Platycopiidae is a 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...

 of 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. Until the description of Nanocopia in 1988, it contained the single genus Platycopia. It now contains four genera, three of which are monotypic; the exception is Platycopia, with 8 species.

Systematics

The family Platycopiidae was erected by Georg Ossian Sars when he described the new species P. perplexa, and included it in the order Calanoida

Calanoida

Calanoida is an order of copepods, a kind of zooplankton. They include around 40 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world's oceans, making up 55%–95% of plankton samples...

. In 1948, Karl Georg Herman Lang

Karl Georg Herman Lang

Karl Georg Herman Lang was a Swedish zoologist, specialising in crustaceans, especially harpacticoid copepods and tanaids. He was born in Malmö and gained a doctoral degree from the Lund University in 1924. He spent much of his early career working as a teacher in elementary schools in Eslöv, Lund...

 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. Most recently, Huys & Boxshall inferred that Platycopiidae was the earliest branching copepod lineage, making it the sister taxon to all other copepods; they therefore raised Progymnoplea to the rank

Taxonomic rank

In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

 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

Most recent common ancestor

In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...

 of all copepods. Few synapormorphies

Synapomorphy

In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...

 have been found to unite the family, but they include the presence of a second dorsal seta

Seta

Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....

 (hair) on particular segments of the legs. They share with calanoid copepods

Calanoida

Calanoida is an order of copepods, a kind of zooplankton. They include around 40 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world's oceans, making up 55%–95% of plankton samples...

 the possession of Von Vaupel Klein's organ, a sensory organ near the base of the first swimming leg.

Members

Antrisocopia prehensilis Fosshagen, 1985 is a critically endangered

Critically Endangered

Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....

 species from a limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 anchialine cave

Cave

A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...

 in Bermuda

Bermuda

Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...

, 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 534 metres (1,752 ft) in the Barents Sea

Barents Sea

The Barents Sea is a marginal sea of the Arctic Ocean, located north of Norway and Russia. Known in the Middle Ages as the Murman Sea, the sea takes its current name from the Dutch navigator Willem Barents...

.

Platycopia comprises eight species, distributed in the North Sea

North Sea

In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

, the eastern seaboard

East Coast of the United States

The East Coast of the United States, also known as the Eastern Seaboard, refers to the easternmost coastal states in the United States, which touch the Atlantic Ocean and stretch up to Canada. The term includes the U.S...

 of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, the Bahamas, Mauritania

Mauritania

Mauritania is a country in the Maghreb and West Africa. It is bordered by the Atlantic Ocean in the west, by Western Sahara in the north, by Algeria in the northeast, by Mali in the east and southeast, and by Senegal in the southwest...

 and Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. The first species to be described was P. perplexa, named by Georg Ossian Sars in 1911.