In 2017, hundreds of fossil eggs in China revealed that Pterosaurs or ancient flying reptiles may have raised their young

A remarkable fossil discovery in northwestern China has opened a new window into the lives of pterosaurs, the ancient flying reptiles that shared the Earth with dinosaurs. Researchers uncovered hundreds of fossilized eggs alongside the remains of young and adult animals, offering rare clues about how these prehistoric creatures developed. The findings, published in Science, have also sparked fresh debate over whether pterosaurs cared for their hatchlings.

What Makes This Fossil Discovery So Remarkable?

An extraordinary collection of fossils found in northwestern China is helping researchers better understand one of the most mysterious groups of prehistoric animals.


According to a study published in the journal Science, researchers uncovered more than 200 fossilized eggs belonging to Hamipterus tianshanensis, an ancient pterosaur species. The eggs were discovered together with the bones of juvenile and adult animals inside a three-meter-square block of rock excavated from the Turpan-Hami Basin.

The discovery immediately drew attention from paleontologists around the world.

David Unwin, a paleontologist at the University of Leicester in the United Kingdom who was not involved in the research, described the site as "one of the most extraordinary fossil [finds] I've ever seen."

Scientists believe the fossils date back roughly 120 million years.

The research team, led by Wang Xiaolin and Jiang Shunxing from the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, suggests that a sudden flood may have transformed an active nesting ground into a fossil site.

According to the researchers, heavy rain likely caused a river to overflow, washing away hundreds of eggs buried in shallow sand or beneath leaves and grass. Older pterosaurs were also caught in the disaster before the entire area was rapidly buried under sediment. That quick burial prevented decay and preserved both the eggs and skeletons for millions of years.

Unwin believes the site captures something exceptionally rare.

"You've captured the life history of pterosaurs," he said.

Before this discovery, only a handful of fossilized pterosaur eggs had been found, including specimens from Argentina and China. This new collection, however, dramatically expands what scientists can study.

Among the more than 200 eggs, researchers identified fossilized embryonic bones inside 16 specimens. Although many eggs suffered damage while being carried downstream, enough skeletal material remained to allow researchers to compare embryos with older individuals preserved at the same location.

Alexander Kellner of the National Museum at the Federal University of Rio de Janeiro, who helped analyze the fossils, called the discovery remarkable.

"It's amazing," he said. "We never thought we would find so many eggs."

Could Baby Pterosaurs Care for Themselves?

To better understand how the embryos developed, researchers examined the fossils using computerized tomography scans and microscopic analysis of bone samples.

One especially well-preserved embryo revealed that its hind limbs appeared to be more developed than its forelimbs.

According to Kellner, this suggests young pterosaurs may have been capable of walking soon after hatching but were probably unable to fly immediately.

Researchers also found that the embryos appeared to be toothless, unlike some dinosaur embryos.

Taken together, these observations led the authors to suggest that newly hatched pterosaurs may not have been able to search for food on their own.

"They needed some sort of parental care," Kellner said.

What Questions Still Remain?

While the discovery has generated excitement, not every researcher believes the fossils provide conclusive proof that pterosaurs cared for their young.

David Unwin of the University of Leicester says more evidence is needed before reaching that conclusion. He pointed out that the smallest hatchlings preserved at the site are around 40% larger than the embryos found inside the eggs. Because of that size difference, he suggests the forelimbs may have continued developing before the animals actually hatched, meaning the young pterosaurs could still have been capable of flight shortly after emerging from their eggs.

Charles Deeming, an expert on reptile reproduction at the University of Lincoln in the United Kingdom, also urged caution.

Although he described the fossil discovery as remarkable, he warned researchers against drawing broad conclusions from a relatively small number of closely studied eggs.

"One of the dangers … is that they are often overinterpreted," Deeming said.

Jiang agreed that the criticism is reasonable, but believes the enormous collection of eggs will eventually allow researchers to answer many of the remaining questions.

As additional specimens are examined, scientists expect to build a much clearer picture of how these ancient flying reptiles lived and reproduced.

Unwin also believes the sheer size of the fossil collection changes what researchers can accomplish.

"The numbers [of eggs and bones] mean that we can move on from positing ideas to testing ideas," he said. The site itself also offers another important clue. Researchers found pterosaur remains scattered through multiple layers of rock, suggesting the location served as a nesting ground for many years rather than during a single breeding season.

According to Unwin, that repeated use indicates the animals regularly returned to the same area to lay their eggs.

"It must have been a great place to bury eggs," Unwin said, "until, periodically, catastrophe struck."

The fossil block described in the Science study may therefore represent only one chapter in a much larger history.

Jiang says researchers have only begun exploring what the site has to offer.

"There are many more eggs."

That possibility excites scientists because every new specimen has the potential to answer long-standing questions about pterosaurs, creatures that lived alongside dinosaurs but remain far less understood.

The discovery reported by researchers from the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology has already transformed what scientists know about pterosaur reproduction. Whether it ultimately proves that these ancient flying reptiles raised and cared for their young remains an open question, but the remarkable fossil site has given researchers something they rarely have in paleontology: enough evidence to keep testing ideas rather than simply proposing them.

With hundreds of eggs, developing embryos and the remains of older animals preserved together, the fossil cache provides one of the richest records ever uncovered of pterosaur life. As further analysis continues, scientists hope the site will reveal even more about how these ancient reptiles nested, grew and survived millions of years ago.



This report is based on information published in Science, featuring research by the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology, with expert commentary from the University of Leicester, the National Museum at the Federal University of Rio de Janeiro, and the University of Lincoln.

FAQs

Why is this fossil discovery important?

It includes more than 200 rare pterosaur eggs and embryos.

Did pterosaurs care for their young?

The fossils suggest they might have, but scientists are still investigating.