The first-known shell-crushing ray-finned fish, Fouldenia, is shown swimming along the bottom of a tropical freshwater floodplain about 348 million years ago. The Fouldenia fossils came from a site in Scotland that also produced the earliest-known post-extinction tetrapods, four-limbed creatures that later crawled ashore and evolved into amphibians, reptiles, birds and mammals. An early tetrapod is shown at the top of the image. (Credit: Painting by John Megahan)
