Between the Jurassic and Cretaceous periods, during the last half of the age of the dinosaurs, pterosaurs evolved from small bird-sized flying reptiles to massive creatures. They stood taller than modern-day giraffes and boasted wings as wide as those of small airplanes.
How this happened presents an ongoing scientific mystery, especially since the eggs laid by pterosaurs changed little in size as the dinosaurs grew to become monsters. What special adaptation allowed them to grow so rapidly after their hatching?
Parenting and Pterosaur Evolution
A new study proposes that a pivotal behavior made the difference: doting parents. Giant pterosaurs came out of their shells in a weak state and received extensive postnatal care, which helped them to grow to an immense size. The earlier, smaller pterosaurs, by contrast, hatched out ready to fly – or they developed the ability soon after and grew relatively little from there on.
“Minimal childcare makes sense in the early evolutionary history of these ancient reptiles because it saves energy. But to grow huge, the larger pterosaurs had a problem,” said Zixiao Yang, a paleontologist from University College Cork, in a statement. “It basically took much longer to become an adult, and therefore parents needed to protect their young from accidents.”
The researchers concluded that the giant pterosaurs had doubled down on parenting by measuring how quickly their young’s wings and limbs had grown during early life. Because those parts had developed more quickly than the rest of the body, the paleontologists concluded that the flying creatures had gone through intensive early growth and nurturing.
What Was the Largest Flying Animal?
The study relied on a mix of new and old fossil specimens, including those of the large pteranodon, which lived about 100 million years ago and had a wingspan of 23 feet or more.
Its immense size had many drawbacks.
For one, its wings were too ungainly to flap repeatedly, meaning it spent most of its time aloft soaring over coastal areas, hunting for fish with its large, pelican-like bill. In general, the creature’s great size made it impossible (or at least unwise) to fit into more confined quarters, where collision with a tree could crack its hollow bones. At a millimeter thick, they made flight possible but everyday existence was a delicate operation.
Nature saved the greatest pterosaur of all, Quetzalcoatlus, for the latter days of the Cretaceous, only a few million years before a large asteroid would strike the earth. With a 40-foot wingspan, Quetzalcoatlus was longer than a Tyrannosaurus rex, taller than a giraffe and clearly the largest flying animal to ever live. Unlike pteranodon, it likely cast its long shadow over land, where it hunted.