Tertiary: 65–2.6 million years ago*

Modern animal groups

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The Tertiary environment was similar to the Daintree National Park.
Image: Juergen Sack
Source: istock

65 million years ago.
Image: Creator Ron Blakey. Altered by Cally Bennet and Fons VandenBerg
Source: Colorado Plateau Geosystems

Tertiary

Following the extinction of the dinosaurs, the surviving birds, mammals and reptiles diversified. Drifting continents continued to change the face of the planet, building mountains, creating new ocean currents and causing major climate changes.

The extinction of the giant marine reptiles left the niche of large ocean predators vacant. In the warm oceans, early whales evolved from hoofed, deer-like land mammals that lived in shallow water. When Australia and South America separated from Antarctica, cool water began circulating around the pole. Plankton thrived there and plankton-feeding baleen whales evolved.

Tropical and temperate forests covered large areas of Australia. The area we know as Bass Strait was largely dry land with floodplains, lakes and peaty swamps bordered by forest, and seams of brown coal began to form. During several periods of significant volcanic eruptions in Victoria, lava flows covered parts of western and central Victoria. Australia’s marsupial mammals began to diversify in isolation, evolving into carnivores, herbivores and scavengers. High sea levels frequently covered parts of the continent and the skeletons of bryozoans, echinoderms, molluscs and other animals that thrived here created the large volume of limestone deposits that now form most of the coast along southern Australia. 

* The Tertiary is an informal term originally given to this period of time in the 1800s. While not recognised by the International Commission of Stratigraphy, it is still in common use to describe collectively the Paleocene, Eocene, Oligocene, Miocene and Pliocene epochs.