ABSTRACT: Three Pennsylvanian stratigraphic units in southwestern Missouri that have long been recognized as preceding the Cherokee Group (and as pre-Desmoinesian Stage) are compared on the basis of their conodont faunas: the Riverton Shale, the Ladden Branch Limestone Member of the Riverton Shale, and the type Burgner Formation from the subsurface. Shale at the base of the Riverton was sampled where it occurs above a well-developed underclay. It produced a conodont fauna that is mostly similar to that of the Ladden Branch Limestone Member, which occurs at the base of the Riverton Shale at other localities. Both units produced biostratigraphically important Neognathodus bothrops and N. colombiensis s.l.. A difference is that the Ladden Branch Limestone Member commonly produced specimens of Idiognathoides, whereas none were recovered from the basal Riverton shales. Both are assigned to the upper Atokan Neognathodus colombiensis Zone, and most likely are age-equivalent facies. Strata at the Republic coal pit, previously considered correlative with the type Burgner Formation, are now correlated with the Riverton Shale based on its N. colombiensis Zone conodonts and overall similarity to the basal Riverton. The core that represents the type Burgner Formation produced a conodont fauna somewhat different from the other sections, including specimens of an advanced morphotype of Neognathodus nataliae. The type Burgner Formation is, therefore, assigned to the upper part of the lower Atokan N. nataliae Zone.
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