The earliest turtles appear in the fossil record towards the end of the Triassic, before recognisably modern squamates (lizards and snakes) or crocodilians. For a long time, features of the turtle skull (which, unlike that of other living reptiles, lacks openings at the sides of the head) were thought to reflect a distinct origin for this lineage, separate from that which gave rise to all other surviving reptiles. By contrast, modern nuclear DNA analysis places turtles within the archosaurs, alongside crocodiles, pterosaurs and dinosaurs (including birds). This is supported by features of the earliest known turtle, Osteochelys semitestacea; described in 2008, this animal exhibits greater similarity to diapsids (the group that includes the other modern reptiles) than previously-known early turtles. Morphologically, turtles share few features in common with other archosaurs, or indeed with many other animals. Turtles have
lost internal ribs, lack teeth and possess a hard case consisting of an upper carapace and a lower plastron into which the head,
limbs and tail can be partially or wholly retracted. In some families, a hinge at the front of the plastron allows the anterior portion to seat itself against the lip of the carapace, completely enclosing the head and forelimbs.
Modern taxonomy groups turtles into two major lineages, the hidden-neck (Cryptodira) and side-neck (Pleurodira) turtles which, as their names suggest, differ in whether they withdraw their heads backwards into the carapace or sideways beneath it, as well as in details of their bone structure. Side-neck turtles are an ancient lineage; fossils from the early Cretaceous have been assigned to the living family Cheliidae. At least one late Cretaceous forms even appear to be related to specific living species. Fourteen living families of turtles are recognised, eleven of them within the Cryptodira. This classification encompasses over 285 species with a global distribution and diverse range of lifestyles. Diets range from entirely carnivorous to (almost uniquely among reptiles) strictly herbivorous, with the full range of omnivorous stages in-between. While most turtles are partially or fully aquatic in freshwater, one family has become entirely terrestrial. Of all living reptiles, only sea snakes are more fully-adapted to marine life than the seven species of marine turtle, which are notable for their long-distance migrations, large size and tendency to nest on beaches in large numbers, a strategy that ensures the number of hatchlings is so high that even with a high predation rate, enough will survive to breed themselves in later years. The leatherback (Dermochelys coriacea) can dive as deep as half a kilometre. Uniquely among reptiles this species is endothermic, generating its own internal heat through muscle activity, and this ability has allowed it to colonise temperate waters; the leatherback turtle has the widest global distribution of any reptile.
Characteristically, turtles are slow-growing and long-lived (in some cases, surviving well over a century), taking several years to reach reproductive maturity and with relatively small clutches (all turtles lay eggs). At the same time, they suffer particularly from human exploitation; globally, but perhaps especially in Asia, turtles are overharvested for food, some species are collected for their use in traditional Chinese medicine, and several species are taken from the wild for the international pet trade, among them the critically endangered ploughshare and radiated tortoises, both restricted to Madagascar. In common with aquatic species worldwide, turtles are also threatened by loss and pollution of waterways, as well as by the destruction of surrounding terrestrial habitat. Damming rivers may submerge banks on which freshwater turtles lay their eggs, while the development of former nesting beaches for tourism threatens marine turtle populations globally.
AUSTRALOAMERICAN SIDE-NECK TURTLES (CHELIIDAE)
A family of side-neck turtles widespread in tropical South America east of the Andes, and also found throughout New Guinea and much of coastal Australia. The carapace is typically distinctly flattened, and most species are fully-aquatic with extensive webbing on their feet. The neck is typically very long, and cannot be fully retracted under the carapace. Some species are adapted for life in regions with highly seasonal rainfall, and remain dormant throughout the dry season when their breeding pools dry out. Cheliids are largely carnivorous, several Australian species entirely so, and will often eat congregate to feed on carrion such as dead fish.
|Saw-shelled Turtle||Myuchelys latisternum|
|Krefft's Short-necked Turtle||Emydura macquarii krefftii|
AFRICAN MUD TERRAPINS (PELOMEDUSIDAE)
A family of at least 16 species of side-necked turtle, distributed throughout sub-Saharan Africa and its outlying oceanic islands. The carapace is distinctly oblong, and not flattened, and the head is large. The plastron is hinged in all but one species, allowing the turtle to protect its head and forelimbs when retracted. These are semi-aquatic animals of still and slow-moving waters, where they forage for animal prey at the bottom of the waterbody.
|African Helmeted Turtle||Pelomedusa subrufa|
HARD-SHELLED SEA TURTLES (CHELONIIDAE)
Six species of large (carapace length up to 1.4 m), fully marine hard-shelled turtles found throughout the world in tropical and subtropical waters. The forelimbs are modified into flattened flippers; the hindlimbs are smaller and fully-webbed. Animals surface to breathe, but are generally entirely aquatic outside the breeding season, rarely coming to shore to bask. Most species exhibit a pelagic migratory stage until the age of about 12, but then become resident in near-shore habitats. Diet is variable; juveniles are primarily carnivorous, while adults may specialise in sea grass and algae, bottom-dwelling invertebrates or corals and sponges depending on species. Animals generally reach reproductive maturity at the age of 25 or greater, and clutch size is extremely large (typically over 100 eggs, with a female producing up to five clutches in a season).
|Green Sea Turtle||Chelonia mydas|
MUD & MUSK TURTLES (KINOSTERNIDAE)
An exclusively American family, ranging from eastern North America to the Amazon Basin. The head is large, and the carapace elongated. The plastron is usually hinged. Most species are rather small, up to 18 cm in carapace length, although size ranges from 9 to 38 cm. These are almost fully-aquatic turtles that forage along the bottom of swamps, marshes and rivers for animal prey; animals emerge onto land only following heavy rain.
|White-lipped Mud Turtle||Kinosternon leucosternum|
AMERICAN BOX TURTLES (EMYDIDAE)
This is a moderately large and widespread family of 42 species, reflected in a diversity of body forms and ecologies. Most species occur in the Americas, including all of North and Central America with isolated populations in eastern and southern Brazil. European terrapins also belong to this family. The carapace is domed, and varies from oblong to oval. Several species are entirely or largely terrestrial; others are aquatic and occur in a wide range of waterbodies including estuaries. Most species are primarily carnivorous, although some larger species mostly or exclusively eat plant matter.
|Common Slider||Trachemys scripta scripta|
ASIAN RIVER TURTLES (GEOMYDIDAE)
The Geomydidae is the largest family of turtles, with over 65 species, and exhibits a scattered distribution with centres of diversity in south and eastern Asia, the Middle East and North Africa, and Central and northern South America. The carapace may be flattened or domed, and oval to oblong, and range in size from 13 to 80 cm carapace length. THe group is ecologically highly diverse, with terrestrial, semi- and fully-aquatic members and species that range from entirely carnivorous to completely herbivorous. Aquatic habitats range from montane streams to estuaries. This is also the most highly-threatened group of turtles, due primarily to the large number of species that occur in Asia where these animals are most heavily exploited and affected by habitat loss.
