Tracing the evolution of bird reproduction

What really came first — the chicken or the egg? Birds’ reproductive biology is dramatically different from that of any other living vertebrates, and scientists have long wondered how and when the unique features of bird reproduction originated. A new review examines answers from three sources–modern birds, fossils of primitive birds, and fossils of the dinosaurs from which birds are descended — to shed new light on the subject.
Paleontology News — ScienceDaily