Nannotax Enabling nannofossil research

Description: Ring shaped coccoliths without discrete shields.  Bright between cross-polars. Formed of two cycles of elements.  An inner (usually spinose) cycle of R-units is imbricate and wraps around the outer cycle of non-imbricate V-units.

Remarks: The possible interpretation of this coccolith morphology is that it evolved from a Coccolithus type placolith by reduction of the shields. 

Type species: Coronocyclus serratus Hay Mohler & Wade 1966 (subjective junior synonym of C. nitescens Kamptner 1963)

Description: Ring-shaped coccoliths with open central-area. No clear shield development, spines on distal side. Strongly birefringent.

Remarks:

Range: Palaeogene to NN6.

Synonyms:

• Coronocyclus serratus Hay, Mohler and Wade, 1966

Variant: Elliptical forms, with narrow rims, occur in NN5-6.