Diplotsekouri francisjosephii Varol, 2025
From the Greek diplo tsekouri, the double-headed axe, refers to its shape.
Diplotsekouri is characterised by having two fragile, distinctly unequal blades and a ridge.
Optical Properties: The wider blade displays first-order whitish-grey interference colours (weakly birefringent) in a natural settling profile (plan view). Diplotsekouri displays parallel extinction (extinction angle is 0°) and exhibits length-fast (-) elongation.
Diplotsekouri has weakly birefringent, distinctly unequal blades that show first-order whitish-grey interference colours in the plan view, whereas Triquetrorhabdulus has strongly birefringent, equal or slightly unequal blades that show first-order white to yellow interference colours in the plan view. Diplotsekouri is distinguished from Velonalithus and Orthorhabdus because it exhibits length-fast (-) elongation. Orthorhabdus is further differentiated by having a truncated at one end and an inclined extinction, whereas Diplotsekouri has pointed ends and a parallel extinction. Pennalithus has a vertical optic axis relative to the microscope stage that goes to constans extinction in a natural settling position (plan view).
The above optical and morphological distinguishing features help to identify Diplotsekouri and accurately differentiate it from closely related genera.
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222