Nannotax Enabling nannofossil research

Description: Radially symmetrical nannoliths formed from one to several separate cycles of elements that radiate from a common centre or axis. Includes disc-like (discoasters), stellate (discoasters), cylindrical (fasciculiths, helioliths and sphenoliths) and conical (fasciculiths and sphenoliths) morphologies.

Remarks: Hay (1977) described the Order Discoasterales as a broad taxonomic group that included most radial and stellate Mesozoic and Cenozoic nannoliths. Used here as a narrower taxonomic concept that incorporates the type family, the Discoasteraceae, together with the other radially symmetrical Paleogene nannolith groups, the Heliolithaceae, Fasciculithaceae and Sphenolithaceae, which originated within four million years of one another and have common morphological features suggesting phylogenetic affinity.

Range: The Heliolithaceae and Fasciculithaceae were predominantly upper Paleocene groups, but the Sphenolithaceae continued well into the Neogene.