text: Some trace fossils can be used as local index fossils, to date the rocks in which they are found, such as the burrow Arenicolites franconicus which occurs only in a  layer of the Triassic Muschelkalk epoch, throughout wide areas in southern Germany.
  The base of the Cambrian period is defined by the first appearance of the trace fossil Treptichnus pedum.
  Trace fossils have a further utility, as many appear before the organism thought to create them, extending their stratigraphic range.