Answer: Archaeopteryx
Explanation: The Archaeopteryx is known as the transitional form between dinosaurs and birds. Archaeopteryx had features that links it to present-day reptiles and birds. It had feathered wings but a bony tail, and is believed to have evolved into birds in 10 million years.
The Archaeopteryx had a flat sternum, unlike modern day birds. Birds which fly have a keeled sternum and it is possible that the Archaeopteryx did not use sustained flight as a method of movement and the feathers were mostly a means of insulation.
