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The Squamata, or the scaled reptiles, are the largest recent order of reptiles, comprising all lizards and snakes. With over 9,000 species, it is the second-largest order of vertebrates after the perciform fish. 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, which are able to open their mouths very wide to accommodate comparatively large prey. They are the most variably sized order of reptiles, ranging from the 16 mm (0.63 in) dwarf gecko (Sphaerodactylus ariasae) to the 6.6 m (22 ft) green anaconda (Eunectes murinus) and the now-extinct mosasaurs, which reached lengths of 14 m (46 ft).

Among the other reptiles, squamates are most closely related to tuataras, which superficially resemble lizards.

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Squamata
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This article is about the Squamata order of reptiles. For the Roman scale armour, see Lorica squamata.

Squamata is the largest order of reptiles, comprising lizards, snakes and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,000 species,[3] it is also the second-largest order of extant (living) vertebrates, after the perciform fish, and roughly equal in number to the Saurischia (one of the two major groups of dinosaurs). 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 neurocranium. This is particularly visible in snakes, which are able to open their mouths very wide to accommodate comparatively large prey. Squamata is the most variably sized order of reptiles, ranging from the 16 mm (0.63 in) dwarf gecko (Sphaerodactylus ariasae) to the 5.21 m (17.1 ft) green anaconda (Eunectes murinus) and the now-extinct mosasaurs, which reached lengths of over 14 m (46 ft).

Among other reptiles, squamates are most closely related to the tuatara, which superficially resembles lizards.

Evolution

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Slavoia darevskii, a fossil squamate

Squamates are a monophyletic sister group to the rhynchocephalians, members of the order Rhynchocephalia. The only surviving member of Rhynchocephalia is the tuatara. Squamata and Rhynchocephalia form the subclass Lepidosauria, which is the sister group to Archosauria, the clade that contains crocodiles and birds, and their extinct relatives. Fossils of rhynchocephalians first appear in the Early Triassic, meaning that the lineage leading to squamates must have also existed at the time.[4] Scientists believe crown group squamates probably originated in the Early Jurassic based on the fossil record.[4] The first fossils of geckos, skinks and snakes appear in the Middle Jurassic.[5] Other groups like iguanians and varanoids appeared in the Cretaceous. Polyglyphanodontians, a distinct clade of lizards, and mosasaurs, a group of predatory marine lizards that grew to enormous sizes, also appeared in the Cretaceous.[6] Squamates suffered a mass extinction at the Cretaceous–Paleogene (K–PG) boundary, which wiped out polyglyphanodontians, mosasaurs and many other distinct lineages.[7]

The relationships of squamates is debatable. Although many of the groups originally recognized on the basis of morphology are still accepted, our understanding of their relationships to each other has changed radically as a result of studying their genomes. Iguanians were long thought to be the earliest crown group squamates based on morphological data,[6] however, genetic data suggests that geckoes are the earliest crown group squamates.[8] Iguanians are now united with snakes and anguimorphs in a clade called Toxicofera. Genetic data also suggests that the various limbless groups; snakes, amphisbaenians and dibamids, are unrelated, and instead arose independently from lizards.

A study in 2018 found that Megachirella, an extinct genus of lepidosaur that lived about 240 million years ago during the Middle Triassic, was a stem-squamate, making it the oldest known squamate. The phylogenetic analysis was conducted by performing high-resolution microfocus X-ray computed tomography (micro-CT) scans on the fossil specimen of Megachirella to gather detailed data about its anatomy. This data was then compared with a phylogenetic dataset combining the morphological and molecular data of 129 extant and extinct reptilian taxa. The comparison revealed Megachirella had certain features that are unique to squamates. The study also found that geckos are the earliest crown group squamates not iguanians.[9][10]

Reproduction

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Trachylepis maculilabris skinks mating

