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Boidae (constricting snakes; order Squamata, suborder Serpentes) A family of large, mainly tropical snakes that kill their prey by constriction. They have a flexible skull, paired lungs, and enlarged ventral scales. Rudimentary hind limbs are present internally and continue externally as anal spurs. The family includes the pythons (all Old World in distribution) and the boas (mainly New World in distribution). Boa constrictor occurs in a wide range of habitats from Mexico to Argentina and on some W. Indian islands, but seldom enters water. The exclusively aquatic Eunectes murinus (anaconda), of S. and Central America, is the largest extant snake, allegedly reaching 11 m in length. Python reticulatus (reticulated python) of the Indo-Malayan region, is similar to the anaconda, the largest authenticated specimen being 8.5 m long, and is often found near water, sometimes swimming out to sea. There are about 70 species of Boidae.