A New Bug For An Old Collection

[Caleb]

On Sunday Sept. 8th, my father and I had to make a trip to Northeast Iowa to pick up a cupboard. Since we were in the area, naturally we thought we should go fossil collecting as well. After doing a lot of research last week, we decided to do some scouting and see if we could find any new productive sites.

The first site we stopped at for only a few minutes. All we were finding were stromatolites and the occasional Favosites coral. Later in the day we realized that the site was not in the Ordovician but in the Silurian. I may have to go back to collect some stromatolites to cut and see how well they polish, they were extremely abundant.

We continued on and looked at our notes and topo maps(on paper even) to locate likely sites in the Maquoketa Formation. We found one site that showed the contact between the Clermont and Ft. Atkinson members of the Maquoketa and searched for a while. It seemed pretty void of trilobite material, but I did find a beat up cephalon of a Bumastoides beckeri that I didn't collect. I was surprised to find a small crinoid and despite my father's heckling I collected a section of worm tube/burrow free of matrix.

Our next location turned this fun scouting trip into a fantastic outing. After spending some time looking at the shale my father shouted "We're going to be here a while!" I asked why and he told me to come and see. I walked over and he showed me a rock and I immediately recognized what it was, though I have never seen one it person. It was a cephalon of an Ectenaspis beckeri, one of the strangest looking trilobites in the Maquoketa Formation. Shortly after that I picked up another cephalon in similar condition. After 2 more hours of battling brush, grass and the occasional snake we left with 4 cephalons and a pygidium. I also picked up a sponge and an unusual curved cephalopod, but that was quickly overshadowed by the trilobite parts. After decades of collecting the Ordovician of the Upper Mississippi River Valley it's very unusual to be able to add a species to our collection that we haven't collected before.

The final stop of the day was an oldie but goodie. I didn't really have high hopes of finding a complete trilobite and was primarily looking for Ceraurus parts for study. After a while crawling around, my father yet again shouted out. He found a nice laid out Calyptaulax sp.; the cephalon is slightly covered so I can't properly ID it yet. And just like the Ectenaspis cephalons, I quickly repeted that I had just found a Calyptaulax, though his was much much nicer. Mine was a little disarticulated, the head was broken in half, it was rolled and smashed flat. Kind of a sad excuse for a bug, but it was a Calyptaulax! I continued my crawl and after collecting a few more trilobite parts I noticed a laid out Cybeloides iowensis! It was broken in a few spots, but I believe I have all of the rocks so it can be glued together. It looks like it should turn out quite nice.

So the day started out as a scouting mission and ended up being one of the best collecting days of the season!

Maquoketa first stop finds:

Brachiopod

And an out of focus crinoid calyx. I'll try to get a better photo tonight

Maquoketa second stop

Ectenaspis berckeri cephalons and pygidium:

Sponge

Curved cephalopod

Final site photos on next post...

[Caleb]

Final Maquoketa site:

Sphaerocoryphe maquoketensis

Cybeloides iowensis

Calyptaulax larrabeei top and bottom

[Caleb]

And here are a couple of the parts with scale and notes:

Ectenaspis beckeri

[piranha]

Attached for comparison with Caleb's incredible discovery is the figured holotype and plate description (Raymond, 1925).

The 1959 Treatise 'O' (fig. 4) finally got the long eye-stalks corrected. Congrats on finding the elusive Ectenaspis eyes!

 

 

Fig. 7. Ectenaspis beckeri (Slocom).

The holotype. The eyes are unknown, and the restoration of them is wholly conjectural.

 

Raymond, P.E. (1925)
Some Trilobites of the Lower Middle Ordovician of Eastern North America.
Bulletin of the Museum of Comparative Zoology 67(1):3-180

 

 

 

[piranha]

Hi Caleb,

 

Just curious if you have ever seen any of Robert Sloan's Ectenaspis specimens in person? The MAPS 2010 Digest has one with amazing elongated genal spines and I just read that Sloan had another dozen examples and was working up a revision of Ectenaspis. I'm assuming the reference to the complete immature individual means the others with long genal spines confirm that was a feature expected for holaspids as well?

 

 

Sloan, R.E. (1992 )

The Evolution of Ectenaspis.

Geological Society of America Abstracts with Programs, v. 23

North Central section, Iowa City Meeting

 

 

 

[Caleb]

Hi Caleb,

Just curious if you have ever seen any of Robert Sloan's Ectenaspis specimens in person? The MAPS 2010 Digest has one with amazing elongated genal spines and I just read that Sloan had another dozen examples and was working up a revision of Ectenaspis. I'm assuming the reference to the complete immature individual means the others with long genal spines confirm that was a feature expected for holaspids as well?

