Yixian Formation in the context of "Institute of Vertebrate Paleontology and Paleoanthropology"

A Fossil-Lagerstätte (German pronunciation: [ˈlaːɡɐˌʃtɛtə] – from Lager 'storage, lair' and Stätte 'place'; pl. Lagerstätten) is a sedimentary deposit that preserves an exceptionally high amount of palaeontological information. Konzentrat-Lagerstätten preserve a high concentration of fossils, while Konservat-Lagerstätten offer exceptional fossil preservation, sometimes including preserved soft tissues. Konservat-Lagerstätten may have resulted from carcass burial in an anoxic environment with minimal bacteria, thus delaying the decomposition of both gross and fine biological features until long after a durable impression was created in the surrounding matrix. Fossil-Lagerstätten span geological time from the Neoproterozoic era to the present.

Worldwide, some of the best examples of near-perfect fossilization are the Cambrian Maotianshan shales and Burgess Shale, the Ordovician Fezouata Biota, Beecher's Trilobite Bed, and Soom Shale, the Silurian Waukesha Biota, the Devonian Hunsrück Slates and Gogo Formation, the Carboniferous Mazon Creek, the Triassic Madygen Formation, the Jurassic Posidonia Shale and Solnhofen Limestone, the Cretaceous Yixian, Santana, and Agua Nueva formations and the Tanis Fossil Site, the Eocene Fur Formation, Green River Formation, Messel Formation and Monte Bolca, the Miocene Foulden Maar and Ashfall Fossil Beds, the Pliocene Gray Fossil Site, and the Pleistocene Naracoorte Caves and La Brea Tar Pits.

Oviraptorosaurs ("egg thief lizards") are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot-like skulls, with or without bony crests atop the head. They ranged in size from Caudipteryx, which was the size of a turkey, to the 8-meter-long, 1.4-ton Gigantoraptor. The group (along with all maniraptoran dinosaurs) is close to the ancestry of birds. Some researchers such as Maryanska et al (2002) and Osmólska et al. (2004) have proposed that they may represent primitive flightless birds. The most complete oviraptorosaur specimens have been found in Asia. The North American oviraptorosaur record is sparse.

The earliest and most basal ("primitive") known oviraptorosaurs are Ningyuansaurus wangi, Protarchaeopteryx robusta and Incisivosaurus gauthieri, both from the lower Yixian Formation of China, dating to about 125 million years ago during the Aptian age of the early Cretaceous period. A tiny neck vertebra reported from the Wadhurst Clay Formation of England shares some features in common with oviraptorosaurs, and may represent an earlier occurrence of this group (at about 140 million years ago).