Five New Species of the Tapeworm Genus Anthocephalum (Rhinebothriidea: Anthocephaliidae) Parasitizing A Single Species of Indo-Pacific Stingray and A Revised Diagnosis of the Genus

Five new species of the elasmobranch tapeworm genus Anthocephalum Linton, 1890 (Rhinebothriidea: Anthocephaliidae Ruhnke, Caira and Cox, 2015) are described from the mangrove whipray, Urogymnus granulatus (Macleay) from the Solomon Islands and northern Australia. Anthocephalum blairi n. sp., Anthocephalum gravisi n. sp., Anthocephalum haroldsoni n. sp., Anthocephalum mounseyi n. sp., and Anthocephalum ruhnkei n. sp. differ from one another and their congeners based on quantitative and qualitative features of the scolex and proglottid anatomy. Species boundaries recognized by these distinguishing morphological features are supported by a maximum likelihood phylogenetic analysis based on combined 18S rDNA and 28S rDNA (D1–D3) sequence data showing the new species as independent lineages among 13 of the 18 species of Anthocephalum described to date. Several morphological features (the possession of columns of vitelline follicles that are interrupted by the ovary, a uterus that does not extend to the anterior margin of the proglottid but stops short in the anterior region of the field of testes, proximal surfaces of the marginal loculi covered with acicular filitriches only throughout, or with gladiate spinitriches and acicular filitriches throughout, and proximal bothridial surfaces with gladiate spinitriches and acicular filitriches) are collectively exhibited by the 5 new species and have not been documented previously in other species of Anthocephalum. The genus is herein amended to reflect these features. Additionally, the replacement name Anthocephalum centrurum (Southwell, 1925) Ruhnke, 1994 is reinstated as the valid name for the type species of the genus, Anthocephalum gracile Linton, 1890, with the latter being the junior secondary homonym of A. gracile (Wedl, 1855) Ruhnke, 1994. The description of these new species increases the number of valid species of Anthocephalum from 18 to 23.