Viperidae

(vertebrate zoology) A family of reptiles in the suborder Serpentes found in Eurasia and Africa; all species are proglyphodont.

(Viperidae)

Class: Reptilia

Order: Squamata

Suborder: Serpentes

Family: Viperidae

Thumbnail description
Small to large venomous snakes with hollow fangs attached to shortened, movable maxillary bones

Size
ca. 1–11.8 ft (30–360 cm)

Number of genera, species
36 genera; 256 species

Habitat
Deserts, steppes, mountains, forests, meadows, and savannas

Conservation status
Critically Endangered: 7 species; Endangered: 4 species; Vulnerable: 7 species; Data Deficient: 1 species

Distribution
Africa, Europe, Asia, North America, Central America, and South America

Evolution and systematics

Researchers have devoted considerable effort to reconstructing the phylogenetic history of the Viperidae, and, consequently, extensive revision of the classification of these snakes was done throughout the end of the twentieth century and has continued into the twenty-first century. Monophyly of the Viperidae is well supported by molecular and anatomical data. Available evidence suggests that the Viperidae is the most basal family of the Colubroidea, which also includes the Colubridae, Elapidae, and Atractaspididae. Four subfamilies are recognized.

The Causinae includes a single genus, Causus, with six species; the Viperinae includes 12 genera with 75 species; the Azemiopinae contains a single genus and species (Azemiops feae); and the pitvipers are classified in the Crotalinae, in which 22 genera and 174 species are recognized. With the possible exception of the Viperinae, the monophyly of each viperid subfamily is well supported by anatomical and molecular data. A potential synapomorphy of the Viperinae is the ventral course of the facial carotid artery, providing at least some support for the monophyly of this subfamily. The Causinae is thought to be sister to either all other viperids or only the Viperinae. The Azemiopinae is sister to the Crotalinae. As of 2002 almost all genera and subgenera recognized are monophyletic, although relationships among genera are not yet resolved fully.

Viperinae consists of Vipera, Macrovipera, Pseudocerastes, Eristicophis, Daboia, Echis, Cerastes, Atheris, Bitis, Proatheris, Adenorhinos, and Montatheris. The Eurasian genus Vipera is divided into the subgenera Vipera, Pelias, Montivipera, and Acridophaga, each with an evolutionary history that can be traced back to the Miocene through the fossil record or "molecular clock" calibrations. It is the same with the African genus Bitis, which is divided into the subgenera Bitis, Macrocerastes, Calechidna, and Keniabitis, each with its own evolutionary history, as inferred from molecular data. Unfortunately, there are no viper fossils known from tropical Africa. The genera of Old World pitvipers are Calloselasma, Deinagkistrodon, Ermia, Gloydius, Hypnale, Ovophis, Protobothrops, Triceratolepidophis, Trimeresurus, and Tropidolaemus, and the genera of New World pitvipers are Agkistrodon, Atropoides, Bothriechis, Bothriopsis, Bothrocophias, Bothrops, Cerrophidion, Crotalus, Lachesis, Ophryacus, Porthidium, and Sistrurus.

The region of origin for viperids remains undetermined. The earliest fossil specimens of this family are known from the Lower Miocene (ca. 20 million years ago) of Europe and West Asia. These findings are well documented, but there are no fossil records from the Oligocene, and there is a general opinion that the viperines arose somewhere else. The origin of African viperines has been dated to at least 50 million years before the present based on molecular evidence, and there is much support for a tropical African origin of the Viperidae.

The striking examples of convergent evolution between the Asian and American pitviper radiations had long obscured attempts to understand the phylogeny of these snakes; however, data from mitochondrial DNA sequences strongly suggest that pitvipers originated in Asia, and these findings are consistent with other lines of evidence. For example, the closest living relative of all pitvipers, Azemiops feae, is an Asian species. The earliest known fossil pitviper from the New World is from the Miocene. All New World pitvipers are descended from a single pitviper species that extended its range across the Bering Land Bridge into North America. Phylogenetic studies suggest that the original American pitviper resembled Gloydius blomhoffi in many respects.

