The family Equidae (Equidae or Equines)
The horse family (Equidae)
Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. The family evolved around 50 million years ago from a small, multi-toed ungulate into larger, single-toed animals. All extant species are in the genus Equus, which originated in North America. Equidae belongs to the order Perissodactyla, which includes the extant tapirs and rhinoceros, and several extinct families.
The term equid refers to any member of this family, including any equine.
Origin
The evolution of the family followed the path of adaptation to fast, prolonged running in open spaces and to a diet of hard plant food. In the course of evolution, the limbs of the horse ancestors lengthened, the joints straightened, the middle toe became increasingly massive, and the lateral toes gradually reduced.
Description
Modern Equidae have long slender legs with a highly developed third toe covered by a horny hoof, the second and fourth toes are reduced to thin slate bones under the skin, while the first and fifth toes are completely atrophied. Only one genus of horses has survived to the present day with 7 species. All have a slight build and an elongated head with large, lively eyes, movable pointed ears and wide open nostrils. Their neck is long and muscular and their body is barrel-shaped due to their very long guts (up to 26 m). Horses have striking molars with flat chewing surfaces: they grow continuously throughout their lives, as in rodents.
Classification
Order Perissodactyla (In addition to Equidae, Perissodactyla includes four species of tapir in a single genus, as well as five living species (belonging to four genera) of rhinoceros.) † indicates extinct taxa.
- Family Equidae:
- Subfamily †Eohippinae:
- Genus †Epihippus;
- Genus †Haplohippus;
- Genus †Eohippus;
- Genus †Minippus;
- Subfamily †Propalaeotheriinae:
- Genus †Orohippus;
- Genus †Pliolophus;
- Genus †Protorohippus;
- Genus †Sifrhippus;
- Genus †Xenicohippus;
- Genus †Eurohippus;
- Genus †Propalaeotherium;
- Subfamily †Anchitheriinae:
- Genus †Anchitherium;
- Genus †Archaeohippus;
- Genus †Desmatippus;
- Genus †Hypohippus;
- Genus †Kalobatippus;
- Genus †Megahippus;
- Genus †Mesohippus;
- Genus †Miohippus;
- Genus †Parahippus;
- Genus †Sinohippus;
- Subfamily Equinae:
- Genus †Merychippus;
- Genus †Scaphohippus;
- Genus †Acritohippus;
- Tribe †Hipparionini:
- Genus †Eurygnathohippus;
- Genus †Hipparion;
- Genus †Hippotherium;
- Genus †Nannippus;
- Genus †Neohipparion;
- Genus †Proboscidipparion;
- Genus †Pseudhipparion;
- Tribe Equini:
- Genus †Haringtonhippus;
- Genus †Heteropliohippus;
- Genus †Parapliohippus;
- Subtribe Protohippina:
- Genus †Calippus;
- Genus †Protohippus;
- Subtribe Equina:
- Genus †Astrohippus;
- Genus †Dinohippus;
- Genus Equus (22 species, 7 extant):
- Equus ferus Wild horse;
- Equus ferus caballus Domestic horse;
- †Equus ferus ferus Tarpan;
- Equus ferus przewalskii Przewalski's horse;
- †Equus algericus;
- †Equus alaskae;
- †Equus lambei Yukon wild horse;
- †Equus niobrarensis;
- †Equus scotti;
- †Equus conversidens Mexican horse;
- †Equus semiplicatus;
- Subgenus †Amerhippus (this subgenus and its species are possibly synonymous with E. ferus):
- †Equus andium;
- †Equus neogeus;
- †Equus insulatus;
- Subgenus Asinus:
- Equus africanus African wild ass;
- Equus africanus africanus Nubian wild ass;
- Equus africanus asinus Domestic donkey;
- †Equus africanus atlanticus Atlas wild ass;
- Equus africanus somalicus Somali wild ass;
- Equus hemionus Onager or Asiatic wild ass;
- Equus hemionus hemionus Mongolian wild ass;
- †Equus hemionus hemippus Syrian wild ass;
- Equus hemionus khur Indian wild ass;
- Equus hemionus kulan Turkmenian kulan;
- Equus hemionus onager Persian onager;
- Equus kiang Kiang;
- Equus kiang chu Northern kiang;
- Equus kiang kiang Western kiang;
- Equus kiang holdereri Eastern kiang;
- Equus kiang polyodon Southern kiang;
- †Equus hydruntinus European ass;
- †Equus altidens;
- †Equus tabeti;
- †Equus melkiensis;
- †Equus graziosii;
- Subgenus Hippotigris:
- Equus grevyi Grévy's zebra;
- †Equus koobiforensis;
- †Equus oldowayensis;
- Equus quagga Plains zebra;
- Equus quagga boehmi Grant's zebra;
- Equus quagga borensis Maneless zebra;
- Equus quagga burchellii Burchell's zebra;
- Equus quagga chapmani Chapman's zebra;
- Equus quagga crawshayi Crawshay's zebra;
- †Equus quagga quagga Quagga;
- Equus quagga selousi Selous' zebra;
- Equus zebra Mountain zebra;
- Equus zebra hartmannae Hartmann's mountain zebra;
- Equus zebra zebra Cape mountain zebra;
- †Equus capensis;
- †Equus mauritanicus;
- Subgenus †Parastylidequus:
- †Equus parastylidens Mooser's horse;
- †Subgenus Sussemionus;
- †Equus ovodovi;
- incertae sedis;
- †Equus simplicidens Hagerman horse;
- †Equus cumminsii;
- †Equus livenzovensis;
- †Equus sanmeniensis;
- †Equus teilhardi;
- †Equus numidicus;
- †Equus plicidens;
- †Equus cedralensis;
- †Equus stenonis group;
- †Equus stenonis Stenon zebra;
- †Equus stenonis guthi;
- †Equus stenonis senezensis;
- †Equus stenonis pamirensis (Hippotigris pamirensis);
- †Equus stenonis petraloniensis;
- †Equus stenonis vireti;
- †Equus sivalensis;
- †Equus stehlini;
- †Equus sussenbornensis;
- †Equus verae;
- †Equus namadicus;
- †Subgenus Allozebra:
- †Equus (A.) occidentalis western horse;
- †Equus (A.) excelsus;
- †Subgenus Hesperohippus:
- †Equus (H.) pacificus;
- †Equus (H.) mexicanus;
- †Equus complicatus;
- †Equus fraternus;
- †Equus major;
- †Equus giganteus;
- †Equus pectinatus;
- †Equus crenidens;
- Genus †Hippidion;
- Genus †Onohippidium;
- Genus †Pliohippus.
