October 7, 2022

Dinosaurs were in decline when asteroid hit, egg study says

3 min read

At the end of the Cretaceous period, most information about dinosaurs comes from what is now the United States, especially Hell Creek formation, which provides a picture of relatively rich dinosaur diversity during the last million years of this period.

However, fossil records from other regions are 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 fossilized dinosaur eggs from Shanyang. basin in central China. Dinosaur diversity was already disappearing at the end of the Cretaceous, suggests the study, published on September 19. Scientific journal Proceedings of the National Academy of Sciences.

Eggs and eggshell fragments represent the last 2 million years of the dinosaurs, with fossils representing every 100,000 year interval. The study involved analyzing more than 5,500 geological samples and applying computer modeling to obtain a detailed estimate of the age of the rock layers.

Analysis found the whole Eggs and eggshell pieces Only three species of dinosaurs, the researchers said, suggest low dinosaur biodiversity during this time.

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

A fragment of the asteroid that killed the dinosaurs may have been found.

The researchers They said their findings from the fossilized eggs are consistent with dinosaur bones found in the same and surrounding area, although they have discovered a few additional dinosaur bones from the region that show that. Tyrannosaurs and sauropods also lived in the area between 66.4 million and 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 around 66 million years ago,” the study said, “which likely set the stage for the Cretaceous nannovian dinosaur mass extinction.”

Most of the dinosaurs went extinct, but Some survived as small, bird-like creatures and evolved into the birds we see today.

Opponents of the sudden death theory point to asteroids. A period of global cooling that made life difficult for many dinosaur species.. His death has also been linked to one. A series of massive volcanic eruptions in the Deccan Traps In which India is now.
Epidemiologist Alfeo Alessandro Chirenza, A A postdoctoral research fellow at the University of Vigo in Spain who has worked on it. Paleoclimate records From this period, said fossils are eggs There is no reliable record of dinosaur diversity. He was not involved in the study.
He points to recent research that many Dinosaurs probably had soft-shelled eggs. It is unlikely to become a fossil. Also, no eggs have been found for many dinosaurs Species, even well-known ones like Tyrannosaurus Rex, Chirenza said.
The asteroid that killed the dinosaurs hit in the spring

“These findings also contrast with the diversity of egg remains found in places like Spain and the diversity of bones, teeth and other remains we know based on the North American record,” he said by email. “So I believe these authors are misinterpreting these signals.”

He believes an asteroid strike was the real driver. Extinction of the dinosaurs

“Dinosaurs were probably fine and diverse and if it hadn’t been for the last time, Cretaceous asteroids (they) might still be dominant today as far as we know.”

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