Aegialoalaimidae Lorenzen, 1981 (taxonomy source)
Anoplostomatidae Gerlach & Riemann, 1974 (taxonomy source)
Anticomidae Filipjev, 1918 (taxonomy source)
Araeolaimida (taxonomy source)
Axonolaimidae Filipjev, 1918 (taxonomy source)
Benthimermithida accepted as Plectida (taxonomy source)
Benthimermithidae Petter, 1980 (taxonomy source)
Bodonematidae Jensen, 1991 (taxonomy source)
Camacolaimidae Micoletzky, 1924 (taxonomy source)
Campydoroidea Thorne, 1935 (taxonomy source)
Ceramonematidae Cobb, 1933 (taxonomy source)
Ceramonematina (taxonomy source)
Chromadorida (taxonomy source)
Chromadoridae Filipjev, 1917 (taxonomy source)
Comesomatidae Filipjev, 1918 (taxonomy source)
Coninckiidae Lorenzen, 1981 (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)
Diplopeltidae Filipjev, 1918 (taxonomy source)
Diplopeltoididae Tchesunov, 1990 (taxonomy source)
Dorylaimia (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)
Epsilonematidae Steiner, 1927 (taxonomy source)
Ethmolaimidae Filipjev & Schuurmans Stekhoven, 1941 (taxonomy source)
Haliplectidae Chitwood, 1951 (taxonomy source)
Ironidae de Man, 1876 (taxonomy source)
Ironina (taxonomy source)
Ironoidea de Man, 1876 (taxonomy source)
Leptolaimidae Örley, 1880 (taxonomy source)
Leptosomatidae Filipjev, 1916 (taxonomy source)
Linhomoeidae Filipjev, 1922 (taxonomy source)
Linhomoeina (taxonomy source)
Marimermithida (taxonomy source)
Marimermithidae Rubtzov & Platonova, 1974 (taxonomy source)
Meyliidae De Coninck, 1965 (taxonomy source)
Microlaimidae Micoletzky, 1922 (taxonomy source)
Microlaimoidea Micoletzky, 1922 (taxonomy source)
Monhysterida (taxonomy source)
Monhysteridae de Man, 1876 (taxonomy source)
Monhysterina (taxonomy source)
Monhysteroidea Filipjev, 1929 (taxonomy source)
Monoposthiidae Filipjev, 1934 (taxonomy source)
Neotonchidae Wieser & Hopper, 1966 accepted as Ethmolaimidae Filipjev & Schuurmans Stekhoven, 1941 (taxonomy source)
Oncholaimidae Filipjev, 1916 (taxonomy source)
Oncholaimina (taxonomy source)
Oncholaimoidea Filipjev, 1916 (taxonomy source)
Oxystominidae Chitwood, 1935 (taxonomy source)
Pandolaimidae Belogurov, 1980 (taxonomy source)
Paramicrolaimidae Lorenzen, 1981 (taxonomy source)
Phanodermatidae Filipjev, 1927 (taxonomy source)
Plectida (taxonomy source)
Plectina (taxonomy source)
Rhabdodemaniidae Filipjev, 1934 (taxonomy source)
Rhadinematidae Lorenzen, 1981 (taxonomy source)
Rhaptothyreida accepted as Enoplida (taxonomy source)
Rhaptothyreidae Hope & Murphy, 1969 (taxonomy source)
Selachinematidae Cobb, 1915 (taxonomy source)
Siphonolaimidae Filipjev, 1918 (taxonomy source)
Siphonolaimoidea Filipjev, 1918 (taxonomy source)
Sphaerolaimidae Filipjev, 1918 (taxonomy source)
Sphaerolaimoidea Filipjev, 1918 (taxonomy source)
Tarvaiidae Lorenzen, 1981 (taxonomy source)
Thoracostomopsidae De Coninck, 1965 (taxonomy source)
Triplonchida (taxonomy source)
Tripyloidina (taxonomy source)
Tripyloidoidea Filipjev, 1928 (taxonomy source)
Xyalidae Chitwood, 1951 (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]