Many, see text 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. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria which are neither sphenodonts (i.e., Tuatara) nor.

Lizards are a very large and widespread group of squamate Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the braincase. This is particularly visible in snakes, reptiles Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded amniotes that have skin covered in scales or scutes as opposed to hair or feathers. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane. Modern reptiles inhabit every continent with the exception of Antarctica, and four living, with nearly 5,000 species There are many definitions of what kind of unit a species is . A common definition is that of a group of organisms capable of interbreeding and producing fertile offspring, and separated from other such groups with which interbreeding does not (normally) happen. Other definitions may focus on similarity of DNA or morphology. Some species are, ranging across all continents except Antarctica Antarctica (pronounced /ænˈtɑrktɪkə/ , is Earth's southernmost continent, underlying the South Pole. It is situated in the Antarctic region of the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14.0 million km² (5.4 million sq mi), it is the fifth-largest continent in area as well as most oceanic island chains. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria The Lepidosauria are reptiles with overlapping scales. They include the tuataras, lizards, snakes and amphisbaenians. Lepidosaurians are the most successful of modern reptiles (reptiles with overlapping scales) which are neither sphenodonts Sphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara . Despite its current lack of diversity, the Sphenodontia at one time included a wide array of genera in several families, and represents a lineage stretching back to the Mesozoic Era (i.e., Tuatara The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common ancestor with any other extant group is with the) nor snakes Snakes are elongate legless carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic amniote vertebrates covered in overlapping scales. Like lizards, from which they evolved, they have loosely articulated skulls and most can. While the snakes are recognized as falling phylogenetically Cladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry. It can be distinguished from other taxonomic systems, such as phenetics, by its focus on evolutionary relationships; while other systems usually use morphological similarities to group similar species into genera, families and other within the anguimorph Anguimorphs of the infraorder Anguimorpha include the anguids , monitor lizards, mosasaurs, and helodermatids (Gila monster and beaded lizard). The infraorder was named by Fürbringer in 1900 to include all autarchoglossans closer to Varanus and Anguis than Scincus. These lizards, along with iguanians and snakes, comprise the proposed "venom lizards from which they evolved, the sphenodonts are the sister group Cladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry. It can be distinguished from other taxonomic systems, such as phenetics, by its focus on evolutionary relationships; while other systems usually use morphological similarities to group similar species into genera, families and other to the squamates, the larger monophyletic In common cladistic usage, a monophyletic group is a clade, consisting of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly group which includes both the lizards and the snakes.

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. Lizards and snakes share a movable quadrate bone The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids , and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint (the other part is the articular bone at the rear end of the lower jaw), distinguishing them from the sphenodonts Sphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara . Despite its current lack of diversity, the Sphenodontia at one time included a wide array of genera in several families, and represents a lineage stretching back to the Mesozoic Era which have a more primitive and solid diapsid skull The skull is a bony structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury. Many lizards can detach their tails in order to escape from predators, an act called autotomy Autotomy or self amputation is the act whereby an animal severs one or more of its own appendages, usually as a self-defense mechanism designed to elude a predator's grasp. The lost body part may be regenerated later, 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 A pheromone is a chemical signal that triggers a natural response in another member of the same species. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Their use among insects has been particularly well documented. In addition, some vertebrates and plants communicate by using. The adult length of species within the suborder ranges from a few centimeters A centimetre is a unit of length in the metric system, equal to one hundredth of a metre, which is the current SI base unit of length. Centi is the SI prefix for a factor of 10−2. Hence a centimetre can be written as 10 × 10−3 m (engineering notation) or 1E−2 m (scientific E notation) — meaning 10 × 101 mm or 1 m/100 respectively, for some chameleons The family Chamaeleonidae are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, and the possession by many of a prehensile tail, crests or horns on and geckos Geckos are small to average sized lizards belonging to the family Gekkonidae, found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. An estimated 2,000 different species of geckos exist worldwide, with many likely yet to be discovered to nearly three meters (9 feet, 6 inches) in the case of the largest living varanid lizard, the Komodo Dragon The Komodo dragon is a species of lizard that inhabits the islands of Komodo, Rinca, Flores, and Gili Motang in Indonesia. A member of the monitor lizard family (Varanidae), it is the largest living species of lizard, growing to an average length of 2 to 3 metres (6.6 to 9.8 ft) and weighing around 70 kilograms (150 lb). Their unusual size is. 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.

