Equidae in the context of Perissodactyl

The first evidence of horses in warfare dates from Eurasia between 4000 and 3000 BC. A Sumerian illustration of warfare from 2500 BC depicts some type of equine pulling wagons. By 1600 BC, improved harness and chariot designs made chariot warfare common throughout the Ancient Near East, and the earliest written training manual for war horses was a guide for training chariot horses written about 1350 BC. As formal cavalry tactics replaced the chariot, so did new training methods, and by 360 BC, the Greek cavalry officer Xenophon had written an extensive treatise on horsemanship. The effectiveness of horses in battle was also revolutionized by improvements in technology, such as the invention of the saddle, the stirrup, and the horse collar.

Many different types and sizes of horses were used in war, depending on the form of warfare. The type used varied with whether the horse was being ridden or driven, and whether they were being used for reconnaissance, cavalry charges, raiding, communication, or supply. Throughout history, mules and donkeys, as well as horses played a crucial role in providing support to armies in the field.

The horse (Equus ferus caballus) is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of Equus ferus. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, Eohippus, into the large single-toed animal of today, originally in North America. Humans began domesticating horses around 4000 BCE in Central Asia, and their domestication is believed to have been widespread by 3000 BCE. Horses in the subspecies caballus are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, which are horses that have never been domesticated. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior.

Horses are adapted to run, allowing them to quickly escape predators, and possess a good sense of balance and a strong fight-or-flight response. Related to this need to flee from predators in the wild is an unusual trait: horses are able to sleep both standing up and lying down, with younger horses tending to sleep significantly more than adults. Female horses, called mares, carry their young for approximately 11 months and a young horse, called a foal, can stand and run shortly following birth. Most domesticated horses begin training under a saddle or in a harness between the ages of two and four. They reach full adult development by age five, and have an average lifespan of between 25 and 30 years.

A chariot is a type of vehicle similar to a cart, driven by a charioteer, usually using horses to provide rapid motive power. The oldest known chariots have been found in burials of the Sintashta culture in modern-day Chelyabinsk Oblast, Russia, dated to c. 1950–1880 BC and are depicted on cylinder seals from Central Anatolia in Kültepe dated to c. 1900 BC. The critical invention that allowed the construction of light, horse-drawn chariots was the spoked wheel.

The chariot was a fast, light, open, two-wheeled conveyance drawn by two or more equids (usually horses) that were hitched side by side, and was little more than a floor with a waist-high guard at the front and sides. It was initially used for ancient warfare during the Bronze and Iron Ages, but after its military capabilities had been superseded by light and heavy cavalries, chariots continued to be used for travel and transport, in processions, for games, and in races.

Equinae is a subfamily of the family Equidae, known from the Hemingfordian stage of the Early Miocene (16 million years ago) onwards. They originated in North America, before dispersing to every continent except Australia and Antarctica. They are thought to be a monophyletic grouping. Members of the subfamily are referred to as equines; the only extant equines are the horses, asses, and zebras of the genus Equus, with two other genera Haringtonhippus and Hippidion becoming extinct at the beginning of the Holocene, around 11–12,000 years ago.

The subfamily contains two tribes, the Equini and the Hipparionini, as well as two unplaced genera, Merychippus and Scaphohippus. Members of the family ancestrally had three toes, while members of the tribe Equini from the Middle Miocene onwards developed monodactyl feet.

Palaeotherium is an extinct genus of equoid that lived in Europe and possibly the Middle East from the Middle Eocene to the Early Oligocene. It is the type genus of the Palaeotheriidae, a group exclusive to the Palaeogene that was closest in relation to the Equidae, which contains horses plus their closest relatives and ancestors. Fossils of Palaeotherium were first described in 1782 by the French naturalist Robert de Lamanon and then closely studied by another French naturalist, Georges Cuvier, after 1798. Cuvier erected the genus in 1804 and recognized multiple species based on overall fossil sizes and forms. As one of the first fossil genera to be recognized with official taxonomic authority, it is recognized as an important milestone within the field of palaeontology. The research by early naturalists on Palaeotherium contributed to the developing ideas of evolution, extinction, and succession and demonstrating the morphological diversity of different species within one genus.

