Pterosaurs May Have Flown as Soon as They Hatched

A new analysis of the flying reptile’s embryos indicates the bones needed for flight were highly developed in the egg

Pterosaur Babies
Zhao Chuang

For baby birds learning how to fly, it takes some practice, positive reinforcement and sometimes a bit of a push. As we know, our feathered friends are survivors of dinosaurs, ironically a terrestrial species that couldn’t fly yet called theropods. Instead, pterosaurs were the kings and queens of the sky during the time of the dinosaurs, but these winged-reptiles bear no relation to modern birds.

Another ability that sets pterosaurs apart could be the ability to fly from the moment they cracked open their shell—little to no parental involvement needed, according to a new study in the Proceedings of the Royal Society B.

Previous research had concluded that pterosaurs probably learned to fly like today’s birds. Observations of prehistoric embryos found that they had poorly developed wings, meaning they likely needed some help from mom or dad until they reached nearly full size. But Cara Giaimo at The New York Times reports the current study had a wealth of new data to analyze that led them to reach the opposite conclusion.

In 2017, paleontologists unearthed a pterosaur colony from the species Hamipterus tianshanensis that was covered with mud 100 to 145 million years ago during floods in Jinzhou, China. Not only were there hundreds of fossilized bones from adults and juveniles, there were also 300 ancient eggs, including 16 with embryos at various stages of development.

Paleobiologists David Unwin of the University of Leicester and Charles Deeming of the University of Lincoln suspected there were enough samples to accurately chart out the development of pterosaur embryos. Unwin tells The New York Times that previous attempts to map the development process had been “kind of ad hoc — just look-at-it-and-guess.”

The duo and their team carefully examined the Jinzhou embryo fossils along with others recently found in China and Argentina. Previous research had assumed that the Jinzhou embryos were all at a similar stage of development. But after analyzing egg size and shape, limb length, and other age markers, they found the embryos were at various stages of development—from freshly laid to close to hatching.

They also looked at data from juveniles of nine other pterosaur species as well as modern crocodiles and quails to understand the sequence in which their bones harden. The team’s conclusion is that the little pterosaurs, known as flaplings, came out of their shells with the right proportions and strong enough bones to let them take to the skies.

“The extraordinary thing about those embryos is they have a set of bones that in many respects match those of adults in terms of proportions," Unwin tells Chelsea White at New Scientist. “When they come out of the egg, they are like mini-adults.”

One of the strongest pieces of evidence that the pterosaurs were precocious fliers is the fact that their wing bone—equivalent to the middle finger in humans and an important bone for flying—hardens very early. In most vertebrates, it’s one of the last bones to ossify.

“It’s extremely unlikely that they would equip themselves with a flight apparatus if they were not going to use it,” Unwin tells Giaimo. “What do you need mummy and daddy for if you can do everything yourself?”

David Martill, paleobiologist at the University of Portsmouth who was not involved in the study, tells Ryan F. Mandelbaum at Gizmodo that the interpretation is solid. “That paper was super,” he says. “If you look at flying animals, even precocious birds, their wing skeletons aren’t as developed. Bats’ aren’t as developed. Pterosaurs, they’re developed with the same aspect ratio of adults.”

But not everyone thinks the tiny pterosaurs were born air-worthy. Kevin Padian, museum curator at the University of California, Berkeley, tells New Scientist that there is an important piece of the flight puzzle missing: muscles. He points out that even precocial birds can only support about 10 percent of their own bodyweight right out of the egg.

“It is quite a stretch to assume that hatchling pterosaurs could support 100 per cent of the body mass in the air, especially with no data on muscle mass of hatchlings,” Padian says.

Unwin points out that this study makes one thing clear: Pterosaurs developed differently than modern birds and bats, making them an imperfect comparison. “It’s that sheer alienness of pterosaurs that is really fascinating about them,” he tells The New York Times’ Giaimo. “These were creatures that were really different than anything that’s around today.”

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