Sternoptychidae
Encyclopedia
The marine hatchetfish
es or deep-sea hatchetfishes as well as the related bottlelights, pearlsides and constellationfishes are small deep-sea bathypelagic ray-finned fish of the stomiiform family
Sternoptychidae. They should not be confused with the freshwater hatchetfish
es, which are not particularly closely related Teleostei
in the characiform family Gasteropelecidae. The Sternoptychidae have 10 genera
and about 70 species
altogether.
The scientific name means "Sternoptyx-family", from Sternoptyx
(the type genus
) + the standard animal
family suffix
"-idae". It ultimately derives from Ancient Greek
stérnon (στέρνον, "breast") + ptýx (πτύξ, "a fold/crease") + Latin
forma ("external form"), the Greek part in reference to the thorax
shape of marine hatchetfishes.
, Pacific
and Indian Ocean
s, marine hatchetfishes range in size from Polyipnus danae at 2.8 cm (1.1 in) to the c.12 cm (4.7 in)-long Giant Hatchetfish
(Argyropelecus gigas).
Like the convergent
freshwater hatchetfishes, among the marine forms the subfamily Sternoptychinae has narrow, laterally compressed, deeply keeled and roughly disc-shaped bodies, somewhat resembling a hatchet
(with the thorax
being the "blade" and the caudal peduncle being the "handle"); the pelvis
is rotated to a vertical
position. The members of the disputed subfamily Maurolicinae have a more conventional fish shape. The mouth is located at the tip of the snout and directed downwards, more so in the Sternoptychinae.
Unlike other Stomiiformes
, they still have fully developed pseudobranch
s. Their branchiostegal rays are 6-10, three of them attach to the posterior ceratohyal (epihyal). Their bodies are covered in delicate silvery scales which abrade easily. In some species, such as the Highlight Hatchetfish (Sternoptyx pseudobscura), large sections of the body at the base of the anal fin and/or caudal fin are transparent. The anal fin has 11-38 rays and may be divided in two parts. An adipose fin is usually present. The Sternoptychinae have preopercular spines and blade-like pterygiophores in front of the dorsal fin
. Their large, sometimes tube-shaped eyes can collect the faintest of light and focus
well on objects both close and far. In many genera
, the eyes are fixed gazing permanently upwards, enabling them to discern the silhouette
s of prey moving overhead against the slightly brighter upper waters.
Sternoptychidae undertake nightly mass migrations
from depths of 3,600 metres to the upper 50-100 metres of the starlit water column. There they feed throughout the night, returning to the depths by daybreak. Their prey consists primarily of tiny crustacean
s, such as amphipods, copepod
s, euphausiids (krill) and ostracod
s (seed shrimp), and of fish smaller than themselves. What little is known of their life cycle
suggests that at least some members of this family are short-lived, dying after no more than a year. They spawn
in the open water, and do not guard or otherwise care for their offspring; species with a short lifespan are presumably semelparous The fry – even of Sternoptychinae – look like tiny pearlsides (Maurolicus).
s from below. Indeed, many fishes that consider Sternoptychidae prey do so, and to foil their predaceous attempts, the Sternoptychidae have evolved an astounding ability: bioluminescent counter-illumination
.
Counterillumination (or counter-lighting) involves the production of light by the fish for the purpose of camouflaging
its silhouette from observers lurking below. Sternoptychidae produce this light with organ
s called photophore
s, of which they have between 3 and 7 – usually 6 – on the branchiostegal membrane along the lower edge of the chest and belly. The intensity of the light produced is controlled by the fish, an appropriate brightness chosen according to how much light reaches the eyes from above. The patterns of light created by the photophores are also unique to each species
, probably playing a role in courtship.
Stomiiformes
, which is often placed in the teleost superorder Stenopterygii
, usually together with the Ateleopodiformes (jellynoses), but sometimes on their own. But it may well be that the closest living relatives of the "Stenopterygii" are found among the superorder Protacanthopterygii
, and that the former would need to be merged in the latter. In some classifications, the "Stenopterygii" are kept separate but included with the Protacanthopterygii and the monotypic
superorder Cyclosquamata in an unranked clade
called Euteleostei. That would probably require splitting two additional monotypic superorders out of the Protacanthopterygii, and thus result in a profusion of very small taxa.
The Stomiiformes have also been considered close relatives of the Aulopiformes
. The latter are otherwise placed in a monotypic superorder "Cyclosquamata" but also appear to be quite close to the Protacanthopterygii indeed. The relationships of these – and the Lampriformes
or Myctophiformes
, which are also usually treated as monotypic superorders – to the taxa mentioned before is still not well resolved at all, and regardless whether one calls them Protacanthopterygii sensu lato or Euteleostei, the phylogeny of this group of moderately advanced Teleostei is in need of further study.
