Ceratioidei

Ceratioidei, the deep-sea anglerfishes or pelagic anglerfishes, is a suborder of marine ray-finned fishes, one of four suborders in the order Lophiiformes, the anglerfishes. These fishes are found in tropical and temperate seas throughout the world. One of the better known traits of the deep-sea anglerfishes is their extreme sexual dimorphism where the males are many times smaller than the females, the males seek out females and use their sharp teeth to clamp onto the females where he remains for the rest of his life, in some species he becomes part of the female. This is the only known natural example of a process called parabiosis. Another common trait of deep-sea anglerfishes is that they use bioluminescence on their esca to attract prey in the darkness of the deep oceans they inhabit.

Taxonomy
Ceratioidei was first proposed as a grouping in 1912 by the English ichthyologist Charles Tate Regan as the division Ceratiformes within the suborder Lophoidea of the order Pediculati, which included the Batrachoididae. The Batrachoididae are not now cosidered to be closely related to the anglerfishes which are now included in the order Lophiiformes. Ceratioidei are in the same clade as the Chaunacoidei with the Antennarioidei and the Ogcocephaloidei as the sisters of that clade. The 5th edition of Fishes of the World treats this grouping as a suborder within the Lophiiformes.

Evolution
A 2024 study found that although the ceratioids likely diverged from the Chaunacidae during the Paleocene, the diversification into their multiple modern families only occurred throughout the Eocene following the Paleocene-Eocene Thermal Maximum. This likely also coincides with their colonization of deep-sea habitats. Prior to these radiations, ancestral ceratioids evolved extreme sexual size dimorphism and independently lost adaptive immune genes such as aicda, which allowed male anglerfishes to fuse with females, ultimately leading to the evolution of their sexual parasitism.

Etymology
Ceratioidei takes its name from the genus Ceratias, the type genus of the family Ceratidae and of the suborder. Ceratias means "horn bearer", an allusion to the esca sticking up from the snout.

Families
Ceratioidei contains the following families:
 * Caulophrynidae Goode & Bean, 1896 (Fanfins)
 * Neoceratiidae Regan, 1926 (Spiny seadevils)
 * Melanocetidae Gill, 1878 (Black seadevils)
 * Himantolophidae Gill, 1861 (Footballfishes)
 * Diceratiidae Regan & Trewavas, 1932 (Double anglers)
 * Oneirodidae Gill, 1878 (Dreamers)
 * Thaumatichthyidae Smith & Radcliffe, 1912 (Wolftrap anglers)
 * Centrophrynidae Bertelsen, 1951 (Prickly seadevils)
 * Ceratiidae Gill, 1861 (Warty seadevils)
 * Gigantactinidae Boulenger, 1904 (Whipnose anglers)
 * Linophrynidae Regan, 1925 (Leftvents)