Ectenaspis.jpg

Sloan, R.E. (1992 )

The Evolution of Ectenaspis.

Geological Society of America Abstracts with Programs, v. 23

North Central section, Iowa City Meeting

.

I have not seen it in person. I will have to dig out the MAPS 2010 digest and take a look at it. From what Sloan says, the complete specimens have all come from a 10km area, and I have collected that area extensively with no luck. These specimens were found outside of that 10km range.

There are 2 species of Ectenaspis in the Maquoketa, but for some reason only E. beckeri is described. The other species does not have the long eye stalks or genal spines and is considerably more common and widespread. It tends to look more like Isotelus gigas, only with very triangular cephalon and pygidium, we have a photo of a 6inch specimen on midwestpaleo.com. Sloan noted that at one site in Minnesota they were finding abundant pygidiums of E. beckeri. I have collected the site he noted quite a bit and it is my belief that they were finding the pygidiums of the undescribed specimen and writing off the cephalons as I. gigas.

[AgrilusHunter]

Hi Caleb,

Congrats on a great find! That Ectenaspis is just unreal!

[Fossildude19]

Great finds, Caleb!

Thanks for the report and pics.

Regards,

[fossilcrazy]

I found two large Pygidium of Ectenaspis on one plate. The rock was from Utah in the Wah-Wah formation. Strange that more Pygidium show up than complete Ectenaspis.

[Caleb]

I found this line drawing in Sloans book "Minnesota Fossils and Fossiliferous Rocks".

[Al Dente]

Here's my Ectenaspis.

Obviously it is a plaster cast. Dr. Sloan made many of these casts and would give them away at his talks. I went to one of his talks on Ectenaspis in the early 1990s. A person I knew in the 90s claimed he found several examples in Iowa. He said he had to split rock to find them, they weren't on the bedding planes.

[Caleb]

Here's my Ectenaspis.

ectenaspis.jpg

Obviously it is a plaster cast. Dr. Sloan made many of these casts and would give them away at his talks. I went to one of his talks on Ectenaspis in the early 1990s. A person I knew in the 90s claimed he found several examples in Iowa. He said he had to split rock to find them, they weren't on the bedding planes.

I heard about that but I have never seen any of them. That is very cool you were able to get your hands on one!

[piranha]

Here's my Ectenaspis.

Obviously it is a plaster cast. Dr. Sloan made many of these casts and would give them away at his talks. I went to one of his talks on Ectenaspis in the early 1990s. A person I knew in the 90s claimed he found several examples in Iowa. He said he had to split rock to find them, they weren't on the bedding planes.

That is certainly a prized possession.... Thanks for posting!

[Malcolmt]

Excellent find.....I am envious...... ectanaspis has purportedly been found in the Ordovician quarry I have been hunting this summer but I have yet to find even a fragment nor have I been there when anyone else has found even a piece. Keep looking at every isotelus fragment to see if the pygidium might be ectanapsis instead with its distinct shape.

Edited September 11, 2013 by Malcolmt

[squalicorax]

Looks like one showed up on the interwebs aka ebay

http://www.ebay.com/itm/Crazy-rare-Ectenaspis-trilobite-Ordovician-Canada-/141058029078?pt=LH_DefaultDomain_2&hash=item20d7b6b616

[Caleb]

I noticed that one too. Once in a while a Canadian one will pop up on ebay which is exciting to see. I think the species for it is E. homalonotoides. They lack the extremely stalked eyes and genal spines. Still a rare bug. Crinus has one on his website: http://www.crinus.info/trilobites/data/ecten.htm

[trilobiteruss]

Saw that one on ebay also, was tempted he he

[Malcolmt]

Yes the quarry where that one was found is close to the quarry some of us on the forum still hunt. Unfortunately the quarry we are in really only has a tiny bit of the Bob Cageon that you can get to at the very bottom of the pit. Having said that there is a small chance that a fossil someone else found this weekend at the bottom of the quarry once fully prepped (it is 80% covered in matrix) may turn out to be ectenaspis. Regardless it will be a beautiful prone 4 to 5 inch isotelus at the least........

[Caleb]

There wasn't a whole lot of prep to be done, but all of the parts we found that day are now done.

Cephalon 1

Cephalon 2

Pygidium

And a very nice free-cheek showing the entire eye, genal spine and the anterior border

[trilobiteruss]

Still pretty cool material!

[piranha]

Spectacular additions to your research collection. Congrats on the great prep!

[PennyT.]

all that and the eye, too, fantastic!