The male members of the group Squamata have hemipenes, which are usually held inverted within their bodies, and are everted for reproduction via erectile tissue like that in the human penis.[11] Only one is used at a time, and some evidence indicates that males alternate use between copulations. The hemipenis has a variety of shapes, depending on the species. Often it bears spines or hooks, to anchor the male within the female. Some species even have forked hemipenes (each hemipenis has two tips). Due to being everted and inverted, hemipenes do not have a completely enclosed channel for the conduction of sperm, but rather a seminal groove that seals as the erectile tissue expands. This is also the only reptile group in which both viviparous and ovoviviparous species are found, as well as the usual oviparous reptiles. Some species, such as the Komodo dragon, can reproduce asexually through parthenogenesis.[12]

 src=
The Japanese striped snake has been studied in sexual selection

There have been studies on how sexual selection manifests itself in snakes and lizards. Snakes use a variety of tactics in acquiring mates.[13][dubious discuss] Ritual combat between males for the females they want to mate with includes topping, a behavior exhibited by most viperids, in which one male will twist around the vertically elevated fore body of its opponent and forcing it downward. It is common for neck biting to occur while the snakes are entwined.[14]

Facultative parthenogenesis

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The effects of central fusion and terminal fusion on heterozygosity

Parthenogenesis is a natural form of reproduction in which the growth and development of embryos occur without fertilization. Agkistrodon contortrix (copperhead snake) and Agkistrodon piscivorus (cotton mouth snake) can reproduce by facultative parthenogenesis. That is, they are capable of switching from a sexual mode of reproduction to an asexual mode.[15] The type of parthenogenesis that likely occurs is automixis with terminal fusion (see figure), a process in which two terminal products from the same meiosis fuse to form a diploid zygote. This process leads to genome wide homozygosity, expression of deleterious recessive alleles and often to developmental abnormalities. Both captive-born and wild-born A. contortrix and A. piscivorus appear to be capable of this form of parthenogenesis.[15]

Reproduction in squamate reptiles is ordinarily sexual, with males having a ZZ pair of sex determining chromosomes, and females a ZW pair. However, the Colombian Rainbow boa, Epicrates maurus, can also reproduce by facultative parthenogenesis resulting in production of WW female progeny.[16] The WW females are likely produced by terminal automixis.

Inbreeding avoidance

When female sand lizards mate with two or more males, sperm competition within the females reproductive tract may occur. Active selection of sperm by females appears to occur in a manner that enhances female fitness.[17] On the basis of this selective process, the sperm of males that are more distantly related to the female are preferentially used for fertilization, rather than the sperm of close relatives.[17] This preference may enhance the fitness of progeny by reducing inbreeding depression.

Evolution of venom

See also: Venom

Recent research suggests that the evolutionary origin of venom may exist deep in the squamate phylogeny, with 60% of squamates placed in this hypothetical group called Toxicofera. Venom has been known in the clades Caenophidia, Anguimorpha, and Iguania, and has been shown to have evolved a single time along these lineages before the three groups diverged, because all lineages share nine common toxins.[18] The fossil record shows the divergence between anguimorphs, iguanians, and advanced snakes dates back roughly 200 Mya to the Late Triassic/Early Jurassic.[18] But the only good fossil evidence is from the Jurassic.[1]

Snake venom has been shown to have evolved via a process by which a gene encoding for a normal body protein, typically one involved in key regulatory processes or bioactivity, is duplicated, and the copy is selectively expressed in the venom gland.[19] Previous literature hypothesized that venoms were modifications of salivary or pancreatic proteins,[20] but different toxins have been found to have been recruited from numerous different protein bodies and are as diverse as their functions.[21]

Natural selection has driven the origination and diversification of the toxins to counter the defenses of their prey. Once toxins have been recruited into the venom proteome, they form large, multigene families and evolve via the birth-and-death model of protein evolution,[22] which leads to a diversification of toxins that allows the ambush predators the ability to attack a wide range of prey.[23] The rapid evolution and diversification is thought to be the result of a predator–prey evolutionary arms race, where both are adapting to counter the other.[24]

Humans and squamates

Bites and fatalities

See also: Snakebite
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Map showing the global distribution of venomous snakebites

An estimated 125,000 people a year die from venomous snake bites.[25] In the US alone, more than 8,000 venomous snake bites are reported each year.[26]

Lizard bites, unlike venomous snake bites, are not fatal. The Komodo dragon has been known to kill people due to its size, and recent studies show it may have a passive envenomation system. Recent studies also show that the close relatives of the Komodo, the monitor lizards, all have a similar envenomation system, but the toxicity of the bites is relatively low to humans.[27] The Gila monster and beaded lizards of North and Central America are venomous, but not deadly to humans.

