Paleotectonic reconstructions for the late Proterozoic have differed over t
he timing of the Cordilleran rifting between Laurentia and the East Gondwan
a cratons. Parsimony Analysis of Endemism (PAE) and phenetic clustering of
the "Ediacara biota" were carried out, for comparison with competing paleot
ectonic hypotheses. All analyses show a common pattern of similarities amon
g biotas. The biotas of Charnwood Forest and Newfoundland consistently grou
p together, while the south Australian biota is closest to those of Baltica
, northern Laurentia, and Siberia. The biota of southwest North America, th
ough still poorly known, strikingly resembles that of Namibia-not that of n
orthwestern Canada. This pattern is not obviously due to facies-related or
preservational bias and is very different from Cambrian biogeographic patte
rns. The overall pattern is most consistent with the hypothesis that the we
stern margin of Laurentia was in close contact with East Gondwana, with rif
ting taking place either during or just before the Vendian. This arrangemen
t has been previously proposed as a paleotectonic hypothesis; however, most
recent paleomagnetic and structural studies support the alternate hypothes
is that this rifting took place more than 100 million years before the Vend
ian. Resolving this contradiction will require much more data on both organ
ismal distribution and cratonal position.