Are a family of venomous snakes found in tropical and subtropical regions around the world, terrestrially in Asia, Australia, Africa, North America, and South America, and aquatically in the Pacific and Indian Oceans.
Elapid snakes exhibit a wide range of sizes, from 18-cm species of Drysdalia to the 5.6-m king cobra. All elapids are characterized by hollow, fixed fangs through which they inject venom. Currently, 325 species in 61 genera are recognized.
All elapids have a pair of proteroglyphous fangs used to inject venom from glands located towards the rear of the upper jaws. In outward appearance, terrestrial elapids look similar to the Colubridae: almost all have long and slender bodies with smooth scales, a head covered with large shields and not always distinct from the neck, and eyes with round pupils. In addition, their behavior is usually quite active, and most are oviparous. Exceptions to all these generalizations occur: e.g. the death adders (Acanthophis) include short and fat, rough-scaled, very broad-headed, cat-eyed, live-bearing, sluggish ambush predators with partly fragmented head shields.
Some elapids are strongly arboreal (African Pseudohaje and Dendroaspis, Australian Hoplocephalus), while many others are more or less specialised burrowers (e.g. Ogmodon, Parapistocalamus, Simoselaps, Toxicocalamus, Vermicella) in either humid or arid environments. Some species have very generalised diets (euryophagy), but many taxa have narrow prey preferences (stenophagy) and correlated morphological specialisations, e.g. for feeding on other snakes, elongate burrowing lizards, squamate eggs, mammals, birds, frogs, fish, etc.
Sea snakes (Hydrophiinae, sometimes considered to be a separate family) have adapted to a marine way of life in different ways and to various degrees. All have evolved paddle-like tails for swimming and the ability to excrete salt. Most also have laterally compressed bodies, their ventral scales are much reduced in size, their nostrils are located dorsally (no internasal scales) and they give birth to live young (ovoviviparous). In general, they have the ability to respire through their skin; experiments with the yellow-bellied sea snake, Pelamis platurus, have shown that this species can satisfy about 20% of its oxygen requirements in this manner, allowing for prolonged dives. The sea kraits (Laticauda spp.) are the sea snakes least adapted to aquatic life. They spend much of their time on land, where they lay their eggs. They have wide ventral scales, the tail is not as well-developed for swimming, and their nostrils are separated by internasal scales.
On land, these snakes are found worldwide in tropical and subtropical regions, except in Europe. Sea snakes occur mainly in the Indian Ocean and the southwest Pacific. However, the range of one species, Pelamis platura, extends across the Pacific to the coasts of Central and South America.
All elapids are venomous snakes which are potentially deadly. Their venom is mainly neurotoxic, although many of them also possess several other types of toxins, including cardiotoxins and cytotoxins. This family has some members which are considered to be amongst the world's most venomous land snakes based on the murine LD50 of their venom, such as the inland taipan. Besides, some large-sized elapids, such as the Asiatic king cobra, African black mamba and Egyptian cobra, and Australasian coastal taipan, can inject a high quantity of venom during envenomation.
Elapids use their venom both to immobilize their prey and in self-defense.