The first dinosaur egg may be soft.

Author | Ren Fangyan

At the National Museum of Natural History in Chile, a fossil specimen has never been marked as a classification.

I brought it back from the South Pole in 20 1 1 year. It is about 28 cm long and 18 cm wide, which is a bit like a deflated football.

In the past ten years, scientists have been at a loss to confirm the origin of this fossil.

Coincidentally, Mark Norell, a paleontologist at the American Museum of Natural History, also has a problem that has not been solved for more than ten years.

In 2005, he and his colleagues discovered some protoceratops egg fossils in southern Mongolia. These eggs contain the skeleton of a baby dragon, but no one can explain why there is a mysterious white ring on the edge of the egg.

On June 18, Nature published two papers, which solved two puzzles and pointed to a key conclusion: the eggs laid by early dinosaurs were soft.

This also explains why among dinosaur fossil specimens, egg fossils are particularly rare-eggs in soft shell state are more fragile and more difficult to evolve into fossils.

Julia Clark is a paleontologist at the University of Texas at Austin.

Thanks to the efforts of her and her colleagues, the "discouraged football" finally got its identity-it is actually a fossil egg of a large underwater predator black dragon, which came from 66 million years ago.

Through a series of microscopic observations, they confirmed that the fragile outer wall of fossil folds is actually the layered structure of eggs.

The white ring on the fossil discovered by Norell and others is only a strong proof of soft-shelled eggs. To solve this problem, he and his colleagues put fossil samples into lasers to record the changes caused by the interaction between light and the sample surface.

The research team used two sets of fossil samples, one is the protoceratops egg fossil unearthed in Mongolia 75 million years ago, and the other is the black dragon egg fossil about 2150,000 years ago.

The molecular fingerprints of soft eggshells are different from those of hard eggshells. Norell and others finally confirmed that the white halos on two fossils are actually fossil versions of molecular fingerprints of soft eggshells.

Black dragon lived in the early age of dinosaurs.

Previous studies have pointed out that early dinosaur eggs are likely to be soft. Protoceratops's egg fossils mean that soft-shelled eggs existed even in the late dinosaur era when hard-shelled eggs appeared.

Last year, researchers at the University of Leicester in England also found that pterosaurs also laid soft-shelled eggs, and the hatched pterosaurs could fly immediately.

Clark and others also pointed out that black dragon is likely to hatch its shell within a few minutes after the soft-shelled egg is laid.

Some researchers pointed out that dinosaurs on land buried soft-shelled eggs, probably for safety reasons. After all, several tons of adult dinosaurs hatched directly on eggs, and the eggshells were easily destroyed.

Some researchers also said that this practice can prevent eggs from losing water. However, this may also lead to lower temperature and slower development of eggs.

These two studies have changed people's understanding of dinosaur growth and feeding methods.

Ricardo araujo, a paleontologist at Lisbon University of Science and Technology, pointed out that the conclusions of Norell and others were convincing, and their research reminded people that "we know very little about the diversity of dinosaur breeding strategies".