Post by Gorilla king on Jul 19, 2021 8:33:10 GMT -5
The African elephant (Loxodonta) is a genus comprising two living elephant species, the African bush elephant (L. africana) and the smaller African forest elephant (L. cyclotis). Both are social herbivores with grey skin, but differ in the size and color of their tusks and in the shape and size of their ears and skulls.
African bush elephant bull in Kruger National Park
Both species are considered at heavy risk of extinction on the IUCN Red List; as of 2021, the bush elephant is considered endangered and the forest elephant is considered critically endangered. They are threatened by habitat loss and fragmentation, and poaching for the illegal ivory trade is a threat in several range countries as well.
Loxodonta is one of two extant genera of the family Elephantidae. The name refers to the lozenge-shaped enamel of their molar teeth. Fossil remains of Loxodonta species have been excavated in Africa, dating to the Middle Pliocene.
Taxonomy
The first scientific description of the African elephant was written in 1797 by Johann Friedrich Blumenbach, who proposed the scientific name Elephas africanus.[3]Loxodonte was proposed as generic name for the African elephant by Frédéric Cuvier in 1825. This name refers to the lozenge-shaped enamel of the molar teeth, which differs significantly from the rounded shape of the Asian elephant's molar enamel.[4] An anonymous author used the Latinized spelling Loxodonta in 1827.[5] Anonymous was recognized as authority by the International Code of Zoological Nomenclature in 1999.[1]
Elephas (Loxodonta) cyclotis was proposed by Paul Matschie in 1900, who described three African elephant zoological specimens from Cameroon whose skulls differed in shape from elephant skulls collected elsewhere in Africa.[6] In 1936, Glover Morrill Allen considered this elephant to be a distinct species and called it 'forest elephant';[7] later authors considered it to be a subspecies.[8][9][2] Morphological and genetic analyses provided evidence for species-level differences between the African bush elephant and the African forest elephant.[10][11][12][13][14]
In 1907, Richard Lydekker proposed six African elephant subspecies based on the different sizes and shapes of their ears.[15] They are all considered synonymous with the African bush elephant.[1]
A third species, the West African elephant, has also been proposed but it needs confirmation; it is thought that this lineage has been isolated from the others for 2.4 million years.[16]
Extinct African elephantsEdit
Between the late 18th and 20th centuries, the following extinct African elephants were described on the basis of fossil remains:
North African elephant (Loxodonta africana pharaohensis) proposed by Paulus Edward Pieris Deraniyagala in 1948 was a specimen from Fayum in Egypt.[17]Loxodonta atlantica was proposed as Elephas atlanticus by Auguste Pomel in 1879 based on a skull and bones found in Ternifine, Algeria.[18]Loxodonta exoptata proposed by Wilhelm Otto Dietrich in 1941 was based on teeth found in Laetoli, Tanzania.[19]Loxodonta adaurora proposed by Vincent Maglio in 1970 was a complete skeleton found in Kanapoi, Kenya.[20]PhylogenyEdit
Analysis of nuclear DNA sequences indicates that the genetic divergence between African bush and forest elephants dates 2.6 – 5.6 million years ago. The divergence between the Asian elephant and the woolly mammoths is estimated 2.5 – 5.4 million years ago, which strongly supports their status as distinct species. The African forest elephant was found to have a high degree of genetic diversity, perhaps reflecting periodic fragmentation of their habitat during the climatic changes in the Pleistocene.[13]
Gene flow between the two African elephant species was examined at 21 locations. The analysis revealed that several African bush elephants carried mitochondrial DNA of African forest elephants, indicating they hybridised in the savanna-forest transition zone in ancient times.[21]
Sequence analysis of DNA from fossils of the extinct Eurasian Palaeoloxodon antiquus shows it to be much closer related to the African forest elephant than to the African bush elephant. The validity of Loxodonta has therefore been questioned.[22]
Description
African elephants have grey folded skin up to 30 mm (1.2 in) thick that is covered with sparse bristled dark-brown to black hair. Short tactile hair grows on the trunk, which has two finger-like processes at the tip, whereas Asian elephants only have one.[8] Their large ears help to reduce body heat; flapping them creates air currents and exposes the ears' inner sides where large blood vessels increase heat loss during hot weather. The trunk is a prehensile elongation of its upper lip and nose. This highly sensitive organ is innervated primarily by the trigeminal nerve, and thought to be manipulated by about 40,000–60,000 muscles. Because of this muscular structure, the trunk is so strong that elephants can use it for lifting about 3% of their own body weight. They use it for smelling, touching, feeding, drinking, dusting, producing sounds, loading, defending and attacking.[23] Elephants sometimes swim underwater and use their trunks as snorkels. [24][25]
Tusks and molarsEdit
