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,
American Champion Male Turf Horse to create the Eclipse Award. From 1953 through 1978 it was awarded to male or female horses although the only female champion was Dahlia in 1974. In 1979 an individual category was created for each of the sexes. Starting with the 2015 Eclipse Awards it is no longer possible for a Champion Male Turf Horse to also win Champion Older Male Horse, as the latter category is now restricted to horses proficient in dirt or main track races. The last such winner of both awards was Main Sequence in 2014. Most wins: Most wins by a trainer: Most wins by