Order Squamata ; Suborder Serpentes
Family Elapidae includes the most venomous land snakes in the country, with three highly venomous snakes (The Indian Cobra and two Kraits) and a single moderately venomous, little known snake, the Sri Lankan Coral snake or Calliophis melanurus sinhaleyus. The actual toxicity of this species is unknown to a great extent, but some herpetologists consider it to have potential lethal envenoming, thus categories it as a highly venomous snake. The Blood-bellied coralsnake (Calliophis haematoetron) was the last elapid to be described from Sri Lanka and is found in the Wasgomuwa and Knuckles regions. The two subspecies of the Sri Lankan Krait (Bungarus ceylonicus) are endemic to the island. Other than for the Coral snake, which is sub-fossorial, the other species are terrestrial and are found within close proximity of human habituations. The Cobra is predominantly diurnal but the two Bungarus species are largely nocturnal.
Some scientists believe that the taxonomical placement of sea snakes in a separate family is wrong and that they are simply elapid snakes that have colonized the ocean. One of the greatest myths about sea snakes has been that their venom is far more toxic than any land snake. This is simply wrong as even the most toxic sea snake (Duboi's sea snake, Aipysurus duboisii), is still less toxic than the Inland Taipan (Oxyuranus microlepidotus) and the Eastern Brown Snake (Pseudonaja texilis), two of the most venomous land snakes in the world (based on LD50 values). But hydrophids are probably the most venomous snakes in Sri Lanka. All Sri Lankan species are completely marine and in general sea snakes have undergone some remarkable adaptations to an aquatic life by having laterally compressed bodies and paddle tails, which help in propulsion; respiratory system changes such as valves on their nostrils and the left lungs that run almost the entire length of their bodies (while the right lung is highly reduced in size) etc. One of the most intriguing adaptations is that sea snakes can remove nitrogen through their skin while diving which prevent nitrogen bubble formations in the body. Sea snakes mainly inhabit the coastal coral reefs and sea grass beds etc. and are usually shy animals. The venom comprises a mixture of neurotoxins (effects the nervous system) and myotoxins (effects the muscles). The Sri Lankan coastal waters are known to harbor 15 species of sea snakes but there’s a possibility of few more species including Hydrophis fasciatus fasciatus, Hydrophis caerulescens and Hydrophis nigrocinctus being recorded in Sri Lankan waters.