The type area for the Springerian stratigraphic sequence is in southern Oklahoma (Carter County) and that of the Morrowan is in northwestern Arkansas (Washington County). In the past, both series have been employed as comprising successive time-stratigraphic serial subdivisions of the North American Lower Pennsylvanian. A conodont zonal scheme developed herein provides a means for correlations between both type sections and demonstrates that the Springerian overlaps with the underlying Chesterian and overlying Morrowan. Therefore, usage of the Springerian as a viable subdivision of the Lower Pennsylvanian should be discontinued. In the type Springerian, the upper part of the Goddard Formation and Rod Club Member of the Springer Formation correlate with the Menard through the Grove Church sequence in the Illinois Basin. The “B” Shale Member contains an undiagnostic Upper Mississippian fauna, and the Target Limestone Lentil of the Lake Ardmore Member contains conodonts that correlate with the Cane Hill Member of the Hale Formation of the type Morrowan. The Lake Ardmore through Primrose sequence correlates with the Hale through Woolsey Member of the Bloyd Formation in Arkansas. The Dye Shale and Kessler Members of the Bloyd contain two upper Morrowan conodont zones, and the position of the Trace Creek Shale Member with respect to the Morrowan-Derryan (=Atokan) Boundary cannot be precisely determined. Morrowan conodont collections from northeastern Oklahoma can be correlated with the type Morrowan zonal scheme. The zonal scheme developed in both areas is present in Morrowan rocks in west Texas and Nevada. One taxon is newly described.

Investigations in the southern Midcontinent, the southwestern United States, and the central Appalachians demonstrate the potential biostratigraphic value of North American Pennsylvanian conodonts. Morrowan conodonts from the Boston and Arbuckle Mountains in the southern Midcontinent reveal four biostratigraphic units characterized, in ascending order, by Spathognathodus muricatus, Idiognathoides noduliferus, Gnathodus bassleri symmetricus, and Gnathodus bassleri bassleri. The first occurrence of Idiognathoides noduliferus (⇌ Streptognathodus noduliferus and Gnathodus noduliferus of authors) indicates basal Morrowan. In addition, Idiognathodus dominates in the upper Morrowan. In the Great Basin, the first occurrence of Streptognathodus noduliferus is immediately above the Mississippian-Pennsylvanian boundary. The Streptognathodus noduliferus-Idiognathoides convexus Assemblage Zone characterizes most of the Morrowan, and its lower part corresponds to the I. noduliferus unit in the southern Midcontinent. Gnathodus bassleri does not occur above the Atokan, and Gnathodus roundyi ranges from Desmoinesian through Virgilian. In the central Appalachians, the Pennsylvanian Gnathodus lineage begins with Gnathodus noduliferus and reaches its maximum morphologic complexity in G. bassleri bassleri (upper Pottsville). Subsequently, the group gradually simplifies by loss of ornamentation to Gnathodus dilatus in the upper Allegheny. Streptognathodus seems to have been both successor and ancestor of Idiognathodus several times. Biostratigraphic subdivision of the Conemaugh Group is based on the evolution within Streptognathodus because Idiognathodus rarely occurs in the upper Conemaugh where Streptognathodus attains its maximum development.