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Lizards (
suborder In biological classification, the order ( la, wikt:ordo#Latin, ordo) is # a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. The well-known ranks in descending order are: life, domain (biology), do ...
Lacertilia) are a widespread group of
squamate Squamata (, Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman R ...

squamate
reptile Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or ...

reptile
s, with over 6,000
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
, ranging across all continents except
Antarctica Antarctica ( or ) is Earth's southernmost continent. It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Oc ...

Antarctica
, as well as most oceanic
island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atoll An atoll (), sometimes known as a coral atoll, i ...

island
chains. The group is
paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The group is said to be paraphyleti ...

paraphyletic
as it excludes the
snake Snakes are elongated, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Many species of snakes ...

snake
s and
Amphisbaenia Amphisbaenia (called amphisbaenians or worm lizards) is a group of usually legless squamates, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. As ...
; some lizards are more closely related to these two excluded groups than they are to other lizards. Lizards range in size from
chameleon Chameleons or chamaeleons (family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and ...

chameleon
s and
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder#Hierarchy of ranks, infraorder Gekkota, geckos are found in warm climates throughout the world. T ...

gecko
s a few centimeters long to the 3 meter long
Komodo dragon The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a member of the monitor lizard Monitor lizards are large lizard Lizards (suborder Lacertilia) are a widespread group of Squamata, squamate reptiles, with ...

Komodo dragon
. Most lizards are quadrupedal, running with a strong side-to-side motion. Some lineages (known as "
legless lizard Legless lizard may refer to any of several groups of lizard Lizards are a widespread group of Squamata, squamate reptiles, with over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The grou ...
s"), have secondarily lost their legs, and have long snake-like bodies. Some such as the forest-dwelling ''
Draco DRACO (double-stranded RNA Ribonucleic acid (RNA) is a polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning t ...
'' lizards are able to glide. They are often
territorial A territory is an administrative division Administrative division, administrative unitArticle 3(1). , country subdivision, administrative region, subnational entity, first-level subdivision, as well as many similar terms, are generic names f ...
, the males fighting off other males and signalling, often with brightly colours, to attract mates and to intimidate rivals. Lizards are mainly carnivorous, often being
sit-and-wait predators Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey by stealth or by strategy (typically not conscious), rather than by speed or by strength. Ambush predation, predators sit and wait for prey, often from a ...
; many smaller species eat insects, while the Komodo eats mammals as big as
water buffalo The water buffalo (''Bubalus bubalis''), also called the domestic water buffalo or Asian water buffalo, is a large bovid The Bovidae comprise the biological family Family ( la, familia, plural ') is one of the eight major hierarchical tax ...

water buffalo
. Lizards make use of a variety of
antipredator adaptation Anti-predator adaptations are mechanisms developed through evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to thei ...
s, including
venom Venom is a type of poison In biology, poisons are Chemical substance, substances that can cause death, injury or harm to organs, Tissue (biology), tissues, Cell (biology), cells, and DNA usually by chemical reactions or other activity (chemi ...

venom
,
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard The leopard (''Pan ...

camouflage
, reflex bleeding, and the ability to
sacrifice and regrow their tails
sacrifice and regrow their tails
.


Anatomy


Largest and smallest

The adult length of species within the
suborder In biological classification, the order ( la, wikt:ordo#Latin, ordo) is # a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. The well-known ranks in descending order are: life, domain (biology), do ...
ranges from a few centimeters for
chameleon Chameleons or chamaeleons (family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and ...

chameleon
s such as ''
Brookesia micra
Brookesia micra
'' and
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder#Hierarchy of ranks, infraorder Gekkota, geckos are found in warm climates throughout the world. T ...

gecko
s such as '' Sphaerodactylus ariasae'' to nearly in the case of the largest living varanid lizard, the
Komodo dragon The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a member of the monitor lizard Monitor lizards are large lizard Lizards (suborder Lacertilia) are a widespread group of Squamata, squamate reptiles, with ...

Komodo dragon
. Most lizards are fairly small animals.


