<P> The largest living snakes in the world, measured either by length or by weight, are various members of the boidae and pythonidae families . They include anacondas, pythons, and boa constrictors, which are all non-venomous constrictors . The longest venomous snake, with a length up to 18.5--18.8 ft (5.6--5.7 m), is the king cobra, and the heaviest venomous snake is likely to be the Gaboon viper (which also has the longest fangs and delivers the largest amount of venom) or possibly the Eastern diamondback rattlesnake--all three of which reach maximum weights in the range of 6--20 kilograms (13--44 lb). </P> <P> There are ten living snakes, listed below according to their maximum known or reported mass, that have a maximum mass that may reach or exceed 50 pounds (23 kg). Pending the acceptance of its taxonomic status, the Bolivian anaconda (Eunectes beniensis) may also merit inclusion, and the northern and southern variations of African rock python could be considered separately . </P> <P> In terms of length, in addition to those listed here, there are two other species that may possibly reach a length of 20 feet (6.1 m) or more--the Oenpelli python (Morelia oenpelliensis) and the olive python (Liasis olivaceus)--however, the information available about those species is rather limited . The Oenpelli python, in particular, has been called the rarest python in the world . </P> <P> It is important to be aware that there is considerable variation in the maximum reported size of these species, and most measurements are not truly verifiable, so the sizes listed should not be considered definitive . In general, the reported lengths are likely to be somewhat overestimated . In spite of what has been, for many years, a standing offer of a large financial reward (initially $1,000 offered by U.S. President Theodore Roosevelt in the early 1900s, later raised to $5,000, then $15,000 in 1978 and $50,000 in 1980) for a live, healthy snake over 30 ft (9.1 m) long by the New York Zoological Society (later renamed as the Wildlife Conservation Society), no attempt to claim the reward has ever been made . </P>

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