Harbour porpoise skeleton
Biosonar by cetaceans
"Rooster tail" spray around swimming Dall's porpoises
Harbour porpoise in captivity
Traditional catch of harbour porpoise by lancing in Bay of Fundy
A vaquita swimming in the Gulf of California.
A porpoise sculpture in Kelowna, British Columbia, Canada

Porpoises are a group of fully aquatic marine mammals, similar in appearance to a dolphin, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales).

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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"

Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, the closest living relatives of the Hippopotamidae are cetaceans (whales, dolphins, porpoises, etc.), from which they diverged about 55 million years ago.


Aquatic mammal within the infraorder Cetacea.

A bottlenose dolphin
Dolphins display convergent evolution with fish and aquatic reptiles.
The anatomy of a dolphin showing its skeleton, major organs, tail and body shape.
Biosonar by cetaceans.
Diagram illustrating sound generation, propagation and reception in a toothed whale. Outgoing sounds are in cyan and incoming ones are in green
The face of a common bottlenose dolphin
A pod of Indo-Pacific bottlenose dolphins in the Red Sea
Dolphins surfing at Snapper Rocks, Queensland, Australia
A skin-skeletal preparation.
Sleeping dolphin in captivity: a tail kick reflex keeps the dolphin's blowhole above the water.
Spectrogram of dolphin vocalizations. Whistles, whines, and clicks are visible as upside down V's, horizontal striations, and vertical lines, respectively.
Pacific white-sided dolphins porpoising.
Lesions in the dorsal fin of a bottlenose dolphin caused by lobomycosis, a fungal infection of the skin.
Dead Atlantic white-sided dolphins in Hvalba on the Faroe Islands, killed in a drive hunt.
Fresco of dolphins, c. 1600 BC, from Knossos, Crete.
Silver stater from Tarentum c. 290 BC showing Phalanthos riding a dolphin on one side and a rider with a shield decorated with a dolphin on the other side.
Vessel in form of orca, Nazca culture, circa 200 AD. American Museum of Natural History collections.
SeaWorld show featuring bottlenose dolphins and pilot whales.
SeaWorld San Diego pilot whale with trainers.
Shamu in 2009, with a collapsed dorsal fin.
A military dolphin.
Plate of dolphin sashimi.

This term has often been applied in the US, mainly in the fishing industry, to all small cetaceans (dolphins and porpoises) are considered to be porpoises, while the fish dorado is called dolphin fish.

Finless porpoise

Neophocaena is a genus of porpoise native to the Indian and Pacific oceans, as well as the freshwater habitats of the Yangtze River basin in China.


Whales are a widely distributed and diverse group of fully aquatic placental marine mammals.

Basilosaurus skeleton
Features of a blue whale
Features of a sperm whale skeleton
Skeleton of a bowhead whale; notice the vestigial pelvis. Richard Lydekker, 1894
Biosonar by cetaceans
Sperm whale skeleton. Richard Lydekker, 1894.
Bubble net feeding
A southern right whale sailing
Polar bear with the remains of a beluga
"Whale pump" – the role played by whales in recycling ocean nutrients.
Whale Fishing: Woodcut by Thevet, Paris, 1574
Dutch whalers near Spitsbergen, their most successful port. Abraham Storck, 1690
World population graph of blue whales
World map showing International Whaling Commission (IWC) members in blue
Whale watching off Bar Harbour, Maine
Engraving by Gilliam van der Gouwen depicting a stranded sperm whale being butchered on the Dutch coast, 1598
Illustration by Gustave Doré of Baron Munchausen's tale of being swallowed by a whale. While the Biblical Book of Jonah refers to the Prophet Jonah being swallowed by "a big fish", in later derivations that "fish" was identified as a whale.
Whalers off Twofold Bay, New South Wales. Watercolour by Oswald Brierly, 1867
Beluga whales and trainers in an aquarium

They are an informal grouping within the infraorder Cetacea, which usually excludes dolphins and porpoises.


Medium-sized toothed whale that possesses a large "tusk" from a protruding canine tooth.

