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Lacertilia

(Suborder)

Overview

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Lizards are a very large and widespread group of reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains. The group, traditionally recognized as the suborder Lacertilia, is defined as all extant members of the Lepidosauria (reptiles with overlapping scales) which are neither sphenodonts (i.e., Tuatara) nor snakes. While the snakes are recognized as falling phylogenetically within the anguimorph lizards from which they evolved, the sphenodonts are the sister group to the squamates, the larger monophyletic group which includes both the lizards and the snakes.

Lizards typically have limbs and external ears, while snakes lack both these characteristics. However, because they are defined negatively as excluding snakes, lizards have no unique distinguishing characteristic as a group. Lizards and snakes share a movable quadrate bone, distinguishing them from the sphenodont s which have a more primitive and solid diapsid skull. Many lizards can detach their tails in order to escape from predators, an act called autotomy, but this trait is not universal. Vision, including color vision, is particularly well developed in most lizards, and most communicate with body language or bright colors on their bodies as well as with pheromones. The adult length of species within the suborder ranges from a few centimeters for some chameleons and geckos to nearly three meters (9 feet, 6 inches) in the case of the largest living varanid lizard, the Komodo Dragon. Some extinct varanids reached great size. The extinct aquatic mosasaurs reached 17.5 meters, and the giant monitor Megalania prisca is estimated to have reached perhaps seven meters.

Physiology

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A feral Jackson's Chameleon from a population introduced to Hawaii in the 1970s.

Sight is quite important for most lizards, both for locating prey and for communication, and as such, many lizards have highly acute color vision. Most lizards rely heavily on body language, using specific postures, gestures and movements to define territory, resolve disputes, and entice mates. Some species of lizard also utilize bright colors, such as the iridescent patches on the belly of Sceloporus. These colors would be highly visible to predators, so are often hidden on the underside or between scales and only revealed when necessary.

A particular innovation in this respect is the dewlap, a brightly colored patch of skin on the throat, usually hidden between scales. When a d isplay is needed, the lizards erect the hyoid bone of their throat, resulting in a large vertical flap of brightly colored skin beneath the head which can be then used for communication. Anoles are particularly famous for this display, with each species having specific colors, including patterns only visible under ultraviolet light, as lizards can often see UV.

Evolution and Relationships

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The fossil mosasaur Prognathodon, a varanid.

The retention of the basic 'reptilian' amniote body form by lizards makes it tempting to assume any similar anim al, alive or extinct, is also a lizard. However, this is not the case, and lizards as squamates are part of a well-defined group.

The earliest "lizard" was superficially lizard-like, but had a solid, box-like skull, with openings only for eyes, nostrils, etc (termed Anapsid). Turtles retain this skull form. Early anapsids later gave rise to two new groups with additional holes in the skull to make room for and anchor larger jaw muscles. Those with a single hole, the Synapsids, gave rise to the superficially lizard-like Pelycosaurs which include Dimetrodon and the Therapsids, including the Cynodonts, from which would evolve the modern mammals.

The Diapsids, possessing one temporal fenestra before the eye and one behind it, continued to diversify. One branch, the Archosaurs, retained the basic Diapsid skull, and gave rise to a bewildering array of animals, most famous being the crocodilians, the pterosaurs, the dinosaurs and their descendants, birds. The Ic hthyosaurs and Plesiosaurs radiated from the same basal Diapsid group.

The smaller Lepidosaurs which would give rise to the lizards began to reduce the skull bones, making the skull lighter and more flexible. The modern Tuatara retains the basic Lepidosaur skull, distinguishing it from true lizards in spite of superficial similarities. Squamates, including snakes and all true lizards, further lightened the skull by eliminating the lower margin of the lower skull opening.

Lizard Diversification

Within the Lacertilia are found four generally recognized suborders, Iguania, Gekkota, Amphisbaenia and Autarchoglossa, with the "blind skinks" in the family Dibamidae having an uncertain position. While traditionally excluded from the lizards, the snakes are usually classified as a clade with a similar subordinal rank.[1]

Iguania

Anoles mating, Gainesville, FL

The suborder Iguania, found in Africa, south Asia, Australia, the New World, and with iguanas colonizing the islands of the west Pacific, form the sister group to the remainder of the squamata. They are largely arboreal, and have primitively fleshy, non-prehensile tongues, but this condition is obviously highly modified in the chameleons. This clade includes the following families:

Gekkota

Active hunters, the Gekkota includes three families comprising the distinctive cosmopolitan geckos and the legless flap-footed lizards of Australia and New Zealand. Like snakes, the geckos and the flap-footed lizards lack eyelids. Unlike snakes, they use their tongues to clean their often highly developed eyes. While gecko feet have unique surfaces which allow them to cling to glass and run on ceilings, the flapfoot has lost its limbs. The three families of this suborder are:

Relationship With Humans

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Komodo dragons on Rinca

Most lizard species are harmless to humans. Only the very largest lizard species pose threat of death; the Komodo dragon, for example, has been known to stalk, attack, and kill humans. The venom of the Gila monster and beaded lizard is not usually deadly but they can inflict extremely painful bites due to powerful jaws. Numerous species of lizards are kept as pets.

