Clayton Lake in the northeast corner of New Mexico was formed by construction of a dam. In the 1980s, a flood scoured the top surface off the dam spillway, revealing a layer of Cretaceous mudstone that contains about 300 dinosaur footprints (and at least one groove from a dragged dinosaur tail). On the day I was there, there had been a rainstorm the previous night. This had the happy effect of making many of the footprints visible as the locations of small puddles, so pretty much every puddle in this picture (and many smaller depressions with no water in them) is a dinosaur footprint.