PRECAMBRIAN (EDIACARAN) to PLEISTOCENE PERIOD: 583 million - 10,000 years ago
Sponges belong to the scientific group called PORIFERA. These creatures have an origin that dates back to over 500 million years ago. Sponges are extremely primitive creatures that live attached to the ocean floor, in some cases, at extreme depths. They are one of the earliest known examples of coordination between cells of differing functions in an organism. Their bodies are made up of a porous covering over a skeleton composed of calcium or silicon. The skeleton and its spicules form a latticework whereby water is drawn into the sponge body. Oxygen and food is filtered out and the water is expelled either out the upper or outer surface of the sponge. Flagellae beat inside the main hollow tube to keep the water circulating within the body. Fossil sponges have been found dating back to the Lower Cambrian while associated fossilized body parts have been found in Pre-Cambrian deposits. Due to their structure, fossils of sponges are almost always found in very poor states of preservation and in fragments. Because sponges lived mostly in marine environments, their presence indicates the location of prehistoric seas.