Platycopiidae is a

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 ...

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

s. Until the description of ''Nanocopia'' in 1988, it contained the single genus ''Platycopia''. It now contains four genera, three of which are

monotypic 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 "unisp ...

; the exception is ''Platycopia'', with 8 species.

Systematics

The family Platycopiidae was erected by

Georg Ossian Sars Prof Georg Ossian Sars HFRSE (20 April 1837 – 9 April 1927) was a Norway, Norwegian marine biology, marine and freshwater biology, freshwater biologist. Life Georg Ossian Sars was born on 20 April 1837 in Kinn (former municipality), Kinn, No ...

when he described the new species ''P. perplexa'', and included it in the order

Calanoida Calanoida is an order of copepods, a group of arthropods commonly found as zooplankton. The order includes around 46 families with about 1800 species of both marine and freshwater copepods between them. Description Calanoids can be distinguish ...

. In 1948, Karl Georg Herman Lang erected a new suborder, Progymnoplea, for the family, and in 1985, Audun Fosshagen & Thomas Iliffe created the order Platycopioida to contain the Platycopiidae, initially placed alongside Calanoida in the superorder

Gymnoplea Calanoida is an order of copepods, a group of arthropods commonly found as zooplankton. The order includes around 46 families with about 1800 species of both marine and freshwater copepods between them. Description Calanoids can be distinguish ...

. Most recently, Huys & Boxshall inferred that Platycopiidae was the earliest branching copepod lineage, making it the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to all other copepods; they therefore raised Progymnoplea to the

rank A rank is a position in a hierarchy. It can be formally recognized—for example, cardinal, chief executive officer, general, professor—or unofficial. People Formal ranks * Academic rank * Corporate title * Diplomatic rank * Hierarchy ...

of infraclass, to accommodate Platycopioida alone, with all other copepods being placed in the Neocopepoda. Members of the Platycopiidae have a primitive form, thought to be similar to the

most recent common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...

of all copepods. Few synapormorphies have been found to unite the family, but they include the presence of a second dorsal

seta In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae, ...

(hair) on particular segments of the legs. They share with calanoid copepods the possession of Von Vaupel Klein's organ, a

sensory organ A sense is a biological system used by an organism for sensation, the process of gathering information about the surroundings through the detection of stimuli. Although, in some cultures, five human senses were traditionally identified as su ...

near the base of the first swimming leg.

Members

''Antrisocopia prehensilis'' Fosshagen, 1985 is a

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

species from a

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

anchialine An anchialine system (, from Greek ''ankhialos'' 'near the sea') is a landlocked body of water with a subterranean connection to the ocean. Depending on its formation, these systems can exist in one of two primary forms: pools or caves. The primary ...

cave Caves or caverns are natural voids under the Earth's Planetary surface, surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance undergrou ...

Bermuda Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest. Bermuda is an ...

, known from only five mature specimens. ''Nanocopia minuta'' Fosshagen, 1988 is a critically endangered species from the same anchialine cave as ''Antrisocopia'', and is known from only two specimens. ''Sarsicopia polaris'' Martínez Arbizu, 1997 was collected in 1993 from a depth of in the

Barents Sea The Barents Sea ( , also ; , ; ) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territorial waters.World Wildlife Fund, 2008. It was known earlier among Russi ...

. ''Platycopia'' comprises eight species, distributed in the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

, the eastern seaboard of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, the

Bahamas The Bahamas, officially the Commonwealth of The Bahamas, is an archipelagic and island country within the Lucayan Archipelago of the Atlantic Ocean. It contains 97 per cent of the archipelago's land area and 88 per cent of its population. ...

Mauritania Mauritania, officially the Islamic Republic of Mauritania, is a sovereign country in Maghreb, Northwest Africa. It is bordered by the Atlantic Ocean to the west, Western Sahara to Mauritania–Western Sahara border, the north and northwest, ...

and

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. The first species to be described was ''P. perplexa'', named by

in 1911.

References

{{Authority control Copepod families Copepods