Ordovician

The Ordovician Period lasted from 485 to 443 million years ago, a time when global oceans experienced an unprecedented surge in biodiversity known as the Great Ordovician Biodiversification Event. Marine life tripled in variety, dominated by trilobites, brachiopods, snails, and massive, shelled cephalopods that acted as the apex predators of their time. The first primitive, jawless fish also continued to evolve in these shallow, tropical seas. On land, the very first adventurous organisms - likely simple, moss-like plants and fungi - began clinging to damp shorelines. The period ended catastrophically due to intense tectonic activity and the migration of the supercontinent Gondwana to the South Pole. This movement triggered a massive ice age that locked up seawater into glaciers, causing sea levels to plummet. The resulting environmental shock caused a severe mass extinction, wiping out roughly 85 percent of marine species.