Designation of a Brazilian topotypic neotype for Dardanus pectinatus (Ortmann, 1892) and establishment of D. ctenodon sp. nov. for the East Atlantic hermit crab previously misidentified with it (Crustacea, Decapoda, Anomura, Diogenidae)

The type locality of the hermit crab, Pagurus striatus var. pectinata Ortmann, 1892, as given in its original description, is Brazil. After its original brief taxonomic account, the species was first treated as amphi-Atlantic and later the name Dardanus pectinatus (Ortmann, 1892) was systematically applied to an African Atlantic species. No explicit reason has ever been given for this application. However, it transpires from the literature that carcinologists believed that the gastropod shell, Tonna galea (Linnaeus, 1758), occupied by the holotype of Pagurus striatus var. pectinata Ortmann, 1892 was endemic to the Mediterranean and Eastern Atlantic, and that the specimen had therefore been mislabelled. In fact, Tonna galea is amphi-Atlantic and the shell occupied by the hermit crab cannot be used to argue that it has been mislabelled. The holotype of Pagurus striatus var. pectinata Ortmann, 1892 is lost and its original description and illustration are insufficient to establish its true identity. Two steps are taken to stabilise the nomenclature in accepting the hypothesis by far most likely, i.e. that the holotype of Pagurus striatus var. pectinata did indeed come from Brazil. First action: a Brazilian neotype is designated for Pagurus striatus var. pectinata, with a specimen of a species compatible with its original description, namely Dardanus insignis (de Saussure, 1857). As a result of this action, Dardanus pectinatus (Ortmann, 1892) becomes a junior synonym of Dardanus insignis (de Saussure, 1857). Second action: the African Atlantic species is described as a new species, Dardanus ctenodon sp. nov., with a holotype from Senegal. The three similar Atlantic species Dardanus arrosor (Herbst, 1796), Dardanus ctenodon sp. nov. and Dardanus insignis (de Saussure, 1857) are the subject of an illustrated taxonomic account and an identification key is given for all the Atlantic species of Dardanus.