Scope of and proposal for systematics of the Amphistomida (Lühe, 1909) Odening, 1974 (Trematoda)

Parasit hung. 21. 1988 Scope of and proposal for systematics of the Amphistomida (Lühe, 1909) Odening, 1974 (Trematoda) Dr. Ottó SEY Department of Zoology, Janus Pannonius University, Pécs, Hungary "Scope of and proposal for systematics of the Amphistomida (Lühe, 1909) Odening, 1974 (Trematoda)". - Sey., O. - Parasit, hung., 21: 17-30. 1988. ABSTRACT. The taxon Amphistomida contains a monophyletic group of digenetic trematodes, parasitic in all higher vertebrate taxa. The posteriorly located ventral sucker, both in adult and in larval stage, and the epidermal cell formula of the miracidium are the main in-group character states of the taxa. The taxonomic position of the monostome groups of trematodes, assigned to amphistomes by previous authors, is analyzed. The outline of a new scope of amphistomes is formularized and a new classification scheme is proposed. Caballerodiscus gen.n. is described. system KEY WORDS: Amphistomida, scope and phyletic relationship, proposed atics, Caballerodiscus gen. n. The taxon Amphistomida comprises a natural group of digenetic trematodes and has the rank of order in the modern classification of higher taxa of trematodes. Morphologically, their generalized, in-group feature is the postero-terminally spaced ventral sucker. Biologically they are one of the few groups of flukes whose representatives are parasitic in all higher taxa of vertebrate hosts. The scope of amphistomes has considerably varied since the 19the century, when the name Amphistoma was established by RUDOLPHI (1809). It referred to the erroneous observation of they having a mouth-opening at both ends of the body. RUDOLPHI's category, however, embraced also those flukes which, in the present interpretation, belong to another natural taxon, Strigeida. The generic name Amphistomum was set up by NITZSCH (1819), and of RUDOLPHI's species those were allocated to this genus which were characterized by the presence of an oral opening at the anterior body and by ventral sucker posterio-terminally. By the turn of the century it became evident that the species assigned to this genus, Amphistomum, are a heterogeneous assemblage of flukes. In his endeavour to establish the homogeneous structure of this taxon, the genus Amphistomum was divided into various genera (Paramphistomum, Cladorchis etc.) by FISCHOEDER (1901, 1903), and they were transfered to the family Paramphistomidae: a category created by the same author. Subsequent authors have accepted FISCHOEDER's nomenclature and the suprafamiliar categories, implying that the whole group of amphistomes were constituted from this name (e. g. Paramphistomatoidea Stiles et Goldberger, 1910, Paramphistomata Szidat, 1936; Paramphistomiformes Travassos, Freitas et Kohn, 1963; Brooks et al. 1985). Recently ODENING (1974), with the meanwhile intention of designating the natural higher taxa of trematodes, proposed the usage of the name Amphistomida (Lühe. 1909) for the order, em-

bracing amphistomes of all kinds. ODENING (1963, 1974) pointed out that it would be reasonable to retain the name of the suprafamiliar category even if the rank of the original group was altered by subsequent taxonomic rearrangements. Moreover, as the taxon Amphistomida is 'nowadays considered a natural taxon as it was in LÜHE's time and was :it nominated by him, as the first suprafamiliar category, and finally as there is no nomenclatural regulation to apply one of the valid generic names to nominate higher taxon, the present writer agrees with ODENING's notion on the priority of the taxonomic name Amphistomida (Lühe, 1909) Odening, 1974. (Amphistomida was formed of LÜHE's Amphistomata with the aid of the -ida, added to the root of the word.) Since the beginning of this century the scope of the amphistomes has been considerably enlarged not only by the discovery of newer.forms but also by the allocation of groups of flukes of debated taxonomic position to the amphistomes. The family Microscaphidiidae was assigned to the amphistomes by ODHNER (1911); Opistholebetidae and Opisthoporidae by FU RTH (1929); Gyliauchenidae by OZAKI (1937); Cephaloporidae by TRAVASSOS (1934); Mesometridae and Notocotylidae by SZIDAT (1939); Metacetabulidae by SKRJABIN (1949); Heronimidae by