Kingdom Animalia Linnaeus, 1758 - animals
   Phylum Nematoda Gegenbaur, 1859 - round worms
     Class Chromadorea Inglis, 1983
       Subclass Plectia Hodda, 2007
         Superorder Monhysterica Hodda, 2007 [monotypic]
           Order Monhysterida Filipjev, 1929
             Suborder Monhysterina De Coninck & Schuurmans Stekhoven, 1933
               Superfamily Sphaerolaimoidea Filipjev, 1918
                 1 Family Sphaerolaimidae Filipjev, 1918
                 2 Family Xyalidae Chitwood, 1951