57-543: The Lacertoidea is a group of squamate reptiles that includes the Lacertidae , Teiidae , Gymnophthalmidae , and Amphisbaenia . The finding from molecular phylogenetic studies that the burrowing Amphisbaenia were nested in a clade with the lizard forms led Vidal & Hedges (2005) to propose a new name for the group based on shared morphogical characters, Laterata , "referring to the presence of tile-like (squarish or quadrangular, and sometimes raised) scales that form
114-547: A stem -squamate, making it the oldest known squamate. The phylogenetic analysis was conducted by performing high-resolution microfocus X-ray computed tomography (micro-CT) scans on the fossil specimen of Megachirella to gather detailed data about its anatomy . These data were then compared with a phylogenetic dataset combining the morphological and molecular data of 129 extant and extinct reptilian taxa . The comparison revealed Megachirella had certain features that are unique to squamates. The study also found that geckos are
171-406: A clade called Toxicofera . Genetic data also suggest that the various limbless groups – snakes, amphisbaenians , and dibamids – are unrelated, and instead arose independently from lizards. The male members of the group Squamata have hemipenes , which are usually held inverted within their bodies, and are everted for reproduction via erectile tissue like that in the mammalian penis . Only one
228-653: A major radiation endemic to Africa. The Teiidae are diverse in South America, but some members of the group occur in southern North America as well. The Amphisbaenia are especially widespread, occurring in North America, Europe, Africa, South America, and the Caribbean. The origins of the group are unclear. The oldest definitive lacertoid is the amphisbaenian Plesiorhineura , from the early Paleocene of North America. Given that it resembles modern worm lizards,
285-423: A narrow range of prey - for example, Salvadora only eat lizards. The remaining lizards are omnivores and can consume plants or insects. The broad carnivorous diet of the tuatara may be facilitated by its specialised shearing mechanism, which involves a forward movement of the lower jaw following jaw closure. While birds, including raptors, wading birds and roadrunners, and mammals are known to prey on reptiles,
342-872: A passive envenomation system. Recent studies also show that the close relatives of the Komodo, the monitor lizards, all have a similar envenomation system, but the toxicity of the bites is relatively low to humans. The Gila monster and beaded lizards of North and Central America are venomous, but not deadly to humans. Though they survived the Cretaceous–Paleogene extinction event , many squamate species are now endangered due to habitat loss, hunting and poaching, illegal wildlife trading, alien species being introduced to their habitats (which puts native creatures at risk through competition, disease, and predation), and other anthropogenic causes. Because of this, some squamate species have recently become extinct , with Africa having
399-460: A seminal groove that seals as the erectile tissue expands. This is also the only reptile group in which both viviparous and ovoviviparous species are found, as well as the usual oviparous reptiles. The eggs in oviparous species have a parchment-like shell. The only exception is found in blind lizards and three families of geckos (Gekkonidae, Phyllodactylidae and Sphaerodactylidae), where many lay rigid and calcified eggs. Some species, such as
456-499: A year die from venomous snake bites. In the US alone, more than 8,000 venomous snake bites are reported each year, but only one in 50 million people (five or six fatalities per year in the USA) will die from venomous snake bites. Lizard bites, unlike venomous snake bites, are usually not fatal. The Komodo dragon has been known to kill people due to its size, and recent studies show it may have
513-495: Is a subclass or superorder of reptiles , containing the orders Squamata and Rhynchocephalia . Squamata also includes lizards and snakes . Squamata contains over 9,000 species, making it by far the most species-rich and diverse order of non-avian 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:
570-570: Is also the option of animal refuges. This concept is helpful to contain the reptiles and keep them from human dwellings. However, environmental fluctuations and predatorial attacks still occur in refuges. Reptile skins are still being sold. Accessories, such as shoes, boots, purses, belts, buttons, wallets, and lamp shades, are all made out of reptile skin. In 1986, the World Resource Institute estimated that 10.5 million reptile skins were traded legally. This total does not include
627-933: Is an abundance of rodent and insect prey. However, these reptiles are seen as pests and are often exterminated . Snakes are commonly feared throughout the world. Bounties were paid for dead cobras under the British Raj in India ; similarly, there have been advertised rattlesnake roundups in North America . Data shows that between 1959 and 1986 an average of 5,563 rattlesnakes were killed per year in Sweetwater, Texas , due to rattlesnake roundups, and these roundups have led to documented declines and local extirpations of rattlesnake populations, especially Eastern Diamondbacks in Georgia. People have introduced species to
