Skin impression fossils are a type of trace fossil, as opposed to a body fossil that preserves actual body parts. Instead, these types of fossils are created when skin creates an imprint on substrate which is preserved when that substrate turns to rock, usually when the body is at least partly buried but then completely deteriorates to leave only the skin impression. While skin impression fossils can theoretically come from any kind of animal which has skin, most of them come from larger vertebrates, especially those that lived during the Mesozoic and Cenozoic eras.
