The Fossil History of Australia

Mesozoic Era
- Cretaceous Period

(from the Latin Creta - meaning chalk)

(144 to 86.4 million years ago)

During the Cretaceous period, Australia separated from the Gondwana landmass and, at first, had an inland sea, which later formed the Great Artesian Basin. The climate was warm, with considerable volcanic activity, although Australia was still close to the polar region.

Most of the dinosaur fossils found on Australia come from this period. Although many types of dinosaurs, some quite small and others large, were known, very few full skeletons have been discovered so far. The types included the theropod called Allosaurus, which also existed in other parts of the world, and the more unusual hypsilophodontids, small dinosaurs that walked on two feet.

Small turtles first appeared at this time, and large marine reptiles continued to dominate the seas over and around Australia. Ammonites were still prolific but became extinct at the end of the Cretaceous period. Numerous fossil remains of fish and lungfish exist from this time.

Reptiles able to fly were known as the pterosaurs, and these could grow to a very large wing span. Some evidence exists of the presence of birds, mainly in traces of their feathers.

Ptesosaur

Some very beautiful fossils of marine animals and early bird forms are found around the opal fields of New South Wales some with opal forming part of the remaining structure. There is also evidence of monotreme mammals from this area, including the ancestors of the platypus.

The flora of conifers, ferns and cycads still covered the landscape as they did in the Jurassic time. A most significant step for the flora of Australia was the appearance of angiosperms, flowering plants. This was detected from microscopic fossil remains of pollen. It is likely that the relationship between flying insects and these plants began at this time.

Towards the end of the Cretaceous period, the Australian landmass rose above the inland sea, which dried up. The general shape of the continent began to look like the area we see today.

At the end of the Cretaceous period, the dinosaurs, marine reptiles, and many other groups became extinct. There are several theories for this, including an asteroid hitting the earth, volcanic activity on a large scale, or climate which changed to a much cooler time. Whatever caused the mass extinction, this event ended the Mesozoic era, in which the reptiles and dinosaurs had been the dominant groups.

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