Since Cuvier's descriptions, many other naturalists from Europe and the Americas recognized many species of Palaeotherium, some valid, some reclassified to different genera afterward, and others being eventually rendered invalid. The German palaeontologist Jens Lorenz Franzen modernized its taxonomy due to his recognition of many subspecies as part of his dissertation in 1968, which were subsequently accepted by other palaeontologists. Today, there are sixteen known species recognized, many of which have multiple subspecies. In 1992, the French palaeontologist Jean-Albert Remy recognized two subgenera that most species are classified to based on cranial anatomies: the specialized Palaeotherium and the more generalized Franzenitherium.

Ungulates are members of the diverse clade Euungulata, which primarily consists of large mammals with hooves. Once part of the taxon "Ungulata" along with paenungulates and tubulidentates, as well as several extinct taxa, "Ungulata" has since been determined to be a polyphyletic grouping based on molecular data. As a result, true ungulates had since been reclassified to the newer clade Euungulata in 2001 within the clade Laurasiatheria, while Paenungulata and Tubulidentata had been reclassified to the distant clade Afrotheria. Alternatively, some authors use the name Ungulata to designate the same clade as Euungulata.

Living ungulates are divided into two orders: Perissodactyla including equines, rhinoceroses, and tapirs; and Artiodactyla including cattle, antelope, pigs, giraffes, camels, sheep, deer, and hippopotamuses, among others. Cetaceans such as whales, dolphins, and porpoises are also classified as artiodactyls, although they do not have hooves. Most terrestrial ungulates use the hoofed tips of their toes to support their body weight while standing or moving. Two other orders of ungulates, Notoungulata and Litopterna, both native to South America, became extinct at the end of the Pleistocene, around 12,000 years ago.

Perissodactyla (/pəˌrɪsoʊˈdæktɪlə/, from Ancient Greek περισσός, perissós 'odd' and δάκτυλος, dáktylos 'finger, toe'), or odd-toed ungulates, is an order of ungulates. The order includes about 17 living species divided into three families: Equidae (horses, asses, and zebras), Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They typically have reduced the weight-bearing toes to three or one of the five original toes, though tapirs retain four toes on their front feet. The nonweight-bearing toes are either present, absent, vestigial, or positioned posteriorly. By contrast, artiodactyls (even-toed ungulates) bear most of their weight equally on four or two (an even number) of the five toes: their third and fourth toes. Another difference between the two is that perissodactyls digest plant cellulose in their intestines, rather than in one or more stomach chambers as artiodactyls, with the exception of Suina, do.

The order was considerably more diverse in the past, with notable extinct groups including the brontotheres, palaeotheres, chalicotheres, and the paraceratheres, with the paraceratheres including the largest known land mammals to have ever existed.

The evolution of the horse, a mammal of the family Equidae, occurred over a geologic time scale of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the large, single-toed, modern-day horse. Paleozoologists have been able to piece together a more complete outline of the evolutionary lineage of the modern horse than of any other animal. Much of this evolution took place in North America, where horses originated but became extinct about 10,000 years ago, before being reintroduced in the 15th century.

The horse belongs to the order Perissodactyla (odd-toed ungulates), the members of which share hooved feet and an odd number of toes on each foot, as well as mobile upper lips and a similar tooth structure. This means that horses share a common ancestry with tapirs and rhinoceroses. The perissodactyls arose in the late Paleocene, less than 10 million years after the Cretaceous–Paleogene extinction event. This group of animals appears to have been originally specialized for life in tropical forests, but whereas tapirs and, to some extent, rhinoceroses, retained their jungle specializations, modern horses are adapted to life in the climatic conditions of the steppes, which are drier and much harsher than forests or jungles. Other species of Equus are adapted to a variety of intermediate conditions.