Distinguishing features

Lizards typically have rounded torsos, elevated heads on short necks, four limbs and long tails, although some are legless. Lizards and snakes share a movable
quadrate bone The quadrate bone is a skull The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of ...
, distinguishing them from the rhynchocephalians, which have more rigid
diapsid Diapsids ("two arches") are a group of amniote tetrapods that developed two holes (temporal fenestra) in each side of their skulls about 300 million years ago during the late Carboniferous period. The diapsids are extremely diverse, and include all ...

diapsid
skull The skull is a bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North A ...

skull
s. Some lizards such as chameleons have
prehensile A prehensile tail. Prehensility is the quality of an appendage An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism In biology, an organism (from Ancient Greek, Greek: ὀργ ...
tails, assisting them in climbing among vegetation. As in other reptiles, the skin of lizards is covered in overlapping
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory)In the mathematical discipline of descriptive set theory, a scale is a certain kind of object defined on a set (mathematics), set of point (mathematics), points in some Poli ...
made of
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of fibrous structural proteins known as Scleroprot ...

keratin
. This provides protection from the environment and reduces water loss through evaporation. This adaptation enables lizards to thrive in some of the driest deserts on earth. The skin is tough and leathery, and is shed (sloughed) as the animal grows. Unlike snakes which shed the skin in a single piece, lizards slough their skin in several pieces. The scales may be modified into spines for display or protection, and some species have bone
osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis The dermis or corium is a layer of skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three ...
s underneath the scales. The dentitions of lizards reflect their wide range of diets, including carnivorous, insectivorous, omnivorous, herbivorous, nectivorous, and molluscivorous. Species typically have uniform teeth suited to their diet, but several species have variable teeth, such as cutting teeth in the front of the jaws and crushing teeth in the rear. Most species are
pleurodont Pleurodont is a form of tooth implantation common in Reptile, reptiles of the order Squamata, as well as in at least one temnospondyl. The labial (cheek) side of pleurodont teeth are fused (Ankylosis, ankylosed) to the inner surface of the jaw bones ...
, though agamids and chameleons are
acrodontAcrodonty (from Greek ''akros'' ''dont'', highest tooth) is an anatomical placement of the teeth at the summit of the alveolar ridge of the jaw, without sockets, characteristic of Osteichthyes, bony fish. Functionally, acrodont tooth implantation ...
. The tongue can be extended outside the mouth, and is often long. In the beaded lizards, whiptails and monitor lizards, the tongue is forked and used mainly or exclusively 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 geckos, the tongue is used to lick the eyes clean: they have no eyelids. Chameleons have very long sticky tongues which can be extended rapidly to catch their insect prey. Three lineages, the
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder#Hierarchy of ranks, infraorder Gekkota, geckos are found in warm climates throughout the world. T ...

gecko
s,
anole Dactyloidae are a family of lizards commonly known as anoles () and native to warmer parts of the Americas, ranging from southeastern United States to Paraguay. Instead of treating it as a family, some authorities prefer to treat it as a subfami ...

anole
s, and
chameleon Chameleons or chamaeleons (family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and ...

chameleon
s, have modified the scales under their toes to form adhesive pads, highly prominent in the first two groups. The pads are composed of millions of tiny setae (hair-like structures) which fit closely to the substrate to adhere using
van der Waals force In molecular physics Molecular physics is the study of the physical properties of molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings ...
s; no liquid adhesive is needed. In addition, the toes of chameleons are divided into two opposed groups on each foot ( zygodactyly), enabling them to perch on branches as birds do.


Physiology


Locomotion

Aside from legless lizards, most lizards are quadrupedal and move using
gait Gait is the pattern of movement Movement may refer to: Common uses * Movement (clockwork), the internal mechanism of a timepiece * Motion (physics), commonly referred to as movement Arts, entertainment, and media Literature * Movemen ...
s with alternating movement of the right and left limbs with substantial body bending. This body bending prevents significant respiration during movement, limiting their endurance, in a mechanism called
Carrier's constraint Carrier's constraint is the observation that air-breathing vertebrates which have two lungs and flex their bodies sideways during animal locomotion, locomotion find it very difficult to move and breathe at the same time, because the sideways flexin ...
. Several species can run bipedally, and a few can prop themselves up on their hindlimbs and tail while stationary. Several small species such as those in the genus ''
Draco DRACO (double-stranded RNA Ribonucleic acid (RNA) is a polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning t ...
'' can glide: some can attain a distance of , losing in height. Some species, like geckos and chameleons, adhere to vertical surfaces including glass and ceilings. Some species, like the common basilisk, can run across water.


