A 66-million-year old dinosaur embryo now dubbed ‘Baby Yingliang’ was recently discovered in southern China. Now, the perfectly preserved Oviraptorosaur fossil is helping shed light on the link between modern birds and dinosaur behaviours.


Baby Yingliang is one of the most complete dinosaur embryos ever found. The fossil suggests that these dinosaurs developed postures that are similar to birds when they were close to hatching.

Thanks to a joint study from the University of Birmingham and China University of Geosciences, researchers published some key findings on this embryo, most importantly on pre-hatching posture.

The fossil shows that the dinosaur embryo was in a curled up position which is similar to that of modern bird embryos. This is a behaviour that was previously unrecognised in dinosaurs but for modern birds, this is known as ‘hatching’. This behaviour is controlled by the central nervous system and is critical for a successful hatching.

© Lida Xing
Reconstruction of Oviraptorosaur embryo © Lida Xing

Previously, this pre-hatching behaviour was thought to be unique to birds, but the researchers in this study now believe it may have originated among non-avian theropods (a type of dinosaur). Bird embryos that didn't adopt the hatching posture tend to have a higher chance of death due to unsuccessful hatching.

This type of discovery is rare due to the typical condition of dinosaur fossils. “Dinosaur embryos are some of the rarest fossils and most of them are incomplete with the bones dislocated’’ said Fion Waisum MA, the joint first author and PhD researcher at the University of Birmingham.

“We are very excited about the discovery of ‘Baby Yingliang - it is preserved in a great condition and helps us answer a lot of questions about dinosaur growth and reproduction with it.”

Luckily this embryo has been mostly undisrupted and is captured in its live position. It Is estimated to be around 27cm long from head to tail. It has been identified as an Oviraptorosaur (which strangely means ‘egg thief lizard' if you were wondering… ) based on its deep, toothless skull.

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These are feathered dinosaurs that are closely related to modern-day birds. Their inconsistent beak shapes and body sizes meant they likely adopted a wide range of diets including herbivory, omnivory and carnivory.

By comparing this perfectly preserved embryo with similar dinosaur embryos, the team has come up with the proposal that tucking behaviour first originated in theropod dinosaurs tens or hundreds of millions of years ago. More discoveries of dinosaur embryo fossils are now needed to further test this hypothesis.

This dinosaur embryo inside its egg is one of the most beautiful fossils I have ever seen. This little prenatal dinosaur looks just like a baby bird curled in its egg, which is yet more evidence that many features characteristic of today’s birds first evolved in their dinosaur ancestors,” said Professor Steve Brusatte, part of the research team from University of Edinburgh.

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Alex is a staff writer at BBC Science Focus. He has worked for a number of brands covering technology and science with an interest in consumer tech, robotics, AI and future technology.