Physical characteristics

In vipers or adders (Viperinae) and pitvipers (Crotalinae), the head is roughly triangular and is distinct from the rest of the body. The head bears nine symmetrical plates (as in Agkistrodon and Gloydius), fragmented head plates (as in many Vipera), or numerous small scales (as in Bitis and Ophryacus). The pupils are usually vertical and elliptical. All the face bones are movable. Each of the two shortened, retractile upper jawbones (maxillae) bears only the tubular venom fang (which can be activated only for a short period of time) and often one to several significantly smaller reserve teeth of various sizes, none being a firmly positioned poison fang. The tail is short, and the male copulatory organ is bifid (forked).

Viperines are generally compact, sturdy snakes, and their length ranges from 11.8 in (30 cm: dwarf puff adder) to 5.9 ft (180 cm: Gaboon adder). Coloration is usually drab, and in the genus Vipera it often includes a dark zigzag pattern or a rhomboid band along the back. Desert species are sand yellow, whereas jungle vipers often have a colorful carpet marking.

Pitvipers exhibit great variety of size, shape, and color, but any pitviper can be recognized easily by the deep, heat-sensitive pits, one on each side of the head, between the eye and the nostril. Color variation within the Crotalinae reflects the diversity of habitats occupied by these snakes: invariably, pitvipers are cryptic in their native haunts. In general, pitvipers are relatively stout, although some arboreal species may be more slender. Tail length varies from quite short in rattlesnakes to relatively long in most arboreal species. The tail is prehensile in species that are adapted fully to an arboreal existence. The longest viperids are pitvipers of the genus Lachesis, some specimens of which are known to reach 11.8 ft (3.6 m).

One of the most well-known and interesting features of pitvipers is the rattle, which is unique to the genera Crotalus and Sistrurus. A neonatal rattlesnake has a keratinized "button" at the tip of its tail; each time the snake sheds, a rattle segment is added. Segments of the rattle fit loosely together, so that a clearly audible sound is produced when the tail is vibrated. Interspecific variation in rattle size has considerable effect on the sound, with large species producing particularly loud and effective warnings. Because most rattlesnakes shed more than once a year and because the ends of rattles tend to break off in wild snakes, the number of rattle segments cannot be used as a direct indication of age.

Sometimes known as night adders, species of Causus are relatively small, terrestrial snakes with a stout body covered by weakly keeled scales. Nine plates cover the top of the head. The pupils are round, and the fangs are relatively short. Despite the short fangs, some species have very long venom glands. The sole living species of Azemiopinae is characterized by smooth scales and nine large plates on top of the head.

The most important distinguishing characteristic in all viperids is the venom apparatus. Their poison fangs have no sign of grooves; they actually have enclosed canals within the fangs that transmit venom out of the body, very much like a hypodermic needle. The two upper jawbones (maxillae), which bear the fangs, are very short. Each maxilla has a special joint that permits this bone, along with the fang anchored firmly within it, to rotate 90°. When the viper closes its mouth, the fangs lay back, tip inward, and are covered by a fold in the mucous membrane. When the mouth is opened, a lifting mechanism is activated, putting the fangs into a vertical position by means of the rod-shaped ectopterygoid bones and the pterygoid. The fangs are then in position to bite and inject venom. The fangs (or, more precisely, the maxillae) are laid back with the same action as when a pocketknife is snapped together. The adaptation of folding back the fangs (referred to as solenoglyphous dentition) permits them to be extremely long, far exceeding the length of those in such snakes as cobras, which bear fangs that are fixed in the down, or vertical, position. The fangs of the giant king cobra are not much longer than those of the rather small adder. The long fangs enable vipers to bite deeply into the tissues and cause the victim to suffer severe necrosis. The fangs fold back into the mouth after they are withdrawn from the victim.

