Causinae
Encyclopedia
The Causinae are a monotypic
subfamily of venomous
viper
s found only in subsaharan Africa. It was created for the genus
Causus; a group considered to be among the most primitive members of the family Viperidae
based on head scalation, oviparity, venom apparatus and the fact that they have round pupils. However, this is contradicted by recent molecular studies. Six species are currently recognized. They are commonly known as night adders.
As opposed to most viper
s where the head is distinct from the neck and covered with small scales, in Causus the head is only slightly distinct from the neck and covered with 9 large symmetrical head shields. Also, the eyes have pupils that are round instead of elliptical like other vipers. The rostral scale is broad, sometimes pointed or upturned. The nostril is located between 2 nasals and an internasal. The frontal and supraocular scales
are long. A loreal scale is present, separating the nasal and preoculars. The suboculars are separated from the supralabials. The mandible has splenial and angular elements.
The fangs are different too. Unlike other vipers there is no hinge action where the prefrontal bone engages the frontal. However, since the maxillary bones rotate almost as far, the fangs can still be erected. The fangs themselves are relatively short. A fine line, or suture, is also present along the length of the fang, representing the vestigial edge where the groove lips meet (from incomplete fang canal closure).
The body is cylindrical or slightly depressed and moderately slender. The dorsal scales are smooth or weakly keeled with apical pits. The ventral scales are rounded and the anal plate single. The tail is short and the subcaudals can be either single or paired.
Among the viperids, another unique characteristic of this genus is that several species have venom glands that are not confined to the temporal area as with most vipers, but are exceptionally long and extend well down the neck. These venom glands, located on either side of the spine, may be up to 10 cm in length, with long ducts connecting them to the fangs.
There are also other internal differences that set the Causinae apart: they have unusually long kidneys, a well-developed tracheal lung with two tracheal arteries, and the liver overlaps the tip of the heart.
s and frog
s. There are reports of gluttony: when prey is abundant, they may eat until they are literally unable to swallow any more food.
s is considered to be a more primitive trait, though not unique. The average clutch consists of some two dozen eggs that require an incubation period of about 4 months. Hatchlings are 4-5 inches (10-12.5 cm) in length.
Causus venom is weak and tends only to dribble from the fangs, so that relatively little is ever injected. Envenomation normally causes only local pain and swelling. Antivenin treatment should not be necessary. Nevertheless, South African polyvalent serum is known to be effective against the venom of at least two species.
No recent deaths have been reported due to this species. Earlier reports of fatalities were based on anecdotal evidence; it is likely the species involved were not properly identified or that the cases were grossly mismanaged.
T) Type species
.
s to make assumptions regarding the phylogenetic
position of this group. McDiarmid et al. suggested that the consensus among the experts in 1999 was that Causus was basal to all viperids
and therefore deserved a separate subfamily. However, two more recent molecular phylogenitic studies have shown that Causus is not only not basal to all viperids
, but in fact appears to be nested within the viperines
. Consequently, recognition of the subfamily Causinae is inappropriate.
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
subfamily of venomous
Venomous snake
"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...
viper
Viperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
s found only in subsaharan Africa. It was created for the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Causus; a group considered to be among the most primitive members of the family Viperidae
Viperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
based on head scalation, oviparity, venom apparatus and the fact that they have round pupils. However, this is contradicted by recent molecular studies. Six species are currently recognized. They are commonly known as night adders.
