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Even more like birds Ecological convergence between pterosaurs and birds is often invoked, but to what degree the two groups share behavior is debated. Wang et al. describe a site with more than 100 fossilized pterosaur eggs that reveals that hatchling pterosaurs were likely not as precocial as previously thought (see the Perspective by Deeming). Furthermore, the overlaying of multiple clutches suggests that the pterosaurs may have exhibited breeding site fidelity, similar to rookery-breeding seabirds. Thus, the similarity between these two groups goes beyond wings. Science, this issue p. 1197; see also p. 1124 Possible pterosaur rookery reveals secrets of embryo development. Fossil eggs and embryos that provide unique information about the reproduction and early growth of vertebrates are exceedingly rare, particularly for pterosaurs. Here we report on hundreds of three-dimensional (3D) eggs of the species Hamipterus tianshanensis from a Lower Cretaceous site in China, 16 of which contain embryonic remains. Computed tomography scanning, osteohistology, and micropreparation reveal that some bones lack extensive ossification in potentially late-term embryos, suggesting that hatchlings might have been flightless and less precocious than previously assumed. The geological context, including at least four levels with embryos and eggs, indicates that this deposit was formed by a rare combination of events, with storms acting on a nesting ground. This discovery supports colonial nesting behavior and potential nesting site fidelity in the Pterosauria.