|Stream Terrapin||Cyclemys dentata|
|Rice-field Terrapin||Malayemys subtijuga|
|Black River Turtle||Rhinoclemmys funerea|
In contrast to other large turtle families, the 45 or more species of tortoise are ecologically and morphologically conservative. All are entirely terrestrial animals, most are herbivores, and the majority occur in semi-arid or desert habitats. The carapace is almost always more strongly-domed than in other turtle families, and the limbs are robust and with unwebbed feet. However, tortoises can be found in a range of habitats, including mountains and rainforest, throughout a wide range which encompasses eastern South America, Southeast Asia, Europe, the Middle East, sub-Saharan Africa and the Caribbean, as well as isolated areas of southern North America. Many tortoises have historically been heavily harvested for meat and the international pet trade; the Indian Ocean giant tortoise now survives only on the island of Aldabra in the Seychelles, several subspecies of the Galapagos tortoise are extinct, and the ploughshare tortoise of Madagascar (Astrochelys yniphora) may be the world's most endangered turtle.
|Radiated Tortoise||Astrochelys radiata|
|Red-footed Tortoise||Chelonoidis carbonaria|
|Yellow Tortoise||Indotestudo elongata|
Species List - Crocodilians (Order Crocodylia)
Crocodiles are often seen as an example of a group that has remained almost unchanged since long before the extinction of the dinosaurs. Most of the 23 living crocodilian species are, indeed, very similar to one another in both morphology and ecology, supporting the notion of an ancient, low-diversity lineage. It is then perhaps surprising that the modern crocodilian families are among the youngest of all extant reptile groups, first appearing towards the end of the Cretaceous or early in the Tertiary (around 65 million years ago). These animals are the remaining members of a moderately diverse group of archosaurian reptiles with their origins in the Triassic, which included small herbivorous terrestrial species and several highly-adapted marine forms with their limbs modified into fins. Many earlier forms do, nevertheless, closely resemble modern crocodiles in having robust bodies, thickened limbs and thick, flattened tails adapted to an aquatic lifestyle, and a covering of bony plates (osteoderms). The crocodile lineage includes some of the largest land predators the world has ever seen; at up to 12 m and 8.5 tonnes the Late Cretaceous Deinosuchus was almost as long as and somewhat heavier than Tyrannosaurus rex, and is likely to have eaten the same large dinosaur prey. The African species Sarcosuchus imperator, which resembled modern gharials, lived around 110 million years old and may have been slightly larger.
Living crocodiles are semi-aquatic ambush predators, and occur in a wide range of tropical, subtropical and some temperate environments. The estuarine crocodile is the largest and most widespread species, occurring throughout tropical Asia and Australasia. This species will enter marine waters, and may sometimes forage along coastlines. Most crocodilians are opportunistic, and will take animal matter ranging from insects to large mammals depending on species and body size. Exceptions include are the two species of gharial, which possess highly elongated, slender snouts adapted for a specialist diet of fish, and the Chinese alligator, which preys primarily on molluscs.
Crocodiles are well-known for their reproductive strategy; all species nest on land, in mounds created by the female to protect the eggs. In many species, animals (usually but not always the female parent) then guard the nest until the young hatch, fending off monitor lizards and other predators. In at least some species, females return to the nest as hatchlings are about to emerge, excavate the nest and carry newly-emerged young to water. The mother may then remain with the young during part of their early development. One species, the American alligator (Alligator mississippiensis), excavates a 'crèche' pool for its young, where they can develop away from predators.
Today several species of crocodilian are threatened; perhaps ironically, these don't include the two known to be most dangerous to humans. The Siamese crocodile is now largely confined to a small area of Cambodia, and the Chinese alligator too is on the verge of extinction. In the Americas, the black caiman, Orinoco crocodile, Cuban and American crocodiles are in decline. No crocodile has become extinct in historic times, although a species formerly endemic to Madagascar may have been lost since humans settled the island two millennia ago.
Nine species of alligator and caiman exist, eight in the Americas and one in China. The lower teeth are concealed within the jaw when the mouth is closed; in crocodiles these are visible. The American alligator is a rare success story for crocodilian conservation, with populations rebounding after harvesting of wild animals for food and leather was banned. Conversely, the Chinese alligator (Alligator siamensis) remains heavily threatened, with little suitable habitat remaining within its historic range. Alligators exhibit the broadest ecological and physiological tolerance of any living crocodilians; ranging into temperate areas where they encounter freezing temperatures in winter, as well as south throughout Central and South America. The Chinese alligator is the only crocodilian known to hibernate. American alligators and several species of caiman range widely and occur in a variety of aquatic habitats; American alligators have been known to use swimming pools in parts of Florida.
|Spectacled Caiman||Caiman crocodylus|
|Jacare Caiman||Caiman yacare|
Crocodiles can be recognised by the presence of externally visible lower teeth, and particularly the enlarged fourth tooth, at the sides of the jaw when the mouth is closed; otherwise they share a typical crocodilian body form with the alligators. The twelve species occur over much of the world, generally preferring large tropical rivers and lakes with little or no canopy cover. Most crocodiles are active both day and night, but are principally nocturnal. The largest species, the estuarine and Nile crocodiles, are potentially dangerous to humans and are known to be aggressive; human fatalities are rare or unknown in other crocodiles.
|American Crocodile||Crocodylus acutus|
|Nile Crocodile||Crocodylus niloticus|
|Estuarine Crocodile||Crocodylus porosus|
Species List - Lizards (Order Squamata (Sauria))
Lizards are by far the most successful of the surviving reptile lineages, with around 4,500 known species and, for vertebrates, a high rate of new discoveries. In the strictest sense, the more than 3,000 species of snake ought to be added to this number, evolving as they did from lizard ancestors. A third, small group traditionally regarded as a separate lineage, the worm lizards or amphisbaeneans, are also legless lizards and are today usually regarded as such. The basic lizard body form is ancient. Although lizards and their descendants (collectively the Squamata or squamates) are relative newcomers in the fossil record, first appearing in the mid Jurassic around 180-160 million years ago, an essentially lizard-like body form is associated with some of the earliest ancestral reptiles and synapsids (mammal ancestors). Fully modern lizard groups are known with certainty by the mid-Cretaceous, where they appear to have displaced sphenodonts (animals related to the modern tuatara) throughout the Northern Hemisphere. Squamate origins are not well-documented in the fossil record, as most lizards are small and so unlikely to be preserved. Nevertheless, from the fact that the lizards appear to have been late arrivals in the southern continent of Gondawana, where sphenodonts remained widespread and apparently diverse at least until the end of the Cretaceous 65 million years ago, it can be inferred that squamates genuinely did evolve in the northern continents after the breakup of Pangaea. This in turn indicates that squamates cannot be much older as a group than the known fossils suggest.
Modern lizards occur throughout the world, in tropical, subtropical, temperate and, in at least one case, arctic regions. With the exception of the extinct mosasaurs, most lizards are rather small, with only the monitors (Varanidae) growing to lengths of more than about a metre (excluding the tail, which is very long in some lizard groups). One island species, the Komodo dragon (Varanus komodoensis), reaches more than 3 m in length, a size that likely evolved as a response to a lack of other large predators with which to compete. One extinct Australian monitor, Megalania, was half as long again as the Komodo dragon.
