Early Ordovician

Early Ordovician

The Early Ordovician is the first part of the Ordovician period. It happened a very long time ago, from about 486.85 to 471.3 million years ago. It came after the Cambrian period and was followed by the Middle Ordovician.

During the Early Ordovician, many new kinds of animals began to appear in the oceans. Two main ages make up this time: the Tremadocian and the Floian. Scientists study rocks and fossils from this time to learn about how Earth and its living things were changing.

The Early Ordovician is divided into smaller time slices using fossils like conodonts and graptolites. Some areas have their own special zones. For example, the Tetragraptus approximatus Zone is used in the UK and Australia, while the Didymograptus protobifidus Zone is used in North America, Australia, and Baltoscandia.

In North America, scientists use conodont zones to study Early Ordovician rocks. In Asia, graptolite and conodont zones help divide the time. In Australia, the Early Ordovician matches local stages such as the Lancefieldian, Bendigonian, Chewtonian, and lower Castlemainian.

The Early Ordovician had many interesting ancient life forms. In places like Argentina, scientists found tiny microfossils called calcisphers or calcitarchs. These were likely simple algae. Another type of algae, Amsassia, lived along the coasts of ancient lands such as Laurentia and Cuyania.

Echinoderms, star-like animals, became more diverse during this time. New groups appeared, such as starfish-like animals, sea cucumbers, and feather stars. Fossils of these and other creatures have been found in Utah, Morocco, and France. Large arthropods like Aegirocassis, which could grow over 2 meters long, also lived during this period. Other interesting fossils include sponges, worms, and trilobites, showing the variety of life in the Early Ordovician oceans.

The Early Ordovician was also a time when many types of sea creatures appeared and became more varied. This was one of the biggest times for new life in Earth's history, along with the Cambrian explosion. During this event, many different kinds of tiny sea plants and animals, as well as sea life that lived on the ocean floor, began to spread and change. Scientists have found special rock layers with fossils from this time in South Korea.