Scientists on December 21 announced the discovery of an exquisitely preserved dinosaur embryo from at least 66 million years ago that was preparing to hatch from its egg just like a chicken.

The fossil was discovered in Ganzhou, southern China and belonged to a toothless theropod dinosaur, or oviraptorosaur, which the researchers dubbed “Baby Yingliang”.

University of Birmingham researcher Fion Waisum Ma and colleagues found Baby Yingliang’s head lay below its body, with the feet on either side and back curled – a posture that was previously unseen in dinosaurs, but similar to modern birds.

In birds, the behaviour is controlled by the central nervous system and called “tucking”. Chicks preparing to hatch tuck their head under their right wing in order to stabilise the head while they crack the shell with their beak.

“This indicates that such behaviour in modern birds first evolved and originated among their dinosaur ancestors,” said Ma.

Oviraptorosaurs, which means “egg thief lizards”, were feathered dinosaurs that lived in what is now Asia and North America during the Late Cretaceous period.

Baby Yingliang measures around 27cm long from head to tail, and lies inside a 17cm-long egg at the Yingliang Stone Nature History Museum.

Researchers believe the creature is between 72 and 66 million years old, and was probably preserved by a sudden mudslide that buried the egg, protecting it from scavengers for eons.

It would have grown 2-3m long if it had lived to be an adult, and would have likely fed on plants.

The specimen was one of several egg fossils that were forgotten in storage for decades.

The research team suspected they might contain unborn dinosaurs, and scraped off part of Baby Yingliang’s egg shell to uncover the embryo hidden within.

The team hopes to study Baby Yingliang in greater detail using advanced scanning techniques to image its full skeleton, including its skull bones, because part of the body is still covered by rock.