minnbuckeye Posted May 9, 2020 Share Posted May 9, 2020 Couldn't help myself yesterday and returned to an outcrop of the Decorah Shale, Ordovician in NE Iowa. Found many nice specimens. (Adam, I may need to substitute some of my current finds with what is in your package) Here is something that perplexes me. I thought it was a partial trilobite cephalon/ genial spine but after looking at the species mentioned to occur in the formation, I struck out. Sooooo can anyone provide an identification? Thanks!!!!! Mike 4 Link to comment Share on other sites More sharing options...
piranha Posted May 9, 2020 Share Posted May 9, 2020 Ceraurinus sp. is reported from the Decorah Shale: 2 Link to comment Share on other sites More sharing options...
minnbuckeye Posted May 9, 2020 Author Share Posted May 9, 2020 @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 Link to comment Share on other sites More sharing options...
piranha Posted May 9, 2020 Share Posted May 9, 2020 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." 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. 3 Link to comment Share on other sites More sharing options...
minnbuckeye Posted May 9, 2020 Author Share Posted May 9, 2020 Thanks! Link to comment Share on other sites More sharing options...
GerryK Posted May 9, 2020 Share Posted May 9, 2020 The free cheek is large and the ornamentation is characteristic of Gabriceraurus herrmanni, which does occur in the Decorah. 3 Link to comment Share on other sites More sharing options...
piranha Posted May 9, 2020 Share Posted May 9, 2020 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! 1 Link to comment Share on other sites More sharing options...
minnbuckeye Posted May 10, 2020 Author Share Posted May 10, 2020 @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!!!! Link to comment Share on other sites More sharing options...
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