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1 Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, #142 XiZhiMenWai DaJie, Beijing 100044, China
2 UMR CNRS 5125, Paléoenvironnements et Paléobiosphère, Université Lyon1, 2 rue Raphaël Dubois, 69622 Villeurbanne Cedex, France
3 CNRS (UMR 8538, Laboratoire de Géologie de l'Ecole Normale Supérieure), 24 rue Lhomond, 75231 Paris Cedex 05, France
4 Institut Universitaire de France, 103 bld Saint-Michel, 75005 Paris, France
5 European Synchrotron Radiation Facility, BP220, 6 rue Jules Horowitz, 38043 Grenoble Cedex, France
6 Department of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand
*Corresponding author (e-mail: romain.amiot{at}ivpp.ac.cn)
Phosphatic remains (tooth enamel, turtle shell fragments and fish scales) of continental vertebrates (freshwater fish, crocodilians, turtles, and theropod and sauropod dinosaurs) recovered from eight localities of NE Thailand ranging in age from the Late Jurassic to the late Early Cretaceous have been analysed for their oxygen isotopic compositions (
18Op). From these preliminary data, local meteoric water 18Ow values estimated using 18Op values of crocodilians and turtles range from –4.1±2
at the end of the Jurassic to –8.3±2 during the Early Cretaceous, suggesting a transition from dry to wetter climates with increasing amount of seasonal precipitation from several hundred millimetres per year to several thousand millimetres. Measurable offsets in 18Op values observed between dinosaur taxa (the spinosaurid theropod Siamosaurus, other theropods and nemegtosaurid sauropods) are interpreted in terms of differences in water strategies, and suggest that Siamosaurus had habits similar to those of semi-aquatic vertebrates such as crocodilians or freshwater turtles.
