The small shelly fauna
Millimetre-scale shells, spines and plates flood the fossil record — animals discover hard parts.
- When
- —
- Duration
- 29 million years
- Known to
- ± 3 million years
- Era
- Neoproterozoic, Proterozoic
From about 539 million years ago sediments fill with tiny mineralised sclerites: tubes, cones, spines and scales belonging to early molluscs, brachiopods and animals whose affinities are still unknown. Many are pieces of larger scaly animals rather than whole organisms. Biomineralisation appears independently in numerous lineages within a few million years, which is itself one of the strongest signals that something fundamental had changed — most plausibly the arrival of predators worth armouring against.