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 Order Monogenea see Infraclass Monogenea 1 Suborder Monopisthocotylea Odhner, 1912 see Subclass Monopisthocotylea 2 Suborder Polyopisthocotylea Odhner, 1912 see Subclass Polyopisthocotylea