Watznaueria parvobliqua
Set number: 1777
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10µm
Watznaueria parvobliqua Varol, in prep.
Small to medium-sized species of Watznaueria (<8.0 μm) are characterised by an elliptical placolith in which the tube cycles are obliquely orientated relative to the long axis of the shield, with a rotation angle of approximately 28°. The distal shield is slightly larger than the proximal shield. A dim cycle separates the tube cycle from the shields.
From Latin parvus, meaning small, and obliquus, meaning oblique or slanting, referring to the smaller size of the coccolith and the oblique orientation of the tube cycles relative to the long axis of the shield.
Under cross-polarised light in plan view, the species displays white interference colours, inclined extinction lines, and length-fast (–) elongation. On the distal side, the extinction angle in the shields is approximately 69°. This angle cannot be measured directly in the tube cycles because of the oblique orientation of their constituent elements; however, the apparent angle between extinction directions in the tube cycle is approximately 71°, corresponding to an element obliquity of approximately 19°.
The locking cycle remains in constant extinction and produces a dim boundary between the tube cycle and the shield.