Calloselasma
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae
Subfamily:	Crotalinae
Genus:	Calloselasma Cope, 1860
Species:	C. rhodostoma
Binomial name
Calloselasma rhodostoma (Kuhl, 1824)
Synonyms
Agkistrodon Palisot de Beauvois, 1799 Trigonocephalus Kuhl, 1822 Tisiphone Fitzinger, 1843 Leiolepis A.M.C. Duméril, 1853 Ancistrodon Baird, 1854 Calloselasma Cope, 1860[2] [Trigonocephalus] rhodostoma Kuhl, 1824 [Trigonocephalus] rhodostoma – F. Boie, 1827 [Trigonocephalus] praetextatus Gravenhorst, 1832 Tisiphone rhodostoma – Fitzinger, 1843 L[eiolepis]. rhodostoma – A.M.C. Duméril, 1853 [Calloselasma] rhodostomus – Cope, 1860 T[isiphone]. rhodostoma – W. Peters, 1862 T[rigonocephalus]. (Tisiphone) rhodostoma – Jan, 1863 Calloselasma rhodostoma – Günther, 1864 Calloselma rhodostoma – Morice, 1875 Ancistrodon rhodostoma – Boettger, 1892 Ancistrodon rhodostoma – Boulenger, 1896 Agkistrodon rhodostoma – Barbour, 1912 Ancistrodon (Calloselasma) rhodostoma – Bourret, 1927 Ancistrodon annamensis Angel, 1933 [Agkistrodon] annamensis – Pope, 1935 Calloselasma rhodostoma – Campden-Main, 1970[2]

Common names: Malayan ground pit viper, Malayan pit viper, Malayan ground snake, Malayan moccasin.

Calloselasma is a monotypic genus^[3] created for a pit viper species, Calloselasma rhodostoma, which is endemic to Southeast Asia from Thailand to northern Malaysia and on the island of Java.^[2] No subspecies are currently recognized.^[4]

Attains an average total length of 76 cm (30 in), with females being slightly longer than males. Occasionally, they may grow as long as 91 cm (36 in).^[5]

A specimen with a total length of 81 cm (32 in) has a tail 9 cm (3.5 in) long.

Dorsally it is reddish, grayish, or pale brown, with two series of large, dark brown, black-edged triangular blotches, which are alternating or opposite. There is also a thin dark brown vertebral stripe, which may be interrupted or indistinct in some specimens. The upper labials are pink or yellowish, and powdered with brown. There is a broad, dark brown, black-edged diagonal stripe from the eye to the corner of the mouth, with a narrower light-colored stripe above it. Ventrally it is yellowish, uniform or powdered or spotted with grayish brown.

The smooth dorsal scales are arranged in 21 rows at midbody. Ventrals 138-157; anal plate entire; subcaudals 34-54 pairs.

Snout pointed and upturned. Rostral as deep as broad. Two internasals and two prefrontals. Frontal as long as or slightly longer than its distance from tip of snout, as long as or slightly shorter than the parietals. 7-9 upper labials. Loreal pit not in contact with the upper labials.^[6]

This is the only Asian pit viper with large crown scales and smooth dorsal scales.^[7]

Found in Nepal, Thailand, Cambodia, Laos, Vietnam, northern West Malaysia and on the Indonesian island of Java. The type locality is listed as "Java".^[2] There are unconfirmed, but credible reports from southern Myanmar (Burma), northern Sumatra and northern Borneo.

Prefers coastal forests, bamboo thickets, unused and overgrown farmland, orchards, plantations as well as forests around plantations,^[5] where it searches for rats and mice.

