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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 Pholidota Proboscidea Monotremata
Neotragus moschatus

Neotragus moschatus

Neotragus moschatus

Features:The overall color varies, and the ears are thin-skinned, large and round, and appear translucent pink in the sun.

Neotragus moschatus (scientific name: Neotragus moschatus): It is the only species of the genus Neotragus in the order Artiodactyla, family Bovidae, and is a very small antelope with 4 subspecies.The Sangdao Neogaur and its many subspecies were from 1972 to 2005, belonging to the genus Neotragus, wh...

Neotragus pygmaeus

Neotragus pygmaeus

Neotragus pygmaeus

Features:One of the smallest ungulates

Royal Antelope (scientific name: Neotragus pygmaeus) English Royal Antelope, French Antilope royale, German Kleinstbokchen, no subspecies.The Bess Island Antelope is very similar to the Royal Antelope, but is only found in central Africa. The Baird's Island Oryx has small black and white marking...

Neotragus batesi

Neotragus batesi

Neotragus batesi

Features:Small black and white spots on the ears

Bates' Pygmy Antelope (scientific name: Neotragus batesi) English: Bates' Pygmy Antelope, Dwarf Antelope, German: Batesbokchen, no subspecies.The Bet's Island Oryx is similar in appearance to the Royal Island Oryx (Neotragus pygmaeus) of West Africa, but can be distinguished by its large...

Madoqua saltiana

Madoqua saltiana

Madoqua saltiana

Features:The English name is Dik-dik, which comes from its call.

Madoqua saltiana (Scientific name: Madoqua saltiana) English: Salt's Dik-dik, French Dik-dik de Salt, German: Eritrea-Dikdik, Somalia: Sagaro, there are 5 subspecies.The antelope is diurnal and most active in the morning and afternoon. Sometimes it is active well into the afternoon and into the...

Madoqua piacentinii

Madoqua piacentinii

Madoqua piacentinii

Features:The smallest antelope

Silver Dik-dik (scientific name: Madoqua piacentinii) English: Silver Dik-dik, French: Dik-dik argente, German: Piacentini Dik-dik, no subspecies.East (1999) estimated the total population on the Somali coast to be 30,000 based on an average density of 2.0/km2 (similar to M.saltiana) and an occupied...

Madoqua kirkii

Madoqua kirkii

Madoqua kirkii

Features:Long mouth and nose

Kirk's Dik-dik (scientific name: Madoqua kirkii) English: Kirk's Dik-dik, French: Dik-dik de Kirk, German: Kirk-Dikdik, there are 4 subspecies.Cuvier's antelope use well-defined routes when crossing their territory. All families mark their territory through a process called the "def...

Madoquaguentheri

Madoquaguentheri

Madoquaguentheri

Features:A small, slender antelope with a long neck and a small head.

Madoquaguentheri (scientific name: Madoquaguentheri) English: Guenther's Dik-dik, Günther's Dik-dik, French: Dik-dik de Günther, Somalia: Ghussli, there are 2 subspecies.The Gunn's gazelle is mainly active during the day, but also active at night, usually until about 3 a.m., and then r...

Litocranius walleri

Litocranius walleri

Litocranius walleri,Kirin Antelope

Features:mammal whose name originated from the somali language

Giraffe (scientific name: Litocranius walleri), also known as Kirin antelope. Its name originates from the Somali word for mammal.Giraffes usually live alone or in pairs, and occasionally 6 or 7 females live together in small groups led by a male. Unlike other antelopes, giraffes do not eat low-lyin...

Nanger soemmerringii

Nanger soemmerringii

Nanger soemmerringii,Sudanese antelope, Sumerian antelope

Features:The general body color is light yellow-brown, the lower body is white, with a clear dividing line

Somali gazelle (scientific name: Nanger soemmerringii) is also known as Soemmerring's Gazelle in foreign languages. There are three subspecies.Once upon a time, the attractive Somali gazelle would gather in large groups of hundreds during seasonal migration. This spectacular sight is already ver...

Nanger granti

Nanger granti

Nanger granti,Grant's gazelle, Grant's gazelle

Features:It has long horns and legs, and its white rump forms a distinct rectangle with the brown back.

Grant's gazelle (scientific name: Nanger granti) is a large, light-haired antelope with three subspecies.Grant's gazelle is migratory, and they migrate seasonally throughout their range, except in areas where there is abundant forage supply throughout the year. The species migrates in herds,...

Nanger dama

Nanger dama

Nanger dama,Fallow deer gazelle, Damma gazelle

Features:It is the largest species of all antelopes.

