The list of things that happened start from bottom to top of the spiral are:

1. Earth formed.
2. Photosynthetic organisms appeared (e.g., blue-green algae).
3. Coral reefs appeared.
4. Vertebrates appeared (e.g., Hemicyclapsis).
5. More complex types of unicellular life appeared.
6. Multicellular soft-bodied animals appeared (e.g., worms and jellyfish).
7. Shelled invertebrates appeared (e.g., trilobites).
8. Marine animals and plants flourished.
9. Land plants appeared (e.g., Cooksonia).
10. Amphibians appeared (e.g., Ichthyostega).
11. Dinosaurs became extinct.
12. Small mammals appeared (e.g., Crusafontia).