Ordovician Period

Cambrian Period - Ordovician Period - Silurian Period

The Ordovician is the second period of the Paleozoic Era and of the Phanerozoic Eon. The period begins with the Cambrian-Ordovician extinction event and ends with the Ordovician-Silurian extinction event. While life on land existed during the Ordovician, as it had since the Cambrian Period, there was little diversity among non-aquatic species. During the extinction event that ended the period, sixty percent of marine genera went extinct.

Early in the Ordovician, sea levels reached their highest point in the planet's history. The supercontinent of Gondwana moved during the Ordovician from equatorial regions towards the South Pole. Baltica and Laurentia, two of the three other continents of the Cambrian, slowly moved nearer to each other during the period, while Siberia would remain distinct. A small fifth continent, Avalonia, would separate from Gondwana during the period. Avalonia corresponds to part of modern day Canada, the United Kingdom, and the United States. The Taconic orogeny had begun during the Cambrian, and persisted throughout the Ordovician and into the Silurian, and created an arc of volcanic islands that eventually collided with Laurentia to form the Appalachian Mountains. The Iapetus Ocean shrank as Baltica and Laurentia drew near, and the Rheic Ocean formed between Avalonia and Gondwana.

The nautiloid Cameroceras became the planet's apex predator, while brachiopods, cephalopods, and crinoids were abundant in the Ordovician marine environment. Molluscs first became common during the Ordovician, and the first sharks evolved during this period.

The Ordovician is subdivided into three epochs: the Early Ordovician, the Middle Ordovician, and the Late Ordovician.

Ordovician Timescale:

Ordovician Period - 485.4-443.8 MYA

-Early Ordovician Epoch - 485.4-470 MYA

--Tremadocian Age - 485.4-477.7 MYA

--Floian Age - 477.7-470 MYA

-Middle Ordovician Epoch - 470-458.4 MYA

--Dapingian Age - 470-467.3 MYA

--Darriwilian Age - 467.3-458.4 MYA

-Late Ordovician Epoch - 458.4-443.8 MYA

--Sandbian Age - 458.4-453 MYA

--Katian Age - 453-445.2 MYA

--Hirnantian Age - 445.2-443.8 MYA