Some lizard species, including the glass lizard and legless lizards, have some vestigial structures though no functional legs. They are distinguished from true snakes by the presence of eyelids and ears and a tail that can sometimes break off as a physical defence mechanism. Many lizards are good climbers or fast sprinters. Some can run bipedally, such as the collared lizard and the world's fastest lizard, the spiny-tailed iguana of the genus Ctenosaura.
Many lizards can change colour in response to their environments or in times of stress. The most familiar example is the chameleon, but more subtle colour changes occur in other lizard species as well such as the anole, also known as the "American chameleon," "house chameleon" or "chamele".
Lizards in the Scincomorpha family, which include skinks (such as the blue-tailed skink), often have shiny, iridescent scales that appear moist. They are dry-skinned and generally prefer to avoid water. All lizards are capable of swimming if needed and a few (such as the Nile monitor) are quite comfortable in aquatic environments.
Lizards are reptiles of the order Squamata, normally possessing four legs and external ear openings. The adult length of species within the order range from a few centimeters (some Caribbean geckos) to nearly three meters (Komodo Dragons). Lizards are reptiles, often four-legged, with an integumentary system comprising scales, with a skull composed of quadrate bones. Lizards possess external ears and most have movable eyelids. Encompassing forty families, there is tremendous variety in colour, appearance and size. Due to their smooth, shiny appearance, some lizards can appear slimy or slippery although their skin is actually very dry due to a lack of pores to excrete water and oils. Lizards have scales on their skin which may be tubercular or have ossified encrustations called osteoderms.Most lizards are oviparous, though a few species are viviparous. Many are also capable of regeneration of lost limbs or tails.
