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I Found a Fossil on the Beach and Wondered
Discovering Common Fossils on Great Lakes Beaches
A favorite past time for many is combing the beaches for interesting items the surf washes in. Whether you're walking along the shoreline of the ocean or the Great Lakes in the USA, your imagination is on high alert to pick something up you just can't pass by! Suddenly, something catches your eye! But, it's not driftwood or beach glass or even a pretty rock. You may not know exactly why, but you suspect you found something that was once a living creature.
Has this ever happened to you? A deep sense of curiosity and childlike imagination drives us to find out what we may have picked up along our saltwater or freshwater shorelines. Having collected quite a few samples from Lake Michigan's shoreline, myself, I finally decided one day to fulfill my nagging curiosity and followed through with a rewarding investigation. The more I learned about my stony sand-smoothed findings, the more I wanted to know. I wondered what the creatures may have looked like when alive and how they survived. I also wanted to know how they showed up so prevalent along the fresh water beaches. Some time later, after many answered questions, I can honestly say I enjoy a cool hobby. Taking things a step further, I have drawn illustrations of their living beings and started a fossil site. You can find the link at the end.
Some of the most prevalent fossils found along the Great Lake's beaches are crinoids (shown in the photos to the right). They have been coined with a several names due to the animal's features and by the character of their fossils discovered throughout history. One common name for them is "Indian Beads". Native Americans were known to make necklaces with their broken up pieces which resemble the shape of beads perfect for stringing. They've also been referred to as "Lucky Stones"! Spotting one takes a keen eye as most of the pieces are quite small.
As living creatures, each circular section was stacked one over the other constructing the animal's entire framework. They possessed branching arms that sat atop long single stems. They were sessile creatures, in other words, they remained attached to the sea floor. Some varieties are known to have towered several meters in length. Their loose structure resulted in the living organism's beautifully colored and flower like appearance which granted them the nickname of "Sea Lilies". They captured tiny food particles passing by on ocean currents with their feathery network of arms that functioned like traps. Crinoids fit into the phylum of Echinoderm, meaning spiny skin, and are cousins of starfish, sea urchins and feather stars.
Sea lily crinoid's lengthy history began during the Ordovician Period around 500 million years ago, although most fossils are from the Mississipian Period around 345 mya and are preserved in limestone. Today there are far fewer species and most lack the long meandering stem common in Paleozoic varieties.
In the course my investigation, I had often wondered why so many crinoid fossils ended up along the Great Lakes; particularly by the fact that they had thrived in saltwater environments. I've since learned they can be found widespread in North America. Part of the answer to my inquiry is easy enough to explain. During their lifetime, much of the world's continents were covered under warm shallow oceans, including parts of North America. So how is it their fossils are so common near the big lakes? The answer is because ten thousand years ago when the giant glaciers sculpted the deep basins forming the Great Lakes, they also dug into the deep layers where their remains rested. In the process, they were deposited where we now can discover them and revel in their secrets, as well as that of other species from the same era.
Another common beach find, bryozoans are often called lace corals because of their delicately threaded appearance, but they are not true corals. Instead, they are moss-like animals belonging to the family of Fenestellida for their fan-shaped, mesh appearance. They live in tight colonies sculpted by hard, limy, branching structures. The colony consists of thousands of individual animals called “zooids”. Each individual zooid lives inside its own limy tube called a zooecium. The zooecium are the size of sewing needles. A single zooid begins the colony. A bryozoan colony has been observed growing from a single zooid to 38,000 in just five months. Each additional zooid is a clone of the very first one.
Interesting how they feed, Each zooid has an opening through which the animal can extend its ring of tentacles called lophophores. Their lophophores capture microscopic plankton from the water passing by. If one zooid receives food, it nourishes the neighboring zooids because they are joined by strands of protoplasm. If only we humans could be more like them ensuring everyone on the planet is fed!
Their fossil record dates back 500 mya with 15,000 known species. Today there are about 3,500 living species.
I found these clam fossils on the shore of Oval Beach in Southwestern Michigan. The shell of the darker sample has been completely replaced by minerals and is petrified to stone. Its smooth surface is a telltale demonstration of the lake's sand and water action. The lighter colored sample clearly reveals the hardened muddy sediment that has completely encrusted its shell.
"Clam" can be a term that covers all bivalves. Some clams bury themselves in sand and breathe by extending a tube to the water’s surface. Bivalve oysters and mussels attach themselves to hard objects and scallops can free swim by flapping their valves together. All types lack a head and usually have no eyes, although scallops are a notable exception. With the use of two adductor muscles they can open and close their shells tightly. Very fittingly, the word “clam” gives rise to the metaphor “to clam up”, meaning to stop speaking or listening.
Bivalves have occupied Earth as early as the Cambrian Period 510 million years ago, but they were particularly abundant during the Devonian Period around 400 million years ago. Their fossils are discovered in all marine ecosystems and most commonly in near shore environments. In 2007, off the coast of Iceland, a clam was discovered to be at least 405 years old. It was declared the world’s oldest living creature by North Wales, Bangor University researchers.
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.
Brachiopods look like clams but are very different inside. To tell them apart, clams have uneven shaped shells, but both top and bottom halves are identical. Brachiopods are symmetrical at a glance, but the bottom shell is smaller. Brachiopods are commonly called "lampshells" due to their similarity in shape to a Roman oil lamp.
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.
During the Devonian time slot, over 350 million years ago, Michigan was covered by a shallow saltwater sea. That's where mass colonies of corals called Hexagonaria, percarinata, commonly known as Petoskey Stones, thrived and flourished. The saltwater seascape must have been lit up with a quilt-work of colors by the mass colonies. Unfortunately, they became extinct at the end of the Permian Period's mass extinction.
The name “Petoskey” originated from an Ottawa fur-trader chief named Petosegay. A northern Michigan city was named after him, only the name was modified to Petoskey. Because of their abundance along Michigan shorelines, especially in the northern regions near Petoskey, Governor George Romney signed a bill in 1965 that made the Petoskey Stone the official state stone.
When observing one of the fossils, each coral hexagon structure, visible to the eye, held a single animal which opened a mouth to expose tentacles. The tentacles took in food and were also used to sting any organism or other corallite that came too close. Calcite, silica and other minerals replaced the original corallite exoskeleton.
An extinct order of coral called tabulate corals also formed reefs and lived in warm shallow waters during the same period as the Petoskey Stone corals. They were the favosite corals. The tabulae (horizontal internal layers) were built outward as the organism grew. These layers can clearly be seen in the photo to the right. The favosites can also be identified by the honeycomb pattern on the exterior of their fossilized remains.
Hope you've enjoyed my fossil discoveries. Next time you visit the beach, keep your eyes open for a fossil discovery of your own. You're welcome to use my hub or visit my fossil blog to help make an identification!
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© 2010 Kathi