Lizard

lizardsLacertiliaLacertilia indet.Lacertilianterrestrial lizardsCheckered whiptail lizardcommon lizardslizard (''kami'')lizard-likesaurian
Lizards are a widespread group of squamate reptiles, with over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains.wikipedia
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Squamata

squamatesquamatesscaled reptiles
Lizards are a widespread group of squamate reptiles, with over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains.
Squamata is the largest order of reptiles, comprising lizards, snakes and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles.

Reptile

reptilesReptiliaSauropsida
Lizards are a widespread group of squamate reptiles, with over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains.
Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives.

Gecko

geckosspatulaeGecko adhesion
Lizards range in size from chameleons and geckos a few centimeters long to the 3 meter long Komodo dragon. Three lineages, the geckos, anoles, and chameleons, have modified the scales under their toes to form adhesive pads, highly prominent in the first two groups.
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world.

Komodo dragon

Komodo dragonsVaranus komodoensisKomodo
Lizards range in size from chameleons and geckos a few centimeters long to the 3 meter long Komodo dragon.
The Komodo dragon (Varanus komodoensis), also known as the Komodo monitor, is a species of lizard found in the Indonesian islands of Komodo, Rinca, Flores, and Gili Motang.

Snake

snakesserpentSerpentes
The group is paraphyletic as it excludes the snakes and Amphisbaenia; some lizards are more closely related to these two excluded groups than they are to other lizards. 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).
Lizards have evolved elongate bodies without limbs or with greatly reduced limbs about twenty-five times independently via convergent evolution, leading to many lineages of legless lizards.

Draco (genus)

Dracoflying lizardDraco taeniopterus
Some such as the forest-dwelling Draco lizards are able to glide.
Draco is a genus of agamid lizards that are also known as flying lizards, flying dragons or gliding lizards.

Paraphyly

paraphyleticembedded*
The group is paraphyletic as it excludes the snakes and Amphisbaenia; some lizards are more closely related to these two excluded groups than they are to other lizards.
Other commonly recognized paraphyletic groups include fish, monkeys, and lizards.

Dactyloidae

anoleanole lizardanoles
Three lineages, the geckos, anoles, and chameleons, have modified the scales under their toes to form adhesive pads, highly prominent in the first two groups.
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.

Autotomy

autotomizeautotomisecaudal autotomy
Lizards make use of a variety of antipredator adaptations, including venom, camouflage, reflex bleeding, and the ability to sacrifice and regrow their tails.
Some lizards, salamanders and tuatara when caught by the tail will shed part of it in attempting to escape.

Rhynchocephalia

sphenodontiasphenodontssphenodont
Lizards and snakes share a movable quadrate bone, distinguishing them from the rhynchocephalians, which have more rigid diapsid skulls.
Many of the niches occupied by lizards today were then held by sphenodontians.

Common basilisk

basiliskBasiliscus basiliscusJesus Christ lizard
Some species, like the common basilisk, can run across water.
The common basilisk (Basiliscus basiliscus) is a species of lizard in the family Corytophanidae.

Venom

venomousvenomsvenomous animals
Lizards make use of a variety of antipredator adaptations, including venom, camouflage, reflex bleeding, and the ability to sacrifice and regrow their tails.

Gila monster

Heloderma suspectumdesert lizarddragon-shaped
Until 2006 it was thought that among lizards, only the Gila monster and the Mexican beaded lizard were venomous.
The Gila monster (Heloderma suspectum, ) is a species of venomous lizard native to the southwestern United States and northwestern Mexican state of Sonora.

Tuatara

SphenodonBrothers Island tuataraSphenodon punctatus
Some lizards, particularly iguanas, have retained a photosensory organ on the top of their heads called the parietal eye, a basal ("primitive") feature also present in the tuatara.
Although resembling most lizards, they are part of a distinct lineage, the order Rhynchocephalia.

Diapsid

Diapsidadiapsidsboth
Lizards and snakes share a movable quadrate bone, distinguishing them from the rhynchocephalians, which have more rigid diapsid skulls.
The diapsids are extremely diverse, and include all crocodiles, lizards, snakes, tuatara, turtles, and birds.

Mexican beaded lizard

beaded lizardHeloderma horridumH. horridum
Until 2006 it was thought that among lizards, only the Gila monster and the Mexican beaded lizard were venomous.
The Mexican beaded lizard (Heloderma horridum) is a species of lizard in the family Helodermatidae, one of the two species of venomous beaded lizards found principally in Mexico and southern Guatemala.

Osteoderm

osteodermsbony armorbony scutes
The scales may be modified into spines for display or protection, and some species have bone osteoderms underneath the scales.
Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amphibians), various groups of dinosaurs (most notably ankylosaurs and stegosaurians), phytosaurs, aetosaurs, placodonts, and hupehsuchians (marine reptiles with possible ichthyosaur affinities).

Evolution of snake venom

these genes evolved in the common ancestor
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).
Venom in snakes and some lizards is a form of saliva that has been modified into venom over its evolutionary history.

Vomeronasal organ

Jacobson's organvomeronasalVomeronasal system
As in snakes and many mammals, all lizards have a specialised olfactory system, the vomeronasal organ, used to detect pheromones.
It is present and functional in all snakes and lizards, and in many mammals, including cats, dogs, horses, cattle, pigs, and some primates; in humans it is present, but is vestigial and non-functional.

Parietal eye

pineal eyethird eyepineal foramen
Some lizards, particularly iguanas, have retained a photosensory organ on the top of their heads called the parietal eye, a basal ("primitive") feature also present in the tuatara.
The parietal eye is found in the tuatara, most lizards, frogs, salamanders, certain bony fish, sharks, and lampreys (a kind of jawless fish).

Green iguana

Iguana iguanaiguanagreen iguanas
Recent studies (2013 and 2014) on the lung anatomy of the savannah monitor and green iguana found them to have a unidirectional airflow system, which involves the air moving in a loop through the lungs when breathing.
The green iguana (Iguana iguana), also known as the American iguana, is a large, arboreal, mostly herbivorous species of lizard of the genus Iguana.

Prehensility

prehensileprehensiongrasping
Some lizards such as chameleons have prehensile tails, assisting them in climbing among vegetation.

Hemipenis

hemipenessnake penishemipenal
As with all amniotes, lizards rely on internal fertilisation and copulation involves the male inserting one of his hemipenes into the female's cloaca.
A hemipenis (plural hemipenes) is one of a pair of intromittent organs of male squamates (snakes, lizards and worm lizards).

Horned lizard

Phrynosomahorned toadHorned lizards
Horned lizards are also well known for specializing on ants.
Horned lizards (Phrynosoma), also known as horny toads or horntoads, are a genus of North American lizards and the type genus of the family Phrynosomatidae.

Prairie skink

Northern Prairie Skink
The female prairie skink uses respiratory water loss to maintain the humidity of the eggs which facilitates embryonic development.
It is one of only seven species of lizards that occur in Canada.