Rat snakes are a large, polyphyletic, group of snakes from the Colubrid subfamily Colubrinae. There is considerable variation between different types of rat snake but most are medium to large, rodent eating snakes. In biology, a taxon is polyphyletic if it is descended from more than one root form (in Greek poly = many and phyletic = racial). ... Genera According to ITIS: Adelophis Adelphicos Alsophis Amastridium Arizona Arrhyton Atractus Bogertophis Boiga Carphophis Cemophora Cerberus Chersodromus Chilomeniscus Chionactis Clelia Clonophis Coluber Coniophanes Conophis Conopsis Contia Cryophis Dendrelaphis Dendrophidion Diadophis Dipsas Dryadophis Drymarchon Drymobius Elaphe Enulius Eridiphas Erythrolamprus Farancia Ficimia Geagras Geophis Gyalopion Heterodon Hypsiglena Imantodes Lampropeltis Leptodeira Leptophis Liochlorophis...

Previously most were assigned to the genus Elaphe but many have been since renamed. The validity of some genera is debatable but for the purpose of this article a more liberal taxonomic stance will be taken. Rat snakes have traditionally been divided into two groups, New World and Old World species. Taxonomy (from Greek ταξινομία from the words taxis = order and nomos = law) may refer to either a hierarchical classification of things, or the principles underlying the classification. ...

New World Rat Snakes

New World rat snakes belong to the Colubrine tribe Lampropeltinae, and as such are closely related to Lampropeltis (milk snakes and king snakes), Pituophis (gopher snakes, pine snakes and bull snakes (http://en.wikipedia.org/wiki/Bull_Snake)), Rhinocheilus (longnose snakes), Arizona (glossy snakes) and Stilosoma (short-tailed snakes). The entire Lampropeltinid group is descended from Old World rat snakes that crossed the Bering Land Bridge sometime within the last twenty to thirty million years. Species Lampropeltis alterna Lampropeltis calligaster Lampropeltis getula Lampropeltis mexicana Lampropeltis pyromelana Lampropeltis ruthveni Lampropeltis triangulum Lampropeltis zonata The genus Lampropeltis of colubrid snakes includes the King snakes and also the milk snake. ... Binomial name Lampropeltis triangulum Lacépède, 1789 The Milk Snake (Lampropeltis triangulum) is a species of king snake. ... Species Lampropeltis alterna Lampropeltis calligaster Lampropeltis getula Lampropeltis mexicana Lampropeltis pyromelana Lampropeltis ruthveni Lampropeltis triangulum Lampropeltis zonata The genus Lampropeltis of colubrid snakes includes the King snakes and also the milk snake. ... State nickname: The Grand Canyon State, The Copper State Other U.S. States Capital Phoenix Largest city Phoenix Governor Janet Napolitano Official languages English Only State Area 295,254 km² (6th)  - Land 294,312 km²  - Water 942 km² (0. ... The Bering land bridge, also known as Beringia, was a land bridge roughly 1600 km (1000 miles) north to south at its greatest extent, which joined present-day Alaska and eastern Siberia at various times during the ice ages. ...

The New World rat snakes consist of the genera Bogertophis (Trans Pecos and Baja rat snakes), Pantherophis (Corn snakes, Fox snakes and American rat snakes), Psuedelaphe (Central American rat snake) and Senticola (Green rat snake). Binomial name Elaphe guttata (Linnaeus, 1766) The Corn Snakes (Elaphe guttata) are a species of Rat Snake. ... Binomial name Elaphe vulpina (Baird and Girard, 1853) A Fox Snake (Elaphe vulpina) is a species of rat snake. ...

Old World Rat Snakes

The Genera Elaphe, Euprepiophis, Oreophis, Orthriophis, Rhinechis, and Zamenis constitute Old-World rat snakes.

Additional Note

It is worth noting that, though the polyphyletic nature of the genus is almost undisputed, many species are conservatively referred to as Elaphe sp.