Conservation

Though they survived the Cretaceous–Paleogene extinction event, many squamate species are now endangered due to habitat loss, hunting and poaching, illegal wildlife trading, alien species being introduced to their habitats (which puts native creatures at risk through competition, disease, and predation), and other anthropogenic causes. Because of this, some squamate species have recently become extinct, with Africa having the most extinct species. However, breeding programs and wildlife parks are trying to save many endangered reptiles from extinction. Zoos, private hobbyists and breeders help educate people about the importance of snakes and lizards.

Classification and phylogeny

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Desert iguana from Amboy Crater, Mojave Desert, California

Historically, the order Squamata has been divided into three suborders:

Of these, the lizards form a paraphyletic group,[28] since "lizards" excludes the subclades of snakes and amphisbaenians. Studies of squamate relationships using molecular biology have found several distinct lineages, though the specific details of their interrelationships vary from one study to the next. One example of a modern classification of the squamates is[2][29]

.mw-parser-output table.clade{border-spacing:0;margin:0;font-size:100%;line-height:100%;border-collapse:separate;width:auto}.mw-parser-output table.clade table.clade{width:100%}.mw-parser-output table.clade td{border:0;padding:0;vertical-align:middle;text-align:center}.mw-parser-output table.clade td.clade-label{width:0.8em;border:0;padding:0 0.2em;vertical-align:bottom;text-align:center}.mw-parser-output table.clade td.clade-slabel{border:0;padding:0 0.2em;vertical-align:top;text-align:center}.mw-parser-output table.clade td.clade-bar{vertical-align:middle;text-align:left;padding:0 0.5em}.mw-parser-output table.clade td.clade-leaf{border:0;padding:0;text-align:left;vertical-align:middle}.mw-parser-output table.clade td.clade-leafR{border:0;padding:0;text-align:right} Squamata Dibamia

Dibamidae

Bifurcata Gekkota Pygopodomorpha

Diplodactylidae Underwood 1954Hoplodactylus pomarii white background.jpg

     

Pygopodidae Boulenger 1884The zoology of the voyage of the H.M.S. Erebus and Terror (Lialis burtonis).jpg

   

Carphodactylidae

      Gekkomorpha

Eublepharidae

Gekkonoidea

Sphaerodactylidae Underwood 1954

     

Phyllodactylidae Phyllodactylus gerrhopygus 1847 - white background.jpg

   

Gekkonidae

          Unidentata Scinciformata Scincomorpha

ScincidaeBilder-Atlas zur wissenschaftlich-populären Naturgeschichte der Wirbelthiere (Plate (24)) Tribolonotus novaeguineae.jpg

Cordylomorpha

Xantusiidae

     

GerrhosauridaeGerrhosaurus ocellatus flipped.jpg

   

CordylidaeIllustrations of the zoology of South Africa (Smaug giganteus).jpg

        Episquamata Laterata Teiformata

Gymnophthalmidae Merrem 1820PZSL1851PlateReptilia06 Cercosaura ocellata.png

   

Teiidae Gray 1827Bilder-Atlas zur wissenschaftlich-populären Naturgeschichte der Wirbelthiere (Tupinambis teguixin).jpg

    Lacertibaenia Lacertiformata

Lacertidae Brockhaus' Konversations-Lexikon (1892) (Lacerta agilis).jpg

Amphisbaenia

Rhineuridae Vanzolini 1951

     

Bipedidae Taylor 1951Bilder-Atlas zur wissenschaftlich-populären Naturgeschichte der Wirbelthiere (Bipes canaliculatus).jpg

       

Blanidae Kearney & Stuart 2004Blanus cinereus flipped.jpg

   

Cadeidae Vidal & Hedges 2008

       

Trogonophiidae Gray 1865

   

Amphisbaenidae Gray 1865Amphisbaena microcephalum 1847 - white background.jpg

              ToxicoferaAnguimorpha Palaeoanguimorpha Shinisauria

Shinisauridae Ahl 1930 sensu Conrad 2006

Varanoidea

Lanthanotidae

   

VaranidaeZoology of Egypt (1898) (Varanus griseus).png

      Neoanguimorpha Helodermatoidea

Helodermatidae Gray 1837Gila monster ncd 2012 white background.jpg

    Xenosauroidea

Xenosauridae

Anguioidea

Diploglossidae

     

