| Ophidiiformes | |
|---|---|
 | |
| Fawn cusk-eel,Lepophidium profundorum | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Clade: | Percomorpha |
| Order: | Ophidiiformes L. S. Berg, 1937 |
| Type species | |
| Ophidion barbatum Linnaeus 1758 | |
| Suborders | |
See text | |
Ophidiiformes/ɒˈfɪdi.ɪfɔːrmiːz/ is anorder ofray-finned fish that includes thecusk-eels (familyOphidiidae),pearlfishes (familyCarapidae),viviparous brotulas (familyBythitidae), and others. Members of this order have small heads and long slender bodies. They have either smooth scales or no scales, a long dorsal fin and an anal fin that typically runs into the caudal fin. They mostly come from the tropics and subtropics, and live in both freshwater and marine habitats, including abyssal depths. They have adopted a range of feeding methods and lifestyles, includingparasitism. The majority areegg-laying, but some areviviparous.
The earliest fossil members are known from theMaastrichtian, and include the basal ophidiiformPastorius fromItaly and several species of the basal cusk-eelAmpheristus from the United States and Germany.[1][2][3]
This order includes a variety of deep-sea species, including the deepest known,Abyssobrotula galatheae, found at 8,370 metres (27,460 ft) in thePuerto Rico Trench. Many other species, however, live in shallow water, especially near coral reefs, while a few inhabit freshwater. Most species live in tropical or subtropical habitats, but some species are known from as far north as the coast of Greenland, and as far south as theWeddell Sea.[4]
Ophidiiform fish typically have slender bodies with small heads, and either smooth scales, or none at all. They have longdorsal fins, and ananal fin that is typically united with thecaudal fin. The group includespelagic,benthic, and evenparasitic species, although all have a similar body form. Some species areviviparous, giving birth to live young, rather than laying eggs. They range in size fromGrammanoides opisthodon which measures just 5 centimetres (2.0 in) in length, toLamprogrammus shcherbachevi at 2 metres (6.6 ft) in length.[4]
The familiesRanicipitidae (tadpole cods) andEuclichthyidae (eucla cods) were formerly classified in this order, but are now preferred inGadiformes; Ranicipitidae has been absorbed within the familyGadidae.
The order Ophidiiformes is subdivided into suborders and families as follows:[5][6]
Until recent taxonomic revisions, the suborder Ophidioidei was aparaphyletic grouping.[6] However, the Bythitoidei areviviparous and seem to make up amonophyleticgroup,[7] while the Ophidioidei areoviparous.[8]
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