Adults usually grow to a length of 40–60 cm (16–24 in) and have a relatively slender build. Females grow larger than males and are often more than 60 cm (24 in) in length, while males are usually about 45 cm (18 in). One exceptional specimen, a female, was reported to measure 77 cm (30 in).
The color pattern consists of a tan, brown, gray or grayish-brown ground color overlaid with a narrow white, yellow or rust brown vertebral stripe and 24–40 dark brown to almost black blotches that oppose or alternate across the vertebral line. The blotches have thin white borders that extend at roughly a right angle from the vertebral line.
Found in Central America in Guatemala, El Salvador, Honduras, Nicaragua and Costa Rica. The type locality given is "les terres chaudes du versant occidental de la Cordillère Escuintla (Guatémala)" (= warm regions on western slope of Cordillera, Escuintla, Guatemala).
When threatened, these snakes have been known to defend themselves vigorously, often striking with such force that the body is thrown forwards or even leaves the ground.
No deaths have been reported resulting from bites from this species. They are, however, quick to strike and several cases of serious envenomation have required hospitalization. According to Bolaños (1984), of the 477 cases of snakebite in Costa Rica in 1979, three were due to these snakes.
- List of crotaline species and subspecies
- Crotalinae by common name
- Crotalinae by taxonomic synonyms
- McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
- Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. 2 volumes. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
- Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. ISBN 0-8069-6460-X.
- "Porthidium ophryomegas". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=634902. Retrieved 6 August 2008.