Hognose snake is a common name for several unrelated species of snake with upturned snouts, classified in 2 colubrid snake genera and 1 pseudoxyrhophiid snake genus. They include the following genera: * Heterodon, which occur mainly in the United States and northern Mexico * Leioheterodon, the hognose snakes native to Madagascar * Lystrophis, the South American hognose snakes. The North American Heterodon species are known for their habit of thanatosis: playing dead when threatened.