Nanger dama (scientific name: Nanger dama) is also known as Dama Gazelle, Addra Gazelle, and Mhorr Gazelle. There are three subspecies.Nanger dama migrates for a long time, moving into the Sahara Desert in the rainy season and to the open jungle in the dry season. When in the desert, they live toget...

Gazella spekei

Gazella spekei

Gazella spekei

Features:The smallest gazelle

The Gazella spekei is the smallest gazelle. The Gazella spekei was once considered a subspecies of the mountain gazelle.The population size of the Gazella spekei is relatively small, consisting of five to ten individuals, and occasionally larger groups. The territorial males control the herd and ter...

Gazella marica

Gazella marica

Gazella marica,Sand Gazelle

Features:

Arabian Sand Gazelle (Scientific name: Gazella marica) English: Arabian Sand Gazelle, Arabic: Reem, no subspecies. The Arabian Sand Gazelle was previously classified as a subspecies of the Goitered Gazelle. DNA evidence shows that although the two species are closely related, they represent differen...

Gazella leptoceros

Gazella leptoceros

Gazella leptoceros,Slender-horned Oryx

Features:It is the palest gazelle species.

Slender-horned Gazelle (scientific name: Gazella leptoceros) English: Slender-horned Gazelle, French: Gazelle Leptocère, Gazelle à Cornes Fines, Spanish: Gacela de Astas Delgadas, Arabic: Ghazal abiad, Reem, German: Dunengazelle, has 2 subspecies.Slender-horned gazelles live in groups, usually con...

Gazella gazella

Gazella gazella

Gazella gazella

Features:Dark brown upper body, white lower body, light brown flanks and limbs

Mountain Gazelle (scientific name: Gazella gazella) is also known as Mountain Gazelle and Idmi in foreign languages. There are 6 subspecies.Mountain gazelles gather in groups, usually in small groups of 3-8, sometimes more. The social structure is that of a male leader who has his own territory and...

Gazella dorcas

Gazella dorcas

Gazella dorcas,Dorcas gazelle

Features:One of the most desert-adapted gazelles may never drink water in its entire life

Deer gazelle (scientific name: Gazella dorcas) foreign name Dorcas Gazelle, there are 6 subspecies.Adult male deer gazelles are territorial and will deposit feces within their territory. These feces are deposited in a striking display, with males first making footprints on the ground, then urinating...

Gazella cuvieri

Gazella cuvieri

Gazella cuvieri,Cuvier's Gazelle, Knight's Gazelle

Features:It is the darkest antelope in terms of fur color.

Cuvier's Gazelle (scientific name: Gazella cuvieri) is also known as Cuvier's Gazelle, Mountain Gazelle, Uvier's Gazelle, Cuviers Gazelle, and has no subspecies.Cuvier's gazelles live in small groups of 3-5, sometimes up to 82 in large groups, these groups are composed of females and...

Gazella bilkis

Gazella bilkis

Gazella bilkis,Queen of Sheba's Gazelle

Features:

The Yemen Gazelle (scientific name: Gazella bilkis, English name: Queen of Sheba's Gazelle) is a bovine animal originally distributed in the mountains of Yemen. It became extinct between 1985 and 1986.Protect wild animals and eliminate game.Maintaining ecological balance is everyone's respon...

Gazella bennetti

Gazella bennetti

Gazella bennetti

Features:The skull is fairly short and flat, with an elongated premaxilla that is slightly curved.

Indian Gazelle (scientific name: Gazella bennetti) is also known as Chinkara and Indian Gazelle in foreign languages. There are 6 subspecies.Indian Gazelle marks its territory on piles of feces. Like other gazelles, adult males are territorial and stay in demarcated areas. They will chase away other...

Gazella arabica,

Gazella arabica,

Features:

The Arabian gazelle (Gazella arabica) is an enigmatic gazelle that was hunted to extinction in its Middle Eastern habitat of Saudi Arabia and is known only from a specimen found in 1825 on the Red Sea island of Farasen. The species was listed as extinct on the IUCN Red List of Threatened Species in...

Eudorcas tilonura

Eudorcas tilonura

Eudorcas tilonura

Features:There are two large white rings around the eyes, a reddish forehead, and long, light-colored ears.

Eritrean Gazelle (scientific name: Eudorcas tilonura) English Heuglin's Gazelle, Eritrean Gazelle, French Gazelle d'Erythrée, German Eritreagazelle, no subspecies.The Eritrean gazelle lives east of the Nile. In the past, the species was considered to be distinct from the Thomson's gazel...