Dry Dredgers Field Trip
October 29, 2011
Horn Coral Heaven, A country road cut in Southern Ohio
Whitewater Formations, Late Ordovician Period

A Garden Gnome selects a new hat from the many Grewingkia canadensis Horn Coral found on this site.

It was a foggy late October morning driving along country roads about a 90 minutes from Cincinnati, Ohio.

There was still frost on the ground when we arrived at 10 am.

We had a light but decent turn out of members at the field trip. They had been informed at the meeting the night before to bring a bucket (not a bag or basket) with them to find tons of the largest specimens of horn corals in the Cincinnatian.

Large horn coral littered the upper edges of the road cut where it's really hard to keep from rolling down due to the 1 to 2 feet of loose fossil material. 

The site exposes the Lower Whitewater formation of the Richmondian Stage. The rocks and fossils are somewhere in the neighborhood of 438 million years old.

Fossils Found That Day

The best find of the day was a series of plates from a Cyclocystoid. This is a rare Echinoderm that has been found complete on this site on a previous field trip.


The most common horn coral found on the site is the large Grewingkia canadensis.

Here are the septa from a horn coral from the site.

Mysterious forms were unearthed at the field trip that turned out to be coral septa as well. The picture below is of a mystery fossil found that day that too closely resembles coral septa to be anything else.

There have been previous cases on Dry Dredgers field trips where these septa are found separated from the rest of the coral structure and have confused fossil finders.


The second most common horn coral genera found on the site was Streptelasma. This coral attaches themselves to objects on the sea floor giving their narrow end a flattened effect. Streptelasma also have a wider opening then Grewingkia and are generally smaller in size.

Another type of coral found are colonial corals. These corals attach to each other to form a mesh. The next two pictures are a very interesting example of  Protaraea growing on the "feeding edge" of a Strophomenid Brachiopod. If this Brach were removed from the rock, you might find the colonial coral has covered the entire convex surface of the brachiopod, which is thought to be the upper surface of the brach in life.

Another colonial coral we found was Tetradium. This coral formed a thick mat over the ocean floor, particularly when you look at the top of the Lower Whitewater formation where you see the Saluda layers exposed.


Bryozoans look superficially like coral. They too were found in great numbers on the site.

Trace Fossils


Pelecypods (Bivalves/clams)

We found lots of internal molds of the clam Ambonychia.

We found even more examples of a clam with calcite preservation of its shell. It's called Caritodens.

This next example of Caritodens is nice because it has both the negative and positive molds preserved. This was donated by a member for a current study by a California paleontologist on clam shell microstructure.

Nautiloid Cephalopods

One of the things this site is known for is finding curved or coiled shelled Nautiloids. One was found this trip as well. (below)

Most of the Nautiloid Cephalopods found were straight-shelled (next 3 pics).

Above is an interesting Cephalopod fragment in that it shows the inner surface of the shell. 



Here's an interesting crinoid fragment found that day. It's a stem that had cirri (arms) coming off of the stem. It is likely to be an undescribed variety of Cincinnatian crinoid. 

Other rocks contained plates that appear to be from a crinoid calyx.

According to our local crinoid experts, the crinoid columnals below are likely to be Glyptocrinus fornshelli.

This next crinoid stem was originally coiled around something as part of a holdfast.  It too is likely to be Glyptocrinus fornshelli







It was also easy to find minerals at this site because they are found on the interior of most brachiopods. In the photo below, the white crystals are calcite and the red square crystals are dolomite.

That's all for this month. 

Now let's look at our February 2012 field trip to the Geier Collections

See photos of our previous trip to this site
October 2007

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