 The genus "Iapetognathus" and related denticulate groups still require extensive taxonomic clarification.In 2011, a study discovered that the First appearance datum (FAD) of "Iapetognathus fluctivagus" in the Global Boundary Stratotype Section and Point (GSSP) section in Green Point may not actually be the earliest species of "Iapetognathus" to appear as was earlier believed.Its true FAD lies above another species, "Iapetognathus preaengensis", and is not present at the Cambrian–Ordovician boundary (COBWG).