Achromadoridae Gerlach & Riemann, 1973 (taxonomy source)
Actinolaimidae Thorne, 1939 (taxonomy source)
Aegialoalaimidae Lorenzen, 1981 (taxonomy source)
Aetholaimidae Jairajpuri, 1965 (taxonomy source)
Alaimina (taxonomy source)
Alaimoidea Micoletzky, 1922 (taxonomy source)
Alaimonema Cobb, 1920 (taxonomy source)
Anatonchidae Jairajpuri, 1969 (taxonomy source)
Andrassyidae Tchesunov & Gagarin, 1999 (taxonomy source)
Anoplostomatidae Gerlach & Riemann, 1974 (taxonomy source)
Anticomidae Filipjev, 1918 (taxonomy source)
Aphanolaimidae Chitwood, 1936 (taxonomy source)
Aponchiidae Gerlach, 1963 (taxonomy source)
Aporcelaimidae Heyns, 1965 (taxonomy source)
Araeolaimida (taxonomy source)
Aulolaimidae Jairajpuri & Hopper, 1968 (taxonomy source)
Aulolaimoididae Jairajpuri, 1964 (taxonomy source)
Axonolaimidae Filipjev, 1918 (taxonomy source)
Bastianiidae De Coninck, 1965 (taxonomy source)
Bathyodontidae Clark, 1961 (taxonomy source)
Belondiridae Thorne, 1939 (taxonomy source)
Benthimermithida accepted as Plectida (taxonomy source)
Benthimermithidae Petter, 1980 (taxonomy source)
Bodonematidae Jensen, 1991 (taxonomy source)
Bradylaimus Stekhoven, 1931 (new combination reference)
Camacolaimidae Micoletzky, 1924 (taxonomy source)
Campydoridae Thorne, 1935 (taxonomy source)
Campydoroidea Thorne, 1935 (taxonomy source)
Ceramonematidae Cobb, 1933 (taxonomy source)
Ceramonematina (taxonomy source)
Chromadorida (taxonomy source)
Chromadoridae Filipjev, 1917 (taxonomy source)
Chronogastridae Gagarin, 1975 (taxonomy source)
Cobbonchidae Jairajpuri, 1969 (taxonomy source)
Comesomatidae Filipjev, 1918 (taxonomy source)
Coninckiidae Lorenzen, 1981 (taxonomy source)
Cryptonchidae Chitwood, 1937 (taxonomy source)
Cyatholaimidae Filipjev, 1918 (taxonomy source)
Desmodorida (taxonomy source)
Desmodoridae Filipjev, 1922 (taxonomy source)
Desmodoroidea Filipjev, 1922 (taxonomy source)
Desmoscolecida (taxonomy source)
Desmoscolecidae Shipley, 1896 (taxonomy source)
Desmoscolecoidea Shipley, 1896 (taxonomy source)
Dioctophymidae Railliet, 1915 (taxonomy source)
Dioctophyminae Railliet, 1915 (taxonomy source)
Diphtherophoridae Micoletzky, 1922 (taxonomy source)
Diplopeltidae Filipjev, 1918 (taxonomy source)
Diplopeltoididae Tchesunov, 1990 (taxonomy source)
Dorylaimia (taxonomy source)
Dorylaimidae de Man, 1876 (taxonomy source)
Dorylaimina (taxonomy source)
Draconematidae Filipjev, 1918 (taxonomy source)
Enchelidiidae Filipjev, 1918 (taxonomy source)
Enoplea (taxonomy source)
Enoplia (taxonomy source)
Enoplida (taxonomy source)
Enoplidae Dujardin, 1845 (taxonomy source)
Enoplina (taxonomy source)
Enoploidea Dujardin, 1845 (taxonomy source)
Eophasmidae Poinar, 2011 † (taxonomy source)
Epsilonematidae Steiner, 1927 (taxonomy source)
Ethmolaimidae Filipjev & Schuurmans Stekhoven, 1941 (taxonomy source)
