Lizards

Lizards are a 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. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria reptiles with overlapping scales) which are neither sphenodonts (i.e., Tuatara) nor snakes. While the snakes are recognized as falling phylogenetically within the anguimorph lizards 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.

Lizards typically have four 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. Lizards and snakes share a movable quadrate bone, distinguishing them from the sphenodonts which have a more primitive and solid diapsid skull. Many lizards can detach their tails in order to escape from predators, an act called autotomy, but this trait is not universal. 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. The adult length of species within the suborder ranges from a few centimeters for some chameleons and geckos to nearly three meters (9 feet, 6 inches) in the case of the largest living varanid lizard, the Komodo Dragon. Some extinct varanids reached great size. The extinct aquatic mosasaurs reached 17.5 meters, and the giant monitor Megalania prisca is estimated to have reached perhaps seven meters.

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.

Evolution and relationships

The retention of the basic tetrapod body form by lizards makes it tempting to assume any similar animal, alive or extinct, is also a lizard. However, this is not the case, and lizards are part of a well-defined group.

The first reptile was superficially lizard-like, but had a solid, box-like skull, with openings only for eyes, nostrils, etc (termed Anapsid). These organisms later gave rise to two new groups with additional holes in the skull to make room for and anchor larger jaw muscles.Those with a single hole, the Synapsids, became modern mammals. The Diapsids, possessing two holes, continued to diversify. The Archosaurs retained the basic Diapsid skull, and gave rise to a bewildering array of animals, most famous being the dinosaurs and their descendants, birds. The Lepidosaurs began to reduce the skull bones, making the skull lighter and more flexible. Modern tuataras retain the basic Lepidosaur skull, distinguishing them from true lizards in spite of superficial similarities. Squamates, including snakes and all true lizards, further lightened the skull by eliminating the lower margin of the lower skull opening.

Relationship to humans

Most lizard species are harmless to humans. Only the very largest lizard species pose threat of death; the Komodo dragon, for example, has been known to stalk, attack, and kill humans. The venom of the Gila monster and beaded lizard is not usually deadly but they can inflict extremely painful bites due to powerful jaws. The chief impact of lizards on humans is positive as they are significant predators of pest species; numerous species are prominent in the pet trade.

Lizard symbolism plays important, though rarely predominant roles in some cultures (e.g. Tarrotarro in Australian mythology). The Moche people of ancient Peru worshiped animals and often depicted lizards in their art. According to a popular legend in Maharashtra, a Common Indian Monitor, with ropes attached, was used to scale the walls of the Sinhagad fort in the Battle of Sinhagad.

Lizards as food

Green Iguanas are eaten in Central America and Uromastyx in Africa and India. In North Africa, Uromastyx are considered dhaab or fish of the desert and eaten by Islamic nomad tribes. In India too, these lizards are caught for their meat, about which Malcolm Smith says ..with certain castes of Hindoos it is a regular article of diet..the meat is said to be excellent and white like chicken...the head and feet are not eaten, but the tail is considered a great delicacy...the fat of the body is boiled down and the resulting oil is used as an embrocation and also as a cure for impotence. lucas is a type of lizard from Madagascar.

Classification
Plumed Basilisk, Basiliscus plumifrons
Zebra-tailed Lizard, Callisaurus draconoides
Red-headed rock agama, Agama agama
Gila monster, Heloderma s. suspectum
A Komodo dragon Varanus komodoensis; notice the large, curved claws used in fighting and eating.

Suborder Lacertilia (Sauria) - (Lizards)

* Family ┼Bavarisauridae
* Family ┼Eichstaettisauridae
* Infraorder Iguania
o Family ┼Arretosauridae
o Family ┼Euposauridae
o Family Corytophanidae (casquehead lizards)
o Family Iguanidae (iguanas and spinytail iguanas)
o Family Phrynosomatidae (earless, spiny, tree, side-blotched and horned lizards)
o Family Polychrotidae (anoles)
+ Family Leiosauridae (see Polychrotinae)
o Family Tropiduridae (neotropical ground lizards)
+ Family Liolaemidae (see Tropidurinae)
+ Family Leiocephalidae (see Tropidurinae)
o Family Crotaphytidae (collared and leopard lizards)
o Family Opluridae (Madagascar iguanids)
o Family Hoplocercidae (wood lizards, clubtails)
o Family ┼Priscagamidae
o Family ┼Isodontosauridae
o Family Agamidae (agamas)
o Family Chamaeleonidae (chameleons)
* Infraorder Gekkota
o Family Gekkonidae (geckos)
o Family Pygopodidae (legless lizards)
o Family Dibamidae (blind lizards)
* Infraorder Scincomorpha
o Family ┼Paramacellodidae
o Family ┼Slavoiidae
o Family Scincidae (skinks)
o Family Cordylidae (spinytail lizards)
o Family Gerrhosauridae (plated lizards)
o Family Xantusiidae (night lizards)
o Family Lacertidae (wall lizards or true lizards)
o Family ┼Mongolochamopidae
o Family ┼Adamisauridae
o Family Teiidae (tegus and whiptails)
o Family Gymnophthalmidae (spectacled lizards)
* Infraorder Diploglossa
o Family Anguidae (glass lizards)
o Family Anniellidae (American legless lizards)
o Family Xenosauridae (knob-scaled lizards)
* Infraorder Platynota (Varanoidea)
o Family Varanidae (monitor lizards)
o Family Lanthanotidae (earless monitor lizards)
o Family Helodermatidae (gila monsters & beaded lizards)
o Family ┼Mosasauridae (marine lizards)

References

1. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueologico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
2. ^ Auffenberg, Walter (1994). The Bengal Monitor. University Press of Florida. pp. 494. ISBN 0813012953.
3. ^ pg 48, Grzimek,Bernhard. Grzimek's Animal Life Encyclopedia (Second Edition) Vol 7 - Reptiles. (2003) Thomson - Gale. Farmington Hills, Minnesota. Vol Editor - Neil Schlager. ISBN 0-7876-5783-2 (for vol.7)
4. ^ pp 244-247, Smith, Malcolm A. (1935) The Fauna of British India including Ceylon and Burmah, Reptilia and Amphibia, Vol II - Sauria, Taylor and Francis, London.

General references

* Byiiuo, John L.; King, F. Wayne (1979). The Audubon Society Field Guide to Reptiles and Amphibians of North America. New York: Alfred A. Knopf. pp. 581. ISBN 0394508246.
* Capula, Massimo; Behler (1989). Simon & Schuster's Guide to Reptiles and Amphibians of the World. New York: Simon & Schuster. ISBN 0671690981.
* Cogger, Harold; Zweifel, Richard (1992). Reptiles & Amphibians. Sydney: Weldon Owen. ISBN 0831727861.
* Conant, Roger; Collins, Joseph (1991). A Field Guide to Reptiles and Amphibians Eastern/Central North America. Boston, Massachusetts: Houghton Mifflin Company. ISBN 0395583896.
* Ditmars, Raymond L (1933). Reptiles of the World: The Crocodilians, Lizards, Snakes, Turtles and Tortoises of the Eastern and Western Hemispheres. New York: Macmillian. pp. 321.
* Freiberg, Dr. Marcos; Walls, Jerry (1984). The World of Venomous Animals. New Jersey: TFH Publications. ISBN 0876665679.

Web Reference: http://en.wikipedia.org/wiki/Lizard