Which came first?

Look: Dinosaur embryo appears freakishly like a chicken in an egg

Lida Xing

Shutterstock

Dinosaurs are thought to be the ancestors of today’s birds.

Emily Willoughby/Stocktrek Images/Stocktrek Images/Getty Images

Many prehistoric beasts shared traits with avian species today: They hatched from eggs, had beaks, and were covered in feathers.

These similarities may have started before they even hatched.

A newly-described fossil egg reveals an uncanny resemblance to unhatched chickens.

Esther van Hulsen/Stocktrek Images/Stocktrek Images/Getty Images

Lida Xing

Researchers writing in the journal iScience on December 21 detail a near-complete baby theropod dinosaur fossil, still in its egg.

Lida Xing

Identified as an Oviraptorsaur, a group of dinosaurs known for their coats of feathers and hollow, toothless skulls, it looks surprisingly familiar.

Lida Xing

Nicknamed “Baby Yingliang,” the fossil was unearthed in Ganzhou, a city in southern China where a number of therapod fossils have turned up in recent years.

Such excellently preserved, unhatched dinosaur fossils are extremely rare, the researchers say.

Shutterstock

Baby Yingliang’s remains, which date to the Late Cretaceous period up to 72 million years ago, could reveal new details of early development in dinosaurs — and today’s chickens.

The dinosaur is curled up like how chicken embryos position themselves to prepare for hatching.

iScience

“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.”

Stephen Brusatte, study co-author

Shutterstock

fzant/E+/Getty Images

In chickens, this posture is known as tucking and typically occurs right before the bird hatches.

Snap Decision/Photographer's Choice RF/Getty Images

The researchers looked at other types of dinosaur eggs, such as those of sauropods and other theropods, but this behavior appears unique to Oviraptosaurs — so far.

Shutterstock

More fossil evidence is needed to establish when dinosaurs started tucking — and how widespread it was across species. But Baby Yingliang reveals a previously unknown commonality with its modern descendants.