivorous. 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. Most species are pleurodont, though agamids and chameleons are acrodont.
The tongue can be extended outside the mouth, and is often long. 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. In geckos, the tongue is used to lick the eyes clean: they have no eyelids. Chameleons have very long sticky tongues which can be extended rapidly to catch their insect prey. 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.