Kingdom Animalia Linnaeus, 1758 - animals
   Phylum Nematoda Gegenbaur, 1859 - round worms
     Class Chromadorea Inglis, 1983
       Subclass Plectia Hodda, 2007
         Superorder Rhabditica Hodda, 2007
           Order Spirurida Railliet, 1914
             Suborder Oxyurina Railliet, 1916
               Superfamily Thelastomatoidea Travassos, 1929
                 1 Family Hystrignathidae Travassos, 1929
                 2 Family Protrelloididae Chitwood, 1932
                 3 Family Pseudonymidae Adamson, 1989
                 4 Family Thelastomatidae Travassos, 1929
                 5 Family Travassosinematidae Rao, 1958