China News Service, Beijing, September 20 (Reporter Sun Zifa) From the appearance of the Late Triassic 235 million years ago to the disappearance of the Cretaceous 66 million years ago, dinosaurs have survived on the earth for 170 million years. The mystery has long attracted the attention of the academic circles and the public.
Wang Qiang, the corresponding author of the paper and an associate researcher at the Institute of Paleo-Spine of the Chinese Academy of Sciences, introduced the dinosaur egg fossil specimens in this study and the restoration renderings of three types of dinosaurs in the Shanyang Basin.
Photo by China News Agency reporter Sun Zifa
Chinese scientists have recently completed a study of more than 1,000 in situ buried dinosaur eggs and eggshell specimens collected from the Shanyang Basin, Shaanxi Province, showing that the extinction of dinosaurs has its own external factors, in addition to the two traditional hypotheses of asteroid impact and volcanic eruption. The reason - During the 2 million years from 68 million years ago to 66 million years ago, the diversity of dinosaurs continued to decline. The combined effect of this internal and external cause led to the extinction of dinosaurs.
Wang Qiang, the corresponding author of the paper and an associate researcher at the Institute of Paleo-Spine of the Chinese Academy of Sciences, presented the dinosaur egg fossil specimens introduced in this study.
Photo by China News Agency reporter Sun Zifa
This important research paper on dinosaurs was jointly completed by researchers from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (Institute of Paleoanthropology, Chinese Academy of Sciences), the Institute of Geology and Geophysics, Chinese Academy of Sciences, and China University of Geosciences (Wuhan), Beijing time on the 20th. In the early morning, it was published online in the form of a cover article in the internationally renowned academic journal Proceedings of the National Academy of Sciences (PNAS).
Through systematic research on paleontology, magnetostratigraphy, and cycle stratigraphy in Shanyang Basin, Shaanxi, the cooperative team put forward new insights for solving the mystery of the extinction of dinosaurs.
Restoration renderings of three types of dinosaur fossils in Shanyang Basin, Shaanxi Province.
Photo by Zhao Chuang
Wang Qiang, the corresponding author of the paper and an associate researcher at the Institute of Paleo-Spine of the Chinese Academy of Sciences, was interviewed by a reporter from China News Agency on the 20th and pointed out that scientists have never stopped looking for the reasons for the disappearance of dinosaurs from the earth. Among the various hypotheses about the extinction of dinosaurs, the most representative views are some There are external factors, such as the hypothesis of an asteroid hitting the earth, and there are also internal factors, such as the eruption of the Deccan volcano in India, etc., but they are all related to major geological events.
In fact, to answer the mystery of the extinction of dinosaurs, the most important thing is to rely on the time and space records of dinosaurs living on the earth. However, due to the incompleteness of terrestrial stratigraphic records and regional differences, the answer to this question caused a global comparison difficulties on.
The Shanyang Basin in Shaanxi is one of the few terrestrial basins in China that can study the mystery of the extinction of dinosaurs in the Late Cretaceous-Paleocene. Dinosaur skeletons, dinosaur eggs and Paleocene mammals have been collected, and a continental stratigraphic framework of the Cretaceous-Paleogene in this area has been initially established, laying the foundation for the development of related scientific researches on dinosaurs.
Figure AB shows the change of dinosaur diversity in the Eastern Qinling Basin during the Late Cretaceous; Figure C shows the global distribution of dinosaur fossils found 66 million years ago.
Photo courtesy of the research team
He said that dinosaur eggs, as the main carrier of dinosaurs multiplying on the earth, not only can reflect the reproductive habits of dinosaurs, but also reflect the ancient environment information of dinosaurs' survival period because of their enrichment and burial rules in the stratum.
In this collaborative study, the research team collected more than 1,000 late Cretaceous in situ buried dinosaur eggs and eggshell specimens in the Shanyang Basin. The main types of dinosaur eggs are Yaotun giant eggs, elongated eggs and Pingling. Stacked eggs, whose parent dinosaurs are oviraptorosaurs and hadrosaurs, are very consistent with the types of dinosaurs represented by the dinosaur skeleton fossils in the Shanyang Basin. In addition, there are also a small number of tyrannosaurs and sauropods in the basin. skeletal fossils.
Dinosaur eggs and bones show that dinosaur diversity in the basin was at a relatively low level at that time.
In order to determine the geological age of the layers where the dinosaur fossils are located in the Shanyang Basin, the collaborative team carried out detailed magnetic stratigraphy, biostratigraphy and cyclostratigraphy studies in the Shanyang Basin.
They collected 3,538 paleomagnetic directional samples from four representative sections in the Shanyang Basin. After analyzing the results of paleomagnetic experiments on the samples, they determined their age to be 66.38 million to 65.7 million years ago. The Yang Basin did not experience major tectonic activities from the Late Cretaceous to the Paleogene, and its sedimentary strata are basically continuous.
In order to further improve the age accuracy of the stratigraphy, the research team collected 5,466 rock samples continuously at 5 cm intervals in the Shanyang Basin, and used the astronomical orbit tuning method to divide the stratigraphic age with a resolution of 100,000 years based on the results of magnetic stratigraphy. .
So far, the research team has obtained the high-resolution ages of 44 consecutive dinosaur egg fossil layers in the Shanyang Basin, thus providing a reliable chronological basis for analyzing the changes in dinosaur diversity and its driving factors at the end of the Cretaceous.
Lithological column AB, magnetic polarity sequence C, astronomical tuning result D, dinosaur fossil distribution E and ocean oxygen isotope changes at the end of Cretaceous FG in Shanyang Basin.
Photo courtesy of the research team
Wang Qiang said that the comprehensive chronological results show that the time limit for the distribution of dinosaur fossils in the Shanyang Basin is 68.24 million to 66.38 million years ago, indicating that the diversity of dinosaurs in the Shanyang Basin has been relatively low for about 2 million years before its extinction. s level.
The research team combined dinosaur fossils found in other Late Cretaceous basins in the eastern Qinling Mountains, as well as in Laiyang, Shandong, Nanxiong, Guangdong and other places. There are similarities in the distribution characteristics of dinosaur fossils. They believe that the decline of dinosaur diversity in the Late Cretaceous is likely to be a global phenomenon.
The latest research results of dinosaur eggs in China provide a new basis and perspective for people to understand the extinction process and mechanism of dinosaurs: Dinosaurs are oviparous animals, and the success rate of dinosaur eggs hatching directly determines the prosperity of dinosaur populations.
At the same time, the incubation of dinosaur eggs requires suitable temperature, humidity and even carbon dioxide concentration.
"Therefore, during the Late Cretaceous period, with the co-evolution of natural ecosystems and dinosaurs themselves, dinosaur diversity continued to decline, reducing the ability of dinosaurs to adapt to the environment and preventing them from recovering from volcanic eruptions or asteroid impacts. It can survive and recover from the drastic changes in the environment caused by major disaster events, so as to eventually go to extinction." Wang Qiang said.
(Finish)