Nannotax Enabling nannofossil research

Description: D. calcaris is a 6-rayed species with asymmetric ray tips. There are usually weak bifurcations on the distal side, one of which is underlain by a clockwise deflected (in distal view) proximal extension. The central area is small. A proximal knob is usually present.In many specimens the asymmetry of the ray tips is increased by the blade sloping away from the ray. Diagenetic overgrowth occurs preferentially on the blade, further increasing the asymmetry. The overgrown forms are sometimes distinguished as D. neohamatus.

Remarks: D. calcaris occurs in the NN9 to NN11A interval and seems to be associated with the evolution of D. brouweri from D. exilis, it can be hard to differentiate it from either of these species. D. hamatus is a 5-rayed species with the same structure, but it has a shorter and better defined range, hence differentiation of the two is important.

Original description:

Variant: D. neohamatus Bukry and Bramlette, 1969 - with more obviously asymmetric tips