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This is a swamp debate in paleontology. an action A large asteroid hit Earth 66 million years ago Wipe out a thriving and diverse group of dinosaurs, or will they already be struggling to survive when that catastrophic day arrives?
Most of the information about dinosaurs came in the late Cretaceous from what is now the United States, mainly hell river formation – compositionAnd which provides an overview of the relatively rich diversity of dinosaurs over the last million years of that period.
However, fossil information from that time in other regions is much thinner, and it is not known whether the patterns seen in North America represent global dinosaur diversity. then.
To fill this gap in the fossil record, researchers in China have studied more than 1,000 dinosaur egg fossils from Shanyang. Central China Basin. The study, published on September 19 in Proceedings of the National Academy of Sciences . scientific journal.
Egg and egg shell fragments represent the last two million years of dinosaur age, with fossils counted every 100,000 years. The study included obtaining detailed age estimates for rock layers by analyzing and applying computer modeling to more than 5500 geological samples.
analysis found Full Eggs and egg shell fragments from There were only three types of dinosaurs, the researchers said, indicating a decline in dinosaur biodiversity over that time period.
Macroolithus yaotunensis and Elongatoolithus elongatus belong to the group of toothless dinosaurs known as oviraptors, while the third includes, Stromatoolithus adalah pinglingensis Plant-eating hadrosaurs, or members of the group of duck-billed dinosaurs.
Researcher They said their findings from the egg fossils were consistent with dinosaur bone fossils found in the same and surrounding areas, although they did find some additional dinosaur bones from the area. Tyrannosaurs and sauropods also lived in the area between 66.4 million and 68.2 million years ago.
“Our results support a long-term decline in the biodiversity of the world’s dinosaurs 66 million years ago,” the study said, possibly paving the way for the mass extinction of non-Cretaceous dinosaurs at the end of the Cretaceous.
Most of the dinosaurs went extinct, but Some of the smaller birds survived and evolved into the birds we see today.
Opponents of the sudden asteroid death theory point to A period of global cold that may have troubled many dinosaur species. Their deaths have also been linked to A series of major volcanic eruptions in the Deccan Traps in what is now India.
Paleontologist Alvio Alessandro Chiarenza, Post-doctoral research fellow at the University of Vigo in Spain where he works Catatan paleoclimate From that period, he said that the petrified egg Not a reliable record of dinosaur diversity. He did not participate in the research.
He pointed out that there is a lot of recent research Dinosaurs may have had soft-shelled eggs Impossible to decompose. Moreover, no eggs were found for many dinosaurs Species, even well-known species like Tyrannosaurus rex, Chiarinza said.
“These findings also contradict what comes out of the egg remains and the diversity of bones, teeth and other remains found in places like Spain, (and) what we know based on North American records,” he said by email. “So I think these authors misinterpreted these signals.”
Still convinced that the asteroid strike was the real motive from the extinction of the dinosaurs.
“Maybe dinosaurs were nice and diverse, and if Cretaceous asteroids (they) weren’t around, they might be dominant today as far as we know.”