Illustration of a narwhal (lower image) and a beluga (upper image), its closest related species
Complete skeleton at the Zoological Museum of the Zoological Institute of the Russian Academy of Sciences
This narwhal skull has rare double tusks. Usually, the canine tooth only on the left side of the upper jaw becomes a tusk. Rarely, males develop two tusks. This specimen, however, was of a female (Zoologisches Museum, Hamburg; collected in 1684)
Narwhals in the Creswell Bay at Somerset Island
A polar bear scavenging a narwhal carcass
Beluga and narwhal catches
Male narwhal captured and satellite tagged
The head of an Inuit lance made from a narwhal tusk with a meteorite iron blade (British Museum)
Image of narwhal from Brehms Tierleben (1864–1869)
A pod off Greenland

The white whales, dolphins (Delphinidae) and porpoises (Phocoenidae) together comprise the superfamily Delphinoidea, which are of likely monophyletic origin.

Toothed whale

A whale as depicted by Conrad Gesner, 1587, in Historiae animalium
Fossil of Squalodon
Anatomy of the bottlenose dolphin
Features of a sperm whale skeleton
Biosonar by cetaceans
Diagram illustrating sound generation, propagation and reception in a toothed whale. Outgoing sounds are red and incoming ones are green
Pacific white-sided dolphins porpoising
Spectrogram of dolphin vocalizations. Whistles, whines, and clicks are visible as upside down V's, horizontal striations, and vertical lines, respectively.
Killer whale hunting a Weddel seal
The nose of the whale is filled with a waxy substance that was widely used in candles, oil lamps, and lubricants
Atlantic white-sided dolphin caught in a drive hunt in Hvalba on the Faroe Islands being taken away with a forklift
A killer whale by the name of Ulises performing at SeaWorld, 2009

The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales.


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

Plains zebra
Black rhinoceros
Père David's deer
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.

Cetaceans such as whales, dolphins, and porpoises are also classified as even-toed ungulates, although they do not have hooves.

Beluga whale

Arctic and sub-Arctic cetacean.

Skull of a cross between a narwhal and a beluga whale, at the Zoological Museum, Copenhagen
The skeleton
The cranium and mandible of the Charlotte whale (white) restored with the skull of a modern beluga whale (black)
Front view of a beluga whale in captivity
Head of a beluga showing its distinctive white colouring and the large frontal prominence that houses the melon
Spiracle in the back of a beluga's head
The skull
A beluga showing its tail fin in shallow water in Vancouver Aquarium, Canada
Emission and reception of sounds in a toothed whale
Aerial view of a pod of belugas swimming at the surface
Pacific salmon, the staple diet of belugas from Alaska
Female and calf
Circumpolar distribution of beluga populations showing the main subpopulations
Beluga in the mouth of the Churchill River in the Hudson Bay, Canada
Beluga and narwhal catches
Illustration from 1883 showing Dena'ina hunting party harpooning a beluga in Cook Inlet, Alaska
Russian scientists working on the White Whale Program place transmitters onto whales in Sea of Okhotsk
Beluga aims echolocation beam to choose a spot on an acoustic "touch screen" of hydrophones in the water
Beluga whales in an aquarium interacting with trainers
Beluga at the confluence of the Saint Lawrence and Saguenay rivers
Pictured on Faroe Islands stamp
Engravings on beluga bones
Airbus Beluga

Monodontids then split from dolphins (Delphinidae) and later from porpoises (Phocoenidae), their closest relatives in evolutionary terms.


Fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife.

Shrimp bycatch
Double-rigged shrimp trawler hauling in nets
Shrimp bycatch
Group of Fraser's dolphins
A Dall's porpoise caught in a fishing net
Black-browed albatross hooked on a long-line
Loggerhead sea turtle
A turtle excluder device
Seabirds chase longline fishing vessel
One of the mitigation methods is using streamer lines (in orange).

Cetaceans, such as dolphins, porpoises, and whales, can be seriously affected by entanglement in fishing nets and lines, or direct capture by hooks or in trawl nets.

Dall's porpoise

William Healey Dall's 1873 field notes on Phocoenoides from the Smithsonian Institution's Field Books collection
Dorsal view of a Dall's porpoise
A Dall's porpoise on a calm day in the Shelikof Strait
A group of Dall's porpoises near Point Reyes
Dall's porpoise in Prince William Sound causing a "rooster tail"
Dall's porpoises at market in Japan

Dall's porpoise (Phocoenoides dalli) is a species of porpoise endemic to the North Pacific.