Dinosaur embryo suggests bird-like pre-hatching posture

Over the last century, scientists have discovered many fossilized dinosaur eggs and nests all over the world, but finding one with a well-preserved embryo is an extremely rare event. Now, a research team led by the China University of Geosciences described an oviraptosaur embryo perfectly preserved inside a fossilized egg. 

The analysis of the embryo suggests that oviraptorids (a group of theropod dinosaurs from the Late Cretaceous that were closely related to birds) took on a distinctive tucking posture before hatching – a behavior previously thought to be unique to birds.

The fossilized dinosaur embryo comes from Ganzhou, a city in the Jiangxi Province of Southern China, and had been acquired in 2000 by Liang Liu, the director of the company Yingliang Group, a leading mining and stone sales company. The egg ended up in storage until it was rediscovered ten years later, when the fossils were unearthed during the construction of the Yingliang Stone Nature History Museum.

“Most known non-avian dinosaur embryos are incomplete with skeletons disarticulated,” said study co-author Waisum Ma, a paleontologist at the University of Birmingham. “We were surprised to see this embryo beautifully preserved inside a dinosaur egg, lying in a bird-like posture. This posture had not been recognized in non-avian dinosaurs before.”

In their analyses, the scientists reported that the embryo’s head lied ventral to the body, with the feet on either side, while the back curled along the blunt pole of the egg, in a posture previously not found in a non-avian dinosaur. 

The comparison of this specimen to other late-stage oviraptosaur embryos suggests that, before hatching, oviraptorids developed bird-like postures in a late stage of their incubation. In modern birds, such coordinated embryonic movements are associated with tucking, a behavior known to be critical for hatching success.

Further research is needed to understand whether pre-hacking behavior may have originated among non-avian theropods. According to the study authors, future discoveries of embryo fossils will be essential for clarifying this issue.

The study is published in the journal iScience.

Image Credit Lida Xing

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By Andrei Ionescu, Earth.com Staff Writer