New research by an international team of scientists led by the University of Saskatchewan has revealed novel information about the most important transition in the history of life: the Ediacaran-Cambrian boundary.
The Ediacaran-Cambrian boundary (about 541 million years ago) represents a major divide in the history of the biosphere. Ediacaran biotas were dominated by soft-bodied organisms that are now considered for the most part to be unrelated to modern metazoans.
On the other hand, the Cambrian witnessed the rapid development of almost all modern groups of animals, including the rise of skeletal faunas, a major evolutionary event known as the Cambrian explosion.
Field work undertaken by this research team in South Africa has shown that the fossil burrow used to place the position of this boundary (a zigzag burrow known as Treptichnus pedum) is found in sediments that were laid down in a wide range of shallow-marine settings, and is present not only in deposits that formed offshore in several meters of water, but also in intertidal deposits right at the shoreline.
The use of this burrow (most likely produced by soft-bodied worms known as priapulids) to delineate the Ediacaran-Cambrian boundary has been controversial because many scientists believed its presence was restricted to certain environments, therefore reducing its utility as a general fossil guide. To establish the broad environmental tolerance of this form, the research team combined detailed field work with conceptual and methodological tools employed in the recently established field of Stratigraphic Paleobiology.
This study provides a solid base to the paleontologic criteria employed to establish the Ediacaran-Cambrian boundary, a topic that is receiving huge attention within the paleobiological and geological community because of its implications for the early evolution of life.
Environmental tolerance and range offset of Treptichnus pedum: Implications for the recognition of the Ediacaran-Cambrian boundary
Luis A. Buatois et al., Dept. of Geological Sciences, University of Saskatchewan, Posted online 7 Feb. 2013;