Sphenolithus milanetti

Sphenolithus milanetti Maiorano & Monechi, 1998

Valid because described as a new species not amended from invalid citation

Sphenolithus sp. 1 Olafsson, 1989

Sphenolithus milanetti Fornaciari et. al., 1990 [nomen nudum] Invalid ICN Art. 41

Sphenolithus pospichalii Jiang, Wang, Varol, da Gama & Blaj, 2016

Medium to large size (6.0-12.0µm) plier-like species of Sphenolithus have three distinct cycles of segments. The proximal cycle in the semi-open umbrella shape predominates the lateral cycle and the three-bladed apical spine. The boundary between the hollow semi-open umbrella shape proximal cycle and the lateral cycle is flat and aligned with the short axis of species. The segments of the small lateral cycle are always aligned with the length at 0°. The monolithic looking three-bladed apical spine is extinct (dim) at 0° and shows maximum birefringence at 45 ° in cross-polarized light.

Sphenolithus milanetti is easy to identify from Sphenolithus heteromorphus Deflandre,1953 and Sphenolithus preasii Bergen & de Kaenel in Bergen et al., 2017 by having a semi-open umbrella shape proximal cycle and short lateral cycle aligned with the length of the sphenolith at 0°. The proximal cycle is a short frustum shape in Sphenolithus heteromorphus but an open umbrella shape in Sphenolithus preasii.

Bergen, J. A., de Kaenel, E., Blair, S. A., Boesiger, T. M., Browning, E., 2017. Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research 37(2-3), 77-112.

Deflandre, G., 1953. Hétérogénéité intrinsèque et pluralité des éleménts dans les coccolithes actuels et fossiles. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences, Paris 237, 1785-1787.

Fornaciari, E., Raffi, I., Rio, D., Villa, G., Backman, J., Olafsson, G., 1990. Quantitative distribution patterns of Oligocene and Miocene calcareous nannofossils from the western equatorial Indian Ocean. Proceedings of the Ocean Drilling Program, Scientific Results 115, 237-254.

Jiang, S., Wang, Y., Varol, O., da Gama, R. O. B. P., Blaj, T., 2016. A new early Miocene Sphenolithus species from the South China Sea. Journal of Nannoplankton Research 36(1), 61-63.

Maiorano, P., Monechi, S., 1998. Revised correlations of early and middle Miocene calcareous nannofossil events and magnetostratigraphy from DSDP Site 563 (North Atlantic Ocean). Marine Micropaleontology 35(1989), 235-255

Olafsson, G., 1989. Quantitative calcareous nannofossil biostratigraphy of upper Oligocene to middle Miocene sediment from ODP Hole 667A and middle Miocene sediment from DSDP Site 574. Proceedings of the Ocean Drilling Program, Scientific Results 108, 9-22.