Gnathiidae

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: Crustacea
Superclassis: Multicrustacea
Classis: Malacostraca
Subclassis: Eumalacostraca
Superordo: Peracarida
Ordo: Isopoda
Cladus: Scutocoxifera
Subordo: Cymothoida
Superfamilia: Cymothooidea

Familia: Gnathiidae
Genera (11): Bathygnathia – Bythognathia – Caecognathia – Elaphognathia – Euneognathia – Gibbagnathia – Gnathia – Monodgnathia – Paragnathia – Tenerognathia – Thaumastognathia
References

Ota, Y. 2012: Gnathiidae from Kumejima Island in the Ryukyu Archipelago, southwestern Japan, with description of three new species (Crustacea: Isopoda). Zootaxa 3367: 79–94. Preview Reference page.
Ota, Y. 2013: Redescription of five gnathiid species from Japan (Crustacea: Isopoda). Zootaxa 3737(1): 33–56. DOI: 10.11646/zootaxa.3737.1.3 Reference page.
Svavarsson, J. 2006: New species of Gnathiidae (Crustacea, Isopoda, Cymothoida) from seamounts off northern New Zealand. Zootaxa 1173(1): 39–56. DOI: 10.11646/zootaxa.1173.1.2 Open access. Reference page.
Svavarsson, J.; Bruce, N.L. 2012: New and little-known gnathiid isopod crustaceans (Cymothoida) from the northern Great Barrier Reef and the Coral Sea. Zootaxa 3380: 1–33. Preview PDF Reference page.
Svavarsson, J. & Bruce, N.L. 2019. New gnathiid isopod crustaceans (Cymothoida) from Heron Island and Wistari Reef, southern Great Barrier Reef. Zootaxa 4609(1): 31–67. DOI: 10.11646/zootaxa.4609.1.2 Paywall Reference page.

The Gnathiidae are a family of isopod crustaceans. They occur in a wide range of depths, from the littoral zone to the deep sea. The adults are associated with sponges and may not feed.[1] The juvenile form is known as a 'praniza', and it is a temporary parasite of marine fish.[1][2] These forms are not larvae; Gnathiidae instead become parasitic during the manca stage. Mancae of the Gnathiidae closely resemble the adult form, however they lack the final pair of pereiopods.
Drawings of Gnathiidae by Hesse (1864)[2]

Taxonomy in the family relies on male characters, such that females and juveniles cannot be reliably identified.[1] The family contains 182 species,[3] divided among the following genera:[4]

Afrignathia Hadfield & Smit, 2008
Bathygnathia Dollfus, 1901
Bythognathia Camp, 1988
Caecognathia Dollfus, 1901
Elaphognathia Monod, 1926
Euneognathia Stebbing, 1893
Gibbagnathia Cohen & Poore, 1994
Gnathia Leach, 1814
Monodgnathia Cohen & Poore, 1994
Paragnathia Omer-Cooper & Omer-Cooper, 1916
Tenerognathia Tanaka, 2005
Thaumastognathia Monod, 1926

References

Richard Brusca, Vania R. Coelho & Stefano Taiti (2001). "Suborder Gnathiidae [sic]". Guide to the Coastal Marine Isopods of California. Tree of Life Web Project. Retrieved August 28, 2010.
Hesse, Eugène (1864). Mémoire sur les pranizes et les ancées et sur les moyens curieux à l'aide desquels certains crustacés parasites assurent la conservation de leur espèce. Extrait du Tome XMII des Mémoires Présentés par Divers Savants à l'Institut Impérial de France. Paris, J. B. Baillière et Fils, Libraire de l’Académie Impériale de Médecine. BHL PDF in BHL
Jörundar Svavarsson (2006). "New species of Gnathiidae (Crustacea, Isopoda, Cymothoida) from seamounts off northern New Zealand" (PDF). Zootaxa. 1173: 39–56.
WoRMS (2010). M. Schotte; C. B. Boyko; N. L. Bruce; G. C. B. Poore; S. Taiti; G. D. F. Wilson (eds.). "Gnathiidae". World Marine, Freshwater and Terrestrial Isopod Crustaceans database. World Register of Marine Species. Retrieved August 28, 2010.