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minnbuckeye

Decorah Shale Trilobite Cephalon???

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piranha

Ceraurinus sp. is reported from the Decorah Shale:

 

image.png.fd195ee243c7fc32df4e056013b5f13f.png

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minnbuckeye

@piranha, Thanks!! Initially I considered the possibility of Ceraurinus species but discounted it because of the pits in the preglabellar field/ eye?. I thought Ceraurinus had bumps. I have since looked at examples from the Decorah Shale and see none that have the tiny nodules all the way down the genial spine nor the pits.  I am still confused. 

 

Mike

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piranha
2 hours ago, minnbuckeye said:

@piranha, Thanks!! Initially I considered the possibility of Ceraurinus species but discounted it because of the pits in the preglabellar field/ eye?. I thought Ceraurinus had bumps. I have since looked at examples from the Decorah Shale and see none that have the tiny nodules all the way down the genial spine nor the pits.  I am still confused.

 

Ceraurinus cheeks are pitted:

 

"Ornaments of a different type, consisting of perforations of the test, have been noted in several species. Rather large perforations extend through the cheek lobes in Ceraurinus,
Pseudosphaerexinella and Holia. These are of a type long known and described in many species of Ceraurus and Ceraurinus."

 

image.thumb.png.ff64b5fadfe94130b49f657e6a12f94b.png

 

text from:

 

Evitt, William R. 1950

Trilobites from the Lower Lincolnshire Limestone near Strasburg, Shenandoah County, Virginia.

PhD Thesis, The Johns Hopkins University, 392 pp.

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minnbuckeye

Thanks!

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GerryK

The free cheek is large and the ornamentation is characteristic of Gabriceraurus herrmanni, which does occur in the Decorah.

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piranha
39 minutes ago, GerryK said:

The free cheek is large and the ornamentation is characteristic of Gabriceraurus herrmanni, which does occur in the Decorah.

 

 

I looked at this one too quickly and did not account for the scale or the fact that is not a genal spine.  Gabriceraurus indeed! :fistbump:

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minnbuckeye

@piranha, @GerryKYour help is appreciated. My confusion on ID was based on assuming the pointed end was in fact a genial spine. Now, knowing the  piece showing in the matrix is anatomically a free cheek, your suggestions make sense!!!!

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