Phylum Nematoda Gegenbaur, 1859 - round worms Class Secernentea Von Linstow, 1905 Subclass Tylenchia (Thorne, 1949) Inglis, 1983 Order Tylenchida G. Thorne, 1949 Suborder Hexatylina Siddiqi, 1980 Genus Helionema Brzeski, 1962, nom. dub.