Dry Dredgers Field Trip
April 23, 2016

Ponderosa Ranch, Ohio
Bellevue and Corryville Formations
Report and photos by Bill Heimbrock

The Dry Dredgers April field trip returns us to a road cut in southern Ohio we call "Ponderosa Ranch" for the abundant Vinlandostrophia ponderosa and Rafinesquina ponderosa. Normally we find a lot of fossils from the Bellevue formation at the bottom of the road cut. This year we see that there has been some flooding that has washed more of Corryville Formation fossils down the hill, covering up the Bellevue fossils. This Corryville wash-down material is now weathered enough to find nice Corryville fossils.

Here are some photos of our group collecting fossils on the site. As you can see, the weather was pleasant and slightly cool in the morning.

Best Finds of the Day

By far, the best find of the day was this perfect Edrioastroid Isorophus cincinnatiensis (the Official Cincinnati City Fossil). Congratulations Barb! Barb's goal for this field trip was to find an Edrioasteroid - and she did it. That's what I call "Power Fossil Hunting".


The next best finds were prone trilobites of the species Flexicalymene meeki. In the photo below, you can see how excited people get with they find a trilobite.

Here is the other prone Flexi found that day.

Most people on the trip found only parts of a trilobite. The photo below is of the glabella of a Flexicalymene sp. The second photo is a few thorax segments.

Isotelus maximus

Someone found this huge underside of trilobite pygium. It is an Isotelus sp. In the second shot, we see a fragment that is probably also from the underside of the pygidium.


Fewer of the large brachiopod Vinlandostrophia ponderosa were found this year because of the mud, clay and rock that had washed down the hill. But a few were still found weathering from exposed Bellevue layers as the photo below points out.

Here are a few of the Vinlandostrophia ponderosa found that day.

One thing to note about these large brachiopods. They have calcite crystals inside. You don't need to break one open to find out. Most of the V. ponderosas we found were already broken open revealing the crystals, much like a geode.

A smaller species that were even more abundant than V. ponderosa was Vinlandostrophia laticosta and V. cypha.

A satisfying number of the beautiful brachiopod Hebertella occidentalis was also found.

In addition to this site, there was another road cut down the road exposing more of the Bellevue layers and had abundant Rafinesquina sp.

Here's a different looking brachiopod. Found in what was probably the Corryville rocks is what looks like an example of Plectorthis jamesi.

The tiniest of brachipods we were able to find with only a hand lens was Zygospira modesta.

One member had the foresight to bring his new computer microscope and used it to examine this Zygospira modesta in more detail. How about that?



Bryzoans are ubiquitous in the late Ordovician strata of the Cincinnati Arch. Today's site was no exception. Here's an interesting byrozoan colony.  You would this is a horn coral that has been completely encrusted with bryozoans. But it was found in the Bellevue or Corryville formations so it's probably not a horn coral.

Another interesting bryozoan shape was this ball. It superficially resembles a dasyclad algae called Cyclocrinites. It's actually entirely bryozoan as you can see on the bottom side (second photo).

Other trepostome bryzoans were found in a wide variety of shapes.

Even more common were ramose (branching) bryozoans.

Here's an interesting kind of bryozoan. These are Cyclostomate bryozoans. They form a network as the encrust brachiopod surfaces like this Rafinesquina sp.

Nautiloid Cephalopods

It was not hard to find straight-shelled nautiloid cephalopods. They were simply weathering out of everywhere. Can you spot the cephalopods in the photo of weathered fossils below?

Some of the nautiloid cephalopods were in rock and many were weathered free from matrix.


As far as I know, no one found a crinoid calyx. Only stems like the one shown below were found.



We were pleased to see a fair number of the snail Cyclonema sp.. This gastropod is one of the only Cincinnatian varieties that has external shell features preserved.


We also found clams that had shell details preserved on it. This one is called Caritodens demissa.

Most clam fossils we founc were Internal molds resembling Ambonychia sp.

Here is a typical haul in the trunk of a car.

That's all for this field trip. Thanks for reading.

Now check out our tour of the road cuts along a Kentucky state route.

See photos of our previous trips to the Ponderosa Ranch.


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