Platycopiidae

The family Platycopiidae was erected by Georg Ossian Sars when he described the new species P. perplexa, and included it in the order Calanoida.[2] 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.[2] 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 of infraclass, to accommodate Platycopioida alone, with all other copepods being placed in the Neocopepoda.[2]

Members of the Platycopiidae have a primitive form, thought to be similar to the most recent common ancestor of all copepods. Few synapormorphies have been found to unite the family, but they include the presence of a second dorsal seta (hair) on particular segments of the legs.[3] They share with calanoid copepods the possession of Von Vaupel Klein's organ, a sensory organ near the base of the first swimming leg.[3]

Antrisocopia prehensilis Fosshagen, 1985 is a critically endangered species from a limestone anchialine cave in Bermuda, known from only five mature specimens.[4]

Nanocopia minuta Fosshagen, 1988 is a critically endangered species from the same anchialine cave as Antrisocopia, and is known from only two specimens.[5]

Sarsicopia polaris Martínez Arbizu, 1997 was collected in 1993 from a depth of 534 metres (1,752 ft) in the Barents Sea.[2]

Platycopia comprises eight species, distributed in the North Sea, the eastern seaboard of North America, the Bahamas, Mauritania and Japan.[2] The first species to be described was P. perplexa, named by Georg Ossian Sars in 1911.[2]