The ancestral Stomiiformes probably resembled the Gonostomatidae
, with thin brownish bodies, rows of egg-shaped photophore
s adorning the lower body parts, and mouths with numerous teeth. The family
Gonostomatidae is the closest living relative of the Sternoptychidae, and these two form the suborder Gonostomatoidei. Indeed, some Sternoptychidae are called "bristlemouths", like the bulk of the Gonostomatidae. Compared to their relatives, the marine hatchetfishes are a more apomorphic group, but they have evolved in an entirely different direction from the other "advanced" lineage of Stomiiformes, the huge family Stomiidae
.
) do actually belong in the Maurolicinae, it is unlikely that the two-subfamily arrangement is correct. It may even be that the Maurolicinae are just an indiscriminate assemblage of unrelated basal Sternoptychidae and are altogether invalid. The Sternoptychinae – the "true" marine hatchetfishes – on the other hand are monophyletic.
.gif)
The provisional arrangement of families
and genera
of Sternoptychidae is as follows:
Marine hatchetfish
Marine hatchetfishes or deep-sea hatchetfishes are small deep-sea mesopelagic ray-finned fish of the stomiiform subfamily Sternoptychinae...
es or deep-sea hatchetfishes as well as the related bottlelights, pearlsides and constellationfishes are small deep-sea bathypelagic ray-finned fish of the stomiiform family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Sternoptychidae. They should not be confused with the freshwater hatchetfish
Freshwater hatchetfish
The freshwater hatchetfishes are a family, Gasteropelecidae, of ray-finned fish. The common hatchetfish is the most popular member among fish keeping hobbyists...
es, which are not particularly closely related Teleostei
Teleostei
Teleostei is one of three infraclasses in class Actinopterygii, the ray-finned fishes. This diverse group, which arose in the Triassic period, includes 20,000 extant species in about 40 orders; most living fishes are members of this group...
in the characiform family Gasteropelecidae. The Sternoptychidae have 10 genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
and about 70 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
altogether.
The scientific name means "Sternoptyx-family", from Sternoptyx
Sternoptyx
Sternoptyx is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the type genus of the Sternoptychidae, as well as the marine hatchetfish subfamily Sternoptychinae.It contains only four living species:...
(the type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
) + the standard animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
family suffix
Suffix
In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs...
"-idae". It ultimately derives from Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
stérnon (στέρνον, "breast") + ptýx (πτύξ, "a fold/crease") + Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
forma ("external form"), the Greek part in reference to the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
shape of marine hatchetfishes.
Description and ecology
Found most often at depths of 200-600 meters in tropical and subtropical waters of the AtlanticAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
and Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
s, marine hatchetfishes range in size from Polyipnus danae at 2.8 cm (1.1 in) to the c.12 cm (4.7 in)-long Giant Hatchetfish
Giant hatchetfish
The Giant Hatchetfish or Greater Silver Hatchetfish a marine hatchetfish of the genus Argyropelecus, is found in every ocean except the north Pacific in deep tropical and subtropical waters.-References:...
(Argyropelecus gigas).
Like the convergent
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
freshwater hatchetfishes, among the marine forms the subfamily Sternoptychinae has narrow, laterally compressed, deeply keeled and roughly disc-shaped bodies, somewhat resembling a hatchet
Hatchet
A hatchet is a single-handed striking tool with a sharp blade used to cut and split wood...
(with the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
being the "blade" and the caudal peduncle being the "handle"); the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
is rotated to a vertical
Vertical direction
In astronomy, geography, geometry and related sciences and contexts, a direction passing by a given point is said to be vertical if it is locally aligned with the gradient of the gravity field, i.e., with the direction of the gravitational force at that point...
position. The members of the disputed subfamily Maurolicinae have a more conventional fish shape. The mouth is located at the tip of the snout and directed downwards, more so in the Sternoptychinae.
Unlike other Stomiiformes
Stomiiformes
Stomiiformes is an order of deep-sea ray-finned fishes of very diverse morphology. It includes for example dragonfishes, lightfishes, loosejaws, marine hatchetfishes and viperfishes. The order contains 4 families with more than 50 genera and almost 400 species...