Viper venom contains primarily hematoxic material (i.e., substances injurious to the blood and the blood vessels). Thus, a viper bite typically has a very different effect from a cobra or mamba bite (their venom being primarily neurotoxic, that is, injurious to the nervous system). Viper bites are accompanied by prominent local irritation and symptoms of severe blood poisoning, with burning pain, inflamed swellings, pronounced discoloration, sudden drop in blood pressure, internal bleeding, degeneration of the tissues, and the formation of an abscess. Death ensues because the heart stops, not as the result of respiratory arrest, as in cobra bites. Some vipers, whose venom contains neurotoxic as well as hematoxic substances, are especially dangerous.

Distribution

Viperines, Causus, and Azemiops are found only in the Old World (Europe, Asia, and Africa), but crotalines inhabit both the Eastern and Western Hemispheres. Australia lacks viperids, suggesting that this family evolved after the Australian continent became a separate landmass. The distribution of Causus is restricted to sub-Saharan Africa. Azemiops occurs in southern China, Burma (Myanmar), Laos, and Vietnam. Viperines are distributed in Africa, Europe, and Asia. Crotalines are found in North America, Central America, and South America as well as East Asia and Central Asia. One species (Gloydius halys) enters Europe north of the Caspian Sea.

Habitat

Viperines occur in both tropical and temperate environments, and species have adapted to numerous microhabitats. In temperate regions, species also migrate between different habitats during their active season. The common adder, Vipera berus, moves to meadow habitats with populations of rodents during the summer feeding period, whereas it often occurs on south-facing rocky slopes during the spring and mating periods. Distinct groups of vipers have different connections to special habitats. Macrovipera species occur in dry steppe habitats, whereas the subgenus Montivipera is affiliated with rocky habitats in mountains, the subgenus Pelias with moist grasslands, the subgenus Acridophaga with dry grasslands, and so on. In tropical habitats most species are terrestrial, but Atheris species are arboreal. Of the terrestrial species, some are connected to wet forests (Bitis gabonica and B. nasicornis), and others are savanna inhabitants (B. arietans).

Pitvipers also occupy a wide variety of habitats in temperate and tropical regions. These habitats include temperate forests (Gloydius caliginosus and Agkistrodon contortrix), tropical wet forests (Hypnale hypnale and Bothrocophias hyoprora), tropical deciduous forests (Calloselasma rhodostoma and Porthidium ophryomegas), montane pine-oak forests (Crotalus willardi), cloud forests (Atropoides nummifer), deserts (Crotalus cerastes), and grasslands (Sistrurus catenatus). Several genera of tropical pitvipers (Bothriechis, Bothriopsis, Trimeresurus, and Tropidolaemus) are specialized for an arboreal existence, but most pitviper species are primarily terrestrial. Even terrestrial species occasionally are encountered in trees or shrubs, however. The cottonmouth (Agkistrodon piscivorus) is semiaquatic.

Behavior

Some viperids move over large areas in search of prey during their active season, whereas others are more sedentary. In temperate areas vipers and pitvipers hibernate for several months, and some species (Vipera dinniki, V. darevskii, and Gloydius monticola) at high elevations can hibernate for twothirds of the year. There is no real territoriality, but in some species, such as V. berus, the males actively protect areas around reproductive females during the mating period.

Some vipers inflate their bodies into sausage shapes when they are excited. Almost all vipers also can assume a plate-shaped coiled position as a threat gesture, in which they lift up the neck and hold it in an S shape. Other threat behaviors include loud hissing and rapid forward jerks of the head. Some sand dwellers, such as the saw-scaled vipers, create a particularly impressive sound by rubbing their scales together. Many species of pitvipers vibrate their tails when disturbed, and the evolution of the rattle resulted in amplifiction of the sound produced by this behavior. Several pitviper species (e.g., Agkistrodon piscivorus and Bothriechis schlegelii) give a silent but effective warning by gaping to reveal the bright white lining of the mouth.

