The Fossil History of Australia

Paleozoic Era - Devonian Period

(named after Devonshire, England)

(408 to 354 million years ago)

During the Devonian period, Australia, still part of the great southern landmass of Gondwana, moved from its equatorial position to a more southerly position, becoming slightly cooler in the process.

The water still held the main interest with the arrival of fish with jaws, found both in the sea and in the inland waters. Many different unusual varieties of fish evolved, including the placoderm, which was covered in part by overlapping bones. Fossils of these have been found in Western Australia.

As well as the unusual varieties, we know that the ancestors of many of today's fish came from this era, including early sharks with quite restricted jaw movement compared to modern sharks.

Many species from earlier times, such as brachiopods and corals, continued on their evolutionary path. Some were nearly extinct, such as trilobites, which were decreasing rapidly, and graptolites which were not found after this time. In their place, were new-comers, such as ammonites, with their coiled shells, often showing ribs on the whorls radiating from the centre.

Ammonite fossil

The most interesting development in the Devonian period is the further colonization of the land. As well as the smaller plants of the Silurian time, forests of larger plants developed, including giant lycopods with stronger root systems. Early seed producing plants appeared towards the end of this period, and the ancestors of some current fern species are also found.

In the Devonian period, swamps were home to early amphibians, which were the earliest tetrapods, animals with four feet. Spiders and other insects were also found from the time onwards, and have been with us ever since.

Towards the end of the Devonian period, Eastern Australia and Tasmania, which had mostly been under water, now were dry land, with a land bridge between Tasmania and Victoria.

 

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