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Ungulata

In traditional classification, "Ungulata" is a general term used to refer to mammals with hooves, including Perissodactyla and Artiodactyla. However, with the progress of molecular phylogenetic research, the traditional "ungulates" or "Ungulata" is not a strict monophyletic concept. In modern classification, whales (Cetacea) are included in even-toed ungulates and merged with even-toed ungulates (Artiodactyla) into "Cetartiodactyla". Therefore, when discussing ungulates today, they are usually broken down into two independent major living groups:

  1. Perissodactyla: including horses, rhinos, tapirs, etc., with an odd number of toes (the middle toe bears weight).

  2. Cetartiodactyla: integrates traditional even-toed ungulates (such as pigs, cattle, deer, camels) and cetaceans (whales, dolphins, porpoises) into a natural monophyletic group. Even-toed ungulates are characterized by an even number of toes on each foot (usually 2 or 4), while the evolution of whales shows that they are closely related to hippos.

Historically, "Ungulates" also included some extinct primitive groups (such as Callostomidae and "Obtsodontia" in a broad sense), but here we mainly focus on the two major living groups: Perissodactyla and Cetiformes.

I. Introduction to Hoofed Mammals

1. Traditional vs. Modern Classification:
Traditionally, “Ungulata” was used as a broad term to include all hoofed mammals. This encompassed horses, rhinos, tapirs (odd-toed) as well as pigs, camels, deer, cattle, and others (even-toed). However, with advances in molecular phylogenetics, it became clear that whales (Cetacea) share a close evolutionary relationship with hippopotamuses (Hippopotamidae), which are even-toed ungulates. As a result, whales have been placed within the same clade as even-toed ungulates, creating the order Cetartiodactyla. This modern grouping better reflects their evolutionary origins.

2. The Two Main Orders of “Ungulates”:

  • Perissodactyla (Odd-toed Ungulates): Horses, rhinos, and tapirs—characterized by having an odd number of toes (usually one or three) and bearing weight mainly on the middle toe.

  • Cetartiodactyla (Even-toed Ungulates + Whales): This group combines traditional Artiodactyla (even-toed ungulates like pigs, camels, deer, bovids) with Cetacea (whales, dolphins, porpoises). Even-toed ungulates typically have two or four toes, and whales are highly specialized aquatic descendants of ancient terrestrial ungulate ancestors.


II. Evolutionary History

  • In the Paleogene and Neogene periods (roughly 20–50 million years ago), hoofed mammals underwent extensive adaptive radiations, spreading across the globe.

  • Perissodactyls once included a much greater diversity, but only three families survive today. They dominated certain habitats in the past but declined due to changing climates and the rise of grasslands.

  • Artiodactyls diversified more extensively, giving rise to a broad range of large herbivores on land. Within the even-toed lineage, one group returned to the water, evolving into modern whales and dolphins. Molecular data confirm that whales are nested within the even-toed ungulates, closely related to hippos, leading to the modern concept of Cetartiodactyla.


III. Classification Tables

A. Perissodactyla (Odd-Toed Ungulates)

FamilyExample Genera/SpeciesNotes
Equidae (Horses, Zebras, Donkeys)Equus (horses, zebras, donkeys)Weight-bearing on a single central toe; adapted for running in open habitats.
Rhinocerotidae (Rhinoceroses)Rhinoceros (Indian rhino), Ceratotherium (white rhino)Thick-skinned herbivores with one or two horns, found in Africa and Asia.
Tapiridae (Tapirs)Tapirus (tapirs of Central/South America, Southeast Asia)Short, flexible proboscis; forest dwellers that feed on leaves and fruits.

B. Cetartiodactyla (Even-Toed Ungulates + Whales)

Even-Toed Ungulates (Artiodactyla)

FamilyExample Genera/SpeciesNotes
Suidae (Pigs)Sus (wild boar, domestic pig), Phacochoerus (warthog)Omnivorous, often with prominent canines; Old World distribution.
Hippopotamidae (Hippos)Hippopotamus amphibiusSemi-aquatic, closely related to whales at the molecular level; African.
Camelidae (Camels, Llamas)Camelus (camels), Lama (llamas), Vicugna (vicuñas)Adapted to arid and high-altitude environments in Africa, Asia, and South America.
Cervidae (Deer)Cervus (red deer), Rangifer (reindeer), Muntiacus (muntjacs)Males typically bear antlers (bone structures shed annually); widespread across Eurasia and the Americas.
Giraffidae (Giraffe, Okapi)Giraffa (giraffe), Okapia (okapi)African endemics, the giraffe is adapted to browsing high foliage.
Bovidae (Cattle, Sheep, Goats, Antelopes)Bos (cattle), Ovis (sheep), Capra (goats), various antelopesExtremely successful and diverse herbivores in Africa, Eurasia, and North America.

Whales (Cetacea, included in Cetartiodactyla)

FamilyExample Genera/SpeciesNotes
Balaenopteridae (Rorqual Whales)Balaenoptera (blue whale), Megaptera (humpback whale)Baleen whales filter-feeding on krill and small fish.
Balaenidae (Right Whales)Eubalaena (right whales)Slow-moving baleen whales that feed on zooplankton.
Physeteridae (Sperm Whales)Physeter (sperm whale)Deep-diving predators of squid; have a large, oil-filled head.
Delphinidae (Dolphins, Orcas)Tursiops (bottlenose dolphin), Orcinus (killer whale)Tooth-bearing whales, highly social and widespread.
Phocoenidae (Porpoises)Phocoena (harbor porpoise)Small toothed whales with shorter beaks, found in coastal waters.

