Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia although some lizards are more closely related to these two excluded groups than they are to other lizards. Lizards range in size from chameleons and geckos a few centimeters long to the 3-meter-long Komodo dragon.
Reptiles, as most commonly defined, are the animals in the class Reptilia, a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates and rhynchocephalians (tuatara). As of March 2022, the Reptile Database includes about 11,700 species. In the traditional Linnaean classification system, birds are considered a separate class to reptiles. However, crocodilians are more closely related to birds than they are to other living reptiles, and so modern cladistic classification systems include birds within Reptilia, redefining the term as a clade. Other cladistic definitions abandon the term reptile altogether in favor of the clade Sauropsida, which refers to all amniotes more closely related to modern reptiles than to mammals. The study of the traditional reptile orders, customarily in combination with the study of modern amphibians, is called herpetology.
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes. Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads. To accommodate their narrow bodies, snakes' paired organs appear one in front of the other instead of side by side, and most have only one functional lung. Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca. Lizards have independently evolved elongate bodies without limbs or with greatly reduced limbs at least twenty-five times via convergent evolution, leading to many lineages of legless lizards. These resemble snakes, but several common groups of legless lizards have eyelids and external ears, which snakes lack, although this rule is not universal.
The king cobra is a venomous snake endemic to Asia. With an average length of 3.18 to 4 m and a maximum record of 5.85 m (19.2 ft), it is the world's longest venomous snake. Coloration of this species varies across habitats, from black with white stripes to unbroken brownish grey. The sole member of the genus Ophiophagus, it is not taxonomically a true cobra despite its common name. The king cobra inhabits forests from South to Southeastern Asia where it preys chiefly on other snakes, including those of its kind. A female king cobra builds a nest to hold its eggs which will be protected throughout the incubation period.
The Lepidosauria is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizards, and amphisbaenians. Squamata contains over 9,000 species, making it by far the most species-rich and diverse order of reptiles in the present day. Rhynchocephalia was a formerly widespread and diverse group of reptiles in the Mesozoic Era. However, it is represented by only one living species: the tuatara, a superficially lizard-like reptile native to New Zealand.
Squamata is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians, which are collectively known as squamates or scaled reptiles. With over 10,900 species, it is also the second-largest order of extant (living) vertebrates, after the perciform fish. Members of the order are distinguished by their skins, which bear horny scales or shields, and must periodically engage in molting. They also possess movable quadrate bones, making possible movement of the upper jaw relative to the neurocranium. This is particularly visible in snakes, which are able to open their mouths very wide to accommodate comparatively large prey. Squamates are the most variably sized living reptiles, ranging from the 16 mm (0.63 in) dwarf gecko to the 6.5 m (21 ft) Reticulated python. The now-extinct mosasaurs reached lengths over 14 m (46 ft).
Lesser bushbabies, or lesser galagos, are strepsirrhine primates of the genus Galago. They are classified, along with the bushbabies and the rest of the galagos, in the family Galagidae. They are probably the most numerous primate in Africa, and can be found in every large forest on the continent, inhabiting forested areas, savannas, riverine bush and open woodlands.
Amphisbaenia 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 many species have a pink body and scales arranged in rings, they have a superficial resemblance to earthworms. While the genus Bipes retains forelimbs, all other genera are limbless. Although superficially similar to the snakes, legless lizards, and blind lizards, recent phylogenetic studies suggest that they are most closely related to wall lizards of the family Lacertidae. Amphisbaenians are widely distributed, occurring in North America, Europe, Africa, South America, Western Asia and the Caribbean. Most species are less than 6 inches (15 cm) long.
Pygopodidae, commonly known as legless lizards, snake-lizards, or flap-footed lizards, is a family of squamates with reduced or absent limbs, and are a type of gecko. At least 35 species are placed in two subfamilies and eight genera. They have unusually long, slender bodies, giving them a strong resemblance to snakes. Like snakes and most geckos, they have no eyelids, but unlike snakes, they have external ear holes and flat, unforked tongues. They are native to Australia and New Guinea.
The broad-headed skink or broadhead skink is species of lizard, endemic to the southeastern United States. The broadhead skink occurs in sympatry with the five-lined skink and Southeastern five-lined skink in forest of the Southeastern United States. All three species are phenotypically similar throughout much of their development and were considered a single species prior to the mid-1930s.
Ophidia is a group of squamate reptiles including modern snakes and reptiles more closely related to snakes than to other living groups of lizards.
Mosasaurs comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. They belong to the order Squamata, which includes lizards and snakes.
The Cylindrophiidae are a monotypic family of secretive, semifossorial, non-venomous snakes containing the genus Cylindrophis found in southeastern Asia. These are burrowing snakes and most have a banded pattern on the belly. Currently, 13 species are recognized, all with no subspecies. Common names include Asian pipe snakes or Asian cylinder snakes.
Toxicofera is a proposed clade of scaled reptiles (squamates) that includes the Serpentes (snakes), Anguimorpha and Iguania. Toxicofera contains about 4,600 species, of extant Squamata. It encompasses all venomous reptile species, as well as numerous related non-venomous species. There is little morphological evidence to support this grouping, however it has been recovered by all molecular analyses as of 2012.
The Iberian worm lizard, Mediterranean worm lizard, or European worm lizard is a species of reptile in the family Blanidae of the clade Amphisbaenia. The Iberian worm lizard is locally known as cobra-cega (Portuguese), culebrilla ciega (Spanish), and colobreta cega (Catalan), all meaning "blind snake". Recent studies into the mitochondrial and nuclear genomic data of 47 isolated B. cinereus populations show rather large sequence divergence between two apparent clades, leading some researchers to call for a division of the Iberian worm lizard into two species. While little is known of B. cinereus in comparison with some other reptile species, new insight is growing about this primitive, ancestral reptile.
Burton's legless lizard is a species of lizard in the family Pygopodidae. The species lacks forelegs and has only rudimentary hind legs. Pygopodid lizards are also referred to as "legless lizards", "flap-footed lizards" and "snake-lizards". This species is native to Australia and Papua New Guinea.
The western terrestrial garter snake is a western North American species of colubrid snake. At least five subspecies are recognized.
Lampropeltis rhombomaculata, commonly known as the mole kingsnake or the brown kingsnake, is a species of snake in the family Colubridae. It is a relatively medium-sized snake that occupies a variety of habitats from Baltimore, Maryland, south through the Florida Panhandle and west into Mississippi and Tennessee.
Platynota is a polyphyletic group of anguimorph lizards and thus belongs to the order Squamata of the class Reptilia. Since it was named in 1839, it has included several groups, including monitor lizards, snakes, mosasaurs, and helodermatids. Its taxonomic use still varies, as it is sometimes considered equivalent to the group Varanoidea and other times viewed as a distinct group. It is phylogenetically defined as a clade containing Varanidae. It also includes many extinct species.
Sexual selection in scaled reptiles studies how sexual selection manifests in snakes and lizards, which constitute the order Squamata of reptiles. Each of the over three thousand snakes use different tactics in acquiring mates. Ritual combat between males for the females they want to mate with includes topping, a behavior exhibited by most viperids in which one male will twist around the vertically elevated fore body of its opponent and forcing it downward. It is common for neck biting to occur while the snakes are entwined.
