A New Occurrance Of A Cheirurid From The Maquoketa Fm

[Caleb]

While my father and I have been collecting the Maquoketa Formation in Southeast Minnesota and Northeast Iowa for over 15 years, we're starting to run out of surprises. However, we had a massive surprise last week while prepping what we thought was just a Gabriceraurus elginensis. Wile prepping, some very unusual features started showing up. There was some unusual ornimentation exposed followed by a very shocking occipital spine. With some help from a certain forum member(Thanks!) we obtained a paper that discribed very closely what we were looking at... a very rare cheirurid Borealaspis sp.

The genus Borealaspis was established in the paper New cheirurinid trilobites from the lower Whittaker Formation(Ordovician), southern Mackenzie Mountains (Ludvigsen, 1976). The paper lists 2 new species of Borealaspis, B. whittakerensis, B. biformis, and one reasigned from Cheirurus numitor(Billings, 1866) to B. numitor. The one that most resembles our specimen is B. numitor. B. numitor was originally described from a specimen collected on Anticosti Island from the Richmondian aged Vaureal Fm. While this conforms with the age of the unit we found this in (Clermont mbr, Maquoket Fm.) the holotype has been lost and the neotype is not very complete for an definitive ID. Also in the original description of B. numitor, Billings states "the eyes are small and about opposite or a little in advance of the second pair of furrows". While the placement of the eyes match, the eyes on our specimen are anything but small.

I'm also looking for a copy of "A revision of the American species of Ceraurus" by Percy E. Raymond and Donald C. Barton, 1913 which has an image of another specimen of B. numitor if anyone knows of a PDF version.

Holotype: Neotype:

Our specimen:

Edited July 20, 2012 by Caleb

[pleecan]

That is a super find! Congratulations!!!

[Auspex]

Holy cow! This is exciting!

Your specimen itself is gorgeous

[Caleb]

Thanks! We sent some photos to someone working on Cheirurids and were told that this was one of the most complete cephalons he's seen, which is also exciting!

[piranha]

Hi Caleb,

The paper is available but missing the plate (pl. 1, fig. 5) you are looking for: LINK It might be available in another format and I will try to source it for you. The Ludvigsen paper mentions Nieszkowskia by comparison of the preoccipital spine. Although Borealaspis is allied with a Ceraurus lineage, I thought it was curious because you recently discovered an unusual acanthoparyphinid pygidium as well. Strange coincidence on another great discovery. Congrats

[Northern Sharks]

... just a Gabriceraurus elginensis.

Must be nice to be so spoiled. Congrats on the find

[Missourian]

Interesting specimen, including the color.

[Caleb]

Hi Caleb,

The paper is available but missing the plate (pl. 1, fig. 5) you are looking for: LINK It might be available in another format and I will try to source it for you. The Ludvigsen paper mentions Nieszkowskia by comparison of the preoccipital spine. Although Borealaspis is allied with a Ceraurus lineage, I thought it was curious because you recently discovered an unusual acanthoparyphinid pygidium as well. Strange coincidence on another great discovery. Congrats

We now have a cephalon to go with the partial Acanthoparyphinid from the Maquoketa, both came from the same location. However, we have seen a mystery pygidium of another Cheirurid that we've had trouble with from the same area. Since no photos of B. nimitor are knowen, I'm wondering if this may be one? I also found an image of figure 5 which shows another spine which our specimen seems to lack.

Figure 5 of Borealaspis from "A revision of the American species of Ceraurus" by Percy E. Raymond and Donald C. Barton, 1913

Acanthoparyphinid

Unknown Cheirurid

[sward]

Unbelievable find! You must be awfully proud.

A find like this is what makes all those hours out in the hot and/or cold and terrible weather and conditions worthwhile.

Congratulations!

[piranha]

Glad you found the plate. Attached are a few more interesting Silurian analogs that appear to be confidently placed within the Acanthoparyphinae. Parayoungia and Youngia were mentioned so thought you would want to see them as well. Certainly good candidates as descendant genera. I just sent you the following papers:

Systematics of the Acanthoparyphinae (Trilobita), with Species from the Silurian of Arctic Canada

Journal of Paleontology, Vol. 72, No. 4 (Jul., 1998), pp. 698-718

Author: Jonathan M. Adrain

Silurian (Wenlockian) trilobites from Baillie-Hamilton Island, Canadian Arctic Archipelago

Canadian Journal of Earth Sciences, 1977, 14(2): 285-317

Authors: D. G. Perry and B. D. E. Chatterton

[Caleb]

Glad you found the plate. Attached are a few more interesting Silurian analogs that appear to be confidently placed within the Acanthoparyphinae. Parayoungia and Youngia were mentioned so thought you would want to see them as well. Certainly good candidates as descendant genera. I just sent you the following papers:

Systematics of the Acanthoparyphinae (Trilobita), with Species from the Silurian of Arctic Canada

Journal of Paleontology, Vol. 72, No. 4 (Jul., 1998), pp. 698-718

Author: Jonathan M. Adrain

Silurian (Wenlockian) trilobites from Baillie-Hamilton Island, Canadian Arctic Archipelago

Canadian Journal of Earth Sciences, 1977, 14(2): 285-317

Authors: D. G. Perry and B. D. E. Chatterton

Thanks Scott! I have the paper by Adrain, but I didn't have the Perry and Chatterton one. It will make a nice adition to my growing pdf library.

While I'm not absolutely sure, I think Hessin related Borealaspis with the genus Bufoceraurus in the paper "Ceraurus and related trilobites from the Middle Ordovician Bobcaygeon Formation of south-central Ontario, Canada" Hessin, 1989. I don't have that paper yet, but my father has a hardcopy and I will try to scan the segment next week sometime(if I'm not mistaken and thinking of some other paper or just dreaming it).

[Caleb]

... just a Gabriceraurus elginensis.

Must be nice to be so spoiled. Congrats on the find

Actually, since this didn't turn out to be a G. elginensis, it means we still don't have one in our collection. Someday... someday...

Interesting specimen, including the color.

The color is quest astonishing. I'm curious if it's just from the type of preservation, or if it's actual color preservation of the original shell material. We have one other Cheirurid part that exhibits the same color, but it's from a different formation and about 50 miles away.

[Caleb]

Thanks Scott! I have the paper by Adrain, but I didn't have the Perry and Chatterton one. It will make a nice adition to my growing pdf library.

While I'm not absolutely sure, I think Hessin related Borealaspis with the genus Bufoceraurus in the paper "Ceraurus and related trilobites from the Middle Ordovician Bobcaygeon Formation of south-central Ontario, Canada" Hessin, 1989. I don't have that paper yet, but my father has a hardcopy and I will try to scan the segment next week sometime(if I'm not mistaken and thinking of some other paper or just dreaming it).

I found the quote from "Ceraurus and related trilobites from the Middle Ordovician Bobcaygeon Formation of south-central Ontario, Canada" Hessin, 1989: