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...