Nannotax

Description: Ray tips non-bifurcate and with marked proximal extensions giving it a distinctive concavo-convex form. The distal surface is usually rather smooth, proximal surface more sculpted with proximal boss often present. Probably evolved from D. exilis and first ocurrence is very gradational.

Remarks:

Range: ca, NN9 to 18. Very common NN11-18.

Variants:

Eu-discoaster brouweri ssp streptus Theodoridis, 1984 - with twisted proximal boss

Discoaster blackstockae Bukry, 1973 - 4-rayed form with inter-ray angles of 60 and 120° (this is a rare morphotype but such specimens are occasionally produced by most 6-rayed discoasters and do not seem worth describing as separate species)

Eu-discoaster giganteus Theodoridis, 1984 - very large, ray tips blunt but with long proximal extensions. If used should be recombined in Discoaster.