Mixcoatlus melanurus


 * Common names: black-tailed horned pitviper. 

Mixcoatlus melanurus is a venomous pitviper species endemic to the mountains of southern Mexico. No subspecies are currently recognized.

Description
Adults grow to between 37.5 and 50 cm in length and have a moderately stout build. In Mexico, it is called a necazcoatl, from the Nahualt words necaztli and coatl which means "eared-serpent" referring to its "horns".

Geographic range
It is found in two Mexican states, southern Puebla and Oaxaca, at elevations of 1600 –. The type locality given is "Mexico".

Conservation status
This species is classified as Endangered (EN) on the IUCN Red List of Threatened Species with the following criteria: B1ab(iii) (v3.1, 2001). A species is listed as such when the best available evidence indicates that the geographic range, in the form of extent of occurrence, is estimated to be less than 5,000 km2, that estimates indicate it to be severely fragmented or known to exist at no more than 5 locations, and that a continuing decline has been observed, inferred or projected, in area, extent and/or quality of habitat. It is therefore considered to be facing a very high risk of extinction in the wild. In 2007 when it was last assessed, the population trend was down.

Behavior
Terrestrial.