Trachylithos nuryaziciae

Trachylithos nuryaziciae Varol, 2025

The rough-appearing, large, elliptical species of Trachylithos features a distally protruding double tube cycle that blocks the entire central area and impinges on the distal shield. The outer tube cycle causes a rough appearance. The distal shield is made up of about 35-45 segments. The locking cycle is visible in the side view.

In honour of Nur Yazici, London, United Kingdom

Diameter of distal shield = 10.39 μm; Diameter of proximal shield = 8.18 μm (upper layer) and 6.74 μm (lower tier); Diameter of tube cycle = 6.45 μm (outer) and 4.43 μm (inner); Height = 4.58 μm; all measurements from the side view.

Optical Properties: In the plan view, the smooth inner tube cycle and the lower tier of the proximal shield show inclined extinction lines. The inner tube cycle displays length-slow (+), whereas the outer tube cycle displays length-fast (-) elongation. The distal shield and the upper tier of the proximal shield are in constant extinction because their optic axis is vertical relative to the microscope stage in the plan view. Observing and measuring extinction lines can be challenging. In the side view, the tube cycles, the distal shield, and the proximal shield’s upper tier exhibit length-slow (+) elongation, whereas the lower tier of the proximal shield shows length-fast (-) elongation.

Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222