suborder of reptiles
Lizards ( suborder Lacertilia ) are a widespread group of squamate reptiles, with over 6,000 species, [ 1 ] ranging across all continents except Antarctica, deoxyadenosine monophosphate well as most oceanic island chains. The group is paraphyletic as it excludes the snakes and Amphisbaenia ; some lizards are more close related to these two excluded groups than they are to early lizards. Lizards range in size from chameleons and geckos a few centimeters long to the 3 meter retentive Komodo dragon. Most lizards are quadrupedal, running with a hard side-to-side motion. Some lineages ( known as “ legless lizards “ ), have secondarily lost their legs, and have long snake-like bodies. Some such as the forest-dwelling Draco lizards are able to glide. They are often territorial, the males fighting off other males and sign, often with brilliantly colours, to attract mates and to intimidate rivals. Lizards are chiefly carnivorous, much being sit-and-wait predators ; many smaller species eat insects, while the Komodo eats mammals deoxyadenosine monophosphate big as water american bison. Lizards make use of a variety of antipredator adaptations, including malice, disguise, automatic run, and the ability to sacrifice and regrow their tails.

anatomy

Largest and smallest

The adult length of species within the suborder ranges from a few centimeters for chameleons such as Brookesia micra and gecko such as Sphaerodactylus ariasae [ 2 ] to about 3 thousand ( 10 foot ) in the case of the largest live varanid lounge lizard, the Komodo dragon. [ 3 ] Most lizards are fairly minor animals .

Distinguishing features

Lizards typically have rounded torso, elevated heads on short necks, four limbs and long tails, although some are legless. [ 4 ] Lizards and snakes share a chattel quadrate bone, distinguishing them from the rhynchocephalians, which have more rigid diapsid skulls. [ 5 ] Some lizards such as chameleons have prehensile tails, assisting them in climbing among vegetation. [ 6 ] As in other reptiles, the bark of lizards is covered in overlapping scales made of keratin. This provides protection from the environment and reduces water personnel casualty through vaporization. This adaptation enables lizards to thrive in some of the driest deserts on earth. The skin is baffling and coriaceous, and is shed ( sloughed ) as the animal grows. Unlike snakes which shed the peel in a single piece, lizards slough their skin in respective pieces. The scales may be modified into spines for display or protection, and some species have bone osteoderms underneath the scales. [ 6 ] [ 7 ] Tupinambis rufescens) skull, showing teeth of differing types crimson taegu ( ) skull, showing teeth of differing types The dentitions of lizards reflect their wide stove of diets, including carnivorous, insectivorous, omnivorous, herbivorous, nectivorous, and molluscivorous. Species typically have consistent teeth suited to their diet, but several species have variable teeth, such as cutting tooth in the front of the call on the carpet and crushing teeth in the rear. Most species are pleurodont, though agamids and chameleons are acrodont. [ 8 ] [ 6 ] The tongue can be extended outside the mouth, and is frequently long. In the beaded lizards, whiptails and monitor lizards, the natural language is forked and used chiefly or entirely to sense the environment, continually flicking out to sample the environment, and back to transfer molecules to the vomeronasal organ responsible for chemosensation, analogous to but different from smell or taste. In gecko, the tongue is used to lick the eyes clean : they have no eyelids. Chameleons have very long gluey tongues which can be extended quickly to catch their insect prey. [ 6 ] Three lineages, the gecko, anoles, and chameleons, have modified the scales under their toes to form adhesive pads, highly big in the first two groups. The pads are composed of millions of bantam seta ( hair-like structures ) which fit closely to the substrate to adhere using van five hundred Waals forces ; no liquid adhesive material is needed. [ 9 ] In addition, the toes of chameleons are divided into two opposed groups on each foundation ( zygodactyly ), enabling them to perch on branches as birds do. [ a ] [ 6 ]

physiology

locomotion

adhesive pads enable gecko to climb vertically. aside from legless lizards, most lizards are quadrupedal and move using gaits with alternating movement of the correct and left limbs with hearty body flex. This body bending prevents meaning respiration during movement, limiting their survival, in a mechanism called Carrier ‘s restraint. several species can run bipedally, [ 10 ] and a few can prop themselves up on their hindlimbs and buttocks while stationary. several little species such as those in the genus Draco can glide : some can attain a distance of 60 metres ( 200 feet ), losing 10 metres ( 33 feet ) in acme. [ 11 ] Some species, like gecko and chameleons, adhere to erect surfaces including field glass and ceilings. [ 9 ] Some species, like the common basilisk, can run across urine. [ 12 ]

