Metazoa Haeckel 1874 - multicellular animals see Kingdom Animalia Linnaeus, 1758 Phylum Platyhelminthes Gegenbaur, 1859 - flatworms Class Trematoda Rudolphi, 1808 - flukes see Infraclass Trematoda Rudolphi, 1808 1 Order Monogenea see Infraclass Monogenea 2 Order Aspidogastrea Faust & Tang, 1936 3 Order Digenea Carus, 1863