Craspedocephalus trigonocephalus, the Sri Lankan pit viper, Ceylon pit viper, Sri Lankan green pitviper or locally, pala polonga, () is a venomous pit viper species endemic to Sri Lanka. No subspecies are currently recognized. Description Craspedocephalus trigonocephalus is a sexually dimorphic, mid-sized, cylindrical species. These snakes measure at birth, and males grow to a maximum total length of . The neck is distinct from the flattened, triangular head. There is a loreal pit on each side of the head. Mid-sized eyes and a short, rounded, broad snout are present. The males are considerably smaller than females, which can grow up to in total length. The ground color of the snake is variable and cryptic. Typically, it is a green snake with a black variegated pattern, and a black temporal line is usually present. The wet zone snakes have these black patterns more clearly marked. The vertebral area has a tinge of yellow. The tail is black. The ventral scales are light greenish-yellow or may even be grey. Some snakes have only the black temporal line and the black tail, with the rest of the body being green. In addition, males tend to have a blue coloration, whereas the females are predominantly green. These are bulky snakes with prehensile, short tails, suiting their arboreal lifestyle. Reproduction These are viviparous snakes. About five to 25 young are produced at once. Scales These snakes have two or three large supraocular scales, and their nasal scales are partially divided into two or may not be divided. They have three preoculars, two or three postoculars, 9–10 supralabial scales, three or four infralabials, and 142–160 ventrals; The anal scale is not divided; their 53–69 subcaudals are divided. At midbody, the 17–19 rows of dorsal scales may or may not have keels. Most head shields are small and smooth. Common names Common names include: Sri Lankan green pit viper, Sri Lankan pit viper, pala polonga (පළා පොළඟා), and green pit viper. Geographic range It is an endemic species to Sri Lanka and widely distributed in all three climatic zones of the island, except higher hills and arid zones, while relatively more common in wet zone grasslands and rain forest areas and occasionally in plantations of cardamom, cocoa, coffee, and tea, from the lower altitudes from . The type locality given is "l'île S.-Eustache" (Sri Lanka). Behavior It is arboreal and nocturnal, occasionally descending to the ground in