CRANDALL (1960); and Zonocotylidae by YAMAGUTI (1963) and PADI LH A (1978). ODHNER (1911) was of the opinion that the m onostqme microscaphidiid trematodes had been amphistomes but they lost their ventral sucker, and their organological resemblances (pharyngeal appendages, lymphatic system etc.) make them similar to amphistomes. GROSCHAFT (1977) clarified that the pharyngeal appendages are glandular in nature in microscaphidiids and thus they are not homologous with those of amphistomes. Since that time it has been pointed out that the lymphatic system of is present not only in the taxa in question but also in several others being phylogenetically distant (SEY, 19 77). CABLE (1956), studying the development of Opistholebes diodontis in the final host, came to the conclusion that the amphistome plan of the taxa Opistholebetidae and probably the Gyliauchenidae and Cephaloporidae should be considered secondary in ontogeny and in phylogeny alike. STUNKARD (1930) re-examined MacCALLUM's species Paramphistomum aspidonectes, for which FUKUI (1929) set up the genus Opisthoporus and the family Opisthoporidae respectively, and stated that it should be transferred to the family of Pronocephalidae. ODENING (1961, 1974) emphasized that the taxa Notocotylidae and Mesometridae assigned by SZIDAT (1939) to amphistomes is not acceptable due to their monostome structure, both in adult and in developmental stages (Notocotylidae). In the taxon Metacetabulidae it was recently elucidated by BILQEES (1974) that the rudimentary ventral sucker, which was the basis of putting this taxon to the amphistomes (SKRJABIN, 1949), is in fact not a sucker at all but a secondary excretory bladder. Beside the above-mentioned families, the species Khalilloossia ali-ibrahimi Hilmy, 1949 (Cephaloporidae), Choanomyzus tasmaniae Manter et Crowcroft, 19 50 (Opistholebetidae); Podocnemitrema papillosus Alho et Vincente, 1964 ( Microscaphidiidae) have also been allocated to the amphistomes. Now these species belong to the families indicated in brackets, whose taxonomic position and non-amphistome nature were discussed above. At the same time it has been convincingly demonstrated (CABLE, 1956) that the monostome taxon Heronimidae (shared traits with amphistomes are epidermal cell formula of miracidia and position of ventral sucker of the cercariae) and Zonocotylidae (PADILHA, 1978) (shared features with amphistomes are the epidermal structure of miracidia) should be considered as amphistomes. From the above presented controversial views on the scope of amphistomes and from the modern demand that the outline of groups of flukes should be based on the totality of characters, it seems to be obvious that the scope of amphistomes can be formulated by their holo-

follow morphological features at hand. In this context amphistomes are characterized by the ing traits. Adults are amphistome type or monostome evolving from amphistome plan; usually conical, with strongly muscular body; hermaphroditic; with strongly developed postero-terminally located acetabulum. Oral opening surrounded by well-developed and muscular pharynx, oesophagus may be muscular (with sphincter, muscular thickening or bulb) or without it. Caeca usually straight, rarely undulating. Lymphatic system present; excretory system etenostome, excretory bladder saccular, two main descending trunks open to bladder. Parasitic in each class of vertebrates. Metacercariae usually encyst freely; cercariae large, amphistome-type with unforked tail. Body either with dense pigmentation (Cercaria pigmentata) or with light pigmentation (Cercaria intermedia) or without pigmentation (Cercaria diplocotylea). A pair of eyespots and a lot of cystogen cells present (except Heronimus). Protonéphridial system well-developed, excretory bladder non-epithelial; new-born cercariae poorly developed. Rediae and sporocysts rarely absent; rediae without collar. Intermediate hosts usually pulmonate freshwater snails. Miracidium with 6:8:4:2 and 6:6:4:2 epidermal cell formula and without pigment spot. Eggs: large in size, egg-shell thin (freshwater developed) or thick (marine developed); viviparity, ovoviviparity, ovoparity present. Life-cycle dixen type, with one intermediate host. Summarizing, the main, in-group character states of the amphistomes are the posteroterminally located ventral