This is one of the more unusual fossil finds from our shores of Lake Michigan in Southwestern Michigan USA! I’m 99.9 % sure it’s a fossilized sponge and not a coral due to the lack of septa, vertical growth walls. From the side view, you can see how the tubes, or pores, permeate down into the structure.

INTERESTING SPONGE FACTS:   The most fascinating fact about sponges is their long extended history on Earth beginning 580 million years ago. The type of sponges we’re most familiar with are the ones we use for our households. Those are actually referred to as, demosponges, having entirely soft fibrous skeletons with no hard elements of which there are only a few species. After thousands of years, humans had almost harvested them to extinction by the 1950’s.  Many are now being researched for a possible source of medicines.

HOW SPONGES LIVE: Sponges have delicate skeletons and rely on a constant water flow through their bodies to capture food and obtain oxygen. They don’t have a digestive or circulatory system like we do. They can actually change the shape of their bodies for maximum water flow.  Most species have the ability to contract and squeeze the water out of their pores in order to flush out sediments clogging them. They can even  escape from predators by squeezing out the water and shrinking themselves. For further defense, many shed spiky spicules to create a dense hazardous carpet around them which keeps away predators such as star fish.

SPONGE CLASSIFICATION

Kingdom:  Animalia       Phylum:  Porifera (means to possess pores)

Four Classes

Demosponges – Largest class; Inner structure reinforced with collagen fibers and spine-like spicules made of silica minerals; Usually barrel shaped; Can live in a wide variety of habitats

Hexactinellida – Glass Sponges; Spiny spicules made of silica minerals forming inner scaffolding structure with gelatin substance weaved in between framework; likes Polar Regions

Calcareous – Outer exoskeleton and inner spicules made of calcium carbonate. Restricted to shallow marine waters where production of calcium carbonate is easiest to obtain.

Scleropongiae (Coralline or Tropical Reef Sponges) soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite.  The layered skeletons look similar to reef corals, therefore are also called coralline sponges.