Ophidiiformes


Ophidiiformes is an order of ray-finned fish that includes the cusk-eels, pearlfishes, viviparous brotulas, 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, including parasitism. The majority are egg-laying, but some are viviparous.

Distribution

This order includes a variety of deep-sea species, including the deepest known, Abyssobrotula galatheae, found at in the Puerto 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 the Weddell Sea.

Characteristics

Ophidiiform fish typically have slender bodies with small heads, and either smooth scales, or none at all. They have long dorsal fins, and an anal fin that is typically united with the caudal fin. The group includes pelagic, benthic, and even parasitic species, although all have a similar body form. Some species are viviparous, giving birth to live young, rather than laying eggs. They range in size from Grammanoides opisthodon which measures just in length, to Lamprogrammus shcherbachevi at in length.
The families Ranicipitidae and Euclichthyidae were formerly classified in this order, but are now preferred in Gadiformes; Ranicipitidae has been absorbed within the family Gadidae.

Timeline of genera


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color:eocene bar:NAM4 from: -55.8 till: 0 text: Onuxodon
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Classification

The order Ophidiiformes is subdivided into suborders and families as follows:
The suborder Ophidioidei may be a paraphyletic grouping but the suborder Bythitoidei are viviparous and seem to make up a monophyletic clade, while the Ophidioidei are oviparous.