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,
Australopithecus africanus of the Witwatersrand in Johannesburg, South Africa, became interested in fossils found at a limestone quarry at Taung near Kimberley, South Africa in 1924. The most promising of these was a skull of an odd ape-like creature presenting human traits at the eye orbits, teeth, and, most importantly, the hole at the base of the skull over the spinal column (the foramen magnum); its placement indicated a human-like upright posture and implied a high probability that this hominid-to-hominin primate had achieved bipedal, as opposed to quadrupedal locomotion. Dart assigned the specimen the name "Australopithecus africanus" ("southern ape of Africa"); it