THE REPRODUCTION OF TITANOSAURS FROM THE QUEBRADA DE SANTO DOMINGO, PRECORDILLERA OF LA RIOJA (NW ARGENTINA): INDICATIONS FROM STABLE ISOTOPES

LEA LEUZINGER; STEFANO BERNASCONI; TROSTEN VENNEMANN; HECHENLEITNER, E. MARTÍN; FIORELLI, LUCAS E.; ROCHER, SEBASTIÁN; PABLO ALASINO

La Plata

Congreso; RCAPA; 2019

Titanosaur egg clutches have recently been discovered at the Quebrada de Santo Domingo locality (QSD), Precordillera of La Rioja (NW Argentina) in several levels of the Ciénaga del Río Huaco Formation (Late Cretaceous). They are found in two subsites located on either side of the valley, and their preservation greatly differs from one subsite to the other due to differential exposure to weathering. We performed stable isotope analyses (δ18O, δ13C, Δ47) as well as EDAX, CL, XRF and XRD on several eggshell fragments, associated geological material and a titanosaur tooth, to check for the preservation of the fossils and their potential as local palaeoenvironmental and palaeoecological proxy. While the eggshells of the most exposed subsite result in isotopic values suggesting extensive diagenesis and recrystallization, those of the other subsite conserved ?at least partly? their original isotopic composition. The isotopic signal of altered eggshells corresponds to meteoric diagenetic fluids and DIC (dissolved inorganic carbon), while that of well-preserved ones reflects the original water ingested by the titanosaurs, and the organic carbon directly linked to their herbivorous diet. Comparing the δ18O of the well-preserved eggshells to that of the titanosaur tooth, we conclude that titanosaur reproduction occurred under above-average arid conditions at QSD. The question of knowing if this arid signal results from behavior (migration to arid areas for reproduction) or seasonal breeding remains open. As for the Δ47eggshells, corresponding to the carbonate precipitation temperature when pristine (i.e., body temperature of the mother), it is not preserved in the study material.