Description
These snakes are fairly stout, never growing to more than 1 m in length.As opposed to most viper
Viperinae
The Viperinae, or viperines, are a subfamily of venomous vipers found in Europe, Asia and Africa. They are distinguished by their lack of the heat-sensing pit organs that characterize their sister group, the Crotalinae. Currently, 12 genera and 66 species are recognized...
s where the head is distinct from the neck and covered with small scales, in Causus the head is only slightly distinct from the neck and covered with 9 large symmetrical head shields. Also, the eyes have pupils that are round instead of elliptical like other vipers. The rostral scale is broad, sometimes pointed or upturned. The nostril is located between 2 nasals and an internasal. The frontal and supraocular scales
Supraocular scales
In scaled reptiles, supraocular scales are scales on the crown immediately above the eye. The size and shape of these scales are among the many characteristics used to differentiate species from each another....
are long. A loreal scale is present, separating the nasal and preoculars. The suboculars are separated from the supralabials. The mandible has splenial and angular elements.
The fangs are different too. Unlike other vipers there is no hinge action where the prefrontal bone engages the frontal. However, since the maxillary bones rotate almost as far, the fangs can still be erected. The fangs themselves are relatively short. A fine line, or suture, is also present along the length of the fang, representing the vestigial edge where the groove lips meet (from incomplete fang canal closure).
The body is cylindrical or slightly depressed and moderately slender. The dorsal scales are smooth or weakly keeled with apical pits. The ventral scales are rounded and the anal plate single. The tail is short and the subcaudals can be either single or paired.
Among the viperids, another unique characteristic of this genus is that several species have venom glands that are not confined to the temporal area as with most vipers, but are exceptionally long and extend well down the neck. These venom glands, located on either side of the spine, may be up to 10 cm in length, with long ducts connecting them to the fangs.
There are also other internal differences that set the Causinae apart: they have unusually long kidneys, a well-developed tracheal lung with two tracheal arteries, and the liver overlaps the tip of the heart.
Behavior
Despite their common name, this genus is active during the day as well as at night. When disturbed, they will engage in a ferocious hissing and puffing threat display. It may lift the first part of its body off the ground in a coil and make a powerful swiping strike—juveniles have been known to come off the ground. Others specimens may raise the first part of their body off the ground, flattening the neck and moving forward, tongue extended, like a small cobra. The rather frantic strikes are often combined with attempts to quickly glide away.Feeding
The diet consists almost exclusively on toadToad
A toad is any of a number of species of amphibians in the order Anura characterized by dry, leathery skin , short legs, and snoat-like parotoid glands...
s and frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s. There are reports of gluttony: when prey is abundant, they may eat until they are literally unable to swallow any more food.
Reproduction
All Causus species lay eggs (oviparious), which among viperViperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
s is considered to be a more primitive trait, though not unique. The average clutch consists of some two dozen eggs that require an incubation period of about 4 months. Hatchlings are 4-5 inches (10-12.5 cm) in length.
Captivity
Best kept in dry and well-ventilated cages that include places to hide, fresh water and a basking spot slightly warmer than the rest of the cage (26 to 27 °C). They will accept pre-killed mice as food, but as they are voracious feeders, care must be taken to prevent obesity by overfeeding.Venom
In spite of their enormously developed venom glands, night adders don't always use them to subdue their prey. The venom would act fast enough, but often they simply seize and swallow their prey instead.Causus venom is weak and tends only to dribble from the fangs, so that relatively little is ever injected. Envenomation normally causes only local pain and swelling. Antivenin treatment should not be necessary. Nevertheless, South African polyvalent serum is known to be effective against the venom of at least two species.
No recent deaths have been reported due to this species. Earlier reports of fatalities were based on anecdotal evidence; it is likely the species involved were not properly identified or that the cases were grossly mismanaged.
