Helicosphaera

Coccosphaera carterii Wallich, 1877

Helicopontosphaera Hay & Mohler 1967

Coccolith has a helical flange, proximal plate and symmetrical blanket, which is birefringent under polarized light that covers the entire distal surface of the flange (Type III, Helicosphaera carteri type blanket).

Blanket Type of Helicosphaera: Symmetrical blanket covers the entire distal surface of the flange (Type III, Helicosphaera carteri type blanket).

Flange Termination:

• Often expanded flange termination as in Helicosphaera carteri
• rarely flush flange termination as in Helicosphaera ampla
• occasionally truncated flange termination as in Helicosphaera acuta

Bar: a structure spanning the central opening

• Conjuct bar: formed from the elements of pelaga [optical continuation of pelaga] as in Helicosphaera bownii

• Disjunct bar: disconnected from the pelaga (optically discontinuous) as in Helicosphaera intermedia

The orientation of the bar:

• Inverse bar: diagonal bar having a frontal/anterior end at the side of flange termination as in Helicosphaera acuta (conjunct inverse). Helicosphaera species with disjunct inverse bar is not observed.
• Traverse bar: bar aligned with the short axis of coccolith as in Helicosphaera mediterranea (conjunct traverse) and Helicosphaera truempyi (disjunct traverse)
• Oblique bar: diagonal bar having a latter/posterior end at the side of flange termination as in Helicosphaera wallichii (conjunct oblique) and Helicosphaera intermedia (disjunct oblique).

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.

Hay, W. W., Mohler, H. P., Roth, P. H., Schmidt, R. R., Boudreaux, J. E., 1967. Calcareous nannoplankton zonation of the Cenozoic of the Gulf Coast and Caribbean-Antillean area, and transoceanic correlation. Transactions of the Gulf-Coast Association of Geological Societies 17, 428-480.

Kamptner, E., 1954. Untersuchungen über den Feinbau der Coccolithen. Archiv für Protistenkunde 100, 1-90.

Wallich, G. C., 1877. Observations on the coccosphere. Annals and Magazine of Natural History 19, 342-350.