ABSTRACT: Sphenolithus avis n. sp. is a new calcareous nannofossil species described in materials recovered from Ocean Drilling Program (ODP) sites in the equatorial region. Sphenolithus avis n. sp. is small to medium size with a short tapered apical spine and a large flaring proximal cycle. Its stratigraphic range spans Martini Zones NP23 to NP25, and it is widely distributed in three different equatorial regions, ranging from marginal to deep-sea locations. Because of its relatively short range and global distribution, S. avis n. sp. is a potential secondary Sphenolithus zonal marker in the upper Oligocene.