[Science] Baby pterosaurs may have hatched ready to fly right out of the egg – AI

Born ready to take to the skiesXinhua News Agency/PA Images By Chelsea WhytePterosaurs were born to fly. An analysis of a cache of pterosaur eggs discovered in 2017 adds to the debate over whether these winged reptiles hatched ready to fly – and shows that they may have broken out of their eggs with their wings fully formed. “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. When they come out of the egg, they are like mini-adults,” says David Unwin at the University of Leicester in the UK. He and his colleague, Denis Charles Deeming at the University of Lincoln in the UK, analysed the size and shape of 37 eggs from a collection of 300 found at a site in Jinzhou, China. They found that as the eggs developed, they changed shape from long and slender to relatively round. Advertisement “What happens is rather like me as I got older, they tend to get wider around the middle bit, rather than taller,” says Unwin. Pterosaurs laid their eggs on the ground, and the shells were pliable and porous like modern reptile eggs, so they took up water as they grew. That allowed the parent to use less energy to lay the eggs, says Unwin. Read more: Stunning fossils show pterosaurs had primitive feathers like dinosaurs The team also analysed scans of four embryos, all belonging to the pterosaur Hamipterus, midway through development to see how much of the skeleton had formed. Compared to the rest of the skeleton, they found a greater amount of ossification, or bone tissue formation, in the bones that give the wings structure. This indicates that pterosaurs hatched ready to fly and hunt their own food, says Unwin, a condition at birth biologists describe as precocial. “Whereas it is true, as the authors say, that flight muscle attachment surfaces do not have to be fully ossified in order to function in living birds and bats, even the most precocial of birds can only generate the support of about 10 per cent of its body weight,” says Kevin Padian at the University of California, Berkeley. “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.” Unwin says it’s true that estimating muscle mass is difficult with the data we have, but argues that it makes little sense for these animals to evolve an adaptation that could take up valuable resources in their early life, as they try to grow enough to hunt for themselves. Journal reference: Proceedings of the Royal Society B: Biological Sciences, DOI: 10.1098/rspb.2019.0409 More on these topics: fossils