Preliminary clumped isotope data from Late Cretaceous titanosaur (Sauropoda) eggshells: preservation of the original isotopic signal and implications for palaeoecological and palaeobiological interpretations

LÉA LEUZINGER; STEFANO BERNASCONI; FIORELLI, LUCAS ERNESTO; HECHENLEITNER, ESTEBAN MARTÍN; PABLO HORACIO ALASINO

Congreso; VI Symposium on Dinosaur Eggs and Babies; 2017

For several decades, scientists have relied on stable isotope analyses on fossils and associated sediments for palaeoecological and palaeoenvironmental reconstructions. The fractionation of oxygen and carbon isotopes between a mineral and the original fluid it precipitated from depends on temperature. Information related to climate, environment and/or physiology can thus be inferred from the isotopic composition of both, the mineral and original fluid, by means of established fractionation equations. The most limiting factor of this method is that the isotopic composition of the original fluid (e.g. meteoric water, body water, marine water) is unknown for geological and fossil samples and must consequently be estimated.A recently developed stable isotope method called ?carbonate clumped isotope thermometry? now allows to calculate the precipitation temperature of a mineral independently of the isotopic composition of its original fluid, basing only on the abundance of 13C-18O bonds within a carbonate molecule, which is temperature-dependant. When applied on fossils (eggshells, carbonate fraction in tooth apatite?), clumped isotope analyses give direct information on the body temperature of the animal, provided that the primary isotopic composition is preserved.We ran classical oxygen and carbon, as well as clumped isotope analyses on Late Cretaceous dinosaur eggshells, associated pedogenic carbonate nodules and hydrothermal crystals from three different titanosaur nesting sites of La Rioja province, NW Argentina. The results show that the eggshells of two sites are isotopically poorly preserved, meaning that the calculated precipitation temperature (>40°C) most probably corresponds to that of secondary calcite. However, the eggshells of the third one show values different from associated, diagenetic carbonate and can thus be used to answer palaeophysiological questions. We will provide preliminary information on body temperature of titanosaurs and on the environmental conditions that prevailed in these three study sites, likely ideal for nesting.