Both body form and ecology are highly diverse; burrowing habits have evolved numerous times in the group, producing several lineages of elongate, limbless or reduced-limb lizards adapted for a subterranean lifestyle. Lizards are better-adapted than other reptiles for survival in deserts or semi-arid conditions, and in some regions exhibit their highest diversity in these habitats. yet a high proportion also occur in the tropical rainforests of Asia and the Americas. Several groups have become highly-adapted for an arboreal lifestyle; chameleons have thick, prehensile tails and feet adapted for grasping branches, while geckos possess the ability to cling to vertical surfaces and even hang upside down using specially-adapted scales on their toes. Numerous others are leaf-litter or rock-dwellers. Aquatic lifestyles have evolved to differing degrees; the Komodo dragon may swim between islands, while the Galapagos marine iguana (Amblyrynchus cristatus) famously dives into the sea to forage for marine algae. A number of lizards evade predators by diving into freshwater, either by dropping from overhanging vegetation, as some large iguanian lizards do, or by retreating into water from poolside basking spots. Basilisks (Basiliscus sp.) are capable of running along the water surface using a bipedal motion. Most lizards are carnivorous or omnivorous, typically feeding on invertebrates, amphibians and small reptiles, although some larger species are mostly or entirely herbivorous as adults. Life histories too are variable, with most lizards laying eggs but a number, especially in colder climates, give birth to live young.
In general the conservation status of lizards is poorly-known, but in common with other reptiles they are at high risk from habitat destruction, especially in the Indo-Malayan region where reptiles are at their most diverse. Some of the world's most threatened reptiles are island lizards, among them the Cayman blue iguana, the Bermuda skink, and the El Hierro giant lizard. A number of species are wild-caught for the pet trade, including chameleons and day geckos from Madagascar. In general lizards may be less threatened by human activities than other reptiles, and possibly than other vertebrate groups, as many species live in inhospitable arid habitats that suffer little human disturbance, and some species benefit from the sunny, open conditions of cleared land that provide them with greater opportunities for basking and foraging. Recently, however, concerns have been raised that rising temperatures resulting from climate change may fatally inhibit the ability of these animals to regulate their body temperature by moving from open to shaded areas, and consequently the potential loss of species to heat stress.
The agamids are a large and morphologically diverse family of often large-bodied lizards. All have four well-developed limbs, and commonly robust bodies. Distinctively, the head is large and generally wedge-shaped in adults, and the tail is extremely long (almost invariably longer than the body). The tooth structure of dragon lizards more closely resembles that of tuatara than other squamates. Approximately 450 species of dragon are widespread throughout Asia, Australasia and Africa, with a representative in southeastern Europe. Many agamids are arboreal, and some are among the largest living lizards (up to 350 mm excluding the long tail). This diverse group contains members with large sail-like crests, similar to the American basilisks; a large group of small 'flying' lizards that glide between trees using extensible membranes along their flanks (from which the dragons take their common name); several species with distinctive 'horns' projecting from the tip of the snout; and others with thick, spiny tails. The Australian frilled dragon (or frill-neck lizard) extends a large frill at the back of its head outwards when threatened, and will typically flee from danger by running bipedally on its hind legs.
|Nobbi Dragon||Amphibolurus nobbi|
|Green Tree Dragon||Broncochela cristatella|
|Crested Forest Lizard||Calotes emma|
|Common Garden Lizard||Calotes versicolor|
|Frilled Dragon||Chlamydosaurus kingii|
|Central Netted Dragon||Ctenophorus nuchalis|
|Two-lined Dragon||Diporiphora australis|
|Blanford's Flying Dragon||Draco blanfordii|
|Boyd's Forest Dragon||Hypsilurus boydii|
|Chinese Water Dragon||Physignathus cocincinus|
|Eastern Water Dragon||Physignathus leseurii|
|Common Bearded Dragon||Pogona barbata|
Chameleons are readily distinguishable from other lizards by their eyes mounted in 'cones' that are capable of moving independently, and by features of their toes, which are heavily-thickened and shaped into glove-like structures in which the first two digits oppose the other three. In larger species, the tail is long, thick and prehensile, and may be coiled under the body at rest. The head is large and triangular, with a casque that extends backwards above the neck, and often with 'horns' projecting from the nose or eye orbits. Several genera of dwarf chameleon, many largely terrestrial, lack long tails and well-developed casques. Most other chameleons are fully or primarily arboreal. Chameleons' ability to change colour, which to a lesser extent is shared with other iguanian lizards and some geckos, is primarily an aid to communication, indicating stress or readiness to breed, but in some species may indeed be used as a form of camouflage. These lizards are notable for their extremely long, prehensile tongues, which can be projected at high speed to catch insect prey, chameleons being predominantly carnivorous (although omnivory has been documented). Over half of the more than 200 chameleon species occur in Madagascar, where the group is likely to have evolved; others are found in Africa (particularly East Africa) and the Middle East, with isolated species in eastern Europe and India. Chameleons inhabit a wide range of forest habitats, and many species are endemic to mountainous areas.
|Brown Leaf Chameleon||Brookesia superciliaris|
|Short-horned Chameleon||Calumma brevicorne|
|Short-nosed Chameleon||Calumma gastrotaenia|
|Nose-horned Chameleon||Calumma nasutum|
|Parson's Chameleon||Calumna parsonii|
|White-lined Chameleon||Furcifer lateralis|
|Panther Chameleon||Furcifer pardalis|
|Oustalet's Chameleon||Furcifer oustaleti|
|Warty Chameleon||Furcifer verrucosus|
IGUANID LIZARDS (IGUANIDAE)
This is a large group that dominates the lizard fauna of the Americas and has diversified into a wide range of forms, many paralleling adaptations in Old World agamids, their close relatives. The 900 or so species of iguanid have often been treated as eight distinct families, each highly distinct in appearance and with its own common name. Several iguanids are very large, reaching lengths of up to 750 mm. Most are carnivorous or omnivorous, but the marine iguana is a true herbivore throughout its life, and a number of other species, including the green iguana commonly kept as a pet, eat mainly plant material as adults. Iguanids occur in a range of terrestrial and arboreal habitats in the Americas and Pacific islands; terrestrial members of the group also occur in Madagascar.
Casque-headed Lizards (Coryptophaninae)
Nine species of large, arboreal tropical lizard, most readily-distinguished by the presence of a large helmet or casque atop the head, at least in males. Members of the genus Basiliscus also have a tall, sail-like crest running down the length of the back. One species gives birth to live young, but the remainder are egg-layers. Most live high in the forest canopy and rarely descend to ground level, but basilisks are often active on the ground and may bask on the banks of waterbodies. Their ability to run across the water surface on their hind legs without sinking has earned basilisks the alternative common name of "Jesus Christ lizard".
|Brown Basilisk||Basiliscus basiliscus|
|Green Basilisk||Basiliscus plumifrons|
|Striped Basilisk||Basiliscus vittatus|
A small, widely-distributed family of large and mostly herbivorous lizards. Iguanas occur from North America south to southern Brazil, and members of the genus Brachylophus range as far as Fiji in the South Pacific. Although the familiar green iguana (Iguana iguana) is a predominantly arboreal, forest-associated lizard in its natural habitat, typical iguanas are terrestrial and prefer drier, more open country, with some species occurring in deserts. Unusually for lizards, several species of iguana migrate to historical nest sites during the breeding season to lay eggs. Several iguanas are among the world's most threatened reptiles.
