Fossil egg analysis in China adds to debate of what may have caused dinosaurs' demise

Did the massive asteroid that struck Earth 66 million years ago wipe out a thriving and diverse population of dinosaurs, or were they already struggling to survive when that cataclysmic day dawned?
However, fossil information from that time in other regions is much thinner, and it’s not known whether the pattern seen in North America is representative of global dinosaur diversity then.
To fill in this gap in the fossil record, researchers in China have studied more than 1,000 fossilized dinosaur eggs from the Shanyang basin in central China.
Dinosaur diversity was already on the wane at the end of the Cretaceous, suggested the study, published September 19 in the scientific journal Proceedings of the National Academy of Sciences.
The eggs and eggshell fragments represent the last 2 million years of the dinosaur era, with fossils representing each 100,000-year interval.
The study involved obtaining detailed age estimates of rock layers by analyzing and applying computer modeling to over 5,500 geological samples.
The analysis found whole eggs and eggshell fragments from just three species of dinosaurs, which suggested low dinosaur biodiversity during that time period, the researchers said.
Opponents of the theory of sudden death by asteroid point to a period of global cooling that may have made life hard for many dinosaur species.
He pointed to recent research that many dinosaurs probably had soft-shelled eggs that would be unlikely to fossilize.
Plus, no eggs have been found for many dinosaur species, even well-known ones such as Tyrannosaurus rex, Chiarenza said.
“So I do believe these authors are misinterpreting these signals.”He remains convinced the asteroid strike was the true driver of dinosaur extinction.
“Dinosaurs were probably fine and diverse and if it wasn’t for the end Cretaceous asteroid (they) might as well be dominating today as far as we know.”
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