At about six o'clock in the morning, long before light broke on a cold November day in 2014, I pushed through the Beijing station and fought my way onto a crowded train. I was headed for Jinzhou, a Chicago-sized city in the northeastern fringes of China. I tried to steal back some sleep as we crawled past concrete factories and hazy cornfields, but I was too excited to nod off. Something rumored to be incredible was waiting for me at my destination—a mysterious fossil that a farmer had stumbled on while harvesting his crops.