At the beginning of the Mesozoic, Gondwana formed the southern part of the single continent Pangaea. When Pangaea split about 200 million years ago, Gondwana began its own isolated journey and gradual break-up into the landmasses we know today – Australia, South America, Africa, India, Madagascar, Antarctica and New Zealand. This palaeo-history is recorded in identical rocks and fossils found across these modern landmasses. When we reconnect them as they were in the past, the rocks and fossils clearly match up.
Australian dinosaurs lived ‘on the edge’ at the far eastern end of East Gondwana, which at the time lay well to the south of Australia’s present position.
While the global climate was warm and humid during the Cretaceous, Australia position so far south at the time meant that it experienced much cooler temperatures. One form of evidence we have for cool temperatures in Australia at the time comes from the presence of glendonites, Glendonites resemble spiky balls of rock. Originally they were formed by the mineral ikaite, which only occurs in near-freezing temperatures. However, later this ikaite was replaced by other minerals as the rock was buried and heated over time. Many parts of Australia would have also experienced the extremes of daylight found in high latitudes today. Much of central Australia was submerged under a shallow inland (‘epicontinental’) sea, leaving the higher areas as large but isolated islands for much of the Cretaceous. This unusual habitat along with Australia’s geographic isolation during the latter part of the Mesozoic meant that many of Australia’s dinosaurs evolved as unique species adapted to extreme conditions.