Description of the first lithostrotian titanosaur embryo in ovo with Neutron characterization and implications for lithostrotian Aptian migration and dispersion

摘要: Abstract Although titanosaurs represent one of the most diverse radiations non-avian dinosaurs during Cretaceous, our knowledge their early developmental stages was restricted to Auca Mahuevo (Argentina) embryos in ovo . Here, we present first complete lithostrotia titanosaur embryo The relatively small spherical 87.07 91.1 mm egg discovered at Lower Cretaceous locality Algui Ulaan Tsav Mongolia, and is, date, smallest positively identified egg. Through taphonomic processes, transformed into a calcite geode bottom which embryonic bones settled down are now partially exposed on lower surface. Neutron tomography characterization reveals fully developed fossilized within thin (7.6 mm–8.6 mm) layer. EBSD, SEM-based diffraction technique, measures crystallographic orientation crystal lattice from submicron area sample surface, is used for time an extinct dinosaur eggshell. Observations its combined with eggshell microcharacterizations suggest that this new intermediate robusticity index shares mosaic skeletal characters Diamantinasaurus matildae Queensland (Australia) nemegtosaurid Rapetosaurus krausei (Madagascar) more than any other titanosaurs. Early age implies specimen greatly predates previously described lithostrotian Late sediments Mongolia. In addition, recognized amount similar eggs has been recovered last 70 years suggests well-established population site as nesting site. observations provide important addition Mongolian fossil richness alter understanding paleodispersion sauropod group. It appears sauropods would have reached Mongolia Aptian–Albian, thus suggesting existence passage before separation Laurasian Gondwanan continents. Possibly, north eastward migration could occurred between North Africa, Spain, rest Europe prior fragmentation large islands justifying presence lithostrotians Romanian Hateg Island.