Analysis of Calliobothrium (Tetraphyllidea:Onchobothriidae) with descriptions of three new species and erection of a new genus.

Examination of voucher or type material, or both, of 9 of the 10 currently recognized species of Calliobothrium resulted in redescriptions of C. evani, C. lintoni, and C. pellucidum, and emendations of the descriptions of C. eschrichti and C. leuckarti. New collections of Calliobothrium from the spiral intestines of Mustelus spp. led to the discovery of 3 new species: Calliobothrium hayhowi n. sp. from Mustelus antarcticus in Australia, Calliobothrium riseri n sp. from Mustelus henlei in the Sea of Cortéz, México, and Calliobothrium violae n. sp. from Mustelus canis in the Northwestern Atlantic Ocean. New collections of C. evani from the Sea of Cortéz established Mustelus lunulatus as a host for this species. Six species of Calliobothrium were examined with scanning electron microscopy. A cladistic analysis was performed on 12 of the 13 species of Calliobothrium recognized after the descriptions of the new taxa, using 34 characters and 4 outgroup taxa. This analysis yielded a single most parsimonious tree with a consistency index of 0.68. This tree suggests that Calliobothrium is monophyletic only when the biloculated species Calliobothrium pritchardae is excluded from the genus. The new genus Biloculuncus is erected to house C. pritchardae so that the monophyly of Calliobothrium can be maintained. A key to the species of onchobothriids bearing 2 pairs of hooks per bothridium is presented.