• Abathymermis acuticauda Rubzov, 1974
• Abathymermis adventitia Rubzov & Kokordyak, 1973
• Abathymermis arenaria (Coman, 1961) Rubzov, 1971
• Abathymermis bissacea Rubzov, 1973
• Abathymermis bissoidea Rubzov, 1972
• Abathymermis brevicauda (Rubzov, 1972)
• Abathymermis fiseri Johnson & Kleve, 1995
• Abathymermis ivaschkini Gafurov, 1980
• Abathymermis jugulata (Coman, 1961) accepted as Isthmusimermis jugulata (Coman, 1961)
• Abathymermis microamphidis Rubzov, 1972
• Abathymermis oesophaga Gafurov & An, 1989
• Abathymermis ovtschinnikovi Ipatjeva & Pimenova, 1980
• Abathymermis oxycerca (Steiner, 1929)
• Abathymermis parva Rubzov, 1973 accepted as Amphibiomermis parva (Rubzov, 1976)
• Abathymermis parvula Rubzov, 1976
• Abathymermis paucipapilla (Coman, 1961) accepted as Isthmusimermis paucipapilla (Coman, 1963)
• Abathymermis shocki Johnson & Kleve, 1995
• Abathymermis tenuicauda (Rubzov, 1967)
• Abbreviata (Abbreviata) abbreviata (Rudolphi, 1819)
• Abbreviata (Abbreviata) kazachstanica Markov & Paraskiv, 1956
• Abbreviata (Abbreviata) turkomanica Andrushko & Markov, 1956
• Abbreviata baltazardi Chabaud, 1953
• Abelbolla boucheri Huang & Zhang, 2004
• Abelbolla huanghaiensis Huang & Zhang, 2004
• Abelbolla maemulensis Hong & Lee, 2014
• Abelbolla major Hiang, Wang & Huang, 2015
• Abelbolla warwicki Huang & Zhang, 2004
• Abirovulva insolita Hunt, 2002
• Ablechroiulus acartus (Rühm in Osche, 1952) Andrássy, 1966 accepted as Choriorhabditis acarta (Rühm, 1956)
• Ablechroiulus anchisporus Andrássy, 1966 accepted as Choriorhabditis anchispora (Andrássy, 1966)
• Ablechroiulus broughtonalcocki (Buckley, 1931) Andrássy, 1983 accepted as Rhabditis brassicae Southern, 1909
• Ablechroiulus castaneanus Abolafia & Peña-Santiago, 2009 accepted as Choriorhabditis castaneana (Abolafia & Peña-Santiago, 2009) Sudhaus, 2011
• Ablechroiulus castaneus Abolafia & Peña-Santiago, 2009 accepted as Choriorhabditis castaneana (Abolafia & Peña-Santiago, 2009) Sudhaus, 2011
• Ablechroiulus ciliatus (Fuchs, 1931) Andrássy, 1966 accepted as Choriorhabditis ciliata (Fuchs, 1931)
• Ablechroiulus crenatus (Paesler, 1946) Andrássy, 1966 accepted as Choriorhabditis crenata (Paesler, 1946) Sudhaus, 2011
• Ablechroiulus cristatus (Hirschmann, 1952) Andrássy, 1966 accepted as Choriorhabditis lacustris (Micoletzky, 1913)
• Ablechroiulus dudichi Andrássy, 1970 accepted as Choriorhabditis dudichi (Andrássy, 1970)
• Ablechroiulus gongyloides (Reiter, 1928) Andrássy, 1966 accepted as Choriorhabditis gongyloides (Reiter, 1928)
• Ablechroiulus lacustris (Micoletzky, 1913) Andrássy, 1966 accepted as Choriorhabditis lacustris (Micoletzky, 1913)
• Ablechroiulus maculosus Andrássy, 1982 accepted as Choriorhabditis maculosa (Andrássy, 1982) Sudhaus, 2011
• Ablechroiulus paraciliatus (T. Goodey, 1943) Andrássy, 1966 accepted as Cephaloboides paraciliatus (T. Goodey, 1943)
• Ablechroiulus querquelutanus Abolafia & Peña-Santiago, 2009
• Ablechroiulus querquetulanus Abolafia & Peña-Santiago, 2009 accepted as Choriorhabditis querquetulana (Abolafia & Peña-Santiago, 2009) Sudhaus, 2011
• Ablechroiulus spelaeus Abolafia & Peña-Santiago, 2011 accepted as Choriorhabditis spelaea (Abolafia & Peña-Santiago, 2011) Sudhaus, 2011
• Ablechroiulus stercorarius Andrássy, 1987 accepted as Choriorhabditis stercoraria (Andrássy, 1987) Sudhaus, 2011
• Ablechroiulus verminosus Abolafia & Peña-Santiago, 2009 accepted as Choriorhabditis verminosa (Abolafia & Peña-Santiago, 2009) Sudhaus, 2011
