Ordovician Period 488 to 444 mya

The continents were mostly covered by shallow oceans during the Ordovician Period, named after a Welsh tribe.

Life was still limited to the sea, where molluscs and arthropods were the dominant forms. Fish, which probably first appeared during the Cambrian, continued to develop and we will discuss them here.

The Ordovician Period ended with a mass extinction.

Continents 450 mya

Earth 450 mya. Click here for key. Previous image. Next image. Image courtesy of TimeTrek

Gondwana moved into the south polar region, producing a glaciation, lowering of sea levels and perhaps producing the mass extinction which ended the period: the Ordovician-Silurian event.

Being far apart and not colliding with each other, the continents were low and mostly covered by shallow seas. These left many fossils.