THE photograph right shows a fossil pterosaur (an extinct flying reptile) called Darwinopterus. The fossil itself is in Zhejiang Museum of Natural History, in Hangzhou, China, and was found in the mid-Jurassic strata of Lianong province. It has just been described by Lu Junchang of the Chinese Academy of Geological Sciences, in Beijing, and his colleagues in a paper in Science. What is remarkable is the feature marked with an arrow, an egg. That both identifies the specimen as female and casts light on how pterosaurs reproduced.
Until recently the assumption was that, like birds, pterosaurs looked after their hatchlings in nests. This specimen suggests that is not true. The egg seems designed for burial rather than for the nurturing embrace of a mother pterosaur. Its outer layer is parchmentlike, which is characteristic of the ova of modern egg-burying reptiles such as turtles. Just as baby turtles can swim as soon as they have hatched, this find suggests that baby pterosaurs—of this species, at least—could fly.
The specimen also helps confirm the previously unproven belief that Darwinopterus was sexually dimorphic, with the males sporting crests and the females lacking them. Both crested and crestless specimens are known, but this one suggests crestlessness was a female trait. This is no great surprise, since it is usually the male of any dimorphic species who is encumbered with any expensive ornamentation. But it is a nice confirmation that Darwin's observations about sexual selection being a matter of males showing off to females were as true 160m years ago as today.