Sphenolithus radians Deflandre in Grassé, 1952
Sphenaster Wilcoxon, 1970.
Nannoturbella Brönnimann & Stradner 1960
Dart shape nannolith with a concave base. All the segments radiate from a common origin within three cycles.
Sphenolithus is easily distinguished from Furcatolithus Martini (1965) by having three cycles of segments whilst later has only two cycles of segments.
Species of Sphenolithus are identified based on the overall shape, heights, width and the construction of proximal, lateral and apical cycles and their ratios.
Species with biconical clustered apical cycle
Species with a bouquet of flower shape clustered apical cycle
Species with diverging/radiating apical cycle
Species with three-bladed apical spine
Species with possibly three-blade apical spine (having parallel extinction)
Species with four or more bladed apical spine
Species with the duolithic apical spine which are dark at 45° [inclined extinction]
Species with vestigial apical cycle
Brönnimann, P. & Stradner, H., (1960): Die Foraminiferen- und Discoasteriden-zonen von Kuba und ihre interkontinentale Korrelation. - Erdoel-Zeitschrift. 76(10): 364-369.
Deflandre, G., (1952): Classe des Coccolithophoridés. (Coccolithophoridae. Lohmann, 1902). In, Grassé, P. P. (ed.) - Traité de Zoologie. Masson, Paris 439-470.
Martini, E., (1965): Mid-Tertiary calcareous nannoplankton from Pacific deep-sea cores. - Colston Papers. 17: 393-411.
Wilcoxon, J. A., (1970b): Sphenaster new genus, a Pliocene calcareous nannofossil from the tropical Indo-Pacific. - Tulane Studies in Geology and Paleontology. 8: 78-81.