Upper Cretaceous amniotic eggs from Gobi Desert

Abstract

There are described several types of Upper Cretaceous fossil amniote eggs, clutches and eggshells, collected during the Polish-Mongolian Paleontological Expeditions (1963-1971) in several localities of the Gobi Desert. Isotopic ratios of C and 0 are reported and discussed. The eggs may be attributed to saurischian and ornithischian dinosaurs, and palaeognathous birds. Four types of problematica are also described. Taphonomy and restoration of eggshells ' dif-fusive properties as compared with modern hard-shelled eggs suggest paleoeco-logical interpretation of the nesting conditions as rather dry for smooth--shelled eggs, humid for ornamented eggs, and very humid for the thickestahelled eggs. Different nest types are postulated for ornamented and smooth egg, based on taphonomy and shell parameters.