Equine anatomy encompasses the gross and microscopic anatomy of horses, ponies and other equids, including donkeys, mules and zebras. While all anatomical features of equids are described in the same terms as for other animals by the International Committee on Veterinary Gross Anatomical Nomenclature in the book Nomina Anatomica Veterinaria, there are many horse-specific colloquial terms used by equestrians.

A mare is an adult female horse or other equine. In most cases, a mare is a female horse over the age of three, and a filly is a female horse three and younger. In Thoroughbred horse racing, a mare is defined as a female horse more than four years old. The word can also be used for other female equine animals, particularly mules and zebras, but a female donkey is usually called a "jenny". A broodmare is a mare used for breeding.

Zebras (US: /ˈziːbrəz/, UK: /ˈzɛbrəz, ˈziː-/) (subgenus Hippotigris) are African equines with distinctive black-and-white striped coats. There are three living species: Grévy's zebra (Equus grevyi), the plains zebra (E. quagga), and the mountain zebra (E. zebra). Zebras share the genus Equus with horses and asses, the three groups being the only living members of the family Equidae. Zebra stripes come in different patterns, unique to each individual. Several theories have been proposed for the function of these patterns, with most evidence supporting them as a deterrent for biting flies. Zebras inhabit eastern and southern Africa and can be found in a variety of habitats such as savannahs, grasslands, woodlands, shrublands, and mountainous areas.

Zebras are primarily grazers and can subsist on lower-quality vegetation. They are preyed on mainly by lions, and typically flee when threatened but also bite and kick. Zebra species differ in social behaviour, with plains and mountain zebra living in stable harems consisting of an adult male or stallion, several adult females or mares, and their young or foals; while Grévy's zebra live alone or in loosely associated herds. In harem-holding species, adult females mate only with their harem stallion, while male Grévy's zebras establish territories which attract females and the species is polygynandrous. Zebras communicate with various vocalisations, body postures and facial expressions. Social grooming strengthens social bonds in plains and mountain zebras.

Asinus is a subgenus of Equus that encompasses several subspecies of the Equidae commonly known as wild asses or wild donkeys, characterized by long ears, a lean, straight-backed build, lack of a true withers, a coarse mane and tail, and a reputation for considerable toughness and endurance.

The common donkey is the best-known domesticated representative of the subgenus, with both domesticated and feral varieties. Among the wild ass species, several never-domesticated species live in Asia and Africa, with the extinct European wild ass species formerly inhabiting Europe.

Equus (/ˈɛkwəs, ˈiːkwəs/) is a genus of mammals in the perissodactyl family Equidae, which includes horses, asses, and zebras. Within the Equidae, Equus is the only recognized extant genus, comprising seven living species. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. The genus originated in North America and dispersed into the Old World and South America during the Early and Middle Pleistocene. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes (erect in most subspecies), and long tails. All species are herbivorous, and mostly grazers, with simpler digestive systems than ruminants but able to subsist on lower-quality vegetation.

While the domestic horse and donkey (along with their feral descendants) exist worldwide, wild equine populations are limited to Africa and Asia. Wild equine social systems are in two forms; a harem system with tight-knit groups consisting of one adult male or stallion/jackass, several females or mares/jennets, and their young or foals; and a territorial system where males establish territories with resources that attract females, which associate very fluidly. In both systems, females take care of their offspring, but males may play a role as well. Equines communicate with each other both visually and vocally. Human activities have threatened wild equine populations.

Merychippus is an extinct proto-horse of the family Equidae that was endemic to North America during the Miocene, 15.97–5.33 million years ago. It had three toes on each foot and is the first horse known to have grazed.

Scaphohippus is an extinct Miocene genus of equine, with two known species, known from fossils found in California, New Mexico, Montana, and Nebraska.