Fossil embryos
Microscopic clusters of dividing cells, preserved in phosphate, 600 million years old.
- When
- Known to
- ± 10 million years
- Era
- Neoproterozoic, Proterozoic
The Doushantuo Formation of South China preserves spectacular fossils of dividing cells at the two-, four- and eight-cell stages, some inside egg cysts. Their identity has been argued for decades, but cleavage patterns matching those of modern animal embryos indicate at least some are metazoan. Whatever they were, they are among the most detailed windows into the microscopic biology of the era.