Equinae is a

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Equidae Equidae (commonly known as the horse family) is the Taxonomy (biology), taxonomic Family (biology), family of Wild horse, horses and related animals, including Asinus, asses, zebra, zebras, and many extinct species known only from fossils. The fa ...

, known from the

Hemingfordian The Hemingfordian on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 20,600,000 to 16,300,000 years BP. It is usually considered to overlap the lates ...

stage of the

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

(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 In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

grouping. Members of the subfamily are referred to as equines; the only extant equines are the

horse 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 mi ...

ass Ass most commonly refers to: * Buttocks (in informal American English) * Donkey or ass, ''Equus africanus asinus'' **any other member of the subgenus ''Asinus'' Ass or ASS may also refer to: Art and entertainment * Ass (album), ''Ass'' (albu ...

es, and

zebra Zebras (, ) (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. ...

s of the genus ''Equus'', with two other genera ''

Haringtonhippus ''Haringtonhippus'' is an extinct genus of equine from the Pleistocene of North America The genus is monospecific, consisting of the species ''H. francisci'', initially described in 1915 by Oliver Perry Hay as ''Equus francisci''. Members of the ...

'' and ''

Hippidion ''Hippidion'' (meaning ''little horse'') is an extinct genus of equine that lived in South America from the Late Pliocene to the end of the Late Pleistocene (Lujanian), between 2.5 million and 11,000 years ago. They were one of two lineages of eq ...

'' becoming extinct at the beginning of the Holocene, around 11–12,000 years ago. The subfamily contains two tribes, the Equini and the

Hipparionini Hipparionini is a tribe of three-toed horses in the subfamily Equinae. They had body forms similar to modern equines, with high-crowned teeth. They first appeared in North America during the Early Miocene around 17 million years ago, before migrat ...

, as well as two unplaced genera, ''

Merychippus ''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 Grazing (behaviour), grazed ...

'' and ''

Scaphohippus ''Scaphohippus'' is an extinct Miocene genus of equine, with two known species, known from fossils found in California, New Mexico, Montana, and Nebraska. History Both species in the genus were originally described as members of the wastebaske ...

''. Members of the family ancestrally had three toes, while members of the tribe Equini from the Middle Miocene onwards developed monodactyl feet.

Sister taxa

Anchitheriinae The Anchitheriinae are an extinct subfamily of the Perissodactyla family Equidae, the same family which includes modern horses, zebras and donkeys. This subfamily is more primitive than the living members of the family. The group first appeared ...

Hyracotheriinae ''Hyracotherium'' ( ; " hyrax-like beast") is an extinct genus of small (about 60 cm in length) perissodactyl ungulates that was found in the London Clay formation. This small, fox-sized animal is (for some scientists) considered to be the ea ...

References

Miocene horses Pliocene Perissodactyla Pleistocene horses Equidae Extant Miocene first appearances {{horse-stub