Anniellidae

   

Anguidae Gray 1825

            Iguania Acrodonta

ChamaeleonidaeZoology of Egypt (1898) (Chamaeleo calyptratus).jpg

   

Agamidae Gray 1827Haeckel Lacertilia (Chlamydosaurus kingii).jpg

    Pleurodonta

Leiocephalidae

     

IguanidaeStamps of Germany (Berlin) 1977, Cyclura cornuta.jpg

       

Hoplocercidae Frost & Etheridge 1989

     

Crotaphytidae

   

Corytophanidae

         

Tropiduridae

       

Phrynosomatidae

     

Dactyloidae

   

Polychrotidae

         

Liolaemidae

     

Leiosauridae

   

Opluridae

                    Serpentes Scolecophidia

Leptotyphlopidae Stejneger 1892Epictia tenella 1847 -white background.jpg

     

Gerrhopilidae Vidal et al. 2010

     

Xenotyphlopidae Vidal et al. 2010

   

Typhlopidae Merrem 1820Typhlops vermicularis3 white background.jpg

           

Anomalepididae

Alethinophidia Amerophidia

Aniliidae

   

Tropidophiidae Brongersma 1951

    Afrophidia Booidea    

UropeltidaeUropeltis ceylanica (2) flipped.jpg

     

Anomochilidae

   

CylindrophiidaeCylind resplendens Wagler white background.JPG

           

Xenopeltidae Bonaparte 1845

     

Loxocemidae

   

Pythonidae Fitzinger 1826Python natalensis Smith 1840 white background.jpg

         

BoidaeBoa Iconographia Zoologica white background.tif

     

Xenophidiidae

   

Bolyeriidae Hoffstetter 1946

          Caenophidia

Acrochordidae Bonaparte 1831

     

Xenodermidae

Colubroidea

Pareidae

     

ViperidaeOur reptiles and batrachians; a plain and easy account of the lizards, snakes, newts, toads, frogs and tortoises indigenous to Great Britain (1893) (Vipera berus).jpg

Proteroglypha

Homalopsidae

     

ColubridaeXenochrophis piscator 1 Hardwicke white background.jpg

     

Lamprophiidae

   

ElapidaeBilder-Atlas zur wissenschaftlich-populären Naturgeschichte der Wirbelthiere (Naja naja).jpg

                                 

All recent molecular studies[18] suggest that several groups form a venom clade, which encompasses a majority (nearly 60%) of squamate species. Named Toxicofera, it combines the groups Serpentes (snakes), Iguania (agamids, chameleons, iguanids, etc.), and Anguimorpha (monitor lizards, Gila monster, glass lizards, etc.).[18]


Frost & Etheridge, 1989== List of extant families == The over 10,000 extant squamates are divided into 58 families.

