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Lizard
Lizards are a widespread group of squamate reptiles, with approximately over 6,000 species,〔(Reptile Database ). Retrieved on 2012-04-22〕 ranging across all continents except Antarctica, as well as most oceanic island chains. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria (reptiles with overlapping scales) that are neither sphenodonts (i.e., tuatara) nor snakes – they form an evolutionary grade. While the snakes are recognized as falling phylogenetically within the Toxicofera clade from which they evolved, the sphenodonts are the sister group to the squamates, the larger monophyletic group, which includes both the lizards and the snakes.
==Biology==
Lizards typically have feet and external ears, while snakes lack both of these characteristics. However, because they are defined negatively as excluding snakes, lizards have no unique distinguishing characteristic as a group. Lizards and snakes share a movable quadrate bone, distinguishing them from the sphenodonts, which have more primitive and solid diapsid skulls. Many lizards can detach their tails to escape from predators, an act called autotomy. Vision, including color vision, is particularly well developed in most lizards, and most communicate with body language or bright colors on their bodies, as well as with pheromones. Lizards are the most speciose among extant reptiles, comprising about 60% of all living species.
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. Some extinct varanids reached great size. The extinct aquatic mosasaurs reached , and the giant monitor ''Megalania'' is estimated to have reached up to long.
The name Sauria was coined by James Macartney (1802);〔James Macartney: Table III ''in'': George Cuvier (1802) "Lectures on Comparative Anatomy" (translated by William Ross under the inspection of James Macartney). Vol I. London, Oriental Press, Wilson and Co.〕 it was the Latinisation of the French name ''Sauriens'', coined by Alexandre Brongniart (1800) for an order of reptiles in the classification proposed by the author, containing lizards and crocodilians,〔Alexandre Brongniart (1800) "Essai d’une classification naturelle des reptiles. 1ère partie: Etablissement des ordres." Bulletin de la Science. Société Philomathique de Paris 2 (35): 81-82〕 later discovered not to be each other's closest relatives. Later authors used the term "Sauria" in a more restricted sense, i.e. as a synonym of Lacertilia, a suborder of Squamata that includes all lizards but excludes snakes. This classification is rarely used today because Sauria so-defined is a paraphyletic group. It was defined as a clade by Jacques Gauthier, Arnold G. Kluge and Timothy Rowe (1988) as the group containing the most recent common ancestor of archosaurs and lepidosaurs (the groups containing crocodiles and lizards, as per Mcartney's original definition) and all its descendants. A different definition was formulated by Michael deBraga and Olivier Rieppel (1997) who defined Sauria as the clade containing the most recent common ancestor of Choristodera, Archosauromorpha and Lepidosauromorpha and all their descendants. However, neither of these uses have gained wide acceptance among researchers specializing in lizards.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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