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Title: New Silurian trilobites from the Sexton Creek Formation, southeastern Missouri

Abstract: 
Little work has been done on the Sexton Creek Formation, a fossiliferous limestone deposit located in southeastern Missouri and southwestern Illinois. Only one species of trilobite, Dalmanites croneisi Ball and Delo, 1940, has previously been reported from the unit. Recent conodont work has constrained the age of the unit to Telychian, with the lower part possibly Aeronian. Current research primarily focuses on the systematics and taxonomy of a new trilobite fauna collected from the formation exposed on the banks of Blue Shawnee Creek, Cape Girardeau County, southeastern Missouri. Ten species—all new—are present, with single species assigned to each of Anacaenaspis? (Odontopleuridae), Ceratocephalina (Odontopleuridae), Curriella (Encrinuridae), Daytonia (Dalmanitidae), Dekalymene (Calymenida), Dicranopeltis (Lichidae), Exallaspis (Odontopleuridae), Failleana (Styginidae), Harpidella (Aulacopleuridae), and Lichas (Lichidae). The material is mostly disarticulated, but a single articulated specimen of Exallaspis lacking librigenae, two cephala of Dekalymene, a cephalon of Ceratocephalina, and a thoracopygidium of Curriella are known. Many of the trilobite specimens were colonized by encrusting bryozoans, suggesting they were the primary available hard substrate in a muddy bottom benthic community. Bryozoans overgrow various surfaces (eyes, articulating facets) that indicate they could not have been epibionts on living trilobites, but rather colonized molted or post-mortem specimens. Some specimens have echinoderm holdfasts. The assemblage compares with coeval faunas from the Brassfield Formation in Ohio (Daytonia, Dekalymene) and the Jupiter Formation in Québec (Daytonia, Exallaspis, Lichas).