Calcidiscineae
Diagnosis
Circular to elliptical placoliths with single-layered distal and proximal shields. These shields feature open central areas with or without internal structures, or closed central areas. Under light microscopy (plan view), the single-layered distal shield exhibits constant extinction, indicating a vertical optic axis relative to the microscope stage. The single-layered proximal shield displays inclined extinction with a length-fast (-) elongation or, alternatively, constant extinction.
Remarks
Suborder of Coccolithales
References
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222
