|University of Bristol|
|Adolf Seilacher and his team (references Seilacher et al. 1998)
claim to have discovered fossilized worm burrows from rocks over one billion years old. The traces
are attributed to undermat miners, animals which excavate burrows under microbial mats growing over
the surface of sediments. The markings are described as too irregular to be syneresis cracks, too
delineated to be wrinkles and too large (5mm diameter) to be attributed to protists or fungi. This
along with other features has convinced the team that the traces have a metazoan origin. Other
researchers are sceptical, inorganically produced bedding features have often before been misidentified
as trace fossils, the age of these structures means that many palaeontologists will require a lot
The potential Precambrian trace fossil. Science, Seilacher et al. 1998, 282, p81.
A spectacular new fossil deposit has been recently unearthed in the Doushantuo formation of Southern China. Preserved in 570 million year old phosphorites are algae and tiny spheres believed to be embryos in early cleavage states (references Xiao et al. 1998)
The embryo fossils are a millimetre across and seem to be divided into two, four, eight or more compartments. The fossils are a constant size regardless of the number of compartments they are split into - this fits in with a pattern of early embryonic development.
These fossils are potentially so important because the cleavage states they exhibit are very similar to those of modern nematode, flatworm and arthropod embryos. It is therefore possible that these fossils represent diverged metazoan lifeforms older than the Ediacara. They also represent a potential untapped source of Precambrian metazoan fossils, previously overlooked due to their minute size.
Back to: timing of metazoan origins