"Found a pregnant dinosaur?" Didn't dinosaurs hatch dinosaur eggs, but also fetal? ”
"It's a dinosaur, not a dinosaur!"
On the afternoon of February 14, 2017, Liu Jun repeatedly stressed to the surging news (www.thepaper.cn).
A few hours later, at 00:00 on February 15, 2017, one of his research papers will be published online in the international academic journal Nature Communications. The paper will publish a surprising fossil of a huge dinosaur with an extra-long neck that had a small dinosaur wrapped around its belly.
Restoration of a pregnant dinosaur. The pictures in this article are provided by Liu Jun.
"Did you swallow a fellow creature, or did you give birth to a fetus?"
Six years ago, when Liu Jun was a Doctoral student at the University of Hong Kong, he was also thinking about this possibility. Whether it is cannibalism or birth, any hypothesis confirmed would be an unusual discovery.
Now Jun Liu has graduated from the University of Hong Kong, completed postdoctoral research at the University of Sydney, and is currently an associate professor at the School of Resources and Environmental Engineering of Hefei University of Technology.
This fossil was discovered 9 years ago, in 2008. At that time, Zhang Qiyue, a researcher at the Chengdu Institute of Geology and Mineral Resources, and his team organized field excavations and collected them at the Luoping National Geopark in Luoping County, Qujing City, Yunnan Province. But the fossils are wrapped in limestone, and only a little bit can be seen, and if you want to study, you have to carefully peel the fossils out.
Dinosaur fossil excavation site.
The dinosaur lives in the ocean, it has no gills, and after a while it will float to the surface of the sea to breathe. Liu Jun said he was thrilled after the laboratory of the Chengdu Institute of Geology and Mineral Resources completed the overall repair of the fossil. He found that the torso of the small dinosaur wrapped in the fossil abdomen pointed in front of the mother as a whole, but the dinosaur devoured the hunt in an ambush manner through a long neck, and if it was undigested prey, its head was generally stored backwards in the body cavity of the dinosaur. In addition, the maternal dinosaur fossil "protects" the baby dinosaur in a completely wrapped form, and it is impossible for the fossils to overlap.
Researchers such as Liu Jun also found that the bones of the dinosaur fetus had grown, and no calcareous eggshell components were detected in or around the fossil, and the neck was so long that it was difficult for dinosaurs living in the ocean to nest and hatch.
The increasing number of clues has made researchers more and more certain that dinosaurs reproduce in a fetal way.
The fossil is 245 million years old, "and the findings confirm for the first time the presence of births in plesiosaurs." This discovery has pushed our understanding of the reproductive patterns of The Pre-Jurassic to the Triassic, spanning 50 million years," Liu said.
Fossils of dinosaurs found in this study; enlarged parts are embryonic bones; the scale is 10 cm.
Talking about the difference between dinosaurs and dinosaurs, in short, dinosaurs are more primitive than dinosaurs.
Liu Jun explained that dinosaurs appeared earlier, it lived in the middle of the Triassic, and the current evidence shows that dinosaurs appeared in the late Triassic. Dinosaurs belonged to protosplexes and dinosaurs belonged to PrimordialOsaurus, and together they formed part of the Group of Predontosaurus-type animals.
About a third of the world's amnioidates are now Prednissophores, birds of course, and make up the majority, the paper said.
The Primordials include extant crocodiles, birds, and extinct reptiles such as dinosaurs and pterosaurs, and there are currently more than 10,000 species. However, in the group of prenatural animals, the reproductive mode of fetal birth has never been discovered, and it has been found that it is oviparous (egg laying).
The results of the study by Liu Jun and others showed that the dinosaur was born in the womb. This has upended people's previous perceptions.
Since dinosaurs were born, what about dinosaurs?
Liu Jun said that no evidence has been found to show that dinosaurs have the possibility of viviparity.
So why do birds lay eggs and lay eggs, but there is no fetal birth?
Previously, there were many assumptions in the academic community, such as birds to fly, lack of physiological structure required for viviparation, lack of corresponding natural selection pressure, etc., but the relevant research has not yet been conclusive, and further research work is needed to explore its mechanism.
A reviewer of the paper commented that "this very important finding reshapes our understanding of the evolution of reptile reproduction and will shift the focus of current research from what limits the emergence of procreation in prenatural animals to exploring the role of natural selection in the evolution of primordial animals."
In addition, the study simulated biological lineages and found that the sex of dinosaur offspring was genetically determined. However, the living taxa most closely related to dinosaurs, including turtles and crocodiles, have descendants whose sex is determined by the temperature of the environment. The difference also surprised the researchers.
Liu Jun and others believe that the combination of the sex gene determination mechanism of fetal birth and offspring has enabled animals such as dinosaurs to become overlords in the ocean.
The paper is titled "Live birth in an archosauromorph reptile," with Liu Jun as the first author and corresponding author, and the other four researchers are from Montana State University, the University of Bristol in the United Kingdom, the University of Sydney in Australia, and the University of Queensland.