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I am hoping someone out there is extremely familiar with the surface texture of late Ordovician trilobites of the Cincinnatian. I found this in St. Leon, Indiana. I believe it is a trilobite glabella, and there might be a little bit more to expose. Normally I wouldn't get excited about a trilobite fragment, but finding anything other than Isotelus or Flexicalymene at this site is a bit rare, and this could add a new taxon to my collection for that site. Taxa that I thought might be candidates include: * Ceraurus milleranus * Amphilichas shideleri * Tricopelta breviceps Thanks for any help. (scale is in mm)
Caleb posted a topic in General Fossil DiscussionWhile 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: