Lizard
Overview
Lizards are a widespread group of squamate
Squamata
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...

 reptiles, with nearly 3800 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, 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
Lepidosauria
The Lepidosauria are reptiles with overlapping scales. This subclass includes Squamata and Sphenodontidae. It is a monophyletic group and therefore contains all descendents of a common ancestor. The squamata includes snakes, lizards, tuataras, and amphisbaenia. Lepidosauria is the sister taxon...

 (reptiles with overlapping scales), which are neither sphenodonts
Sphenodontia
Sphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara , and only two living species...

 (i.e., tuatara
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...

) nor snakes – they form an evolutionary grade
Evolutionary grade
In alpha taxonomy, a grade refers to a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit.-Definition:...

.
Encyclopedia
Lizards are a widespread group of squamate
Squamata
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...

 reptiles, with nearly 3800 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, 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
Lepidosauria
The Lepidosauria are reptiles with overlapping scales. This subclass includes Squamata and Sphenodontidae. It is a monophyletic group and therefore contains all descendents of a common ancestor. The squamata includes snakes, lizards, tuataras, and amphisbaenia. Lepidosauria is the sister taxon...

 (reptiles with overlapping scales), which are neither sphenodonts
Sphenodontia
Sphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara , and only two living species...

 (i.e., tuatara
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...

) nor snakes – they form an evolutionary grade
Evolutionary grade
In alpha taxonomy, a grade refers to a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit.-Definition:...

. While the snakes are recognized as falling phylogenetically
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

 within the Toxicofera
Toxicofera
Toxicofera , is a hypothetical clade which represents about 4600 species of extant squamates It encompasses all venomous reptile species, as well as numerous related non-venomous species....

 clade 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 limbs and external ears, while snakes lack both of 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
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 .- Evolutionary variation :In snakes, the quadrate bone has become elongated...

, distinguishing them from the sphenodonts
Sphenodontia
Sphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara , and only two living species...

, which have a more primitive and solid diapsid
Diapsid
Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...

 skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

. Many lizards can detach their tails to escape from predators, an act called autotomy
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...

, but this ability is not shared by all lizards. 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 cm for some chameleon
Chameleon
Chameleons 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, the possession by many of a...

s and gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....

s to nearly 3 m (9.8 ft) in the case of the largest living varanid lizard, the Komodo Dragon
Komodo dragon
The Komodo dragon , also known as the Komodo monitor, is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang and Gili Dasami. A member of the monitor lizard family , it is the largest living species of lizard, growing to a maximum length of in rare cases...

. Some extinct varanids reached great size. The extinct aquatic mosasaurs reached 17 m (55.8 ft), and the giant monitor Megalania prisca is estimated to have reached perhaps 7 m (23 ft).

Physiology

Sight is very 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.

The particular innovation in this respect is the dewlap
Dewlap
A dewlap is a longitudinal flap of skin that hangs beneath the lower jaw or neck of many vertebrates. While the term is usually used in this specific context, it can also be used to include other structures occurring in the same body area with a similar aspect, such as those caused by a double...

, 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
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 (UV) light, as many lizards can see UV light.

Evolution and relationships

The retention of the basic 'reptilian' amniote
Amniote
The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...

 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 amniotes were superficially lizard-like, but had solid, box-like skulls, with openings only for eyes, nostrils, termed the anapsid
Anapsid
An anapsid is an amniote whose skull does not have openings near the temples.While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a monophyletic group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related...

 condition. 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. The Synapsids, with a single fenestra, gave rise to the superficially lizard-like Pelycosaurs, which include Dimetrodon
Dimetrodon
Dimetrodon was a predatory synapsid genus that flourished during the Permian period, living between 280–265 million years ago ....

and the Therapsids, including the Cynodonts, from which the modern mammals would evolve.

The modern Tuatara
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...

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.

The earliest known fossil remains of a lizard belong to the iguanian
Iguania
Iguania is the suborder of Squamata that contains the iguanas, chameleons, agamids, and "New World lizards" such as anoles and Phrynosomatidae...

 species Tikiguania estesi from the Tiki Formation
Tiki Formation
The Tiki Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.-See also:* List of dinosaur-bearing rock formations...

 of India
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 with over 1.2 billion people, and the most populous democracy in the world...

