Recent Find (Halysite Coral)

Golden Beach grass dune

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 in winter. The sample below is an extinct tabulate coral, a reef building colony type coral called halysite. But we often find these saltwater varieties 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 the mild weather with little snow has allowed winter winds to push sand off the under layers. It’s 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 halysite corals grew, they built up walls of tube-like chambers called theca which steadily multiplied adding more links to the chain. In their hay-day 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.

Cephalopod Nautiloids Have a Long History

Cephalopod nautiloids date back to the Early Ordovician Period almost 500 mya and survived to the Late Triassic about 230 mya. Some believe they even survived through the Cretaceous about 150 mya.  Wow!  Their fossilized shells are often discovered all around the world in large assemblages and commonly occur in marine rock, especially lime stone .

Orthoceras Nautiloid

The straight shelled nautiloids were closely related to the ammonites which evolved spiraled shells. But due to their long linear shells and a weak muscle, they probably weren’t as agile. They moved about the same way, though, with the use of a siphuncle tube that runs the entire length of the shell through each of the chambers. Once filled with water, the nautiloid could force the water out, propelling itself backward with a kind of jet propulsion. By releasing the water and leaving air space, the tube could serve as a buoyancy device allowing the animal to rise and lower itself to different depths.

Orthoceras Nautiloid Fossil

Their fossils have been quarried by Europeans for many years and adorn floors, stairs, jewelry,  gravestones and more with their durable and desirable beauty.

The Orthoceras nautidoids display extreme diversity in size from a few inches to 14 feet in length. One of the largest cephalopod nautiloid giants from the earliest years, Cameroceras, reached 30 feet in length.





Kingdom:  Animalia

Phylum:    Mollusk  (large diverse group of invertebrates with soft bodies  encased in a shell i.e. clams, snails, oysters )

Class:      Cephalopoda  (means prominent head and tentacles i. e. squid, octopus, nautilus, cuttlefish)

Subclass: Nautiloidea   (series of chambers of increasing size connected by a central tube)

Order:     Orthocerida  (extinct group of  cephalopods possessing long straight shells)

Family:     Orthoceridae

Genus:    Orthoceras (means straight horn)



Cephalopod Nautiloid Drawing Rendition





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