Order Monhysterida Filipjev 1929
Family Linhomoeidae Filipjev 1922
Genus Desmolaimus de Man 1880
- Desmolaimus zeelandicus De Man 1880 – marine, littoral, free-living, dominant - Чесунов, 1991.
Genus Eleutherolaimus Filipjev 1922
- Eleutherolaimus stenosoma (De Man 1907) – marine, littoral, free-living, dominant – Чесунов, 1991 (= Eleutherolaimus sp.).
Genus Linhomoeus Bastian 1865
- Linhomoeus elongatus Bastian 1865 – marine, sublittoral, free-living, common – own data
Genus Metalinhomoeus De Man 1907
- Metalinhomoeus typicus De Man 1907 – marine, sublittoral, free-living, common – own data
Genus Terschellingia De Man 1888
- Terschellingia longicaudata De Man 1907 – marine, sublittoral, free-living, dominant – Чесунов, 1991.
- Terschellingia distalamphida Yuario 1974 – marine, sublittoral, free-living, dominant, Kastyan island - own data
Family Siphonolaimidae Filipjev 1918
Genus Siphonolaimus De Man 1893
- Siphonolaimus roervikensis Allgén 1946 – marine, sublittoral, free-living, common – own data
Family Fusivermidae Tchesunov 1996
Genus Fusivermis Tchesunov 1996
- Fusivermis fertilis Tchesunov 1996 – type locality, marine, sublittoral, free-living, common – Tchesunov, 1996.
Family Monhysteridae De Man 1876
Genus Diplolaimella Allgén 1929
- Diplolaimella ocellata (Bütschli 1874) – marine, littoral, free-living, common - own data
Genus Diplolaimelloides Meyl 1954
- Diplolaimelloides altherri Meyl 1954 – marine, littoral, free-living, rare – own data
Genus Gammarinema Kinne et Gerlach 1953
- Gammarinema gammari Kinne et Gerlach 1953 – marine, littoral, symbiont of gammarid amphipods, common – Чесунов, Плетникова, 1986.
Genus Geomonhystera Andrássy 1981
- Geomonhystera disjuncta (Bastian 1865) – marine, supralittoral, littoral, free-living, common – own data
Genus Monhystrella Cobb 1918
- Monhystrella anophthalma (Lorenzen 1969) – marine, littoral, free-living, common – own data
Family Xyalidae Chitwood 1951
Genus Amphimonhystera Allgén 1929
- Amphimonhystera anechma (Southern 1914) – marine, sublittoral, free-living, rare – own data
- Amphimonhystera galea Fadeeva 1984 – marine, sublittoral, free-living, rare, Kastyan island - own data
Genus Cobbia De Man 1907
- Cobbia trefusiaeformis De Man 1907 – marine, sublittoral, free-living, common – own data
Genus Daptonema Cobb 1920
- Daptonema kornoeense (Allgén 1929) – marine, sublittoral, free-living, common – own data
- Daptonema modestum Tchesunov 1990 – type locality, marine, sublittoral, free-living, rare, Kastyan island – Чесунов, 1990г.
- Daptonema procerum (Gerlach 1951) – marine, littoral, free-living, common – own data
- Daptonema setosum (Bütschli 1874) – marine, littoral, free-living, dominant – Чесунов, 1990а.
- Daptonema voskresenskii Tchesunov 1990а – type locality, marine, littoral, free-living, rare. – Чесунов, 1990а.
Genus Filipjeva Ditlevsen 1928
- Filipjeva filipjevi Tchesunov 1988 – type locality, marine, sublittoral, free-living, common, Kastyan island – Чесунов, 1988а.
- Filipjeva teratospicula Tchesunov 1988 – type locality, marine, sublittoral, free-living, rare, Kastyan island – Чесунов, 1988а.
Genus Metadesmolaimus Stekhoven 1935
- Metadesmolaimus similis Tchesunov 1990 – type locality, marine, sublittoral, free-living, common – Чесунов, 1990г.
Genus Paramonhystera Steiner 1916
- Paramonhystera filamentosa (Ditlevsen 1928) – marine, littoral, sublittoral, free-living, common – own data
Genus Pseudosteineria Wieser 1956
- Pseudosteineria ventropapillata Tchesunov 2000 – type locality, marine, sublittoral, free-living, common – Tchesunov, 2000a.
Genus Rhynchonema Cobb 1920
- Rhynchonema lyngei (Allgén 1940) – marine, littoral, free-living, common – Чесунов, 1990в.
Genus Steineria Micoletzky 1922
- Steineria pilosa (Cobb 1914) – marine, sublittoral, free-living, common – Чесунов, 1990а.
Genus Theristus Bastian 1865
- Theristus acer Bastian 1865 – marine, littoral, free-living, rare – own data
- Theristus blandicor Rachor 1971 – marine, littoral, free-living, common – own data
- Theristus flevensis Stekhoven 1935 – marine, littoral, free-living, common – Чесунов, 1990б.
- Theristus pertenuis Bresslau et Stekhoven in Stekhoven 1935 – marine, supralittoral, free-living, dominant – own data
Genus Xyala Cobb 1920
- Xyala striata Cobb 1920 – marine, sublittoral, free-living, rare - own data
Family Sphaerolaimidae Filipjev 1918
Genus Sphaerolaimus Bastian 1865
- Sphaerolaimus balticus G. Schneider 1906 – marine, littoral, free-living, common – Чесунов, 1987.
Genus Parasphaerolaimus Ditlevsen 1918
- Parasphaerolaimus paradoxus Ditlevsen 1918 – marine, sublittoral, free-living, rare – own data