Physiology

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 'reptilian' amniote 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 as squamates are part of a well-defined group.

The earliest "lizard" was superficially lizard-like, but had a solid, box-like skull, with openings only for eyes, nostrils, etc (termed Anapsid). Turtles retain this skull form. Early anapsids 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, gave rise to the superficially lizard-like Pelycosaurs which include Dimetrodon and the Therapsids Therapsida is a group of synapsids that include mammals and their immediate evolutionary ancestors. Other than the mammals, all lineages of the therapsids are extinct, with the last known non-mammalian therapsids dying out in the Early Cretaceous period, including the Cynodonts Cynodonts, or 'dog teeth', are a taxon of Therapsids which includes modern mammals and their extinct close relatives. They were one of the most diverse groups of therapsids. They are named after their dog-like teeth, from which would evolve the modern mammals.

The Diapsids, possessing one temporal fenestra The skull is a bony structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury before the eye and one behind it, continued to diversify. One branch, the Archosaurs Archosaurs are a group of diapsid amniotes represented by modern birds and crocodilians. This group also includes extinct non-avian dinosaurs, pterosaurs and relatives of crocodiles, retained the basic Diapsid skull, and gave rise to a bewildering array of animals, most famous being the crocodilians, the pterosaurs, the dinosaurs and their descendants, birds. The Ichthyosaurs and Plesiosaurs radiated from the same basal Diapsid group.

The smaller Lepidosaurs which would give rise to the lizards began to reduce the skull bones, making the skull lighter and more flexible. The modern Tuatara The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common ancestor with any other extant group is with the retains the basic Lepidosaur skull, distinguishing it 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.

Lizard diversfication

Within the Lacertilia are found four generally recognized suborders, Iguania, Gekkota, Amphisbaenia and Autarchoglossa, with the "blind skinks" in the family Dibamidae having an uncertain position. While traditionally excluded from the lizards, the snakes are usually classified as a clade with a similar subordinal rank.^[1].

Iguania

The suborder Iguania, found in Africa, south Asia, Australia, the New World, and with iguanas colonizing the islands of the west Pacific, form the sister group Cladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry. It can be distinguished from other taxonomic systems, such as phenetics, by its focus on evolutionary relationships; while other systems usually use morphological similarities to group similar species into genera, families and other to the remainder of the squamata. They are largely arboreal, and have primitively fleshy, non-prehensile tongues, but this condition is obviously highly modified in the chameleons. This clade Ever since Darwin showed that all organisms share common ancestry, taxonomy has consistently attempted to represent and reflect the evolutionary history of organisms. The DNA and RNA analysis used in modern molecular biology has greatly helped in illuminating this history, by providing large amounts of new phylogenetic information which was includes the following families:

• Family Agamidae Agamids, lizards of the family Agamidae, include more than 300 species in Africa, Asia, Australia, and a few in Southern Europe. Phylogenetically they may be sister to the Iguanidae, and have a similar appearance. Agamids usually have well-developed, strong legs. Their tails cannot be shed and regenerated like those of geckoes, though a certain – Agamid Lizards, Old World Arboreal Lizards
• Family Chamaeleonidae – Chameleons
• Family Corytophanidae Corytophanidae is a family of lizards also called casque head lizards or helmeted lizards. They typically have well-developed head crests in the shape of a casque. This crest is a sexually dimorphic characteristic, found only on males[citation needed]. There are 9 known species of casque heads from 3 genera – Helmet Lizards
• Family Crotaphytidae – Collared Lizards, Leopard Lizards
• Family Hoplocercidae – Dwarf and Spiny Tail Iguanas
• Family Iguanidae – American Arboreal Lizards, Chuckwallas, Iguanas, Iguanids
• Family Opluridae – Malagasy Iguanas
• Family Phrynosomatidae – North American Spiny Lizards
• Family Polychrotidae – Anoles and kin
• Family Tropiduridae – Tropidurid Lizards

