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,
Clothed female, naked male exchange where the more traditionally dominant male is objectified, debased, or humiliated by a more traditionally submissive female. As a result, CFNM fiction frequently includes the clothed female taking on the role of a dominatrix over the nude male. The opposite of CFNM is clothed male, naked female (CMNF). In classical antiquity, the portrayal of nude male form in art (including the exposure of genitals) was considered to be more acceptable than that of the naked female form. By the renaissance, this view had reversed. For example, in Titian's "treatment of Perseus and Andromeda" in the mid-1550s, it is Andromeda