Cavearhynchus, a new genus of tapeworm (Cestoda: Trypanorhyncha: Pterobothriidae) from Himantura lobistoma Manjaji-Matsumoto & Last, 2006 (Rajiformes) off Borneo, including redescriptions and new records of species of Pterobothrium Diesing, 1850

A new genus of trypanorhynch cestode is described from the tubemouth whipray Himantura lobistoma Manjaji-Matsumoto & Last, 2006 in the South China Sea off Malaysian Borneo. Cavearhynchus foveatus n. g., n. sp. possesses four pedicellate bothria in a cruciform arrangement, a heteroacanthous, heteromorphous metabasal tentacular armature with five hooks per principle row and an alternating longitudinal file of intercalary hooks on the bothrial surface of each tentacle, but lacks prebulbar organs and gland-cells within the bulbs. It, thus, closely resembles taxa belonging to the lacistorhynchoid family Pterobothriidae Pintner, 1931. However, the new genus differs from other genera within this family in the possession of bothrial pits. Although a distinguishing characteristic of the superfamily Otobothrioidea Dollfus, 1942, representatives of this group exhibit two bothria and the bothrial pits are lined with spiniform microtriches, whereas the pit-like structures.of C. foveatus n. g., n. sp. entirely lack microtriches. Redescriptions of two species of Pterobothrium, namely P. lesteri Campbell & Beveridge, 1996 and P. platycephalum (Shipley & Hornell, 1906) Dollfus, 1930 are provided from material collected off Borneo and several localities off Australia. Moreover, new host and locality records are added for P. australiense Campbell & Beveridge, 1996 and P. pearsoni (Southwell, 1929) Beveridge & Campbell, 1989.