Dry Dredgers Field Trip
March 27, 2010
Southeast Indiana
Upper Arnheim, Waynesville, Liberty and Lower Whitewater Formations, Late Ordovician Period

The first field trip of the season is always a good one. The winter brought a miserable February with lots of freezes and thaws that break up rock and expose fossils. It was a great February for fossil hunters to enjoy in March. It was a beautiful early spring day with plenty of sun. So the turn-out was the best ever, with more than 50 people attending. As you can see from these pictures, there is plenty of room on the site for everyone and a plethora of fossils. As our field trip chair, Bob Bross, phrased it at the meeting the night before, "the site is fossiliferous. That means lots of fossils." He was right.

The chosen site was a large road cut in southeast Indiana that is very popular with colleges and fossil clubs for field trips. It exposes the Waynesville, Liberty and Whitewater formations of the Richmondian stage of the Cincinnatian Series. The age of the rocks is approx 430 to 440 million years old.

Here are some photos of the great time we had.

Best Finds of the Day

There were many good finds that day. I think the best was a Tricopelta breviceps (formerly Chasmops breviceps) Trilobite. Shown in the four photos below, it is not whole, but there are signs that there are actually two specimens of Tricopelta in this one specimen. Note in the second picture below how you can see three compound eyes, two of the articulated above the Glabella and one below the Glabella. Very nice find!

I think the next best find is this crinoid calyx. It appears to be a Cupulocrinus polydactylus, but missing the basal plates.

Photo Courtesy of Cynthia Striley

Next in the "best find" category are two Cephalopod entries. The first shown below is an impression of the surface of a Cephalopod. I think the impression was made by bryozoans that were attached to the Nautiloid.

The next best was this curved or coiled Cephalopod.

Also in the best find category is what I think is either the Bryozoan Graptodictya. But I'm not sure which. Graptodicta are typically from the Farview formation, which makes me uncertain. You be the judge. It's an interesting specimen, in any case.

Another good find was the Monoplacophoran, known as Phragmolites dyeri.

Here are the rest of the finds that day.

Trilobites Found: Flexicalymene retrorsa

This is one of our best sites to find trilobites. The most common of these is the Flexicalymene retrorsa.

The next two specimens are the burrows known as Rusophycus of trilobite Flexicalymene.


Trilobites Found: Isotelus

A nice pygidium (tail plate) of Isotelus was found.

And also found was a genal spine.

Horn Coral


A young member found a nice Grewingkia.

Streptelasma, which are smaller and are attaching solitary coral, were also found.

Streptelasma Horn Coral

The Streptelasma can be distinguished from Grewingkia by a smaller size, wider opening and a narrow end that shows  it attached to an object.

Another type of coral that was found is not a solitary coral but a colonial coral that encrusts brachiopods and other hard shells. Here is an example of the coral Protaraea richmondensis encrusting the brachiopod Rafinesquina.

Here is another example of a colonial coral. Note the septa on the sides of each chamber.

Crinoids Found

It was easy to find articulated crinoid stem sections on the surface of rocks (next 2 pics).

Gastropods (snails)

Most of the Gastropods found that day were internal molds with no external shell featuers. (next 3 pics.)

Some gastropods, though, did show external features and were preserved in Calcite.

Another type of mollusk found was this Bellerophontid Monoplacophoran.


The most common kind of Articulate Brachiopod found that day was Rafinesquina.

In some layers, the Rafinesquina were "shingled" and compacted in a slab of rock, probably as the result of a storm event 445 million years ago.

The next most common Brach is similar to the Rafinesquina. It's Strophomena. (next 2 pics)

This site is rich for it's variety of Brachiopods. This includes the common Articulate Brachiopod genus, Lepidocyclus. (next 3 pics)

The Brachiopod Hebertella could also be found here and there. (next 5 pics).

People also found examples of Glyptorthis.

One type of Brachiopod found here is similar to the Sowerbyella of the Kope Formation. Here in the Richmondian, though, we find Eochonetes, a Sowerbyellid.

Here are some inarticulate brachiopods called Petrocrania scabiosa, attaching to a Rafinesquina, a type of articulate brachiopod.

Pelecypods (clams)

Quite a few different kinds of clams were found. Most were internal molds. One type, however, was commonly found with the external surface features of the shell preserved. The clam is named Caritodens

Another genera of clam, Ambonycha, also had surface features, not so completely preserved, but visible.

The internal molds could be identified, at least as clams, by the presence of a hinge line where it was clear there were two separate, but equal valves. (next 2 pics)

Here's a group shot showing a Caritodens alongside two internal molds. Note that black coloring on one. This is of particular interest in that it's a remnant of the original shell.


Among the Bryozoans that could be easily identified was Constellaria. It's identified by the star patterns on it's surface. Thus the name.

There were plenty of ramose (branching) Bryozoan pieces found.

Other Bryozoans found had a flat, "leafey" shape.

Many fossils and rocks revealed beautiful Calcite crystals on the inside of them. These are the the carbonates from which many our rocks and fossils in the greater Cincinnati area are made.

Nautiloid Cephalopods

There were plenty of good examples of straight shelled nautiloid cephalopods found. These are often prized finds when they are large, articulated or well preserved.

Above and below photo courtesy of Betty Yan.

The above is a group shot of one member's finds. Can you now identify everything in the picture from the previous ID's in this field trip report?

Another cephalopod that was found was this fine and rare type of curved cephalopod. I did not see this specimen but Greg Courtney caught it on video. See the video of this field trip from our education chair, Greg Courtney, on Youtube.

Meet our education chair, Greg Courtney, and see all his videos on on Youtube.

That's all for this month. Join us for our April field trip to Northern Kentucky.

See photos of previous field trips to this Southeast Indiana fossil meca.

September 2008
September 2007
September 2006
March 2006

March 2004

October 2003

April 2002


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