, they still have fully developed pseudobranch
Pseudobranch
The pseudobranch, also pseudobranchia is the reduced first gill arch of a fish ....
s. Their branchiostegal rays are 6-10, three of them attach to the posterior ceratohyal (epihyal). Their bodies are covered in delicate silvery scales which abrade easily. In some species, such as the Highlight Hatchetfish (Sternoptyx pseudobscura), large sections of the body at the base of the anal fin and/or caudal fin are transparent. The anal fin has 11-38 rays and may be divided in two parts. An adipose fin is usually present. The Sternoptychinae have preopercular spines and blade-like pterygiophores in front 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...
. Their large, sometimes tube-shaped eyes can collect the faintest of light and focus
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...
well on objects both close and far. In many genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
, the eyes are fixed gazing permanently upwards, enabling them to discern the silhouette
Silhouette
A silhouette is the image of a person, an object or scene consisting of the outline and a basically featureless interior, with the silhouetted object usually being black. Although the art form has been popular since the mid-18th century, the term “silhouette” was seldom used until the early decades...
s of prey moving overhead against the slightly brighter upper waters.
Sternoptychidae undertake nightly mass migrations
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
from depths of 3,600 metres to the upper 50-100 metres of the starlit water column. There they feed throughout the night, returning to the depths by daybreak. Their prey consists primarily of tiny crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, such as amphipods, copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, euphausiids (krill) and ostracod
Ostracod
Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species have been identified, grouped into several orders....
s (seed shrimp), and of fish smaller than themselves. What little is known of their life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
suggests that at least some members of this family are short-lived, dying after no more than a year. They spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
in the open water, and do not guard or otherwise care for their offspring; species with a short lifespan are presumably semelparous The fry – even of Sternoptychinae – look like tiny pearlsides (Maurolicus).
Bioluminescence
Marine hatchetfishes are not the only animals that seek out prey by watching for silhouetteSilhouette
A silhouette is the image of a person, an object or scene consisting of the outline and a basically featureless interior, with the silhouetted object usually being black. Although the art form has been popular since the mid-18th century, the term “silhouette” was seldom used until the early decades...
s from below. Indeed, many fishes that consider Sternoptychidae prey do so, and to foil their predaceous attempts, the Sternoptychidae have evolved an astounding ability: bioluminescent counter-illumination
Counter-illumination
Counterillumination is a method of camouflage in which bioluminescent light from within an organismon the ventral surface is matched to the light radiating from the environment. The bioluminescent is used to obscure the organism's silhouette produced by the down-welling light. Some midwater...
.
Counterillumination (or counter-lighting) involves the production of light by the fish for the purpose of camouflaging
Crypsis
In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency, and mimicry...
its silhouette from observers lurking below. Sternoptychidae produce this light with organ
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
s called photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...
s, of which they have between 3 and 7 – usually 6 – on the branchiostegal membrane along the lower edge of the chest and belly. The intensity of the light produced is controlled by the fish, an appropriate brightness chosen according to how much light reaches the eyes from above. The patterns of light created by the photophores are also unique to each species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, probably playing a role in courtship.
Systematics
The Sternoptychidae belong to the orderOrder (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Stomiiformes
Stomiiformes
Stomiiformes is an order of deep-sea ray-finned fishes of very diverse morphology. It includes for example dragonfishes, lightfishes, loosejaws, marine hatchetfishes and viperfishes. The order contains 4 families with more than 50 genera and almost 400 species...
, which is often placed in the teleost superorder Stenopterygii
Stenopterygii
Stenopterygii are a superorder of ray-finned fish in the infraclass Teleostei. Their validity is somewhat doubtful, as the group was established to separate, out of a large group of closely related Teleostei, a mere two rather peculiarly autapomorphic orders at best...
, usually together with the Ateleopodiformes (jellynoses), but sometimes on their own. But it may well be that the closest living relatives of the "Stenopterygii" are found among the superorder Protacanthopterygii
Protacanthopterygii
Protacanthopterygii is a ray-finned fish taxon ranked as a superorder of the infraclass Teleostei. They inhabit both marine and freshwater habitat...
, and that the former would need to be merged in the latter. In some classifications, the "Stenopterygii" are kept separate but included with the Protacanthopterygii and the monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
superorder Cyclosquamata in an unranked clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
called Euteleostei. That would probably require splitting two additional monotypic superorders out of the Protacanthopterygii, and thus result in a profusion of very small taxa.
The Stomiiformes have also been considered close relatives of the Aulopiformes
Aulopiformes
Aulopiformes is an order of marine ray-finned fish consisting of some 15 extant and several prehistoric families with about 45 genera and over 230 species. The common names grinners, lizardfishes and allies or aulopiforms are sometimes used for this group...
