152 



H.W. PALM 



characterised by a cosmopolitan distribution pattern, which distin- 

 guishes those trypanorhynchs from species such as the 

 eutetrarhynchids of endemic Australian and South American rays 

 (see also Palm et al, 1997, Rego & Dias, 1976). A low level of 

 specialisation of tentaculariids with a flexible, unspecialised life 

 cycle pattern might be essential for these oceanic trypanorhynchs, 

 which would explain for example their occurrence in marine plank- 

 ton (Dollfus, 1974) as well as the enigmatic infestation of humans 

 (Fripp & Mason, 1983). 



The present and previous studies demonstrate that several species 

 exist which change their kind of tentacular armature continuously 

 along the tentacle, such as N. africana and N. lingualis. Some 

 species change more abrupt between a characteristic basal and 

 metabasal armatures, such as H. scoliodoni and M. southwelli, while 

 others retain their general hook shape but continuously increase the 

 hook size, such as in H. estigmena and H. robusta. In N. aequidentata, 

 the hook size decreases towards the basal and apical part of the 

 tentacle. It is evident that the tentacular armature within the group is 

 highly variable, making the description of completely evaginated 

 tentacles essential for identification. However, these differences in 

 hook type and size along the tentacles represent an ideal tool for 

 future taxonomic work within these tentaculariid genera. 



CLASSIFICATION 



The subgroupings of Palm et al. (1997) remain a basis for further 

 taxonomic work within tentaculariid trypanorhynchs. Together with 

 the studies of Palm & Walter (1999) (N. southwelli) and Jones & 

 Beveridge (1998) (N. queenslandensis), 48 species belong to the 

 genera Nybelinia (31 species), Heteronybelinia (15) and Mixo- 

 nybelinia (2). The current classification of tentaculariid cestodes is 

 as follows: 



1. Genus: Tentacularia Bosc, 1797 



(type and only species: Tentacularia coryphaenae Bosc, 1797) 



2. Genus Nybelinia Poche, 1926 (subgroup I in Palm et al., 1997) 

 (type species: Nybelinia lingualis (Cuvier, 1817)) 



A Species without characteristic basal armature 



a Size of basal hooks smaller than metabasal hooks: 



N. aequidentata (Shipley & Hornell, 1906), N. anthicosum 

 Heinz & Dailey, 1974, N. edwinlintoni Dollfus, 1960, N. 

 goreensis Dollfus, 1960, N. jayapaulazariahi Reimer, 

 1980, N. palliata (Linton, 1924), N. queenslandensis 

 Jones & Beveridge, 1998, N. riseri Dollfus, 1960, N. 

 sakanariae sp. nov., N. schmidti sp. nov., N. sphyrnae 

 Yamaguti, 1952, N. thyrsites Korotaeva, 1971 



b Size of basal hooks equal to metabasal hooks 



N. anantaramanorum Reimer, 1980, N. bengalensis 

 Reimer, 1980, N. oodes Dollfus, 1960, N. pintneri 

 Yamaguti, 1934, N. rhynchobatus Yang Wenchuan, Lin 

 Yuguang, Liu Gencheng & Peng Wenfeng, 1995, N. 

 strongyla Dollfus, 1960, N. surmenicola Okada, 1929, N. 

 syngenes (Pintner, 1929), TV. tenuis (Linton, 1890), 

 Nybelinia sp. 



c Size of basal hooks larger than metabasal hooks 



N. basimegacantha Carvajal, Campbell & Cornford, 1976 



B Species with characteristic basal armature 



a Size of basal hooks smaller than or equal to metabasal 

 hooks 



N. africana Dollfus, 1960, N. anguillae Yamaguti, 1952, 

 N. bisulcata (Linton, 1889), N. erythraea Dollfus, 1960, 

 N indica Chandra, 1986, N lingualis (Cuvier, 1817), N. 

 manazo Yamaguti, 1952, N. scoliodoni (Vijayalakshmi, 

 Vijayalakshmi & Gangadharam, 1996) 



b Size of basal hooks larger than metabasal hooks 

 N. gopalai Chandra & Hanumantha Rao, 1985 



3. Heteronybelinia gen. nov. (subgroup II in Palm et al., 1997) 



(type species: Heteronybelinia estigmena (Dollfus, I960)) 



A Without characteristic basal armature 



a Size of basal hooks smaller than metabasal hooks 



H. alloiotica (Dollfus, 1960), H. cadenati (Dollfus, 1960), 

 H. e/oftgata(Shah&Bilqees, \919),H. est/gmena (Dollfus, 

 1960),//. eureia (Dollfus, 1960),//. heteromorphisp. nov., 

 H. karachii (Khurshid & Bilqees, 1988), H. minima sp. 

 nov., H.punctatissima (Dollfus, 1960),//. robusta (Linton, 

 1890), H. senegalensis (Dollfus, 1960) 



b Size of basal hooks equal to or larger than metabasal hooks 



H. perideraeus (Shipley & Hornell, 1906) 



B With characteristic basal armature 



a Size of basal hooks smaller or equal than metabasal hooks 

 H. nipponica (Yamaguti, 1952), H. rougetcampanae 

 (Dollfus, 1960), H. yamagutii (Dollfus, 1960) 



4. Mixonybelinia gen. nov. 



(type species: Mixonybelinia beveridgei (Palm, Walter, 

 Schwerdtfeger & Reimer, 1997)) 



Mixonybelinia beveridgei (Palm, Walter, Schwerdtfeger & 

 Reimer, 1997), M. southwelli (Palm & Walter, 1999) 



5. Kotorella Euzet & Radujkovic, 1989 



(type and only species: Kotorella pronosoma (Stossich, 1901)) 



Nybelinia lingualis has been considered as belonging to subgroup 

 IAa by Palm etal. (1997) and is assigned to subgroup Ba on basis of 

 the gradual change of hook form along the tentacle (see Figs 7-9). 

 The basal hooks without an anterior extension of the base easily 

 distinguish the species from most Nybelinia, and therefore are 

 interpreted as a characteristic basal armature. Some other species 

 listed in this classification might change their position after re- 

 examination of the type-material. However, classification as well as 

 comparative discussions on species validity is simplified if using the 

 presented scheme. How strobila morphology such as the shape of 

 segments and structure of the genital complex can be incorporated 

 into this classification will be an important task for future studies. 



PHYLOGENY 



The above classification most probably does not reflect the phylogeny 

 within tentaculariid trypanorhynchs. Palm et al. (1997) failed with 

 their cladistic analysis of the genus Nybelinia and the present study 



