Iapetognathus is a genus of cordylodanconodonts. It is one of the oldest denticulate euconodont genera known.[2]
Like other members of the genus, Iapetognathus fluctivagus had ramiform (branching) array of elements (apparatus). It is believed that the ramiform apparatus in Iapetognathus fluctivagus evolved from the coniform (cone-like) apparatus of Iapetonudus ibexensis. 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. Its true FAD lies above another species, Iapetognathus preaengensis, and is not present at the Cambrian–Ordovician boundary (COBWG). 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.[4]
Iapetus Ocean, an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago)
^Iapetonudus (N. gen.) and Iapetognathus Landing, unusual Earliest Ordovician multielement conodont taxa and their utility for biostratigraphy. Robert S. Nicoll, J.F. Miller, G.S. Nowlan, J.E. Repetski, and Raymond L. Ethington, Brigham Young University Geology Studies, 1999, volume 44, pages 27–101
^The conodont Iapetognathus and its value for defining the base of the Ordovician System. Frederick Miller, John E. Repetski, Robert S. Nicoll, Godfrey Nowlan and Raymond L. Ethington, GFF, Volume 136, Issue 1, 2014, pages 185-188, doi:10.1080/11035897.2013.862851
^Fredrik Terfelt; Gabriella Bagnoli; Svend Stouge (2011). "Re-evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP". Lethaia. 45 (2): 227–237. doi:10.1111/j.1502-3931.2011.00275.x.
