Stoverius msakyae
Set number: 1857
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10µm
Rotelapillus msakyae Lees, 2007
Corollithion msakyae (Lees, 2007) Varol, 2025a
A narrowly elliptical species of Stoverius has four arms forming a symmetrical diagonal cross, creating an acute angle along the short axis in the central area.
The outer protolith wall remains in constant extinction, indicating that the optic axis (c-axis) is oriented perpendicular to the microscope stage. In contrast, the inner protolith wall displays a white interference colour, whereas the radial bars exhibit whitish-grey interference colours all in plan view under cross polars.
This species is assigned to Stoverius based on the absence of diagnostic features of Rotelapillus, notably the protruding short spines at the distal end of the wall, and on its elliptical outline, which contrasts with the hexagonal morphology characteristic of Corollithion.
Lees, J. A. 2007. New and rarely reported calcareous nannofossils from the Late Cretaceous of coastal Tanzania: outcrop samples and Tanzania Drilling Project Sites 5, 9 and 15. Journal of Nannoplankton Research 29(1): 39-65.
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222