Senses

Lizards make use of their senses of sight, touch, smell and learn like other vertebrates. The balance of these varies with the habitat of different species ; for exemplify, skinks that live largely covered by loose territory rely heavily on smell and touch, while gecko depend largely on acute vision for their ability to hunt and to evaluate the distance to their raven before striking. Monitor lizards have acute vision, learn, and olfactory senses. Some lizards make unusual manipulation of their sense organs : chameleons can steer their eyes in different directions, sometimes providing non-overlapping fields of opinion, such as forwards and backwards at once. Lizards lack external ears, having rather a circular opening in which the tympanic membrane ( eardrum ) can be seen. many species rely on hearing for early warn of predators, and flee at the slightest sound. [ 13 ] Nile monitor using its tongue for smell As in snakes and many mammals, all lizards have a specialised olfactory system, the vomeronasal harmonium, used to detect pheromones. Monitor lizards transfer aroma from the tip of their natural language to the organ ; the natural language is used only for this information-gathering determination, and is not involved in manipulating food. [ 14 ] [ 13 ] Some lizards, particularly common iguana, have retained a photosensory organ on the top of their heads called the parietal center, a basal ( “ primitive ” ) feature besides present in the tuatara. This “ eye ” has only a fundamental retina and lens and can not form images, but is sensitive to changes in light and black and can detect bowel movement. This helps them detect predators stalking it from above. [ 15 ]

malice

Until 2006 it was thought that the Gila monster and the Mexican beaded lounge lizard were the lone poisonous lizards. however, several species of monitor lizards, including the Komodo dragon, produce mighty venom in their oral glands. Lace admonisher venom, for example, causes swift passing of consciousness and across-the-board run through its pharmacological effects, both lowering blood atmospheric pressure and preventing blood clot. Nine classes of toxin known from snakes are produced by lizards. The crop of actions provides the likely for new medicative drugs based on lounge lizard malice proteins. [ 16 ] [ 17 ] Genes associated with malice toxins have been found in the salivary glands on a across-the-board range of lizards, including species traditionally thought of as non-venomous, such as iguanas and bearded dragons. This suggests that these genes evolved in the common ancestor of lizards and snakes, some 200 million years ago ( forming a single clade, the Toxicofera ). [ 16 ] however, most of these putative malice genes were “ housekeeping genes ” found in all cells and tissues, including skin and cloacal scent glands. The genes in question may frankincense be evolutionary precursors of malice genes. [ 18 ]

respiration

holocene studies ( 2013 and 2014 ) on the lung human body of the savanna monitor and k common iguana found them to have a unidirectional airflow system, which involves the breeze moving in a loop through the lungs when breathing. This was previously thought to entirely exist in the archosaur ( crocodilians and birds ). This may be testify that unidirectional airflow is an ancestral trait in diapsids. [ 19 ] [ 20 ]

reproduction and lifecycle

As with all amniotes, lizards rely on internal fertilization and sexual intercourse involves the male inserting one of his hemipenes into the female ‘s cloaca. [ 21 ] The majority of species are oviparous ( egg laying ). The female deposits the eggs in a protective structure like a nest or crack or merely on the ground. [ 22 ] Depending on the species, clutch size can vary from 4–5 percentage of the females consistency weight to 40–50 percentage and clutches range from one or a few big eggs to dozens of small ones. [ 23 ] In most lizards, the eggs have leathery shells to allow for the exchange of water, although more arid-living species have calcified shells to retain water. Inside the eggs, the embryo use nutrients from the egg yolk. Parental care is uncommon and the female normally abandons the eggs after laying them. Brooding and protection of eggs does occur in some species. The female prairie skink uses respiratory body of water loss to maintain the humidity of the eggs which facilitates embryonic development. In lace monitors, the young hatch close to 300 days, and the female returns to help them escape the termite knoll where the eggs were laid. [ 22 ] Around 20 percentage of lizard species reproduce via viviparity ( live parturition ). This is peculiarly park in Anguimorphs. viviparous species give birth to relatively develop youthful which look like miniature adults. Embryos are nourished via a placenta -like structure. [ 24 ] A minority of lizards have parthenogenesis ( reproduction from unfertilized eggs ). These species consist of all females who reproduce asexually with no need for males. This is known in happen in diverse species of whiptail lizards. [ 25 ] Parthenogenesis was besides recorded in species that normally reproduce sexually. A prisoner female Komodo dragon produced a batch of eggs, despite being separated from males for over two years. [ 26 ] arouse decision in lizards can be temperature-dependent. The temperature of the eggs ‘ micro-environment can determine the sexual activity of the hatched young : depleted temperature incubation produces more females while higher temperatures produce more males. however, some lizards have sex chromosomes and both male heterogamety ( XY and XXY ) and female heterogamety ( ZW ) occur. [ 25 ]

