The Cyproniscidae are a family of marine isopod crustaceans in the suborder Cymothoida. The original description was made by Bonnier in 1900.Giard, A., and Bonnier, J. (1887) Contributions a l'etude des bopyriens. Travaux de l'Institut Zoologique de Lille et du Laboratoire Marine de Wimereux 5: 1-272. Members of this family are parasitic on other isopods.

The family contains these genera and species:World Register of Marine Species Cyproniscus Kossmann, 1884 Cyproniscus crossophori Stebbing, 1901 Cyproniscus cypridinae (G.O. Sars, 1883) Cyproniscus decemspinosus Menzies & George, 1972 Cyproniscus octospinosus Menzies & George, 1972 Cyproniscus peruvicus Menzies & George, 1972 Onisocryptus Schultz, 1977 Onisocryptus kurilensis Rybakov, 1998 Onisocryptus ovalis (Shiino, 1942) Onisocryptus sagittus Schultz, 1977

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