[NOTE: This paper should be free from the Chinese journal website after it is officially published.]
Shundong ÂBi, Romain Amiot, Claire Peyre de FabrÃgues, Michael Pittman, Matthew C.Lamanna, Yilun Yu, Congyu Yu, Tzuruei Yang, Shukang Zhang, Qi Zhao & Xing Xu (2020)
An oviraptorid preserved atop an embryo-bearing egg clutch sheds light on the reproductive biology of non-avialan theropod dinosaurs
Science Bulletin (advance online publication)
DOI:
https://doi.org/10.1016/j.scib.2020.12.018 https://www.sciencedirect.com/science/article/abs/pii/S2095927320307635Recent studies demonstrate that many avialan features evolved incrementally prior to the origin of the group, but the presence of some of these features, such as bird-like brooding behaviours, remains contentious, in non-avialan dinosaurs. Here we report the first non-avialan dinosaur fossil known to preserve an adult skeleton atop an egg clutch that contains embryonic remains. The preserved positional relationship of the adult to the clutch, coupled with the advanced growth stages of the embryos and their high estimated incubation temperatures, provides strong support for the brooding hypothesis. Furthermore, embryos in the clutch are at different developmental stages, suggesting the presence of asynchronous hatching--a derived feature even among crown-group birds--in non-avialan theropods. These findings demonstrate that the evolution of reproductive biology along bird-line archosaurs was a complex rather than a linear and incremental process, and suggest that some aspects of non-avialan theropod reproduction were unique to these dinosaurs.