What really did come first--the chicken or the egg? Birds' reproductive biology is dramatically different from that of any other living vertebrates, and ornithologists and paleontologists have long ...

Fossil by fossil, paleontologists have traced birds back to their dinosaur ancestors. As they’ve done so, traits once thought to be distinct characteristics of avians – such as feathers and air sacs – ...

As winged dinosaurs underwent a series of evolutionary changes during the transition into Aves, or birds, one pivotal transformation was the appearance of a single-ovary reproductive system. "The most ...