Pterosaurs, extinct winged reptiles that lived alongside the dinosaurs, may have hatched with the ability to walk, but not to fly. The bones of their hips were fully formed at birth, allowing them to support their own weight on their hind legs and take their first steps. However, the bone structure that would support pectoral muscle movement—which is essential for flight—was underdeveloped. The hatchlings were also born without teeth, meaning they probably could not feed on their own. They likely had to remain under the care of their parents for quite some time until they had teeth and the bones needed to support flight were fully formed. This theory on the embryonic development and early movements of young pterosaur hatchlings was proposed in a study by Brazilian and Chinese paleontologists (Science, December 1). “The mismatch between the development of the hips and the pectoral muscles suggests that pterosaurs could not fly at birth,” says paleontologist Alexander Kellner, from the National Museum at the Federal University of Rio de Janeiro (UFRJ), one of the authors of the paper. With the aid of computed tomography imaging, the group examined the inside of 16 pterosaur eggs of the Hamipterus tianshanensis species, which lived about 120 million years ago in the Turpan-Hami basin, in northwest China. At about five centimeters high, the eggs had not been flattened and therefore maintained their three-dimensionality. The studied fossils were part of the largest known collection of pterosaur eggs (215 in total), which were found alongside dozens of adult specimens in a sandstone block.
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