Senses

Lizards make use of their
sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to Stimulus (physiology), stimuli. (For example, in the human body, the brain receives signals from the senses ...

sense
s of
sight Visual perception is the ability to interpret the surrounding environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biol ...

sight
,
touch The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system In biology, the classical doctrine of the nervous system determines that it is a Complex system, highly comple ...

touch
,
olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting hazards, and pheromones, and plays a role in taste. It occurs when an odor binds ...
and
hearing Hearing, or auditory perception, is the ability to perceive sounds In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, ...

hearing
like other
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an indiv ...
s. The balance of these varies with the habitat of different species; for instance, skinks that live largely covered by loose soil rely heavily on olfaction and touch, while geckos depend largely on acute vision for their ability to hunt and to evaluate the distance to their prey before striking. Monitor lizards have acute vision, hearing, and olfactory senses. Some lizards make unusual use of their sense organs: chameleons can steer their eyes in different directions, sometimes providing non-overlapping fields of view, such as forwards and backwards at once. Lizards lack external ears, having instead a circular opening in which the tympanic membrane (eardrum) can be seen. Many species rely on hearing for early warning of predators, and flee at the slightest sound. As in snakes and many mammals, all lizards have a specialised olfactory system, the
vomeronasal organ The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory Olfaction, or the sense of smell, is the special sense through which smells (or odors) are perceived. It occurs when an odor binds to a olfactory receptor, re ...

vomeronasal organ
, used to detect
pheromone A pheromone (from Ancient Greek ' "to bear" and hormone) is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the s ...

pheromone
s. Monitor lizards transfer scent from the tip of their tongue to the organ; the tongue is used only for this information-gathering purpose, and is not involved in manipulating food. Some lizards, particularly iguanas, have retained a photosensory organ on the top of their heads called the
parietal eye A parietal eye, also known as a third eye or pineal eye, is a part of the epithalamus The epithalamus is a (dorsal) posterior segment of the diencephalon The diencephalon is a division of the forebrain (embryonic ''prosencephalon''), and is ...
, a
basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is neces ...
("primitive") feature also present in the
tuatara Tuatara (''Sphenodon punctatus'') are reptiles Endemism, endemic to New Zealand. Although resembling most lizards, they are part of a distinct lineage, the order Rhynchocephalia. Their name derives from the Māori language, and means "peaks on ...

tuatara
. This "eye" has only a rudimentary retina and lens and cannot form images, but is sensitive to changes in light and dark and can detect movement. This helps them detect predators stalking it from above.


Venom

Until 2006 it was thought that the
Gila monster The Gila monster (''Heloderma suspectum'', ) is a species of venom Venom is a type of poison, especially one secreted by an animal. Venom has evolved in a wide variety of animals, both predators and prey, and both vertebrates and invertebrate ...

Gila monster
and the Mexican beaded lizard were the only venomous lizards. However, several species of monitor lizards, including the
Komodo dragon The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a member of the monitor lizard Monitor lizards are large lizard Lizards (suborder Lacertilia) are a widespread group of Squamata, squamate reptiles, with ...

Komodo dragon
, produce powerful venom in their oral
gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...

gland
s. venom, for instance, causes swift loss of consciousness and extensive bleeding through its pharmacological effects, both lowering
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mas ...

blood pressure
and preventing
blood clotting Coagulation, also known as clotting, is the process by which blood Blood is a body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mech ...
. Nine classes of
toxin A toxin is a harmful substance produced within living cells or organisms; synthetic toxicants created by artificial processes are thus excluded. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived from the word toxic ...
known from snakes are produced by lizards. The range of actions provides the potential for new medicinal drugs based on lizard venom
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s. Genes associated with venom toxins have been found in the salivary glands on a wide 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
snake Snakes are elongated, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Many species of snakes ...

snake
s, some 200 million years ago (forming a single
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
, the
Toxicofera Toxicofera (Greek for "those who bear toxins") is a proposed clade of squamata, scaled reptiles (squamates) that includes the snake, Serpentes (snakes), Anguimorpha (monitor lizards, gila monster, and alligator lizards) and Iguania (iguanas, Agam ...
). However, most of these putative venom genes were "housekeeping genes" found in all cells and tissues, including skin and cloacal scent glands. The genes in question may thus be evolutionary precursors of venom genes.


Respiration

Recent studies (2013 and 2014) on the lung anatomy of the savannah monitor and
green iguana The green iguana (''Iguana iguana''), also known as the American iguana or the common green iguana, is a large, arboreal, mostly Herbivory, herbivorous species of lizard of the genus ''Iguana''. Usually, this animal is simply called the iguana. ...

green iguana
found them to have a unidirectional airflow system, which involves the air moving in a loop through the lungs when breathing. This was previously thought to only exist in the
archosaurs Archosauria ("ruling reptiles") is a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common ancestor an ...
(
crocodilian Crocodilia (or Crocodylia, both ) is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, ...
s and
bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

bird
s). This may be evidence that unidirectional airflow is an ancestral trait in
diapsid Diapsids ("two arches") are a group of amniote tetrapods that developed two holes (temporal fenestra) in each side of their skulls about 300 million years ago during the late Carboniferous period. The diapsids are extremely diverse, and include all ...

diapsid
s.


