Watznaueria paenepelagica

Coccolithus paenepelagicus Stover, 1966

Elliptical species of Watznaueria measuring greater than 8.0 µm in length and characterised by a closed central area.

The extinction angle measured on the distal side is typically about 67° on the distal shield, but it can not be measured in the tube cycle due to the oblique orientation of the tube cycle segments. The apparent angle between extinction on the tube cycle is 62°, corresponding to an obliquity angle of 28°. The locking cycle remains in constant extinction, forming a narrow dim suture between the shield and tube cycle.

Watznaueria paenepelagica differs from the similarly sized Watznaueria leesiae in the optical properties of the tube cycle. Both species exhibit inclined extinction in the tube cycle; however, the extinction angle cannot be determined in Watznaueria deflandrei owing to the oblique orientation of its segments. In the holotype of Watznaueria leesiae, the extinction angle is approximately 2°, provided that the specimen was not rotated during preparation of the plate montage.

The two species further differ in the optical properties of the locking cycle. In Watznaueria paenepelagica, the locking cycle remains in constant extinction and is expressed as a narrow, dim suture separating the shield from the tube cycle. In Watznaueria leesiae, the locking cycle exhibits interference colours, producing a transitional boundary between the tube cycle and the shield.

Watznaueria paenepelagica is further distinguished from Watznaueria deflandrei by its larger size (>8.0 µm), although both species display broadly similar extinction characteristics.

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Stover, L. E. 1966. Cretaceous coccoliths and associated nannofossils from France and the Netherlands. Micropaleontology 12(2): 133-167.

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