Thousands of dinosaur prints have been discovered on a vertical rock face in northern Italy. The prints, which are aligned in parallel rows, stretch hundreds of metres. It seems that some 210 million years ago, when the wall, in the Stelvio National Park, was a tidal flat, herds of prosauropods (large, long-necked herbivores) moved across it, and left their tracks in the soft sediment. The prints were in plain sight, but the wall is usually in shade, making them hard to spot – until a wildlife photographer trained a powerful lens on the wall.