The Fossil History of Australia

Paleozoic Era - Ordovician Period

(named in 1879 by Charles Lapworth for a Celtic tribe)

(505 to 434 million years ago)

Australia still part of the Gondwana land mass and was initially near the equator but moved southwards during this period. Many parts of Australia were under water at this time. A significant event in this period was the colonization of the land by early land plants, which are detected mainly as microfossils.

Brachiopods and trilobites both continued their presence in the Ordovician Period, although the trilobites were very much reduced in number and thus allowed the development of other species.

Fossils indicate the presence of new life in the form of conodonts, whose remains are tooth like, from microscopic to just over one inch long. Crinoids, also called "sea lilies", were first noticed from this time. Crinoids often grew in clusters. Relatives of crinoids may be seen in the waters around Australia (eg Exmouth in W.A.) and are often a feature of diving tours.

The remains of jawless fish who kept their mouths open, were found in several parts of the world including Australia. These are some of the earliest vertebrate fossils found.

Graptolites, which were present in the Cambrian period, became one of the main species of this time and the various developments are used to indicate differing time zones within the Ordovician period. Graptolites were marine animals, which lived in colonies, inside hollow tubes, mostly floating freely in the ocean, and sometimes attached to the sea floor.

Towards the end of the Ordovician period, the world experienced a colder climate, and the sea level dropped. Many species became extinct and a new period began.


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