Egg research says dinosaur numbers dwindle when asteroid hits

Most information about dinosaurs of the late Cretaceous period came from what is now the United States, especially Hell Creek The making progress, 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 is representative of global dinosaur diversity. afterward.

To fill this gap in the fossil record, researchers in China studied more than 1,000 fossil dinosaur eggs from Shanyang. basin in central China. The study, which shows that dinosaur diversity waned at the end of the Cretaceous, is published September 19 in the journal Nature. 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 representing each 100,000 year period. The research involved gathering detailed age estimates of rock layers by analyzing and applying computer models to more than 5,500 geological samples.

Analysis found full eggs and eggshell fragments from The researchers said there were only three species of dinosaurs, which suggests that dinosaur biodiversity was low during that time period.

Macroolithus yaotunensis and Elongatolithus elongatus belong to a group of toothless dinosaurs known as oviraptors, while the third, Stromatoolithus pinglingensis, is a herbivorous dinosaur, or a member of the group of duck-billed dinosaurs.

Fragment of asteroid that killed dinosaurs may have been found

Researchers say their findings from fossil eggs are consistent with fossil dinosaur bones found in the same area and around, although they have discovered several other dinosaur bones from the area that suggest Tyrannosaurs and sauropods also lived in this area between 66.4 million and 68.2 million years ago.

Pictured is a fossilized egg of the species Macroolithus yaotunensis, seen as part of the study.

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

Most dinosaurs are extinct, but several smaller, birdlike species survived and evolved into the birds we see today.

Opponents of the sudden death by asteroid theory point to The global cooling may have made life difficult for many dinosaurs. Their downfall is also related to a a series of large volcanic eruptions in the Deccan Trap in what is now India.
Paleontologist Alfio Alessandro Chiarenza, a postdoctoral fellow at the University of Vigo in Spain, who worked Paleozoic climate records from that period, saying that fossil eggs are not a reliable record of dinosaur diversity. He was not involved in the study.
He points to recent research that many Dinosaurs can have soft shell eggs that would be hard to fossilize. In addition, no eggs have been found for many dinosaurs Even well-known species like Tyrannosaurus rex, says Chiarenza.
The asteroid that destroyed the dinosaurs struck in the spring

“These results also contradict what emerges from egg carcasses and the diversity of bones, teeth and other remains found in places like Spain, (and) other remains,” he said by email. What we know is based on North American records. “So I believe these authors are misinterpreting these signals.”

He still believes the asteroid strike is the real driving force of the extinction of the dinosaurs.

“Dinosaurs were probably very good and varied and if it weren’t for the late Cretaceous asteroids (they) might as well dominate today as far as we know.”

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