The Late Precambrian fossil Kimberella is a mollusc-like bilaterian organism

摘要

The fossil Kimberella quadrata was originally described from late Precambrian rocks of southern Australia. Reconstructed as a jellyfish, it was later assigned to the cubozoans ('box jellies'), and has been cited as a clear instance of an extant animal lineage present before the Cambrian. Until recently, Kimberella was known only from Australia, with the exception of some questionable north Indian specimens. We now have over thirty-five specimens of this fossil from the Winter Coast of the White Sea in northern Russia. Our study of the new material does not support a cnidarian affinity. We reconstruct Kimberella as a bilaterally symmetrical, benthic animal with a non-mineralized, univalved shell, resembling a mollusc in many respects. This is important evidence for the existence of large triploblastic metazo-ans in the Precambrian and indicates that the origin of the higher groups of protostomes lies well back in the Precambrian.