A new species of Halectinosoma Vervoort, 1962 (Copepoda: Harpacticoida) from Argentina, including a key to species with unusual leg armature patterns, notes on wrongly assigned taxa and an updated key to ectinosomatid genera

Both sexes of a new brackish water species, Halectinosoma parejae sp. nov. (Harpacticoida: Ectinosomatidae), are described from the Bahía Blanca estuary (38°53′S, 62°07′W) in Buenos Aires Province. The species represents the first confirmed record of the genus in Argentinean waters and can be readily differentiated from its 68 valid congeners by its unique armature pattern on the swimming legs. A key to the 17 species displaying seta/spine formulae that diverge from the common plesiomorphic condition is provided, as well as an updated key to the genera of the Ectinosomatidae. The status of some species that had previously been assigned to the wrong genus has been re-evaluated. Pseudobradya lanceta Coull, 1986 is transferred to Halectinosoma Vervoort, 1962 as H. lancetum (Coull, 1986) comb. nov., while the closely related H. spinicauda Wells, 1961, H. pterinum Moore, 1974 and H. paraspinicauda Bodin, 1979 are removed from Halectinosoma and placed in Pseudobradya Sars, 1904 as P. spinicauda (Wells, 1961) comb. nov., P. pterina (Moore, 1974) comb. nov. and P. paraspinicauda (Bodin, 1979) comb. nov., respectively. The inadequately described H. littorale (Nicholls, 1939) is relegated to species inquirenda in Pseudobradya. The Japanese “population” of the Brazilian H. arenicola (Rouch, 1962) has been attributed distinct specific status as H. pseudarenicola sp. nov., while H. smirnovi (Chislenko, 1967) is reinstated as a valid species distinct from H. unicum Lang, 1965.