Cambrian (Guzhangian Stage) trilobites from Ohio, USA, and modification of the Cedaria Zone as used in Laurentia

Two Cambrian trilobites, Olenoides? sp. from the Mount Simon Sandstone and Cedaria woosteri from the Eau Claire Formation, are described from the subsurface of western Ohio, USA. The definition of the Cedaria Zone is modified to reflect differing interpretations of the zone as used historically in restricted-shelf and open-shelf lithofacies of the Laurentian palaeocontinent. The Cedaria prolifica Zone is proposed for use primarily in open-shelf lithofacies, and the C. woosteri Zone is proposed for use in more restricted, inner-shelf lithofacies. Olenoides? sp. from the Mount Simon Formation is interpreted as representing the C. prolifica Zone, and C. woosteri is the eponymous species of the C. woosteri Zone. Both polymerid trilobite biozones are in the Guzhangian Stage (Cambrian, provisional Series 3). Based on trilobite zonation, the Mount Simon Sandstone and most of the Eau Claire Formation of western Ohio are interpreted as being Guzhangian in age.