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Przewalski's Horse (Equus ferus) Fact Sheet: Taxonomy & History

Przewalski's Horse (Equus ferus)

Taxonomy and Nomenclature


  • Horses were previously assigned to 2 different species, Equus caballus and E. przewalskii.  In 1986 and 1994 Colin Groves, a leading taxonomist, proposed using E caballus for all domestic horses and E. ferus for the 2 wild horses: 
    • E ferus przewalskii = Przewalski horse
    • E ferus ferus = Tarpan (extinct in the wild around 1897 ) 
  • The Equus ferus przewalskii has 66 chromosomes, Equus caballus has 64; interbreeding results in fertile offspring with 65 chromosomes.  
    • Note: It is a popular misconception that different species cannot interbreed.  Species do not interbreed under natural conditions.)


  • Named for 19th century Russian explorer, Colonel Nikolai Przewalski (pronounced zheh-VAHL-skee) who sent a skull and skin to the St. Petersburg Zoological Museum.  I.S. Poliakov, conservator, declared the horse a new species : Equus przewalskii.
  • Common Names: Przewalski’s wild horse, Asiatic wild horse, Mongolian wild horse, Mongolian takh, Takhi (spirit horse)

Evolutionary History

  • Horses diverged from rhinos between 54 and 58 million years ago (Early Eocene) (Ryder 2009)
    • Horse lineages are called the hippomorphs; tapirs and rhinos are the ceratomorphs.
  • Most likely horses first dispersed from Europe to North America at the beginning of the Eocene (Hooker 2008)
    • Pliolophus is now considered the earliest horse; it is closely related Hyracotherium from North America (Froehlich 2002) (Hooker 2008)
    • Pliolophus had four hooves on front limbs, three on rear, with short legs and was half the size of a fox terrier (Hooker 2008) (Agusti & Anton 2005)
  • The horse family, Equidae, has three main divisions based on anatomy and DNA studies (Oakenfull et al 2000)
    • The caballines - include domestic horse and Equus przewalskii, a wild ancestor (Forstén 1988)
    • The asses - include domestic donkey, African wild asses, and the hemionines (Asiatic onager and kiang)
    • Zebras
  • The genus Equus likely originated 4.0-4.5 million years ago (Orlando et al. 2013)
    • Conclusions based on genome sequences of a Late Pleistocene horse, 5 modern domestic horse breeds (Equus ferus caballus), a Przewalski’s horse (E. f. przewalskii), and a donkey (E. asinus) (Orlando et al. 2013)
    • Previously believed to have emerged 2-4 million years ago (Pliocene) (Oakenfull et al 2000) (Steiner & Ryder 2011)
  • Equus dispersed from North America to Eurasia around 2.6 million years ago (Steiner & Ryder 2011)
  • The modern horse genus Equus probably evolved in North America and migrated across the Bering land bridge into Asia and Europe (Steiner & Ryder 2011)
  • Przewalski's horses are closely related to but not direct ancestors of modern domestic horses, according to recent DNA studies (Goto et al. 2011; Lau 2009; Orlando et al. 2013; Vilà et al. 2001)
    • Diverged from modern domestic horses about 38,000-72,000 years ago (Orlando et al. 2013)
    • Nucleotide diversity values indicate unique evolutionary histories for Przewalski's and domestic horses (Lau 2009)
    • Przewalski's horses are only surviving wild horse - DNA evidence shows no recent admixture with domestic horses (Orlando et al. 2013)

Cultural History

  • 30,000 years ago wild horses were hunted as prey by prehistoric man.
  • 20,000 years ago rock art engravings/paintings of wild horses in Italy, France and Spain
  • 10,000 years ago massive extinctions in North and South America wiped out all horse species, mammoths, and saber-tooth tigers.  In Eurasia and Africa, 7 equid species survived.
  • 3,000 BC domestication began – wildest horses killed for food, tamest kept for breeding
  • 900 A.D. First account of wild horse written by a Tibetan monk
  • 1226 A.D. Seen by Genghis Khan during one of his Mongolian campaigns
  • 1750 Manchurian emperor shot 200-300 in a single day
  • 1881 Skull and hide presented to Zoological Museum in St. Petersburg and Przewalski’s horse became known to the western world
  • After WWII a dramatic declines due to hunting, military activities, climate change, livestock competition and numerous collecting expeditions
  • 1969 last confirmed sighting in southwestern part of Mongolia


Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Perissodactyla

Family: Equidae

Genus: Equus

Species: Equus ferus - Wild Horse

Subspecies: Equus ferus przewalkskii - Przewalski's Horse

Equus caballus, Linnaeus (1758); Syst. Nat., 10th ed., 1:73
Equus ferus, Boddaert (1785)
Equus przewalskii, Polyakov (1881)
Equus ferus przewalskii, Groves (1986)

Page Citations

Agusti & Anton (2005)
Bennett & Hoffmann (1999)
Bowling & Ruvinsky (2000)
Boyd (1994)
Forstén (1988)
Froehlich (2002)
Groves (2002)
Groves & Ryder (2000)
Hooker (2008)
Oakenfull et al. (2000)
Ryder (2009)

Steiner & Ryder 2011)
Villa et al. (2001)
Wilson & Reeder (2005)

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