Scientists think the adult was an expectant pterosaur mother that somehow broke her left wing, causing her to fall into the lake and drown. The body sank to the bottom and eventually expelled the egg.
"During the decay process, you get a buildup of gases and pressure inside the carcass, and that tends to expel things out," said study co-author David Unwin, a paleontologist at the University of Leicester in the U.K. The egg "didn't go very far. It just came out of the body and sat there."
In addition to the associated egg, the fossil has a larger pelvis than other known Darwinopterus fossils, which is consistent with the animal being a female.
Chemical analysis of the egg suggests that, instead of laying hard-shell eggs and watching over the chicks, as most birds do, pterosaur mothers laid soft-shell eggs, which they buried in moist ground and abandoned.
The fossil gives clues as to how the eggs were formed and hatched, and since this is the first conclusively female fossil, we're finding out more about sex differences in pterosaurs. Read more at National Geographic News. Link -Thanks, Marilyn!
(Image courtesy of Lü Junchang, Institute of Geology, Beijing)