sucker in adult or cercarial stage and the epidermal cell formula of miracidia. Analysing the character states of the trematodes, now regarded to be the monophyletic group of amphistomes, three equally high level taxa can be differentiated: Heronimata Skrjabin et Schultz, 1937; Zonocotylata n. suborder and Paramphistomata Szidat, 1936. Heronimata is a monotypic taxon, its taxonomic ránk is determined by monostome type, and by its special morphological structure of the adults, and by the ancient type of reproduction. The taxon Zonocotylata is a reduced one, including one genus and its species. It has morphological characters of its own (reproductive system, fixative apparatus, etc. ) which justify its taxonomic position in the systematics of the Amphistomida in the present sense. The most successful evolutionary line of the amphistomes seems to be the taxon Paramphistomata whose representatives can be found in each higher taxa of the vertebrate definitive hosts. This group includes the typical forms of amphistomes, species comprising, the amphistomes in a narrow sense (sensu stricto). Several schemes have been proposed in the history of the amphistome systematics, and the amphistomes represented either by familial rank (FISCHOEDER, 1903; STUNKARD, 1925; FUHRMANN, 1938; N'A S MARK, 1937), superfamilial rank (STILES and GOLDBERGER, 1910; MAPLESTONE, 1923; TRAVASSOS, 1934; SOUTHWELL and KIRSHNER, 1937; BAER and JOYEUX, 1961; YAMAGUTI, 1971), subordinal rank (SZIDAT, 1936; LA RUE, 1957; SKRJABIN, 1949) or ordinal rank (TRAVASSOS et al. 1969; ODENING, 1974; BROOKS et al. 1985). In the taxonomic structure of the above-mentioned schemes, the involvement of monostome groups emerges several times even in that of the latest one (BROOKS et al. 1985). As it was previously indicated, it is advisable to exclude monostomes in question from the scope of amphistomes which preserve the monophyly of the group until the structure of their larval stage does not support their actual taxonomic position. Hence, the order-level diagnosis of Amphistomida agrees well with ODENING's (1974) description, supplemented with the newer information referring to the taxa now attached to Amphistomida. The new systematic structure proposed by the present writer (see later) can be best compared with SKRJABIN's (1949) and YAMAGUTI's (1971) schemes which are the most comprehensive ones and the latter is a relatively recent classification. Both of these systematics, however, were based on morphological features of the adults and little attention was paid to the weighted characters of the ontogenetic cycle, bearing phylogenetic information. The concept of phylogenetic systematics, formulated by HENNIG (1966) renders classification

of organisms possible on the basis of their observable traits. At the present state of amphistome investigations, the holomorphological (macro- and histomorphological and semaphoront traits), ecological (intermediate and definitive hosts) and distributional data offer usable characters in the analysis of phyletic relationships. Whatever kind of characters are taken into account, the most valuable ones seem to be those which 1) show an altering series of character states within the taxon, 2) show alterations of character states related with one another, 3) are not adaptive in nature. In this context and at the level of the present taxonomic analysis (subfamilial level), the greatest confidence was attributed to the structure of the reproductive system, the excretory system, the type of cercariae, the structure of the pharynx and^he habitat of the adults. The reproductive system is regarded to be one of the most conservative ones because the programme of propagation (which is, among others, the prerequisite of the existance of a given species) requires a definitive structure of its own. Thus, it is subject to variability to a lesser extent than that of the somatic ones and reflects phylogenetic relationship more reliably than the others do. The excretory system is also characterized by its own conservative nature. At subfamilial level the position of its pore in relation to that of Laurer's canal and the position of the excretory bladder were taken into account. In the early stage of the study, the cercariae were differentiated on the basis of their pigmentation (Cercaria pigmentata