A taxonomic revision of Paradoris sea slugs (Mollusca, Gastropoda, Nudibranchia, Doridina)

Paradoris, traditionally a generic taxon of discodorid sea slugs, is revised for the first time. One hundred and thirty specimens were examined, including all types and most of the nontype specimens available. New records for Paradoris are provided: South Africa, Tanzania, Seychelles, Western Australia, Thailand, Philippines, shallow waters of New Caledonia, southern Japan, and Hawaii. The individual variation of all taxonomic characters is thoroughly evaluated. Prior to the present study, Paradoris included 15 nominal species: 12 valid names and three synonyms. Three additional names, Discodoris erythraeensis, D. lora, and D. cavernae, are re-allocated to Paradoris, based on phylogenetic analysis. A phylogenetic diagnosis is provided for Paradoris: in particular, two new synapomorphies are described. Eight species names are regarded as valid: P. araneosa, P. dubia, P. erythraeensis, P. indecora, P. liturata, P. lopezi, P. mulciber, and P. tsurugensis. However, most of these species are poorly known, i.e. from very few specimens, and their taxonomic status might change when more individuals are available. P. lora is regarded as a nomen dubium. Six new synonymies are proposed, and explained by the fact that: (1) species names were created for one or a few specimens, without considering individual variation; (2) authors have not worked within a phylogenetic framework and have created new species names without considering all the existing species names already available within Paradoris. Three new morphospecies are described, but not formally named because their taxonomic status is still uncertain for several reasons (e.g. lack of knowledge of individual variation for some critical features).