Amphisbaenia Family Species count Common names Example species Example photo Amphisbaenidae
Gray, 1865 Over 120 Tropical worm lizards Darwin's worm lizard (Amphisbaena darwinii) – Bipedidae
Taylor, 1951 4 Bipes worm lizards Mexican mole lizard (Bipes biporus) Bipes biporus.jpg Blanidae 7 Mediterranean worm lizards Mediterranean worm lizard (Blanus cinereus) – Cadeidae
Vidal & Hedges, 2008[30] 2 Cuban worm lizards Cadea blanoidesRhineuridae
Vanzolini, 1951 1 North American worm lizards North American worm lizard (Rhineura floridana) Amphisbaenia 1.jpg Trogonophidae
Gray, 1865 5 Palearctic worm lizards Checkerboard worm lizard (Trogonophis wiegmanni) – Gekkota (incl. Dibamia) Family Species count Common names Example species Example photo Dibamidae
Boulenger, 1884 23 Blind lizards Dibamus nicobaricumGekkonidae
Gray, 1825 (paraphyletic) About 1,000 Geckos Thick-tailed gecko (Underwoodisaurus milii) Underwoodisaurus milii.jpg Pygopodidae
Boulenger, 1884 44 Legless lizards Burton's snake lizard (Lialis burtonis) Lialis burtonis.jpg Iguania Family Species count Common names Example species Example photo Agamidae
Spix, 1825 Over 300 Agamas Eastern bearded dragon (Pogona barbata) Bearded dragon04.jpg Chamaeleonidae
Gray, 1825 202 Chameleons Veiled chameleon (Chamaeleo calyptratus) Chamaelio calyptratus.jpg Corytophanidae
Frost & Etheridge, 1989 9 Casquehead lizards Plumed basilisk (Basiliscus plumifrons) Plumedbasiliskcele4 edit.jpg Crotaphytidae
Frost & Etheridge, 1989 12 Collared and leopard lizards Common collared lizard (Crotaphytus collaris) Collared lizard in Zion National Park.jpg Hoplocercidae
Frost & Etheridge, 1989 16 Wood lizards or clubtails Club-tail iguana (Hoplocercus spinosus) – Iguanidae 40 Iguanas Marine iguana (Amblyrhynchus cristatus) Marineiguana03.jpg Leiosauridae
Frost et al., 2001 21 – Darwin's iguana (Diplolaemus darwinii) – Liolaemidae
Frost & Etheridge, 1989 Over 200 Swifts Shining tree iguana (Liolaemus nitidus) Atacama lizard1.jpg Opluridae
Frost & Etheridge, 1989 8 Madagascan iguanas Chalarodon (Chalarodon madagascariensis) – Phrynosomatidae
Frost & Etheridge, 1989 136 Earless, spiny, tree, side-blotched and horned lizards Greater earless lizard (Cophosaurus texanus) Reptile tx usa.jpg Polychrotidae
Frost & Etheridge, 1989 (+ Dactyloidae) 7 Anoles Carolina anole (Anolis carolinensis) Anolis carolinensis.jpg Tropiduridae
Frost & Etheridge, 1989 At least 130 Neotropical ground lizards (Microlophus peruvianus) Mperuvianus.jpg Lacertoidea (excl. Amphisbaenia) Family Species count Common Names Example Species Example Photo Alopoglossidae
Goicoechea, Frost, De la Riva, Pellegrino, Sites Jr., Rodrigues, & Padial, 2016 23 Ptychoglossus vallensis Ptychoglossus vallensis.jpg Gymnophthalmidae
Fitzinger, 1826 Over 270 Spectacled lizards Bachia bicolor Bachia bicolor.jpg Lacertidae
Oppel, 1811 Over 300 Wall or true lizards Ocellated lizard (Lacerta lepida) Perleidechse-20.jpg Teiidae 151 Tegus or whiptails Gold tegu (Tupinambis teguixin) Goldteju Tupinambis teguixin.jpg Neoanguimorpha Family Species count Common names Example species Example photo Anguidae
Oppel, 1811 About 100 Glass lizards, alligator lizards and slowworms Slowworm (Anguis fragilis) Anguidae.jpg Anniellidae
Gray, 1852 6 American legless lizards California legless lizard (Anniella pulchra) Anniella pulchra.jpg Helodermatidae 5 Gila monsters Gila monster (Heloderma suspectum) Gila.monster.arp.jpg Xenosauridae
Cope, 1866 10 Knob-scaled lizards Mexican knob-scaled lizard (Xenosaurus grandis) Paleoanguimorpha or Varanoidea Family Species count Common names Example species Example photo Lanthanotidae 1 Earless monitor Earless monitor (Lanthanotus borneensis) Real Lanthanotus borneensis.jpg Shinisauridae 1 Chinese crocodile lizard Chinese crocodile lizard (Shinisaurus crocodilurus) Chin-krokodilschwanzechse-01.jpg Varanidae 75 Monitor lizards Perentie (Varanus giganteus) Perentie Lizard Perth Zoo SMC Spet 2005.jpg Scincoidea Family Species count Common Names Example Species Example Photo Cordylidae About 70 Spinytail lizards Girdle-tailed lizard (Cordylus warreni) Cordylus breyeri1.jpg Gerrhosauridae 34 Plated lizards Sudan plated lizard (Gerrhosaurus major) Gerrhosaurus major.jpg Scincidae