(There are many other whale families; the above are representative examples.)


IV. Summary

The concept of “hoofed mammals” as a single order is outdated. Modern evolutionary and molecular studies have clarified their relationships, placing whales within the lineage of even-toed ungulates. Thus, today we speak of:

  • Perissodactyla (Odd-Toed Ungulates): Horses, rhinos, tapirs.

  • Cetartiodactyla (Even-Toed Ungulates + Cetaceans): Pigs, hippos, camels, deer, cattle, antelopes, and whales/dolphins.

This modern classification highlights the incredible evolutionary journey of some terrestrial herbivores that eventually took to the oceans and became fully aquatic cetaceans. By understanding these relationships, users can appreciate how modern taxonomy accurately reflects the deep evolutionary history and adaptation of hoofed mammals.

Carnivora Primates Rodents Chiroptera Eulipotyphla Ungulata Cetacea Lagoiformes Pangolins Proboscidea Monotremata
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Sus verrucosus

Sus verrucosus,Javan pig、Sanglier pustule,Javan warty pig, warty wild pig

Features:There are three pairs of warts on the face, one pair in front of the eye sockets, two pairs infraorbital and a larger pair on the jaw.

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Sus scrofa

Sus scrofa

Sus scrofa, Wild Boar、Eurasian Wild Pig、Ryukyu Islands Wild Pig, Sanglier、Sanglier d'Eurasie,Jabalí, Schwarzwild、Wildschwein, Zerleg Gakhai

Features:The Eurasian wild boar is the most widespread land mammal on Earth.

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Sus philippensis

Sus philippensis

Sus philippensis,Philippine Warty Pig,Philippine warthog

Features:

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Sus oliveri

Sus oliveri

Sus oliveri,Oliver's Warty Pig,Mindoro Warty Pig, Oliver's Warty Pig

Features:Males have a crown of black and straw-colored hair and well-developed warts in front of the eyes.

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Sus celebensis

Sus celebensis

Sus celebensis,Sulawesi Warty Pig,Celebes wild boar

Features:Piglets are born with five dark brown and six lighter parallel stripes along the length of their bodies.

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Sus cebifrons

Sus cebifrons

Sus cebifrons,Visayan warty pig,Visayan warty pig, curly-haired wild boar

Features:There are obvious white stripes on the face

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Sus bucculentus

Sus bucculentus

Sus bucculentus,ndo-chinese Warty Pig、Heude's Pig、 Vietnam Warty Pig,Vietnamese wild boar, big-mouthed wild boar

Features:A mysterious species

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Porcula salvania

Porcula salvania

Porcula salvania,Pygmy Hog, Sanglier nain、Sanglier pygmée, Jabalí Enano、Jabalí Pigmeo, Nal Gahori、Takuri Borah, Sano Banel,Pygmy pig, pygmy boar

Features:It is the smallest wild boar known in the world.

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Sus barbatus

Sus barbatus

Sus barbatus,Bearded Pig,Western Bearded Pig

Features:The head is large and the body is small, with a coarse, thick "beard" of hair on the bridge of the nose and cheeks.

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Sus ahoenobarbus

Sus ahoenobarbus

Sus ahoenobarbus,Palawan Bearded Pig

Features:It is the largest wild boar in the Philippines and has the longest "beard" on its lower jaw among its species.

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Potamochoerus larvatus

Potamochoerus larvatus

Potamochoerus larvatus,Bushpig,Jungle Pig

Features:The male has warts on his nose and a long tail with a tuft of coarse hair at the tip.

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Potamochoerus porcus

Potamochoerus porcus

Potamochoerus porcus,Red River Hog,West African bush pig, tufted pig, red river hog

Features:The smallest and most colorful of all African pigs

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Hylochoerus meinertzhageni

Hylochoerus meinertzhageni

Hylochoerus meinertzhageni,Forest Hog

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Phacochoerus africanus

Phacochoerus africanus

Phacochoerus africanus,Common Warthog,Common warthog, Eritrean warthog

Features:Named after the warts under the eyes

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Phacochoerus aethiopicus

Phacochoerus aethiopicus

Phacochoerus aethiopicus,Desert Warthog,Desert warthog, Cape warthog, Somali warthog

Features:High reproductive capacity, but high mortality rate of young

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Babyrousa togeanensis

Babyrousa togeanensis

Babyrousa togeanensis,Togian Islands Babirusa,Malengewi babirusa, Celebes babirusa, Celebes wild boar

Features:Very sparse hair, white on the belly and inside of the legs

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Babyrousa celebensis

Babyrousa celebensis

Babyrousa celebensis,Kalowatan,Celebes Babirusa, Togian Babirusa

Features:Almost no hair on the body

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Babyrousa babyrussa

Babyrousa babyrussa

Babyrousa babyrussa,Hairy Babirusa、Babiroussa,Moluccan wild boar, Babirusa pig deer, Maluku babirusa

Features:It is the wild boar with the smallest skull shape.

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Lama glama

Lama glama

Lama glama,llama,Domestic Alpaca

Features:Long limbs, protruding and curved ears

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Vicugna pacos

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Vicugna pacos, Alpaca,Grass Mud Horse,Alpaca

Features:One of the top ten mythical beasts made fun of by Chinese netizens

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Lama guanicoe

Lama guanicoe

Lama guanicoe,Guanaco

Features:The wild ancestor of domestic camels and alpacas

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