Evidence for Low Temperatures and Biologic Diversity in Cretaceous High Latitudes of Australia

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Abstract
A diverse terrestrial biota inhabited polar latitudes during the Cretaceous, 105 to 130 Ma (million years ago), along what is now the southeast coast of Australia. This biota, from rocks in the Otway and Strzelecki groups, consisted of more than 150 taxa of vertebrates, invertebrates, and plants. Oxygen isotope ratios in diagenetic calcite suggest that mean annual temperatures were most likely less than 5°C, and rings present in the fossil araucarian-podocarp-ginko woods indicate seasonality. Southeastern Australia, thus, seems to have had a cool, seasonal, nontropical climate. Dinosaurs that have been recovered are up to five species and three genera of hypsilophodontids, all of which were endemic, and three species of theropods. The occurrence of Allosaurus sp. and labyrinthodont amphibians, which had become extinct elsewhere in the Jurassic, indicate that isolation may have allowed extended survival of these taxa in Australia. In that dinosaurs coped with high latitudes for at least 65 million years [Valanginian to Albian time in Australia and Campanian to Maastrictian time (80 to 65 Ma) in Alaska] suggests that cold and darkness may not have been prime factors bringing about the extinction of dinosaurs and some other groups at the Cretaceous-Tertiary boundary, unless they were prolonged.