Leptocephalus is a genus that was used for species of larval eels, called leptocephali, that were thought to be new fish species, or whose adult eel species were not known. Leptocephali differ so much in appearance from their adults that the larvae and adults of eels are not easily matched, and when first discovered, leptocephali were thought to be a distinct type of fishes, but not eels. Because of this, the genus designation of Leptocephalus was used for a while for unidentified leptocephali even after it was known that these were the larvae of eels thus becoming a "wastebasket taxon", but this practice is no longer used. Examples of marine congrid larvae, found in the western Indian Ocean and the Red Sea that were named this way are listed below. Only two species in two families are currently treated as having any validity, though the validity of L. bellottii is strongly in doubt.
Serrivomer is a genus of deep-sea eel in the family Serrivomeridae. It contains nine described species. Member species are distributed widely, being found in the Atlantic, Pacific and Indian Oceans. The smallest species in this genus is Serrivomer jesperseni, which has a maximum length of 40.6 cm (16 in) the largest species in this genus is Serrivomer beanii with a maximum length of 78 cm (31 in). Most members reach a maximum length of 60–70 cm (24–28 in).
Acromycter perturbator is an eel in the family Congridae. It was described by Albert Eide Parr in 1932, originally under the genus Ariosoma. It is a marine, deep water-dwelling eel which is known from the northwestern and western central Atlantic Ocean, including the Bahamas, the United States, and Jamaica. It dwells at a depth range of 1299–1318 metres.
The large-toothed conger is an eel belonging to the family Congridae. It was described by Léon Vaillant in 1888, originally as a species of the genus Uroconger.
Gnathophis capensis, the Southern Atlantic conger or southern conger, is an eel in the family Congridae. It was described by Johann Jakob Kaup in 1856, originally under the genus Leptocephalus. It is a subtropical, marine eel which is known from the southeastern Atlantic Ocean, including from False Bay to Plettenberg Bay, South Africa and also on Tristan da Cunha Island. It is known to dwell at a depth of 100 metres. Males can reach a maximum total length of 37 cm.
Gnathophis mystax, the thinlip conger or blacktailed conger, is an eel in the family Congridae. It was described by François Étienne Delaroche in 1809, originally under the genus Muraena. It is a subtropical, marine eel which is known from the eastern Atlantic Ocean, including southern Portugal, the Mediterranean, and Morocco. It dwells at a depth range of 75–800 metres, and inhabits mud and sand on the continental slope. Males can reach a maximum total length of 60 centimetres, but more commonly reach a TL of 35 centimetres.
The brown garden eel, also known simply as the garden eel, is an eel in the family Congridae. It was described by Albert Günther in 1870. It is a tropical, marine eel which is known from the eastern and western Atlantic Ocean, including Madeira, the Canary Islands, Senegal, the Bahamas, the Florida Keys, the Caribbean, Mexico, Belize, Honduras, and Brazil. It dwells at a depth of 10–60 m, most commonly between 20 and 60 m, and leads a nonmigratory, benthic lifestyle, inhabiting reefs in colonies. They likely spawn during the warm season. The larval state of development lasts for about 6–8 months. Adult males can reach a maximum total length of 51 centimetres.
Nessorhamphus ingolfianus, the duckbill oceanic eel, duckbilled eel or Ingolf duckbill eel,) is an eel in the family Derichthyidae. It was described by Johannes Schmidt in 1912. It is a marine, deep water-dwelling eel which is known from France, Morocco, the Cape of Good Hope, and South Africa in the eastern Atlantic Ocean, as well as from the western Atlantic, southwestern Indian, and southwestern Pacific. It dwells at a depth range of 0–1800 metres, inhabiting the mesopelagic zone. Males can reach a maximum total length of 58.9 centimetres.
Echelus pachyrhynchus is an eel in the family Ophichthidae. It was described by Léon Vaillant in 1888. It is a marine, deep water-dwelling eel which is known from the eastern Atlantic Ocean, including Morocco, Angola, Cape Verde, and Namibia. It dwells at a depth range of 200–500 metres, and inhabits burrows in mud or sand on the continental shelf. Males can reach a maximum total length of 48.5 centimetres.
The rufus snake eel is an eel in the family Ophichthidae. It was described by Constantine Samuel Rafinesque in 1810, originally under the genus Echelus. It is a marine, subtropical eel which is known from throughout the Mediterranean and the Black Sea, in the northeastern Atlantic Ocean, including Algeria, Albania, Croatia, Egypt, France, Cyprus, Gibraltar, Greece, Italy, Israel, Montenegro, Lebanon, Libya, Malta, Morocco, Monaco, Slovenia, Spain, Tunisia, the Syrian Arab Republic, and Turkey. It inhabits mud sediments on the continental shelf. Males can reach a maximum total length of 60 centimetres (24 in).
