''Polyipnus'' 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 ...

ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...

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 ...

in 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 ...

Sternoptychidae. This is the largest genus of the

marine hatchetfish Marine hatchetfishes or deep-sea hatchetfishes are small deep-sea mesopelagic ray-finned fish of the stomiiform subfamily Sternoptychinae. They should not be confused with the freshwater hatchetfishes, which are not particularly closely relate ...

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Sternoptychinae and indeed of the entire

Sternoptychidae The marine hatchetfishes or deep-sea hatchetfishes as well as the related bottlelights, pearlsides and constellationfishes are small deep-sea ray-finned fish of the stomiiform family Sternoptychidae. They are not closely related to and shoul ...

. It is not quite as

apomorph In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ha ...

ic as their relatives; it may be that the genus is actually a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

assemblage of less advanced Sternoptychinae and would need to be split.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s of this genus show that they have existed at least since the

Early Oligocene The Rupelian is, in the geologic timescale, the older of two age (geology), ages or the lower of two stage (stratigraphy), stages of the Oligocene epoch (geology), Epoch/series (stratigraphy), Series. It spans the time between . It is preceded b ...

, about 30

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

Species

There are currently 34 recognized species in this genus: * '' Polyipnus aquavitus'' R. C. Baird, 1971 (aquavit hatchetfish) * '' Polyipnus asper'' Harold, 1994 * '' Polyipnus asteroides'' L. P. Schultz, 1938 * '' Polyipnus bruuni'' Harold, 1994 * '' Polyipnus clarus'' Harold, 1994 (slope hatchetfish) * '' Polyipnus danae'' Harold, 1990 * '' Polyipnus elongatus'' Borodulina, 1979 * '' Polyipnus fraseri'' Fowler, 1934 * '' Polyipnus indicus'' L. P. Schultz, 1961 * '' Polyipnus inermis'' Borodulina, 1981 * '' Polyipnus kiwiensis'' R. C. Baird, 1971 (kiwi hatchetfish) * '' Polyipnus laruei'' Vourey, Dupoux & Harold, 2017 (bigeye hatchetfish) * '' Polyipnus laternatus'' Garman, 1899 * '' Polyipnus latirastrus''

Last A last is a mechanical form shaped like a human foot. It is used by shoemakers and cordwainers in the manufacture and repair of shoes. Lasts come in many styles and sizes, depending on the exact job they are designed for. Common variations ...

& Harold, 1994 (comb-side hatchetfish) * '' Polyipnus limatulus'' Harold & Wessel, 1998 * '' Polyipnus matsubarai'' L. P. Schultz, 1961 * ''

Polyipnus meteori ''Polyipnus meteori'' is a species of ray-finned fish in the genus '' Polyipnus'' found in the Indian and Pacific Oceans The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends f ...

'' Kotthaus, 1967 * '' Polyipnus notatus'' Harold, I. M. Kemp &

Shore A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

, 2016 * '' Polyipnus nuttingi'' C. H. Gilbert, 1905 (Nutting's hatchetfish) * '' Polyipnus oluolus'' R. C. Baird, 1971 * '' Polyipnus omphus'' R. C. Baird, 1971 * '' Polyipnus ovatus'' Harold, 1994 * '' Polyipnus parini'' Borodulina, 1979 * '' Polyipnus paxtoni'' Harold, 1989 (Paxton's hatchetfish) * '' Polyipnus polli'' L. P. Schultz, 1961 (round hatchetfish) * '' Polyipnus ruggeri'' R. C. Baird, 1971 (rugby hatchetfish) * '' Polyipnus soelae'' Harold, 1994 (Soela hatchetfish) * '' Polyipnus spinifer'' Borodulina, 1979 * '' Polyipnus spinosus'' Günther, 1887 (spiny hatchetfish) * '' Polyipnus stereope'' D. S. Jordan & Starks, 1904 * '' Polyipnus surugaensis'' Aizawa, 1990 * '' Polyipnus tridentifer'' McCulloch, 1914 (three-spined hatchetfish) * '' Polyipnus triphanos'' L. P. Schultz, 1938 (three-light hatchetfish) * '' Polyipnus unispinus'' L. P. Schultz, 1938

References

* Sternoptychidae Extant Rupelian first appearances Taxa named by Albert Günther Ray-finned fish genera Rupelian genus first appearances {{Stomiiformes-stub