The Saccopharyngiformes are a derived lineage of unusual eels within the order Anguilliformes, and includes families Cyematidae, Monognathidae, Eurypharyngidae, Saccopharyngidae, and the proposed family Neocyematidae. Most of the fish in this group are deep-dwelling and rarely seen, typically known from only a handful of specimens. Species include recognizable fish such as pelican eels and bobtail eels. Some can live deep in the ocean, well into the aphotic zone, approximately 500 to 1,800 meters deep. Extensive research has not been conducted on them due to being indirectly observed, with some species known only from their larvae. All families except for the exceptionally rare individuals of proposed family Neoceymatidae are found in all major oceans.
The pelican eel is a deep-sea eel. It is the only known member of the genus Eurypharynx and the family Eurypharyngidae. It belongs to the "saccopharyngiforms", members of which were historically placed in their own order, but are now considered true eels in the order Anguilliformes. The pelican eel has been described by many synonyms, yet nobody has been able to demonstrate that more than one species of pelican eel exists. It is also referred to as the gulper eel, pelican gulper, and umbrella-mouth gulper. The specific epithet pelecanoides refers to the pelican, as the fish's large mouth is reminiscent of that of the pelican.
Ophichthidae is a family of fish in the order Anguilliformes, commonly known as the snake eels. The term "Ophichthidae" comes from Greek ophis ("serpent") and ichthys ("fish"). Snake eels are also burrowing eels. They are named for their physical appearance, as they have long, cylindrical, snake-like bodies. This family is found worldwide in tropical to warm temperate waters. They inhabit a wide range of habitats, from coastal shallows and even rivers, to depths below 800 m (2,600 ft). Most species are bottom dwellers, hiding in mud or sand to capture their prey of crustaceans and small fish, but some are pelagic.
The superorder Elopomorpha contains a variety of types of fishes that range from typical silvery-colored species, such as the tarpons and ladyfishes of the Elopiformes and the bonefishes of the Albuliformes, to the long and slender, smooth-bodied eels of the Anguilliformes. The one characteristic uniting this group of fishes is they all have leptocephalus larvae, which are unique to the Elopomorpha. No other fishes have this type of larvae.
Monognathus, or onejaw, is the only genus of the family Monognathidae of deep-sea eels. The name comes from the Greek monos meaning “one” and gnathos meaning “jaw”, a reference to the large mouth in comparison with the rest of the fish, and also the absence of an upper jaw.
Gymnothorax is a genus of fish in the family Muraenidae found in Atlantic, Indian, and Pacific Oceans. With more than 120 species, it the most speciose genus of moray eels.
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.
Eels are ray-finned fish belonging to the order Anguilliformes, which consists of eight suborders, 20 families, 164 genera, and about 1000 species. Eels undergo considerable development from the early larval stage to the eventual adult stage and are usually predators.
Apterichtus is a genus of fish in the family Ophichthidae. Many of its species are called finless eels.
Dysomma is a genus of eels in the cutthroat eel family Synaphobranchidae.
Ophidion is a genus of cusk-eels.
Otophidium is a genus of cusk-eels, part of the subfamily Ophidiinae in the family Ophidiidae. They are found in the western Atlantic and eastern Pacific.
Ariosoma meeki is an eel in the family Congridae. It was described by David Starr Jordan and John Otterbein Snyder in 1900, originally under the genus Congrellus. It is a subtropical, marine eel which is known from Japan and the Peng-hu Islands, in the northwestern Pacific Ocean. Males are known to reach a maximum total length of 53 centimetres.
The Bullish conger is an eel in the family Congridae. It was described by David G. Smith and Robert H. Kanazawa in 1977, originally under the genus Rhechias. It is a marine, deep water-dwelling eel which is known from the Gulf of Mexico to the Amazon, in the western Atlantic Ocean. It dwells at a depth range of 366–475 meters. Males can reach a maximum total length of 39.5 centimeters.
Gnathophis grahami, or Graham's conger, is an eel in the family Congridae. It was described by Emma Stanislavovna Karmovskaya and John Richard Paxton in 2000. It is a subtropical, marine eel which is known from New South Wales, Australia, in the southwestern Pacific Ocean. It dwells at a depth range of 50–350 metres.
Saccopharynx ampullaceus, referred to as the gulper eel, gulper, taillight gulper or pelican-fish, is an ocean-dwelling eel found in the North Atlantic Ocean. They are found up to a depth of 3,000 m (9,800 ft). These fish are rarely observed, so little information is currently known about their habits or full distribution.
Monognathus boehlkei is a deep-sea eel inhabiting all oceans at depths up to 2,000 metres (6,600 ft). Little is known of this species.
Saccopharynx lavenbergi is a species of gulper eel, also known as the whiptail gulper. This fish is known for its large mouth and long whiplike tail. This species is not commonly found in the wild, with fewer than twenty sightings over 30 years of ROV operation by MBARI. Even though it has rarely been sighted, this gulper eel was chosen to be the logo for MBARI.
Saccopharynx berteli is a species of ray-finned fish within the family Saccopharyngidae. It is known from a single holotype collected from the central Pacific Ocean through an open fishing net at a depth of 1,100 metres (3,600 ft) in 1977. The individual caught was an immature male with a length of 89.5 centimetres (35.2 in). It has been classified as a 'Data deficient' species by the IUCN Red List as there is little information regarding its population, ecology, distribution, and potential threats.
Saccopharynx paucovertebratis is a species of ray-finned fish within the family Saccopharyngidae. The species is known from a single a single holotype collected from a fishing trawl west of Madeira in the Atlantic Ocean at a depth up to 1,700 m (5,600 ft) in 1931. The holotype was measured at 30.5 centimetres (12 in) in length. The IUCN Red List has assessed the species as 'Data deficient' as there is there is little information regarding population, ecology, distribution, and potential threats.
