We propose that the digit reduction in oviraptorosaurians was accompanied by a general forelimb reduction and an increased strength of the pectoral girdle. Combining anatomical, phylogenetic, and osteohistological evidence, we assign the new specimen to Yulong mini, representing the first non-hatchling specimen of this taxon. Osteohistological analysis suggests that it likely represents a subadult approximately five (or six) years old. Phylogenetic analysis recovered the new specimen as a sister taxon of Yulong mini and is closely related to Nankangia from Ganzhou, which is located at the base of the oviraptorid phylogenetic tree. The new specimen includes three dorsal and 29 caudal vertebrae, partial pectoral girdles, and forelimbs. Here, we describe a new non-hatchling individual of Yulong mini, which came from the same deposit of Luanchuan County. Yulong mini is the first oviraptorid hatchling collected from the Upper Cretaceous Qiupa Formation of Luachuan, central China. Oviraptorosauria is a clade of maniraptoran dinosaurs that lived in the Cretaceous, with primitive toothed forms known from the Early Cretaceous, while the toothless forms lived towards the end of Cretaceous. 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. 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. 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.
![does the oviraptor effect stack does the oviraptor effect stack](https://i.stack.imgur.com/6zpxF.png)
Here we report the first non-avialan dinosaur fossil known to preserve an adult skeleton atop an egg clutch that contains embryonic remains. Recent 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.