Helicosphaerella truncata

Helicosphaera truncata Bramlette & Wilcoxon, 1967

Sub-rectangular helicolith has an asymmetrical blanket (Type II, Helicosphaerella recta type), truncated flange termination and a central area with a large central opening spanned by a traverse conjunct bar.

Helicosphaerella truncata differs from Helicosphaerella recta (Haq, 1966) Aubry, Liu, de Vargas, & Probert in Aubry & Bord (2009) by having larger central pores.

It is distinguished from Helicosphaerella robinsoniae (Bown & Dunkley Jones, 2012) Varol, n. comb. by having a conjunct bar rather than a disjunct bar

Aubry, M. -P., Bord, D., 2009. Reshuffling the cards in the photic zone at the Eocene/Oligocene boundary. In: Koeberl, C., Montanari, A. (eds), The Late Eocene Earth-Hothouse, Icehouse, and Impacts. Geological Society of America, Special Papers 452, 279-301.

Bown, P. R., Dunkley Jones, T., 2012. Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research 32(2), 3-51.

Bramlette, M. N., Wilcoxon, J. A., 1967. Middle Tertiary calcareous nannoplankton of the Cipero section, Trinidad, W.I. Tulane Studies in Geology and Paleontology 5, 93-131.

Haq, B. U., 1966. Electron microscope studies on some upper Eocene calcareous nannoplankton from Syria. Stockholm Contributions in Geology 15, 23-37.

Jafar, S. A., Martini, E., 1975, On the validity of the calcareous nannoplankton genus Helicosphaera. Senckenbergiana Lethaea 56, 381-397.