Did the meteor hit the dinosaurs at the height of its run, or was it more of a bang at the end of the slow retreat? A study now provides further evidence that the catastrophe occurred about 66 million years ago in the world of dinosaurs already marked by the extinction of species. Using egg fossils, paleontologists have shown that during the last chapter of the Cretaceous period, a decline in biodiversity was also recorded in Asia. The researchers say the decline in biodiversity may have contributed to the fact that, with the exception of birds, no dinosaurs survived Caesarea.
For millions of years, they dominated the animal world of the world and produced a huge variety of species: dinosaurs were successful models in every sense of the history of evolution. The end of the Cretaceous period was still clearly marked by these highly developed organisms. But then suddenly there was a bullet: about 66 million years ago, a huge meteorite crashed into the Earth in the area of the Yucatan Peninsula today and caused a global catastrophe. Paleontologists largely agree that this sealed the age of the dinosaurs: all species except the ancestors of modern birds swept through the stage of evolutionary history by the direct and indirect effects of influences.
Did the blow come out of nowhere?
However, there has been debate for some time about the state of the dinosaur world at the time of the apocalypse. Some research indicates that this group of animals experienced a professional peak at the end of the Cretaceous period. But since then there have been increasing indications that the impact of the meteorite has weakened them somewhat. Recently, a study of the development of dinosaur biodiversity in present-day North America revealed a decline in biodiversity in the lead-up to the meteor impact. But someone objected that it could have been a more regional phenomenon rather than a global trend.
As part of their study, scientists led by Fei Han of the China University of Geosciences in Wuhan wanted to know to what extent finds from Asia also show a declining trend in the biodiversity of dinosaurs in the Maastricht era. Their findings are based largely on an examination of fossil eggs found in the Shanyang Basin in central China. It comes from a multi-layered rock formation with a total thickness of about 150 meters. The special feature of the study lies in the relatively accurate dating of the sediments, and the researchers confirm: by analyzing more than 5,500 geological samples, they were able to identify finds from about two million years before the end of the Cretaceous period. About 1,000 of these egg fossils have been assigned to dinosaur species based on their characteristics.
decrease in biodiversity
As the team reported, there was a very low level of biodiversity in the era of the last chapter of the Cretaceous period: in sediments about 68 to 66 million years ago, researchers found eggs from three different types of dinosaurs, which in turn could be assigned only two groups: the oviraptor and hadrosaurs, also known as duck-billed dinosaurs. There is also information from other sites, according to representatives of the dinosaur family and the sauropod family who lived in the Maastricht era. Scientists reported that from the previous period – the so-called Campanians – representatives of eight dinosaur groups were known from the East Qinling region.
Han and colleagues conclude that the results also show a significant decline in dinosaur species in Asia at the end of the Cretaceous period. In conjunction with previous study findings from North America, this finding supports the assumption that this animal group was in decline even before its extinction. Scientists explain that this may be due to global climatic fluctuations and volcanic eruptions at the end of the Cretaceous period.
According to them, many specialists may have fallen victim to the instability of ecosystems. The more adaptable representatives may also have acclimatized to the adverse conditions of Maastricht, as they may be able to use a wide variety of food plants. However, in the end, they were also apparently unable to deal with the severe consequences of the meteor impact. Fewer species may mean less basic potential for survivors: Low biodiversity may have contributed to the fact that no dinosaur species survived the catastrophic time, researchers say, except for the ancestors of birds.
Source: Chinese Academy of Sciences, professional article: Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2211234119
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