''Bitis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

venomous Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

vipers found in

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and the southern

Arabian Peninsula The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plat ...

. It includes the largest and the smallest vipers in the world. Members are known for their characteristic threat displays that involve inflating and deflating their bodies while hissing and puffing loudly. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

for this genus is '' B. arietans'', which is also the most widely distributed viper in Africa. Currently, 18

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

are recognized. Members of the genus are commonly known as African adders,Mallow D, Ludwig D, Nilson G. 2003. ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. 359 pp. . African vipers,Spawls S, Branch B. 1995. ''The Dangerous Snakes of Africa''. Dubai: Ralph Curtis Books. Oriental Press. 192 pp. . or puff adders.

Description

Size variation within this genus is extreme, ranging from the very small '' B. schneideri'', which grows to a maximum of and is perhaps the world's smallest viperid, to the very large '' B. gabonica'', which can attain a length over and is the heaviest viper in the world. All have a wide, triangular head with a rounded snout, distinct from the neck, and covered in small, keeled, imbricated scales. The

canthus The canthus (pl. canthi, palpebral commissures) is either corner of the eye where the upper and lower eyelids meet. More specifically, the inner and outer canthi are, respectively, the medial and lateral ends/angles of the palpebral fissure. T ...

is also distinct. A number of species have enlarged

rostral Rostral may refer to: Anatomy * Rostral (anatomical term), situated toward the oral or nasal region * Rostral bone, in ceratopsian dinosaurs * Rostral organ, of certain fish * Rostral scale, in snakes and scaled reptiles Other uses * Rostral ...

or supraorbital scales that resemble horns. Their eyes are relatively small. They have large nostrils that are directed outwards and/or upwards. Up to six rows of small scales separate the rostral and

nasal scales In reptiles, the nasal scale refers to the scale that encloses the nostril.Mallow D, Ludwig D, Nilson G. 2003. True Vipers: Natural History and Toxinology of Old World Vipers. Malabar, Florida: Krieger Publishing Company. 359 pp. . Sometimes this ...

. All species have a well-developed supranasal sac. The fronts of the maxillary bones are very short, supporting only one pair of recurved fangs.U.S. Navy. 1965. ''Poisonous Snakes of the World''. Washington, District of Columbia: United States Government Printing Office. 212 pp. These snakes are moderately to extremely stout. Their bodies are covered with

keeled scales Keeled scales refer to reptile scales that, rather than being smooth, have a ridge down the center that may or may not extend to the tip of the scale, Campbell, J. A., Lamar, W. W. (2004). ''The Venomous Reptiles of the Western Hemisphere''. Itha ...

that are imbricated (overlapping) with apical pits. At midbody, the

dorsal scales In snakes, the dorsal scales are the longitudinal series of plates that encircle the body, but do not include the ventral scales. Campbell JA, Lamar WW (2004). ''The Venomous Reptiles of the Western Hemisphere''. Ithaca and London: Comstock Publ ...

number 21–46. Laterally, the dorsal scales may be slightly oblique. The

ventral scales In snakes, the ventral scales or gastrosteges are the enlarged and transversely elongated scales that extend down the underside of the body from the neck to the anal scale. When counting them, the first is the anteriormost ventral scale that cont ...

, which number 112–153, are large, rounded, and sometimes have slight lateral keels. Their tails are short. The

anal scale Anal may refer to: Related to the anus *Related to the anus of animals: ** Anal fin, in fish anatomy ** Anal vein, in insect anatomy ** Anal scale, in reptile anatomy *Related to the human anus: ** Anal sex, a type of sexual activity involving ...

is single. The paired subcaudal scales number 16-37 and are sometimes keeled laterally.

Geographic range

Puff adders are found in

and the southern

Behavior

''Bitis'' species are known for their behavior of inflating and deflating their bodies in loud hissing or puffing threat displays. They are

terrestrial Terrestrial refers to things related to land or the planet Earth. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...

ambush predators, and appear sluggish, but can strike with amazing speed. In contrast to the pitvipers of the subfamily

Crotalinae The Crotalinae, commonly known as pit vipers,Mehrtens JM (1987). ''Living Snakes of the World in Color''. New York: Sterling Publishers. 480 pp. . crotaline snakes (from grc, κρόταλον ''krotalon'' castanet), or pit adders, are a subfa ...

, ''Bitis'' species appear to lack heat-sensitive organs and showed no differences in their behavior in laboratory tests towards warm and cool objects that mimicked prey.

Reproduction

All members are

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...

and some give birth to large numbers of offspring.

Venom

All members of this genus are dangerous – some extremely so. At least six different polyvalent antivenoms are available. Five are produced by Aventis Pasteur (France), Pasteur Merieux (France) and SAIMR (South Africa). All of these specifically protect against '' B. arietans'' and four also cover '' B. gabonica''.''Bitis arietans'' antivenoms
a
Munich AntiVenom INdex
Accessed 25 August 2006.
a
Munich AntiVenom INdex
Accessed 25 August 2006. At least one protects specifically against bites from '' B. nasicornis'': India Antiserum Africa Polyvalent.Miami-Dade Fire Rescue Venom Response Unit
a
VenomousReptiles.org
. Accessed 5 September 2006. In the past, such antivenoms have been used to treat bites from other ''Bitis'' species, but with mixed results.

Species

''*) Not including the nominate subspecies.''
^T'')

Type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

Taxonomy

Other species may be encountered in literature, such as: * ''B. albanica'' – Hewitt, 1937 * ''B. armata'' – Smith, 1826 Lenk et al. (1999) used molecular data (immunological distances and mitochondrial DNA sequences) to estimate the phylogenetic relationships among species of ''Bitis''. They identified four major monophyletic groups for which they created four

subgenera In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between ...

: * ''Bitis'' – '' B. arietans'' * ''Calechidna'' – ''B. albanica'', ''B. armata'', '' B. atropos'', '' B. caudalis'', '' B. cornuta'', '' B. heraldica'', '' B. inorata'', '' B. peringueyi'', '' B. rubida'', '' B. schneideri'', '' B. xeropaga'' * ''Macrocerastes'' – '' B. gabonica'', '' B. nasicornis'', '' B. parviocula'' * ''Keniabitis'' – '' B. worthingtoni'' For now, this division is of little consequence as far as the nomenclature is concerned. However, the definition of subgenera within a genus is often the sign of an impending split. Therefore, those interested in these snakes would do well to familiarize themselves with these new subgenera.

References

External links

*
Southern adder (''Bitis armata'')
a
ARKive
Accessed 5 October 2006. {{Taxonbar, from=Q574527 Snake genera Taxa named by John Edward Gray