Sponges are globular, cylindrical, conical, or irregular in shape.
The interior of a sponge may be hollow or filled with branching canals. Sponges are primarily marine and may be either solitary or colonial. The skeletal elements of sponges are called spicules, and they may be separate or joined. Fossil sponges are common in the fossil record from the Cambrian to the Present. Introduction to Porifera .