The Ordovician Period

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The Ordovician Period

During this period, the area north of the tropics was almost entirely ocean, and most of the world's land was collected into the southern supercontinent Gondwana. Throughout the Ordovician, Gondwana shifted towards the South Pole and much of it was submerged underwater. During the Ordovician, most of the world's land (southern Europe, Africa, South America, Antarctica, and Australia) was collected together in the super-continent Gondwana. By the late Paleozoic, continental collisions formed the supercontinent Pangaea.


The Ordovician period lasted for almost 45 million years. Beginning 488.3 million years ago and ending 443.7 million years ago.

Fossils help scientists infer about the past when they are examined. Scientists could gather clues and facts about the fossil like: "Where did it come from?" or "How did this organism move?" Fossilized teeth can help us understand what a prehistoric creature ate and the bones help us understand how they moved. The location of the artifacts and fossils can tell us what the area was like in the past. Using radioactive dating, scientists can determine when the fossil lived. And now that we have more advanced technology, we can infer about what the organism looked when it roamed the Earth.

The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. Fish, arthropods, amphibians and reptiles all evolved during the Paleozoic. Plant life began to transition onto land during the Silurian and Devonian periods. During the Triassic period, Pangaea was generally dry. In the early Mesozoic dinosaurs began appearing. As the temperatures in the seas increased, the larger animals of the early Mesozoic gradually began to disappear while smaller animals of all kinds, including lizards, snakes, and perhaps primates, evolved. The Cenozoic era marked the beginning of the "age of mammals". The planet was dominated by small fauna including mammals, birds, and reptiles. These three eras and their periods have many similarities and differneces. For example, as time went on, animals evolved to adapt to new climates. But, during most of the Paleozoic era, most life happened underwater. During the periods between the start of the Mesozoic and Cenozoic eras, life had evolved and transitioned onto land.

The Ordovician Period

Trilobite fossil

The Ordovician is best known for its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts, or early vertebrates. Despite the appearance of coral fossils during this time, reef ecosystems continued to be dominated by algae and sponges, and in some cases by bryozoans. However, there apparently were also periods of complete reef collapse due to global disturbances. The extinctions occurred approximately 447–444 million years ago and mark the boundary between the Ordovician and the following Silurian Period. At that time all complex multicellular organisms lived in the sea, and about 49% of fauna disappeared forever. Brachiopods and bryozoans were greatly reduced, along with many trilobite, conodont and graptolite families.





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