Lizard symbolism plays important, though rarely predominant ro les in some cultures (e.g. Tarrotarro in Australian Aboriginal mythology). The Moche people of ancient Peru worshiped animals and often depicted lizards in their art.[2] According to a popular legend in Maharashtra, a Common Indian Monitor, with ropes attached, was used to scale the walls of the Sinhagad fort in the Battle of Sinhagad.[3]

Green iguanas (Iguana iguana), are popular exotic pets

Green Iguanas are eaten in Central America and Uromastyx in Africa and India. In North Africa, Uro mastyx are considered dhaab or 'fish of the desert' and eaten by nomadic tribes.[4] In India too, these lizards are caught for their meat, about which Malcolm Smith says ..with certain castes of Hindoos it is a regular article of diet..the meat is said to be excellent and white like chicken...the head and feet are not eaten, but the tail is considered a great delicacy...the fat of the body is boiled down and the resulting oil is used as an embrocation and also as a cure for impotence.[5]

Classification

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Gekko gecko in Thailand
Close-up of the head of the legless fossorial amphisbaenid Rhineura
Underside of a Thorny devil, an agamid, Western Australia
The Eastern blue-tongued lizard, a scincomorph
The venomous Gila monster, Heloderma s. suspectum
Oriental Garden Lizard in Malaysia

Suborder Lacertilia (Sauria) - (Lizards)

Photos

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Taxonomy

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The Suborder Lacertilia is a member of the Order Squamata. Here is the complete "parentage" of Lacertilia:

The Suborder Lacertilia is further organized into finer groupings including:

Families

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Agamidae

Agamids, of the family Agamidae, include more than 300 species in Africa, Asia, Australia, and a few in Southern Europe. Phylogenetically they may be sister to the Iguanidae, and have a similar appearance. Agamids usually have well-developed, strong legs. Their tails cannot be shed and regenerated like those of geckoes, though a certain amount of regeneration is observed in some[citation needed]. Many agamid species are capable of limited change of their colors[citation needed]. They inhabit warm environments, ranging from hot deserts to tropical rainforests. [more]

Aigialosauridae

[more]

Amphisbaenidae

The Amphisbaenidae are a family of , commonly known as worm lizards. They are found in North and South America, some Caribbean islands, and in sub-Saharan Africa. One primitive and somewhat aberrant genus, Blanus, is native to Europe, and may represent a distinct family. [more]

Anguidae

The Anguidae is a large and diverse family of lizards native to the northern hemisphere. The group includes the , glass lizards, and alligator lizards, among others. Their closest living relatives are the helodermatid lizards. They have hard osteoderms beneath their scales, and many of the species have reduced or absent limbs, giving them a snake-like appearance, although others are fully limbed. [more]

Anniellidae

The family Anniellidae, known as American contains two species in a single genus Anniella: A. pulchra, the California legless lizard, with two subspecies A. p. pulchra and A. p. nigra, and the rare A. geronimensis, the Baja California legless lizard. [more]

Ardeosauridae

[more]

Bipedidae

Bipedidae, are a of amphisbaenians. They are found only in Mexico. Ajolotes are carnivorous, burrowing reptiles, but unlike other species of amphisbaenian, they possess two stubby forelimbs placed far forward on the body. The shovel-like limbs are used to scrape away soil while burrowing through the soil, in a similar manner to a mole. [more]

Chamaeleonidae

The family Chamaeleonidae are a distinctive and highly specialized of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, and the possession by many of a prehensile tail, crests or horns on their distinctively shaped heads, and the ability of some to change color. Uniquely adapted for climbing and visual hunting, the approximately 160 species of chameleon range from Africa, Madagascar, Spain and Portugal, across south Asia, to Sri Lanka, have been introduced to Hawaii and California, and are found in warm habitats that vary from rain forest to desert conditions. [more]

Cordylidae

Cordylidae is a family of mid-sized lizards that inhabit arid and semi-arid regions in and eastern Africa. T They are commonly known as the Spinytail lizards or Girdle-tailed lizards. [more]

Corytophanidae

Corytophanidae is a of lizards also called casque head lizards or helmeted lizards. They typically have well-developed head crests in the shape of a casque. This crest is a sexually dimorphic characteristic, found only on males[citation needed]. There are 9 known species of casque heads from 3 genera. [more]

Crotaphytidae

[more]

Dibamidae

[more]

Dolichosauridae

[more]

Gekkonidae

Geckos are small to average sized belonging to the family Gekkonidae, found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. An estimated 2,000 different species of geckos exist worldwide, with many likely yet to be discovered. The name stems from the Indonesian/Javanese word Tokek, inspired by the sound these animals make. The Malay word for gecko is cicak. [more]

Gerrhosauridae

The Gerrhosauridae is a family of lizards native to Africa and Madagascar. Also known as plated lizards, they live in a range of habitats, from rocky crevices to sand dunes. Their form is variable, with some species having four fully developed limbs, and others with vestigial hind limbs only. Most species are believed to be . [more]

