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It’s a quagmire debate in paleontology. an act A huge asteroid hit Earth 66 million years ago Wiping out a thriving, diverse group of dinosaurs, or were they already struggling to survive when that disastrous day dawned?
Most of the information about dinosaurs comes at the end of the Cretaceous period from what is now the United States, especially Hell Creek formation – compositionAnd the which provides a picture of the relatively rich dinosaur diversity during 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 pattern seen in North America represents global dinosaur diversity. and then.
To fill this gap in the fossil record, researchers in China have studied more than 1,000 fossilized dinosaur eggs from Shanyang. Central China Basin. The study, published on September 19 in Scientific journal Proceedings of the National Academy of Sciences.
Egg fragments and eggshell represent the last two million years of the age of the dinosaurs, with fossils accounting for every 100,000 years. The study included obtaining detailed age estimates for rock layers by analyzing and applying computer modeling on more than 5500 geological samples.
analysis found Full Eggs and eggshell fragments from There were only three types of dinosaurs, the researchers said, indicating a decline in dinosaur biodiversity during that time period.
Macroolithus yaotunensis and Elongatoolithus elongatus belong to a group of toothless dinosaurs known as oviraptors, while the third belongs to, Stromatoolithus was pinglingensis A plant-eating hadrosaur, or a member of the duck-billed dinosaur group.
Researchers They said their find from fossilized eggs was consistent with fossilized dinosaur bones found in the same and surrounding area, although they did discover some additional dinosaur bones from the area showing Tyrannosaurus 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 world’s dinosaur biodiversity 66 million years ago,” the study said, likely paving the way for the mass extinction of non-Cretaceous dinosaurs at the end of the Cretaceous period.
Most of the dinosaurs became extinct, but Some of the smaller birds survived and evolved into the birds we see today.
Opponents of the theory of sudden asteroid death refer to A period of global cold that may have made life difficult for many species of dinosaurs. Their demise has also been linked to a A series of massive volcanic eruptions in the Deccan Traps in what is now India.
Paleontologist Alvio Alessandro Chiarenza, Postdoctoral Research Fellow at the University of Vigo in Spain on which he worked Paleoclimatic records From that period, he said that petrified eggs Not a reliable record of dinosaur diversity. He did not participate in the study.
He pointed out that there is a lot of recent research Dinosaurs may have had soft-shelled eggs It is unlikely to decompose. In addition, no eggs were found for many dinosaurs Species, even well-known species like Tyrannosaurus rex, Chiarinza said.
“These findings also go against what appears from the egg remains and the diversity of bones, teeth and other remains found in places like Spain, (and) what we know based on the North American record,” he said by email. “So I think these authors are misinterpreting these signals.”
Still convinced that the asteroid strike was the real motive from the extinction of the dinosaurs.
“Maybe the dinosaurs were good and varied, and if it wasn’t for the Cretaceous asteroid[they]would have dominated the day as far as we know.”
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