Pagenstecher, 1857; Cercaria pigmentata Sonsino, 1892). Later, the presence or absence of the pharyngeal appendages were used. Recently, JAIN (1972) pointed out the diagnostic value of the existence of the cross-connection between the main descending excretory trunks. In 1930 WILLEY described Cercaria poconensis, characterized by the branching of the main excretory ducts. The writer regards it to be a new type, and he named it "Cercaria intermedia", due to the intermediate position of the structure of the main excretory ducts. Accordingly, three types of cercariae can be distinguished in Paramphistomata viz. I. Cercaria diplocotylea, II. Cercaria intermedia. III. Cercaria pigmentata. There is well-defined correlation between the structure of the cercariae and the structure of the adults' reproductive organs. The structure of the pharynx is of variable appearance. The pharynx consists of the pharyngeal body itself and the appendages attached to it when they are present. There are well recognizable concordances among the development of the pharyngeal body, the appendages and the habitat of the flukes (consistency of the gut content). Accordingly, the structure of the pharynx can appear to be an adaptive character state in nature and it has lower taxonomic value in the phylogenetic analysis, whereas it is a very valuable character for traditional taxonomic purposes. Amphistomes are inhabitants of the alimentary tract or the organs connected with it (liver, lung). Their occurrence in the intestines or even lower parts of the digestive tube is characteristic for the amphistomes of lower vertebrates (with a few exceptations) and it is one of the plesiomorphic ecological traits. The aim of the analysis of character states, listed above, is to distinguish between the characters of general significance (plesiomorphic) and those of special significance (apomorphic) which is the first step to establish a phyletic relationship. Combining all traits at hand in such a manner, the cladograms and classification schemes, based on these weighted characters, will prove to be the best representatives of the phyletic relationships. Two character states offer possibility for dichotomy within the suborder Paramphistomata. One of them is the presence or absence of the cirrus pouch and the other is the position of the excretory pore and the opening of Laurer's canal. The present writer prefers the former trait because this feature is rather in concordance with the type of cercariae, habitat of the flukes and, furthermore, it produces a more symmetrical dichotomy. This trait des-

ignates the superfamily Cladorchoidea Skrjabin, 1949, the ancient branch of the suborder and the Paramphistomoidea Stiles et Goldberger, 1910, the derived sister group of Paramphistomata (Fig. 1). Cladorchoidea Paramphistomoidea 0) Fig. 1. Phylogenetic relationships among families of amphistomes Analysing the morphological similarities of species of the taxon Cladorchoidea, five monophyletic groups with equal taxonomic level (family) have been separated: Cladorchiidae Skrjabin, 1949; Diplodiscidae Skrjabin, 1949; Gastrodiscidae Stiles et Goldberger, 1910; Balanorchiidae Ozaki, 19 37 and Brumptiidae Skrjabin, 1949. The monophyly of Cladorchiidae is justified by the simple structure of the cirrus pouch and by the presence of the primary pharyngeal sacs. Diplodiscidae is characterized by a single testis. Gastrodiscidae has a cirrus pouch with untypical structure (musculature of cirrus pouch poorly developed and pars prostatica and pars musc'ulosa are enclosed) and pharyngeal bulb and the secondary pharyngeal sacs are attached to the pharynx. The identity of Balanorchiidae is determined by the unique feature of its ovary being pretesticular. Brumptiidae is characterized by having hermaphroditic pouch and pharyngeal bulb and secondary pharyngeal sacs. Phyletic relationship of the families is depicted by the cladogram (Fig. 1) and the following key is given for distinction of the families. 1. Two testes present, 2 - One testis present Diplodiscidae 2. Ovary post-testicular 3 - Ovary pretesticular Balanorchiidae 3. Cirrus pouch present 4 - Hermaphroditic pouch present Brumptiidae 4. Primary pharyngeal sacs present Cladorchiidae Pharyngeal bulb and secondary pharyngeal sacs present Gastrodiscidae Of the families designated above, the family Cladorchiidae includes several subfamilies, the rest of them have no subfamiliar differentiation,