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#1732787002338684-441: Is automixis with terminal fusion (see figure), a process in which two terminal products from the same meiosis fuse to form a diploid zygote . This process leads to genome-wide homozygosity , expression of deleterious recessive alleles, and often to developmental abnormalities. Both captive-born and wild-born A. contortrix and A. piscivorus appear to be capable of this form of parthenogenesis. Reproduction in squamate reptiles
741-465: Is common among lepidosaurs. Other species, such as the Echinosauria , have evolved the defense of feigning death. Viperines can sense their prey's infrared radiation through bare nerve endings on the skin of their heads. Also, viperines and some boids have thermal receptors that allow them to target their prey's heat. Many snakes are able to obtain their prey through constriction . This
798-416: Is done by first biting the prey, then coiling their body around the prey. The snake then tightens its grip as the prey struggles, which leads to suffocation. Some snakes have fangs that produce venomous bites, which allows the snake to consume unconscious, or even dead, prey. Also, some venoms include a proteolytic component that aids in digestion. Chameleons grasp their prey with a projectile tongue. This
855-493: Is made possible by a hyoid mechanism, which is the contraction of the hyoid muscle that drives the tip of the tongue outwards. Within the subclass Lepidosauria there are herbivores , omnivores , insectivores , and carnivores . The herbivores consist of iguanines, some agamids, and some skinks . Most lizard species and some snake species are insectivores. The remaining snake species, tuataras, and amphisbaenians, are carnivores. While some snake species are generalist, others eat
912-411: Is not always complete and is made of a solid rod of cartilage rather than individual vertebrae. In snakes, the tail separates between vertebrae and some do not experience regrowth. Third, the scales in lepidosaurs are horny ( keratinized ) structures of the epidermis , allowing them to be shed collectively, contrary to the scutes seen in other reptiles. This is done in different cycles, depending on
969-456: Is ordinarily sexual, with males having a ZZ pair of sex-determining chromosomes, and females a ZW pair. However, the Colombian rainbow boa, Epicrates maurus , can also reproduce by facultative parthenogenesis, resulting in production of WW female progeny. The WW females are likely produced by terminal automixis. When female sand lizards mate with two or more males, sperm competition within
1026-552: Is quite distinct from that of snakes, Amphisbaenia have a reduced right lung as opposed to snakes which have their left lung reduced. However, they do not closely resemble any other group of lizards. Recent molecular studies suggest that amphisbaenians are grouped with the Lacertidae, in a group named the Lacertibaenia. Lacertoids have a wide geographic distribution. The Lacertidae are found throughout Europe and Asia, with
1083-402: Is so common in squamates, and is also found in the tuatara, it is assumed that it is an original trait in the group. Most lepidosaurs rely on camouflage as one of their main defenses. Some species have evolved to blend in with their ecosystem, while others are able to change their skin color to blend in with their current surroundings. The ability to autotomize the tail is another defense that
1140-400: Is the largest order of reptiles , comprising lizards and snakes . With over 12,162 species , it is also the second-largest order of extant (living) vertebrates , after the perciform fish . Squamates 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
1197-467: Is then split into Squamata and Rhynchocephalia. More recent morphological studies and molecular studies also place turtles firmly within Diapsida, even though they lack temporal fenestrations. The reptiles in the subclass Lepidosauria can be distinguished from other reptiles by a variety of characteristics. Lepidosaurs are suggested to be distinguished from more primitive lepidosauromorphs by
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#17327870023381254-427: Is thought to be a reversion rather than retention. The temporal bar is thought to stabilise the skull during biting. Male squamates have evolved a pair of hemipenises instead of a single penis with erectile tissue that is found in crocodilians , birds , mammals , and turtles . The hemipenis can be found in the base of the tail. The tuatara does not have a hemipenis, but instead has shallow paired outpocketings of
1311-431: Is used at a time, and some evidence indicates that males alternate use between copulations . The hemipenis has a variety of shapes, depending on the species. Often it bears spines or hooks , to anchor the male within the female. Some species even have forked hemipenes (each hemipenis has two tips). Due to being everted and inverted, hemipenes do not have a completely enclosed channel for the conduction of sperm , but rather
1368-588: The Archosauria , the clade that contains crocodiles and birds, and their extinct relatives. Fossils of rhynchocephalians first appear in the Early Triassic , meaning that the lineage leading to squamates must have also existed at the time. A study in 2018 found that Megachirella , an extinct genus of lepidosaurs that lived about 240 million years ago during the Middle Triassic , was
