Opisthokonta Cavalier-Smith 1987, nom. cl. inval. see Clade Opisthokonta Cavalier-Smith 1987 [Simpson & Medina 2020] Metazoa Haeckel 1874 - multicellular animals see Kingdom Animalia Linnaeus, 1758 Porifera Grant, 1836 - sponges Silicea Bowerbank, 1864 - siliceous sponges see [unranked] Silicispongia Schmidt, 1862 Hexactinellida Schmidt, 1870 see Class Hexactinellida Schmidt, 1870