Xin Wang and colleagues have discovered the earliest known example of a flower bud in a 164-million-year-old plant fossil in China. The researchers have named the new species Florigerminis jurassica. They believe that the discovery pushes the emergence of flowering plants, or angiosperms, back to the Jurassic period, which occurred between 145 million and 201 million years ago.

According to the text, how old was the fossil that Wang and colleagues discovered?