1425-690: The Bathonian age of the Middle Jurassic of the Northern Hemisphere, with the first appearance of many modern groups, including snakes, during this period. Scientists believe crown group squamates probably originated in the Early Jurassic based on the fossil record, with the oldest unambiguous fossils of squamates dating to the Middle Jurassic. Squamate morphological and ecological diversity substantially increased over
1482-553: The Komodo dragon , can reproduce asexually through parthenogenesis . Studies have been conducted on how sexual selection manifests itself in snakes and lizards . Snakes use a variety of tactics in acquiring mates. Ritual combat between males for the females with which they want to mate includes topping, a behavior exhibited by most viperids , in which one male twists around the vertically elevated fore body of his opponent and forcing it downward. Neck biting commonly occurs while
1539-584: The Middle East , North Africa , sub-Saharan Africa , South America , and the Caribbean . The tuatara is confined to only a few rocky islands of New Zealand, where it digs burrows to live in and preys mostly on insects. Climate change has led to the need for conservation efforts to protect the existence of the tuatara . This is because it is not possible for this species to migrate on its own to cooler areas. Conservationists are beginning to consider
1596-609: The Permian period. The earliest members of Lepidosauromorpha date the Early Triassic. Sophineta from the Early Triassic may be the oldest known lepidosaur, but its exact placement is uncertain. The earliest rhynchocephalian , Wirtembergia , is known from the Middle Triassic . While the lepidosaur Megachirella may represent a stem-group squamate from the Middle Triassic the earliest modern members of
1653-681: The most extinct species . Breeding programs and wildlife parks, though, are trying to save many endangered reptiles from extinction. Zoos, private hobbyists, and breeders help educate people about the importance of snakes and lizards. Historically, the order Squamata has been divided into three suborders: Of these, the lizards form a paraphyletic group, since the "lizards" are found in several distinct lineages, with snakes and amphisbaenians recovered as monophyletic groups nested within. Although studies of squamate relationships using molecular biology have found different relationships between some squamata lineagaes, all recent molecular studies suggest that
1710-402: The tuatara ( Sphenodon punctatus), a superficially lizard-like reptile native to New Zealand . Lepidosauria is a monophyletic group (i.e. a clade ), containing all descendants of the last common ancestor of squamates and rhynchocephalians. Lepidosaurs can be distinguished from other reptiles via several traits, such as large keratinous scales which may overlap one another. Purely in
1767-478: The tuatara , the last surviving member of the once diverse Rhynchocephalia , with both groups being placed in the clade Lepidosauria . Squamates are a monophyletic sister group to the rhynchocephalians , members of the order Rhynchocephalia. The only surviving member of the Rhynchocephalia is the tuatara . Squamata and Rhynchocephalia form the subclass Lepidosauria , which is the sister group to
Lacertoidea - Misplaced Pages Continue
1824-537: The upper jaw relative to the neurocranium . This is particularly visible in snakes, which are able to open their mouths very widely to accommodate comparatively large prey . Squamates are the most variably sized living reptiles, ranging from the 16 mm (0.63 in) dwarf gecko ( Sphaerodactylus ariasae ) to the 6.5 m (21 ft) reticulated python ( Malayopython reticulatus ). The now- extinct mosasaurs reached lengths over 14 m (46 ft). Among other reptiles, squamates are most closely related to
1881-502: The complete loss of their limbs. The upper jaw of Squamates is movable on the cranium , a configuration called kinesis . This is made possible by a loose connection between the quadrate and its neighboring bones. Without this, snakes would not be able consume prey that are much larger than themselves. Amphisbaenians are mostly legless like snakes, but are generally much smaller. Three species of amphisbaenians have kept reduced front limbs and these species are known for actively burrowing in
1938-437: The context of modern taxa , Lepidosauria can be considered the sister taxon to Archelosauria , which includes Testudines (turtles), Aves (birds) and Crocodilia (crocodilians). Lepidosauria is encompassed by Lepidosauromorpha , a broader group defined as all reptiles (living or extinct) closer to lepidosaurs than to archosaurs . Lepidosauromorpha is thought to have split off from the ancestor of Archelosauria during
1995-451: The copy is selectively expressed in the venom gland. Previous literature hypothesized that venoms were modifications of salivary or pancreatic proteins, but different toxins have been found to have been recruited from numerous different protein bodies and are as diverse as their functions. Natural selection has driven the origination and diversification of the toxins to counter the defenses of their prey. Once toxins have been recruited into
