The cyclorhagid kinorhynch Echinoderes cavernus sp. nov. is described from a submarine cave in New South Wales, Australia. This finding represents the first kinorhynch, which probably lives in caves, exclusively. The usual sexual dimorphism in Echinoderes is absent in the new species, i.e. lateral terminal accessory spines are present in both sexes. Further sexually peculiar characters in E. Cavernus sp. nov. are genital setae on the arthrocorium between segments 12 and 13 in both sexes, and the presence of only two penile spines in the males. The new species has interstitial placids and blunt (short and broad) lateral terminal spines. The blunt lateral terminal spines are proposed to be an autapomorphic character for a monophyletic clade consisting of Echinoderes abbreviatus, E. brevicaudatus and E. Cavernus sp. nov. which all inhabit coarse coralligenous sand.