Fossils Collected in Southwest Ohio


Several years ago my family collected fossils from several sites in the area. All the fossils were created in the Ordovician Age, about 500 million years ago, and are of creatures that dwelt in the sub-tropical ocean then covering Ohio. By "created" I refer to the fossilizing process where the actual material of a plant or animal is gradually replaced by minerals, literally leaving a mineral cast of the original.

Most of the fossils in this collection were found at the spillway dam at Ceasar's Creek State Park near Waynesville. This is a flat area about a hundred yards wide and several hundred yards long which is loaded with fossils. On any given sunny day you can find at least a dozen people at one time searching for fossils through the rubble. We also found two fossils at a creek near the south campus of Southern State Community College in Fincastle.

The following are pictures of our best specimens representing all the common and not so common fossils to be found in the area. All were once animals, though one or two may have appeared to be plantlike. Each picture is a "thumbnail." To view a larger picture just click on the desired thumbnail.



Brachiopods are probably the most common fossil in the area. These are the forerunners of modern sea shells, though true modern brachiopods are uncommon. The shells may resemble clams but the animal itself is quite different from clams. Brachiopods attached themselves to the sea bottom or other objects.

Here are three views of a very nice specimen.


Here is a different species of brachiopod. By viewing the enlarged image you can see very many tiny ridges.


Here are two small specimens, the tiniest just a quarter inch across. Brachiopods this small are quite plentiful in the area.



Bryozoans are tiny creatures which live in colonial structures. Each secretes calcite to help form the structure and each creature is attached to a pit inside the structure, feeding on microscopic organisms floating by. Their fossils are quite common and are usually found in branch formations. By viewing the enlarged photo you can see the little pit structures in the left specimen.



Cephalopods were squidlike creatures with tentacles which occupied a tube-like shell. I've never found or seen a complete cephalopod shell, and these fossils are uncommon, though easy to spot. Here is the top and bottom view of our largest specimen.



Crinoids are a sort of sea lily. It is an animal which attaches itself to the ocean floor, has a columnar stem and a flowery type of head. Modern crinoids are uncommon. Almost all fossilized crinoids are fragments of the stems and are easily found. Here is the longest intact stem fragment we've collected.


Crinoid heads are exceedingly rare. They were much more delicate than the stems and seldom became fossilized. When my ex-wife showed the following specimen (found by me) to her Wright State University geology professor the professor squealed in delight; the professor had never found one herself, and proclaimed this an outstanding example! Here are both sides of our most prized fossil. The enlarged photos reveal delicate details.


To get an idea how interesting these creatures looked I took a picture of what must be one of the best crinoid fossils in existence. This one is sitting in a case at a visitor's center at the South Rim of the Grand Canyon. I do not recall if it is from the Ordivician Age.



Gastropod means "stomach foot." These are mollusks which crawl on their stomachs. Those with shells are snails, those without are slugs. Gastropod fossils are fairly common. Here are two specimens.


Horn Coral

Horn corals are, like all corals, structures formed by tiny animals. These are uncommon fossils, but the pointed tips are very distinctive. Below are two photos of the same specimen. You can see a little inner detail in the left photo and some faint striations in the right photo.



Trilobites are likely the most popular of Ordovician Age fossils. One imagines that most people rummaging in the gravel at Ceasar's Creek are mostly looking for trilobites, and they are quite hard to find. Fossilized trilobites appear around the world in many species and sizes. The state fossil of Ohio is isoteles, which grew as large as two feet long. One such specimen is housed at the Ceasar's Creek visitor center.

All trilobite species are extinct, but the closest modern relative is the horseshoe crab.

Below are three specimens of the smaller species found at Ceasar's Creek. Trilobites are so named because of the three lengthwise sections which provided some lateral flexibility. These are apparent in the left photo. The other two photos display the facial features, even the eyes of these tiny creatures. We have never found a trilobite in its normal stretched out position. Apparently trilobites could curl up in a defensive posture much like wood lice ("pill bugs").



Below is a unique specimen in our collection. It is uncertain what it is, but trilobite tracks appear to be a plausible explanation.