Sphenolithus pseudoradians Bramlette & Wilcoxon, 1967
Large (>12.0µm), strongly birefringent sphenolith having bladed compound apical spine, lateral cycle and a frustum shape proximal cycle.
The long-bladed compound apical spine has an axial median line at 0° and often with a short bifurcation at the distal end.
Sphenolithus pseudoradians differs from Sphenolithus radians Deflandre in Grassé,1952 by being large and having an apical spine with short bifurcation.
The first occurrence of Sphenolithus pseudoradians marks the NP19-NP20 boundary. Many people combined the above zones because they couldn't distinguish Sphenolithus pseudoradians from the long-ranging Sphenolithus radians. Reliable identification of these forms is only possible with the strict species concept.
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.
Deflandre, G., 1952. Classe des Coccolithophoridés. (Coccolithophoridae. Lohmann, 1902). In: Grassé, P. P. (ed.), Traité de Zoologie. Masson, Paris 439-470.
Bramlette & Wilcoxon, 1967
Cipero Section, Trinidad