Confusion With Other Types of Fossils
Trace fossils are not body casts. The Ediacara biota, for instance, primarily comprises the casts of organisms in sediment. Similarly, a footprint is not a simple replica of the sole of the foot, and the resting trace of a seastar has different details than an impression of a seastar.
Early paleobotanists misidentified a wide variety of structures they found on the bedding planes of sedimentary rocks as fucoids (Fucales, a kind of brown algae or seaweed). However, even during the earliest decades of the study of ichnology, some fossils were recognized as animal footprints and burrows. Studies in the 1880s by A. G. Nathorst and Joseph F. James comparing 'fucoids' to modern traces made it increasingly clear that most of the specimens identified as fossil fucoids were animal trails and burrows. True fossil fucoids are quite rare.
Pseudofossils, which are not true fossils, should also not be confused with ichnofossils, which are true indications of prehistoric life.
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Numerous borings in a Cretaceous cobble, Faringdon, England; see Wilson (1986).
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Sponge borings (Entobia) and encrusters on a modern bivalve shell, North Carolina.
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Helminthopsis ichnosp.; a trace fossil from the Logan Formation (Lower Carboniferous) of Wooster, Ohio.
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Gigandipus, a dinosaur footprint in the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm, southwestern Utah.
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Lockeia from the Dakota Formation (Upper Cretaceous).
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Lockeia from the Chagrin Shale (Upper Devonian) of northeastern Ohio. This is an example of the trace fossil ethological group Fugichnia.
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