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. [ [http://www.stratigraphy.org/ediacaran/ Subcommission on Neoproterozoic Stratigraphy] - URL retrieved November 27, 2006] However, it has since been discovered below the originally defined GSSP [Cite journal
last = Gehling
first = James
last2 = Jensen
first2 = Sören
last3 = Droser
first3 = Mary
last4 = Myrow
first4 = Paul
last5 = Narbonne
first5 = Guy
title = Burrowing below the basal Cambrian GSSP, Fortune Head, Newfoundland
journal = Geological Magazine
volume = 138
issue = 2
pages = 213–218
month = March | year = 2001
year = 2001
url = http://www.journals.cambridge.org/action/displayAbstract?fromPage=online&aid=74669
doi = 10.1017/S001675680100509X] .

"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. [cite book | last = McMenamin | first = Mark A. | coauthors = Dianna L. McMenamin | title = The Emergence of Animals | origdate = 1990-01-15 | publisher = Columbia University Press | id = ISBN 0-231-06647-3] It is considered more complex than earlier Ediacaran fauna; and these trace fossils, which occur worldwide, are usually found in strata above them. [cite web | url = http://www.uni-wuerzburg.de/palaeontologie/Stuff/casu8.htm | title = Life in the Cambrian | accessdate = 2006-03-09]

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. [cite book | last = Altermann | first = Wladyslaw | title = Precambrian Sedimentary Environments | origdate = 2002-07-01 | publisher = Blackwell Publishing | id = ISBN 0-632-06415-3]

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