Species
| Species | Taxon author | Common name | Geographic range |
|---|---|---|---|
| C. bilineatus Causus bilineatus Causus bilineatus is a venomous viper species found in south central Africa. No subspecies are currently recognized. Common names include lined night adder and two-striped night adder.-Description:... |
Boulenger George Albert Boulenger George Albert Boulenger FRS was a Belgian-British zoologist who identified over 2000 new animal species, chiefly fish, reptiles and amphibians.-Life:... , 1905 |
Two-striped night adder | Africa Africa Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area... in Angola Angola Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city... , Zambia Zambia Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west.... , and southern DR Congo Democratic Republic of the Congo The Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world... . |
| C. defilippii Causus defilippii Causus defilippii is a venomous viper species found in East Africa. No subspecies are currently recognized. Its common name is snouted night adder.-Description:The average length is 20–35 cm, rarely exceeding 50 cm.... |
(Jan Giorgio Jan Giorgio Jan was an Italian taxonomist, zoologist, botanist, herpetologist, and writer. He is also known as Georg Jan or Georges Jan.... , 1863) |
Snouted night adder | Southeast Africa. |
| C. lichtensteinii Causus lichtensteinii Causus lichtensteinii is a venomous viper species found in western and central Africa. No subspecies are currently recognized. The specific name, or epithet, "lichtensteinii", honors German herpetologist Martin Hinrich Lichtenstein.-Description:... |
(Jan Giorgio Jan Giorgio Jan was an Italian taxonomist, zoologist, botanist, herpetologist, and writer. He is also known as Georg Jan or Georges Jan.... , 1859) |
Lichtenstein's night adder | Equatorial Africa Equatorial Africa Equatorial Africa is an ambiguous term that is sometimes used to refer to tropical Africa, or the region of Sub-Saharan Africa traversed by the equator.... from Zambia and Cameroon Cameroon Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the... to Ivory Coast. |
| C. maculatus Causus maculatus Causus maculatus is venomous viper species found mainly in West- and Central Africa. No subspecies are currently recognized. Common names include forest rhombic night adder, West African night adder and spotted night adder.... |
(Hallowell Edward Hallowell Edward Hallowell was an American herpetologist and physician.He studied and practiced medicine in Philadelphia. He also was a renowned herpetologist who described 55 new species of reptiles.... , 1842) |
West African night adder | Most of Sub-Saharan Africa Sub-Saharan Africa Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara... north of the equator. |
| C. resimus Causus resimus Causus resimus is a venomous viper species found in isolated populations distributed across tropical Africa. No subspecies are currently recognized.-Description:Averages 30-60 cm in length with a maximum of 75 cm. They appear relatively stout.... |
(Peters Wilhelm Peters Wilhelm Karl Hartwich Peters was a German naturalist and explorer.He was assistant to Johannes Peter Müller and later curator of the Berlin Zoological Museum. In September 1842 he travelled to Mozambique via Angola. He returned to Berlin with an enormous collection of natural history specimens... , 1862) |
Green night adder | Most of equatorial Africa. |
| C. rhombeatus Causus rhombeatus Causus rhombeatus is a venomous viper species found in subsaharan Africa. No subspecies are currently recognized.-Description:With an average length of 60 cm, this is the largest member of the genus Causus. The longest individual ever recorded was a 93 cm male collected in eastern Zimbabwe.The head... T |
(Lichtenstein Martin Lichtenstein Martin Hinrich Carl Lichtenstein was a German physician, explorer, zoologist, and herpetologist.-Biography:... , 1823) |
Common night adder | Sub-Saharan Africa. |
T) Type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
.
Taxonomy
There has been a long-standing tendency among herpetologistHerpetology
Herpetology is the branch of zoology concerned with the study of amphibians and reptiles...
s to make assumptions regarding the phylogenetic
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
position of this group. McDiarmid et al. suggested that the consensus among the experts in 1999 was that Causus was basal to all viperids
Viperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
and therefore deserved a separate subfamily. However, two more recent molecular phylogenitic studies have shown that Causus is not only not basal to all viperids
Viperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
, but in fact appears to be nested within the viperines
Viperinae
The Viperinae, or viperines, are a subfamily of venomous vipers found in Europe, Asia and Africa. They are distinguished by their lack of the heat-sensing pit organs that characterize their sister group, the Crotalinae. Currently, 12 genera and 66 species are recognized...
. Consequently, recognition of the subfamily Causinae is inappropriate.