Elapidae

Elapidae (Greek ἔλλοψ éllops, "sea-fish") is a major 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 exist in a wide range of sizes, from 18 cm species of Drysdalia to the 5.6 m (18 ft) Ophiophagus hannah (King cobra), and are characterized by hollow, fixed fangs through which they inject venom. Currently, 61 genera that include 325 species are recognized.

Taxonomy
In the past, many subfamilies were recognized, or have been suggested for the Elapidae, including the Elapinae, Hydrophiinae (sea snakes), Micrurinae (coral snakes), Acanthophiinae (Australian elapids) and the Laticaudinae (sea kraits). Currently, none are universally recognized. There is now good molecular evidence via karyotyping and protein electrophoretic analysis, immunological distance, DNA sequence analysis etc. for reciprocal monophyly of two groups: the African, Asian and New World Elapinae, and Australasian and marine Hydrophiinae. Thus, the Australian terrestrial elapids are 'hydrophiines', though not sea snakes, while it is believed that Laticauda and the 'true sea snakes' evolved separately from among the Australasian land-snakes. Asian cobras, coral snakes, and American coral snakes also appear to be monophyletic, while African cobras do not.

The type genus for the Elapidae was originally Elaps, but that group was moved to another family. In contrast to what usually happens in botany, the Elapidae family was not renamed. In the meantime, Elaps was renamed Homoroselaps and moved back to the Elapidae. However, Nagy et al. 2005 regard it as a sister taxon to Atractaspis which should therefore have been assigned to the Atractaspididae.

Description
In an examination of morphological characters, concluded that elapids fall into two groups: the palatine draggers and palatine erectors. "Palatine draggers" include Australasian terrestrial elapids (except Parapistocalamus) and hydrophiine sea snakes. In these species, the palatine acts as an anterior extension of the pterygoid, remaining horizontal even when the maxilla is erected. The "palatine erectors" include terrestrial African, Asian, and American elapids, the marine Laticauda, and Parapistocalamus. In these species, the palatine is erected along with the maxilla during protraction of the palate (McDowell, 1970). McDowell’s hypothesis was used in the snake classification of Smith et al. (1977), who divided Elapidae sensu lato into Elapidae sensu stricto and Hydrophiidae for the palatine erectors and draggers, respectively.

All elapids have a pair of proteroglyphous fangs that are used to inject venom from glands located towards the rear of the upper jaws. In outward appearance terrestrial elapids look similar to the family Colubridae: almost all have long and slender bodies with smooth scales, a head that is 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. There are exceptions to all these generalizations, for example, 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, 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 and others.

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, ventral scales are much reduced in size, their nostrils are located dorsally (no internasal scales) and 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 (Laticaudinae), are the sea snakes least adapted to an 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.

Geographic distribution
On land, these snakes are found worldwide in tropical and subtropical regions, except in Europe. They occur in Africa, Asia, Oceania (Australia), the Middle East, North America and South America. Sea snakes occur mainly in the Indian Ocean and the southwest Pacific Ocean. However, the range of one species, Pelamis platura, extends across the Pacific to the coasts of Central and South America.

Venom
All elapids are venomous snakes which are potentially deadly. Their venom is mainly neurotoxic, although many of them also possess several other toxins, including cardiotoxin and cytotoxin. Some large-sized elapids, such as the Asiatic king cobra, African black mamba, 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. The most venomous snake in the world is Belcher's sea snake, but on land the Inland taipan is considered to be the most venomous with a subcutaneous LD50 of 0.025 mg/kg.

Genera
* Not including the nominate subspecies