A trace fossil is not part of an organism that has been preserved, but a piece of evidence left by an organism that has been fossilized. This includes egg shells, footprints, fecal matter or burrows.

These trace fossils are as important as the fossilized organisms themselves, because they give us hints as to what the organism ate, where exactly it lived in its envionment, its size during life and the size of offspring. These clues aid scientists to put the pieces of the evolutionary puzzle together.