Phaenomonas longissima, also known as the short-maned sand eel in St. Helena, is an eel in the family Ophichthidae. It was described by Jean Cadenat and Émile Marchal in 1963, originally under the genus Callechelys. It is a marine, tropical eel which is known from the Atlantic Ocean, including Ascension Island, St. Helena, Brazil, Senegal, Ghana, and Cape Verde. It dwells at a depth range of 25 to 35 metres, and forms burrows in sand and mud sediments on the continental shelf. Males can reach a maximum total length of 50 centimetres (20 in).
The rice-paddy eel is an eel in the family Ophichthidae. It was described by Francis Buchanan-Hamilton in 1822, originally in the genus Ophisurus. It is a tropical, marine eel which is known from the Indo-West Pacific, including Somalia, Tanzania, South Africa, India, Pakistan, Sri Lanka, Indonesia, Polynesia, Australia, Bangladesh, Cambodia, Kenya, Madagascar, the Philippines, Malaysia, Mozambique, Seychelles, Saudi Arabia, Taiwan, China, Thailand, Vietnam, and southern Yemen. It is an anadromous species and spawns in freshwater, often in rice paddies during the rainy season, earning it its common name. It also spends time in lagoons, estuaries and coastal rivers, in which it lives in burrows in the river bottom and bank. Males can reach a maximum total length (TL) of 100 centimetres, but more commonly reach a TL of 70 cm.
Avocettina acuticeps, the southern snipe eel or southern fintail snipe eel, is an eel in the family Nemichthyidae. It was described by Charles Tate Regan in 1916, originally under the genus Leptocephalus. It is a marine, deep water-dwelling eel which is known from throughout the southern regions of the ocean, with the exception of the eastern Pacific. It is known to dwell at a maximum depth of 2,000 metres (6,600 ft). Males can reach a maximum total length of 77 centimetres (30 in).
The Bean's sawtooth eel is an eel in the family Nemichthyidae. It was described by Theodore Gill and John Adam Ryder in 1883. It is a marine, deep water-dwelling eel which is known from throughout the Atlantic Ocean, the Indian Ocean, and the Western Pacific Ocean, including Iceland, South Africa, Réunion, and Australia. It dwells at a depth range of 0–5998 metres, and leads a solitary lifestyle. It migrates vertically at night. Males can reach a maximum total length of 78-80 centimetres, making it the largest sawtooth eel.
The thread eel is an eel in the family Nemichthyidae. It was described by Marie-Louise Bauchot in 1959. It is a marine, temperate water-dwelling eel which is known from the Indo-Pacific and Chile in the southwestern Pacific Ocean. It is known to dwell at a depth of 1,750 metres (5,740 ft).
Serrivomer garmani is an eel in the family Serrivomeridae. It was described by Léon Bertin in 1944. It is a marine, deep water-dwelling eel which is known from the Indian Ocean. It is known to dwell at a depth range of 30 to 2,250 metres.
The crossthroat sawpalate is an eel in the family Nemichthyidae. It was described by Marie-Louise Bauchot in 1953. It is a marine, deep water-dwelling eel which is known from the western and eastern Pacific Ocean, including Papua New Guinea, British Columbia, Canada; the Gulf of Panama and Chile. It dwells at a maximum depth of 825 metres. Males can reach a maximum total length of 40.6 centimetres.
Serrivomer schmidti is an eel in the family Serrivomeridae. It was described by Marie-Louise Bauchot in 1953. It is a marine, deep water-dwelling eel which is known from the eastern and western Atlantic Ocean, including Cape Verde, Senegal, the Gulf of Guinea, and Brazil. It is known to dwell at a depth range of 0 to 2,000 metres. Males can reach a maximum total length of 65.7 centimetres (25.9 in), but more commonly reach a TL of 34 centimetres (13 in).
Serrivomer sector, known commonly as the sawtooth eel, the saw-tooth snipe or the deep-sea eel, is an eel in the family Serrivomeridae. It was described by Samuel Garman in 1899. It is a marine, deep water-dwelling eel which is known from the eastern and western Pacific Ocean, including Japan, Chile, and California, USA. It dwells at a depth range of 0 to 3,243 metres, most often around 305 metres (1,001 ft). Males can reach a maximum total length of 76 centimetres (30 in).
The Kaup's arrowtooth eel is an eel in the family Synaphobranchidae. It was described by James Yate Johnson in 1862. It is a marine, deep water-dwelling eel which is known from the Indo-Western Pacific and eastern and western Atlantic Ocean, including the Faroe Islands, Iceland, Cape Verde, the Western Sahara, Nigeria, Namibia, South Africa, Greenland, France, Saint Pierre and Miquelon, the United Kingdom, Ireland, the Philippines, Portugal, Spain, the Bahamas, Brazil, Canada, Cuba, Japan, Australia, Mauritania, Morocco, and Hawaii. It dwells at a depth range of 120 to 4,800 metres, most often between 400 and 2,200 metres, and inhabits the upper abyssal zone on the continental slope. It is intolerant of the temperatures of higher waters. Males can reach a maximum total length of 100 centimetres (39 in).
