Fossilized dinosaur eggs discovered in China provide new evidence that dinosaurs were already in decline before the asteroid impact that eventually wiped them out. The eggs, which date back to the Late Cretaceous period, show signs of stress and disease, suggesting that the dinosaurs were facing environmental challenges even before the asteroid hit.

The study, published in the journal "Scientific Reports," examined fossilized dinosaur eggs from the Gobi Desert in Mongolia. The eggs were laid by oviraptorosaurs, a group of bird-like dinosaurs that lived in Asia and North America during the Cretaceous period.

The researchers found that many of the eggs showed signs of stress, such as abnormal shapes and thin shells. They also found evidence of disease, including lesions on the eggshells. These findings suggest that the dinosaurs were facing a number of challenges, including climate change, habitat loss, and competition from other animals.

"Our findings provide new evidence that dinosaurs were already in decline before the asteroid impact," said study co-author Dr. Darla Zelenitsky, a paleontologist at the University of Calgary. "This suggests that the asteroid impact may have been the final blow for dinosaurs, but it was not the only factor that led to their extinction."

The findings are consistent with other recent studies that have found evidence of declining dinosaur populations in the Late Cretaceous period. For example, a 2017 study found that the number of dinosaur species in North America decreased by about half in the last 10 million years of the Cretaceous period.

These studies suggest that the dinosaurs were already facing a number of challenges before the asteroid impact. The asteroid impact may have been the final blow, but it was not the only factor that led to their extinction.