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Temporal range: 7.4–0  Ma
Late Miocene-Recent
Hippo pod edit.jpg
Common hippopotamus
Pygmy hippopotamus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Suborder: Whippomorpha
Superfamily: Hippopotamoidea
Family: Hippopotamidae
Gray, 1821

Trilobophorus Geze, 1985

Hippopotamidae is a family of stout, naked-skinned, and semiaquatic artiodactyl mammals, possessing three-chambered stomachs and walking on four toes on each foot. While they resemble pigs physiologically, their closest living relatives are the cetaceans. They are sometimes referred to as hippopotamids.


There are two living species of hippopotamid in two genera; the pygmy hippo, Choeropsis liberiensis of the forests of west Africa, and the common hippo, Hippopotamus amphibius . The term hippopotamus can also be applied to hippopotamids in general, although it is most frequently used for the common hippo and its respective genus.


Hippopotamids are large mammals, with short, stumpy legs, and barrel-shaped bodies. They have large heads, with broad mouths, and nostrils placed at the top of their snouts. Like pigs, they have four toes, but unlike pigs, all of the toes are used in walking. Hippopotamids are unguligrade, although, unlike most other such animals, they have no hooves, instead using a pad of tough connective tissue on each foot. Their stomachs have three chambers, but they are not true ruminants.

The living species are smooth-skinned and lack both sebaceous glands and sweat glands. The outer epidermis is relatively thin, so hippos dehydrate rapidly in dry environments. [1]

Both the incisors and canines are large and tusk-like, although the canine tusks are by far the larger. The tusks grow throughout life. The postcanine teeth are large and complex, suited for chewing the plant matter that comprises their diets. The number of incisors varies even within the same species, but the general dental formula is given in the table below:



Hippopotamus skeleton at Ghar Dalam Hippopotamus amphibius Linn at Ghar Dalam, Malta.png
Hippopotamus skeleton at Għar Dalam

The hippopotamids are descended from the anthracotheres, a family of semiaquatic and terrestrial artiodactyls that appeared in the late Eocene, and are thought to have resembled small- or narrow-headed hippos. The hippos split off from the anthracotheres some time during the Miocene. The oldest records of Hippopotamidae are from Afro-Arabia and date to the late Miocene, approximately 7.4 million years ago, expanding into Eurasia around 6 million years ago. [2] After the appearance of the hippopotamids, the remaining anthracotheres went into a decline brought about by a combination of climatic change and competition with their descendants, until the last genus, Merycopotamus , died out in the early Pliocene of India.

There were once many species of hippopotamid, but only two survive today: Hippopotamus amphibius, and Choeropsis liberiensis. They are the last survivors of two major evolutionary lineages, the hippos proper and the pygmy hippos, respectively; these lineages could arguably be considered subfamilies, but their relationship to each other – apart from being fairly distant relatives – is not well resolved.

The enigmatic Miocene Kenyapotamus is insufficiently known to be assigned a place in the hippo phylogeny with any degree of certainty. In addition, the genus Hexaprotodon , which is now largely restricted to South Asia and Southeast Asia, formerly included many fossil hippopotamuses that are now thought to be unrelated. [3]


Hippopotamidae's placement within Artiodactyla can be represented in the following cladogram: [4] [5] [6] [7] [8]


  Tylopoda (camels and kin) Cladogram of Cetacea within Artiodactyla (Camelus bactrianus).png


  Suina (pigs and kin) Recherches pour servir a l'histoire naturelle des mammiferes (Pl. 80) (white background).jpg


  Ruminantia (ruminants) Walia ibex illustration white background.png  


 Hippopotamidae (hippopotamids) Voyage en Abyssinie Plate 2 (white background).jpg

  Cetacea (whales) Bowhead-Whale1 (16273933365).jpg

  (or  Whippomorpha)  

Analogous structures

The lower canine teeth of hippopotamids are similar in function and structure to the tusks of elephants. While hippopotamids and elephants are only very distantly related within the Mammalia, the lower canine teeth of both groups are long and have a slight curve, and species of both families use this structure when fighting.


The systematics and taxonomy used here mostly follows a review by J.-R. Boisserie [9] [lower-alpha 1] and the American Society of Mammalogists. [10]

Recent species

Fossil species


  1. 1 2 Boisserie (2005) [9] identified the species Hippopotamus minor as Phanourios minutus, but this genus is not widely recognized.

Related Research Articles

<span class="mw-page-title-main">Ungulate</span> Group of animals that walk on the tips of their toes or hooves

Ungulates are members of the diverse clade Euungulata which primarily consists of large mammals with hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined to be a polyphyletic and thereby invalid clade based on molecular data. As a result, true ungulates had since been reclassified to the newer clade Euungulata in 2001 within the clade Laurasiatheria while Paenungulata has been reclassified to a distant clade Afrotheria. Living ungulates are divided into two orders: Perissodactyla including equines, rhinoceroses, and tapirs; and Artiodactyla including cattle, antelope, pigs, giraffes, camels, sheep, deer, and hippopotamuses, among others. Cetaceans such as whales, dolphins, and porpoises are also classified as artiodactyls, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving. Two other orders of ungulates, Notoungulata and Litopterna, both native to South America, became extinct at the end of the Pleistocene, around 12,000 years ago.

