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This study had two main objectives: (1) to construct an extensive, explicit list of characters and character states that might serve as a starting point, and perhaps even a model, for the compilation of a more complete list of characters for all cestode taxa; and (2) to use this character list to generate a hypothesis of the phylogenetic relationships among species representing most of the tetraphyllidean, lecanicephalidean and diphyllidean genera. Specimens of one species in each of 48 genera of tetraphyllideans, eight genera of lecanicephalideans, the three genera of diphyllideans, two genera of proteocephalideans and two genera of trypanorhynchs, were examined as whole-mounts and sections, with light and scanning electron microscopy. A list of 120 morphological characters was compiled. Four phylogenetic analyses were conducted using PAUP* and/or NONA. The first was a comprehensive analysis with the 56 tetraphyllidean and lecanicephalidean species as ingroups and the remaining seven species as outgroups. The second was an analysis of the three diphyllidean species as ingroups and the two proteocephalidean and the two trypanorhynch species as outgroups. The third was an analysis of the eight lecanicephalidean species and the "tetraphyllideans" Echeneibothrium sp. and Pseudanthobothrium n. sp. as ingroups and an outgroup consisting of the seven species used as outgroups in the first analysis. In the fourth analysis, the ingroup consisted of the 14 hooked tetraphyllideans (onchobothriids), and the outgroup consisted of the seven species used as outgroups in the first analysis. The results of these analyses support the following phylogenetic hypotheses: The diphyllideans are monophyletic and Echinobothrium n. sp. and Macrobothridium sp. are more closely related to one another than either is to Ditrachybothridium macrocephalum. The tetraphyllideans, lecanicephalideans and proteocephalideans are more closely related to each other than they are to the diphyllideans or the trypanorhynchs. The ordinal status of the lecanicephalideans is dubious. The lecanicephalidean species are more closely related to some of the tetraphyllidean taxa than these tetraphyllidean taxa are to the remainder of the tetraphyllidean taxa. The proteocephalideans appear to belong within the tetraphyllidean clade. The "tetraphyllidean" species Echeneibothrium sp. and Pseudanthobothrium n. sp. are members of the lecanicephalidean clade. The position of "Discobothrium" n. sp. within the lecanicephalideans is dubious. Within the tetraphyllideans, the non-acetabulate species Litobothrium daileyi, Disculiceps galapagoensis and Cathetocephalus sp. are the most basal members of the group. The family Onchobothriidae is monophyletic, as it is currently defined. Within the onchobothriids, the uniloculate species are basal to the multiloculate species; the species with unipronged hooks are basal to the species with multipronged hooks. Although relationships among the phyllobothriids, as they are currently defined, remain poorly resolved, the family Phyllobo...

Three new Rhinebothrium Linton, 1890 species, R. kinabatanganensis n. sp., R. megacanthophallus n. sp., and R. abaiensis n. sp., collected from the spiral intestines of 6 freshwater whiprays (Himantura chaophraya, Dasyatidae) in the Kinabatangan River, Malaysian Borneo, are described. This is the first record of cestodes from the Kinabatangan River and from H. chaophraya. The new Rhinebothrium species are differentiated from the 34 valid Rhinebothrium species in addition to 2 species, Echeneibothrium hui Tseng, 1933 and E. oligotesticularis Subramaniam, 1940 that are herein transferred to Rhinebothrium. Each of the new species was examined with light and scanning electron microscopy. Two of the new species possess cilia on their bothridia, which have not previously been reported for members of this genus.

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Two new species of Paraorygmatobothrium Ruhnke, 1994, P. janineae n. sp. and P. kirstenae n. sp., are described from the spiral intestine of 2 shark species of the Family Hemigaleidae: Hemigaleus microstoma and Hemipristis elongata. The 2 new cestode species differ from other members of Paraorygmatobothrium in vitelline follicle distribution and possession of a cephalic peduncle. The 2 new species differ from 1 another in total length, maximum width, scolex size, number of proglottids per strobila, and number of testes per proglottid. The generic diagnosis of Paraorygmatobothrium is emended to include the new species. The results of this study extend the distribution of Paraorygmatobothrium to include the carcharhinid shark family Hemigaleidae.

A revision of Platybothrium Linton, 1890 is presented, based on available type and voucher material, as well as extensive new collections from elasmobranchs belonging to the Carcharhinidae (requiem sharks) and Sphyrnidae (hammerhead sharks). All 10 nominal Platybothrium species are treated or redescribed herein. Four of these 10 nominal species, in addition to one former member of Dicranobothrium Euzet, 1953, are considered valid members of Platybothrium. Five new Platybothrium species are described: P. angelbahiense n. sp. ex Carcharhinus leucas, P. coshtaprum n. sp. ex C. plumbeus, P. jondoeorum n. sp. ex Negaprion acutidens and C. melanopterus, P. kirstenae n. sp. ex C. obscurus, and P. tantulum n. sp. ex Sphyrna lewini and S. zygaena. Sixty-three morphological characters were employed in cladistic analyses of nine Platybothrium species and five outgroup species. Coding and analysis strategies were varied to assess the effects of coding inapplicable characters as missing or as a separate character state, and of excluding characters for which data are missing in more than 10% of the taxa. The analysis in which inapplicable characters were coded as a separate character state and no characters were excluded produced the best-supported and most conservative estimate of the interrelationships of Platybothrium spp. Platybothrium appears to be a monophyletic assemblage, with the most basal species being P. spinulifera Southwell, 1912. The group of species possessing an accessory piece between the hooks forms a clade within the genus. Species lacking an accessory piece, which had previously been placed in Dicranobothrium Euzet, 1953, do not appear to be each other's closest relatives; thus, Dicranobothrium is considered a synonym of Platybothrium. An examination of host associations indicated that Platybothrium species are broadly distributed among, and entirely restricted to, carcharhinid and sphyrnid shark species. Most Platybothrium species exhibit oioxenous host-specificity, with all but two species each parasitising only a single host species. In several host species, multiple Platybothrium congeners parasitise the same host individual, a phenomenon not previously reported for Platybothrium.

Phoreiobothrium manirei n. sp. is described from the spiral intestines of 3 immature individuals of the great hammerhead shark Sphyrna mokarran collected off of the west coast of Florida. This cestode is unusual in that it possesses 4 muscular papillae on the anterior margin of the accessory sucker. Numerous small protrusions with central cilium-like projections were conspicuous throughout the posterior margin of each bothridium. This species possesses the unique combination of bothridia posteriorly subdivided into subloculi and hooks with extended bases and 2 rather than 3 prongs. In fact, the hooks are strikingly like those of species in the genera Dicranobothrium and Platybothrium. This combination of characters suggests that the bifid hook condition is plesiomorphic with respect to the trifid hook condition within the Onchobothriidae. These data further suggest that the triloculated bothridial condition is plesiomorphic relative to the biloculated condition.