Se Minnesota Hunt For An Unusual Trilobite

[Caleb]

With a slight chance of rain, my father and I decided to go hunt the Maquoketa, Galena, and Dubuque formations in Southeast Minnesota. We got to the first spot at about 6:30am and were getting rained on before 7:00. The site was in the Maquoketa Formation and the best way to find stuff is by splitting the limestone. After almost 2 hours of prying up slabs and splitting them we decided to call it quits and move on. The rain and the fact we weren't finding much were the primary motivators.

No photos because all I brought home were a couple Hindia Sponges which are now at my father's house.

Our next stop was a site where I had found a slab with very rare Celtencrinurus sp. parts earlier this month. I had wanted to get back to see if we could find more of the layer and possibly some more parts. I also wanted to take a measurement so I could record exactly how high above the Cummingsville Formation contact the previous specimens were collected. They were in place on the bedding plane so an accurate measurement would have been possible... if I had remembered my tape measure. Guess I'll have to go back. Anyway we didn't find any more parts of Celtencrinurus sp. in the rest of the slab or anywhere else. We continued to hunt for a little while longer and I found an interesting piece that could turn out to be a decent Ceraurus sp. A bit of prep will reveal if it's a complete specimen or not. By this time it was about 11:30 and we were getting hungry so we went to grab some lunch.

Ceraurus sp. (Complete?)

Cephalopod

During lunch we decided to hit two more quarries in the area, one in the Galena Formation and one in the Dubuque Formation. We got to the Galena quarry and started looking slabs over for trilobite parts and echinoderms. After not finding a whole lot I stumbled across a large Thaleops laurentiana. It has a chunk broken out of it's head, but there are thoracic segments showing so hopefully it will prep out decent(pictures to be taken). I also picked up a rather interesting geodized cepahlopod that I thought was pretty cool.

Geodized Cephalopod

Final stop of the day in next post.

[Caleb]

This is where the day got really exciting for me...

Two years ago we had gone into a quarry the exposed the Dubuque Formation. While there I had found a very interesting Odontopleurid (trilobite) pygidium. Well, we decided to go back to that quarry and see if we could find more parts. Within the first 15minutes there I had found a free-cheek of an Odontopleurid which I found quite exciting. Pictured below are some of the parts we found. The specimens are extremely tiny as you can see from the scale in some of the photos. The scale is mm. In total, we found 8 free-cheeks and 3 pygidia. A cephalon eluded us this time, but we'll be back.

Fee-cheek. Note the spines coming off the spine.

with scale

The whole piece with a brachiopod, prasopora, and other hash

The very unusual pygidium. I'll try to get better photos later

With scale

Two more of the unusual pygidiums

And a three more free-cheeks

[crinoid1]

That certainly is a very unusual pygidium. I would've glanced right over that. Awesome finds!

[Caleb]

The pygidium is quite odd. I have done quite a bit of research and have yet to find a match. I have also emailed photos to a Professor who has done a lot of work with Odontopleurids, but never received a response.

Here is a photo of the original specimen I found 2 years ago. It shows the most detail, I need to work on rephotographing the material I picked up this last trip.

Unknown Odontopleurid

Dubuque Formation

Late Ordovician, Edenian

Southeast Minnesota

[piranha]

That pygidium is still haunting me as nothing even looks close after looking through scores of images! It certainly deserves some attention now that you found another one, perhaps Jonathan Adrain might take a stab at it?

[Caleb]

That pygidium is still haunting me as nothing even looks close after looking through scores of images! It certainly deserves some attention now that you found another one, perhaps Jonathan Adrain might take a stab at it?

I'm going to try Dr. Adrain again with more images now that we have more than one specimen. It would be very nice to hear his thoughts on this specimen.

Some better photos of the specimens:

Another specimen of note I picked up was the pygidium of a Cybeloides winchelli. This is the first one I have found, but there were a few others we spotted later at the quarry.

Cybeloides winchelli

Dubuque Formation

Upper Ordovician, Edenian

Southeast Minnesota

Edited July 1, 2013 by Caleb

[Caleb]

I emailed the collections manager at the University of Iowa yesterday and was surprised to hear back today. She forwarded the photos to Jonathan Adrain and "he believes they most likely belong to a new species. However, without the cranidium, it would be impossible to describe it." The University displayed interest in having these specimens, so I'm going to try to collect a wider sample and hopefully a couple cephalons and donate them. We'll see how the cephalon hunt goes when I eventually make it back to the quarry.

[piranha]

A bizarre new odontopleurid that certainly deserves describing. Hope you find a bunch of them soon.... Congrats on getting the ball rolling!

[Roz]

Very cool, Caleb!

[Caleb]

Well I mentioned I had found a Thaleops laurentiana that had potential. Well, it's prepped and ended up a rather interesting piece. It's a molt that is in a jumbled pile, but it's all there except the free-cheeks and the chunk out of the left side of the cephalon.

This is all I saw, imagine the specimen covered with matrix above it.

This is the right side of the cephalon. Behind it you can see part of the pygidium and a couple thoracic segments.

Here is the left side of the cephalon with the rest of the thorax.

And this is the overhead. The cephalon laying on top of the pygidium which happens to be at the wrong end of the trilobite.

Nature does very interesting and confusing things sometimes.

Edit:

I forgot to add a photo with scale.

Edited July 3, 2013 by Caleb

[PennyT.]

As you say, most unusual mix up and the odontopleurid is like a necklace, lovely.

[Bev]

Incredible finds Caleb! Congratulations!

Bev :-D