Hippopotamidae

Hippopotamus skeleton at Għar Dalam

For the common hippopotamid species, see Hippopotamus

- Hippopotamidae

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Cetacea

Infraorder of aquatic mammals that includes whales, dolphins, and porpoises.

Infraorder of aquatic mammals that includes whales, dolphins, and porpoises.

Dolphin anatomy
Humpback whale fluke
Biosonar
Bubble net feeding
Killer whale porpoising
Two views of the skeletons of Dorudon atrox, extinct for 40 million years, and Maiacetus inuus, extinct for 47.5 million years, in the swimming position for comparison.
Cetaceans display convergent evolution with fish and aquatic reptiles
Fossil of a Maiacetus (red, beige skull) with fetus (blue, red teeth) shortly before the end of gestation
Whales caught 2010–2014, by country
Dominoes made of baleen
A whale as depicted by Conrad Gesner, 1587, in Historiae animalium
"Destruction of Leviathan" engraving by Gustave Doré, 1865
Silver coin with Tarus riding a dolphin
Constellation Cetus
Depiction of baleen whaling, 1840
Stranded sperm whale engraving, 1598
Sea World show featuring bottlenose dolphins and false killer whales
Ulises the orca, 2009
Dawn Brancheau doing a show four years before the incident
SeaWorld pilot whale with trainers

Despite their highly modified bodies and carnivorous lifestyle, genetic and fossil evidence places cetaceans as nested within even-toed ungulates, most closely related to hippopotamus within the clade Whippomorpha.

Ruminant

Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions.

Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions.

Stylised illustration of a ruminant digestive system
Different forms of the stomach in mammals. A, dog; B, Mus decumanus; C, Mus musculus; D, weasel; E, scheme of the ruminant stomach, the arrow with the dotted line showing the course taken by the food; F, human stomach. a, minor curvature; b, major curvature; c, cardiac end G, camel; H, Echidna aculeata. Cma, major curvature; Cmi, minor curvature. I, Bradypus tridactylus Du, duodenum; MB, coecal diverticulum; **, outgrowths of duodenum; †, reticulum; ††, rumen. A (in E and G), abomasum; Ca, cardiac division; O, psalterium; Oe, oesophagus; P, pylorus; R (to the right in E and to the left in G), rumen; R (to the left in E and to the right in G), reticulum; Sc, cardiac division; Sp, pyloric division; WZ, water-cells. (from Wiedersheim's Comparative Anatomy)
Food digestion in the simple stomach of nonruminant animals versus ruminants

The Hippopotamidae (comprising hippopotami) are well-known examples.

Pachydermata

Obsolete order of mammals described by Gottlieb Storr, Georges Cuvier, and others, at one time recognized by many systematists.

Obsolete order of mammals described by Gottlieb Storr, Georges Cuvier, and others, at one time recognized by many systematists.

Outside strict biological classification, the term "" remains commonly used to describe elephants, rhinoceroses, tapirs, and hippopotamuses.

Ungulate

Ungulates are members of the diverse clade Ungulata which primarily consists of large mammals with hooves.

Ungulates are members of the diverse clade Ungulata which primarily consists of large mammals with hooves.

Plains zebra
Black rhinoceros
Père David's deer
Hippopotamus
Blue whale
Common dolphin
Uintatherium anceps, a dinoceratan
Cladogram showing relationships within Ungulata
Restoration of Eurohippus parvulus, a mid- to late Eocene equid of Europe (Natural History Museum, Berlin)
The thick dermal armour of the Rhinoceros evolved at the same time as shearing tusks
Arctocyon an arctocyonid
Restoration of Mesonyx
Skeleton of Ambulocetus natans, a stem whale
Skeleton of a horse
The anatomy of a dolphin, showing its skeleton, major organs, tail, and body shape
Cloven hooves of Roe Deer (Capreolus capreolus), with dew claws
Pacific white-sided dolphin skeleton (missing pelvic bones), on exhibit at The Museum of Osteology, Oklahoma City, Oklahoma
Velvet covers a growing antler and provides it with blood, supplying oxygen and nutrients.

Hippopotamidae: Hippopotamuses

Entelodonts were stocky animals with a large head, and were characterized by bony bumps on the lower jaw.

Even-toed ungulate

Even number) of their five toes: the third and fourth.

Even number) of their five toes: the third and fourth.

