Acanthocolpidae Lühe, 1906 (basis of record)
Acanthostomum Looss, 1899 (basis of record)
Acanthostomum absconditum (Looss, 1901) Gohar, 1934 accepted as Proctocaecum absconditum (Looss, 1901) Lamothe-Argumedo & Ponciano-Rodriguez, 1986 (basis of record)
Acanthostomum balthicum Reimer, Hildebrand, Scharberth & Walter, 1996 accepted as Timoniella balthica (Reimer, Hildebrand, Scharberth & Walter, 1996) Miller & Cribb, 2008 accepted as Timoniella imbutiforme (Molin, 1859) Brooks, 1980 accepted as Timoniella imbutiformis (Molin, 1859) Brooks, 1980 (basis of record)
Acanthostomum inerme (Stossich, 1905) Yamaguti, 1958 accepted as Aphallus tubarium (Rudolphi, 1819) Poche, 1926 (basis of record)
Acanthostomum saoudi Hassan, Khidr & Abu Samak, 1990 (basis of record)
Acanthotrema Travassos, 1928 (basis of record)
Accacladocoelium Odhner, 1928 (basis of record)
Accacladocoelium alveolatum Robinson, 1934 (basis of record)
Accacladocoelium macrocotyle (Diesing, 1858) Robinson, 1934 (basis of record)
Accacladocoelium nigroflavum (Rudolphi, 1819) Robinson, 1934 (basis of record)
Accacladocoelium petasiporum Odhner, 1928 (basis of record)
Accacoeliidae Odhner, 1911 (basis of record)
Accacoelium Monticelli, 1893 (basis of record)
Accacoelium contortum (Rudolphi, 1819) Looss, 1899 (basis of record)
Adinosoma Manter, 1947 (basis of record)
Adinosoma robusta (Manter, 1934) Manter, 1947 (basis of record)
Allocreadiidae Looss, 1902 (basis of record)
Allocreadioidea Looss, 1902 accepted as Gorgoderoidea Looss, 1901 (basis of record)
Allopodocotyle Pritchard, 1966 (basis of record)
Allopodocotyle jaffensis (Fischthal, 1980) Bray, 1987 (basis of record)
Allopodocotyle margolisi Gibson, 1995 accepted as Bathypodocotyle margolisi (Gibson, 1995) Martin, Huston, Cutmore & Cribb, 2019 (basis of record)
Allopodocotyle pedicellata (Stossich, 1887) Pritchard, 1966 (basis of record)
Allopseudocolocyntotrema Yamaguti, 1970 (basis of record)
Allopseudocolocyntotrema alioshkini Pozdnyakov, 1994 (basis of record)
Anacetabulitrema Deblock & Rosé, 1964 (basis of record)
Anacetabulitrema samarae Deblock & Rosé, 1964 (basis of record)
Ancylocoelium Nicoll, 1912 (basis of record)
Ancylocoelium typicum Nicoll, 1912 (basis of record)
Anisocladium Looss, 1902 (basis of record)
Anisocladium fallax (Rudolphi, 1819) Looss, 1902 (basis of record)
Anisocladium gracile (Looss, 1901) Vlasenko, 1931 (basis of record)
Anisocoelium Lühe, 1900 (basis of record)
Anisocoelium capitellatum (Rudolphi, 1819) Lühe, 1900 (basis of record)
Anoiktostoma Stossich, 1899 (basis of record)
Anoiktostoma coronatum (Wagener, 1852) Stossich, 1899 (basis of record)
Anomalotrema Zhukov, 1957 (basis of record)
Anomalotrema koiae Gibson & Bray, 1984 (basis of record)
Apatemon Szidat, 1928 (basis of record)
Apatemon gracilis (Rudolphi, 1819) Szidat, 1928 (basis of record)
Aphalloides Dollfus, Chabaud & Golvan, 1957 (basis of record)
Aphalloides coelomicola Dollfus, Chabaud & Golvan, 1957 (basis of record)
Aphallus Poche, 1926 (basis of record)
Aphallus tubarium (Rudolphi, 1819) Poche, 1926 (basis of record)
Aphanurus Looss, 1907 (basis of record)
Aphanurus stossichii (Monticelli, 1891) Looss, 1907 (basis of record)
Apharyngostrigea Ciurea, 1927 (basis of record)
