Recent Find (Halysite Coral)

Oval Beach in winter 2012

Oval Beach Saugatuck, Michigan  Winter 2012

I was super excited to discover some fossils on Oval Beach in Saugatuck, Michigan (USA) that are highly unusual to find this time of year (winter). The sample below is an extinct tabulate coral, a reef building colony type coral called halysite. We often find salt water fossils from the Paleozoic Era on our fresh water Lake Michigan shores. To explain this phenomenon I’ve written an article  entitled “I Found a Fossil on the Beach and Wondered” at where I’m also the fossillady. A link is provided in the box to the right.

This halysite coral is easy to distinguish due to the chain link appearance coining it with the common name “chain coral”. It was lying under layers of sand that aren’t usually exposed during the winter months. But with the mild winter (meaning no snow) the winds have push sand off the under layers. Also, due to low water levels from a long dry spell during summer 2012, there’s more beach to explore.

The extinct halysite corals displayed small tubes from which resided the jelly-like coral animals called polyps.  The coral polyps contained stinging cells for protection and also grasped plankton food that passed by in the ocean currents. As the corals grew, they built up walls of tube-like chambers called theca which steadily multiplied adding more links to the chain.  As they continued to multiply, they built large limestone reef structures on the seabed. They thrived mostly during the Silurian period up to 425 million years ago!


Kingdom: Animal

Phylum: Cnidaria (means stinging animal)

Class: Anthozoa (means flower animal)

Order:  Tabulata (possess inner horizontal dividing walls from growth patterns)

Family: Halisitidae (means chain coral)

Genus: Halysite  Species:unknown

Halysite Coral

Halysite Coral Fossil


Halysite Colony “Chain Coral” Rendering

Mysterious Sponges


Sponge Fossil Side View


Sponge Fossil


This is one of the more unusual fossil finds on the shores of a Lake Michigan beach in Southwestern Michigan USA! My best guess is that it’s a sponge and not a coral because of the way its dotted with pores lacking septa, vertical walls. From the side view, you can see how the tubes permeate down into the structure.


INTERESTING 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; and 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.


Popular Tourist Spot Selling Natural Sponges

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 their spiky spicules to create a dense hazardous carpet around them which keeps away predators such as star fish.


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.

Brachiopod Fossils Are Signifcant

No other organisms typify the Age of Invertebrates more than brachiopods. They are the most abundant Paleozic fossils, except for maybe trilobites. Paleontologists use them to date rocks and other fossils.  Countless billions accumulated on the ocean floor with over 30,000 forms . Today there are far fewer species, only about 300 which live mostly in cold water, deep ocean environments.

Brachiopod #1

Brachiopod #2

Brachiopods were the first of their kind to lose mobility and develop a hard covering. They look like clams but are very different inside. To tell them apart, clams have uneven shaped left and right sides of their shells, but the tops and bottoms are identical. Brachiopods have evenly shaped (symmetrical) left and right sides of their shells, but the bottom is smaller. Thick shell forms are ribbed and live in shallow water. Thin shell forms are smooth and live in deep water. Some grow to 9 inches across, but most are about an inch in diameter. They live in communities attached to objects by a muscular foot called a pedicle. They strain water in and out of their shells filtering microorganisms with their lophophores, a crown of tentacles.


Common Name: Brachiopod or Lamp Shell (named for resemblance to ancient Roman oil lamps)

Kingdom: Animalia

Phylum:   Brachiopoda (means arm and foot)

Class:      Articulated (shells clamp together by a hinge)

Inarticulated (shells clamp together by a muscle)

Genus: #1 possibly Pseudoatrypa sp   / #2 possibly Atrypa,reticularis

Brachiopods in the Ocean Mist

Brachiopods in the Ocean Mist