Trichophycus pedum

Trichophycus pedum (or Treptichnus pedum; formerly Phycodes pedum) is regarded as the earliest widespread complex trace fossil. Its earliest appearance, which was contemporaneous with the last of the Ediacaran biota, is used to define the dividing line between the Ediacaran and Cambrian Periods. However, it has since been discovered below the originally defined GSSP.

Trichophycus pedum has a fairly complicated and distinctive burrow pattern: along with a central, sometimes sinuous or looping burrow. It was made by successive probes upward through the sediment in search of nutrients, generating a trace pattern reminiscent of a fan or twisted rope. It is considered more complex than earlier Ediacaran fauna; and these trace fossils, which occur worldwide, are usually found in strata above them.

Since the Trichophycus animal presumably lacked any hard anatomical features, such as shells or bones, only its burrows have been found. Its morphology and relationship to modern animals is therefore unknown, and some dispute even its inclusion within the animal kingdom.

It may have been produced by under-mat mining rather than vertical burrowing.