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In one of the most well-preserved dinosaur embryos ever found, a baby dinosaur curled its back and tucked its head in a position that is similar to modern birds before they hatch, a discovery that scientists say could shed new light on how dinosaurs developed in their early stages.
A peer-reviewed article, published Tuesday by iScience, said the dinosaur had its head placed between its legs and under its body, with its back bent along the eggshell. The research team said this position, previously not found in any non-avian dinosaurs, is comparable to pre-tucking in a bird embryo like that of a chicken.
By tucking their heads under their wings in the days before hatching, chicks can stabilize them and have a better chance of surviving the birthing process, the paper explained, adding that this behavior was thought to be unique in birds but now may be traced to dinosaurs.
Fion Waisum Ma, one of the co-authors of the report, said she was “amazed” when she first saw photos of the egg because it is rare to find a dinosaur embryo with most of its skeleton developed and preserved in its original anatomical composition.
The dearth of well-preserved embryos means that scientists are limited in their understanding of dinosaurs before they hatch, Ma said, a situation that she hopes the discovery could change.
About 6 by 3 inches, the egg encases a baby oviraptorosaur, a species commonly found in Asia and North America that is noted for its strong jaw, used to crack hard food.
The egg was discovered over two decades ago in Ganzhou, a city in southern China where many oviraptorosaur fossils have been unearthed in recent years. But it sat in storage at a museum in Yingliang, in Fujian province, for 15 years before the curator saw some of the preserved bones through the cracks of the fossilized egg, said Ma, who is also a PhD student at Britain’s University of Birmingham.
Now known as Baby Yingliang, the oviraptorosaur measured at over 9 inches and took up most of the space within the egg, the research team said, making it a late-stage embryo that would have been close to hatching.
Researchers estimated that the egg containing Baby Yingliang was laid between 72 million and 66 million years ago. It may have been buried rapidly by mud or sand, a process that protected the egg from scavengers and natural erosion, Ma said.
Birds evolved from a type of dinosaur during the Mesozoic era (250 million to 66 million years ago). While this evolutionary link has been established, Anthony Romilio of the Dinosaur Lab at the University of Queensland in Australia said Baby Yingliang shows that “the bird-dinosaur relationship extends to shared postures whilst growing inside the egg.” (Romilio helped create a three-dimensional model of Baby Yingliang for Tuesday’s paper.)
Earlier this year, a team of Chinese and American researchers said they discovered a fossil of an oviraptorosaur, also from the Ganzhou area, perched on top of a nest of its own eggs in an incubation pose, similar to what modern birds do.