Feeding ecology and diet

Viperids feed chiefly on small vertebrates, particularly rats, mice, and lizards, and less often on frogs and birds, paralyzing or killing their prey by biting it. Some of the smallest vipers prefer locusts, and various other vertebrate and invertebrate prey types are known. Many viperids are ambushers and generally lie in wait for their prey, sitting quietly in one spot for long periods of time. Other species may forage actively or employ a combination of active and ambush foraging. The most specialized ambushers may feed quite infrequently. Many species show an ontogenetic shift in prey preference, feeding on small ectotherms (e.g., lizards and frogs) as juveniles and taking endotherms (e.g., rodents) when they are adults. Caudal luring has been observed in juveniles of several viperid species (e.g., Bitis peringueyi and Agkistrodon contortrix), and this behavior is retained in adults of Bothriopsis bilineata. Associated with caudal luring is a distinctive coloration of the tail tip—from black to brown to bright yellow or bright green, depending on the species. Many species withdraw the head immediately after striking prey and subsequently locate the prey by using their Jacobson's organ. Other species, including many arboreal species, hold the prey until it is immobilized and then swallow it. Many vipers are useful for controlling rodent pests.

Reproductive biology

Most viperids have an annual or biennial breeding cycle. A biennial cycle normally is encountered in females in temperate regions, as in Europe, but in some species (e.g., Crotalus horridus) females may reproduce much less frequently. Males always have annual reproduction, which means that reproductive males always outnumber reproductive females in the local population. In Vipera berus the production of sperm takes place during the fall and the following spring, whereas in V. aspis ripe sperm is ready in late fall. In the former species mating is a spring event, triggered by the first molt for the season in males; in the latter species mating can take place during both fall and spring, even if spring mating is most common. In this case the spring molt is not involved in the start of mating activities.

In some genera, such as Vipera, Bitis, Agkistrodon, and Crotalus, males engage in ritualized fights that once were interpreted falsely as mating ceremonies. They lift their heads and approach each other in this vertical position, wrap their bodies around each other, and push with their fore bodies, head to head. In Vipera berus a male hierarchy becomes established, and the dominant male is the first to copulate with a female. By activating a sphincter muscle in the female genital tract, a copulatory plug effect is created temporarily. This lessens the possibility that additional males will fertilize the eggs. In some tropical genera a more lengthy breeding season is reported.

Most viperids are ovoviviparous, bearing live young that hatch from membranous eggs. Pregnancy time, meaning the time from ovulation to birth, is normally about 2.5 months for European vipers. Some viperids (e.g., Lachesis and Deinagkistrodon) lay eggs. The night adders (Causinae) of Africa and the rare Fea's viper (Azemiopinae) of Asia also lay eggs. Incubation has not been noted in any viperine species, nor has any kind of parental care, but egg or neonate attendance has been documented in various pitviper species.

Conservation status

Four viperine species are listed in CITES: Indian Daboia russelii is in Appendix III; Vipera wagneri is in Appendix II, and V. latifii and populations of V. ursinii from regions outside former Soviet territories are in Appendix I. Honduras has seven pitviper species listed in CITES Appendix III: Agkistrodon bilineatus, Atropoides nummifer, Bothriechis schlegelii, Bothrops asper, Crotalus durissus, Porthidium nasutum, and P. ophryomegas. The IUCN lists 19 viperid taxa: 7 as Critically Endangered, 4 as Endangered, 7 as Vulnerable, and 1 as Data Deficient. Habitat destruction is a serious threat to viperid species throughout their range, and several species are threatened by intentional persecution by humans. Many species have extremely limited distributions (e.g., Bothrops insularis and B. alcatraz), leaving them vulnerable to local disturbances. Details of the natural history (including geographic distribution and species limits) of most viperids are not well known, and the number of species listed by CITES and the IUCN probably represents a serious underestimate of the conservation problems affecting this family.

