Archaeopotamus

Taxobox
name = "Archaeopotamus"
fossil_range = Late Miocene to Late Pliocene
regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Artiodactyla
familia = Hippopotamidae
genus = †"Archaeopotamus"
genus_authority = Boisserie (2005)cite journal |last=Boisserie |first=Jean-Renaud |year=2005 |title=The phylogeny and taxonomy of Hippopotamidae (Mammalia: Artiodactyla): a review based on morphology and cladistic analysis |journal=Zoological Journal of the Linnean Society |volume= 143 |pages= 1–26 |url= http://www.blackwell-synergy.com/links/doi/10.1111/j.1096-3642.2004.00138.x/abs/ |accessdate= 2007-06-01 |doi=10.1111/j.1096-3642.2004.00138.x]
subdivision_ranks = Species
subdivision = †"A. lothagamensis" (Weston 2000)
†"A. harvardi" (Coryndon 1977)

"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.

Characteristics

Many prehistoric hippo fossils are known primarily through fossils of the lower jaw. "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.

"A. lothagamensis"

"A. lothagamensis" is a species whose fossils were discovered at Lothagam, a site southwest of Lake Turkana 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.cite journal |last= Weston |first= E.M. |year=2000 |month=March |title= A New Species of Hippopotamus "Hexaprotodon Lothagamensis" (Mammalia: Hippopotamidae) From the Late Miocene of Kenya|journal=Journal of Vertebrate Paleontology|volume= 20|issue= 1|pages=177–185 |url = http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634(2000)020%5B0177%3AANSOHH%5D2.0.CO%3B2 | accessdate = 2007-06-01 |doi= 10.1671/0272-4634(2000)020 [0177:ANSOHH] 2.0.CO;2 |doilabel= 10.1671/0272-4634(2000)020[0177:ANSOHH]2.0.CO;2]

"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.

"A. harvardi"

"A. harvardi" is a species of hippo first described in 1977, originally as "Hexaprotodon harvardi". [Coryndon, 1977] 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 Turkana, Kenya; near Lake Victoria in Kenya and in Abu Dhabi and thus likely ranged across East Africa and the Arabian Peninsula.

Evolution

The immediate ancestor of "Archaeopotamus" is unknown. Whether or not "Archaeopotamus" is descended from "Kenyapotamus" 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.

References