<span class="mw-page-title-main">Hippopotamus</span> Large semi-aquatic mammal native to sub-Saharan Africa

The hippopotamus, also shortened to hippo, further qualified as the common hippopotamus, Nile hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two extant species in the family Hippopotamidae, the other being the pygmy hippopotamus. Its name comes from the ancient Greek for "river horse" (ἱπποπόταμος).

<span class="mw-page-title-main">Artiodactyl</span> Order of mammals

Artiodactyls are mammals belonging to the order Artiodactyla. Typically, they are ungulates which bear weight equally on two of their five toes: the third and fourth, often in the form of a hoof. The other three toes are either present, absent, vestigial, or pointing posteriorly. By contrast, most perissodactyls bear weight on an odd number of the five toes. Another difference between the two is that many artiodactyls digest plant cellulose in one or more stomach chambers rather than in their intestine as perissodactyls do. The advent of molecular biology, along with new fossil discoveries, found that cetaceans fall within this taxonomic branch, being most closely related to hippopotamuses. Some modern taxonomists thus apply the name Cetartiodactyla to this group, while others opt to include cetaceans within the existing name of Artiodactyla. Some researchers use "even-toed ungulates" to exclude cetaceans and only include terrestrial artiodactyls, making the term paraphyletic in nature.

<span class="mw-page-title-main">Pygmy hippopotamus</span> Small species of hippopotamus from West Africa

The pygmy hippopotamus or pygmy hippo is a small hippopotamid which is native to the forests and swamps of West Africa, primarily in Liberia, with small populations in Sierra Leone, Guinea, and Ivory Coast. It has been extirpated from Nigeria.

<i>Hippopotamus</i> (genus) Genus of mammals

Hippopotamus is a genus of artiodactyl mammals consisting of one extant species, Hippopotamus amphibius, the river hippopotamus, and several extinct species from both recent and prehistoric times. It belongs to the family Hippopotamidae, which also includes the pygmy hippopotamus and a number of extinct genera.

<i>Anthracotherium</i> Extinct genus of mammals

Anthracotherium is an extinct genus of artiodactyls characterized by having 44 teeth, with five semi-crescentic cusps on the crowns of the upper molars. The genus ranged from the middle Eocene period until the early Miocene, having a distribution throughout Eurasia. Material subjectively assigned to Anthracotherium from Pakistan suggests the last species died out soon after the start of the Miocene.

<i>Hippopotamus gorgops</i> Extinct species of mammal

Hippopotamus gorgops is an extinct species of Hippopotamus known from remains found in Northern and Eastern Africa as well as the Levant. It first appeared during the late Pliocene-Early Pleistocene, and became extinct during the early Middle Pleistocene.

<i>Hexaprotodon</i> Extinct hippopotamus genus

Hexaprotodon is an extinct genus of hippopotamid known from Asia and possibly Africa and Europe. The name Hexaprotodon means "six front teeth" as some of the fossil forms have three pairs of incisors.

<span class="mw-page-title-main">Anthracotheriidae</span> Extinct family of mammals

Anthracotheriidae is a paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, Elomeryx, first appeared during the middle Eocene in Asia. They thrived in Africa and Eurasia, with a few species ultimately entering North America during the Oligocene. They died out in Europe and Africa during the Miocene, possibly due to a combination of climatic changes and competition with other artiodactyls, including pigs and true hippopotamuses. The youngest genus, Merycopotamus, died out in Asia during the late Pliocene, possibly for the same reasons. The family is named after the first genus discovered, Anthracotherium, which means "coal beast", as the first fossils of it were found in Paleogene-aged coal beds in France. Fossil remains of the anthracothere genus were discovered by the Harvard University and Geological Survey of Pakistan joint research project (Y-GSP) in the well-dated middle and late Miocene deposits of the Pothohar Plateau in northern Pakistan.

Kenyapotamus is a possible ancestor of living hippopotamuses that lived roughly 16 million to 8 million years ago during the Miocene epoch. Its name reflects that its fossils were first found in modern-day Kenya.

<span class="mw-page-title-main">Whippomorpha</span> Suborder of mammals

Whippomorpha or Cetancodonta is a group of artiodactyls that contains all living cetaceans and hippopotamuses. All Whippomorphs are descendants of the last common ancestor of Hippopotamus amphibius and Tursiops truncatus. This makes it a crown group. Whippomorpha is a suborder within the order Artiodactyla. The placement of Whippomorpha within Artiodactyla is a matter of some contention, as hippopotamuses were previously considered to be more closely related to Suidae (pigs) and Tayassuidae (peccaries). Most contemporary scientific phylogenetic and morphological research studies link hippopotamuses with cetaceans, and genetic evidence has overwhelmingly supported an evolutionary relationship between Hippopotamidae and Cetacea. Modern Whippomorphs all share a number of behavioural and physiological traits; such as a dense layer of subcutaneous fat and largely hairless bodies. They exhibit amphibious and aquatic behaviors and possess similar auditory structures.

