9.1: Types of Fossils
Despite the incredible diversity and complexity of the fossil record, we can lump fossils into three main types:
Body fossils are preserved portions of the actual body parts of plants, animals, and other organisms. They include a wide variety of types including bones, teeth, scales, feathers, hair, shells, soft tissue (skin, muscle, etc.), as well as wood, roots, leaves, seeds, and many others.
Trace fossils are structures that are formed by the activity of an organism and commonly include features that disrupt layers of sediment (tracks, trails, burrows), erosion (boring, scraping, orbiting), the creation of layering or organization (various types), and even fossilized excrement ( coprolites ). Trace fossils record a wide variety of behaviors including feeding, resting, movement, dwelling and many others. It's worth noting that growth is not a behavior, so things like roots and stromatolites are best considered as body fossils.
Geochemical fossils are subtle chemical clues that are created by organisms and preserved in the geologic record. Perhaps the most common example is a mineral or rock that is enriched in carbon-12 because of the activity of photosynthetic organisms.
With practice, you will learn to identify pseudofossils - naturally occurring crystals, sedimentary structures, and weathering features that resemble body or trace fossils.