Reproduction and lifecycle

As with all amniotes, lizards rely on internal fertilisation and copulation involves the male inserting one of his s into the female's
cloaca In animal anatomy, a cloaca (plural cloacae or ) is the posterior that serves as the only opening for the , reproductive, and s (if present) of many animals. All s, s, birds, and a few mammals (s, s, s, and s) have this orifice, from which ...
. The majority of species are
oviparous Oviparous animals are female animals that lay their egg Diagram of a chicken egg in its 9th day. Membranes: allantois, chorion, amnion, and vitellus/ yolk. An egg is the organic vessel containing the zygote in which an embryo develops un ...
(egg laying). The female deposits the eggs in a protective structure like a nest or crevice or simply on the ground. Depending on the species, clutch size can vary from 4–5 percent of the females body weight to 40–50 percent and clutches range from one or a few large eggs to dozens of small ones. 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 embryos use nutrients from the
yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example beca ...

yolk
. Parental care is uncommon and the female usually abandons the eggs after laying them. and protection of eggs does occur in some species. The female uses respiratory 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 mound where the eggs were laid.Pianka and Vitt, pp. 115–116. Around 20 percent of lizard species reproduce via
viviparity Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the mo ...
(live birth). This is particularly common in Anguimorphs. Viviparous species give birth to relatively developed young which look like miniature adults. Embryos are nourished via a
placenta The placenta is a temporary fetal organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. ...

placenta
-like structure. A minority of lizards have
parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction Asexual reproduction is a typ ...
(reproduction from unfertilised eggs). These species consist of all females who reproduce asexually with no need for males. This is known in occur in various species of whiptail lizards.Pianka and Vitt, pp. 119. Parthenogenesis was also recorded in species that normally reproduce sexually. A captive female Komodo dragon produced a clutch of eggs, despite being separated from males for over two years. Sex determination in lizards can be temperature-dependent. The temperature of the eggs' micro-environment can determine the sex of the hatched young: low temperature incubation produces more females while higher temperatures produce more males. However, some lizards have
sex chromosomes A sex chromosome, (also referred to as an allosome, heterotypical chromosome, gonosome, or heterochromosome, or idiochromosome) is a chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. M ...
and both male heterogamety (XY and XXY) and female heterogamety (ZW) occur.


Behaviour


Diurnality and thermoregulation

The majority of lizard species are active during the day, though some are active at night, notably geckos. As
ectotherm An ectotherm (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population i ...
s, lizards have a limited ability to regulate their body temperature, and must seek out and bask in sunlight to gain enough heat to become fully active. In high altitudes, the Podarcis hispaniscus responds to higher temperature with a darker dorsal coloration to prevent UV-radiation and background matching. Their thermoregulatory mechanisms also allow the lizard to maintain their ideal body temperature for optimal mobility.


Territoriality

Most social interactions among lizards are between breeding individuals.Pianka and Vitt, pp. 86.
Territoriality In ethology Ethology is the scientific and objective study of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, anima ...
is common and is correlated with species that use sit-and-wait hunting strategies. Males establish and maintain territories that contain resources which attract females and which they defend from other males. Important resources include basking, feeding, and nesting sites as well as refuges from predators. The habitat of a species affects the structure of territories, for example, rock lizards have territories atop rocky outcrops.Pianka and Vitt, pp. 94–106. Some species may aggregate in groups, enhancing vigilance and lessening the risk of predation for individuals, particularly for juveniles.
Agonistic behaviour Agonistic behaviour is any social behaviour related to fighting. The term has broader meaning than aggressive behaviour because it includes threats, displays, retreats, placation, and conciliation. The term "agonistic behaviour" was first implemente ...
typically occurs between sexually mature males over territory or mates and may involve displays, posturing, chasing, grappling and biting.


