The mysterious deaths were discovered in the Sichuan Basin by Chinese scientists in the beginning of the 1970s. In Zigong alone, fossils of more than 100 dinosaurs were unearthed within a radius of three square kilometers. Most of them were vegetarians.

A group of Chinese paleontologists have studied fossil bones of 50 dinosaurs from different eras of the Jurassic period. These fossils were unearthed in the central, northern and southern parts of the Sichuan basin along with fossils of fish, turtles and plants of the corresponding periods.

Neutron activation analysis shows some abnormality in trace elements in the fossil bones of the dinosaurs.

"The content of arsenic, chrome and other trace elements in the fossil bones are apparently high," said Li Kui, Curator of the Museum of the Chengdu College of Polytechnics. "It is most likely that dinosaurs took in too much plants containing lethal elements."

The study of fossilized plants found in the same areas as the dinosaurs revealed that the content of arsenic in the plants is also very high.

"Perhaps dinosaurs suffered from chronic arsenic poisoning due to excessive intake of plants containing that element," he said. "When the lethal element accumulated, it caused dinosaurs to die during a span of dozens of years or even 100 years," he explained.

Another group of scientists from Peking University and the National Geologic Testing Center arrived at a similar conclusion after studying a large concentration of fossil bones of dinosaurs unearthed in North China's Shanxi Province. They used methods such as inductive coupling plasma spectrometry, atomic absorption spectrometry and inductive coupling plasma mass spectrometry.

Chinese paleontologists have also discovered a similar phenomenon in fossilized dinosaur eggs. The phenomenon could also be associated with the food intake of dinosaurs.

(China Daily)