The Silurian period was the time when reefs got their act together, grew really big and created a completely new type of ecosystem for marine life. Silurian reefs weren't built by the same types of coral around now, but by a host of tabulate and rugose corals, crinoids and sponges. As the Ordovician ice ages ended, sea levels rose, making the Silurian a period of extensive seas. Bony fish made their first appearance. Meanwhile, on land, plants became more established, and grew in a zone along the edges of rivers and lakes to give Earth its first riverine and wetland habitats.
Ordovician-Silurian mass extinction
443 million years ago
Ended: 417 million years ago
Reconstruction of the Earth in the Archean era, 3.8 billion - 2.5 billion years ago. Credit: Dr Ron Blakey, NAU Geology.
During this period the following extinction level events are thought to have occurred.