2052-633: The course of the Cretaceous , including the appeance of groups like iguanians and varanoids , and true snakes. Polyglyphanodontia , an extinct clade of lizards, and mosasaurs , a group of predatory marine lizards that grew to enormous sizes, also appeared in the Cretaceous. Squamates suffered a mass extinction at the Cretaceous–Paleogene (K–Pg) boundary , which wiped out polyglyphanodontians, mosasaurs, and many other distinct lineages. The relationships of squamates are debatable. Although many of
2109-448: The development of a conch on the quadrate , allowing for the development of a tympanic membrane in the ear (a trait lost in the tuatara, but present in early rhynchocephalians), as well as the development of a subolfactory process on the frontal bones of the skull. The group Squamata includes snakes, lizards, and amphisbaenians. Squamata can be characterized by the reduction or loss of limbs. Snakes and legless lizards have evolved
2166-478: The divergence between anguimorphs, iguanians, and advanced snakes dates back roughly 200 million years ago (Mya) to the Late Triassic / Early Jurassic , but the only good fossil evidence is from the Middle Jurassic. Snake venom has been shown to have evolved via a process by which a gene encoding for a normal body protein, typically one involved in key regulatory processes or bioactivity, is duplicated, and
2223-548: The earliest crown group squamates, not iguanians. However, a 2021 study found the genus to be a lepidosaur of uncertain position, in a polytomy with Squamata and Rhynchocephalia . In 2022, the extinct genus Cryptovaranoides was described from the Late Triassic ( Rhaetian age) of England as a highly derived squamate belonging to the group Anguimorpha , which contains many extant lineages such as monitor lizards , beaded lizards and anguids . The presence of an essentially modern crown group squamate so far back in time
2280-407: The evolutionary origin of venom may exist deep in the squamate phylogeny, with 60% of squamates placed in this hypothetical group called Toxicofera . Venom has been known in the clades Caenophidia , Anguimorpha , and Iguania , and has been shown to have evolved a single time along these lineages before the three groups diverged, because all lineages share nine common toxins. The fossil record shows
2337-624: The female lays eggs. A few species within Squamata have the ability to reproduce asexually . The tuatara lays eggs that are usually about one inch in length and which take about 14 months to incubate. While in the egg, the Squamata embryo develops an egg tooth on the premaxillary that helps the animal emerge from the egg. A reptile will increase three to twentyfold in length from hatching to adulthood. There are three main life history events that lepidosaurs reach: hatching/birth, sexual maturity, and reproductive senility. Because gular pumping
Lacertoidea - Misplaced Pages Continue
2394-450: The female's reproductive tract may occur. Active selection of sperm by females appears to occur in a manner that enhances female fitness. On the basis of this selective process, the sperm of males that are more distantly related to the female are preferentially used for fertilization, rather than the sperm of close relatives. This preference may enhance the fitness of progeny by reducing inbreeding depression . Recent research suggests that
2451-414: The ground. The tuatara and some extinct rhynchocephalians have a more rigid skull with a complete lower temporal bar closing the lower temporal fenestra formed by the fusion of the jugal and quadrate / quadratojugal bones, similar to the condition found in primitive diapsids. However early rhynchocephalians and lepidosauromorphs had an open lower temporal fenestra, without a complete temporal bar, so this
2508-433: The group are known from the Middle Jurassic. Squamates underwent a great radiation in the Cretaceous , while rhynchocephalians declined during the same time period. Extant reptiles are in the clade Diapsida , named for two pairs temporal fenestrae present on the skull behind the eye socket. Until recently, Diapsida was said to be composed of Lepidosauria and their sister taxa Archosauria. The subclass Lepidosauria
2565-432: The groups originally recognized on the basis of morphology are still accepted, understanding of their relationships to each other has changed radically as a result of studying their genomes . Iguanians were long thought to be the earliest crown group squamates based on morphological data, but genetic data suggest that geckos are the earliest crown group squamates. Iguanians are now united with snakes and anguimorphs in
2622-671: The lacertoids most likely appeared and diversified in the Cretaceous. However, Berriasian taxon Purbicella may be a lacertoid, and would be the oldest known. Within the Laterata there are many species listed on IUCN Redlist conservation status. This family listed 5 species extinct, 31 species critically endangered, 53 species endangered, 40 species vulnerable, 53 species near threatened, and 569 species as least concerned. [REDACTED] Data related to Lacertoidea at Wikispecies Squamate Squamata ( / s k w æ ˈ m eɪ t ə / , Latin squamatus , 'scaly, having scales')
