Fossils are often the remains of a solitary creature, but sometimes they are dramatic scenes of our entire ecosystem, preserved forever. These mass mortality fossils form when a group of animals is wiped out in a cataclysm, an image of their sudden extinction but also a preservation of how they lived. 

These specimens are fossil snail clusters, preserving the remains of an Elimia tenera colony, dated to 48 million years ago. Found in the Green River Formation in Wyoming, these fossil snails are estimated to number in the billions.