Sponges are the most simple form of animal found as fossils in Kentucky.
They all live in water and most live in seawater. They have a wide variety of shapes, but all have pores through which they pump large quantities of seawater. Most modern sponges do not secrete a hard skeleton that would be preserved after death. Some forms secrete calcium carbonate or silica, and these are the types that have been preserved as fossils in Kentucky. One of the most unusual sponge fossils in Kentucky is Brachiospongia digitata , a silica sponge.