Preservation of ovarian follicles reveals early evolution of avian reproductive behaviour

Newly discovered fossils of primitive birds from China, preserved with ovarian follicles intact, show that birds only had one functioning ovary at any given time from a very early date, but that other features, such as skeletal and sexual maturity, remained very dinosaur-like. A window on the evolving reproductive capacities of birds is opened by the analysis of newly discovered fossils of primitive birds from the Mesozoic era of China. The...