Zoological Division of Today’s Equidae Family (Equids).

     At the end of the Cenozoic era a large variety of three-toed ancestors of the horse existed.  A presumption can be made that further phylogenetic development of the “single –toed” type had matured to various forms of perissodactyls (odd-toed), which is obvious in today’s fauna. The present family of perissodactyl (odd (single)-toed mammals) is commonly separated into zebras, asses (Asinus), half-Asinus (Hemionus) and genuine horses (Equus). These forms differentiate from one another by distinct external attributes, but the skeletal dissimilarity is minor; the only exception being the skull where it is more noticeable.

Equus Grewyi (female & male)
(Berlin Zoo)

Quagga Chappmani (female) with a zebroid by an Andalusian donkey.
(Berlin Zoo)

Quagga Wahlbergi
(Berlin Zoo)

Quagga Burchelii

E. zebra Hartmanni

Asinus somalicus

Asinus Africanus

Kulan (E. hemionus Pallas)

     Z e b r a s (Hippotigris) stand among today’s perissodactyls at the lowest evolutionary level. During the Pliocene era, they remained geographically limited to the African continent. Their common attribute is their stripe colored hair coat, but in the external shapes (especially in the head) they differ, as some resemble asinus and others resemble the horse. All of them have hair only at the end of their tails. They have chestnuts only on the front legs. The foals grow tough and short manes on the neck, and as do some zebras, on the entire back, often all the way to the tail. During the normal aging process however, this “back” mane disappears. This is obviously a phylogenetic atavism from the Oligocene three-toed ancestors of the Equidae (Equids), as the Mesohippus had a short upright mane from the top of his head to the tail already.

           The most primitive of the zebras and the most resembling the ass is the Grewyi zebra (Equus Grewyi O u s t..   They live in fairly large numbers in the company of antelopes on the steppes of the Somalian peninsula in Abyssinia and spread further to the equator. It is the tallest of all zebras and when full-grown, reaches the height of 150 cm. in the withers.  The head is large, meanwhile the face part narrow, with long and wide ears rounded at the top. Foals have the “back” mane and even in maturing, the mane grows further down the back than in most zebras. This zebra is more densely striped with narrowing stripes all over the body (except on the belly) converging almost vertically. The striped markings of the Grewyi zebra defers from others in the so-called “bars”, cross-stripes on the hindquarters, which arise from the hip across the back stripe. The legs are densely and horizontally striped all the way down to the hoofs. The variety E. Grewyi var. Faurei has white hair on the tail. The Grewyi zebra produces hybrids with a asinus much more easily than with a horse. The normal length of gestation period is one week over 12 months, as does the female asinus.
( R z a s n i c k i).

            Zebras resembling horses, also known as quaggas, have shorter earlobes; the mane is somewhat longer; the hair on the tail grows higher and closer to the top, and in captivity they tend to be more subjective than the genuine zebras resembling the asinus. The quagga zebras reach the furthest geographical spread from the equator to the south. Antonius took into consideration one zebra type: the Burcheli zebra – dauw (E. quagga Burchelii). One of the Burcheli zebra variety which is striped down to the hoofs, is the Chappman zebra (E. quagga Chappmani L a y a r d) living in the central and southern part of Africa. The narrow-striped variety of the Burcheli zebra is the Wahlberg zebra (E. quagga Wahlbergi P o c o c k), which is white under the belly with lighter colored legs almost without any striping. The obviously striped variety, known as kaoko (E. Burhcelii var. kaokensis), lives in southwestern Africa.

           The genuine quagga (Equus quagga L.), at one time, belonged to these south African zebras and most resembled the horse.  They had shorter earlobes and the tail had more hair growing closer to the top of the tail than in any other zebras. This zebra had chestnut brown color and only the head, neck and back was decorated with gray-white stripes turning reddish. The belly, legs and insides of the thighs were white.

            The genuine asinus geographical spread is limited to northern Africa bordering the southerly end of the zebras’ habitat. They have long ears, narrow back and “roof” slanted ribs, short and steep pelvis and only the end of the tail grows hair. There are two types of wild asinus recognized. The smaller Nubian (Equus asinus africanus  F i t z) and the taller Somalian asinus (Equus asinus somalicus I n o a c k).

           The half-asinus (Hemionus) live in the front and central regions of Asia. These are of medium form between the genuine asinus and the genuine horse. They have shorter ears than asinus, but longer than horses, the colors on the side of the body are brown or yellowish, under the belly and the bottom of the legs are white, the mane and back stripe is brown. They are missing the cross stripe as well as the ring coloring on the legs. The tail is covered with hair only at the bottom, just as the donkey. The Hemionus have longer heads, but are narrower in the forehead than the asinus and the head resembles the horse overall. As do the zebras and asinus, they have chestnuts only on the front legs. The voice of half-asinus (Hemionus) is clear and resembles the horse’s. At one time, the Syrian yellow onager (E. hemihippus Geoffr.) belonged to the half-asinus which was, according to Xenofon’s writings, abundant in Mesopotamia.

            The Persian onager (E. onager  P a l l a s) is smaller than the wild equids reaching the height over one meter (about 10 hands) in the withers. The kulan (E. hemionus Pall), lives abundantly in the steppes of Mongolia and Turkemnistan. The Mongolians called the kulan, “Jegetai”, which in the beginning of the Quaternary Period, spread with the rest of the Asian fauna all the way to western Europe. The most massive of the half-asinus, the kiang (E. kiang Morcr.) most resembles the horse, being darker than the onager, with a light red-brown color; a white belly and a lighter color to the bottom of the legs. The kiang’s exterior characteristics shows a heavy Roman-nosed head with half of his tail growing hair.  The kiang lives in Tibet.

      The genuine horses (Equus) have short ears and chestnuts on all four legs, but they can sometimes be missing exclusively on the hind legs in some domestic breeds. Genuine horses have their tail covered with hair from top to bottom. The original color is yellow, gray-yellow or gray with a black mane, black stripe on the back and black on the bottom of the legs with a more or less noticeable black stripe across the chest. The hock and (front) knees of the wild horse are noticeably marked with rings like striping. The original mane is short, upright; the voice of genuine horses is referred to as neighing or whinnying.

Kiang (E. kinag Morer.)

Kulan (E. hemionus Pallas) male.

Genuine horses
Equus Przewalskii

Related Articles: Evolutionary stages of the equine species - equids  (Horse Origins)
                              Equine Groups of Origins  

Edited by R.A. March 16, 2004

Translated by Ludvik K Stanek a.k.a. Lee Stanek from the 1953 Special Zoo-Technique - Breeding of Horses
Published in 1953 by the Czechoslovakian Academy of Agricultural Science and certified by the Ministry of Agriculture.
Written by: MVDr Ludvik Ambroz, Frabtisek Bilek, MVDr Karel Blazek, Ing. Jaromir Dusek, Ing. Karel Hartman, Hanus Keil, pro. MVDr Emanuel Kral, Karel Kloubek, Ing. Dr. Frantisek Lerche, Ing. Dr Vaclav Michal, Ing. Dr Zdenek Munki, Ing. Vladimir Mueller, MVDr Julius Penicka, pro. MVDr Emil Pribyl, MVDr Lev Richter, prof. Ing. Dr Josef Rechta, MVDr Karel Sejkora and Ing. Dr Jindrich Steinitz.