Metlapilcoatlus occiduus is a pit viper subspecies endemic to southern Mexico, Guatemala, and El Salvador.
Adults are usually in total length. The largest specimens reported are a male of from Baja Verapaz, Guatemala, and a female of from Volcán de Agua, Escuintla, Guatemala. The build is very stout, although not so much as that of M. mexicanus.
Found in southern Mexico (southeastern Chiapas), southern and central Guatemala, and western El Salvador. The type locality given is "Saint-AugustÃÂn (Guatemala), versant occidentale de la Córdillère. 610 mètres [2,000 ft] dôaltitude". Actually, San AugustÃÂn is on the southern slope of Volcán Atitlán.
Its habitat includes subtropical wet forest on the Pacific versant from southeastern Chiapas, Mexico to western El Salvador. It also inhabits the pine-oak forest near Guatemala City. It can be found at altitudes varying from .
Regarded as a full species, Metlapilcoatlus occiduus, by Campbell and Lamar (2004).