Fossil group

Stromatolites (rare)

Microflora & algae · Archean – Recent

Layered, mound- or sheet-like structures built as microbial mats (usually cyanobacteria) trap and bind sediment grain by grain. Among the oldest evidence of life on Earth, they ruled shallow seas for billions of years before grazing animals appeared.

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