Ornate Unknown, Echinoderm or Trilo-bit?

[minnbuckeye]

I was busting up a few rocks from the Ordovician/ Galena of SE Minnesota when I noticed this unknown peeking out at me. It would be nice to understand what it is so a decision as to whether to expose more of it can be made. Thanks! By the way, it is 6 mm in length.

 

Mike

 

 

 

 

 

 

 

 

 

 

[Al Dente]

Trilobite cephalon. Ceraurus?

Edited September 5, 2022 by Al Dente

[FossilDAWG]

I agree, cerarid trilobite glabellum.

 

Don

[minnbuckeye]

 I concidered Gabriceraurus mifflinensis  initially because is the common cerarid locally.  But the larger bumps do not seem to be typical of this species. Any though to a species? @piranha

[piranha]

Ceraurus plattinensis and Gabriceraurus mifflinensis have similar tubercles. The PhD thesis of Congreve 2013 has a bunch of figures for comparison. Congreve 2013 suggested that G. mifflinensis should be reassigned to Ceraurus based on phylogenetic analysis. A revision of the North American Cheiruridae has been in the works for the last 10 years. Hopefully this highly anticipated monograph will be published in the not-too-distant future.

 

 

Congreve, C.R. 2013

Evolutionary Patterns of Trilobites Across the End Ordovician Mass Extinction.

PhD Thesis, University of Kansas, 255 pp.  PDF LINK