''Monognathus'', or onejaw, is the only genus of the family Monognathidae of

deep-sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres (656 feet) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combin ...

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

s. The name comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''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 (

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

and

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

bones are absent).

Description

The dorsal and

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as s ...

s lack bony supports and the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

s are missing. The snout has a fang connected to glands, which are venomous in adults. These eels are virtually blind, with rudimentary eyes and small olfactory organs, although the male olfactory organs are enlarged, perhaps suggesting a method of "sniffing out" a mate. Typical lengths are from 4 to 10 cm (1.5–4 in), the maximum length recorded is 15.9 cm (6.3 in).

Distribution

They are found at depths of over 2,000 m (6,600 ft), and are found in all oceans.

Species

The fifteen known species are: * '' Monognathus ahlstromi'' Raju, 1974 (Paddletail onejaw) * '' Monognathus berteli'' J. G. Nielsen & Hartel, 1996. * '' Monognathus bertini'' Bertelsen & J. G. Nielsen, 1987. * ''

Monognathus boehlkei ''Monognathus boehlkei'' is a deep-sea eel inhabiting all oceans at depths up to 2,000 meters. Little is known of this species. Description The species is characterized by a distinctive high number of anal fin rays and a short, blunt head wit ...

'' Bertelsen & J. G. Nielsen, 1987. * '' Monognathus bruuni'' Bertin, 1936. * '' Monognathus herringi'' Bertelsen & J. G. Nielsen, 1987. * '' Monognathus isaacsi'' Raju, 1974. * ''

Monognathus jesperseni ''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 ...

'' Bertin, 1936. * ''

Monognathus jesse ''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 ...

'' Raju, 1974. * ''

Monognathus nigeli ''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 ...

'' Bertelsen & J. G. Nielsen, 1987. * ''

Monognathus ozawai ''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 ...

'' Bertelsen & J. G. Nielsen, 1987. * ''

Monognathus rajui ''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 ...

'' Bertelsen & J. G. Nielsen, 1987. * ''

Monognathus rosenblatti ''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 ...

'' Bertelsen & J. G. Nielsen, 1987. * ''

Monognathus smithi ''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 ...

'' Bertelsen & J. G. Nielsen, 1987. * ''

Monognathus taningi ''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 ...

'' Bertin, 1936.

References

Monognathidae Deep sea fish Marine fish genera Taxa named by Léon Bertin {{Saccopharyngiformes-stub