Abstract

Ninety years have passed since Roy Chapman Andrews returned from his exploration of Mongolia with tales of fossilized dinosaur eggs (1). Fossils interpreted as dinosaur eggs had been described before, but Chapman's crew had found fossils that could only be interpreted as clutches of eggs. Recent fossil evidence of dinosaur reproduction has confirmed that all dinosaurs laid eggs, whereas other Mesozoic groups, such as the aquatic ichthyosaurs, evolved live birth (2). However, the reproductive biology of a key group of extinct Mesozoic species, the flying pterosaurs (see the image), has remained elusive. On page 1197 of this issue, Wang et al. (3) report the largest accumulation of Hamipterus pterosaur eggs found to date. The work is a crucial advance in understanding pterosaur reproduction.