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,
Now What (horse) the 1952 American Co-Champion Older Female Horse. Now What (horse) Now What (foaled 1937, in Kentucky) was an American Thoroughbred Champion racehorse. Her dam was That's That, and her sire was the 1927 American Horse of the Year and two-time Leading sire in North America, Chance Play. Raced by Alfred G. Vanderbilt II, Now What was trained by Bud Stotler and was a champion at two. As a three-year-old, she finished second in the Molly Brant Handicap, Pimlico Nursery Stakes, and Juvenile Stakes. Now What served as a broodmare for Vanderbilt. Her most successful foal to race was Next Move,