Evidence for earlier multicellular animal forms, which may have been the precursors of this radiation, date from 600 million years ago. Notable among these are trace fossils in the form of imprints of animals and their activities, such as burrows in mud, produced by animals that paleontologists call the Ediacaran fauna. These organisms were soft-bodied and are found with various strange body forms. The so-called Small shelly fauna of the ensuing Tommotian period included Cloudinia and its kin.
The original and most widely-publicized source of fossils from the actual radiation period is the Burgess Shale in British Columbia. Some Burgess Shale organisms display strikingly unusual body plans that are not easily connected with any phyla known since.