Significance to humans

Bites from viperids are problems at the local level. Snake bites kill 30,000–40,000 people in the world each year. The majority of snakebite cases occur in Asia, with India having the highest number, 10,000–15,000 deaths per year. Vipers such as Daboia russellii and Echis carinatus contribute to a large number of these incidents. Viperids have figured prominently in the legends and religious ceremonies of many cultures. For example, in the first edition of Grzimek's Animal Life Encyclopedia, H.-G. Petzold provided an account of the Hopi snake dance. Certain Christian groups in the southeastern United States "take up serpents" such as Crotalus horridus and Agkistrodon contortrix, as part of their religious ceremonies, grasping the snakes at midbody and dancing with them. The pharmaceutical ancrod (an anticoagulant) is derived from the venom of Calloselasma rhodostoma. In the Old World, viperids are hunted for use in traditional medicine, and in the New World they are persecuted during organized events called rattlesnake roundups. Viperids play critical roles in food webs that affect humans.

Species accounts

Resources

Campbell, Jonathan A., and Edmund D. Brodie Jr. Biology of the Pitvipers. Tyler, TX: Selva, 1992.

Campbell, Jonathan A., and William W. Lamar. The Venomous Reptiles of Latin America. Ithaca, NY: Cornell University Press, 1989. ——. The Venomous Reptiles of the Western Hemisphere. Ithaca, NY: Cornell University Press, 2003.

Ernst, Carl H. Venomous Reptiles of North America. Washington, DC: Smithsonian Institution Press, 1992.

Gloyd, Howard K., and Roger Conant. Snakes of the Agkistrodon Complex: A Monographic Review. Vol. 6, Contributions to Herpetology. Oxford, OH: Society for the Study of Amphibians and Reptiles, 1990.

Jena, I. Snakes of Medical Importance and Snake-bite Treatment. New Delhi: Ashish Publishing House, 1985.

Mallow, D., D. Ludwig, and G. Nilson, True Vipers: Natural History and Toxinology of Old World Vipers. Melbourne, FL: Krieger Publishing Company, 2003.

Nilson, G., and C. Andrén. "Evolution, Systematics and Biogeography of Palearctic Vipers." In Venomous Snakes: Ecology, Evolution and Snakebite, edited by R. S. Thorpe, W. Wüster, and A. Malhotra. Symposia of the Zoological Society of London. London: Oxford University Press, 1997.

Palmer, T. Landscape with Reptile: Rattlesnakes in an Urban World. New York: Ticknor and Fields, 1992.

Schuett, Gordon W., Mats Höggren, Michael E. Douglas, and Harry W. Greene, eds. Biology of the Vipers. Eagle Mountain, UT: Eagle Mountain Publishing, 2002.

Spawls S., and B. Branch. The Dangerous Snakes of Africa. Sanibel Island, FL: Ralph Curtis Books, 1995.

Lenk P., S. Kalyabina, M. Wink, and U. Joger. "Evolutionary Relatonships Among the True Vipers (Viperinae) Inferred from Mitochondrial DNA Sequences." Molecular Phylogenetics and Evolution 19, no. 1 (2001): 94–104.

Parkinson, C. L. "Molecular Systematics and Biogeographical History of Pitvipers as Determined by Mitochondrial Ribosomal DNA Sequences." Copeia (1999): 576–586.

Parkinson, C. L., K. M. Zamudio, and H. W. Greene. "Phylogeography of the Pitviper Clade Agkistrodon: Historical Ecology, Species Status, and Conservation of Cantils." Molecular Ecology 9 (2000): 411–420.

Warrell D. "Tropical Snakebite: Clinical Studies in South East Asia." Toxicon 23 (1985): 543.

[Article by: Göran Nilson, PhD; Ronald L. Gutberlet, Jr., PhD]

The noun has one meaning:

Meaning #1: Old World vipers
  Synonym: family Viperidae

Vipers
Asp viper, Vipera aspis
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae Oppel, 1811
Synonyms
Viperae - Laurenti, 1768 Viperini - Oppel, 1811 Viperidae - Gray, 1825[1]

Common names: vipers, viperids.

