Two New Species of Tetraphyllidean Cestodes in \u3ci\u3eHimantura pacifica\u3c/i\u3e (Chondrichthyes: Myliobatiformes: Dasyatididae) from the Northwest Coast of Costa Rica

Two new species of tetraphyllidean cestodes inhabiting Himantura pacifica from the northwest coast of Costa Rica are apparently most closely related to species inhabiting Himantura schmardae from the Atlantic coast of Colombia. Acanthobothroides pacificus n. sp. differs from Acanthobothroides horsoni, the only other species in the genus, primarily by having smaller lateral (98-123 μm rather than 168-198 μm long) and medial (handles 92-116 μm rather than 162-168 μm long) hooks, and more testes (up to 125 rather than up to 97) per proglottis. The generic diagnosis of Acanthobothroides is modified to include the presence of a small inner prong on the large medial bothridial hooks. Rhinebothrium geminum n. sp. and Rhinebothrium magniphallum are the only two species in the genus possessing unusually long cirrus sacs, extending from the genital atrium all the way to the ovarian isthmus; R. geminum averages 12 (12-14) loculi per bothridium and 11 (9-12) testes, whereas R. magniphallum averages 17 (16-18) loculi and 14 (10-16) testes per proglottis