Males of Kalcerrytus yacuruna sp. nov. are similar to those of K. amapari, K. merreti, K. filipi and K. amplexus by having a short, stout RTA, but can be distinguished from K. amapari by the sinuous embolus with a wide base and bifurcated tip . They can be distinguished from those of K. filipi, K. merreti and K. amplexus by having a short RTA , trapezoidal in shape (RTA having a triangular in shape in K. filipi, qua-drangular in shape in K. merreti with an inferior apophy-sis and expanded bifurcated tip in K. amplexus). Females are similar to those of K. edwarsi, K. excultus, K. leucodonby having a similar shape of copulatory ducts and sper-mathecae but can be distinguished from them by having an oval-shaped copulatory openings