Most venomous marine snake

The Dubois' seasnake (Aipysurus duboisii), found around Papua New Guinea, New Caledonia and the northern, eastern and western coastal areas of Australia, is the most venomous marine snake. With an LD₅₀ of 0.044 mg/kg (i.e., the amount, in relation to body weight, that kills 50% of those envenomated), this makes A. duboisii not only the most venomous seasnake but one of the most venomous snakes in the world overall.

However, the beaked seasnake (Hydrophis schistosus) is responsible for the most deaths from seasnake envenomation due to it being a specialist for in-shore estuary habitats, and therefore being commonly entangled in fishermen’s nets.

On land, meanwhile, the most toxic snake is the inland taipan, aka small-scaled snake (Oxyuranus microlepidotus) of Queensland and western New South Wales in Australia, with an LD50 of around 0.01–03 mg/kg. This up-to-1.7-m-long (5-ft 7-in) snake is a specialist for the baking heat of the channel country black soil floodplains where it hunts for mammals in the cracked soil. Like the related coastal taipan (O. scutellatus), it preys on dangerous types of native mammals that would be able to injure or even kill a snake. Thus, these snakes evolved under selection pressure to produce extremely potent venom (and large quantities of it) in order to overwhelm their quarry before it can retaliate. The estimated human lethal dose of inland taipan venom is a mere 1 mg (0.00004 oz), and these snakes are capable of delivering over 100 mg (0.004 oz) of venom in one bite. The coastal taipan is less toxic, with the lethal dose estimated at 2 mg (0.00008 oz), but is capable of delivering over 500 mg (0.018 oz) of venom. Therefore, while the inland taipan is more toxic, the coastal taipan delivers proportionally more lethal doses per bite.