Scientists in southern China announced last week the discovery of an extremely well-preserved embryo fossil of duck-billed dinosaurs that should offer insights into the development and evolution of the prehistoric animals. While dinosaur eggs are common worldwide, embryos are rare and the example found in Jiangxi province by the team of scientists from the Fujian Science and Technology Museum and the China University of Geosciences is exceptionally well preserved. The high-quality preservation has the potential to offer unique insights into a genus of dinosaurs called hadrosaurus . Particularly, it could illuminate how they developed and evolved. Because the dinosaur was still in an embryo, and many features had not been developed, the scientists felt more confident calling it a hadrosaurus, but could not identify the species. “Generally when you find dinosaur eggs, scientists do not find anything at all, they only find the sediments that the rest of the fossil is surrounded with,” said Michael Pittman, a palaeontologist from the School of Life Sciences at Chinese University of Hong Kong, who was not involved in the paper. He said that finding an embryo as well preserved as the discovery in China is valuable because it offers “clues as to how the animal behaves in real life.” “If we find an egg with an embryo that is halfway through its hatching journey, or right at the start, then we get an earlier snapshot in that developmental process. Having the embryo in the egg is the only way to find out how development happens,” he said. Finding embryos is also important because the more scientists unearth, the better understanding we get of a species’ development. One embryo is useful, but it is only a snapshot in time. If scientists were to discover, say, hundreds of embryos from the same species, they could develop an idea of how it developed from fertilisation to birth. More importantly, this embryo was not fully developed, offering scientists insights into how the hadrosaurus might have matured earlier in the process. The team wrote: “It is probable, therefore, that these embryos were yet several embryonic stages away from hatching.” According to the paper published in BMC Ecology and Evolution on May 9, this discovery has already told scientists that the egg, and embryo, are smaller compared to similar hadrosaurus who lived later, implying that the species’ eggs got bigger as it evolved. “A dinosaur that was eating these eggs would not have had as much to eat as it would have had if it could have waited a few million years,” said Pittman. This same team of scientists announced in December 2021 that they had found another well-preserved dinosaur embryo from an oviraptorosaur, a flightless dinosaur that was closely related to birds. That dinosaur had engaged in “tucking”, basically pinching its head into its chest so it could fit inside the egg. It was the first time the behaviour had been observed in a non-avian dinosaur and added further evidence that deepened the connection between certain dinosaurs and modern birds. The scientists concluded the paper by pointing out this discovery was made in an area of China a that is geographically rich with natural resources that they said would surely unveil more interesting discoveries. “These [sediments] promise to reveal many more clues about early pre-birth development in dinosaurs,” they wrote.