Communication

Lizards signal both to attract mates and to intimidate rivals. Visual displays include body postures and inflation, push-ups, bright colours, mouth gapings and tail waggings. Male
anole Dactyloidae are a family of lizards commonly known as anoles () and native to warmer parts of the Americas, ranging from southeastern United States to Paraguay. Instead of treating it as a family, some authorities prefer to treat it as a subfami ...

anole
s and iguanas have
dewlap A dewlap is a longitudinal Longitudinal is a geometric term of location which may refer to: * Longitude ** Line of longitude, also called a meridian (geography), meridian * Longitudinal engine, an internal combustion engine in which the cranksha ...
s or skin flaps which come in various sizes, colours and patterns and the expansion of the dewlap as well as head-bobs and body movements add to the visual signals. Some species have deep blue dewlaps and communicate with
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, ...

ultraviolet
signals.
Blue-tongued skink Blue-tongued skinks comprise the Australasian genus ''Tiliqua'', which contains some of the largest members of the skink family (biology), family (Scincidae). They are commonly called blue-tongued lizards or simply blue-tongues or blueys in Austra ...
s will flash their tongues as a
threat display A threat is a communication of intent to inflict harm or loss on another person. IntimidationIntimidation (also called cowing) is intentional behavior that "would cause a person of ordinary sensibilities" to fear injury Injury, also known a ...
. Chameleons are known to change their complex colour patterns when communicating, particularly during agonistic encounters. They tend to show brighter colours when displaying aggression and darker colours when they submit or "give up". Several gecko species are brightly coloured; some species tilt their bodies to display their coloration. In certain species, brightly coloured males turn dull when not in the presence of rivals or females. While it is usually males that display, in some species females also use such communication. In the bronze anole, head-bobs are a common form of communication among females, the speed and frequency varying with age and territorial status. Chemical cues or
pheromone A pheromone (from Ancient Greek ' "to bear" and hormone) is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the s ...

pheromone
s are also important 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 scent.Pianka and Vitt, pp. 87–94. Acoustic communication is less common in lizards. Hissing, a typical reptilian sound, is mostly produced by larger species as part of a threat display, accompanying gaping jaws. Some groups, particularly geckos, 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 growls. The mating call of the male
tokay gecko The tokay gecko (''Gekko gecko'') is a nocturnal Nocturnality is an animal behavior Ethology is the scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branc ...
as "tokay-tokay!". Tactile communication involves individuals rubbing against each other, either in courtship or in aggression. Some chameleon species communicate with one another by vibrating the substrate that they are standing on, such as a tree branch or leaf.


Ecology


Distribution and habitat

Lizards are found worldwide, excluding the far north and Antarctica, and some islands. They can be found in elevations from sea level to . They prefer warmer, tropical climates but are adaptable and can live in all but the most extreme environments. Lizards also exploit a number of habitats; most primarily live on the ground, but others may live in rocks, on trees, underground and even in water. The marine iguana is adapted for life in the sea.


Diet

The majority of lizard species are
predatory Predation is a biological interaction In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical envi ...
and the most common prey items are small, terrestrial invertebrates, particularly
insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in ...

insect
s. Many species are
sit-and-wait predators Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey by stealth or by strategy (typically not conscious), rather than by speed or by strength. Ambush predation, predators sit and wait for prey, often from a ...
though others may be more active foragers. Chameleons prey on numerous insect species, such as
beetle Beetles are a group of insect Insects (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known a ...

beetle
s,
grasshopper Grasshoppers are a group of insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''comm ...

grasshopper
s and winged
termites Termites are s that are classified at the of Isoptera, or alternatively as Termitoidae, within the order (along with es). Termites were once classified in a separate from cockroaches, but recent studies indicate that they evolved from c ...

termites
as well as
spider Spiders (order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and the ...

spider
s. They rely on persistence and ambush to capture these prey. An individual perches on a branch and stays perfectly still, with only its eyes moving. When an insect lands, the chameleon focuses its eyes on the target and slowly moves towards it before projecting its long sticky tongue which, when hauled back, brings the attach prey with it. Geckos feed on
cricket Cricket is a Bat-and-ball games, bat-and-ball game played between two teams of eleven players each on a cricket field, field at the centre of which is a cricket pitch, pitch with a wicket at each end, each comprising two Bail (cricket), bai ...
s, beetles, termites and
moth Moths are a paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The g ...

moth
s. Termites are an important part of the diets of some species of Autarchoglossa, since, as
social insect Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping gene ...
s, they can be found in large numbers in one spot.
Ant Ants are eusocial Eusociality (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population i ...

Ant
s may form a prominent part of the diet of some lizards, particularly among the lacertas.
Horned lizard Horned lizards (''Phrynosoma''), also known as horny toads or horntoads, are a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific s ...