, which dates to the Carnian
Carnian
The Carnian is the lowermost stage of the Upper Triassic series . It lasted from about 228.7 till 216.5 million years ago . The Carnian is preceded by the Ladinian and is followed by the Norian...

 stage of the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 period, about 220 million years ago. However, mitochondrial phylogenetics suggests that the first lizards evolved in the late Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

. Most evolutionary relationships within the squamates are not yet completely worked out, with the relationship of snakes to other groups being most problematic. From morphological data, Iguanid lizards have been thought to have diverged from other squamates very early, but recent molecular phylogenies
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...

, both from mitochondrial
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

 and nuclear DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

, do not support this early divergence. Because snakes have a faster molecular clock
Molecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...

 than other squamates, and there are few early snake and snake ancestor fossils, it is difficult to resolve the relationship between snakes and other squamate groups.

Lizard diversification

Within the Lacertilia are found four generally recognized suborders, Iguania
Iguania
Iguania is the suborder of Squamata that contains the iguanas, chameleons, agamids, and "New World lizards" such as anoles and Phrynosomatidae...

, Gekkota
Gekkota
Gekkota is an infraorder of reptiles in the suborder Scleroglossa, comprising all geckos and the limbless Pygopodidae. The legless lizards of the family Dibamidae are also referred to as blind lizards but recent molecular phylogenies suggest they are not gekkotans.Gekkota are a suborder of...

, Amphisbaenia
Amphisbaenia
The Amphisbaenia are a usually legless suborder of squamates closely related to lizards and snakes. As many species possess a pink body coloration and scales arranged in rings, they have a superficial resemblance to earthworms. They are very poorly understood, due to their burrowing lifestyle...

 and Autarchoglossa
Autarchoglossa
Autarchoglossa is a previously recognized taxonomic suborder of reptiles which includes skinks, snakes and relatives.The recent proposal of the Toxicofera clade places Iguania within Autarchoglossa, which would may lead to confusion as Autarchoglossa means "free-tongued"...

, with the "blind skinks" in the family Dibamidae
Dibamidae
Dibamidae is a family of legless lizards found in tropical forests. Relatively little is known about the dibamid lizards, which are native to Mexico, SE Asia, Indonesia, the Philippine Islands and western New Guinea....

 having an uncertain position. While traditionally excluded from the lizards, the snakes are usually classified as a clade with a similar subordinal rank.

Iguania

The suborder Iguania
Iguania
Iguania is the suborder of Squamata that contains the iguanas, chameleons, agamids, and "New World lizards" such as anoles and Phrynosomatidae...

, found in Africa, south Asia, Australia, the New World
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...

, and with iguanas colonizing the islands of the west Pacific, form the sister group to the remainder of the squamata. They are largely arboreal, and have primitively fleshy, non-prehensile tongues, some even have scales, but this condition is obviously highly modified in the chameleons. This clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 includes the following families:
  • Family Agamidae
    Agamidae
    Agamids, lizards of the family Agamidae, include more than 300 species in Africa, Asia, Australia, and a few in Southern Europe. Many species are commonly called dragons or dragon lizards. Phylogenetically they may be sister to the Iguanidae, and have a similar appearance. Agamids usually have...

     – Agamid lizards, Old World arboreal lizards
  • Family Chamaeleonidae – Chameleons
  • Family Corytophanidae
    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 in males of Basiliscus, but is present in both sexes of Corytophanes and Laemanctus...

     – Helmet lizards
  • Family Crotaphytidae
    Crotaphytidae
    The family Crotaphytidae, or collared lizards, are desert-dwelling reptiles native to the southwest USA and northern Mexico. They are very fast-moving animals, with long limbs and tails, and are carnivorous, feeding mainly on insects....

     – Collared lizards, leopard lizards
  • Family Hoplocercidae
    Hoplocercidae
    Family Hoplocercidae, or the hoplocercids, are a family of lizards native to the tropical forests of Central and South America. There are ten described species in three genera...

     – Dwarf and spiny tail iguanas
  • Family Iguanidae
    Iguanidae
    Iguanidae is a family of lizards, composed of iguanas and related species.-Classification of Iguanidae:Two different classification schemes have been used to define the structure of this family. These are the "traditional" classification and the classification presented by Frost et al. .Frost et...

     – American arboreal lizards, chuckwallas, iguanas, iguanids
  • Family Opluridae
    Opluridae
    The Opluridae, or Madagascan iguanas, are a family of moderately sized lizards native to Madagascar. There are seven species in two genera, with most of the species being in Oplurus. The family includes species that live amongst rocks, some that live in trees, and one that inhabits sand dunes...

