Thursday, October 22, 2009

Do You See The Lizard ?

Lizards are a very large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains.Lizards typically have limbs and external ears, while snakes lack both these characteristics. However, because they are defined negatively as excluding snakes, lizards have no unique distinguishing characteristic as a group.Sight is quite important for most lizards, both for locating prey and for communication, and as such, many lizards have highly acute color vision. Most lizards rely heavily on body language, using specific postures, gestures and movements to define territory, resolve disputes, and entice mates. Some species of lizard also utilize bright colors, such as the iridescent patches on the belly of Sceloporus. These colors would be highly visible to predators, so are often hidden on the underside or between scales and only revealed when necessary.A particular innovation in this respect is the dewlap, a brightly colored patch of skin on the throat, usually hidden between scales. When a display is needed, the lizards erect the hyoid bone of their throat, resulting in a large vertical flap of brightly colored skin beneath the head which can be then used for communication. Anoles are particularly famous for this display, with each species having specific colors, including patterns only visible under ultraviolet light, as lizards can often see UV.

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