<span class="mw-page-title-main">Cyprus dwarf hippopotamus</span> Species of mammal (fossil)

The Cyprus dwarf hippopotamus or Cypriot pygmy hippopotamus is an extinct species of hippopotamus that inhabited the island of Cyprus from the Pleistocene until the early Holocene. The 200-kilogram (440 lb) Cyprus dwarf hippo was roughly the same size as the extant pygmy hippopotamus. Unlike the modern pygmy hippo, the Cyprus dwarf became small through the process of insular dwarfism. H. minor is the smallest hippopotamus of all known insular hippopotamuses. It is estimated to have measured 76 cm (2.5 ft) tall and 121 cm (4.0 ft) long.

<i>Merycopotamus</i> Extinct genus of Asian anthracothere mammal.

Merycopotamus is an extinct genus of Asian anthracothere that appeared during the Middle Miocene, and died out in the Late Pliocene. At the height of the genus' influence, species ranged throughout southern Asia. With the extinction of the last species, M. dissimilis, the lineage of anthracotheres came to an end. Merycopotamus was closely related to the anthracothere genus Libycosaurus, which, unlike the former, never left Africa. In fact, some African fossils originally placed in Merycopotamus, but are now referred to Libycosaurus.

Archaeopotamus is an extinct genus of Hippopotamidae that lived between 7.5 and 2.58 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.

<span class="mw-page-title-main">Malagasy hippopotamus</span> Extinct species of hippopotamus

Several species of Malagasy hippopotamus lived on the island of Madagascar but are now believed to be extinct. The animals were very similar to the extant hippopotamus and pygmy hippopotamus. The fossil record suggests that at least one species of hippopotamus lived until about 1,000 years ago and other evidence suggests that the species may have survived until much more recently. The taxonomy of these animals is not resolved and not widely studied.

<span class="mw-page-title-main">Suinae</span> Subfamily of mammals

Suinae is a subfamily of artiodactyl mammals that includes several of the extant members of Suidae and their closest relatives – the domestic pig and related species, such as babirusas. Several extinct species within the Suidae are classified in subfamilies other than Suinae. However, the classification of the extinct members of the Suoidea – the larger group that includes the Suidae, the peccary family (Tayassuidae), and related extinct species – is controversial, and different classifications vary in the number of subfamilies within Suidae and their contents. Some classifications, such as the one proposed by paleontologist Jan van der Made in 2010, even exclude from Suinae some extant taxa of Suidae, placing these excluded taxa in other subfamilies.

Hippopotamus laloumena is an extinct species of hippopotamus from Pleistocene and Holocene Madagascar, making it the oldest of Malagasy hippopotamus. H. laloumena was much larger than other Malagasy hippopotamus, but was still somewhat smaller than the common hippopotamus. However, little is known about the species because it was identified with only a lower jaw and limb bones. It was described in 1990 by French palaeontologists M. Faure and Guerin, the fossils recovered from a site near Mananjary on the east coast of Madagascar. The species name derives from Malagasy laloumena "hippopotamus".

<i>Hippopotamus madagascariensis</i> Extinct species of mammal

Hippopotamus madagascariensis, the Madagascar or Madagascan dwarf hippopotamus, is an extinct species of hippopotamus, endemic to the island of Madagascar. Known only from bones, it is believed to have gone extinct sometime after 1500. It was one of three hippopotamus species, the Malagasy hippopotamuses, which were native to Madagascar and are all extinct.

Saotherium is an extinct genus of hippopotamid from the Early Pliocene of Africa, specifically Chad. It is represented by a single species, S. mingoz. The earliest fossils appear at the start of the Pliocene, while the latest are dated to about 4 mya.

<span class="mw-page-title-main">Ancodonta</span> Infraorder of mammals

Ancodonta is an infraorder of semiaquatic artiodactyl ungulates including modern hippopotamus and all mammals closer to hippos than to cetaceans (whales). Ancodonts first appeared in the Middle Eocene, with some of the earliest representatives found in fossil deposits in Southeast Asia. Throughout their evolutionary history they have occupied different browsing and grazing niches in North America, Eurasia and Africa. The last continent is notable as they were among the first laurasiatherian mammals to have migrated to Africa from Europe, where they competed with the native afrothere herbivores for the same niches. Of the nearly 50 genera that have existed, only two of them are extant – Choeropsis and Hippopotamus. The interrelationships within the ancodonts has been contended. The traditional notion is that there at minimum two families Anthracotheriidae and Hippopotamidae and were merely sister taxa. However many detailed research of the dentition among ancodonts, as well as how some anthracotheres were similar to hippos in appearance, lead the current consensus where Anthracotheriidae is paraphyletic to Hippopotamidae. Among the anthracotheres members of Bothriodontinae are among the closest to the ancestry of hippos, with the Oligocene aged Epirigenys from Lokon, Turkana, Kenya being the sister taxon to hippos. In response of this many similar clade names have been used for this clade.


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Further reading