Horned lizard
s are also well known for specializing on ants. Due to their small size and indigestible
chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. The second most abundant polysaccharide in nature (behind only cellulose), it ...

chitin
, ants must be consumed in large amounts, and ant-eating lizards have larger stomachs than even
herbivorous A herbivore is an animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All ...

herbivorous
ones. Species of skink and
alligator lizard An alligator lizard is any one of various species of lizards in the Family (biology), family Anguidae that have some shared characteristics. The term may specifically refer to: Species of the genus ''Elgaria'': *Northern alligator lizard (''Elgaria ...
s eat
snail A snail is, in loose terms, a shelled gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the pr ...

snail
s and their power jaws and molar-like teeth are adapted for breaking the shells. Larger species, such as monitor lizards, can feed on larger prey including fish, frogs, birds, mammals and other reptiles. Prey may be swallowed whole and torn into smaller pieces. Both bird and reptile eggs may also be consumed as well. Gila monsters and beaded lizards climb trees to reach both the eggs and young of birds. Despite being venomous, these species rely on their strong jaws to kill prey. Mammalian prey typically consists of
rodent Rodents (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republi ...

rodent
s and ; the Komodo dragon can kill prey as large as
water buffalo The water buffalo (''Bubalus bubalis''), also called the domestic water buffalo or Asian water buffalo, is a large bovid The Bovidae comprise the biological family Family ( la, familia, plural ') is one of the eight major hierarchical tax ...

water buffalo
. Dragons are prolific
scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation Predation is a biological interaction In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study ...
s, and a single decaying carcass can attract several from away. A dragon is capable of consuming a carcass in 17 minutes.Pianka and Vitt, pp. 41–51. Around 2 percent of lizard species, including many iguanids, are herbivores. Adults of these species eat plant parts like flowers, leaves, stems and fruit, 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 Microbiota are "ecological communities of commensal, symbiotic Symbiosis (from Ancient Greek, Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between tw ...
necessary for their transition to a plant-based diet. Perhaps the most herbivorous species is the marine iguana which dives to forage for
alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

alga
e,
kelp Kelps are large brown algae The brown algae (singular: alga), comprising the class (biology), class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Most b ...

kelp
and other marine plants. Some non-herbivorous species supplement their insect diet with fruit, which is easily digested.


Antipredator adaptations

Lizards have a variety of
antipredator adaptation Anti-predator adaptations are mechanisms developed through evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to thei ...
s, including running and climbing,
venom Venom is a type of poison In biology, poisons are Chemical substance, substances that can cause death, injury or harm to organs, Tissue (biology), tissues, Cell (biology), cells, and DNA usually by chemical reactions or other activity (chemi ...

venom
,
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard The leopard (''Pan ...

camouflage
, tail
autotomy Autotomy (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

autotomy
, and reflex bleeding.


Camouflage

Lizards exploit a variety of different camouflage methods. Many lizards are disruptively patterned. In some species, such as Aegean wall lizards, individuals vary in colour, and select rocks which best match their own colour to minimise the risk of being detected by predators. The Moorish gecko is able to adaptive camouflage, change colour for camouflage: when a light-coloured gecko is placed on a dark surface, it darkens within an hour to match the environment. The
chameleon Chameleons or chamaeleons (family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and ...

chameleon
s in general use their ability to change their coloration for signalling rather than camouflage, but some species such as Smith's dwarf chameleon do use active colour change for camouflage purposes. The flat-tail horned lizard's body is coloured like its desert background, and is Camouflage#Eliminating shadow, flattened and fringed with white scales to minimise its shadow.


Autotomy

Many lizards, including
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder#Hierarchy of ranks, infraorder Gekkota, geckos are found in warm climates throughout the world. T ...

gecko
s and skinks, are capable of shedding their tails (
autotomy Autotomy (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

autotomy
). The detached tail, sometimes brilliantly coloured, continues to writhe after detaching, distracting the predator's attention from the fleeing prey. Lizards partially regeneration (biology), regenerate their tails over a period of weeks. Some 326 genes are involved in regenerating lizard tails. The fish-scale gecko ''Geckolepis megalepis '' sheds patches of skin and scales if grabbed.


Escape, playing dead, reflex bleeding

Many lizards attempt to escape from danger by running to a place of safety; for example, wall lizards can run up walls and hide in holes or cracks. Horned lizards adopt differing defences for specific predators. They may thanatosis, play dead to deceive a predator that has caught them; attempt to outrun the rattlesnake, which does not pursue prey; but stay still, relying on their cryptic coloration, for ''Masticophis'' whip snakes which can catch even swift prey. If caught, some species such as the greater short-horned lizard puff themselves up, making their bodies hard for a narrow-mouthed predator like a whip snake to swallow. Finally, horned lizards can autohaemorrhaging, squirt blood at Felidae, cat and Canidae, dog predators from a pouch beneath its eyes, to a distance of about ; the blood tastes foul to these attackers.