     – Malagasy iguanas
  • Family Phrynosomatidae
    Phrynosomatidae
    Phrynosomatidae is a diverse family of lizards, found from Panama to the extreme south of Canada. Many members of the group are adapted to life in hot, sandy deserts, although the spiny lizards prefer rocky deserts or even relatively moist forest edges, and the short-horned lizard lives in prairie...

     – North American spiny lizards
  • Family Polychrotidae
    Polychrotidae
    Polychrotidae is a family of lizards commonly known as anoles . NCBI places the anole in subfamily Polychrotinae of the family Iguanidae. Four genera are common: Anolis, Norops, Phenacosaurus, and Polychrus....

     – Anoles and kin
  • Family Tropiduridae
    Tropiduridae
    The Tropiduridae is a family of iguanid lizards native to South America and the West Indies. Commonly known as Neotropical ground lizards, most are ground-dwelling animals, and the family includes some lizards adapted to relatively cold climates, including those of the Andes mountains and Tierra...

     – Tropidurid lizards

Gekkota

Active hunters, the Gekkota
Gekkota
Gekkota is an infraorder of reptiles in the suborder Scleroglossa, comprising all geckos and the limbless Pygopodidae. The legless lizards of the family Dibamidae are also referred to as blind lizards but recent molecular phylogenies suggest they are not gekkotans.Gekkota are a suborder of...

 includes three families comprising the distinctive cosmopolitan geckos and the legless flap-footed lizards of Australia and New Zealand. Like snakes, the flap-footed lizards and most geckos lack eyelids. Unlike snakes, they use their tongues to clean their often highly developed eyes. While gecko feet have unique surfaces that 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 – 'Eyelid' geckos
  • Family Gekkonidae – Geckos
  • Family Pygopodidae
    Pygopodidae
    Pygopodidae is a family of squamates that have reduced or absent limbs and are related to the geckos. There are at least 35 species in two subfamilies and eight genera. They have unusually long, slender, bodies, giving them a strong resemblance to snakes...

     – Flap-footed lizards

Relationship with humans

Most lizard species are harmless to humans. Only the largest lizard species, the Komodo dragon
Komodo dragon
The Komodo dragon , also known as the Komodo monitor, is a large species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, Gili Motang and Gili Dasami. A member of the monitor lizard family , it is the largest living species of lizard, growing to a maximum length of in rare cases...

, which reaches 3.3 m (11 feet) in length and weighs up to 166 kg (365 pounds), has been known to stalk, attack, and, on occasion, kill humans. An eight-year-old Indonesian boy died from blood loss after an attack in 2007. The venom of the Gila monster
Gila monster
The Gila monster is a species of venomous lizard native to the southwestern United States and northwestern Mexican state of Sonora...

 and beaded lizard
Beaded lizard
The Beaded lizard is a species of venomous lizard found principally in Mexico and southern Guatemala. Along with its congener, the Gila monster , it is the only lizard to have evolved an overt venom delivery system, and has long been considered the only venomous lizard...

 is not usually deadly but they can inflict extremely painful bites due to powerful jaws.

Numerous species of lizard are kept as pet
Pet
A pet is a household animal kept for companionship and a person's enjoyment, as opposed to wild animals or to livestock, laboratory animals, working animals or sport animals, which are kept for economic or productive reasons. The most popular pets are noted for their loyal or playful...

s.

Lizard symbolism plays important though rarely predominant roles in some culture
Culture
Culture is a term that has many different inter-related 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...

s (e.g., Tarrotarro in Australian Aboriginal mythology
Australian Aboriginal mythology
Australian Aboriginal myths are the stories traditionally performed by Aboriginal peoples within each of the language groups across Australia....

). The Moche
Moche
'The Moche civilization flourished in northern Peru from about 100 AD to 800 AD, during the Regional Development Epoch. While this issue is the subject of some debate, many scholars contend that the Moche were not politically organized as a monolithic empire or state...

 people of ancient Peru
Peru
Peru , officially the Republic of Peru , 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....

 worshipped animals and often depicted lizards in their art. According to a popular legend in Maharashtra
Maharashtra
Maharashtra is a state located in India. It is the second most populous after Uttar Pradesh and third largest state by area in India...