Malagasy Iguanas (Oplurinae)
The seven species in this family are a biogeographic oddity, occurring exclusively in Madagascar and the Comoros in the Indian Ocean, far from any other members of the Iguanidae. Nonetheless, molecular evidence confirms that they belong to the Iguanidae rather than the similar Agamidae. These are small to moderate-sized terrestrial lizards of the dry rocky and sandy habitats that characterise Madagascar's south and west. Most are heavy-bodied lizards with prominent whorls of spines forming rows around the tail; patterning is usually cryptic and may include a dark 'collar' around the neck.
|Three-eyed Lizard||Chalaradon madagascariensis|
|Merrem's Madagascar Swift||Oplurus cyclurus|
Spiny Lizards (Phrynosomatinae)
A large subfamily distributed in the United States and throughout Central America, with around 110 species. Most are adapted for dry conditions, and decline in diversity in the humid climates of Central America; in the US and Mexico, however, this is the most diverse iguanid subfamily. Body form is diverse, although the majority of species possess strongly keeled, triangular scales that give them a characteristically spiny appearance. The horned lizards (genus Phrynosoma) are unusually robust, round-bodied members of this group; most phrynosomatines are slender with moderate to long timbs. Members of this subfamily feed predominantly on insects and most are terrestrial ambush predators, rarely climbing far off the ground.
|Rose-bellied Spiny Lizard||Sceloporus variabilis|
The largest iguanid subfamily, and one of the most widely-distributed, occurring throughout the American tropics and the Caribbean and ranging into southern North America. These are the characteristic small tree- and shrub-dwelling lizards of the Neotropical realm, and are especially diverse in the islands of the West Indies. These are day-active lizards that feed by ambushing insect and spider prey, and so most are nondescript shades of green, brown or grey that enable them to blend into their surroundings. Anoles are notable for their mating displays, in which males extend a rounded and usually brightly-coloured dewlap (an extensible pocket on skin beneath the throat) to court females. Uniquely among lizards, anoles are physiologically capable of laying eggs continuously throughout the year.
|Ghost Anole||Norops lemurinus|
|Smooth Anole||Norops rodriguezii|
A very large family with approximately 1,000 known species, distributed throughout the Southern Hemisphere and tropical regions worldwide. The group is ancient, being the first to appear in the lizard fossil record, although this contrasts with other evidence placing iguanians (agamids, chameleons and iguanas) at the base of the squamate evolutionary tree. Geckos are immediately recognisable lizards, with large rounded heads, blunt snouts, large eyes sometimes with vertical pupils (and in most cases without eyelids), and large, flattened toes. Most geckos are arboreal, and famously capable of adhering to walls and ceilings through the action of specialised structures (lamellae) on the underside of the toes. Unlike the preceding lizard families geckos exhibit caudal autotomy, the ability to shed their tails as a response to a threat. One unusual genus from Madagascar (Gekkolepis) is even capable of shedding its entire body covering of scales to evade predators. In contrast to most lizards, geckos are nocturnal and many are capable of communicating through vocalisations; in much of the tropical world, the chit-chat call of the widely-introduced Malaysian house gecko (Hemidactylus frenatus) is part of the background noise. Size is variable; most geckos are rather small, and indeed the family contains the world's smallest lizard, but several reach lengths greater than 30 cm. Geckos are insectivorous and many adopt highly cryptic colouration; by contrast, the day-active African geckos of the genus Phelsuma are often conspicuous and brightly-coloured in shades of green, red, yellow and blue, and supplement their diet with nectar from fruit or aphids.
Australasian Geckos (Diplodactylinae)
Most of the geckos in Australia and New Zealand belong to this subfamily, which resemble the typical geckos of the rest of the world. This is a diverse group, containing both nocturnal and diurnal, and terrestrial as well as arboreal, forms. At 370 mm long the world's largest gecko occurs in this subfamily, although most are relatively small. Some species include nectar in their diet but most are entirely insectivorous. Habitats range from desert to scrubland and rainforest. Unusually for geckos, several species give birth to live young.
|Northern Velvet Gecko||Oedura castenaui|
|Fat-tailed Gecko||Diplodactylus conspicillatus|
|Northern Leaf-tailed Gecko||Saltuarius cornuntus|
|Northern Spiny-tailed Gecko||Strophurus ciliaris|
Typical Geckos (Gekkoninae)
The largest and most widespread gecko subfamily, containing over 800 species with a worldwide distribution centred in the tropics and Southern Hemisphere, and extending into temperate Asia and southern Europe. These lizards have the typical gecko form, with four well-developed limbs and a soft-textured body covering composed of numerous small, generally rounded scales. Some species are tiny (below 30 mm in length); a number are over three times as long. Ecological diversity is the highest in any lizard group; although most species are arboreal, many are terrestrial rock or leaf litter-dwellers, and several species burrow or inhabit termite nests. One Asian genus has members with an extensive fringe of skin along the sides of the body or tail; these flying or parachute geckos are able to glide in much the same way as dragons of the genus Draco. Several lineages are diurnal, and nectar forms part of the diet for a number of species. Parthenogenesis (asexual reproduction) is known in several widespread species.
|Kendall's Day Gecko||Cnemapsis kendallii|
|Flat-tailed Gecko||Cosymbotus platyurus|
|Banded Gecko||Cyrtodactylus angularis|
|Peter's bent-toed gecko||Cyrtodactylus consobrinus|
|Tree Dtella||Gehyra dubia|
|Tokay Gecko||Gekko gecko|
|Warty House Gecko||Gekko monarchus|
|Malaysian House Gecko||Hemidactylus frenatus|
|African House Gecko||Hemidactylus mabouia|
|Bynoe's Prickly Gecko||Heteronotia binoei|
|Madagascar Spiny-tailed Gecko||Paroedura bastardi|
|Panther Gecko||Paroedura picta|
|Gold Dust Day Gecko||Phelsuma laticauda|
|Lined Day Gecko||Phelsuma lineata|
|Thick-tailed Day Gecko||Phelsuma mutabilis|
|Dwarf Gecko||Lygodactylus tuberosus|
|Southern Leaf-tailed Gecko||Uroplatus sikorae|
|Siamese Leaf-toed Gecko||Phyllodactylus siamensis|
|Kuhl's Flying Gecko||Ptychozoon kuhlii|
|Canary Island Wall Gecko||Tarentola angustimentalis|
|Turnip-tailed Gecko||Thecadactylus rapicauda|
Legless Lizards (Pygopodinae)
An extremely unusual group of Australian lizards often treated as a separate family, but falling within the Gekkonidae in molecular analyses. Although known as legless lizards for obvious reasons, and possessing the elongate, slender and usually rounded body form typical of burrowing lizards, pygopodines retain vestigial flaps of skin where their limbed ancestors' hind legs would have been, giving rise to the alternative common name 'flap-foots'. Like other geckos pygopodines lack eyelids, but they do not possess the large, bulging eyes of typical geckos and the head itself is often narrow, wedge-shaped and sharply-pointed. Most species are insectivores, but larger species may specialise on small reptiles.
