Which of these is the heaviest and one of the longest known extant snake species?

The green anaconda ('Eunectes murinus'), also known as common anaconda or common water boa, is a non-venomous boa species found in South America. It is the heaviest and one of the longest known extant snake species. The term "anaconda" often refers to this species, though the term could also apply to other members of the genus Eunectes.

The green anaconda's scientific name is derived from the Greek εὐνήκτης, meaning "good swimmer", and the Latin murinus, meaning "of mice", for being thought to prey on mice.

The color pattern consists of an olive green background overlaid with black blotches along the length of the body. The head is narrow compared to the body, usually with distinctive orange-yellow striping on either side. The eyes are set high on the head, allowing the snake to see out of the water while swimming without exposing its body.