Fig. 1

a Map showing the fossil site. b Section of the fossil bearing strata, and layer f is the main level where specimens of c were collected. Two specimens in this article were also collected in layer f (legend: 1, coarse grained sandstone with pellets; 2, middle grained sandstone; 3, fine sandstone; 4, cross beddings; 5, parallel beddings; 6, scour marks; 7, pterosaur bones; 8, pterosaur eggs). c Eggs of H. tianshanensis preserved with pterosaur bones in sandstone (IVPP V 18941–18943). d The close-up view of egg fossils (IVPP V 18942). Figure 1b, c, d reproduced with permission of Ref. [40], Copyright of ©2017 Science