Gekkota

Active hunters, the Gekkota includes three families comprising the distinctive cosmopolitan geckos and the legless flap-footed lizards of Australia and New Zealand. Like snakes, the geckos and the flap-footed lizards lack eyelids. Unlike snakes, they use their tongues to clean their often highly developed eyes. While gecko feet have unique surfaces which allow them to cling to glass and run on ceilings, the flapfoot has lost its limbs. The three families of this suborder are:

• Family Eublepharidae – Eublepharid Geckos
• Family Gekkonidae Geckos are small to average sized lizards belonging to the family Gekkonidae, found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. An estimated 2,000 different species of geckos exist worldwide, with many likely yet to be discovered – Geckos
• Family Pygopodidae – Flap-footed Lizards

Relationship with humans

Most lizard species are harmless to humans. Only the very largest lizard species pose threat of death; the Komodo dragon The Komodo dragon is a species of lizard that inhabits the islands of Komodo, Rinca, Flores, and Gili Motang in Indonesia. A member of the monitor lizard family (Varanidae), it is the largest living species of lizard, growing to an average length of 2 to 3 metres (6.6 to 9.8 ft) and weighing around 70 kilograms (150 lb). Their unusual size is, for example, has been known to stalk, attack, and kill humans. The venom of the Gila monster The Gila monster , Heloderma suspectum, is a species of venomous lizard native to the southwestern United States and northern Mexico (but not Baja California). A heavy, slow-moving lizard, up to 60 centimetres (2.0 ft) long, the Gila monster is the only venomous lizard native to the United States, and one of only two known species of venomous and beaded lizard The beaded lizard is a species of venomous lizard found in Guatemala and Mexico. It and its congener, the Gila monster (Heloderma suspectum), are the only lizards to have evolved an overt venom delivery system and have long been considered the only venomous lizards. The beaded lizard is larger than the Gila monster but has duller coloration, being is not usually deadly but they can inflict extremely painful bites due to powerful jaws. Humans generally have a positive opinion of lizards as many are significant predators of pests A pest is an organism which has characteristics that are regarded by humans as injurious or unwanted. This is most often because it causes damage to agriculture through feeding on crops or parasitising livestock, such as codling moth on apples, or boll weevil on cotton. An animal can also be a pest when it causes damage to a wild ecosystem or such as insects; numerous species of lizards are common pets A pet is an animal kept for companionship and enjoyment or a household animal, as opposed to livestock, laboratory animals, working animals or sport animals, which are kept for economic reasons. The most popular pets are noted for their loyal or playful characteristics, for their attractive appearance, or for their song. Pets also generally seem.

Lizard symbolism plays important, though rarely predominant roles in some cultures Culture is a term that has different meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions. However, the word "culture" is most commonly used in three basic senses: (e.g. Tarrotarro in Australian Aboriginal mythology Australian Aboriginal myths are the stories traditionally performed by Aboriginal peoples within each of the language groups across Australia). The Moche The Moche civilization flourished in northern Peru from about 100 A.D. to 800 A.D., during the Regional Development Epoch. While still the subject of some debate, many scholars contend that the Moche were not politically organized as a monolithic empire or state but rather as a group of autonomous polities that shared a common elite culture as people of ancient Peru Peru , officially the Republic of Peru (Spanish: República del Perú, pronounced [reˈpuβlika ðel peˈɾu] ( listen)), is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean worshiped animals and often depicted lizards in their art.^[2] According to a popular legend in Maharashtra Maharashtra (Marathi: महाराष्ट्र mahārāṣṭra, IPA [məharaːʂʈrə] ) is a state located on the western coast of India. Maharashtra is a part of Western India. It is India's third largest state by area and second largest by population, a Common Indian Monitor, with ropes attached, was used to scale the walls of the Sinhagad fort in the Battle of Sinhagad.^[3]