Gymnophthalmidae

Gymnophthalmidae is a of lizards, sometimes known as spectacled lizards or microteiids. They are called 'spectacled' because of their transparent lower eyelids, so they can still see with closed eyes. Like most lizards, but unlike geckos, these eyelids are movable. [more]

Helodermatidae

[more]

Hoplocercidae

[more]

Iguanidae

The Iguanidae is a family of , composed of iguanas and related species. [more]

Lacertidae

Lacertidae is the of the wall lizards, or true lizards, which are native to Europe, Africa, and Asia. The group includes the genus Lacerta, which contains some of the most commonly seen lizard species in Europe. [more]

Lanthanotidae

The earless monitor lizard (Lanthanatus boreneensis) is a semi-aquatic, brown lizard native to northern . It is the only species in the family Lanthanotidae, a group related to the true monitor lizards, as well as to the beaded lizards. [more]

Leiosauridae

[more]

Mosasauridae

Mosasaurs (from Mosa meaning the 'Meuse river' in the Netherlands, and Greek sauros meaning 'lizard') were serpentine marine reptiles. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. These ferocious marine predators are now considered to be the closest relatives of snakes, due to cladistic analysis of symptomatic similarities in jaw and skull anatomies. Mosasaurs were not dinosaurs but lepidosaurs, reptiles with overlapping scales. These predators evolved from semi-aquatic squamates known as the aigialosaurs, close relatives of modern-day monitor lizards, in the Early Cretaceous Period. During the last 20 million years of the Cretaceous Period (Turonian-Maastrichtian), with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators. [more]

Opluridae

The Opluridae, or Madagascan Iguanas, are a family of moderately sized lizards native to . The family includes species that live amongst rocks, some that live in trees, and one that inhabits sand dunes. All of the species lay eggs, and have teeth that resemble those of the true iguanas. [more]

Phrynosomatidae

Phrynosomatidae is a diverse family of , found from Panama to the extreme 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 environments. The group includes both egg-laying and viviparous species, with the latter being more common in species living at high elevation. [more]

Polychrotidae

Polychrotidae is a family of commonly known as Anoles . NCBI places the anole in subfamily Polychrotinae of the family Iguanidae. Four genera are common: Anolis, Norops, Phenacosaurus and Polychrus. [more]

Pygopodidae

Pygopodidae (or fogs) is a family of snakes with legs related to the . They have unusually long, slender, bodies, giving them a strong resemblance to snakes. Like both snakes and most geckos, they have no eyelids, but unlike snakes, they have external ear-holes and flat, non-forked tongues. They are native to Australia and New Guinea. [more]

Scincidae

A Family in the Kingdom Animalia. [more]

Teiidae

[more]

Trogonophidae

[more]

Tropiduridae

The Tropiduridae is a family of lizards native to and the West Indies. Most are ground-dwelling animals, and the family includes some lizards adapted to relatively cold climates, including those of the Andes mountains and Tierra del Fuego. Several species give birth to live young. [more]

Varanidae

Varanidae is a group of lizards of the Varanoidea. The family is a group of carnivorous lizards which includes the heaviest living lizard, the Komodo dragon, and the crocodile monitor which is the longest lizard in the world. Varanidae contains the living genus Varanus and a number of extinct taxa. Their closest living relatives are the anguid and helodermatid lizards. [more]

Xantusiidae

Night lizards ( name Xantusiidae) are a group of very small, viviparous (live-bearing) lizards, averaging from less than 4 cm to over 12 cm long. The family has only three genera, with approximately 23 living species. The genera are divided by geographic range: Xantusia in southwestern North America and Baja California, Cricosaura in Cuba, and Lepidophyma, the most populous night lizard genus, in Central America. [more]

Xenosauridae

The Xenosauridae is a family of native to Central America and China. Also known as knob-scaled lizards, they have rounded, bumpy scales and osteoderms. Most species prefer moist or semi-aquatic habitats, although they are widespread within their native regions, with some even inhabiting semi-arid scrub environments. They are carnivorous or insectivorous, and give birth to live young. [more]

At least 20 species and subspecies belong to the Family Xenosauridae.

More info about the Family Xenosauridae may be found here.

References

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  1. ^ ITIS http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=173861
  2. ^ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.
  3. ^ Auffenberg, Walter (1994). The Bengal Monitor. University Press of Florida. pp. 494. ISBN 0813012953. 
  4. ^ pg 48, Grzimek,Bernhard. Grzimek’s Animal Life Encyclopedia (Second Edition) Vol 7 - Reptiles. (2003) Thomson - Gale. Farmington Hills, Minnesota. Vol Editor - Neil Schlager. ISBN 0-7876-5783-2 (for vol.7)
  5. ^ pp 244-247, Smith, Malcolm A. (1935) The Fauna of Brit ish India including Ceylon and Burmah, Reptilia and Amphibia, Vol II - Sauria, Taylor and Francis, London.

Sources

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Last Revised: September 22, 2009
2009/09/22 09:11:46