, a Common Indian Monitor, with ropes attached, was used to scale the walls of the Sinhagad
Sinhagad
Sinhagad, Sinhgarh, or Sinhgad , is a fortress located roughly 30 kilometres southwest of the city of Pune, India. Previously called Kondhana , the fort has been the site of many important battles, most notably the battle of Sinhagad in 1670...

 fort in the Battle of Sinhagad
Battle of Sinhagad
The Battle of Sinhagad was a night battle that took place on February 4, 1670 in the fort of Sinhagad, near the city of Pune, Maharashtra, India. It was fought between Tanaji Malusare, a commander of Maratha ruler Shivaji and Udaybhan Rathod, fortkeeper under Jai Singh I...

.

Green Iguana
Green Iguana
The Green Iguana or Common Iguana is a large, arboreal herbivorous species of lizard of the genus Iguana native to Central and South America...

s are eaten in Central America and Uromastyx
Uromastyx
The Uromastyx is a genus of lizard whose members are better-known as Spiny-tailed lizards, uromastyxes, mastigures, or dabb lizards. Uromastyx are primarily herbivorous, but occasionally eat insects, especially when young. They spend most of their waking hours basking in the sun, hiding in...

 in Africa
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...

. In North Africa, Uromastyx are considered dhaab or 'fish of the desert' and eaten by nomadic tribes.

Classification

Suborder Lacertilia (Sauria) – (Lizards)
  • Family †Bavarisauridae
  • Family †Eichstaettisauridae
  • Infraorder Iguania
    • Family †Arretosauridae
    • Family †Euposauridae
      Euposauridae
      Euposauridae was a family of lizards from the Jurassic of Europe. They were small to medium sized.-External links:* at Paleos.com...

    • Family Corytophanidae
      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 in males of Basiliscus, but is present in both sexes of Corytophanes and Laemanctus...

       (casquehead lizards)
    • Family Iguanidae
      Iguanidae
      Iguanidae is a family of lizards, composed of iguanas and related species.-Classification of Iguanidae:Two different classification schemes have been used to define the structure of this family. These are the "traditional" classification and the classification presented by Frost et al. .Frost et...

       (iguana
      Iguana
      Iguana is a herbivorous genus of lizard native to tropical areas of Central America and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena...

      s and spinytail iguanas)
    • Family Phrynosomatidae
      Phrynosomatidae
      Phrynosomatidae is a diverse family of lizards, found from Panama to the extreme south of Canada. Many members of the group are adapted to life in hot, sandy deserts, although the spiny lizards prefer rocky deserts or even relatively moist forest edges, and the short-horned lizard lives in prairie...

       (earless
      Earless lizard
      Earless lizards are two genera of small lizards native to the semi-arid and grassland habitats of the southwestern United States and Mexico. The genus Cophosaurus and the genus Holbrookia are both characterized by having no external ear openings, presumably to prevent sand from entering the body as...

      , spiny
      Spiny lizard
      The spiny lizards are the genus Sceloporus in the family Phrynosomatidae. This genus includes some of the most commonly seen lizards in the United States.- Taxonomy :...

      , tree
      Urosaurus
      The North American genus Urosaurus belongs to the New World Iguanian family Phrynosomatidae. They can be distinguished from members of the genus Sceloporus by the presence of a gular fold and granular lateral scales...

      , side-blotched
      Side-blotched lizard
      Side-blotched lizards are lizards of the genus Uta. They are some of the most abundant and commonly observed lizards in the deserts of western North America. They commonly grow to six inches including the tail, with the males normally being the larger sex. Males often have bright throat colors....

       and horned
      Horned lizard
      Horned lizards are a genus of lizards which are the type genus of the family Phrynosomatidae. 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...

       lizards)
    • Family Polychrotidae
      Polychrotidae
      Polychrotidae is a family of lizards commonly known as anoles . NCBI places the anole in subfamily Polychrotinae of the family Iguanidae. Four genera are common: Anolis, Norops, Phenacosaurus, and Polychrus....

       (anoles
      Anolis
      Anolis is a genus of lizards belonging to the family Polychrotidae. 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...

      )
      • Family Leiosauridae
        Leiosauridae
        Leiosauridae is a family of lizards. It contains the following genera:*Genus Diplolaemus*Genus Leiosaurus*Genus Pristidactylus...

         (see Polychrotinae)
    • Family Tropiduridae
      Tropiduridae
      The Tropiduridae is a family of iguanid lizards native to South America and the West Indies. Commonly known as Neotropical ground lizards, most are ground-dwelling animals, and the family includes some lizards adapted to relatively cold climates, including those of the Andes mountains and Tierra...

       (neotropical ground lizards)
      • Family Liolaemidae
        Liolaemidae
        Liolaemidae are a family of iguanian lizards. They are traditionally included in the Iguanidae as subfamily Liolaeminae, which some more recent authors prefer to delimit in a more restricted way...

