Trace fossils aren't the actual body parts of an organism, but rather evidence of their activity or behavior. Some examples include:

* Footprints: Show where an animal walked

* Burrows: Holes dug by animals for shelter or nesting

* Coprolites: Fossilized dung (poop)

* Gastroliths: Stones swallowed by dinosaurs to help grind food

* Nests: Evidence of where animals built their homes

These trace fossils give us clues about the lives of ancient organisms, even if we don't have their actual bones or shells.