1. ^*,  Department of Vertebrate Paleontology, and ^† Department of Biological Sciences, George Washington University, Lisner Hall 307, 2023 G Street NW, Washington DC 20052, USA
2. ^‡ Department of Ornithology American Museum of Natural History, 79th Street at Central Park West, New York, New York 10024-5192, USA
3. ^§ Geological Institute, Mongolian Academy of Sciences, Ulaan Baatar 11, Mongolia

Abstract

A SPECTACULAR fossil specimen that suggests the presence of an avian type of nesting behaviour in oviraptorids, a clade of non-avian maniraptoran theropods, is reported here. The substantial evidence indicating that birds are a type of theropod dinosaur has led to copious discussion concerning the origin and possible presence of advanced avian reproductive behaviour in non-avian dinosaurs. Although the inference of behaviour from fossils is problematic, some remarkable discoveries, such as the incontrovertible evidence of dinosaur nests¹, and more controversial claims made on the basis of dinosaur nesting grounds² and juvenile morphology³, hint at the occurrence of advanced reproductive behaviour in a variety of non-avian dinosaurs. But there is no direct fossil evidence implying advanced parental systems such as those found in modern birds. The closest associations between presumed parents and nests occur in oviraptorid dinosaurs from Late Cretaceous deposits of the Gobi Desert^4,5. The specimen described here is the first preserved well enough to determine its precise relationship with the nest. It is a large oviraptorid positioned over a nest of oviraptorid eggs in the same posture taken by many living birds when brooding. This provides the strongest evidence yet for the presence of avian brooding behaviour in non-avian dinosaurs.