The Ordovician period was dominated by marine life, with a quadrupling of marine fauna genera and an explosion of bioeroding organisms. Arthropods were the largest organisms, including the fearsome eurypterids. Trilobites were present but their diversity was reduced by an extinction event. The first vertebrates, including simple fish, evolved during this period.
The Ordovician period is the second geological period of the Paleozoic era, which constitutes the last 542 million years of life on Earth, the period during which complex multicellular organisms appear in the fossil record. The Ordovician period spans from about 490 to 440 million years ago. It is preceded by the Cambrian period and followed by the Silurian period. During this period, the Earth’s biosphere built on the evolutionary successes of the Cambrian period. The number of genera of marine fauna quadrupled, and toward the end of the Ordovician period, the intensity and diversity of bioeroding organisms exploded, leading to fewer well-preserved fossils than before.
During the Ordovician period, marine life dominated. There were simple plants and fungi on the land, but otherwise not much. The southern continents were aggregated into a supercontinent called Gondwana, which began near the equator and eventually moved to cover the South Pole. The seabed was relatively warm and shallow, making it possible for numerous marine organisms to grow. Eurypterids, huge aquatic scorpions whose closest relative is the horseshoe crab, were among Earth’s most fearsome predators at the time. The largest eurypterid species, Pterygotus, was the largest artopod ever to have lived, up to 2m in length. Arthopods in general were the largest organisms during the Ordovician.
Trilobites were present in large numbers, though their diversity was severely reduced by an extinction event that separated the Ordovician period and the Cambrian period that preceded it. This extinction wiped out about half of all marine fauna, including the first apex predator, Anomalocaris, the “strange crayfish.” Ammonites were numerous in the oceans, while the organisms that built coral reefs were well established.
The first vertebrates existed during the Ordovician period, but they were not numerous. They originally evolved during the Cambrian Period. These included simple fish, especially the jawless fish (agnathan), some similar in appearance to tube-like lampreys, others more similar in appearance to modern fish. The fish began to evolve armor during this time.
Protect your devices with Threat Protection by NordVPN
