The embryo’s location indicates that it was about to hatch.
A tiny ostrich-like dinosaur wriggled within its egg some 70 million years ago, positioning itself in the optimum position to hatch. The embryo, called “Baby Yingliang,” perished and stayed in its egg for tens of millions of years, until its petrified bones were discovered in China by experts.
Over the last century, scientists have uncovered several old dinosaur eggs and nests, but Baby Yingliang is unique. “This skeleton is not only complete from the tip of its snout to the end of its tail; it is curled in a life pose within its egg as if the animal died just yesterday,” said Darla Zelenitsky, an assistant professor of paleontology at the University of Calgary in Alberta, Canada, who was not involved in the study.
Researchers are drawn to this curled-up position. To assist them hatch from their eggs, living bird embryos are known to shift into the ideal position, known as tucking behaviors. Until today, however, similar behaviors had never been seen in dinosaurs.
“The discovery of this embryo suggests that some pre-hatching behaviors (such as tucking), which were previously thought to be unique to birds, may have a deeper ancestor in dinosaurs many tens or hundreds of millions of years ago,” study co-lead researcher Fion Waisum Ma, a doctoral student of paleobiology at the University of Birmingham in the United Kingdom, told Live Science in an email.
The egg of Baby Yingliang, discovered in the city of Ganzhou in southern China in 2000, was not studied until 2015. During the building of the Yingliang Stone Natural History Museum, a public museum in Xiamen, China, the Yingliang Group, a Chinese stone firm that had purchased the egg and stored it, unearthed the fossil.
“Fossil preparation was carried out, revealing the embryo’s magnificent skeleton,” Ma explained. “It’s one of the best-preserved dinosaur embryos ever discovered,” says the researcher.
The oviraptorid embryo was about 11 inches (27 centimeters) long, yet it was coiled up to fit within its 6.7-inch-long (17 centimeters) oval egg. The skeleton was squished up, its head resting on the dino’s midsection and its legs on each side. “It looks to be a late-stage embryo,” Ma said in an email, “approximately corresponding to a 17-day-old chicken embryo (which hatches on day 21).”
Baby Yingliang was preparing to hatch, much like a well-placed chicken embryo. A few days before hatching, the embryo in chicken eggs shifts its body and limbs into a sequence of tucking positions, she explained. The embryo is in the optimum position to break out of the egg on hatching day, with its body coiled and right wing on top of its head. When the chicken embryo uses its beak to shatter the eggshell, this position is supposed to help support and steer the head. “Failure to do so raises the risk of mortality since the embryo is less likely to effectively burst out of the egg,” Ma explained.
The unusual posture of Baby Yingliang implies a pre-hatching approach similar to that used by chickens and other contemporary birds. “We truly didn’t knew how dinosaurs were positioned in their eggs before this study since earlier fossil embryos were too fragmented,” Zelenitsky said in an email to Live Science. “Now we can clearly observe that oviraptorid dinosaurs had bird-like postures while brooding their eggs,” says the researcher.
According to Zelenitsky, birds got these pre-hatching habits from their dinosaur predecessors. “This research adds to our knowledge of the strong evolutionary link that exists between dinosaurs and birds,” she added.
Originally published on Live Science.