Eustrongylides Jägerskiöld, 1909 (taxonomy source)
Eustrongylides acrocordi Jones, 1978 (taxonomy source)
Eustrongylides africanus Jägerskiöld, 1909 (taxonomy source)
Eustrongylides elegans (Olfers, 1816) (taxonomy source)
Eustrongylides formosensis Sugimoto, 1933 accepted as Eustrongylides excisus Jägerskiöld, 1909 (taxonomy source)
Eustrongylides gadopsis Johnston & Mawson, 1940 (taxonomy source)
Eustrongylides galaxias Johnston & Mawson, 1940 (taxonomy source)
Eustrongylides indicus Ali, 1971 accepted as Eustrongylides excisus Jägerskiöld, 1909 (taxonomy source)
Eustrongylides perpapillatus Jägerskiöld, 1909 accepted as Eustrongylides tubifex (Nitzsch in Rudolphi, 1819) Jägerskiöld, 1909 (taxonomy source)
Eustrongylides phalacrocoracis Johnston & Mawson, 1941 accepted as Eustrongylides excisus Jägerskiöld, 1909 (taxonomy source)
Eustrongylides plotinus Johnston & Mawson, 1941 accepted as Eustrongylides excisus Jägerskiöld, 1909 (taxonomy source)
Eustrongylides tricolor Sugimoto, 1931 accepted as Eustrongylides excisus Jägerskiöld, 1909 (taxonomy source)
Eustrongylides wenrichi Canavan, 1929 (taxonomy source)
Fusivermidae Tchesunov, 1996 (taxonomy source)
Haliplectidae Chitwood, 1951 (taxonomy source)
Hystrichis Dujardin, 1845 (taxonomy source)
Hystrichis acanthocephalicus Molin, 1861 (taxonomy source)
Hystrichis africanus Vuylsteke, 1964 (taxonomy source)
Hystrichis coronatus Molin, 1861 (taxonomy source)
Hystrichis corvi Hendricks, Harkema & Miller, 1969 (taxonomy source)
Hystrichis neglectus Jägerskiöld, 1909 accepted as Hystrichis tricolor Dujardin, 1845 (taxonomy source)
Hystrichis orospinus Molin, 1861 accepted as Hystrichis tricolor Dujardin, 1845 (taxonomy source)
Hystrichis pachycephalus Molin, 1861 (taxonomy source)
Hystrichis tricolor Dujardin, 1845 (taxonomy source)
Hystrichis variospinosus Jägerskiöld, 1909 accepted as Hystrichis tricolor Dujardin, 1845 (taxonomy source)
Iotonchidae Jairajpuri, 1969 (taxonomy source)
Ironidae de Man, 1876 (taxonomy source)
Ironina (taxonomy source)
Ironoidea de Man, 1876 (taxonomy source)
Leptolaimidae Örley, 1880 (taxonomy source)
Leptonchidae Thorne, 1935 (taxonomy source)
Leptosomatidae Filipjev, 1916 (taxonomy source)
Linhomoeidae Filipjev, 1922 (taxonomy source)
Linhomoeina (taxonomy source)
Longidoridae Thorne, 1935 (taxonomy source)
Marimermithida (taxonomy source)
Marimermithidae Rubtzov & Platonova, 1974 (taxonomy source)

 Biology

 for Tripylium Cobb, 1920

Commensal or ectoparasitic on gills of land crabs. [details]

 Biology

 for Tripylium calkinsi Chitwood, 1935

Commensal or ectoparasitic on gills of land crabs. [details]

 Biology

 for Tripylium carcinicola (Baylis, 1915) Cobb, 1920

Commensal or ectoparasitic on gills of land crabs. [details]

 Biology

 for Tripylium carcinicolum Baylis, 1915

Commensal or ectoparasitic on gills of land crabs. [details]