Dry Dredgers Field Trip
April 24, 2010
Northern Kentucky Kope Site
Southgate Member, Kope Formation, Late Ordovician Period

The April field trip was to a site that we like to hit in the spring, when the freezes and thaws of winter have broken rocks and washed away the gray Ordovician clay leaving the heavier carbonate fossils behind. The site is just a short drive from downtown Cincinnati. It exposes the Southgate member of the Latonia (Kope) Formation.

Best Finds of Day

I think the best find of the day was this Primaspis crosotus on a slab of limestone. The head may be under the hard calcified rock, so it will be hard to expose. Very nice find, though.

Most members, whether they knew it or not (if you've been in the Dry Dredgers at least few year, you knew it.) found parts of Primaspis crosotus. Notice in the second pic below, how one of the spines is encrusted with Bryozoans. A study of Ontopleurid trilobite epizoans (attachments) is needed! (hint to the professionals.) Dry Dredgers often supply specimens to professional paleontologists for their papers and studies.

But the more common trilobite on this site, which is mostly limited near Cincinnati to the Kope, is the the Lace Collar trilobite, Cryptolithus tesselatus.

At the meeting the night before, we were prepped for what we might find. The only Dr. John Pojeta Jr. gave a feature presentation on fossil chitons. It is our hope that we will find another chiton in the Cincinnati Ordovician rocks as good as the ONE specimen in existence. John brought that from the museum to the meeting for us to see. (See photos of the April Meeting and John Pojeta's talk).

No one found a fossil chiton unfortunately. Although lots of living animals were found that bare a bit of a resemblance to them and at some point in history, a common ancestry (1 photo below).

Trilobite: Flexcicalymene granulosa:

In the Kope formation, the most common species of the common trilobite Flexicalymene you will find will be the species "granulosa." Here are some examples found that day.

The glabella (face of the head) of Flexicalymene has a classic shape that can be easily recognized.

Similarly, the tail section, which is one solid piece called the pygidium, in unmistakable once you've seen a photo such as the one below.

All of these trilobite parts can be found commonly on the surfaces of rocks in the Kope formation of Cincinnati. Here's a picture of a typical rock. Can you find the trilobite fragments?

Trilobite: Isotelus

Hypostoma (mouth plate)

Crinoids Found

Ectenocrinus

Anomolocrinus

Cincinnaticrinus

Above photo complements of Bruce Gibson

Crinoid Stems

Cephalopods

Probably the best find that day of a Nautiloid Cephalopod was this curved shelled Nautiloid external mold.

Above photo complements of Bruce Gibson

Other curved shelled Nautilods were found as internal molds.

In the Kope exposed at this site, many of the Cephaloopds have as much brown calcite coloring as the brachiopods, making them very collectable. The calcite preserves the surface features of the shell and occasionally the microstructure which makes them very desirable for professional study.

Other Cephalopods are very collectable because they are encrusted with Bryozoans.

Worm Tubes


Cornulites

Pelecypods (bivalves i.e. clams)

Many of the clam fossils on this site are preserved in a beautiful brown calcite. This next specimen is a compaction of mollusk shells in calcite. The large clam at bottom is called Ambonychia. (next 2 pics)

Ambonychia are also preserved as molds. Here's a rock with several external molds of Ambonychia.

Most Upper Ordovician clams are preserved as casts or internal molds, however. The original aragonite shell of the clam does not survive the test of time.

Snails

Snails also are occasionally preserved in a brown calcite. Here's an example of what looks to be Cyclonema.

Most snails are preserved as internal molds. See the examples below from this site.

Brachiopods

 

Bryozoans

Trace Fossils



Above photo complements of Bruce Gibson

Coral

Graptolites

Our next field trip is in May 2010 to the famous Caesar Creek, Ohio

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