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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
Cephalophus spadix

Cephalophus spadix

Tanzanite, Abbott's duiker

Features:Relatively tall, with short legs, a thick neck, and a short, shiny coat that is generally dark brown or black.

Tanzanian duiker (scientific name: Cephalophus spadix) English Abbott's Duiker, Minde, French Céphalophe d'Abbott, German Abbott-Ducker, Abbottducker, no subspecies. Tanzanian duiker and yellow-backed duiker are similar in size and color, but the yellow-backed duiker has a unique yellow wed...

Cephalophus silvicultor

Cephalophus silvicultor

Cephalophus silvicultor,Yellow-backed antelope,

Features:One of the largest forest duiker species

Yellow-backed Duiker (scientific name: Cephalophus silvicultor) English: Yellow-backed Duiker, French: Céphalophe géant, Céphalophe à dos jaune, Spanish: Duiquero de Lomo Amarillo, German: Gelbrückenducker, Riesenducker, there are 4 subspecies.The yellow-backed duiker is an unsociable species....

Cephalophus rufilatus

Cephalophus rufilatus

Cephalophus rufilatus

Features:Flame-marked face, large ears, and a tuft of black hair on a dark forehead

Red-flanked Duiker (scientific name: Cephalophus rufilatus) is called Red-flanked Duiker in English, Céphalophe à Flancs Roux in French, Blaurückenducker and Rotflankenducker in German, and has no subspecies.In the wild, red-rumped duikers occupy different habitats that rarely overlap. They live...

Cephalophus ogilbyi

Cephalophus ogilbyi

Cephalophus ogilbyi,Ehrlich's Muntjac

Features:Has a lighter gold color and a narrow dorsal stripe

Ogilby's Duiker (Cephalophus ogilbyi) is known as Ogilby's Duiker in English, Céphalophe d'Ogilby in French, Duiquero de Ogilby in Spanish, Fernando-Po-Ducker, Ogilby-Ducker, Ogilbyducker in German, and has three subspecies.The Osmanthus duiker is one of the least known antelopes. The f...

Cephalophus nigrifrons

Cephalophus nigrifrons

Cephalophus nigrifrons

Features:There is a tuft of well-developed long hair on the forehead, mainly black or red

Black-fronted Duiker (scientific name: Cephalophus nigrifrons) English: Black-fronted Duiker, French: Céphalophe à front noir, German: Schwarzstirnducker, there are 6 subspecies.Black-fronted duikers are thought to be territorial, using feces and preorbital gland markings to demarcate territorial...

Cephalophus niger

Cephalophus niger

Cephalophus niger

Features:Black in color, with a usually red face and a tuft of bright red hair on the forehead

Black Duiker (scientific name: Cephalophus niger) is called Black Duiker in English, Céphalophe noir in French, and Schwarzducker in German. There is no subspecies.The Tanzanian Duiker and the Black Duiker are both dark in color, but the Tanzanian Duiker has a bright reddish-brown crest on its fore...

Cephalophus natalensis

Cephalophus natalensis

Features:Both sexes have yellow-brown fur, with individuals in the northern part of the range having a brighter, more reddish-brown fur.

The Red Duiker (Cephalophus natalensis) is the only red duiker in its range; it is larger and has a more reddish-brown coat than the blue duiker and the natalensis. The Habsburg duiker is sometimes considered a subspecies of the Red Duiker, but can be distinguished by its darker legs and black facia...

Cephalophus jentinki

Cephalophus jentinki

Cephalophus jentinki,Jane's gazelle, Long-headed gazelle

Features:It is one of the largest antelopes and its coloration is similar to that of the Asian tapir.

Jentink's duiker (scientific name: Cephalophus jentinki) is called Jentink's duiker in English, Céphalophe de Jentink in French, Duiquero de Jentink in Spanish, and Jentinkducker in German. There are no subspecies.The Jans's Gazelle was discovered in 1884, but was not formally described...

Cephalophus harveyi

Cephalophus harveyi

Cephalophus harveyi,Harbour's gazelle

Features:There is a black flame line extending from the nose to the eyes to the forehead.

Harvey's Duiker (scientific name: Cephalophus harveyi) English: Harvey's Duiker, East African Red Duiker, Harvey's Red Duiker, French: Céphalophe de Harvey, German: Céphalophe de Harvey, no subspecies.The Harbour's and Black-fronted Duikers do not have dorsal stripes, and the Red D...

Cephalophus dorsalis

Cephalophus dorsalis

Cephalophus dorsalis,Bay Duiker, Céphalophe bai、Céphalophe à bande dorsale noire, Duiquero Bayo,Schwarzrückenducker,Black-backed antelope, Gulf antelope

Features:Bright white spot above each eye

Bay Duiker (scientific name: Cephalophus dorsalis) English: Bay Duiker, French: Céphalophe bai, Céphalophe à bande dorsale noire, Spanish: Duiquero Bayo, German: Schwarzrückenducker, has 2 subspecies.In the wild, the similar “red duiker” species are often difficult to tell apart based on a bri...

