The beardfishes consist of a single extant genus, Polymixia, of deep-sea marine ray-finned fish named for their pair of long hyoid barbels. They are classified in their own order Polymixiiformes. But as Nelson says, "few groups have been shifted back and forth as frequently as this one, and they were recently added to Paracanthoptergii". For instance, they have previously been classified as belonging to the Beryciformes, and are presently considered either paracanthopterygians or the sister group to acanthopterygians. They are of little economic importance.
The Zeiformes are a small order of exclusively marine ray-finned fishes most notable for the dories, a group of common food fish. The order consists of about 33 species in six extant families, mostly deep-sea types. The boarfishes (Caproidae) have been previously included in this order though they are currently included in the Perciformes.
The Congridae are the family of conger and garden eels. Congers are valuable and often large food fishes, while garden eels live in colonies, all protruding from the sea floor after the manner of plants in a garden. The family includes over 180 species in 32 genera.
The herring smelts or argentines are a family, Argentinidae, of marine smelts. They are similar in appearance to smelts but have much smaller mouths.
Berycopsis is an extinct genus of marine ray-finned fish from the Late Cretaceous period. Fossils are known from England, Germany, and Lebanon. A potential specimen is known from the Czech Republic.
The roughskin dogfish is a sleeper shark of the family Somniosidae, found around the world on continental shelves in tropical, subtropical and temperate seas, at depths of between 100 and 1,500 m. It reaches a length of 121 cm.
Paraulopus is the only genus in the family Paraulopidae, a family of grinners in the order Aulopiformes. They are commonly known as cucumberfishes, but locally some other Teleostei are also known by that name. They were considered in the Chlorophthalmidae or greeneye family until 2001.
Coriops is an extinct genus of freshwater osteoglossomorph fish, possibly a hiodontiform, with a single species known from the Late Cretaceous of western North America.
Apateodus is a genus of prehistoric marine ray-finned fish which was described by Woodward in 1901. It was a relative of modern lizardfish and lancetfish in the order Aulopiformes, and one of a number of prominent nektonic aulopiforms of Cretaceous marine ecosystems.
The Heterenchelyidae or mud eels are a small family of eels native to the Atlantic, Mediterranean, and eastern Pacific.
Casierius is an extinct genus of marine ray-finned fish that lived during the Albian stage of the Early Cretaceous epoch. It was a relative of the modern bonefish in the extinct family Phyllodontidae, although some authorities consider it either a true albulid or a very early eel. It contains a single species, C. heckeli, known from the Glen Rose Formation near Hood County, Texas.
Berycopsia is an extinct genus of beardfish that lived during the Turonian stage of the Late Cretaceous. It contains a single species, B. inopinnata, that inhabited marine habitats of the Tethys Sea around what is now Croatia.
Ampheristus is an extinct genus of prehistoric marine ray-finned fish. It was a basal or stem member of the family Ophidiidae, which contains modern cusk-eels. Fossils are known from worldwide from the Late Cretaceous to the late Paleogene, making it a rather successful survivor of the Cretaceous-Paleogene extinction event.
Dapalis is an extinct genus of prehistoric glassfish known from the Late Cretaceous to the Early Miocene. It is known from both freshwater and marine habitats of India, Australia, New Zealand, and Europe.
Dalmatichthys is an extinct genus of marine beardfish from the Late Cretaceous. It contains a single species, D. malezi from Croatia. It is the only member of the family Dalmatichthyidae, which is sometimes considered synonymous with Polymixiidae. Its exact relationship to modern beardfish in Polymixia likely needs further research.
The Argentiniformes is an order of marine ray-finned fish whose distinctness was recognized only fairly recently. In former times, they were included in the Osmeriformes as suborder Argentinoidei. That term refers only to the suborder of marine smelts and barreleyes in the classification used here, with the slickheads and allies being the Alepocephaloidei. These suborders were treated as superfamilies Argentinoidea and Alepocephaloidea, respectively, when the present group was still included in the Osmeriformes.
Pythonichthys is a genus of eels of the family Heterenchelyidae that occur in tropical waters of the eastern Pacific Ocean off of Panama and in the Atlantic Ocean near the Caribbean Sea and the west coast of Africa. It contains the following described species:
Argentina is a genus of fishes in the family Argentinidae.
Bolinichthys is a genus of lanternfishes.
Rosalindidae is a family of cnidarians belonging to the order Anthoathecata.
