Ready for Takeoff

Baby pterosaurs, imagined by an artist

James Brown

Modern flying vertebrates, such as birds and bats, cannot fly at birth and need parental care until their bones and muscles have developed. Researchers previously thought such limitations also applied to pterosaurs, Mesozoic flying reptiles. Recently, however, scientists discovered fossil evidence in China and Argentina that show some baby pterosaurs, or “flaplings,” may have been able to fly at birth.

Paleobiologist David Unwin of the University of Leicester and zoologist Charles Deeming of the University of Lincoln, both in the U.K., analyzed the development of nineteen pterosaur embryos across four different species from the Late Jurassic–Early Cretaceous. They determined the relative developmental stage of each sample by the shape and mass of its egg. Larger, rounder eggs were thought to contain more developed embryos, because the eggs grew bigger and changed shape as they absorbed water.

The two scientists observed that the tiny pterosaurs inside each egg were developing skeletal features, such as long limbs, that would enable them to fly upon hatching. This early ability for flight is what Unwin and Deeming call “superprecocial,” or exceptionally mature upon hatching. Modern reptiles, too, are superprecocial in other ways. “None fly, of course, but they can run, swim, or climb almost immediately after birth, and are quite capable of looking after themselves without any parental support,” said Unwin.

Based on the discovery of egg deposits and adult pterosaur fossils in close proximity, some researchers believe adult pterosaurs lived with and cared for their young. Unwin and Deeming counter, however, that these fossils may have been together because they were in a location suitable for laying and hatching eggs, and not because the pterosaurs cared for their young.

Early independence could have interesting implications for other pterosaur behavior. For instance, Unwin said, it is possible that flaplings had a different diet from adults, so as not to compete with them for food, a strategy also used by modern crocodiles. “Overall,” he said, “it would seem that pterosaurs were very different from modern fliers.” (Proceedings of the Royal Society B)