Behaviour

Diurnality and thermoregulation

The majority of lounge lizard species are active during the day, [ 27 ] though some are active at night, notably gecko. As ectotherms, lizards have a restrict ability to regulate their body temperature, and must seek out and bask in sunlight to gain enough heat to become fully active. [ 28 ] Thermoregulation behavior can be beneficial in the short term for lizards as it allows the ability to buffer environmental variation and digest climate calefacient. [ 29 ] In high gear altitudes, the Podarcis hispaniscus responds to higher temperature with a blue abaxial coloration to prevent UV-radiation and background duplicate. Their thermoregulatory mechanisms besides allow the lizard to maintain their ideal body temperature for optimum mobility. [ 30 ]

territoriality

Most social interactions among lizards are between breeding individuals. [ 27 ] Territoriality is park and is correlated with species that use sit-and-wait hunt strategies. Males establish and maintain territories that contain resources which attract females and which they defend from early males. crucial resources include basking, feed, and nesting sites equally well as refuges from predators. The habitat of a species affects the structure of territories, for model, rock lizards have territories atop rocky outcrops. [ 31 ] Some species may aggregate in groups, enhancing watchfulness and lessening the risk of depredation for individuals, particularly for juveniles. [ 32 ] Agonistic behavior typically occurs between sexually fledged males over territory or mates and may involve displays, model, chase, grappling and biting. [ 31 ]

communication

Lizards signal both to attract mates and to intimidate rivals. ocular displays include body postures and inflation, push-ups, bright colours, mouth gapings and chase waggings. male anoles and iguanas have dewlaps or bark flaps which come in diverse sizes, colours and patterns and the expansion of the dewlap adenine well as head-bobs and body movements add to the ocular signals. [ 33 ] [ 6 ] Some species have deep blue dewlaps and communicate with ultraviolet signals. [ 27 ] Blue-tongued skinks will flash their tongues as a threat display. [ 34 ] Chameleons are known to change their complex color patterns when communicate, peculiarly during agonistic encounters. They tend to show bright colours when displaying aggression [ 35 ] and dark colours when they submit or “ give up ”. [ 36 ] respective gecko species are brilliantly coloured ; some species tilt their bodies to display their coloration. In certain species, brilliantly coloured males turn dull when not in the presence of rivals or females. While it is normally males that display, in some species females besides use such communication. In the bronze american chameleon, head-bobs are a common class of communication among females, the speed and frequency varying with age and territorial status. Chemical cues or pheromones are besides authoritative in communication. Males typically direct signals at rivals, while females direct them at potential mates. Lizards may be able to recognise individuals of the same species by their odorize. [ 33 ] acoustic communication is less common in lizards. Hissing, a distinctive reptile voice, is by and large produced by larger species as part of a threat display, accompanying gaping chew the fat. Some groups, peculiarly gecko, snake-lizards, and some iguanids, can produce more complex sounds and vocal apparatuses have independently evolved in different groups. These sounds are used for courtship, territorial defense and in distress, and include clicks, squeaks, barks and grumble. The mating call of the male tokay gecko is heard as “ tokay-tokay ! “. [ 34 ] [ 33 ] [ 37 ] Tactile communication involves individuals rubbing against each other, either in courtship or in aggression. [ 33 ] Some chameleon species communicate with one another by vibrating the substrate that they are standing on, such as a corner branch or leaf. [ 38 ]

