The dinosaur fossils excavated in the Pingba district of the city of Anshun in Southwest China's Guizhou Province. Photo: Courtesy of the Pingba District Cultural Relics Management Office and Guizhou Provincial Museum. (Photo from web)

China has found its oldest dinosaur egg nest and the world's oldest dinosaur fossil group preserving both dinosaur eggs and adults in Southwest China's Guizhou Province. According to one of the experts on the project on Tuesday, the dinosaur fossil group dates back to 190 million years ago and contained at least three adult dinosaurs and 50 eggs across five nests, all the same species.

The unique fossil group was excavated from purple-red sandy mudstone in the Pingba district of the city of Anshun in Guizhou. The group contained a type of bipedal herbivorous sauropod dinosaur whose fossils are widely distributed in Early Jurassic strata around the world.

As the dinosaur group discovered in Pingba revealed a relatively complete skull and postcranial skeletal materials and possesses unique characteristics and combinations of features different from other sauropod dinosaurs, researchers from the China University of Geosciences (Wuhan), Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, and Guizhou Provincial Museum, named the new genus Qianlong shouhu and published the results of their research in the National Science Review. Researchers estimate that adult Qianlong shouhu could grow to over six meters in length and weigh up to one ton.

"Qian" is the short name for Guizhou Province, while "Shouhu," or protect, refers to the theory the dinosaur cared for its young, which can be seen from the fact the adult fossils and the nests were preserved together, said Han Fenglu, the first author of the research paper and a professor from the School of Earth Sciences of China University of Geosciences (Wuhan).

Han told the Global Times on Tuesday that dinosaur eggs from a similar period have been discovered in countries like South Africa and Argentina, but the eggs of Qianlong shouhu preserved the most complete eggshell structure.

Han said that the study reveals numerous behavioral patterns of early dinosaurs, such as group breeding and synchronized hatching, which provides important evidence for understanding the reproductive and survival strategies of early dinosaurs.

By observing and evaluating the developmental stages of the embryo skeletons in different dinosaur eggs found in the nests, researchers have discovered that they all were at similar stages of development, just like modern sea turtles, which hatch simultaneously. This synchronous hatching is advantageous for individuals to escape predation, said Zeng Rong, director of the Natural Department of the Guizhou Provincial Museum.

"After analysis, we came to believe its eggshell was semi-rigid, falling between soft ones like snakes' eggs and rigid ones like hen's eggs. Different from the existing arguments that the earliest dinosaurs' eggs were soft or rigid, we argue for the first time that the earliest dinosaurs' eggs were semi-rigid," said Han.