<ref name = "Martin2000">According to {{cite journal | author = Martin, M.W.; Grazhdankin, D.V.; Bowring, S.A.; Evans, D.A.D.; Fedonkin, M.A.; Kirschvink, J.L. | date = 5. maj 2000 | title = Age of Neoproterozoic Bilatarian Body and Trace Fossils, White Sea, Russia: Implications for Metazoan Evolution | journal = Science | volume = 288 | issue = 5467 | pages = 841 | issn =  | doi = 10.1126/science.288.5467.841 | url = http://www.scienceonline.org/cgi/content/abstract/288/5467/841 | access-date = 2007-05-10 | archive-date = 28. september 2007 | archive-url = https://web.archive.org/web/20070928163307/http://www.scienceonline.org/cgi/content/abstract/288/5467/841 | url-status = dead }}, but for a more cynical perspective see {{cite journal | author = Butterfield, N.J. | date = 2006 | title = Hooking some stem-group ‘‘worms’’: fossil lophotrochozoans in the Burgess Shale | journal = Bioessays | volume = 28 | issue = 12 | pages = 1161-6 | issn =  | doi =  | url = http://doi.wiley.com/10.1002/bies.20507 | access-date = 2007-05-21 }}</ref>
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