Lizard
Lizard, common name for certain reptiles in the order that also contains snakes, amphisbaenians (Worm Lizard), and the extinct mosasaurs. Lizards constitute the largest living group of reptiles, with more than 4,300 species in a wide variety of shapes and sizes.
Although lizards may resemble salamanders and other amphibians, they differ in that lizards have dry scaly skin, and most have clawed feet and external ear openings. Most lizards are small, with four legs and a long tail that in many species is fragile and easily broken but will regenerate; the tail of such arboreal species as the chameleon is adapted for grasping branches. The legs of some lizards are greatly shortened, or vestigial, making animals such as the glass lizard or slowworm snakelike in appearance; they are distinguished from true snakes by their movable eyelids and by differences in the structure of the skull bones, especially those of the lower jaw. The bones of the two halves of a lizard’s lower jaw are firmly united; those of a snake are separable.
Lizards move in a variety of ways, depending on body structure and habitat. The collared lizard and the basilisk run quickly on well-developed hind legs. Geckos have scaled disks on each toe that allow them to cling to smooth surfaces. Some lizards are good swimmers, and a number are adapted for climbing trees.
The diets of lizards vary greatly, depending on species. While most are insectivorous, some, such as the green iguana, are generally vegetarians. The Gila monster, which lives in desert areas, eats reptile and bird eggs as well as small rodents; it also has a fat reserve stored in its tail. Depending on their size, monitors prey on insects, birds and reptiles and their eggs, small mammals, and carrion. One species, the Komodo dragon, is large enough to be a threat to humans.
Scientific classification: Lizards belong to the order Squamata.
Although lizards may resemble salamanders and other amphibians, they differ in that lizards have dry scaly skin, and most have clawed feet and external ear openings. Most lizards are small, with four legs and a long tail that in many species is fragile and easily broken but will regenerate; the tail of such arboreal species as the chameleon is adapted for grasping branches. The legs of some lizards are greatly shortened, or vestigial, making animals such as the glass lizard or slowworm snakelike in appearance; they are distinguished from true snakes by their movable eyelids and by differences in the structure of the skull bones, especially those of the lower jaw. The bones of the two halves of a lizard’s lower jaw are firmly united; those of a snake are separable.
Lizards move in a variety of ways, depending on body structure and habitat. The collared lizard and the basilisk run quickly on well-developed hind legs. Geckos have scaled disks on each toe that allow them to cling to smooth surfaces. Some lizards are good swimmers, and a number are adapted for climbing trees.
The diets of lizards vary greatly, depending on species. While most are insectivorous, some, such as the green iguana, are generally vegetarians. The Gila monster, which lives in desert areas, eats reptile and bird eggs as well as small rodents; it also has a fat reserve stored in its tail. Depending on their size, monitors prey on insects, birds and reptiles and their eggs, small mammals, and carrion. One species, the Komodo dragon, is large enough to be a threat to humans.
Scientific classification: Lizards belong to the order Squamata.
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