title: Mixcoatlus melanurus
text: # 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 centimetres (14+3⁄4 and 19+5⁄8 inches) 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 1,600–2,400 m (5,200–7,900 ft). 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 $km^2$ (1,900 sq mi), 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.
  
  