Examination of the scope of the definitive hosts of the amphistomes having plesiomorphic characters shows that they successfully colonized each class grade of vertebrates. If we visualize the process of amphistome parasitism as it is accepted in general, viz. parasite evolution has been accomplished parallel with the development of their definitive hosts, it means in the time perspective that the sequence of the vertebrate hosts represented newer and newer areas for colonization. This process included series of adaptation, thereafter adaptive radiation with diversification and specialization of parasites to their colonized hosts. Hence, each vertebrate grade has its own special group of amphistomes and it can be said that the host or hos^agroups are so characteristic of parasites as parasites are of their hosts. Nevertheless, there is no direct connection between the taxonomic level of the amphistomes and their hosts. The tempo of the higher level differentiation of amphistomes seems to be slower than that of their definitive hosts. Namely, the amphistomes of the lower vertebrates and those of some of the mammals, have fundamentally the same general plan of structure, in dicating that the amphistomes have their own phylogeny. Hence, the groups of hosts and their sequence reveal rather the evolutionary trends of the amphistomes than those of their developmental level. Bearing the phylogenetic value of the structure of the reproductive organ system in mind, the proposed systematics of the family Cladorchiidae necessitates the designation of some new subfamilies (Travassosiniinae - monotypic, characterized by the extracaecal position of u- terus; Colocladorchiinae - monotypic, characterized by the position of testes and the compact vitellaria; Megalodiscinae - with two genera (Megalodiscus, Opisthodiscus), characterized by two testes and by accessory sucker or muscular plug in the acetabulum; Caballerodiscinae - with two genera (Caballerodiscus gen.n.* for species Schizamphistomoides resupinatus and S. tabascensis, characterized by more or less horizontal testes, and Elseyatrema); Chiorchiinae - with three genera (Chiorchis, Chiostichorchis, Paraibatrema), characterized by the tandem position of testes. At the same time, several previously described subfamilies disappeared and the systematics of all the subfamilies, now regarded to be valid, should be rearranged with a few excreptions. Splitting of the family Cladorchiidae in several subfamilies is in connection with the ancestry of this taxon and thus there is no solid morphological ground to elevate the subfamilies series to family level. In the analysis of the phylogenetic relationships among the subfamilies, the position of the testes was considered as the main guiding principles in establishing the transformation series: anterior tandem» horizontal»posterior tandem. Accordingly, the Cladorchiidae were divided into 20 subfamilies. Their phylogenetic relationship is depicted by the cladogram (Fig. 2) and a key to the subfamilies is given below. 1. One or both testes caecal or extracaecal, vitellaria follicular or compact 2 - Testes and uterus intercaecal, vitellaria follicular 4 - Testes intercaecal, uterus mainly extracaecal, vitellaria follicular Travassosiniinae 2. Testes caecal, horizontal, 3 - Anterior testis either caecal or extracaecal Sandoniinae - Testes extracaecal, uterus partly extracaecal Osteochilotrematinae 3. Ovary intertesticular, vitellaria compact Colocladorchiinae - Ovary post-testicular, vitellaria follicular, testes caecal Pseudocladorchiinae 4. Acetabulum simple 5 - Acetabulum with accessory sucker or with prominence Megalodiscinae m Description of Caballerodiscus gen.n. DIAGNOSIS. Caballerodiscinae. Body elongate oval. Pharynx terminal with extramural appendages, oesophagus short, caeca convoluted, sinuous. Testes tandem or slightly diagonal, in middle part of body, lobate of irregulat in outline. Ovary submedian spherical, in front of acetabulum. Uterine coils post-testicular. Vitelline follicules along posterior part of caeca. Acetabulum ventroterminal. Intestinal parasites of freshwater turtles. Type species: Caballerodiscus tabascensis (Caballero et Sokoloff, 19 34) n. comb.

