Central American Bushmaster

Adults of L. stenophrys commonly grow to more than 200 cm (6 feet 6¾ inches) and may exceed 330 cm (10 feet 10 inches) in total length (including tail). Ditmars (1910) reported a specimen from Costa Rica that was 11 feet 4 inches (349 cm). Many accounts exist of much larger specimens, but these are poorly documented. Solórzano (2004) cites historical records that put the maximum length at 360 cm (11 feet 9¾ inches). It has a broadly rounded head and a snout that is not elevated. Typically, the species has a pronounced middorsal ridge that is most distinct on the last quarter of the body. The color pattern is darker than that of L. muta.

L. stenophrys is found in Central America in the Atlantic lowlands of southern Nicaragua, Costa Rica and Panama, as well as the Pacific lowlands of central and eastern Panama. The type locality given is "Sipurio" (Limón Province, Costa Rica).

The specific name, stenophrys, is derived from the Greek words stenos, meaning "narrow", and ophrys, meaning "brow" or "eyebrow". There are no subspecies that are recognized as being valid. Campbell and Lamar (2004) also recognized Lachesis acrochorda (García, 1896) as a valid species, which McDiarmid et al. (1999) had treated as a synonym of L. stenophrys. The Reptile Database follows the position of Campbell and Lamar.