Treptichnus

Treptichnus is an ichnogenus of trace fossils produced by organisms burrowing through soft sediment. The genus encompasses several ichnospecies, with Treptichnus pedum being the best known and the one most frequently discussed in evolutionary and stratigraphic contexts. Treptichnus pedum has been used as a marker for the base of the Cambrian Period in many sections around the world.

The traces attributed to Treptichnus are typically complex, consisting of networks of burrows that may branch and vary in depth. They are interpreted as the result of repeated digging and retreating episodes by a mobile, bilaterian animal or animals that engaged in organized sediment feeding or processing. The traces reflect behavioral sophistication that is seen as a significant step in the early history of animal activity on the seafloor.

Geological significance: Treptichnus pedum appears in late Ediacaran to early Cambrian deposits, and its first widespread appearance around 541 million years ago has made it an important marker for the boundary between the Precambrian and Cambrian. Its global distribution supports the view that complex burrowing behavior arose early in metazoan evolution. However, the precise regional appearance of Treptichnus pedum can vary, and interpretations of boundary timing have evolved with new data.

Taxonomic note: Treptichnus is an ichnogenus, representing a trace fossil type rather than a specific organism. Treptichnus pedum is the type species, and its occurrence is often cited in discussions of early Cambrian stratigraphy and the emergence of complex trace-making behavior.