Nannotax Enabling nannofossil research

Distinctive group of Late Oligocene to Mid Miocene Helicosphaera species, with flange terminating abruptly rather than expanding into a wing. Blanket confined to central area, so flange is dark is dark in cross-polars. Central area openings usually show inverse orientation (i.e. they point toward the flange termination). Bar conjunct with rim.

Drawing	Outline description	Range
	H. recta - large pores separated by horizontal bar	NP24-NN1
	H. obliqua - tear-drop shaped with narrow, distinctly oblique, openings	NP24-NN6
	H. perch-nielseniae - more rectangular shape than obliqua	NP23-NN6
	H. orientalis - small, quadrate, with tow large openings	NN6-11