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Trilobite Identification Rock & More

Posted by on January 5, 2017
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Caleb Scheer of found and labeled this rock.

Caleb Scheer of found and labeled this rock.


You should be able to right click and copy and paste this onto your desktop for close examination–open with Paint. So often we see pictures and photos of prepared specimens, however identifying them while in matrix is a whole new adventure. I had asked Caleb ( on the sidebar–everything trilobite!) to take the time to do this for me, so that I can become better at identifying trilobites, etc.

I hope this helps you as much as it has me!

Thanks Caleb!

Here is an Excellent website for trilobite information:  Dr. Sam Gon also has a 90 page color PDF book on trilobites for only $6.00! Just take it a bite at a time, not to get overwhelmed and realize that there are something like 5,000 different types of trilobites!

Caleb has 14 different species of trilobite labeled on this one rock. And 5 other classes or creatures. I found it much easier to have the list separated from the picture when I opened the copied picture with Paint, magnified it and moved around to all of the different numbered spots. So, I am going to type the list in and hopefully you will be able to copy it, print, and have a less frustrating time identifying things. 🙂

In Red: Trilobites

1. Celtencrinus spicitus parts

2. Proetus species cephalons (heads)

3. Ceraurus species cephalons

4. Flexicalymene species parts

5. Calyptaulax callicephalus

6. Hypodicranotus species

7. Anataphrus boreaus pygidium (tail)

8. Achatella

9. Spaerocoryphe

10. Thaleops laurentiana

11. Hardpidella

12. Encrinuroides species

13. Ceraurinus marginatus

14. Eomonorachas


In Green:

1. Tiny crinoids

2. Brachiopod

3. Clam

4. Bryozoan

5. Cystoid Plates


Isotelus Trilobite: I have found several of these, so they are fairly common in this area. A very large trilobite that can get over 2 feet long! Note the triangular shape? Bits of the shell left on? The final note for identification are the “crinkles” on the bottom two sides of the triangle. This guy probably would have been a foot long! I got him on the Cty. 11 cut about 4 miles northeast of Fountain–and this may well be Maquoketa Shale. But I have also found them above Rifle Hill Quarry in the Maquoketa Shale formation.

Isotelus Pygidium (tail)

Isotelus Pygidium (tail)


Here is a hash plate I found at the Hwy. 52 cut just below Fountain with at least 8 Eomonorachas trilobite pygidiums-2 on the “front” and 6 on the “back”! Just tap to make the pictures larger. What do YOU see?!

Front side of hash plate with at least two trilobite pygidiums in it.

Front side of hash plate with at least two trilobite pygidiums in it.


One pygidium on front.

One pygidium on front.


One pygidium on the side of the front.

One pygidium on the side of the front.




Back side of hash plate with at least 6 trilobite pygidium.

Back side of hash plate with at least 6 trilobite pygidium.


2 pygidium on back.

2 pygidium on back.


Two more pygidium on back.

Two more pygidium on back.


And another pair on the back!

And another pair on the back!


Some of those brown shell casings are probably from trilobites. I am really only recognizing the pygidiums so far, so there may well be far more trilobites and more species on this plate. 😀 But hopefully this helps you on your hunts!

At this point, if I were going to recommend 3 proven trilobite hunt locations, they would be:

1. The Maquoketa Shale about 1 to 2 miles north of the village of Fillmore on County 5, go to the upper end. I have pulled 4 whole rollers out of there.

2. Just south of Fillmore about 2 miles on Cty. 5 is a huge roadcut on the west side. Great for receptaculitids but the upper end is good for trilobites–don’t miss the shelf in the middle if you dare!

3. The hash plates on Hwy. 52, like just below Fountain not a quarter of a mile, the ditch going south on the west side of the highway–yeah, lots of trilos in there! And hey, jump over to my blog about Adventure and Fun in Bluff Country and do a search on Fountain–several nice places to take a break and eat!







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2 Responses to Trilobite Identification Rock & More

  1. PennyT.

    Thankyou Bev for a very informative website and for your generosity in sharing your love and knowledge of fossils with us. Fillmore County is so beautiful. I enjoyed the all too short time I was able to spend there and plan to return to give it the time it deserves. And Caleb, thank you for being a great teacher in all things trilobite!


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