Sandoniinae -Microrchiinae Daaaytrematinae Travassosiinae C olocladorchiinae -Pseudocladorchiinae -Osteochilotrematinae Caballeroiinae Helostomatinae Pisciamphistominae Orientodiscinae Megalodiscinae Schi zamphi s tominae Nematophiliinae Caballerodiscinae Solenorchiinae Chiorchiinae Pfenderiinae Stichorchiinae Cladorchiinae Fig. 2. Phylogenetic relationships among subfamilies of Cladorchoidae

5. Genital pore bifurcal, slightly prebifurcal or postbifurcal 6 - Genital pore near to pharynx Helostomatinae 6. Testes pre-equatorial * 7 - Testes in middle zone 10 7. Testes horizontal '. 8 - Testes tandem Microrchiinae 8. Testes round in outline 9 - Testes branched Cladorchiinae 9. Vitelline follicules post-testicular Caballeroiinae Vitelline follicules along body sides Pisciamphistominae 10. Testes tandem or diagonal 11 - Testes horizontal.14 11. Excretory bladder post-testicular 12 - Excretory bladder- intertesticular Solenorchiinae 12. Testes spherical or lobate 13 - Testes branched Stichorchiinae 13. Testes deeply lobed, vitelline follicules lateral, parasitic in reptiles, Nematophiliinae - Testes slightly lobed, vitelline follicules lateral, parasitic in fishes Orientodiscinae - Testes spherical or slightly lobed, vitelline follicules lateral, parasitic in mammals Chiorchiinae - Testes spherical or slightly lobed, vitelline follicules lateral or post-testicular, parasitic in reptiles Schizamphistominae - Testes entire or slightly lobed, vitelline follicules confined post-testicular zone Dadaytrematinae 14. Vitelline follicules lateral Pfenderiinae - Vitelline follicules post-testicular Caballerodiscinae The other developmental line of the Paramphistomata, determined by the apomorphic feature (absence of cirrus pouch) is the monophyletic taxon Paramphistomoidea (Fig. 1). Examinations aiming at the recognition of the equal taxonomic subgroups (families) within the taxon clearly showed the necessity of designation of a new family (Zygocotylidae fam. n. ), beside uphelding the validity of the families set up previously (Gastrothylacidae, Paramphistomidae). In the representatives of the taxon, the mosaic nature of the plesiomorphic characters (presence of pharyngeal appendages, position of excretory pore, habitat, in part) and apomorphic characters (absence of cirrus pouch, habitat, in part) can be observed. It comprises five equal ranks of taxa (subfamilies) whose monophyly is determined by the position of testes and the structure of the pharyngeal appendages. Phyletic relationships are indicated by the cladogram (Fig. 3) and the following key is given for differentiation of the families and the subfamilies of the taxon Zygocotylidae. 1. Primary pharyngeal sacs present, no crossing of excretory and Laurer's canal. Zygocotylidae 2. Primary pharyngeal sacs absent, ventral pouch present, no crossing of excretory duct and Laurer's canal Gastrothylacidae 3. Primary pharyngeal sacs and ventral pouch absent, excretory duct and Laurer's canal either cross or do not cross each other Paramphistomidae Key to subfamilies of Zygocotylidae 1. Pharynx with primary pharyngeal sacs 2 - Pharynx with pharyngeal bulb and secondary pharyngeal sacs 4 2. Pharynx with oesophagus having regular structure 3 - Pharynx with muscular oesophagus Olveriinae 3. Pharynx with paired primary pharyngeal sacs Zygocotylinae - Pharynx with unpaired primary pharyngeal sacs Stephanopharynginae 4. Testes horizontal Pseudodiscinae - Testes tandem Watsoniinae