Evolution


Fossil history

The earliest known fossil remains of a lizard belong to the iguanian species ''Tikiguania estesi'', found in the Tiki Formation of India, which dates to the Carnian stage of the Triassic period, about 220 million years ago. However, doubt has been raised over the age of ''Tikiguania'' because it is almost indistinguishable from modern agamid lizards. The ''Tikiguania'' remains may instead be late Tertiary or Quaternary in age, having been washed into much older Triassic sediments. Lizards are most closely related to the Rhynchocephalia, which appeared in the Late Triassic, so the earliest lizards probably appeared at that time. Mitochondrial phylogenetics suggest that the first lizards evolved in the late Permian. It had been thought on the basis of morphological data that iguanid lizards diverged from other squamates very early on, but molecular phylogeny, molecular evidence contradicts this. Mosasaurs probably evolved from an extinct group of aquatic lizards known as Aigialosauridae, aigialosaurs in the Early Cretaceous. Dolichosauridae is a family of Late Cretaceous aquatic varanoid lizards closely related to the mosasaurs.


Phylogeny


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.


Internal

Both the snakes and the
Amphisbaenia Amphisbaenia (called amphisbaenians or worm lizards) is a group of usually legless squamates, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. As ...
(worm lizards) are
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
s deep within the Squamata (the smallest clade that contains all the lizards), so "lizard" is
paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The group is said to be paraphyleti ...

paraphyletic
. The cladogram is based on genomic analysis by Wiens and colleagues in 2012 and 2016. Excluded taxa are shown in upper case on the cladogram.


Taxonomy

In the 13th century, lizards were recognized in Europe as part of a broad category of ''reptiles'' that consisted of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, […], assorted amphibians, and worms", as recorded by Vincent of Beauvais in his ''Mirror of Nature''. The seventeenth century saw changes in this loose description. The name Sauria was coined by James Macartney (anatomist), James Macartney (1802); 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 author, containing lizards and crocodilians, later discovered not to be each other's closest relatives. Later authors used the term "Sauria" in a more restricted sense, i.e. as a synonym of Lacertilia, a suborder of Squamata that includes all lizards but excludes
snake Snakes are elongated, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Many species of snakes ...

snake
s. This classification is rarely used today because Sauria so-defined is a
paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and all descendants of that ancestor excluding a few—typically only one or two—Monophyly, monophyletic subgroups. The group is said to be paraphyleti ...

paraphyletic
group. It was defined as a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
by Jacques Gauthier, Arnold G. Kluge and Timothy Rowe (1988) as the group containing the most recent common ancestor of archosaurs and Lepidosauria, lepidosaurs (the groups containing crocodiles and lizards, as per Mcartney's original definition) and all its descendants. A different definition was formulated by Michael deBraga and Olivier Rieppel (1997), who defined Sauria as the clade containing the most recent common ancestor of Choristodera, Archosauromorpha, Lepidosauromorpha and all their descendants. However, these uses have not gained wide acceptance among specialists. Suborder Lacertilia (Sauria) – (lizards) * Family †Bavarisauridae * Family †Eichstaettisauridae * Infraorder Iguania ** Family †Arretosauridae ** Family †Euposauridae ** Family Corytophanidae (casquehead lizards) ** Family Iguanidae (iguanas and spinytail iguanas) ** Family Phrynosomatidae (Earless lizard, earless, spiny lizard, spiny, Urosaurus, tree, side-blotched lizard, side-blotched and horned lizard, horned lizards) ** Family Polychrotidae (
anole Dactyloidae are a family of lizards commonly known as anoles () and native to warmer parts of the Americas, ranging from southeastern United States to Paraguay. Instead of treating it as a family, some authorities prefer to treat it as a subfami ...

anole
s) *** Family Leiosauridae (see Polychrotinae) ** Family Tropiduridae (neotropical ground lizards) *** Family Liolaemidae (see Tropidurinae) *** Family Leiocephalidae (see Tropidurinae) ** Family Crotaphytidae (crotaphytus, collared and gambelia, leopard lizards) ** Family Opluridae (Madagascar iguanids) ** Family Hoplocercidae (wood lizards, clubtails) ** Family †Priscagamidae ** Family †Isodontosauridae ** Family Agamidae (Agama (lizard), agamas, Chlamydosaurus, frilled lizards) ** Family Chamaeleonidae (
chameleon Chameleons or chamaeleons (family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and ...

