Unusually large cells appear
Spheres up to a third of a millimetre across turn up in 3.2-billion-year-old shale — far bigger than bacteria.
- When
- Known to
- ± 50 million years
- Era
- Mesoarchean, Archean
Well-documented spheroidal vesicles 30 to 300 micrometres wide occur in Mesoarchean shales, an order of magnitude larger than typical prokaryotes. Size alone does not make them eukaryotes, and no internal structure survives, so what they were remains open. They are among the few morphological fossils from this interval that are broadly accepted as biological.