|Legless Lizard||Delma mitella|
|Excitable Delma||Delma tincta|
|Burton's Legless Lizard||Lialis burtoni|
NIGHT LIZARDS (XANTUSIIDAE)
A small family found in the American tropics and the western United States. These are small lizards with a body covering of small tubercles, four limbs (reduced in some species) and large, distinct heads. Despite their name and their possession of elliptical pupils, night lizards are generally active during the day or at dawn and dusk, but favour naturally dark environments such as caves, closed-canopy forest or beneath leaf litter. The ecology of this group is poorly-known, but most species probably have very small home ranges and all appear to be insectivorous. Unusually, these lizards are long-lived, reproduce slowly and give birth to live young. Some species are parthenongenetic.
|Yellow-spotted Night Lizard||Lepidophyma flavimaculatum|
ROCK & WALL LIZARDS (LACERTIDAE)
These are the familiar lizards of Europe, where they are by far the dominant element of the reptile fauna. Lacertids also occur throughout the Asian and African mainland. One tropical species, the long-tailed lizard (Takydromus sexlineatus), occurs in tropical Southeast Asia as far east as Borneo. Lacertids include species with the most northerly global distribution of any lizard, occurring as far as northern Scandinavia. Most of the 220 species are small, but several species on the Canary Islands approach 30 cm in body length. All lacertids exhibit a typical lizard body form, with four well-developed limbs and a long, generally slender tail that can be shed in response to danger. Most species are terrestrial, and are often associated with grassland, rocky or arid habitats. Most species are insectivorous, although at least one eats seeds.
|Atlantic Lizard||Gallotia atlantica|
|Viviparous Lizard||Zootoca vivipara|
|Common Wall Lizard||Podarcis muralis|
In ecology and morphology, whiptails have been considered American counterparts to the Old World lacertids, with which they share the typical lizard body form. Tegus are among the largest lizards in the world, but most whiptails are small. Most are terrestrial, actively foraging for insect prey and in some species breaking into termite mounds. Whiptails are most familiar in the tropics, where they are highly diverse and often very abundant in a wide variety of habitats. However, species occur throughout the Americas and their associated islands, although several are widespread and abundant in the Arctic.
|Common Ameiva||Ameiva ameiva|
|Middle American Ameiva||Ameiva festiva|
PLATED LIZARDS (CORDYLIDAE)
A small family confined to sub-Saharan Africa. These are large-bodied lizards with four, sometimes reduced limbs, and are most readily distinguished by the large, often rectangular scales across the back and flanks that give the animals an 'armoured' appearance, and by a fold of skin running along part or all of the flank. In extreme cases, strongly keeled scales give the animal a prickly or even 'pinecone'-like appearance, as in the sungazer (Cordylus giganteus). All species are day-active, basking lizards, typically of arid and semi-desert habitats, and many give birth to live young. Unusually, some Madagascan species in the subfamily Gerrhosaurinae are forest-associated. Malagasy girdled lizards typically lack armour, and resemble large skinks. Plated lizards eat a variety of prey, and some larger species will take small vertebrates.
|Western Girdled Lizard||Zonosaurus laticaudatus|
|Madagascar Girdled Lizard||Zonosaurus madagascariensis|
|Madagascar Keeled Plated Lizard||Tracheloptychus madagascariensis|
Around 1,200 of the world's lizard species are skinks, making the Scincidae the largest lizard family by some way. This diversity reflects a wide variety of body forms and ecological adaptations. A 'typical' skink is an active, terrestrial, smooth-scaled lizard with a small head, indistinct neck and four relatively short limbs that give the animal an elongated appearance; favoured habitats include forest leaf litter, desert and in many cases open, disturbed areas, and the lizards are typically coloured to blend into their surroundings. There are, however, numerous departures from this body form. Many skinks are burrowing animals, often with two or no limbs. Some species have keeled scales; a few have short bodies with well-developed limbs. A small number of species are arboreal, among them the herbivorous prehensile-tailed skink (Corucia zebrata), at up to 35 cm in body length the family's largest member. Skinks are distributed nearly worldwide in the Southern Hemisphere and the tropics, and in some warm temperate areas of the Northern Hemisphere, and can be found in practically every habitat type within this range. Some species exhibit parental care; most lay eggs but a few give birth to live young.
|Jewel Skink||Carlia foliorum|
|Lined Rainbow Skink||Carlia jarnoldae|
|Macfarlan's Litter Skink||Carlia macfarlani|
|Open-litter Rainbow Skink||Carlia pectoralis|
|Hooded Rainbow Skink||Carlia rostralis|
|Northern Red-throated Skink||Carlia rubrigularis|
|Bicarinate Rainbow Skink||Carlia schmeltzii|
|Cream-striped Shinning Skink||Cryptoblepharus virgatus|
|Eastern Striped Skink||Ctenotus robustus|
|Copper-tailed Skink||Ctenotus taeniolatus|
|Pink-tongued Skink||Cyclodomorphus gerrardii|
|Major Skink||Egernia major|
|Eastern Water Skink||Eulamprus quoyii|
|Speckled Forest Skink||Eutropis macularia|
|Many-lined Sun Skink||Eutropis multifasciata|
|Prickly Forest Skink||Gnypetoscincus queenslandiae|
|Garden Skink||Lampropholis delicata|
|Striped Tree Skink||Lipinia vittigera|
|Central American Mabuya||Mabuya unimarginata|
|Fire-tailed Skink||Madascincus igneocaudatus|
|Basal Shade Skink||Saproscincus basiliscus|
|Indian Forest Skink||Sphenomorphus indicus|
|Streamside Skink||Sphenomorphus maculatus|
|Eastern Blue-Tongue Skink||Tiliqua scincoides|
|Bright Skink||Trachylepis elegans|
|Boulder Mabuya||Trachylepis vato|
|Water Skink||Tropidophorus brookei|
GLASS & ALLIGATOR LIZARDS (ANGUIDAE)
Modern anguids comprise a relatively small family of lizards with a peculiar, disjunct distribution centred in North and Central America, but with representatives throughout western Eurasia and central South America. This pattern of occurrence is likely to represent the ancient evolutionary history of this lineage, one of the earliest to occur in the lizard fossil record, and reflects morphological and molecular divisions between American and Eurasian taxa. Anguids are typically robustly-built, with nonoverlapping scales that may give the animal an armoured appearance. European glass lizards and slow worms are all elongated, limbless lizards with an autotomous tail twice the length of the body; species of this group also occur in North America. Other anguids are restricted to the Americas, where most have four well-developed (but often small) limbs; alligator lizards are especially heavily-armoured representatives of the family. Habitat preferences are varied and range from forests to arid lands, the former being preferred by the tropical galliwasps (Diploglossinae). Several species are highly tolerant of human disturbance. Most limbless anguids are burrowing animals; the remainder are terrestrial. Most lay eggs, and feed on arthropods or burrowing invertebrates.
|Slow Worm||Anguis fragilis|
MONITOR LIZARDS (VARANIDAE)
This small family contains the world's largest lizards, and the smallest representative is over 20 cm in total length. Monitors have well-developed limbs, relatively small but sometimes elongated heads, distinct necks, heavyset bodies and thick, powerful tails. The tongue is forked, a characteristic shared with snakes. Adults typically hunt for mammals and other vertebrates as adults; the largest species, the Komodo dragon, takes goats and pigs, while the water monitor (Varanus salvator) are a pest species in areas of Asia where they feed on domestic chickens. Several species are carrion-eaters, and many will actively seek out the eggs of crocodiles and other reptiles. Habitat preferences are variable; most species are terrestrial and many are desert-associated, although juveniles of some may climb trees to escape predation by larger monitors, a few are fully arboreal and one (Varanus mertensi) almost fully aquatic in paperbark swamps. Living Monitors have an Old World distribution throughout the southern continents, preferring warm temperate to tropical regions, and with their highest diversity in Australia. Fossil species assigned to this family are also known from North America and Europe.