• Aborjinia corallicola Westerman, de Moura Neves, Ahmed & Holovachov, 2021 accepted as Paraborjinia corallicola (Westerman, de Moura Neves, Ahmed & Holovachov, 2021) Zograf, Semenchenko & Mordukhovich, 2024
• Aborjinia eulagiscae (Tchesunov & Spiridonov, 1985) Özdikmen, 2010
• Aborjinia profunda Zograf, Semenchenko & Mordukhovich, 2024
• Abos bathycola Rubtzov, 1980 accepted as Benthimermis bathycola (Rubtzov, 1980) Chesunov, 1997 accepted as Trophomera bathycola (Rubtzov, 1980) Miljutin, 2004
• Abunema indicum Khera, 1971
• Abursanema iranicum Yaghoubi, Pourjam, Pedram, Siddiqi & Atighi, 2014
• Abursanema quadrilineatum Qing, Slos, Claeys & Bert, 2017
• Acanthoatractis xinguensis Jesus & Melo in Jesus, Nandyara & Melo, 2024
• Acanthocheilonema dracunculoides Cobbold, 1870
• Acanthocheilonema odendhali (Perry, 1967) Measures, Gosselin & Bergeron, 1997
• Acanthocheilonema reconditum (Grassi, 1889)
• Acanthocheilonema spirocauda (Leidy, 1858) Anderson, 1992
• Acanthocheilus australis (Johnston & Mawson, 1945) accepted as Acanthocheilus rotundatus (Rudolphi, 1819)
• Acanthocheilus bicuspis (Wedl, 1855) accepted as Acanthocheilus rotundatus (Rudolphi, 1819)
• Acanthocheilus intermedius Örley, 1895 (uncertain > taxon inquirendum)
• Acanthocheilus nidifex Linton, 1901 accepted as Terranova nidifex (Linton, 1901) Johnston & Mawson, 1945
• Acanthocheilus quadridentatus Molin, 1858 accepted as Acanthocheilus rotundatus (Rudolphi, 1819)
• Acanthocheilus rotundatus (Rudolphi, 1819)
• Acantholaimus aequisetosus Soetaert, 1989 (unaccepted > nomen nudum)
• Acantholaimus aheneus Bussau, 1993
• Acantholaimus akvavitus Gerlach, Schrage & Riemann, 1979
• Acantholaimus angustus Bussau, 1993
• Acantholaimus arminius Gerlach, Schrage & Riemann, 1979
• Acantholaimus arthrochaeta Miljutina & Miljutin, 2012
• Acantholaimus barbatus Miljutina & Miljutin, 2012
• Acantholaimus bidentatus Manoel, Esteves & Neres, 2022
• Acantholaimus caecus Bussau, 1993
• Acantholaimus calathus Gerlach, Schrage & Riemann, 1979
• Acantholaimus cornutus Miljutina & Miljutin, 2012
• Acantholaimus coruscus Bussau, 1993
• Acantholaimus crenatus Soetaert, 1989 (unaccepted > nomen nudum)
• Acantholaimus cyathibucca Vivier, 1985
• Acantholaimus effilatus Soetaert, 1989 (unaccepted > nomen nudum)
• Acantholaimus elegans Jensen, 1988
• Acantholaimus ewensis Platt & Zhang, 1982 accepted as Acantholaimus polydentatus Gerlach, 1951
• Acantholaimus filicaudatus Soetaert, 1989 (unaccepted > nomen nudum)
• Acantholaimus formosus Miljutina, Miljutin & Tchesunov, 2013
• Acantholaimus gathumai Muthumbi & Vincx, 1997
• Acantholaimus geraerti Muthumbi & Vincx, 1997
• Acantholaimus gigantasetosus Vivier, 1985
• Acantholaimus heipi Muthumbi & Vincx, 1997
• Acantholaimus incomptus Vivier, 1985
• Acantholaimus invaginatum Muthumbi & Vincx, 1997
• Acantholaimus iubilus Gerlach, Schrage & Riemann, 1979
• Acantholaimus longisetosus Allgén, 1933
• Acantholaimus longistriatus Gourbault & Vincx, 1985
• Acantholaimus macramphis Gourbault & Vincx, 1985
• Acantholaimus maks Gerlach, Schrage & Riemann, 1979
• Acantholaimus marliae Manoel, Silva & Esteves, 2017
• Acantholaimus megamphis Vivier, 1985
• Acantholaimus microdontus Gourbault & Vincx, 1985
• Acantholaimus minima (Vitiello, 1970) Gerlach, Schrage & Riemann, 1979 accepted as Acantholaimus minutus (Vitiello, 1972) Gerlach, Schrage & Riemann, 1979
• Acantholaimus minutus (Vitiello, 1972) Gerlach, Schrage & Riemann, 1979
• Acantholaimus mirabilis Soetaert, 1989 (unaccepted > nomen nudum)