Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
Equus (film) Equus (film) Equus is a 1977 British-U.S. drama film directed by Sidney Lumet and written by Peter Shaffer, based on his play of the same name. The film stars Richard Burton, Peter Firth, Colin Blakely, Joan Plowright, Eileen Atkins, and Jenny Agutter. The story concerns a psychiatrist treating a teenager who has blinded horses in a stable, attempting to find the root of his horse worship. Lumet's translation of the acclaimed play to a cinematic version incorporated some realism, in the use of real horses as opposed to human actors, and a graphic portrayal of the blinding. Despite some criticism