ecology

Lizard in tree. many species are tree-dwellingA lizard from Thar desert A lounge lizard from Thar desert

distribution and habitat

Lizards are found worldwide, excluding the far north and Antarctica, and some islands. They can be found in elevations from ocean flush to 5,000 megabyte ( 16,000 foot ). They prefer warmer, tropical climates but are adaptable and can live in all but the most extreme environments. Lizards besides exploit a number of habitats ; most chiefly live on the flat coat, but others may live in rocks, on trees, underground and even in water. The nautical common iguana is adapted for life in the ocean. [ 6 ]

diet

The majority of lizard species are marauding and the most coarse prey items are belittled, sublunar invertebrates, peculiarly insects. [ 6 ] [ 39 ] many species are sit-and-wait predators though others may be more active foragers. [ 40 ] Chameleons prey on numerous worm species, such as beetles, grasshoppers and winged termites adenine well as spiders. They rely on perseverance and ambush to capture these prey. An individual perches on a arm and stays absolutely placid, with merely its eyes moving. When an insect lands, the chameleon focuses its eyes on the prey and slowly moves towards it before projecting its long gluey tongue which, when hauled back, brings the attach prey with it. Geckos feed on crickets, beetles, termites and moths. [ 6 ] [ 39 ] Termites are an significant region of the diets of some species of Autarchoglossa, since, as social insects, they can be found in big numbers in one spotlight. Ants may form a outstanding separate of the diet of some lizards, peculiarly among the lacertas. [ 6 ] [ 39 ] Horned lizards are besides well known for specializing on ants. Due to their little size and indigestible chitin, ants must be consumed in large amounts, and ant-eating lizards have larger stomachs than even herbivorous ones. [ 41 ] Species of skink and alligator lizards consume snails and their exponent jaw and molar-like teeth are adapted for breaking the shells. [ 6 ] [ 39 ] Young Komodo dragon feeding on a water buffalo carcase Marine common iguana foraging under water system at Galápagos Islands, Ecuador. Larger species, such as monitor lizards, can feed on larger prey including fish, frogs, birds, mammals and early reptiles. Prey may be swallowed whole and torn into smaller pieces. Both bird and reptile eggs may besides be consumed a well. Gila monsters and beaded lizards climb trees to reach both the eggs and youthful of birds. Despite being deadly, these species rely on their strong chew the fat to kill prey. mammal prey typically consists of rodents and leporids ; the Komodo draco can kill prey arsenic bombastic as water system buffalo. Dragons are fecund scavengers, and a single decay carcase can attract several from 2 km ( 1.2 secret intelligence service ) away. A 50 kilogram ( 110 pound ) dragon is able of consuming a 31 kilogram ( 68 pound ) carcase in 17 minutes. [ 39 ]

Around 2 percentage of lounge lizard species, including many iguanids, are herbivores. Adults of these species eat implant parts like flowers, leaves, stems and yield, while juveniles eat more insects. plant parts can be hard to digest, and, as they get closer to adulthood, juvenile iguanas eat faeces from adults to acquire the microflora necessary for their transition to a plant-based diet. possibly the most herbivorous species is the marine common iguana which dives 15 thousand ( 49 foot ) to forage for alga, kelp and early marine plants. Some non-herbivorous species supplement their worm diet with fruit, which is easily digested. [ 6 ] [ 39 ]

Antipredator adaptations

The frilled-neck lizard with amply extended frill. The frilled serves to make it look bigger than it actually is. Lizards have a variety of antipredator adaptations, including running and climbing, venom, disguise, buttocks autotomy, and automatic bleed .

disguise

Lizards exploit a variety show of different disguise methods. many lizards are disruptively patterned. In some species, such as Aegean wall lizards, individuals vary in color, and choice rocks which best match their own color to minimise the risk of being detected by predators. [ 42 ] The Moorish gecko is able to change tinge for camouflage : when a light-coloured gecko is placed on a dark surface, it darkens within an hour to match the environment. [ 43 ] The chameleons in general use their ability to change their coloration for signalling rather than disguise, but some species such as Smith ‘s shadow chameleon do practice active agent colour change for camouflage purposes. [ 44 ] The flat-tail horned lounge lizard ‘s body is coloured like its desert backdrop, and is flattened and fringed with white scales to minimise its trace. [ 45 ]

