Dinosaurs were in decline when asteroid hit, egg study says

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It is a hard-fought paleontological debate. did Giant asteroid collided with Earth 66 million years ago Wiped out a thriving and diverse population of dinosaurs, or were they already struggling to survive when that doomsday came?

Most of the information about dinosaurs at the end of the Cretaceous era now comes from the United States, specifically hell creek Build, 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 very thin, and it is not known whether the pattern seen in North America is representative of global dinosaur diversity. Then.

To fill this gap in the fossil record, researchers in China have studied more than 1,000 fossil dinosaur eggs from Shenyang Basin in Central China. Dinosaur diversity was already declining at the end of the Cretaceous, suggested the study published September 19. Scientific journal Proceedings of the National Academy of Sciences,

Eggs and eggshell fragments represent the last 2 million years of the dinosaur era, with fossils each representing a 100,000-year interval. The study involved analyzing more than 5,500 geological samples and using computer modeling to obtain detailed age estimates of the rocks’ layers.

analysis found whole Eggs and egg shell pieces The researchers said there were just three species of dinosaurs, which suggested low dinosaur biodiversity during that time.

Macroolithus yaotunensis and Elongatolithus elongatus belonged to a group of toothless dinosaurs known as Oviraptors, while the third, Stromatolithus pinglingensis, was A plant-eating hadrosaur, or member of the duck-billed dinosaur group.

researcher stated that their discovery from fossilized eggs was consistent with fossil dinosaur bones found in the same and surrounding area, although they discovered some additional dinosaur bones from that area that showed Tyrannosaurs and sauropods also lived in the area from 66.4 million to 68.2 million years ago.

Pictured is a fossilized egg belonging to Macroolithus yaotunensis, which was examined as part of the research.

“Our results support a long-term decline in global dinosaur biodiversity by 66 million years ago,” the study said, “which potentially set the stage for the end-Cretaceous nonavian dinosaur mass extinction.”

Most dinosaurs went extinct, but Some small, birdlike birds survived and evolved into the birds we see today.

Opponents of the theory of sudden death by asteroid indicate Period of global cooling that may have made life difficult for many dinosaur species, His death has also been linked to a Series of massive volcanic eruptions in the Deccan Traps What is in India now?

Paleontologist Alfio Alessandro Chiarenza, a Postdoctoral Research Fellow at the University of Vigo in Spain who has worked paleoclimate record From that period, said fossil eggs are There is no reliable record of dinosaur diversity. He was not involved in the study.

He pointed to recent research that many Dinosaurs probably had soft-shelled eggs Which is not likely to be a fossil. Also, no eggs have been found for many dinosaurs. species, even well-known ones such as Tyrannosaurus rex, Chiarenza said.

“These results also contrast with the diversity of egg remains and bones, teeth and other remains found in places like Spain,[and]what we know,” he said via email. “So I believe these authors are misinterpreting these signs.”

He remains convinced that asteroid strike was the true driver the extinction of the dinosaurs.

“Dinosaurs were probably fine and diverse and if it weren’t for the end Cretaceous asteroids[they]might still dominate today as far as we know.”

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