The winds along Lake Michigan reveal many buried fossils I often find that I like to share with you, but sometimes they are a complete mystery. My hope is that somebody can wage a guess or provide a knowledgeable answer about the following mystery fossils below in the comment box.
UPDATE: C. Chavez wrote me about Mystery Fossil #2: I believe your “Mystery Fossil 2″ is not a fossil, but a reductive rock. If you were to crack it open you’d find the perfect circle is actually a sphere. It is created by some foreign material that is introduced into the rock which results in bleaching. It is the same idea as if you were to put a drop of bleach on blue jeans and it would expand into a circle. We have many reductive rocks where I live in NM, but they are not common elsewhere. You can find me and many more people helping to identify fossils at “thefossilforum.com”. Thank you C. Chavez
Update: The fossil above is a section of an extinct soft shell turtle
Collectors with a keen eye love to find these tiny crinoid fossils intermingled within the sand and debris along the shores of Lake Michigan. The largest in the photo above is just under the size of a dime. One of several common names for crinoids includes “Lucky Stones” which likely came from the honest luck in finding one. The extinct species are also referred to as “Sea Lilies“ explained by their colorful flower-like appearance when living, but they were actually a type of animal. They possessed long branching arms and a midsection that sat atop of a single slender stem, sometimes reaching two meters high above the seafloor. Feathery tentacles at the tips of their branching arms trapped tiny food particles floating by in ocean currents.
Crinoids were sessile creatures, meaning they attached themselves directly to the seafloor or underwater rocks or even sunken wood. A spawning of their offspring from these bottom bound creatures may have resembled the spring releasing of thousands of dandelion seeds blowing by in gusty breezes.
Crinoid skeleton fossils are usually found broken up into individual “cheerio” shaped sections or partial stems. Each circular section was stacked one over the other forming the entire animal framework. The Native Americans used the fragmented fossilized sections, perfect for stringing, to craft necklaces. Consequently, yet another fitting, common name for them is “Indian Bead”.
Theiramazing history dates as early as the Ordovician Period around 500 million-years-ago, although, most fossils are from the Mississippian Period around 345 mya, preserved in limestone. Their fossil remains are found widespread in North America explained by the fact that much more of the continents were then covered under warm shallow seas. The sea lily crinoids were a dominant feature in the Paleozoic Era seas. Most varieties succumbed to the great Permian extinction, but a few species still live today, although, they subsist in colder deep-water environments and dwarf in length compared to the ancient varieties.
Most trilobites grew to only about 3 inches (7.6 cm) long, while a few reached almost 3 feet (1 meter) long. This Calymene, celebra fossil fits nicely into a man’s palm. In life, it was a scavenger finding food on the ocean floor where it could easily burrow underneath the sand to hide from predators. Many of their fossils are often found rolled up in a defensive position. They were able to bend because their chiton exoskeletons were fitted with overlapping sections. Think of roly-poly bugs, or pill bugs, as some call them; it’s the same idea.
Lifestyle of Trilobites
But trilobites, in general, had several life styles; some moved over the seabed as predators or scavengers, while others were filter feeders, yet some swam along the ocean strata feeding on plankton. Most were sluggish swimmers, while some later varieties were designed precisely for speed and swam in the mid-ocean, pelagic zones where more predators existed.
This little Calymene trilobite crawled on the ocean floor over 400 million years ago during the Devonian time period. His species had smaller eyes than many other trilobite species and was probably a sluggish swimmer. A good number of their fossils are found in Michigan and other Midwest states where warm shallow oceans once dominated the continents.
Trilobites have the distinction of possessing a segmented body, multiple jointed limbs and an armored outer shell, placing them in the category of arthropods related to insects and crustaceans. Trilobite means three lobes in Greek, from tri and lobos, named for their three major lengthwise sections.
All trilobites died out at the end of thePermian mass extinction event, 251 million-years-ago, which removed over 90% of all species on Earth.
Find out about a few giant sized trilobites here in another article I’ve written.