A life reconstruction of Hamipterus tianshanensis, a species of pterosaur that lived in what's now China more than a hundred million years ago. Paleontologists just found hundreds of their eggs, dramatically improving our understanding of how the winged reptiles bred.

In a world first, paleontologists working in northwestern China have discovered a cache of hundreds of ancient eggs laid by pterosaurs, the flying reptiles that lived alongside the dinosaurs. Some of the eggs contain the most detailed pterosaur embryos ever found.

Although scientists have studied pterosaurs for more than two centuries, no eggs were discovered until the early 2000s, and fewer than a dozen turned up in the intervening years. The new haul, discovered by Chinese Academy of Sciences paleontologist Xiaolin Wang, includes at least 215—and perhaps as many as 300— stunningly preserved pterosaur eggs.

His team also found 16 embryos within the eggs, and they suspect that more remain locked away in the stone. Wang and his colleagues announced the finds today in Science.

“We get a lot of hyperbole in paleontology, but it’s pretty phenomenal,” says David Hone, a researcher at Queen Mary, University of London who wasn’t involved with the study. “The science is at the absolute start, but the mere raw material is game-changing, potentially.”

Two of the newfound pterosaur eggs. Paleontologists say that they have found hundreds of eggs so far, including at least 215 within a single sandstone block. More are probably hidden within the block's interior.

The newfound eggs belong to Hamipterus tianshanensis, a previously known species of pterosaur that lived in northwestern China more than a hundred million years ago. With a maximum wingspan of 10 feet and a probable taste for fish, these animals may have resembled today’s herons, living near waters that crisscrossed inland terrain.