Trace fossils.

Ichnology (from the ancient Greek ichnos, a footprint or track) is the study of ichnofossils, or trace fossils. These are all the fossils that cannot be called 'body fossils' (skeletons, shells, preserved bodies and body parts). Trace fossils are typically tracks, trails or burrows, and they provide information on ancient environments and ancient behaviour. Ichnologists and palaeobiologists can identify whether a suite of trace fossils was produced in an ancient desert or on the deep abyssal ocean floor. Even more startling is that a trackway of dinosaur footprints can reveal the animal's speed, or even a behavioural shift like walking to the edge of a lake and then leaping in and swimming away.