Newly discovered embryo fossils illustrate the pterosaur's early life

Scientists have discovered a site in China that once served as a nesting ground for pterosaurs — the flying reptiles of the dinosaur age. They recovered more than 200 egg fossils, 16 of which show pterosaur embryos and provide a host of new insights into the ancient creature's early life, per a paper published today in the journal Science.

Why it matters: There is very little existing evidence about pterosaur hatchlings, Michael Habib, a paleontologist from the University of Southern California who was not involved in the study, told Axios. "We don't know what the babies looked like of most animals in the fossil record." The newly-discovered fossils provide details about how young pterosaurs developed and how their mothers nested.

Key takeaways, per Alexander Kellner, one of the study's authors and a paleontologist at the Federal University of Rio de Janeiro:

• Pterosaur eggs have a fragile, almost leathery exterior, so the fact that they were preserved in fossils tells us that whatever killed the dinosaurs happened fast, Kellner says.
• The volume of eggs found at the site and their discovery across layers of the ground suggests pterosaur mothers nested communally and repeatedly returned to the same nesting ground.
• The bones in pterosaur hatchlings' wings were less developed than their femur bones, indicating pterosaurs may not have been able to fly immediately after hatching. They may have needed assistance from adults to survive in the earliest stages of life. But that interpretation depends on the stage of development captured by the discovered embryo fossils, Habib said. If the embryos were only partially developed, its unclear what their wings and legs were like at hatching. Also, in some cases, the bones in embryos' wings were larger — and therefore likely mechanically stronger — than their femur bones, even though they were less developed, he said. This could indicate the hatchlings were indeed capable of flight at birth.

One caveat: Of the 16 embryos scientists found, several were incomplete. Kellner believes more such egg fossils exist at the site in China because it appears to have been a popular nesting ground for pterosaurs. More fossils will solidify scientists conclusions about Pterosaurs' development.