Brief history of the earth 3

rdovisium era (500 - 440 million years ago)

Ordovisium era characterized by the emergence of fish with no jaw (most vertebrate old) and some vertebrate animals that appear first as Tetrakoral, Graptolit, Ekinoid (Landak Sea), asteroid (Star Sea), Krinoid (Lili Sea) and Bryozona.

Alaga and coral reefs form a developed, where trilobit and Brakiopoda search for prey. Graptolit and Trilobit abundant, while Ekinodermata and start Brakiopoda spread.
when the overflow from the Ocean Ice era is part of the event this time. Gondwana-continent and other continents began closing the rift in the ocean of them.