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 (magazine) Carrying the slogan, "The horse owner's resource", "Equus" is meant to be collected by subscribers so they might use articles in past issues as a reference. Each issue has a prominent issue identification number on the cover (e.g., the June 2005 issue is ""Equus" 332"), and an index to articles is published annually. After the June 1998 sale of Shinitzky's Fleet Street Publishing to PRIMEDIA, the magazine was published by the PRIMEDIA Equine Group. From 2007 to 2010, with the completion of the sale of the PRIMEDIA Enthusiast Media group, the publisher was Source Interlink. Since 2010, "Equus" has been