Fossil group

Nummulites mamillatus

Foraminifera · Paleocene – Oligocene

Large, coin- or lens-shaped benthic foraminifera whose tightly-coiled tests can reach several centimetres across. They swarmed on warm, shallow Paleogene shelves, hosting symbiotic algae, and piled up into "nummulitic limestone" — the very rock ancient Egypt’s pyramids are cut from. Successive species are premier index fossils of the Paleocene–Oligocene.

A broad fossil group rather than a single taxon — the units below record it among their fauna or flora.