Both male and female African elephants have tusks that grow from deciduous teeth called tushes, which are replaced by tusks when calves are about one year old. Tusks are composed of dentin, which forms small diamond-shaped structures in the tusk's center that become larger at its periphery.[23] Tusks are used for digging for roots and stripping the bark from trees for food, for fighting each other during mating season, and for defending themselves against predators. The tusks weigh from 23 to 45 kg (51–99 lb) and can be from 1.5 to 2.4 m (5–8 ft) long. They are curved forward and continue to grow throughout the elephant's lifetime.[26]
The dental formula of elephants is 1.0.3.30.0.3.3 × 2 = 26.[23] Elephants have four molars; each weighs about 5 kg (11 lb) and measures about 30 cm (12 in) long. As the front pair wears down and drops out in pieces, the back pair moves forward, and two new molars emerge in the back of the mouth. Elephants replace their teeth four to six times in their lifetimes. Around 40 to 60 years of age, the elephant loses the last of its molars and will likely die of starvation, a common cause of death. African elephants have 24 teeth in total, six on each quadrant of the jaw. The enamel plates of the molars are fewer in number than in Asian elephants.[27]
SizeEdit
The African bush elephant is the largest terrestrial animal. Cows are 2.2–2.6 m (7.2–8.5 ft) tall at the shoulder and weigh 2,160–3,232 kg (4,762–7,125 lb), while bulls are 3.2–4 m (10–13 ft) tall and weigh 4,700–6,048 kg (10,362–13,334 lb).[8] Its back is concave-shaped, while the back of the African forest elephant is nearly straight.[10] The largest recorded individual stood 3.96 metres (13.0 ft) at the shoulder, and is estimated to have weighed 10,400 kg (22,900 lb).[28][29] The tallest recorded individual stood 4.21 m (13.8 ft) at the shoulder and weighed 8,000 kg (18,000 lb).[30]
The African forest elephant is smaller with male shoulder heights of up to 2.5 metres (8.2 ft).[31] It is the third largest terrestrial animal. Their thickset bodies rest on stocky legs.[32]
DevelopmentEdit
Elephants have the longest gestation period of any mammal, with each elephant species having a gestation period of roughly 22 months. However, there's slight variations between the African elephant(640–673 days), and the Asian elephant(623-729)(nbci.gov).[33] As the largest land mammal on Earth, calves are born at about 200 pounds (90 kg).[34] The elephant is a complex organism, with the trunk alone having roughly 100,000 muscles, making development stages very drawn out.
For the development of the calf in the womb, it takes about 62 days for the embryo to be detectable,[35] with a heartbeat detected by 71 days. The placenta is detected by an endometrial reaction on day 80, and the basic shape of the calf(head, rump, and trunk) are detected by day 95(embryology.med.unsw.edu). By day 95, the umbilical cord is also visible. At around day 100, the head makes up half of the length of the calf, and the toes can be discerned on all four limbs. Later on, by day 120, the trunk of an African calf has the two lip-like protrusions seen in adults.
en.m.wikipedia.org/wiki/African_elephant
African bush elephant bull in Kruger National Park
Both species are considered at heavy risk of extinction on the IUCN Red List; as of 2021, the bush elephant is considered endangered and the forest elephant is considered critically endangered. They are threatened by habitat loss and fragmentation, and poaching for the illegal ivory trade is a threat in several range countries as well.
Loxodonta is one of two extant genera of the family Elephantidae. The name refers to the lozenge-shaped enamel of their molar teeth. Fossil remains of Loxodonta species have been excavated in Africa, dating to the Middle Pliocene.
Taxonomy
The first scientific description of the African elephant was written in 1797 by Johann Friedrich Blumenbach, who proposed the scientific name Elephas africanus.[3]Loxodonte was proposed as generic name for the African elephant by Frédéric Cuvier in 1825. This name refers to the lozenge-shaped enamel of the molar teeth, which differs significantly from the rounded shape of the Asian elephant's molar enamel.[4] An anonymous author used the Latinized spelling Loxodonta in 1827.[5] Anonymous was recognized as authority by the International Code of Zoological Nomenclature in 1999.[1]
Elephas (Loxodonta) cyclotis was proposed by Paul Matschie in 1900, who described three African elephant zoological specimens from Cameroon whose skulls differed in shape from elephant skulls collected elsewhere in Africa.[6] In 1936, Glover Morrill Allen considered this elephant to be a distinct species and called it 'forest elephant';[7] later authors considered it to be a subspecies.[8][9][2] Morphological and genetic analyses provided evidence for species-level differences between the African bush elephant and the African forest elephant.[10][11][12][13][14]
In 1907, Richard Lydekker proposed six African elephant subspecies based on the different sizes and shapes of their ears.[15] They are all considered synonymous with the African bush elephant.[1]
A third species, the West African elephant, has also been proposed but it needs confirmation; it is thought that this lineage has been isolated from the others for 2.4 million years.[16]
Extinct African elephantsEdit
Between the late 18th and 20th centuries, the following extinct African elephants were described on the basis of fossil remains:
