Phylum Porifera Grant, 1836 - sponges Class Demospongea Sollas, 1875 see Class Demospongiae Sollas, 1885 Subclass †Lithistida Schmidt, 1870 Order Tetralithistida Lagneau-Hérenger, 1962 Suborder Tetracladina Zittel, 1878 Family †Plinthosellidae Schrammen, 1910 Genus †Pycnodesma Schrammen, 1910