The taxon including gastrothylacid flukes has been regarded to be of family rank due to the occurrence of the special evolutionary novelties (ventral pouch and pharynx without appendages and habitat). Their ancient character state is the position of the excretory pore. The latter trait provides connection towards the Zygocotylidae and the former ones bridge it with Paramphistomidae. The taxon Paramphistomidae is the youngest group of amphistomes from the phylogenetic point of view. It divides into two equal ranks of taxa (subfamilies: Orthocoeliinae and Paramphistominae), the former with a plesiomorphic feature (position of excretory pore) and with several other apomorphic character states. Paramphistominae comprises the most apomorphic group of amphistomes. Beside the series of apomorphic characters, plesiomorph traits can be found in the circular musculature (sphincter) of the pharynx. Zygocotylidae Paramphistomidae r i i 1 Fig. 3. Phylogenetic relationships among families and subfamilies of Paramphistomoidea

-To sum up, a proposed classification scheme is given below, based on the weighted character states of amphistomes at hand. Amphistomida (Lühe, 1909) Odening, 1974 Heronimata Skrjabin et Schulz, 19 37 Heronimidae Ward, 1917 Heronimus McCallum, 1902 Zonocotylata n. suborder Zonocotylidae Yamagüti, 1963 Zonocotyle Travassos, 1948 Paramphistomata Szidat, 1936 Cladorchoidea Skrjabin; 1949 Cladorchiidae Southwell et Kirshner, 1937 Sandoniinae Ukoli, 1972 Sandonia McClelland, 19 57 Basidiodiscus Fischthal et Kuntz, 1959 Pretestis Angel et Manter, 1970 Australotrema Khalil, 1981 Microrchiinae Yamaguti, 1958 Microrchis Daday, 190 7 Dadaytrematinae Yamaguti, 19 58 Dadaytrema Travassos, 1931 Dadayius Fukui, 1929 Dadaytremoides Thatcher, 1979 Panamphistomum Manter et Pritchard, 19 64 Neocladorchis Bhalerao, 1937 Cleptodiscus Linton, 1910 Macrorchitrema Perez Vigueras, 1940 Ophioxenus Sumwalt, 1926 Travassosiniinae subfam. n. Travassosinia Vaz, 19 32 Colocladorchiinae subfam. n. Colocladorchis Thatcher, 1979 Pseudocladorchiinae (Näsmark, 19 37) Yamaguti, 1958 Pseudocladorchis Daday, 1907 Bravicaecum McClelland, 1957 Kalitrema Travassos, 1933 Nicollodiscus Srivastava, 19 38 Osteochilotrematinae Jones et Leong, 1986 Osteochilotrema Jones et Leong, 1986 Caballeroiinae Yamaguti, 1971 Caballeroia Thapar, 19 60 Bancroftrema Angel, 19 66 Platycladorchis Sey, 1985 Helostomatinae Skrjabin, 1949 Helostomatis (Fukui, 1929) Travassos, 1934 Protocladorchis Willey, 1935 Amurotrema Achmerov, 1959 Pisciamphistominae Yamaguti, 1971 Pisciamphistoma Yamaguti, 1958 Orientodiscinae Yamaguti, 1971 Orientodiscus Srivastava, 1938 Megalodiscinae subfam. n. Megalodiscus Chandler, 1923 Opisthodiscus Cohn, 1904 Schizamphistominae Looss, 1912 Schizamphistomum Looss, 1912 Schizamphistomoides Stunkard, 1925

