Dry Dredgers Field Trip
October 24, 2015

Horn Coral Heaven, Southern Ohio
Whitewater Formation
Late Ordovician Period

Words by Bill Heimbrock
Photos by Bill Heimbrock and Dave Janosko

When we were ready to leave the house that Saturday morning to come to the field trip, it was raining. Rain had been predicted for some areas. Attendance was light with about a dozen people, although one member drove down from Cleveland to fossil hunt.  For those in Cincinnati, the site was about an hour north. It's not easy to know if it will be raining an hour later at the fossil site. The road was dry when we arrived and it didn't rain while we were there - and it was a pleasant temperature!

The site was a road cut exposing the Whitewater Formation of the Cincinnatian Series. The age was Late Ordovician, about 437 million years old. This was a return to "Horn Coral Heaven," which we visited last year at this time

Fossils Found That Day

Horn Coral

This site is famous for abundant horn coral. This time we found record numbers. The most common species we found was the large Grewingkia canadensis.  Below are photos of two different members' take homes. I brought home about 140 specimens. They will be donated to the Dry Dredgers for their educational outreach efforts.

Here's an interesting specimen. It's a horn coral growing inside another horn coral. Note also a brachiopod cemented to it. I think the brachiopod was a coincidental burial. Note also the borings on the surface of the brachiopod.

Are you drooling over delicious fruit in the photo below? No, you are actually drooling over the clearly visible septa of these large and abundant horn coral. In this case they are Grewingkia canadensis.

If Horn Coral make you drool, check out these cool horn coral - Streptelasma divaricans.

We found lots of the colonial coral Protaraea richmondensis, which encrusted all kinds of shells. In the next two photos P. richmondensis is encrusting gastropods.

Here are two pics of Protaraea encrusting brachiopods.

And given so many horn corals on this site, it was not impossible to find Protaraea encusting horn coral!


Since this site exposed the Whitewater Formation, more than a dozen species of brachiopods can be found. Here is a nice photo of one such assemblage from that day, complements of  Dave Janosko. I count at least 8 different species of brachiopods in this photo.

This first two photos shows the brachiopod species Vinlandostrophia moritura.  (front and back views)

I think this next brachiopod is best described as Vinlandostrophia acutilirata. (pedicle and brachial valve views).

 I think this next one is also Vinlandostrophia acutilirata. 

Here's a grouping of mixed species Vinlandostrophia sp. (picture below). For more help identifying these Vinlandostrophia, see the Ordovician Atlas.

Another really common brachiopod we found on the Horn Coral Heaven site was Lepidocyclus perlamellosum. (next 2 pics)

A very similar brachiopod we found was Hiscobeccus capax. See the Ordovician Atlas page for identifying these.

We found a few Hebertella occidentalis . (2 pics below are top and bottom views).

The brachiopod Holtedahlina sulcata is less common and very collectable. You can find it at this site easily, however (one picture below).

And without a doubt the tiniest brachiopod on the site was Zygospira sp..

A bit larger than the previous is Rhynchotrema dentatum (next 2 pics).

Common throughout the Cincinnatian Series are Rafinesquina sp.. This one may be R. alternata.

A cousin of Rafinesquina that is somewhat more limited in range is Strophomena sp..


This was a really good site for finding massive trepostomate bryozoans.

If you look closely at the broken edges of these massive bryozoan colonies, you can not only see the individual zoecia (holes that contained individual animals) but also  borings called Trypanites.

Here are more photos of trepostomate bryozoans.

The trepostomate bryozoan below had encusted a clam. You can still see the clam shape. On the other side (second pic), you can see Trypanites borings.

It's unclear what this next trepostomate bryozoan was encrusting, but you can see on the underside (second picture) a circular pattern indicating where the object was once located.

Below is a photo of a stone that is filled with branching bryozoans. The stone's coloration and smooth edges tell me it's not from the layers exposed on this road cut, but is probably gravel brought in during road construction or possibly by a glacial deposition.

Pelecypods (clams)

This was a good site for finding clam fossils. This first one is an external mold of the surface of the clam Ambonychia sp. It was probably preserved all these years by the bryozoan that encrusted its surface.

Most of the clams we found were internal molds with no trace of surface features. But often we can see the hinge line and some general shape of the inside surface of the original shell. (next 5 pics).

Gastropods (snails)

Perhaps misleading to call them snails, many of the gastropods were Bellerophontids. See one collection of gastropods in the photo below.

Even stranger are the examples of Cyrtolites sp. we found (1 pic).

Plenty of plain ordinary internal molds of snails were also found.


What's that you say? Did anyone find an extinct arthropod called a trilobite? Well the site was really rubbly with mostly broken rocks - an environment that easily preserve trilobite fossils. One person did find part of a thorax of Flexicalymene sp.

To close, here are a couple of nice group shots of what people were collecting. Note the use of the bucket and gloves. They were needed on this site.

That's all for this field trip.

You can see pictures of our previous recent field trips to Horn Coral Heaven.



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