The conodont Iapetognathus and its value for defining the base of the Ordovician System

Abstract

Nicoll et al. (1999, Brigham Young University Geology Studies 44, 27–101) published the taxonomy of species of the ramiform conodont Iapetognathus Landing in Fortey et al. (1982, The Cambrian–Ordovician boundary: sections, fossil distributions, and correlations, National Museum of Wales, Geological Series No. 3, Cardiff, 95–129) and its ancestor Iapetonudus Nicoll et al., 1999. Cooper et al. (2001, Episodes 24, 19–28) used the First Appearance Datum of Iapetognathus fluctivagus Nicoll et al., 1999 to mark the base of the Ordovician System at Green Point, Newfoundland. Terfelt et al. (2012, Lethaia 45, 227–237) re-evaluated Iapetognathus at Green Point and made several taxonomic and stratigraphic conclusions, nearly all of which we refute herein.

Keywords::

• Iapetognathus
• Iapetonudus
• Clavohamulus
• Hirsutodontus
• Ordovician
• Green Point

Acknowledgements

We thank Tatiana Tolmacheva for a helpful review of the draft manuscript and for providing occurrences of Iapetognathus in Gornyi Altai, Russia. Robert Ripperdan provided the carbon-isotope profiles and correlations in Fig. 2.