Here is a rare agnostid trilobite of the species Acadagnostus syrma from the Wheeler Formation of Utah . Acadagnostus syrma is better known under the synonym Peronopsis fallax (Tullberg, 1880) which, however, was revised in 2012 by Naimark *, together with 100 other taxa of the Agnostida.

* Naimark, E.B. (2012). "Hundred species of the Genus Peronopsis Hawle et Corda, 1847". Paleontological Journal. 46 (9): 945–1057. doi:10.1134/S0031030112090018.

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