. The latter are otherwise placed in a monotypic superorder "Cyclosquamata" but also appear to be quite close to the Protacanthopterygii indeed. The relationships of these – and the Lampriformes
Lampriformes
Lampriformes is an order of ray-finned fish. They are collectively called "lamprids" or lampriforms, and unite such open-ocean and partially deep-sea Teleostei as the crestfishes, oarfish, opahs and ribbonfishes...
or Myctophiformes
Myctophiformes
Myctophiformes is an order of ray-finned fish consisting of two families of deep-sea marine fish, most notably the highly abundant lanternfishes...
, which are also usually treated as monotypic superorders – to the taxa mentioned before is still not well resolved at all, and regardless whether one calls them Protacanthopterygii sensu lato or Euteleostei, the phylogeny of this group of moderately advanced Teleostei is in need of further study.
The ancestral Stomiiformes probably resembled the Gonostomatidae
Gonostomatidae
Gonostomatidae is a family of deep-water marine fish, commonly named bristlemouths, lightfishes or anglemouths. It is a relatively small family, containing only eight known genera and 32 species...
, with thin brownish bodies, rows of egg-shaped photophore
Photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...
s adorning the lower body parts, and mouths with numerous teeth. The family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Gonostomatidae is the closest living relative of the Sternoptychidae, and these two form the suborder Gonostomatoidei. Indeed, some Sternoptychidae are called "bristlemouths", like the bulk of the Gonostomatidae. Compared to their relatives, the marine hatchetfishes are a more apomorphic group, but they have evolved in an entirely different direction from the other "advanced" lineage of Stomiiformes, the huge family Stomiidae
Stomiidae
Stomiidae is a family of deep-sea ray-finned fish, including the barbeled dragonfishes, stareaters and loosejaws.Stomiids are generally elongated fish with black or near-black bodies, but they are highly variable in form, and are sometimes grouped into multiple different families as a result. The...
.
Classification
Typically, the Sternoptychidae are divided into two subfamilies, with the more plesiomorphic members making up the Maurolicinae. Symplesiomorphies are no reliable indicator of actual relationships, however. While it remains to be seen what Sternoptychidae other than the pearlsides (Maurolicus, the type genusType genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
) do actually belong in the Maurolicinae, it is unlikely that the two-subfamily arrangement is correct. It may even be that the Maurolicinae are just an indiscriminate assemblage of unrelated basal Sternoptychidae and are altogether invalid. The Sternoptychinae – the "true" marine hatchetfishes – on the other hand are monophyletic.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
and genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
of Sternoptychidae is as follows:
- Subfamily Maurolicinae
- Genus AraiophosAraiophosAraiophos is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae.Its type species is A. gracilis, and only one additional species is placed here:* Araiophos eastropas Ahlstrom & Moser, 1969...
(2 species) - Genus ArgyripnusArgyripnusArgyripnus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. They are commonly known as bristle-mouth fishes, but that may also refer to the related bristlemouth family . A...
– bristle-moth fishes (6 species) - Genus DanaphosDanaphosDanaphos is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. A common name is bottlelights.Only two extant species are placed here, one of them of questionable validity valid:...
– bottlelights (1-2 species) - Genus MaurolicusMaurolicusMaurolicus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. They are commonly known as pearlsides, but the brilliant pearlside is the related Argyripnus iridescens...
– pearlsides (15 species) - Genus SonodaSonodaSonoda is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae.Its type species is S. megalophthalma, and only one additional species is placed here:* Sonoda megalophthalma Grey, 1959* Sonoda paucilampa Grey, 1960...
(2 species) - Genus ThorophosThorophosThorophos is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae.Its type species is T. euryops. Only one additional species is placed here, and that was initially separated in a monotypic genus Neophos....
(2 species) - Genus ValenciennellusValenciennellusValenciennellus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. They are commonly known as constellationfishes.Its type species is V...
– constellationfishes (2 species)
- Genus Araiophos
- Subfamily Sternoptychinae – marine hatchetfishes, deep-sea hatchetfishes
- Genus ArgyropelecusArgyropelecusArgyropelecus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. A collective name is "silver hatchetfishes", but this can also refer to a species of the freshwater hatchetfishes which are not particularly closely related but merely convergent...
– silver hatchetfishes (7 species) - Genus PolyipnusPolyipnusPolyipnus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the largest genus of the marine hatchetfishes and indeed of the entire Sternoptychidae...
(32 species) - Genus SternoptyxSternoptyxSternoptyx is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the type genus of the Sternoptychidae, as well as the marine hatchetfish subfamily Sternoptychinae.It contains only four living species:...
(4 species)
- Genus Argyropelecus