Collecting Fossils in Missouri

hand beside a large, cone-shaped fossil that is light tan in color with concentric rings around it.
Straight shelled Cephalopod collected by Terry Frank.

Cam here–

I have been quite busy for the past couple of months. In late May I had the chance to visit the state of Missouri to collect fossils and visit museums. Missouri is the farthest I have traveled so far to look for fossils. In this post I will highlight some of the trips I took and the fossils I collected along the way.

On Sunday morning we traveled up to Jefferson County, Missouri to collect fossils from the Decorah Formation. The Decorah Group was deposited in shallow tropical seas during the Late Ordovician Period (~445 million years ago). It is humbling to realize that what we were standing on used to be the seafloor. We found a variety of fossils such as brachiopods, bryozoans, bits of trilobites and corals. The biggest fossil found in the Decorah Group are the shells of huge straight shelled nautiloid cephalopods. These were top predators during the Ordovician Period. I did not realize the sheer size these animals could grow up to until Terry Frank showed me examples he collected on past trips. 

Hand holding a light-tan rock, with the thumb next to a dark brown, triangular-shaped sharks tooth, about half an inch long.
Shark tooth I found from the Salem Limestone. Probably from the genus Orodus.

We also went to search for shark and fish remains from the Salem Formation. These rocks were deposited in a shallow sea during the Lower Carboniferous (Mississippian) Period. We were guided by a former geology student Adam Marty. Adam knew the stratigraphy of the region like the back of his hand. He took us to a locality that was hard to get to but ended up being very rewarding. We had to hike up a steep hill and cross bushes to get to the collecting area. Adam told us to break open the limestone blocks and look for shark teeth. Not only did we find teeth but we found cartilage, which is hard to fossilize. Many of the teeth were round in shape due to the animals using them to crush shells such as brachiopods and ammonoids. These were the only vertebrate fossils we found on our long week trip. It was a special treat because my research papers are on cartilaginous fish teeth.

Thumb beside a brachiopod shell impression, contained in light tan stone.
A brachiopod shell in limestone that was used to build a local restaurant.

The trip was a great success. The geology was different from what I am used to seeing. Even the buildings that we walked by had fossils in them from the local rock that was used. The rocks in Missouri play an important role in the industrial growth of the state. I had a good time exploring parts of the Midwest and I plan on visiting again soon.


A hand beside a light grey rock that is covered in D-shaped brachiopod shells, that are darker grey than the surrounding rock.
A cluster of brachiopod shells from the Decorah Limestone.

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