The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, New Zealand, Ireland, Madagascar, Hawaii and the Arctic Circle. All have relatively long hinged fangs that permit deep penetration and injection of venom. Four subfamilies are currently recognized.^[2]

Contents 1 Description 2 Geographic range 3 Behaviour 4 Venom 5 Subfamilies 6 Taxonomy 7 See also 8 References 9 Further reading 10 External links

Description

All viperids have a pair of relatively long solenoglyphous (hollow) fangs that are used to inject venom from glands located towards the rear of the upper jaws. Each of the two fangs is at the front of the mouth on a short maxillary bone that can rotate back and forth. When not in use, the fangs fold back against the roof of the mouth and are enclosed in a membranous sheath. The left and right fangs can be rotated together or independently. During a strike, the mouth can open nearly 180° and the maxilla rotates forward, erecting the fangs as late as possible so as the fangs do not become damaged. The jaws close on impact and powerful muscles that surround the venom glands contract to inject the venom as the fangs penetrate. This action is very fast; in defensive strikes it can be more a stab than a bite. Viperids use this mechanism primarily for immobilization and digestion of prey. Secondarily it is used for self-defense, though in most cases with non-prey items such as humans they are more likely to give a dry bite (not inject any venom).

Almost all vipers have keeled scales, a stocky build with a short tail, and, due to the location of the venom glands, a triangular-shaped head distinct from the neck. The great majority have vertically elliptical, or slit-shaped, pupils that can open wide to cover most of the eye or close almost completely, which helps them to see in a wide range of light levels. Typically, vipers are nocturnal and ambush their prey.

Compared to many other snakes, vipers often appear rather sluggish. Most are ovoviviparous, giving birth to live young, but a few lay eggs; the word "viper" is derived from Latin vivo = "I live" and pario = "I give birth".^[3]

Geographic range

Found in the Americas, Africa and Eurasia. In the Americas from southern Canada south through the United States, Mexico, Central America and into South America as far south as Argentina. Throughout Africa. In Eurasia from Spain, England and most of Scandinavia in the west, to within the Arctic Circle in the north, to the Sea of Okhotsk in the east, and to the Arabian Peninsula, India, and Maritime Southeast Asia in the south (including Java, Celebes and the Philippines).^[1] The Viperidae can be located on all continents except Antarctica and Australia.

Behaviour

Experiments have shown that these snakes are capable of making decisions on how much venom to inject depending on the circumstances. In all cases, the most important determinant of venom expenditure is generally the size of the snake, with larger specimens being capable of delivering much more venom. The species is also important, since some are likely to inject more venom than others, may have much venom available, strike more accurately, or deliver a number of bites in a short space of time. In predatory bites, factors that influence the amount of venom injected include the size of the prey, the species of prey, and whether the prey item is held or released. The need to label prey for chemosensory relocation after a bite and release may also play a role. In defensive bites, the amount of venom injected may be determined by the size or species of the predator (or antagonist), as well as the assessed level of threat, although larger assailants and higher threat levels may not necessarily lead to larger amounts of venom being injected.^[4]

Venom

Viperid venoms typically contain an abundance of protein-degrading enzymes, called proteases, that produce symptoms such as pain, strong local swelling and necrosis, blood loss from cardiovascular damage complicated by coagulopathy, and disruption of the blood clotting system. Death is usually caused by collapse in blood pressure. This is in contrast to elapid venoms that generally contain neurotoxins that disable muscle contraction and cause paralysis. Death from elapid bites usually results from asphyxiation because the diaphragm can no longer contract. However, this rule does not always apply: some elapid bites include proteolytic symptoms typical of viperid bites, while some viperid bites produce neurotoxic symptoms.^[5]

Proteolytic venom is also dual-purpose: it is used for defense and to immobilize prey, as with neurotoxic venoms, and also many of the enzymes have a digestive function, breaking down molecules in prey items, such as lipids, nucleic acids, and proteins.^[5] This is important, as many vipers have weak digestive systems.^[6]

