Demospongiae skeletons are composed of spongin fibers or siliceous spicules, in contrast to the calcareous sponges. The common sponges come in a wide range of colors and shapes, with few common features.
This is the most diverse class of sponges, including more than 90 % of all known species. The taxonomy of the common sponges has been under heavy revision. Traditionally the class is divided into a rather large number of orders. A recent genetic study suggests that there should be only five clades of Demospongiae.