         (see Tropidurinae)
      • Family Leiocephalidae (see Tropidurinae)
    • Family Crotaphytidae
      Crotaphytidae
      The family Crotaphytidae, or collared lizards, are desert-dwelling reptiles native to the southwest USA and northern Mexico. They are very fast-moving animals, with long limbs and tails, and are carnivorous, feeding mainly on insects....

       (collared
      Crotaphytus
      Classification of the genus Crotaphytus, a type of lizard.-Genus Crotaphytus:*Venerable Collared Lizard, Crotaphytus antiquus*Desert Collared Lizard, Crotaphytus bicinctores*Common Collared Lizard, Crotaphytus collaris...

       and leopard
      Gambelia
      Gambelia is the genus name for the Leopard Lizards in the family Crotaphytidae. One difference between the genera Gambelia and Crotaphytus is that the former has fracture planes in their tails, allowing the tails to break off when grasped by predators.-Genus Gambelia:*Cope's Leopard Lizard,...

       lizards)
    • Family Opluridae
      Opluridae
      The Opluridae, or Madagascan iguanas, are a family of moderately sized lizards native to Madagascar. There are seven species in two genera, with most of the species being in Oplurus. The family includes species that live amongst rocks, some that live in trees, and one that inhabits sand dunes...

       (Madagascar iguanids)
    • Family Hoplocercidae
      Hoplocercidae
      Family Hoplocercidae, or the hoplocercids, are a family of lizards native to the tropical forests of Central and South America. There are ten described species in three genera...

       (wood
      Enyalioides
      Enyalioides is a genus of lizard from the Hoplocercidae family which is found in the northern part of South America.- Species :Currently 9 species are recognized::* Cofan Wood Lizard, Enyalioides cofanorum Duellman, 1973...

       lizards, clubtails)
    • Family †Priscagamidae
    • Family †Isodontosauridae
    • Family Agamidae
      Agamidae
      Agamids, lizards of the family Agamidae, include more than 300 species in Africa, Asia, Australia, and a few in Southern Europe. Many species are commonly called dragons or dragon lizards. Phylogenetically they may be sister to the Iguanidae, and have a similar appearance. Agamids usually have...

       (agamas
      Agama (lizard)
      An agama is any one of the various small, long-tailed, insect-eating lizards of the genus Agama. The agamid genus is composed of at least 37 species across Africa, where they are the most common lizard. They can be found in many sizes, from 12.5 to 30 cm in length and a wide variety of colours...

      )
    • Family Chamaeleonidae (chameleon
      Chameleon
      Chameleons 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, the possession by many of a...

      s)
  • Infraorder Gekkota
    Gekkota
    Gekkota is an infraorder of reptiles in the suborder Scleroglossa, comprising all geckos and the limbless Pygopodidae. The legless lizards of the family Dibamidae are also referred to as blind lizards but recent molecular phylogenies suggest they are not gekkotans.Gekkota are a suborder of...

    • Family Gekkonidae (gecko
      Gecko
      Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....

      s)
    • Family Pygopodidae
      Pygopodidae
      Pygopodidae is a family of squamates that have reduced or absent limbs and are related to the geckos. There are at least 35 species in two subfamilies and eight genera. They have unusually long, slender, bodies, giving them a strong resemblance to snakes...

       (legless lizard
      Legless lizard
      Legless lizard may refer to any of several groups of lizards which have independently lost limbs or reduced them to the point of being of no use in locomotion. It is the common name for the family Pygopodidae, but often refers to other groups, such as limbless anguids, depending upon the region of...

      s)
    • Family Dibamidae
      Dibamidae
      Dibamidae is a family of legless lizards found in tropical forests. Relatively little is known about the dibamid lizards, which are native to Mexico, SE Asia, Indonesia, the Philippine Islands and western New Guinea....

       (blind lizards)
  • Infraorder Scincomorpha
    Scincomorpha
    Scincomorpha is an infraorder of saurians....

    • Family †Paramacellodidae
    • Family †Slavoiidae
    • Family Scincidae (skink
      Skink
      Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...

      s)
    • Family Cordylidae
      Cordylidae
      Cordylidae is a family of small to medium sized lizards that occur in southern and eastern Africa. They are commonly known as "Girdled", Spinytail lizards or Girdle-tail lizards. Girdled lizards are diurnal and insectivorous...

