lakes on an alluvial plain (flat land consisting of sediments deposited by highland rivers) with a combination of dune field paleoenvironments, under a semi-arid climate. The formation is known for its vertebrate fossils in life-like poses, most of which are preserved in unstructured sandstone, indicating a catastrophic rapid burial. The paleofauna of Bayan Mandahu is very similar in composition to the nearby Djadokhta Formation, with both formations sharing several of the same genera, but differing in the exact species. In this formation, P. hellenikorhinus is the representative species, and it shared its paleoenvironment with numerous dinosaurs such as dromaeosaurids Linheraptor and Velociraptor osmolskae; oviraptorids Machairasaurus and Wulatelong; and troodontids Linhevenator, Papiliovenator, and Philovenator. Other dinosaur members include the alvarezsaurid Linhenykus; ankylosaurid Pinacosaurus mephistocephalus; and closely related protoceratopsid Bagaceratops. Additional fauna from this unit comprises nanhsiungchelyids turtles, and a variety of squamates and mammals. Djadokhta Formation Protoceratops is known from most localities of the Djadokhta Formation in Mongolia, which dates back to the Late Cretaceous about 71 million to 75 million years ago, being deposited during a rapid sequence of polarity changes in the late part of the Campanian stage. Dominant sediments at Djadokhta include dominant reddish-orange and pale orange to light gray, medium to fine-grained sands and sandstones, caliche, and sparse fluvial (river-deposited) processes. Based on these components, the paleoenvironments of the Djadokhta Formation are interpreted as having a hot, semiarid climate with large dune fields/sand dunes and several short-lived water bodies, similar to the modern Gobi Desert. It is estimated that at the end of the Campanian age and into the Maastrichtian the climate would shift to the more mesic (humid/wet) conditions seen in the Nemegt Formation. The Djadokhta Formation is separated into a lower Bayn Dzak Member and upper Turgrugyin Member. Protoceratops is largely known from both members, having P. andrewsi as a dominant and representative species in the overall formation. The Bayn Dzak member (mostly the Bayn Dzak locality) has yielded the dromaeosaurids Halszkaraptor and Velociraptor mongoliensis; oviraptorid Oviraptor; ankylosaurid Pinacosaurus grangeri; and troodontid Saurornithoides. Ukhaa Tolgod, a highly fossiliferous locality is also included in the Bayn Dzak member. and its dinosaur paleofauna is composed of alvarezsaurids Kol and Shuvuuia; ankylosaurid Minotaurasaurus; birds Apsaravis and Gobipteryx; dromaeosaurid Tsaagan; oviraptorids Citipati and Khaan; troodontids Almas and Byronosaurus; and a new, unnamed protoceratopsid closely related to Protoceratops. In the Turgrugyin Member (mainly Tugriken Shireh locality), P. andrewsi shared its