2679-478: The lepidosaurs' natural habitats that have increased predation on the reptiles. For example, mongooses were introduced to Jamaica from India to control the rat infestation in sugar cane fields. As a result, the mongooses fed on the lizard population of Jamaica, which has led to the elimination or decrease of many lizard species. Actions can be taken by humans to help endangered reptiles. Some species are unable to be bred in captivity, but others have thrived. There
2736-574: The major predator is other reptiles. Some reptiles eat reptile eggs, for example the diet of the Nile monitor includes crocodile eggs, and small reptiles are preyed upon by larger ones. The geographic ranges of lepidosaurs are vast and cover all but the most extreme cold parts of the globe. Amphisbaenians exist in Florida , mainland Mexico , including Baja California , the Mediterranean region ,
2793-487: The possibility of translocating them to islands with cooler climates. The range of the tuatara has already been minimized by the introduction of cats, rats, dogs, and mustelids to New Zealand. The eradication of the mammals from the islands where the tuatara still survives has helped the species increase its population. An experiment observing the tuatara population after the removal of the Polynesian rat showed that
2850-406: The posterior wall of the cloaca . Second, most lepidosaurs have the ability to autotomize their tails. However, this trait has been lost on some recent species. In lizards and rhynchocephalians, fracture planes are present within the vertebrae of the tail that allow for its removal. Some lizards have multiple fracture planes, while others just have a single fracture plane. The regrowth of the tail
2907-587: The rings in Amphisbaenia, and are also present ventrally in Lacertiformata and Teiformata ". Studies of anatomy have traditionally grouped the lacertoids with skinks ; however, more recent studies focusing on DNA have placed them as a distinct group of lizards, more closely related to the venomous Toxicofera . The relationships of the Amphisbaenia to other lizards have long been a mystery; although superficially snakelike, their anatomy and locomotion
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#17327870023382964-429: The snakes are entwined. Parthenogenesis is a natural form of reproduction in which the growth and development of embryos occur without fertilization. Agkistrodon contortrix (copperhead snake) and Agkistrodon piscivorus (cottonmouth snake) can reproduce by facultative parthenogenesis; they are capable of switching from a sexual mode of reproduction to an asexual mode. The type of parthenogenesis that likely occurs
3021-404: The species. However, lizards generally shed in flakes while snakes shed in one piece. Unlike scutes, lepidosaur scales will often overlap like roof tiles . Squamates are represented by viviparous , ovoviviparous , and oviparous species. Viviparous means that the female gives birth to live young, Ovoviviparous means that the egg will develop inside the female's body and Oviparous means that
3078-466: The tuatara expressed an island-specific increase of population after the rats' removal. However, it may be difficult to keep these small mammals from reinhabiting these islands. Habitat destruction is the leading negative impact of humans on reptiles. Humans continue to develop land that is important habitat for the lepidosaurs. The clear-cutting of land has also led to habitat reduction. Some snakes and lizards migrate toward human dwellings because there
3135-432: The venom proteome , they form large, multigene families and evolve via the birth-and-death model of protein evolution, which leads to a diversification of toxins that allows the ambush predators the ability to attack a wide range of prey. The rapid evolution and diversification is thought to be the result of a predator–prey evolutionary arms race , where both are adapting to counter the other. An estimated 125,000 people
3192-1446: The venomous groups are united in a venom clade. Named Toxicofera, it encompasses a majority (nearly 60%) of squamate species and includes Serpentes (snakes), Iguania (agamids, chameleons, iguanids, etc.), and Anguimorpha (monitor lizards, Gila monster, glass lizards, etc.). One example of a modern classification of the squamates is shown below. Dibamidae Diplodactylidae Underwood 1954 [REDACTED] Pygopodidae Boulenger 1884 [REDACTED] Carphodactylidae Eublepharidae Sphaerodactylidae Underwood 1954 Phyllodactylidae [REDACTED] Gekkonidae Scincidae [REDACTED] Xantusiidae Gerrhosauridae [REDACTED] Cordylidae [REDACTED] Gymnophthalmidae Merrem 1820 [REDACTED] Teiidae Gray 1827 [REDACTED] Lacertidae [REDACTED] Rhineuridae Vanzolini 1951 Bipedidae Taylor 1951 [REDACTED] Blanidae Kearney & Stuart 2004 [REDACTED] Cadeidae Vidal & Hedges 2008 Trogonophidae Gray 1865 Amphisbaenidae Gray 1865 [REDACTED] Shinisauridae Ahl 1930 sensu Conrad 2006 Lanthanotidae Varanidae [REDACTED] Helodermatidae Gray 1837 [REDACTED] Xenosauridae Diploglossidae Anniellidae Lepidosauria The Lepidosauria ( / ˌ l ɛ p ɪ d oʊ ˈ s ɔː r i ə / , from Greek meaning scaled lizards )
3249-458: Was unexpected, as their diversification was previously thought to have occurred during the Jurassic and Cretaceous. A 2023 study found that Cryptovaranoides most likely represents an archosauromorph with no apparent squamate affinities, though the original describers maintained their original conclusion that this taxon represents a squamate. The oldest unambiguous fossils of Squamata date to
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