FANTASTIC IDIOGNATHODIDS AND HOW TO REVISE THEM: I. IOWAENSIS AND I. RECTUS FROM THE TYPE LOCALITY

Conodont-bearing cyclothems are a powerful tool for biostratigraphic correlation during the Pennsylvanian. Upper Pennsylvanian biozone- and cyclothem-level correlation is generally well developed in Midcontinent North America and global zonation is robust. The Desmoinesian (Middle- lower Upper Pennsylvanian), however, has a dual Idiognathodus and Neognathodus biozonation in North America due to faunal provinciality, and some correlations at the biozone and cyclothem levels are problematic. Taxonomic revisions of zonal name bearer species of Idiognathodus are therefore critically important for improving Desmoinesian biostratigraphy. The Verdigris cyclothem as exposed near Knoxville, Iowa, is the type locality of two key zonal species: Idiognathodus iowaensis and Idiognathodus rectus. Both species were established in the 1940s and have subsequently been reported across North America. However, the species concepts have come to include a wide variety of morphology because neither I. iowaensis or I. rectus have been revised recently. This heavily impacts the reliability of the biozones and accurate correlation of the Verdigris. The type locality was recently rediscovered, and new samples presented herein allow the first modern documentation of the morphology of type area I. iowaensis and I. rectus.