autotomy

A skink chase continuing to move after autotomy many lizards, including gecko and skinks, are adequate to of shedding their tails ( autotomy ). The detach dock, sometimes brilliantly coloured, continues to writhe after detaching, distracting the predator ‘s care from the fleeing prey. Lizards partially regenerate their tails over a period of weeks. Some 326 genes are involved in regenerating lounge lizard tails. [ 46 ] The fish-scale gecko Geckolepis megalepis sheds patches of skin and scales if grabbed. [ 47 ]

escape, playing dead, reflex bleed

many lizards attempt to escape from danger by running to a space of safety ; [ 48 ] [ b-complex vitamin ] for example, wall lizards can run up walls and hide in holes or cracks. [ 9 ] Horned lizards adopt differing defences for specific predators. They may play dead to deceive a marauder that has caught them ; attack to outrun the rattlesnake, which does not pursue raven ; but stay still, relying on their cryptic color, for Masticophis whip snakes which can catch even swift raven. If caught, some species such as the greater short-horned lizard pant themselves up, making their bodies hard for a narrow-mouthed marauder like a worst snake to swallow. last, horned lizards can squirt blood at big cat and frump predators from a pouch below its eyes, to a distance of about two metres ( 6.6 feet ) ; the blood tastes foul to these attackers. [ 50 ]

development

Fossil history

The earliest know fossil remains of a lounge lizard belong to the iguanian species Tikiguania estesi, found in the Tiki Formation of India, which dates to the Carnian stage of the Triassic time period, about 220 million years ago. [ 51 ] however, doubt has been raised over the age of Tikiguania because it is about identical from modern agamid lizards. The Tikiguania remains may alternatively be late Tertiary or Quaternary in old age, having been washed into much older triassic sediments. [ 52 ] Lizards are most close related to the Rhynchocephalia, which appeared in the Late Triassic, so the earliest lizards credibly appeared at that clock. [ 52 ] Mitochondrial phylogenetics suggest that the first lizards evolved in the recently permian. It had been thought on the footing of morphologic data that iguanid lizards diverged from early squamates identical early on, but molecular evidence contradicts this. [ 53 ] Mosasaurs probably evolved from an extinct group of aquatic lizards [ 54 ] known as aigialosaurs in the early Cretaceous. Dolichosauridae is a family of Late Cretaceous aquatic varanoid lizards closely related to the mosasaurs. [ 55 ] [ 56 ]

evolution

external

The position of the lizards and other Squamata among the reptiles was studied using fossil evidence by Rainer Schoch and Hans-Dieter Sues in 2015. Lizards form about 60 % of the extant non-avian reptiles. [ 57 ]

Internal

Both the snakes and the Amphisbaenia ( worm lizards ) are clade deep within the Squamata ( the smallest clade that contains all the lizards ), so “ lounge lizard ” is paraphyletic. [ 58 ] The cladogram is based on genomic analysis by Wiens and colleagues in 2012 and 2016. [ 59 ] [ 60 ] Excluded taxonomic group are shown in amphetamine case on the cladogram .

taxonomy

Prognathodon aesthetic restitution of a mosasaur, In the thirteenth hundred, lizards were recognized in Europe as part of a broad category of reptiles that consisted of a florilegium of egg-laying creatures, including “ snakes, assorted fantastic monsters, [ … ], assorted amphibians, and worms ”, as recorded by Vincent of Beauvais in his Mirror of Nature. [ 61 ] The seventeenth hundred saw changes in this loosen description. The name Sauria was coined by James Macartney ( 1802 ) ; [ 62 ] it was the Latinisation of the french name Sauriens, coined by Alexandre Brongniart ( 1800 ) for an order of reptiles in the classification proposed by the generator, containing lizards and crocodilians, [ 63 ] belated discovered not to be each other ‘s closest relatives. Later authors used the term “ Sauria ” in a more restricted feel, i.e. as a synonym of Lacertilia, a suborder of Squamata that includes all lizards but excludes snakes. This classification is rarely used today because Sauria so-defined is a paraphyletic group. It was defined as a clade by Jacques Gauthier, Arnold G. Kluge and Timothy Rowe ( 1988 ) as the group containing the most late coarse ancestor of archosaurs and lepidosaurs ( the groups containing crocodiles and lizards, as per Mcartney ‘s original definition ) and all its descendants. [ 64 ] A different definition was formulated by Michael deBraga and Olivier Rieppel ( 1997 ), who defined Sauria as the clade containing the most late common ancestor of Choristodera, Archosauromorpha, Lepidosauromorpha and all their descendants. [ 65 ] however, these uses have not gained wide acceptance among specialists .
Anguis, are among over twenty groups of lizards that have [66] The slowworms, , are among over twenty groups of lizards that have convergently evolved a legless body design

