 These fossils, which include spicules, pinacocytes, porocytes, archeocytes, sclerocytes and the internal cavity, have been classified as demosponges.Fossils of glass sponges have been found from around in rocks in Australia, China and Mongolia.Early Cambrian sponges from Mexico belonging to the genus "Kiwetinokia" show evidence of fusion of several smaller spicules to form a single large spicule.