Tiny Jurassic Bird Reveals Stepwise Tail Evolution in Early Birds

Chinese paleontologists describe Zhengheornis buyu, a small 148–150 million-year-old Jurassic bird with a 15-vertebra tail that remains unfused (no pygostyle), showing that vertebral tail shortening occurred before pygostyle formation in early birds. With an estimated body mass of 74–163 g, this mosaic anatomy suggests a stepwise tail evolution and supports a rapid diversification of avialans by the late Jurassic, published in Science Advances.