Oppel, 1811 Over 1500 Skinks Western blue-tongued skink (Tiliqua occipitalis) Tiliqua occipitalis.jpg Xantusiidae 34 Night lizards Granite night lizard (Xantusia henshawi) Xantusia henshawi.jpg Alethinophidia Family Species count Common names Example species Example photo Acrochordidae
Bonaparte, 1831[31] 3 File snakes Marine file snake (Acrochordus granulatus) Wart snake 1.jpg Aniliidae
Stejneger, 1907[32] 1 Coral pipe snakes Burrowing false coral (Anilius scytale) Anomochilidae
Cundall, Wallach and Rossman, 1993.[33] 3 Dwarf pipe snakes Leonard's pipe snake, (Anomochilus leonardi) Boidae
Gray, 1825[31] (incl. Calabariidae) 49 Boas Amazon tree boa (Corallus hortulanus) Corallushortulanus.png Bolyeriidae
Hoffstetter, 1946 2 Round Island boas Round Island burrowing boa (Bolyeria multocarinata) Colubridae
Oppel, 1811[31] sensu lato (incl. Dipsadidae, Natricidae, Pseudoxenodontidae) Nearly 2,000 Colubrids Grass snake (Natrix natrix) Natrix natrix (Marek Szczepanek).jpg Cylindrophiidae
Fitzinger, 1843 8 Asian pipe snakes Red-tailed pipe snake (Cylindrophis ruffus) Cylindrophis rufus.jpg Elapidae
Boie, 1827[31] 325 Cobras, coral snakes, mambas, kraits, sea snakes, sea kraits, Australian elapids King cobra (Ophiophagus hannah) Ophiophagus hannah2.jpg Homalopsidae
Bonaparte, 1845 Over 50 – Lamprophiidae
Fitzinger, 1843[34] 315 Bibron's burrowing asp (Atractaspis bibroni) Loxocemidae
Cope, 1861 1 Mexican burrowing snakes Mexican burrowing snake (Loxocemus bicolor) Loxocemus bicolor.jpg Pareatidae
Romer, 1956 20 – Pythonidae
Fitzinger, 1826 31 Pythons Ball python (Python regius) Ball python lucy.JPG Tropidophiidae
Brongersma, 1951 34 Dwarf boas Northern eyelash boa (Trachyboa boulengeri) Uropeltidae
Müller, 1832 About 50 Shield-tailed snakes, short-tailed snakes Cuvier's shieldtail (Uropeltis ceylanica) Silybura shortii.jpg Viperidae
Oppel, 1811[31] 224 Vipers, pitvipers, rattlesnakes European asp (Vipera aspis) Xenodermatidae
Fitzinger, 1826 About 18 – Xenopeltidae
Gray, 1849 2 Sunbeam snakes Sunbeam snake (Xenopeltis unicolor) XenopeltisUnicolorRooij.jpg Scolecophidia (incl. Anomalepidae) Family Common names Example species Example photo Anomalepidae
Taylor, 1939[31] 15 Dawn blind snakes Dawn blind snake (Liotyphlops beui) Gerrhopilidae
Vidal et al., 2010[30] Over 16 – Leptotyphlopidae
Stejneger, 1892[31] 87 Slender blind snakes Texas blind snake (Leptotyphlops dulcis) Leptotyphlops dulcis.jpg Typhlopidae
Merrem, 1820[35] Over 200 Blind snakes European blind snake (Typhlops vermicularis) Typhlops vermicularis.jpg Xenotyphlopidae
Vidal et al., 2010[30] 2 Xenotyphlops grandidieri

References

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  3. ^ http://www.reptile-database.org/db-info/SpeciesStat.html
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Squamata: Brief Summary
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This article is about the Squamata order of reptiles. For the Roman scale armour, see Lorica squamata.

Squamata is the largest order of reptiles, comprising lizards, snakes and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,000 species, it is also the second-largest order of extant (living) vertebrates, after the perciform fish, and roughly equal in number to the Saurischia (one of the two major groups of dinosaurs). 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 neurocranium. This is particularly visible in snakes, which are able to open their mouths very wide to accommodate comparatively large prey. Squamata is the most variably sized order of reptiles, ranging from the 16 mm (0.63 in) dwarf gecko (Sphaerodactylus ariasae) to the 5.21 m (17.1 ft) green anaconda (Eunectes murinus) and the now-extinct mosasaurs, which reached lengths of over 14 m (46 ft).

Among other reptiles, squamates are most closely related to the tuatara, which superficially resembles lizards.

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