Isespetrinesaspides foteinokentro Varol, 2025a
From the Greek Isespetrinesaspides, the equal stone shields – refer to equal size distal and proximal shields
Placoliths consist of distinctly striated, equal-sized, non-concave-convex distal and proximal shields comprising 28-32 segments and a smooth tube cycle. When viewed from the side, these placoliths resemble a UFO.
Optical Properties: The shields exhibit first-order greyish-white interference colours, while the tube cycle displays first-order white interference colours. Isespetrinesaspides exhibit length-fast (-) elongation and inclined laevogyre extinction line angles of 67° when measured on the tube cycle and shield on the distal side.
Isespetrinesaspides differ from other genera in the family Noelaerhabdaceae by having non-concave-convex shields of equal size that exhibit dextrogyre extinction lines. All species in Noelaerhabdaceae display laevogyre extinction lines, making their assignment to Noelaerhabdaceae questionable.
In the plan view, Isespetrinesaspides’ distal shield shows inclined extinction lines. In contrast, the genera in Coccolithaceae display constant extinction on their distal shield (vertical optic axis relative to the microscope stage).
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222