       (spinytail lizards)
    • Family Gerrhosauridae
      Gerrhosauridae
      The Gerrhosauridae is a family of lizards native to Africa and Madagascar. Also known as plated lizards, they live in a range of habitats, from rocky crevices to sand dunes. Their form is variable, with some species having four fully developed limbs, and others with vestigial hind limbs only...

       (plated lizards)
    • Family Xantusiidae (night lizard
      Night lizard
      Night lizards are a group of very small, viviparous lizards, averaging from less than 4 cm to over 12 cm long. The family has only three genera, with approximately 23 living species...

      s)
    • Family Lacertidae
      Lacertidae
      Lacertidae is the family of the wall lizards, true lizards, or sometimes simply lacertas, which are native to Europe, Africa, and Asia. The group includes the genus Lacerta, which contains some of the most commonly seen lizard species in Europe...

       (wall lizard
      Wall lizard
      The common wall lizard is a species of lizard with a large distribution in Europe and well-established introduced populations in North America, where it is also called the European wall lizard. It can grow to about in total length.-Identification:The common wall lizard is a small, thin lizard...

      s or true lizards)
    • Family †Mongolochamopidae
    • Family †Adamisauridae
    • Family Teiidae
      Teiidae
      Teiidae is a family of lizards native to the Americas, generally known as whiptails. The group includes the parthenogenic genera Cnemidophorus and Aspidoscelis, and the non-parthenogenic Tupinambis. It has over 230 member species in ten genera...

       (tegus and whiptails)
    • Family Gymnophthalmidae
      Gymnophthalmidae
      Gymnophthalmidae is a family of lizards, sometimes known as spectacled lizards or microteiids. They are called 'spectacled' because of their transparent lower eyelids, so they can still see with closed eyes...

       (spectacled lizards)
  • Infraorder Diploglossa
    • Family Anguidae
      Anguidae
      The Anguidae is a large and diverse family of lizards native to the northern hemisphere. The group includes the slowworms, glass lizards, and alligator lizards, among others. Anguidae is divided into three subfamilies and contains 94 species in eight genera. Their closest living relatives are the...

       (glass lizard
      Glass lizard
      The glass lizards or glass snakes, genus Ophisaurus, are a group of reptiles that resemble snakes, but are actually lizards. Although most species have no legs, their head shape and the fact that they have movable eyelids and external ear openings identify them as lizards. A few species have very...

      s)
    • Family Anniellidae (American legless lizard
      American legless lizard
      The family Anniellidae, known as American legless lizards contains two species in a single genus Anniella: A. pulchra, the California Legless Lizard, and the rare, A. geronimensis, Baja California Legless Lizard....

      s)
    • Family Xenosauridae
      Xenosauridae
      The Xenosauridae is a family of lizards native to Central America and China. Also known as knob-scaled lizards, they have rounded, bumpy scales and osteoderms. Most species prefer moist or semi-aquatic habitats, although they are widespread within their native regions, with some even inhabiting...

       (knob-scaled lizards)
  • Infraorder Platynota
    Platynota
    Platynota is a group of anguimorph lizards. Since it was named in 1839, it has included several groups, including monitor lizards, snakes, mosasaurs, and helodermatids. Its taxonomic use still varies, as it is sometimes considered equivalent to the group Varanoidea and other times viewed as a...

     (Varanoidea
    Varanoidea
    Varanoidea is a superfamily of lizards, including the well-known family Varanidae . Also included in the Varanoidea are such extinct marine and semi-aquatic forms as mosasaurs and dolichosaurs, the venomous helodermatids , the Lanthanotidae , and the extinct Necrosauridae.Throughout their long...

    )
    • Family Varanidae
      Varanidae
      Varanidae is a group of lizards of the superfamily Varanoidea. The family is a group of carnivorous lizards which includes the largest living lizard, the Komodo dragon, and the crocodile monitor. Varanidae contains the living genus Varanus and a number of extinct taxa...

       (monitor lizards)
    • Family Lanthanotidae
      Lanthanotidae
      The Earless monitor lizard is a semi-aquatic, brown lizard native to northern Borneo. It is the only species in the family Lanthanotidae, a group related to the true monitor lizards, as well as to the beaded lizards....

       (earless monitor lizards)
    • Family Helodermatidae (gila monster
      Gila monster
      The Gila monster is a species of venomous lizard native to the southwestern United States and northwestern Mexican state of Sonora...

      s & beaded lizards)
    • Family †Mosasaur
      Mosasaur
      Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...

      idae (marine lizards)
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