evidence: Scientists have discovered a previously undocumented species of giant anaconda in the Amazon which they say can grow up to 7.5m and weighing close to 500kg, making it the largest and heaviest snake yet known in the world. Until now, four species of anacondas were known, with the largest one – the green anaconda – inhabiting tropical parts of South America such as the basins of the Amazon, Orinoco, and Esequibo rivers, as well as some smaller watersheds. These anacondas, found in the rivers and wetlands of South America, are well known for their lightning speed and ability to squeeze the life out of prey by coiling around, asphyxiating them, and swallowing them whole.