SERENDIP-DEBORAHAE N-GEN AND N-SP (EUCESTODA, TETRAPHYLLIDEA, SERENDIPIDAE N FAM) IN RHINOPTERA-STEINDACHNERI EVERMANN AND JENKINS, 1891 (CHONDRICHTHYES, MYLIOBATIFORMES, MYLIOBATIDAE) FROM SOUTHEASTERN ECUADOR

Cestodes collected in spiral valves of Rhinoptera steindachneri from t he southern coast of Ecuador represent an undescribed species of Tetra phyllidea. The new species has bothridia possessing septa but lacking apical suckers. It is diagnosably distinct from all other tetraphyllid ean genera by possessing a scolex comprising 4 triangular bothridia th at are fused together forming a platelike structure, each of which is subdivided by 2 simple and 1 bifurcating septa radiating from its base and ringed by marginal loculi; therefore, a new genus is proposed for it. By exhibiting some degree of bothridial fusion, testes arranged i n 2 layers in the proglottis and postovarian testes, the new species a ppears to be a member of a clade containing Dioecotaenia, Duplicibothr ium, and Glyphobothrium. The new species possesses vitelline fields th at converge dorsally in each proglottis, except for the ovarian and te rminal genitalia areas, a feature that has been reported previously on ly in Duplicibothrium and Glyphobothrium. Furthermore, Duplicibothrium and Glyphobothrium, like the new species, are markedly protandric. Th erefore, we propose that Duplicibothrium, Glyphobothrium, and the new species comprise the sister group of the Dioecotaeniidae, and propose a new family name for the clade. Tritaphros is rejected as a possible sister group for the clade; suggested alternatives include some specie s of Caulobothrium, Rhodobothrium, or some members of the Phyllobothri um centrurum group.