This Perfectly Preserved Dinosaur Embryo Shows Link to Modern-Day Birds

In a pose never seen in non-avian dinosaurs, but similar to those of modern birds, the embryo’s head lies ventral to the body, with the feet on either side, and the back curled along the blunt pole of the egg. Bird embryos attain such postures with a process called “tucking,” which helps stabilize and direct the head when a bird is breaking through the eggshell and is critical to hatching success, according to Fion Ma Wai-sum, a University of Birmingham researcher who worked on the discovery. 

The posture of Baby Yingliang looks similar to a roughly 17-day-old “pre-tucking” chicken embryo, Ma wrote in an analysis on The Conversation this week, suggesting tucking could have first evolved among theropod dinosaurs. 

“This would add to the body of evidence indicating that many characteristics of modern birds evolved in their dinosaurian ancestors,” she wrote. 

The researcher says more detailed analysis should be conducted to compare Baby Yingliang with the embryos of modern birds and crocodiles, the closest living relatives of dinosaurs.