Mikriexoterikiaspida fionajacovidesiae
Set number: 1760
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10µm
Mikriexoterikiaspida fionajacovidesiae Varol, 2025a
The small, concave-convex circular placolith comprises single-tiered, narrower distal and broader proximal shields , and a distally protruding inner tube cycle that entirely closes the central area. The distal shield consists of about 22-28 segments.
In honour of Fiona Jacovides, Gloucester, United Kingdom
Diameter of distal shield = 5.32 μm; Diameter of proximal shield = 4.58 μm; Diameter of tube cycle = 2.00 μm; Height = 2.27 μm; all measurements from the side view
Optical Properties: In the plan view, the shields and the inner tube cycle exhibit inclined extinction lines and length-fast (-) elongation. In contrast, the outer tube cycle shows constant extinction because the optic axis is vertical relative to the microscope stage. The extinction lines are dextrogyre on the distal side, and their typical angle is about 73° on the distal shield and 48° on the tube cycle.
The extinction lines of Mikriexoterikiaspida fionajacovidesiae are dextrogyre on the distal side, similar to Cyclagelosphaera, but differ from it by having a narrower distal shield.
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222
Holotype
Mikriexoterikiaspida fionajacovidesiae
Varol, 2025a
Late Paleocene
DSDP Leg 25, Site 245, Mozambique Channel (Davie Ridge), Indian Ocean