This remarkable egg was rediscovered in 2015, while Yingliang staff were sorting fossils unearthed by the company in preparation for opening a natural history museum. Slightly longer than an ostrich egg and shaped like a capsule, it had a crack in the surface, which allowed an employee to spot a few pieces of bone.
“He then understood that it probably contained an embryo,” explains Waisum Ma, author of the study and doctoral student at the University of Birmingham, in the United Kingdom.
A technician carefully removed the shell from one side of the fossil and the sediment that had penetrated the egg, revealing the juvenile dinosaur curled up as if it were still alive. Taking stock of the discovery, Yingliang contacted the study’s lead author, Lida Xing, of the University of Geosciences of China in Beijing. He formed a team to study the baby dinosaur in perfect condition.
Although many dinosaur eggs have been discovered, embryos are rare, and even more embryos in a good state of preservation. “They’re mostly piles of bones at the bottom of the egg,” notes Matthew Lamanna, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, United States, who was not involved in the study.
To date, only two other nearly complete oviraptorosaur embryos have been unearthed, Waisum Ma points out. She remembers being impressed when she saw the first photos of the fossil. “It’s the most beautiful dinosaur embryo I’ve ever seen,” she confides. Only a few bones are missing, including a front leg and a section of the tail.
For the other two fossils, scientists used CT scanning to see in detail the bones hidden inside the shell. But because of the type of sediment inside the eggs, scientists were unable to properly discern the skeleton. However, the team was able to carefully study the exposed surface of the Baby Yingliang fossil to compare it to that of the two other oviraptorosaur embryos previously discovered.
Its head rests on its stomach, while its knees are bent up to the level of its tiny front legs. Its curved back is pressed against one of the ends of the egg, where a space undoubtedly contained the air sac, which has now disappeared. All these characteristics are similar to those of modern chick embryos: as they develop, they gradually curl up, nestling their head under their right wing. This position is essential for a successful hatching.
If Baby Yingliang isn’t as curled up as a chick about to burst its shell, “he’s almost there,” says Darla Zelenitsky. The slight difference in position compared to the other two oviraptorosaur embryos could illustrate changes in postures similar to those observed in chicks during their development. According to the researchers, the origins of birds’ cowering in the shell date back millions of years, to the time of baby oviraptorosaurs.