Green Iguanas are eaten in Central America and Uromastyx in Africa Africa is the world's second-largest and second most-populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area. With a billion people (as of 2009, see table) in 61 territories, it accounts for about 14.8% of the World's human population and India India, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal on the east, India has a coastline of 7,517. In North Africa, Uromastyx are considered dhaab or 'fish of the desert' and eaten by nomadic tribes.^[4] 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.^[5]

Classification

Suborder Lacertilia (Sauria) - (Lizards)

• Family †Bavarisauridae
• Family †Eichstaettisauridae
• Infraorder Iguania
  • Family †Arretosauridae
  • Family †Euposauridae
  • Family Corytophanidae Corytophanidae is a family of lizards also called casque head lizards or helmeted lizards. They typically have well-developed head crests in the shape of a casque. This crest is a sexually dimorphic characteristic, found only on males[citation needed]. There are 9 known species of casque heads from 3 genera (casquehead lizards)
  • Family Iguanidae (iguanas Iguana is a genus of lizard native to tropical areas of Central and South America and the Caribbean. The genus was first described by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena in 1768. The genus Iguana includes two species: the green iguana and and spinytail iguanas)
  • Family Phrynosomatidae (earless, spiny, tree, side-blotched and horned Horned lizards are a genus of the Phrynosomatidae family of lizards. The horned lizard is popularly called a "horned toad," "horny toad", or "horned frog," but it is neither a toad nor a frog. The popular names come from the lizard's rounded body and blunt snout, which make it resemble a toad or frog. (Phrynosoma lizards)
  • Family Polychrotidae (anoles Anolis is a genus of lizards belonging to the family Iguanidae. With nearly 400 species, Anolis represents the world's most species rich amniote genus. Several species of Anolis are occasionally ascribed to the genus Norops, but the validity of the Norops genus is not widely accepted. The green anole has recently become the first non-avian reptile)
    • Family Leiosauridae (see Polychrotinae)
  • Family Tropiduridae (neotropical ground lizards)
    • Family Liolaemidae (see Tropidurinae)
    • Family Leiocephalidae (see Tropidurinae)
  • Family Crotaphytidae (collared and leopard lizards)
  • Family Opluridae (Madagascar iguanids)
  • Family Hoplocercidae (wood lizards, clubtails)
  • Family †Priscagamidae
  • Family †Isodontosauridae
  • Family Agamidae (agamas)
  • Family Chamaeleonidae (chameleons)
• Infraorder Gekkota
  • Family Gekkonidae (geckos)
  • Family Pygopodidae (legless lizards)
  • Family Dibamidae (blind lizards)
• Infraorder Scincomorpha
  • Family †Paramacellodidae
  • Family †Slavoiidae
  • Family Scincidae (skinks)
  • Family Cordylidae (spinytail lizards)
  • Family Gerrhosauridae (plated lizards)
  • Family Xantusiidae (night lizards)
  • Family Lacertidae (wall lizards or true lizards)
  • Family †Mongolochamopidae
  • Family †Adamisauridae
  • Family Teiidae (tegus and whiptails)
  • Family Gymnophthalmidae (spectacled lizards)
• Infraorder Diploglossa
  • Family Anguidae (glass lizards)
  • Family Anniellidae (American legless lizards)
  • Family Xenosauridae (knob-scaled lizards)
• Infraorder Platynota (Varanoidea)
  • Family Varanidae (monitor lizards)
  • Family Lanthanotidae (earless monitor lizards)
  • Family Helodermatidae (gila monsters & beaded lizards)
  • Family †Mosasauridae (marine lizards)

References

1. ^ ITIS http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=173861
2. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
3. ^ Auffenberg, Walter (1994). The Bengal Monitor. University Press of Florida. pp. 494. ISBN 0813012953.
4. ^ 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)
5. ^ 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.

• Gibbons, J. Whitfield; Gibbons, Whit (1983). Their Blood Runs Cold: Adventures With Reptiles and Amphibians. Alabama: University of Alabama Press. pp. 164. ISBN 978-0817301354.
• Rosenfeld, Arthur (1989). Exotic Pets. New York: Simon & Schuster. pp. 293. ISBN 067147654.

Categories: Lizards

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