This species is oviparous and the eggs are guarded by the female after deposition.^[7]

This species has a reputation for being bad-tempered and quick to strike. In northern Malaysia it is responsible for some 700 incidents of snakebite annually with a mortality rate of about 2 percent. Remarkably sedentary, it has often been found in the same spot several hours after an incident involving humans.^[7] Its venom causes severe pain and local swelling and sometimes tissue necrosis, but deaths are not common. Many victims are left with dysfunctional or amputated limbs due to the lack of antivenom and early treatment. In a 2005 study of 225 Malayan pit viper (Calloselasma rhodostoma) bites in Thailand, most victims had mild to moderate symptoms, but 27 of 145 patients (18.6%) developed permanently swollen limbs.^[8] There were only two deaths (related to intracerebral hemorrhage) and no amputations. The antivenin manufactured in Thailand seemed effective in reversing the blood clotting caused by the venom. Most patients remained stable and did not require antivenin. The authors suggested that victims not use traditional healers and avoid overuse of tourniquets. In a prospective phase of the study, bites occurred throughout the year but mostly early in the monsoon season (May and June).

The venom of this species is used to isolate a thrombin-like enzyme called ancrod.^[9] This enzyme is used clinically to break down and dissolve thrombi (blood clots) in patients and lower blood viscosity to help prevent heart attack and stroke.^[9][10]

• Kuhl, H. 1824. Sur les Reptiles de Java. Bull Sci. nat. Géol. 2: 79-83. (Trigonocephalus rhodostoma)
• Warrell DA, Looareesuwan S, Theakston RD, et al. (November 1986). "Randomized comparative trial of three monospecific antivenoms for bites by the Malayan pit viper (Calloselasma rhodostoma) in southern Thailand: clinical and laboratory correlations". The American Journal of Tropical Medicine and Hygiene. 35 (6): 1235–47. doi:10.4269/ajtmh.1986.35.1235. PMID 3538922.
• Ho M, Warrell DA, Looareesuwan S, et al. (May 1986). "Clinical significance of venom antigen levels in patients envenomed by the Malayan pit viper (Calloselasma rhodostoma)". The American Journal of Tropical Medicine and Hygiene. 35 (3): 579–87. doi:10.4269/ajtmh.1986.35.579. PMID 3706625.
• Au LC, Lin SB, Chou JS, Teh GW, Chang KJ, Shih CM (September 1993). "Molecular cloning and sequence analysis of the cDNA for ancrod, a thrombin-like enzyme from the venom of Calloselasma rhodostoma". The Biochemical Journal. 294 (2): 387–90. doi:10.1042/bj2940387. PMC 1134466. PMID 8373353.
• Ponnudurai, G.; Chung, M.C.M.; Tan, N.H. (1994). "Purification and Properties of the L-Amino Acid Oxidase from Malayan Pit Viper (Calloselasma rhodostoma) Venom". Archives of Biochemistry and Biophysics. 313 (2): 373–378. doi:10.1006/abbi.1994.1401. ISSN 0003-9861. PMID 8080286.
• Yingprasertchai, Senee; Bunyasrisawat, Srisurat; Ratanabanangkoon, Kavi (2003). "Hyaluronidase inhibitors (sodium cromoglycate and sodium auro-thiomalate) reduce the local tissue damage and prolong the survival time of mice injected with Naja kaouthia and Calloselasma rhodostoma venoms". Toxicon. 42 (6): 635–646. doi:10.1016/j.toxicon.2003.09.001. ISSN 0041-0101. PMID 14602119.
• Ouyang, Chaoho; Yeh, Horng-I; Huang, Tur-Fu (1986). "Purification and characterization of a platelet aggregation inducer from Calloselasma rhodostoma (Malayan pit viper) snake venom". Toxicon. 24 (7): 633–643. doi:10.1016/0041-0101(86)90026-7. ISSN 0041-0101. PMID 3775783.
• Daltry, Jennifer C.; Ross, Toby; Thorpe, Roger S.; Wuster, Wolfgang (1998). "Evidence that humidity influences snake activity patterns: a field study of the Malayan pit viper Calloselasma rhodostoma". Ecography. 21 (1): 25–34. doi:10.1111/j.1600-0587.1998.tb00391.x. ISSN 0906-7590.

Wikimedia Commons has media related to Calloselasma.

• Calloselasma at the Reptarium.cz Reptile Database. Accessed 9 August 2007.
• C. rhodostoma at Thailand Snakes. Accessed 21 Dec 2014.