Apharyngostrigea intermedia (Tubangui, 1932) Bychovskaja-Pavlovskaja, 1952 accepted as Parastrigea intermedia Tubangui, 1932 (basis of record)
Apocreadiidae Skrjabin, 1942 accepted as Megaperidae Manter, 1934 (basis of record)
Apocreadium Manter, 1937 accepted as Homalometron Stafford, 1904 (basis of record)
Apocreadium galaicus Sanmartin, Alvarez, Quinteiro & Paniagua, 1995 accepted as Homalometron galaicus (Sanmartin, Alvarez, Quinteiro & Paniagua, 1995) Cribb & Bray, 1999 (basis of record)
Aponurus Looss, 1907 (basis of record)
Aponurus laguncula Looss, 1907 (basis of record)
Aponurus tschugunovi Issaitschikov, 1927 (basis of record)
Apophallus Lühe, 1909 (basis of record)
Apophallus brevis Ransom, 1920 (basis of record)
Apophallus muehlingi (Jägerskiöld, 1899) Lühe, 1909 (basis of record)
Aporchis Stossich, 1905 (basis of record)
Aporchis massiliensis Timon-David, 1955 (basis of record)
Aporchis rugosus Linton, 1928 (basis of record)
Aporocotyle Odhner, 1900 (basis of record)
Aporocotyle simplex Odhner, 1900 (basis of record)
Aporocotyle spinosicanalis Williams, 1958 (basis of record)
Arnola Strand, 1942 (basis of record)
Arnola microcirrus (Vlasenko, 1931) Yamaguti, 1958 (basis of record)
Ascocotyle Looss, 1899 (basis of record)
Ascocotyle coleostoma (Looss, 1896) Looss, 1899 (basis of record)
Asymphylodora Looss, 1899 (basis of record)
Asymphylodora demeli Markowski, 1935 (basis of record)
Azygiidae Lühe, 1909 (basis of record)
Bacciger Nicoll, 1914 (basis of record)
Bacciger bacciger (Rudolphi, 1819) Nicoll, 1914 (basis of record)
Bacciger grandispinatus Naidenova, 1970 (basis of record)
Bacciger israelensis Fischthal, 1980 (basis of record)
Bacciger minutus Gaevskaja & Naidenova, 1996 (basis of record)
Bathycreadium Kabata, 1961 (basis of record)
Bathycreadium biscayense Bray, 1973 (basis of record)
Bathycreadium elongata (Maillard, 1970) Bray, 1973 accepted as Bathycreadium elongatum (Maillard, 1970) Bray, 1973 (basis of record)
Bathycreadium flexicollis Kabata, 1961 (basis of record)
Bathymonorchis Bray & Gaevskaya, 1993 (basis of record)
Bathymonorchis polyipni (Reimer, 1985) Bray & Gaevskaya, 1993 (basis of record)
Botulus Guiart, 1938 (basis of record)
Botulus microporus (Monticelli, 1889) Gibson & Bray, 1977 (basis of record)
Brachycladiidae Odhner, 1905 (basis of record)
Brachycladium Looss, 1899 (basis of record)
Brachycladium palliatum (Looss, 1885) Looss, 1899 (basis of record)
Brachycoeliidae Looss, 1899 (basis of record)
Brachyenteron Manter, 1934 (basis of record)
Brachyenteron campbelli Bray & Gibson, 1986 (basis of record)
Brachyenteron pycnorganum (Rees, 1953) Overstreet & Pritchard, 1977 (basis of record)
Brachyenteron rissoanum Bray & Campbell, 1995 (basis of record)
Brachylaima Dujardin, 1843 (basis of record)
Brachylaima fuscatum (Rudolphi, 1819) Joyeux, Baer & Timon-David, 1932 accepted as Brachylaima fuscata (Rudolphi, 1819) Joyeux, Baer & Timon-David, 1932 (basis of record)
Brachylaimidae Joyeux & Foley, 1930 (basis of record)
Brachylecithum Shtrom, 1940 (basis of record)
Brachylecithum microtesticulatum Timon-David, 1955 (basis of record)
Brachyphallus Odhner, 1905 (basis of record)
Brachyphallus crenatus (Rudolphi, 1802) Odhner, 1905 (basis of record)
Braunina Heider, 1900 (basis of record)
Braunina cordiformis Wolf, 1903 (basis of record)