Fossil sponge Raphidonema faringdonense, photographed by Mark A. Wilson

Porifera, known as sponges, are multicellular organisms with pores and channels allowing water to circulate through them.

Modern sponges are found in both salt and fresh water. Sponges lived on the ocean floor 500 million years ago in the Cambrian Period. Found commonly in northern Illinois, they had a hard external skeleton of calcium carbonate or silica.