An article published in the journal “Proceedings of the Royal Society B: Biological Sciences” reports evidence that pterosaurs were able to fly from birth. Dr. David Unwin, a paleobiologist at the University of Leicester, and Dr. Charles Deeming, a zoologist at the University of Lincoln, studied fossil pterosaur embryos at the base of the idea that they could fly only after they grew and compared them with embryos of birds and crocodiles concluding that they were only at the beginning of their development. The discovery in China and Argentina of fossil embryos that were about to hatch provided evidence that pterosaurs could fly from birth.
The idea that pterosaurs should grow like birds and bats before they could fly comes from the discovery of fossil embryos in China that had poorly developed wings. Doctors David Unwin and Charles Deeming tested that idea by examining fossil eggs of the species Hamipterus tianshanensi comparing them with those belonging to other species of pterosaurs and to embryos of birds and crocodiles to compare their development.
The two researchers analyzed the size and shape of the eggs of Hamipterus tianshanensi, which were previously considered at a similar developmental stage. However, their analysis showed the variety of size and in general small and narrow eggs indicate early-stage embryos while large and more round eggs indicate embryos in the final stages of development. The comparison with embryos of flying animals such as birds and with those of their crocodile cousins indicates that pterosaur bones were at a more advanced stage of development that included bone structures important for flight.
The image (Courtesy James Brown. All rights reserved) shows an artistic concept of a landscape from 124 million years ago, in the Lower Cretaceous period, where a pterosaur emerges from the sand. Other hatchling pterosaurs, also called flaplings, are lying on the beach or crawling to a safe place among the trees. A Sinosauropteryx caught a hatchling and is eating it.
This scenario indicates that pterosaurs could run from carnivorous dinosaurs from birth even if in that group of reptiles there was little or no parental care. However, natural selection probably remained harsh and only flaplings who managed to control flight first were able to survive.
Data are lacking regarding pterosaur embryos’ muscles because those soft tissues weren’t preserved. According to the researchers it’s difficult to estimate the mass of their muscles but believe that it would make little sense that they had developed a flight adaptation in their skeleton at such an early stage of development if they couldn’t exploit it from birth.
This precocial flight skills could explain the enormous wingspan that various species of pterosaurs could reach. Large wings would have been a hindrance for animals that couldn’t fly, a problem that doesn’t exist for animals that can fly from birth and therefore with wings that are useful from their birth that grew together with these reptiles.
There are still points to clarify about the development of pterosaurs, but this research shows a really interesting possibility. The availability of several pterosaur eggs to examine and compare could have offered a key to understanding the first flying vertebrates much better.