Due to the nature of proteolytic venom, a viperid bite is often a very painful experience and should always be taken seriously, even though it is not necessarily fatal. Even with prompt and proper treatment, a bite can still result in a permanent scar, and in the worst cases the affected limb may even have to be amputated. A victim's fate is impossible to predict as this depends on many factors, including (but not limited to) the species and size of the snake involved, how much venom was injected (if any), and the size and condition of the patient before being bitten. The patient may also be allergic to the venom and/or the antivenin.

Subfamilies

Subfamily[2]	Taxon author[2]	Genera[2]	Species[2]	Common name	Geographic range[1]
Azemiopinae	Liem, Marx & Rabb, 1971	1	1	Fea's viper	Myanmar, southeastern Tibet across southern China (Fujien, Guangxi, Jiangxi, Kweichow, Sichuan, Yunnan, Zhejiang) to northern Vietnam.
Causinae	Cope, 1859	1	6	Night adders	Subsaharan Africa
Crotalinae	Oppel, 1811	18	151	Pit vipers	In the Old World from eastern Europe eastward through Asia to Japan, Taiwan, Indonesia, peninsular India and Sri Lanka. In the New World from southern Canada southward through Mexico and Central America to southern South America.
Viperinae	Oppel, 1811	12	66	True or pitless vipers	Europe, Asia and Africa.

Type genus = Vipera - Laurenti, 1768^[1]

Taxonomy

That Viperidae is attributed to Oppel (1811), as opposed to Laurenti (1768) or Gray (1825), is subject to some interpretation. However, the consensus among leading experts is that Laurenti used viperae as the plural of vipera (Latin for "viper", "adder", or "snake") and did not intend for it to indicate a family group taxon. Rather, it is attributed to Oppel, based on his Viperini as a distinct family group name, despite the fact that Gray was the first to use the form Viperinae.^[1]

See also

• Viperidae by common name
• Viperidae by taxonomic synonyms
• List of snakes, overview of all snake families and genera.
• Snakebite

References

1. ^ ^{a b c d e} McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
2. ^ ^{a b c d e} Viperidae (TSN 174294). Integrated Taxonomic Information System. Retrieved on 10 August 2006.
3. ^ Schuett GW, Höggren M, Douglas ME, Greene HW. 2002. Biology of the Vipers. Eagle Mountain Publishing, LC. 580 pp. 16 plates. ISBN 0-9720154-0-X.
4. ^ Hayes WK, Herbert SS, Rehling GC, Gennaro JF. 2002. Factors that influence venom expenditure in viperids and other snake species during predatory and defensive contexts. In Schuett GW, Höggren M, Douglas ME, Greene HW. 2002. Biology of the Vipers. Eagle Mountain Publishing, LC. 580 pp. 16 plates. ISBN 0-9720154-0-X.
5. ^ ^{a b} Slowinski J. 2000. Striking Beauties: Venomous Snakes at California Wild. Vol. 53:2. Accessed 2 December 2006.
6. ^ Smith SA. 2004. Did Someone Say... SSSSnakes? at Maryland Dept. of Natural Resources. Accessed 2 December 2006.

Further reading

• Gray JE. 1825. A synopsis of the genera of reptiles and Amphibia, with a description of some new species. Annals of Philosophy, new ser., 10: 193-217.
• Laurenti JN. 1768. Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena et antidota reptilium Austriacorum. J.T. de Trattnern, Wien. 214 pp.
• Oppel M. 1811. Mémoire sur la classification des reptiles. Ordre II. Reptiles à écailles. Section II. Ophidiens. Annales du Musée National d'Histoire Naturelle, Paris 16: 254-295, 376-393.

External links

• Sri Lanka Reptile database

Wikimedia Commons has media related to: Viperidae

• Viperidae at the TIGR Reptile Database. Accessed 3 November 2008.

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