Conodont Zonation of the North American Mississippian

More than 20 characteristic conodont faunas have been recognized in North American Mississippian rocks. Although best known in the Mississippi Valley and southwestern Missouri, they are widespread on the continent. Six zones and four subzones in the Kinderhookian Series are based on lineages of Siphonodellaand Gnathodus.A succession of primitive gnathodids in the lowermost part of the series— Protognathodus meischneri, P. kockeliand P. kuehni—matches that in the lower part of the Gattendorfia-Stufein Germany. The occurrence of Gnathodus punctatusin Missouri, Oklahoma and Arkansas identifies the youngest Kinderhookian and protably correlates with the lower part of the German Pericyclus-Stufe, and with the middle part of the ZaphrentisZone of the British Avonian. Significant differences are found in the ranges of siphonodellid and gnathodid species in western Europe and America. Several species found together abroad are stratigraphically separate in the central United States. Bactrognathus, Pseudopolygnathus, Gnathodus, Taphrognathus, Polygnathusand Doliognathussubdivide the lower Valmeyeran (Osagian) Series where Bactrognathus distortusmarks an especially widespread zone. The occurrence of Pseudopolygnathus triangulus pinnatusin the Doliognathus latusfauna, accompanied in some places by Scaliognathus anchoralis, correlates with part of the S. anchoralisZone in the German Sauerland. The upper Valmeyeran (Meramecian) zones are characterized by Apatognathus, Taphrognathusand Cavusgnathus,but are more generalized than underlying zones. The base of the Chesterian Series is not easily distinguished by conodonts, but the upper limits of Gnathodus bilineatusand G. girtyiin the Mississippi Valley mark the top of the Glen Dean Limestone and may approximate the lowermost Namurian, the base of the European Upper Carboniferous. Streptognathodus unicornisoccurs at the top of the type Chesterian and in Nevada ranges to the top of the Gnathodus girtyi simplexZone, which apparently contains youngest Mississippian rocks.