Zyxibothrium (Tetraphyllidea: Phyllobothriidae), a New Genus of Cestodes from Skates, with Suggestions for Diagnoses, Classification, and Revision of the Rhinebothriinae Euzet, 1953

Abstract

A new tetraphyllidean cestode, Zyxibothrium kamienae gen. et sp. n., is described from the spiral valve of Raja senta Garman, 1885, taken in the northwest Atlantic. The genus is placed in the family Phyllobothriidae Braun, 1900, and distinguished by sessile, loculated bothridia fused anteriorly, smooth strobila, preovarian lateral genital pore, lateral vitellaria, and bilobed ovary. The relationship to tetra- phyllideans of the superfamily Phyllobothrioidea Southwell, 1930, is discussed, particularly with regard to the generic characters used to differentiate members of the Rhinebothriinae Euzet, 1953. Rhabdoto- bothrium Euzet, 1953, is synonymized with Caulobothrium Baer, 1948, because of variable development and occurrence of the cephalic peduncle; Caulobothrium is synonymized with Rhinebothrium Linton, 1890, because distribution of testes is not a reliable generic character in tetraphyllideans. Alternatively, three new subgenera are proposed in order to organize the species of Rhinebothrium on the basis of bothridial morphology and distribution of testes. Definitions of genera and suprageneric taxa are discussed, and a format is proposed to limit them accurately to true categorical differences. Authors are asked to name the classification scheme being followed, to specify the categories of placement within it, and to limit their definitions of new taxa accordingly.