The Arct ic hosts an extraordinary wealth of terrestrial fossil biotas of Late Cretaceous age representing a diverse and highly productive near-polar ecosystem that has no modern analogue. Compared to the rest of the...The Arct ic hosts an extraordinary wealth of terrestrial fossil biotas of Late Cretaceous age representing a diverse and highly productive near-polar ecosystem that has no modern analogue. Compared to the rest of the Late Cretaceous Maastrichtian plant diversity was at its lowest and the temperature regime the coolest, yet the semi-open forests supported a rich dinosaur fauna made up of a wide range of body sizes and feeding strategies. The combination of mild winter temperatures and continuous darkness lasting several months imposed severe constraints on primary productivity. Plant survival strategies involved almost universal winter loss of foliage, which in turn limited food supply for non-migratory overwintering herbivorous animals. A combination of leaf form and tree ring studies has been used to quantify year round variations in temperature and determine the tim-ing of spring bud-break and autumnal leaf fall. While Maastrichtian winter temperatures were cold enough （down to - 10°C for brief intervals） for frequent frosts and snowfall, summer temperatures were cool but highly variable and at -830N along the north Alaskan coast frequently fel l below ＋ 10°C . Theropod egg shell frag-ments at - 76° N in the Maastrichtian of Northeastern Russia may indicate that dinosaur reproduction took place in the Arctic ecosystem, as distinct from taking place at lower latitude breeding grounds reached by migration. This raises the question of nest management and specifically the maintenance of incubation temperatures, and the duration of incubation. Of critical importance to year-round residency is the timing of hatching and juvenile care before winter darkness set in, temperatures fell to near freezing and food resources became limited.展开更多
Recent studies demonstrate that many avialan features evolved incrementally prior to the origin of the group,but the presence of some of these features,such as bird-like brooding behaviours,remains contentious in non-...Recent studies demonstrate that many avialan features evolved incrementally prior to the origin of the group,but the presence of some of these features,such as bird-like brooding behaviours,remains contentious in non-avialan dinosaurs.Here we report the first non-avialan dinosaur fossil known to preserve an adult skeleton atop an egg clutch that contains embryonic remains.The preserved positional relationship of the adult to the clutch,coupled with the advanced growth stages of the embryos and their high estimated incubation temperatures,provides strong support for the brooding hypothesis.Furthermore,embryos in the clutch are at different developmental stages,suggesting the presence of asynchronous hatching—a derived feature even among crown-group birds—in non-avialan theropods.These findings demonstrate that the evolution of reproductive biology along bird-line archosaurs was a complex rather than a linear and incremental process,and suggest that some aspects of non-avialan theropod reproduction were unique to these dinosaurs.展开更多
基金the American Chemical Society Petroleum Research FundNorth Atlantic Treaty Organization,through Grants for International Scientific Cooperation 646184 and RG. 84 /0646 +10 种基金U. S. Geological Survey British Petroleum Oxford University The University of London The Open University,INTAS Grant No. 95 -0949 The Royal Society of London The Crafoord Foundation The U. S. National Museum ,Smithsonian Institution The State of Alaska Geological and Geophysical Surveys the State project No. 01201459177 ( Geological Institute, Russian Acad. Sci. )the Russian Foundation for Basic Research,Project no. 15 -04 -05688 for their financial or in kind support
文摘The Arct ic hosts an extraordinary wealth of terrestrial fossil biotas of Late Cretaceous age representing a diverse and highly productive near-polar ecosystem that has no modern analogue. Compared to the rest of the Late Cretaceous Maastrichtian plant diversity was at its lowest and the temperature regime the coolest, yet the semi-open forests supported a rich dinosaur fauna made up of a wide range of body sizes and feeding strategies. The combination of mild winter temperatures and continuous darkness lasting several months imposed severe constraints on primary productivity. Plant survival strategies involved almost universal winter loss of foliage, which in turn limited food supply for non-migratory overwintering herbivorous animals. A combination of leaf form and tree ring studies has been used to quantify year round variations in temperature and determine the tim-ing of spring bud-break and autumnal leaf fall. While Maastrichtian winter temperatures were cold enough （down to - 10°C for brief intervals） for frequent frosts and snowfall, summer temperatures were cool but highly variable and at -830N along the north Alaskan coast frequently fel l below ＋ 10°C . Theropod egg shell frag-ments at - 76° N in the Maastrichtian of Northeastern Russia may indicate that dinosaur reproduction took place in the Arctic ecosystem, as distinct from taking place at lower latitude breeding grounds reached by migration. This raises the question of nest management and specifically the maintenance of incubation temperatures, and the duration of incubation. Of critical importance to year-round residency is the timing of hatching and juvenile care before winter darkness set in, temperatures fell to near freezing and food resources became limited.
基金supported by the Double First-Class Joint Program of Yunnan Science and Technology Department and Yunnan University (2018FY001-005)the China-Myanmar Joint Laboratory for Ecological and Environmental Conservation+2 种基金the University of Hong Kong Faculty of Science RAE Improvement Fundsupported by the CNRS Program INSU INTERRVIEthe National Natural Science Foundation of China(41688103)。
文摘Recent studies demonstrate that many avialan features evolved incrementally prior to the origin of the group,but the presence of some of these features,such as bird-like brooding behaviours,remains contentious in non-avialan dinosaurs.Here we report the first non-avialan dinosaur fossil known to preserve an adult skeleton atop an egg clutch that contains embryonic remains.The preserved positional relationship of the adult to the clutch,coupled with the advanced growth stages of the embryos and their high estimated incubation temperatures,provides strong support for the brooding hypothesis.Furthermore,embryos in the clutch are at different developmental stages,suggesting the presence of asynchronous hatching—a derived feature even among crown-group birds—in non-avialan theropods.These findings demonstrate that the evolution of reproductive biology along bird-line archosaurs was a complex rather than a linear and incremental process,and suggest that some aspects of non-avialan theropod reproduction were unique to these dinosaurs.
