Lizards of the United States
There are 17 families of lizards found in the United States, with 205 species, including established introduced species. Known from the Triassic Period to the present, lizards today comprise the largest living group of reptiles. They come in a bewildering array of sizes, shapes, and colors, from tiny gecko species less than 3 inches long to the giant dragon lizard of Komodo nearly 10 feet long. Typical lizards superficially resemble salamanders, but their dry skin, clawed feet, and external ear openings quickly separate them from their distant moist skinned ancestors. Legless lizards may be confused with snakes, but unlike snakes, they possess moveable eyelids. The pattern and color of lizards vary greatly, males and females of the same species often show color differences, juveniles are frequnetly distinct from adults. Subspecies, too, may differ stikingly.
Lizards have varied life styles. Although generally diurnal, the majority of geckos, the night lizards, and the Gila monster are nocturnal. Only two species of venomous - the Gila Monster of the southwest and Mexico and the Beaded Lizard of Mexico. Courtship is brief, and fertilization is internal. Most lizards are egg layers, but occasionally young are born alive.
There are 6 species, representing 4 genus found on the United States, all of which have been Introduced.
Agamidae is a family of over 300 species of iguanian lizards indigenous to Africa, Asia, Australia, and a few Southern Europe. Many species are commonly called dragons or dragon lizards.
There are 11 species, representing 4 genus, found in the United States with 10 species that are native, while 1 has been Introduced.
Anguid lizards are characterized by elongated, shiny, and stiff bodies and tails, closeable eyelids, external ear openings, and tiny (or absent) legs and toes. The stiffness is a result of an abundance of bony armor (osteoderms) in the skin. Many species are so stiff they could not expand to breathe were it not for a lengthwise flexible groove of soft granular scales along the sides. All the species in North America have this groove.
Most anguids are terrestrial or burrowing. While some species will bite, the primary defenses are fleeing, smearing an attacker with excrement, and giving up part of the tail. In some species the tail vertebrae have fracture planes along which the tail will readily break, leaving the writhing tip to be eaten by the predator while the rest of the lizard crawls to safety. In legless species, in which the tail may account for more than half the total length, the loss of a tail may give the impression that the lizard has been broken in two. Contrary to foklore, the part will not grow together again, but the body will grow a new tail in several weeks. Anguids are carnivores, they consume insects, small mammals, and other lizards. Most are egg layers, but a few mountain dwellers bear live young.
There are only 1 genus, with 5 species, found only in California and adjacent Baja California, Mexico.
These are long and slender lizards with moveable eyelids. Although legless, they still retain hip and shoulder bones internally. They are related to the anguid lizards, from which they differ by the absence of external ear openings, and body armor within the skin. Califronia legless lizards burrow in the loose soil and are seldom seen on the surface. They eat insects and the young are born alive.
There are 3 species, representing 2 genus found on the United States, all of which have been Introduced.
Chameleons or Chamaeleonidae are a distinctive and highly specialized clade of Old World Lizards with 202 species described as of June 2015. The members of this family are best known for their distrinct range of colors as they are able to shift in different hues and brightness. Because of the large number of species in their family, there is a large variability in their ability to change color. For some, it is more of a shift of brightness (shades of brown) whereas others it is a plethora of combinations of colors (reds, yellows, greens, and blues).
There are 1 species, representing 1 genus found on the United States, and it was Introduced.
Corytophanidae is a fmaily of iguanian lizards also called casquehead lizards or helmeted lizards, endemic to the New World.
There are 8 species, representing 2 genus found on the United States, all of which are native species.
The Crotaphytidae, or collared lizards, are a family of desert dwelling reptiles native to the Southwestern United States and northern Mexico. Alternatlively they are reciognized as a subfamily, Crotaphytinae, within the clade Pleurodonta. They are very fast moving animals, with long limgs and tails, some species are capable of achieving bipedal running at top speed.
There 12 species, representing 1 genus, found in the United States, all but 1 species (Anolis carolinensis) have been Introduced.
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 is as a family, some authorities prefer to treat it as a subfamily, Dactyloidae, of the family Iguanidae.
Gekkonidae (te common geckos) is the largest family of geckos, containing over 950 described species in 64 genera. Members of the comprise many of the most widespread gecko species, including house geckos (Hemidactylus), tokay geckos (Gekko), day geckos (Phelsuma), mourning geckos (Lepidodactylus) and dtellas (Gehyra). Gekkonoid geckos occur globally and are particularly species-rich in tropical areas.
There are 31 species, representing 12 genus found in the United States. Only 8 species are native to the U.S. while 23 have been Introduced.
There is only 1 genera, with 2 species, in the United States.
Gila monsters are heavy bodied, with short stout legs and a thick tail. With an abundance of food the tail becomes fat. During periods of scarcity, the tail may lose up to 20% of its bulk as the stored fat is used up. On the back and head are non overlapping beadlike scales of shiny black, pink, or yellow. The scales contain osteoderms, a sort of body armor.
Gila monsters are venomous carnivores that seems to rely more on taste and smell to locate their quarry than on sight. They have been observed tracking prey by tasting the ground with their long thick tongues. Their venom causes great pain, but rarely human death. It is the persistent grip of a Gila monster's jaw that is the single most important reason for handling these lizards carefully.
There are 4 genera, with 7 species found in the United States, only 2 are native with the other 5 species being Introduced.