Cephalophus callipygus

Cephalophus callipygus

Cephalophus callipygus

Features:The horns are surrounded by a rich tuft of tawny hair

Blue-rumped duiker (scientific name: Cephalophus callipygus) English: Peters' Duiker, Gabon Duiker, French: Céphaplophe de Peter, German: Petersducker, Schönsteißducker, no subspecies.In the wild, the "red duikers" are often difficult to tell apart, especially when they're runni...

Cephalophus adersi

Cephalophus adersi

Cephalophus adersi,Ehrlich's duiker, Sang Island duiker

Features:Considered one of the most beautiful antelopes

Cephalophus adersi (English: Aders' Duiker, German: Aders-Ducker, Adersducker, Sansibar-Ducker, Swahili: Paa Nunga, no subspecies.The Sangdao duiker is a typical solitary animal that lives in pairs during the breeding season. It is territorial, and the scent marking of the preorbital glands and...

Philantomba walteri

Philantomba walteri

Philantomba walteri,Walter's Gazelle, Walter's Gazelle

Features:It is the only mammal to appear on the list of the top ten new species in 2011.

Walter's Duiker (scientific name: Philantomba walteri), foreign name Walter's Duiker, no subspecies.The Walter's duiker is a deer-like mammal and a new species of antelope that was first discovered in a bushmeat market in West Africa. The paper confirming the new species was published in...

Philantomba monticola

Philantomba monticola

Features:Has a distinctive stocky body with large hindquarters, an arched back and short, slender legs

Blue Duiker (scientific name: Philantomba monticola) is also known as Blue Duiker in English. There are 12 subspecies.Blue Duiker is most active at dawn and dusk. It mainly feeds on fruits, leaves, flowers, fungi, seeds, and sometimes insects and even small animals. Like other antelopes, they can fo...

Philantomba maxwellii

Philantomba maxwellii

Philantomba maxwellii,Macartney's gazelle, Macartney's gazelle

Features:The smooth fur is a dark blue-grey or grey-brown, with paler underparts and markings on the underside of the neck and belly.

Brown duiker (scientific name: Philantomba maxwellii) English Maxwell's Duiker, French Céphalophe de Maxwell, German Céphalophe de Maxwell, has 2 subspecies.The ranges of the brown duiker have set areas with paths through the vegetation around them. Males mark their territories before feeding...

Tragelaphus strepsiceros

Tragelaphus strepsiceros

Tragelaphus strepsiceros,Greater kudu, Greater scimitar-horned antelope, Greater kudu, African kudu, Greater kudu

Features:The male has a spectacular spiral horn that can reach over a meter in length.

Tragelaphus strepsiceros (scientific name: Greater Kudu) has four subspecies.Tragelaphus strepsiceros is generally not very active during the day and hides in the woods. They forage in the morning and evening. Although they tend to stay in the same place, they will migrate to farther places during t...

Tragelaphus spekii

Tragelaphus spekii

Tragelaphus spekii

Features:Able to stand on dirt and floating vegetation mats without sinking

Sitatunga (scientific name: Tragelaphus spekii) is also known as Sitatunga and Marshbuck. It has no subspecies.Sitatunga is active in the early morning, but sometimes during the day or at night, but is most active at dawn and dusk. Females tend to live in groups, while males spend most of their time...

Tragelaphus scriptus

Tragelaphus scriptus

Tragelaphus scriptus,bush antelope

Features:Mainly brownish red or yellowish brown, with distinct vertical stripes, males have long spiral horns

Bushbuck (scientific name: Tragelaphus scriptus) is also known as Bushbuck in foreign languages. There are 10 subspecies.Bushbuck is the least social of the African antelopes. Often seen alone, although sometimes small groups of females and their young are found. Bushbucks are not territorial specie...

Tragelaphus oryx

Tragelaphus oryx

Tragelaphus oryx,Eland antelope, Eland antelope, Eland antelope

Features:The fur is brown or tan with some vertical white stripes

Common Eland (scientific name: Tragelaphus oryx) is also known as Common Eland or Eland in foreign languages. It has no subspecies.The antelope is a social species that usually forms loose and mobile herds of 25-60 individuals, but can occasionally gather in groups of more than 1,000, especially dur...

Tragelaphus imberbis

Tragelaphus imberbis

Tragelaphus imberbis

Features:Not good at running, fur has camouflage color

Lesser Kudu (scientific name: Tragelaphus imberbis) is also known as Lesser Kudu in English. There are 2 subspecies.Lesser Kudu is mainly nocturnal, foraging in the lush and dense jungle within a few hours after sunrise. They do not seem to be dependent on water sources, but do not usually live in w...

Tragelaphus eurycerus

Tragelaphus eurycerus

Tragelaphus eurycerus

Features:The fur is reddish brown with fine white stripes

There are two subspecies of the eurycerus (scientific name: Tragelaphus eurycerus), and the names come from Greek. "Tragelaphus" is a combination of "goat" (trag) and "deer" (elaphos), and "eurycerus" is composed of "universal" (eurus) and "horn...