I recently came across some "old" fossils I found a few many years ago, which included some slabs of fossils from the Imo formation in Van Buren County, Arkansas. The site is an abandoned phosphate mine known as the Peyton Creek site. It is about 0.5 miles east of highway 65, and there are also some exposures of the same rocks along the highway roadcuts nearby. The Imo is upper Mississippian and is sometimes included as part of the Pitkin limestone. It is apparently an outstanding site for cephalopods and ammonoids, but I didn't know that back then. The slabs contain several small trilobite pygidia, and below is a photo of the best one (about 5mm wide) along with a couple of others (now you have to look for them ). I was going to post here to see if I could identify the genus and possibly the species, but I think I found my answer already. I decided to post anyway, as a reference and to hopefully confirm the id, although I doubt the pygidia alone are enough. I believe this is Paladin imoensis, as I just discovered that the holotype was collected from the same abandoned quarry.