chameleon
s) * Infraorder Gekkota ** Family Gekkonidae (
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder#Hierarchy of ranks, infraorder Gekkota, geckos are found in warm climates throughout the world. T ...

gecko
s) ** Family Pygopodidae (legless geckos) ** Family Dibamidae (blind lizards) * Infraorder Scincomorpha ** Family †Paramacellodidae ** Family †Slavoiidae ** Family Scincidae (skinks) ** Family Cordylidae (spinytail lizards) ** Family Gerrhosauridae (plated lizards) ** Family Xantusiidae (night lizards) ** Family Lacertidae (wall lizards or true lizards) ** Family †Mongolochamopidae ** Family †Adamisauridae ** Family Teiidae (tegus and whiptails) ** Family Gymnophthalmidae (spectacled lizards) * Infraorder Diploglossa ** Family Anguidae (slowworms, glass lizards) ** Family Anniellidae (American legless lizards) ** Family Xenosauridae (knob-scaled lizards) * Infraorder Platynota (Varanoidea) ** Family Varanidae (monitor lizards) ** Family Lanthanotidae (earless monitor lizards) ** Family Helodermatidae (
Gila monster The Gila monster (''Heloderma suspectum'', ) is a species of venom Venom is a type of poison, especially one secreted by an animal. Venom has evolved in a wide variety of animals, both predators and prey, and both vertebrates and invertebrate ...

Gila monster
s and Mexican beaded lizard, beaded lizards) ** Family †Mosasauridae (marine lizards)


Convergence

Lizards have frequently convergent evolution, evolved convergently, with multiple groups independently developing similar morphology and ecological niches. Anolis ecomorphs, ''Anolis'' ecomorphs have become a model system in evolutionary biology for studying convergence. Limbs have been lost or reduced independently legless lizard, over two dozen times across lizard evolution, including in the Anniellidae, Anguidae, Cordylidae, Dibamidae, Gymnophthalmidae, Pygopodidae, and Scincidae; snakes are just the most famous and species-rich group of Squamata to have followed this path.


Relationship with humans

Most lizard species are harmless to humans. Only the largest lizard species, the
Komodo dragon The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a member of the monitor lizard Monitor lizards are large lizard Lizards (suborder Lacertilia) are a widespread group of Squamata, squamate reptiles, with ...

Komodo dragon
, which reaches in length and weighs up to , 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. Numerous species of lizard are kept as pets, including Pogona, bearded dragons, iguanas,
anole Dactyloidae are a family of lizards commonly known as anoles () and native to warmer parts of the Americas, ranging from southeastern United States to Paraguay. Instead of treating it as a family, some authorities prefer to treat it as a subfami ...

anole
s, and
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder#Hierarchy of ranks, infraorder Gekkota, geckos are found in warm climates throughout the world. T ...

gecko
s (such as the popular leopard gecko). Lizards appear in myths and folktales around the world. In Australian Aboriginal mythology, Tarrotarro, the lizard god, split the human race into male and female, and gave people the ability to express themselves in art. A 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 forever, but the chameleon was held up, and another lizard brought a different message, that the time of humanity was limited. A popular legend in Maharashtra tells the tale of how a Bengal monitor, common Indian monitor, with ropes attached, was used to scale the walls of the fort in the Battle of Sinhagad. In the Bhojpuri language, Bhojpuri speaking region of India and Nepal, there is a belief among children that, on touching Skunk's tail three (or five) time with the shortest finger gives money. Green 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 supposedly chicken-like taste, while Uromastyx, spiny-tailed lizards are eaten in Africa. In North Africa, ''Uromastyx'' species are considered ''dhaab'' or 'fish of the desert' and eaten by nomadic tribes. Lizards such as the Gila monster produce toxins with medical applications. Gila toxin reduces plasma glucose; the substance is now synthesised for use in the anti-diabetes drug exenatide (Byetta). Another toxin from Gila monster saliva has been studied for use as an anti-Alzheimer's drug. Lizards in many cultures share the symbolism of snakes, especially as an emblem of resurrection. This may have derived from their regular moulting. 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.


Notes


References


General sources

*


Further reading

* * * * * * * * *


External links

* * {{DEFAULTSORT:Lizard Lizards, Paraphyletic groups Obsolete vertebrate taxa Extant Hettangian first appearances