[2] Like other members of the genus, Iapetognathus fluctivagus had ramiform (branching) array of elements (apparatus).

It can be readily distinguished from other conodonts existing during the same age by the sideward orientation of the major teeth-like projections (denticulate processes).

[3] 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.

The authors of the study recommended a reevaluation of the Green Point GSSP section, as well as possible redefinitions of the associated horizons using other index fossils.