The multiple faces of Nannopus palustris auct. reconsidered: A morphological approach (Copepoda: Harpacticoida: Nannopodidae)

Specimens attributable to the genus Nannopus and sampled on three intertidal mudflats e.g. Longyearbyen (Spitsbergen, Svalbard archipelago), the river banks of “De Schelde” in Belgium and from its estuary, the “Oosterschelde”, in the Netherlands are compared. This revealed the presence of a series of specific features allowing the discrimination of different species: N. didelphis spec. nov., N. scaldicola spec. nov., N. procerus spec. nov. and N. hirsutus spec. nov. In view of this, the poor original description of Nannopus palustris Brady, 1880 is reinterpreted and compared with the few descriptions available and the materials studied herein. “Norwegian” specimens identified by Sars as N. palustris turn out to be conspecific with N. procerus spec. nov., N. flexibilis (Lilljeborg) is re-instated as a separate species with N. palustris tiberiadis Por, 1968, N. palustris sensu Sars, 1927, Damian-Georgescu, 1970, and Nannopus spec. Hemsen, 1952 as junior synonyms. Nannopus may turn out to comprise of two different phylogenetic lineages each sustained by derived character states exhibited in the structure of the leg 4 armature and the morphology of the male leg 6 and the male genital apparatus.