Whippomorpha or Cetancodonta is a group of artiodactyls that contains all living cetaceans (whales, dolphins, and porpoises) and the hippopotamids.

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).

[3][4] 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.

[5] Modern whippomorphs all share a number of behavioural and physiological traits; such as a dense layer of subcutaneous fat and largely hairless bodies.

The name Whippomorpha is a combination of English (wh[ale] + hippo[potamus]) and Greek (μορφή, morphē = form).

[2] Some attempts have been made to rename the suborder Cetancodonta, due to the misleading utilization of the suffix -morpha for a crown group,[6] as well as the risk of confusion with the clade Hippomorpha (which consists of equid perissodactyls);[7] however Whippomorpha maintains precedence.

Some cetaceans live exclusively within a single marine body, such as the narwhal, whose range is limited to the Arctic Ocean.

The birthing process also takes place underwater, meaning calves must swim to the surface in order to breathe for the first time.

[citation needed] Cetaceans generally reach sexual maturity around 10 years of age, and have a gestation period of around 12 months.

Whippomorpha is considered a sister clade to Ruminantia (which contains cattle, sheep and deer), as well as the extinct Raoellidae.

Early support for the existence of a Cetacea/Hippopotamidae clade originated from analysis of the molecular composition of a blood-clotting protein γ-fibrinogen taken from whales and hippopotamuses.

[28] One evolutionarily significant whale ancestor was the raoellid Indohyus, which was a Himalayas-dwelling, digitgrade omnivore roughly the size of a raccoon.

Evidence for this includes the fact that the tooth enamel of Indohyus was considerably less worn than would be expected for an animal with an exclusively terrestrial diet.

It also likely represented a transitional organism from freshwater to seawater, as the isotopic analysis of the bones and teeth of Ambulocetus indicate that it inhabited estuaries.

[20] These findings somewhat explain the once confusing paleontological age gap that existed as a major piece of evidence against an evolutionary link between Hippopotamidae and Cetacea.

Additionally, both animals bear single-lobed lungs (similar to other aquatic mammals), which allow to be filled with air more rapidly.

[32] Hippos' bodies contain a layer of dense fat, reminiscent of a whales' blubber, and situated between skin and muscle.

Hippos are incredibly territorial and protective of their young, and are the deadliest mammal in Africa, killing between two and three thousand people each year.

Common hippopotamuses are classed as vulnerable, and are subject to habitat destruction as a result of agriculture, water management, climate change and development of housing and urban areas.

The few surviving pygmy hippopotamuses occupy a much smaller habitat area in Liberia, Sierra Leone, and the Ivory Coast.

Stories of dolphins typically include them playing a role in helping shipwrecked sailors or guiding lost ships.

Cetaceans are revered for their immense size, intelligent and playful dispositions, displays of speed in water, and contributions to scientific research.