Archaeopotamus
Encyclopedia
Archaeopotamus is an extinct genus
of Hippopotamidae
that lived between 7.5 and 1.8 million years ago in Africa
and the Middle East
. The genus was described in 2005 to encompass species of hippos that were previously grouped in Hexaprotodon
.
Archaeopotamus means "the ancient of the river". Of all identified hippos, only Kenyapotamus
is older. Kenyapotamus, however, is only known from partial fossils; Archaeopotamus is the oldest well-identified hippo.
. Archaeopotamus, like Hexaprotodon, has three pairs of incisors. Unlike other Hexaprotodon, Archaeopotamus has a highly elongate mandibular symphysis
. The informal name "narrow muzzled hippos" has been suggested for this genus.
in Kenya
and first described in 2000. When first described, the species was classified as Hexaprotodon lothagamensis, although the significant morphological differences between other Hexaprotodon species, were noted.
A. lothagamensis was smaller than the modern hippopotamus
and also smaller than A. harvardi and with a more slender skeleton. It was, however, significantly larger than the modern pygmy hippopotamus
.
Another group of fossils, originally described as Hexaprotodon sahabiensis or the Abu Dhabi Hippopotamus, are now considered to belong to A. harvardi or A. lothagamensis. The fossil record for A. harvardi is more extensive than for other Archaeopotamus.
A. harvardi is believed to have had a more riparian lifestyle than A. lothagamensis.
, Kenya; near Lake Victoria
in Kenya and in Abu Dhabi
and thus likely ranged across East Africa
and the Arabian Peninsula
.
cannot be determined from the few fossils available. Although Archaeopotamus is more primitive than any member of the genus Hippopotamus, it is likely a sister group of both hippopotamuses and Hexaprotodon.
Fossils similar to Archaeopotamus have been dated to as recently as about 2 million years ago, the end of the Pliocene
epoch. These fossils are significantly different from those of Hippopotamus and Hexaprotodon of the same time.
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...
of Hippopotamidae
Hippopotamidae
Hippopotamuses are the members of the family Hippopotamidae. They are the only extant artiodactyls which walk on four toes on each foot.- Characteristics :...
that lived between 7.5 and 1.8 million years ago in 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...
and the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
. The genus was described in 2005 to encompass species of hippos that were previously grouped in Hexaprotodon
Hexaprotodon
Hexaprotodon is a genus of Hippopotamidae that is sometimes applied to the pygmy hippopotamus. Pygmy hippos may be classified as either Choeropsis liberiensis or Hexaprotodon liberiensis...
.
Archaeopotamus means "the ancient of the river". Of all identified hippos, only Kenyapotamus
Kenyapotamus
Kenyapotamus is a possible ancestor of living hippopotamids that lived in Africa roughly 16 million to 8 million years ago during the Miocene epoch...
is older. Kenyapotamus, however, is only known from partial fossils; Archaeopotamus is the oldest well-identified hippo.
Characteristics
Many prehistoric hippo fossils are known primarily through fossils of the lower jawMandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
. Archaeopotamus, like Hexaprotodon, has three pairs of incisors. Unlike other Hexaprotodon, Archaeopotamus has a highly elongate mandibular symphysis
Symphysis menti
The external surface of the mandible is marked in the median line by a faint ridge, indicating the symphysis menti, mandibular symphysis, or line of junction of the two pieces of which the bone is composed at an early period of life....
. The informal name "narrow muzzled hippos" has been suggested for this genus.
A. lothagamensis
A. lothagamensis is a species whose fossils were discovered at Lothagam, a site southwest of Lake TurkanaLake Turkana
Lake Turkana , formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's largest alkaline lake...
in Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
and first described in 2000. When first described, the species was classified as Hexaprotodon lothagamensis, although the significant morphological differences between other Hexaprotodon species, were noted.
A. lothagamensis was smaller than the modern hippopotamus
Hippopotamus
The hippopotamus , or hippo, from the ancient Greek for "river horse" , is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest...
and also smaller than A. harvardi and with a more slender skeleton. It was, however, significantly larger than the modern pygmy hippopotamus
Pygmy Hippopotamus
The pygmy hippopotamus is a large mammal native to the forests and swamps of western Africa . The pygmy hippo is reclusive and nocturnal...
.
A. harvardi
A. harvardi is a species of hippo first described in 1977, originally as Hexaprotodon harvardi. Although the proportions of A. harvardi and A. lothagamensis are similar, the former species is significantly smaller. Femurs of A. harvardi are approximately the same size as those of the modern hippopotamus.Another group of fossils, originally described as Hexaprotodon sahabiensis or the Abu Dhabi Hippopotamus, are now considered to belong to A. harvardi or A. lothagamensis. The fossil record for A. harvardi is more extensive than for other Archaeopotamus.
A. harvardi is believed to have had a more riparian lifestyle than A. lothagamensis.
Distribution
Fossils of Archaeopotamus have been unearthed near Lake TurkanaLake Turkana
Lake Turkana , formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's largest alkaline lake...
, Kenya; near Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
in Kenya and in Abu Dhabi
Abu Dhabi
Abu Dhabi , literally Father of Gazelle, is the capital and the second largest city of the United Arab Emirates in terms of population and the largest of the seven member emirates of the United Arab Emirates. Abu Dhabi lies on a T-shaped island jutting into the Persian Gulf from the central western...
and thus likely ranged across East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
and the Arabian Peninsula
Arabian Peninsula
The Arabian Peninsula is a land mass situated north-east of Africa. Also known as Arabia or the Arabian subcontinent, it is the world's largest peninsula and covers 3,237,500 km2...
.
Evolution
The immediate ancestor of Archaeopotamus is unknown. Whether or not Archaeopotamus is descended from KenyapotamusKenyapotamus
Kenyapotamus is a possible ancestor of living hippopotamids that lived in Africa roughly 16 million to 8 million years ago during the Miocene epoch...
cannot be determined from the few fossils available. Although Archaeopotamus is more primitive than any member of the genus Hippopotamus, it is likely a sister group of both hippopotamuses and Hexaprotodon.
Fossils similar to Archaeopotamus have been dated to as recently as about 2 million years ago, the end of the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
epoch. These fossils are significantly different from those of Hippopotamus and Hexaprotodon of the same time.