Nannotax Enabling nannofossil research

Description: 6-rayed discoaster with trifurcate ray-tips. Similar to D. variabilis but with proximal ray tip extensions giving trifurcate appearance to ray tips. Usually slightly concavo-convex with well-developed central area and showing strong differentiation of proximal and distal surface.

Remarks: In LM through focusing is often needed to see the ray tip extensions. D. surculus, like D. variabilis, varies considerably in size, and in ray tip morphology. It has not, however, been subdivided.

Range: Common from NN11A to top NN17. Its last occurrence is used as a datum, the first occurrence is not since it is rather gradational.