Entelodonts were stocky animals with a large head, and were characterized by bony bumps on the lower jaw.
Sivatherium was a relative of giraffes with deer-like forehead weapons.
Richard Owen coined the term "even-toed ungulate".
Molecular and morphological studies confirmed that cetaceans are the closest living relatives of hippopotamuses.
Hippos are a geologically young group, which raises questions about their origin.
The mesonychids were long considered ancestors of whales.
Camels are now considered a sister group of Artiofabula.
The pronghorn is the only extant antilocaprid.
Reconstruction of Indohyus
Blue duiker (Philantomba monticola) skeleton on display at the Museum of Osteology.
The mouse deer is the smallest even-toed ungulate.
Diagrams of hand skeletons of various mammals, left to right: orangutan, dog, pig, cow, tapir, and horse. Highlighted are the even-toed ungulates pig and cow.
Outgrowths of the frontal bone characterize most forehead weapons carriers, such as the gemsbok and its horns.
The canines of Suinas develop into tusks.
The Japanese serow has glands in the eyes that are clearly visible
Artiodactyls, like impalas and giraffes, live in groups.
Most artiodactyls, such as the wildebeest, are born with hair.
Some artiodactyls, like sheep, have been domesticated for thousands of years.
The aurochs has been extinct since the 17th century.
Hippopotamuses have all four toes pointing out.
For pigs and other biungulates the second and fifth toes are directed backwards.
When camels have only two toes present, the claws are transformed into nails.
alt=A warthog.|Pigs (such as this warthog) have a simple sack-shaped stomach.
alt=A male deer|As with all ruminants, deer have such a multi-chambered stomach, which is used for better digesting plant food.

Family Hippopotamidae: hippos (two species)

Pygmy hippopotamus

Showing its teeth at the Lagos Zoo in Portugal
Skull
Anthracotheres like Anthracotherium resembled pygmy hippos and are among their likely ancestors
Resting at Louisville Zoo. The skull of a pygmy hippo has less pronounced orbits and nostrils than a common hippopotamus.
Nuzzling couple at the Duisburg Zoo in Germany
Two dive in water at Singapore Zoo, Singapore
Eating a vegetable
Baby stands near its parent in the Jihlava Zoo, Czech Republic
Mother and child taking a bath at Lisbon Zoo
Pair at the Mount Kenya Wildlife Conservancy
Pair at the Mount Kenya Wildlife Conservancy

The pygmy hippopotamus (Choeropsis liberiensis or Hexaprotodon liberiensis) 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.

Hippopotamus

Large semiaquatic mammal native to sub-Saharan Africa.

Large semiaquatic mammal native to sub-Saharan Africa.

Detail of the head
Evolutionary relationships among hippo and Cetacea (whales, dolphins)
Anthracotherium magnum from the Oligocene of Europe
Choeropsis madagascariensis skeleton with a modern hippopotamus skull
Hippo's skull, showing the large canines and incisors used for fighting
Characteristic "yawn" of a hippo
Completely submerged hippo (San Diego Zoo)
Ugandan tribespeople with hippo slain for food (early 20th century)
Incised hippopotamus ivory tusk, upper canine. Four holes around top (Naqada Tomb 1419, Egypt; Naqada period)
Hippopotamus pod
Male hippos fighting
Cow with calf
Preserved hippopotamus fetus
A hippopotamus and Nile crocodile side by side in Kruger National Park
Hippopotamus ("William"), Middle Kingdom of Egypt, c. undefined 1961–1878 BC
Obaysch lounging at the London Zoo in 1852
Ijaw hippopotamus masks
The "Hippopotamus Polka"

It is one of only two extant species in the family Hippopotamidae, the other being the pygmy hippopotamus (Choeropsis liberiensis or Hexaprotodon liberiensis).

In this phylogenetic tree, the green group is paraphyletic; it is composed of a common ancestor (the lowest green vertical stem) and some of its descendants, but it excludes the blue group (a monophyletic group) which diverged from the green group.

Paraphyly

Paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups.

Paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups.

In this phylogenetic tree, the green group is paraphyletic; it is composed of a common ancestor (the lowest green vertical stem) and some of its descendants, but it excludes the blue group (a monophyletic group) which diverged from the green group.
Reptilia (green field) is a paraphyletic group comprising all amniotes (Amniota) except for two subgroups: Mammalia (mammals) and Aves (birds); therefore, Reptilia is not a clade. In contrast, Amniota itself is a clade, which is a monophyletic group. Aves are included in Reptilia in modern cladistic classification systems.
Cladogram of the primates, showing a monophyly (the simians, in yellow), a paraphyly (the prosimians, in blue, including the red patch), and a polyphyly (the night-active primates, the lorises and the tarsiers, in red).
Wasps are paraphyletic, consisting of the clade Apocrita without ants and bees, which are not usually considered to be wasps; the sawflies ("Symphyta") too are paraphyletic, as the Apocrita are nested inside the Symphytan clades.

For example, the Neogene evolution of the Artiodactyla (even-toed ungulates, like deer, cows, pigs and hippopotamuses - note that Cervidae, Bovidae, Suidae and Hippopotamidae, the families that contain these various artiodactyls, are all monophyletic groups) has taken place in environments so different from that of the Cetacea (whales, dolphins, and porpoises) that the Artiodactyla are often studied in isolation even though the cetaceans are a descendant group.

Anthracotheriidae

Paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales.

Paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales.

Microbunodon skull

However, one study suggests, instead of anthracotheres, another pig-like group of artiodactyls, called palaeochoerids, are the true stem group of Hippopotamidae.

Hippopotamus (genus)

Genus of artiodactyl mammals consisting of one extant species, Hippopotamus amphibius, the river hippopotamus , and several extinct species from both recent and prehistoric times.

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 (Choeropsis liberiensis) and a number of extinct genera.