''Diceratias'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of deep sea marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Diceratiidae, the double anglers. These fishes are found in the Eastern Atlantic and

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

regions.

Taxonomy

''Diceratias '' was first proposed as a

monospecific genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

in 1887 by the German-born British

herpetologist Herpetology (from Ancient Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is a branch of zoology concerned with the study of amphibians (including frogs, salamanders, and caecilians (Gymnophiona)) and reptiles (in ...

and

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2 ...

Albert Günther when he described ''Diceratias bispinosus''. When he described ''D. bispinosus'' Günther gave the type locality as off Banda Island at a depth of on the

Challenger expedition The ''Challenger'' expedition of 1872–1876 was a scientific programme that made many discoveries to lay the foundation of oceanography. The expedition was named after the naval vessel that undertook the trip, . The expedition, initiated by W ...

of 1872-1876. This genus is one of two genera in the family Diceratiidae which the 5th edition of ''

Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...

'' classifies within the

suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...

Ceratioidei Ceratioidei, the deep-sea anglerfishes or pelagic anglerfishes, is a suborder of marine ray-finned fishes, one of five suborders in the order Lophiiformes, the anglerfishes. These fishes are found in tropical and temperate seas throughout the wor ...

within the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Lophiiformes The anglerfish are ray-finned fish in the order Lophiiformes (). Both the order's common and scientific name comes from the characteristic mode of predation, in which a modified dorsal fin ray acts as a lure for prey (akin to a human angler, ...

, the anglerfishes.

Etymology

''Diceratias'' prefixes ''di'', meaning "two" onto the genus name ''Ceratias''. This genus was thought to be a

subgenus In biology, a subgenus ( subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the ge ...

of ''Ceratias'' with two cephalic spines instead of one.

Species

''Diceratias'' contains the following species: * ''

Diceratias bispinosus ''Diceratias bispinosus'', the two-rod angler, is a species of deep sea marine Actinopterygii, ray-finned fish belonging to the Family (biology), family Double angler, Diceratiidae, the double anglers. This species is found in the Indo-Pacific re ...

'' Günther, 1887 (Two-rod anglerfish) * ''

Diceratias pileatus ''Diceratias pileatus'' is a species of deep sea marine ray-finned fish belonging to the family Diceratiidae, the double anglers. The fish is bathypelagic and has been found at depths ranging from . This species was thought to be endemic to the A ...

'' Uwate, 1979 * ''

Diceratias trilobus ''Diceratias trilobus'' is a species of deep sea marine ray-finned fish belonging to the family Diceratiidae, the double anglers. The fish is bathypelagic and has been found as deep as . It is endemic to the northwest Pacific Ocean. A distinct c ...

'' Balushkin &

Fedorov Fyodorov or Fedorov (, masculine) and Fyodorova or Fedorova (Фёдорова, feminine) is a common Russian last name that is derived from the given name Fyodor and literally means ''Fyodor's''. It is transliterated in Polish as Fiodorow (masculin ...

, 1986

Characteristics

''Direcatias'' double anglers are

sexually dimorphic Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. The metamorphosed females can be separated from other females in the suborder Ceratioidei by the possession of a second, club-like exposed cephalic spine bearing a

bioluminescent Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some fungi, microorganisms inc ...

organ at its tip. In this genus the spine is on the snout rather than being located at the back of the head as in ''

Bufoceratias ''Bufoceratias'' is a genus of marine ray-finned fishes belonging to the family Diceratiidae, the double anglers. Fishes in this genus are found in the Indian, Pacific and Western Atlantic Oceans. Taxonomy ''Bufoceratias'' was first proposed as ...

'', the forward tip of the illicium's

pterygiophore A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine biology, marine environments, so the fins are not all Homology (biol ...

is exposed while in ''Bufoceratias'' it is hidden and it has a deep trough it can be retracted into. The spine is shorter than in ''Bufoceratias'' having a length equivalent to between 27% and 47% of the standard length. They also have a large mouth which reaches back beyond the eye, a well developed spine on the

symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...

of the

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

which reaches just past the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

, the presence of

vomerine teeth The vomer (; ) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones. The vomer forms t ...

, there are large spines in the skin, the

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

has between five and seven rays while the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

has four rays and they have a small pelvic bone which is joined to the

cleithrum The cleithrum (: cleithra) is a membrane bone which first appears as part of the skeleton in primitive Osteichthyes, bony fish, where it runs vertically along the scapula. Its name is derived from Greek κλειθρον = "key (lock)", by analogy ...

. The second cephalic spine is positioned directly behind the base of the first cephalic spine, or

illicium ''Illicium'' is a genus of flowering plants treated as part of the family Schisandraceae,

and can be pulled down beneath the skin in individuals with a total length greater than leaving a small pore to show its location. The males have spinules in the skin, they have two teeth on the snout and two transverse rows of 4 or 5 teeth on the lower jaw, all separate from each other. The eyes and nostrils of the males are directed laterally. The largest species in the genus is ''D.pileatus'' with a maximum published

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

for a metamorphosed female of .

Distribution and habitat

''Diceratias'' double anglers are found in the Eastern Atlantic Ocean and the Indo-Pacific, they are

bathypelagic The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypela ...

fishes which are found in tropical and subtropical waters, on or near the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

at depths between .

References

Diceratiidae , Marine fish genera Taxa named by Albert Günther {{Lophiiformes-stub