Lü L., Unwin D.M., Deeming D.C., Jin X., Liu Y. and Ji Q., 2011, An Egg-Adult Association, Gender, and Reproduction in Pterosaurs. Science 21 January 2011: Vol. 331 no. 6015 pp. 321- 324 DOI: 10.1126/science.1197323
A pterosaur find in 2009, from the Cretaceous deposits of Liouning Province in North Eastern China, has allowed sex determination in the pterosaur Darwinopterus. A number of specimens of this pterosaur are known and this recent find has revealed an uncrested individual with a ready to lay egg. These specimens are about 160 million years old.
Dr Charles Deeming of Lincoln University assisted in the analysis of the pterosaur fossil when it was in the UK. The fossil is currently held in the Zhejiang Museum of Natural History, Hangzhou, Zhejiang province, China