convergence

Lizards have frequently evolved convergently, with multiple groups independently developing like morphology and ecological niches. Anolis ecomorphs have become a model system in evolutionary biology for studying overlap. [ 67 ] Limbs have been lost or reduced independently over two twelve times across lounge lizard development, including in the Anniellidae, Anguidae, Cordylidae, Dibamidae, Gymnophthalmidae, Pygopodidae, and Scincidae ; snakes are just the most celebrated and species-rich group of Squamata to have followed this path. [ 66 ]

kinship with humans

Interactions and uses by humans

Most lizard species are harmless to humans. entirely the largest lizard species, the Komodo dragon, which reaches 3.3 m ( 11 foot ) in duration and weighs up to 166 kg ( 366 pound ), has been known to stalk, attack, and, on affair, kill humans. An eight-year-old indonesian boy died from rake passing after an approach in 2007. [ 68 ] Green iguanas (Iguana iguana), are popular pets. ), are popular pets. numerous species of lizard are kept as pets, including beard dragons, [ 69 ] common iguana, anoles, [ 70 ] and gecko ( such as the popular leopard gecko ). [ 69 ] Monitor lizards such as the savanna monitor and taegu such as the Argentine taegu and crimson taegu are besides kept. k iguanas are eaten in Central America, where they are sometimes referred to as “ chicken of the tree ” after their habit of resting in trees and their purportedly chicken-like smack, [ 71 ] while spiny-tailed lizards are eaten in Africa. In North Africa, Uromastyx species are considered dhaab or ‘fish of the defect ‘ and eaten by mobile tribes. [ 72 ] Lizards such as the Gila giant produce toxins with aesculapian applications. Gila toxin reduces plasma glucose ; the means is immediately synthesized for function in the anti- diabetes drug exenatide ( Byetta ). [ 17 ] Another toxin from Gila monster saliva has been studied for use as an anti- Alzheimer ‘s drug. [ 73 ]

In culture

Lizards appear in myths and folktales around the world. In australian Aboriginal mythology, Tarrotarro, the lounge lizard idol, split the human race into male and female, and gave people the ability to express themselves in artwork. A lounge lizard king named Mo’o features in Hawaii and other cultures in Polynesia. In the Amazon, the lizard is the king of beasts, while among the Bantu of Africa, the god UNkulunkulu sent a chameleon to tell humans they would live constantly, but the chameleon was held up, and another lizard brought a different message, that the time of humanity was limited. [ 74 ] A democratic caption in Maharashtra tells the narrative of how a common amerind monitor, with ropes attached, was used to scale the walls of the fort in the Battle of Sinhagad. [ 75 ] In the Bhojpuri speaking region of India and Nepal, there is a belief among children that, on touching skink ‘s buttocks three ( or five ) time with the shortest finger gives money. Lizards in many cultures plowshare the symbolism of snakes, particularly as an emblem of resurrection. This may have derived from their regular shed. The motif of lizards on christian candle holders probably alludes to the same symbolism. According to Jack Tresidder, in Egypt and the classical world they were beneficial emblems, linked with wisdom. In African, Aboriginal and Melanesian folklore they are linked to cultural heroes or ancestral figures. [ 76 ]

Notes

  1. ^[6] Chameleon forefoot have groups composed of 3 inner and 2 forbidden digits ; the hindfeet have groups of 2 inner and 3 out digits .
  2. ^Planet Earth II showed a sequence of newly-hatched [49] The BBC ‘s 2016showed a sequence of newly-hatched marine common iguana running to the sea past a waiting crowd of racer snakes. It was edited for dramatic effect but the sections were all actual .

References

General sources

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