North African elephant (Loxodonta africana pharaohensis) proposed by Paulus Edward Pieris Deraniyagala in 1948 was a specimen from Fayum in Egypt.[17]Loxodonta atlantica was proposed as Elephas atlanticus by Auguste Pomel in 1879 based on a skull and bones found in Ternifine, Algeria.[18]Loxodonta exoptata proposed by Wilhelm Otto Dietrich in 1941 was based on teeth found in Laetoli, Tanzania.[19]Loxodonta adaurora proposed by Vincent Maglio in 1970 was a complete skeleton found in Kanapoi, Kenya.[20]PhylogenyEdit
Analysis of nuclear DNA sequences indicates that the genetic divergence between African bush and forest elephants dates 2.6 – 5.6 million years ago. The divergence between the Asian elephant and the woolly mammoths is estimated 2.5 – 5.4 million years ago, which strongly supports their status as distinct species. The African forest elephant was found to have a high degree of genetic diversity, perhaps reflecting periodic fragmentation of their habitat during the climatic changes in the Pleistocene.[13]
Gene flow between the two African elephant species was examined at 21 locations. The analysis revealed that several African bush elephants carried mitochondrial DNA of African forest elephants, indicating they hybridised in the savanna-forest transition zone in ancient times.[21]
Sequence analysis of DNA from fossils of the extinct Eurasian Palaeoloxodon antiquus shows it to be much closer related to the African forest elephant than to the African bush elephant. The validity of Loxodonta has therefore been questioned.[22]
Description
African elephants have grey folded skin up to 30 mm (1.2 in) thick that is covered with sparse bristled dark-brown to black hair. Short tactile hair grows on the trunk, which has two finger-like processes at the tip, whereas Asian elephants only have one.[8] Their large ears help to reduce body heat; flapping them creates air currents and exposes the ears' inner sides where large blood vessels increase heat loss during hot weather. The trunk is a prehensile elongation of its upper lip and nose. This highly sensitive organ is innervated primarily by the trigeminal nerve, and thought to be manipulated by about 40,000–60,000 muscles. Because of this muscular structure, the trunk is so strong that elephants can use it for lifting about 3% of their own body weight. They use it for smelling, touching, feeding, drinking, dusting, producing sounds, loading, defending and attacking.[23] Elephants sometimes swim underwater and use their trunks as snorkels. [24][25]
Tusks and molarsEdit
Both male and female African elephants have tusks that grow from deciduous teeth called tushes, which are replaced by tusks when calves are about one year old. Tusks are composed of dentin, which forms small diamond-shaped structures in the tusk's center that become larger at its periphery.[23] Tusks are used for digging for roots and stripping the bark from trees for food, for fighting each other during mating season, and for defending themselves against predators. The tusks weigh from 23 to 45 kg (51–99 lb) and can be from 1.5 to 2.4 m (5–8 ft) long. They are curved forward and continue to grow throughout the elephant's lifetime.[26]
The dental formula of elephants is 1.0.3.30.0.3.3 × 2 = 26.[23] Elephants have four molars; each weighs about 5 kg (11 lb) and measures about 30 cm (12 in) long. As the front pair wears down and drops out in pieces, the back pair moves forward, and two new molars emerge in the back of the mouth. Elephants replace their teeth four to six times in their lifetimes. Around 40 to 60 years of age, the elephant loses the last of its molars and will likely die of starvation, a common cause of death. African elephants have 24 teeth in total, six on each quadrant of the jaw. The enamel plates of the molars are fewer in number than in Asian elephants.[27]
SizeEdit
The African bush elephant is the largest terrestrial animal. Cows are 2.2–2.6 m (7.2–8.5 ft) tall at the shoulder and weigh 2,160–3,232 kg (4,762–7,125 lb), while bulls are 3.2–4 m (10–13 ft) tall and weigh 4,700–6,048 kg (10,362–13,334 lb).[8] Its back is concave-shaped, while the back of the African forest elephant is nearly straight.[10] The largest recorded individual stood 3.96 metres (13.0 ft) at the shoulder, and is estimated to have weighed 10,400 kg (22,900 lb).[28][29] The tallest recorded individual stood 4.21 m (13.8 ft) at the shoulder and weighed 8,000 kg (18,000 lb).[30]
The African forest elephant is smaller with male shoulder heights of up to 2.5 metres (8.2 ft).[31] It is the third largest terrestrial animal. Their thickset bodies rest on stocky legs.[32]
DevelopmentEdit
Elephants have the longest gestation period of any mammal, with each elephant species having a gestation period of roughly 22 months. However, there's slight variations between the African elephant(640–673 days), and the Asian elephant(623-729)(nbci.gov).[33] As the largest land mammal on Earth, calves are born at about 200 pounds (90 kg).[34] The elephant is a complex organism, with the trunk alone having roughly 100,000 muscles, making development stages very drawn out.
For the development of the calf in the womb, it takes about 62 days for the embryo to be detectable,[35] with a heartbeat detected by 71 days. The placenta is detected by an endometrial reaction on day 80, and the basic shape of the calf(head, rump, and trunk) are detected by day 95(embryology.med.unsw.edu). By day 95, the umbilical cord is also visible. At around day 100, the head makes up half of the length of the calf, and the toes can be discerned on all four limbs. Later on, by day 120, the trunk of an African calf has the two lip-like protrusions seen in adults.
en.m.wikipedia.org/wiki/African_elephant