Crestfishes are lampriform fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

es in the family Lophotidae. They are elongate ribbon-like fishes, silver in color, found in deep tropical and subtropical waters worldwide. Their scientific name is from Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 lophos meaning "crest" and refer to the crest (part of the dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

) that emerges from the snout and head; this structure gives them their other name of unicorn fishes.

They possess ink sacs that open into their cloaca

Cloaca

In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

 from which they can produce a cloud of black ink when threatened (as in many cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s).

Species

There are three extant species in two genera:

• Genus Eumecichthys
  • Unicorn crestfish
    Unicorn crestfish
    The unicorn crestfish or unicornfish, Eumecichthys fiski, is a very rare, little-known species of crestfish in the family Lophotidae, and the only member of its genus...
    
    , Eumecichthys fiski (Günther, 1890).
• Genus Lophotus
  • North Pacific crestfish
    North Pacific crestfish
    The North Pacific crestfish or unicornfish, Lophotus capellei, is a crestfish of the genus Lophotus, found in the tropical and subtropical waters of the Pacific and Atlantic oceans, in deep water...
    
    , Lophotus capellei (Temminck
    Coenraad Jacob Temminck
    Coenraad Jacob Temminck was a Dutch aristocrat and zoologist.Temminck was the first director of the National Natural History Museum at Leiden from 1820 until his death. His Manuel d'ornithologie, ou Tableau systematique des oiseaux qui se trouvent en Europe was the standard work on European birds...
    
     & Schlegel
    Hermann Schlegel
    Hermann Schlegel was a German ornithologist and herpetologist.-Early life and education:Schlegel was born at Altenburg, the son of a brassfounder. His father collected butterflies, which stimulated Schlegel's interest in natural history...
    
    , 1845).
  • Crested oarfish, Lophotus lacepede Giorna, 1809.