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.
Facciolella is a genus of eels in the duckbill eel family Nettastomatidae.
The rusty spaghetti eel, also known as the rusty worm eel, the slender worm eel, or the intermediate thrush-eel is an eel in the family Moringuidae. It was described by Richard Bliss Jr. in 1883. It is a tropical, marine eel which is known from the Indo-Pacific region, including East Africa, Easter Island, the Ryukyu Islands, Australia, and Micronesia. It leads a benthic lifestyle, burrowing into sandy regions in reefs at a depth range of 1–40 m. Males can reach a maximum total length of 140 cm.
Gorgasia cotroneii is an eel in the family Congridae. It was described by Umberto D'Ancona in 1928, originally under the genus Leptocephalus. It is a marine, tropical eel which is known from the Red Sea, in the western Indian Ocean.
Heteroconger congroides is an eel in the family Congridae. It was described by Umberto D'Ancona in 1928, originally under the genus Leptocephalus. It is a marine, deepwater-dwelling eel which is known from the Kamaran Islands in Yemen, in the Red Sea, in the western Indian Ocean. It is known only from larvae, which are known from a depth of 522 m (1,713 ft).
The Guinean pike conger is an eel in the family Muraenesocidae. It was described by Oronzio Gabriele Costa in 1846. It is a marine, subtropical eel which is known from the eastern Atlantic Ocean, including Gibraltar, the western Mediterranean, and Angola. It dwells at a depth range of 10 to 100 metres ; larger individuals are usually found from 75 to 100 metres. It inhabits sand and mud substrates on the continental shelf. Males can reach a maximum total length of 200 centimetres (79 in), but more commonly reach a TL of 150 centimetres (59 in).
Gavialiceps arabicus is an eel in the family Muraenesocidae. It was described by Umberto D'Ancona in 1928, originally under the genus Leptocephalus. It is a marine, deep water-dwelling eel which is known from the western Indian Ocean, including the Gulf of Aden, the southeastern Arabian Sea, Socotra, Yemen and Maldives. It dwells at a depth range of 380 to 497 metres. Males can reach a maximum total length of 84 centimetres.
Facciolella castlei is an eel in the family Nettastomatidae. It was described by Nikolai Vasilyevich Parin and Emma Stanislavovna Karmovskaya in 1985. It is a marine, deep water-dwelling eel which is known from Chile, in the southeastern Pacific Ocean. The type specimen was retrieved from a depth of 230 metres.
The dogface witch eel is an eel in the family Nettastomatidae. It was described by Charles Henry Gilbert in 1891. It is a marine, deep water-dwelling eel which is known from the eastern central Pacific Ocean, including Point Conception, California, USA; Panama, Guadalupe, and the Galapagos Islands. The fish is known to dwell at an approximate depth of 734 meters. Males can reach a maximum total length of 90 centimetres.
Facciolella gilbertii, known commonly as the Dogface witch-eel, is an eel in the family Nettastomatidae. It was described by Samuel Garman in 1899. It is a marine, deep water-dwelling eel which is known from the eastern central Pacific Ocean, including California, USA, and Panama. It is known to dwell at a depth of 935 metres. It is often caught in bottom trawls. Females are oviparous, and the larvae are planktonic. Males can reach a maximum total length of 61 centimetres.
Facciolella karreri is an eel in the family Nettastomatidae. It was described by Wolfgang Klausewitz in 1995. It is a marine, deep water-dwelling eel which is known from the eastern and western Indian Ocean and the western central Pacific Ocean, including the Red Sea, Egypt, Eritrea, Somalia, Saudi Arabia, Yemen and Sudan, and possibly northern Australia. It dwells at a depth range of 700–2000 metres, and is believed to inhabit holes in soft sediments on the sea-bottom. Males can reach a maximum total length of 36.1 centimetres.
Facciolella saurencheloides is an eel in the family Nettastomatidae. It was described by Umberto D'Ancona in 1928. It is a marine, deep water-dwelling eel which is known from the northwestern and western Indian Ocean, including the Red Sea. It dwells at a depth range of 700–2000 metres.
The duck-billed eel also known as the shortsnouted sorcerer or the smallhead duckbill eel, is an eel in the family Nettastomatidae. It was described by Albert Günther in 1877. It is a marine, deep water-dwelling eel which is known from the Indo-Pacific and the southeastern Pacific Ocean, including Japan, Hawaii, eastern Australia, southeastern Africa, and Chile. It dwells at a depth range of 60–1190 metres, and inhabits the continental shelf and slope. Males can reach a maximum total length of 82 centimetres.
The slender sorcerer is an eel in the family Nettastomatidae. It was described by Wilhelm Peters in 1864. It is a marine, tropical eel which is known from the eastern Atlantic and Indian Ocean, including the River Congo and the Mediterranean. It dwells at a depth range of 185 to 700 metres. Males can reach a maximum total length of 65 centimetres (26 in).
The whipsnout sorcerer is an eel in the family Nettastomatidae. It was described by Léon Vaillant in 1888, originally under the genus Nettastoma. It is a marine, deep water-dwelling eel which is known from tropical, subtropical and temperate areas throughout the world. It dwells at a depth range of 385 to 2,200 metres, and inhabits the lower region of the continental slope. Males can reach a maximum total length of 100 centimetres (39 in).
The Pacific worm eel is an eel in the family Ophichthidae. It was described by David Starr Jordan and Charles Henry Gilbert in 1883. It is a marine, subtropical eel which is known from the eastern central and southeastern Pacific Ocean, including California, USA, Colombia, Costa Rica, El Salvador, Ecuador, Honduras, Mexico, Guatemala, Panama, Nicaragua, and Peru. It dwells at a depth range of 1 to 12 metres, and inhabits sand and mud sediments. Unlike many species of eel, it does not form burrows. Males can reach a maximum total length of 46 centimetres.
Ophichthus echeloides is an eel in the family Ophichthidae. It was described by Umberto D'Ancona in 1928. It is a marine, tropical eel which is known from the Gulf of Aqaba and the Red Sea, in the western Indian Ocean. Males can reach a maximum total length of 51 centimetres (20 in).
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).
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.
Dysomma brevirostre, the pignosed arrowtooth eel or Batnose eel,) is an eel in the family Synaphobranchidae. It was described by Luigi Facciolà in 1887. It is a marine, deep water-dwelling eel which is known from the eastern and western Atlantic Ocean, including Madeira Island, the Gulf of Guinea, the Ligurian Sea, Italy, and Florida and Hawaii, USA. It dwells at a depth range of 200 to 1,000 metres, and inhabits soft sediments on the continental slope. Males can reach a maximum total length of 30 centimetres (12 in).