Stunkardia Bhalerao, 1931 Allassostoma Stunkard, 1916 Allassostomoides (Stunkard, 1924) Fuhrmann, 1928 Pseudocleptodiscus Caballero, 1961 Pseudoallassostomoides Yamaguti, 1971 Quasichiorchis Skrjabin, 1949' Lobatodiscus Rohde, 1984 Nematophiliinae Skrjabin, 1949 Nematophila Travassos, 1934 Pseudallassostoma Yamaguti, 1958 Parachiorchis Caballero, 1943 Caballerodiscinae subfam. n. Caballerodiscus gen. n. Elseyatrema Rohde, 1984 Solenorchiinae (Hilmy, 1949) Yamaguti, 1958 Solenorchis Hilmy, 1949 Chiorchiinae subfam. n. Chiorchis Fischoeder, 1901 Chiostichorchis Artigas et Pacheco, 19 33 Paraibatrema Ueta, Deraraldini, Cordero et Artigas, 1981 Pfenderiinae Fukui, 1929 Pfenderius Stiles et Goldberger, lilo. Stichorchiinae Näsmark, 19 37 Stichorchis (Fischoeder, 1901) Looss, 1902 Cladorchiinae (Fischoeder, 1901) Lühe, 1909 Cladorchis Fischoeder, 1901 Taxorchis (Fischoeder, 1901) Stiles et Goldberger, 1910 Diplodiscidae Skrjabin, 1949 Diplodiscus Diesing, 1936 Australodiscus Sey, 1983 Catadiscus Cohn, 1904 Dermatemytrema Price, 1937 Progonimodiscus Vercammen-Grandjean, 1960 Pseudodiplodiscus Szidat, 1939 Gastrodiscidae Stiles et Goldberger, 1910 Gastrodiscus Leukart, 1877 Balanorchiidae Ozaki, 1937 Balanorchis Fischoeder, 1901 Brumptiidae (Skrjabin, 1949) Yamaguti, 1971 Brumptia Travassos, 1921 Choerocotyle Baer, 19 59 Hawkesius Stiles et Goldberger, 1910 Paramphistomoidea Stiles et Goldberger, 1910 Zygocotylidae fam. n. Zygocotylinae Ward, 1917 Zygocotyle Stunkard, 1917 Wardius Barker et East, 1915 Choerocotyloides Prudhoe, Yeh et Khalil, 1969 Olveriinae Srivastava, Maurya et Prasad, 1980 Olveria Thapar et Sinha, 1945 Stephanopharynginae Stiles et Goldberger, 1910 Stephanopharynx Fischoeder, 1910 Pseudodiscinae Näsmark, 1937 Pseudodiscus Sonsino, 1895 Macropotrema Blair, Beverige et Speare, 1979 Watsoniinae Nasmark, 1937 Watsonius Stiles et Goldberger, 1910 Homalogaster Poirier, 1883.

Gastrodiscoides Leiper, 1913 Skrjabinocladorchis Chertkova, 19 59 Gastrothylacidae Stiles et Goldberger, 1910 Gastrothylax Poirier, 1883 Carmyerius Stiles et Goldberger, 1910 Fischoederius Stiles et Goldberger, 1910 Paramphistomidae Fischoeder, 1901 Orthocoeliinae Price et Mcintosh, 19 53 Orthocoelium (Stiles et Goldberger, 1910) Price et Mcintosh, 19 53 Leiperocotyle Eduardo, 1980 Paramphistomoides Yamaguti, 19 58 Platyamphistoma Yamaguti, 19 58 Buxifrons Näsmark, 1937 Gigantatrium Yamaguti, 1958 Nilocotyle Näsmark, 1937 Sellsitrema (Yamaguti, 1958) Eduardo, 1980 Pseudoparamphistoma Yamaguti, 19 58 Macropharynx Näsmark, 1937 Bilatorchis Eduardo, 1980 Gemellicotyle Prudhoe, 1975 Glyptamphistoma Yamaguti, 19 58 Palamphistomum Srivastava et Tripathi, 1980 Paramphistominae Fischoeder, 1901 Ugandocotyle Näsmark, 1937 Explanatum Fukui, 1922 Gigantocotyle Näsmark, 1937 " Cotylophoron Stiles et Goldberger, 1910 Calicophoron Näsmark, 1937 Paramphistomum Fischoeder, 1901 SEY, O.: Az amfîsztomum taxon tartalma és az Amphistomida (Lühe, 1909) Odening, 1974 rend (Trematoda) javasolt rendszertani beosztása A szerző definiálja a mételyeknek azt a körét, amelyet amfisztomumoknak nevezünk. Számos monosztomum mételycsoport kizárásával megalkotja.az Amphistomida monofiletikus csoportot, bemutatja a nagyobb taxonómiai egységek fiietikus kapcsolatát és javaslatot tesz az amfisztomumok rendszertani beosztására.

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