|Water Monitor||Varanus salvator|
Species List - Snakes (Order Squamata (Serpentes))
Fossils of early snakes date to 127 million years ago, although they are too fragmentary to assign to modern groups. As a result it is unclear which group gave rise to the 3,000 species of legless, earless, forked-tongued lizards collectively known as snakes. Animals related to either living monitor lizards or glass lizards are considered the most likely snake ancestors. Early snakes possessed hindlimbs and diversified into both terrestrial and marine forms; subsequently, different lineages appear to have lost their limbs independently of one another. One group of living snakes, the boids (boas and pythons), do retain rudimentary hindlimbs in the clawed spurs males use to grasp females when mating.
Snakes can reliably be distinguished from lizards by the absence of a tympanum (eardrum), which renders them deaf to airborne sounds. Although a few lizard species lack visible ears, all such forms have developed limbs. Similarly, the only lizards with forked tongues are quadrupedal. Unlike most legless lizards, snakes (other than blind snakes) have a single row of ventral scales running down the length of the body and tail; these are large and rectangular, and are used to assist the animal's locomotion. Snakes, in common with some lizards, lack eyelids, and instead have a transparent spectacle covering the eye. Internally, snakes possess additional vertebrate and ribs, and the left lung is either atrophied or completely absent. Most distinctively, snakes' jaws are each split into a left and right half that can move independently, an adaptation that allows them to handle and manipulate prey using their mouth alone to orientate it and manoeuvre it into the gullet.
In most snakes, certain teeth have evolved into enlarged, curved fangs; the principal function of these teeth is to grasp and manoeuvre prey; species with moveable fangs can 'walk' food items down the gullet using their fangs to gain purchase. In venomous species, the fangs also act as a venom delivery system, toxins in the animal's saliva passing down grooves in the fang to pass into any wound. The venom itself is derived from digestive enzymes, and depending on the species or family acts as either a neurotoxin to paralyse and subdue prey, or haemotoxins that destroy body tissue and cause organ failure. Most venomous snakes belong to the families Viperidae and Elapidae. A number of rear-fanged snakes (Colubridae), the largest and most widespread family, also have venom glands but only a very few, most infamously the African boomslang (Dispholidus typus), are potentially dangerous to humans.
All snakes are carnivorous, but prey items range from large vertebrates such as crocodiles and deer (in larger pythons) to slugs and insect eggs in blind snakes and small colubrids. Snakes vary widely in size; many blind snakes are less than 150 mm long while the largest reticulated pythons (Python reticulatus), at up to 10 m, are over 65 times this length. The recently-discovered fossil Titanoboa reached at least 13 m, and would have weighed more than a ton. The largest living snake, the green anaconda (Eunectes murinus), has a maximum weight of 550 kg.
Ecologically snakes are equally diverse; the European adder (Vipera berus) occurs further north into the Arctic than any other reptile, and species are distributed throughout the temperate and tropical zones worldwide. Snakes are rather poor colonisers of islands, although in some areas where they have been long-established a small number of colonists have radiated into a large number of species. Examples include the elapid snakes of Australia and the colubrids of Madagascar. Snakes probably evolved from burrowing lizards, and many have retained or re-evolved this habit. Others are terrestrial, aquatic or arboreal; one group of Southeast Asian snakes (genus Chrysopelia) has developed the ability to parachute from branches by leaping and flattening its body to increase drag as it falls. This ability may also occur in several other Asian colubrids. The Australian elapid radiation has given rise to a number of fully marine species, mostly live-bearing animals with flattened, rudder-like tails that surface to breathe but rarely or never come ashore.
Snakes are heavily persecuted in much of the world. Often this is due to misidentification of harmless with less common venomous species, yet even in areas with no dangerously venomous snakes (such as Madagascar), an inherent dislike of or superstitious fear of snakes leads to many unnecessary killings. During notorious 'rattlesnake round ups' in parts of the United States, snake-hunters will actively go looking for animals in areas that are otherwise uninhabited by humans. In fact, even highly venomous snakes only rarely pose a danger to people; many live in inaccessible areas such as desert or deep forest, and few snakes will bite in defence except as a last resort, as venom is energetically expensive to produce and the animals need it to forage. Snakes often provide a valuable pest control service in rural areas, as many species tolerant of human disturbance will eat rodents in fields or houses; others are popular as pets.
BLIND SNAKES (TYPHLOPIDAE)
Due to their tiny size (a few approach a metre in length, but most are well below a quarter of this size), blind snakes lack a detailed fossil record, but evidence places them in a separate lineage from the remaining, morphologically 'advanced' snakes. Blind snakes are burrowing animals with a shiny appearance and rows of scales around the torso (there are no large ventral scales). The head is small and rounded, and the forked tongue and presence of scales distinguishes the animals from worms. The tail is pointed, and its shape is important in distinguishing between species. Around 400 species of blind snake are known worldwide, although this is likely an underestimate due to difficulties in separating typically very similar species. Blind snakes naturally have a tropical and Southern Hemisphere distribution. One species, the flowerpot snake (Rhamphotyphlops braminus), has been introduced more widely and has become the world's most widespread snake. This species exhibits the only known example of parthenogenesis in snakes. Blind snakes feed on small insects and soil invertebrates; they can very rarely be encountered in trees, but most are exclusively subterranean.
|Flowerpot Snake||Rhamphotyphlops braminus|
|Blind Snake||Rhamphotyphlops proximus|
Pythons are almost exclusively large snakes, characterised by robust bodies, distinctly triangular heads (usually with a distinct neck), the presence of spurs (hindlimb remnants) that are usually concealed within the cloaca, and often the presence of a row of heat-sensitive pits along the line of the lip. In contrast to boas, all pythons lay eggs (but see the following entry). Most species exhibit egg-guarding behaviour, and in some cases incubate their young by surrounding the eggs and shivering to increase their temperature. Pythons include the world's longest snake, the reticulated python, and mostly hunt for vertebrate prey. Typically birds and mammals are taken, which snakes may locate using heat pits. Pythons occur in habitats from rainforest to desert, and some are semi-aquatic. This small family is most diverse in Australia, but also occurs through tropical Asia and sub-Saharan Africa.
|Water Python||Liasis mackloti fuscus|
|Carpet Python||Morelia spilota|
Boas very closely resemble pythons in most aspects of their morphology, and like pythons typically posses a hindlimb spur and heat-sensing pits. As presently defined, boas differ from pythons in giving birth to live young; however, this is a problematic distinction as the Madagascar 'boas' appear to be closely-related to African rock pythons, and must therefore have evolved viviparity independently. Nevertheless, these live-bearing pythons are currently included within the Boidae. Some boas are more heavy-bodied than pythons; although the green anaconda, the largest member of the family, grows to a maximum of 7 m, it is heavier than the longer reticulated python. Boas hunt diverse vertebrate prey; smaller species forage for frogs and lizards; larger animals will take caiman and large mammals (in the case of the green anaconda, occasionally but very rarely including humans). The green anaconda is almost fully aquatic; most other species are arboreal forest-dwellers in the American tropics; the sand and rosy boas are small, terrestrial or burrowing snakes in the deserts of temperate North America and Asia.
