Dinosaurs have fascinated paleontologists for a long time. After a fiery meteorite bombarded Earth 66 million years ago, it was a tumultuous end to the reign of these once dominant beasts.
According to an analysis of over 1,000 eggshells found in central China, dinosaurs were already leaving the planet millions of years before the meteorite hit.
According to the South China Morning Post, the author of the study said dinosaurs went extinct gradually over millions of years.
The conclusions will be tested. There is a long and see-sawing debate about whether non-avian dinosaurs met an abrupt end or if they were already on the edge of extinction.
Birds are the only living descendants of dinosaurs, according to new research from a team of geologists and paleontologists in China.
Several complete and incomplete dinosaur eggs, preserved in 150-meter-thick layers of rock, were found in a collection of egg fossils.
One of the most abundant dinosaur records from the late Cretaceous period can be found in the area where the egg fossils were discovered. Compared to older fossil records, the researchers only found three taxa of dinosaurs in the fossilized eggshells.
The researchers think that the decline in variation may have weakened the dinosaurs' ability to recover from the impact of the asteroid that hit Mexico. They were snookered by the lack of options.
"Our results support a long-term decline in global dinosaur biodiversity prior to 66 million years ago, which likely set the stage for the end-Cretaceous non-avian dinosaur mass extinction," the researchers wrote.
Han and colleagues used a number of techniques to estimate the age of the rock samples, construct a timeline with the data that had a resolution of 100,000 years, and make a map of the area.
Two of the three dinosaur eggs were from a group of toothless, parrot-like dinosaurs called oviraptors, with the third group of egg-laying dinosaurs being herbivorous.
The low species diversity that the researchers found matches with skeletons of ancient dinosaurs that have been found in southern and eastern China, as well as some bonebeds in North America that hint at declining dinosaur diversity during the same period.
Han and colleagues suggest that the decline may have been caused by global climate fluctuations and volcanic eruptions.
Dinosaurs are thought to be prone to extinction, and other studies suggest that their diversity may have begun to decline as early as 10 million years ago.
Past studies have found something else. Less than 20% of dinosaurs were in decline before the asteroid impact, but other species were thriving, according to a recent analysis.
Han and colleagues conclude that the only way to resolve these conflicting interpretations is to find, sample, and analyze more fossils and to integrate existing data from fossil sites around the world.
It's not an easy task, but one that could help settle what happened during the dinosaurs' reign.
The study of fossils in Asia is a big step in that direction.
The study was published in a peer reviewed journal.