Abstract

New protoceratopsid fossils from Bayan Mandahu include the smallest specimens of Protoceratops and Bagaceratops recovered to date. None of these specimens were found associated with dinosaur eggshells, but all are small enough to fit within any of the eggs that have been attributed to protoceratopsians. It is concluded that they represent embryonic dinosaurs. No specimens are complete, but together they allow a better understanding of the cranial anatomy of the embryos.The absence of embryos in the thousands of eggs collected from Cretaceous sediments of China and Mongolia may represent a taphonomic condition whereby embryos were destroyed by the decomposing contents of the eggs. If this is correct, embryonic dinosaurs from central Asia may only have been preserved when the eggs were broken so that the liquid contents drained.

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