Dinosaur eggshell and tooth enamel geochemistry as an indicator of Mongolian Late Cretaceous paleoenvironments

The Late Cretaceous fossiliferous beds of Mongoliaʹs Gobi Desert have yielded spectacular articulated remains of a remarkable diversity of fossil mammals, lizards, turtles, birds, and non-avian dinosaurs. Paleoenvironmental interpretations of the deposits at these localities have ranged from arid wind-blown dune fields to more mesic, moist environments. Among the diversity of fossils, dinosaur eggshells and teeth are commonly found at these localities. Dinosaur eggs, like modern avian eggs, are constructed of biomineralized calcite (CaCO3) and proteins, allowing carbon and oxygen stable isotopes to be quantified to provide information about the environment in which the egg-laying animals were living. Here it is shown that dinosaur eggshell and teeth from the Djadokhta and Nemegt Formations have not been significantly altered and reflect an environment of dry dunes during deposition of the Djadokhta Formation and a more mesic stream environment for conditions in the Nemegt Formation. Carbonate nodules from the same eggshell-bearing layers also independently reflect a similar environmental signal. This study represents the first geochemical analysis of dinosaur remains from the Cretaceous of Mongolia and illustrates the potential of utilizing dinosaur fossil geochemistry of both eggs and teeth to reconstruct Mesozoic environments.