What are Trace Fossils?
As the words suggest, trace fossils are fossil traces left by organisms, many ancient and extinct. The oldest are from the Twitya Formation in northwestern Canada, dated to 610 million years ago. Within paleontology, the formal name for trace fossils are ichnofossils, from the Greek ichno meaning “trace” or “track.” Trace fossils are found in sedimentary rock, and dated by examining isotope ratios of zircons embedded in the same layer. Although trace fossils may not be as fantastic as the more familiar body fossils, they are much easier to find, and provide a crucial reference point for unraveling the behavior and anatomy of organisms. On the other hand, many trace fossils may be of ambiguous origin, with thousands made by organisms that are unidentified. In these circumstances, scientists have to settle for educated guesses and debate. Trace fossils can be broken down into various categories. There are Domichnia, trace fossils of dwelling structures, such as underground chambers; Fodi
Trace fossils include any impression or other preserved sign of activity (for example, feeding, scratching, burrowing, walking, or resting). Many animals, plants, protists, and bacteria have left their traces in the fossil record. These can be tubes, lines, scratches, or other features. They have various characteristics, such as types of symmetry or resemblance to traces made by modern organisms, that indicate they were most likely made by an organism. In some cases, such as dinosaur footprints or certain shrimp burrows, it may be possible to say what group of animal made a particular trace. However, unless a body fossil of the organism is preserved with the trace fossil, determining who made the trace is usually difficult. Because of this, trace fossils are described and given their own names, regardless of whether they match up with a particular organism. Trace fossils most often were created in soft sediments, and are usually preserved only if the sediment remains undisturbed until
