Ryuguderes iejimaensis, a new genus and species of Campyloderidae (Xenosomata: Cyclorhagida: Kinorhyncha) from a submarine cave in the Ryukyu Islands, Japan

Ryuguderes iejimaensis gen. et sp. nov. (Xenosomata: Cyclorhagida: Kinorhyncha) is described from the Daidokustu submarine cave off Iejima Island, Ryukyu Islands, Japan. The species is characterized by the presence of outer oral styles with incompletely fused proximal parts and separate distal parts; primary spinoscalids with several internal septa; spinoscalids in ring 02 short; 14 placids, with the midventral one broadest and six broader placids alternating with seven narrower ones; middorsal acicular spines on segments 2–11 in males and on segments 2–9 in females; lateroventral acicular spines on segments 4, 6–7, and 9; short, blunt lateroventral spines on segment 5; midterminal, lateral terminal and lateral terminal accessory spines with a thick proximal cuticle around a central cellular cavity. The placid numbers and morphology of the outer oral styles, spinoscalids, and lateral terminal accessory and midterminal spines suggest Ryuguderes to be closely related with Campyloderes. In addition, morphological similarities between Ryuguderes, Campyloderes, and different genera of Kentrorhagata suggest Xenosomata and Kentrorhagata to be closely related.