Fossil group

Larger foraminifera (Nummulites, Assilina)

Foraminifera · Carboniferous – Recent

Large, complex-shelled benthic foraminifera — single-celled marine protists whose internally-partitioned tests grow big enough to see with the naked eye. Many hosted symbiotic algae and thrived on warm, well-lit carbonate shelves, where their shells piled up in such numbers that they build entire limestones. Their rapid evolution makes them key index fossils for shallow-marine Cenozoic strata.

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