Anacondas (Eunectes spp.) are viviparous South American snakes of the family Boidae. There are four species of which the green anaconda (Eunectes murinus) is the heaviest known snake. Green anacondas reach 6 m (20 ft) and weigh up to 130 kg (286 lbs). They are brownish-green to greyish-green with brown or black ovoid markings. The yellow anaconda (Eunectes notaeus) usually does not exceed 3 to 4 m (10 to 13 ft).