Lizard

Lizard is the common name used for all squamatereptiles that are not snakes (and to a lesser extent amphisbaenians or "worm lizards"), encompassing over 7,000 species. They have a cosmopolitan distribution, ranging across all continents except Antarctica, as well as most oceanic island chains. Extant lizard species vary in size from the 13.5 mm (0.53 in) nano-chameleon and the 14–18 mm (0.55–0.71 in) Jaragua dwarf gecko to the 3-meter-long Komodo dragon.

Most lizards are quadrupedal with a side-to-side swaying gait, although some lizards are capable of running on hindlimbs. Some lineages (known as "legless lizards") have secondarily lost their limbs and developed a snake-like elongated body due to convergent evolution. Some lizards, such as the arborealDraco, are capable of gliding flight using fanned-out gular membranes and costalpatagia as wings. 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 ambush predators; smaller lizard species eat insects and other invertebrates, while the larger monitor lizards can prey upon tetrapods as big as water buffalo.

Lizards are able to thrive in a wide range of habitats, from wetlands to deserts, from alpinemeadows to coastalcaves, from arctic tundra to tropical islands like the Galápagos. Some small lizards like the common house gecko and pale-flecked garden sunskink are able to adapt to niches within human settlements and become a part of the urban wildlife. As most lizards are relatively small, they are preyed upon by larger animals such as mammals, birds, other reptiles, and even fish and large frogs, as well as predatory invertebrates such as spiders, praying mantises and giant centipedes, and thus have a variety of antipredator adaptations including venom, camouflage, reflex bleeding and the ability to self-amputate their tail as a decoy that distracts the predator.

Snakes descended from lizards, so cladistic classification systems often regard "lizard" as a paraphyletic group, and some lizards are more closely related to snakes than they are to other lizards. To regard lizards as a monophyletic group, one would have to classify snakes as a clade/subgroup of specialized lizards, and this would also make "lizards" and "squamates" synonyms.