Middle American indigo snake

The Middle American indigo snake (Drymarchon melanurus), also known commonly as the blacktail cribo, is a species of large, nonvenomous, snake in the family Colubridae. The species is native to the southwestern United States, Mexico, Central America, and northern South America. In addition to the nominate subspecies, it has four other recognized subspecies, including D. m. erebennus, commonly known as the Texas indigo snake.

Description
D. melanurus is a large species that can grow to a total length (including tail) of 1.80 m to over 2.40 m. This species has predominantly olive-brown glossy dorsal scales evolving to black at the tail. The underside is a lighter olive-yellow, olive-tan color. D. melanurus has distinctive dark markings round the eyes, a vertical dark slash just behind the jaw. and a heavy diagonal dark slash on both sides of the neck. The subspecies D. m. erebennus is predominantly solid black, though there can be lighter shaded variations.

Geographic range and habitat
The geographic range of D. melanurus extends from southern Texas southwards through the Gulf Coast of Mexico, the Yucatán Peninsula, Guatemala and Belize. On the Pacific coast, its range extends from Sinaloa in Mexico, southward to Guatemala, as far south as Colombia, Venezuela and Ecuador. Its elevational distribution goes from near sea level up to around 1,900 m asl (6,230 feet). The subspecies D. m. erebennus is found in southern Texas and southwards into Mexico as far as Veracruz.

Subspecies
There are five subspecies of D. melanurus which are recognized as being valid, including the nominate subspecies.
 * Drymarchon melanurus erebennus (Cope, 1860)
 * Drymarchon melanurus melanurus (A.M.C. Dumeril, Bibron & A.H.A. Dumeril, 1854)
 * Drymarchon melanurus orizabensis (Dugès, 1905)
 * Drymarchon melanurus rubidus H.M. Smith, 1941
 * Drymarchon melanurus unicolor H.M. Smith, 1941

Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Drymarchon.