Sclerosponge

High Quality Content by WIKIPEDIA articles! Sclerosponges are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite. Because of their long life span (500-1,000 years) it is thought that analysis of the aragonite skeletons of these sponges could extend data regarding ocean temperature, salinity, and other variables farther into the past than has been previously possible. Their dense skeletons are deposited in an organized chronological manner, in concentric layers or bands. The layered skeletons look similar to reef corals. Therefore sclerosponges are also called coralline sponges.