Dinosaur embryo found inside fossilized egg from more than 66 million years ago

A fossilized dinosaur egg more than 66 million years old was found with an embryo inside, and international researchers say the discovery creates a link between dinosaurs and modern-day birds. 

The egg was found in 2000 in Ganzhou, Jiangxi Province, in southern China by Yingliang Group, a company that mines stones. Company workers suspected they had found dinosaur fossils, so the discoveries were put in storage.

It wasn't until the company began building the Yingliang Stone Nature History Museum in 2010 that museum staff found the fossils and noticed bones within the egg. After scientists examined the fossils, they said one of the eggs contained an embryo, which they named "Baby Yingliang." 

Their findings have been published in the peer-reviewed journal iScience.

"Dinosaur embryos are some of the rarest fossils, and most of them are incomplete with the bones dislocated. We are very excited about the discovery of 'Baby Yingliang,'" Fion Waisum Ma, author of the study and researcher at the University of Birmingham in England, said in a statement. "It is preserved in a great condition and helps us answer a lot of questions about dinosaur growth and reproduction with it."

Life reconstruction of a close-to-hatching oviraptorosaur dinosaur embryo.

The dinosaur, an oviraptorosaur, is closely related to birds and part of the therapod group. Therapods were carnivorous dinosaurs with small forelimbs that walked on two feet, like other creatures in that group such as the Tyrannosaurus rex and the velociraptor.

But a distinct feature scientists noticed about the embryo was it shared a very similar pose to birds before hatching, something thought to be unique in the animal kingdom.

Researchers said the oviraptorosaur embryo was in a tucking position, with the feet on the side of its head and its back against the shell. Today, birds stay in that position before hatching; if they don't, they have a higher chance of dying before or at birth.

This dinosaur did not fly, so this is the first time the tucking position had been observed in a non-avian animal. The findings suggest modern bird hatching practices may have come from nonflying dinosaurs hundreds of millions of years ago. The embryo is estimated to be 66 million to 72 million years old.

"It is interesting to see this dinosaur embryo and a chicken embryo pose in a similar way inside the egg, which possibly indicates similar prehatching behaviours," Waisum Ma said. "This posture had not been recognized in non-avian dinosaurs before."

The oviraptorosaur did not fly, so the embryo fossil represents the first time the tucking position had been observed in a non-avian animal, researchers said.

The embryo will undergo further evaluation in an attempt to understand its anatomy and learn more about dinosaur embryos, as well as learn more of how dinosaurs and birds today are related.

"This dinosaur embryo inside its egg is one of the most beautiful fossils I have ever seen," said Steve Brusatte, co-author and paleontologist at the University of Edinburgh in Scotland. "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."

Follow Jordan Mendoza on Twitter: @jordan_mendoza5.

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