Dry Dredgers Field Trip
March 26, 2011
Return to an old Indiana Road Cut
Liberty Formation, Late Ordovician Period

Some of the younger members of our group.

The Dry Dredgers return to a site we have not visited on a field trip since May 1997. It's a road cut near Brookville Lake, Indiana that exposes the Liberty formation, which is part of the upper Ordovician strata of the Cincinnatian Series of formations.

The site have evolved. In the 90's, it was a great site where more than 6 kinds of crinoids have been found. But now, one side has been resurfaced and sodded. The other side is picked over and is all "float" (material fallen from higher up the cut).

Fossils Found that Day


At least a couple of calyxes of Cincinnaticrinus pentagonus were found (next 2 pics)

Another interesting find was a two separate examples of the anal sac from Plicodendocrinus casei encased in matrix.

Quite a few examples of crinoid arms and calyxes in matrix were found that don't show quite enough for identification. (next 4 pics)

But lots of crinoid stems were found. 

Here's an interesting crinoid stem on matrix that not only is a cross section showing internal parts, but extends down and shows the holdfast where the crinoid fastened itself to the sea floor. Nice!


By far, the most common trilobite found that day was Flexicalymene retrorsa. Some may have been of the subspecies minuens. As shown in the 8 photos below, most were enrolled but some were prone (stretched out).

A more rare trilobite that was found were these fragments of Acidaspis cincinnatiensis. Note the spines on the pygidium (first photo) and the genal area (second photo).

Also, lots of fragments of the very large trilobite Isotelus were found. 

This first photo looks mysterious. It looks somewhat like a variety of exciting and rare Cincinnatian fossils. But closer examination reveals that it is a fragment of Isotelus.

Close examination of the surface of Isotelus fragments can reveal contour lines that are diagnostic of the specific trilobite. The specimen below (2 pics) is a genal area leading to the genal spine which is missing from this example of Isotelus.

At least one almost complete pygidium (tail section) of an Isotelus was found.

Mostly, though, fragments on the surface of rocks were everywhere on the site.


The most interesting coral I saw that day was a tabulate coral.

There were lots of examples of an encrusting coral called Proterea richmondensis.

The most common coral was the large horn coral (solitary coral) Grewingkia

Another type of horn coral found was the smaller attaching coral, Streptelasma. This can be distinguished from Grewingkia by the opening that "bells" out more and the tip at the other end is flatter and bent because it attached to something hard. 

Articulate Brachiopods

Thousands and thousands of the the small brachiopod Cincinnetina (or Cincinnetina) were found on the surface of slabs.

Cincinnetina were found loose from the rock also. The species for these upper Richmondian Cincinnetina is currently being discussed among the Dry Dredgers. The documentation refers to them as meeki for the entire Richmondian. But it is becoming clear that other species may exist. In the world of Cincinnati fossils, even amateurs can discover and name new species. 

An interesting brachiopod that is common to the Richmondian formations but largely absent from the Maysvillian formations is Leptaena. Good quantities were found on this site.

Even more common was the ubiquitous articulate Strophomenid brachiopod, Rafinesquina.

Another abundant Strophomenid brachiopod found was Strophomena.

A someone less common Strophomenid brachiopod found was Eochonetes.

Two very similar Orthid brachiopods found were Plaesiomys and Glyptorthis  

This first group of specimens (3 pics) look more like Plaesiomys. One valve is much flatter than the other valve. The sulcus is almost absent, compared to Glyptorthis. Plaesiomys also has a more rectangular outline.

Glyptorthis have two valves that are more similar to each other in how convex they are. The sulcus is deeper than Plaesiomys.

Here's a batch where the two specimens on the right are more similar to Glyptorthis. Note the sulcus and more rounded outline. Note also a "herring bone" pattern to the growth lines on the specimen on the right. This can also distinguish it from Plaesiomys. 

The batch below is more like Plaesiomys. Note the more rectangular outline.

Another similar brachiopod to the Plaesiomys and Glyptorthis is Hebertella. Hebertella are most easily identified by a triangular pedicle opening and a deaper sulcus than Glyptorthis. For a glossary of brachiopod anatomy, see our Brachiopod Page.

At least a couple of species of the brachiopod Vinlandostrophia were found. 

And huge quantities of the Rhynchonellid brachiopod Lepidocyclus were also found. Note the "herring bone" pattern on the first specimen pictured below. This is an easy way to distinguish it from Vinlandostrophia. Another way is that Lepidocyclus and Hiscobeccus have a more rounded profile than Vinlandostrophia.

Inarticulate Brachiopods

Attached to the articulate brachiopods are inarticulate brachiopods. There were  many genera found that day.

First we found the very common inarticulate, Petrocrania scabiosa.  

Another inarticulate brachiopod found was Philhedra laelia.

And a third type of inarticulate Brachiopod found was Trematis.

Pelecypods (Bivalves or Clams)



Harder to identify bivalves

This next internal mold of a clam has a worm tube attached to it. The position of the worm tube on the clam may give us a clue as to the life position of the clam. 

This next specimen found that day is a mystery. When I photographed it, I was interested in the honeycomb pattern on the right, suspecting it could be the algae Cyclocrinites. Now that I'm looking at the photo, I'm interested in the whole specimen. It may be a clam or possible something more interesting. I did not record whose specimen this was. So if this is your specimen, please email me (Bill Heimbrock) at admin@drydredgers.org. You may have something nice here.

Gastropods (Snails)



Ichnofossils (traces)

Nautiloid Cephalopods

That's all for this field trip. Now let's continue with photos of the April 2011 field trip.

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