Marine benthic harpacticoid copepods are poorly known in Korea due to the difficulty in obtaining specimens. Currently, the genus Stylicletodes Lang, 1936, which is known to occur in subtidal sediments, has not been reported in this area so far. During surveys on the subtidal meiofauna, we found a new species of Stylicletodes from several subtidal muddy sediments in the Yellow Sea and South Sea.
In this study, we describe both sexes of a new species of Stylicletodes collected from the Yellow Sea and South Sea of Korea. Stylicletodes trifidus sp. nov. differs from its congeners in the following characteristics: the trifid rostrum, relative length ratio of the endopods to exopods on legs 1–4, reduced armature formulae on legs 3–4, constricted shape at mid-length of the anal somite, and structure of the sexually dimorphic male leg 3 with a two-segmented endopod. The new species underwent loss of the maxilliped, which is very rare in harpacticoids and is probably an important clue for the phylogeny of the species of Stylicletodes.