The Breakup of the Supercontinent Pangaea

Figure 10.14 shows that Australia was once part of the supercontinent Pangaea. The southern portion of Pangaea (known as Gondwana or Gondwanaland) dominated the southern hemisphere. About 180 million years ago, Gondwanaland broke up to form the landmasses of Africa, South America, the Indian subcontinent, the Arabian Peninsula, Antarctica, Australia, and New Zealand. Consequently, any species that lived together on these landmasses were separated and evolved independently.

Figure 10.14 also shows the stages of the break up of the supercontinents and their drift to their present locations. Australia and New Zealand were particularly isolated, given their distance from other landmasses and the length of time they have been separated. Tectonic stability in Australia, climate patterns, and other factors over geologic time have contributed to the high number of unique species on the continent. Scientists estimate that more than 80% of Australia's mammals are not found anywhere else in the world. Although many of Australia's and New Zealand's species are descendants of those that existed on Gondwana, some flew there, floated there, or were brought by humans.