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.
Sclerosponges were first proposed as a class of sponges, Sclerospongiae, in 1970 by Hartman and Goreau. However, it was later found by Vacelet that sclerosponges occur in different classes of Porifera. That means that sclerosponges are not a closely related (taxonomic) group of sponges. Like bats and birds that independently developed the ability to fly, different sponges developed the ability to build a calcareous skeleton independently and during different times in Earth history. Fossil sclerosponges are already known from the Cambrian period.
Sclerosponges include the species Ceratoporella nicholsoni, Stromatospongia vermicola, Hispidopetra miniana, S. norae, Goreauiella auriculatra, and Merlia sp., which were described in detail by Lang et al. in 1975.