|Madagascar Tree Boa||Sanzinia madagascariensis|
Vipers include some of the most feared snakes in the world; the gaboon viper (Bitis gabonica) has the longest fangs of any snake, while the puff adder (Bitis arietans) has the fastest strike and is responsible for the largest number of human fatalities from a single species. In the Neotropics, the name 'two-step' is variously applied to species of fer-de-lance and bushmaster, reflecting the (erroneous) belief that if bitten, you will be dead in two steps. This is also the family to which the American rattlesnakes belong. Despite this fearsome reputation, vipers are small to moderate in size, frequently secretive and usually nocturnal animals of woodland, mountain or desert environments where human contact is rare, and usually non-aggressive. Vipers are most readily recognised by their strongly triangular heads and very robust, often short bodies; pit vipers (Crotalinae) also have paired heat-sensitive pits, one below each eye, that help them to hunt small mammals such as rodents, although a number of species feed on amphibians and lizards. The fangs are more mobile than that of other venomous snakes. Viper venom is haemotoxic and highly variable in its strength and effects. Vipers occur and are widespread on all continents except Australasia and Antarctica; they are also absent from Madagascar.
|Big-eyed Pit Viper||Cryptelytrops macrops|
|Temple Viper||Tropidolaemus wagleri|
REAR-FANGED SNAKES (COLUBRIDAE)
"Colubridae" is the collective name for the largest group of snakes, members of which have fangs at the rear of the jaw (in contrast to vipers which are 'front-fanged'). About 60% of living snakes are colubrids, which are distributed worldwide and in all habitats. Taxonomically, the family contains a number of loosely-related lineages, and there is no single character that can be used to identify a particular snake as a 'colubrid'. Rather, the family is defined by the absence of characters associated with elapids or mole vipers. Generally, however, colubrid snakes have rounded heads, and they are often slender-bodied.
Colubrine Snakes (Colubrinae)
With over 650 species, this is the largest and most diverse group of rear-fanged snakes. The group is found throughout the world and includes many familiar nonvenomous snakes, including American racers and rat snakes. Mildly venomous cat snakes (Boiga) also belong to this group; one of these species, the brown tree snake (B. irregularis) is infamous for eradicating the native bird and reptile faunas on the Pacific island of Guam following its accidental introduction in the 1940s. Colubrines also include one of the world's most venomous snakes, the southern African boomslang. Colubrines occur in all habitats occupied by colubrid snakes, and have similarly varied diets. A few species are highly specialised to prey on certain animals, such as particular groups of insects, but the majority will eat any animal prey of suitable size. The only reliable generalisation is that most colubrines lay eggs, although even this is not universal.
|Green Cat Snake||Boiga cyanea|
|Brown Tree Snake||Boiga irregularis|
|Green Tree Snake||Dendrelaphis punctulata|
|Common Bridle Snake||Dryocalamus davisonii|
|Banded Kukri Snake||Oligodon fasciolatus|
|Tiger Ratsnake||Spilotes pullatus|
A large but restricted-range lineage, lamprophiine snakes are confined to sub-Saharan Africa. The colubrid snakes of Madagascar belong to this group. A few are mildly venomous, including the Malagasy spear-nosed snake (genus Langaha); most are not. In general lamprophiines are small, although the large hognose snakes of Madagascar exceed a metre in length. Most are slender, terrestrial snakes with a typical 'racer'-like body form, although there are arboreal species and these may have large, rounded heads.
|Malagasy Giant Hognose Snake||Leioheterodon madagascariensis|
|Madagascar Blond Hognose Snake||Leioheterodon modestus|
|Big-eyed Snake||Mimophis mahfalensis|
Water Snakes (Natricinae)
A moderately large, widely-distributed family found throughout the Northern Hemisphere, and extending into southern Africa. Size is variable; the grass snake (Natrix natrix) of Western Europe is among the largest representatives at 2 m in adult length and typifies the natricine body form, while some are as small as blind snakes. Many species are strongly associated with freshwater (and in rare cases saltwater), although in contrast with truly aquatic snakes natricines spend much of their time on land while basking, mating or hibernating. Several such 'aquatic' species may also use terrestrial as well as freshwater habitats for foraging. Aquatic species mostly hunt fish and frogs. Most terrestrial natricines are smaller, and forage on the ground or in soil and leaf litter for soft-bodied invertebrates. Old World species lay large clutches of eggs, while American natricines are all live-bearers. It is possible that this reflects a division between two evolutionarily separate lineages which should be recognised as distinct subfamilies.
|Grass Snake||Natrix natrix|
|Common Mock Viper||Psammodynastes pulverulentus|
|Green Keelback||Rhabdophis nigrocinctus|
|Red-necked Keelback||Rhabdophis subminiata|
|Eastern Garter Snake||Thamnophis sirtalis|
Slug Snakes (Pareatinae)
With around 20 species, this is a very small but widely-distributed family, with members throughout Southeast Asia and China. These are moderate (from nearly half to almost a metre), slender snakes with a characteristically blunt snout that gives the large head a squarish appearance. As their common name suggests, these snakes specialise in feeding on slugs and snails. Slug snakes typically forage among vegetation at night, their bodies being adapted for moving across twigs and branches while hunting prey. Slug snakes lay eggs and clutch size is small.
|Keeled Slug Snake||Pareas carinatus|
This is a highly diverse subfamily found throughout the Americas. Over 500 species differ widely in ecology and appearance; the group includes heavy-set semi-aquatic species alongside slender, big-headed cat-eyed tree snakes. A few species specialise in feeding on molluscs, but most are generalist carnivores. Otherwise, few generalisations can be made about xenodontines. Diurnal vine snakes are highly distinctive tree snakes, with narrow, elongated snouts and relatively robust bodies, while nocturnal species with a similar habitat have larger, rounder heads and eyes and narrow bodies. Terrestrial, burrowing and freshwater forms display a greater diversity of body types. Most species are rather small, with few exceeding a metre in length.
|Cat-eyed Snake||Leptodeira annulata|
|Velvety Swamp Snake||Liophis typhlus|
|Red Coffee Snake||Ninia sebae|
COBRAS, CORAL SNAKES AND KRAITS (ELAPIDAE)
Elapids occur worldwide in tropical and subtropical regions and there is a great deal of regional variation in the common names used to describe these snakes. In general, rounded, banded, typically brightly-coloured elapids are known as coral snakes; African and Asian species with extendible 'hoods' are cobras, and thick-bodied, banded Asian snakes with a characteristic triangular body form are known as kraits. This diversity of names gives an idea of the variability within the Elapidae. Characteristic features of the family are rounded, colubrid-like heads and fixed, hollow fangs. The majority of the world's most venomous snakes are elapids, including the Australian inland taipan (Oxyuranus microlepidotus) and the sea snakes. In contrast to vipers, elapid venom is neurotoxic; although some small species are physically incapable of puncturing human skin or injecting a lethal dose, it is supposed that all elapid species are venomous enough to be lethal to humans. Although there are around 300 species of elapid snake, the ecological diversity of the group is limited; very few species are arboreal, and aside from the two lineages of sea snakes, most are fully terrestrial or burrowing animals. Most eat vertebrate prey, although different species specialise in hunting different vertebrate groups. Sea snakes give birth to live young; most other species (including the sea krait) lay eggs.
