Stable isotope distribution in Maastrichtian vertebrates and paleosols from the Hateg Basin, South Carpathians

Located in the South Carpathians in Romania, the Hateg Basin contains a thick sequence of Maastrichtian continental deposits yielding a rich dinosaur and mammalian fauna. Stable isotope analyses of both calcretes and dinosaur, crocodilian and turtle remains from two localities (Tustea and Sibisel) were integrated in order to reconstruct environmental conditions during Maastrichtian time and to gain further insights into the metabolism and behaviour of the vertebrates. The large difference observed between the delta O-18 and delta C-13 of the eggshells and the surrounding mudstones, as well as the preservation of the 9 parts per thousand difference between the oxygen isotope composition of the Telmatosaurus eggshell and tooth enamel, indicate that diagenesis has not significantly altered the primary isotopic signal. The presence of smectite in the fraction less than 2 mu m and the preservation of dinosaur eggshell structure also indicate that diagenesis was not significant in the studied outcrops. Stable isotope compositions of both calcretes and phosphatic remains suggest warmer conditions during the deposition of the Tustea sequence (mean annual temperature of around 14 degrees C) than during the deposition of the Sibisel sequence (mean annual temperature of 10 degrees C). The intra-tooth delta O-18 patterns for Zalmoxes and Allodaposuchus show different magnitudes of isotopic variation, with lower values for Tustea and higher for Sibisel. The calculated delta O-18(body) (water) enrichment for Kallokibotion bajazidi is similar to that found in living turtle taxa. By contrast, in the case of Allodaposuchus, the isotopic enrichment is higher than for recent taxa. This suggests that, for Allodaposuchus, the body water was less buffered by a watery environment, which probably indicates more time spent outside water (i.e. more terrestrial habit). The delta O-18 values for the teeth of Telmatosaurus and Zalmoxes are similar to those of Allodaposuchus, suggesting that, at the investigated sites, the body temperature of both dinosaurs was similar to that of the crocodile. The isotopic composition of calcretes, teeth and eggshells indicates a C3 vegetation and diet with delta C-13 values between -27 and -29 parts per thousand (PDB) and the absence of large-scale habitat partitioning between the dinosaurs. (C) 2009 Elsevier B.V. All rights reserved.