The oldest evidence of bioturbation on Earth

Mar 20, 2012

The Ediacaran Period, an interval in Earth's history after the Snowball Earth glaciations but before the Cambrian radiations, marks the introduction of complex macroscopic organisms synchronously in unrelated groups. It has been proposed that the increase in size in marine organisms was triggered by the oxygenation of Ediacaran oceans.

New research shows that animals, rather than a late Neoproterozoic increase in , could equally lead to a revolution in the structure and evolution of marine paleocommunities.

In the course of studying Ediacaran-age rocks in a remote region of arctic Siberia, Vladimir Rogov and fellow researchers from Institute of Petroleum Geology and Geophysics in Novosibirsk (Russia) unexpectedly came across the oldest evidence of bioturbation (disruption of fine-laminated sediments by purposeful burrowing of animals in search for food) that significantly precedes the Cambrian radiations.

Of special interest is that the advent of bioturbation in the fossil record coincides with the earliest ecological differentiation of macroscopic Ediacaran communities, which is interpreted to be a direct consequence of ecosystem engineering by animals.

Bioturbation in modern seafloor habitats substantially affects key ecosystem process, including biogeochemical interactions, , and primary productivity; the first appearance and expansion of bioturbation in the Ediacaran, therefore, must have had a profound effect on ecosystem structure and functioning.

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More information: Vladimir Rogov et al., Geology, Posted online 19 Mar. 2012; doi: 10.1130/G32807.1

Journal reference: Geology search and more info website

Provided by Geological Society of America

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Graeme
not rated yet Mar 21, 2012
One of the features of the Ediacaran has been the lack of bioturbation which destroyed many fossil impressions later in the geologic time. The trace fossil observed is called Nenoxites. It excavates a tunnel up to 5cm deep which is backfilled. The authors call this the first example of engineering, and also the most reliable evidence of the presence of bilaterians. However this was already described in "Planetary Systems and the Origins of Life" see http://books.goog...pg=PA201 which has a picture. It describes the tunnels as being on the underside of the microbial mat, and were known at least since 1990. There have been prior claims of Kimberella being a bilaterian and having feeding traces.

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