Cobras & Allies (Elapinae)
These are the terrestrial elapids that occur in most of the world; hydrophiines replace them in Australia and New Guinea. Ecologically they resemble their Australian equivalents in being largely terrestrial animals, although the African mambas are a rare exception in being predominantly arboreal. Some cobras exhibit the most sophisticated venom delivery system of any snake; as well as injecting venom into prey, these animals can fire it at high pressure through holes in the front of their fangs. Spitting cobras can project their venom several metres in this way; used as a defence, this spray of venom is non-lethal but can blind the attacker, potentially permanently. The world's largest venomous snake is the king cobra (Ophiophagus hannah), that can reach lengths of nearly 6 m; most species are much smaller, often a metre or less.
|Malayan Krait||Bungarus candidus|
|Variable Coral Snake||Micrurus diastema|
|Indonesian Spitting Cobra||Naja sputatrix|
Australopapuan Elapids (Hydrophiinae)
Famously. most snakes in Australia are venomous, an accident of biogeography which is thought to result from the colonisation of the continent by a small number of individuals belonging to a single ancestral species. Today, Australia has around 90 terrestrial elapids, and both the sea snakes and sea kraits distributed through the Indian and Pacific Oceans can trace their lineage to this ancestral Australian colonist. Hydrophiines include the world's most venomous snakes; however, due to their choice of desert or marine habitats very few encounter humans. No fatalities have ever been reported from the inland taipan, which rejoices in the title of the world's most venomous terrestrial snake. Most Australian species retain the typical elapid body form; slender, with a rounded head and no distinct neck. Some species commonly known as 'death adders', however, very closely resemble viperine snakes, being short, robust and with large triangular heads. True vipers are absent from Australia. Most remarkable of all, however, are the sea snakes. Of all the surviving lineages of marine reptiles, none is as fully-adapted to life at sea as these species. The body is modified as extensively as a serpentine body can be; the tail is flattened into a long paddle that acts as a rudder, while the enlarged ventral scales that allow snakes to move on land have been lost. All 'true' sea snakes are live-bearing. Sea kraits, by contrast, retain the conventional snake body form and the egg-laying habit, and will come ashore both to lay eggs and to bask.
|Yellow-faced Whipsnake||Demansia psammophis|
|Lesser Black Whipsnake||Demansia vestigiata|
|Orange-naped Snake||Furina ornata|
|Black-bellied Swamp Snake||Hemiaspis signata|
|Red-bellied Black Snake||Pseudechis porphyriacus|
|Small-eyed Snake||Rhinoplocephalus nigriscens|
Wikipedia Snake Venom
Apesteguía, S. and Novas, F.E. (2003) Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana Nature 425: 609-612
Collen, B., Ram, M., Dewhurst, N., Clausnitzer, V., Kalkman, V., Cumberlidge, N. and Baillie, J.E.M. (2008) Broadening the coverage of Red List assessments IUCN, Gland, Switzerland
Leanza, H.A., Apesteguía, S., Novas, F.E. and de la Fuente, M.S. (2004) Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages Cretaceous Research 25: 61-87
Li, C., Wu, X-C., Rieppel, O., Wang, L-T., Zhao, L-J. (2008) An ancestral turtle from the Late Triassic of southwestern China Nature 456: 497-501
Reisz, R.R. and Head, J.J. (2008) Turtle origins out to sea Nature 456: 450-451
Rincon, P. (2009) Largest snake 'as long as a bus' BBC News Online, 4 February 2009
Vitt, L.J. and Caldwell, J.P. (2009) Herpetology: An introductory biology of amphibians and reptiles Third Edition. Academic Press, Burlington, Massachusetts: 697 pp
Reptiles, along with amphibians, have traditionally been regarded as 'primitive' terrestrial vertebrates. In fact, they are more closely-related to mammals (with which they share a common ancestor) and birds, and share with them adaptations to a fully-terrestrial lifestyle, especially an impermeable skin covering that limits water loss and the development of embryos within amniotic fluid, either within a shelled egg or inside the mother's womb. In a strict taxonomic sense, there are some 18,000 living reptile species divided into two major lineages; approximately 8,000 within the Lepidosauria (lizards and their derivatives, and sphenodonts), and 10,000 within the Archosauria (turtles, crocodiles and birds). Conventionally, of course, the birds are regarded as a class in their own right, and so they will not be covered here. The remaining reptiles are themselves the survivors of 300 million years of evolution which have seen the emergence, diversification and extinction of entire major lineages, among them the icthyosaurs, pterosaurs, plesiosaurs and, most famously, the 'bird-hipped' and sauropod dinosaurs.
This evolutionary history is reflected in the high diversity of body forms among living reptiles, which is greater than in any other vertebrate group. Lizards may have four, two or no legs; one group of limbless lizards includes over 3,000 species and is traditionally treated as a separate group of reptiles in its own right, the snakes. Reptiles vary in size from the estuarine crocodile (Crocodylus porosus), which measures over 7 m long and weighs up to one and a half tonnes, to a species of dwarf gecko with a maximum length of 16 mm, smaller than any known mammal or bird. Reptiles' ecological roles are similarly diverse. Although most are primarily or exclusively carnivorous, some turtles and lizards subsist primarily on plant material. On the island of Madagascar, day geckos (genus Phelsuma) supplement their diet with nectar and may be important pollinators; one member of the genus is known to harvest the sugary waste excreted by aphids, and even to stimulate the insects to provide it with a food 'reward'. Reptiles may be fully terrestrial, arboreal or burrowing animals, and all major lineages have given rise to forms that have become readapted to a fully marine existence. In Canada, Europe and Tasmania a number of lizard and snake species have adapted to life above the snow line; many more species are adapted to a desert lifestyle, and in areas of North America, Africa and Australia reptiles are the dominant vertebrates in arid habitats. Reptiles are, however, at their most diverse and abundant in the tropics, with their global centre of diversity within the rainforests of Southeast Asia.
Reptiles are the most-maligned of vertebrate groups; however, they are of particular importance to humans, both historically and in modern times. Some species are revered as religious symbols, while lizards and snakes are often valuable for controlling insect and rodent pests. While, as with other animal groups, habitat loss is the major factor threatening reptile populations (25% of which are thought to be in decline), overexploitation by humans is an important factor in many declines, a fact which testifies to the importance of these animals for food, traditional medicines and, especially, the international pet trade. Indeed, reptiles recently overtook cats to become the most popular pets in the United Kingdom. By contrast, very few reptiles pose any danger to humans. Of 600 species of venomous snake, most are too small or their venom is too weak to be lethal to people, and many of the remainder live in environments where human contact is rare; most importantly, it is very rare for a snake to bite unprovoked, and human fatalities are almost invariably the result of humans distressing or mishandling animals. Only five species of crocodile have been responsible for documented attacks on humans, and only two (the estuarine crocodile and the Nile crocodile) are regarded as aggressive.