The first putative metazoans (animal) fossils dated to the late Tonian (c. 800 Mya). A notable example of this is the Otavia antiqua, which has been described as a sponge by its discoverers and numerous other scholars. This dating is consistent with molecular data recovered through genetic studies on modern metazoan species; more recent studies have concluded that the base of the animal phylogenetic tree is in the Tonian.
^Macdonald, F. A.; Schmitz, M. D.; Crowley, J. L.; Roots, C. F.; Jones, D. S.; Maloof, A. C.; Strauss, J. V.; Cohen, P. A.; Johnston, D. T.; Schrag, D. P. (4 March 2010). "Calibrating the Cryogenian". Science. 327 (5970): 1241-1243. doi:10.1126/science.1183325. PMID20203045. (Duration and magnitude are enigmatic)