Iguanids range from 4 to 72 inches in length. A typical iguanid is of moderate size, has 5 clawed toes on each of its 4 legs, and a long tail, its teeth are attached to the ledge on the inside of the jaw. Most species are either arboreal or terrestrial, they feed on insects and other invertebrates, but some, like Dipsosaurus and Sauromalus eat leaves, fruit, and blossoms. Except for a very few species that live in cool mountain habitats and give birth to living young, iguanids are egg layers.
Iguanids are possibly the most visually oriented of all lizards. They communicate at a distance by a show of color and behavioral signals. Mates are courted, territories defended, and interlopers driven off by elaborate and precisely timed combinations of head bobbing, body push-ups, and open mouthed displays that are unique to each species. Some further enhance the effect by curling the tail, inflating the chest and throat, or extending the throatfan, all of which expose a bright patch of color to the view of another lizard. Finally, many species exhibit intense color during the mating season.
Only 3 species, representing 2 genus, found in the United States, all of which have been Introduced.
Lacertids are characterized by slender round bodies, well developed legs, and long tails. The back is covered with hexagonalsclaes, the underside scales are large and rectangular. The large head shields usually contain bony plates (osteoderms) and are not fused to the skull. Most species have moveable eyelids. Terrestrial species are variouly colored, while arboreal species are green. Males have slightly larger heads and may be differently colored from females. Lacertids are daytime hunters of insects, spiders, scorpions, and small vertebrates. All North American lacertids are egg layers.
There 2 species, representing 1 genus, found in the United States, both of which have been Introduced.
Leiocephalidea, also known as Curly-Tailed Lizards or curlytail lizards, is a family of iguanian lizards restricted to the West Indies. One of the defining features of these lizards is that their tail often curls over. They were previously regarded as members of the subfamily Leiocelphalidae with the family .
There 48 species, representing 9 genus, found in the United States, all of which have are Native species.
The Phrynosomatidae are a diverse family of lizards, sometimes classified as a subfamily (PHrynosomitinae), found from Panama to exrteme south of Canada. Many members of the group are adapted to life in hot, sandy deserts, although the spiny lizards prefer rocky deserts or even relatively moist forest edges, and the short-horned lizard lives in prairie or sagebrush enviroments. The group includes both egg laying asnd viviporous species, with the latter being more common in species living in high elevations.
Only 1 species and it is found only in Florida.
Amphisbaenids resemble earthworms in appearance. Body scales are fused into rings which encircle the body. Specialized for burrowing, family members lack external ear openings, have eyes buried under skin, and with the exception of one genus, Bipes, which has short front legs, they are limbless. Amphisbaenids live underground much of their lives feeding on insects and worms. The breeding biology is poorly known. Most seem to be egg layers.
There 24 species, representing 10 genus, found in the United States, with 14 species being native and 10 species being Introduced.
A skink has a long cylindrical body and tail covered with smooth sleek scales containing bony plates (osteoderms). Terrestrial skinks have small legs, those adapted for burrowing have tiny legs or none. A clear window in the lower eyelid of the burrowing forms enables the animal to see when the eyelid is closed to keep out dirt. Fracture planes in the tails of many species allow the tail to break off easily when grasped by a predator. In such cases usually the tail is vividly colored to draw the attack of the predator away from the vulnerable body.
Skinks are diurnal. Most are insect eaters, but a few giant species are herbivorous. All species have thick oval tongues with a shallow notch at the tip. Most will nip the hand that catches them, and large species can inflict a painful bite. All North American species are egg layers. Females may tend the eggs during incubation.
There are 29 species, representing 4 genus, found in the United States with 24 species being native and 5 species being Introduced.
Teiids are long slender lizards with long whiplike tails and well developed legs. Movements are characteristically rapid and jerky. They range from 4 to 48 inches in length. Typically they have small round, non overlapping scales on the back and large rectangular scales on the underside. There are no bony plates (oteoderms) in the skin. The large regular head shields are fused to the skull.
Whiptails are diurnal, terrestrial carnivores. Small species feed on insects and other invertebrates, while large species consume small mammals, birds and bird eggs, and other reptiles. Prey is located both by sight and by smell or taste, by means of a long deeply forked tongue. All teiids are egg layers. In most species, females produce fertile eggs only after breeding with males of the same species. However, there are true unisexual species among Cnemidophorus. All individuals are females, so there is no mating. A mature female lays fertile, but unfertilized, eggs that hatch into more females.
There 3 species, representing 1 genus, found in the United States, all of which have been Introduced.
The Varanidae are a family of lizards in the superfamily Varanoidea within the Anguimorpha groujp. The family, a group of carnivorous and frugivorous lizards, includes the living genus of Varanus and a number of extinct genera.
There is only 1 genera with 8 species found in the United States.
The night lizards are related to the geckos and like them have soft skin, a somewhat flattened body, and no moveable eyelids. But unike the geckos, the night lizards have small round scales on the back, large rectangular scales on the belly, and large shields on the head. The toes end in a sharp claw.
As the name implies, night lizards are mostly active at night, hiding in rocky crevices or under brush and leafy debris during the day. The light sensitive eyes have vertically elliptical pupils. Developing embryos are nourishd by a primitive placenta while in the mothers's oviduct. Young are born tail first and alive.
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