Evidence for Low Temperatures and Biologic Diversity in Cretaceous High Latitudes of Australia
Evidence for Low Temperatures and Biologic Diversity in Cretaceous High Latitudes of Australia
复制标题
澳大利亚白垩纪高纬度地区低温和生物多样性的证据
作者：
P. Rich;T. Rich;B. Wagstaff;J. M. Mason;C. Douthitt;R. Gregory;E. Felton
一个多样化的陆生生物群居住在极地纬度地区在105至130 Ma（百万年前），沿着现在的澳大利亚东南海岸。这个生物群来自奥特韦和斯特泽莱茨基群的岩石，包括150多个脊椎动物、无脊椎动物和植物分类群。成岩方解石中的氧同位素比率表明，年平均温度很可能低于5摄氏度，而南洋杉-罗汉果-银杏树化石中的年轮表明其具有一定的季节性。因此，澳大利亚东南部似乎具有凉爽、季节性、非热带气候。已被发现的恐龙有五种和三个属的hypsilophodontids，所有这些都是地方性的，还有三种兽脚亚目。异特龙（英语：Allosaurus sp.）和无齿两栖动物的出现，在侏罗纪的其他地方已经灭绝，这表明隔离可能使这些分类群在澳大利亚的生存时间延长。恐龙在高纬度地区生存了至少6500万年[澳大利亚的Valaginian到Albian时间，阿拉斯加的Campanian到Maastrictian时间（80到65 Ma）]，这表明寒冷和黑暗可能不是导致恐龙和其他一些群体在南极-第三纪边界灭绝的主要因素，除非它们被延长。
A diverse terrestial biota inhabited polar latitudes during the Cretacous, 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, cnsisted 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 saonality. Southeastern Austalia, 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 surival of these taxa in Australia. In that dinosaurs coped with high latitude for at least 65 million years [Valaginian 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.